- An asteroid called Apophis, after the ancient Egyptian god of chaos, will fly by Earth Friday night.
- The space rock is more than 1,100 feet wide - wider than the Eiffel Tower is tall.
- When Apophis returns in 2029, its path could intersect with high-altitude satellites in Earth's orbit.
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An asteroid nearly four football fields wide is about to zoom by Earth.
The space rock is named 99942 Apophis, after the ancient Egyptian god of chaos. It's is wider than the Eiffel Tower is tall: about 1,115 feet (340 meters).
On Friday night at 8:15 p.m. ET, the asteroid will come within 10.4 million miles of Earth's surface. That's about 44 times the distance between Earth and the moon. But Apophis' next close flyby, on April 13, 2029, will bring the asteroid within 19,000 miles of Earth - that's in between our planet and the moon. It will be the closest any asteroid of Apophis' size has come to Earth's surface that scientists have known about in advance, according to NASA.
That future approach will even be close enough that the asteroid could collide with high-altitude communications satellites orbiting Earth.
The animation below shows what the distance between Apophis and Earth will be eight years from now. The blue dots represent orbiting satellites, and the International Space Station is in pink.
Preparing for Apophis' return
Apophis won't be visible to the naked eye tonight - you'd need a telescope with at least a foot-long diameter to see it. But Rome's Virtual Telescope Project is offering an online viewing session at 7 p.m. ET.
The asteroid's discovery made waves in 2004, since astronomers calculated at the time that there was a small chance it could hit the planet in 2029. NASA scientists have since revised that estimate.
"We have known for some time that an impact with Earth is not possible during the 2029 close approach," Dave Tholen, a researcher at the University of Hawai'i Institute for Astronomy who helped discover Apophis, said in October.
Every time an asteroid nears Earth, it's a chance for astronomers to study the space rock and learn about its shape and spin.
When scientists first spotted Apophis in June 2004, they had just two days to inspect it before weather and technical issues got in the way. No images exist of the rock's surface. So this imminent close pass, as well as the one in 2029, will help scientists investigate Apophis' composition.
"The Apophis close approach in 2029 will be an incredible opportunity for science," Marina Brozović, a radar scientist at NASA's Jet Propulsion Laboratory, said in 2019. "We'll observe the asteroid with both optical and radar telescopes. With radar observations, we might be able to see surface details that are only a few meters in size."
During that 2029 flyby, Apophis will be visible to the naked eye, appearing as a fast-moving point of light that starts in the night sky over the Southern Hemisphere and moves across the globe from east to west.
The NASA animation below shows Apophis' path on April 13, 2029.
Apophis has a 1 in 380,000 chance of striking Earth in 2068
Apophis originated from the asteroid belt between Mars and Jupiter. So far, NASA knows it is made up of silicate rocks, nickel, and iron. Radar images suggest it looks like a peanut.
After 2029, Apophis will have more near-Earth encounters, passing by again in 2036 and 2068. There's no chance of an impact in 2036, but NASA calculations suggest a 1 in 380,000 chance that Apophis could strike in 2068.
Until last year, astronomers thought it was impossible that Apophis would strike Earth in 2068, but that changed after Tholen's team presented new research at the annual meeting of the American Astronomical Society. The group showed the asteroid was changing speed and direction over time.
These changes come from a process known as Yarkovsky acceleration: As asteroids absorb energy from the sun, they radiate the energy out as heat, which slightly changes their orbital paths.
The recent research found that this is happening to Apophis.
The asteroid's orbit is shifting by about 558 feet per year, Tholen said - which is "enough to keep the 2068 impact scenario in play."