Looks like Earth has a new natural moon

The International Astronomical Union’s Minor Planet Center (MPC) announced late yesterday that Earth has a new “temporary captured object”: a tiny new moon apparently captured into Earth orbit three years ago. This object has been designated 2020 CD3. In a Minor Planet Electronic Circular (MPEC) for February 25, 2020, astronomers wrote that multiple observations confirmed:

… this object is temporarily bound to the Earth. No evidence of perturbations due to solar radiation pressure is seen, and no link to a known artificial object has been found. Further observations and dynamical studies are strongly encouraged.

2020 CD3 was discovered on February 15 by astronomers at the Catalina Sky Survey, based in Tucson, Arizona. More than 30 observations were made of the object by February 17, according to asteroid- and comet-hunter Kacper Wierzchos, one of its discoverers along with astronomer Theodore Pruyne. Those observations were needed to refine an orbit for the object, and to confirm it does appear to be orbiting Earth.

The object is very small and faint. Sunlight reflected from it helps provide an estimate of its diameter. The estimate is about 6 to 12 feet (1.9-3.5 meters) at this time, but that could easily change. Still … it’s small! It’s amazing astronomers can identify something so small orbiting Earth. Much of the information we have at this time about the object comes from Wierzchos, who is actively tweeting about it; you’ll find him at @WierzchosKacper. The following tweets are from yesterday. Apparently, these astronomers were holding off a bit in speaking openly about the object until the MPEC was published, but now they are. Expect more info as the days pass!

BIG NEWS (thread 1/3). Earth has a new temporarily captured object/Possible mini-moon called 2020 CD3. On the night of Feb. 15, my Catalina Sky Survey teammate Teddy Pruyne and I found a 20th magnitude object. Here are the discovery images. pic.twitter.com/zLkXyGAkZl — Kacper Wierzchos (@WierzchosKacper) February 26, 2020

(2/3) The object has just been announced by the MPC and its orbit shows that it entered Earth's orbit some three years ago. Here is a diagram of the orbit created with the orbit simulator written by Tony Dunn: pic.twitter.com/2wsJGtexiO — Kacper Wierzchos (@WierzchosKacper) February 26, 2020

(3/3) The object has a diameter between 1.9 – 3.5 m assuming a C-type asteroid albedo. But it's a big deal as out of ~ 1 million known asteroids, this is just the second asteroid known to orbit Earth (after 2006 RH120, which was also discovered by the Catalina Sky Survey). — Kacper Wierzchos (@WierzchosKacper) February 26, 2020

Bottom line: Earth apparently has a new natural satellite – albeit a temporary one – captured into orbit around our planet three years ago. The object has been designated 2020 CD3.