There are at least as many planets in the galaxy as there are stars. And even that is probably a vast underestimate.

That’s the latest bombshell from astronomers looking for planets beyond our solar system. Phil Plait at Bad Astronomy will have a post on this soon, but for now, here’s a little quote salad for you:

“Planets are like bunnies; you don’t just get one, you get a bunch,” said Seth Shostak, a senior astronomer at the SETI Institute who was not involved in this research. “So really, the number of planets in the Milky Way is probably like five or 10 times the number of stars. That’s something like a trillion planets.” (via PopSci)

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When Fomalhaut b was announced in 2008, images showed it following a clear orbit around its star.

What’s the News: Even if you don’t know an exoplanet from an exoskeleton, you probably saw the gorgeous images of Fomalhaut, aka “Sauron’s Eye,” making their way around the web in 2008. A tiny, bright dot in the star’s surrounding dust cloud had moved, showing itself to be a planet—the first planet beyond our solar system to actually be seen, rather than detected with nonoptical instruments. Cue the champagne!

But new pictures show something odd: Fomalhaut b, as the planet was named, is veering off in an unexpected direction. Does this mean it’s not a planet after all, or is there another explanation? (more…)

Artist’s concept of the pulsar and its planet. The system could fit into our Sun, represented by the yellow surface.

What’s the News: An international team of astronomers has found an exotic planet possibly made of diamond, located about 4,000 light-years away from Earth. The researchers believe that the unusual planet was once a sun-like star, transformed into its current state by its hungry stellar companion, a millisecond pulsar.

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What’s the News: While the Kepler spacecraft is busy finding solar system-loads of new planets, other astronomers are expanding our idea where planets could potentially be found. One astronomer wants to look for habitable planets around white dwarfs, arguing that any water-bearing exoplanets orbiting these tiny, dim stars would be much easier to find than those around main-sequence stars like our Sun. Another team dispenses with stars altogether and speculates that dark matter explosions inside a planet could hypothetically make it warm enough to be habitable, even without a star. “This is a fascinating, and highly original idea,” MIT exoplanet expert Sara Seager told Wired, referring to the dark matter hypothesis. “Original ideas are becoming more and more rare in exoplanet theory.”

How the Heck:

• Because white dwarfs are much smaller than our Sun, an Earth-sized planet that crossed in front of it would block more of its light, which should make these planets easier to spot. So astronomer Eric Agol suggests survey the 20,000 white dwarfs closest to Earth with relatively meager 1-meter ground telescopes.
• And because white dwarfs are so cool, a planet in a white dwarfs habitable zone would be very close, meaning its transit would happen very fast. Agol says we’d only need to watch a star for 32 hours to pick up on any transiting, habitable planets.
• One leading theory about dark matter is that it’s made of theoretical particles called WIMPS (weakly interacting massive particles). It’s thought that when WIMPs collide (if, of course, they exist), they would explode. Astronomers think that these WIMP explosions could possibly heat a planet enough to make it habitable.
• There are no immediate plans to test the dark matter hypothesis, which is quite theoretical, and any plan to find dark matter-fueled planets would need to look far from here: our part of the universe doesn’t have nearly enough dark matter to bring a planet to habitability.

What’s the Context:

• In other white dwarf news, astronomers have discovered a red dwarf in an extremely tight orbit with a white dwarf.
• And others are still wrangling over what dark matter really is.
• As for exoplanets, astronomers have actually seen one—as in, with visible light—orbiting its star.

Not So Fast:

• It’s not at all clear if white dwarfs have any planets, and if so, whether any of them could possibly support water or life as we know it. For one thing, planets in the habitable zone would be tidally locked with the star—permanent scalding daylight on one side; permanent frozen nighttime on the other.
• Taking 32 hours to find a planet orbiting a white dwarf may seem like a short time, but when you’re looking at tens of thousands of stars, it adds up. Agol told UW Today, “This could take a huge amount of time, even with [a network of telescopes].”
• And just like star-orbiting planets have their Goldilocks zones (not to hot or too cold), dark matter-containing planets would need the right amount of dark matter to be habitable. “It’s not something that’s likely to produce a lot of habitable planets,” Fermilab researcher Dan Hooper told Wired. “But in very special places and in very special models, it could do the trick.” 

References: Eric Agol. “TRANSIT SURVEYS FOR EARTHS IN THE HABITABLE ZONES OF WHITE DWARFS.” doi: 10.1088/2041-8205/731/2/L31

Dan Hooper and Jason H. Steffen. “Dark Matter And The Habitability of Planets.” arXiv:1103.5086v1

Image: NASA/European Space Agency

What’s the News: Based on early Kepler data, astronomers say that the Milky Way galaxy may house at least two billion Earth-like planets—one for every several dozen sun-like stars. As NASA researcher Joseph Catanzarite told Space.com, “With that large a number, there’s a good chance life and maybe even intelligent life might exist on some of those planets. And that’s just our galaxy alone — there are 50 billion other galaxies.” But while 2 billion sounds like a lot, it’s actually far below many scientists’ expectation; Catanzarite says his teams’ findings actually show that Earth-like planets are “relatively scarce.”

How the Heck:

• Using mathematical models to plot the size and orbital distance for all the potential planets spotted during four months’ worth of Kepler data, astronomers extrapolated the data and calculated that 1.4 to 2.7% of the Milky Way’s sun-like stars may have an Earth analog.
• Two percent of the Milky Way’s roughly one hundred billion sun-like stars means that “you have two billion Earth analog planets in the galaxy,” Catanzarite told National Geographic.

What’s the Context:

• The Kepler team recently announced a mother lode of 1,200 potential alien worlds (68 of them about Earth size), a tightly scrunched-up mini solar system, and a bizarro “styrofoam” world; unfortunately, the “most Earth-like planet” planet it found so far got a major demotion: it’s not actually habitable.

Not So Fast:

• MIT astronomer Sara Seager says that the team “completely underestimates the frequency of Earths.” The calculations are based on only four months of Kepler data—too early to be making an accurate projection.
• There’s also the fact that Kepler can only detect the size and orbital distance (and occasionally the masses) of planets, which doesn’t tell you whether life as we know it could actually live there; Venus, for example, would roughly like Earth to aliens peering at us from many light-years away, but because of its atmosphere’s runaway greenhouse effect, it’s way too hot to be habitable.

Next Up: The astronomers plan on calculating an even more accurate number once all of Kepler’s data is in.

Reference: Joseph Catanzarite and Michael Shao. “The Occurrence Rate of Earth Analog Planets Orbiting Sunlike Stars.” arXiv:1103.1443v1 Image: Kepler/NASA

Young. Old. Scalding hot. Icy cold. Terrestrial midgets. Gas giants. As the cavalcade of planets spotted beyond our solar system continues to grow, we get to see worlds of all sorts—and we get to speculate on the staggering number of exoplanets that might inhabit just our own galaxy.

Today’s first piece of otherworldly news involves baby exoplanets. Astronomer Christian Thalmann says his team may have spotted planets in the process of forming around three different stars, the first time scientists have spotted the process in action.

An infant star forms from a collapsing cloud of dust and gas and gathers a dense, flat disk of material that rotates with the star like a record album. The material in the disk will eventually clump up into nascent planets. Theoretical models of planet formation predicted that those protoplanets should suck up more gas and dust with their gravity, clearing a wide gap in the otherwise solid disk. [Wired]

Peering at young stars like T Chamaeleontis (T Cha) LkCa15 and AB Auriga, Thalmann and colleagues saw those telltale gaps in the dusty rings (their study is forthcoming in the Astrophysical Journal Letters). The stars are much like our own sun, so these pictures of infant solar systems could resemble what our own looked like as a baby. But though the stars are nearby in cosmic terms—T Cha lies just 350 light years away—the gaps are faint enough that it’s difficult to tell for certain if newly forming planets, and not the influence of binary stars or other objects, are creating them.

If Thalmann’s team is right, catching the birth of new worlds would be a great scientific coup. Our galaxy, however, isn’t exactly hurting for planets.

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For months we here at DISCOVER have been waiting impatiently for the Kepler mission to open up its vault of new exoplanets, hopefully filled with a bevy of Earth-like worlds and other exotic planets. Today planet lovers got a new peek at the Kepler findings, and those findings are stunning.

First, the Kepler scientists announced more than 1,200 candidate planets, which got DISCOVER blogger Phil Plait excited:

This is incredible! Even though I was expecting a number like this, actually hearing it for real is stunning. In 15 years we’ve found about 500 planets orbiting other stars, but in the almost two years since Kepler launched it may have easily tripled that number! Now, to be careful: these are candidate planets, which means they have not been confirmed. But in most cases these look pretty good, and if these numbers hold up it indicates that our galaxy is lousy with planets. They’re everywhere.

While those 1,200 are candidates, astronomers have confirmed a peculiar and fascinating set of six. From Phil Plait:

Using NASA’s orbiting Kepler observatory, astronomers have found a complete solar system of six planets orbiting a sun-like star… and it’s really weird: five of the six planets huddle closer to their star than Mercury does to the Sun!

None of them is what I would call precisely earth-like — they’re all more massive and much hotter than Earth — but their properties are intriguing, and promise that more wonderful discoveries from Kepler are coming.

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ESO/L. Calçada

The Kepler space telescope, launched nearly two years ago, has already proven its worth as an exoplanet hunter many times over. But the discoveries keep on coming. NASA just announced that Kepler has found its first rocky planet–and that the rocky world is only 1.4 times the size of Earth, making it the smallest exoplanet ever found.

Phil Plait explains that this nearly Earth-sized isn’t actually Earth-like and habitable:

[I]t orbits extremely close in to its star, circling over the star’s surface at a distance of roughly 3 million kilometers (1.8 million miles) — amazingly, it takes less than an Earth day to make one circuit. But being that close to a star comes at a price: the surface temperature of the planet must be several thousand degrees!

The planet, Kepler-10b, may not be habitable to life as we know it, but Plait is still plenty excited. Get the rest of the story on how the planet was found and what its discovery means over at Bad Astronomy.

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A couple of new exoplanets are leaving researchers scratching their heads in confusion.

So bright, so vivid! So prismatic!

A planet called WASP-12b is the first planet that’s been found to have more carbon than oxygen in its atmosphere, unlike most planets in our solar system. In the paper published in Nature, researchers suggest that the gas giant probably has a carbon-based core. And all that carbon has set the researchers eyes a-sparkle with possibilities:

The researchers say their discovery supports the idea there may be carbon-rich, rocky planets whose terrains are made up of diamonds or graphite. “You might see land masses and mountains made up of diamonds,” [said] lead researcher Dr Nikku Madhusudhan. [BBC News]

The alien planet was discovered in 2009 and is about 870 light-years away. It’s about 1.4 times as massive as Jupiter and sits just 2 percent as far from its parent star as the Earth is from the sun. Sadly, we can’t go mining there, since the hypothetical diamonds are surrounded by the gas giant’s scorching atmosphere (4,200 degrees Fahrenheit) of hydrogen. Even if you got down to its rocky core, any diamonds would likely be mixed in with graphite and even liquid carbon.

“This study shows that there is this extreme diversity out there,” study lead author Nikku Madhusudhan, now of Princeton University, told SPACE.com. “Fifteen years or so since the discovery of the first exoplanet, we’re just beginning to appreciate how different they can be.” [Space.com]

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A study by Yale astronomer Pieter van Dokkum just took the estimated number of stars in the universe—100,000,000,000,000,000,000,000, or 100 sextillion—and tripled it. And you thought nothing good ever happens on Wednesdays.

Van Dokkum’s study in the journal Nature focuses on red dwarfs, a class of small, cool stars. They’re so small and cool, in fact, that up to now astronomers haven’t been able to spot them in galaxies outside our own. That’s a serious holdup when you’re trying to account for all the stars there are.

As a consequence, when estimating how much of a galaxy’s mass stars account for – important to understanding a galaxy’s life history – astronomers basically had to assume that the relative abundance of red-dwarf stars found in the Milky Way held true throughout the universe for every galaxy type and at every epoch of the universe’s evolution, Dr. van Dokkum says. “We always knew that was sort of a stretch, but it was the only thing we had. Until you see evidence to the contrary you kind of go with that assumption,” he says. [Christian Science Monitor]

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From Phil Plait:

Last year, astronomers discovered a remarkable planet orbiting another star: it has a mass and radius that puts it in the “super-Earth” category — meaning it’s more like the Earth than a giant Jupiter-like planet. Today, it has been announced that astronomers have been able to analyze the atmosphere of the planet (the very first time this has ever been accomplished for a super-Earth), and what they found is astonishing: the air of the planet is either shrouded in thick haze, or it’s loaded with water vapor… in other words, steam!

…

Astronomers observed the planet when it passed in front of the star, analyzing the light very carefully. As starlight passes through the planet’s atmosphere, certain colors of it get absorbed, and these are like fingerprints that can be used to figure out the atmospheric composition. Most models predicted a heavy hydrogen content, but the observations indicate none is there! That means either there are thick layers of haze in the upper atmosphere of the planet, obscuring any hydrogen below them — much like Venus or Saturn’s moon Titan, blocking the view lower down — or there is a vast amount of water in the planet’s air. And at a temperature of 200° C, that water would be in the form of vapor. In other words, steam.

For the full scoop on GJ 1214b, located about 42 light years from here, check out Phil’s entire post at Bad Astronomy.

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Image: ESO

A fascinating discovery from today’s edition of the journal Science: Astronomers from Germany report a new exoplanet with two startling characteristics. First, it closely orbits a star that has already exhausted its hydrogen supply and moved past the red giant stage, so this hot Jupiter has so far survived without being evaporated (despite its proximity—just 0.12 astronomical units).

But second, and most striking: This planet and star came from another galaxy.

From Phil Plait:

OK, first, this planet is in our own Milky Way galaxy. The star, called HIP 13044, is about 2000 light years away, well inside our galaxy. So how do we know it’s from a different galaxy? All the stars in our galaxy orbit the galactic center, like planets orbit around a star. But many years ago, astronomers noticed that many stars in the sky have the same sort of motion as they orbit, as if they all belong to streams of stars, flowing like water in a river. Many such streams exist, and eventually astronomers figured out that these were the leftover remnants of entire small galaxies that had collided with, been torn apart, and basically eaten by our Milky Way.

HIP 13044 is part of one of those streams, called the Helmi Stream. It’s the remains of a dwarf galaxy the Milky Way tore apart probably more than 6 billion years ago. So the star and its planet formed in an actual other galaxy, one that either orbited the Milky Way or had an unfortunately too-close pass to it. Either way, wow!

During a web conference this morning, study coauthor Rainer Klement said we shouldn’t be surprised the star and planet are still together even though our galaxy tore theirs apart. Galaxies are structures of stars, but the stars themselves are still so far away that even during a galactic breakup they don’t pass near enough to one another to gravitationally influence a planet. “The timescale upon which such stars play a role is larger than the age of the universe,” he said.

Read the rest of Phil’s post at Bad Astronomy.

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Image: ESO

The universe abounds with Earth-sized planets. That hopeful notion has been reinforced by individual planets finds like possible Goldilocks planet Gliese 581g, by the hordes of planet candidates discovered by the Kepler mission, and now, by a census of a small space in the sky that tells us one in four sun-like stars should possess worlds that are close to the size of Earth.

Take a moment to think about that: One in four.

In Science, exoplanet hunters Geoffrey Marcy and Andrew Howard published their team’s census of 166 nearby stars like ours, of which they picked 22 at random to investigate for planets. They watched the stars’ doppler shifts to hunt for planets over the last five years, and used the results to extrapolate how common terrestrial planets must be far beyond just this set of stars.

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A group of Swiss astronomers announced yesterday at the International Astronomical Union’s annual meeting in Turin, Italy, that they couldn’t detect the “goldilocks” exoplanet found by U.S. researchers a few weeks ago. That news of that planet, dubbed Gliese 581g, generated much excitement, since researchers said it was only three times the size of Earth, and it appeared to lie in the habitable zone where liquid water could exist on the surface.

It didn’t take long for some cold water to be thrown on the astronomical community and the space-loving public. Presenter Francesco Pepe and his colleagues claim that it will be years before the data is clear enough to see such a planet.

“We do not see any evidence for a fifth planet … as announced by Vogt et al.,” Pepe wrote Science in an e-mail from the meeting. On the other hand, “we can’t prove there is no fifth planet.” No one yet has the required precision in their observations to prove the absence of such a small exoplanet, he notes. [ScienceNOW].

Such small planets are very hard to find. Astronomers discover these planets by calculating how they interact with the star they orbit, making it wiggle ever so slightly. The American team that identified the planet a few weeks ago saw the wiggles when analyzing a combination of two sets of data.

Astronomer Paul Butler, a member of the U.S. team who is at the Carnegie Institution for Science in Washington, D.C., says he can’t comment on the Swiss work because he wasn’t at the meeting and the data are unpublished. He notes, however, that more observations will likely be needed to solidify the existence of Gliese 581g. “I would expect that on the time scale of a year or two this should be settled.” [ScienceNOW].

There will be more information available when the Swiss team releases its data and methods, but for now you might want to unpack your bags.

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Image: NSF

From Phil Plait:

Astronomers have announced the discovery of a planet with about three times the Earth’s mass orbiting the nearby red dwarf star Gliese 581. That in itself is cool news; a planet like that is very hard to detect.

But the amazing thing is that the planet’s distance from the star puts it in the Goldilocks Zone: the region where liquid water could exist on its surface!

Gliese 581 is about 20 light years away, and astronomers think the planet in the habitable zone is one of at least six in that star system. The new exoplanet orbits much closer to its star than Earth orbits the sun, but its star is a red dwarf, so it needs to be closer to stay warm enough to support liquid water.

But just how like the Earth is this new world? And what does it mean for the prevalence of ‘Goldilocks” planets out there? To find out, read the rest of the post at Bad Astronomy. And check out the scientists’ paper about Gliese 581 (pdf).

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Image: ESO