Strange New Worlds: Is Earth Special?

Phil Plait is an American astronomer, skeptic, writer and brainchild behind the popular science blog “Bad Astronomy,” on which he tries to debunk scientific myths and misconceptions. Though never a NASA employee, he has worked as part of the Hubble Space Telescope team as well as engaging in public outreach advocacy for several NASA missions focused on high-energy forms of light emitted by black holes, exploding stars and super-dense neutrons stars. Plait is the author of two books, Bad Astronomy and Death from the Skies!, in which he provides real science behind all the ways astronomical events could wipe out life on Earth. Plait attended the University of Michigan and earned a Ph.D. in astronomy from the University of Virginia

A Candidate Substellar Companion to HR 7329

We present the discovery of a candidate substellar companion from a survey of nearby, young stars with the NICMOS coronagraph on the Hubble Space Telescope. The H ~ 12 mag object was discovered approximately 4" from the young A0V star HR 7329. Using follow-up spectroscopy from STIS, we derive a spectral type between M7V and M8V with an effective temperature of ~ 2600 K. We estimate that the probability of a chance alignment with a foreground dwarf star of this nature is ~ 10^(-8) and therefore suggest the object (HR 7329B) is physically associated with HR 7329 with a projected separation of 200 AU. Current brown dwarf cooling models indicate a mass of less than 50 Jupiter masses for HR 7329B based on age estimates of < 30 Myr for HR7329A.Comment: 8 pages LATEX, 5 ps figures, accepted for Ap

An Infrared Coronagraphic Survey for Substellar Companions

We have used the F160W filter (1.4-1.8 um) and the coronagraph on the Near-InfraRed Camera and Multi-Object Spectrometer (NICMOS) on the Hubble Space Telescope (HST) to survey 45 single stars with a median age of 0.15 Gyr, an average distance of 30 pc, and an average H-magnitude of 7 mag. For the median age we were capable of detecting a 30 M_Jup companion at separations between 15 and 200 AU. A 5 M_Jup object could have been detected at 30 AU around 36% of our primaries. For several of our targets that were less than 30 Myr old, the lower mass limit was as low as a Jupiter mass, well into the high mass planet region. Results of the entire survey include the proper motion verification of five low-mass stellar companions, two brown dwarfs (HR7329B and TWA5B) and one possible brown dwarf binary (Gl 577B/C).Comment: 11 figures, accepted by A

# 2005. The American Astronomical Society. All rights reserved. Printed in U.S.A. AN INFRARED CORONAGRAPHIC SURVEY FOR SUBSTELLAR COMPANIONS

We have used the F160W filter (1.4–1.8 m) and the coronagraph on the Near-Infrared Camera and Multi-Object Spectrometer (NICMOS) on the Hubble Space Telescope to survey 45 single stars with a median age of 0.15 Gyr, an average distance of 30 pc, and an average H magnitude of 7 mag. For the median age we were capable of detecting a 30M J companion at separations between 15 and 200 AU. A 5M J object could have been detected at 30 AU around 36 % of our primaries. For several of our targets that were less than 30 Myr old, the lower mass limit was as low as 1M J, well into the high mass planet region. Results of the entire survey include the proper-motion verification of five low-mass stellar companions, two brown dwarfs (HR7329B and TWA5B), and one possible brown dwarf binary (Gl 577B/C). Key word: stars: low-mass, brown dwarf