The upper image of Comet Leonard, the ‘Christmas star’ that approaches its closest point to Earth, has been taken from the Calar Alto telescope, in the Sierra de Los Filabres, north of Almería (Andalusia, Spain)
It is not a Christmas miracle, nor the star of Bethlehem: the Comet Leonard is quite common, and has a trajectory typical of a comet, around the Sun. However, there is something that has done to it special, and it is that the approach of Christmas can be seen with the naked eye, from Earth, on very special dates. As December 12 approaches, and the days after, it is possible that when looking at the night sky, better away from the illuminated cities, we will be surprised by a ‘Christmas star’, Comet Leonard.
Composite real color image of Comet Leonard
The top image, in real color, shows Comet Leonard streaking through the sky on the morning of December 7, 2021, taken by the ESA Near Earth Object Coordination Center (NEOCC) [19459006 ], part of the Agency’s Planetary Defense Office, using the Calar Alto Schmidt telescope in Spain.
By superimposing a ‘stack’ of 90 images every five seconds of ‘duration’, the comet is revealed buzzing among the background stars that appear here as colored stripes ranging from green to red to blue, colors chosen for represent the three different filters used to observe Leonard.
Centered around the comet’s bright nucleus, these colors come together to create a bright white glow of the nucleus, while the surrounding bluish-green hue is true to life, the typical color that comets emit due to their composition. chemistry.
Comet near Earth? Not even close
Comet Leonard is currently traveling at tens of kilometers per second in its orbit around the Sun. On December 12 at 13:52 UTC, it will make its closest approach to Earth during this rotation, still at an enormous distance of 35 million kilometers.
Comet Leonard’s orbital path sees it approach the Sun before returning back to the outer Solar System.
Currently, we know of 3,775 comets in the Solar System. These small bodies are believed to be icy remnants from the early phases of the outer planet formation. Orbiting the Sun, they head into the inner Solar System, emitting particles and gases when heated by solar radiation producing their characteristic tail, and then returning to farther afield about 50,000 times the distance from Earth to the Sun.
Interestingly, these long tails remain in place even after the comet has moved. It is when the Earth sporadically passes through the ancient trail of ancient comets that meteor showers occur, a beautiful and safe reminder of the fragility of the Earth in the Solar System.
Near Earth Comets (NEC) are defined as those that complete one complete revolution of the Sun in 200 years, with a closest distance to the Sun within 1.3 Astronomical Units, the distance between the Sun and Earth.
These comets are kept under the watchful eye of ESA’s NEOCC because, like asteroids, any impact with Earth could have a very damaging effect. Fortunately, these comets are rare – only 100 are known today and only one or two are added to the books each year.
Unique? Not really. Beautiful? Yes.
While not many people will have witnessed a comet appear in the sky, Comet Leonard is not particularly unique. In fact, it is quite typical:
“This is a bright comet that we see in the skies on average once a year. As it gets a little closer, it could become visible to the naked eye, creating some attractive images, but, for those of us who are concerned about objects that could pose a threat to Earth, this comet is thankfully not spectacular, ”explains Marco Micheli. , astronomer. at the ESA Center for the Coordination of Near-Earth Objects
For everyone else, it will be worth checking the skies for this icy passerby in the days after its close approach on December 12 (at its closest it will not be visible as it will be too close to the glaring sun) .
In a cosmic coincidence, this same period will be perfect for detecting shooting stars, as, with a peak around December 13-14, it will be the Geminid meteor shower. The Geminids are one of only two meteor showers that occur because Earth passes the ‘tail’ of an asteroid, (3200) Phaethon, rather than a comet.