The asteroid Apophis sits atop a shortlist of potentially dangerous objects that could one day hit Earth. And in March, the asteroid the size of an aircraft carrier will make its last short path to Earth before 2029, a year when astronomers wondered if it would hit our planet. We now know that Apophis will not hit Earth anytime soon, but the upcoming long-haul flight will still provide a relatively rare opportunity to study the space rock up close.
As the asteroid approaches, it will also make an accidental passage in front of a relatively bright star, allowing amateur astronomers to get in on the action. On Sunday 21 February at around 11:50 pm. Central Time, Apophis will move across the surface of a distant star, what astronomers call an occultation. It's like a miniature version of what happens when Earth's moon obscures the sun. Such occultations are a great opportunity to learn about the size, shape, and composition of planetary bodies.
Over the past century, occultations have provided a range of insights into distant objects that were otherwise difficult to discover from Earth. For example, the faint atmosphere of Pluto and the rings of Uranus were both discovered when those planets covered distant stars.
And that is why researchers are calling on amateur astronomers to bring out their telescopes on Feb. 21 to try to document the occultation of Apophis.
How to observe Apophis
The telescope company Unistellar has put together an article with detailed instructions about it how to observe the Apophis occultation. Due to the specifics of its alignment, it is visible only from a very thin, squiggly line that stretches across the Pacific Northwest's surface all the way to West Africa.
The lack of large observatories along that path means that professional telescopes are unlikely to get a good view. In the past, astronomers have recorded other close-flybys of Apophis using the Arecibo Observatory in Puerto Rico. But after that Arecibo & # 39; s collapseresearchers must find other ways to study the asteroid near Earth.
However, there are legions of amateur astronomers along the occult path, all with telescopes in the backyard. And the cameras used on modern telescopes are now so advanced that many should be able to detect the diminishing starlight even if the human eye cannot detect it through an eyepiece. Astronomers can combine data from citizen scientists around the world and try to gain insights into the asteroid.
Radar observations of the asteroid Apophis, including this one from 2012, have helped refine the space rock's orbit. (Credit: NASA / JPL-Caltech)
The asteroid Apophis
Apophis rose to disgrace in 2004 after observations suggested there was a nearly 3 percent chance it could collide with Earth in April 2029. large asteroids.
Astronomers also thought there was a slim chance that Apophis could pass through something called a gravity keyhole. This small area of space occupies only half a mile or so between the Earth and the Moon. But if Apophis passed through it, the asteroid's orbit could be altered enough to put it on a direct collision course with Earth.
However, in the years since, astronomers have shown that Apophis is extremely unlikely to hit Earth in the coming decades. In 2029, it will safely pass approximately 19,800 miles (31,900 kilometers) from Earth's surface, according to NASABut that's still close enough to get between us and a spacecraft in orbit.
Studying Near-Earth Asteroids
Small asteroids often pass close to Earth, but it's rare for such a large object to get so close.
Apophis will get close again in 2036, but observations by astronomers in 2012, including researchers at NASA's Near-Earth Object Program Office, helped rule out the possibility of a cosmic attack.
The next major chance of an Apophis hitting Earth isn't until April 2068, when the odds are still scarce at 1 in 150,000. Plus, results released this month may have lowered those odds even more.
So why are astronomers so eager to observe Apophis?
Even if the likelihood of a devastating impact is low, there are likely other asteroids like Apophis waiting to be discovered. This space rock is part of a larger group called the Atens asteroids, all of which traverse Earth's orbit. As a result, many are considered potentially dangerous.
And for all of the studies of Apophis over the years, there is still a lot to learn about it, including his exact job. There are many factors that could change the trajectory somewhat over the next half century. And while the asteroid is large enough to seriously damage our planet if it hits us, it is also small enough to be difficult to observe. So getting more precise measurements of where it is currently located can be very helpful in predicting whether it is a long-term threat.
"One of the main mysteries about Apophis is how its orbit changes when the asteroid is illuminated by the sun," Franck Marchis, senior astronomer at the SETI Institute and Chief Scientific Officer at Unistellar, said in a press release. "This effect, called" Yarkovsky ", is very difficult to simulate, so a direct observation of an occultation will give us an extremely accurate estimate of the asteroid's position."
If you are interested in participating in observing the occultation, Unistellar and its partner SETI have set up a page that will help you prepare.