433 Eros
433 Eros is a near-Earth asteroid (NEA) that holds significant interest in the field of astronomy. Discovered in August 1898 by Gustav Witt and Auguste Charlois, Eros is notable for its irregular, peanut-like shape and its classification as an S-type asteroid, which means it is primarily composed of silicates and metals. With a diameter of approximately 17 kilometers, it is the second-largest NEA. Eros orbits the sun at an average distance of 1.46 astronomical units and completes one orbit every 1.76 Earth years.
In February 2001, Eros became the first asteroid to be orbited and landed on by a spacecraft, the NEAR Shoemaker, launched by NASA in 1996. This mission aimed to gather data on Eros’s surface features and composition, contributing valuable information about the early solar system. Eros is classified as an Amor asteroid, which approaches Earth without crossing its orbit, and is considered non-hazardous based on simulation data. Its surface is marked by craters and pits, indicators of past collisions in space. Overall, Eros represents a unique opportunity to study primordial materials that have remained largely unchanged since the solar system's formation.
433 Eros
FIELDS OF STUDY: Observational Astronomy; Cosmology; Sub-planet Astronomy
ABSTRACT: 433 Eros is a large near-Earth asteroid (NEA). Eros was the first NEA to be discovered and the second-largest known. It was also the object of study of the NEAR Shoemaker mission, which sent a spacecraft to orbit the asteroid for one year beginning in 2000. Planetary scientists were unexpectedly able to land the spacecraft on the asteroid before it lost power.
Near-Earth Asteroids
433 Eros is an asteroid, or a relatively small, irregularly shaped space object that orbits the sun. Asteroids are believed to be matter left from the formation of the solar system about 4.6 billion years ago.
There are millions of asteroids in the solar system. Most of these are located in the asteroid belt, a doughnut-shaped ring of space between the orbits of Mars and Jupiter. The asteroid belt is about 2.2 to 3.2 astronomical units (AU), or 200 to 300 million miles, from the sun. Researchers theorize that after the gas giant Jupiter formed, the massive gravity surrounding it caused many small, nearby planetary bodies to crash into each other, creating asteroids.
Not all asteroids stay in the asteroid belt, however. Some asteroids are ejected from the belt when they collide with each other or get too close to the gravity surrounding Jupiter. The asteroids can be flung into the larger solar system. Near-Earth asteroids (NEAs) are asteroids that orbit within 0.3 AU (about 44.8 million kilometers, or about 31 million miles) of Earth. Eros is a NEA that has passed Earth at a distance of 0.178 AU.
NEAs are classified as one of three types (Amor, Aten, or Apollo) based on their average distance from the sun and the size and shape of their orbit. Eros is considered an Amor asteroid. Amor is the type of asteroid that approaches Earth but does not cross its orbit. However, like most other Amor asteroids, Eros does cross the orbit of the nearby planet Mars.
Asteroids vary greatly in size. The largest known asteroid, Ceres, measures about 952 kilometers (592 miles) in diameter. However, most asteroids are much smaller. Most asteroids are the size of small rocks. Eros is the second-largest NEA, at around seventeen kilometers in diameter.
Characteristics of Eros
Eros was the first NEA to be discovered. Two different observers spotted Eros on the same date in August 1898: Gustav Witt of Berlin, Germany, and Auguste Charlois of Nice, France. Eros attracted their attention because it was observed orbiting near Mars rather than in the asteroid belt, which defied astronomical knowledge of the time.
Eros is an S-type asteroid, or one that is mainly composed of silicates (stone) and metals such as iron and magnesium. S-class asteroids are among the brightest asteroids in the solar system due to their ability to reflect the light of the sun. They are also the most common type of asteroid found in the inner asteroid belt.
Eros is shaped like a giant peanut or a horse’s saddle. Two thicker, more rounded ends flank its thinner midsection. Craters and pits mark its surface. Scientists believe that these types of marks, which are seen on most asteroids, are the result of collisions with other objects in space. Eros is non-hazardous due to simulation data suggesting its fewer chances of collision with Earth. It is considered primordial solar system material because it was never subjected to melting and segregation. The average distance of Eros from the sun is 1.46 AU.
Eros circles the sun once every 1.76 Earth years, at an inclination of 10.8 degrees, and spins on its axis once every 5.27 hours. Its gravitational force is relatively weak but is strong enough to hold a spacecraft, as shown by the NEAR Shoemaker mission. Eros made relatively close approaches to Earth on January 31, 2012, and January 15, 2019, with a distance of 0.179 AU and 0.209 AU, respectively.
NEAR Shoemaker Mission
Eros was the first asteroid ever to be orbited by a space probe and to have the probe touch down on its surface. The Near-Earth Asteroid Rendezvous (NEAR) mission, later named the NEAR Shoemaker mission in honor of renowned geologist Eugene M. Shoemaker, sent the NEAR Shoemaker spacecraft to orbit Eros for one year beginning in 2000.
The mission was launched in February 1996 by NASA. The goal of the mission was to orbit the asteroid and send back data on its characteristics, including properties such as surface features, chemical composition, internal mass distribution, and magnetic field. The mission also sought to clarify the relationship among asteroids, comets, and meteorites, as well as to increase general understanding of the solar system. Although the spacecraft was not designed with landing gear, the mission ended with a touchdown of the spacecraft in the saddle region of Eros in February 2001. The spacecraft lost power shortly thereafter. It collected data from the Eros' surface that helped determine its elemental composition, internal structures, and crater density.
PRINCIPAL TERMS
- asteroid: a small, irregularly shaped celestial body made of rock, silicates, and metals.
- near-Earth asteroid (NEA): a small, irregularly shaped celestial body with an orbital path that brings it close to Earth. NEAs travel within 0.3 astronomical units (AU) of Earth’s orbit and within 1.3 AU of the sun. An astronomical unit is equal to about 149.6 million kilometers (about 93 million miles).
- S-type asteroid: one of three broad classes of asteroids. S-type ("silicaceous") asteroids are mainly composed of silicate (stone) and metals such as iron and nickel.
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