The boom-causing meteor that shot over Salt Lake City early Saturday left onlookers with more questions than answers. But local experts have shed some light on the event.
Those who were lucky enough to see the meteor would have noticed its sound only after it briefly streaked across the sky. That’s because Saturday’s meteor broke the sound barrier due to its speed and size, resulting in the sonic boom heard across the region, Paul Ricketts, the director for the South Physics Observatory at the University of Utah, said.
Usually, sonic booms consist of a single boom, he added. But the sound heard as far north as southern Idaho on Saturday more closely resembled thunder, with a bit of rumbling after the initial blast.
“For me, that sounds like we were maybe hearing other pieces being broken off, also causing smaller sonic booms,” Ricketts said.
It also is possible that the meteor broke off of Comet 109P/Swift-Tuttle, more commonly known as Comet Swift-Tuttle. That comet is responsible for the Perseids meteor shower, which descends on Earth’s atmosphere sometime between mid-July and late August each year.
This year, the Perseids peaked on Aug. 11 and Aug. 12. Saturday morning’s date was Aug. 13.
‘The size of a basketball to the size of a smaller car’
Ricketts thought the loud “boom” outside his window was thunder when it startled him awake early Saturday.
Emily Lehnardt, a NASA solar system ambassador based in Holladay, was getting ready for the day when she heard it.
“It literally shook and rattled the house a little bit,” Lehnardt, who is also the founder of the Utah Women Astronomical Society, said. “My dog started barking and I thought it was an earthquake.”
The National Weather Service office in Salt Lake City and Gov. Spencer Cox soon confirmed that it was neither: The noise heard as far south as Orem around 8:30 a.m. on Saturday was a meteor hurtling through Earth’s atmosphere.
It’s not rare for objects 1 meter in diameter or larger to strike the Earth’s atmosphere, Lehnardt said. But most of those instances occur over less-populated areas, like the ocean or the desert, and are not reported.
“It was probably fairly large,” Ricketts said. “It could be anywhere between about the size of a basketball to the size of a smaller car.”
Ricketts said that it has been difficult to discern the height of the meteor above the earth. It could have been traveling at few thousand miles per hour or up to tens of thousands of miles per hour, he noted.
Part of the Perseids?
Comets are icy bodies — Lehnardt likened them to “dirty space snow balls” — that leave debris as they orbit the sun. Asteroids are more metallic bodies.
When chunks break off of comets or asteroids and enter the Earth’s atmosphere, they are called meteors. The pieces of meteors that do not burn up in the atmosphere and reach the Earth are called meteorites.
Most debris from Comet Swift-Tuttle are the size of grains of sand that fall through earth’s atmosphere in a stunning display of shooting stars in the evening sky, Lehnardt said.
The timing of the meteor early Saturday makes it more likely that it may have been a larger piece of debris that broke off of Comet Swift-Tuttle, though the meteor could have also broken off of an asteroid, making the timing purely coincidental. There is no way to confirm either way until astronomers can examine the composition of a meteorite from this event.
“It’s likely, just because of the timing, but there’s no way to definitively say,” said Ricketts.
In order to confirm that the boom-causing meteor was a part of Comet Swift-Tuttle, astronomers would have to test a meteorite from the event. But it has been difficult to tell in what direction the meteor traveled; when meteors break up in the Earth’s atmosphere, meteorites can be scattered over hundreds of miles, Ricketts said.
Astronomers also are unsure about the meteor’s composition. Meteors that shoot through the sky for a longer period of time usually have a higher composition of metals and are more compact. Meteors with a shorter flight are often composed of loose, rocky stuff from when the solar system first formed.
“Meteorites don’t look a lot like Earth rocks, because Earth’s weather patterns and erosion smooth out a lot of its rocks,” she said. “When you find a meteorite, most of them have burned parts to it and sharp components.”
Unless scientists are able to locate and study meteorites from the latest event, more information about Saturday’s spectacle will remain out of reach.
“When it comes to these kinds of things, they can remain mysterious,” Ricketts said, “and not really have any definite answers.”
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