We know only two interstellar visitors – that is, visitors from other stellar systems – to our solar system. They are 1I / ‘Oumuamua and 2I / Borisov. “Oumuamua receives a lot of press as a strange-shaped traveler, who could be anything from a piece of exoplanet to an alien spacecraft. The least known 2I / Borisov is more clearly a comet that could have come from a red dwarf star. His chemical signature suggests that he may have never interacted with a star before. If so, said Stefano Bagnulo of the Armagh Observatory and Planetarium in Northern Ireland, UK:
2I / Borisov could be the first truly pure comet ever observed
Bagnulo conducted a new study on comet 2I / Borisov, published on March 30, 2021, in the peer-reviewed journal Communications about nature.
He and his team believe that 2I / Borisov never passed close to any star before flying past our sun in 2019. If so, this object could still have clues to the cloud of gas and dust in which it formed. .
Comet 2I / Borisov passed by our sun at the end of 2019. In this photo from the very large Telescope in northern Chile, the comet is the fuzzy object in the center. The stars appear as stripes because the telescope was trained on the moving comet, not the stars. The colors of the stars’ rainbow are the result of combining observations at different wavelengths into a composite image. Image by ESO / O. Hainaut.
A team of scientists led by Bagnulo used a technique called polarimetry to measure the polarized light in 2I / Borisov. Light is polarized as it passes through filters, such as sunglasses or comet material. By studying the properties of sunlight polarized by the dust of a comet, researchers can learn about the physics and chemistry of comets.
This analysis showed that 2I / Borisov is different from almost all other comets studied, except Hale-Bopp. Astronomers believe that Comet Hale-Bopp passed the sun only once before its magnificent return in the late 1990s. This earlier return is thought to have occurred thousands of years ago, in 2215 BC, when Hale-Bopp may have had a near collision with Jupiter, altering its orbit and bringing it to the sun for the first time. . Due to its few interactions with the sun, Hale-Bopp is also considered a clean comet, having a composition very similar to that of the cloud of gas and dust formed by our solar system 4.5 billion years ago.
Polarization data show that 2I / Borisov is even cleaner than Hale-Bopp. 2I / Borisov shows smooth signatures of the gas and dust cloud since its formation. Evidence also shows that both comets formed under similar conditions, only in different solar systems. As Alberto Cellino of the Astrophysics Observatory in Turin said:
The fact that the two comets are remarkably similar suggests that the environment in which 2I / Borisov came from is not so different in composition from the environment in the early solar system.
Comet Hale-Bopp, seen here on April 4, 1997, was another of the purest known comets, which means that it had few interactions with its star, in this case our sun. Comet 2I / Borisov is also clean, with its flight near the sun in 2019 considered to be its first interaction with any star. Image by E. Kolmhofer / H. Raab / Johannes-Kepler-Observatory / Wikimedia.
A second team of scientists used telescopic data to analyze dust grains from 2I / Borisov and published their findings on March 30, 2021, in the peer-reviewed journal. Nature Astronomy.
They discovered that the comet’s coma – which is the envelope of dust that surrounds the main body of a comet – contains compact pebbles. These pebbles are grains about 1 millimeter (0.04 inches) or larger. The team also noted that the relative amounts of carbon monoxide and water in the comet changed dramatically as it approached the sun. According to these scientists, these changes indicate:
… that the comet is made up of materials that have formed in different places in its planetary system.
Observations of [Bin Yang, an astronomer at ESO in Chile] and her team suggests that the matter in 2I / Borisov’s planetary house was shuffled from its star to further, perhaps due to the existence of giant planets, whose strong gravity shakes the material in the system.
Astronomers believe that a similar process took place at the beginning of the life of our solar system.
When amateur astronomer Gennady Borisov discovered comet 2I / Borisov in August 2019, it became only the second known object to visit our solar system in interstellar space. The first discovery was “Oumuamua in October 2017.” Oumuamua was traveling at a fast speed of 94,900 km per hour, until its swing through the sun accelerated to 315,800 km per hour.
These zippy interstellar visitors are now removed from the solar system and back on their way to interstellar space.
This diagram compares the paths of the two known interstellar objects that entered our solar system, 1I / ‘Oumuamua (red, discovered in 2017) and 2I / Borisov (yellow, discovered in 2019). Image via Wikimedia / Tony873004.
Bottom line: The second known interstellar object, called comet 2I / Borisov by Earth astronomers, may be one of the cleanest objects ever seen, according to a new study.
Source: Unusual polarimetric properties for interstellar comet 2I / Borisov
Source: Compact pebbles and the evolution of birds in the interstellar comet 2I / Borisov
Through ESO
