For an introduction to APOGEE, take an hour to listen to this interview on WMRA radio’s Virginia Insight featuring APOGEE PI Steve Majewski, Gail Zasowski, and John Wilson.
APOGEE + Kepler Collaboration Highlighted in New Scientist:
The New Scientist reports in its April 2012 issue (subscription required) on searches for stars formed along with our Sun. The article highlights the SDSS-III APOGEE experiment and the new collaboration between SDSS-III and the Kepler asteroseismology team to jointly study stars in the Milky Way. The New Scientist article explains that while APOGEE
is not looking explicitly for the sun’s siblings, “it’s very possible that these stars will be in the sample”, says Steven Majewski of the University of Virginia in Charlottesville. One advantage of APOGEE is that 10 per cent of the stars it surveys are shared by NASA’s Kepler spacecraft, whose observations of flickering starlight will tell us the ages of these stars. This is crucial, says Majewski, because any solar sibling must be the same age as the sun, as well as share its chemical composition and motion.
(New Scientist, 2012 April 7, pp 40-41, “The sun’s sibilings” by Ken Croswell)
Kepler is a space satellite observing 100,000 stars in our Milky Way galaxy to look for planets around Sun-like stars. Its photometric observations are so precise that it can detect the pulsations of distant stars as they resonate with sound waves, much like the many frequencies of vibration in a ringing bell. The science of studying these pulsations is called asteroseismology.
Image: APOGEE’s targets include star clusters like M67 that have an elemental composition very similar to that of the Sun. This image illustrates the APOGEE spectrum (the blue line in the lower part of the image) of just one of the hundreds of stars APOGEE can observe at one time. By studying M67 and other clusters APOGEE will provide insights into the conditions in which our Sun was born.
Image Credit: Peter Frichaboy (TCU), Robert Lupton (Princeton), and the SDSS collaboration.
The Kepler observations reveal the many frequencies of oscillation of individual stars, data that can be used to determine very precisely the radii and masses of these stars. In principle, the stellar radii and masses can be used to determine very precisely the evolutionary state — and, therefore, the age — of each star, but there remains some uncertainty if the chemical composition of the star is unknown. Thus the APOGEE team and Kepler seismologists are now collaborating on a program to use APOGEE spectroscopy to uncover the chemical compositions of a sample of about 10,000 Kepler asteroseismology targets and to create the largest sample of Milky Way field stars with known ages. In addition to providing a set of very well studied stars for understanding the evolution of the Milky Way, the combined data set will improve the calibration of science done with all of the stars in each project.