Toutatis near Aldebaran on December 19th.
It’s a shooting gallery out there. As the scarred surface of our Moon attests, the inner solar system is routinely criss-crossed by comets and asteroids that would do our precious niche of the universe harm.
This week, we’re in for several fine examples of debris in our neighborhood; a dependable meteor shower in the form of the Geminids, a possible “wild-card” meteor outburst, and a chance to spot one of the most well known and studied Earth-crossing asteroids.
The Geminid meteor shower peaks this week with a Zenithal Hourly Rate (ZHR, or the number on meteors you can expect to see under ideal conditions) of 120. This is centered on December 13th at 23:30 UTC, which would place Asia and Indian Ocean longitudes in an optimal position for viewing early on the morning of the 14th. Of course, its always worth watching for Geminids worldwide a few mornings on either side of the target date. This year is particularly favorable, as the Moon also reaches New earlier on the 13th and is thus safely out of view, Though meteors may seem brilliant, they’re actually tiny dust-sized grains of cometary debris strewn along a comet’s orbit, a sort of calling card saying “a comet was here.” Where the Earth intersects that trail, we get an annual meteor shower, and these streams evolve and fade or intensify over time. In the case of the Geminids, there’s an especially strange twist, in that the source is an asteroid named 3200 Phaethon. Is Phaethon an inactive cometary nucleus, or some strange asteroid/comet hybrid? Thoughts to ponder this Geminid season… the Geminids radiant lies very close to the bright star Castor at its peak.
There’s also another meteor shower worth watching for this week; the “46P-ids” may come into play. Predictions are for a respectable ZHR of 10-30 meteors with multiple peaks from December 10-14th. The suspected shower draws its tentative name from comet 46P/Wirtanen. The radiant lies at declination +3.6° right ascention 357° very near the circlet of Pisces… could a new shower dubbed the “Piscids” be in the works? What ever the case, keep an eye out for all things meteoritic and tweet those sightings to #Meteorwatch!
The path of 4179 Toutatis from December 10th to the 26th. (Graphics created by the author in Starry Night).
This week also sees the chance to spot a bright and nearby asteroid. 4179 Toutatis has been pinged with radar at Goldstone on previous passes and is in our solar neighborhood again this week. 4179 Toutatis is in a 3:1 resonance with Jupiter and a 1:4 resonance with Earth in a 4 year orbit that just crosses inside our own. Although the chances of a collision with Earth in the near future (i.e. for the next few centuries) are extremely low, 4.5 kilometer wide (on its longest axis) 4179 Toutatis makes for a fascinating study of near Earth asteroids, should we ever have to move one out of the way. The Chinese spacecraft Chang’e-2 is scheduled to pass within a few hundred kilometers of 4179 Toutatis on December 13th.
For backyard observers, 4179 Toutatis passes within two degrees of the bright star Aldebaran on the night of Dec 19 at about 9th magnitude. Its closest approach is on December 12th at 18 times the distance of the Moon or 4.5 million miles, (0.0465 Astronomical Units) and the asteroid will shine at around 10th-9th magnitude in the constellation Cetus and Pisces. Apparent speed at closest approach will be about 1 degree every 3 hours or 1’ arc minute every 3 minutes, noticeable after a few minutes of observation.
4179 Toutatis made its last close approach on November 9th, 2008 (0.05AU), and its Next close passage isn’t until November 5th, 2069 (0.019AU). One of the closest passes in recent times was on September 29th, 2004 (0.01AU) when we observed it as a slowly gliding “star” with moment visible after only a few seconds of observation… be sure to watch for 4179 Toutatis if you can!