Watch a Large Asteroid Streak Through the Night Sky

Only a small telescope will be needed

A composite image of asteroid 2014 JO25 created with data from NASA's Goldstone Solar System Radar. NASA/JPL-Caltech/GSSR

A large asteroid will swing by the Earth on Wednesday April, 19th. The 2,000-foot wide space rock will pass within 1.1 million miles of our planet, a distance about 4.6 times the interval between the Earth and the Moon, according to a press release from NASA.

Vaguely alarming headlines notwithstanding, the asteroid has no chance of colliding with Earth, according to the release.

While several small asteroids buzz through the near space of Earth every week, this asteroid will be the largest to visit since the 3.1-mile-diameter Toutatis zoomed by in 2004. Asteroid watchers will have to wait until 2027 for the next chance to appreciate the movements of the solar system, when asteroid 1999 AN10 whizzes by at one lunar distance.

This week's asteroid was discovered three years ago in May and dubbed 2014 JO25. Astronomers working on the Catalina Sky Survey near Tucson, Arizona, discovered the object and estimated its size and brightness. Additional astronomy by Joseph Masiero, a scientist at the Jet Propulsion Laboratory in California, helped determine the exact orbital path the asteroid carves through the solar system. This encounter is the closest the asteroid has come for at least 400 years, according to the researchers.

Armed with those calculations, astronomers will be able to aim telescopes at the passing rock on its visit this time around. Two large systems in the United States are being brought in for the task. There's the Goldstone Solar System Radar, a system involving a huge transmitter and receiver in the desert near Barstow, California. And there's the Arecibo Observatory, a large radio telescope suspended over a karst sinkhole in Arecibo, Puerto Rico.

But amateur astronomers with their own small telescopes will be able join the fun as well, writes Fiza Pirani for The Atlanta Journal-Constitution. Astronomers have nicknamed the asteroid "The Rock" because it's as massive as the Rock of Gibraltar, she writes. It will travel about half a degree of the sky in about half an hour, a speed fast enough that its motion will be visible against the backdrop of stars. And "The Rock" is about twice as bright as the moon, thanks to a relatively reflective surface, so should be visible through backyard telescopes. 

Skywatchers in the U.S. had their first chance to see the asteroid on Tuesday, April 18th in the evening. By nightfall on Wednesday, it reaches the constellation called Coma Berenices and reaches its brightest glow at +11 magnitude. On Thursday night, the asteroid will appear a little dimmer and move into the Cup of Virgo.

Bob King, writing for Sky and Telescope, has viewing tips and charts to help hopeful skywatchers locate the asteroid. But don’t get caught up in its exact locale at each moment. King writes:

"The key to spotting the asteroid is to allow time to identify and get familiar with the star field the asteroid will pass through 10 to 15 minutes in advance — then lay in wait for the moving object. Don't be surprised if 2014 JO25 deviates a little from the predicted path depending on parallax and late changes to its orbit, so keep watch not only on the path but around it, too."

The tumbling motion of the asteroid may even be noticeable as changes in the apparent brightness.

The asteroid isn't the only object visible in the sky at this time. According to NASA's press release, the comet PanSTARRS C/2015 ER61 can be spotted in the dawn sky with binoculars or a small telescope.

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