From NASA
March 11, 2021
This photo shows the view from the dome of NASA’s infrared telescope facility during a night of observation. The 3.2-meter telescope on Hawaii’s Mauna Kea is used to measure the infrared spectrum of the asteroid 2001 FO32. Credits: UH / IfA
The interplanetary invader will get no closer than 1.25 million miles to Earth, but it will represent a valuable scientific opportunity for astronomers.
The largest asteroid, expected to pass our planet in 2021, will be closest on March 21, providing astronomers with the rare opportunity to get a good look at a rocky relic that formed at the beginning of our solar system.
The near-Earth asteroid, named FO32 in 2001, comes closest at a distance of about 2 million kilometers – or 5 1/4 times the distance from Earth to the Moon. There is no danger of a collision with our planet now or for centuries to come.
“We are very familiar with the 2001 FO32 orbital path around the Sun as it was discovered 20 years ago and has been tracked ever since,” said Paul Chodas, director of the Center for Near-Earth Object Studies (CNEOS), which is administered by Jet Propulsion NASA Laboratory in Southern California. “There’s no chance the asteroid will get closer to Earth than 1.25 million miles.”
However, this distance is astronomically narrow, which is why in 2001 FO32 was designated as a “potentially dangerous asteroid”. CNEOS calculates high-precision orbits for near-earth objects (NEOs) in support of NASA’s Planetary Defense Coordination Office, using telescopes and ground-based radar to precisely characterize the orbit of each NEO and improve long-term hazard assessments.
During this approach, the 2001 FO32 will pass at a speed of 124,000 km / h – faster than the speed at which most asteroids hit Earth. The reason the asteroid’s unusually fast approach is due to its highly inclined and elongated (or eccentric) orbit around the sun, an orbit that is 39 degrees inclined to the Earth’s orbit. This orbit brings the asteroid closer to the Sun than Mercury and twice as far from the Sun as Mars.
As FO32 begins its journey through the inner solar system in 2001, the asteroid picks up speed like a skateboarder rolling down a half pipe and then slows down after being thrown back into space and swung back towards the sun. It completes an orbit every 810 days (approx. 2 1/4 years).
This diagram shows the oblong and inclined orbit of the FO32 from 2001 on its way around the sun (white ellipse). Because of this orbit, as the asteroid approaches Earth, it moves at an unusually high speed of 124,000 km / h. Credits: NASA / JPL-Caltech
After its brief visit, the FO32 will continue its lonely journey in 2001 and will not come so close to earth again until 2052, when it will pass by at about seven lunar distances or 2.8 million kilometers.
Astronomical geology
> Asteroid 2001 FO32 was discovered in March 2001 by the Lincoln Near-Earth Asteroid Research (LINEAR) program in Socorro, New Mexico, and was estimated to be approximately 1 km wide based on optical measurements. In recent NEOWISE follow-up observations in 2001, FO32 appears to be weak at infrared wavelengths, suggesting that the object is likely less than 1 kilometer in diameter. The NEOWISE team’s analysis shows that it is between 440 and 680 meters wide.
Even if it’s on the smaller end of the scale, 2001 FO32 will still be the largest asteroid to pass this close to our planet in 2021. The last particularly large asteroid approach was that of 1998 OR2 on April 29, 2020. While 2001 FO32 is slightly smaller than 1998 OR2, it will be three times closer to Earth.
The March 21 encounter will provide astronomers with a better understanding of the asteroid’s size and albedo (i.e., how bright or reflective its surface is), and to get a rough idea of its composition.
This is accomplished in part through the use of NASA’s Infrared Telescope Facility (IRTF), a 3.2-meter telescope on Hawaii’s Mauna Kea that will observe the asteroid in the days leading up to the approach with its workhorse infrared spectrograph, SpeX . “We’re trying to do geology with a telescope,” said Vishnu Reddy, associate professor at the University of Arizona Lunar and Planetary Laboratory in Tucson.
When sunlight hits the surface of an asteroid, minerals in the rock absorb some wavelengths and reflect others. By examining the spectrum of light reflected from the surface, astronomers can measure the chemical “fingerprints” of the minerals on the surface of the asteroid. “We’re going to use the IRTF to get the infrared spectrum to see its chemical composition,” explained Reddy. “Once we know that, we can make comparisons with meteorites on Earth to see which minerals in 2001 contain FO32.”
For example, should 2001 FO32 be identified as iron-rich, it would mean that it is denser and therefore more massive than a stony asteroid of similar size. Observations that show a low albedo surface (meaning it’s dark) may suggest that the asteroid is high in carbon, suggesting that it could be the core of a long-dead comet.
A closer look
In addition, radar observations can be made through the Deep Space Network (DSN) for a detailed view of the asteroid. The DSN is an operation of NASA’s Space Communication and Navigation (SCaN) program and includes three ground stations – one in California (Goldstone), one in Spain (Madrid), and one in Australia (Canberra). Their antennas can be used to bounce radio signals from the 2001 FO32 so that other radio antennas can receive them. Such radar observations can provide additional insight into the asteroid’s orbit, provide a better estimate of its dimensions and rate of rotation, and help identify surface features (such as large boulders or craters). They might even reveal small satellites that may be in tow.
“Twenty years of observations showed that about 15% of near-Earth asteroids, comparable in size to 2001 FO32, have a small moon,” said Lance Benner, chief scientist at JPL. “Little is known about this object at this time, so the very close encounter provides an excellent opportunity to learn a lot about this asteroid.”
Over 95% of near-Earth asteroids the size of FO32 2001 or larger have been discovered, tracked, and cataloged. None of the large asteroids in the catalog stand a chance of affecting Earth over the next century, and it is extremely unlikely that any of the remaining undiscovered asteroids of this size will affect Earth as well. Nonetheless, all asteroids that could pose a risk of impact are still being discovered. The more information that can be gathered about these objects, the better mission designers can prepare to distract them in case they threaten Earth in the future.
In the meantime, amateur astronomers can gather their own information about the FO32 2001. “The asteroid will be brightest as it moves through the southern sky,” said JPL’s Chodas. “Amateur astronomers in the southern hemisphere and low northern latitudes should be able to see this asteroid with medium-sized telescopes with openings of at least 8 inches on the nights leading to the closest approach, but they will likely need star maps to get to it Find. ”
JPL hosts CNEOS for NASA’s near-earth object observation program in NASA’s Planetary Defense Coordination Office. The University of Hawaii manages the IRTF on behalf of NASA. The SpeX instrument was built at the University of Hawaii.
For more information on CNEOS, asteroids, and near-earth objects, visit:
https://cneos.jpl.nasa.gov
For more information on NASA’s Planetary Defense Coordination Office, visit:
https://www.nasa.gov/planetarydefense
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