Astronomers have confirmed the discovery of the largest known comet. Comet Bernardinelli-Bernstein, named for the astronomers who found it, is about a thousand times more massive than other comets and between 62 and 124 miles (100 and 200 kilometers) across.
The giant comet, also known as C/2014 UN271, likely came from the Oort Cloud, the birthplace of icy, ancient comets and a place more distant from the sun than anything in our solar system. This comet will make its closest approach to our sun in 2031, but you'll likely need a large amateur telescope to see it.
This is also the most distant comet to be discovered on its inbound journey, which will provide scientists a chance to observe and study it for years to come. Based on the amount of light it reflects, comet Bernardinelli-Bernstein is currently about 1.8 billion miles (3 billion kilometers) away - about the distance of Uranus from the sun - and at its closest point in 2031, it will be just a bit more than Saturn's distance to the sun.
Scientists predict this trajectory will take the icy rock from its current point just past Neptune's orbit near Saturn's orbit in 2031, which will be the closest it gets to Earth.
Despite its whopping size and mass, there’s nothing to worry about - Bernardinelli-Bernstein will steer far clear of Earth. When it does reach perihelion, the closest point in its orbit to the Sun, in 2031, it will still be 11 Astronomic Units (AU) from our beloved star.
Bernardinelli-Bernstein is hopefully just the first discovery in a wealth of large, icy objects flung to the far outer reaches of the solar system as the giant outer planets jockeyed for position billions of years ago. Because it will execute its turnaround so far away, even such a massive comet probably won’t grow very bright and still require a large amateur telescope to spot.
Uncovering new objects to learn what they can teach us about our past is exactly why Pedro Bernardinelli and Gary Bernstein, both of the University of Pennsylvania, were combing through thousands of images. These images were taken as part of the Dark Energy Survey (DES) by the 570-megapixel Dark Energy Camera (DECam) mounted on the 4-meter Victor M. Blanco Telescope in Chile.
Within a subset of 80,000 DECam images, Bernardinelli and Bernstein identified more than 800 solar system objects passing through the shots. The comet that now bears their names appeared in 32 of those images, traveling along a trajectory perpendicular to the plane of the planets.
And based on recent images, its surface has warmed up enough to develop a coma — a cloud of dust and gas that surrounds a comet as its surface ices begin to sublimate or turn directly from a solid to a gas. That coma officially clinches Bernardinelli-Bernstein’s classification as a comet.
Comets are thought to come from the outer regions of our solar system, from an area beyond the Kuiper Belt, a region of the solar system beyond the orbit of Neptune.
The Kuiper Belt is truly a frontier in space – it's a place we're still just beginning to explore, and our understanding is still evolving. It shouldn't be confused with the Oort Cloud, a much more distant region of icy, comet-like bodies surrounding the solar system, including the Kuiper Belt. Both the Oort Cloud and the Kuiper Belt are thought to be sources of comets.
Throughout recorded history, hundreds of Earth impacts have been reported, with some occurrences causing deaths, injuries, property damage, or other significant localized consequences. One of the best-known recorded events in modern times was the Tunguska event in Siberia, Russia, in 1908. The 2013 Chelyabinsk meteor event is the only known incident in modern times to result in numerous injuries.
The tremendous mass of ice, rock, and space dust is definitely real, happening, and coming. But contrary to what many sensationalist social media posts claim, it didn't “just” enter our solar system. And it's no threat to Earth.
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