Astronomers clock rock that hit the moon during total lunar eclipse at 61,000 km/h
Researchers estimate the resulting crater could be up to 15 metres across
On the night of January 20–21, the moon slowly glided through Earth's shadow, treating people across North America to a total lunar eclipse. For the lucky few who happened to be looking at the right time with keen eyes, another rarely seen event occurred: a bright meteorite slammed into the moon.
Now, a team of scientists from Spain have gleaned a lot of information from that impact, including the size of the rock, the speed at which it hit and the size of the crater it left. (A small part of Spain experienced the total lunar eclipse. However, the rest of the country saw a partial lunar eclipse.)
The impact was captured by the Moon Impacts Detection and Analysis System (MIDAS), a group of telescopes in Seville, Spain, which was able to catch the flash of impact at different wavelengths.
In the study, published in the Monthly Notices of the Royal Astronomical Society, scientists estimate that the impacting object weighed roughly 45 kilograms and measured 30 to 60 centimetres across.
"An object of this size, if it came into Earth's atmosphere, would be completely destroyed," said Robert Massey, deputy executive director at the Royal Astronomical Society in London. "It would be a bright meteor, probably one we call a fireball, but it certainly wouldn't make it to the ground intact. But on the moon, it stays in one piece."
That's because, unlike Earth, the moon has virtually no atmosphere, which would cause incoming rocky debris to burn up and slow down.
Watch as the moon is hit by a meteorite:
While catching a lunar impact is somewhat fortuitous, lead researcher Jose Madiedo said he had a good feeling about his chances that night.
"I don't know why, but ... I thought this time, maybe I will be lucky," he said. So, instead of his usual four-telescope set-up, he decided to use eight. One failed, leaving him with seven.
And then he saw it: An extremely bright flash on the moon's outer edge.
Unsure if he had actually witnessed an event or not, he went and checked his software, which confirmed it.
Madiedo took to Twitter to share the news. But he wasn't the only one who'd seen it.
"I saw other people who were asking: 'What happened on the moon? I saw something strange, … I saw a light. What was this?'" he said.
The flash happened on Jan. 20 at 11:41 p.m. E.T. (it was Jan. 21 in Spain) and lasted just 0.28 seconds. It released the equivalent of 1.5 tonnes of TNT, creating a crater that researchers estimate could be up to 15 metres across. And the debris that was ejected is believed to have reached a peak temperature of 5,400 C, which is about the same as the surface of the sun.
Though it had been attempted before, this was the first time an impact was filmed during a lunar eclipse.
'It was worth it'
The eclipse lasted roughly until sunrise in Spain, but Madiedo was so excited, he wasn't about to head to bed.
"When I was in the middle of the night, with the seven telescopes working, I told myself, 'What are you doing? Tomorrow you have to go to work. You can't sleep. Is this really worth it?' Yes. It was worth it."
Here on Earth, we see debris entering our atmosphere as meteors, bright lights streaking against the black backdrop of our night sky. (Once it reaches the ground, it is then called a meteorite.)
It's estimated that the particles falling on Earth each year — large pieces to dust-sized ones — amount to 33,000 to 71,000 tonnes.
The new findings are a reminder that things are constantly colliding in our solar system.
"It tells us a lot about the frequency of impacts in the solar system," Massey said. "And it reminds us that the solar system is quite dynamic. You haven't just got the planets and the sun, but also lots of smaller bodies, as well."
Those are important facts as explorers plan to return to the moon.
"[The findings] demonstrate that, actually, if you want to go back there — and certainly if you want to build a base, and so on — you have to be aware of this risk and mitigate it," Massey said.
- An earlier version of the story said the meteorite was 30 to 60 metres across. In fact, it was 30 to 60 centimetres.May 02, 2019 9:21 AM ET