One more favorite blue spiral galaxy: NGC 3310
Posted: Sun Nov 14, 2010 1:28 pm
As Chris would rightly point out, there exists one picture of NGC 3310 that is better than all the others, and that is the Hubble picture. Personally I don't like it, and you can guess why. I think the Hubble picture of NGC 3310 is much too yellow in overall color balance:
If Chris were here, he would say two things. First he'd say that the color balance of the Hubble picture is excellent, and here I'd disagree.
But second, Chris would say that the main purpose of the Hubble picture was not to create a "natural color image" but to learn more about NGC 3310. And here I'd have to agree.
To create their image of NGC 3310, the Hubble people used the following filters: F336W (U), F439W (B), F814W (I), F300W (Wide U), F814W (I). You can see that they have used two ultraviolet filters, one blue filter and one infrared one. To get a three-color picture, they must have shown the picture taken through the blue filter as green, the infrared picture as red, and only the ultraviolet images were shown as blue. Why would the Hubble people do that? Obviously they must have been trying to find the very youngest star clusters in this starburst galaxy and separate the newborn clusters from the merely young ones. Bear in mind that this starburst galaxy may well contain quite a lot of dust, too, so that the arms would contain a mixture of ultraviolet, blue and infrared sources. That is why such large parts of the galaxy ended up looking white or greenish in the Hubble picture.
So the Hubble picture contains a lot of new information about NGC 3310, I'll grant you that. But now, I'll feast my eyes on the SDSS image of the galaxy:
I love it! The galaxy's dramatic shape shows up very well, and it becomes obvious why it is called "The Bow and Arrow Galaxy". Note the jet, the "arrow", and the large arc, the bow.
Note the green parts of the arms. The green areas represent red emission nebulae, because red is shown as green in this image. There green parts cover so much of the arms! I can almost here the star formation hissing and roaring here!
And then there is all the blue stuff to look at. Ahhh. This galaxy, and this picture of this galaxy, make me happy!
Ann
If Chris were here, he would say two things. First he'd say that the color balance of the Hubble picture is excellent, and here I'd disagree.
But second, Chris would say that the main purpose of the Hubble picture was not to create a "natural color image" but to learn more about NGC 3310. And here I'd have to agree.
To create their image of NGC 3310, the Hubble people used the following filters: F336W (U), F439W (B), F814W (I), F300W (Wide U), F814W (I). You can see that they have used two ultraviolet filters, one blue filter and one infrared one. To get a three-color picture, they must have shown the picture taken through the blue filter as green, the infrared picture as red, and only the ultraviolet images were shown as blue. Why would the Hubble people do that? Obviously they must have been trying to find the very youngest star clusters in this starburst galaxy and separate the newborn clusters from the merely young ones. Bear in mind that this starburst galaxy may well contain quite a lot of dust, too, so that the arms would contain a mixture of ultraviolet, blue and infrared sources. That is why such large parts of the galaxy ended up looking white or greenish in the Hubble picture.
So the Hubble picture contains a lot of new information about NGC 3310, I'll grant you that. But now, I'll feast my eyes on the SDSS image of the galaxy:
I love it! The galaxy's dramatic shape shows up very well, and it becomes obvious why it is called "The Bow and Arrow Galaxy". Note the jet, the "arrow", and the large arc, the bow.
Note the green parts of the arms. The green areas represent red emission nebulae, because red is shown as green in this image. There green parts cover so much of the arms! I can almost here the star formation hissing and roaring here!
And then there is all the blue stuff to look at. Ahhh. This galaxy, and this picture of this galaxy, make me happy!
Ann