Two years ago, it was not possible to image the first discovered interstellar visitor. We have now succeeded in doing so with the second who honors us with a visit. NASA has published a photo of this comet, named Borisov, using the Hubble Telescope.
The image was taken by the Hubble Telescope on Oct. 12 and is the sharpest image of the comet yet, according to NASA. The photo shows that there is a central concentration of dust around the nucleus and that nucleus itself is too small to be visible on the image. When the photo was taken, the comet was 418 million kilometers from Earth. The object will come closest to Earth on December 7, at 305 million kilometers.
It is almost certain that C/2019 Q4, also called 2I/Borisov, originates from outside our solar system. The speed and hyperbolic trajectory around the sun indicate this. The comet is traveling at about 177,000 km/h. This relatively high speed is a good indication that the object is coming out of interstellar space and returning there. According to Hubble research team leader David Jewitt of the University of California, the comet is flying so fast that it “almost ignores that the sun is there.”
According to Amaya Moro-Martin of the US Space Telescope Science Institute, it is remarkable that the properties of the comet are very similar to those of the building blocks of our solar system, because the comet comes from another system that may be very different from our own. As the comet skims through our solar system, scientists can learn more about the chemical makeup, structure and dust properties of planetary building blocks believed to have formed long ago in a distant system.
C/2019 Q4 was discovered on August 30 by amateur astronomer Gennady Borisov from southern Crimea. A week later, the object was confirmed to come from outside our solar system. Two years ago there was also an interstellar object that graced our solar system with a visit, albeit for a short time. That object, called ‘Oumuamua, could not be visualized partly due to the relatively late discovery. ‘Oumuamua was the first interstellar visitor to be discovered. Presumably ‘Oumuamua was an inactive boulder, but Borisov is actually very active and therefore resembles a regular comet. Researchers think that interstellar objects skim through our solar system much more often, but are usually too small to be detected.