Using pictures and data from the Hubble Space Telescope, astronomers have been able to precisely determine the diameter of a massive comet heading in our direction. 4 billion years old, it fortunately does not constitute a direct threat.
C/2014 UN271
The comets, which are among the oldest objects in the Solar System, were unceremoniously thrown out of it during a game of gravity pinball between the massive outer planets. These icy bodies have taken up residence in the cloud of Oorta vast reservoir of comets encircling the Solar System and spanning billions of miles.
If their queueor hair, can extend over more than a million kilometres, the core of the latter are generally less than ten wide. Far exceeding these measurements, the comet heading towards the Solar System, recently described in The Astrophysical Journal Lettershas a diameter of regarding 129 kilometers, which makes it the most massive ever observed.
From five shots taken by Hubble on January 8, astronomers calculated that C/2014 UN271 (Bernardinelli-Bernstein) was heading towards the Solar System at a speed of 35,406 kilometers per hour. Estimated at 500 trillion tons, its mass turns out to be a hundred thousand times greater than that of a typical comet found much closer to Earth. Soleiland its nucleus regarding 50 times larger than that of most known comets.
But before you worry, know that it should not approach within a billion kilometers of the Soleil (i.e. approximately the distance separating the Terre from Saturn), implying an almost zero risk of collision with our planet. According to forecasts, it should reach this point during 2031.
A complex measure
The gigantic C/2014 UN271 was first spotted by astronomers Pedro Bernardinelli et Gary Bernstein eight years ago, when it was 4.3 billion kilometers from the Sun. Due to the thick dusty veil surrounding it, its recent measurement was a real challenge.
The icy body still proving too distant for the shots toHubble make it possible to visually and directly distinguish its nucleus, the researchers highlighted a luminous peak (corresponding to the position of the latter) in the data of the space telescope. A computer model of the surrounding hair was made, and the glow from it subtracted.
The brightness of the core was compared to previous radio data from the network ALMA (Atacama Large Millimeter/submillimeter Array) au Chili which, combined, made it possible to determine its diameter and its reflectivity. Close to initial estimates, the new measurements convincingly suggest that its surface is significantly darker than previously believed.