Enigmatic disappearance around a star
TYC 8241 2652 1 is a star
of about 10 million years. Next to our Sun and its almost 4.6 billion years, it
is a young child. But this is not really a baby who is born. In its short
existence - scale astronomical - residues of its formation (gas, ice, dust)
have had the time to try agglomerate in planet (s). It is not known if this
process has resulted because no companion has for the moment been detected
around this star not really close, but astronomers believe that the dust disk
that a few years ago, surrounded TYC 8241 2652 1 was not the original disk from
which to manufacture the planets but rather a secondary diskconsisting of grain
from the multiple collisions that embryos of planets (planetesimals) had
suffered. Heated by the Sun, these dust fishnets in infra-red and it is in this
wavelength that they had been detected as early as 1983.
That have thus been exactly astronomers?They
followed the evolution in time of infra-red radiation of this drive by
recovering data from four space telescopes working in this field - IRAS in 1983, Akari in
2006, WISE in
2010 and Herschel in 2011-,
that they were supplemented by observations on the ground made with the telescope
at Gemini South in the Chile (in 2008, 2009, 2012) and the NASA Infrared Telescope Facility of Hawaii (2011). Until 2008, the amount
of light emitted by the disk is stable. When new measures are carried out in
2009, it fell close to a third party. And in 2010, this figure has again been
divided by ten and what is left of the disk is at the limit of detectable. "It is as if the rings of Saturn were missing,
said one of the authors of the Naturearticle,
Benjamin Zuckerman, Professor in the Department of physics and Astronomy of the
University of California (Los Angeles)." " Is even more surprising because this dusty debris
disk was larger and much more massive than Saturn's rings."
The problem of the researchers,
is that no known model is able to do away with such a quantity of matter within
two years. "Nothing
similar has never been observed around hundreds of stars that astronomers have
studied the disks of dust, adds Benjamin
Zuckerman." " The
disappearance of the dust around TYC 8241 2652 1 was so weird and so fast as in
the beginning, I thought that strange stuff had distorted our
observations."But that was not the case. In
addition, during the two years in question, the star demonstrated stability and
seems to have known no violent anger to sweep the dust.
For the moment, the astronomers have
in hand than two assumptions a little dysfunctional to try to understand what
happened. The first imagine that the presence of gas in the disk causes
accretion of dust in the direction of the star. The problem is there, to
succeed such cleaning in such a short time, a mass of gas 10 times superior to
that of the disk of dust and that the authors of the study are well confused to
explain where such a quantity of gas could come. The latter staged a violent
collision between planetesimals or even the breakup of one of them. In both
cases, a large amount of small debris is ejected in the disk. Under certain
conditions, they would be able to cause a snowball effect, hitting grains of
dust from the disk, with chips, in turn, going to hit other grains, etc. This
avalanche of collisions could lead to the disintegration and the evacuation of
the majority of the grain. The scenario is pretty but, also, it faces a problem
of size because the model that he resumed, conceived in 2006,
refers to a process for about... one thousand years, not two.
The puzzle of the TYC 8241 2652 1 star adds
yet more complexity to the poorly known phenomena that are at work in these
disks of dust. Phenomena that interest astronomers because they are responsible
for the formation of the planets and all systems solar, more or less exotic,
that researchers discovered since 15 years.
