Have you ever seen an asteroid? If not, this week is an excellent time to do so: Vesta, the brightest asteroid, will be well placed for observation with binoculars in the constellation Leo.
Vesta was discovered in 1807 by Heinrich Wilhelm Olbers. An active German astronomer, he also discovered the asteroid Pallas and a comet named after him, but is most famous today for stating Olbers? paradox: the darkness of the night sky conflicts with the supposition of an infinite and eternal static universe.
Vesta is the second largest asteroid, after Ceres, and by far the brightest, having a greater albedo (percentage of light reflected) than any other asteroid. This seems to be partly the result of a collision with another asteroid about a billion years ago. Its mean diameter is 329 miles (529 km), but it is rather irregular in shape because of its violent history.
Vesta is at a point in its orbit called "opposition," which is its closest approach to Earth, NASA officials said in a statement. At high noon on Wednesday, when the sun is over your head, Vesta will be about 131,700,000 miles (211,980,000 km) below your feet, they added.
Unlike some other asteroids, Vesta also has a brighter-than-typical surface (the albedo) which makes the space rock reflect more sunlight and stand out more to observers, NASA officials said.
This week Vesta will be traveling rapidly through Leo. It will be around magnitude 6.2, bright enough to be easily visible in binoculars. However, because of its small diameter and distance, it will appear as a star-like point of light except in the very largest telescopes.
What gives Vesta away is its obvious movement from night to night against the starry background.
You can find Vesta tonight very close to the popular 2nd magnitude double star Algieba (Gamma Leonis). Leo looks like a right angle triangle on the left and a sickle or reversed question mark on the right, as seen from the northern hemisphere. Algieba is the second star up from the dot under the question mark, the bright star Regulus.
Vesta will be visible in binoculars just to the right of Algieba tonight, forming a tiny equilateral triangle with Algieba (magnitude 2.0) and 40 Leonis (magnitude 4.8). Over the next few nights it will travel to the right, stretching this triangle out. The chart shows Vesta?s position each night at 10 p.m. EST over the next week.
Make a simple sketch of these three ?stars? over the next few nights, and Vesta?s movement will be obvious.
You will be able to follow Vesta?s motion over the next few months by plotting its position in Starry Night.
If you look at Vesta with a small telescope, be sure to check out Algieba, one of the prettiest double stars in the sky.
Vesta is one of two asteroid targets for NASA's Dawn spacecraft. The ion drive-powered probe is headed toward the asteroid belt to swing by Vesta in 2011 and Ceres, which is big enough to qualify as a dwarf planet.
- Images - Asteroids in Space
- Video - Spacecraft to Visit Asteroid Vesta
- More Night Sky Features from Starry Night Education