BellaOnline Forums Education Astronomy Look out - there's a comet about! And it's green!

Comet Hartley is back and will be at its nearest approach in the next few days. It's just visible with the unaided eye near the star Capella, but won't look like much without binoculars.

An interesting feature is that it is green, as you can see in the picture below taken by Doug Zubenel, which is on the SpaceWeather.Com website.

Here is a sky map showing the comet over the next several days: Sky map to find Comet Hartley


Comet Hartley by Doug Zubenel

Why is the comet green?

Its nucleus is sending out jets that contain cyanogen (a poisonous gas) and a form of carbon, both of which glow green when sunlight energizes them.

To learn more about comets, see Introducing Comets


This is a long exposure of the comet taken through a telescope by Filipe Alves in Portugal (SpaceWeather.com).

Thanks for the comet tip, Mona! I went out this morning at about 5:30 and was able to see it as a faint smudge near Capella with the help of my binocs. I'll check again tomorrow, weather permitting. I live too close to the city to see many stars, the sky is so full of ambient light here.

Great, Claybird! I could just barely see the Moon this evening, so probably won't be getting the binoculars out.

Let us know if you get a better view.