An assumption can be made that while asteroids have tremendous destructive power, they hold no other interest for us. Indeed, they are just space rocks of various sizes in a far-away orbit between Mars and Jupiter.
However, as we are about to learn, nothing involving nature is ever that simple.
While the first asteroid was discovered in 1801, a hundred more had been discovered by 1868. Today, the estimated number of bodies measuring at least 0.6 miles in diameter is between 1.1 and 1.9 million, with millions more that are smaller.
Initially, asteroids were given female names from Greek and Roman mythology. As the numbers grew, male names were allowed. Today, a naming system by the Minor Planet Center creates a designation based on the year of discovery, the half month it was discovered in, and how many other bodies were observed prior to it during that same half month.
Therefore, 1989AC tells us that the body was discovered in 1989, “A” signifies it was discovered between Jan. 1 and Jan. 15, and the “C” tells us that it was the third body discovered in that time period. Once an orbit is established for the body in question, it can be given a name (i.e. Ceres) by the discoverer, instead of the original numerical designation. This name must be acceptable to the International Astronomical Union.
Over time it became apparent there were similarities — such as orbit between some of the asteroids — creating what are now recognized as asteroid families. It is thought that families arose from two possible scenarios. The first would be collisions between asteroids such that both bodies are shattered, yielding a family of smaller asteroids.
The second is the result of cratering, meaning the impacted body had been large enough to have not been destroyed, but instead ejected material from that impact that formed a swarm linked with the original body. There are now about 20 to 30 recognized families — most, but not all, in the main belt that lie between Mars and Jupiter.
The main belt itself stretches 2.2 to 3.2 AU (or “astronomical unit” — one AU is 93 million miles) from the sun, and is 1 AU thick. Because of the huge volumes of space involved, there are enormous distances between one asteroid and another, thereby making it safe for spacecraft to travel within the belt.
At one time it was thought that the asteroids were the remnants of another hypothetical solar planet that disintegrated. However, the four largest asteroids in size order – Ceres (now considered a dwarf planet), Vesta, Pallas, and Hygiea — are believed to contain approximately half the mass of the entire belt. That being the case, if all the scattered material coalesced into a single body, it would be smaller than our moon.
Instead, it is now hypothesized that asteroids are the remnants of the primordial material that formed at the same time as our sun and the planets, and can give insight into both the materials and the processes by which our solar system was formed.
Although asteroids are divided into three main groups based on their reflectivity — known as albedo and their color — there are 11 other minor types.
This represents 75 percent of all asteroids, where “C” stands for “carbonaceous.” These asteroids have low reflectivity, meaning they are grayish and appear quite dark.
They are composed of carbon, rock and minerals, although there is some evidence that they contain amino acids, which are the building blocks of proteins on Earth.
They occupy the far outside edge of the Mars-Jupiter belt.
This represents the 17 percent of asteroids known as S-type (silicaceous), and are the brightest asteroids. They are composed of metallic iron as well as iron-silicates and magnesium-silicates, and dominate the inside edge of the asteroid belt, the section closest to the sun.
They appear somewhat reddish.
For “metallic,” these asteroids also are slightly reddish, making up much of the remaining 8 percent. They are also fairly bright, slightly reddish, and are composed of metallic iron and occupy the center section of the main belt.
It turns out that there are three families of asteroids that are in proximity to the Earth and are known as “near Earth objects.”
In 1918, German astronomer Max Wolf discovered asteroids that cross Earth’s orbit, naming them “Apollos.” The Chelyabinsk meteor, for example, was an Apollo.
In 1932, Eugene Delporte discovered the Amor asteroids, which approach Earth from the direction of Mars but do not cross its orbit. Eros, which was visited by the NEAR Shoemaker probe in 1998, was an Amor asteroid.
In 1976, American astronomer Eleanor Helin discovered another group of Earth-crossing asteroids named the Atens.
By now, you are probably wondering what else is out in space.
Actually, there is a whole universe just waiting to be explored!
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