We can expect a totally different kind of trick-or-treater this coming Halloween. A rather large asteroid—discovered less than three weeks ago—is set to to fly past the Earth at a distance not seen in nearly a decade.Yikes! But don't worry: NASA says 2015 TB145 will "safely pass by the Earth and continue to following along its exceptionally eccentric and high-inclination orbit—which may explain why it wasn't discovered until only a few weeks ago."
The asteroid, dubbed 2015 TB145, was discovered on October 10 by astronomers using the Pan-STARRS telescope. The object measures about 280 to 620 meters (920 to 2,034 feet) in diameter, so it's pretty big—about the size of a skyscraper. Or two. Not only that, it's moving at a velocity of 35 km/s (78,830 mph or 12,600 km/h), which NASA describes as "unusually high."
When 2015 TB145 makes its closest approach on October 31, it will zoom past the Earth at a scant 0.0032 AU, or 1.3 lunar distances. That's about 479,000 km or 297,000 miles.
In case you're inclined to check out our asteroid friend as it flies by, it will "reach a magnitude luminosity of 10, so it should be observable to astronomers with telescopes. It'll be seen best in the Northern Hemisphere, but the moon will be a relatively bright 80% waning gibbous at the time. Bad news for astronomers, but good news for the trick-or-treaters."
I love everything about this, obviously. And "Unexpected Asteroid" is totally my new band name.