U of I professor and PhD student part of dwarf planet discovery team

Siegfried Eggl and his graduate student Samuel Cornwall are on the team of scientists that discovered a dwarf planet from some of the first images collected by the Vera C. Rubin Observatory. Eggl is an aerospace engineering professor in The Grainger College of Engineering, University of Illinois Urbana-Champaign and holds a joint appointment in the Department of Astronomy.

Eggl said his team’s role was to optimize discovery rates for asteroids and to confirm that the astrometric measurements of solar system objects observed by Rubin Observatory including that of the new object were correct and unbiased.

“When a new object is identified in the Solar System, we need to verify its exact location; the astrometry needs to be accurate,” he said. “The further out it is in the solar system, the more difficult this becomes, because any error or uncertainty in these observations scales with the distance to the object.”

He used the analogy of the beam of a flashlight. If an object is close, the beam is narrow and focused, but at a long distance, the cone of light from the flashlight is much larger. This is analogous to how uncertainty in astrometry and large distances are making the position of an object much more uncertain.

“The orbit is quite amazing,” Eggl said. “Today it is at a distance of about 47 astronomical units from the sun. Its semi-major axis is between 71 and 77 astronautical units – that’s way past Pluto which orbits at approximately 39.5 au.”

Because the newly discovered dwarf planet is so big, Eggl said he’s surprised it hadn’t been discovered yet. It’s bright enough, however, that it may have blended into the very crowded stellar field.

Eggl is particularly excited about the information this new discovery can add to our understanding of how the solar system formed.

“When an object is beyond the orbit of Pluto, then we think it was one of the early building blocks of the solar system that was likely thrown out of the inner solar system in some sort of violent event.”

He is looking forward to more discoveries when the Rubin Observatory is back to being fully online.

Read the full story written and posted today by the University of Washington, the Center for Astrophysics at Harvard and Smithsonian and the National Science Foundation’s NOIRLab.