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Tales From the Superbowl of Astronomy

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.

We published one of the early meeting highlights, a new Hubble image of the Eagle Nebula’s Pillars of Creation, on Monday. The next day, the planet-hunting Kepler mission announced a handful of new exoworlds, including a clutch of planet candidates that could be true Earthy twins. And Thursday, we reported that one of the galaxy’s most massive and peculiar star systems, Eta Carinae, has produced the brightest X-ray flares yet recorded (don’t miss the stunning 3-D simulations that helped scientists peer into the unstable heart of this “erratic stellar monster”).

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.)


                                                                                                            — Nadia

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.

For more: “Galaxy seen shuddering from ancient collision,” by Ron Cowen, Nature.

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

Exomoons could also host life as we know it -- so let's go find some. (NASA/JPL-Caltech)
Exomoons could also host life as we know it — so let’s go find some. (NASA/JPL-Caltech)

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.


Did You Know? ESA’s Gaia spacecraft, which is mapping the locations of roughly one billion stars, observes about 5,000 stars each second. (On average.)

Meeting Brief: Searching For Earth’s Twisted Sister

Venus in the ultraviolet, as seen by Hubble. (L. Esposito/NASA)

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.

The Venus Zone is the area around a star in which a planet is likely to exhibit atmospheric and surface conditions similar to the planet Venus. The amount of energy a planet receives is plotted on the X-axis, and the Y-axis represents different star types. (Chester Harman, Pennsylvania State University)
The Venus Zone is where an exoplanet is likely to exhibit atmospheric and surface conditions similar to the planet Venus. (Chester Harman, Pennsylvania State University)

“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

Super-Earths can have long-lasting oceans. (David Aguilar/CfA)
Super-Earths can have long-lasting oceans. (David Aguilar/CfA)

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.

Astronomers have determined the recipe for making rocky planets. (David Aguilar/CfA)
Astronomers have determined the recipe for making rocky planets. (David Aguilar/CfA)

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.

For more: “New Super Earths Double the Number of Life-Friendly Worlds,” by Victoria Jaggard, at Smithsonian.com.

Fun Fact: Astronomy images can be very popular. (Here’s more information about that ALMA image)

Meeting Brief: Earth Isn’t Flat, But the Universe Is

BOSS mapped more than 1 million galaxies and used their positions to study the expanding universe. (Eric Huff, the SDSS-III team, and the South Pole Telescope team. Graphic by Zosia Rostomian)
BOSS mapped more than 1 million galaxies and used their positions to study the expanding universe. (Eric Huff, the SDSS-III team, and the South Pole Telescope team. Graphic by Zosia Rostomian)

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.”

As described at the meeting, results from the European Space Agency’s Planck satellite also point to a flat cosmology. Speaking of Planck, the team still hasn’t released its joint analysis with the BICEP2 team, which in March of last year announced the detection of primordial gravitational waves – a key piece of evidence supporting the theory of cosmic inflation. There’s been much discussion over the past year about whether the BICEP analysis was done correctly, and scientists are eager to see whether the Planck data confirm or refute the BICEP finding. Planck promised results by late December, but we’re still waiting.

Any week now, the team says.

For more on the BOSS survey: “BOSS: A Ruler to Measure Them All,” by Monica Young, Sky and Telescope

For more on cosmology: “The Status of the Universe: 2015,” by Ethan Siegel, Medium

Fun Fact. The Jet Propulsion Laboratory made these fantastic exoplanet travel posters. Let’s go.

Meeting Brief: The Disappearing Pulsar

Globular cluster Terzan 5, where the wobbling binary pulsar is located. (ESA/Hubble & NASA)
Globular cluster Terzan 5, where the wobbling binary pulsar is located. (ESA/Hubble & NASA)

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.

For More: “’Bent time’ tips pulsar out of view,” by Jonathan Webb, BBC.

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

X-rays detected by NASA's NuSTAR telescope are overlaid on an image of two colliding galaxies, called Arp 299. (NASA/JPL-Caltech/GSFC)
X-rays detected by NASA’s NuSTAR telescope are overlaid on an image of two colliding galaxies, called Arp 299. Click to enlarge. (NASA/JPL-Caltech/GSFC)

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.

For more: “Black Holes Inch Ahead to Violent Cosmic Union,” by Dennis Overbye, The New York Times

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

A strange exoplanetary system includes both a brown dwarf and giant Jupiter orbiting a binary sunlike star. (T. Riecken/SDSS)
A strange exoplanetary system includes both a brown dwarf and giant Jupiter orbiting a binary sunlike star. (T. Riecken/SDSS)

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.

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Find the Planets in This Image of a Young Solar System

The image above is not an illustration. If your eyes could detect the long wavelengths between radio and infrared, and were sharp enough to resolve structures around a star 450 light-years away, you might see something like that.

The psychedelic swirl is actually a dusty disk of debris surrounding the young, sunlike star HL Tau. Only about 1 million years old, this star — and that disk — have been captured in the process of birthing planets. It’s the most detailed image of planetary genesis shot so far, and was made with a cluster of telescopes in the southern hemisphere called the Atacama Large Millimeter/submillimeter Array.

Normally, planets grow from the swirling mass of gas and dust surrounding a young star; as clumps of that material begin sticking together, they form larger and larger bodies whose gravity attracts more and more material. Put simply, scientists think the outcome of this clumping differs depending on where the process is happening in the disk, which is why you sometimes end up with a rocky Earth, other times with a gassy Jupiter, and other times with an icy Neptune.

So where are the planets in this image?

Sometimes, the answers lie in what you don’t see. When planets grow big enough, they carve gaps in their disks (cc: Pluto). The new worlds sweep up or push away all those particles in their orbits, leaving a telltale void that suggests the presence of a young, mighty planet.

Scientists think that is what’s happening in the image above: Some of those dark, concentric stripes and splotches are the gaps produced by growing planets. The observation is a little surprising because HL Tau is still incredibly young, and it takes planets a while to grow big enough to produce those rings and splotches.

“These features are almost certainly the result of young planet-like bodies that are being formed in the disc. This is surprising since such young stars are not expected to have large planetary bodies capable of producing the structures we see in this image,” Stuartt Corder, ALMA Deputy Director, said in a statement.

To capture HL Tau and its curious disk, astronomers arranged the array’s 66 telescopes in a new configuration that allowed higher-resolution imaging. The result is an image even the Hubble Space Telescope would have a tough time generating. In the wavelengths Hubble sees, HL Tau and its disk are obscured by the surrounding gas and dust. But ALMA’s eyes can pierce that shroud and see the structures it hides.

Composite image of the young star HL Tau and its surroundings, using data from ALMA (enlarged in box at upper right) and the NASA/ESA Hubble Space Telescope (rest of the picture). This is the first ALMA image where the image sharpness exceeds that normally attained with Hubble. (Image and caption: ALMA/ESA/Hubble/NASA)
Composite image of the young star HL Tau and its surroundings, using data from ALMA (enlarged in box at upper right) and the NASA/ESA Hubble Space Telescope (rest of the picture). This is the first ALMA image where the image sharpness exceeds that normally attained with Hubble. (Image and caption: ALMA/ESA/Hubble/NASA)
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A Planet With Three Suns?

Twinkling some 450 light-years away in the constellation Taurus is a complex starry trio known as GG Tau A. Two of the triad’s three stars closely circle one another, like a classic binary pair. But that pair also swings around the third star, creating a turbulent environment that seems like the last place you’d expect to find hints of planet formation.

Except that is exactly what astronomers might be seeing.

Imagine, for a moment, a world with three suns. Shadows would come in triplets, the suns would be continually eclipsing themselves, sunrises and sunsets would be spectacularly variable. We don’t know of any such circumtriple worlds yet, but new observations suggest a planet could be forming around GG Tau A’s three stars.

And what’s more, those observations point to a gassy conveyor belt that’s supplying vital planet-building ingredients to a spot deep within the system.

“If all goes well, in a few million years we may have a circumtriple planet and a circumstellar planet in the same system,” says astronomer William Welsh of San Diego State University, who was not involved in the recent observations. “This system would be off the charts in terms of the coolness factor.”

Astronomers have been observing the GG Tau A system for decades. In 1993, they detected a large, dusty ring encircling the trio (though it wasn’t yet known to be a trio. That was discovered more recently). Made of diffuse gas and dust, the ring itself is about 90 times wider than the Earth-Sun distance (called an astronomical unit), and its inner edge begins about 190 astronomical units from the system’s central stars.

The presence of that ring is not surprising. But recent observations made with the European Southern Observatory’s Atacama Large Millimeter Array reveal a “puzzling” condensation near the outer edge of that ring – something scientists suspect might be a young planet.

“The hot spot we observe may be the signature of an embedded planet, but its nature has to be confirmed and we are still working on it,” says astronomer Anne Dutrey of the University of Bordeaux and France’s National Center for Scientific Research. She and her colleagues report their observations today in Nature.

But finding planets around GG Tau A wasn’t the main goal of the team’s observations. Dutrey and her colleagues were hoping to better understand the longevity of a large disk of planet-building material that lives deep inside the system. Swirling around the singleton of the three stars – called GG Tau Aa – the disk is about 15 astronomical units wide. Normally, planets condense within these disks and form over millions of years, which is what happened in our solar system.

In a close binary system, however, these star-circling disks don’t live long enough to grow planets. They’re sucked into their parent stars in a few thousand years.

Yet GG Tau A is about one million years old, Dutrey says, and the disk is still there. So how is it managing to survive?

What Dutrey and her colleagues found is that there’s a streamer of gas connecting the system’s outer ring with the inner disk, kind of like a lifeline. Material appears to be flowing in from the outer reservoir and replenishing the disk around that single star, keeping it alive long enough to (maybe) grow planets.

The team’s observations are important both for understanding how planets form in complex systems, and for understanding the galactic planet census, Welsh says. He works with NASA’s Kepler spacecraft and has spotted several twin-sunned planets, the first of which landed with a splash in 2011. Now, scientists have confirmed about a dozen of these real-life Tatooines.

“A very sizable fraction of all stars are born in binary systems,” Welsh says. “So a better understanding of planet formation in binaries leads to having a much better grasp about the true planet population in the galaxy.”

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Here’s What Exoplanets Really Look Like — For Now

This post has been updated to include GU Psc b, a directly imaged exoplanet announced today. More information below.

We know of more than 1,700 exoplanets. But most of these planets have been detected indirectly, by the way they darken their stars’ faces, their gentle tugs on their home stars, or by the effects of their gravity on distant starlight.

Thus, though there are many, many worlds out there, most of them are hiding from Earthly eyes. We have yet to actually see the majority of exoplanets. So, most exoplanet discoveries are accompanied by detailed artistic renderings of what that planet, or planetary system, might look like.

This beautiful rendering of Kepler 186 f includes oceans on the planet’s surface. (NASA Ames/SETI Institute/JPL-Caltech)

The few real images we have of exoplanets don’t yet contain those fantastic details: There are no clouds, no continents, no shimmering alien oceans. Instead, the images are of a few blurry pixels that represent a distant world. But hiding in those pixels is a potential flood of information – details about the planet’s size, temperature, and atmospheric composition. In the future, high-resolution direct images of planets will be crucial for helping scientists determine whether life — like planets — is common in the cosmos.

On May 12, a team of scientists reported the best picture yet of an alien planet called Beta Pictoris b, in the Proceedings of the National Academy of Sciences. Using the Gemini Planet Imager, which detects infrared radiation emitted by young, hot planets, the team was able to capture the exoplanet in a super-short, 1-minute exposure. About 63 light-years away, Beta Pictoris b is bigger than Jupiter and orbits more than 1.3 billion kilometers (about nine astronomical units) from its star. This isn’t the first image snapped of Beta Pictoris b – that was done (albeit accidentally) in 2003 – it’s just the best.

Beta Pictoris b is a fairly common observation target. Just two weeks ago, a different team of scientists calculated how fast the planet spins: 100,000 kilometers per hour. In other words, a day on the planet lasts just eight hours. Its year, however, is the equivalent of 20.5 Earth-years.

The total number of planetary systems scientists have directly imaged is very small – around a dozen. This is because it’s incredibly difficult to take pictures of such dim, relatively small, faraway objects (it’s tricky to do this in our solar system, too  — we don’t have high-resolution images of Pluto, yet).

If you could see it, planet GJ 504 b would look like a bigger, magenta version of Jupiter. (NASA’s Goddard Space Flight Center/S. Wiessinger)

But imaging exoplanets is especially hard because of the extraordinary amount of light produced by parent stars, which overwhelm the faint reflections of their small planetary companions. It’s kind of like trying to see a blinking firefly hovering near a much larger searchlight.

So, one of the ways astronomers take images of these planets is by blocking out the host star’s light. This way, they can see the tiny, bright pixels that betray the presence of a planet. Some of the images in the gallery above have big, mostly blank circles near their centers; normally, the host star would be there, but it’s masked. Other images in the gallery are composites of the star and planet.

The Gemini Planet Imager is now systematically searching for exoplanets near some 600 stars. Maybe soon, we’ll be able to use those data to find out what kinds of molecules live in exoatmospheres, and if there are living, breathing organisms on other worlds.

Beta Pictoris b is bigger than Jupiter and orbits inside the dusty debris disk surrounding its star, 63 light-years away. (ESO/L Calcada/N Risinger)
Beta Pictoris b is bigger than Jupiter and orbits inside the dusty debris disk surrounding its star, 63 light-years away. (ESO/L Calcada/N Risinger)

Update, 10 a.m. EDT: Another directly imaged planet has been announced. In The Astrophysical Journal, a team of astronomers reports the presence of a gas giant called GU Psc b, which orbits a star 155 light-years away. The planet is pretty hefty — between 9 and 13 times as massive as Jupiter (that upper mass limit is on the boundary separating planets and brown dwarf stars). But its year is even heftier: At 2,000 times the Earth-sun distance from its star, GU Psc b’s year lasts the equivalent of 80,000 Earth-years. The immense distance between the planet and its star sets this system apart from the others detected so far; the team, led by scientists at the Universite de Montreal, is about to survey several hundred more stars and search for planets in similar orbits. I’ve added GU Psc b’s image to the gallery above. The artist’s representation of the planet is below.

GU Psc b and its very far away star. (Lucas Granito)
GU Psc b and its very far away star. (Lucas Granito)