One of the biggest comets ever is on our way

Nearly four and a half billion kilometers from the sun — 29 times more than the Earth’s orbit — a tiny speck of sunlight bounced off an object accelerating toward our cosmic environment. Ice object. And something old and unimaginably large.

About four hours later, at dawn on October 20, 2014, a telescope in Chile’s Atacama Desert focused its sharp look at the night sky and captured a giant image of the southern mantle, showing the first glimpse of the reflected light. Look.

But it will take another seven years before researchers can identify the strange bright spot as a visitor from the early days of the solar system – and possibly the largest comet ever seen with modern telescopes. The object is called Bernardinelli-Bernstein and its existence was announced last June. Astronomers now have all the information they can gather about a celestial body in one The first scientific description in Astrophysical Journal Letters Posted.

“My phone kept ringing – I didn’t expect the scientific community to be so excited about the discovery,” said Pedro Bernardinelli, a postdoctoral researcher at the University of Washington. The comet was discovered in the final weeks of his Ph.D. research at the University of Pennsylvania, with his mentor at the time, Gary Bernstein. “All in all, it was very overwhelming.”

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According to the latest estimates, the diameter of the comet’s nucleus – the actual celestial body – is about 150 kilometers. This is by far the largest comet estimate in decades. For comparison, comet 67P/Churyumov-Gerasimenko, examined between 2014 and 2016 by The European Space Agency’s space probe Rashid, no more than four kilometers in diameter.

“We are going from city-sized comets to island-sized comets,” said Michelle Bannister, an astronomer at the University of Canterbury in New Zealand, who was not involved in the first publication on the comet. Comet Bernardinelli-Bernstein may belong to the historical ‘Great Comet’ series, which includes a very bright (and possibly massive) comet. Travel through the inner solar system in 1729.

When Bernardinelli Bernstein approaches the Sun, the comet will light up and penetrate from below to the level of the disk in which the inner planets revolve around the Sun. Its closest approach to Earth will be January 21, 2031, when it will be more than a billion miles from the sun – just a little farther from Saturn’s average orbit. Then Bernardinelli-Bernstein will begin its long journey back to the floodplains of the solar system, remaining well visible until the 1940s and possibly decades longer.

Depending on how much gas a comet ejects as its icy surface is evaporated by sunlight, Bernardinelli Bernstein could shine in the night sky as bright as Titan, Saturn’s largest moon. In this case, the comet should be visible with a reasonable amateur telescope in 2031.

But Bernardinelli-Bernstein is also special because of the enormous distance at which it was first seen. The icy body comes from the Oort Cloud, a huge spherical nebula of smaller celestial bodies revolving around the Sun, at a distance thousands of times greater than the distance between the Earth and the Sun.

Astronomers calculated that this comet takes millions of years to complete one revolution around the sun. So far, only three “long-range comets” have been detected en route from the Oort cloud to the inner solar system, and Bernardinelli-Bernstein has been observed about 4.4 billion kilometers from Earth. sinner. Since the orb was observed so early, a whole generation of astronomers will have the opportunity to decipher the mysteries of this comet.

a speck of light

Bernardinelli Bernstein has captured the attention of mankind thanks to the highly sensitive digital camera installed on the Víctor M. Blanco telescope, with a mirror diameter of four meters, part of the Cerro Tololo Inter-American Observatory in the Atacama Desert in Chile.

The camera was not specifically looking for celestial bodies from the farthest regions of the solar system. It was the primary data collection tool for the Dark Energy Survey, a long-term project that took more than 80,000 images of large swaths of the southern night sky between 2013 and 2019. This data set pioneered the search for possible explanations for dark energy, the mysterious force believed to be responsible. About the accelerating expansion of the universe. But images aimed at studying dark energy and other cosmic phenomena can also be used to discover objects close to home.

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In his doctoral research, Bernardinelli used images from the Dark Energy Survey to track previously undiscovered objects in orbit around the Sun outside of Neptune’s orbit. This was not an easy task. Each shot was so large that at maximum resolution it would cover a network of 275 HDTV screens. Bernardinelli searched tens of thousands of these images for points of light with a diameter of a few pixels.

To facilitate his research, Bernardinelli wrote a computer code that allowed him to search the Dark Energy Survey images for spots of light moving against the stationary backgrounds of distant stars. After six months of complex calculations on a set of about two hundred computers at the Fermi National Accelerator Laboratory in Batavia, Illinois, Bernardinelli kept a data set. From 817 newly discovered items about their orbits that do not coincide with the orbits of the known celestial bodies in the solar system. As a final step, Bernardinelli and Bernstein personally checked the accounts on this list to ensure that the computer code did its job properly.

That was also when they noticed the UFO: a celestial body with a brightness comparable to that of worlds about 150 kilometers in diameter. The object lies outside the orbit of Neptune but has a very anomalous orbit, which indicates that the object came from an area thousands of billions of kilometers from the Sun, as is common with long-period comets.

Tracking a comet, Bernstein says, was like “a needle in a real haystack.” “But we managed to find the thing, like a little icing on a cake!”