Astronomers Discovered Two Extremely Red Main-belt Asteroids (Planetary Science)

A team of international astronomers discovered two extremely red main-belt asteroids: 203 Pompeja and 269 Justitia. These were identified from combined visible and near-infrared spectroscopic observations collected at the IRTF and SAO observatories. Their study recently appeared in Arxiv.

The majority of asteroids in the Solar System are found in the main asteroid belt (MBA). This is located between the orbits of Mars and Jupiter, with the greatest concentration of asteroids between 2.12 and 3.3 AU. Early in the history of the solar system, the gravity of newly formed Jupiter brought an end to the formation of planetary bodies in this region and caused the small bodies to collide with one another, fragmenting them into the asteroids we observe today. But, not all MBAs experienced catastrophic destruction. Some are larger than 110 km in diameter and still exists, means these objects can be regarded as the last remains of the original population of planetesimals that initially populated the inner solar system. Moreover, if such MBA’s escaped catastrophic destruction, their orbital elements have not been substantially altered which means, those orbital elements maintained their state at the end of migration state of solar system.

Now, a team of international astronomers performed their observations on the 3.0-m NASA Infra-red Telescope Facility (IRTF) on Mt. Mauna Kea, Hawaii, USA and at the 1.0- m Seoul National University Astronomical Observatory (SAO), Republic of Korea. They also recorded asteroidal spectroscopic data by two different instruments mounted on these telescope and discovered two extremely red main-belt asteroids: 203 Pompeja and 269 Justita.

The first extremely red asteroid called, “203 Pompeja” was discovered by chance in the visible to near-infrared wavelength range during spectroscopic survey. It has diameter if 111.3 km and an albedo of 0.045. It is located in the middle main-belt.

While, the second very red asteroid called “269 Justitia” had already been discovered and have a diameter of 54.4 km and an albedo of 0.080. It is also located in the middle main-belt.

Figure 1. Spectra of the very red spectral slope MBAs 203 Pompeja and 269 Justitia and other dark (low-albedo) objects in the visible and near-infrared region. Comparison of the very red asteroids with: top left panel: typical spectral types of dark asteroids from the Bus-DeMeo classification scheme, top right: typical Hildas and Jovian Trojans, bottom left: meteorites with a very red spectral slope, bottom right: dark outer Solar System objects spectrally similar to the very red asteroids © Hasegawa et al.

They also found that, these two asteroids have a redder spectral slope than any other D-type body, which are the reddest objects in the asteroid belt, and similar to RR and IR-class objects found in the outer Solar System among trans-Neptunian objects (TNO’s) and Centaurs.

In addition, their spectroscopic results suggested the presence of complex organic materials on the surface layer of these asteroids, implying that they could have formed in the vicinity of Neptune and been transplanted to the main belt region during a phase of planetary migration.

Finally, 203 Pompeia is the only very red asteroid known so far among the ∼250 bodies with diameter larger than 110 km (i.e. presumably structurally intact) found in the asteroid belt.

“These discoveries add another piece of evidence that the main asteroid belt hosts a population of bodies that were formed in the outskirt of the Solar System.”, concluded authors of the study.


To know more: Read on The Astrophysical Journal Letters the article ” Discovery of two TNO-like bodies in the asteroid belt “, by Sunao Hasegawa, Michael Marsset, Francesca E. DeMeo, Schelte J. Bus, Jooyeon Geem, Masateru Ishiguro, Myungshin Im, Daisuke Kuroda and Pierre Vernazza


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