Dimorphos got its name last week, just in time to reflect on the importance of understanding the threat from near-Earth asteroids. Near-Earth objects are asteroids and comets whose orbits place them 30 million miles from Earth.
In 1908, a powerful asteroid hit the Podkamennaya Tunguska River in a remote Russian Siberian forest. The event razed trees and destroyed forests in 770 square miles, equivalent to the size of three-quarters of the US state of Rhode Island. The impact knocked people to the ground in a city 40 miles away.
In 2013, an asteroid entered Earth’s atmosphere above Chelyabinsk, Russia. It exploded in midair, releasing 20 to 30 times more energy than that of the first atomic bombs, generating a brightness greater than that of the sun, exuding heat, damaging more than 7,000 buildings and injuring more than 1,000 people. The blast wave smashed the windows 58 miles away. It was not detected because the asteroid came from the same direction and path as the sun.
And it explains why astronomers and the Asteroid Day group want people to be aware. Detecting the threat of near-Earth objects, or NEOs, that could cause serious damage is a primary focus of NASA and other space organizations around the world.
And in 2022, NASA will test its asteroid deflection technology to see how it impacts the motion of a near-Earth asteroid in space.
Didymos and Dimorphos
Two decades ago, a binary system involving a near-Earth asteroid was discovered to have an orbiting moon, called Didymos. In Greek, Didymos means “twin,” which was used to describe how the largest asteroid, which is nearly half a mile in diameter, is orbited by a smaller moon that is 525 feet in diameter. At that time, the moon was known as Didymos b.
But when the binary system became the target of NASA’s 2022 Double Asteroid Redirect Test, or DART, mission, it was time for the moon to get an official name.
Last week, the International Astronomical Union officially named the moon Dimorphos. Kleomenis Tsiganis, a planetary scientist at Aristotle University of Thessaloniki and a member of the DART team, suggested the name.
“Dimorphos, which means ‘two shapes’, reflects the status of this object as the first celestial body to have the ‘shape’ of its orbit significantly changed by humanity, in this case, by the impact of DART,” he said. Tsiganis. As such, it will be the first object known to humans in two very different ways, one seen by DART before impact and the other seen by Hera from the European Space Agency a few years later. “
By the end of 2022, Didymos and Dimorphos will be relatively close to Earth and 6,835,083 miles from our planet, the perfect time for the DART mission to occur.
DART will deliberately crash into Dimorphos to change the motion of the asteroid in space, according to NASA. This collision will be recorded by LICIACube, a CubeSat or cube satellite provided by the Italian Space Agency. The CubeSat will travel on DART and then deploy from it before impact so you can record what happens.
“Astronomers will be able to compare observations of ground-based telescopes before and after the kinetic impact of DART to determine how much Dimorphos’s orbital period changed,” said Tom Statler, a DART program scientist at NASA headquarters, in a statement. “That is the key measure that will tell us how the asteroid responded to our diversion effort.”
A few years after the impact, the Hera mission of the European Space Agency will carry out a follow-up investigation of Didymos and Dimorphos.
While the DART mission was developed for NASA’s Planetary Defense Coordination Office and was administered by the Johns Hopkins University Applied Physics Laboratory, the mission team will work with the Hero mission team under international collaboration. known as Asteroid Impact and Deflection Assessment, or AIDA.
“DART is a first step in testing methods for the diversion of dangerous asteroids,” Andrea Riley, a DART program executive at NASA headquarters, said in a statement. “Potentially dangerous asteroids are a global concern, and we are excited to work with our Italian and European colleagues to collect the most accurate data possible from this kinetic impact deflection demonstration.”
A first mission
Dimorphos was chosen for this mission because its size is relative to asteroids that could pose a threat to Earth.
DART will collide with Dimorphos moving at 14,763.8 miles per hour. A DART camera, called DRACO, and autonomous navigation software will help the spacecraft detect and collide with Dimorphos.
This rapid impact will only change Dimorphos speed while orbiting Didymos by 1%, which doesn’t sound like much, but it will change the moon’s orbital period in several minutes. That change can be observed and measured from ground-based telescopes on Earth. It will also be the first time that humans have altered the dynamics of a body in the solar system in a measurable way, according to the European Space Agency.
The DART launch window opens in July 2021 with the expected impact in 2022.
Three years after the impact, Hera will arrive to study Dimorphos in detail, measure the moon’s physical properties, study the impact of DART, and study its orbit.
This may seem like a long time to wait between impact and follow-up, but it builds on lessons learned in the past.
In July 2005, NASA’s Deep Impact spacecraft launched an 815-pound copper impact into a comet, Tempel 1. But the spacecraft was unable to see the resulting crater because the impact released tons of dust and ice. However, NASA’s Stardust mission in 2011 was able to characterize the impact: a 492-foot wound.
Together, the valuable data collected by DART and Hero will contribute to planetary defense strategies, especially by understanding what kind of force is needed to change the orbit of a near-Earth asteroid that can collide with our planet.
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