Astronomers have validated 41 new exoplanets following four years of observations from the W.M. Keck Observatory’s Keck I telescope atop Mauna Kea.
The validations confirm that numerous NASA Kepler spacecraft discoveries are in fact planets ranging in size from that of our Earth to that of Neptune, the observatory reported Wednesday. Using the Keck I telescope, scientists on Hawaii Island’s tallest mountain were able to confirm the 41 exoplanets — planets outside our solar system — as well as the masses of 16 of those exoplanets.
With the mass and diameter of the exoplanets provided by Kepler, scientists were able to also determine the density of the planets, characterizing them as rocky or gaseous, or a combination of the two, the observatory reported. Among the findings are five new rocky planets ranging in size from 10 to 80 percent larger than Earth.
According to the scientists, two of those rocky planets — Kepler- 99b and 406b — are each 40 percent larger 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 prepared statement from the observatory reads.
More than three quarters of the planet candidates discovered by NASA’s Kepler spacecraft, which now stands at more than 3,500 according to NASA, have sizes ranging from that of Earth to that of Neptune. 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 composed of rock, gas or water.
The Kepler Mission seeks to survey a portion of our region of the Milky Way galaxy to discover dozens of Earth-size planets in or near the habitable zone and determine how many of the billions of stars in our galaxy have such planets, according to NASA.
The validation of 41 new exoplanets was highlighted at the winter American Astronomical Society conference held Jan. 5 to 9 in Washington, D.C. Two other Keck-related results were highlighted during the event, including the first image showing the structure of a normal galaxy in the early universe and the unveiling of a deep sea of small and faint early galaxies.
A major component of the Keck observations that confirmed the exoplanets was Doppler measurements of the planet’s host stars, the observatory said. By measuring the reflex wobble of the host star, which is caused by the gravitational pull on the star exerted by the orbiting planet, scientists can reveal the wobble of the planet. The greater the wobble of the star, the greater the mass of the planet.
“This marvelous avalanche of information about the mini-Neptune planets is telling us about their core-envelope structure, not unlike a peach with its pit and fruit,” said Geoff Marcy, a professor of astronomy at the University of California at Berkeley who led the summary analysis of the Doppler study using a high-resolution echelle spectrometer system installed on the Keck I telescope. “We now face daunting questions about how these enigmas formed and why our solar system is devoid of the most populous residents in the galaxy.”
The density measurements identify the possible chemical compositions of the planets, the observatory said. The measurements from Keck I suggest that the planets smaller than Neptune have a rocky core but the proportions of hydrogen, helium and hydrogen-rich molecules in the envelope surrounding that core vary dramatically, with some having no gaseous envelope.
Marcy was able to validate 38 planets, of which six are considered nontransiting planets, only seen in the Doppler data, according to the observatory. Marcy’s findings were recently published in The Astrophysical Journal.
Another method used to determine the mass and in turn density of a plant is by measuring the transit timing variations. Much like the gravitational force of a planet on its star, neighboring planets can tug on one another causing one planet to accelerate and another to planet to slow along its orbit, according to the observatory.
Ji-Wie Xie, of the University of Toronto, used the variations to validate 15 pairs of Kepler planets ranging from Earth-sized to a little larger than Neptune. Her results, which provide more insight on characteristics of exoplanets, were also recently published in The Astrophysical Journal.
“Kepler’s primary objective is to determine the prevalence of planets of varying sizes and orbits. Of particular interest to the search for life is the prevalence of Earth-sized planets in the habitable zone,” said Natalie Batalha, Kepler mission scientist at NASA’s Ames Research Center in Moffett Field, Calif. “But the questions in the back of our minds are: are all planets the size of Earth rocky? Might some be scaled-down versions of icy Neptunes or steamy water worlds? What fraction are recognizable as kin of our rocky, terrestrial globe?”
The results from the Keck, Doppler and transit timing variations hint that a large fraction of planets smaller than 1.5 times the radius of Earth may be comprised of the silicates, iron, nickel and magnesium that are found in the terrestrial planets here in the solar system. Using this information, scientists will now be able to determine which stars harbor bona fide rocky planets versus just Earth-sized planets.
“And, that’s a step closer to finding a habitable environment beyond the solar system,” the observatory said in the prepared statement.
Keck, Hubble unveil faint early galaxies
A team of scientists led by astronomers at the University of California at Riverside has used NASA’s Hubble Space Telescope and the W.M. Keck Observatory atop Mauna Kea to unveil a long-suspected underlying population of galaxies that produces the bulk of new stars during the universe’s early years.
The 59 galaxies are the smallest, faintest and most numerous ever seen in the remote universe, and were captured by Hubble deep exposures taken in ultraviolet light, and confirmed using the Keck I telescope, according to the observatory. They were photographed by Hubble as they appeared more than 10 billion years ago, during the heyday of star birth.
The newly discovered galaxies are 100 times more numerous than their more massive cousins. But they are 100 times fainter than galaxies typically detected in previous deep-field surveys of the early universe.
The team then confirmed the redshift, and the age of the galaxies, on 12 of the sample 58 galaxies with Keck Observatory’s 10-meter telescope.
Study leader Brian Siana and the team believes with the find that is has completed the census of galaxies at an epoch when the universe was roughly 3.4 billion years old. If this sample of galaxies is representative of the entire population at this early time, then the majority of new stars formed in these small galaxies.
Uncovering these galaxies also helps bolster claims that hot stars in small galaxies pumped out enough radiation to ionize hydrogen by stripping off electrons. This process, called “reionization,” occurred about 13 billion years ago, within the first billion years after the big bang. Reionization made the universe transparent to light, allowing astronomers to look far back into time, according to Siana.
Results from the study appear in the Jan. 10 issue of The Astrophysical Journal and were presented during the 223rd meeting of the American Astronomical Society earlier this month in Washington, D.C.
Keck captures first image of normal galaxy structure in the early universe
A University of Hawaii at Manoa astronomer has obtained the first spatially resolved image that shows the structure of a normal galaxy in the early universe using the W.M. Keck Observatory.
The galaxy, called DLA2222-0946, is so faint that it is virtually invisible at all but a few specific wavelengths. It is a member of a class of galaxies thought to be progenitors — or something that is a model for something else — of spiral galaxies like the Milky Way.
These galaxies are known to contain most of the neutral gas that is required for star formation, meaning they are an important tool for understanding star and galaxy formation and evolution, according to the observatory. They were first discovered and classified three decades ago.
The galaxy was detected using the 10-meter Keck I telescope fitted with an OH-Suppressing Infrared Imaging Spectrograph and Laser Guide Star Adaptive Optics system. The galaxy is located at a redshift of 2.354, which corresponds about 10.8 million years ago, a key period of galaxy formation.
The findings will be published in The Astrophysical Journal.