The solar system is being hurled by a massive comet. It may be the largest known comet. The new icy object is not likely to threaten any planet or us. The comet, a massive mass of ices and dust made up of rocks and ices, is 60 miles in diameter, or possibly even more. It's a unique visitor to our area.Recent announcements by astronomers about the existence of the comet, originally called 2014 UN271, but now called Comet Bernardinelli–Bernstein (after the two astronomers who discovered it: Gary Bernstein and Pedro Bernardinelli). A large telescope placed in the high Chilean desert picked up hundreds more icy bodies at the outer edges of the solar system. Although the galactic survey did detect the massive object in 2014, it took scientists many years to sort through the countless observations. They finally identified the distant object after half a century.Astronomers now know that the comet came from the Oort cloud. This is a sphere of old, icy objects around the solar system. It is normal for comets that are ejected from Oort clouds to fly through the solar system. This one will pass close to Saturn's orbit in 2031, which is more than 1 million miles from the sun.This is not an ordinary transient. It is thought to have come from a distance of 3.7 trillion miles, has not visited for millions of years, but it is also unusually large. Most comets are less than one kilometer in diameter (0.6 miles) and can be seen only because they melt closer to the sun. This creates an iconic "tail" or "coma".This one is 60 miles across, 10 times bigger than the asteroid which exterminated dinosaurs.Samantha Lawler, an astronomer at University of Regina who studies deep objects in the solar system, said that "the physical size of this comet is what's really amazing about it." "This comet is so large that it was discovered before it even got near the sun."She added, "It's by far the largest known comet in modern times."Where is the giant comet heading?Comet Bernardinelli Bernstein is located 1.8 billion miles away from the sun. The icy rock is moving "under" us. This means it's coming from below Earth’s orbit around the sun. It will swing upwards near Saturn's orbit, then zoom back to the deep, dark solar system. This is the trajectory shown below.How can astronomers determine exactly where it is headed?Jean Creighton, an Astronomer and Director of the Manfred Olson Planetarium, University of WisconsinMilwaukee, said that the comet's path is revealed by dozens of sightings. Astronomers use the cosmic background of stars to measure the speed and location of the comet. It's similar to watching distant trees from the window of a moving car. They then factor in the strong gravitational pull from the sun, as well as gravity from the planets, to determine how it will affect its path.Lawler explained, "Combining current distance, speed, gravity, and the gravitys of the sun, planets, and we can make an extremely accurate prediction of their future locations." We know from observations that this new comet will approach the sun close to [Saturn’s orbit], and then its high speed will propel it back out of our solar system.The 2014 UN271 (Comet Bernardinelli Bernstein) trajectory. It is shown below entering the planetary region, then returning out (tealline). Credit: Wikimedia/user Tony873004Comet Bernardinelli Bernstein was observed in 2017 with a powerful telescope. It was located 25 AU away from the sun. 1 AU is an astronomical unit. It's approximately 93 million miles. Credit: Dark Energy Survey / DOE / FNAL /DECam/ CTIO /NOIRLab / AURA / P. Bernardinelli & G. Bernstein / DESI Legacy Image SurveysComet Bernardinelli Bernstein's path will not bring it near Earth or any other planet. "One hundred kilometers [or sixty miles] is a huge distance. Creighton stated that it is very, very dangerous. "We are happy it isn't coming near to us."What if it struck Earth or another planet?Comet Shoemaker Levi 9 (1.2 miles or 2 km in size) collided with Jupiter in 1994. It was broken into about a dozen pieces before the collision. The impact was still significant. Lawler stated that each piece of debris that hit Jupiter created a mushroom cloud about the size of the Earth and left strange dark bruises on Jupiter's surface for several months. A 100-kilometer-long comet colliding to Saturn would be quite spectacular."We are pleased that it isn't coming near to us."Yes. However, such a collision could be devastating to the Earth's life support systems. It is crucial to know what's out there and which objects pose threats. Creighton stated, "We want to monitor whether there's anything coming close to us." NASA has a Planetary Defense Coordination Office that can monitor the skies for dangerous objects and warn of potential impacts. Humanity might one day develop spacecraft capable to deflect dangerous comets and asteroids away from Earth. This would be a smart investment.Although astronomers know where the comet is heading, the exact cause of its icy trajectory through the heart and core of the solar system is still unknown. Perhaps a larger object in deep space or another large object passing by could have given the comet the gravitational push it needed to head toward the sun.Creighton explained, "Whatever happened, probably occurred many millions of years ago."Peter Veres, an astronomer, said that even a small perturbation by a nearby star could have nudged a comet. This collaboration research group includes the Smithsonian Astrophysical Observatory (Smithsonian), and Harvard College Observatory. Stars move constantly through the galaxy and throw their mass around.Fascinating objectAstronomers would love to get a close-up view of this comet.Veres stated, "I wish there were a spacecraft capable of flying there and telling us what the object looks like."It is likely that the ship did indeed sail. To send a spacecraft to Saturn's orbit, it takes more than a decade.However, this doesn't mean that astronomers cannot still learn from the colossal object. Lawler stated, "We can obtain loads of interesting information."Comet Halebopp seen in 1997 from Earth's skyAstronomers can measure the orbit of the comet as it travels through space. This allows them to simulate, via computer simulations how the comet last touched the sun. It is possible that much of the ice on the comet's surface has melted, leaving behind a more rock-like core. Advanced telescopes are able to determine the composition of the comet. This information is extremely valuable. Knowing the origins of this comet and its composition gives rare insight into our solar system's early years, around 4 billion years ago.The comet can be viewed by a new giant telescope. Lawler noted that the Vera Rubin Observatory in Chile will have a mirror as large as a tennis court. The mirror is a good size to allow for the observation of Comet Bernardinelli–Bernstein. In the next year or so, the telescope will be available online. (When the comet gets closer, it should be visible with larger amateur telescopes.Vera Rubin could also find other icy giants tearing through the solar system. Lawler stated that "It will almost certainly discover more large comets such as this because they never get close enough to our sun," Lawler said.Astronomers and the general public will have at least one great comet to explore and learn about over the next decade. It is a benign object that invites curiosity.Creighton stated, "Any object that draws people in and makes them look up is a good one in my opinion."
