Comet 2I/Borisov
Comet 2I/Borisov
Video
Animation of Comet 2I/Borisov
On 12 October 2019, the NASA/ESA Hubble
Space Telescope provided astronomers with their best look yet at an
interstellar visitor — Comet 2I/Borisov — which is believed to have
arrived here from another planetary system elsewhere in our galaxy.
This observation is the sharpest view ever of the
interstellar comet. Hubble reveals a central concentration of dust
around the solid icy nucleus.
Comet 2I/Borisov is only the second such interstellar
object known to have passed through our Solar System. In 2017, the first
identified interstellar visitor, an object dubbed ‘Oumuamua, swung
within 38 million kilometres of the Sun before racing out of the Solar
System.
“Whereas ‘Oumuamua looked like a bare rock, Borisov is
really active, more like a normal comet. It’s a puzzle why these two are
so different,” explained David Jewitt of UCLA, leader of the Hubble team who observed the comet.
As the second interstellar object found to enter our Solar
System, the comet provides various invaluable insights. For example, it
offers clues to the chemical composition, structure, and dust
characteristics of a planetary building block presumably forged in an
alien star system a long time ago and far away.
“Because another star system could be quite different
from our own, the comet could have experienced significant changes
during its long interstellar journey. Yet its properties are very
similar to those of the Solar System’s building blocks, and this is very
remarkable,” said Amaya Moro-Martin of the Space Telescope Science Institute in Baltimore, Maryland.
Hubble photographed the comet at a distance of approximately 420 million kilometres from Earth [1].
The comet is travelling toward the Sun and will make its closest
approach to the Sun on 7 December, when it will be twice as far from the
Sun as Earth. It is also following a hyperbolic path around the Sun,
and is currently blazing along at the extraordinary velocity of over 150
000 kilometres per hour.
By the middle of 2020, the comet will be on
its way back into interstellar space where it will drift for millions of
years before maybe one day approaching another star system.
Crimean amateur astronomer Gennady Borisov first discovered
the comet on 30 August 2019. After a week of observations by amateur
and professional astronomers all over the world, the International
Astronomical Union’s Minor Planet Center computed an orbit for the comet
which showed that it came from interstellar space. Until now, all
catalogued comets have come either from a ring of icy debris at the
periphery of our Solar System, called the Kuiper belt, or from the Oort
cloud, a shell of icy objects which is thought to be in the outermost
regions of our Solar System, with its innermost edge at about 2000 times
the distance between the Earth and the Sun.
2I/Borisov and ‘Oumuamua are only the beginning of the
discoveries of interstellar objects paying a brief visit to our Solar
System. There may be thousands of such interstellar objects here at any
given time; most, however, are too faint to be detected with present-day
telescopes.
Observations by Hubble and other telescopes have shown that
rings and shells of icy debris encircle young stars where planet
formation is underway. A gravitational interaction between these
comet-like objects and other massive bodies could hurtle them deep into
space where they go adrift among the stars.
Future Hubble observations of 2I/Borisov are planned through January 2020, with more being proposed.
Notes
[1] This observation was made as part of DD Program #16009.
More Information
The Hubble Space Telescope is a project of international cooperation between ESA and NASA.
Image credit: NASA, ESA, D. Jewitt (UCLA)
Links
Contact
David Jewitt
UCLA, Los Angeles, California
USA
Email: djewitt@gmail.com
Stuart Wolpert
UCLA, Los Angeles, California
USA
Email: swolpert@stratcomm.ucla.edu
Bethany Downer
ESA/Hubble, Public Information Officer
Garching, Germany
Email: bethany.downer@partner.eso.org
Source: ESA/HUBBL/News
