Ithaca College

The Astrophysical Journal has published a recent study of planet formation led by Luke Keller, Dana Professor in the Department of Physics and Astronomy, in collaboration with an international team of astronomers including seven IC alumni. 

Using data from the Spitzer Space Telescope, Hubble Space Telescope, and several Earth-based telescopes they have analyzed stars located in a galaxy outside the Milky Way that appear to be very young and have gas and dust orbiting them. This orbiting material, which may be in the process of forming planets, is not visible in images of the stars because of their extreme distance from us—200,000 light years or 1.2 million trillion miles—but it is detectable when their light is dispersed into a spectrum. The stars are in an environment very different from that of the sun: the abundances of chemical elements heavier than hydrogen and helium are much lower. This environment is more like that of our Milky Way galaxy several billion years ago, so these observations will enable a future study of how planets formed in the early universe.

IDENTIFICATION OF HERBIG Ae/Be STARS IN THE SMALL MAGELLANIC CLOUD (2019, Astrophysical Journal, 878:147)

by Luke Keller, Gregory C. Sloan , Joana M. Oliveira , Kathleen E. Kraemer , Jacco T. van Loon, Peter R. Wood , Albert Zijlstra , Joshua D. Simon , Rafael Ferreira (IC Class of 2015), Mart'in Garay-MacLean (IC Class of 2014), Jordan T. Hyatt (IC Class of 2010), Kevin Geidel (IC Class of 2010), Joseph Quinn (IC Class of 2017), Daniel Santoro (IC Class of 2017), and Tori Knapp (IC Class of 2019)

Link to Article: https://iopscience.iop.org/article/10.3847/1538-4357/ab204a

Technical Abstract: Protoplanetary disks orbiting intermediate-mass stars, Herbig Ae/Be stars, that have formed in a metal-poor environment may evolve differently than their Galactic cousins. A study of the planet-formation process in such an environment requires identification and characterization of a sample of candidates. We have observed several stars in the Small Magellanic Cloud, a nearby metal-poor dwarf galaxy, that have optical spectral properties of Herbig Ae/Be stars, including strong H-alpha emission, blue continuum excess, and spectral types ranging from early F to B. Infrared spectra of these sources from the Spitzer Space Telescope show strong excess emission indicating the presence of silicate dust, molecular and atomic gas, and polycyclic aromatic hydrocarbons. We present analysis of the likelihood that these candidates are Herbig Ae/Be stars. This identification is the necessary first step to future investigations that will examine the role of metallicity in the evolution of protoplanetary disks.