Extrasolar Planets Archives

February 17, 2014December 23, 2015 by Shannon Hall

Zooniverse Reaches One Million Volunteers

A global map showing where all the volunteers are based. Image Credit: Zooniverse

Zooniverse — the renowned home of citizen science projects — is now one million strong. That’s one million registered volunteers since the project began less than seven years ago.

It all began when Galaxy Zoo launched in July 2007. The initial response to this project was overwhelming. Since then the Zooniverse team has created almost 30 citizen science projects ranging from astronomy to zoology.

“We are constantly amazed by the effort that the community puts into our projects,” said the Zooniverse team in an email regarding the news late last week.

Many projects have produced unique scientific results, ranging from individual discoveries to classifications that rely on input from thousands of volunteers. As of today there are 60+ papers listed on the websites publications page, many of which have made the news.

In the first two weeks after Galaxy Zoo’s launch, registered citizen scientists classified more than a million galaxies. Each volunteer was presented with an image from the Sloan Digital Sky Survey and asked to classifiy the galaxy as belonging to one of six categories: elliptical, clockwise spiral, anticlockwise spiral, edge-on, merger, or unsure.

An example of an unknown galaxy needing classification. Image credit: Galaxy Zoo

But citizen scientists weren’t simply labeling galaxies, they were helping astronomers to answer crucial questions and raise new ones about our current understandings of galaxy evolution. One significant finding showed that bar-shaped features in spiral galaxies has doubled over the latter half of the history of the Universe. This confirms that bars signify maturity in spiral galaxies and play an important role in shutting down star formation.

Another finding downplayed the importance of collisions in forming supermassive black holes. Citizen scientists found 13 bulgeless galaxies — suggesting they had never experienced a major collision — with supermassive black holes, nonetheless. All healthy black holes, with masses at least millions of times that of the Sun, must have grown through less dramatic processes.

Planet Hunters — a citizen science project developed in 2010 — has also seen wide success. Ordinary citizens examine the Kepler Space Telescope’s light curves of stars and flag any slight dips in brightness that might indicate a planet crossing in front of the star. Many eyes examine each light curve, allowing some to cross check others.

An example light curve. — An example light curve asking for any obvious dips. Image Credit: Planet Hunters

In roughly three years, citizen scientists examined more than 19 million Kepler light curves. Contrary to what many astronomers expected, ordinary citizens were able to spot transiting objects that many computer algorithms missed.

In 2012, Planet Hunter volunteers, Kian Jek and Robert Gagliano discovered an exoplanet in a four-star system. The Neptune-size planet, labeled “Planet Hunters 1” (PH1), orbits its two parent stars every 138 days. A second pair of stars, approximately 90 billion miles away, are also gravitationally bound to the system. This wacky system was later confirmed by professional astronomers.

In 2013, Planet Hunter volunteers discovered yet another planet candidate, which, if confirmed, would make a known six-planet system really the first seven-planet system. The five innermost planets are smaller than Neptune, while the two outer planets are gas giants. All orbit within Earth’s orbit around the Sun.

These are only a few of Zooniverse’s citizen science projects. Others allow ordinary citizens to help analyze how whales communicate with one another, study the lives of the ancient Greeks, and even look at real life cancer data. So join today and become number one million and one.

Zooniverse is produced by the Citizen Science Alliance, which works with many academic and other partners worldwide.

February 11, 2014December 23, 2015 by Shannon Hall

New Technique Puts Exoplanets on the Scale

Meet Kepler-22b, an exoplanet with an Earth-like radius in the habitable zone of its host star. Unfortunately its mass remains unknown. Image Credit: NASA

Astronomers constantly probe the skies for the unexpected. They search for unforeseen bumps in their data — signaling an unknown planet orbiting a star, a new class of astronomical objects or even a new set of physical laws that will rewrite the old ones. They are willing to embrace new ideas that may replace the wisdom of years past.

But there’s one exception to the rule: the search for Earth 2.0. Here we don’t want to find the unexpected, but the expected. We want to find a planet so similar to our own, we can almost call it home.

While, we can’t exactly image these planets with great enough detail to see if one’s a water world with luscious green plants and civilizations, we can use indirect methods to find an “Earth-like” planet — a planet with a similar mass and radius to the Earth.

There’s only one problem: the current techniques to measure an exoplanet’s mass are limited. To date astronomers measure radial velocity — tiny wobbles in a star’s orbit as it’s tugged by the gravitational pull of its exoplanet — to derive the planet-to-star mass ratio.

But given that most exoplanets are detected via their transit signal — dips in light as a planet passes in front of its host star — wouldn’t it be great if we could measure its mass based on this method alone? Well, astronomers at MIT have found a way.

Graduate student Julien de Wit and MacArthur Fellow Sara Seager have developed a new technique for determining mass by using an exoplanet’s transit signal alone. When a planet transits, the star’s light passes through a thin layer of the planet’s atmosphere, which absorbs certain wavelengths of the star’s light. Once the starlight reaches Earth it will be imprinted with the chemical fingerprints of the atmosphere’s composition.

The so-called transmission spectrum allows astronomers to study the atmospheres of these alien worlds.

But here’s the key: a more massive planet can hold on to a thicker atmosphere. So in theory, a planet’s mass could be measured based on the atmosphere, or the transmission spectrum alone.

Of course there isn’t a one to one correlation or we would have figured this out long ago. The atmosphere’s extent also depends on its temperature and the weight of its molecules. Hydrogen is so light it slips away from an atmosphere more easily than, say, oxygen.

So de Wit worked from a standard equation describing scale height — the vertical distance over which the pressure of an atmosphere decreases. The extent to which pressure drops off depends on the planet’s temperature, the planet’s gravitational force (a.k.a. mass) and the atmosphere’s density.

According to basic algebra: knowing any three of these parameters will let us solve for the fourth. Therefore the planet’s gravitational force, or mass, can be derived from its atmospheric temperature, pressure profile and density — parameters that may be obtained in a transmission spectrum alone.

With the theoretical work behind them, de Wit and Seager used the hot Jupiter HD 189733b, with an already well-established mass, as a case study. Their calculations revealed the same mass measurement (1.15 times the mass of Jupiter) as that obtained by radial velocity measurements.

This new technique will be able to characterize the mass of exoplanets based on their transit data alone. While hot Jupiters remain the main target for the new technique, de Wit and Seager aim to describe Earth-like planets in the near future. With the launch of the James Webb Space Telescope scheduled for 2018, astronomers should be able to obtain the mass of much smaller worlds.

The paper has been published in Science Magazine and is now available for download in a much longer form here.

February 5, 2014December 23, 2015 by Shannon Hall

High Potential for Life Circling Alpha Centauri B, our Nearest Neighbor

While exoplanets make the news on an almost daily basis, one of the biggest announcements occurred in 2012 when astronomers claimed the discovery of an Earth-like planet circling our nearest neighbor, Alpha Centauri B, a mere 4.3 light-years away. That’s almost close enough to touch.

Of course such a discovery has led to a heated debate over the last three years. While most astronomers remain skeptical of this planet’s presence and astronomers continue to study this system, computer simulations from 2008 actually showed the possibility of 11 Earth-like planets in the habitable zone of Alpha Centauri B.

Now, recent research suggests that five of these computer-simulated planets have a high potential for photosynthetic life.

The 2008 study calculated the likely number of planets around Alpha Centauri B by assuming an initial protoplanetary disk populated with 400 – 900 rocks, or protoplanets, roughly the size of the Moon. They then tracked the disk over the course of 200 million years through n-body simulations — models of how objects gravitationally interact with one another over time — in order to determine the total number of planets that would form from the disk.

While the number and type of exoplanets depended heavily on the initial conditions given to the protoplanetary disk, the eight computer simulations predicted the formation of 21 planets, 11 of which resided within the habitable zone of the star.

A second team of astronomers, led by Dr. Antolin Gonzalez of the Universidad Central de Las Villas in Cuba, took these computer simulations one step further by assessing the likelihood these planets are habitable or even contain photosynthetic life.

The team used multiple measures that asses the potential for life. The Earth Similarity index “is a multi-parameter first assessment of Earth-likeness for extrasolar planets,” Dr. Gonzalez told Universe Today. It predicts (on a scale from zero to one with zero meaning no similarity and one being identical to Earth) how Earth-like a planet is based on its surface temperature, escape velocity, mean radius and bulk density.

Planets with an Earth Similar index from 0.8 – 1 are considered capable of hosting life similar to Earth’s. As an example Mars has an Earth Similar index in the range of 0.6 – 0.8. It is thus too low to support life today.

However, the Earth Similarity index alone is not an objective measure of habitability, Gonzalez said. It assumes the Earth is the only planet capable of supporting life. The team also relied on the P model for biological productivity, which takes into account the planet’s surface temperature and the amount of carbon dioxide present.

At this point in time “there is no way to predict, at least approximately, the partial pressure of carbon dioxide with the known data, or the variations from a planet to another,” Gonzalez said. Instead “we assumed a constant partial pressure of carbon dioxide for all planets simplifying the model to a function of temperature.”

Gonzalez’s team found that of the 11 computer-simulated planets in the habitable zone, five planets are prone for photosynthetic life. Their Earth Similarity index values are 0.92, 0.93, 0.87, 0.91 and 0.86. If we take into account their corresponding P model values we find that two of them have better conditions than Earth for life.

According to this highly theoretical paper: if there are planets circling our nearest neighbor, they’re likely to be teeming with life. It’s important to note that while these indexes may prove to be very valuable years down the road (when we have a handful of Earth-like planets to study), we are currently only looking for life as we know it.

The paper has been published in the Cuban journal: Revista Cubana de Fisica and is available for download here. For more information on Alpha Centauri Bb please read a paper available here published in the Astrophysical Journal.

February 4, 2014December 23, 2015 by Elizabeth Howell

‘Wobbly’ Alien Planet Has Weird Seasons And Orbits Two Stars

Diagram of Kepler-413b's unusual orbit around red and orange dwarf stars. Its orbit "wobbles" or precesses around the stars every 11 years. Credit: NASA, ESA, and A. Feild (STScI)

We’re lucky to live on a planet where it’s predictably warmer in the summer and colder in the winter in many regions, at least within a certain range. On Kepler-413b, it’s a world where you’d have to check the forecast more frequently, because its axis swings by a wild 30 degrees every 11 years. On Earth, by comparison, it takes 26,000 years to tilt by a somewhat lesser amount (23.5 degrees).

The exoplanet, which is 2,300 light-years away in the constellation Cygnus, orbits two dwarf stars — an orange one and a red one — every 66 days. While it would be fun to imagine a weather forecast on this planet, in reality it’s likely too hot for life (it’s close to its parent stars) and also huge, at 65 Earth-masses or a “super-Neptune.”

What’s even weirder is how hard it was to characterize the planet. Normally, astronomers spot these worlds either by watching them go across the face of their parent star(s), or by the gravitational wobbles they induce in those stars. The orbit, however, is tilted 2.5 degrees to the stars, which makes the transits far more unpredictable. It took several years of Kepler space telescope data to find a pattern.

“What we see in the Kepler data over 1,500 days is three transits in the first 180 days (one transit every 66 days), then we had 800 days with no transits at all,” stated Veselin Kostov, the principal investigator on the observation. “After that, we saw five more transits in a row,” added Kostov, who works both with the the Space Telescope Science Institute and Johns Hopkins University in Baltimore, Md.

It will be an astounding six years until the next transit happens in 2020, partly because of that wobble and partly because the stars have small diameters and aren’t exactly “edge-on” to our view from Earth. As for why this planet is behaving the way it does, no one is sure. Maybe other planets are messing with the orbit, or a third star is doing the same thing.

The next major question, the astronomers added, is if there are other planets out there like this that we just can’t see because of the gap between transit periods.

You can read more about this finding in The Astrophysical Journal (a Jan. 29 publication that doesn’t appear to be on the website yet) or in preprint version on Arxiv.

Source: Space Telescope Science Institute

February 4, 2014December 23, 2015 by Elizabeth Howell

Super-Earths Could Be More ‘Superhabitable’ Than Planets Like Ours

Artists impression of a Super-Earth, a class of planet that has many times the mass of Earth, but less than a Uranus or Neptune-sized planet. Credit: NASA/Ames/JPL-Caltech

Alien planets that are slightly bigger than Earth could be more life-friendly than exoplanets closer to our own size, a new study implies. These so-called “super-Earths” that are about two to three times that of our own planet could be “superhabitable” — implying that our own planet is a rare bird indeed when it comes to being good for life.

Bigger rocky planets would have a host of advantages, argue McMaster University’s Rene Heller and Weber State University’s John Armstrong in a paper recently published in Astrobiology. Among them: These worlds would have tectonic activity that takes longer to happen, meaning that the conditions would be more stable for life. Also, a bigger mass implies it’s easier to hang on to a thick atmosphere and to have “enhanced magnetic shielding” to hold a planet’s own against solar flares.

“Our argumentation can be understood as a refutation of the Rare Earth hypothesis. Ward and Brownlee (2000) claimed that the emergence of life required an extremely unlikely interplay of conditions on Earth, and they concluded that complex life would be a very unlikely phenomenon in the Universe,” stated the authors in their paper “Superhabitable Worlds.”

Information about Alpha Centauri Bb. Information about Alpha Centauri Bb. Credit: Planetary Habitability Laboratory/University of Puerto Rico/Arecibo

“While we agree that the occurrence of another truly Earth-like planet is trivially impossible, we hold that this argument does not constrain the emergence of other inhabited planets. We argue here in the opposite direction and claim that Earth could turn out to be a marginally habitable world. In our view, a variety of processes exists that can make environmental conditions on a planet or moon more benign to life than is the case on Earth.”

As a start, the scientists suggest looking at the Alpha Centauri system, where researchers in 2012 discovered a planet close to Earth’s size that is likely not habitable because it orbits so close to its sun.

The star system, however, is about the right age and has low enough radiation to allow life to occur on a planet or moon that “evolved similarly as it did on Earth”, providing the planet or moon “had the chance to collect water from comets and planetesimals beyond the snowline.” Further, it’s just four light-years from Earth, making it a good target for telescopic observations.

January 31, 2014April 26, 2016 by Elizabeth Howell

Young Planets Migrated In Double-Star Systems, Model Shows

Artist's conception of Kepler 34b, which orbits two stars. Credit: David A. Aguilar (CfA)

Binary star systems are downright dangerous due to their complex gravitational interactions that can easily grind a planet to pieces. So how is it that we have found a few planets in these Tattooine-like environments?

Research led by the University of Bristol show that most planets formed far away from their central stars and then migrated in at some point in their history, according to research collected concerning Kepler-34b and other exoplanets.

The scientists did “computer simulations of the early stages of planet formation around the binary stars using a sophisticated model that calculates the effect of gravity and physical collisions on and between one million planetary building blocks,” stated the university.

“They found that the majority of these planets must have formed much further away from the central binary stars and then migrated to their current location.”

You can read more about the research in Astrophysical Journal Letters. It was led by Bristol graduate student Stefan Lines with participation from advanced research fellow and computational astrophysicst Zoe Lienhardt, among other collaborators.

January 24, 2014December 23, 2015 by David Dickinson

Nearby Brown Dwarf Captured in a Direct Image

A direct image of a brown dwarf companion (arrowed) taken at the Keck Observatory. (Credit: Crepp et al. 2014 APJ).

A recent find announced by astronomers may go a long ways towards understanding a crucial “missing link” between planets and stars.

The team, led by Friemann Assistant Professor of Physics at the University of Notre Dame’s Justin R. Crepp, recently released an image of a brown dwarf companion to a star 98 light years or 30 parsecs distant. This discovery marks the first time that a T-dwarf orbiting a Sun-like star with known radial velocity acceleration measurement has been directly imaged.

Located in the constellation Eridanus, the object weighs in at about 52 Jupiter masses, and orbits a 0.95 Sol mass star 51 Astronomical Units (AUs) distant once every 320-1900 years. Note that this wide discrepancy stems from the fact that even though we’ve been following the object for some 17 years since 1996, we’ve yet to ascertain whether we’ve caught it near apastron or periastron yet: we just haven’t been watching it long enough.

The T-dwarf, known as HD 19467 B, may become a benchmark in the study of sub-stellar mass objects that span the often murky bridge between true stars shining via nuclear fusion and ordinary high mass planets.

Brown dwarfs are classified as spectral classes M, L, T, and Y and are generally quoted as having a mass of between 13 to 80 Jupiters. Brown dwarfs utilize a portion of the proton-proton chain fusion reaction to create energy, known as deuterium burning. Low mass red dwarf stars have a mass range of 80 to 628 Jupiters or 0.75% to 60% the mass of our Sun. The Sun has just over 1,000 times Jupiter’s mass.

Researchers used data from the TaRgeting bENchmark-objects with Doppler Spectroscopy (TRENDS) high-contrast imaging survey, and backed it up with more precise measurements courtesy of the Keck observatory’s High-Resolution Echelle Spectrometer or HIRES instrument.

An artist's conception of a T-type brown dwarf. (Credit: Tyrogthekreeper under a Wikimedia Commons Attribution-Share Alike 3.0 Unported license). — An artist’s conception of a T-type brown dwarf. (Credit: Tyrogthekreeper under a Wikimedia Commons Attribution-Share Alike 3.0 Unported license).

TRENDS uses adaptive optics, which relies on precise flexing the telescope mirror several thousands of times a second to compensate for the blurring effects of the atmosphere. Brown dwarfs shine mainly in the infrared, and objects such as HD 19467 B are hard to discern due to their close proximity to their host star. In this particular instance, for example, HD 19467 B was over 10,000 times fainter than its primary star, and located only a little over an arc second away.

“This object is old and cold and will ultimately garner much attention as one of the most well-studied and scrutinized brown dwarfs detected to date,” Crepp said in a recent Keck observatory press release. “With continued follow-up observations, we can use it as a laboratory to test theoretical atmospheric models. Eventually we want to directly image and acquire the spectrum of Earth-like planets. Then, from the spectrum, we should be able to tell what the planet is made of, what its mass is, radius, age, etc… basically all of its relevant properties.

Discovery of an Earth-sized exoplanet orbiting in a star’s habitable zone is currently the “holy grail” of exoplanet science. Direct observation also allows us to pin down those key factors, as well as obtain a spectrum of an exoplanet, where detection techniques such as radial velocity analysis only allow us to peg an upper mass limit on the unseen companion object.

This also means that several exoplanet candidates in the current tally of 1074 known worlds beyond our solar system also push into the lower end of the mass limit for substellar objects, and may in fact be low mass brown dwarfs as well.

Another key player in the discovery was the Near-Infrared Camera (second generation) or NIRC2. This camera works in concert with the adaptive optics system on the Keck II telescope to achieve images in the near infrared with a better resolution than Hubble at optical wavelengths, perfect for brown dwarf hunting. NIRC2 is most well known for its analysis of stellar regions near the supermassive black hole at the core of our galaxy, and has obtained some outstanding images of objects in our solar system as well.

The hexagonal primary mirror of the Keck II telescope. (Credit: SiOwl. A Wikimedia Commons image under a Creative Commons Attribution 3.0 Unported liscense). — The hexagonal primary mirror of the Keck II telescope. (Credit: SiOwl. A Wikimedia Commons image under a Creative Commons Attribution 3.0 Unported license).

What is the significance of the find? Free floating “rogue” brown dwarfs have been directly imaged before, such as the pair named WISE J104915.57-531906 which are 6.5 light years distant and were spotted last year. A lone 6.5 Jupiter mass exoplanet PSO J318.5-22 was also found last year by the PanSTARRS survey searching for brown dwarfs.

“This is the first directly imaged T-dwarf (very cold brown dwarf) for which we have dynamical information independent of its brightness and spectrum,” team lead researcher Justin Crepp told Universe Today.

Analysis of brown dwarfs is significant to exoplanet science as well.

“They serve as an essential link between our understanding of stars and planets,” Mr. Crepp said. “The colder, the better.”

And just as there has been a controversy over the past decade concerning “planethood” at the low end of the mass scale, we could easily see the debate applied to the higher end range, as objects are discovered that blur the line… perhaps, by the 23^rd century, we’ll finally have a Star Trek-esque classifications scheme in place so that we can make statements such as “Captain, we’ve entered orbit around an M-class planet…”

Something that’s always been fascinating in terms of red and brown dwarf stars is also the possibility that a solitary brown dwarf closer to our solar system than Alpha Centauri could have thus far escaped detection. And no, Nibiru conspiracy theorists need not apply. Mr. Crepp notes that while possible, such an object is unlikely to have escaped detection by infrared surveys such as WISE. But what a discovery that’d be!

January 7, 2014December 23, 2015 by Jason Major

Super-sensitive Camera Captures a Direct Image of an Exoplanet

The Gemini Planet Imager’s first light image of Beta Pictoris b (Processing by Christian Marois, NRC Canada)

The world’s newest and most powerful exoplanet imaging instrument, the recently-installed Gemini Planet Imager (GPI) on the 8-meter Gemini South telescope, has captured its first-light infrared image of an exoplanet: Beta Pictoris b, which orbits the star Beta Pictoris, the second-brightest star in the southern constellation Pictor. The planet is pretty obvious in the image above as a bright clump of pixels just to the lower right of the star in the middle (which is physically covered by a small opaque disk to block glare.) But that cluster of pixels is really a distant planet 63 light-years away and several times more massive — as well as 60% larger — than Jupiter!

And this is only the beginning.

GPI installed on the Gemini South 8m telescope. GPI is the boxed suite mounted under the platform. (Gemini Observatory) — GPI installed on the Gemini South 8m telescope. GPI is the boxed suite mounted beneath the platform. (Gemini Observatory)

While many exoplanets have been discovered and confirmed over the past couple of decades using various techniques, very few have actually been directly imaged. It’s extremely difficult to resolve the faint glow of a planet’s reflected light from within the brilliant glare of its star — but GPI was designed to do just that.

“Most planets that we know about to date are only known because of indirect methods that tell us a planet is there, a bit about its orbit and mass, but not much else,” said Bruce Macintosh of the Lawrence Livermore National Laboratory, who led the team that built the instrument. “With GPI we directly image planets around stars – it’s a bit like being able to dissect the system and really dive into the planet’s atmospheric makeup and characteristics.”

And GPI doesn’t just image distant Jupiter-sized exoplanets; it images them quickly.

“Even these early first-light images are almost a factor of ten better than the previous generation of instruments,” said Macintosh. ” In one minute, we were seeing planets that used to take us an hour to detect.”

Despite its large size, Beta Pictoris b is a very young planet — estimated to be less than 10 million years old (the star itself is only about 12 million.) Its presence is a testament to the ability of large planets to form rapidly and soon around newly-formed stars.

“Seeing a planet close to a star after just one minute, was a thrill, and we saw this on only the first week after the instrument was put on the telescope!” added Fredrik Rantakyro a Gemini staff scientist working on the instrument. “Imagine what it will be able to do once we tweak and completely tune its performance.”

Another of GPI’s first-light images captured light scattered by a ring of dust that surrounds the young star HR4796A , about 237 light-years away:

GPI first-light images of HR4796A. (Processing by Marshall Perrin, Space Telescope Science Institute.)

The left image shows shows normal light, including both the dust ring and the residual light from the central star scattered by turbulence in Earth’s atmosphere. The right image shows only polarized light. Leftover starlight is unpolarized and hence removed. The light from the back edge of the disk (to the right of the star) is strongly polarized as it reflects towards Earth, and thus it appears brighter than the forward-facing edge.

It’s thought that the reflective ring could be from a belt of asteroids or comets orbiting HR4796A, and possibly shaped (or “shepherded,” like the rings of Saturn) by as-yet unseen planets. GPI’s advanced capabilities allowed for the full circumference of the ring to be imaged.

The GPI integration team celebrates after obtaining first light images (Gemini Observatory) — The GPI integration team celebrating after obtaining first light images (Gemini Observatory)

GPI’s success in imaging previously-known systems like Beta Pictoris and HR4796A can only indicate many more exciting exoplanet discoveries to come.

“The entire exoplanet community is excited for GPI to usher in a whole new era of planet finding,” says physicist and exoplanet expert Sara Seager of the Massachusetts Institute of Technology. “Each exoplanet detection technique has its heyday. First it was the radial velocity technique (ground-based planet searches that started the whole field). Second it was the transit technique (namely Kepler). Now, it is the ‘direct imaging’ planet-finding technique’s turn to make waves.”

This year the GPI team will begin a large-scale survey, looking at 600 young stars to see what giant planets may be orbiting them.

“Some day, there will be an instrument that will look a lot like GPI, on a telescope in space. And the images and spectra that will come out of that instrument will show a little blue dot that is another Earth.”

– Bruce Macintosh, GPI team leader

The observations above were conducted last November during an “extremely trouble-free debut.” The Gemini South telescope is located near the summit of Cerro Pachon in central Chile, at an altitude of 2,722 meters.

Source: Gemini Observatory press release

January 6, 2014December 23, 2015 by Jason Major

Kepler Finds an Earth-Sized “Gas Giant”

Artist's impression of KOI-xxx, fjkdshfkdsajhkfdkfd

Gas planets aren’t always bloated, monstrous worlds the size of Jupiter or Saturn (or larger) they can also apparently be just barely bigger than Earth. This was the discovery announced earlier today during the 223rd meeting of the American Astronomical Society in Washington, DC, when findings regarding the gassy (but surprisingly small) exoplanet KOI-314c were presented.

“This planet might have the same mass as Earth, but it is certainly not Earth-like,” said David Kipping of the Harvard-Smithsonian Center for Astrophysics (CfA), lead author of the discovery. “It proves that there is no clear dividing line between rocky worlds like Earth and fluffier planets like water worlds or gas giants.”

Discovered by the Kepler space telescope — ironically, during a hunt for exomoons — KOI-314c was found transiting a red dwarf star only 200 light-years away — “a stone’s throw by Kepler’s standards,” according to Kipping. (Kepler’s observation depth is about 3000 light-years.)

Relative size comparison of KOI-314c and Earth; both have similar mass. (J. Major)

Kipping used a technique called transit timing variations (TTV) to study two of three exoplanets found orbiting KOI-314. Both are about 60% larger than Earth in diameter but their respective masses are very different. KOI-314b is a dense, rocky world four times the mass of Earth, while KOI-314c’s lighter, Earthlike mass indicates a planet with a thick “puffy” atmosphere… similar to what’s found on Neptune or Uranus.

Unlike those chilly worlds, though, this newfound exoplanet turns up the heat. Orbiting its star every 23 days, temperatures on KOI-314c reach 220ºF (104ºC)… too hot for water to exist in liquid form and thus too hot for life as we know it.

In fact Kipping’s team found KOI-314c to only be 30 percent denser than water, suggesting that it has a “significant atmosphere hundreds of miles thick,” likely composed of hydrogen and helium.

It’s thought that KOI-314c may have originally been a “mini-Neptune” gas planet and has since lost some of its atmosphere, boiled off by the star’s intense radiation.

Not only is KOI-314c the lightest exoplanet to have both its mass and diameter measured but it’s also a testament to the success and sensitivity of the relatively new TTV method, which is particularly useful in multiple-planet systems where the tiniest gravitational wobbles reveal the presence and details of neighboring bodies.

(Watch the latest Kepler Orrery video here)

“We are bringing transit timing variations to maturity,” Kipping said. He added during the closing remarks of his presentation at AAS223: “It’s actually recycling the way Neptune was discovered by watching Uranus’ wobbles 150 years ago. I think it’s a method you’ll be hearing more about. We may be able to detect even the first Earth 2.0 Earth-mass/Earth-radius using this technique in the future.”

Source: Harvard Smithsonian CfA press release

December 17, 2013December 23, 2015 by Elizabeth Howell

How Scientists Confirmed The Mass Of An Invisible Exoplanet

Artist's conception of Kepler-88. Credit: Center for Astrophysics of the University of Porto

Planets are so very tiny next to stars outside of the solar system, making it really hard to spot exoplanets unless they transit across the face of their star (or if they are very, very big). Often, astronomers can only infer the existence of planets by their effect on the host star or other stars.

That’s especially true of the curious case of Kepler-88 c, which researchers using the Kepler space telescope said was a possible planet due to its effects on the orbit of Kepler-88 b, a planet that goes across the host of its host star. European astronomers just confirmed the Kepler data using the SOPHIE spectrograph at France’s Haute-Provence Observatory.

It’s the first time scientists have successfully used a technique to independently verify a planet’s mass based on what was found from the transit timing variation, or how a planet’s orbit varies from what is expected as it goes across the face of its sun. That means TTV can likely be used as a strong method on its own, advocates say.

Illustration of the Kepler spacecraft (NASA/Kepler mission/Wendy Stenzel)

SOPHIE’s technique relies on measuring star velocity, which also can reveal a planet’s mass by seeing its effect on the star.

“This independent confirmation is a very important contribution to the statistical analyzes of the Kepler multiple planet systems,” stated Magali Deleuil, an exoplanet researcher at Aix-Marseille University who participated in the research. “It helps to better understand the dynamical interactions and the formation of planetary systems.”

Actually, the two planets behave similarly to Earth and Mars in our own solar system in terms of orbits, according to work from a previous team (led by David Nesvorny of the Southwest Research Institute). They predicted the planets have a two-to-one resonance, which is approximately true of our own solar system since Mars takes about two Earth years to orbit the sun.

The new research was led by S.C.C. Barros at Aix-Marseille University in France. You can read the study in the Dec. 17 edition of Astronomy & Astrophysics, or in preprint version on Arxiv.

Source: Center for Astrophysics at the University of Porto