Wednesday marks Caroline Herschel’s 266th birthday. She was an astronomer (and sister to another astronomer, William Herschel), who studied the heavens avidly. Besides breaking a lot of new ground as a female astronomer, she is probably best known for her discovery of many comets.
Google honored her Wednesday with her own Google Doodle, which is pretty cool.*
That’s nice, but I have to point out: The Doodle is showing meteors, not comets. This is a common misconception; a lot of people confuse them, thinking comets streak across the sky.
They don’t. Comets are huge chunks of rock and ice orbiting the Sun, usually on fairly elliptical orbits. They can take weeks or months to move across the sky as they pass through the space between planets, and in general are many tens or hundreds of millions of kilometers from Earth.
Meteors are smaller bits of rock that burn up in Earth’s atmosphere, usually 100 km above the ground. They move at roughly the same physical speed as comets, but they’re a lot closer, so they appear to zip across the sky in a second or two.
The two are connected in one way: Meteor showers come from debris left behind as comets orbit the Sun. If the Earth passes through that stream of jetsam, we get lots of meteors. Sometimes it’s a few per hour, with good showers producing up to 100 per hour. Sometimes the debris field is denser, and we get thousands per hour! But those meteor storms are quite rare.
Now, having said all that, there are also sporadic meteors, random ones that may actually be from rockier and more metallic asteroids. These can appear at any time, and you can usually see a half dozen or so per hour on average on a nice night. So maybe—maybe—the Google Doodle can be retconned to depict those. But since they talk about Herschel discovering comets in their writeup of the Doodle, I’m thinking they just made a little mistake. Or, to be more generous, just gave the Doodle a little artistic license.
So I’m not going to make a big deal out of it. I just like being able to use situations like these to spread a little astronomy. I think Herschel herself would have approved of that.
*The Doodle wasn’t served to every country on Earth, so you may have missed it. I did; happily Caroline Herschel herself on Twitter pointed it out to me!
Correction, March 16, 2016: I misstated that she was married to William, but she was his sister.