Comments on: A swiftly UV galaxy

By: Mr Squid

Mr Squid — Thu, 28 Feb 2008 13:57:11 +0000

The Ultraviolet/Optical Telescope on Swift (affectionately called UVOT) is a modified Ritchey-Chrétien telescope with a 30 cm primary mirror, a focal ratio of f/12.7, a field of view of 17′ x 17′ and a pixel scale of 0.5″/pixel. It can observe from about 1600 Angstrom to about 6000 Angstrom. It is one of three ultraviolet telescopes in orbit. There are more details at .

By: Kilgore Trout

Kilgore Trout — Wed, 27 Feb 2008 15:25:14 +0000

Thanks for the explanation’s,
Just to be sure I’m understanding correctly. The haloed spot really is a very bright star, but it looks bigger and brighter than it should because it screws up the camera? Basically. And the streak through it is just a seam from putting the composite pictures together? I would have thought they would be at right angles to the picture, of course maybe they were before the picture was rotated and cropped.
Thanks again everyone, I’m really enjoying this site. Just makes me wish it wasn’t cold and cloudy at night.

By: Allen Thomson

Allen Thomson — Wed, 27 Feb 2008 14:29:00 +0000

Also for the Pareidolia Files. In the bigger version of the picture there are two eyes, a mouth and an ear in the nucleus.

By: Regner Trampedach

Regner Trampedach — Wed, 27 Feb 2008 13:28:13 +0000

DenverAstro, 1cm = 10mm (centi = 1/100, milli=1/1000).
Also units cannot be freely capitalized or decapitalized(?!?); 1mm is
1 millimeter, but 1Mm is 1 megameter (mega = 1,000,000 = million)
- that’s a difference of a factor of 10^9 (billion in US lingo).
In the end you do work out the numbers correctly, though,
with 30cm=300mm. That’s a pretty large refractor you have there,
by the way – 127mm… Should be pretty good for M33.
Cheers, Regner Trampedach

By: DenverAstro

DenverAstro — Wed, 27 Feb 2008 03:06:26 +0000

Let’s see…a CM is 100 times larger than a MM, right? My refractor is 127mm which works out to about 5 inches, 300mm would then be about 12 inches in aperture, right? What kind of optics does this scope have and what is its focal length? This also says alot about what a telescope can do as you know better than I, Phil. I’m just curious here. I didn’t know that SWIFT had a scope like that on board. This is really cool, thanks for the post.

By: John Paradox

John Paradox — Wed, 27 Feb 2008 01:22:06 +0000

The Andromeda Galaxy is male?!
Here I’ve been calling it “she” the whole time… I’m so embarrassed!

Obviously M33 is female, since it (she?) is making more stars.

J/P=?

By: Jeffersonian

Jeffersonian — Tue, 26 Feb 2008 18:39:01 +0000

“For a fun game, think of things that CCD can stand for in the context of “streaking”.

Ha! Love it.

By: Damon B.

Damon B. — Tue, 26 Feb 2008 18:25:12 +0000

“It’s actually visible with binoculars as a fuzzy patch not too far from its big brother, the Andromeda galaxy.”

The Andromeda Galaxy is male?!

Here I’ve been calling it “she” the whole time… I’m so embarrassed!

By: Carey

Carey — Tue, 26 Feb 2008 18:10:31 +0000

SOHO’s the best for CCD streaking.

For a fun game, think of things that CCD can stand for in the context of “streaking”.

By: Navneeth

Navneeth — Tue, 26 Feb 2008 17:52:33 +0000

I think that streak could be what’s called a “diffraction spike.” This happens in a reflector due to the spider-vanes that hold the secondary mirror standing in the path of the light from the source to the primary mirror. If the ‘scope’s a refractor, which I think the Swift is not, then you can artificially create one. (Amateur astrophotographers use strings in front of the primary lens, or create them using photoshop.)

By: Pleco

Pleco — Tue, 26 Feb 2008 17:22:50 +0000

Could be an angel!

/I jest

By: The Bad Astronomer

The Bad Astronomer — Tue, 26 Feb 2008 17:03:21 +0000

Swift uses CCDs, detectors pretty much like what’s in a your digital camera, but a lot more expensive. But they all suffer from what’s called blooming: when an object is too bright, the electrons in the detector can bleed down a column of pixels. You see it all the time in Hubble images, for example.

In this case, it looks to me like the star was too bright and bled. The image itself was probably rotated before publishing, which is why the line isn’t vertical.

As for the halo, I am not sure exactly why that’s there, but in CCDs it’s usually a problem with light being absorbed and basically scattered inside the detector. In the camera I used to use (STIS), the CCD was translucent to near infrared light, so the red light would get smeared a little bit around a bright red source. I had a project looking for low mass red dwarfs, so that made them easy to spot: just look for stars with halos!

By: billsmithaz

billsmithaz — Tue, 26 Feb 2008 16:56:29 +0000

RE: the streak in the bottom right corner

As the BA said, this image is a composite of a bunch of smaller images. The ‘streaks’ are simply some of the seams where the smaller images are joined together. If you look closely enough, you’ll find other similar, but smaller, streaks in the photo.

By: KaiYves

KaiYves — Tue, 26 Feb 2008 16:43:37 +0000

Oooh, a galaxy that’s my favorite color for my birthday!

By: Kilgore Trout

Kilgore Trout — Tue, 26 Feb 2008 16:37:43 +0000

I’m a Noobie so go easy on me, whats that odd spot to the right and a little below the centerline? It’s looks to me like maybe an issue with the telescope or the camera or but I’m curious in case it really is some sort of giant star with a glowing aura around it and some sort of stripe coming from it. I guess it could also be a much closer star but it looks like something that was added, at least to my untrained eye. Again I have no astronomy background, just a curious person. Thanks!

By: madge

madge — Tue, 26 Feb 2008 16:24:02 +0000

Very pretty indeed. Just goes to show that size ISN’T everything (she lied)

By: Mark

Mark — Tue, 26 Feb 2008 16:13:15 +0000

What’s up with that star(?) in the lower right part of M33 with the big UV(?) halo and the white streak going throught it?