NASA Releases Kepler Survey Catalog with Hundreds of New Planet Candidates

NASA’s Kepler space telescope team has released a mission catalog of planet candidates that introduces 219 new planet candidates, 10 of which are near-Earth size and orbiting in their star's habitable zone, which is the range of distance from a star where liquid water could pool on the surface of a rocky planet.

This is the most comprehensive and detailed catalog release of candidate exoplanets, which are planets outside our solar system, from Kepler’s first four years of data. It’s also the final catalog from the spacecraft’s view of the patch of sky in the Cygnus constellation.

With the release of this catalog, derived from data publicly available on the NASA Exoplanet Archive, there are now 4,034 planet candidates identified by Kepler. Of which, 2,335 have been verified as exoplanets. Of roughly 50 near-Earth size habitable zone candidates detected by Kepler, more than 30 have been verified.

Additionally, results using Kepler data suggest two distinct size groupings of small planets. Both results have significant implications for the search for life. The final Kepler catalog will serve as the foundation for more study to determine the prevalence and demographics of planets in the galaxy, while the discovery of the two distinct planetary populations shows that about half the planets we know of in the galaxy either have no surface, or lie beneath a deep, crushing atmosphere – an environment unlikely to host life.

The findings were presented at a news conference Monday at NASA's Ames Research Center in California's Silicon Valley.

“The Kepler data set is unique, as it is the only one containing a population of these near Earth-analogs – planets with roughly the same size and orbit as Earth,” said Mario Perez, Kepler program scientist in the Astrophysics Division of NASA’s Science Mission Directorate. “Understanding their frequency in the galaxy will help inform the design of future NASA missions to directly image another Earth.”

The Kepler space telescope hunts for planets by detecting the minuscule drop in a star’s brightness that occurs when a planet crosses in front of it, called a transit.

This is the eighth release of the Kepler candidate catalog, gathered by reprocessing the entire set of data from Kepler’s observations during the first four years of its primary mission. This data will enable scientists to determine what planetary populations – from rocky bodies the size of Earth, to gas giants the size of Jupiter – make up the galaxy’s planetary demographics.

To ensure a lot of planets weren't missed, the team introduced their own simulated planet transit signals into the data set and determined how many were correctly identified as planets. Then, they added data that appear to come from a planet, but were actually false signals, and checked how often the analysis mistook these for planet candidates. This work told them which types of planets were overcounted and which were undercounted by the Kepler team’s data processing methods.

“This carefully-measured catalog is the foundation for directly answering one of astronomy’s most compelling questions – how many planets like our Earth are in the galaxy?” said Susan Thompson, Kepler research scientist for the SETI Institute in Mountain View, California, and lead author of the catalog study.

One research group took advantage of the Kepler data to make precise measurements of thousands of planets, revealing two distinct groups of small planets. The team found a clean division in the sizes of rocky, Earth-size planets and gaseous planets smaller than Neptune. Few planets were found between those groupings.

Using the W. M. Keck Observatory in Hawaii, the group measured the sizes of 1,300 stars in the Kepler field of view to determine the radii of 2,000 Kepler planets with exquisite precision.

“We like to think of this study as classifying planets in the same way that biologists identify new species of animals,” said Benjamin Fulton, doctoral candidate at the University of Hawaii in Manoa, and lead author of the second study. “Finding two distinct groups of exoplanets is like discovering mammals and lizards make up distinct branches of a family tree.”

It seems that nature commonly makes rocky planets up to about 75 percent bigger than Earth. For reasons scientists don't yet understand, about half of those planets take on a small amount of hydrogen and helium that dramatically swells their size, allowing them to "jump the gap" and join the population closer to Neptune’s size.

The Kepler spacecraft continues to make observations in new patches of sky in its extended mission, searching for planets and studying a variety of interesting astronomical objects, from distant star clusters to objects such as the TRAPPIST-1 system of seven Earth-size planets, closer to home.

Ames manages the Kepler missions for NASA’s Science Mission Directorate. NASA's Jet Propulsion Laboratory in Pasadena, California, managed Kepler mission development. Ball Aerospace & Technologies Corporation operates the flight system with support from the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder.

Researchers Identify Two 'Species' Of Exoplanets: Kepler Planet Family Gets Two Distinct Branches

“Getting the spectra from Keck Observatory is like going out and grabbing a magnifying glass. We could see details that we couldn’t before.”

Just like creatures in the animal kingdom, exoplanets could have species too. That’s how the two distinct branches of exoplanets were termed in a new study on so-called Kepler planets.

A report from Big Island Now took a look at the study led by California Institute of Technology researchers, who discovered that the planets spotted from the W.M. Keck Observatory in Hawaii and NASA’s Kepler mission can mostly be divided into two branches — one “species” including rocky, Earth-like planets and so-called “super-Earths,” and the other including gaseous, Neptune-like planets orbiting distant stars.

As Big Island Now explained, Kepler planets are the ones spotted during NASA’s Kepler Mission, which launched in 2009 with the goal of finding Earth-like planets. There have been over 2,300 exoplanets confirmed over the past eight years through this mission. That’s more than 60 percent of the 3,500 or so exoplanets discovered since the first such planet was discovered in the mid 1990s, and with the revelation that these planets have “species,” the researchers believe they may be on to something.

“Astronomers like to put things in buckets,” said lead author Benjamin Fulton in a statement.

“In this case, we have found two very distinct buckets for the majority of the Kepler planets.” 

Principal investigator and Caltech professor of astronomy Andrew Howard added that the new discovery is similar to how scientists previously discovered that mammals and reptiles made up distinctive families on the tree of life.

Looking closer at the study’s findings, the Milky Way in specific usually has rocky planets that may be as much as 1.75 times the size of Earth, or “mini-Neptunes,” gaseous planets that are about twice to 3.5 times as massive. Interestingly, the study also suggests that the Milky Way only rarely creates planets between the two exoplanet species, regardless of size.

The researchers, which included scientists from Caltech, the University of California in Berkeley, the University of Hawaii, Harvard, and other institutions, made use of the Keck Observatory’s HIRES (High-Resolution Echelle Spectrometer) instrument to determine the size of the Kepler planets. Big Island Now added that the scientists spent multiple years gathering this data and coming up with sizes for orbiting planets that were four times more accurate than established statistics from previous studies.

“Before, sorting the planets by size was like trying to sort grains of sand with your naked eye,” Fulton commented.

“Getting the spectra from Keck Observatory is like going out and grabbing a magnifying glass. We could see details that we couldn’t before.”

Meanwhile, NASA released a catalog of 219 new Kepler planet candidates, including 10 near-Earth-sized planets orbiting within the habitable zone of their host star, or in an area where liquid water could potentially form on the surface. The space agency’s official press release describes the new catalog as the “most comprehensive and detailed” such list of exoplanet candidates, boosting the list of Kepler planet candidates to 4,034, with a total of 2,335 confirmed and verified to be actual exoplanets and 30 planets in the habitable zone.

Cosmic chiral spiral: Water forms 'spine of hydration' around DNA

Water is the Earth's most abundant natural resource, but it's also something of a mystery due to its unique solvation characteristics – that is, how things dissolve in it.

"It's uniquely adapted to biology, and vice versa," said Poul Petersen, assistant professor of chemistry and chemical biology. "It's super-flexible. It dissipates energy and mediates interactions, and that's becoming more recognized in biological systems."

How water relates to and interacts with those systems – like DNA, the building block of all living things – is of critical importance, and Petersen's group has used a relatively new form of spectroscopy to observe a previously unknown characteristic of water.

"DNA's chiral spine of hydration," published May 24 in the American Chemical Society journal Central Science, reports the first observation of a chiral water superstructure surrounding a biomolecule. In this case, the water structure follows the iconic helical structure of DNA, which itself is chiral, meaning it is not superimposable on its mirror image. Chirality is a key factor in biology, because most biomolecules and pharmaceuticals are chiral.

"If you want to understand reactivity and biology, then it's not just water on its own," Petersen said. "You want to understand water around stuff, and how it interacts with the stuff. And particularly with biology, you want to understand how it behaves around biological material – like protein and DNA."

Water plays a major role in DNA's structure and function, and its hydration shell has been the subject of much study. Molecular dynamics simulations have shown a broad range of behaviors of the water structure in DNA's minor groove, the area where the backbones of the helical strand are close together.

The group's work employed chiral sum frequency generation spectroscopy (SFG), a technique Petersen detailed in a 2015 paper in the Journal of Physical Chemistry. SFG is a nonlinear optical method in which two photon beams – one infrared and one visible – interact with the sample, producing an SFG beam containing the sum of the two beams' frequencies, or energies. In this case, the sample was a strand of DNA linked to a silicon-coated prism.

More manipulation of the beams and calculation proved the existence of a chiral water superstructure surrounding DNA.

In addition to the novelty of observing a chiral water structure template by a biomolecule, chiral SFG provides a direct way to examine water in biology.

"The techniques we have developed provide a new avenue to study DNA hydration, as well as other supramolecular chiral structures," Petersen said.

The group admits that their finding's biological relevance is unclear, but Petersen thinks the ability to directly examine water and its behavior within biological systems is important.

"Certainly, chemical engineers who are designing biomimetic systems and looking at biology and trying to find applications such as water filtration would care about this," he said.

Another application, Petersen said, could be in creating better anti-biofouling materials, which are resistant to the accumulation of microorganisms, algae and the like on wetted surfaces.