Lunar Eclipse Helps Locate 3 Near-Earth Asteroids

Astronomers on Haleakalā raced against a brief 60-minute window during the May 26, 2021 total lunar eclipse — when the sky was darkened during a full moon — to search for faint Near-Earth Objects. And, using the University of Hawaiʻi Pan-STARRS telescopes, they pinpointed three to the northwest of the eclipsed moon.

One of them, an asteroid about the size of 1½ football fields, hadn’t been seen since 2001. The Near-Earth asteroid, 2001 MY7, does not pose a threat to Earth, according to UH astronomers.

During the 60-minute window, when the Earth came between the Sun and the full moon to create the rare blood moon, Pan-STARRS astronomers also saw two new Near-Earth Objects.

The larger object, 2021 KM2, now with additional observations, has a well established orbit, and is approximately 450 feet in diameter. It poses no threat to Earth. The other object is smaller and has proven to be more elusive. Astronomers hope that it will be seen again in the next few weeks when the waning moon lets the sky become darker, so that an accurate orbit can be determined.

UH Institute for Astronomy Astronomer Richard Wainscoat said asteroid 2001 MY7 only comes close to the sun once every 5 years, when it becomes bright enough to see, making this kind of asteroid very difficult to discover,.

“This object reminds us that some near-Earth objects can be very difficult to find,” he said. “For example, objects that come close to Earth in the daytime sky, and objects with long periods.”

Every night, the University of Hawaiʻi Pan-STARRS telescopes on Haleakalā scan the sky for Near-Earth Objects, asteroids or comets that may come close to or even hit Earth in the future.

For a few days each month, the bright full moon hinders the search by making the sky brighter, which makes it more difficult to see these faint objects. That’s why May 26, when Hawaiʻi was in line for prime viewing of the total lunar eclipse – when the full moon enters Earth’s shadow – observers at Pan-STARRS were excited about the opportunity to observe with the sky darkened.  

The next lunar eclipse visible from Hawaiʻi is a partial eclipse on the night of Nov. 18. Pan-STARRS astronomers are planning a similar deep search for Near-Earth Objects on that night when the full moon enters Earth’s shadow.

The search is funded by NASA’s Near-Earth Object Observations Program.