Strange asteroid near Earth is spinning faster every year – and scientists aren’t sure why
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A potentially dangerous near-Earth the asteroid Each year is spinning faster and faster, and researchers aren’t sure why.
The space rock, known as 3200 Phaethon, is about 3.4 miles (5.4 km) wide and its orbit solar system Takes it closer the sun More than any other named asteroid, the minimum distance from the Sun is about 13 million miles (20.9 million km)—less than half the distance from Wednesday During Phaethon’s orbit around the Sun, which lasts about 524 days, the space rock travels quite close to the Sun. the world be considered “potentially dangerous”. But the closest Phaethon came to our planet came in 2017 when it passed about 6.4 million miles (10.3 million km) from Earth, or about 27 times further away from Earth. the moon. The asteroid’s dusty path is responsible for the Geminids meteor shower, which peaks in early December each year and is visible around the world.
On October 7, a group of researchers is making this year’s presentation American Astronomical Society Division for Planetary Sciences Conference (opens in new tab) Reveal that Phaethon has an accelerated spin. The space rock takes about 3.6 hours for one complete rotation. But every year, that spin gets shorter by about 4 milliseconds, the researchers said. That may not sound like much, but the change over thousands or millions of years can change the asteroid’s orbit, the team added.
Related: Could an asteroid destroy the earth?
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Astronomers first detected Phaethon in 1983 and have been tracking its orbit ever since using light curves — observations of an object’s brightness over time that show how it rotates — and radio telescopes, as well as the occasional stellar phenomenon, when light from the asteroid is intercepted. a distant star. As a result, Phaethon has one of the most well-known orbital paths of any asteroid in the Solar System, The researchers said in a statement (opens in new tab).
Using decades-old datasets, the new team attempted to simulate Phaethon’s size, shape and rotational properties in greater detail than ever before.
The team discovered that the near-Earth asteroid is shaped like a spinning top, meaning it is somewhat spherical with a bulge around its equator. This size is common among large asteroids, such as 162173 Ryugu, which in 2018, became First asteroid landed by spacecraftWhen the Japanese Space Agency (JAXA) mounted the space rock with a probe and Successfully snatch the precious specimen from it.
However, when the researchers began analyzing Phaethon’s rotation, they found that nothing added up.
“The shape model predictions do not match the data,” lead researcher Sean Marshall (opens in new tab), an astronomer at the US National Science Foundation’s Arecibo Observatory in Puerto Rico, said in the statement. “The times when the model was brightest were clearly out of sync with the times when Phaethon was actually thought to be brightest.” After reanalyzing the data, the researchers concluded that the only explanation is that Phaethon’s spin has been increasing over the years, Marshall added.
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Asteroid rotation changes are very unusual. According to the statement, Phaethon is only the 11th asteroid observed with an accelerated rotation. For context, there are more than 1.1 million known asteroids, according to NASA (opens in new tab).
The Phaethon is unusual in other ways as well. First, it has a comet-like tail made up of pieces of debris that break off its rocky surface. These rocky bits make up the spectacular Geminids meteor shower, one of only two known meteor showers that are caused by asteroids and not comet. Second, sunlight reflected from Phaethon has a bluish tint, similar to most comets but almost unheard of in asteroids. As a result, Phaethon is often nicknamed the “rock comet” by astronomers, according to the statement.
Related: Why are the shapes of asteroids and comets strange?
Exactly why Phaethon’s spin is accelerating is not clear. An asteroid’s comet-like tail means its mass is slowly decreasing, but that doesn’t mean its spin will change. However, researchers think the asteroid’s unusual tail is the result of its surface superheating as it zooms closer to the Sun. Therefore, the most likely explanation is that the surface of the asteroid is being damaged by solar radiation, which is changing its spin – this is known as the Yarkowski-O’Keefe-Radziewski-Paddack effect. Science alert (opens in new tab) reports but that theory is difficult to prove with the available data.
Because of Phaethon’s unusual characteristics, JAXA chose the near-Earth space rock as a target for its next asteroid mission. In 2024, the DESTINY+ mission will launch a spacecraft that will eventually fly by Phaethon in 2028, according to the statement.
JAXA’s mission scientists will likely find the new discovery of Phaethon’s accelerated rotation very helpful, the researchers said.
“This is great news for the Destiny+ team,” said Marshall. “A steady shift means Phaethon’s orientation during spacecraft flybys can be accurately predicted.” For example, scientists will be able to determine which side of the asteroid will be illuminated by the sun when the spacecraft arrives, which will help them decide which areas to target for research, he added.
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