NASA's Hubble Space Telescope has just taken a peek at the second interstellar object to visit the solar system -- a comet.
Based on its current speed and trajectory, 2I/Borisov likely came from outside our solar system. It is the second such object after the asteroid 'Oumuamua (identified in 2017). However, the two are very different beasts -- while 'Oumuamua was a rocky, solid body, 2I/Borisov is a comet. The image taken by Hubble is the best look we've had at 2I/Borisov so far and reveals a body of dust around a central core (which is too small to be seen in the image).
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Whereas 'Oumuamua appeared to be a rock, Borisov is really active, more like a normal comet. It's a puzzle why these two are so different," said David Jewitt of the University of California, Los Angeles (UCLA), leader of the Hubble team who observed the comet.
Being the second interstellar object we've found so close to home, researchers are very keen to study the properties and nature of 2I/Borisov. Its chemical composition, structure, and the dust around it are products of its host star system and can teach us about how they form. We won't know for sure without further observation, but so far, the comet's properties appear to be very similar to those in the Solar System.
The comet was 260 million miles from Earth when Hubble took its picture. It is on a hyperbolic path around the Sun, currently moving at around 110,000 miles per hour. Its closest approach will be on Dec. 7, 2019, when it will be twice as far from the Sun as Earth. By mid-2020, NASA adds, it will make its way past Jupiter and onto interstellar space.
"It's traveling so fast it almost doesn't care that the Sun is there," said Jewitt.
2I/Borisov was first discovered by Crimea-based amateur astronomer Gennady Borisov on Aug. 30, 2019. After a week of observations, the International Astronomical Union's Minor Planet Center and the Center for Near-Earth Object Studies at NASA's Jet Propulsion Laboratory in Pasadena, California, confirmed that it came from interstellar space. Future Hubble observations of 2I/Borisov are planned through January 2020, with more being proposed.
