It’s no secret that the search for extrasolar planets leads to big news. This field seems to be taking the American Astronomical Society meeting by storm, as evidenced by the number of press conferences and how packed the exoplanet science sessions are — standing room only. The first press conference highlighted five different announcements about worlds orbiting other stars.
The Kepler mission has found 2,740 candidate planets around stars other than the Sun. This chart shows the sizes of those discovered, and the percentages show the increase since February 2012. Most of the newest candidates have diameters twice Earth’s or less. // photo by NASA/Kepler mission
First, Christopher Burke of the Kepler
mission team announced that it has found another 461 candidate planets in its data, to bring the total up to 2,740. (These aren’t confirmed
planets … they will require follow-up observations to rule out false positives.) Many of the candidate planets are Earth- and super-Earth-sized, and some sit within their stars’ habitable zone, which is the region within which liquid water could exist on a planet’s surface. One planet that Burke specifically called out was KOI 172.02. This world is comparable to Earth: It orbits its star in 242 days within the habitable zone and is about 1.5 times our planet’s size.
The next announcement came from Francois Fressin of the Harvard-Smithsonian Center for Astrophysics. His team says that 17 percent of stars have Earth-sized planets that orbit within Mercury’s distance from the Sun. (Fressin added that it’s too early in Kepler’s data collection to determine the number of Earth-sized planets in Earth-like orbits. Scientists will need a total of seven or eight years of observations before getting a large enough sample to then estimate from, and they currently have about three years of Kepler data.) He added that astronomers used to think that small planets were more common orbiting small stars, but these new Kepler results (that Burke announced) show that small planets are equally common around all types of stars. Exoplanet discoveries continue to ramp up.
During the question-and-answer portion of the press conference, Kepler scientists described in more detail the difference between a candidate planet and a verified one. So far, researchers have confirmed 105 Kepler planets and found that about 10 to 15 percent of the candidate worlds end up being false positives. John Johnson of Caltech explained that scientists usually can rule out false positives by just looking at light curves, which is a “testament to the quality of Kepler.” With so many more science talks (and press conferences) to come in this meeting, I’m sure we’ll hear more about Kepler’s discoveries.
Then in the afternoon, I attended a press conference about high-energy astrophysics discoveries. First up: results from the NuSTAR mission. This is one of NASA’s Small Explorer missions — less expensive projects (under $120 million) that typically focus on one area of astronomy, as opposed to a project like Hubble that can be used for many different research topics.
NuSTAR imaged the supernova remnant Cassiopeia A in three different frequency ranges. Blue shows the highest-energy X-rays, which have never before been observed in such detail. // photo by NASA/JPL-Caltech/DSS
NuSTAR is a telescope that observes the highest energy X-rays. Fiona Harrison of Caltech (also the NuSTAR principal investigator) discussed the first images from the observatory and the mission’s importance. High-energy astronomers are trying to piece together the distribution of energies in celestial objects, and a portion of the X-ray regime that NuSTAR is looking at has barely been studied. Once scientists collect information about this radiation range, they then can compare these spectra to models to learn how high-energy particles are accelerated to those energies. One thought is supernova shock waves, another thought is instead gamma-ray bursts … but scientists don’t know.
The rest of the day involved looking at some of the poster presentations, attending two of the invited talks (one about the importance of studying galaxy clusters with X-ray radiation and the other about star formation through cosmic time), and attempting to find a seat in a session about characterizing exoplanet atmospheres.
Tomorrow promises to be another packed day, and I’ll post another recap about Tuesday's big news.