Astronomers have captured the best images of Kleopatra, a 168-kilometer-long asteroid nicknamed “dog bone” for its unusual shape. The latest observations offer new insights into the shape and purpose of the object precarious turn and how their moons probably appeared.
We can now comfortably add the asteroid Kleopatra among the strangest objects in the solar system. In addition to its unusual bone shape, it hosts two small moons i has a remarkably low density for a metal object. In addition, Kleopatra rotates so fast along its axis that it is in danger of falling completely. In fact, this rapid spin rate may explain the presence of its two moons, named AlexHelios and CleoSelene.
These are the findings of two new articles published today in Astronomy & Astrophysics. He first role is an investigation of the physical properties of the asteroid, such as its shape and chemical composition, and was led by Franck Marchis, planetary astronomer at the SETI Institute and chief scientific officer at Unistellar. He second role analyzed the orbital characteristics of the object and its two moons and was directed by Miroslav Brož, an astronomer at Charles University in the Czech Republic.
Marchis credited the Very Large Telescope of the Southern European Observatory to make these discoveries possible. In fact, Kleopatra may be relatively large (270 km) along its axis, but it is very far away, in the main asteroid belt between Mars and Jupiter, which makes it very weak. The asteroid never comes close to Earth about 200 million kilometers away.
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To see details of Kleopatra’s shape and detect its moons, “we have to overcome the blurring effect of the Earth’s atmosphere,” Marchis explained in an email. “This is feasible thanks to the adaptive optics of a large telescope like the VLT.” TTo achieve the desired quality level, the team used the Spectro-Polarimetric High Contrast (SPHERE) exoplanet search instrument connected to the VLT.
“The SPHERE instrument is one of themgeneration adaptive optical systems that are now able to work with visible light, “Marchis said.” Consequently, it provides images in optical light —in this case in red— with the maximum resolution of the 8 m telescope, as if the VLT were in space ”. To this he added: “Thanks to this incredible image quality, we can now see details about the shape of the asteroid, see the two lobes and the bridge that connects them.”
Astronomers have known about this object for a long time. The Czech astronomer Johann Palisa discovered Kleopatra in 1880 and discovered it it seems to be stranger with each subsequent observation. Astronomers discovered the first of its two moons in 1980, the result of a fortuitous eclipse. Radar observations made in 2000 suggested a very unusual shape, which gave it the nickname “dog bone asteroid”, as the object appears to have two lobes connected by a relatively narrow “neck”. . In 2011, a team led by Marchis announced the discovery of the second moon, which they found with the Keck II optical telescope. The moons were formally recognized and named after Cleopatra’s children.
Despite this observations, many questions remained. The orbits of AlexHelios and CleoSelene were to be “approximate, since we had a few data points,“And the shape of Kleopatra also had to be approximated,” so we couldn’t say for sure the density of the asteroid or the origin of the moons, “Marchis explained.. “We already knew that this triple asteroid system was unique in the form of [Kleopatra]“Other outstanding questions had to do with the size, orbit, and rotation of the object. Consequently, new studies broaden our understanding of this unique triple system.
The team observed Kleopatra and her moons in 2017 and 2019 from different angles, resulting in a three-dimensional view of the asteroid. The team understood better size and I learned that one of its lobes is larger than the other.
Plus, them finally determined the exact orbits of the moons. It turns out that the previous estimates were quite wrong, leading to erroneous inferences. Miroslav Brož, an astronomer at Charles University in the Czech Republic and first author of the second article, said the updated orbital calculations are important because this allowed them to calculate the actual mass and radius of the asteroid (or at least an estimate). improved of these parameters).
Another key finding suggests that the asteroid rotates close to its critical speed; faster and you run the risk of breaking. The object rotates once every five hours.
“We actually know that more accurately, at 5,385,287 hours,” Brož said in an email. “This may seem normal to an asteroid, but Kleopatra is so long that, at its extremes, the rotational speed is very close to the escape velocity.” Brož refers to the speed required for an object to escape its gravitational limits. He suspects that if Kleopatra were hit by another asteroid, an even faster spin could occur, causing it to break on its own.
With the correct orbits determined, the team found a figure for Kthe leopard mass that is 35% lower than previous estimates. Kleopatra is a metal object, but appears to have less than half the density of iron. This suggests that the asteroid is a porous “pile of debris” that formed from a large impact. Kleopatra is a relatively loose conglomerate of small objects, but given its high rotational speed, it may be throwing debris into space. And, in fact, this could explain how AlexHelios and CleoSelene came about.
“Due to the shape and rotation of the main asteroid, we have calculated that there are some areas of Kleopatra … unstable, that is to say, that a rock located there would be expelled ”, explained Marchis. “We can’t prove it yet, but it is possible that the moons are children of the main asteroid, ejected after an oblique impact. and formed by the accretion of pebbles and expelled pebbles “.
Astronomers know of other extremely elongated asteroids, such as the Trojan asteroid 624 Hektor and the main asteroid in the belt 121 Hermione. Marchis said it’s probably not a currencytheredathat so much of thoasteroids have their own moons.
The team also learned new things about the two moons. AlexHelios is the faThe other of the two, 405 miles (655 km) away from Kleopatra, while CleoSelene is 310 miles (499 km) away (measured from the center of Kleopatra). The moons are slightly less than 10 km in size and possibly spherical, but scientists don’t really know it.
“Hopefully, they will be observed in the future, during a concealment event, when Kleopatra and the moons pass in front of a star, so that Earth observers can measure their shadows,” Brož said.
Looking to the future, the team would like to re-measure the orbits of the moons, which they plan to do next year. They to wait to find some anomalies in his movement, due to tidal effects and unexpected disturbances due to Kleopatra’s unusual shape. Finding a third moon is not out of the realm of possibility, Marchis said.
In fact, astronomers have been observing this those of dogs asteroid for over 140 years and there is no reason to believe it will not continue to be stranger.
Month: This is one of the strangest objects ever discovered in the solar system.