The Christmas asteroid challenge starts tonight. Here's how to join in

An illustration of the Christmas asteroid as it approaches Earth this December offering amateur astronomers the chance to spot it.
An illustration of the Christmas asteroid as it approaches Earth this December offering amateur astronomers the chance to spot it. (Image credit: NASA/Robert Lea)

This year Earth is getting a very special guest for Christmas.

An asteroid that could be as large as the Great Pyramid of Giza makes its close approach today and skywatchers have been challenged to spot it. The European Space Agency (ESA) issued the challenge to spot the Christmas asteroid, officially designated 2015 RN35, and encouraged anyone who does so to share their observation on social media using the hashtag #ESAChristmasAsteroid, adding information about themselves and from where they spotted the space rock. 

The challenge starts in the early morning hours on Thursday (Dec. 15), when 2015 RN35 comes to within around 430,000 miles (686,000 kilometers) of Earth, around twice the distance to the moon, at 3:12 a.m. EST (0812 am GMT). 

Related: Amateur astronomers challenged to spot an asteroid for Christmas

Budding asteroid hunters will have until next week to spot the Christmas asteroid as despite traveling at an estimated speed of around 13,500 mph (21,700 km/h) past Earth, 2015 RN35 will remain visible until Monday (Dec. 19).

With a magnitude of around 14, making it about as bright as Pluto, it won't take a James Webb Space Telescope in your backyard to spot the Christmas asteroid, either. In good viewing conditions with clear and dark skies, 2015 RN35 should be visible with telescopes that are 11.8 inches (30 centimeters) and larger.

The ESA's challenge offers citizen scientists the chance to get in on the ground floor of discovery when it comes to 2015 RN35, which was first identified in 2015. That's because despite having a rough estimate of this asteroid's size, between 200 to 460 feet (60 and 140 meters), and knowing it takes 654 days to orbit the sun, little else is known about this space rock including its composition.


A Celestron telescope on a white background

(Image credit: Celestron)

Want to try to spot the Christmas asteroid for yourself? You're going to need a telescope. We recommend the Celestron Astro Fi 102 as the top pick in our best beginner's telescope guide.

The Christmas asteroid challenge coincidences with the release of the ESA's free-to-use Near-Earth Object (NEO) toolkit which lets users visualize the orbit of asteroids around the sun and their close flybys past Earth. The toolkit lets the general public see how scientists study mid-sized NEO asteroids like 2015 RN35 which despite not posing the risk of hitting Earth for at least 100 years could help gather information about similar-sized Potentially Hazardous Objects (PHOs).

Though these don't pose the same level of risk as massive "planet-killing asteroids" like the one that struck our planet 65 million years ago and wiped out over half of its species including the dinosaurs, mid-sized asteroids could still cause havoc at a local level if they were to hit Earth. 

Read more: Asteroid apocalypse: How big must a space rock be to end human civilization?

That means while 2015 RN35 won't impact Earth, the ESA is seizing the opportunity to ensure its close approach has an impact on the message that asteroid detection and planetary defense is something we should all be getting involved in. 

Editor's Note: If you snap a picture of the Christmas asteroid 2015 RN35 and would like to share it with's readers, send your photo(s), comments, and your name and location to

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Robert Lea
Senior Writer

Robert Lea is a science journalist in the U.K. whose articles have been published in Physics World, New Scientist, Astronomy Magazine, All About Space, Newsweek and ZME Science. He also writes about science communication for Elsevier and the European Journal of Physics. Rob holds a bachelor of science degree in physics and astronomy from the U.K.’s Open University. Follow him on Twitter @sciencef1rst.