OrbitalHub

NASA dicit:

NASA’s Neil Gehrels Swift Observatory tallied the water lost from an interstellar comet as it approached and rounded the Sun. The object, 2I/Borisov, traveled through the solar system in late 2019.

Comets are frozen clumps of gases mixed with dust, often called “dirty snowballs.” As a one approaches the Sun, frozen material on its surface warms and converts to gas.

When sunlight breaks apart water molecules, one of the fragments is hydroxyl, a molecule composed of one oxygen and one hydrogen atom. Swift detects the fingerprint of ultraviolet light emitted by hydroxyl using its Ultraviolet/Optical Telescope (UVOT). Between September and February, Swift made six observations of Borisov with Swift. It saw a 50% increase in the amount of hydroxyl — and therefore water — Borisov produced between Nov. 1 and Dec. 1, which was just seven days from the comet’s closest brush with the Sun.

At peak activity, Borisov shed eight gallons (30 liters) of water per second, enough to fill a bathtub in about 10 seconds. During its trip through the solar system, the comet lost nearly 61 million gallons (230 million liters) of water — enough to fill over 92 Olympic-size swimming pools. As it moved away from the Sun, Borisov’s water loss dropped off — and did so more rapidly than any previously observed comet.

Swift’s water production measurements also helped show that Borisov’s minimum size is just under half a mile (0.74 kilometer) across. The team estimates at least 55% of Borisov’s surface was actively shedding material when it was closest to the Sun. That’s a large fraction compared to most observed solar system comets.

Video credit: NASA’s Goddard Space Flight Center/Scientific Visualization Studio/Scott Wiessinger (USRA): Lead Producer/Jeanette Kazmierczak (University of Maryland College Park): Lead Science Writer/Scott Wiessinger (USRA): Lead Animator/Dennis Bodewits (Auburn University): Scientist/Zexi Xing (University of Hong Kong): Scientist/Francis Reddy (University of Maryland College Park): Science Writer

NASA dicit:

When amateur astronomer Gennady Borisov discovered an interstellar comet zipping through our solar system on Aug. 30, 2019, scientists promptly turned their telescopes toward it hoping to catch a glimpse of this rare and ephemeral event. After all, no one had ever set eyes on a confirmed comet from a foreign star system, and it was clear from its projected trajectory that the alien visitor, named 2I/Borisov, would soon disappear from the sky forever.

Before it dimmed from view, a team of international scientists led by Martin Cordiner and Stefanie Milam at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, probed it with the world’s most powerful radio telescope: the Atacama Large Millimeter/submillimeter Array (ALMA) in northern Chile. The comet was near its closest approach to Earth at about 180 million miles, or nearly 300 million kilometers, away.

When the scientists peeked inside the halo of gas that formed around the comet as it came closer to the Sun and its ices began to vaporize, they detected something peculiar: 2I/Borisov was releasing gas with a greater concentration of carbon monoxide (CO) than anyone had detected in any comet at a similar distance from the Sun (within less than 186 million miles, or 300 million kilometers). 2I/Borisov’s CO concentration was estimated to be between nine and 26 times higher than that of the average solar system comet.

Video credit: NASA’s Goddard Space Flight Center/James Tralie (ADNET): Lead Producer, Lead Editor, Narrator/Lonnie Shekhtman (ADNET): Lead Writer/Martin Cordiner (Catholic University of America): Scientist, Stefanie Milam (NASA/GSFC): Scientist/ Aaron E. Lepsch (ADNET): Technical Support

Wikipedia dicit:

2I/Borisov, originally designated C/2019 Q4 (Borisov), is the first observed interstellar comet and the second observed interstellar interloper after ʻOumuamua. 2I/Borisov has a heliocentric orbital eccentricity of 3.36 and is not bound to the Sun. The comet passed through the ecliptic of the Solar System at the end of October 2019, and made its closest approach to the Sun at just over 2 AU on 8 December 2019. In November 2019, astronomers from Yale University said that the comet (including coma and tail), was 14 times the size of Earth, and stated, “It’s humbling to realize how small Earth is next to this visitor from another solar system.” In the middle of March, 2020, the comet was observed to fragment; and later, in April, even more evidence of fragmentation was reported.

Video credit: NASA