The Hidden Galaxy (Caldwell 5 or IC 342) - Deep Sky Videos

0:00 Okay, professor, you've been out with your telescope again.

0:02 I've been out with my telescope looking at Coldwell 5 since we're

0:06 working our way through this Coldwell catalog and we've got to number five.

0:12 How lovely is that?

0:15 I mean, that is pretty good.

0:16 It's a beautiful galaxy.

0:17 It is the third largest galaxy in the sky.

0:20 Oh, okay.

0:20 So, it was an easy one then.

0:22 Yeah.

0:22 Although it's a galaxy that no one's heard of for it.

0:25 It's you know the famous ones like the Andromeda galaxy,

0:28 the biggest one in the sky everyone's heard of.

0:29 No one's heard of IC 342.

0:32 What's the second biggest one on the sky?

0:34 M33, the triangulum galaxy, another spiral galaxy.

0:37 And then this one, has this one got

0:39 like a cool name like the dragon or anything?

0:41 It's sometimes called the hidden galaxy

0:43 for reasons which we'll come to, but yeah,

0:45 it's not a particularly well-known galaxy.

0:47 So you remember the galaxies are generally put

0:49 into cataloges and most of the famous ones,

0:51 some of them are in the Messier catalog,

0:53 but actually most galaxies don't make it to the Messier catalog.

0:56 They're in a thing called the New General Catalog,

0:58 which is why a lot of them are called NGC something or other,

1:00 which was a catalog compiled kind of towards the end of the 19th century.

1:04 This one didn't make it into the NGC.

1:05 It was too late.

1:06 So after the NGC was made by a guy

1:08 called Dreer and I think it was published in 1888,

1:11 he published a couple of kind of supplements to the NGC

1:14 that were called the index catalog or the IC.

1:16 And this made it into the index catalog.

1:19 Wow.

1:19 Third biggest in appearance to us, not third biggest in actual size.

1:23 No, third biggest in Angular size.

1:24 It's kind of a It's a little bit smaller than the full moon.

1:27 Okay.

1:27 What do you want to tell me about it?

1:28 I'll tell you.

1:29 Well, let's go back to it its discovery.

1:30 As I say, it slightly missed the boat in that it didn't make it into the NGC.

1:34 That's because it was discovered in let's get the date right,

1:37 1893 by a guy called William Denning, who was an amateur astronomer.

1:42 So, the reason why kind of various things

1:44 didn't sort of quite make it into the NGC,

1:46 but then there were a whole bunch of more galaxies were

1:47 found is really because photographic astronomy was coming along at that point.

1:51 So people were taking photographs of things that hadn't made it,

1:54 you know, weren't really that visible just through telescopes,

1:56 but as soon as you started taking pictures,

1:58 suddenly you could see much faint things.

2:00 This galaxy is a bit interesting because it wasn't a photographic discovery.

2:03 Um, it was an optical discovery.

2:05 It was just the discovery of somebody looking through

2:07 an eyepiece by this amateur astronomer from Bristol in the UK

2:10 who was mainly looking for comets and was interested in meteor

2:13 showers and all sorts of things he's quite famous for.

2:16 But in one of his sweeps for looking for comets,

2:18 he found this galaxy and it was published

2:20 in this shortlived journal called Astronomy and Astrophysics.

2:24 There's a current journal called Astronomy and Astrophysics without the hyphen,

2:26 but there was this shortlived journal at the end of the 19th century.

2:30 So I sort of dug down and managed to find

2:32 the original copy of his claiming to have discovered this galaxy.

2:35 And it's quite entertaining because it's

2:36 this wonderful piece of um passive aggressive writing.

2:40 I think it's fair to say is the way to describe it.

2:42 It's nice to know that astronomers haven't actually

2:44 changed in the last 100 or so years.

2:46 So, let me read a bit from this.

2:47 It says, "Professor Swift writes in the August

2:50 number of astronomy and astrophysics about a new

2:51 nebula independently picked up by Professor Barard

2:54 and myself at certain coordinates blah blah blah.

2:57 He claims to have seen this nebula many years

2:59 ago with his 4 and a half inch comet seeker.

3:01 My purpose now is not, however,

3:02 to discuss the question as the priority of discovery,

3:05 but to mention that while hunting for comets,

3:07 I found another one." So basically he's he,

3:09 you know, he wants to just put it on the record

3:11 that he actually found that other object as well,

3:14 but actually he's he's passed that now.

3:16 He's not going to raise that again, even though he's just raised it again.

3:19 And uh here's this other object that he found in passing.

3:22 And then he goes on to describe it.

3:23 He talks about this new object he found.

3:25 It's rather faint with the nucleus about 12 magnitude and very small.

3:29 It's kind of interesting because I just told you

3:30 it was the third largest galaxy on the sky,

3:32 but it was sufficiently conspicuous to be

3:34 discovered with his 10-in reflecting telescope.

3:36 And then he goes on to give the coordinates of the right

3:39 ascension and declination of where it is in the sky.

3:41 Turns out the coordinates are quite important for this galaxy.

3:44 And so that's where they were and again I went and checked

3:45 and indeed that's exactly where this galaxy is on the sky.

3:48 What's going on?

3:49 Why has it been so elusive?

3:50 So actually interestingly it kind of comes down to its coordinates.

3:53 Um and so there are various ways you can measure where something is on the sky.

3:57 Basically you know you need some way of saying left to right,

4:00 some way of saying up and down.

4:01 You just basically need two two coordinates

4:03 to specify where something is on the sky.

4:05 So the ones that astronomers typically use and so

4:07 the ones that we used in this discovery

4:08 are these things called right ascension and declination

4:10 which are essentially related to the earth.

4:12 They're to do with how far north or south the thing

4:14 is relative to the earth and how far east or west having

4:17 to allow for the fact that the earth rotates which complicates things

4:19 a little bit but basically it's it's a sort of earthbased coordinate system.

4:22 There are other coordinate systems that astronomers sometimes use.

4:25 For example uh sometimes they use this thing called ecliptic

4:27 coordinates which is a measure relative to the solar system.

4:30 Essentially, it's how far along things are in the plane

4:33 of the solar system or how far out of that plane they are.

4:36 That's useful for measuring planets and asteroids and those kinds of things.

4:38 But there's another coordinate system.

4:40 So, I looked this up in its other coordinate system.

4:42 So, here are the various ways you can measure the coordinates of this galaxy.

4:45 So, we talked about right ascension

4:46 and declination and there were these ecliptic coordinates,

4:49 but the one I wanted to talk about are galactic coordinates.

4:51 So another way you can measure where something is in the sky is you can

4:54 set your zero point for your coordinate system

4:56 to be the center of the Milky Way.

4:58 And then you can measure how far out of the plane of the Milky

5:00 Way they are or how far along the plane of the Milky Way they are.

5:03 And again that gives you these two directions.

5:04 And so in this particular case this galaxy is at a galactic longitude.

5:09 That's how far along the plane it is of 138° but a galactic

5:13 latitude that's how far out of the plane it is of only 10°.

5:16 So it's very close to the plane of the Milky Way.

5:18 And that's why it wasn't discovered for so long

5:20 because close to the plane of the Milky Way,

5:22 you've got all this dust, all this obscuration,

5:24 all this material which makes anything that lies behind it appear very faint.

5:29 So that's why uh when this object was discovered,

5:32 it was small and faint cuz you could only see

5:33 a little bit of light from the center of it.

5:35 So what you're saying is like basically you're looking

5:37 through a big thick chunk of the Milky Way,

5:40 like almost looking straight through the whole thing.

5:43 Absolutely.

5:43 I mean, you're 10° out, so you're not quite in the plane of the Milky Way,

5:46 but even so, that's looking through a lot of Milky Way.

5:48 And in fact, you can sort of see that just by looking at it,

5:51 cuz there's an awful lot of stars here.

5:52 And these are just stars from the Milky Way that you're looking through.

5:55 But not only are you looking past the stars,

5:56 but you're looking through all this dusty material.

5:59 So, Denning wasn't seeing much of it.

6:01 He didn't realize just how big a thing he was looking at, right?

6:04 Because he didn't have the luxury of integrating

6:06 for a long time by taking a picture.

6:07 He was really just looking through his eyepiece.

6:09 And with the eyepiece, even with a moderately large telescope he was using,

6:13 you really can't see much of this galaxy.

6:15 It's only when so I think this was a 2-hour exposure I ended up taking.

6:18 It's only when you take a relatively long exposure of it,

6:20 you see quite what a big dramatic galaxy it is.

6:22 It's about the same size as the Milky Way.

6:24 So it's actually kind of a twin of the Milky Way.

6:27 Nice.

6:26 I mean, it's not really a bar galaxy.

6:28 The Milky Way has a one of these sort of rectangular bar structures in it,

6:31 but other than that, in terms of it's a spiral galaxy.

6:33 It has roughly the same kind of spiral structure as the Milky Way.

6:36 It's the same luminosity as the Milky Way.

6:38 So, it's pretty much at least a close cousin of the Milky Way.

6:41 One last question.

6:42 It's in the Cordwell catalog,

6:43 and we've discussed the Cordwell catalog before that Patrick Moore

6:46 cataloged these objects that he thought were good to look at.

6:49 They were good sport.

6:50 This sounds like this isn't though,

6:51 unless you're using the tech that you were able to use.

6:53 This isn't one you're going to have fun in the backyard with, is it?

6:56 Like, you're not going to see much.

6:57 You can just about glimpse it with a telescope, just with an eyepiece.

7:00 But, I think the CWall catalog was at least

7:02 in part designed with taking pictures in mind.

7:04 So actually and and it's big enough

7:06 that if you're prepared to look for long enough,

7:08 it does make a pretty dramatic picture.

7:10 It is a beautiful spiral, undeniably.

7:14 Yeah, for all perpetuity now,

7:15 I'm going to be traveling around the solar system with my dad,

7:17 which is kind of nice, isn't it?

7:19 It is nice.

7:20 Have you looked up anything more about them?

7:22 Are they are they big?

7:23 Are they small?

7:24 Are is there anything about them that's special?

7:25 Are they pretty, you know, run-of-the-mill average Joe's?

7:28 I mean, what's interesting about them is they're both very similar.

7:30 They're on very similar orbits.

7:31 They're very similar sizes.

7:32 I think they're estimated to be about six or seven kilometers across