Warm dust in the BD +20 307 system could be what remains of a planetary collision

Artist's concept of a planetary collision in the BD +20 307 system (Image NASA/SOFIA/Lynette Cook)
Artist’s concept of a planetary collision in the BD +20 307 system (Image NASA/SOFIA/Lynette Cook)

An article published in “The Astrophysical Journal” reports a study of the BD +20 307 binary system in which the presence of dust too warm to be the equivalent of the Kuiper belt was detected, therefore they have been interpreted as the remains of a planetary collision. A team of researchers led by Maggie Thompson of the University of California at Santa Cruz used the SOFIA flying telescope to detect infrared emissions, which increased over time.

About 300 light years from Earth, the BD +20 307 system is composed of two stars slightly more massive than the Sun. Their age was estimated at least a billion years so astronomers expected to find only cold dust around them, debris left after the formation of planets in regions far from them like the Kuiper Belt in the solar system. Instead, over the past decade, ground-based observations using the Keck and Gemini Nord telescopes and especially the ones conducted from space with NASA’s Spitzer telescope revealed the presence of warm dust that would be expected to be found in very young systems.

For this type of study it’s important to be able to detect infrared emissions, which are blocked by the Earth’s atmosphere. The SOFIA (Stratospheric Observatory for Infrared Astronomy) flying observatory, a project by NASA and DLR, the German space agency, uses a modified Boeing 747SP to allow the use of a 2.5 meter diameter telescope at a altitude where all infrareds can be detected.

The data collected in those years had already led to the hypothesis of a planetary collision in the BD +20 307 system. Now the observations conducted in particular with the SOFIA’s flying telescope’s Forcast (Faint Object infraRed CAmera for the Sofia Telescope) instrument of the showed infrared emissions 10% higher than the previous ones. There are processes such as the approach of dust to the stars or a heat absorption due to other causes but a planetary collision is the one that determines a quick spread of warm dust that can generate that type of infrared detections.

Alycia Weinberger of the Carnegie Institution for Science, who participated in this study, called it a rare opportunity to study catastrophic collisions that occur later in a planetary system’s history. SOFIA’s observations show changes in the dust disk on a time scale of only a few years. These are catastrophic events that can have important consequences on the evolution of a star system. For example, probably the primordial Earth was hit by a planet and the consequence was the Moon’s formation. The formation of Pluto and Charon could also be the consequence of a similar catastrophe.

The researchers have already conducted follow-up observations of the BD +20 307 system and are analyzing the data to check any further changes. Obtaining greater certainty about the phenomenon that generated warm dust would be important. If it were really the collision between two exoplanets, it would offer the possibility to study the long-term consequences of such an event.

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