Dear Iggy

Dear Iggy,
How far away are the stars?
- Kira, age 10

Hi Kira,

According to J. Newlin, the Science Museum's Director of Physical Sciences and Technology, our ancient ancestors imagined that the sky was like a big bowl turned upside-down over the Earth, with all the stars on the inside. The Greeks and Arabs spoke about the "sphere of fixed stars" which turned around the Earth, one rotation every day. If the stars were located on the surface of a sphere with the Earth at the center, then it makes sense to believe that they were all the same distance from us.

Today, we know that the stars are at very different distances from us. J. explains that the nearest stars are in our own galaxy. They're the ones with names you may have heard: Sirius, Arcturus, and Alpha Centauri. Many more stars lie in other far away galaxies.

The nearest star to Earth is our Sun, and it's 93 million miles away. It would take us eight minutes to get there if we were traveling the speed of light. If you wanted to take a fast rocket there, it would take you 106 days traveling at 36,500 miles per hour.

Beyond the sun, we'd have to go 4.2 light years to get to Proxima Centauri, which is close to Alpha Centauri, one of the brightest stars in the sky. Let's calculate that distance! Light travels at 186,000 miles per second. We'd have to go 186,000 miles per second x 60 seconds x 60 minutes x 24 hours x 365 days x 4.2 years...that's more than 24 trillion miles!

Nobody knows how far away the farthest star is. The farthest star you can see without a telescope (the Andromeda galaxy—not even a star at all!) is almost 2 1/2 million light years away.

Look out some winter night for Sirius, the Dog Star. First, find the belt stars in Orion. Hold your two fists up at arm’s length in line with Orion's belt and to the left. The very bright star to the left of your fists is Sirius. It's about 8.6 light years away.

Keep those questions coming!
Iggy

Iggy, the beloved metal iguana that greets school field trip visitors at the Science Museum's Education Entrance, has been guarding the museum for more than 25 years. That's a lot of experience with science learning and fun! Because of his long history with the Science Museum, Iggy invites you to ask him your science questions. If he doesn't know the answer, he'll consult our staff of scientists to find it for you!

Iggy's looking forward to hearing from YOU soon! Email him at .