Earth Has Captured a Temporary New “Mini-Moon” Called 2020 CD3 In Its Orbit

Earth rise from the Moon during Apollo 11 mission, 1969. (Credit: NASA)

Earth has a new companion: a mini-moon called 2020 CD3. On Feb. 15, scientists discovered a small rocky chunk that was captured by our planet’s gravity. But don’t get too excited, because it’s likely only a temporary fixture and moving away from our planet now. However, it could be a harbinger of new small moons to come..

Our planet has only one natural satellite, our moon, but for the last couple of years, there’s been another lurking out in space. Astronomers spotted what is likely a carbonaceous asteroid with the help of the Catalina Sky Survey. The mini-moon is between 6.2 and 11.5-feet (1.9 to 3.5-m) in diameter, and roughly the size of a car.

Typically, temporarily captured objects, like 2020 CD3, only hang around for a brief time (from a few months to a year or two) before they are flung back out into space, or in some cases, burn up in our planet’s atmosphere as they’re pulled in by Earth’s gravitational tug.  But according to astronomers, it’s been orbiting the Earth for up to three years now.

The celestial real estate encircling the Earth is pretty crowded, which is probably why we’ve just now noticed it. Asteroids — which are piles of planetary rubble, remnants left over from the birth of the solar system — are usually very small and dark, making them difficult to spot.

So, discovering 2020 CD3 is kind of a big deal. To date, there have been only a handful of proposed potential mini-moons with only one confirmed — an asteroid named 2006 RH120. The three-foot-wide space rock orbited the Earth for just over a year, from 2006-2007“Out of 1 million known asteroids, this is just the second asteroid known to orbit Earth,” Kacper Wierzchos, the astronomer who detected the object, said on Twitter.

The existence of 2020 CD3 is an exciting discovery for a number of reasons, including providing the chance to study asteroids up close. Most asteroids orbit between Mars and Jupiter, in the main asteroid belt and it takes sending a spacecraft out into the solar system to study one of these celestial objects in detail.

Mini-moon 2020 CD3 was detected by the Catalina Sky Survey and imaged by the Gemini Observatory. (Credit: Gemini Observatory)

2020 CD3 could provide astronomers with the chance to study asteroids in detail and better understand how they’re captured by planets. Unfortunately,  computer simulations indicate that the mini-moon could be back on a journey around the sun as early as April. That’s because it’s caught in a game of tug-of-war between the Earth and the moon.

Analysis of 2020 CD3’s orbital motion indicates it’s heavy for its size, which leads astronomers to believe it is in fact, an asteroid. But scientists will use the next few weeks to continue studying the enigmatic object in order to definitively determine whether it is indeed an asteroid or perhaps a rogue piece of space junk.

There’s no time to plan a mission to 2020 CD3, as the object is already growing fainter and fainter in images, but astronomers say it will likely be back in a few decades. With more advanced telescopes coming online in the near future, these types of sightings could become more and more common.

Why it matters: Objects like this one — which is thought to be a washing machine-sized asteroid captured by Earth’s gravity — could allow scientists to one day study space rocks without needing to head all the way out to the asteroid belt.

  • “Because they have such similar orbits to the Earth … they don’t take as much energy to get to, on average, so they could be good places for us to send spacecraft,” asteroid researcher Amy Mainzer told Axios.

What’s happening: The mini-moon, named 2020 CD3, has likely been orbiting Earth for the past year, but it’s taken until now for scientists to spot the small object.

  • The Catalina Sky Survey discovered 2020 CD3 on Feb. 15, marking only the second time in history that an object like this has been spotted.
  • According to NASA, the mini-moon has orbited Earth at least three times, with orbital periods that swing between 70 and 90 days, bringing it as far away as four times the distance between the Earth and our Moon.
  • The object’s closest approach to Earth was about 25,000 miles from the planet’s surface on Feb. 13.
  • 2020 CD3 is now expected to leave Earth behind early this month, escaping the planet’s gravitational pull and moving into orbit around the Sun.

What’s next: Scientists think there is likely some kind of mini-moon orbiting Earth at any given time.

  • Observatories expected to come online in the next few years will likely be able to spot far more of these objects than scientists are able to study today.
  • Space-based small satellite missions might even be able to one day meet up with a mini-moon to get a close-up look at it.

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