NASA's venerable Hubble Space Telescope recently turned to the interstellar visitor Komet 2I / Borisov, causing a surprise: The intruder is highly similar to comets from our own solar system, and the structure and chemical composition of the interstellar comet resemble those of comets our own cosmic neighborhood. Among the observed features was the classic dust halo that comets usually have around their cores or hearts.
"Even if another star system could be different from ours, the comet's characteristics seem very similar to those of it." Amaya Moro-Martin, a deputy astronomer at the Space Telescope Science Institute in Baltimore, which manages Hubble operations, said in a statement by NASA: "
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Until Comet 2I / Borisov appeared all the cataloged comets of two places: the Kuiper Belt – an area near the edge of our Sun A system in which are larger objects such as Pluto and MU69 – and the Oort cloud of icy objects, which is about 1 light-year away from our Sun. (A light year is the distance that light travels in a year, which is about 6 billion miles or 10 trillion kilometers.)
Comets that emerge on the edge of the solar system can become visible to people on Earth when they reach it by gravitational shocks entered the inner solar system, perhaps by passing stars. When a comet approaches the sun, its icy surface begins to evaporate, leaving behind a "tail" of dust and gas. Comet orbits are usually elliptical, meaning that the comet's path in space appears as an extended oval that makes a tight orbit around the sun before heading toward the outskirts of the solar system. But Comet 2I / Borisov is different; Its orbit is hyperbolic and resembles an open bow as it enters the solar system just before its final departure.
Comet 2I / Borisov is only the second known interstellar visitor to our solar system. The first was an object called 1I / 'Oumuamua, an elongated, stone-like object that made a short passage in Mercury's orbit in 2017 before it zoomed off, presumably forever. Fortunately, it is expected that Borisov will stay in the solar system until mid-2020, allowing more time for observations. The comet's closest approach to the sun, which will occur in December, is approximately 300 million kilometers (186 million miles) or twice the Earth's average distance from the Sun.
Although interstellar visitors have recently been proven by observations, a new study suggests that interstellar objects are quite common, Hubble astronomers said. There could be thousands of such objects in the solar system at any time, though most are beyond the reach of the observational capabilities of today's telescopes. This makes the observation of Borisov valuable, especially because it is different from & # 39; Oumuamua & # 39; different.
"While 'Oumuamua appeared to be a rock, Borisov is truly active, more like a normal comet,' observatory director David Jewitt of the University of California, Los Angeles, said in the same statement. "It's a mystery why these two are so different."
Hubble's observations of Borisov happened on October 12, when the comet was about 260 million miles (418 million kilometers) from Earth. Future Hubble observations are scheduled to run until at least January, with further proposals to be considered later in 2020.