© NOIRLab/NSF/AURA/J. da Silva/Spaceengine Acknowledgment: M. Zamani (NSF’s NOIRLab))
The second Earth Trojan asteroid known to date will remain Trojan — that is, it will be located at the Lagrangian point — for 4,000 years.
The second Earth Trojan asteroid known to date will remain Trojan — that is, it will be located at the Lagrangian point — for 4,000 years.
A rocky body spotted orbiting in Earth's path is a "Trojan asteroid" that escorts our planet around the sun, astronomers have confirmed.
Asteroid 2020 XL5 is the second Trojan asteroid ever discovered. It's three times larger than the only other known Earth Trojan, called Asteroid 2010 TK7, which was confirmed in 2011. These small space rocks orbit along with Earth, but they are hard to spot from our planet — Asteroid 2010 TK7 is sometimes on the other side of the sun from us. They sit in gravitational sweet spots known as Lagrangian points. If Earth and the sun make up two points of an equilateral triangle, the Lagrangian point would be that triangle's third point. Earth and the sun have five of these points.
The newfound Trojan is at a Lagrangian point that has it orbiting ahead of Earth in the two bodies' shared path and the asteroid will stay there for 4,000 more years, researchers reported Tuesday (Feb. 1) in the journal Nature Communications. The asteroid is probably about 0.7 miles (1.18 kilometers) in diameter, though that estimate may be off if the surface of the asteroid is more or less reflective than astronomers assume.
© NOIRLab/NSF/AURA/J. da Silva Acknowledgment: M. Zamani (NSF’s NOIRLab)
There are five Lagrangian points for the Earth-sun system.
There are five Lagrangian points for the Earth-sun system.
The astronomers found that more than 500 years ago, 2020 XL5 was not a Trojan, but that its orbit stabilized in the Lagrangian point around then.
The angles of the orbits of both Asteroid 2010 TK7 and Asteroid 2020 XL5 compared with that of Earth mean it would be infeasible to do a rendezvous mission with either Trojan, the researchers calculated. A flyby — which wouldn't require syncing up a spacecraft with the asteroids' orbits — might be possible, the study found. Of the two, the researchers wrote, the newly discovered Trojan is likely easier to fly by, as its position offers more flexibility for the launch date of a theoretical space probe.
Even if it's not possible to visit either of Earth's orbital buddies, having two orbits to compare will help astronomers understand the orbital math that makes Trojans possible, the researchers wrote.
"The discovery of a second ET [Earth Trojan] asteroid may enhance our knowledge of the dynamics of this elusive population," they wrote.
Stephanie Pappas is a contributing writer for Live Science, covering topics ranging from geoscience to archaeology to the human brain and behavior. She was previously a senior writer for Live Science but is now a freelancer based in Denver, Colorado, and regularly contributes to Scientific American and The Monitor, the monthly magazine of the American Psychological Association. Stephanie received a bachelor's degree in psychology from the University of South Carolina and a graduate certificate in science communication from the University of California, Santa Cruz.
We have seen it up close, 80 km away, the asteroid that could impact the Earth, supposedly in 2182. The date was calculated with mathematical models reported in the study just disclosed by NASA in the journal Icarus.
Of all the hypotheses, the collision scheduled for September 24, 2182 is the most likely: there will be one in 2,700 (or 0.037 percent) that a collision could occur. The risk is remote and none of us will witness it. However, what is striking is the precision with which today's studies are able to predict the threats of the future and perhaps, with the work of the next few decades, even to avoid them.
The asteroid is called " 101955 Bennu" and is part of the Apollo group, the set of bodies that revolve around the sun in an orbit close to that of the Earth. It was discovered in 1999, has a diameter of about 500 meters and is considered one of the most dangerous in the solar system. For this it is continuously monitored.
For the study, entitled "Ephemeris and risk assessment for the near-Earth asteroid (101955) Bennu based on OSIRIS-REx data", NASA researchers, led by Italian Davide Farnocchia, used information from the Osiris spacecraft -Rex who has observed it closely for more than two years, collecting samples and details on size, shape, mass and composition, also monitoring its direction and trajectory. The collected samples, about 60 grams, were safely placed in a capsule that will release from the probe once it reaches Earth, where it is scheduled to land on September 24, 2023.
The name is suggestive, Bennu derives from Benu, a mythological bird consecrated to the Egyptian divinity Ra, which is a symbol of life and rebirth after death, just like the divinity Osiris who inspired the spacecraft.
"NASA's planetary defense mission is to find and monitor asteroids and comets that can approach and pose a danger to our planet," said Kelly Fast, program manager for the Near-Earth Object Observations Program from NASA headquarters in Washington. 'Our work is based on continuous astronomical surveys that collect data to discover previously unknown objects and refine our orbital models. The OSIRIS-REx mission has provided an extraordinary opportunity to refine and test these models, helping us better predict where Bennu will be when he approaches Earth in more than a century. "
In 2135 Bennu will approach Earth. However close, the asteroid will not pose a danger to our planet at that moment: scientists will have to understand the exact trajectory in order to establish how the Earth's gravity can alter its path.
Using NASA's 'Deep Space Network' and state-of-the-art computer models, the scientists were able to significantly reduce the uncertainties in Bennu's orbit, determining that his total probability of impact during the year 2300 is about 1 out of 1,750 (or 0.057%). The researchers were also able to identify September 24, 2182, as the single most significant date in terms of potential impact. In the orbital dynamics study conducted by the mathematics faculty of the University of Pisa, in 2009, however, eight potential impacts with the Earth between 2169 and 2199 were identified.