Thursday, May 24, 2007

Brown Dwarf joins Jet Set

Image Credit: Copyright ESO

Jets of matter have been discovered around a very low mass 'failed star', mimicking a process seen in young stars. This suggests that these 'brown dwarfs' form in a similar manner to normal stars but also that outflows are driven out by objects as massive as hundreds of millions of solar masses down to Jupiter-sized objects.

The brown dwarf with the name 2MASS1207-3932 is full of surprises. Its companion, a 5 Jupiter-mass giant, was the first confirmed exoplanet for which astronomers could obtain an image , thereby opening a new field of research - the direct detection of alien worlds. It was then later found that the brown dwarf has a disc surrounding it, not unlike very young stars.

Now, astronomers using ESO's Very Large Telescope (VLT) have found that the young brown dwarf is also spewing jets, a behaviour again quite similar to young stars.

The outflows were discovered using an amazing technique known as spectro-astrometry, based on high resolution spectra taken with UVES on the VLT. While in normal young stars - known as T-Tauri stars for the prototype of their class - the jets are large and bright enough to be seen directly, this is not the case around brown dwarfs: the length scale of the jets, recovered with spectro-astrometry is only about 0.1 arcsecond long.

The jets stretch about 1 billion kilometres and the material is rushing away from the brown dwarf with a speed of a few kilometres per second. Astronomers had to rely on the power of the VLT because the observed emission is extremely faint and only UVES on the VLT could provide both the sensitivity and the spectral resolution they required.

Using the same technique and the same telescope, the team had previously discovered outflows in another young brown dwarf. The new discovery sets a record for the lowest mass object in which jets are seen.

Outflows in the Universe, are observed rushing away from the active nuclei of galaxies (AGNs) and emerging from young stars. These observations show the outflow mechanism extends over an enormous range of masses, from several tens of millions of solar mass (for AGNs) down to a few tens of Jupiter masses (for brown dwarfs).

VLT Finds Smallest Galactic Object with Jets ESO press release
A Brown Dwarf Joins the Jet Set from Science Daily
Brown Dwarf with jets discovered from Universe Today
Merging Stars create a new class of explosion from Universe Today

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