A Big Chunk of Rock Passes Near Earth
A mile-wide chunk of rock dubbed 2006 VV2 is now whizzing past Earth. At its closest approach, around 11 p.m. Pacific Daylight Time on March 30th, it will be just 2,100,000 miles (3,900,000 kilometers) over the heads of observers in Southern California. It's predicted to be magnitude 10.0 at its brightest, which would normally make it visible through small telescopes. But it's quite close in the sky to a nearly full Moon, which will make the observation more challenging. Even so, it should be readily visible in telescopes with at least 6 inches of aperture, and it should be a treat for astrophotographers.
On the upside, 2006 VV2 is almost opposite the Sun in the sky, so it's well placed all night long. And if you're clouded out on March 30-31, you'll have an equally good opportunity the following night, when the asteroid is predicted to be marginally brighter and only 10% farther from Earth. Even 48 hours later, 2006 VV2 will still be quite bright, though it will be receding rapidly.
Comparable approaches happen every few years. A little more than a year ago, a very similar asteroid named 2000 PN9 passed 1,900,000 miles from Earth. And in September 2004, the somewhat brighter asteroid Toutatis zipped by at a distance of less than one million miles. Smaller rocks have been known to come much closer; in 2002, two asteroids came within 80,000 miles, just one-third the distance to the Moon. But those were less than one-tenth the diameter of 2006 VV2. Lovers of statistics will enjoy framing their own queries for NASA's near-earth object database.
Close asteroid passes offer special opportunities to professional and amateur astronomers alike. At a range of a few million miles, radar imaging can determine the size and shape of asteroids more accurately than any other method short of visiting them by space probes. And amateurs get to see a solar-system object move through the "fixed stars" at an extraordinary speed. At closest approach, 2006 VV2 will traverse a degree of sky in a hour. That's twice the apparent speed of the Moon, and fast enough that you may actually be able to see its motion in real time through a telescope with a tracking drive at high magnification.
Because the asteroid is moving so fast, we've prepared seven full-page charts to cover its path from March 29th to April 2nd. Each chart shows roughly 12 hours of the asteroid's track, alternating between nighttime in the Americas and nighttime in the Old World. To use the charts, you'll need to convert your local time to Universal Time. You may also need the key chart to get you into the right vicinity of the sky.
Chart 1:March 29-30 (America)
Chart 2:March 30-31 (Old World)
Chart 3:March 30-31 (America)
Chart 4:March 31 - April 1 (Old World)
Chart 5:March 31 - April 1 (America)
Chart 6:April 1-2 (Old World)
Chart 7:April 1-2 (America)
Because the asteroid is so close, its position among the stars at any moment depends a little on your position on Earth. The charts show where the asteroid would appear if it were directly overhead, which is more or less the case around 11p.m. at mid-northern latitudes. Earlier in the evening it will appear a bit left of the plotted path, and after midnight a bit right. In extreme cases, it may be up to 7 arcminutes from the plotted position. To plot an exact path custom-calculated for your site, or to find coordinates that can be used by a Go To telescope, you can enter your location into the ephemeris-generating program here.
As long as 2006 VV2 within your field of view and bright enough to see, you won't need charts to identify it. Just watch for a minute or two and pick out the "star" that's moving.