Astronomers have made a surprising discovery about one of the brightest space rocks in the main asteroid belt.
With help from some of the astronomy world’s most powerful ground-based telescopes, astronomers now report new evidence that the asteroid (44) Nysa is vastly unlike most asteroids in appearance, possessing an unusual three-lobed structure.
However, that’s not all the team behind the new research says they have discovered: the object also appears to be accompanied by a previously unknown object.
A Three-Lobed Asteroid with a Mysterious Companion
According to the international team behind the discovery, the roughly 47-mile-wide asteroid Nysa is a rare variety of space object, whose uneven appearance could offer new insights into the violent collisions that played a significant role in shaping the early solar system. Belonging to a rare class of asteroids, the object may also help scientists better understand how such objects preserve material from early in the universe.
While the Nysa’s unusual shape and accompanying object, which astronomers have characterized as a small moon, are all newly-discovered features, knowledge of the asteroid’s existence goes back more than a century, and astronomers have long studied the object due to its unusually bright surface, which is believed to be rich in a translucent crystalline mineral called enstatite.
Based on past observations, astronomers suspected that the object might possess an elongated shape, composed of two connected lobes, although the object’s exact shape remained unknown.
That all changed after astronomers turned the SHARK-VIS instrument on the Large Binocular Telescope in Arizona, and the SPHERE/ZIMPOL instrument on the European Southern Observatory’s Very Large Telescope in Chile, toward the object. Doing so allowed researchers to capture the sharpest images of Nysa ever seen from Earth.
Based on those observations, astronomers have now revealed an asteroid unlike any previously seen.
“A Remarkably Unusual Object”
Kate Minker, a Lowell Observatory astronomer and the lead author of a new paper detailing the discoveries, says the new images reveal a truly unique asteroid, in addition to offering potential clues about its formation.
“The images reveal a remarkably unusual object,” Minker said in a statement. “The most likely explanation is that Nysa is either a contact trinary, consisting of three connected components, or an extremely irregular coherent body unlike anything we’ve previously observed.”
To determine the reasons for its odd shape, the team combined the new imagery made possible with the Large Binocular Telescope’s SHARK-VIS instrument and the SPHERE/ZIMPOL with existing photometric observations obtained by other observatories around the world. The resulting data set offered Minker and her team a detailed three-dimensional model of the asteroid.
Now, the team reports that their reconstruction of Nysa points to strong evidence that it consists of three distinctive lobes, each of which is connected by more narrow regions.
Nysa’s Not Alone
Another intriguing finding from the new data is the identification of the small satellite orbiting Nysa, which the researchers have given the temporary designation of S/2026 (44) 1.
Observed during two separate campaigns, this tiny moon is believed to be only a little more than a half mile across and orbiting at least 106 miles from its host asteroid.
“We borrowed a specialized technique from another field of astronomy, known as ‘high-contrast imaging,’ to detect the small moon whose faint light was overwhelmed by the intense brightness of the primary asteroid,” said Gianluca Li Causi of the Italian National Institute for Astrophysics in a statement.
Further Questions
Right now, scientists believe Nysa’s unusual shape was likely the result of an ancient collision, in which fragments expelled from larger bodies were gradually reassembled over time into a single body.
There are other possibilities, too. One theory holds that Nysa could be a victim of a cosmic hit-and-run incident, resulting from a collision with a much larger asteroid at some point in the very distant past—possibly billions of years ago.
Minker and her team hope that future observations of the asteroid and its newly discovered moon will provide further insights and eventually allow astronomers to calculate Nysa’s mass and density more accurately.
Doing so could ultimately bring to light which of the competing scenarios about its formation is most likely to be accurate, and ultimately, it could elevate Nysa to a small—but quickly growing—class of unusual asteroids that may preserve a record of the catastrophic conditions in our solar system, which helped shape it during its very earliest periods.
The team’s new paper, “Unmasking (44) Nysa: Evidence for a trilobate structure,” was recently uploaded to the arXiv.org preprint server.
Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. A longtime reporter on science, defense, and technology with a focus on space and astronomy, he can be reached at micah@thedebrief.org. Follow him on X @MicahHanks, and at micahhanks.com.