Tag: exoplanets

The Estimated Number of Stars in the Universe Just Tripled

By Andrew Moseman | December 1, 2010 4:41 pm

EGalaxyA 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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CATEGORIZED UNDER: Space

Super-Hot Super-Earth May Have an Atmosphere of Steam

By Andrew Moseman | December 1, 2010 1:35 pm

SteamyexoplanetFrom 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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80beats: Found: An Exoplanet From Another Galaxy
80beats: Astronomers Predict a Bonanza of Earth-Sized Exoplanets
80beats: Um… That “Goldilocks” Exoplanet May Not Exist
Discoblog: So, How Long Would It Take to Travel to That Exciting New Exoplanet?
DISCOVER: How Long Until We Find a Second Earth?

Image: ESO

CATEGORIZED UNDER: Space

Found: An Exoplanet From Another Galaxy

By Andrew Moseman | November 18, 2010 2:44 pm

ExtragalacticExoplanetA 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.

Related Content:
80beats: Astronomers Predict a Bonanza of Earth-Sized Exoplanets
80beats: Um… That “Goldilocks” Exoplanet May Not Exist
Discoblog: So, How Long Would It Take to Travel to That Exciting New Exoplanet?
DISCOVER: How Long Until We Find a Second Earth?

Image: ESO

CATEGORIZED UNDER: Space

Astronomers Predict a Bonanza of Earth-Sized Exoplanets

By Andrew Moseman | October 28, 2010 4:04 pm

keckThe 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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CATEGORIZED UNDER: Space, Top Posts

Um… That "Goldilocks" Exoplanet May Not Exist

By Jennifer Welsh | October 12, 2010 5:44 pm

Gliesewhut2A 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.

Related content:
Bad Astronomy: Possible earthlike planet found in the Goldilocks zone of a nearby star!
Discoblog: So, How Long Would It Take to Travel to That Exciting New Exoplanet?
80beats: New Telescope Could Reveal a Milky Way Packed With Habitable Planets
Bad Astronomy: HUGE NEWS: first possibly Earthlike extrasolar planet found!
80beats: Don’t Pack Your Bags Yet—New Planet-Finder Hobbled by Electronic Glitch

Image: NSF

CATEGORIZED UNDER: Space

How Excited Should We Be About the New "Goldilocks" Exoplanet?

By Andrew Moseman | September 30, 2010 10:03 am

gliese581From 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).

Related Content:
Bad Astronomy: Possible earthlike planet found in the Goldilocks zone of a nearby star!
80beats: Astronomers Find 2 Giant Exoplanets Locked in an Endless Dance
80beats: Kepler’s Early Results Suggest Earth-Like Planets Are Dime-a-Dozen
80beats: Temperate, Jupiter-Sized World Resembles the Planets of Our Solar System

Image: ESO

CATEGORIZED UNDER: Space

Astronomers Find 2 Giant Exoplanets Locked in an Endless Dance

By Andrew Moseman | August 26, 2010 4:19 pm

Kepler2planetsThe two newest planets spied by the Kepler space telescope are locked in a forever back-and-forth.

When Kepler’s scientists saw a star 2,000 light years away dim slightly, they knew there was the chance it was the telltale signature of a planet passing in front. But when the calculations were done and the confirmation came in, they found a surprise—what they’d seen was actually two planets transiting in front of the star.

NASA says it’s the first time they’ve ever caught such a sight, and today the scientists officially announced the finding with a study in Science. While other studies have found multiple planets around a single star–in fact, it happened earlier this week–those studies have used different planet-detection techniques like the wobble method.

The two worlds, both gas giants, do more than orbit the same star on the same plane, though. They push and pull each other in a motion that keeps the two exoplanets close to arithmetic celestial perfection. Kepler-9B, the larger, orbits the star in 19.24 days on average, the astronomers saw. Kepler-9c, the smaller, completes a revolution in an average of 38.91 days. But every time the scientists checked, 9b’s orbit was getting 4 minutes longer, while 9c’s shrank by 39 minutes.

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CATEGORIZED UNDER: Space

Homey-Looking Alien Star System May Host 7 Planets

By Andrew Moseman | August 25, 2010 10:53 am

NewStarSystemIn August 2006, Pluto received its official demotion to dwarf planet status, taking our solar system down to eight planets. In August 2010, exoplanet hunters say they’ve found a haul of new worlds around a single star; that alien solar system may have seven known planets, meaning the system could be more like our home system than any ever discovered. And one of those worlds could be the smallest exoplanet ever found, too.

The star these planets orbit is called HD 10180, and it lies 127 light years from here. Astronomers at the European Southern Observatory in Chile used a spectrograph called HARPS to track tiny variations in the starlight caused by the pull of the planets.

It found clear evidence for five giant planets similar in size to Uranus or Neptune in our own solar system. But there were also tantalising signs that two other planets are also present, one of which would be the smallest, or least-massive, yet found orbiting another star [Christian Science Monitor].

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CATEGORIZED UNDER: Space

Kepler's Early Results Suggest Earth-Like Planets Are Dime-a-Dozen

By Andrew Moseman | July 26, 2010 4:53 pm

KeplerCraftAlthough some publications glossed over the uncertainty in announcing the first findings of the planet-hunting Kepler mission, researchers say the overall point remains true: Earth-like planets (meaning that they’re small and rocky, not that they have aliens writing blogs about science) are not only not rare–they’re the most common type of planet in our galaxy.

The first intimations of this news came out a few days ago in reports like the Daily Mail’s, which blared that NASA’s planet-hunting Kepler mission had found 140 new planets that were like the Earth in size, and that worlds like our own could dominate the Milky Way. That claim came after a presentation now available to view online by one of the scientists behind Kepler, Harvard’s Dimitar Sasselov.

But Sasselov and colleagues responded to Space.com, trying to quell some of the excitement–or at least hedge on the exact magnitude of the find:

“What Dimitar presented was ‘candidates,'” said David Koch, the mission’s deputy principal investigator at NASA’s Ames Research Center in Moffett Field, Calif. “These have the apparent signature we are looking for, but then we must perform extensive follow-up observations to eliminate false positives, such as background eclipsing binaries. This requires substantial amounts of ground-based observing which is done primarily in the summer observing season” [Space.com]

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CATEGORIZED UNDER: Space
MORE ABOUT: exoplanets, Kepler

Osiris: The Scorched Exoplanet With a Comet-Like Tail

By Andrew Moseman | July 16, 2010 10:59 am

OsirisCometTailWe know about exoplanet HD 209458b, nicknamed “Osiris.” We know it’s 153 light years away, that it has water in its atmosphere, and that it orbits its star in three and a half days at a distance 100 times closer than Jupiter is to the sun. But we didn’t know this for sure until now: This planet has a tail.

In a study in The Astrophysical Journal, a research team says Osiris, a gas giant, orbits so close that its star is blasting away its atmosphere. As the planet progresses on its blazing hot and hasty revolutions, a tail like that of a comet follows behind it. The Hubble Space Telescope‘s Cosmic Origins Spectrograph caught the effect as Osiris made repeated transits in front of its star.

The instrument detected the heavy elements carbon and silicon in the planet’s super-hot 2,000 degrees F (1,100 C or so) atmosphere. This detection revealed the parent star is heating the entire atmosphere, dredging up the heavier elements and allowing them to escape the planet.

Jeffrey Linsky, of the University of Colorado, who led the study, said: “We have measured gas coming off the planet at specific speeds, some coming toward Earth. The most likely interpretation is that we have measured the velocity of material in a tail” [Christian Science Monitor].

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CATEGORIZED UNDER: Space
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