Our Newest Celestial Visitor Is a Truly Gigantic Comet

Our Newest Celestial Visitor Is a Truly Gigantic Comet

There is a truly enormous new comet sailing in from the Oort Cloud. It’s always exciting to entertain a new celestial visitor, and this massive Trans-Neptunian Object (TNO) is causing a stir among astronomers worldwide.

First of all, it’s huge. There have been several big, bright comets in the last few decades: Shoemaker-Levy 9 was 1.8km long, Halley’s comet was 15km or so, Hale-Bopp was 40-80km. This one tops all of them by a long shot. Comet Bernardinelli-Bernstein is much larger than Mars’ largest moon. In fact, you could lay out both of Mars’ moons, Phobos and Deimos, end-to-end long-wise and the comet would still be twice the size of the two put together. It’s so big we originally tagged it as a minor planet. A preprint study on arXiv gives a low-end estimate that’s still 10 times the mass of Hale-Bopp, and Hale-Bopp became known as the Great Comet of 1997.

NASA is monitoring the new comet, so there will definitely be better and better portraits of this celestial visitor as time goes by. It is expected that this comet will be in the sky for some years, and we will have ample time to observe it. Scientists currently project that Comet Bernardinelli-Bernstein will make its closest approach to the sun in 2031.

The new comet is also really far away. When it was first discovered, it was the most distant comet we’d ever seen. Its orbit is incredibly elongated: from perihelion to aphelion, Bad Astronomy calculated that it goes from “about 1.6 billion km from the Sun (just outside Saturn’s orbit*) to a mind-numbing 2 trillion km out. That’s a fifth of a light-year!” (emphasis original)

Our Newest Celestial Visitor Is a Truly Gigantic Comet

Despite its distance from Earth, we can already see that the comet has begun to put on a show. Recently, the Las Cumbres Observatory reported an increase in the comet’s brightness. Data from TESS confirms it. Bernardinelli-Bernstein is getting brighter, month by month. Scientists monitoring the comet suspect that it has begun to develop a halo or tail. It’s still far enough away that our images are blurry. Based on measurements of its path, though, we’re certain of a few things.

This comet has such a wildly distorted elliptical path that it can’t pose any threat to Earth. It’s 90 degrees opposed to the orbital plane in our solar system, and the closest it’s expected to get to the Sun is still about as far out as Saturn’s orbit.

Our Newest Celestial Visitor Is a Truly Gigantic Comet

We can also tell something about the comet’s nature, even through these early observations. Based on the way the comet’s coma is expanding relative to how far it is from the Sun, we can make educated guesses about what this giant space snowball is made of. It would be an unpleasant snowball, though: the data suggests that the comet is made of ammonia ice and frozen CO2. The scientists who submitted the arXiv report even suggested that it might have a “dirtmosphere,” because the amount of dust we see in its halo is growing exponentially. Yuck.

Unfortunately, because it will still be quite a ways out from the sun when it reaches its perihelion, it probably won’t be visible to the naked eye. But as we watch it from earthbound and orbiting telescopes, we’ll begin to see it more clearly and understand it better. I can’t wait to see beauty shots of this thing. Stay tuned for updates!

Feature image credit: NOIRLab/NSF/AURA/J. da Silva (Spaceengine)

Continue reading

Interstellar Visitor May Be a Fragment of a Pluto-Like Planet
Interstellar Visitor May Be a Fragment of a Pluto-Like Planet

Two astronomers from Arizona State University have published a paper that claims 'Oumuamua is neither an asteroid nor a comet, but rather a pancake-shaped piece of a Pluto-like world.

Ryzen Revisited: AMD’s 5800X3D, 5800X Are Great Upgrades for X370 Motherboard Owners
Ryzen Revisited: AMD’s 5800X3D, 5800X Are Great Upgrades for X370 Motherboard Owners

AMD's Ryzen 7 5800X and Ryzen 7 5800X3D are great upgrade options for any gamer with a Ryzen 7 1800X still knocking around.

Our First Interstellar Visitor May Have a Violent Past
Our First Interstellar Visitor May Have a Violent Past

Scores of instruments were turned toward the alien asteroid to gather study its size, trajectory, and even check to make sure it wasn't actually an alien spacecraft (it's not). Now, a new analysis suggests that 'Oumuamua may have extremely violent origins.

Astronomers Say Interstellar Visitor ‘Oumuamua Might be a Comet After All
Astronomers Say Interstellar Visitor ‘Oumuamua Might be a Comet After All

Telescopes around the world turned to watch as our visitor rocketed off into oblivion, and scientists eventually decided it was an asteroid. However, some new data calls that assessment into question. ‘Oumuamua may have been a comet after all.