Discovery of Smallest Known Brown Dwarf Announced

Brown Dwarf TWA-5 B The smallest Brown dwarf yet discovered has been observed by astronomers at the European Southern Observatory (ESO). Brown dwarfs are bodies smaller than our sun but many times the size of Jupiter and are often referred to as "failed suns" inasmuch as there was not enough matter present during their formation so as to initiate hydrogen fusion. Yet, at the same time, these objects are much more massive than Jupiter and produce energy as the result of gravity- induced contraction.

The brown dwarf discovered by ESO, known as TWA-5 B, has a mass of between 15 - 40 times that of Jupiter which places it near the borderline between planets and brown dwarfs.

According to a press release "two years ago, a faint companion candidate was found near a young and nearby stars (TWA-5 - also known as CoD -33 7795). This star is about 12 million years old and is a member of a group of about a dozen young stars (of the "T Tauri"-type), seen in the southern constellation Hydra and grouped around the star TW Hya, the first to be found in this area ("TWA" means the "TW Hya Association")".

Measurements of this star system using the Hubble Space Telescope (HST) and ESO's Very Large Telescope (VLT) indicate that TWA-5 B orbits TWA-5 A the central, much heavier and brighter star in this system. TWA-5 A is actually a "close" double star of which each component having a mass of 0.75 that of our sun. TWA-5B may take upwards of 900 years to complete one orbit around TWA-5.

Discoveries such as this help to further understand the range of objects that can form from protoplanetary disks - from stars on down to planets such as our own. With extrasolar planet detection programs now able to detect planets down to the size of Saturn - and the detection of increasingly smaller brown dwarfs, the process of planetary - and stellar formation will better understood.

Image Caption

[Larger images] An image of TWA-5 A (lower, bright object) and TWA-5 B (upper), taken with the FORS-2 multi-mode instrument at the 8.2-m VLT/KUEYEN telescope on 21 February 2000. The integration time was 1 second through an I-band filter (wavelength 900 nm) with the high-resolution collimator (0.1 arcsec per pixel). The image quality is 0.18 arcsec FWHM (full-width-half maximum). The lines emerging from the bright image are caused by optical reflection in the telescope. The angular distance is 2 arcsec, cf. the indicated scale.

Related Links

° Youngest Brown Dwarf Yet in a Multiple Stellar System, European Southern Observatory
° European Southern Observatory

Background Information

° Chandra Observes First X-Ray Flare From A Brown Dwarf, SpaceRef
° The Discovery of Brown Dwarfs, Scientific American

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