The Hubble Telescope takes pictures of the largest comet ever seen – 16/04/2022 – Science

Last year, scientists announced the discovery colossal comet What remains in the orbit of Neptune. They calculated, based on its brightness, that its ice core would be between 99 and 200 kilometers. If the estimates are accurate, it will be the largest comet ever discovered.

But the scientists wanted to make sure the address was appropriate, so they pointed out in January Hubble Space Telescope to the comet and accurately measure its nuclei. As reported this week in Astrophysical Journal lettersThe diameter of the comet’s nucleus can reach 136 km, which is more than twice the width of the US state of Rhode Island (northeastern USA). It also has a mass of 500 trillion tons, which is equivalent to about 2,800 Mount Everest.

“They are a hundred times larger than the typical comets we’ve been studying all these years,” said David Jewett, an astronomer and planetary scientist at the University of California, Los Angeles and one of the study’s authors.

In spite of Impressive proportions, the comet – named C/2014 UN271 (Bernardinelli-Bernstein) after its discoverers – will only be visible to the naked eye for a brief period. It races toward the sun at a speed of 35,200 km/h. But at its closest approach, in 2031, it will be confined to just 1.6 billion kilometers from the sun – just beyond Saturn’s orbit – where it will appear as a faint glow in the night sky before returning to the shadows.

However, with the help of Hubble, astronomers can see and study this sparkling extraterrestrial visitor in all its glory, as if they were flying alongside it – a spectral blue mist surrounding a seemingly glowing white core. He said, “The picture they have is beautiful.” One of the discoverers of the comet, Pedro Bernardinellian astrophysicist at the University of Washington was not involved in the study.

Despite its weight, measuring the size of this comet’s nucleus has been difficult. Although far from the sun, a little sunlight is enough to vaporize the volatile carbon monoxide ice in the core, creating a soil-soaked atmosphere called a coma.

Hubble The comet’s nucleus is not clearly visible through this haze. But by taking these high-resolution images of the comet with a space telescope, Jewett and his colleagues were able to create a computer model of the coma, allowing them to digitally remove it from the images. With only the core remaining, it was easy to scale.

Their analysis also revealed that the ice core is blacker than coal. This may be partly due to it being “penetrated by cosmic rays,” Jewett said. High-energy cosmic rays bombard the core, breaking chemical bonds on its surface. This allowed some of the lighter elements, such as hydrogen, to escape into space, leaving behind dark-colored carbon – making the pulp look like an overly toasted slice of bread.

This dark core indicates that the comet – despite its gigantic size – is not much different from other comets. “Comet cores are always very dark,” said Teddy Caretta, a planetary scientist at the Lowell Observatory in Flagstaff, Arizona, who was not involved in the study. He suggests comparing comets to snowpacks on the side of the road. “Although it’s still mostly icy, just adding a little bit of dirt and grime can make a snow pile look nasty and dark.”

More secrets of the comets will be revealed as they approach Saturn’s orbit. But in 2031, as it begins tracing its 3 million-year circle from the Sun, astronomers won’t know much about its source, which will likely be from the Oort Cloud – a hypothetical and currently unobservable bubble around the filled solar system. … of primitive ice fragments of various shapes and sizes.

The comet is a welcome preview of what lies inside this bubble. “Finding this thing is a reminder of how little we know about the outer solar system,” Jewett said. “There are so many things we haven’t seen and so many things we can’t even imagine.”

He added, “Who knows what the hell is going on there?”

_{Translated by Luis Roberto M. Gonsalves}