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Image of Richard Kowalski

A meteor has been spotted by a human eye, and then predicted to impact Earth, just three times in history.

All three times have occurred in the last decade, and the three observations have been made by the same set of eyes, at the same telescope: those of Richard Kowalski, using a 60-inch reflecting telescope atop Mount Lemmon in the Santa Catalina Mountains outside Tucson.

Kowalski, a senior research specialist at the Lunar and Planetary Laboratory at the University of Arizona, works as an observer for NASA’s Catalina Sky Survey. His latest catch was on Saturday, a 6-foot space rock that was potted at about the distance of the moon, and burned up in the atmosphere over Botswana about eight hours later while traveling approximately 10 miles per second.

Kowalski corresponded with Laboratory Equipment briefly in wake of his latest success.

The asteroid, dubbed 2018 LA, was about as small as detectable rocks come, Kowalski said.

Most asteroids are dark gray, and the smaller they are, the harder it is to see reflected sunlight, Kowalski said. Ones that are similar to the asteroid that created a fireball over the Detroit metro area in January, and 2018 LA, which were each estimated to be 2 meters in diameter, are very faint in the sky, he said.

“They are only detectable for a very short period of time before they enter the Earth’s atmosphere, so if our survey pattern covers the part of the sky even one night earlier, they may be too faint for us to reliably detect,” Kowalski explained.

The restrictions include: what part of the sky is being surveyed on a given night, the sun and the Earth itself that blocks the view of the night sky to the far south of the telescopes in Arizona.

Kowalski previously spotted, and set in motion the warning system, to predict the arrival of asteroids over the Sudan on Oct. 7, 2008, and over the Atlantic Ocean on Jan. 1, 2014.

Some are not predictable, however, despite the best attempts of scientists.

The Chelyabinsk event of 2013, which was a 20-meter hunk of rock which created a major blast over the Siberian city in 2013, was not seen earlier because the timing wasn’t right to see it coming, Kowalski said.

“We can’t see asteroids during the daytime, only at night when the sky is dark,” he said. “This is the issue of why the Chelyabinsk object was not detected ahead of time. That asteroid’s orbit kept it closer to the sun than the Earth most of the time. It approached and hit us from the daylight side, where we can’t observe, because of the bright sky.”

The flip side about not seeing some of the coming threats like 2018 LA is that the smaller they are, like 2018 LA, the less likely they are to pose a threat to humans with the protective atmosphere of our planet, he said.

“On the positive side of this, rocks this small pose no threat to people on the surface,” Kowalski wrote. “But they do make for spectacular light shows.” 

Photo: The University of Arizona
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