This may be the largest remaining piece of the space telescope Hitomi.
New observations suggest that Hitomi, Japan’s flagship X-ray telescope, is tumbling through space in ten or more pieces—and is likely unrecoverable.
“The available data now seem to indicate a real break-up rather than just “some” debris shedding,” writes satellite tracker Marco Langbroek. “If true, then Hitomi is beyond saving.”
The Japanese Aerospace Exploration Agency (JAXA) lost consistent contact with Hitomi (also known as ASTRO-H) on March 26. Early reports showed the spacecraft’s orbit had rapidly changed—and that it had then shed at least five pieces of debris, size unknown. Video footage captured from the ground revealed an object tumbling through space, an ominous observation consistent with the intermittent radio signals JAXA was still receiving from the spacecraft. Altogether, the evidence suggested that some sudden event had disabled Hitomi, which would have peered into the hearts of galaxies and studied the maelstrom of matter swirling around black holes.
Whether that event was some kind of onboard explosion (more probable), or a collision with space debris (less probable) is still unclear.
“Sadly, I now believe that the radio signals were the dying sighs of a fatally wounded ASTRO-H,” tweeted Jonathan McDowell of the Harvard-Smithsonian Center for Astrophysics. “As far as I know, JAXA hasn’t officially given up though!”
Those ten pieces were likely all present on March 26, when the first reports of debris from Hitomi came in, but they weren’t separated enough in space to be reliably observed.
Now, orbital data show that some of those pieces are on quickly decaying trajectories and will burn up in Earth’s atmosphere within a week or so, writes astrophysicist Peter Coles of Sussex University. Those fragments are small, the kinds of things a spacecraft could plausibly shed and still function.
Today’s updated Hitomi debris plot. All the objects now have more than one data point; 3 are decaying rapidly pic.twitter.com/oeUyboyXRH
The two largest fragments, however, suggest that whatever happened to Hitomi is probably a terminal event. Video footage shows that these fragments, now called piece A and piece L, are roughly the same size and are tumbling through space, with one flying about 7 minutes in front of the other.
Japanese Spacecraft Tumbling in Orbit (L Piece)
The first of those pieces, now called piece L, was captured on video last week and mistakenly thought to be the main body of Hitomi. But it’s not. New observations suggest the tumbling fragment is a large, dense piece of Hitomi—perhaps its extendable optical bench, where the spacecraft’s hard X-ray detectors are. An April 2 video from satellite tracker Paul Maley, taken on the ground in Arizona, suggest fragment L is still tumbling through space, flashing about once every 10 seconds.
Fragment A, which is now thought to be the bulk of Hitomi, is trailing piece L by several minutes. Maley’s video shows that A is flashing about once every second.
“It is spinning quite fast with bright flashes,” Maley describes, noting that fragment A is also visible with the unaided eye. “The only question is, what are the real identities of the objects in orbit? Given the brightness of the two that I have seen, one is most likely the primary payload, the other is something sizable but what it is I do not know.”
Pieces A and L are trailed by a third large-ish fragment called K, which is about 26 minutes behind the pair.
The whole situation is unfolding into a heartbreaking disaster for Japan and for astronomers, who’d hoped this attempt to put an X-ray observatory in orbit would be successful (to really see the universe in X-rays, you need a satellite above the Earth’s atmosphere). Since 2000, Japan has tried twice to operate a space-based X-ray telescope; the first crashed during launch, and the second suffered from a leaky helium tank. So, hopes were high for Hitomi, which launched on February 17, and means pupil of the eye.
It could take years for the spacecraft’s two largest fragments to re-enter Earth’s atmosphere, and it’s possible that bits of them could survive the plunge to our planet.
“They aren’t decaying fast, may be a few years before they reenter,” McDowell says. “But when they do we’ll be paying close attention.”
A new video shows Japan’s troubled Hitomi spacecraft tumbling in orbit. As the satellite crosses the screen (from right to left), it varies wildly in brightness—which means it’s shooting unstably through space. The space telescope lost consistent communication with Earth on Saturday.
“If the satellite were not tumbling, it would appear to be the same brightness,” says Paul Maley, an amateur astronomer and former NASA flight controller, who observed Hitomi from the ground in Arizona. “The fact that it is rotating with extreme variations in brightness indicates that it is not controlled and that some event caused it to begin its rotation.”
It’s unknown how big those pieces are (they could be small bits of insulation) or what exactly has happened to the spacecraft, with speculation ranging from an on-board error — such as a battery explosion or gas leak — to a collision with space debris or a micrometeorite. Regardless, the situation is clearly not good news for JAXA, which has already experienced two failures with X-ray observatories. In 2000, its ASTRO-E space telescope failed to reach orbit and likely crashed into the Pacific Ocean, and in 2005, a helium leak disabled the primary instrument on Suzaku, ASTRO-E’s successor. But late last year, JAXA did manage to place its Akatsuki spacecraft in orbit around Venus, five years after a valve malfunction caused the spacecraft to miss its first rendezvous with Earth’s shrouded sister world.
Hitomi, which launched into low-Earth orbit on February 17, was intended to study the highest energy universe and peer at galaxy clusters, supermassive black holes, and exploding stars. Some scientists still think it’s not entirely impossible for the space telescope (whose name means “eye” in Japanese) to recover from this series of still-mysterious unfortunate mishaps and stare at the cosmos.
It’s had a bad day, but I am optimistic this morning that @JAXA_en@ISAS_JAXA will recover contact with Hitomi in the coming days.
Japan has lost contact with its newest space telescope. The spacecraft, which was carrying an instrument from NASA, was intended to study the high-energy universe in X-rays and gamma rays, and observe such objects as supermassive black holes and galaxy clusters.
It’s not clear exactly what has happened on board Hitomi. Scientists are currently investigating the situation, and the Japanese space agency, JAXA, reports that it has gotten a trickle of a signal from the spacecraft. That means it’s possible the five pieces detected by radar are things like insulation, rather than large chunks of debris resulting from a catastrophic explosion; it’s also possible the spacecraft is tumbling, McDowell says, and that signals from Hitomi are periodically sweeping across the Earth.
Still, despite all the bad news, the spacecraft might not be lost.
“I truly have not given up hope,” McDowell says, noting that equally bad space situations in the past have been successfully resolved. “We lost contact with SOHO for months and fully recovered it. ALEXIS had a solar panel break loose and was tumbling, but they learnt how to fly it and began science mission a couple months late. So it’s a long shot—and I refuse to put a number on the probability—but there is precedent for things being this bad and it turning out OK.”
JAXA is no stranger to second chances. Late last year, the Japanese space agency managed to place its Akatsuki spacecraft in orbit around Venus, after failing on the first try. When Akatsuki originally tried to orbit Earth’s twisted sister, a valve broke and sent the spacecraft on a long, 5-year journey through the solar system. But, eventually, Akatsuki caught up with its target and slipped into Venus’ gravitational clutches.
The moral of the story? Space is hard. Things go wrong. But if we never try, we’ll never succeed.
“A long time ago in a galaxy far, far away” doesn’t even begin to describe a small, bright galaxy hovering at the edge of the observable universe. The little cluster of stars, called GN-z11, is the most distant object astronomers have spotted: It existed when the universe was just 400 million years old.
“This is a very early galaxy,” says UC-Santa Cruz’s Garth Illingworth, who described the galaxy in The Astrophysical Journal. “We’re looking back 13.4 billion years, through 97 percent of all time, to the galaxy when it was forming.”
Yep, it took 13.4 billion years for light from the galaxy to zoom through the universe and collide with the Hubble Space Telescope. But that doesn’t mean the galaxy is 13.4 billion light-years away. The universe has been expanding in the meantime, meaning GN-z11 is actually much, much farther from Earth than that.
“Right now, we expect this galaxy to be about 32 billion light-years away from us in distance,” says study coauthor Pascal Oesch of Yale University.
In other words, the galaxy existed a ridiculously long time ago and is really, really, absurdly far away. To put it politely.
A Precocious Star Factory
When you peer into the distant universe, you’re also looking back in time. So the galaxy in its present form would look very different than what Hubble sees now.
But 13.4 billion years ago, this bright little knot of a billion stars was about 1 percent the size of the Milky Way. Despite its size, the precocious galaxy was pumping out stars much more quickly than the Milky Way. Those stars were very hot, very young, and very massive—the types of stars astronomers think existed in the early universe.
They just didn’t expect to see them so soon.
“We really did not expect to find a galaxy this bright, this early, in the history of universe,” Oesch says. “The big question is, how common are galaxies this bright so early in cosmic history? I don’t think there’s too many out there. I think we were lucky.”
Not For Long
History has taught us that astronomical distance records don’t hold up for long. The previous most-distant galaxy, called EGSY8p7, was reported in July 2015. It’s about 200 million or 300 million years younger than GN-z11, and has a redshift of 8.68. (Redshifts measure how much light has stretched as it travels through the cosmos; higher redshift values correspond to greater distances.) Before that? The winner was EGS-zs8-1, a galaxy that’s another 200 million years younger, and was reported in February 2015. It has a redshift of 7.78.
The new record-holder is at redshift 11, which is a number I hadn’t really expected to see at this point. For what it’s worth, light from the cosmic microwave background—a remnant of the Big Bang—has a redshift of 1,089.
Sometimes science happens quickly. Over the weekend, follow-up observations of a faraway galaxy challenged the conclusions of a study published just last week, which was reported with much fanfare by news outlets that didn’t dig deeply enough to uncover already existing skepticism about the results.
For nearly a decade, one of the major goals in understanding FRBs has been finding a burst’s host galaxy—with that information in hand, scientists would know how far away a burst came from (relatively nearby? Far, far away?), and what kinds of stars live in the burst’s neighborhood. Knowing those things would help identify an astrophysical source for the bursts, which have been thought to arise from colliding dead stars, evaporating primordial black holes, magnetars, and a host of other exotic objects.
So when the Square Kilometer Array’s Evan Keane and colleagues identified a candidate galaxy for a burst observed in April 2015, it was a hugely important observation. The team’s data suggested that FRB 150418 came from 6 billion light-years away—well outside the Milky Way—and went off in a neighborhood filled with old, dying stars.
The team interpreted those data to mean the burst may have been triggered by colliding neutron stars, or the dense, crushed corpses of very large stars. When those stars collided, they not only produced a short burst of gamma-rays, but a blast of radio waves as well. What’s more, by measuring the amount of matter between Earth and the burst’s host galaxy, the observation helped solve what’s known as the “missing mass” problem—a longstanding conundrum in which the amount of observable matter in the universe doesn’t quite match predictions.
It’s a nice, clean story. Trouble is, the association between the fast radio burst and its candidate galaxy may have just fallen apart.
Keane and his colleagues identified the host galaxy based on their observation of “a fading radio afterglow” that overlapped with the galaxy. The team interpreted the fading glow to be a remnant of the collision that generated the FRB, meaning the burst must have originated from within the overlapping galaxy.
Even though the work done by Keane and colleagues is “a technical tour de force,” the link between the galaxy and FRB is uncertain, says Caltech’s Gregg Hallinan, who studies the radio sky and looks for transient events and variables.
“It looks like they may have been unlucky in that the rate of transient radio sources at these frequencies is much higher than you might expect,” he says.
Many things in the sky produce variable amounts of radio waves, sometimes getting brighter, sometimes fading, and it’s not clear how common those sources are or how frequently they vary. Without a good understanding of the variable sky, it’s hard to say whether the “afterglow” really is associated with the FRB, or is something else.
“The most important first step is to check whether the radio afterglow has faded away,” Hallinan said to me, last week. “If it is associated with a short gamma-ray burst [the same event that produced the FRB], it will definitely have faded.”
Disappointingly, very few news stories reported any skepticism about the results or the need for more confirmation.
On Feb. 27 and Feb. 28, Harvard University’s Edo Berger and Peter Williams re-observed the FRB’s candidate galaxy, looking for any sign of the radio afterglow. The team already suspected the afterglow wasn’t the work of the FRB: Even though the initial radio glow had faded, it continued to shine too brightly, and for too long, to make sense. Instead, Berger and Williams (and also Hallinan) suspected the “afterglow” was really an active galactic nucleus, the hugely bright and compact region in the center of the galaxy. These nuclei are common and vary in brightness depending on how active the galaxy’s central black hole is. They also produce detectable glows for long periods of time.
Colliding neutron stars, on the other hand, wouldn’t generate a long-lived afterglow.
In short, if the afterglow appeared in Berger and Williams’ follow-up observations, it couldn’t be associated with the FRB. The team moved quickly, once the Nature paper appeared. “We wrote a proposal the next morning, it was approved in the afternoon, we got the data this weekend, and the rest is history,” Berger says.
Not only did the team find the “afterglow,” Berger and his colleagues also observed that it had brightened. That means associating it with the FRB is problematic; the more likely explanation is that it is produced by an active galactic nucleus that happened to overlap with the FRB’s position on the sky.
If that’s true, then the link between the burst and its galaxy has fizzled, along with any implications for the source of fast radio bursts.
“This recent observation has all but confirmed my fears that the fading radio source seen by Keane et al. is just a variable active galactic nucleus,” Hallinan says. “The claimed association is looking very unlikely at this stage, barring the possibility that the fast radio burst was actually produced by this same active galactic nucleus. There is no strong evidence to support this latter possibility at the moment, so it’s just idle speculation.”
Keane and his team say they’re aware of Berger and Williams’ work, and are working on follow-up observations and a response.
“FRBs certainly are an exciting field with a lot happening,” Keane says. “We are aware of that piece of work, and indeed are performing our own ongoing studies. When we’ve completed and fully considered those we will certainly report our findings. That will be in the peer reviewed scientific literature which, as you know, takes time.”
Behind the scenes, science at its best is a messy enterprise, characterized by challenges and disagreements, conflicting interpretations, and always the demand for cleaner, better data. But that’s how the scientific process works—or should work. It’s just that we don’t often get to see it play out under such a bright spotlight.
As it hurtled through space around 300 million years ago, a small, dark matter-dominated galaxy brushed by the Milky Way. It wasn’t exactly a head-on collision, but it shook the gas in the Milky Way’s massive disk, leaving a telltale pattern of ripples at its edges. Today, the dark dwarf is continuing to speed through space at 450,000 miles per hour.
Known as the Norma dwarf, this little galaxy is one of many that buzz around our glittering spiral of stars, some of which are among the most dark matter-dominated objects in the universe.
For years, Chakrabarti has been studying the distribution of dark matter and looking for the fingerprints it can leave on galaxies. Dark matter is a dense, mysterious substance that makes up most of the mass in our universe but doesn’t interact with anything ordinary. That makes it hard to see and detect. Because they can’t see it directly, scientists trying to characterize dark matter in the cosmos have to hunt for its signatures on surrounding, observable matter – and in 2009, Chakrabarti and her colleagues thought they found one of those.
So the question was: Where is that small galaxy? And could the team find it?
As one might expect, searching for something you mostly can’t see in a bottomless sky of stars is not an easy task. But last year, Chakrabarti and her colleagues spotted three, pulsing stars that appeared to be zooming away at a remarkable pace. Known as Cepheid variables, these are the kind of stars astronomers use to determine the distances of relatively nearby objects – they have a periodic dimming and brightening that can be used to determine their absolute brightness, and thus their distance.
When Chakrabarti studied the trio, she learned they were about 300,000 light-years from the Milky Way’s core, and were hurtling outward roughly twenty times faster than the average star ambles through the galaxy. Because stars rarely fly through space on their own – let alone in trios – she suspects the Cepheids are embedded in a small, dark matter-dominated dwarf galaxy – just the kind of object that may have jiggled our galaxy as it flew by 300 million years ago.
Chakrabarti and others are hoping that such observations will open up the field of galactoseismology, where the features in galactic disks can be used to detect unseen dark matter.
“Much in the same way as seismologists analyze earthquakes to map out the Earth’s interior, we should be able to analyze the observed disturbances in galactic disks to map out the unseen material in galaxies that is their dark matter content,” she says.
Larry Widrow, of Queen’s University in Kingston, Ontario, concurs. He says it’s possible for unseen dwarf galaxies to trigger all kinds of changes in their massive hosts, perhaps producing bars and spiral arms, as well as disturbances that are perpendicular to the galactic plane. “It may be that the passage of dwarf galaxies through the disk are responsible for a wide range of disk phenomena,” he says.
So, just as galaxy quakes helped scientists find Galaxy X, they could also point to Galaxies Y and Z.
But these ripples don’t stick around forever, though – 300 million years might seem like a lifetime, but it’s barely more than one galactic year. The Milky Way only rotates around itself once every 250 million years or so, and in the not-too-distant future, that cosmic churning will erase the fingerprints left by the Norma dwarf’s close encounter.
For years, mysterious blasts of radio waves coming from billions of light-years away have stumped scientists on Earth. Lasting a mere several thousandths of a second, the blasts – called fast radio bursts – appear randomly in the sky and are often discovered hiding in data sets, months or years after they’ve arrived on Earth. Scientists haven’t been able to figure out what the blazingly bright bursts are, alternately suggesting the culprits could be evaporating black holes, colliding dense objects or flaring dead stars, among other possibilities.
For a while, some even thought the enigmatic bursts were an artifact produced by life on Earth, rather than signals coming from outside our galaxy. (“Aliens” appeared to be the preferred explanation among readers of stories describing the mystery.)
Now, after studying how the incoming radio waves in a newly detected burst are twisted and scattered, a team of scientists has uncovered some crucial clues about the blast’s origin: It originated far, far away, in an area with dense, highly magnetized plasma – and traveled through two gas clouds before colliding with the Green Bank Telescope in West Virginia.
“It could be from a star-forming region, a supernova remnant, or the dense inner regions of a galaxy. But these all point toward a younger stellar population, a region that’s forming stars or where stars are dying and exploding,” says Kiyoshi Masui, of the University of British Columbia, who described the burst today in Nature. “There are a lot of models for what these fast radio bursts are. I wouldn’t make any strong bets on any one of them, but my favorite one is flares from magnetars,” he said, referring to a type of extremely magnetic, tempestuous neutron star.
Mining the Data
Masui and his colleagues found the burst, called FRB 110523, in data they’d collected while studying the large-scale structure of the universe. After becoming intrigued by fast radio bursts, the team decided to search for the brief-but-bright signals and wrote a computer program to sift through 650 hours of observations. The program came back with 6,496 candidate bursts – and the unlucky task of sorting through those by eye fell to Hsiu-Hsien Lin of Carnegie Mellon University, who easily identified the one real burst among the thousands of imposters.
The burst exploded on May 23, 2011 in the constellation Aquarius and lasted for roughly three milliseconds. Because of how the team was looking at the cosmos, the scientists were able to extract some important information about the burst’s origin. Mapping matter in the universe means getting detailed information about polarization, or how incoming radiation – such as light and radio waves – is oriented.
“They have to take very high quality, very highly calibrated data that includes full polarization information,” says astronomer Scott Ransom of the National Radio Astronomy Observatory. “That’s kind of overkill for most of the pulsar observations, which is where most fast radio bursts have been seen in the past.”
Hiding in that polarization data were some crucial clues. The radio waves had been twisted as they traveled through the cosmos, something that can only happen if they’d passed through a magnetic field. By measuring how twisted the waves were, the team could determine how strong the magnetic field was – and nothing in the Milky Way is strong enough to warp a radio wave to that degree.
“There’s just not enough magnetization there,” Masui says. “And along the line of sight, most of the distance between us and the burst is just really empty space…so the only thing left is that the magnetization came from the source itself.”
But there’s more. The team determined that in addition to originating near an intense magnetic field, the burst traveled through at least two clouds of ionized gas. As it did, the clouds scattered the radio waves and changed the shape of the burst, producing discernible signatures that only appeared when the team looked at the data in millionths-of-a-second intervals. The first of those clouds, Masui says, is at the signal’s origin; the second is somewhere in the Milky Way.
Lastly, the team figured out the burst couldn’t have traveled more than 6 billion light-years before arriving at Earth.
“Well, it could be between 6 billion and 100 million light-years away,” Masui says.
Astronomers who study these bursts say the team’s work is solid, and that the case for the signals coming from outside the galaxy is getting stronger.
“It’s amazing what they got out of such a small amount of data,” Ransom says. “If these things are really coming from outside of our galaxy, they’re just mindboggling – we just don’t understand them.”
Masui and his colleagues suspect the burst originated in a young, star-forming region in a distant galaxy. (But which galaxy? “There’s something like 100 candidate galaxies that it could be in – we don’t have any idea,” Masui says.) Star-forming regions are known for being dusty, turbulent and sporadically violent. Here, young stars ignite when the crush of gravity turns dusty lumps into nuclear furnaces, and the biggest, brightest stars live fast and die explosive deaths.
When some of those large stars die, their corpses turn into magnetars – young, highly magnetic, spinning neutron stars. These are incredibly dense, incredibly exotic objects with magnetic fields millions of times stronger than the strongest magnet we’d find on Earth. Occasionally, starquakes ripple through a magnetar’s crust and disrupt the dead star, producing enormous flares that emit intense gamma rays.
Now, astronomers suspect these flaring magnetars might also emit radio waves – and could be the culprits behind fast radio bursts.
“They are amongst the most powerful — apart from the sun, which happens to be next door — sources of high-energy radiation that we receive on Earth,” says Caltech astrophysicist Shrinivas Kulkarni, who doubted for years that the bursts came from outside the Milky Way.
Now, he says, the preponderance of the evidence suggests an extragalactic origin for the phenomena – a conclusion he published this week in a paper submitted to the arXiv.
“Every test I feel I’ve undertaken to show the bursts are nearby has failed,” he says.
In his recent paper, Kulkarni and colleagues took a close look at a burst that had been detected by the Arecibo Observatory in Puerto Rico. They independently reached conclusions that are very similar to those of Masui and his colleagues: That the burst came from outside the galaxy, in a region with dense, highly magnetized plasma – and that it could be the work of a magnetar.
So, while teams have only pulled this kind of information from two of the 16 known fast radio bursts, the results are still good news for scientists searching for the signals’ origin – a search that should become easier as a new generation of telescopes comes online.
Getting to know a new place in space is kind of like becoming familiar with a new city: It reveals itself slowly, a patch of terrain or a new neighborhood here, a curious landform or hidden garden there. Over time, all those pieces assemble themselves into an image of somewhere we think we know.
But it’s necessarily superficial. For the most part, our glances are too fleeting to disentangle the threads of history, whether geologic or cultural, that really form the fibers of a place. And brief visits don’t offer much of a chance to dig beneath a world’s surface. Think about the richness of information that’s buried beneath cities, in bootleggers’ tunnels and abandoned train stations, in catacombed boneyards and the slices of life that tour operators don’t necessarily want you to see. It takes a bit of effort to really explore a metropolis, to crawl into its nooks and crannies and scoop up enough clues to say you’ve finally started getting to know it. How often have we visited somewhere new and thought, “I’ll have to check that out next time,” with a somewhat wistful pang?
In space, next times are few and far between. Think about Pluto, and all those features we’d take a closer look at if only we could send a second spacecraft zooming by. Or Uranus and Neptune, two giant planets that just now, more than a quarter-century after our first quick visit, might be inching back onto the itinerary. The same is true for distant galaxies, exploding stars, and ghostly nebulae, which often appear in the eyepiece only after competitive observing time is awarded.
Each goodbye could be our last.
Ten days ago, NASA’s Cassini spacecraft took its last close look at Dione, one of Saturn’s small icy moons (some photos from the flyby are in the gallery above). It flew just 474 kilometers above Dione’s surface, part of which is cut with chasms and cliffs, forming a “wispy terrain” that surprised scientists when Cassini brought it into focus in 2004. Dione, at just 1,123 kilometers across, is one of many intriguing worlds orbiting the spectacularly ringed planet; but once the Cassini mission ends in 2017, there’s no guarantee we’ll be going back.
Fortunately, we’ve got another year left to stare at Ceres, the largest world in the asteroid belt and a dwarf planet in its own right. NASA’s Dawn spacecraft has been orbiting the cratered sphere — at 950 kilometers across, it’s pretty close to Dione in size — since March, returning ever-closer and more confusing views of the planet’s enigmatic bright spots and strange, barnacle-shaped mountain. It’s the best kind of world to explore, a world that isn’t performing according to plan.
Rounding out the gallery above are a new Hubble image of an old friend (hooray!), and a composite image showing two colliding galaxy clusters far, far away. As these clusters slammed into one another, they excited a long-dead cloud of electrons that had originally been stirred up and energized by a nearby supermassive black hole. Over time, that bright cloud of electrons faded. But the collision re-energized the cloud, causing it to emit radio waves and producing what’s called a “radio phoenix,” resurrected from cold, cosmic ashes.
More than a half-century after the first modern search for communicating extraterrestrial life, humanity’s quest to find intelligent beings in the cosmos is getting a much-needed boost. Today, Silicon Valley billionaire Yuri Milner announced a $100 million project that will scan the sky for radio signals from other worlds. Called Breakthrough Listen, it will be the most powerful search for extraterrestrial intelligence ever undertaken on Earth.
“In one day, Breakthrough Listen will collect more data than a year of any previous search,” said Milner, who’s also behind the lucrative Breakthrough Prizes in physics, mathematics and the life sciences. “The scope of our search will be unprecedented.”
Milner announced the 10-year initiative at a ceremony in London that included remarks from theoretical physicist Stephen Hawking, who discussed the ubiquity of life’s building blocks in the cosmos, as well as the possibility that Earth’s lights might already be gleaming in alien eyes.
“It’s time to commit to finding the answer to the search for life beyond Earth,” Hawking said. “We are life, we are intelligent, we must know.”
Snooping on the Cosmos
Beginning in early 2016, Breakthrough Listen will eavesdrop on stars in 100 neighboring galaxies, the galactic plane and disk, and the 1 million stars closest to Earth. So far, the Green Bank Telescope, at the National Radio Astronomy Observatory in West Virginia, and the Parkes Observatory in New South Wales, Australia will be helping look for celestial signals of otherworldly origin.
The Green Bank Telescope, located in Green Bank, West Virginia, is home to the largest fully steerable telescope in the world.
“Approximately 20 percent of the annual observing time on the GBT will be dedicated to searching a staggering number of stars and galaxies for signs of intelligent life via radio signals,” said Tony Beasley, director of the National Radio Astronomy Observatory, in a statement.
These telescopes will peer at the sky in a multitude of frequencies, searching for the answer to that timeless question of whether the cosmos is filled with chatter, or if Earth is just a lonely beacon, murmuring messages into a sea of silent, sterile worlds. There is also an optical SETI component that will search for laser signals from other worlds, as well as a competition for interstellar message design (details TBD). Data from the project will be publicly available, ready for digging into by anyone with the tools and motivation. In fact, Milner said, it’s totally possible that any signal in those data might not be found by one of the professional astronomers involved in the project.
“We have the greatest opportunity ever to detect intelligent folks in the Universe,” says astronomer Geoffrey Marcy of UC-Berkeley, who is one of the co-investigators leading the project at Green Bank. Joining Marcy as a co-investigator on the Green Bank portion of the work is astronomer Frank Drake, of the SETI Institute.
“The plausibility of extraterrestrial intelligence has grown, the promise of success in searches has grown,” says Drake, who’s better known to me as Dad. “We will finally have stable funding so that we can plan from one year to the next, we can hire very talented people to carry out the work…it may take a long time, but it’s our best chance to get all of those treasures of knowledge that will accrue if we do indeed detect another intelligent civilization.”
From $2,000 to $100 million
In 1960, Dad performed the first modern search for extraterrestrial intelligence. Called Project Ozma, it looked for signals from alien worlds orbiting the nearby sun-like stars Epsilon Eridani and Tau Ceti. From April through July, astronomers monitored a handful of radio frequencies for artificial signals.
The next year, Dad crafted his eponymous equation. It predicts – based on seven factors – the number of detectable, communicating civilizations in our Milky Way galaxy. Some of those factors, such as the prevalence of planets orbiting other sun-like stars, were total question marks in 1961. No one had ever really tackled these unknowns, so strange was the idea that such a thing could be scientifically respectable.
Even though the skies have stayed eerily quiet, in the half-century since Project Ozma, SETI has grown from an infant field on the fringe of science to a well-known endeavor. Now, some of the factors in the Drake Equation are very well known – including the prevalence of planets around other stars (others, alas, are just as vexing as in 1961). In fact, we now know that most stars have planets, and that a good percentage of those planets happen to be Earth-like.
“We learned only last year from the NASA Kepler mission that one in five sun-like stars harbors an Earth-size planet at lukewarm temperatures, suitable for life,” Marcy says.
A Sky Filled With Life
Based on that estimate, there could be tens of billions of habitable worlds in our galaxy. If you want to see a star that might incubate a habitable planet, all you need to do is go outside on a clear night and gaze into a small patch of sky. What’s more, Marcy says, astronomers are finding that the cosmos has been liberally sprinkled with the building blocks of life as we know it – organic molecules that can be used to form proteins and nucleic acids.
“Among all of those billions of planetary petri dishes, who could doubt that some of them sparked biochemical reactions that spawned replicating molecules, something like DNA,” Marcy says. “The only remaining question is how often Darwinian evolution leads to brainy creatures.”
Explosions are always messy, and this is especially true when combustion occurs on a cosmic scale.
In space, small, dead stars called white dwarfs occasionally blow themselves to smithereens, producing enough light to drown out entire galaxies. Astronomers use these explosions – called type 1a supernovas – to calculate cosmic distances. In the late 1990s, observations based on type 1a supernovas revealed that the universe is flying apart faster and faster as time goes on. The force behind this acceleration, called dark energy, is still enigmatic, but the discovery earned a Nobel Prize in 2011 and is considered one of the most fundamental in cosmology.
Yet despite their role as the workhorses of the cosmological distance ladder, type 1a supernovas are still poorly understood. Blowing up a white dwarf, both in terms of the detonation physics and the necessary stellar ingredients, is still a scientific conundrum. Now, two studies published this week in Nature are helping solve that ingredients problem, even though at first the observations appear to disagree with one another.
Together, the studies tell “a rich and interesting story about the entire system that leads to supernova of type 1a,” says UC Berkeley astronomer Joshua Bloom. “It’s remarkable how important type 1a supernova were – and still are – for cosmology, given how relatively little we know about the diversity of the progenitor channels.”
White dwarfs are the extinguished corpses of stars that were once very much like the sun. They’re incredibly dense, with a sun’s mass of material stuffed into something the size of the Earth. Left alone, a white dwarf will simply fade to black over billions or trillions of years.
But dwarfs with a starry companion can suffer a different fate. Sometimes, the two stars are close enough for the dwarf’s incredible gravity to begin stealing material from the companion. If the dwarf gets too greedy and gains enough mass, a runaway thermonuclear explosion ignites and blasts the star to pieces.
For a long time, scientists thought white dwarfs must be burgling a large companion star – something like a red giant that’s big and gassy and easy to steal from. Yet pre-explosion observations of nearby type 1a supernovas have failed to identify any red giant companions. Nearby supernova remnants show similarly scarce evidence for giant companions, which would not be destroyed during the explosion, just banged up and tossed from the system.
Other observations have suggested the doomed dwarfs could be dancing with a more or less normal star – a main sequence star, like the sun.
And another possibility, supported by multiple observations but thought to be extremely unlikely up until the last decade or so, is that type 1a supernovas could be the nuclear death spasms produced when two white dwarfs merge. These two-dwarf pairs are known as “double-degenerate” systems, because white dwarfs are stabilized by electron degeneracy pressure.
Different pairs of stars producing type 1a explosions is troubling for some scientists, who wonder how such different starting ingredients can produce such similar explosions. For now, the data suggest that as long as a white dwarf is involved, it’s possible that “type 1as can come from essentially anything,” says Brad Tucker, who splits his time between UC Berkeley and the Australian National University.
A Tale of Four Supernovas
This week’s Nature papers make that even more clear.
One of studies reports that when a type 1a supernova exploded in May 2014, the blast debris crashed into the former companion star. The collision produced a pulse of ultraviolet light that scientists could detect using NASA’s Swift satellite, which swiveled to watch the explosion four days after it started. It’s the first time this type of shock-induced brightening has been seen with a type 1a explosion, says lead study author Yi Cao of Caltech, and indicates that the dwarf’s friend is not another white dwarf. Instead, that companion was probably a bigger, normal star.
Those three supernovas, described by the University of Maryland’s Rob Olling, look like type 1a supernovas and are all very far from Earth, between 600 million and 2 billion light-years away. But unlike Cao’s team, Olling and his colleagues saw no brief bump in brightness produced by debris colliding with a companion star. “The data support the idea that the companions are quite compact, with the most likely explanation being double-degenerate systems, two white dwarfs merging,” says Saurabh Jha of Rutgers University, who was not involved in the study.
Apples to Apples
While these results may seem contradictory in that different ingredients are involved, they actually mostly fit together pretty well – and that’s because there’s one more piece of the puzzle to consider.
Over the years, it’s become clear that type 1a supernovas don’t come in just one flavor. Put very simply, some are brighter than normal and others are dimmer. “It’s not just apples,” Olling explains. “There are Granny Smiths and Jonagolds and Braeburns, and we don’t know exactly how many varieties there are.”
The supernova described by Cao, which likely resulted from a white dwarf stealing material from a normal star, is one of those dimmer subtypes. It’s similar to a flavor known as a type 1ax, which is less luminous than your classical kaboom (kind of like a “peculiar cousin,” to borrow Jha’s description, or a “weirdo” to use Tucker’s).
Conversely, the supernovas described by Olling are “normal” type 1a explosions – the type with a predictable brightness that can be used to measure cosmic distances. These likely result from two white dwarfs merging and turning into a giant nuclear bomb.
“Cosmological 1a supernovas do tend to show that they might be doing the same thing, which is great,” Tucker says. “But then there are the weirdoes. I like weirdoes. We all like weirdoes. But cosmology doesn’t like weirdoes.”
So, could it be that two merging dwarfs produce normal type 1a supernovas, while systems with only one white dwarf lead to peculiar explosions?
If yes, then what’s happening is that these observations neatly fall into line. Regardless, not only is it becoming clear that type 1a explosions come from different ingredients, it’s becoming clear that those ingredients don’t all cook the same supernova. And maybe, just maybe, scientists are getting closer to determining exactly how that all works.
In 1995, astronomer Bob Williams wanted to point the Hubble Space Telescope at a patch of sky filled with absolutely nothing remarkable. For 100 hours.
It was a terrible idea, his colleagues told him, and a waste of valuable telescope time. People would kill for that amount of time with the sharpest tool in the shed, they said, and besides — no way would the distant galaxies Williams hoped to see be bright enough for Hubble to detect.
Plus, another Hubble failure would be a public relations nightmare. Perceptions of the project, which had already cost multiple billions of dollars, were pretty dismal. Not much earlier, astronauts had dragged Hubble into the cargo bay of the space shuttle Endeavour and corrected a disastrous flaw in the prized telescope’s vision. After the fix, the previously blind eye in the sky could finally see stars as more than blurred points of light. And now, finally, it was time to start erasing the frustrations of Hubble’s early years.
Except that staring at nothing and coming up empty didn’t seem like the best way to do that.
But Williams was undeterred. And, to be honest, it didn’t really matter how much his colleagues protested. As director of the Space Telescope Science Institute, he had a certain amount of Hubble’s time at his personal disposal. “The telescope allocation committee would never have approved such a long, risky project,” he explains. “But as director, I had 10 percent of the telescope time, and I could do what I wanted.”
Wiliams suspected the billion light-year stare might capture eons of galactic evolution in a single frame and uncover some of the faintest, farthest galaxies ever seen. And to him, the potential observations were so important and so fundamental for understanding how the universe evolved that the experiment was a no-brainer, consequences be damned.
“Scientific discovery requires risk,” Williams says. “And I was at a point in my career where I said, “If it’s that bad, I’ll resign. I‘ll fall on my sword.’”
So, with his job perhaps on the line, Williams went off, put together a small team of post-docs, and did exactly as he’d planned. For 100 hours, between Dec. 18 and 28, Hubble stared at a patch of sky near the Big Dipper’s handle that was only about 1/30th as wide as the full moon. In total, the telescope took 342 pictures of the region, each of which was exposed for between 25 and 45 minutes. The images were processed and combined, then colored, and 17 days later, released to the public.
It turned out that “nothing” was actually stuffed with of galaxies. More than 3,000 of them came spilling out, some roughly 12 billion years old. Spiral, elliptical, irregular – red, white, blue, and yellow – the smudges of light that leapt from the final composite image cracked the universe in ways scientists never could have imagined.
“With this achievement, the estimated number of galaxies in the universe had multiplied enormously — to 50 billion, five times more than previously expected,” wrote John Noble Wilford in The New York Times. And some of the older galaxies – those distant, faint ones that were supposedly impossible for Hubble to see – looked really, really different.
“When the galaxies were young, they were very irregular — they were having collisions, they were erupting, they were having adolescent outbursts,” says Robert Kirshner of the Harvard-Smithsonian Center for Astrophysics. He was among the scientists who initially thought the deep field was a bad idea. “Bob was right, I was wrong. The use of that discretionary time was a courageous thing,” he says.
But there was more. Williams had gotten in touch with astronomers at the Keck telescopes in Hawaii ahead of time and asked them to point their Earth-based guns at the same patch of sky. Together, the observations helped astronomers develop something of a shortcut for determining cosmological distances to these galaxies, unlocking large portions of the universe.
As for public relations? The image now known as the Hubble Deep Field captivated pretty much everyone. To say it was a triumph would be an understatement. “The nerve that it took to say, ‘We’re going to point where there isn’t anything,’ was interesting,” says John Mather, a Nobel Laureate and senior project scientist for the James Webb Space Telescope. “And Bob Williams got a lot of nice recognition for that leadership.”
Not long after, Williams’ experiment was repeated in a different patch of sky in the southern constellation Tucana, and came to be called the Hubble Deep Field South. In 2004, a million-second exposure of nothing produced the Hubble Ultra Deep Field, filled with even more galaxies than the original. And in 2012, combining 10 years of Ultra Deep Field exposures produced the Hubble eXtreme Deep Field.
These images have offered “a glimpse of the hundreds of billions of galaxies that fill the universe,” says Hubble senior scientist Jennifer Wiseman, of NASA’s Goddard Space Flight Center. “That gives me and many people pause to be quiet and contemplate this majestic universe we live in, and be grateful we have a chance to look at it.”
Jason Kalirai, project scientist with the Webb telescope, goes and step further and places the Hubble Deep Field in a rather impressive historical context. “One of the questions that even the earliest civilizations probably asked themselves is, ‘What is our place in the universe?'” There have been a few times in our history when the prevailing answer to that question has been overthrown, he says. Once was when Galileo turned his telescope to Jupiter and its moons and helped show that not everything revolves around the Earth; another was when the astronomer Edwin Hubble showed, in the early 1900s, that not every speck of light in the sky belongs to our own galaxy.
A third is the Hubble Deep Field. “It showed that the universe is teeming with these galaxies, and if you do a census of how many galaxies you see, and think about how many more are in the night sky, you can conclude that there are as many galaxies as there are stars in the Milky Way,” Kalirai says.
As for Williams? Well, he sums up the experience in a characteristically understated way: “It turned out to be a neat image. Really.”
Unfortunately for those of us hoping for aliens, we’ve seen so few of these radio bursts that it’s hard to say whether the “pattern” will hold up.
Blasts from the Past
These blasts of radio waves are known as fast radio bursts – extremely energetic, super-fast cosmic pulses that appear to be originating from billions of light-years away. They’re rare: Scientists reported the first burst in 2007 and have only published another 10 observations since then.
In truth, the question of what these things are can’t really be solved until we know their distances.
Astronomers estimate the bursts’ distances using something called a dispersion measure, which tracks how much interstellar gunk the signal has passed through*. Briefly, bursts that are farther away travel through more gunk than bursts that are closer, and astronomers can figure out how gunked up a signal is by studying how it arrives at Earth.
When Michael Hippke of Germany’s Institute for Data Analysis recently plotted the dispersion measures of the 11 known bursts, he and his colleagues found something surprising: All the dispersion measures are integer multiples of the same number, 187.5.
When graphed, the data certainly look compelling (see Figure 1 on page 2). The team calculated a 5 in 10,000 chance of the pattern being pure coincidence. Furthermore, no astrophysical systems that we know of can produce such a stepwise distribution of dispersion measures, the team argued.
So what’s going on? If the pattern is real, it suggests fast radio bursts are not coming from all over the universe, says astronomer Scott Ransom of the U.S. National Radio Astronomy Observatory. “In that case, they should be smoothly distributed in dispersion measure,” he says. Alternatively, the signals could be coming from closer to Earth. “[The pattern] could point to a very strange kind of radio frequency interference, I suppose,” he says.
As a March 31 story in New Scientist notes, one possible explanation for the mysterious 187.5 is pulsars, perhaps behaving according to physical laws we’re not yet aware of. Another is an unmapped spy satellite, masquerading as a signal from the distant universe.
Or, just maybe, 187.5 is the arrow pointing to ET.
Connecting Cosmic Dots
It’s an exciting possibility. Trouble is, the trend identified in the study isn’t likely to survive – for one simple reason: Newer observations, not included in the study or reported by New Scientist, don’t fit.
Hippke and his colleagues looked at dispersion measures from the 11 fast radio bursts for which published data are available. But more bursts are waiting in the wings.
“There are five fast radio bursts to be reported,” says Michael Kramer of Germany’s Max Planck Institute for Radioastronomy. “They do not fit the pattern.” Kramer is part of the team combing through data gathered by Australia’s Parkes Observatory, where all the fast radio bursts, except for one, have been spotted so far. The paper describing those bursts is close to being submitted for review, he says.
Instead of aliens, unexpected astrophysics, or even Earthly interference, the mysterious mathematical pattern is probably an artifact produced by a small sample size, Ransom says. When working with a limited amount of data – say, a population of 11 fast radio bursts – it’s easy to draw lines that connect the dots. Often, however, those lines disappear when more dots are added.
“My prediction is that this pattern will be washed out quite quickly once more fast radio bursts are found,” says West Virginia University’s Duncan Lorimer, who reported the first burst in 2007. “It’s a good example of how apparently significant results can be found in sparse data sets.”
The probability theories on which statistical tests rely are much more powerful when data sets are larger; it becomes easier to rule out coincidence and rule in significance. That’s why scientists strive to include as many data points as possible, whether they’re studying exoplanets, tumors, rats in a maze, or enigmatic astrophysical signals of unknown origin.
“It is possible that it is only an artifact,” Hippke says, of the pattern. “I know that several new fast radio bursts have been found, yet unpublished. I’d suggest these people release the dispersion measures of these FRBs, perhaps in the form of short research notes, to decide the question.”
Alas, it seems that any potential evidence for communicating extraterrestrial civilizations is slipping away almost as quickly as it emerged.
*More information on dispersion measures: Because fast radio bursts span a range of frequencies, they contain a mix of different radio wavelengths. Higher frequency radio waves are shorter and can travel more easily through the cosmos. Lower frequency waves are longer and tend to get redirected or slowed down while passing through clouds of electrons (i.e., “gunk”).
If a fast radio burst is coming from sufficiently far away, there will be a measurable delay between the arrivals of its high- and low-frequency ingredients. That delay, which corresponds to the amount of interstellar gunk the signal moves through, is called the dispersion measure.
Among the most contentious unsolved mysteries in astronomy is the question of how, exactly, a white dwarf star explodes. Now, as described at the American Astronomical Society’s winter meeting, a team of scientists has come up with an idea that just might solve part of the problem.
Nearly two decades ago, scientists used these exploding stars to measure cosmic distances and came up with a surprising result: The rate at which the universe is flying apart is increasing. Calling that discovery profound is no overstatement – it transformed our understanding of the cosmos and pointed toward the existence of an enigmatic force called dark energy.
But scientists still don’t thoroughly understand how to blow up a white dwarf. It’s kind of like understanding the point of a story without being fluent in the language. The plot is discernible, but important subtleties are lost. Learning how those subtleties shape the final story is crucial if scientists want to understand how dark energy behaves over the lifetime of the universe.
“Say, for example, an exploding white dwarf happens differently in the early universe than it does now. Or it happens differently in different types of galaxies,” says Rosanne Di Stefano, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics. “If we don’t understand the differences, then we can’t correct for them and make a more precise ruler.”
The mile-marking explosions are called type 1a supernovas. They’re the result of a runaway thermonuclear reaction that rips through a white dwarf star and blows its guts into space, transforming the dwarf from a boring point of light into a beacon that shines brighter than entire galaxies. Because those beacons blaze with a predictable brightness that diminishes with distance, scientists can figure out how far away they are.
But it’s the part before the explosion that has everyone so perplexed. A lonely white dwarf won’t spontaneously combust. However, when a dwarf lives with a companion star, its enormous gravity means that it sometimes steals material from its companion. Like an out-of-control shoplifter, the dwarf star will continue stealing until its mass exceeds a threshold beyond which physics can’t keep the star in one piece. Then, boom.
What scientists have been arguing about is the identity of the dwarf’s stellar companion. Opinions have shifted dramatically over the last few decades, with some favoring a large, gassy companion star like a red giant, and others favoring something smaller and denser, perhaps another white dwarf. In the last five years, observational evidence has made it clear that both of those scenarios can happen.
The trouble is, the two recipes don’t account for the frequency of type 1a supernovas. “For some reason, we’re underpredicting them,” Di Stefano says.
So, she and her colleagues began to look for other ways to cook a type 1a.
What if, Di Stefano asks, some white dwarfs don’t need starry companions? Could a passing rocky body – like a large asteroid or a planet – smash into and detonate a dwarf?
The answer, she says, is potentially yes. There’s already a pile of observational evidence suggesting that collisions between white dwarfs and rocky bodies do happen. While it might sound strange, those observations aren’t necessarily unexpected.
White dwarfs are the corpses of collapsed stars that were once very much like the sun. Like the sun, many of them probably have asteroids and other rocky debris lying around that never quite made it to planethood. In our solar system, we see this debris in the asteroid and Kuiper belts, and suspect it’s also in the Oort Cloud (though it hasn’t been directly observed). Many of these bits and pieces are far enough out that they will survive the collapse of their stars unscathed, unlike any planets that happen to be close to their stars.
So, Di Stefano reasons, more than a few white dwarfs are probably flying through the galaxy surrounded by clouds of rocky debris. She calls these clouds “balls of planetoidal gas,” and notes that they can extend up to 100,000 times farther from a star than Earth is from the sun. Every now and then, and especially in crowded places like the galactic bulge, a dwarf will come close enough to another star for its gravity to perturb the rocky bits and pieces.
“These balls, every once in a while, they’ll graze each other. They’ll overlap with each other, and that leads to consequences,” Di Stefano explains. “Some of the planetoids, particularly the asteroids and comets, are thrown out into interstellar space, and some of them are placed on orbits where they’re going to end up coming close to the white dwarf.”
Simulations suggest that maybe 1 percent of those disruptions will lead to collisions with one of the stars.
If the conditions are just right – the collisions energetic enough, the rocky hammer big enough, the dwarf’s history of similar encounters optimal – it’s possible the impact could explode the star. Calculations suggest you’d need something at least as big as Earth to trigger an explosion, but this doesn’t have to happen particularly often to help solve the type 1a supernova frequency problem.
“Even if there’s an explosion one of out every 10 million times, it would actually be a significant contribution to the rate of type 1a supernovas,” Di Stefano says. “It’s worth exploring. And even if they don’t make the white dwarf explode, they’ll do something interesting that we should be able to see.”
Foley likes the idea of exploding a dwarf with a rocky body, and calls it a creative way to address an abiding problem. “The first part seems to be true — it should happen,” he says. “And then the second part just needs to be nailed down. It’s not crazy.”
Coming from far beyond the galaxy, an extremely energetic blast of radio waves has been snared by astronomers lying in wait. Lasting for just a few thousandths of a second, the burst is the first of an enigmatic class of objects to be observed in real-time, astronomers report today in the Monthly Notices of the Royal Astronomical Society.
Called fast radio bursts, these extreme pulses of energy last for just a fraction of a second. They’ve confounded astronomers – who have no idea what they are – since West Virginia University’s Duncan Lorimer reported the first burst in 2007. At the time, it appeared as though the beam of radio waves had traveled roughly 3 billion light-years before colliding with Earth. That’s a reasonably far distance, even by astronomical standards. But not everyone believed the team’s interpretation. Skeptics suggested the burst’s signal could be coming from Earth’s atmosphere, or from inside the galaxy, or even that it was an artifact of the telescope itself, located at the Parkes Observatory in Australia.
Indeed, for five years, that Parkes telescope was the sole spotter of fast radio bursts, and eventually observed another half-dozen or so.
That changed in November 2012, when the Arecibo Observatory spotted a fast radio burst. Like the Parkes signals, it looked as though it came from billions of light-years away. While the observation strongly suggested the bursts were not a telescope artifact, scientists still had yet to see one in real time: All of the observations so far had been pulled from data that were at least a few weeks old.
Then, on May 14, 2014, Swinburne University’s Emily Petroff spotted a fast radio burst in the act of blasting. She and her colleagues determined the signal came from as far as 5.5 billion light-years away and was mildly polarized, suggesting a magnetic field somewhere near its origin has aligned the waves in particular directions.
Petroff had designed a program specifically to spy on these bursts, and once the radio pulse had been detected, she rallied a legion of telescopes to stare at the thing. Tasked with peering deep into the cosmos, the group of 12 telescopes quickly returned data suggesting there was no easily identifiable astrophysical source. The lack of a discernible afterglow eliminated some of the more mundane possibilities, such as distant supernovas or long gamma-ray bursts.
So what are these fast radio bursts? The short answer is, scientists still don’t know. “There are more theories than there are bursts,” Lorimer said last year. Some of those theories implicate rather exotic-sounding, very dense objects: Colliding black holes or neutron stars, evaporating primordial black holes, imploding neutron stars, or enormous flares erupting from magnetic neutron stars, called magnetars.
It’s a mystery that’s still waiting to be solved, but at least scientists now know their suspects live very, very far away and aren’t exceptionally secretive. Whatever the sources are, they regularly hurl beacons of radio light across a vast expanse of cosmic sea.
SEATTLE — Each January, thousands of astronomers get together and spend four days talking about stars, galaxies, planets, the cosmos, and everything in between. This year’s winter meeting of the American Astronomical Society was held in Seattle from Jan. 4-8, and it was so stuffed with science that I didn’t even get a glimpse of the city’s Space Needle…while covering a space conference.
Three time zones away, National Geographic’s Erika Engelhaupt and Dan Vergano worked overtime with me to bring you tales from the stars.
The meeting may have wrapped up, but we’re not done yet. We’ve got one more story in the works and have gotten word of some exciting announcements that will be arriving in the coming months. In the meantime, I’ve written these eight short meeting reports to share some more of the meeting’s celestial happenings, starting with that spectacularly star-studded image of the Andromeda Galaxy, above. (I’ve included a smattering of fun facts and other astronomical interestingness as well.)
Meeting Brief: A Hundred Million Stars
A new image of Earth’s nearest large galactic neighbor, the Andromeda Galaxy, is aglow with the light of more than 100 million stars. Scientists took long looks at a portion of the spiral galaxy’s disk, then published a panorama of 7,398 incredibly high-resolution Hubble Space Telescope images (above). In it, there are 1.5 billion pixels spanning 40,000 light-years. But the galaxyscape is more than just a pretty picture: It’s providing clues about Andromeda’s evolutionary history that teams are using to piece together how the galaxy formed and grew up. Among those clues are hints that Andromeda may have had a much more violent past than the Milky Way, and that older stars in its disk are behaving more erratically than younger stars.
Fun Fact: Scientists can now pinpoint Saturn’s exact location to within roughly one mile, by combining information from NASA’s Cassini spacecraft and NSF’s Very Long Baseline Array.
Meeting Brief: Hunting for Exomoons
If there’s one thing astronomers are learning about exoplanets, it’s that alien worlds are common throughout the galaxy. But planets aren’t the only things capable of supporting life. If those exoworlds are anything like the planets in our solar system, some of them have potentially habitable exomoons. “There are more habitable moons than there are planets in the cosmos,” says David Kipping of the Harvard-Smithsonian Center for Astrophysics. “Anyone who cares about the frequency of Earthlike worlds really can’t ignore this component.”
Kipping searches for exomoons hiding in the Kepler spacecraft’s data. It’s not easy; he first selects worlds that are capable of holding onto a moon, and for which a moon should be detectable. There are about 400 of those. But looking at each candidate world requires about 50,000 hours of processing time, he said at the meeting. So far, Kipping has searched for moons around 40 candidates and found nothing. This year, with upcoming time on NASA’s Pleiades supercomputer and a new computing cluster, he should be able to look at 300 more.
In other words, 2015 could be the year of the exomoon!
Fun Fact: Planetary debris disks can sometimes look like the Eye of Sauron.
Meeting Brief: Searching For Earth’s Twisted Sister
How common are Venus-like planets in the cosmos? That’s the question San Francisco State University astronomer Stephen Kane asked on Thursday, in one of the conference’s exoplanet sessions. While many scientists are focused on figuring out how common exo-Earths are, Kane points out that exo-Venuses could slip into those calculations.
“We know of at least one case where we can have two Earth-size planets with dramatically different atmospheres,” he says. “It behooves us to consider this very carefully when we’re looking at the planets in our sample.” Based on data from NASA’s Kepler spacecraft, Kane and his colleagues estimate that as any as 45 percent of (roughly) sunlike stars could host an exo-Venus. Smaller stars called M-dwarfs are slightly less likely to host these roasted worlds, and Kane suggests exo-Venuses might live around 30 percent of them.
Did You Know? Stars spin more slowly as they age, meaning that the rate at which a star spins should betray how old it is. But this has been a tricky relationship to parse, especially for stars that are cooler than the sun. Now, by measuring the frequency with which rotating star spots appear in a 2.5 billion-year-old cluster, astronomers are getting closer to developing a reliable stellar clock. (For more, see this report from Jonathan Webb at the BBC.)
Meeting Brief: Otherworldly Oceans, and a Recipe for Rocky Planets
Take two parts iron and oxygen, one part each of magnesium and silicon, add a handful of other ingredients, and shape into a sphere. Bake for several million years. Cool until a thin brown crust forms and the ball stops glowing. Then season with water and organic materials.
That’s the recipe astronomer Courtney Dressing figured out for cooking rocky planets – at least those that are 1.6 times Earth’s size and smaller. But, what about larger planets, the mega-Earths or mini-Neptunes? “Can we build them with the same recipe? Turns out, no,” says Dressing, of the Harvard-Smithsonian Institute for Astrophysics. “You can’t double the recipe that much. It doesn’t work.” Perhaps not surprisingly, bigger planets have different compositions. They’re a bit fluffier, a bit more gassy and icy. They’re also, says CfA astronomer Laura Schaefer, likely to have longer-lived oceans on their surfaces – a condition that is necessary for Life As We Know It. But there’s a catch: While oceans might live longer on super-Earths, they might also take longer to form. Conversely, Schaefer’s simulations show, oceans might live fast and die hard on planets smaller than Earth. “They outgas oceans very quickly,” Schaefer says.
Meeting Brief: Earth Isn’t Flat, But the Universe Is
The Universe is still flat – perhaps even flatter than Kansas, which is officially flatter than a pancake – according to the latest results from the Baryon Oscillation Spectroscopic Survey. The survey used sound waves from the early universe to plot the positions of 1.4 million galaxies and 300,000 quasars. Those positions, when combined with data from other projects, strongly confirm the existence of dark matter, says Harvard University’s Daniel Eisenstein, and point to a flat cosmology. What’s more, “Dark energy appears to be constant over time,” Eisenstein says. “The data has driven us back to the simplest case of a flat universe with a cosmological constant.”
For the briefest of moments, a young pulsar blasted jets of radio waves in Earth’s direction, seven times per second. Then, almost as quickly as they had appeared, jets from the dead, spinning star began fading. Puzzled, astronomers raced to study the object, termed J1906+0746, which is 25,000 light-years away in a globular cluster known as Terzan 5. Observations indicated that the incredibly dense, spinning star wasn’t alone: It was orbiting another dense, dead star, once every four hours. That stellar corpse’s gravity was so strong, though, that it had bent the fabric of space-time and was causing the pulsar to wobble in its orbit (or precess). For about a decade, that wobbling directed the pulsar’s beams toward to Earth. And then it wobbled away. Scientists at have estimated that the pulsar will again appear as a beacon in its Earth’s radio sky in 2170.
Did You Know? Long ago, a cascade of catastrophic collisions may have obliterated several planets in the inner solar system and left oddball Mercury as the only survivor. According to the new theory, there were once more planets inside Earth’s orbit than there are today. But as the solar system grew up and the planets shifted in their orbits, chaos descended upon these rocky worlds and hurled them into one another — a violent scenario that some scientists say could explain Mercury’s abnormally high density and strange, elliptical orbit. (For more, see “Mercury may be the sole survivor of planetary pileup,” by Lisa Grossman, New Scientist.)
Meeting Brief: When Supermassive Black Holes Collide
Packed with the mass of many billions of suns, supermassive black holes are like enormous cosmic drains that churn in the hearts of galaxies. Sometimes, these gargantuan drains collide. This is what scientists expect will happen in about 1 million years or so in a distant galaxy known as PG1302-102. There, scientists saw that the bright beacon of light shining from the galaxy’s center wasn’t shining ever so steadily. The team suspects those blips in the quasar’s light are the product of two supermassive black holes orbiting one another, less than a light-year apart. The eventual collision will likely release as much energy as 100 million supernovas and obliterate the galaxy – but it’s 3.7 billion light-years away, so not to worry.
Nearer to Earth, however, another pair of supermassive black holes appear to be on a collision course. Roughly 134 million light-years away, two merging galaxies, collectively called Arp 299, are slowly drifting toward a galactic smashup. But only one of the galaxies, as observed by NASA’s NuSTAR telescope, has an active supermassive black hole. The other cosmic drain appears to be snoozing.
Did You Know? ESA’s Planck satellite managed to indirectly detect what’s called the cosmic neutrino background – particle radiation imprinted on the universe two seconds after the Big Bang. The cosmic neutrino background is both older and colder than the better-known cosmic microwave background, which dates to roughly 400,000 years post-Big Bang. (For more information, here’s a technical talk from earlier this year.)
Meeting Brief: A Curious Exoplanetary System
Astronomers have spotted the first binary star system known to include both a Jupiter-type planet and a brown dwarf – a failed star that’s just a little bit too light to ignite. The two worlds orbit one of the sunlike stars in the binary known as HD 87646. One of the worlds, the planet with 12 Jupiter masses, orbits the star every 13.5 days. A year on the failed star, which has 55 Jupiter masses, takes 674 days. The strange configuration is 314 light-years away and appeared in data collected by the Sloan Digital Sky Survey’s MARVELS observation program. For six years, MARVELS has surveyed 60 stars at a time, looking for wobbles that betray the presence of planets. The “very packed environment” of HD 87646 challenges theories describing how planets form, says University of Florida astronomer Jian Ge.