A&A press release: The coldest brown dwarf ever observed (10 April 2008)
- Details
- Published on 08 April 2008
A&A press release
Released on April 10th, 2008
|
The coldest brown dwarf ever observed: Closing the gap between stars and planets |
“CFBDS J005910.90-011401.3: reaching the T-Y brown dwarf
transition?”, by Delorme et al.
To be published in Astronomy & Astrophysics,
2008
An international team of astronomers has discovered
the coldest brown dwarf star ever observed. This finding, to be
published in Astronomy
& Astrophysics, is a new step toward filling the
gap between stars and planets.
An international team [1] led by French and Canadian astronomers has
just discovered the coldest brown dwarf ever observed. Their results
will soon be published in Astronomy & Astrophysics. This new
finding was made possible by the performance of telescopes worldwide
[2]: Canada France Hawaii Telescope (CFHT) and Gemini North Telescope,
both located in Hawaii, and the ESO/NTT located in Chile.
The brown dwarf is named CFBDS J005910.83-011401.3 (it will be called
CFBDS0059 in the following). Its temperature is about 350°C and
its mass about 15-30 times the mass of Jupiter, the largest planet of
our solar system [3]. Located about 40 light years from our solar
system, it is an isolated object, meaning that it doesn't orbit another
star.
Brown dwarfs are intermediate bodies between stars and giant planets
(like Jupiter). The mass of brown dwarfs is usually less than 70
Jupiter masses. Because of their low mass, their central temperature is
not high enough to maintain thermonuclear fusion reactions over a long
time. In contrast to a star like our Sun, which spends most of its
lifetime burning hydrogen, hence keeping a constant internal
temperature, a brown dwarf spends its lifetime getting colder and
colder after its formation.
The first brown dwarfs were detected in 1995. Since then, this type of
stellar object has been found to share common properties with giant
planets, even though differences remain. For example, clouds of dust
and aerosols, as well as large amounts of methane, were detected in
their atmosphere (for the coldest ones), just as in the atmosphere of
Jupiter and Saturn. However, there were still two major differences. In
the brown dwarf atmospheres, water is always in gaseous state, while it
condenses into water ice in giant planets; and ammonia has never been
detected in the brown dwarf near-infrared spectra, while it is a major
component of Jupiter's atmosphere. CFBDS0059, the newly-discovered
brown dwarf, looks much more like a giant planet than the known classes
of brown dwarfs, both because of its low temperature and because of the
presence of ammonia.
To date, two classes of brown dwarfs have been known: the L dwarfs
(temperature of 1200-2000°C), which have clouds of dust and
aerosols in their high atmosphere; and the T dwarfs (temperature lower
than 1200°C), which have a very different spectrum because of
methane forming in their atmospheres. Because it contains ammonia and
has a much lower temperature than do L and T dwarfs, CFBDS0059 might be
the prototype of a new class of brown dwarfs to be called the Y dwarfs.
This new class would then become the missing link in the sequence from
the hottest stars to giant planets of less than -100°C, by
filling the gap now left in the midrange.
Fig. 1 - Picture of the brown
dwarf CFBDS0059 (small red dot on the top of the picture) and
its near-infrared spectrum (lowest curve) illustrating the presence of
ammonia.
Fig. 2 - From left to right: New Technology
Telescope (© ESO), Canada France Hawaii Telescope (©
J.-C. Cuillandre, CFHT), and Gemini North Telescope (© Gemini
Observatory/AURA)
[1] The team of astronomers includes P. Delorme, X. Delfosse (Observatoire de Grenoble, France), L. Albert (CFHT, Hawaii), E. Artigau (Gemini Observatory, Chile), T. Forveille (Obs. Grenoble/France, IfA/Hawaii), C. Reylé (Observatoire de Besançon, France), F. Allard, A. C. Robin (CRAL, Lyon, France), D. Homeier (Göttingen, Germany), C.J. Willott (University of Ottawa, Canada), M. C. Liu, T. J. Dupuy (IfA, Hawaii).
[2] CFBDS0059 was discovered in the framework of the Canada-France Brown-Dwarfs survey. The object was first identified in pictures from the wide-field camera Megacam installed on the CFHT (Canada France Hawaii Telescope). Infrared pictures were then obtained with the NTT telescope (La Silla, ESO, Chile) and confirmed the low temperature of the object. Finally, the spectrum showing the presence of ammonia was obtained using the Gemini North Telescope (Hawaii).
[3] The mass of Jupiter is about 300 times the Earth's mass and about 1/1000e of the Sun's mass.
CFBDS J005910.90-011401.3: reaching the T-Y brown dwarf transition?
by P. Delorme, X. Delfosse, L. Albert, E. Artigau, T. Forveille, C.
Reylé, F. Allard, D. Homeier, A. C. Robin, C.J. Willott, M.
C. Liu, and T. J. Dupuy
To be published in Astronomy & Astrophysics, 2008.
Full article available in PDF
format
Contacts:
- Science:
Dr. Thierry Forveille
Laboratoire d'Astrophysique de Grenoble
414, Rue de la Piscine
Domaine Universitaire
38400 Saint-Martin d'Heres, France
Email: Thierry.Forveille (at) obs.ujf-grenoble.fr
Phone: +33 (0)4 76 51 42 06
- Press office:
Dr.
Jennifer Martin
Journal Astronomy & Astrophysics
61, avenue de l'Observatoire
75014 Paris, France
Email: aanda.paris (at) obspm.fr
Phone: +33 1 43 29 05 41
© Astronomy & Astrophysics 2008