by Sign up for CNN’s Wonder Theory science newsletter. Explore the universe with news on exciting discoveries, scientific advances and more.
When NASA scientists recently tracked the orbits of two space rocks as they neared Earth, they found a surprise: One of the asteroids is a small moon.
Astronomers regularly track the trajectories of asteroids to ensure that none are on a potential collision course with our planet.
Although neither of the recent asteroids whizzed by much more worrisome, the space rocks are able to give valuable information that NASA uses to prepare for any possible collision scenarios in the future.
Asteroids, which are remnants from the formation of the solar system, are also of interest because capturing data about their size, orbit and composition can reveal insights about our corner of the cosmos.
Astronomers at NASA’s Jet Propulsion Laboratory, located in Pasadena, California, used something called a planetary radar through the Deep Space Network to track and take images of the asteroids.
The Deep Space Network is a radio antenna system on Earth that helps the agency communicate with spacecraft exploring our solar system and emits radio waves to act as radar across space.
A tiny moon spot
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 Earth and the moon. Researchers first discovered the asteroid in 2011 using the Catalina Sky Survey in Tucson, Arizona. But since the space rock was first spotted, its June flyby of Earth is the closest to our planet that has been imaged by radar.
Astronomers transmitted radio waves from the 230-foot (70-meter wide) Goldstone Solar System Radar satellite dish, near Barstow, California, to the rock. The waves were reflected off the asteroid and traveled back to the network satellite dish antenna.
Researchers have designated the nearly mile-wide (1.5 kilometer wide) asteroid as potentially hazardous, meaning it has a chance of impacting Earth in the future. But astronomers do not think it will pose a threat to our planet for the foreseeable future after calculating its future orbit and determining that it will not come too close to Earth.
The radar images showed that the asteroid is roughly spherical and is one of a pair, known as a binary system. The space rock has a small moon as it orbits from a distance of 1.9 miles (3 kilometers).
“About two-thirds of asteroids of 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 relative densities, which which provides important information about how they may have formed,” Lance Benner, principal scientist at JPL who led the observations, said in a statement.
NASA missions, including the Lucy spacecraft that will explore a population of mysterious space rocks known as the Trojans later this decade, have helped reveal how many moons there are around asteroids in our solar system.
And the DART mission intentionally crashed into a moonlet called Dimorphos, orbiting a larger asteroid called Didymos, to change the motion of a celestial body in space for the first time as a way to test asteroid deflection technology in 2022.
Space rock wonder
Sometimes, astronomers do not know that an asteroid is in an orbit that brings it close to Earth until it makes a close approach. That uncertainty is part of the reason NASA is stepping up efforts to better understand the population of asteroids closest to our world.
The researchers discovered asteroid 2024 MK just 13 days before it flew by Earth, passing just 184,000 miles (295,000 kilometers) from our planet – just over three-quarters of the distance between Earth and the moon – on 29 June.
The space rock was spotted by the Terrestrial Impact Alert System, or ATLAS, at the Sutherland Observing Station in South Africa on June 16. Although it is also considered potentially hazardous, the asteroid does not appear to be on a worrisome trajectory with respect to Earth. anytime soon.
Astronomers sent radio waves to the space rock and captured a detailed image of the asteroid 2024 MK. Thirty-foot-wide (10-meter-wide) boulders, along with concave spots and ridges, litter its surface. The asteroid measures 500 feet (150 meters) wide and appears angular and elongated while also having several visible flat and even areas.
As the space rock passed around 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 few years, so astronomers gathered as much data as they could.
“This was a great opportunity to investigate the physical properties and obtain detailed images of a near-Earth asteroid,” said Benner.
For more CNN news and newsletters create an account at CNN.com
