The detection of Oumuamua, a mysterious cigarette-shaped object, revolutionized the scientific community around its possible origin. This object, considered the first interstellar object to be detected in the vicinity of our Solar System, is believed to be, in effect, an asteroid (and not an alien spacecraft), a visitor from deep space.
NASA announced on September 12 the discovery of what would be the second interstellar object next to us. It was discovered on August 30 and was named C / 2019 Q4, or Borisov . The object, probably an asteroid, is still on its way to the Sun, but it is believed that it will not get too close to it, but will remain beyond the orbit of Mars.
On December 8, 2019, it reached its closest point to the Sun, perihelion. Relative to Earth, it did not come closer than about 300 million kilometers. After this quick visit, Borisov races away again towards the immense distance of the cosmos, never to return.
Observations by Karen Meech and her team at the University of Hawaii indicate that the comet’s nucleus is between 2 and 16 kilometers in diameter.
This is an image captured by the NASA / ESA Hubble Space Telescope in mid-December, when it peaked.
How do we know where it comes from?
Precisely, one of the clues that have allowed to conclude that this object is, in effect, a visitor from deep space, is its speed. It is moving at about 150,000 kilometers per hour, much faster than the typical speeds of objects that orbit the Sun at that distance.
Therefore, the high speed indicates not only that the object probably originated outside our Solar System, but that it will not be able to stay: just as it came, it will leave and return to interstellar space.
Borisov is one of the fastest asteroids ever seen; It travels at an impressive speed: more than 175,000 kilometers per hour./ NASA / JPL-Caltech.
Why do we know that it is a comet, and not an alien object?
As published by NASA, C / 2019 Q4 was designated a comet due to its fuzzy appearance, indicating that the object has a central icy body that produces a cloud of surrounding dust and particles as it approaches the Sun and heats up.
Its location in the sky (as seen from Earth) places it close to the Sun, an area of the sky that is generally not scanned by large terrestrial asteroid surveys or NASA’s NEOWISE asteroid-hunting spacecraft.
Following the detection of C / 2019 Q4, the Scout system, located at NASA’s Jet Propulsion Laboratory in Pasadena, California, automatically qualified it as a possible interstellar object.
Davide Farnocchia of NASA’s Center for Near-Earth Object Studies at JPL worked with astronomers and the European Space Agency’s Near-Earth Object Coordination Center in Frascati, Italy, to obtain additional observations. He then worked with the NASA-sponsored Minor Planet Center in Cambridge, Massachusetts, to estimate the comet’s precise trajectory and determine whether it originated within our Solar System or came from another part of the galaxy.
When will you leave?
Visitor C / 2019 Q4 will be observable through professional telescopes in the coming months. The object was scheduled to reach its point of maximum brightness in mid-December, and it will remain observable with moderate-sized telescopes until April 2020. After that, it will only be observable with larger professional telescopes until October 2020.
Astronomers will continue to collect observations to further characterize the comet’s physical properties (exact size, rotation, etc.) and will also continue to better identify its trajectory.
Image: The illustration shows the trajectory of comet C / 2019 Q4, considered a possible interstellar object. Image via NASA / JPL-Caltech.
