An asteroid 1.3 kilometers in size, or the size of the Golden Gate Bridge, will pass close to Earth on Friday.
Thomas Madura, San Jose State associate professor of physics and astronomy who’s also worked at NASA’s Goddard Space Flight Center, said the asteroid is bigger than about 97% of other asteroids.
However, the asteroid, formally known as 2001 CB21, is just 0.02 Astronomical Units or more than 1.8 million miles from Earth’s orbit at its closest point, according to the Space Reference webpage.
This distance is 10 times as far as the moon is from Earth.
Gianluca Masi, an astronomer at the Virtual Telescope Project in Italy, captured an image of the asteroid on Jan. 30, when CB21 was more than 21.5 million miles away, according to a Feb. 2 Newsweek article.
Madura said most asteroids, including CB21, are leftover materials from the original formation of the solar system.
CB21 is predicted to pass by Earth at 3:00 a.m. EST on Friday, traveling at 26,800 miles per hour, according to a Feb. 2 Newsweek article.
Curtis Asplund, SJSU assistant physics professor with a specialization in high-energy theoretical physics, said the speed of the asteroid is not concerning.
“It's not unusual for things in space, including planets like the Earth, to move at thousands and thousands of miles per hour,” he said in a Zoom call. “So the asteroid is not unusual in that sense, things in the solar system move that fast.”
Dan Werthimer, physics researcher at UC Berkeley, said CB21 is a particularly interesting asteroid because it crosses the orbit of the Earth.
“Every time [CB21] comes around, it's gonna cross the orbit of Earth,” he said in a phone call. “And that could be, you know, far away, it could be a couple 100 million miles away, or occasionally comes close.”
Werthimer said there are days every few years in which CB21 passes close to Earth, including this Friday.
The asteroid is predicted to have 14 close approaches to Earth throughout the current century, the next instance occuring on Sept. 29, 2026, according to the same Space Reference webpage.
Werthimer said asteroids of this distance are categorized as “potentially hazardous.”
A potentially hazardous asteroid is defined based on parameters that measure its potential to make “threatening close approaches to Earth,” according to NASA’s webpage.
“What [a potentially hazardous asteroid] simply means is that it's an asteroid whose orbit crosses the orbit of the Earth, and it's predicted to get close to the Earth,” Thomas Madura said.
Madura said about 15,000 to 16,000 of these potentially hazardous asteroids cross the Earth’s orbit.
While potentially hazardous asteroids are not always detrimental to Earth, NASA is working on projects to defend the planet against near-earth objects, including the Double Asteroid Redirection Test (DART) Mission, according to the DART Mission NASA webpage.
The asteroid system is designed to intentionally crash a spacecraft into an asteroid to change its course and prevent a collision with Earth, according to the same webpage.
DART launched on Nov. 24, 2021 and is the world’s first full-scale mission to test defensive Earth technology against asteroids. The DART spacecraft will impact a known, non-threatening asteroid with a goal of changing the trajectory, according to the same webpage.
Professor Asplund said DART is an “interesting mission” and an effective way to prevent a collision.
“That is probably our best bet in terms of, you know, avoiding an impact if it ever comes to that,” he said. “It's all about changing the momentum and applying forces.”
Asplund also mentioned that the DART mission is a “good reminder” of the benefits of investing in astronomy, NASA and science.
“One of the reasons that it's good to [invest in science] is so that we can know about this kind of stuff,” he said. “So it's NASA, but it's also just government funding, like the National Science Foundation and other federal agencies… this is a major benefit to society.”
Madura said while CB21 is a relatively large asteroid, an asteroid would have to be comparable in size to another planet to “completely shatter the Earth,” if it was to strike the planet.
There are currently no known asteroids larger than 140 meters with a significant chance of hitting Earth for the next 100 years, but only 40% of those asteroids have been discovered as of October 2021, according to NASA’s webpage.
Madura said there is “a lot of uncertainty” though, regarding asteroid preparation and prevention because the systems are still being tested.
“We definitely wouldn't want to blow [an asteroid] up, because that would just send a lot of smaller pieces potentially at us,” he said. “But one of the things we would probably try to do is probably try to nudge it - to knock it off course.”
He said with developing technology, CB21 provides an opportunity to study near-Earth asteroids in more detail.
“Our telescopes, and our technology has gotten more powerful over the years,” Madura said. “Now when these things come close, we can study them in more detail and understand them more so that we can prepare for any future ones that may come closer or make it that way we have more information and we can better prepare ourselves.
