Auroral Alert Tonight Dec. 18-19 / Holiday Asteroid Parade

This is one of several coronal mass ejections (CME) - an eruption on the sun's surface - that occurred on Dec. 16. A rarified soup of high-speed electrons and protons is shown departing the sun (arrows) in our direction. Credit: NASA/ESA
This is one of several coronal mass ejections (CMEs) – massive bursts of gas knit by magnetic fields – that occurred on Dec. 16. A rarified soup of high-speed electrons and protons is shown departing the sun (arrows) in our direction. Credit: NASA/ESA

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.

radar image of asteroid 1998 WT24 taken in December 2001 by scientists using NASA's the 230-foot (70-meter) DSS-14 antenna at Goldstone, California. On the right is a radar image of the same asteroid acquired on Dec. 11, 2015, during the asteroid's most recent Earth flyby.
A radar image of the asteroid, 1998 WT24 (similar to 2015 YB), taken during its close flyby on December 11, 2015 using NASA’s the 230-foot (70-meter) DSS-14 antenna at Goldstone, California. Credit: NASA

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.

Asteroid 2003 SD220 was discovered by the Lowell Observatory Near-Earth Object Search (LONEOS) program in 2003. It will pass by Earth again on Christmas Eve at 6.8 million miles away. This image was made with radar using the Arecibo dish. Credit: NASA/NSF
Asteroid 2003 SD220 was discovered by the Lowell Observatory Near-Earth Object Search (LONEOS) program in 2003. It will pass by Earth again on Christmas Eve 6.8 million miles away. This image is a radar image made with the Arecibo radio dish and shows a rugged surface with at least a half dozen craters. Credit: NASA/NSF

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.

A few more images of the pellet-shaped 2003 SD220 from Arecibo Observatory. Some online reports are suggesting the asteroid could cause earthquakes. Asteroids can't and don't do this, unless a large one happens to hit Earth. This will pass over 6 million miles from us. No worries. Credit: NASA/NSF
The 1.1-mile-long, chicken-finger-shaped asteroid 2003 SD220 imaged by Arecibo Observatory earlier this month. Some online reports are suggesting the asteroid could cause earthquakes. Asteroids can’t and don’t do this, unless a large one happens to hit Earth. This will pass over 6 million miles from us. No worries. Credit: NASA/NSF

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.

6 Responses

  1. Rob

    I walked out of my shop about 4:30 this afternoon and it looked like sunrise. There was more color in the sky to the east then there was in the west. What is this phenomenon called?
    Thanks

    1. astrobob

      Hi Rob,
      Was the sky clear or cloudy? If it was mostly cloudy the sun shone through a clearing right at sunset, briefly lighting up the clouds all around the sky.

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