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There are now six comets visible in the sky. The SWAN, which promised us a good show towards the end of the month, does not seem to increase in brightness as planned, but others are coming that are also promising.
Comet explosion
In March our hopes for a good celestial show were pinned on Comet ATLAS (C / 2019 Y4). And there was a spectacle: it occurred around the middle of the month when the comet began to break into pieces . But the fragmentation occurred while the star was very dim (magnitude 8) and could only be observed through telescopes. Those of us who expected to see the comet with the naked eye, and very bright, were left with the desire.
Fortunately, the Hubble Space Telescope was able to take magnificent snapshots of the fragments on April 20 and 23. But since then, the comet has stabilized, becoming very diffuse and not very bright. In addition, since mid-May, the ATLAS / Y4 has been losing elevation above the horizon and is no longer seen due to its line of sight being very close to that of the Sun.
SWAN's hope
After ATLAS / Y4, a new kite arrived that filled us with good expectations again. Amateur astronomer Michael Mattiazzo had discovered it from Australia, although he did not observe it in the sky. Mattiazzo worked in an industrial sector that was severely affected by the covid-19 crisis and this led him to take a sabbatical to devote himself to his passion for kites. It was when examining with his computer some images, which are public access, taken with the SWAN camera of the SOHO solar space telescope, when he discovered that new comet, called SWAN (C / 2020 F8) and that turned out to be very promising.
Mattiazzo was able to observe, already with his telescope, how SWAN soon began to glow as it moved through the sky like a bullet . In late April, the comet experienced an explosion in its activity that caused it to greatly increase in brightness. As the image at the top of this article shows, taken by astrophotographer Gerald Rhemann from Namibia, in early May it reached magnitude 4.7 and displayed a tail of several degrees longitude that was well visible in photographs. The predictions made it observable and brilliant with the naked eye (with magnitude 3) towards the second half of May.
In mid-May it became visible from the northern hemisphere (albeit at low elevation). Its closest approach to Earth was reached on May 12, when it was found about 84 million away. But instead of increasing brightness, the comet seemed to be stable and even dim slightly. You can follow the news of this kite from the account it has dedicated on Twitter @ c2020f8.
The comet's perihelion, that is, the position where it will be closer to the Sun, reached on 27 May, about 64 million kilometers away to the sun . The comet will then be located in the Perseus constellation, but the predictions are no longer as favorable as they were a few weeks ago. In fact, the specialist in comet observations José Chambó alerted us a few days ago from his Twitter @PepeChambo and his Cometografía website that there are no longer many reasons to be optimistic: "with so many ups and downs it is impossible to predict what its future evolution will be, but a few days after the perihelion ... it cannot vary drastically ". It seems that, at the end of May, from our latitudes, the SWAN will only be visible with binoculars, at a very low height above the northeast horizon, during the twilight of the morning.
More kites
Meanwhile, we continue to have four other comets that are visible with binoculars or small telescopes: C / 2017 T2 (PANSTARRS), C / 2019 Y1 (ATLAS), C / 2019 U6 (Lemmon) and C / 2020 F3 (NEOWISE) . Hopes are now placed on the latter.
On May 14, in an observation made by Chambó, the NEOWISE showed a green comma with indications of the beginning of a tail and the forecasts indicate that it could be observable with the naked eye in July.
The charm of comets
Comets that, like SWAN, come from the very far cloud of Oort, take thousands of years to reach the proximity of the Sun. Those that carry the prefix "C /" in their name (like all those mentioned heretofore) are not newspapers. It is the first time that they approach the Sun, which makes them light up quickly. Solar radiation suddenly vaporizes the ices that have covered the comet for millions of years, and then dust and gas are released to form the coma and tails that unfold to glow brightly from sunlight.
They are violent and very unpredictable phenomena. Sometimes the tails of comets can be kept for a long time, but other times, as happened with ATLAS, solar radiation causes the comet to break into pieces and eventually disintegrate and fade away.
But perhaps it is this behavior so variable, and sometimes chaotic, that makes kites so charming. Newspapers, like the Halley, give us a sure show every once in a while (76 years in the case of the Halley), while the ones we now have on our heads can change erratically within a few days to get lost and never return. never appear.
When we look at the night sky, it may seem at first glance that everything is immovable and eternal. And, certainly, many stars can remain relatively stable for thousands or millions of years. However, changes in comets are visible in very short periods of time, sometimes within a few hours. Comets thus come to remind us that there is nothing permanent in the sky.
Rafael Bachiller is director of the National Astronomical Observatory (National Geographic Institute) and academic of the Royal Academy of Doctors of Spain.
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