Everyone is familiar with the fact that the moon changes phases. But what many don’t know is that planets also go through phases. Shown above are the phases for Venus. We look inwards on Venus from a more distant vantage point in our solar system, but in principle, planets in other solar systems would also go through phases as they orbited. While we are far too distant to resolve these phases any time soon, the percentage of reflected light may give clues about the size, composition, and atmosphere of a potential planet.
A new study by astronomers at the University of Bordeaux in France, analyzes differences in the way light would be reflected from various exoplanet configurations.
In a previous paper by the same team, they had analyzed how much light planets at different phases should reflect in different wavelengths of light in the infrared. Planets with atmospheres showed significant lack of emission at some wavelengths while rocky planets with no atmosphere reflected most strongly at one wavelength and faded smoothly off. The heavier the atmosphere, the more pronounced this effect was. As such, the team concluded that simply by looking at the reflected light in a few wavelengths, they could quickly determine whether the planet were likely to have an atmosphere.
The new paper adds to this by exploring what the effects of properties such as stellar type, orbital distance, radius of the planet, and inclination would have on these observations. They found that the presence of an atmosphere made determining many of these properties more difficult since it would be able to retain heat and reradiate it different manners instead of simply reflecting.
Rocky, airless planets were simpler and the light curves could be used more directly to determine the radius of the planet with an accuracy of about 10% with an instrument such as the James Webb Space Telescope. The orbital inclination could be narrowed down to within 10°. Currently, the only way astronomers can determine this property is if the planet is in the narrow ranges of inclination that allow it to transit the star, so while observing the phases to determine this property leaves large uncertainties, it is a start at the very least. These observations could also be used to determine the albedo, or reflectivity of the planet. This property could be used to help constrain the possible chemicals on the surface or in the atmosphere.
Artst concept of the Kepler telescope in orbit. Credit: NASA
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Once again news from the Kepler mission is making the rounds, this time with a research paper outlining a theory that Earth-like planets may be more common around class F, G and K stars than originally expected.
In the standard stellar classification scheme, these type of stars are similar or somewhat similar to our own Sun (which is a Class G star); Class F stars are hotter and brighter and Class K stars are cooler and dimmer. Given this range of stars, the habitable zones vary with different stars. Some habitable planets could orbit their host star at twice the distance Earth orbits our Sun or in the case of a dim star, less than Mercury’s orbit.
How does this recent research show that small, rocky, worlds may be more common that originally thought?
Dr. Wesley Traub, Chief Scientist with NASA’s Exoplanet Exploration Program outlines his theory in a recent paper submitted to the Astrophysical Journal. A possible habitable world? Credit: NASA/JPL
Based on Traub’s calculations in his paper, he formulates that roughly one-third of class F, G, and K stars should have at least one terrestrial, habitable-zone planet. Traub bases his assertions on data from the first 136 days of Kepler’s mission.
Initially starting with 1,235 exoplanet candidates, Traub narrowed the list down to 159 exoplanets orbiting F class stars, 475 orbiting G class stars, and 325 orbiting K class stars – giving a total of 959 exoplanets in his model. For the purposes of Traub’s model, he defines terrestrial planets as those with a radius of between half and twice that of Earth. The mass ranges specified in the model work out to between one-tenth Earth’s mass and ten times Earth’s mass – basically objects ranging from Mars-sized to the theoretical super-Earth class.
The paper specifies three different ranges for the habitable zone: A “wide” habitable zone (HZ) from 0.72 to 2.00 AU, a more restrictive HZ from 0.80 to 1.80 AU, and a narrow/conservative HZ of 0.95 to 1.67 AU.
After working through the necessary math of his model, and coming up with a “power law” that gives a habitable zone to a star depending on its class and then working out how many planets ought to be at those distances, Traub estimated the frequency of terrestrial, habitable-zone planets around Sun-like (Classes F, G and K) stars at (34 ± 14)%.
He added that mid-size terrestrial planets are just as likely to be found around faint stars and bright ones, even though fewer small planets show up around faint stars. But that is likely because of the limits of our currently technology, where small planets are more difficult for Kepler to see, and it’s easier for Kepler to see planets that orbit closer to their stars.
Traub discussed how the quoted uncertainty is the formal error in projecting the numbers of short-period planets, and that the true uncertainty will remain unknown until Kepler observations of orbital periods in the 1,000-day range become available.
Artist’s impression of a Super-Earth planet orbiting a Sun-like star. Credit: ESO/M. Kornmesser
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Yesterday astronomers with the High Accuracy Radial velocity Planet Searcher or HARPS, announced a record-breaking discovery of more than fifty new exoplanets. This is the largest batch of confirmed extra solar planets ever announced at once. Another reason the discovery is noteworthy is that sixteen of the planets that were detected fall under the “super-Earth” classification, meaning the planets are thought to be rocky worlds less than ten times Earth’s mass.
The HARPS team, led by Michel Mayor from the University of Geneva, used the 3.6-metre telescope at ESO’s La Silla Observatory in Chile and claim their spectrograph instrument on the telescope is the most successful planet-finder to date. The team’s data suggests that about 40% of stars similar to our Sun have at least one planet less massive than Saturn.
The announcement of the big planetary haul was made at the Extreme Solar Systems II exoplanet conference taking place this week in Wyoming in the US.
How did Mayor and his team discover so many planets, and how are they certain of their findings?
The HARPS instrument uses a technique called “radial velocity”. Essentially, the instrument detects the slight movement of a star moving toward and away from observers on Earth. The changes in radial velocity shift the star’s light spectrum. When the star moves away from observers on Earth, the light is shifted to longer, redder wavelengths, called redshifting. When the star moves toward Earth, the opposite happens and the star’s light is blueshifted. Through various hardware and software upgrades over the years, HARPS is now so sensitive, it can detect radial velocities of about 1 meter per second and exoplanets less than twice the mass of Earth.
The radial velocity method of exoplanet detection that HARPS uses is different from say, the Kepler mission which uses the “transit” method to detect exoplanet candidates. The transit method, comparatively speaking, still uses the light from a distant star, but instead of measuring redshift or blue shift, Kepler instead looks for a dimming of the star’s light as exoplanets pass in front of their host star.
HARPS has been operating for the past eight years, using the radial velocity technique to discover over 150 new planets. HARPS has also detected a considerable portion of the known exoplanets less massive than Neptune (seventeen Earth masses). “The harvest of discoveries from HARPS has exceeded all expectations and includes an exceptionally rich population of super-Earths and Neptune-type planets hosted by stars very similar to our Sun. And even better — the new results show that the pace of discovery is accelerating,” said Mayor.
Image of the star HD 85512 using red and blue filters. The diffraction spikes are due to the telescope itself and are not caused by the star . Image Credit: ESO/Davide De Martin and Digitized Sky Survey 2. One particular exoplanet Mayor and his team cited was HD85512b, estimated to be just over 3.5 times Earth’s mass. “The detection of HD 85512 b is far from the limit of HARPS and demonstrates the possibility of discovering other super-Earths in the habitable zones around stars similar to the Sun,” added Mayor. HD 85512b also happens to be situated on the edge of the “habitable zone” around its parent star – a zone where conditions could allow for water on the surface of a planet orbited in said zone.
Based on these latest findings, as well as previous HARPS discoveries, the team plans to install an exact copy of the HARPS instrumentation on the Telescopio Nazionale Galileo in the Canary Islands. The duplicate HARPS will allow scientists to survey stars in the northern sky.
“In the coming ten to twenty years we should have the first list of potentially habitable planets in the Sun’s neighborhood,” Mayor said. “Making such a list is essential before future experiments can search for possible spectroscopic signatures of life in the exoplanet atmospheres.”
The total tally of confirmed planets orbiting other stars stands at about 600, depending on who you ask. The Jet Propulsion Laboratory’s PlanetQuest website, shows 564 exoplanets while the Extrasolar Planets Encyclopedia, a database kept by astrobiologist Jean Schneider of the Paris-Meudon Observatory, lists 645 alien worlds. The discrepancy comes because PlanetQuest doesn’t add to their total until an exoplanet has been completely confirmed.
Ray Sanders is a Sci-Fi geek, astronomer and space/science blogger. Visit his website Dear Astronomer and follow on Twitter (@DearAstronomer) or Google+ for more space musings.
Three people enjoy the summer sky over the Delaware river, NJ, USA in August 2006. Image Credit: Wikimedia
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It’s a great time to be an amateur astronomer! Nowadays, “backyard” astronomers armed with affordable CCD imagers, high-quality tracking mounts, inexpensive PC’s and the internet at their fingertips are making real contributions to Astronomy science.
How are people in their backyards contributing to real science these days?
Consider that in 1991, the Hubble Space Telescope launched with a main camera of less than 1 megapixel. (HST’s array was 800×800 pixels – just over half a megapixel). Currently, “off-the-shelf” imaging equipment available for a few hundred dollars or less easily provides 1 megapixel or more. Even with a “modest” investment, amateurs can easily reach the ten megapixel mark. Basically, the more pixels you have in your imaging array, the better resolution your image will have and the more detail you’ll capture (sky conditions notwithstanding).
With access to fairly high resolution cameras and equipment, many amateurs have taken breathtaking images of the night sky. Using similar equipment other hobbyists have imaged comets, supernovae, and sunspots. With easy access to super-precise tracking mounts and high-quality optics, it’s no wonder that amateur astronomers are making greater contributions to science these days.
One spectacular example of amateur discoveries was covered by Universe Todayearlier this year. Kathryn Aurora Gray, a ten year old girl from Canada, discovered a supernova with the assistance of her father and another amateur astronomer, David Lane. The discovery of Supernova 2010lt (located in galaxy UGC 3378 in the constellation of Camelopardalis) was Kathryn’s first, her father’s seventh and Lane’s fourth supernova discovery. You can read the announcement regarding Ms. Gray’s discovery courtesy of The Royal Astronomical Society of Canada at: http://www.rasc.ca/artman/uploads/sn2010lt-pressrelease.pdf
Often times when a supernova is detected, scientists must act quickly to gather data before the supernova fades. In the image below, look for the blinking “dot. The image is a before and after image of the area surrounding Supernova 2010lt.
A before and after animation of Supernova 2010lt. Credit: Dave Lane
Before Kathyrn Gray, astronomer David Levy made headlines with his discovery of comet Shoemaker-Levy 9. In 1994, comet Shoemaker-Levy 9 broke apart and collided with Jupiter’s atmosphere. Levy has gone on to discover over twenty comets and dozens of asteroids. Levy has also published several books and regularly contributes articles to various astronomy publications. If you’d like to learn more about David Levy, check out his internet radio show at http://www.letstalkstars.com/, or visit his site at http://www.jarnac.org/
Hubble image of comet P/Shoemaker-Levy 9, taken on May 17, 1994. Image Credit: H.A. Weaver, T. E. Smith (Space Telescope Science Institute), and NASAThe International Space Station and Space Shuttle Atlantis transiting the sun. Image Credit: Thierry Legault
Rounding out news-worthy astronomers, astrophotographer Thierry Legault has produced many breathtaking images that have been featured here on Universe Today on numerous occasions. Over the past year, Thierry has taken many incredible photos of the International Space Station and numerous images of the last few shuttle flights. Thierry’s astrophotography isn’t limited to just the sun, or objects orbiting Earth. You can read more about the objects Thierry captures images of at: http://www.astrophoto.fr/ You can also read more about Thierry and the equipment he uses at: http://legault.perso.sfr.fr/info.html
Performing science as an amateur isn’t limited to those with telescopes. There are many other research projects that ask for public assistance. Consider the Planet Hunters site at: http://www.planethunters.org/. What Planet Hunters aims to achieve is a more “hands-on” approach to interpreting the light curves from the publicly available data from the Kepler planet finding mission. Planet Hunters is part of the Zooniverse, which is a collection of citizen science projects. You can learn more about the complete collection of Zooniverse projects at: http://www.zooniverse.org
Another citizen science effort recently announced is the Pro-Am White Dwarf Monitoring (PAWM) project. Led by Bruce Gary, the goal of the project is to explore the possibility of using amateur and professional observers to estimate the percentage of white dwarfs exhibiting transits by Earth-size planets in the habitable zone. The results from such a survey are thought to be useful in planning a comprehensive professional search for white dwarf transits. You can read more about the PAWM project at: http://www.brucegary.net/WDE/
Transit simulation. Image Credit: Manuel Mendez/PAWM
One very long standing citizen project is the American Association of Variable Star Observers (AAVSO). Founded in 1911, the AAVSO coordinates, evaluates, compiles, processes, publishes, and disseminates variable star observations to the astronomical community throughout the world. Currently celebrating their 100th year, the AAVSO not only provides raw data, but also publishes The Journal of the AAVSO, a peer-reviewed collection of scientific papers focused on variable stars. In addition to data and peer reviewed journals, the AAVSO is active in education and outreach, with many programs, including their mentor program designed to assist with disseminating information to educators and the public.
If you’d like to learn more about the AAVSO, including membership information, visit their site at: http://www.aavso.org/
For over a decade, space enthusiasts across the internet have been taking part in SETI@Home. The official description of SETI@home is “a scientific experiment that uses Internet-connected computers in the Search for Extraterrestrial Intelligence (SETI)”. By downloading special client software from the SETI@Home website at http://setiathome.berkeley.edu/, volunteers from around the world can help analyze radio signals and assist with SETI’s efforts to find “candidate” radio signals. You can learn more about SETI@Home by visiting http://setiathome.berkeley.edu/sah_about.php
The projects and efforts featured above are just a small sample of the many projects that non-scientists can participate in. There are many other projects involving radio astronomy, galaxy classification, exoplanets, and even projects involving our own solar system. Volunteers of all ages and educational backgrounds can easily find a project to help support.
Ray Sanders is a Sci-Fi geek, astronomer and space/science blogger. Visit his website Dear Astronomer and follow on Twitter (@DearAstronomer) or Google+ for more space musings.
Artist's concept of a free-floating Jupiter-like planet. (NASA / JPL-Caltech)
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We happen to live in a solar system where everything seems to be tucked neatly in place. Sun, planets, moons, asteroids, comets… all turning and traveling through space in relatively neat and orderly fashions. But that may not always be the case; sometimes planets can get kicked out of their solar systems entirely, banished to roam interstellar space without a sun of their own. And these “orphan planets” may be much more numerous than once thought.
Researchers in a joint Japan-New Zealand study surveyed microlensing events near the central part of our galaxy during 2006 and 2007 and identified up to 10 Jupiter-sized orphan worlds between 10,000 and 20,000 light-years away. Based on the number of planets identified and the area studied they estimate that there could literally be hundreds of billions of these lone planets roaming our galaxy….literally twice as many planets as there are stars.
“Although free-floating planets have been predicted, they finally have been detected, holding major implications for planetary formation and evolution models.”
– Mario Perez, exoplanet program scientist at NASA Headquarters in Washington.
From the NASA release:
Previous observations spotted a handful of free-floating, planet-like objects within star-forming clusters, with masses three times that of Jupiter. But scientists suspect the gaseous bodies form more like stars than planets. These small, dim orbs, called brown dwarfs, grow from collapsing balls of gas and dust, but lack the mass to ignite their nuclear fuel and shine with starlight. It is thought the smallest brown dwarfs are approximately the size of large planets.
On the other hand, it is likely that some planets are ejected from their early, turbulent solar systems, due to close gravitational encounters with other planets or stars. Without a star to circle, these planets would move through the galaxy as our sun and other stars do, in stable orbits around the galaxy’s center. The discovery of 10 free-floating Jupiters supports the ejection scenario, though it’s possible both mechanisms are at play.
“If free-floating planets formed like stars, then we would have expected to see only one or two of them in our survey instead of 10. Our results suggest that planetary systems often become unstable, with planets being kicked out from their places of birth.”
– David Bennett, a NASA and National Science Foundation-funded co-author of the study from the University of Notre Dame.
The study wasn’t able to resolve planets smaller than Saturn but it’s believed there are likely many more smaller, Earth-sized worlds than large Jupiter-sized ones.
New research reveals the possible cause of retrograde "hot Jupiters"
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It was once thought that our planet was part of a “typical” solar system. Inner rocky worlds, outlying gas giants, some asteroids and comets sprinkled in for good measure. All rotating around a central star in more or less the same direction. Typical.
But after seeing what’s actually out there, it turns out ours may not be so typical after all…
Astronomers researching exoplanetary systems – many discovered with NASA’s Kepler Observatory – have found quite a few containing “hot Jupiters” that orbit their parent star very closely. (A hot Jupiter is the term used for a gas giant – like Jupiter – that resides in an orbit very close to its star, is usually tidally locked, and thus gets very, very hot.) These worlds are like nothing seen in our own solar system…and it’s now known that some actually have retrograde orbits – that is, orbiting their star in the opposite direction.
“That’s really weird, and it’s even weirder because the planet is so close to the star. How can one be spinning one way and the other orbiting exactly the other way? It’s crazy. It so obviously violates our most basic picture of planet and star formation.”
– Frederic A. Rasio, theoretical astrophysicist, Northwestern University
Now retrograde movement does exist in our solar system. Venus rotates in a retrograde direction, so the Sun rises in the west and sets in the east, and a few moons of the outer planets orbit “backwards” relative to the other moons. But none of the planets in our system have retrograde orbits; they all move around the Sun in the same direction that the Sun rotates. This is due to the principle of conservation of angular momentum, whereby the initial motion of the disk of gas that condensed to form our Sun and afterwards the planets is reflected in the current direction of orbital motions. Bottom line: the direction they moved when they were formed is (generally) the direction they move today, 4.6 billion years later. Newtonian physics is okay with this, and so are we. So why are we now finding planets that blatantly flaunt these rules?
The answer may be: peer pressure.
Or, more accurately, powerful tidal forces created by neighboring massive planets and the star itself.
By fine-tuning existing orbital mechanics calculations and creating computer simulations out of them, researchers have been able to show that large gas planets can be affected by a neighboring massive planet in such a way as to have their orbits drastically elongated, sending them spiraling closer in toward their star, making them very hot and, eventually, even flip them around. It’s just basic physics where energy is transferred between objects over time.
It just so happens that the objects in question are huge planets and the time scale is billions of years. Eventually something has to give. In this case it’s orbital direction.
“We had thought our solar system was typical in the universe, but from day one everything has looked weird in the extrasolar planetary systems. That makes us the oddball really. Learning about these other systems provides a context for how special our system is. We certainly seem to live in a special place.”
– Frederic A. Rasio
Yes, it certainly does seem that way.
The research was funded by the National Science Foundation. Details of the discovery are published in the May 12th issue of the journal Nature.
Main image credit: Jason Major. Created from SDO (AIA 304) image of the Sun from October 17, 2010 (NASA/SDO and the AIA science team) and an image of Jupiter taken by the Cassini-Huygens spacecraft on October 23, 2000 (NASA/JPL/SSI).
Keplers 1200 Planet candidates by size. Finding exoplanets is getting easier, LUVOIR will helps us find signs of life, if any, on them. Credit: NASA/Wendy Stenzel
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With the startling new finding of dozens of Earth-sized extrasolar planets, NASA’s Kepler planet hunting space telescope has just revolutionized our understanding of Earths place in the Universe and the search for Extraterrestrial Life. And the historic science discovery is based on data collected in just the first few months of operation of the powerful telescope as it scans only a tiny portion of the sky.
The discovery of 1235 new extrasolar planet candidates was announced today (Feb.2) by NASA and Kepler scientists at a media briefing. 68 of these planet candidates are Earth-sized. Another 288 are Super-Earth-size, 662 are Neptune-size and 165 are Jupiter-size. Most of these candidates orbit stars like our sun.
Even more significant is that 54 of the planet candidates are located within the ‘habitable zone’ of their host stars and 5 of those are Earth-sized. Before today we knew of exactly ZERO Earth-sized planets within the habitable zone. Now there are 5.
Finding a ‘Pale Blue Dot’ or ‘Second Earth’ inside a habitable zone that harbors water and environmental conditions that can support life is the ‘Holy Grail’ of science.
Are We Alone ?
“We went from zero to 68 Earth-sized planet candidates and zero to 54 candidates in the habitable zone – a region where liquid water could exist on a planet’s surface. Some candidates could even have moons with liquid water,” said William Borucki of NASA’s Ames Research Center, Moffett Field, Calif.. Borucki is the science principal investigator for NASA’s Kepler mission.
“Five of the planetary candidates are both near Earth-size and orbit in the habitable zone of their parent stars.”
Earth-sized water worlds are the most conducive to the formation and evolution of alien life forms. Water is an essential prerequisite for life as we know it.
“Kepler’s blown the lid off everything we know about extrasolar planets,” said Debra Fischer, professor of Astronomy at Yale University, New Haven, Conn
Kepler's over 1200 planet candidates as of Feb. 1, 2011. Credit: NASA/Wendy Stenzel
Kepler is the first NASA mission capable of finding Earth-size planets in or near the habitable zones around their parent stars. The mission uses the transit method to detect the tell tale signatures of planets. The goal is to determine how common are planets the size of Earth orbiting inside the habitable zone of stars like our sun.
Kepler measures the miniscule decreases in the brightness of stars caused by planets crossing in front of them and blocking the starlight. Imagine calculating the difference in light transmission caused by a flea sitting on a cars headlight.
Follow up observations over a period of several years will be required to confirm these results, the scientists explained. Astronomers expect that over 80% of the candidate planets will be positively confirmed as real planets by utilizing ground based observatories and the Spitzer Space Telescope.
For an Earth-sized planet orbiting a sun-like star inside the habitable zone, transits occur about once per year. Since three transits are required to verify a planets status, it will therefore take about three years to reach a definitive conclusion.
These remarkable new planet discoveries are based on observations from only the first four months of Kepler’s telescopic operations – May 12, 2009 to Sept. 17, 2009. The space based observatory continuously monitors more than 156,000 stars using 42 CCD detectors with a field of view that covers only 1/400 of the sky.
“Kepler is making good progress towards its goals,” said Borucki
“We have found over twelve hundred candidate planets – that’s more than all the people have found so far in history.”
“Imagine if we could look wider. Kepler looks at one 400th of the sky. If we had 400 of these fields of view, we’d see 400 times that number of candidates. We would see 400,000 candidate planets.”
Keplers over 1200 Planet candidates sorted by size
“The fact that we’ve found so many planet candidates in such a tiny fraction of the sky suggests there are countless planets orbiting stars like our sun in our galaxy,” Borucki amplified. “Our results indicate there must be millions of planets orbiting the stars that surround our sun.”
“If we find that Earth’s are common in the habitable zones of stars, very likely that means life is common around these stars.”
“Kepler has shown that planetary systems like our own are common,” said Debra Fischer.
Planets in Keplers Field of View.
Before and after the discovery of over 1200 planet candidates by NASA’s Kepler Space Telescope.
“The search for planets is motivated by the search for life,” Fischer added.
“We have allowed the public to participate though the website Planethunters.org,” she added. “And now we have over 16,000 dedicated users. The public is excited to be a part of research and history.”
“Thanks to Kepler for this treasure chest of data!” Fisher concluded.
Kepler is just the first step in finding Earth sized and Earth like planets. “We are building the foundation for future generations of explorers,” said Borucki.
“Future missions will be developed to study the composition of planetary atmospheres to determine if they are compatible with the presence of life. The design for these missions depends on Kepler finding whether Earth-size planets in the habitable zone are common or rare.”
The first planets beyond our solar system were discovered in 1995. Up to today there were just over 500 known extrasolar planets.
Kepler now has 15 confirmed extrasolar planet discoveries and over 1200 possible candidates.
NASA’s Kepler spacecraft was launched on March 6, 2009 from Launch Complex 17-B atop a Delta II rocket at Cape Canaveral Air Force Station in Florida. See spacecraft and launch photos below
Kepler’s science operations are currently funded for three and one half years of operations until November 2012. The mission’s lifetime – and its goal of discovering multitudes of new planets as small as Earth – can be extended if NASA funding is approved by Congress and the President.
William Borucki – Explains Keplers Discovery of Earth Sized Planets
Science principal investigator for NASA’s Kepler mission, NASA’s Ames Research Center
Video Caption: NASA’s Kepler mission has discovered its first Earth-size planet candidates and its first candidates in the habitable zone, a region where liquid water could exist on a planet’s surface. Five of the potential planets are near Earth-size and orbit in the habitable zone of smaller, cooler stars than our sun.
Kepler also found six confirmed planets orbiting a sun-like star, Kepler-11. This is the largest group of transiting planets orbiting a single star yet discovered outside our solar system. Located approximately 2,000 light years from Earth, Kepler-11 is the most tightly packed planetary system yet discovered. All six of its confirmed planets have orbits smaller than Venus, and five of the six have orbits smaller than Mercury’s.
What is an Earth like planet ? Explantion here
David Charbonneau, an exoplanet researcher at Harvard University, explains what scientists mean when they say “earthlike planet” and “super Earth.” This interview was recorded at NASA’s Goddard Space Flight Center on December 10, 2010, by NASA science writer Daniel Pendick.
Kepler Mission Star Field
An image by Carter Roberts of the Eastbay Astronomical Society in Oakland, CA, showing the Milky Way region of the sky where the Kepler spacecraft/photometer will be pointing. Each rectangle indicates the specific region of the sky covered by each CCD element of the Kepler photometer. There are a total of 42 CCD elements in pairs, each pair comprising a square.
Credit: Carter Roberts / Eastbay Astronomical Society.Kepler's target region in the Milky Way. Credit: Jon LombergKepler being prepared in the clean room at Astrotech
prior to launch on March 6, 2009. Credit: nasatech.net
More Kepler photos courtesy of nasatech.net here
Delta 2 rocket streaks to the heavens.
Launch of NASA’s Kepler planet hunting space telescope from Cape Canaveral Air Force Station, FL, Complex 17, on March 6, 2009 at 10:49 p.m. Credit: Ben CooperBen Cooper Featured on Astronomy Picture of the Day (APOD); March 9, 2009
Launch Pad 17 B and a Delta II rocket
from my perch on the 8th floor of Launch Pad 17 A as rocket is encased in launch tower. Credit: Ken KremerView of Launch Complex 17 B and cryogenic storage tanks by Ken Kremer
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.
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NASA’s Kepler planet hunting space telescope has made an historic discovery by finding its first rocky planet – and it’s simultaneously the smallest planet ever found beyond our solar system. The exoplanet, dubbed Kepler-10b, measures barely 1.4 times the diameter of Earth and orbits its star in less than one earth day. Therefore the planet is located well outside the habitable zone and is far too close to the star for liquid water to exist. It is Earth-sized but not Earth-like with respect to the search for life. The finding of such a small and rocky world marks a major milestone for Keplers scientific capabilities in finding another world like our own.
Indeed the scorching hot planet orbits so close to its parent star – once every 0.84 days – that the surface is molten and temperatures exceed 2,500 degrees Fahrenheit, hotter than lava flows here on Earth. Kepler-10b is 20 times closer to its star than Mercury is to our sun. Its density is similar to that of an iron dumbbell.
Check out the amazing video below narrated by Natalie Batalha, Kepler’s deputy science team lead from NASA’s Ames Research Center which describes Kepler’s exciting discovery of the smallest exoplanet known to date – some 560 light years from Erath.
The discovery is based on data that was collected from May 2009 to early January 2010 and was independently confirmed with the W.M. Keck Observatory in Hawaii. A peer reviewed paper has been accepted for publication in the Astrophysical Journal. The spacecraft was launched in March 2009 by a Delta II rocket.
Over 500 exoplanets have been discovered up to now. Kepler uses the transit method to detect exoplanets and monitors 150,000 stars by aiming 42 detectors between the constellations of Cygnus and Lyra.
Kepler Mission Star Field.
An image by Carter Roberts of the Eastbay Astronomical Society in Oakland, CA, showing the Milky Way region of the sky where the Kepler spacecraft/photometer will be pointing. Each rectangle indicates the specific region of the sky covered by each CCD element of the Kepler photometer. There are a total of 42 CCD elements in pairs, each pair comprising a square. Credit: Carter Roberts / Eastbay Astronomical Society.
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.
The discovery of this so-called exoplanet is based on more than eight months of data collected by the spacecraft from May 2009 to early January 2010.
“All of Kepler’s best capabilities have converged to yield the first solid evidence of a rocky planet orbiting a star other than our sun,” said Natalie Batalha, Kepler’s deputy science team lead at NASA’s Ames Research Center in Moffett Field, Calif., and primary author of a paper on the discovery accepted by the Astrophysical Journal. “The Kepler team made a commitment in 2010 about finding the telltale signatures of small planets in the data, and it’s beginning to pay off.”
Kepler’s ultra-precise photometer measures the tiny decrease in a star’s brightness that occurs when a planet crosses in front of it. The size of the planet can be derived from these periodic dips in brightness. The distance between the planet and the star is calculated by measuring the time between successive dips as the planet orbits the star.
Kepler is the first NASA mission capable of finding Earth-size planets in or near the habitable zone, the region in a planetary system where liquid water can exist on the planet’s surface. However, since it orbits once every 0.84 days, Kepler-10b is more than 20 times closer to its star than Mercury is to our sun and not in the habitable zone.
Kepler-10b orbits one of the 150,000 stars that the spacecraft is monitoring between the constellations of Cygnus and Lyra.
We aim our mosaic of 42 detectors there, under the swan’s wing, just above the plane of the Milky Way galaxy. The star itself is very similar to our own sun in temperature, mass and size, but older with an age of over 8 billion years, compared to the 4-and-1/2 billion years of our own sun. It’s a quiet star, slowly spinning with a weak magnetic field and few of the sun spots that characterize our own sun. The star’s about 560 light years from our solar system and one of the brighter stars that Kepler is monitoring. It was the first we identified as potentially harboring a very small transiting planet. The transits of the planet were first seen in July of 2009.
The diameter of Kepler-10b is only about 1.4 times the diameter of Earth and it's mass is about 4.5 times that of Earth. It is the best example of a rocky planet to date.
Kepler-10 was the first star identified that could potentially harbor a small transiting planet, placing it at the top of the list for ground-based observations with the W.M. Keck Observatory 10-meter telescope in Hawaii.
Scientists waiting for a signal to confirm Kepler-10b as a planet were not disappointed. Keck was able to measure tiny changes in the star’s spectrum, called Doppler shifts, caused by the telltale tug exerted by the orbiting planet on the star.
“The discovery of Kepler-10b, a bone-fide rocky world, is a significant milestone in the search for planets similar to our own,” said Douglas Hudgins, Kepler program scientist at NASA Headquarters in Washington. “Although this planet is not in the habitable zone, the exciting find showcases the kinds of discoveries made possible by the mission and the promise of many more to come,” he said.
“Our knowledge of the planet is only as good as the knowledge of the star it orbits,” said Batalha. Because Kepler-10 is one of the brighter stars being targeted by Kepler, scientists were able to detect high frequency variations in the star’s brightness generated by stellar oscillations, or starquakes. “This is the analysis that really allowed us to pin down Kepler-10b’s properties.,” she added.
“We have a clear signal in the data arising from light waves that travel within the interior of the star,” said Hans Keldsen, an astronomer at the Kepler Asteroseismic Science Consortium at Aarhus University in Denmark. Kepler Asteroseismic Science Consortium scientists use the information to better understand the star, just as earthquakes are used to learn about Earth’s interior structure. “As a result of this analysis, Kepler-10 is one of the most well characterized planet-hosting stars in the universe next to our sun,” Kjeldsen said.
Kepler from the high-gain antenna side in the clean room at Astrotech. Credit: nasatech.net
That’s good news for the team studying Kepler-10b. Accurate stellar properties yield accurate planet properties. In the case of Kepler-10b, the picture that emerges is of a rocky planet with a mass 4.6 times that of Earth and with an average density of 8.8 grams per cubic centimeter — similar to that of an iron dumbbell.
“This planet is unequivocally rocky, with a surface you could stand on,” commented team member Dimitar Sasselov, of the Harvard-Smithsonian Center for Astrophysics in Cambridge and a Kepler co-investigator.
“All of Kepler’s best capabilities have converged for this discovery,” Batalha said, “yielding the first solid evidence of a rocky planet orbiting a star other than our sun.”
Ames manages Kepler’s ground system development, mission operations and science data analysis. NASA’s Jet Propulsion Laboratory in Pasadena, Calif., managed Kepler mission development.
Ball Aerospace and Technologies Corp. in Boulder, Colo., developed the Kepler flight system and supports mission operations with the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder. The Space Telescope Science Institute in Baltimore archives, hosts and distributes the Kepler science data.
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Click here to view a hi res 360 degree panorama of Kepler inside the cleanroom. Credit: nasatech.net
Young stars have a disk of gas and dust around them called a protoplanetary disk. Credit: NASA/JPL-Caltech
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Awhile ago I wrote on the difficulty of finding young planets. There, I mentioned one team announcing the potential discovery of a planet a mere 1-5 million years old. But what are astronomers to do if they want to find even younger planets?
The chief difficulty in this instance is that such planets would still be hidden in the circumstellar disks from which they formed, hiding them from direct observation. Additionally, depending on how far along the process had advanced, they may not yet have accreted sufficient mass to show up in radial velocity surveys, if such surveys could even been conducted with interference from the disc.
One way astronomers have proposed to detect forming planets is to observe their effects on the disc itself. This could come in a number of ways. One would be for the planet to carve out grooves in the disc, clearing its orbit as it sweeps up matter. Another possibility is to look for the “shadows” caused by the local overdensity an accreting planet would cause.
But recently, another new method caught my eye. In this one, proposed by astronomers at the Crimean National Observatory in the Ukraine, astronomers could potentially look for again turns to the characteristics of the parent star. Earlier, astronomers had made a link between the properties of the disc around classes of protostars (such as T Tauri and Herbig Ae stars) and the variable luminosity of the star itself.
The authors suggest that, “[t]wo different mechanisms can be involved in interpretation of these results: 1) circumstellar extinction and 2) accretion.” In either scenario, a body present in the disc itself concentrating the material would be necessary to explain these results. In the first case, a protoplanet would draw a swarm of material around it again creating a local overdensity in the disc which would be dragged around with the planet, creating a dimming of the star as it passed near the line of sight. In the second, the planet would draw out tidal structures in the disc in much the same way tidal interactions can draw out spiral structure in galaxies. As these veins of matter fall onto the star, it feeds the star, temporarily causing an outburst and increasing the brightness.
The team conducted an analysis of periodicity in several protostellar systems and found several instances in which the periods were similar to those of planetary systems discovered around mature stars. Around one star, V866 Sco, they discovered, “two distinct periods in light variations, 6.78 and 24.78 days, that persist over several years.” They note that the shorter period is likely “due to axial rotation of the star” but could not offer an explanation for the longer period which leaves it open to the possibility of being a forming planet and they suggest that spectral observations may be possible. Other systems the team analyzed had periods ranging from 25 – 120 days also hinting at the possibility for young planetary systems.
The advantage to this method is that finding candidate systems can be done relatively easily using photometric systems which can survey great numbers of stars at once whereas radial velocity measurements generally require dedicated observations on a single object. This would allow astronomers to discriminate against candidates unlikely to harbor forming planets. Ultimately, finding young systems with forming planets will help astronomers understand how these systems form and evolve and why our own system is so different than many others found thus far.
The warmest part of upsilon Andromedae b is not directly under the light coming from its host star, as would be expected. Image Credit: NASA/JPL-Caltech
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If you set a big black rock outside in the Sun for a few hours, then go and touch it, you’d expect the warmest part of the rock to be that which was facing the Sun, right? Well, when it comes to exoplanets, your expectations will be defied. A new analysis of a well-studied exoplanetary system reveals that one of the planets – which is not a big black rock, but a Jupiter-like ball of gas – has its warmest part opposite that of its star.
The system of Upsilon Andromedae, which lies 44 light years away from the Earth in the constellation Andromeda, is a much studied system of planets that orbit around a star a little more massive and slightly hotter than our Sun.
The closest planet to the star, upsilon Andromeda b, was the first exoplanet to have its temperature taken by The Spitzer Space Telescope. As we reported back in 2006, upsilon Andromeda b was thought to be tidally locked to the star and show corresponding temperature changes at it went around its host star. That is, as it went behind the star from our perspective, the face was warmer than when it was in front of the star from our perspective. Simple enough, right? These original results were published in a paper in Science on October 27th, 2006, available here.
As it turns out, this temperature change scenario is not the case. UCLA Professor of Physics and Astronomy Brad Hansen, who is a co-author on both the 2006 paper and updated results, explains, “The original report was based on just a few hours of data, taken early in the mission, to see whether such a measurement was even possible (it is close to the limit of the expected performance of the instrument). Since the observations suggested it was possible to detect, we were awarded a larger amount of time to do it in more detail.”
Observations of upsilon Andromedae b were taken with the Spitzer again in February of 2009. Once the astronomers were able to study the planet more, they discovered something odd – just how warm the planet was when it passed in front of the star from our perspective was a lot warmer than when it passed behind, just the opposite of what one would expect, and opposite of the results they originally published. Here’s a link to an animation that helps explain this strange feature of the planet.
What the astronomers discovered – and have yet to explain fully – is that there is a “warm spot” about 80 degrees opposite of the face of the planet that is pointed towards the star. In other words, the warmest spot on the planet is not on the side of the planet that is receiving the most radiation from the star.
This in itself is not a novelty. Hansen said, “There are several exoplanets observed with warm spots, including some whose spots are shifted relative to the location facing the star (an example is the very well studied system HD189733b). The principal difference in this case is that the shift we observe is the largest known.”
Upsilon Andromedae b does not transit in front of its star from our vantage point on the Earth. Its orbit is inclined by about 30 degrees, so it appears to be passing “below” the star as it comes around the front. This means that astronomers cannot use the transit method of exoplanetary study to get a handle on its orbit, but rather measure the tug that the planet exerts on the star. It has been determined that upsilon Andromedae b orbits about every 4.6 days, has a mass 0.69 that of Jupiter and is about 1.3 Jupiter radii in diameter. To get a better idea of the whole system of upsilon Andromedae, see this story we ran earlier this year.
So what, exactly, could be causing this bizarrely placed warm spot on the planet? The paper authors suggest that equatorial winds – much like those on Jupiter – could be transferring heat around the planet.A graph and visual representation of the hot spot as the planet orbits the star upsilon Andromedae. Image credit: NASA/JPL-Caltech/UCLA
Hansen explained, “At the sub-stellar point (the one closest to the star) the amount of radiation being absorbed from the star is highest, so the gas there is heated more. It will therefore have a tendency to flow away from the hot region towards cold regions. This, combined with rotation will give a “trade wind”-like structure to the gas flow on the planet… The big uncertainty is how that energy is eventually dissipated. The fact that we observe a hot spot at roughly 90 degrees suggests that this occurs somewhere near the “terminator” (the day/night edge). Somehow the winds are flowing around from the sub-stellar point and then dissipating as they approach the night side. We speculate that this may be from the formation of some kind of shock front.”
Hansen said that they are unsure just how large this warm spot is. “We have only a very crude measure of this, so we have modeled as basically two hemispheres – one hotter than the other. One could make the spot smaller and make it correspondingly hotter and you would get the same effect. So, one can trade off spot size versus temperature contrast while still matching the observations.”
The most recent paper, which is co-authored by members from the United States and the UK, will appear in the Astrophysical Journal. If you’d like to go outside and see the star upsilon Andromedae,here’s a star chart.
