Mercury is at greatest elongation in the morning sky today/tomorrow, but at just under 18 degrees, it’s not a particularly great observing event–I’m not going to rush out of bed to catch it. After all, this is the “western” elongation, meaning, of course, that it appears in the eastern sky before sunrise.
Wait a minute. What? Western elongation means Mercury appears in the east?
Well, yes.
Western elongation means that the planet is west of the Sun, hence it slides over our horizon before the Sun does. Eastern elongation, which happens in the evening, means that the planet will be to the east of the sun (and therefore will set over our horizon later). This much more convenient event will occur on 18 December of this year. If you’d like to plan for a Mercury session, Fourmilab has a convenient online tool.
And unless you’ve been paying close attention, you might not even realize that we have spacecraft attempting to enter a stable orbit around Mercury right now for a planned observing run in 2011. Cleverly named, as always, this mission is called MErcury Surface, Space ENvironment, GEochemistry, and Ranging. That’s Messenger. Get it? Mercury, messenger of the gods. These rocket scientists may be clever at naming things, but at public relations, well, let’s just say it’s been somewhat downhill since the Apollo missions captured the imagination of the entire world.
Be honest. How many of you even knew we had a mission to Mercury going on, right now?
Related Images:
Hey, I did get in! Thanks for the renewal of the password.
I sure didn’t know about the Mercury mission. How did you learn of it?…I mistakenly hit enter when I wanted to go to a new line in my message, so I think theis got split into two messages. I’m learning, but slowly! Pop