Asteroid Size
Asteroid size ranges from the dwarf planet Ceres down to the smallest dust particles. Despite their size difference these asteroids share many things in common. Ceres accounts for 34% of all of the mass of the asteroid belt between Mars and Jupiter, but it shares similar orbital characteristics with thousands of smaller asteroids in the main belt. Asteroid size may distinguish an asteroid, but it does not set it completely apart from its smaller counterparts.
Asteroids are numbered by their discovery order, but if you were to rank asteroid size the top 4 would be Ceres, Vesta, Pallas, and Hygeia. Although these are the largest four asteroids by size, Ceres is the largest by far. Vesta is ranked second, but is just a quarter of the size of Ceres. Pallas is nearly the same size as Vesta, but has a smaller mass. Hygeia is about 1/2 the size of Pallas and is very low in mass.
After Hygeia there are 24 more asteroids with similar mass and size. The next group of asteroids is approximately 1 million strong. This is only an estimate from scientists since there are only 20,000 observed asteroids at this time.
In the early era of the solar system the planets and asteroids are thought to have been formed by a series of impacts. After these impacts, some of the heavenly bodies stuck together to form the asteroids and plants. This process is call accretion. Asteroid size was determined by this process. The larger asteroids are thought to have enough mass for self gravity which makes considered to be dwarf planets. Several asteroids have their own moons; other, smaller asteroids that revolve around them and follow the same orbit. These moons help to determine the mass and size of the parent asteroid.
Many of the asteroids may never be orbited or viewed by a space mission, but the larger ones will. It seems that asteroid size determines NASA's interest. Many of the asteroids have eccentric orbital habits that prevent us from visiting them with our current technology.
Asteroid size may affect our ability to orbit it at this time and it influences science's interest right now, but that will all change as we turn to space for new sources of minerals and ores. Asteroids may become the next frontier for mine exploration in the very near future.
We have written many articles about asteroids on Universe Today. Here's an article about measuring asteroids accurately.
Here are some more useful links. One on from the NASA World Book and the other on asteroids from the Encyclopedia of Space.
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.
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