Photo Credit: NASA, ESA and J. DePasquale (STScI)
NASA's Hubble Space Telescope has given astronomers their best look yet at an interstellar visitor -- comet 2I/Borisov -- whose speed and trajectory indicate it has come from beyond our solar system.
Comet 2I/Borisov is only the second such interstellar object known to have passed through the solar system.
In 2017, the first identified interstellar visitor, an object officially named 'Oumuamua, swung within 24 million miles of the Sun before racing out of the solar system.
"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.
This Hubble image, taken on October 12, 2019, is the sharpest view of the comet to date, revealing a central concentration of dust around the nucleus.
As the second known interstellar object found to enter our solar system, the comet provides invaluable clues to the chemical composition, structure and dust characteristics of planetary building blocks presumably forged in an alien star system a long time ago and far away.
"Though another star system could be quite different from our own, the fact that the comet's properties appear to be very similar to those of the solar system's building blocks is very remarkable," said Amaya Moro-Martin of the Space Telescope Science Institute in Baltimore, US.
Hubble photographed the comet at a distance of 260 million miles from Earth. The comet is falling past the Sun and will make its closest approach to the Sun on December 7 this year when it will be twice as far from the Sun as Earth.
The comet is following a hyperbolic path around the Sun, and currently is blazing along at an extraordinary speed of 110,000 miles per hour.
"It's travelling so fast it almost doesn't care that the Sun is there," said Jewitt.