Earth is about to capture a new 'mini moon' (but it might not be a moon at all)

·2-min read
The March 5 _mini-Moon,î the apogee Moon, the most distant Full Moon of 2015. I processed this image with greatly enhanced vibrance, saturation and contrast to exaggerate the subtle differences in colour in the lunar maria, due to differences in the mineral content of the lava flows that formed the mare ~3.5 to 4 billion years ago. The relatively new impact crater, Tycho, is the bright area at bottom (south) on the luanr disk with bright splash rays emanating from the crater. I shot this with a TMB 92mm refractor with a 2x Barlow lens for an effective f-ratio of about f/12. This is a 1/125th second exposure at ISO100 with the Canon 60Da. (Photo by: Alan Dyer /VW PICS/Universal Images Group via Getty Images)
From October, Earth will have another, much smaller, moon. (VW PICS/Universal Images Group via Getty Images)

A new mini-moon might be about to join Earth’s orbit briefly, before being hurled back into space.

‘Minimoons' are only a few feet across, and each tends to do a stint of around a few months in orbit – before resuming their previous lives as asteroids.

But this particular mini-moon may be a little different – as experts have suggested it’s not a moon at all, but man-made space junk.

Specifically, it may be a discarded part of a rocket launched in 1966, experts have suggested.

The tiny object, known as 2020 SO, was spotted by the Pan-STARRS1 at the Haleakala Observatory on 17 September, ScienceAlert reports.

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It will be captured by Earth this October, and will pass close by Earth in December and February, Sky reports.

It will continue to orbit our planet until May next year.

Alice Gorman, of Flinders University in Australia, says that several measurements about 2020 SO suggest it’s not an asteroid, in an interview with Science Alert.

Vent flowing cryogenic fuel and T/C Rake mounted on a 1/10 scale model Centaur in the l0 x l0 Foot Supersonic Wind Tunnel. The fuel being used is liquid hydrogen. The point of the test is to determine how far to expel venting fuel from the rocket body to prevent explosion at the base of the vehicle. This vent is used as a safety valve for the fumes created when loading the fuel tanks during launch preparation. Liquid hydrogen has to be kept at a very low temperature. As it heats, it turns to gas and increases pressure in the tank. It therefore has to be vented overboard while the rocket sits on the pad.
A scale model of a Centaur rocket, used in the 1966 launch. (Getty)

Gorman said: "The velocity seems to be a big one. What I'm seeing is that it's just moving too slowly, which reflects its initial velocity. That's essentially a big giveaway."

These signs suggest that the object may be space junk, he added.

Astronomer Paul Chodas has suggested that the object is a Surveyor 2 Centaur rocket body, launched on 20 September 1966.

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Chodas suggests that the low Earth encounter velocity is too low even for material ejected from the moon, so it's unlikely to be a natural body.

Spectroscopy may be able to show if the object has been painted, the experts believe.

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"It would be interesting to do some reflectance spectroscopy, which would show how rough the surfaces are, how much it's been pitted and decayed from being bombarded by dust and micro meteorites,” said Gorman.

"It's human material that's been out in a different part of space. So, it would be interesting to compare that to the results you get from stuff in low Earth orbit, which is much, much denser in material."

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