Welcome

As you may have gathered, I’m an astronomer and my name is merrdiff… er… Meredith.

I like to write, and I think a lot about astronomy. You can find me on twitter @merrdiff. But not everything in astronomy is readily explained in 140 characters or fewer, and thus: a blog.

Why “merrdiff”? It’s a nickname that evolved at summer camp. Only two syllables, easy to shout across a room, similar enough to my full name to generate a response. The original spelling may have been closer to “mur-DIFF!” On a bad day it can resemble more of a dog bark than a word or a name. But with “merrdiff” you have a lower chance of accidentally barking, and a higher chance chance of remembering my real name, which I do prefer in real life.

So, welcome aboard. To kick things off, here is a picture of both of us:

Image
Earth and Moon as viewed from Cassini at Saturn.
Image from http://saturn.jpl.nasa.gov/photos/raw/rawimagedetails/index.cfm?imageID=294988.

This picture was taken on July 19, 2013. The distance of 898,414,528 miles (1,445,858,030 kilometers) makes it a little hard to find yourself in the photo, but trust me, you’re there. Also featured in this image: every place human beings have ever set foot.

Image
Typical reflecting telescope that will result in X-shaped diffraction spikes. The secondary mirror and its supports are conveniently labeled as 3. The telescope tube is 1, and the primary mirror is 2.
Image from http://en.wikipedia.org/wiki/Diffraction_spike.

The bright vertical line on the larger dot (Earth) are most likely due to saturation – in essence, there was too much light in one part of the picture, and some of it bled to nearby pixels. The fainter crosshairs are called diffraction spikes. These show up anytime we take a picture of a bright circular or point-like object with a telescope. This particular pattern (an X) means that the telescope’s mirrors are supported by an X-shaped structure. If you ever see more of an asterisk-shaped spike, that means there are three support structures, and so on.

Cassini is a pretty awesome spacecraft, and it does a lot more than take pictures of Earth from a distance. But that’s more than enough for now. Keep looking up, and welcome to AstronoMerrdiff.

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