THE FLOP OF Y4 ATLAS, THE COMET THAT WAS SUPPOSED TO BECOME BRIGHTER THAN THE MOON
Lately we have witnessed several "disappointments" in the astronomical field , starting with the failure of the red hypergiant star Betelgeuse , which promised an unprecedented spectacle.
The disappointment recently was the comet C / 2019 Y4 ATLAS
, which - according to some - should have become second to the Sun for
brightness, however this did not happen, and today we will explain why.
Where everything started
The cosmic stone was discovered by the Asteroid
Terrestrial-impact Last Alert System (ATLAS) program on December 28, 2019. At
the times of its discovery, the comet glowed with magnitude 19.6 in the
constellation Ursa Major. Further observations in the following days identified
a coma (a temporary atmosphere that forms following the sublimation of the
volatile substances present on the surface) and also a cometary tail (a luminous
trail that follows the cosmic stone).
Small excursus: the magnitude of a celestial body is a
measure of its luminosity detectable from the Earth; the greater the luminosity
of the celestial object, the lower its magnitude. For example, the Sun has a magnitude
of -26.74, Venus of -4.47 (not bad for a planet) and Betelgeuse -1.17.
What was considered a normal comet, between the beginning of
February and the end of March increased its brightness by 4000 times , passing
from a magnitude 17 to a magnitude 8. In short, the event attracted the
curiosity of astronomers from all over. the world, which began to point their
eyes, or rather telescopes, towards the sky.
A new hope
The uproar of the news sparked many discussions about the
particular celestial object, which even emitted a green color thanks to the
emissions of diatomic carbon. In March 2020, the comet's brightness increased
by as much as four magnitudes.
In short, the premises for the astronomical event of the
decade (if not of the century) were all proper. Thanks to the rapid increase in
brightness, in fact, the comet led to think that it could have become visible
to the naked eye at the end of April 2020 .
Broken hopes
However, this did not happen, and as early as March 17,
experts noticed signs of a slowdown in brightness. The cosmic stone , in fact,
around 2 April 2020 seemed to have shattered . Blame? Our Sun. Comets
"inhabit" the outside of our Solar System, an extremely cold place
away from the hot rays of our star.
The approach to the Sun causes a notable sublimation of
their ices and a conspicuous emission of dust, accompanied in this case also by
the fragmentation of the nucleus into several parts. Recently, researchers from
the Lulin One-meter Telescope in Taiwan confirmed that the comet is breaking
apart, with a fragment 3,400km in front of the couple following it.
The images also suggest that, before it reaches Mercury's
orbit at the end of May, the comet will break apart entirely . As to the fate
of ATLAS, experts are still uncertain: it could burn completely or produce an
explosive spectacle as it approaches the Sun.
All is not lost?
However, on April 11, amateur astronomer Michael Mattiazzo
appears to have discovered a new comet while observing data from the Solar Wind
Anisotropy (SWAN). The instrument in question was not designed to find comets;
its job is to detect hydrogen in the solar system. However, as the comet is
emitting a fairly significant amount of hydrogen in the form of water ice, it
was observed by SWAN.
The comet appears to be traveling on a very elongated
elliptical orbit over a period of about 25 million years ; this mean that the
last time it crossed the inner solar system may have been during the Oligocene
epoch, the time when the largest terrestrial mammal ever walked our planet:, a
species of rhinoceros about 5 meters tall and 7 meters long.
Currently, comet SWAN is only visible to those residing
south of the equator. As of April 16, it had a magnitude of 7.8 and showed a
head roughly one-sixth the apparent width of the Moon. This celestial object
could "evolve" into an even brighter body , according to experts.
Like ATLAS, comet SWAN appears to be relatively small.
It will pass close to Earth on May 12 at a distance of 83.3
million kilometers and will arrive at perihelion (the closest point to the Sun)
on May 27, when it will be 64.4 million kilometers from our star.
Assuming the cosmic stone continues to illuminate at its
current rate, it could reach a magnitude of 3 during the last week of May.,
bright enough to be seen with the naked eye. Unfortunately, there are still
several doubts and, even, it could follow the same fate as comet ATLAS. I mean,
let's keep our fingers crossed.
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