On Aug. 30, 2019, Gennady Borisov at the MARGO observatory in Nauchnij, Crimea has discovered a comet that is believed to be originated from outside the solar system. The comet designated C/2019 Q4 (Borisov), is currently 260 million miles (420 million kilometers) from the Sun and will reach its closest point, or perihelion, on Dec. 8, 2019, at a distance of about 190 million miles (300 million kilometers).
However, it is not confirmed whether this object is interstellar, but if it is interstellar, it would be only the second such object detected. The first, Oumuamua, was observed and confirmed in October 2017.
After the initial detections of the comet, Scout system, which is located at NASA’s Jet Propulsion Laboratory in Pasadena, California, automatically flagged the object as possibly being interstellar. 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 elsewhere in the galaxy.
Farnocchia said, “The comet’s current velocity is high, about 93,000 mph [150,000 kph], which is well above the typical velocities of objects orbiting the Sun at that distance. The high velocity indicates not only that the object likely originated from outside our solar system, but also that it will leave and head back to interstellar space.”
C/2019 Q4 was established as being cometary due to its fuzzy appearance, which indicates that the object has a central icy body that is producing a surrounding cloud of dust and particles as it approaches the Sun and heats up. Its location in the sky (as seen from Earth) places it near the Sun—an area of the sky not usually scanned by the extensive ground-based asteroid surveys or NASA’s asteroid-hunting NEOWISE spacecraft.
Farnocchia said, “C/2019 Q4 can be seen with professional telescopes for months to come. The object will peak in brightness in mid-December and continue to be observable with moderate-size telescopes until April 2020. After that, it will only be observable with larger professional telescopes through October 2020.”
Observations completed by Karen Meech and her team at the University of Hawaii indicate the comet nucleus is somewhere between 1.2 and 10 miles (2 and 16 kilometers) in diameter. Astronomers will continue to collect observations to further characterize the comet’s physical properties (size, rotation, etc.) and also continue to identify its trajectory better.