The exact size of the newly discovered is not known. But both the low-end estimate (left) and high-end estimate (right) are bugger than the Trump Tower. (Slooh.com)

Several hours before children dressed in their Halloween finery knock on your door, a newly discovered large asteroid dubbed 2015 TB145 offers a cosmic treat.

Zipping across the heavens at a blistering 78,000 miles per hour, the asteroid hurtles by the Earth on Saturday, Oct. 31 – at a relatively close yet safe distance – at about 1:05 p.m., according to NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, Calif. It was discovered only weeks ago, on Oct. 10.

The close approach on Saturday will be about 1.3 times the distance from Earth to the moon, or roughly 300,000 miles away from our own planet.

“The last approach closer than this [from an asteroid approximately the same size] was by 2004 XP14 in July 2006 at 1.1 lunar distances,” says NASA.

Without any intervening discoveries, a larger asteroid named 1999 AN10 will pass close to Earth – at about one lunar distance, or 238,000 miles – in August 2027, NASA says.

[An unexpected asteroid (or maybe comet) will fly surprisingly close to Earth on Halloween]

This new large asteroid 2015 TB145 – up to 2,132 feet in diameter – is the size of a large battleship or an aircraft carrier, explains Geoff Chester, astronomer at the U.S. Naval Observatory.

It was discovered by the University of Hawaii’s Pan-STARRS-1 (Panoramic Survey Telescope and Rapid Response System) on Haleakala, Maui. The search is part of the Near-Earth Object program, funded by NASA.

Watching ‘Spooky’ live

Grab a handful of candy corn and fire up your web browser because during daylight in North America, space broadcaster Slooh.com – nicknaming the asteroid the whimsical “Spooky” – will deliver play-by-play event coverage starting 12:30 p.m. on Saturday.  Hosted by astronomers Paul Cox and Bob Berman, Slooh will possibly use its telescopic observatory in the Canary Islands, and offer views from partner telescopes in Norway, Lithuania, Russia, China as well as other radio telescope observatories.

“Tracking and imaging ‘Spooky’ on Halloween, when it’s making its closest approach to Earth is tricky,” says Cox. “Because of its proximity to Earth, we need to employ some special techniques to track and image it, and treat the asteroid as a ‘satellite’ – in the same way we’ve tracked the International Space Station during special live shows.”

Cox explains that the asteroid’s apparent brightness increases dramatically as it draws closer to Earth this week, as it will appear as a 10th magnitude point of light moving rapidly against the background of stars – even at closest approach.  “Even the largest optical telescope will only show a point of light,” he says.

Radio telescopes are able to map the shape and size of the asteroid, says Cox, “This [flyby] may even show us whether it is an asteroid or a ‘dead’ comet.”

Observing the rock

If you wish to try observing during the night hours of Oct. 30/Oct. 31, you’ll need a telescope or large binoculars. On the evening of Friday Oct. 30, the asteroid 2015 TB145 rises around 10 p.m., in the east, as the bright, waning gibbous moon loiters above the Orion and Taurus constellations.


This is a graphic depicting the orbit of asteroid 2015 TB145. The asteroid will safely fly past Earth slightly farther out than the moon’s orbit on Oct. 31 at 10:05 a.m. Pacific (1:05 p.m. EDT and 17:05 UTC). (NASA/JPL-Caltech)

The asteroid will be about 12th magnitude, dim beyond what the human eye can see. At about 10 p.m., it will be on the star Pi 2 Orionis, in the constellation Orion’s left-hand shield, according to Chester.  The asteroid can be found two hours later – at midnight – a half-degree north of Pi 1 Orionis at 11.7 magnitude – still in the shield.

By 2 a.m. on Saturday morning (Oct. 31), the big rock is about 1.5 degrees away (from our perspective) the star Omicron 2 Orionis. By then, the asteroid has brightened to 11.4 magnitude, according to Chester.  At about 5 a.m., the asteroid has brightened to 11th magnitude and can be seen overhead in the constellation Taurus. At about 6 a.m. it is close to the star Zeta Tauri (seen above Orion’s head) – and the asteroid is 10.7 magnitude. As twilight washes out the night sky at 6:30 a.m., the asteroid passes close to the Crab Nebula.