June 16, 2024
1 Solar System Way, Planet Earth, USA

Webb sees asteroids colliding in another star system

The James Webb Space Telescope (JWST) continues to make amazing discoveries. This time in the Pictor constellation where, in the Beta Pictoris system, a massive asteroid collision occurred. The system is young and just beginning its evolutionary journey and the planets are only now beginning to form. Recently, JWST observations have shown significant changes in the energy emitted by dust grains in the system compared to observations made 20 years ago. Dust production was thought to be ongoing, but results showed that data captured 20 years ago may have been a single event that has since faded, perhaps suggesting an asteroid impact.

Beta Pictoris is a young star located 63 light years away in the Pictor constellation. It has become well known for its fabulous circumstellar disk of gas and dust from which a new system of planets is forming. It has been the subject of much study because not only does it provide an ideal opportunity to study planetary formation, but one such planet Beta Pictoris b has already been detected.

Beta Pictoris is located about 60 light years away, towards the constellation Pictor (the Painter's Ridge) and is one of the best-known examples of a star surrounded by a disk of dusty debris. Previous observations showed disk deformation, a tilted secondary disk, and comets falling on the star, all indirect but telling signs that strongly suggested the presence of a massive planet. Observations made with the NACO instrument on ESO's Very Large Telescope in 2003, 2008 and 2009 have demonstrated the presence of a planet around Beta Pictoris. It is located at a distance of between 8 and 15 times the Earth-Sun separation, or Astronomical Units, which is approximately the distance that Saturn is from the Sun. The planet has a mass of approximately nine Jupiter masses and the mass and correct locations to explain the deformation observed in the internal parts of the disk. This image, based on data from Digitized Sky Survey 2, shows a region of approximately 1.7 x 2.3 degrees around Beta Pictoris. Credit: ESO/Sky Survey II

Fast forward 20 years and the Spitzer Infrared Observatory was observing Beta Pictoris. He was looking for heat emitted by crystalline silicate minerals often found around young stars and in celestial bodies. In 2004-2005, no traces were found to suggest that a collision occurred between asteroids that destroyed them and turned their bodies into dust particles, smaller even than grains of sand or even powdered sugar.

Spitzer detected radiation at wavelengths of 17 and 24 microns, resulting from significant amounts of dust. Using JWST, the team studied the radiation from dust particles around Beta Pictoris and was able to compare them with these Spitzer findings. They were able to identify the composition and size of the particles in the same area around Beta Pictoris that was studied by Spitzer. They found a significant reduction in radiation at the same wavelengths as 20 years ago.

The Spitzer Space Telescope observatory follows Earth as it orbits the Sun. Credit: NASA/JPL-Caltech

According to Christine Chen, senior astronomer at John Hopkins University, “With Webb's new data, the explanation we have is that we in fact witnessed the consequences of a rare cataclysmic event among large asteroid-sized bodies, which which marked a complete change in our understanding of this star system.

By tracing the distribution of particles across the circumstellar disk, the team found that the dust appears to have been scattered outward by radiation from the hot young star. Previously, in Spitzer observations, the star was surrounded by dust, which was heated by its thermal radiation, making it a powerful heat emitter. This is no longer the case because the dust has moved, cooled, and no longer gives off those thermal characteristics.

The discovery has adjusted our view of the formation of planetary systems. Previous theories suggested that small bodies would accumulate and replenish the dust steadily over time. Instead, JWST has shown that dust does not always replenish itself over time, but rather that a catastrophic asteroid impact is needed to seed new planetary systems with new dust. The team estimated that the asteroid that was pulverized was about 100,000 times the size of the asteroid that killed the dinosaurs!


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