A giant comet is walking our way

Artist’s impression of Comet C/2014 UN271: Fortunately, it will not come closer than 1.6 billion km from the Sun. Credit: NOIRLab, NSF, Aura, J. da Silva (Spaceengine)

One huge comet It is about 130 kilometers in diameter, slightly more than the distance between Recife and Joao Pessoa, coming from the edge of the solar system towards us at about 35,400 kilometers per hour. Fortunately, you’ll never get closer to the sun by more than 1.6 billion kilometers (slightly farther than the distance between Earth and Saturn), which will happen in 2031.

said David Jewett, Professor of Planetary Science and Astronomy at the University of California, California, Los Angeles (UCLA, USA) and co-author of a new study on the comet. published in the magazine Astrophysical Journal Letters. He said that the dumped comets settled in the Oort cloud, a huge reservoir of distant comets that orbit the solar system for several billion kilometers in deep space.

The amazing tail of a comet several million kilometers long, making it look like a rocket, belies the fact that the source behind it is a solid core of ice mixed with dust – essentially a dirty snowball. This huge comet, called C/2014 UN271 and discovered by astronomers Pedro Bernardinelli and Gary Bernstein, can be up to 130 kilometers in diameter.

Tip of the iceberg

“This comet is literally the tip of the iceberg of many thousands of comets that are too faint to be seen in the farthest parts of the Solar System,” Jewett said. “We always suspected that this comet must be large because it is so bright at such a great distance. Now we confirm it.”

This comet contains the largest nucleus that astronomers have never seen in a comet. Jewett and colleagues determined the size of its nucleus using the NASA/ESA Hubble Space Telescope. Its nucleus is about 50 times larger than the nucleus of most known comets. Its mass is estimated at 500 trillion tons, 100,000 times greater than the mass of a typical comet found very close to the sun.

Man Tu Hui, lead author of the study, who received his Ph.D. from UCLA in 2019 and is now at the University of Science and Technology at the University of California, Macau in Taipa, Macau (China). “We thought the comet could be very large, but we needed the best data to confirm that.”

So the researchers used Hubble to take five pictures of the comet on January 8, 2022, and incorporated radio observations of the comet into their analyses.

accidentally discovered

Jewett said the comet is now less than 3.2 billion kilometers from the sun, and in a few million years will return to its nesting site in the Oort cloud.

Comet C/2014 UN271 was first observed by chance in 2010, when it was 4.83 billion km from the Sun. Since then, it has been intensively studied by ground and space telescopes.

The challenge in measuring this comet was how to determine the solid core of the massive coma – the dusty cloud of dust and gas – that surrounded it. The comet is currently too far from its nucleus for sufficient optical resolution by Hubble. Instead, the Hubble data show a spike in bright light at the site of the nucleus. Hoy and colleagues made a computer model of the surrounding coma and modified it to fit the Hubble images. So they cast the glare out of the coma, leaving the pulp behind.

Hui and his team compared the brightness of the core with previous radio observations of the Atacama Large Millimeter/submillimeter Array, or ALMA, in Chile. Hubble’s new measurements are close to previous alma size estimates, but convincingly point to a darker nucleus surface than previously thought.

“It’s big and blacker than coal,” Jewett said.

Practically invisible structure

The comet has been heading towards the sun for more than a million years. The Oort Cloud is believed to be the nesting site of trillions of comets. Jewett believes that the Oort cloud extends from a few hundred times the distance between the Sun and Earth to a quarter of the distance of the closest stars to our Sun, in the Alpha Centauri system.

Oort’s cloud comets were thrown out of the solar system billions of years ago by the gravitational pull of massive exoplanets, according to Jewett. The professor said that distant comets return to the sun and planets only if their orbits are perturbed by the gravitational pull of a passing star.

The existence of the Oort cloud was proposed by Dutch astronomer Jan Oort in 1950, and it remains a theory because the comets that compose it are too faint and too distant to be directly observed. This means that the largest structure in the solar system is nearly invisible, Jewett said.