The world’s first terrestrial observations of the bare nucleus of a comet nearing the end of its active life revealed that the nucleus is 800 meters in diameter and covered in large grains of phyllosilicate; on Earth, large grains of phyllosilicate are commonly available as talcum powder. This discovery provides clues to reconstruct the history of how this comet evolved to its current burned-out state.
Comet nuclei are difficult to observe because when they enter the inner solar system, where they are easy to observe from Earth, they heat up and release gas and dust that form a coma that obscures the nuclei. When comet P / 2016 BA14 (PANSTARRS) was discovered in January 2016, it was first mistaken for an asteroid, but subsequent observations revealed weak cometary activity. After many travels through the inner Solar System, this comet is believed to have burned up almost all of its ice and is now nearing the end of its cometary life.
On March 22, 2016, this comet passed 3.6 million kilometers from Earth, only 9 times farther than the Moon. A team of astronomers from the National Astronomical Observatory of Japan (NAOJ) and the Koyama Astronomical Observatory at Sangyo University in Kyoto took this unique opportunity to observe the comet with the Subaru Telescope about 30 hours before its closest approach to Earth.
They successfully observed the nucleus with minimal interference from the dust grains in the coma. Previously, the composition of the surface of a cometary nucleus had only been observed through a few “in situ” observations made by space missions.
Because the team observed thermal infrared radiation, the same region of infrared used by non-contact thermometers, they were able to find evidence that the core is 800 meters in diameter and covered with organic molecules and large grains of phyllosilicate.
This is the first time hydrated silicate minerals such as talc have been found in a comet. Comparison with laboratory measurements of various minerals revealed that the hydrated silicate minerals on the surface of P / 2016 BA14 have been heated to more than approximately 330 degrees Celsius in the past. Since the surface temperature of P / 2016 BA14 cannot exceed 130 degrees Celsius in its current orbit, it is possible that the comet has been in an orbit closer to the Sun in the past.
The next question is whether the comets are covered in talc from the beginning or whether it develops over time as they burn. “This result provides us with a precious clue to study the evolution of comets,” says Dr. Takafumi Ootsubo, lead author of this research, “We believe that further observations of comet nuclei will allow us to learn more about the evolution of comets. kites “.
National Institutes of Natural Sciences
Science and technology, news about asteroid and comet missions
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The first interstellar comet may be the most pristine ever found
Munich, Germany (SPX) March 31, 2021
New observations with the Very Large Telescope from ESO’s European Southern Observatory (VLT) indicate that rogue comet 2I / Borisov, which is only the second and most recent interstellar visitor detected in our Solar System, is one of the most pristine ever observed. Astronomers suspect that the comet most likely never passed close to a star, making it an unaltered relic of the gas and dust cloud from which it formed. 2I / Borisov was discovered by amateur astronomer Gennady Borisov in August 2019 … read more