The comet named Atlas was discovered in December 2019 and is currently close to the orbit of Mars, on its way to the Sun. At its closest approach, in late May, it could become as bright as the crescent moon.
The last time amateur astronomers had the opportunity to see a comet with the naked eye was in 1997, during the passage of the Hale-Bopp. Now we could be on the verge of a new opportunity.
The new astronomical object was discovered on December 28, 2019 by the Asteroid Terrestrial-impact Last Alert System in Hawaii. Back then it was in the Ursa Major constellation, 439 million kilometers from the Sun and with a very faint brightness of magnitude 20 — that’s 398,000 times dimmer than the stars we see with the naked eye.
But comets typically get brighter as they get closer to the star. It is calculated that at its closest approach, on May 31, 2020, Atlas will be located less than 38 million kilometers from the Sun. Such a prodigious change in solar distance will cause the comet to increase its luminosity by 11 magnitudes, enough to be visible from Earth with a small homemade telescope or a good pair of binoculars.
Comet C / 2019 Y4 (ATLAS) – an apparent relation of the “Great Comet of 1844” – is brightening much faster than anticipated! Now up to mag 12. Reaches perihelion May 30, 2020 at just 0.25AU – in the fov of our STEREO HI-1 camera!
– Karl Battams (@SungrazerComets) February 18, 2020
What is striking is that, since its discovery, the comet has been increasing its brightness at unprecedented speed. On March 17, ATLAS already had a magnitude of +8.5, about 600 times brighter than predicted. As a result, astronomers have high expectations for this object, to the point that they believe that there is a possibility that – if the comet continues to behave – it may even reach the brightness of the crescent moon and rival Venus itself!
Another important factor to maintain high hopes is that its orbit is almost identical to that of the so-called Great Comet of 1844. Like this, Atlas follows a trajectory that requires 6,000 years per orbit and takes it beyond the limits of the solar system, to almost 92,000 million kilometers from the Sun. Probably, in the very remote past, a larger comet occupied the same orbit, but fragmented into several pieces — including the 1844 comet and the Atlas.
New comet C / 2019 Y4 (ATLAS) has orbital elements very similar to those for C / 1844 Y1 (Great Comet). The suggestion was initially made by M. Meyer when the 2019-2020 arc was ~ three days. pic.twitter.com/9kRTALy7U5
– Charles Bell (@ cbellh47) January 10, 2020
But any comparison is dangerous. The 1844 comet was not discovered until shortly after its perihelion, so we have no idea of its previous luminosity behavior. On the other hand, that is all the information we have about Atlas so far, and we will not be able to fully observe it until it approaches the Sun.
And let’s not forget that some of the comets in the past had the word “glory” written on them, and they turned out to be true astronomical fiascos, for example: Comet ISON (2013), Comet Austin (1990), and Comet Kohoutek (1974) .
This unpredictability of comets is longstanding. Astronomers use special formulas to try to anticipate how shiny they will become. Unfortunately, individual behavior and characteristics are as varied as people: no two are alike.
“Observing the development of Atlas is going to be a good distraction for the current state of the world. For good health and clear skies, “concludes Carl Hergenrother, a regular Arizona kite watcher.