"An issue that can't be ignored is that "color" means many different things. In stellar photometry, it is a scalar typically derived as the ratio or difference in intensity across two adjacent parts of the spectrum (e.g. B-V)"
Well indeed but I decided not to go into that!
Search found 121 matches
- Sat Feb 08, 2014 6:49 pm
- Forum: The Asterisk Café: Discuss Anything Astronomy Related
- Topic: What can be learnt from star colors?
- Replies: 21
- Views: 1239
- Sat Feb 08, 2014 6:21 pm
- Forum: The Asterisk Café: Discuss Anything Astronomy Related
- Topic: What can be learnt from star colors?
- Replies: 21
- Views: 1239
Re: What can be learnt from star colors?
Also as Annmentions you can use the average colours of stars in different regions of the sky to make a pretty decent statistical dust map of the Milky Way (using a very large dataset like SDSS)
- Sat Feb 08, 2014 6:19 pm
- Forum: The Asterisk Café: Discuss Anything Astronomy Related
- Topic: What can be learnt from star colors?
- Replies: 21
- Views: 1239
Re: What can be learnt from star colors?
Good question Ann. Some of you guys are being a bit dismissive of colour, a colour magnitude diagram (basically HR) can tell you a lot. As you all rightly say the colour is due to the temperature (in the main) as stars are approximately Black Body emitters (OK not all of them and strong absorption f...
- Tue Oct 29, 2013 5:20 pm
- Forum: The Communications Center: Breaking Science News
- Topic: Most Distant Galaxy Ever, Found Using Keck
- Replies: 13
- Views: 5415
Re: Z8_GND_5296 - Furthest Galaxy Discovered
As Chris says this was from a deep survey CANDELS I think. So basically they image the sky in many different filters and then look for faint galaxies with certain properties ie brighter in some filters than others. In this case they were probably looking for 'drop outs' galaxies that have a break in...
- Tue Oct 29, 2013 12:23 pm
- Forum: The Library: Information Desk and Educational Resources
- Topic: What do you think this object is?
- Replies: 9
- Views: 19080
Re: What do you think this object is?
Well, there's a Green Pea in it. And it looks like either a merging pair of ellipticals, or perhaps a foreground lensing effect splitting the one elliptical galaxy into two. I can't tell if all these are in one galaxy cluster or not. If so, I'd guess the Green Pea is not part of the cluster, since ...
- Mon Oct 28, 2013 4:55 pm
- Forum: The Library: Information Desk and Educational Resources
- Topic: What do you think this object is?
- Replies: 9
- Views: 19080
Re: What do you think this object is?
Looks like a Brightest Cluster/Group Galaxy to me. Largest galaxies in the Universe sit in the middle of huge potential wells. From the spectra its showing line emission (particularly all that OIII) so it probably has an accreting black hole in it (AGN) and maybe some residual star formation
- Fri Nov 07, 2008 11:34 pm
- Forum: The Asterisk Café: Discuss Anything Astronomy Related
- Topic: Could Dark Matter Possibly Be . . .
- Replies: 315
- Views: 29854
Re: Could Dark Matter Possibly Be . . .
Whenever I receive a directed 'spam' email to my university account from an 'independent researcher' (I'm trying to be nice here!) they always include a copyright symbol next to some unknown laboratory - in case I copy their work I guess! - its the calling card of the crank
- Mon Oct 27, 2008 9:01 pm
- Forum: The Asterisk Café: Discuss Anything Astronomy Related
- Topic: Do You Have A Favorite Telescope
- Replies: 7
- Views: 1168
- Sat Jul 19, 2008 8:43 pm
- Forum: The Asterisk Café: Discuss Anything Astronomy Related
- Topic: Planet Earth?
- Replies: 21
- Views: 4788
- Fri Sep 07, 2007 10:03 am
- Forum: The Asterisk Café: Discuss Anything Astronomy Related
- Topic: Origins of the UNIVERSE
- Replies: 829
- Views: 148368
- Sun Sep 02, 2007 7:19 pm
- Forum: The Asterisk Café: Discuss Anything Astronomy Related
- Topic: Origins of the UNIVERSE
- Replies: 829
- Views: 148368
well the MACS clusters are at z=0.5 ish and (i should know i've spent the last 2 years studying them!!) this is around 9 billion years after the big bang so thats plenty of time to form a relaxed cluster. so far to my knowledge the furthest cluster known is at z=1.45 from the XCS survey, this is rou...
- Wed Aug 29, 2007 2:48 pm
- Forum: The Asterisk Café: Discuss Anything Astronomy Related
- Topic: APOD Cafe
- Replies: 1
- Views: 1274
APOD Cafe
As Harry suggested I have no authority on this forum but why don't we let people say what they like in this (and only this) thread as long as its not spam. therefore if craterchains et al want to discuss alien warfare and MM wants to chat 'iron sun' they can do so here: moderators delete this if you...
- Thu Aug 09, 2007 10:43 am
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: Is there any way ...
- Replies: 1
- Views: 1355
yes the sdss navigate tool you included http://cas.sdss.org/dr6/en/tools/chart/navi.asp (edit: the explore tool gives all available SDSS information on the selected object. photometry, spectra, redshift) and the Nasa Extra-galactic Database (NED) http://nedwww.ipac.caltech.edu/ the latter gives all ...
- Sat Jul 21, 2007 11:50 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: Is the moon gray or is the picture colorized (20 July 2007)
- Replies: 30
- Views: 10728
- Fri Jul 20, 2007 1:09 pm
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: Is the moon gray or is the picture colorized (20 July 2007)
- Replies: 30
- Views: 10728
because it was all done for £5 in a basement in kent :) or it could be to do with how optical instruments (cameras or eyes) work when presented with a very bright object in the field such as the surface of the moon compared to the very faint stars. camera would be set to a daylight aperture and expo...
- Wed Jul 04, 2007 8:54 am
- Forum: The Asterisk Café: Discuss Anything Astronomy Related
- Topic: Radiometric dating
- Replies: 23
- Views: 6800
- Tue Jul 03, 2007 10:05 pm
- Forum: The Asterisk Café: Discuss Anything Astronomy Related
- Topic: Scientists should know grammar.
- Replies: 12
- Views: 4189
- Mon Jun 25, 2007 10:31 am
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: A Hole in Mars (APOD 28 May 2007)
- Replies: 109
- Views: 36916
- Fri Jun 22, 2007 9:18 am
- Forum: The Bridge: Discuss an Astronomy Picture of the Day
- Topic: Ceres and Vesta (APOD 22 June 2007)
- Replies: 11
- Views: 4133
- Wed Jun 13, 2007 1:41 pm
- Forum: The Asterisk Café: Discuss Anything Astronomy Related
- Topic: Origins of the UNIVERSE
- Replies: 829
- Views: 148368
I was not aware of such case(s), and I would appreciate a reference describing them. I'm talking about normal common elliptical galaxies - they do not contain a great deal of gas/plasma or dust and have negligible new stars to make any more. Put simply they are thought to be formed by the merging o...
- Wed Jun 13, 2007 9:51 am
- Forum: The Asterisk Café: Discuss Anything Astronomy Related
- Topic: Origins of the UNIVERSE
- Replies: 829
- Views: 148368
- Tue Jun 12, 2007 3:41 pm
- Forum: The Asterisk Café: Discuss Anything Astronomy Related
- Topic: Origins of the UNIVERSE
- Replies: 829
- Views: 148368
So you're saying that huge superclusters of normal elliptical galaxies at high redshift are actually nearby and small :) Are they just a collection of globular clusters compared to local clusters which are a collection of ellipticals? :) If you've ever seen the perspective episode of Father Ted with...
- Tue Jun 12, 2007 9:21 am
- Forum: The Asterisk Café: Discuss Anything Astronomy Related
- Topic: Origins of the UNIVERSE
- Replies: 829
- Views: 148368
Another question I'd be interested to hear the plasma/arp view on. What about high redshift non-quasars? my own personal research is the study of normal boring ellipticals at redshift 1. For those of you not familiar with cosmology redshift 1 is half the age of the Universe at around 7 billion years...
- Mon Jun 11, 2007 9:24 am
- Forum: The Asterisk Café: Discuss Anything Astronomy Related
- Topic: Origins of the UNIVERSE
- Replies: 829
- Views: 148368
- Sun Jun 10, 2007 8:33 pm
- Forum: The Asterisk Café: Discuss Anything Astronomy Related
- Topic: CME watch.....
- Replies: 28
- Views: 6172