The 'megacomet' Bernardinelli-Bernstein is the find of a decade. Here's the discovery explained.

space.com ^ | September 7, 2021 | Meghan Bartels

[BenLurkin]

Scientists briefly estimated that Comet Bernardinelli-Bernstein, as it's now known, was the largest such icy body identified to date, perhaps more than 100 miles (160 kilometers) across. Additional observations have cast that into doubt, but given the "megacomet" a new distinction: it sprouted a tail remarkably far from the sun, suggesting more revelations to come. All told, the object offers astronomers an unprecedented opportunity to watch the antics of a comet.

Although what initially stood out to Bernardinelli was the comet's weird orbital characteristics, the discovery made such a splash because of a different trait, the comet's estimated size. Based on the object's brightness and distance, the scientists initially estimated that the comet's nucleus — the icy rock at its core — was 60 to 120 miles (100 to 200 kilometers) wide.

But as far as comets go, that size estimate is truly massive. Among the comets scientists have studied in detail, only two are in the same class: Comet Hale-Bopp, which made a close approach to Earth in 1997, and Comet C/2002 VQ94 (LINEAR), which came no deeper into the solar system than Jupiter's orbit.

Calculating the size of an active comet is much more complicated than measuring a bare nucleus, it turns out, so Kokotanekova said she couldn't offer a new size estimate for the comet, beyond that it would be somewhat smaller than the original calculations.

Comet Bernardinelli-Bernstein remains a stunner....for the very same activity that invalidated the original size estimate. Scientists have only spotted a handful of comets active so far from the sun, where temperatures are still too cold for, say, water ice to turn to vapor, a typical type of cometary activity.

[FroggyTheGremlim]

It’s worse than Watergate!

(Carl Bernstein)

[BenLurkin]

Gentlemen,

This isn’t an article (or headline for all that matter) on how to run into your backyard and see the comet.

It is about the astronomy of the comet’s discovery, and about what is known to date about the comet itself.

If you find fault with the excerpting, then that is entirely on me.

Ben

[SunkenCiv]

Yup. This little thing is a fart in a hurricane, by comparison.

[SunkenCiv]

GIANT comet is on its way! (C/2014 UN271 Bernardinelli-Bernstein)
July 17, 2021
VisibleDark
https://www.youtube.com/watch?v=DH0tq1yAlz0

C/2014 UN271 Bernardinelli-Bernstein - A giant icy visitor from the edge of our solar system is on its way. Thought to be a rare long-period comet that swings into the inner Solar System from the distant Oort Cloud. Astronomers estimate this comet takes roughly three to five million years to make one complete orbit of the sun.