Biggest comet to date is heading towards the inner solar system
Scientists announcement on April 12, 2022, that they created a high quality image confirming that C/2014 UN271 (Bernardinelli-Bernstein), affectionately nicknamed BB, is the largest Oort Cloud comet yet discovered. The new comet coreor nucleus, is about 120 km across, about twice the size of comet Hale-Bopp, which gave us such a good show in 1997. And BB is now heading into the inner regions of the solar system.
The good news is that NASA says it won’t come anywhere near Earth. From NASA official announcement:
The giant comet, C/2014 UN271 (Bernardinelli-Bernstein) is hurtling in this direction at 22,000 miles per hour (35,400 km/h), from the outskirts of the solar system. But do not worry. It will never approach closer than a billion kilometers from the sun, which is slightly further than the distance from the planet Saturn. And it won’t be until 2031.
Discovery of the largest comet to date
University of Pennsylvania astronomers Pedro Bernardinelli and Gary Bernstein discovered the comet. They were examining footage from 2014 to 2018 of the Dark Energy Investigation as part of their computer-aided search for trans-Neptunian objects.
So how big is it?
At the time of the initial discovery, scientists estimated the comet’s icy, dusty core to be 62 to 230 miles (100 to 370 km) wide. The new imagery refines the estimate to a range of between 66 and 86 miles (105 to 140 km), making it about twice the size of comet Hale-Bopp. Comet Hale-Bopp appeared with the naked eye in 1997 and delighted observers around the world. The previous record holder for the largest comet nucleus was C/2002 VQ94 (LINEAR)which measures about 60 miles (100 km) at its widest.
The cosmic block’s new big kid is far from alone, says David Jewitt, professor of planetary sciences and astronomy at UCLA and co-author of the study that refined the measurements of the comet. According to NASA’s announcement:
This comet is literally the tip of the iceberg for many thousands of comets that are too faint to be seen in the farthest parts of the solar system. We always suspected that this comet must be big because it is so bright at such a great distance. Now we confirm it.
Biggest comet to date is getting closer
While the discovery of Comet BB was in 2014, its first appearance on image data was in 2010. At that time, BB was 3 billion miles (4.8 billion km) from Earth , coincidentally around the middle distance of Neptune. Now the object is about a billion kilometers closer, but still well outside the solar system.
Already, the core is releasing gas and dust at an impressive rate of about 2,200 pounds (1,000 kg) per second. The authors of the paper described it as:
…a huge (although uncertain) rate of mass loss.
It was this voluminous outpouring of gas and dust from a body so far away in the solar system that prompted the research team to try to measure what they suspected to be a huge cometary body. Man in Hui from Macau University of Science and Technology, Taipa, Macau, led the team. Hui said:
It’s an amazing object, given how active it is while still so far from the sun. We guessed the comet might be quite large, but we needed the best data to confirm that.
Obtain images of Comet BB
To collect this data, Hui’s team used the Hubble Space Telescope’s Wide Field Camera 3 to take five photos of the comet on January 8, 2022.
In announcing the team’s discovery, NASA described the process the team members used to discern the size of the nucleus against the background of the coma glare and comet tails:
The comet is currently too far away for its nucleus to be visually resolved by Hubble. Instead, the Hubble data shows a bright peak of light at the location of the nucleus. Hui and his team then created a computer model of the surrounding coma and adjusted it to fit the Hubble images. Then the coma glow was subtracted to leave behind the star-shaped core.
By combining the Hubble dataset with radio observations made by the Atacama Large Millimeter/Submillimeter Array (ALMA) in Chile, the team was able to assign upper and lower bounds to the size of C/2014 UN271.
The team also discovered that the comet is less reflective than originally thought. According to Jewitt:
It’s big and it’s blacker than coal.
Conclusion: Comet C/2014 UN271, also known as Comet Bernardinelli-Bernstein or BB, is the largest comet to date, as new images from Hubble confirm. The comet is about twice as large as comet Hale-Bopp, about 120 km wide.