Kepler Goes Silent

This last week we said goodbye to a truly pioneering space telescope. The Kepler mission was designed to find exoplanets, planets that orbit around other stars. The mission succeeded beyond everyone’s expectations.

Artist’s rendition of the Kepler Spacecraft in orbit around the Sun peering at a distant solar system, press release image from the NASA Kepler website
This little space telescope monitored over 500,000 stars during it’s mission, watching for the minuscule dip in brightness as a panet passed in front of the star. For nine years Kepler stared at those thousands of stars, during that time it discovered over 2,600 exoplanets. Along with the planets came a long list of other discoveries such as binary stars, variable stars, and novae.

After nine productive years this engine of discovery has come to an end. With the spacecraft out of fuel NASA flight engineers sent the last commands, shutting the spacecraft down.

The Keck Observatory and the Kepler Spacecraft had a great partnership. It was not possible to confirm most Kepler’s possible exoplanets using only data from the spacecraft. A large telescope using a high resolution spectrograph, like HIRES on Keck 1, would allow astronomers to not only confirm Kepler’s discovery, but to learn more about each exoplanet.

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Unexpected Classification of Exoplanets Discovered

W. M. Keck Observatory press release

Since the mid-1990s, when the first planet around another sun-like star was discovered, astronomers have amassed an ever-expanding collection of nearly 3,500 confirmed exoplanets.

Exoplanet Formation
Assembly Line of Planets: This diagram illustrates how planets are assembled and sorted into two distinct size classes. Image credit: NASA/Kepler/Caltech (R. Hurt)
In a new Caltech-led study, researchers have classified these exoplanets in much the same way that biologists identify new animal species and found the majority of exoplanets fall into two distinct groups: rocky Earth-like planets and larger mini-Neptunes. The team used data from W. M. Keck Observatory and NASA’s Kepler mission.

“This is a major new division in the family tree of planets, analogous to discovering that mammals and lizards are distinct branches on the tree of life,” says Andrew Howard, professor of astronomy at Caltech and a principal investigator of the new research.

The lead author of the new study, to be published in The Astronomical Journal, is Benjamin J. (B. J.) Fulton, a graduate student in Howard’s group.

In essence, their research shows that our galaxy has a strong preference for either rocky planets up to 1.75 times the size of Earth or gas-enshrouded mini-Neptune worlds, which are from 2 to 3.5 times the size of Earth (or somewhat smaller than Neptune). Our galaxy rarely makes planets with sizes in between these two groups.

“Astronomers like to put things in buckets,” says Fulton. “In this case, we have found two very distinct buckets for the majority of the Kepler planets.”

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Astronomy Team Releases Planet-Search Data

UC Santa Cruz press release

An international team of astronomers has released the largest ever compilation of exoplanet-detecting observations made using a technique called the radial velocity method. By making the data public, the team is offering unprecedented access to one of the best exoplanet searches in the world.

Planet Hunters Paul Butler and Steve Vogt
UCSC astronomer Steve Vogt (foreground) with collaborator Paul Butler at the W. M. Keck Observatory in Hawaii. Photo by Laurie Hatch
The data were gathered as part of a two-decade planet-hunting program using a spectrometer called HIRES, built by UC Santa Cruz astronomer Steven Vogt and mounted on the 10-meter Keck-I telescope at the W. M. Keck Observatory atop Mauna Kea in Hawaii.

“HIRES was not specifically optimized to do this type of exoplanet detective work, but has turned out to be a workhorse instrument of the field,” said Vogt, a professor emeritus of astronomy and astrophysics. “I am very happy to contribute to science that is fundamentally changing how we view ourselves in the universe.”

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Over 100 New Exoplanet Candidates Discovered With W. M. Keck Observatory

W. M. Keck Observatory press release

Exoplanet GJ 411
HIRES instrument helps detect potential exoplanets. Artist’s conceptions of the probable planet orbiting a star called GJ 411, courtesy of Ricardo Ramirez.
An international team of astronomers today released a compilation of almost 61,000 individual measurements made on more than 1,600 stars, used to detect exoplanets elsewhere in our Milky Way galaxy. The compilation includes data on over 100 new potential exoplanets. The entire dataset was observed using one of the twin telescopes of the W. M. Keck Observatory on Maunakea over the past two decades. The search for new worlds elsewhere in our Milky Way galaxy is one of the most exciting frontiers in astronomy today. The paper is published in the Astronomical Journal.

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New Planet Imager Delivers First Science

JPL press release

A new device on the W.M. Keck Observatory in Hawaii has delivered its first images, showing a ring of planet-forming dust around a star, and separately, a cool, star-like body, called a brown dwarf, lying near its companion star.

Vortex Coronagraph
The vortex mask with a microscopic view shown on the right. Image Credit: University of Liège/Uppsala University
The device, called a vortex coronagraph, was recently installed inside NIRC2 (Near Infrared Camera 2), the workhorse infrared imaging camera at Keck. It has the potential to image planetary systems and brown dwarfs closer to their host stars than any other instrument in the world.

“The vortex coronagraph allows us to peer into the regions around stars where giant planets like Jupiter and Saturn supposedly form,” said Dmitri Mawet, research scientist at NASA’s Jet Propulsion Laboratory and Caltech, both in Pasadena. “Before now, we were only able to image gas giants that are born much farther out. With the vortex, we will be able to see planets orbiting as close to their stars as Jupiter is to our sun, or about two to three times closer than what was possible before.”

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More Than 100 Planets Confirmed in Single Trove

W. M. Keck Observatory press release

An international team of astronomers have discovered and confirmed a treasure trove of new worlds. The researchers achieved this extraordinary discovery of exoplanets by combining NASA’s K2 mission data with follow-up observations by Earth-based telescopes including the W. M. Keck Observatory on Maunakea, the twin Gemini telescopes on Maunakea and in Chile, the Automated Planet Finder of the University of California Observatories and the Large Binocular Telescope operated by the University of Arizona. The team confirmed more than 100 planets, including the first planetary system comprising four planets potentially similar to Earth. The discoveries are published online in The Astrophysical Journal Supplement Series.

Image montage showing the Maunakea Observatories, Kepler Space Telescope, and night sky with K2 Fields and discovered planetary systems (dots) overlaid. Credit: Karen Teramura/IFA , Miloslav Druckmüller, NASA
Image montage showing the Maunakea Observatories, Kepler Space Telescope, and night sky with K2 Fields and discovered planetary systems (dots) overlaid. Credit: Karen Teramura/IFA , Miloslav Druckmüller, NASA
Ironically, the bounty was made possible when the Kepler space telescope’s pointing system broke.

In its initial mission, Kepler surveyed a specific patch of sky in the northern hemisphere, measuring the frequency with which planets whose sizes and temperatures are similar to Earth occur around stars like our sun. But when it lost its ability to precisely stare at its original target area in 2013, engineers created a second life for the telescope that is proving remarkably fruitful.

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Four Synchronized Planets Reveal Clues to How Planets Form

W. M. Keck Observatory press release

The search for planets orbiting other stars in our galaxy has revealed an extraordinary family of planets whose orbits are so carefully timed that they provide long-term stability for their planetary system. The data came from observations from the Kepler Space Telescope and the W. M. Keck Observatory on Maunakea, Hawaii. A paper describing the formation of this planetary system by a research team was published in the journal Nature today.

Kepler223 Animation
The Kepler–223 planetary system, click on the image for an animation. Credit: W. Rebel
“The Kepler-223 planetary system has unusually long-term stability because its four planets interact gravitationally to keep the beat of a carefully choreographed dance as they orbit their host star,” said Eric Ford, a professor of astronomy and astrophysics at Penn State and a member of the research team. Each time the innermost planet (Kepler-223b) orbits the system’s star 3 times, the second-closest planet (Kepler-223c) orbits precisely 4 times. Thus, these two planets return to the same positions relative to each other and their host star.

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Hot Jupiter-esque Discovery Hints at Planet Formation

W. M. Keck Observatory press release

A team of astronomers discovered a Jupiter-like planet within a young system that could serve as a decoder ring for understanding how planets formed around our sun. The W. M. Keck Observatory on Maunakea, Hawaii confirmed the discovery. The findings were headed by Bruce Macintosh, a professor of physics at Stanford University, and show the new planet, 51 Eridani b, is one million times fainter than its parent star and shows the strongest methane signature ever detected on an alien planet, which should yield additional clues as to how the planet formed. The results are published in the current issue of Science.

51Eri b
Image of 51 Eri b as seen by the NIRC2 instrument on Keck Observatory’s Keck II telescope. Credit: W. M. Keck Observatory, Christian Marois, NRC Canada
“This is the first exoplanet discovered with the Gemini Planet Imager, one of the new generation instruments designed specifically for discovering and analyzing faint, young planets orbiting bright stars,” said Franck Marchis, Senior Planetary Astronomer at the SETI Institute and member of the team that built the instrument and now conducts the survey.

While NASA’s Kepler space observatory has discovered thousands of planets, it does so indirectly by detecting a loss of starlight as a planet passes in front of its star, the Gemini Planet Imager was designed specifically for discovering and analyzing faint, young planets orbiting bright stars.

“To detect planets, Kepler sees their shadow,” said Macintosh, who is also a member of the Kavli Institute for Particle Astrophysics and Cosmology. “The Gemini Planet Imager instead sees their glow, which we refer to as direct imaging.”

Akin to trying to detect a firefly in front of a lighthouse, the team analyzed the light from the star, then blocked it out. The remaining incoming light was analyzed, with the brightest spots indicating a possible planet.

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Telescopes Team Up to Find Distant Uranus-Sized Planet Through Microlensing

W. M. Keck Observatory press release

The W. M. Keck Observatory in Hawaii and NASA’s Hubble Space Telescope have made independent confirmations of an exoplanet orbiting far from its central star. The planet was discovered through a technique called gravitational microlensing. This finding opens a new piece of discovery space in the extrasolar planet hunt: to uncover planets as far from their central stars as Jupiter and Saturn are from our sun. The Hubble and Keck Observatory results will appear in two papers in the July 30 edition of The Astrophysical Journal.

OGLE-2005-BLG-169 Microlensing
A graphic explanation of the microlensing study of OGLE-2005-BLG-169. Credit: NASA, ESA, and A. Feild (STSCI)
The large majority of exoplanets cataloged so far are very close to their host stars because several current planet-hunting techniques favor finding planets in short-period orbits. But this is not the case with the microlensing technique, which can find more distant and colder planets in long-period orbits that other methods cannot detect.

Microlensing occurs when a foreground star amplifies the light of a background star that momentarily aligns with it. If the foreground star has planets, then the planets may also amplify the light of the background star, but for a much shorter period of time than their host star. The exact timing and amount of light amplification can reveal clues to the nature of the foreground star and its accompanying planets.

“Microlensing is currently the only method to detect the planets close to their birth place,” said team member, Jean-Philippe Beaulieu, Institut d’Astrophysique de Paris. “Indeed, planets are being mostly formed at a certain distance from the central star where it is cold enough for volatile compounds to condense into solid ice grains. These grains will then aggregate and will ultimately evolve into planets.”

The system, cataloged as OGLE-2005-BLG-169, was discovered in 2005 by the Optical Gravitational Lensing Experiment (OGLE), the Microlensing Follow-Up Network (MicroFUN), and members of the Microlensing Observations in Astrophysics (MOA) collaborations—groups that search for extrasolar planets through gravitational microlensing.

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Found: Earth’s Closest Cousin Yet

W. M. Keck Observatory press release

The W. M. Keck Observatory has confirmed the first near-Earth-size planet in the “habitable zone” around a sun-like star. This discovery and the introduction of 11 other new small habitable zone candidate planets were originally made by NASA’s Kepler space telescopes and mark another milestone in the journey to finding another “Earth.”

Kepler 452b
This artist’s concept compares Earth (left) to the new planet, called Kepler-452b, which is about 60 percent larger in diameter. Credit: NASA/JPL-Caltech/T. Pyle
“We can think of Kepler-452b as bigger, older cousin to Earth, providing an opportunity to understand and reflect upon Earth’s evolving environment,” said Jon Jenkins, Kepler data analysis lead at NASA’s Ames Research Center in Moffett Field, California, who led the team that discovered Kepler-452b. “It’s awe-inspiring to consider that this planet has spent 6 billion years in the habitable zone of its star; about 1.5 billion years longer than Earth. That’s substantial opportunity for life to arise, should all the necessary ingredients and conditions for life exist on this planet.”

The data from Kepler suggested to the team there was a planet causing the light from it’s host star to dim as is orbited around it. The team then turned to ground-based observatories including the University of Texas at Austin’s McDonald Observatory, the Fred Lawrence Whipple Observatory on Mt. Hopkins, Arizona, and the world’s largest telescopes at Keck Observatory on Maunakea, Hawaii for confirmation.

Specifically, the ten-meter Keck I telescope, fitted with the HIRES instrument was used to confirm the Kepler data as well as to more precisely determine the properties of the star, specifically its temperature, surface gravity and metallicity.

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