Solar System’s fastest orbiting asteroid discovered – Orbiting the Sun in just 113 days

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An artist’s design of the recently discovered asteroid 2021 PH27, which has the shortest known orbital period for an asteroid and the second shortest for any object in our solar system after Mercury. Illustration by Katherine Cain courtesy of the Carnegie Institution for Science. Credit: Illustration by Katherine Cain courtesy of the Carnegie Institution for Science

The Sun has a new neighbor who was hiding in the twilight. An asteroid that orbits the Sun in just 113 days – the shortest known orbital period for an asteroid and the second shortest for any object in our solar system after Mercury – was discovered by Scott S. Sheppard of Carnegie in footage of Twilight taken by Ian Dell of Brown University. ‘Antonio and Shenming Fu.

The new asteroid, called 2021 PH27, measures about 1 kilometer and is in an unstable orbit that intersects that of Mercury and ">Venus. This means that in a few million years, it will likely be destroyed in a collision with one of these planets or the Sun, or it will be thrown from its current position.

Studying objects like this can help scientists understand where asteroids came from and the forces that shaped the architecture of our solar system. “Most likely 2021 PH27 has been dislodged from the main asteroid belt between Jupiter and ">March and the gravity of the inner planets shaped its orbit in its current configuration, ”said Sheppard. “Although, based on its large tilt angle of 32 degrees, it is possible that 2021 PH27 was an extinct comet from the Outer Solar System that ventured too close to one of the planets as the trajectory of her journey brought her closer to the inner solar system.

Orbit of the asteroid 2021 PH27

An illustration of the 2021 PH27 Orbit, by Katherine Cain and Scott Sheppard, courtesy of the Carnegie Institution for Science. It is the fastest known asteroid in orbit. Credit: Katherine Cain and Scott Sheppard, courtesy of the Carnegie Institution for Science

Because 2021 PH27 is so close to the Sun’s massive gravitational field, it experiences the most significant general relativistic effects of any known object in the solar system. This results in a slight angular deviation of its elliptical orbit over time, a movement called precession, which occurs at about one minute of arc per century. Observing Mercury’s precession puzzled scientists until Einstein’s general theory of relativity explained its orbital adjustments over time. The precession of 2021 PH27 is even faster than that of Mercury. “2021 PH27 gets so close to the Sun that its surface temperature reaches around 900 degrees Fahrenheit on the closest approach, hot enough to melt the lead, ”Sheppard said.

Future observations of this object will shed more light on its origins. Comparing 2021 PH27 to objects orbiting beyond Earth will improve researchers’ knowledge of its composition and the materials that allow it to survive in these extreme conditions. An object like 2021 PH27 experiences enormous thermal and internal stresses due to its proximity to the Sun.

A census of asteroids near and within Earth’s orbit is crucial in identifying those that could potentially impact our planet, but are difficult to spot as they approach Earth during the day. These types of asteroids are not easily detected by most surveys, which usually observe at night. The asteroid will soon pass behind the Sun and will be unobservable from Earth until early next year, when observers can refine its orbit with the precision needed to give it an official name.

Asteroid 2021 PH27

A gif showing the discovery of asteroid 2021 PH27, which Scott S. Sheppard of Carnegie found in evening twilight footage taken by Ian Dell’Antonio and Shenming Fu of Brown University. Credit: Discovered by Scott S. Sheppard. Images taken by Ian Dell’Antonio and Shenming Fu

The only effective method of spotting asteroids moving around the Sun in orbits closer to Earth’s is by taking images at sunset or sunrise, which Dell’Antonio and Fu did with the camera at dark energy on the Blanco 4 meters from the National Science Foundation. telescope in Chile. Their main research is part of the Local Volume Complete Cluster Survey, which observes most massive galaxy clusters in the nearby universe in increased detail. Working with Sheppard, Dell’Antonio and Fu moved from focusing on some of the universe’s most distant objects to some of the closest objects, using the first minutes of twilight on August 13 to take images in which Sheppard was able to find 2021 PH27 a few hours later.

“Because the object was already in the Sun’s glare and was heading more towards it, it was imperative that we determine the object’s orbit before it was lost behind our central star,” Dave explained. Tholen of the University of Hawaii, who measured the asteroid’s fast moving position in the sky and predicted where it would be the night after the initial discovery. “I assumed that in order for an asteroid of this size to stay hidden for so long, it must have an orbit that keeps it so close to the Sun that it is difficult to detect from Earth’s position.”

Additional images were obtained the following night using Magellan telescopes at the Carnegie Observatory in Las Campanas in Chile, as well as again with the NSF’s 4-meter Blanco telescope. A third night of follow-up observations was needed to determine the orbit of the new asteroid before it was lost, but cloudy weather in Chile caused a trip around the world to South Africa thanks to the activation of the vast network of the Observatory of Las Cumbres. meter telescopes.

“Although telescope time is very precious, the international nature and love of the unknown make astronomers very willing to bypass their own science and observations to follow exciting new discoveries like this,” Sheppard said. . “We are very grateful to all of our collaborators who allowed us to act quickly on this discovery.”

University of ChicagoAlex Drlica-Wagner, Clara Martinez-Vazquez from NOIRLab, Sidney Mau from Stanford University and Luidhy Santana-Silva from Universidade Cruzeiro do Sul interrupted their first and second nights by using the dark energy camera to observe the asteroid. Princeton UniversityScott Carlsten, Rachael Beaton (Carnegie-Princeton Postdoctoral Fellow) and Jenny Greene were instrumental in the follow-up footage of the second night of Las Campanas and on the third night Cristobal Sifon and Camila Aro-Bunster of the Pontificia Universidad Catolica de Valparaiso have been delayed the start of their Magellan observation program to image the object through some passing clouds. Marco Micheli from the Earth Observation Center of the European Space Agency coordinated the use of the Las Cumbres Observatory network.


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