Asteroid 2013ET, Comet ISON, Pan-STARRS: NASA says asteroid this weekend is one of many cool sights

An asteroid the size of a city block will pass by Earth this weekend, but have no fear: There's no danger of it hitting our planet.

The 80-meter wide asteroid makes its closest approach to Earth on Saturday afternoon in the United States. It will be about 975,000 kilometers (604,500 miles) away, said Don Yeomans, a planetary scientist at NASA's Jet Propulsion Laboratory in California. That's about 2 1/2 times the distance from the Earth to the moon.

"It's a pretty good size, but it's not getting that close, at least by recent standards," Yeomans said.

The 80-meter (262 feet) wide asteroid was only discovered Sunday because search telescopes can't find objects of that size until they get close.

Now that it's in view, Yeomans said, astronomers can accurately chart its orbit. And they assure us this space rock will only make a fly-by.

The asteroid is already observable in the night sky, even with sophisticated amateur telescopes, he said. But get a good look at it now, because after the close approach, the asteroid will appear in the daytime sky and be harder to see, Yeomans said.

Dubbed 2013ET (which is simply code for when it was discovered), the asteroid is the latest object from space to come near our planet.

A meteor exploded over southwestern Russia last month, injuring more than 1,500 people, Russian authorities said. In what astronomers have said was an unrelated coincidence, a larger asteroid passed by Earth the same day, about 17,100 miles away at its closest.

This Friday, a comet called Pan-STARRS will come into view over the Northern Hemisphere. A second comet, called ISON, may be visible in November. Scientists say neither comet poses a threat to Earth.