Astrobites at AAS 225: Day 2

Tuesday marked the second full day of the Seattle AAS meeting, and also the best day (so far, at least), because Astrobites had a poster.

Here are a few more highlights from Tuesday.


Press Conference: Exoplanets and Host Stars II (by Erika Nesvold)

The second exoplanet press conference of this AAS meeting started with some exciting news from Kepler. Remember, Kepler finds exoplanet candidates by measures dips in the light of a star as a (possible) planet passes in front of it. But follow up measurements (with radial velocity techniques, for example) are required to confirm any candidate as a planet.

Fergal Mullally from Kepler announced the release of its sixth catalogue of planet candidates, the first in a little over a year. This data release brings the total number of Kepler planet candidates up to 4,175, and is sensitive to the harder-to-find, smaller planets farther from their stars. Eight of these candidates are in the habitable zone, and sixth of those orbit Sun-like stars. If these candidates are confirmed as planets, that would make them some of the closest analogues to Earth and Venus that we’ve seen to date!

Douglas Caldwell from the SETI Institute then announced the confirmation of eight Kepler candidates as planets, including the 1,000th verified Kepler exoplanet! Three of these planets are smaller than 2 Earth radii (making them potentially rocky) and in their habitable zones, which brings the total number of these Earth-sized habitable zone planets up to eight.

The topic of the press conference then shifted to debris disks. Marc Kuchner talked about Disk Detective, a NASA-led citizen science program to analyze results from NASA’s WISE mission. WISE observed 747 million infrared sources, a few thousand of which are debris disks or protoplanetary disks. These disks have to be identified by eye, so Disk Detective asks citizen scientists to look at each source at different wavelengths to try to weed out objects that are clearly not disks. Disk Detective’s 28,000 volunteers reached 1 MILLION classifications on Christmas Day! The program has identified 478 objects of interest so far, which will be examined with follow-up observations to determine which are actually disks.

Finally, Marshall Perrin talked about exciting results from the Gemini Planet Imager (GPI), which started full science operations in November, although it’s been conducting preliminary and testing operations since 2013. There have been eight science papers from GPI in the last six months, and Perrin highlighted two. First, GPI observed the multi-planet system HR 8799 and obtained high-resolution spectra of planets c and d. They discovered that the two planets have very different atmospheric features! In the second paper, GPI saw an unprecedented level of detail in polarized light images of the HR 4796 debris ring.

Plenary Talk: Cannon Award: New Frontiers in Stellar Astrophysics: Massive Stars as Cosmological Tools (by Meredith Rawls)

Each year, the AAS presents the Annie Jump Cannon Award to a female astronomer who received her Ph.D. in the past five years. This year’s prize talk was by Emily Levesque. She presented a compelling argument for why we need accurate and precise measurements of stars in order to properly address bigger questions about galaxies and our Universe.

For example, as illustrated above, without accurate models of how stars live and evolve, we can’t understand how star formation affects galaxies. This in turn affects what kinds of stars we expect to cause high-energy Gamma Ray Bursts (GRBs). The arrows can go both ways in many of these connections, but the point remains.

Levesque also discussed the recent discovery of the first Thorn-Zytkow object (TZO):

Massive stars truly are diverse, fascinating laboratories for learning more about our Universe.


Press Conference: Sloan Digital Sky Survey (by Erika Nesvold)

The second press conference on Tuesday was all about the third Sloan Digital Sky Survery program, SDSS-III, which operated from 2008-2014. First, Connie Rockosi announced the final public data release from SDSS-III, which contains 5 million spectra and images of 470 million galaxies in stars, in 117 terabytes of data.

Daniel Eisenstein talked about SDSS-III’s BOSS program, which is the world’s largest redshift survey of galaxies. BOSS measures the spectral redshift of galaxies to turn sky maps into 3D images. A key science goal of BOSS is to study the acceleration of the expansion of the universe. Eisenstein announced that BOSS has covered 25% of the sky, mapping 1.4 million new galaxies up to redshift 0.75. They’ve found strong confirmation that dark energy exists, and that it’s constant over time. They also measured the curvature of the universe and found that it is negligible, indicating that the universe is flat.

Jian Ge talked about the SDSS-III program MARVELS, which is the world’s largest precision Doppler radial velocity survey. MARVELS can measure up to 60 stellar spectra at a time, which allowed them to monitor 5,500 Sun-like stars from 2008-2012. They discovered 38 brown dwarf candidates, and doubled the number of known close-in brown dwarfs. Jian Ge also announced the discovery of HD 87646, the first known binary star system that harbors both a brown dwarf and a planet.

Finally, Steve Majewski discussed APOGEE, the first comprehensive, high-resolution spectral survey of all populations of stars in the Milky Way. APOGEE works in the infrared, so it can probe hidden regions of stars behind dust. APOGEE’s spectrograph can observe 300 objects at once, creating the most comprehensive map of galactic chemistry. This allows scientists to study the chemical composition of stars in different regions of the Galaxy at a high level of detail.



Check back in tomorrow for a summary of Wednesday’s events!

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This post was written collectively by multiple members of the Astrobites team. Meet the authors of Astrobites.

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