Astro Bob: Chase asteroid 1994 PC1 across the heavens
A largish, close-approaching asteroid will fly by Earth early this week and shine bright enough to see in a small telescope.
If you've never tracked a potentially hazardous asteroid (PHA) through a telescope you haven't lived. Seeing an asteroid that could potentially slam into the planet feels a little like playing with fire. And who doesn't love a little danger? Seriously though, asteroid (7482) 1994 PC1 will NOT pose a danger to Earth this time around and not for the foreseeable future either.
Discovered on August 9, 1994, 1994 PC1 is about 3,600 feet across (1.1 km) and circles the sun every 1.6 years. Astronomers dub it potentially hazardous (PHA) by their own carefully researched definition: it's at least 460 feet (140 meters) across and passes within 4,650,000 miles (7,480,000 km) of Earth's orbit. This leaves open the potential (not the certainty) for a strike somewhere down the road. There are currently about 2,000 known PHAs. The vast majority of the largest ones from a kilometer up — the kind that can destroy civilization — have already been discovered.
1994 PC1 is a stony asteroid from the Main Belt that will miss the Earth by 1.2 million miles (1.9 million km) or about five times the distance of the moon at its closest approach. That will occur at 3:51 p.m. CST (21:51 UT) on Tuesday, January 18th. At that time, it will be traveling at more than 43,000 miles an hour (70,000 km/hour), about the same speed as a fast-moving meteor streaking across the sky. Lucky for us it will be shine around magnitude 10.0-10.5 on both Monday night (Jan. 17) and Tuesday night (Jan. 18). Although a bright moon will prevail, a 10th magnitude asteroid is bright enough to see in a 4-inch or larger telescope.
On Monday night, it climbs north and west through the constellation Eridanus the River, located southwest of Orion. Then on Tuesday, it scoots across Pisces into Andromeda. The wide-field map gives you a general idea of the asteroid's path and location both nights. For detailed maps to guide you precisely to the target, please see my article on Sky & Telescope's website.
You might imagine that 1994 PC1 zips across the sky in minutes, but no, it takes hours. That's still fast. To find it, locate a brighter star along its track and point your telescope there 5-10 minutes in advance of the asteroid's arrival. Take the time to get acquainted with the star field so you can identify the interloper when it arrives.
The asteroid will move slowly when viewed at low magnification. To increase its "speed," increase the magnification to 100x or more. It's easiest to see 1994 PC1's movement when it passes close to a star or makes a distinctive pattern (and then breaks it) with two or more stars. If for any reason you're unable to spot the object, you can still see it online on Gianluca Masi's Virtual Telescope Project site . Live coverage starts at 2 p.m. CST (20:00 UT) on Jan. 18.
The flying, village-sized rock will look like a star in the telescope but moving at about the pace of a very slow-moving satellite. It's fun to catch up with these little critters. The solar system is crawling with them. Scientists have identified over 800,000 asteroids, but it's estimated they number in the millions. Most are small, and none are predicted to hit the planet anytime soon, so go ahead and order dessert.
"Astro" Bob King is a freelance writer for the Duluth News Tribune.