Near Earth Asteroid 2005 YU55

Most asteroids sit peacefully in the asteroid belt between Mars and Jupiter. Occasionally, some get kicked out due to tidal or gravitational forces between space objects, giving them their own orbit around the sun. Some of the stray asteroids pass fairly close to earth, and when they do we call them near earth asteroids. 

2005 YU55 imaged with the Arecibo radio  telescope

You may have heard talk on the news of a near earth asteroid called 2005 YU55 (pictured above). There's been a bit of hype about this object lately, but its just another member of the group of 8500+ near Earth objects that pass safely by Earth all the time. Now, "near" in the case of 2005 YU55 means that it will be 202,000 miles away from earth at its closest approach on November 8th, 2011. That's just a little bit closer than the moon is to Earth. So don't be alarmed by the news stories entitled "huge asteroid headed for close encounter with Earth"; there's nothing to worry about! NASA has assigned it a risk of 0 on their danger scale (ie. it's no big deal!)

Image credit:  NASA/JPL-Caltech

Comet, Meteor, or Asteroid?

Leonid Meteor Shower

It's a bird! It's a Plane! It's a comet! No wait, a meteor! Or maybe an Asteroid? I know I'm guilty of using these three word synonymously, but each one has a distinct astronomical definition.

Meteoroids are small bodies that range from the size of a grain of sand to the size of a car. Meteoroids that enter Earth's atmosphere are called meteors and when they fall in groups they are called meteor showers. Most meteors break apart completely as they fall through Earth's atmosphere, but those that survive and impact the ground are called meteorites.

Comets are large bodies in the solar system made mostly of ice, dust and small rocks. They range in size from 100m (~300ft) to 100km (~62 miles) and originate from the outer edges of our solar system. Comets are different from other astronomical bodies because they have a visible tail resulting from the solar wind stripping particles off of the comet. About 4,200 different comets have documented in our solar system, and pass by Earth periodically. Comets continue to orbit the sun until they either break apart from solar radiation, crash into the sun, or get ejected from the solar system.

Asteroids are a broad term for pretty much any body in the solar system that's not a planet, moon, meteoroid, or comet. They can be any size or shape and exist in two main areas: the asteroid belt between Mars and Jupiter and the Kuiper belt beyond the orbit of Neptune. Some asteroids orbit closer the to the planets. Astronomers are working on finding and classifying all such asteroids so we can watch for any that might be on a collision course towards Earth!

Image Credit:  Geek.com/gearlog