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When NASA scientists recently tracked the orbits of two space rocks as they approached Earththey discovered a surprise: one of the asteroids has a small moon.
Astronomers regularly track the trajectories of asteroids to ensure that none of them are on a potential collision course with our planet.
While none of the recent asteroids have passed within a worrying distance, space rocks could provide valuable information that NASA uses to prepare for any possible future collision scenarios.
Asteroids, which are remnants from the formation of the solar system, are also of interest because capturing details about their size, orbit and composition can reveal information about our corner of the cosmos.
Astronomers at NASA’s Jet Propulsion Laboratory, located in Pasadena, California, used something called planetary radar through the Deep Space Network to track and image the asteroids.
The Deep Space Network is a system of radio antennas on Earth that helps the agency communicate with spacecraft exploring our solar system and releases radio waves to act as radar in space.
Spotting a little moon
The first space rock, asteroid 2011 UL21, passed Earth on June 27 at a distance of 4.1 million miles (6.6 million kilometers), or 17 times the distance between the Earth and the Moon. first discovered the asteroid in 2011 using the Catalina Sky Survey in Tucson, Arizona. But since the space rock was first spotted, its flyby of Earth in June was the closest it came to our planet that radar could see.
Astronomers transmitted radio waves from the 70-meter-wide satellite dish of the Goldstone Solar System Radar near Barstow, California, to the space rock. The waves reflected off the asteroid and traveled back to the network’s satellite dish antenna.
Researchers have designated the nearly mile-wide (1.5 km wide) asteroid as potentially hazardous, meaning it has a chance of impacting Earth in the future. But astronomers don’t think it will pose a threat to our planet in the near future, after calculating its future orbits and determining that it won’t get too close to Earth.
Radar images showed that the asteroid is roughly spherical and is part of a pair, called a binary system. The space rock has a small moon orbiting it at a distance of 3 kilometers.
“About two-thirds of asteroids this size are thought to be binary systems, and their discovery is particularly important because we can use measurements of their relative positions to estimate their orbits, masses and mutual densities, which provide important information about how they may have formed,” Lance Benner, the JPL principal scientist who led the observations, said in a statement.
NASA missions, including the Lucy probe, which will explore a mysterious population of space rocks called Trojans later this decade, have helped reveal how many there are moons around asteroids in our solar system.
And the DART mission intentionally crashed into a moon called Dimorphos, which orbits a larger asteroid called Didymos, to change the movement of a celestial body in space for the first time as a way to test asteroid deflection technology in 2022.
A space rock surprise
Sometimes astronomers don’t know that an asteroid is in an orbit that takes it close to Earth until just before it approaches. That uncertainty is part of the reason NASA is stepping up efforts to better understand the population of asteroids closest to our world.
Researchers discovered asteroid 2024 MK just 13 days before it passed by Earth, passing at a distance of just 184,000 miles (295,000 kilometers) from our planet – just over three-quarters the distance between Earth and the Moon – on June 29 .
The Asteroid Terrestrial Impact Early Warning System, or ATLAS, at Sutherland Observation Station in South Africa first spotted the space rock on June 16. Although it is also considered potentially dangerous, the asteroid does not appear to be on a worrying trajectory towards Earth. shortly.
Astronomers sent radio waves to the space rock and captured a detailed image of asteroid 2024 MK. 10 meter wide boulders, as well as concave points and ridges, cover its surface. The asteroid measures 150 meters wide and appears angular and elongated, while also having some prominent flat and rounded areas.
As the space rock passed by our planet and encountered Earth’s gravity, its orbit changed. Now, the asteroid’s 3.3-year trip around the Sun has been shortened by about 24 days.
Objects the size of asteroid 2024 MK only come close to Earth every two decades, so astronomers collected as much data as they could.
“This was an extraordinary opportunity to investigate the physical properties and obtain detailed images of a near-Earth asteroid,” said Benner.
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