The Kepler team today reports on four years of observations from the W. M. Keck Observatory targeting Kepler’s exoplanet systems, announcing results this week at the American Astronomical Society meeting in Washington. These observations, from Keck Observatory on the summit of Mauna Kea, confirm that numerous Kepler discoveries are indeed planets and yield mass measurements of these enigmatic worlds that vary between Earth and Neptune in size.
Chart of Kepler planet candidates as of January 2014., credit NASA AmesMore than three-quarters of the planet candidates discovered by NASA’s Kepler spacecraft have sizes ranging from that of Earth to that of Neptune, which is nearly four times as big as Earth. Such planets dominate the galactic census but are not represented in our own solar system. Astronomers don’t know how they form or if they are made of rock, water or gas.
Using one of the two world’s largest telescopes at Keck Observatory in Hawaii, scientists confirmed 41 of the exoplanets discovered by Kepler and determined the masses of 16. With the mass and diameter in-hand, scientists could immediately determine the density of the planets, characterizing them as rocky or gaseous, or mixtures of the two.
More than three-quarters of the planet candidates discovered by NASA’s Kepler spacecraft have sizes ranging from that of Earth to that of Neptune, which is nearly four times as big as Earth. Such planets dominate the galactic census but are not represented in our own solar system. Astronomers don’t know how they form or if they are made of rock, water or gas.
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 websiteThe Kepler team today reports on four years of ground-based follow-up observations targeting Kepler’s exoplanet systems at the American Astronomical Society meeting in Washington. These observations confirm the numerous Kepler discoveries are indeed planets and yield mass measurements of these enigmatic worlds that vary between Earth and Neptune in size.
Included in the findings are five new rocky planets ranging in size from 10 to 80 percent larger than Earth. Two of the new rocky worlds, dubbed Kepler-99b and Kepler-406b, are both 40 percent larger in size than Earth and have a density similar to lead. The planets orbit their host stars in less than five and three days respectively, making these worlds too hot for life as we know it.
A major component of these follow-up observations was Doppler measurements of the planets’ host stars. The team measured the reflex wobble of the host star, caused by the gravitational tug on the star exerted by the orbiting planet. That measured wobble reveals the mass of the planet: the higher the mass of the planet, the greater the gravitational tug on the star and hence the greater the wobble.
In the fable of the town and country mice, the country mouse visits his city-dwelling cousin to discover a world of opulence. In the early cosmos, billions of years ago, galaxies resided in the equivalent of urban or country environments. Those that dwelled in crowded areas called clusters also experienced a kind of opulence, with lots of cold gas, or fuel, for making stars.
Today, however, these galactic metropolises are ghost towns, populated by galaxies that can no longer form stars. How did they get this way and when did the fall of galactic cities occur?
A new study from NASA’s Spitzer Space Telescope finds evidence that these urban galaxies, or those that grew up in clusters, dramatically ceased their star-making ways about 9 billion years ago (our universe is 13.8 billion years old). These galactic metropolises either consumed or lost their fuel. Galaxies in the countryside, by contrast, are still actively forming stars.
“We know the cluster galaxies we see around us today are basically dead, but how did they get that way?” wondered Mark Brodwin of the University of Missouri-Kansas City, lead author of this paper, published in the Astrophysical Journal. “In this study, we addressed this question by observing the last major growth spurt of galaxy clusters, which happened billions of years ago.”
Like many I was watching as comet ISON passed through perihelion. A better show than many other holiday offerings. It is clear that the comet has failed to survive perihelion passage. Disrupted by tidal forces and the extreme solar heating, the comet appears to have come apart even before closest approach.
I have assembled a better resolution animation of the demise of ISON from SOHO LASCO C2 imagery. Fifty frames at the full 1k x 1k resolution of the camera that shows the event from entry to exit from the field of view. Click on the image below for the full resolution version.
Note the lack of a distinct coma, simply a smeared out debris cloud. A cloud of debris and fragments continues along the original orbit. How large are some of these fragments? This is a question that may have to wait for a few days, allowing observations from a larger telescope further from the Sun.
Best laid plans? Not much hope remains for dawn photos as the comet emerges from the Sun’s glare. There remains comet C/2013 R1 Lovejoy in the morning sky, perhaps another photo session?
SOHO C2 camera view of comet C/2012 S1 ISON apparently disintegrating just before perihelion. (click on image for animation)
It does appear that comet C/2012 S1 ISON has come apart at perihelion. Imagery shows the comet coma dimming and smearing out as if the nucleus has totally disrupted. Even worse, the SDO imagery programmed to cover perihelion very near the sun show nothing. The SDO cameras are very good at this sort of thing, it should show traces even if the nucleus had been stripped of the tail by the solar wind.
So long ISON?
SOHO C2 camera view of comet C/2012 S1 ISON apparently disintegrating just before perihelion.
Scientists from University of California, Berkeley, and University of Hawaii, Manoa, have statistically determined that twenty percent of Sun-like stars in our galaxy have Earth-sized planets that could host life. The findings, gleaned from data collected from NASA’s Kepler spacecraft and the W. M. Keck Observatory, now satisfy Kepler’s primary mission: to determine how many of the 100 billion stars in our galaxy have potentially habitable planets. The results are being published November 4 in the journal Proceedings of the National Academy of Sciences.
Artist’s rendering of the planetary system HR 8799 at an early stage in its evolution. Credit: Dunlap Institute for Astronomy & Astrophysics“What this means is, when you look up at the thousands of stars in the night sky, the nearest sun-like star with an Earth-size planet in its habitable zone is probably only 12 light years away and can be seen with the naked eye. That is amazing,” said UC Berkeley graduate student Erik Petigura, who led the analysis of the Kepler and Keck Observatory data.
“For NASA, this number – that every fifth star has a planet somewhat like Earth – is really important, because successor missions to Kepler will try to take an actual picture of a planet, and the size of the telescope they have to build depends on how close the nearest Earth-size planets are,” said Andrew Howard, astronomer with the Institute for Astronomy at the University of Hawaii. “An abundance of planets orbiting nearby stars simplifies such follow-up missions.”
A team of astronomers has found the first Earth-sized planet outside the solar system that has a rocky composition like that of Earth. This exoplanet, known as Kepler-78b, orbits its star very closely every 8.5 hours, making it much too hot to support life. The results are being published in the journal Nature.
Artist impression of the planet Kepler-78b and its host star. Credit: Karen Teramura (UH/IfA)This Earth-sized planet was discovered using data from NASA’s Kepler Space Telescope, and confirmed and characterized with the W. M. Keck Observatory.
Every 8.5 hours the planet passes in front of its host star, blocking a small fraction of the starlight. These telltale dimmings were picked up by researchers analyzing the Kepler data.
The team led by Dr. Andrew Howard (Institute for Astronomy, University of Hawaii at Manoa) then measured the mass of the planet with the Keck Observatory on Mauna Kea, in Hawaii. Using the ten-meter Keck I telescope fitted with the HIRES instrument, the team employed the radial velocity method to measure how much an orbiting planet causes its star to wobble, to determine the planet’s mass. This is another excellent example of the synergy between the Kepler survey, which has identified more than 3,000 potential exoplanet candidates, and Keck Observatory, which plays a leading role in conducting precise Doppler measurements of the exoplanet candidates.
Powerful new survey telescopes led by the California Institute of Technology (Caltech) are being combined with the W. M. Keck Observatory to provide insight into rare, exotic cosmic explosions. Caltech’s intermediate Palomar Transient Factory (iPTF) recently described the first direct detection of the progenitor of a rare type of supernova in a nearby galaxy. The findings were published n the September 20 issue of Astrophysical Journal Letters [http://dx.doi.org/10.1088/2041-8205/775/1/L7].
The paper describes the detection of a Type Ib supernova, a rare explosion in which the progenitor star lacks an outer layer of hydrogen, the most abundant element in the universe. It has proven difficult to pin down which kinds of stars give rise to Type Ib supernovae. One of the most promising ideas, according to graduate student and lead author Yi Cao, is they originate from Wolf-Rayet stars. These objects are 10 times more massive and thousands of times brighter than the Sun and have lost their hydrogen envelope by means of very strong stellar winds. Until recently, no solid evidence existed to support this theory. Cao and colleagues believe that the young supernova they discovered, iPTF13bvn, occurred at a location formerly occupied by a likely Wolf-Rayet star.
Supernova iPTF13bvn was spotted on June 16, less than a day after the onset of its explosion. With the aid of the world-leading adaptive optics system installed on the Keck II telescope, one of Keck Observatory’s two 10-meter telescopes in Hawaii, the team obtained a high-resolution image of this supernova to determine its precise position. Then they compared the Keck Observatory image to a series of pictures of the same galaxy (NGC 5806) taken by the Hubble Space Telescope in 2005, and found one starlike source spatially coincident to the supernova. Its intrinsic brightness, color, and size — as well as its mass-loss history, inferred from supernova radio emissions — were characteristic of a Wolf-Rayet star.
“All evidence is consistent with the theoretical expectation that the progenitor of this Type Ib supernova is a Wolf-Rayet star,” said Cao. “Our next step is to check for the disappearance of this progenitor star after the supernova fades away. We expect that it will have been destroyed in the supernova explosion.”
Though Wolf-Rayet progenitors have long been predicted for Type Ib supernova, the new work represents the first time researchers have been able to fill the gap between theory and observation, according to study coauthor and Mansi Kasliwal from the Carnegie Institution for Science. “This is a big step in our understanding of the evolution of massive stars and their relation to supernovae,” she said.
The iPTF builds on the legacy of the Caltech-led Palomar Transient Factory (PTF), designed in 2008 to systematically chart the transient sky by using a robotic observing system mounted on the 48-inch Samuel Oschin Telescope on Palomar Mountain near San Diego, California. This state-of-the-art, robotic telescope scans the sky rapidly over a thousand square degrees each night to search for transients.
University of Texas at Austin astronomer Steven Finkelstein has led a team that has discovered and measured the distance to the most distant galaxy ever found, using the W. M. Keck Observatory on the summit of Mauna Kea, Hawaii. The galaxy is seen as it was at a time just 700 million years after the Big Bang. The result will be published in the Oct. 24 issue of the journal Nature.
Initial observations from NASA’s Hubble Space Telescope identified many candidates for galaxies in the early universe, but this galaxy is the earliest and most distant definitively confirmed, using the 10-meter, Keck I telescope fitted with Keck Observatory’s newest instrument, MOSFIRE.
This image from the Hubble Space Telescope CANDELS survey highlights the most distant galaxy in the universe with a measured distance, dubbed z8_GND_5296. Credit: V. Tilvi, S.L. Finkelstein, C. Papovich, A. Koekemoer, CANDELS, and STScI/NASAWhat makes this distance so exciting, is “we get a glimpse of conditions when the universe was only about 5 percent of its current age of 13.8 billion years,” said Casey Papovich of Texas A&M University, second author of the study.
Astronomers can study how galaxies evolve because light travels at a finite speed, about 186,000 miles per second. Thus when we look at distant objects, we see them as they appeared in the past. The farther astronomers can push their observations, the farther into the past they can see.
“We want to study very distant galaxies to learn how they change with time,” Finkelstein said. “This helps us understand how the Milky Way came to be.”
The devil is in the details, however, when it comes to making conclusions about galaxy evolution, which means astronomers must employ the most rigorous methods and utilize the most powerful instruments to measure the distances to these galaxies in order to understand at what epoch of the universe they are seen.
The Hubble CANDELS survey uses colors from HST images to identify potentially distant galaxies. Finkelstein’s team selected z8_GND_5296, and dozens of others, for follow-up spectroscopy from the approximately 100,000 CANDELS galaxies. This method is good, but not foolproof, Finkelstein says. Using colors to sort galaxies is tricky because more nearby objects can masquerade as distant galaxies.
In order to accurately determine the distance to these galaxies, astronomers use spectroscopy to measure how much a galaxy’s light wavelengths have shifted toward the red end of the spectrum over their travels from the galaxy to Earth. This phenomenon is called “redshift”, and is due the expansion of the universe.
The team used Keck Observatory’s Keck I telescope in Hawaii, one of the two largest optical/infrared telescopes in the world, to measure the redshift of z8_GND_5296 at 7.51, the highest galaxy redshift ever confirmed. The redshift means this galaxy hails from a time only 700 million years after the Big Bang.
Mark Kassis stands beside the MOSFIRE spectrographKeck I was fitted with the new MOSFIRE instrument, which made the measurement possible, Finkelstein said. “The instrument is great. Not only is it sensitive, it can look at multiple objects at a time,” he said, which allowed his team to observe 43 galaxies in only two nights at Keck Observatory, and obtain the highest quality observations possible.
In addition to its great distance, the team’s observations showed that the galaxy z8_GND_5296 is forming stars extremely rapidly — producing stars at a rate 150 times faster than our own Milky Way galaxy. This new distance record-holder lies in the same part of sky as the previous record-holder (redshift 7.2), which also happens to have a very high rate of star-formation.
“So we’re learning something about the distant universe,” Finkelstein said. “There are way more regions of very high star formation than we previously thought. … There must be a decent number of them if we happen to find two in the same area of the sky.”
In addition to their studies with Keck, the team also observed z8_GND_5296 in the infrared with NASA’s Spitzer Space Telescope. Spitzer measured how much ionized oxygen the galaxy contains, which helps pin down the rate of star formation. The Spitzer observations also helped rule out other types of objects that could masquerade as an extremely distant galaxy, such as a more nearby galaxy that is particularly dusty.
Other team members include Bahram Mobasher of the University of California, Riverside; Mark Dickinson of the National Optical Astronomy Observatory; Vithal Tilvi of Texas A&M; and Keely Finkelstein and Mimi Song of UT-Austin.
Combining observations from the world’s largest telescopes with small telescopes used by amateur astronomers, a team of scientists discovered that the large main-belt asteroid (87) Sylvia has a complex interior, thanks to the presence of two moons orbiting the main asteroid, and probably linked to the way the multiple system was formed. The findings are being revealed today, October 7, at the 45th annual Division of Planetary Sciences meeting in Denver, Colorado.
Artistic representation of the triple asteroid system showing the large 270-km asteroid Sylvia surrounded by its two moons, Romulus and Remus. Credit: Danielle Futselaar/SETI InstituteThis work illustrates a new trend in astronomy in which backyard amateur astronomers team up with professional astronomers to expand our knowledge of our solar system. The study of multiple asteroids such as (87) Sylvia gives astronomers an opportunity to peek through the past history of our solar system and constrain the internal composition of asteroids. The two moons of (87) Sylvia were discovered in 2005.
The team, led by Franck Marchis, senior research scientist at the Carl Sagan Center of the SETI Institute, has continued to observe this triple asteroid system by gathering 66 adaptive optics observations from 8-10m class telescopes including those at the W. M. Keck Observatory, the European Southern Observatory, and Gemini North.
“Because (87) Sylvia is a large, bright asteroid located in the main belt, it is a great target for the first generation of adaptive optics systems available on these large telescopes. We have combined data from our team with archival data to get a good understanding of the orbits of these moons,” Marchis said.
