Atropos

The asteroid 273 Atropos is a main belt asteroid that has not been well studied. Very few facts are directly known about this body. Here are the few that scientists have gathered: It has an approximated diameter of 29 km. It has a perihelion of 2.013 AU and an aphelion of 2.778 AU. It has a semi-major axis 2.396 AU and an eccentricity 0.16. The asteroid has an orbital period of 1,354.216 days with an orbital speed of 19.24 km/s. It presents with an inclination of 20.44, and a longitude of ascending node of 159.145. Scientists have a dearth of information despite the asteroid having been discovered by Johann Palisa on March 8, 1888.

The majority of the mass in our Solar System is concentrated in the Sun and the planets. An overwhelming portion of the remaining mass is in the main asteroid belt. To be considered a main belt asteroid a body must orbit between Mars and Jupiter. This area is sometimes called the asteroid belt, since other asteroids fall in to distinct categories like the Kuiper Belt, trans-Neptunian objects(TNOs), or the scattered disc. The majority of the mass in the main belt lies in the four largest bodies: Ceres, Vesta, Pallas, and Hygeia. All of these have a diameter of more than 400 km. Ceres is the largest at 959 km in diameter and accounts for 25% of the mass in the asteroid belt. It is classified as a dwarf planet like Pluto. On the other end of the size spectrum are asteroids so small that they are thought to be dust that will disappear the next time they impact another object. Some as small as a few cm.

There are a few theories about how the asteroid belt formed. One indicates that the asteroids formed as the dust and gases from the Big Bang collided and slowly formed larger bodies in a process called accretion. Gravitational perturbations from Mars and Jupiter gave the planetesimals too much orbital energy for them to form into a planet, but they continued to collide; eventually shattering into their current sizes and shapes. In 1802 Heinrich Olbers theorized that the asteroid belt was formed by an ancient planet exploding. This planet having either suffered an internal explosion or a cometary impact billions of years ago. The large amount of energy that would have been required to destroy a planet, combined with the belt’s low combined mass tend to negate that theory. Today, the most widely held belief is that the asteroid belt is material left over from the Big Bang that never accreted to a planet. The largest bodies have accreted all of the material that their gravity can pull in.

273 Atropos, like many of the individual asteroids in the main belt is a mystery. The objects are distant enough to have escaped intense scrutiny. The main belt itself is only mildly understood. The Dawn space mission may change all of that after it orbits Vesta and Ceres.

The amount of information about 273 Atropos is limited, but here is the NASA page on the asteroid. Here on Universe Today we have a great article about the main asteroid belt. Astronomy Cast also offers a good episode about the asteroid belt.

Sources:
NASA
NASA: The Main Asteroid Belt

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