Aten Asteroids
Aten asteroids are a specific category of near-Earth asteroids (NEAs) characterized by their orbital paths that primarily reside within the orbit of Earth but also cross it. Named after the first identified Aten asteroid, 2062 Aten, discovered in 1976, these asteroids are tracked closely by astronomers due to their potential to collide with Earth. As of 2020, they make up about 7 percent of known NEAs, which are classified based on their distance from the sun and their orbital behaviors. Aten asteroids are part of a broader group of celestial bodies that include both asteroids and comets, thought to be remnants from the early solar system formation approximately 4.6 billion years ago.
The study of these asteroids is important not only for understanding the solar system's history but also for assessing the risk of potential impacts on Earth. Past collisions, such as the one that created the Chicxulub crater, have had significant effects on Earth’s biosphere, while more recent events, like the 2013 explosion over Russia, highlight the ongoing threats posed by NEAs. NASA has established programs to detect and monitor NEAs, employing advanced technologies and missions to better understand and mitigate the risks associated with these celestial bodies.
Aten Asteroids
FIELDS OF STUDY: Astronomy; Observational Astronomy
ABSTRACT: Aten asteroids are a type of near-Earth asteroid (NEA). These objects orbit around the sun close enough to Earth to cross its orbit. NEAs are important because of the information they can offer about the early solar system as well as their potential to collide with Earth.
Near-Earth Asteroids
Aten asteroids are a type of asteroid that travels in the solar system close to Earth, named after 2062 Aten. The first known asteroid of this type, it was discovered in 1976 by scientist Eleanor Helin (1932–2009) at Palomar Observatory in San Diego, California. Asteroids are small, irregularly shaped space bodies. Like other space objects, they travel around the sun in elliptical (oval-shaped) paths. Asteroids are composed mainly of rock but may also include minerals and metals. Their rocky surfaces are full of visible craters and pits, which show where the asteroids have been struck by other objects in space.
Asteroids vary greatly in size. The largest known asteroid, Ceres, measures about 966 kilometers (600 miles) in diameter and is so large that it is considered a dwarf planet. However, most asteroids are much smaller; in fact, many asteroids are only the size of small rocks.
The solar system contains millions of asteroids. Most are found within the asteroid belt, a doughnut-shaped ring located between the orbits of Mars and Jupiter, about 2 to 4 astronomical units (AU) from the sun, a distance of about 300 million to 600 million kilometers (186 to 370 million miles). Sometimes asteroids within the asteroid belt are pushed into the solar system. For example, if two asteroids collide, one or both of them can be flung into space. Similarly, an encounter with Jupiter’s massive gravity can have the same result. These asteroids sometimes end up orbiting close to Earth and the sun. Those that come within 0.3 AU, or around 45 million kilometers (28 million miles), of Earth are called near-Earth asteroids (NEAs).
Several categories of NEAs exist. These categories are distinguished by characteristics such as the asteroids’ average distance from the sun (near and far) as well as the orbital paths they take through space. As of 2020, about 7 percent of known NEAs are considered Aten asteroids. Because their orbit is smaller than Earth’s, Aten asteroids take an orbital path mainly inside of Earth’s orbit but also cross it. Astronomers keep a close eye on known Aten asteroids because they come close enough to Earth to collide with it.
NEAs are also known as near-Earth objects (NEOs). NEOs include both comets and asteroids that have been pulled closer to Earth’s orbit by gravitational forces, mainly near the four inner planets (Mars, Mercury, Earth, and Venus).
NEA Impacts on Earth
Scientists are interested in asteroids and other NEOs because they are thought to be remaining debris from the formation of the solar system about 4.6 billion years ago. They can provide valuable information about the early solar system.
Additionally, thousands of NEAs come close enough to Earth to raise concerns about potential collisions. Although smaller space objects such as meteors collide with Earth frequently, these objects are usually so small that they burn up in the atmosphere before they reach the planet’s surface and do much damage.
However, major collisions between Earth and NEAs have occurred. For example, a huge crater near Chicxulub, Mexico, is believed to be evidence of a past collision between Earth and a large NEA. Many experts believe this collision, which probably had the force of a nuclear explosion, played a major role in the mass extinction that occurred over 65 million years ago. During this extinction, dinosaurs and other large life forms on the planet died out.
Other NEAs have collided with Earth in more modern times. For example, in February 2013, a relatively small NEA exploded over Russia, releasing more energy into the atmosphere than a large atomic bomb. Another NEA, and Aten asteroid called Apophis, which was discovered in 2004, is expected to pass close to Earth in 2029 and 2068; scientists initially thought this posed a slight risk of collision. However, scientists at the US National Aeronautics and Space Administration (NASA) conducted radar studies on the orbital path of the Apophis in 2021, and concluded that Earth would be safe from any serious collision with Apophis for the next one hundred years.
Near-Earth Object Program
The NASA created the Near-Earth Object Program (NEOP) to detect and track NEOs. This program uses teams around the world to learn more about NEOs and to eventually develop technologies to divert NEOs away from Earth. These teams, such as Deep Space Network (Goldstone, California) and Arecibo Observatory (Puerto Rico), use state-of-the-art technologies to identify and track NEOs. They use radar to bounce radio waves off asteroids in space to provide valuable information. Radar is even capable of generating surface images.
Additionally, NASA has successfully launched many robotic spacecraft missions to study NEOs. For example, the NEAR Shoemaker mission was launched in 1996 to study the asteroid Eros, while the Dawn mission was launched in 2007 to study asteroids Vesta and Ceres. After exploring Vesta in 2012 and Ceres in 2015, the mission ended in 2018.
The Asteroid Redirect Mission (ARM) was NASA’s first attempt to capture and redirect an NEA in order to allow it to be studied directly by humans. ARM was developing technologies that could redirect an NEA to orbit around Earth’s moon. Astronauts would then be able to land on and explore the asteroid. This mission was scheduled for the 2020s. However, in 2017, ARM got canceled due to budget cuts during US president Donald Trump’s tenure. In 2021, NASA started the project Double Asteroid Redirection Test (DART) to change the course of an Earth-bound asteroid through kinetic impact.
PRINCIPAL TERMs
- 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 AU is equal to about 149.6 million kilometers (about 93 million miles).
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