Astronomers spot two unusually red objects in the asteroid belt

Artistic interpretation of an asteroid belt.

Artistic interpretation of an asteroid belt.
Picture: Nasa

They are red, they are big enough, and they have nothing to do in the main asteroid belt, but their discovery confirms the complex conditions in place when the solar system was still forming.

New research published in The Astrophysical Journal Letters details the discovery of two extremely red asteroids in the main belt. Named 203 Pompeja and 269 Justitia, the asteroids have a spectral signature redder than any other asteroid in the main belt, this densely populated band of asteroids located between the orbits of Mars and Jupiter. The new newspaper was headed by Japan Aerospace Exploration Agency (JAXA) astronomer Sunao Hasegawa.

It is important to note that these red asteroids look like transneptunian objects, that is, objects located fafarther than Neptune, the farthest planet from the Sun (without disrespecting the dwarf planet Pluto). This could mean that 203 Pompeja and 269 Justitia formed there in the Kuiper Belt then drifted inward when the solar system was still young. If confirmed, new finding shows how chaotic conditions were back then and that materials from different parts of the solar system sometimes mixed together.

The aim of the study was to document the distribution and composition of large asteroids in the main belt. Large asteroids, especially those over 100 km wide, are likely survivors of the early days of the solar system. By studying these objects, scientists hoped to get a glimpse of what conditions looked like around 4 billion years ago.

To do this, astronomers performed visible and near infrared spectroscopic observations of the main belt using the Telescope Facility (IRTF) and the Seoul National University (SAO) Astronomical Observatory. This international collaboration involved scientists from MIT, University of Hawaii‘i, Seoul National University, Kyoto University and several other institutions.

Asteroid 203 Pompeja is 110 km in diameter, while 269 Justitia is half the size. Both exhibit an unusually red spectrum, which means they reflect a lot of red light. They are even redder than D-type asteroids, which were previously considered the reddest objects in the asteroid belt.

The outer solar system is teeming with material from the formation of the solar system, including planetesimals (asteroids) and centaurs (icy planetesimals located between Jupiter and Neptune). These distant objects are very red, containing complex organic compounds like methane and methanol ice. These compounds, when viewed through a spectrograph, give an asteroid its reddish appearance. In contrast, objects in the inner solar system have rare traces of organic matter, so they tend to reflect blue light.

Asteroids 203 Pompeja and 269 Justitia are believed to have formed near the outer edge of the solar system beyond the distant organic snow line and then moved towards the asteroid belt when the solar system began to form. », Notes a JAXA Press release. By “organic snow line,” scientists refer to the location in the solar system where methanol and methane turn to ice.

This finding suggests that some Main Belt asteroids formed in the Outer Solar System and that a population of these objects likely exists in the Main Belt. A good next step would be to determine the exact proportion of this population of red asteroids. In addition, the new study presents the main belt as a good destination for a future mission. Instead of traveling to the outer edge of the solar system for samples of Kuiper belt objects, all we would have to do would be send a probe into the asteroid belt, where it could study at the both interior object asteroids and those that formed far, far away. .

Following: Comet 67P changed color several times during the historic Rosetta mission.

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