Keep watch on the northern sky tonight. Several recent solar blasts are working their way toward Earth as you read this. Expect the bee-like swarm of subatomic particles to buzz past the planet and possibly link into out magnetic domain by late afternoon. Minor (G1) storming is expected during the early evening hours over the U.S. and Canada with stronger G2 condition kicking in around 9 p.m. CST till midnight. A half-moon will shine but shouldn’t be too bright; it sets shortly after midnight leaving dark skies till dawn.
Tomorrow morning Dec. 19th around 6 a.m. CST, the Lilliputian asteroid 2015 YB, only 42 feet across, will zip just 48,000 miles (77,250 km) from Earth. When closest it’s expected to shine around magnitude +13.3 . As it tracks from Lepus the Hare southeast across Canis Major the Greater Dog, observers in the western half of the U.S. will get the best and brightest (if you can call it that) views. You’ll need at least an 8-inch telescope. For those with sky mapping programs, key in the asteroid’s orbital elements and make a map you can use at the telescope.
The asteroids just keep on coming. 2015 XA378 (102 feet/31 meters) flies within 10 lunar distances (LD) of the planet on the afternoon of the 19th followed four days later on Dec. 23rd by 2015 XN261 at 2.6 LD. The coup de grace comes on Christmas Eve when three near-Earth asteroids ride by like Santa and his reindeer: 2015 XX378, 2011 YD29 and 2003 SD220. The first two are small (155 feet and 79 feet, respectively), but the last measures 1.1 miles (1.8 km) across. 2003 SD220 was discovered back in 2003. This time around, astronomers have been using the Arecibo Observatory to bounce microwaves off the object to study its surface, shape and rotation. NASA has also put the Goldstone antenna to work doing the same.
The trio, along with all the others, pose no threat to Earth. They’ll pass by harmlessly and continue along their orbital tracks around the sun. Things are different however if you’re the asteroid. Earth’s much more powerful gravity will almost certainly alter a few of their orbits, sending them in slightly different directions after the flybys.
While so many asteroids arriving within a short time span might be perceived by some as a sign the world’s about to end, it’s really a sign that automated asteroid surveys like the Catalina Sky Survey and Pan-STARRS are doing a great job finding out who’s passing through the neighborhood. The more flying space mountains we can see and calculate orbits for, the better we can predict if one of them might pose a threat. So far, so good. Nothing bad on the horizon for at least the next hundred years.