Exoplanets

Planet Bonanza Hints at Worlds Similar to Our Own (Press Release)

kepler 715The artist concept depicts multiple-transiting planet systems, which are stars with more than one planet. The planets eclipse or transit their host star from the vantage point of the observer. This angle is called edge-on. Image credit: NASA

Mountain View, CA - For planet hunters, this has been a bountiful year.  A team of astronomers at the SETI Institute and NASA Ames Research Center have used data from NASA’s Kepler space telescope to uncover 715 new exoplanets.  The newly-verified objects orbit 305 different stars, and therefore include multi-world systems that are reminiscent of the Sun’s own planetary family.  The announcement of these discoveries was followed by news that Kepler had also found the first Earth-size planet in the habitable zone of its star, Kepler 186f.  This is a significant milestone in the task of determining the prevalence of terrestrial planets in the Milky Way galaxy.

“These results are showing us that not only are Earth-sized planets common, but so are multi-planet systems containing potentially habitable worlds,” notes Jason Rowe, a SETI Institute astronomer who co-lead the study.  “Most of the new planets orbit their host star much closer than Mercury, but a few are beginning to bear a similarity to our own solar system.”

The deluge of new planets has been intensified by a new analysis scheme called verification by multiplicity. This technique can be applied to many planets at once, allowing the researchers to verify hundreds of new planetary systems in wholesale fashion, rather than teasing them from the Kepler data one-by-one as done in the past.  The new technique uses probability arguments based on the recognition that, of the 150,000 stars observed by Kepler, hundreds were found that have multiple planet candidates.  On this basis, the researchers are assured that their results are not distorted by binary stars that can mimic a multi-world system.  The new discoveries increase  the total number of known exoplanets to over 1,700.

“From this work we’ve also learned that planets in these multiple systems are small, and their orbits are flat and circular, much like our own solar system,” Rowe said.

On April 17th, the Kepler team announced the discovery of Kepler 186f, the first Earth-sized planet found in the habitable zone of its host star, marking a major milestone in determining the frequency of Earth-like planets in the Milky Way galaxy.

“Uncovering these worlds and showing that habitable worlds could be very common has increased the likelihood that there is life – perhaps abundant life – elsewhere in the cosmos,” notes David Black, President and CEO of the SETI Institute.

Data collection from the Kepler mission ended in the spring of last year, due to the failure of a second on-board reaction wheel, essential to accurate pointing of the telescope.  However, on May 20th, NASA announced the approval of the K2 mission, intended to repurpose Kepler to use the pressure of sunlight hitting the side of the spacecraft to act as a third wheel.

“We can’t continue to look at the original Kepler starfield,” said Douglas Caldwell, Kepler Instrument Scientist at the SETI Institute,  “but spacecraft are built and operated by very smart people, and thanks to the hard work of the entire Kepler team we can now search for planets in a wide variety of environments and conditions, including star forming regions.  Doing so will teach us more about how our own planetary system formed and evolved.”

“The more we explore the more we find worlds among the stars that remind us of home,”  Rowe notes.

Jason Rowe is presenting these results at this week's annual meeting of the Canadian Astronomical Society (CASCA) in Quebec [http://casca2014.craq-astro.ca/index_en.php].

The Canadian Astronomical Society (http://casca.ca) is devoted to the promotion and advancement of knowledge of the universe through research and education. Membership is open to persons with a professional involvement with these goals in astronomy and the related sciences. The main activities of the Society are its annual scientific meetings, the planning and realization of scientific projects, the support of the scientific activities of its members, and the dissemination of related information among members and other interested persons.

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Press Release - First Discovery of an Earth-sized Planet in the Habitable Zone

MOUNTAIN VIEW, CA – For the first time, an Earth-sized planet has been found in the habitable zone of its star.  This discovery not only proves the existence of worlds that might be similar to our own, but will undoubtedly shape future investigations of exoplanets that could have terrestrial surface environments.

The new-found body, orbiting the red dwarf star Kepler-186 and designated Kepler-186f, is the fifth – and outermost – world to be discovered in this system.  The results are described in an article appearing in Science.

“This is the first definitive Earth-sized planet found in the habitable zone around another star,” says lead author Elisa Quintana of the SETI Institute at NASA Ames Research Center.  “Finding such planets is a primary goal of the Kepler space telescope.  The star is a main-sequence M-dwarf, a very common type.  More than 70 percent of the hundreds of billions of stars in our galaxy are M-dwarfs.”

Of the nearly 1800 confirmed exoplanets found in the past two decades, approximately twenty orbit their host star in the habitable zone – a range of orbital distances at which surface water on a planet with an atmosphere would neither freeze nor boil.  However, all of these previously discovered worlds are larger than Earth, and consequently their true nature – rocky or gaseous – is unknown.  On the basis of the observed dimming of starlight from Kepler-186, the authors estimate that this newly discovered planet is roughly the same size as the Earth.

“The discovery of Kepler-186f is a  significant milestone in humanity’s efforts to find evidence of life elsewhere in our galaxy,” said Dr. David Black, President and CEO of the SETI Institute. “Finding similar planets around other stars, and ultimately being able to sense remotely signposts of life on those planets, is the next key step toward understanding our place in the cosmos and is what the SETI Institute is about,” Black said.

Thomas Barclay, a staff scientist for the Kepler mission affiliated with both NASA and the Bay Area Environmental Research Institute, notes that “theoretical models of how planets form suggest that those with diameters less than 1.5 times that of Earth are unlikely to be swathed in atmospheres of hydrogen and helium, the fate that’s befallen the gas giants of our own solar system.  Consequently, Kepler-186f is likely a rocky world, and in that sense similar to Venus, Earth and Mars.”

The new planet orbits at a distance of 0.36 astronomical units from its star, or slightly closer than Mercury is to the Sun.  Its orbital period is 130 days. 

Traditionally, planets orbiting red dwarf stars were considered to be poor candidates for life.  The objection was that star-hugging planets in the habitable zone would become tidally locked, and suffer a synchronous or pseudo-synchronous rotation that could make climate on these planets untenable.  However, more recent modeling studies suggest that such worlds are not necessarily inhospitable, since atmospheric winds or ocean currents could even out extreme temperature variations .  In addition, Kepler-186f is far enough away from its host star that it is unlikely to be locked. This greater distance also reduces the danger to any potential life forms posed by stellar flares, which are more common for dwarf stars.

Since 2012, the SETI Institute's Allen Telescope Array has been observing Kepler candidate exoplanets looking for signals that would indicate extraterrestrial intelligence.  A search for emissions from Kepler-186f has been made over the very wide frequency range of 1 to 10 GHz, but none have so far been found. These observations will be repeated.  Note that a detectable signal would require a transmitter approximately 10 to 20 times more powerful than the planetary radar system at Arecibo, in Puerto Rico.
 
According to Quintana, at 490 light-years Kepler-186f may be too dim for follow-up surveys to probe its atmosphere, even with next-generation telescopes.  “However, our research tells us that we should be able to find planets around bright stars that will be ideal targets to  observe with James Webb.”  NASA’s Webb space-based telescope, now under construction, will be able to directly image planets around nearby dwarf stars, and use spectral analysis to characterize their atmospheres.

Finding Kepler-186f is a first, but “it’s not a record we wish to keep,” Quintana says. “We want to find more of these.”

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World’s Most Powerful Planet Finder Turns its Eye to the Sky - Gemini Planet Imager Obtains First Light Images -

comparison of europa color images(Above) Comparison of Europa observed with Gemini Planet Imager in K1 band on the right and visible albedo visualization based on a composite map made from Galileo SSI and Voyager 1 and 2 data (from USGS) on the left. While GPI is not designed for ‘extended’ objects like this, its observations could help in following surface alterations on icy satellites of Jupiter or atmospheric phenomena (e.g. clouds, haze) on Saturn’s moon Titan. The GPI near-infrared color image is a combination of 3 wavelength channels. (Download hi-res tiff) Image credit: Processing by Marshall Perrin, Space Telescope, Science Institute and Franck Marchis, SETI Institute


After nearly a decade of development, construction, and testing, the world’s most advanced instrument for directly imaging and analyzing planets around other stars is pointing skyward and collecting light from distant worlds. 

The instrument, called the Gemini Planet Imager (GPI), was designed, built, and optimized for imaging faint planets next to bright stars and probing their atmospheres, and studying dusty disks around young stars. It is the most advanced such instrument to be deployed on one of the world’s biggest telescopes – the 8-meter Gemini South telescope in Chile. 

“Even these early first-light images are almost a factor of 10 better than the previous generation of instruments. In one minute, we are seeing planets that used to take us an hour to detect,” says Bruce Macintosh of the Lawrence Livermore National Laboratory who led the team that built the instrument. 

GPI detects infrared (heat) radiation from young Jupiter-like planets in wide orbits around other stars, those equivalent to the giant planets in our own Solar System not long after their formation. Every planet GPI sees can be studied in detail. 

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

GPI carried out its first observations last November – during an extremely trouble-free debut for an extraordinarily complex astronomical instrument the size of a small car. “This was one of the smoothest first-light runs Gemini has ever seen” says Stephen Goodsell, who manages the project for the observatory. 

For GPI’s first observations, the team targeted previously known planetary systems, including the well-known Beta Pictoris system; in it GPI obtained the first-ever spectrum of the very young planet Beta Pictoris b. The first-light team also used the instrument’s polarization mode – which can detect starlight scattered by tiny particles – to study a faint ring of dust orbiting the very young star HR4796. With previous instruments, only the ends of this dust ring, (which may be the debris remaining from planet formation), could be seen, but with GPI astronomers can follow the entire circumference of the ring. The group also observed the system of planets orbiting HR8799. 

Although GPI was designed to look at distant planets, it can also observe objects in our Solar System. The accompanying test images of Jupiter’s moon Europa, for example, can allow scientists to map changes in the satellite’s surface composition. The images were released today at the 223rd meeting of the American Astronomical Society in Washington DC. 

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

“Exoplanets are extraordinarily faint and difficult to see next to a bright star,” notes GPI chief scientist Professor James R. Graham of the University of California who has worked with Macintosh on the project since its inception. GPI can see planets a million times fainter than their parent stars. Often described, ‘like trying to see a firefly circling a streetlight thousands of kilometers away,’ instruments used to image exoplanets must be designed and built to “excruciating tolerances,” points out Leslie Saddlemyer of NRC Herzberg (part of the National Research Council of Canada), who served as GPI’s systems engineer. “Each individual mirror inside GPI has to be smooth to within a few times the size of an atom,” Saddlemyer adds.

“GPI represents an amazing technical achievement for the international team of scientists who conceived, designed, and constructed the instrument, as well as a hallmark of the capabilities of the Gemini telescopes.  It is a highly-anticipated and well-deserved step into the limelight for the Observatory”, says Dr. Gary Schmidt, program officer at the National Science Foundation (NSF), which funded the project along with the other countries of the Gemini Observatory partnership.

"After years of development and simulations and testing, it's incredibly exciting now to be seeing real images and spectra of exoplanets observed with GPI. It’s just gorgeous data," says Marshall Perrin of the Space Telescope Science Institute. 

“The entire exoplanet community is excited for GPI to usher in a whole new era of planet finding,” says physicist and exoplanet expert Sara Seager of the Massachusetts Institute of Technology. Seager, who is not affiliated with the project adds, “Each exoplanet detection technique has its heyday. First it was the radial velocity technique (ground-based planet searches that started the whole field). Second it was the transit technique (namely Kepler). Now,” she says, “it is the ‘direct imaging’ planet-finding technique's turn to make waves.” 

In 2014, the GPI team will begin a large-scale survey, looking at 600 young stars to see what giant planets orbit them. GPI will also be available to the whole Gemini community for other projects, ranging from studies of planet-forming disks to outflows of dust from massive, dying stars. 

Looking through Earth’s turbulent atmosphere, even with advanced adaptive optics, GPI will only be able to see Jupiter-sized planets. But similar technology is being proposed for future space telescopes.

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

GPI is an international project led by the Lawrence Livermore National Laboratory (LLNL) under Gemini’s supervision, with Macintosh as Principal Investigator and LLNL engineer David Palmer as project manager. LLNL also produced the advanced adaptive optics system that measures and corrects for atmospheric turbulence a thousand times a second. Scientists at the American Museum of Natural History, led by Ben Oppenheimer, who also led a project demonstrating some of the same technologies used in GPI on the 5-meter Palomar project, designed special masks that are part of the instrument’s coronagraph which blocks the bright starlight that can obscure faint planets. Engineer Kent Wallace and a team from NASA’s Jet Propulsion Laboratory constructed an ultra-precise infrared wavefront sensor to measure small distortions in starlight that might mask a planet. A team at the University of California Los Angeles’ Infrared Laboratory, under the supervision of Professor James Larkin, together with Rene Doyon at the University of Montreal, assembled the infrared spectrograph that dissects the light from planets. Data analysis software written at University of Montreal and the Space Telescope Science Institute assembles the raw spectrograph data into three-dimensional cubes. NRC Herzberg in British Columbia Canada, built the mechanical structure and software that knits all the pieces together. James R. Graham, as project scientist, led the definition of the instrument’s capabilities. The instrument underwent extensive testing in a laboratory at the University of California Santa Cruz before shipping to Chile in August.  The SETI institute in California manages GPI’s data and communications. 

 

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Novel instrument able to probe close binary stars may one day image exoplanets

Berkeley — Most stars in the galaxy are surrounded by swirling disks of dust, circling planets or other orbiting stars, yet astronomers have a hard time studying these companions because of glare from the main star.

A new instrument that combines two high-resolution telescope techniques – adaptive optics and interferometry – has for the first time distinguished and studied the individual stars in a nearby binary star system, demonstrating promise for eventually picking out planets around other stars.

In the December issue of the journal Astronomy & Astrophysics, University of California, Berkeley, astronomers and an international team of colleagues report that they were able to resolve in visible light the two stars in the binary star system Capella, which orbit one another at about the distance of Venus from the sun and until now have been indistinguishable from Earth. Capella is 43 light years from Earth and the brightest star in the constellation Auriga.

The team, led by UC Berkeley assistant research astronomer Gaspard Duchêne, used a prototype instrument called the Fibered Imager foR Single Telescope (FIRST) that was mounted three years ago on the Shane 3-meter telescope at the University of California Lick Observatories in San Jose.

"This really is a window on a unique combination of contrast and resolution that is not available today," Duchêne said.

Earlier this year, the astronomers mounted an improved instrument on the Subaru 8-meter telescope in Hawaii that has the potential to one day resolve exoplanets, or Earth-like planets around M-type "dwarf" stars, which are slightly smaller and cooler than the sun. Imaging exoplanets is a hot field for astronomers, who learned last month that our galaxy may contain 40 billion or more potentially habitable planets circling M stars or stars like the sun.

"With the FIRST instrument at Subaru telescope, we expect to be able to resolve giant and super giant stars and observe the close environment of debris disks around young stars," said coauthor Franck Marchis, a research astronomer at the SETI Institute in Mountain View, Calif. Marchis initiated the Lick project in 2009 while at UC Berkeley.

The FIRST instrument at Lick Observatories uses fiber optic communication cables to channel visible light from 18 different spots on the main mirror of the telescope to a detector, where the light beams interfere to reveal high-resolution detail in the same way radio telescope arrays use interferometry to achieve high-resolution radio images of the sky. The FIRST instrument on the Subaru telescope also uses 18 fiber optic cables to sample spots on a larger 8-meter main mirror. The 3-meter Lick and 8-meter Subaru telescopes are already equipped with adaptive optics, which creates sharper images by removing the jiggle in stars caused by turbulence in the atmosphere. FIRST takes advantage of the stability provided by the adaptive optics system to inject the light from the star into the precise center of the fibers, which have a core a mere 4 micrometers in diameter.

The key advantage of FIRST is that it can resolve very close objects, such as close binary stars or the disks of dust and gas that circle stars in the process of forming planets. It can even resolve the surface features on red super giant stars, which bloat to the diameter of Earth's orbit. Other techniques are limited by the turbulent glare from the stars, which is effectively removed by the use of fibers in FIRST.

At the moment, however, FIRST cannot resolve objects that differ in brightness by more than 50-100 times. Planets the size of Jupiter are typically 10,000-100,000 times fainter than their stars, while Earth-size planets are a million times fainter.

"If we could add enough fibers, we could get very high contrast; that is the goal," Duchêne said. "If we can scale this up to look for planets, it would be very, very exciting."

FIRST also can simultaneously obtain a spectrum of each object, providing critical information on the chemical composition and temperature of the stars, debris disks or planets, he said.

One of the key components of the system is a tiny movable mirror, a microelectromechanical systems or MEMS device, that directs starlight into the optical fibers, which channel the light without much loss to the interferometer. The MEMS device was developed by a UC Berkeley spinoff called IRIS AO, Inc., based only a few blocks from UC Berkeley's astronomy department.

Coauthors with Duchêne and Marchis are E. Huby, S. Lacour, G. Perrin and É. Choquet of the Observatoire de Paris; T. Kotani of the National Astronomical Observatory of Japan; E. L. Gates of Lick Observatory; O. Lai of the Gemini Observatory in Hawaii; and F. Allard of the Université de Lyon.

The project at the Lick Observatories was funded by the Programme National de Physique Stellaire (PNPS) in France, a Small Research Grant of the American Astronomical Society, NASA (grant NNX11AD62G) and the National Science Foundation (award # AAG-0807468).

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