Posted on by Elizabeth Howell

Rocky Alien Planets: What The Heck Is On Their Surfaces?

NASA's Kepler mission confirmed the discovery of its first rocky planet, named Kepler-10b. Measuring 1.4 times the size of Earth, it is the smallest planet ever discovered outside our solar system.

We don’t have the budget yet to send Star Trek‘s U.S.S. Enterprise to probe the surface of strange new worlds, but luckily for humanity, astronomers are figuring out techniques to do that without even needing to leave Earth.

One of Earth’s prolific planet-hunters, the Kepler Space Telescope, has found a lot of planet candidates with rocky surfaces. That’s exciting for astronomers, as rocky planets tend to be smaller than their gas giant counterparts. Also, learning more about rocky planets could give us more clues as to Earth’s history, and that of other planets in our solar system.

But how the heck, from so far away, can we begin to understand the surface? One idea: Check the heat signature, or in more scientific words, look at exoplanets in the infrared part of the light spectrum.

The visible colors, infrared, radio, X-rays and gamma rays are all forms of light and comprise the electromagnetic spectrum. Here you can compare their wavelengths with familiar objects and see how their frequencies (bottom numbers) increase with decreasing wavelength. Credit: ESA
The visible colors, infrared, radio, X-rays and gamma rays are all forms of light and comprise the electromagnetic spectrum. Here you can compare their wavelengths with familiar objects and see how their frequencies (bottom numbers) increase with decreasing wavelength. Credit: ESA

NASA’s Astrobiology Magazine recently published an article about this method, which we encourage you to check out. In summary, the team behind a new research paper (submitted to the Astrophysical Journal) proposes to check out “airless” exoplanets that have surface temperatures below 3,140 degrees Fahrenheit (1,726 Celsius or 2,000 Kelvin.)

Because different kinds of rocks emit “signature” spectrums in different wavelengths, it’s possible we could pick up the signs of silicate rocks or other types of material. There’s a caveat, though.

“With current technology, however, the team cautions that determining surface composition of exoplanets is a very different process than studying their solar system counterparts,” the magazine wrote. “Due to the limits of technology, the team proposes to concentrate on the most prominent mineral signatures detected from exoplanets.”

Check out more details in the scientific journal article here, or the entire Astrobiology Magazine article at this link.

Posted on by Shannon Hall

Blocking Light Sheds New Light on Exoplanet Atmospheres

Kepler-16b is but one example of an uncanny world. It orbits two suns. Credit: Discovery

Exoplanets are uncanny. Some seem to have walked directly out of the best science-fiction movies. For example, we’ve discovered a planet consisting purely of water (GJ 1214b) and one with two suns (Kepler 16b). Some planets nearly scrape their host stars once every orbit, while others exist in darkness without a host star at all. The field of exoplanet research is moving beyond detecting exoplanets to characterizing them – understanding which molecules are present and if they might possibly harbor life.

A key research element in characterizing these alien worlds is observing their atmospheres. But how exactly do astronomers do this? We can’t simply tug the planet toward us to get a closer look.  It’s also incredibly difficult to directly image their atmospheres from afar.  Why? Stars are incredibly bright in comparison to their puny, barely reflective, and nearby exoplanets. So a direct image of an exoplanet’s atmosphere seemed out of the question – until recently.

It may be tricky to directly image an exoplanet’s atmosphere, but astronomers always have quite a few tricks up their sleeves. The first one is in mounting an instrument called a coronagraph on your telescope.  This instrument blocks out the star’s light, leaving an image of the exoplanet alone.  Another trick, known as adaptive optics, is to send a laser beam through the atmosphere.  The changes in the laser allow us to monitor changes in the atmosphere, providing corrections to clean and smooth the image.

HR 8799, a large star orbited by four known giant planets, is relatively nearby (remember that ‘nearby’ is an astronomers way of saying that it is still pretty far, or in this case 130 light years away). In 2008, three of the planets were directly imaged using the Gemini and Keck telescopes on Mauna Kea, Hawaii.  In 2010, the fourth planet, which was closest to the star and therefore the most difficult to see was directly imaged by the Keck telescope.

Direct image of the HR 8799 system. The star has been blocked and all four planets can clearby be seen. Credit: Oppenheimer et al. 2013
Direct image of the HR 8799 system. The star has been blocked and all four planets can clearby be seen. Credit: Oppenheimer et al. 2013

A direct image of an exoplanet’s atmosphere may tell us what color the atmosphere appears to be, and how thick the atmosphere is, but it gives us little more information.  We need to know the atmospheric composition – the specific molecules and their abundances that are present within the atmosphere itself.  If we’re looking at the question of habitability we need to know if there is water in the atmosphere or maybe carbon dioxide.

The key is in mounting a spectrograph on the telescope.  Instead of collecting the overall light from the planet, that light is broken up into a spectrum of wavelengths.  Imagine seeing a rainbow after a thunderstorm.  That rainbow is simply the light from the sun broken up across all visible wavelengths due to ice crystals in our atmosphere.  Molecules emit light at specific wavelengths, leaving well-known fingerprints that may be identified in a lab on Earth, in a rainbow in the sky, or in the spectrum of an exoplanet located 130 light years away.

When astronomers mounted their instrumentation (i.e. a coronagraph, an adaptive optics system, and a spectrograph) known as Project 1640 onboard the Palomar 5m Hale Telescope, they were able to shed new light on the HR 7899 system.  Only last month one of its exoplanets revealed a mixture of water vapor and carbon monoxide in its atmosphere, but the story has changed. See a previous article in Universe Today.

Project 1640 observed not one – but four atmospheres at once.  Gautam Vasisht of JPL explains, “in just one hour, we were able to get precise composition information about four planets around one overwhelmingly bright star.”  These four exoplanets are believed to be coeval, in that they formed from a protoplanetary disk at roughly the same time.  They also have the same luminosity and temperature, leading to the assumption that they are roughly similar to each other.  But results show that they all have radically different spectra, and therefore different chemical compositions!

More specifically, HR 8799 b and d contain carbon dioxide, b and c contain ammonia, d and e contain methane, and b, d, and e contain acetylene.  Noticing a few trends? There really aren’t any! Not only are these planets different from each other, they are also different from any other known objects. Acetylene, for example, has never been convincingly identified in a sub-stellar object outside the solar system.  While the varying spectra pose many questions, one thing is clear: the diversity of planets must be greater than previously thought!

This is only the first exoplanet system for which we’ve obtained direct spectra of all exoplanet atmospheres. Project 1640 will conduct a 3-year survey of 200 nearby stars. The hope is to find hot Jupiters located far from their host star.  While this is what the current technique allows astronomers to detect, it will also teach astronomers how Earth-like planets form.

“The outer giant planets dictate the fate of rocky ones like Earth. Giant planets can migrate in toward a star, and in the process, tug the smaller, rocky planets around or even kick them out of the system. We’re looking at hot Jupiters before they migrate in, and hope to understand more about how and when they might influence the destiny of the rocky, inner planets,” explained Vasisht.

In an attempt to understand our own blue marble, astronomers point their telescopes at uncanny worlds light years away. Project 1640 will block the light of distant stars in order to shed light on distant worlds as well as our own.

Sources: Jet Propulsion Laboratory, and B. R. Oppenheimer et al. 2013 ApJ 768 24

 

Posted on by Nancy Atkinson

More Insight on How NASA Might Revive the Kepler Space Telescope

Artst concept of the Kepler telescope in orbit. Credit: NASA

The future of NASA’s Kepler space telescope mission is in doubt, NASA announced yesterday, as it suffered a failure of a second reaction wheel, losing its ability to precisely point to look for planets orbiting other stars. Reaction wheels enable the spacecraft to aim in different directions without firing thrusters, and the spacecraft needs at least three of the four wheels working to provide the ability to point precisely enough to continue the mission.

But, as we pointed out in our article yesterday, the Kepler team said there are still possibilities of keeping the spacecraft in working order, or perhaps even finding other opportunities for different science for Kepler, something that doesn’t require such precise pointing abilities.

“We’re not ready to call the mission down and out just yet,” said John Grunsfeld, NASA’s associate administrator for the Science Mission Directorate, “but by any measure it’s been a spectacular mission.”

Space expert Scott Hubbard has provided additional insight on the possible ways that NASA could bring the spacecraft back online, and what planet hunters will do next if that’s not possible. Hubbard is a consulting professor of aeronautics and astronautics at Stanford’s School of Engineering, and served as director of NASA Ames Research Center during much of the building phase of the Kepler space telescope. He also worked on the project alongside William Borucki, the Kepler science principal investigator at Ames and the driving force behind the effort, for the decades leading up to formal approval of the mission.

Standford University provided this conversation Hubbard:

Q: How big of a loss will it be if the Kepler space telescope can’t be repaired?

Hubbard: The science returns of the Kepler mission have been staggering and have changed our view of the universe, in that we now think there are planets just about everywhere.

It will be very sad if it can’t go on any longer, but the taxpayers did get their money’s worth. Kepler has, so far, detected more than 2,700 candidate exoplanets orbiting distant stars, including many Earth-size planets that are within their star’s habitable zone, where water could exist in liquid form.

Kepler has done what the program managers said it would do, and that is to give us an inventory of extrasolar planets. It completed its primary observation phase, and had entered its extended science phase. We’re already in the gravy train period – there’s still a year and a half’s worth of data in the pipeline that scientists will analyze to identify other candidate planets, and there will continue to be Kepler science discoveries for quite some time.

Kepler space telescope's field of view. Credit: NASA
Kepler space telescope’s field of view. Credit: NASA

Q: How might NASA engineers go about getting Kepler functional again?

Hubbard: There are two possible ways to salvage the spacecraft that I’m aware of. One is that they could try turning back on the reaction wheel that they shut off a year ago. It was putting metal on metal, and the friction was interfering with its operation, so you could see if the lubricant that is in there, having sat quietly, has redistributed itself, and maybe it will work.

The other scheme, and this has never been tried, involves using thrusters and the solar pressure exerted on the solar panels to try and act as a third reaction wheel and provide additional pointing stability. I haven’t investigated it, but my impression is that it would require sending a lot more operational commands to the spacecraft.

Q: If neither of these options works, Kepler is still an amazing space instrument. Could it conduct other types of experiments?

Hubbard: People have asked about using it to find near-Earth objects, or asteroids. Kepler carries a photometer, not a camera, that looks at the brightness of stars, and so its optics deliberately defocus light from stars to create a nice spread of light on the detector, which is not ideal for spotting asteroids.

Whether or not it could function as a detector for asteroids is something that would have to be studied, but since it wasn’t built as a camera, I would say that I’m skeptical. That said, certainly between Ames Research Center and the Jet Propulsion Laboratory, they’ve got the best people in the world working on it.

Visualization of Kepler's planet candidates shown in transit with their parent stars. Credit: Jason Rowe/Kepler Mission/NASA
Visualization of Kepler’s planet candidates shown in transit with their parent stars. Credit: Jason Rowe/Kepler Mission/NASA

Q: What’s next for exoplanet hunters?

Hubbard: As I said earlier, there is still a year and a half’s worth of data in the pipeline to analyze to identify candidate planets, so there are still discoveries to be made.

It’s important to make clear, though, that in the original queue of missions aimed at finding life elsewhere, a mission like Kepler was a survey mission to establish the statistical frequency of whether these planets are rare or common. It lived the length of its prime mission, and was extremely successful during that time at achieving this goal. It has paved the way for additional missions, such as TESS – Transiting Exoplanet Survey Satellite – and TPF – Terrestrial Planet Finder – which will continue the search for Earth-like exoplanets in the near future.

Posted on by Nancy Atkinson

Using the Theory of Relativity and BEER to Find Exoplanets

"Einstein's planet," formally known as Kepler-76b, is a "hot Jupiter" that orbits its star every 1.5 days. Its diameter is about 25 percent larger than Jupiter and it weighs twice as much. This artist's conception shows Kepler-76b orbiting its host star, which has been tidally distorted into a slight football shape (exaggerated here for effect). The planet was detected using the BEER algorithm, which looked for brightness changes in the star as the planet orbits due to relativistic BEaming, Ellipsoidal variations, and Reflected light from the planet. Credit: David A. Aguilar (CfA)

A new method of detecting alien worlds is full of awesome, as it combines Einstein’s Theory of Relativity along with BEER. No, not the weekend beverage of choice, but the relativistic BEaming, Ellipsoidal, and Reflection/emission modulations algorithm. This new way of finding exoplanets was developed by Professor Tsevi Mazeh and his student, Simchon Faigler, at Tel Aviv University, Israel, and it has been used for the first time to find a distant exoplanet, Kepler-76b, informally named Einstein’s planet.

“This is the first time that this aspect of Einstein’s theory of relativity has been used to discover a planet,” said Mazeh.

The two most-most used and prolific techniques for finding exoplanets are radial velocity (looking for wobbling stars) and transits (looking for dimming stars).

The new method looks for three small effects that occur simultaneously as a planet orbits the star. A “beaming” effect causes the star to brighten as it moves toward us, tugged by the planet, and dim as it moves away. The brightening results from photons “piling up” in energy, as well as light getting focused in the direction of the star’s motion due to relativistic effects.

The team also looked for signs that the star was stretched into a football shape by gravitational tides from the orbiting planet. The star would appear brighter when we observe the “football” from the side, due to more visible surface area, and fainter when viewed end-on. The third small effect is due to starlight reflected by the planet itself.

“This was only possible because of the exquisite data NASA is collecting with the Kepler spacecraft,” said Faigler.

This graphic shows Kepler-76b's orbit around a yellow-white, type F star located 2,000 light-years from Earth in the constellation Cygnus. Although Kepler-76b was identified using the BEER effect (see above), it was later found to exhibit a grazing transit, crossing the edge of the star's face as seen from Earth. Credit: Dood Evan.
This graphic shows Kepler-76b’s orbit around a yellow-white, type F star located 2,000 light-years from Earth in the constellation Cygnus. Although Kepler-76b was identified using the BEER effect (see above), it was later found to exhibit a grazing transit, crossing the edge of the star’s face as seen from Earth.
Credit: Dood Evan.

Although scientists say this new method can’t find Earth-sized worlds using current technology, it offers astronomers a unique discovery opportunity. Unlike radial velocity searches, it doesn’t require high-precision spectra. Unlike transits, it doesn’t require a precise alignment of planet and star as seen from Earth.

“Each planet-hunting technique has its strengths and weaknesses. And each novel technique we add to the arsenal allows us to probe planets in new regimes,” said Avi Loeb from the Harvard-Smithsonian Center for Astrophysics, who first proposed the idea of this planet-hunting method back in 2003.

Kepler-76b is a “hot Jupiter” that orbits its star every 1.5 days. Its diameter is about 25 percent larger than Jupiter and it weighs twice as much. It orbits a type F star located about 2,000 light-years from Earth in the constellation Cygnus.

The planet is tidally locked to its star, always showing the same face to it, just as the Moon is tidally locked to Earth. As a result, Kepler-76b broils at a temperature of about 3,600 degrees Fahrenheit.

Interestingly, the team found strong evidence that the planet has extremely fast jet-stream winds that carry the heat around it. As a result, the hottest point on Kepler-76b isn’t the substellar point (“high noon”) but a location offset by about 10,000 miles. This effect has only been observed once before, on HD 189733b, and only in infrared light with the Spitzer Space Telescope. This is the first time optical observations have shown evidence of alien jet stream winds at work.

The planet has been confirmed using radial velocity observations gathered by the TRES spectrograph at Whipple Observatory in Arizona, and by Lev Tal-Or (Tel Aviv University) using the SOPHIE spectrograph at the Haute-Provence Observatory in France. A closer look at the Kepler data also showed that the planet transits its star, providing additional confirmation.

The paper announcing this discovery has been accepted for publication in The Astrophysical Journal and is available on arXiv.

Source: CfA

Posted on by Tammy Plotner

Hubble Observes Planet-“Polluted” Dead Stars In Hyades

Artist Impression of debris around a white dwarf star. Image credit: NASA, ESA, STScI, and G. Bacon (STScI)

For those of us who practice amateur astronomy, we’re very familiar with the 150 light-year distant Hyades star cluster – one of the jewels in the Taurus crown. We’ve looked at it countless times, but now the NASA/ESA Hubble Space Telescope has taken its turn observing and spotted something astronomers weren’t expecting – the debris of Earth-like planets orbiting white dwarf stars. Are these “burn outs” being polluted by detritus similar to asteroids? According to researchers, this new observation could mean that rocky planet creation is commonplace in star clusters.

“We have identified chemical evidence for the building blocks of rocky planets,” said Jay Farihi of the University of Cambridge in England. He is lead author of a new study appearing in the Monthly Notices of the Royal Astronomical Society. “When these stars were born, they built planets, and there’s a good chance they currently retain some of them. The material we are seeing is evidence of this. The debris is at least as rocky as the most primitive terrestrial bodies in our solar system.”

So what makes this an uncommon occurrence? Research tells us that all stars are formed in clusters, and we know that planets form around stars. However, the equation doesn’t go hand in hand. Out of the hundreds of known exoplanets, only four are known to have homes in star clusters. As a matter of fact, that number is a meager half percent, but why? As a rule, the stars contained within a cluster are young and active. They are busy producing stellar flares and similar brilliant activity which may mask signs of emerging planets. This new research is looking to the “older” members of the cluster stars – the grandparents which may be babysitting.

To locate possible candidates, astronomers have employed Hubble’s Cosmic Origins Spectrograph and focused on two white dwarf stars. Their return showed evidence of silicon and just slight levels of carbon in their atmospheres. This observation was important because silicon is key in rocky materials – a prime ingredient on Earth’s list and other similar solid planets. This silicon signature may have come from the disintegration of asteroids as they wandered too close to the stars and were torn apart. A lack of carbon is equally exciting because, while it helps shape the properties and origins of planetary debris, it becomes scarce when rocky planets are formed. This material may have formed a torus around the defunct stars which then drew the matter towards them.

“We have identified chemical evidence for the building blocks of rocky planets,” said Farihi. “When these stars were born, they built planets, and there’s a good chance they currently retain some of them. The material we are seeing is evidence of this. The debris is at least as rocky as the most primitive terrestrial bodies in our solar system.”

Ring around the rosie? You bet. This leftover material swirling around the white dwarf stars could mean that planet formation happened almost simultaneously as the stars were born. At their collapse, the surviving gas giants may have had the gravitational “push” to relocate asteroid-like bodies into “star-grazing orbits”.

This image shows the region around the Hyades star cluster, the nearest open cluster to us. The Hyades cluster is very well-studied due to its location, but previous searches for planets have produced only one. A new study led by Jay Farihi of the University of Cambridge, UK, has now found the atmospheres of two burnt-out stars in this cluster — known as white dwarfs — to be “polluted” by rocky debris circling the star. Inset, the locations of these white dwarf stars are indicated — stars known as WD 0421+162, and WD 0431+126. Credit: NASA, ESA, STScI, and Z. Levay (STScI)
This image shows the region around the Hyades star cluster, the nearest open cluster to us. The Hyades cluster is very well-studied due to its location, but previous searches for planets have produced only one. A new study led by Jay Farihi of the University of Cambridge, UK, has now found the atmospheres of two burnt-out stars in this cluster — known as white dwarfs — to be “polluted” by rocky debris circling the star.
Inset, the locations of these white dwarf stars are indicated — stars known as WD 0421+162, and WD 0431+126. Credit: NASA, ESA, STScI, and Z. Levay (STScI)

“We have identified chemical evidence for the building blocks of rocky planets,” explains Farihi. “When these stars were born, they built planets, and there’s a good chance that they currently retain some of them. The signs of rocky debris we are seeing are evidence of this — it is at least as rocky as the most primitive terrestrial bodies in our Solar System. The one thing the white dwarf pollution technique gives us that we won’t get with any other planet detection technique is the chemistry of solid planets. Based on the silicon-to-carbon ratio in our study, for example, we can actually say that this material is basically Earth-like.”

What of future plans? According to Farihi and the research team, by continuing to observe with methods like those employed by Hubble, they can take an even deeper look at the atmospheres around white dwarf stars. They will be searching for signs of solid planet “pollution” – exploring the white dwarf chemistry and analyzing stellar composition. Right now, the two “polluted” Hyades white dwarfs are just a small segment of more than a hundred future candidates which will be studied by a team led by Boris Gansicke of the University of Warwick in England. Team member Detlev Koester of the University of Kiel in Germany is also contributing by using sophisticated computer models of white dwarf atmospheres to determine the abundances of various elements that can be traced to planets in the Hubble spectrograph data.

“Normally, white dwarfs are like blank pieces of paper, containing only the light elements hydrogen and helium,” Farihi said. “Heavy elements like silicon and carbon sink to the core. The one thing the white dwarf pollution technique gives us that we just won’t get with any other planet-detection technique is the chemistry of solid planets.”

The team also plans to look deeper into the stellar composition as well. “The beauty of this technique is that whatever the Universe is doing, we’ll be able to measure it,” Farihi said. “We have been using the Solar System as a kind of map, but we don’t know what the rest of the Universe does. Hopefully with Hubble and its powerful ultraviolet-light spectrograph COS, and with the upcoming ground-based 30- and 40-metre telescopes, we’ll be able to tell more of the story.”

And we’ll be listening…

Original Story Source: Hubble News Release.

Posted on by Nancy Atkinson

Watch Live Hangout: TESS and the Search for Exoplanets

Artist's rendition of TESS in space. (Credit: MIT Kavli Institute for Astrophysics Research).

Last month, NASA announced plans to launch the Transiting Exoplanet Survey Satellite (TESS) in 2017. This is a satellite that will perform an all-sky survey to discover transiting exoplanets in orbit around the brightest stars in the Sun’s neighborhood. “TESS will carry out the first space-borne all-sky transit survey, covering 400 times as much sky as any previous mission,” said George Ricker, the mission’s principal investigator. “It will identify thousands of new planets in the solar neighborhood, with a special focus on planets comparable in size to the Earth.”

Read more about the TESS mission here.

Today, Wednesday May 1, at 19:00 UTC (12:00 p.m. PDT, 3:00 pm EDT) you can take part in a live Google+ Hangout, and have your questions answered about TESS and the search for exoplanets with three leading members of NASA’s TESS mission:

George Ricker is principal investigator of the TESS mission and a senior research scientist at the MIT Kavli Institute for Astrophysics and Space Research (MKI) in Cambridge, Mass.

Sara Seager is a professor of planetary science and physics at MKI and a member of the TESS team. Seager’s research focuses on computer models of exoplanet atmospheres, interiors and biosignatures.

Joshua Winn is an associate professor of physics at MKI and deputy science director for the TESS mission. Winn is interested in the properties of planets around other stars, how planets form and evolve, and whether there are habitable planets beyond Earth.

Watch in the viewer above, or at the Kavli Foundation website.

Questions can be submitted ahead of and during this special event via Twitter using the hashtag #KavliAstro and by email to [email protected].

Posted on by Elizabeth Howell

How Do You Measure A Planet Near A Tiny Star?

Artist's conception of the Kepler Space Telescope. Credit: NASA/JPL-Caltech

When you sit back and think about how far away exoplanets are — and how faint — it’s a scientific feat that we can find these distant worlds outside our Solar System at all. It’s even harder to learn about the world if the exoplanet is orbiting a dim star — say, about two-thirds the size of the Sun — that is faint through even the largest telescope.

In response to this problem, there’s one science team that thinks it’s found a way to solve it. Their research bumped a planet from the habitable zone to the not-so-friendly zone of a star. Here’s how it happened:

The usual way to measure a distant star is this: look at the light. A Sun-sized star, for example, would have its light waves measured at different wavelengths. Scientists then match what they see to spectra (light bands) that are created artificially.

This method doesn’t work so well for smaller stars, though. “The challenge is that small stars are incredibly difficult to characterize,” stated Sarah Ballard, a post-doctoral researcher at the University of Washington, in a press release. Worse, these small guys make up about two-thirds of the stars in the universe.

Red Dwarf star and planet. Artists impression (NASA)
Red Dwarf star and planet. Artists impression (NASA)

Ballard led a multi-university team describing a “characterization by proxy” method accepted for publication in The Astrophysical Journal and now available online.

The science team based their work on previous research performed by astronomer Tabetha Boyajian, who is currently at Yale University.

Boyajian combined the resources of several telescopes that measured wavelengths of light, wavelengths that are slightly longer than visible light. This technique allowed the interferometer (the combined telescopes) to figure out the size of stars that are close by.

With that data on hand, Ballard and her colleagues looked out into the universe. Their target was Kepler-61b (Kepler Object 1361.01), a “candidate” planet about double the size of Earth spotted by the planet-hunting Kepler space telescope. The candidate, if proven, is orbiting a low-mass star 900 light-years away that is hard to measure in a telescope.

Kepler space telescope's field of view. Credit: NASA
Kepler space telescope’s field of view. Credit: NASA

Next, the scientists picked four nearby stars that have similar light patterns, reasoning that they would be spectroscopially close enough to Kepler-61b’s parent star to make accurate measurements. The four stars are located in Ursa Major and Cygnus, ranging between 12 to 25 light years away from Earth.

When the scientists compared the measurements to Kepler 61’s star, a surprise emerged.

“Kepler-61 turned out to be bigger and hotter than expected,” the University of Washington stated. “This in turn recalibrated planet Kepler-61b’s relative size upward as well — meaning it, too, would be hotter than previously thought and no longer a resident of the star’s habitable zone.”

The newly refined planetary radius for Kepler-61b is 2.15 times the radius of Earth (plus or minus 0.13 radii). Astronomers estimate it orbits its star about once every 59.9 days and has a temperature of 273 Kelvin (plus or minus 13 Kelvin.)

Artist's impression of the habitable zone around variously sized stars. Credit: NASA
Artist’s impression of the habitable zone around variously sized stars. Credit: NASA

Just to wrap up, here’s a note about how likely it is that Kepler-61b is actually a planet — and not a planetary candidate.

The candidate was first described in this 2011 scientific paper. Kepler-61b is just one in a long list of 1,235 planetary candidates catalogued in that paper, all discovered in just four months — between May 2 and Sept. 16, 2009.

While the NASA Exoplanet Archive still lists Kepler-61b as a candidate planet — one that must be confirmed by independent observations — this 2011 paper says that most Kepler candidates have a strong possibility of being actual planets because the Kepler software is technologically apt.

In other words, Ballard and her co-authors write in the research, Kepler-61b is very likely to be a planet itself — with only 4.8 percent possibility of being a “false positive”, to be exact.

Source: University of Washington

Posted on by Nancy Atkinson

Habitable Worlds? New Kepler Planetary Systems in Images

Relative sizes of Kepler habitable zone planets discovered as of 2013 April 18. Left to right: Kepler-22b, Kepler-69c, Kepler-62e, Kepler-62f, and Earth (except for Earth, these are artists' renditions). Credit: NASA/Ames/JPL-Caltech.

The Kepler mission has discovered two new planetary systems that include three super-Earth-size planets in the “habitable zone,” the range of distance from a star where the surface temperature of an orbiting planet might be suitable for liquid water.

The Kepler-62 system has five planets; 62b, 62c, 62d, 62e and 62f. The Kepler-69 system has two planets; 69b and 69c. Kepler-62e, 62f and 69c are the super-Earth-sized planets. (Read all the details in our full article here.)

The new planets brings the number of confirmed exoplanets to 861. According to the Planetary Habitability Laboratory, there are now nine potential habitable worlds outside of our solar system, with 18 more potentally habitable planetary candidates found by Kepler waiting to be confirmed. Additionally, astronomers predict there are 25 potentially habitable exomoons.

Here is some of the imagery (sorry, but they are artists concepts!), graphs and video used in today’s briefing about the new discoveries, as well as some some from the Planetary Habitability Laboratory:

Here’s a flythrough of the Kepler 62 system:

The diagram compares the planets of the inner solar system to Kepler-69, a two-planet system about 2,700 light-years from Earth. Image credit: NASA Ames/JPL-Caltech
The diagram compares the planets of the inner solar system to Kepler-69, a two-planet system about 2,700 light-years from Earth.
Image credit: NASA Ames/JPL-Caltech
Much like our solar system, Kepler-62 is home to two habitable zone worlds. The small shining object seen to the right of Kepler-62f is Kepler-62e. Orbiting on the inner edge of the habitable zone, Kepler-62e is roughly 60 percent larger than Earth. Image credit: NASA Ames/JPL-Caltech.
Much like our solar system, Kepler-62 is home to two habitable zone worlds. The small shining object seen to the right of Kepler-62f is Kepler-62e. Orbiting on the inner edge of the habitable zone, Kepler-62e is roughly 60 percent larger than Earth. Image credit: NASA Ames/JPL-Caltech.
The diagram compares the planets of the inner solar system to Kepler-62, a five-planet system about 1,200 light-years from Earth. Image credit: NASA Ames/JPL-Caltech
The diagram compares the planets of the inner solar system to Kepler-62, a five-planet system about 1,200 light-years from Earth. Image credit: NASA Ames/JPL-Caltech
Current known potentially habitable exoplanets. Credit: Planetary Habitability Laboratory/University of Puerto Rico, Arecibo.
Current known potentially habitable exoplanets. Credit: Planetary Habitability Laboratory/University of Puerto Rico, Arecibo.
Current potentially habitable exoplanets showing the new additions, Kepler-62e and Kepler-62f. Credit: Planetary Habitability Laboratory/University of Puerto Rico, Arecibo.
Current potentially habitable exoplanets showing the new additions, Kepler-62e and Kepler-62f. Credit: Planetary Habitability Laboratory/University of Puerto Rico, Arecibo.
Comparison of the orbit and size of the exoplanets of Kepler-62 with the terrestrial planets of our Solar Systems. The darker green shaded area corresponds to the 'conservative habitable zone' while its lighter borders to its 'optimistic habitable zone' extension. Planet sizes and orbits are not to scale between them. Credit: Planetary Habitability Laboratory/University of Puerto Rico, Arecibo.
Comparison of the orbit and size of the exoplanets of Kepler-62 with the terrestrial planets of our Solar Systems. The darker green shaded area corresponds to the ‘conservative habitable zone’ while its lighter borders to its ‘optimistic habitable zone’ extension. Planet sizes and orbits are not to scale between them. Credit: Planetary Habitability Laboratory/University of Puerto Rico, Arecibo.

Posted on by Nancy Atkinson

Kepler Team Finds System with Two Potentially Habitable Planets

The newly discovered planets named Kepler-62e and -f are super-Earths in the habitable zone of a distant sun-like star. The largest planet in the image, Kepler-62f, is farthest from its star and covered by ice. Kepler-62e, in the foreground, is nearer to its star and covered by dense clouds. Closer in orbits a Neptune-size ice giant with another small planet transiting its star. Both habitable-zone planets may be capable of supporting life. Credit: David A. Aguilar (CfA)

This might be the most exciting exoplanet news yet. An international team of scientists analyzing data from NASA’s Kepler mission has found a planetary system with two small, potentially rocky planets that lie within the habitable zone of their star. The star, Kepler-62, is a bit smaller and cooler than our Sun, and is home to a five-planet system. Two of the worlds, Kepler-62e and Kepler-62f are the smallest exoplanets yet found in a habitable zone, and they might both be covered in water or ice, depending on what kind of atmosphere they might have.

“Imagine looking through a telescope to see another world with life just a few million miles from your own. Or, having the capability to travel between them on a regular basis. I can’t think of a more powerful motivation to become a space-faring society,” said Harvard astronomer Dimitar Sasselov, who is co-author of a new paper describing the discovery.

Masses and sizes for selected planets. The curves show the mass-radius-relation (average density) for different types of planets: The blue line indicates the loci of planets made mostly (75%) of water, the black line that of planets like our Earth that consist almost exclusively of rock (represented here by the mineral Enstatite, MgSiO3, a member of the pyroxite silicate mineral series that makes up most of the Earth's mantle), and so on. The measured radii of Kepler-62e and Kepler-62f plus an estimate of their mass places them in a region (blue areas) where it is highly probable for them to be earth-like planets, that is: planets with a solid (if possibly covered in water) surface. Kepler-11f, on the other hand, is a Mini-Neptune, showing clearly that a comparatively low mass does not necessarily make for a solid planet. Image: L. Kaltenegger (MPIA)
Masses and sizes for selected planets. The curves show the mass-radius-relation (average density) for different types of planets: The blue line indicates the loci of planets made mostly (75%) of water, the black line that of planets like our Earth that consist almost exclusively of rock (represented here by the mineral Enstatite, MgSiO3, a member of the pyroxite silicate mineral series that makes up most of the Earth’s mantle), and so on. The measured radii of Kepler-62e and Kepler-62f plus an estimate of their mass places them in a region (blue areas) where it is highly probable for them to be earth-like planets, that is: planets with a solid (if possibly covered in water) surface. Kepler-11f, on the other hand, is a Mini-Neptune, showing clearly that a comparatively low mass does not necessarily make for a solid planet. Image: L. Kaltenegger (MPIA)

Kepler-62 in the constellation Lyra, and is about 1,200 light-years from Earth.

62e is 1.61 times Earth’s size, circles the star in 122.4 (Earth) days. 62f is 1.4 times the size of Earth, and orbits its star in 267.3 days. Previously, the smallest planet with known radius inside a habitable zone was Kepler-22b, with a radius of 2.4 times that of the Earth.

A third planet in another star system was also announced at a press briefing today. Kepler-69c is 70 percent larger than the size of Earth, and orbits in the habitable zone of a star similar to our Sun. Researchers are uncertain about the composition of Kepler-69c, but astronomer Thomas Barclay from the BAER Institute said its closer orbit of 242 days around a Sun-like star means it is likely more like a super-Venus rather than a super-Earth.

The habitable zone (in which liquid water on a planet's surface can exist) for different types of stars. The inner planets of our Solar System are shown on top, with Earth and Mars in the habitable zone. Kepler-62 is a notably cooler star, and Kepler-62e and -62f are in its habitable zone. For Kepler-69c, another planet announced today by NASA, the error bars for the star's radiation are such that it could possibly in the habitable zone as well. Kepler-22b, the smallest planet found in a habitable zone before the recent discoveries, is very likely a Mini-Neptune, and not a solid planet. In what is denoted the empirical habitable zone, liquid water can exist on the surface of a planet if that planet has sufficient cloud cover. In the narrow habitable zone, liquid water can exist on the surface even without the presence of a cloud cover. Image: L. Kaltenegger (MPIA)
The habitable zone (in which liquid water on a planet’s surface can exist) for different types of stars. The inner planets of our Solar System are shown on top, with Earth and Mars in the habitable zone. Kepler-62 is a notably cooler star, and Kepler-62e and -62f are in its habitable zone. For Kepler-69c, another planet announced today by NASA, the error bars for the star’s radiation are such that it could possibly in the habitable zone as well. Kepler-22b, the smallest planet found in a habitable zone before the recent discoveries, is very likely a Mini-Neptune, and not a solid planet. In what is denoted the empirical habitable zone, liquid water can exist on the surface of a planet if that planet has sufficient cloud cover. In the narrow habitable zone, liquid water can exist on the surface even without the presence of a cloud cover. Image: L. Kaltenegger (MPIA)

The team says that while the sizes of Kepler 62e and 62f are known, their mass and densities are not. However, every planet found in their size range so far has been rocky, like Earth.

Kepler-62 system. Five planets, two of which are in the Habitable Zone. Credit: NASA
Kepler-62 system. Five planets, two of which are in the Habitable Zone. Credit: NASA

“These planets are unlike anything in our solar system. They have endless oceans,” said lead author Lisa Kaltenegger of the Max Planck Institute for Astronomy and the Harvard Smithsonian Center for Astrophysics. “There may be life there, but could it be technology-based like ours? Life on these worlds would be under water with no easy access to metals, to electricity, or fire for metallurgy. Nonetheless, these worlds will still be beautiful blue planets circling an orange star — and maybe life’s inventiveness to get to a technology stage will surprise us.”

As the warmer of the two worlds, Kepler-62e would have a bit more clouds than Earth according to computer models. More distant Kepler-62f would need the greenhouse effect from plenty of carbon dioxide to warm it enough to host an ocean. Otherwise, it might become an ice-covered snowball.

“Kepler-62e probably has a very cloudy sky and is warm and humid all the way to the polar regions. Kepler-62f would be cooler, but still potentially life-friendly,” said Harvard astronomer and co-author Dimitar Sasselov. “The good news is — the two would exhibit distinctly different colors and make our search for signatures of life easier on such planets in the near future. “

The Kepler spacecraft is able to detect planets that transit or cross the face of their host star. Measuring a transit tells astronomers the size of the planet relative to its star.

“All of the other interesting planets in the habitable zone were until now discovered by what is known as the radial velocity method,” said Kaltenegger. “This method gives you a lower limit for the planet’s mass, but no information about its radius. This makes it difficult to assess whether or not a planet is rocky, like the Earth. A small radius (less than 2 Earth radii), on the other hand, is a strong indicator that a planet around is indeed rocky – unless we are talking about a planet around a very young star.”

“What makes Kepler-62e and Kepler-62f so exciting is a combination of two factors,” Kaltenegger added. “We know their radius, which indicates that these are indeed rocky planets, and they orbit their star in the habitable zone. That makes them our best candidates for habitable planets out there yet.

Kaltenegger provides more details on these exoplanets in this video:

Sources: Max Planck Institute for Astronomy, CfA

Posted on by Nancy Atkinson

The Exoplanet Naming Debate Heats Up

An artist's impression of an extra solar planet Photo credit: David A Hardy, astroart.org Copyright: STFC.

Following last Friday’s press release from the International Astronomical Union (IAU) concerning the naming of extrasolar planets, a heated debate has arisen over two separate but related issues. One is the “official” vs. “popular” names of astronomical objects (and the IAU’s jurisdiction over them) and the other is Uwingu’s intentions in their exoplanet naming contests.

We’re going to talk about the latter first, as this seems to be where much of the contention lies.

As has been reflected in our articles, Universe Today feels that Uwingu has always been upfront that the names chosen in their exoplanet naming contests were never meant to be “officially” recognized by the IAU, but instead are a way to engage the public and to create non-governmental funding for space research. As we said in our article on Nov. 7, 2012 about the first contest that creates a “baby book” of exoplanet names:

The names won’t be officially approved by the International Astronomical Union, but (Alan) Stern said they will be are similar to the names given to features on Mars by the mission science teams (such as the “Jake Matijevic” rock recently analyzed by the Curiosity rover) that everyone ends up using. This also solves the problem of how to come up with names, a task that the IAU has yet to discuss.

Please read these articles on Time and New Scientist which explicitly quote Uwingu CEO Alan Stern as saying the names generated by Uwingu’s contest will not be officially recognized by the IAU, but are a way to get the public involved and excited about exoplanets.

Anyone who implies that Uwingu is like the ‘name a star’ scams, or that they are out to make money to line their own pockets is completely misreading Uwingu’s website and completely missing the point. The profits go towards science research and education. So far Uwingu has given approximately $5,500 to several projects: Astronomers Without Borders, the Galileo Teacher Training Program, the Purdue Multiethnic Training Program, and the Allen Telescope Array for SETI.

Additionally, as the Uwingu Twitter feed confirmed, “No one at Uwingu has ever been paid, we have all worked for free from the start.”

The IAU’s statement on Friday infers that Uwingu is trying to sell “the rights to name exoplanets” and today Uwingu issued a statement that says the IAU’s press release “significantly mischaracterized Uwingu’s People’s Choice contest and Uwingu itself.”

As astronomer Carolyn Collins Petersen wrote on her Spacewriter’s Ramblings blog, nowhere on Uwingu’s website does it say that you’re buying the right to name a planet, as seems to be suggested by the IAU press release.

“If you donate a few dollars, you get to suggest a name,” she wrote. “You donate a few cents and you can vote for the coolest names. The coolest names win prizes. The money goes to research and education.”

And Stern has said the time has come where exoplanets should be named: “The IAU has had ten years to do something about this and they haven’t done anything,” he told Universe Today previously. “What we’re doing might be controversial, but that’s OK. It’s time to step up to the plate and do something.”

And many agree with his point that since the public is obviuosly intrigued and interested in exoplanets, they should be involved in the naming process, if only to suggest names. And as we’ve said before, since the IAU has said it will be difficult to come up with names since there are now hundreds of known explanets, Uwingu’s projects fits the bill of what is needed.

Also from Uwingu’s statement today:

Uwingu affirms the IAU’s right to create naming systems for astronomers. But we know that the IAU has no purview — informal or official — to control popular naming of bodies in the sky or features on them, just as geographers have no purview to control people’s naming of features along hiking trails. People clearly enjoy connecting to the sky and having an input to common-use naming. We will continue to stand up for the public’s rights in this regard, and look forward to raising more grant funds for space researchers and educators this way.

Over the weekend, the debate raged on the various social media outlets, and astronomer Jason Wright wrote a blog post that called out the IAU’s statement, saying it couldn’t be the official IAU policy, because “IAU policy is determined by democratic vote of its commissions and General Assembly. Neither has endorsed any nomenclature for planets, much less the assertions of the press release.”

Wright added that he contacted a member of Commission 53 (the IAU committee that will discuss the future of exoplanet naming) “and learned that they were not consulted for or even informed of this press release before it went out, and that the commission has not established a naming process since it met in Beijing in 2012.”

As far as the difference between “official” and “common” names, the IAU said in their press release that a “clear and systematic system for naming these objects is vital. Any naming system is a scientific issue that must also work across different languages and cultures in order to support collaborative worldwide research and avoid confusion.”

However, many people have pointed out that other sciences — like biology – have scientific names and common names that are both used and there doesn’t appear to be rampant confusion over this.

But stars can have several names as well, as astronomer Stuart Lowe wrote in his Astroblog, “Currently stars can have one proper name but also be in many different catalogues with different IDs.”

Uwingu pointed out in their statement that the star Polaris (its well-known common name!) is also known as the North Star, Alpha Ursae Minoris, HD 8890, HIP 11767, SAO 308, ADS 1477, FK5 907, and over a dozen more designations.

Uwingu also noted how non-scientific, informal names are prevalent in astronomy. Our own Milky Way galaxy is a great example, and “there are many instances where astronomers name things without going through the IAU’s internal process. There are many of features on Mars, ranging from mountains to individual rocks, with names applied by Mars-mission scientists and never adopted by, or even considered by, the IAU. And Apollo astronauts did not seek IAU permission before naming features at their landing sites or from orbit.”

Also, recent press releases reflect where astronomical objects were given names by astronomers without any IAU process such as Supernova Wilson, Galaxy cluster “El Gordo,” and the “Black Eye Galaxy.” “None drew attention from the IAU,” Uwingu said.

Planetary scientist and educator David Grinspoon (who is on Uwingu’s board of advisors) probably summed it up best in a comment he posted on Universe Today: “IAU maintains names for astronomers and that’s fine, but they do not own the sky. Planets are PLACES not just astronomical research objects, and if informal names for these places proliferate, outside of some self-appointed professional “authority”, and the public at large is more engaged in the exoplanet revolution, that is a very good thing indeed.”