First Large Infrared Light Survey of Closest Young Star Pairs YieldsNew Multiple Stellar Systems (Forwarded)

Lowell Observatory
Flagstaff, Arizona

Contact:

Steele Wotkyns
Public Relations Manager, Lowell Observatory
(928) 233-3232

Laura K. Kino****a
Public Information Officer, W. M. Keck Observatory
(808) 881-3827

For Release: 9:20 AM, PST January 10, 2007

First Large Infrared Light Survey of Closest Young Star Pairs Yields New
Multiple Stellar Systems in Ophiuchus Star Forming Region

SEATTLE -- After three years of observations using the 10-meter Keck II
telescope in Hawaii, Lowell Observatory astronomer Lisa Prato announces
discovery of four new low-mass double star systems with separations
similar to the Earth-Sun distance or smaller. This survey also
serendipitously revealed five new wider binaries with separations of about
14 to 140 times the Earth-Sun distance. The results provide significant
new evidence to better characterize the star and planet forming region in
Ophiuchus.

"These very closely spaced young, low-mass star pairs are really
exciting," said Prato, summarizing results of her study presented today at
the American Astronomical Society meeting in Seattle. "We can accurately
measure the mass ratios and ultimately the component masses of these
pairs, along with their abundance and other properties. These measurements
give us new information about star and planet formation in regions just
now being probed at this level of detail and resolution."

This research features the first such analysis for young, low-mass
spectroscopic (closely spaced) binary stars undertaken in infrared light.
The four new spectroscopic binary stars were previously unknown. One of
these new pairs is located in a complex and intriguing hierarchical
quadruple star system. The study comprised a sample of 33 young M stars --
the coolest, lowest mass class of stars -- in the Ophiuchus molecular
cloud and used the Keck II 10-meter telescope atop the 13,796-foot summit
of Mauna Kea in Hawaii. The stars in the survey program are approximately
450 light-years distant with an estimated mass range of between 0.3 to 0.7
solar masses.

The study shows that because the size of a habitable zone around low-mass
stars corresponds to the typical distance between the stars in
spectroscopic binary pairs, the prevalence and properties of such binary
star systems have important consequences for potential terrestrial planet
formation. "These close, or 'spectroscopic binaries' have separations that
are similar to the Earth-Sun separation or even less," said Prato. "This
raises the question about what do these systems do to local planet
formation? It might be possible to have planets very far away orbiting
both stars. On the other hand, if the spectroscopic binary is spaced
widely enough, could planets possibly form close to one star? In any case,
all this complexity throws a wrench in the works, thus making it even more
important to know how many of these systems are out there in the nearby
star and planet forming regions like Ophiuchus."

For this survey, the large aperture Keck telescope was equipped on the
many nights necessary to observe such a large sample size with the
facility's infrared NIRSPEC spectrometer. Because M stars emit most of
their light in the infrared, using NIRSPEC on Keck allowed Prato to study
these faint targets with optimal facilities. Also, young stars still
embedded within this fascinating star and planet forming region are more
readily detectable in infrared light because dust blocks most visible
light. "It is simply most efficient to search in infrared light
wavelengths for young M star spectroscopic binaries with a large aperture
telescope such as Keck," said Prato. Together with colleague Michal Simon
(Stony Brook University), Prato pioneered the powerful application of
infrared spectroscopy to the study of close binary systems.

The paper, "A Survey for Young Spectroscopic Binary K7-M4 Stars in
Ophiuchus," has been accepted for publication by the Astrophysical Journal
(http://arxiv.org/pdf/astro-ph/0611636). Lisa Prato is the sole author.
The research goal was to find young M star spectroscopic binaries in the
target region by searching for variability in radial velocity and to
measure the mass ratios of any new systems discovered. Mass ratios of the
spectroscopic binary stars are determined by the Doppler shift, that is by
measuring the spectral signatures, indicating radial velocities, of both
components in the spectroscopic binary pairs. Prato discovered two
double-lined spectroscopic binary systems, two single-lined systems, and
one radial velocity variable.

The occurrence of the young, low-mass, spectroscopic binary star pairs
discovered in the study is about 12 percent; this compares closely with
other research programs that have measured the abundance of nearby older
star spectroscopic binaries, as well as studies to measure the number of
higher mass young spectroscopic binary stars in various star forming
regions.

"My research so far leads me to suspect that there are more young,
low-mass spectroscopic binary stars in Ophiuchus and other star forming
regions awaiting discovery," Prato said. "These young, exceptionally small
separation binary stars orbiting each other in such close proximity,
possibly interacting with dust and gas distributed throughout the systems,
will help to determine the potential for planet formation in habitable
zones. Young spectroscopic binaries also provide a unique opportunity to
measure very accurate stellar mass ratios and eventually stellar masses --
information that helps astronomers to broadly understand star formation
and evolution."

Prato plans to further explore this rich and diverse sample of stars to
study circumstellar dust, rotational velocities, and the wide binary
properties in future research. Hubble Space Telescope or adaptive optics
observations may detect even more wide binaries. Also, a more dense
sampling is needed to determine the orbital properties of the newly
discovered spectroscopic binaries.

This research was supported by NSF and awards from NASA's Keck PI Data
Analysis Fund. Data for this project were obtained at the W.M. Keck
Observatory from telescope time allocated to NASA through the agency's
scientific partnership with the California Institute of Technology and the
University of California.

About Lowell Observatory

Lowell Observatory is a private, non-profit research institution founded
in 1894 by Percival Lowell. The Observatory has been the site of many
important findings including the discovery of the large recessional
velocities of galaxies by Vesto Slipher in 1912-1914 (a result that led
ultimately to the realization the universe is expanding), and the
discovery of Pluto by Clyde Tombaugh in 1930. Today, Lowell's 19
astronomers use ground-based telescopes around the world, telescopes in
space, and NASA planetary spacecraft to conduct research in diverse areas
of astronomy and planetary science. Lowell Observatory currently has four
research telescopes at its Anderson Mesa dark sky site east of Flagstaff,
Arizona, and is building a 4-meter class research telescope, the Discovery
Channel Telescope, in partnership with Discovery Communications, Inc.

Note to editors: View and download the computer generated illustration to
accompany this release at
http://www.lowell.edu/press_room/spe...rs_images.html