Brown dwarf: A star-planet hybrid was accidentally discovered thanks to a gas shift

Brown dwarfs, which are neither stars nor planets, were first introduced to us 27 years ago.

Now it is time to meet a new one because astronomers have discovered a brown dwarf under the Ophiuchus Disk Survey employing ALMA (ODISEA) project.

ODISEA project, which is intended to study the entire population of protoplanetary disks in the Ophiuchus Molecular Cloud, a group of astronomers led by Dary Ruiz-Rodriguez of the National Radio Astronomy Observatory (NRAO) have investigated "SSTc2d J163134.1-24006," which was initially identified as a faint stellar object.

The report was published by arXive.org on September 2.

With a mass of approximately 0.05 solar masses and an oval carbon monoxide shell, the newly founded brown dwarf appeared to be experiencing a quasi-spherical mass loss.

How did they discover it?

The researchers first made the accidental discovery of an expanding shell of carbon monoxide discharged by a low-temperature particle in the direction of the Ophiuchus Molecular Cloud.

Additional observations showed that this shell belongs to SSTc2d J163134.1.

Ruiz Rodriguez's team considered a number of hypotheses, including the inside-out collapse of a dense molecular core in the Ophiuchus cloud, the mass loss of a giant star in the background, or a shell of gas expelled from a young brown dwarf, in order to explain it.

As a result, the brown dwarf hypothesis is considered to be the most likely one by the researchers, as said in the report.

"We conclude that the source is not a giant star in the distant background (>5–10 kpc) and is most likely to be a young brown dwarf in the Ophiuchus cloud, at a distance of just ∼139 pc," the astronomers explained.

More about brown dwarfs

Brown dwarfs are formed by the collapse of interstellar gas clouds, but they are too light to initiate nuclear reactions to make the object a star. Since they can't reach the 80 Jupiter mass limit, they can't get hot enough and go out.

Despite their name, brown dwarfs would look in a variety of hues to the human eye, depending on their temperature. While cooler brown dwarfs would likely appear magenta to the human eye, the warmest ones may be orange or red. Brown dwarfs could be completely convective, lacking any layers or chemical depth-based differentiation.

Abstract:

We report the serendipitous discovery of an elliptical shell of CO associated with the faint stellar object SSTc2d J163134.1-24006 as part of the “Ophiuchus Disk Survey Employing ALMA” (ODISEA), a project aiming to study the entire population of protoplanetary disks in the Ophiuchus Molecular Cloud from 230 GHz continuum emission and 12CO (J=2-1), 13CO (J=2-1) and C18CO (J=2-1) lines readable in Band-6. Remarkably, we detect a bright 12CO elliptical shape emission of ∼ 3 ” × 4” towards SSTc2d J163134.1-24006 without a 230 GHz continuum detection. Based on the observed near-IR spectrum taken with the Very Large Telescope (KMOS), the brightness of the source, its 3-dimensional motion, and Galactic dynamic arguments, we conclude that the source is not a giant star in the distant background (>5 - 10 kpc) and is most likely to be a young brown dwarf in the Ophiuchus cloud, at a distance of just ∼139 pc. This is the first report of quasi-spherical mass loss in a young brown dwarf. We suggest that the observed shell could be associated with a thermal pulse produced by the fusion of deuterium, which is not yet well understood, but for a sub-stellar object is expected to occur during a short period of time at an age of a few Myr, in agreement with the ages of the objects in the region. Other more exotic scenarios, such as a merger with planetary companions, cannot be ruled out from the current observations.