Asteroid Juno
Written by Jerry Coffey
The asteroid Juno, or 3 Juno, is an S-type(stoney type) asteroid. Although it was the third asteroid found it is ranked about tenth for size. It only has about 3% of the mass of Ceres. The asteroid Juno has a sizable crater near its southern pole that has intrigued astronomers for a number of years. Juno is unusually bright compared to other S-types and is, at times, brighter than Neptune and Titan.
The asteroid Juno was discovered on September 1, 1804 by German astronomer Karl Harding. Because of its exceptional albedo, it was discovered before larger asteroids in the same belt. At most times Juno is at a brightness magnitude of +8.7, but can reach +7.5 at rare opposition. At its brightest, Juno can be seen with binoculars, but usually you need to have a 76mm telescope to resolve it.
The asteroid Juno is 320 km x 200 km and has a mass of 2.67 x 1019 kg. Surface temperature ranges from 15.6°C (163K ) to 28°C (301K ). Pretty cold, but still a lot warmer that Ceres and Vesta. The feature that has made Juno so interesting to astronomers and other scientists is the 100km crater near the southern pole. This crater is thought to be the result of an impact fairly early in Juno's evolution. Juno is also thought to be the source of some stony, iron bearing meteorites that have been found on Earth.
There are no plans to orbit or observe the asteroid Juno at this time. The Dawn space mission may catch a few photos of the asteroid, but it is highly doubtful. It's still a very intriguing asteroid as far as showing evidence of free flying space objects colliding then combining to form a larger mass. This process, called accretion, is how the planets and larger dwarf planets were formed.
We have written many articles about asteroids for Universe Today. Here's an article about a potentially new hazardous asteroid discovered, and here's an article about how we might prepare for an asteroid strike.
Want more resources on asteroids? Here's NASA's Lunar and Planetary Science Page on asteroids. And here's NASA's World Book on Asteroids.
We have recorded two episodes of Astronomy Cast about asteroids. There's Episode 55: The Asteroid Belt, and here's Episode 29: Asteroids Make Bad Neighbors.
Filed under: Astronomy
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