An asteroid about the size of a giraffe was discovered last weekend and will make an extremely close approach to Earth this Thursday just as a much more distant “green comet” is brightening.
Near-Earth asteroid 2023 BU—about 12-28ft./3.8-8.5 m wide according to NASA’s Jet Propulsion Laboratory—won’t threaten our planet (it’s about half the size as the famous Chelyabinsk meteor in 2013), but it will pass well within the orbit of geostationary satellites above South America.
That will make it a particularly close near-miss—the fourth closest ever recorded—and it was only noticed just five days before its closest approach.
Most asteroids pass beyond the distance of the Moon. This one is far closer.
On Thursday, Jan. 26 at 21:17 Universal Time (16:17 EST) asteroid 2023 BU will get to within 6,137 miles/9,877 kilometers of Earth’s center.
That’s only about 2,178 miles/3,506 kilometers above its surface.
That’s further up than low-Earth orbit, where satellites and the International Space Station orbit about 250 miles/400 kilometers up, but only about a fraction of the distance of geostationary satellites 22,000 miles/36,000 kilometers up.
While most asteroids spotted sail beyond the distance to the Moon’s orbit, 2023 BU will come within just 3% of the Earth-Moon distance.
So close, in fact, that large telescopes will easily spot it.
The close pass will be shown in real-time by The Virtual Telescope Project, a set of two powerful 14-inch and 17-inch robotic telescopes based in Ceccano, Italy. Astrophysicist Gianluca Masi will host a live feed on YouTube during which views of 2023 BU will be shown through a telescope. Coverage will begin at 19:15 UTC on Thursday, Jan. 26.
Since it’s so small it will shine at a maximum of 11.3 magnitude, which is too faint for the human eye to see. So only those with large telescopes will be able to see 2023 BU.
2023 BU is an Apollo-type asteroid, a class of objects named for the archetype asteroid 1862 Apollo. Such asteroids have an orbit that is larger than Earth’s orbit around the Sun and their path crosses Earth’s path. 2023 BU orbits the Sun every 425 days and its path does occasionally cross Earth’s orbital path around the Sun.
It was discovered by astronomer Gennadiy Borisov at the Crimean Astrophysical Observatory in Nauchnyi, Crimea on Saturday. Borisov famously discovered 2I/Borisov, the first comet ever discovered that had traveled into the solar system from interstellar space.
2023 BU will next pass relatively close to Earth on December 6, 2036, but on that occasion it will be well beyond the orbit of the Moon.
2023 BU is referred to as a “near-Earth object” (NEO) because its orbits brings it to within 120 million miles/195 million kilometers of the Sun. However, it’s not classed as a “potentially hazardous asteroid” (PHA), which is reserved for a NEO with an orbit that can make close approaches to the Earth and is large enough to cause significant regional damage in the event of impact.
At the size of a giraffe, if 2023 BU struck Earth it would likely breakup and burst into a cloud of fragments some distance above the surface, with some large fragments possibly striking the surface. Anyone nearby would hear a loud bang.
2023 BU is currently in the constellation of Ursa Major—famous for its recognizable Big Dipper asterism— relatively close, visually, to comet C/2022 E3 (ZTF). Although the comet is brightening in the night sky as it gets closer to Earth. However, at its closest on Feb. 2 the comet—on a 50,000 year orbit of the Sun—won’t get any closer than about 26 million miles/42 million kilometers.
Wishing you clear skies and wide eyes.
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