A massive asteroid estimated at 470 meters in diameter (about 1,542 feet) will fly by Earth on Halloween morning about 310,000 miles away—about 30 percent further from the Earth than the moon is, according to NASA's Jet Propulsion Laboratory. The huge rock will pass even closer to the moon, about 180,000 miles, as it travels at 78,000 miles per hour.
On the night of October 30 and the morning of Halloween, you will be able to see the asteroid with a telescope as it is crossing the constellation Orion. It is of particular interest to astronomers because it could be a fragment broken off of a comet. Closest approach is 11:14 am Eastern time on October 31. Asteroid 2015 TB 145 will be the largest asteroid to pass close to earth until 2027.
More eyes on the sky
The Halloween asteroid poses no danger to Earth, but what's mildly alarming is that even with its close pass, 2015 TB 145 was discovered only 10 days ago by the Pan-STARRS telescope at the University of Hawaii. Discovered just 21 days before its closest approach, 2015 TB 145 is a reminder of the ominous comment that NASA Administrator Charles Bolden made to the U.S. House Science, Space, and Technology Committee in March 2013: "From the information we have, we don't know of an asteroid that will threaten the population of the United States. But if it's coming in three weeks…pray."
Source: By Jay Bennett http://www.popularmechanics.com/space/news/a17849/close-call-with-a-massive-asteroid-on-halloween/