Talk:Hertzsprung-Russell diagram
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The text mentions "red giants" which doesn't appear as a label in the diagram. Just to avoid confusion, either the text or diagram should be changed (by someone who knows what they are doing). GreatWhiteNortherner 12:23, Jan 10, 2004 (UTC)
Hi User:Looxix! I have some questions about the diagram. Can you add some informations about the meaning of the numbers on both axis? What is the source of the data points? The statistical distribution on the sheet lets me assume, that this are manually and arbitrary distributed points and not actually existing stars. Is that correct? Is there anybody who knows how to get real data for instance from the Hipparcos satellite? I'm from the german WP, where this diagram is used as well. --Wolfgangbeyer 21:45, 8 Apr 2004 (UTC)
Someone should include where our Sun is on this diagram :) Indosauros 14:00, Jul 14, 2004 (UTC)
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[edit] Mathematical Relationship?
The first sentence: "... Hertzsprung-Russell diagram shows the mathematical relationship between absolute magnitude, luminosity,..." is nonsense. There is no mathematical relationship between these quantities. As a matter of fact, the H-R-diagram doesn's show something like a perfect graph of a function, but a cloud of points. Therefore the diagram "only" shows physical relationships. --CWitte 10:05, 28 Jan 2005 (UTC)
[edit] Ladies get no respect?
So is it true that Annie Cannon and other women astronomers discovered this relationship and had the credit taken by Hertzsprung and Russel? (comment from anon 08:06, 2005 Feb 3)
On a first random check on the internet, it seems he made his diagram about five years earlier (1905 ) than she was working on the topic (1911->1914, same source) and that it's quite correct to credit the diagram to (independently both of) Hertzsprung and Russell, whilst the detailed classification based on it is being correctly attributed to Annie Cannon (again same source). Do you have any more deatail about this? In what way did they take her credit? Mozzerati 08:44, 2005 May 8 (UTC)
[edit] Great A'Tuin
I removed the following link on the grounds of utter irrelevancy. Gene Ward Smith 06:28, 10 October 2005 (UTC)
[edit] Distance
Could someone tell me how distance is calculated from the diagram. Thank you! (Unsigned comment from User:JML)
- I'm not experienced in the field, but I'd guess that since the colour and apparent magnitude are known, one can assume that the absolute magnitude is on the main sequence, and use the ratio of apparent to absolute magnitude to determine the distance. --Stoive 18:40, 23 September 2006 (UTC)
[edit] Names?
Could someone please add a chart of star names by size, instead of lumping them all into "supergiants" and "medium stars?" I mean all of the blue giant, red giant, red dwarf, etc.
[edit] Not a colour magnitude diagram
I am a professional astronomer and I always thought that a HR diagram and a colour magnitude plot were different things. Where a HR diagram uses Absolute magnitude (via knowledge of the distance) a colour mag diagram uses apparent magnitude (Where no distance is known). Though I am not sure if HR also pioneered this as well, I would say that its reference to colour is an indication that it was a plot that could be drawn from photometry alone, and hence useful to astronomers.Soloist 18:18, 18 October 2006 (UTC)
- I am not a professional, but I am currently a student, and my understanding was the same. However, googling color magnitude diagram returns a number of examples of people in astronomy using color magnitude diagram and Hertzsprung Rusell diagram interchangeably. Of course, there were also examples of people using color magnitude diagram to refer to a plot using apparent magnitude. I think I'll just add a note to that effect in the article. James McBride 19:06, 18 July 2007 (UTC)
I am also a professional astronomer, working on stars. A colour-magnitude diagram (CMD) that uses apparent magnitudes is useful for a group of stars that are all at (about) the same distance, such as a cluster or an external galaxy. In the days before good parallaxes were available for large numbers of stars, these were the most common. Since Hipparcos, we can make CMDs using absolute magnitudes for many tens of thousands of stars. Both of these are often called HR diagrams, although I think CMD is better. A plot of luminosity versus effective temperature, such as evolutionary tracks produced from theoretical models, is (I think) more properly called a theoretical HR diagram. I have not checked, but I would be confident that the original diagrams by H and R themselves would have been apparent-magnitude CMDs using V and B photometry of clusters. Timb66 23:59, 18 July 2007 (UTC)
[edit] Bet you find this Interesting?
I had a thought the other day. And tried to find this answer to this on Wikipedia and other sources. But as a complete layman became very confused, parsecs/light years ect. This is my thought, we (the human race) have been sending out RF signals of a reasonable strength since 1922, please correct me on this if I have this wrong. Based on this knowledge, I wondered how far and how many star like suns (G class stars) have these RF signals reached by this year, 2007 ? You know where I'm going with this thought, and yes maybe life is not restricted to G class stars, or maybe it is, or maybe only to G2V, and we all known G2V's are capable! Then there's the age of these stars, and then the metallic make up as well. I wish someone with the right knowledge would draw up a list of theses stars. And using the above knowledge. We could then break the list up into the most lightly to the most unlikely places that intelligent life may exist. And that have also received RF signals from us. I believe this list would be helpful to SETI, to reduce their listing down to size, so they can focus on a more broader range of RF signals. As I also believe the RF's they are searching are far too narrow, and I feel a lot of time and money is going to waist at SETI. If anyone can help me with this please do, maybe I've got this wrong as I'm just a layman. But in any case, post me something, its bugging me! —The preceding unsigned comment was added by 86.10.204.128 (talk) 23:52, 20 March 2007 (UTC).
[edit] Image too big
Image:Hertzsprung-Russell diagram Richard Powell.png is too big. It cannot be used in shrinked dimensions because of blur. It won't be practical to replace it with an SVG. Hence it should be regenerated in a smaller size. How? Said: Rursus 20:12, 30 April 2007 (UTC)
[edit] Confusion about interpretation of diagram
One thing I have never understood is exactly what the logic is that gets astronomers from the observed set of points on the H-R diagram to the knowledge that the diagram represents an evolutionary sequence. How do we know that the main sequence is the longest lifetime of stars, or that the section in the upper right is giant stars?
--Raddick 18:03, 25 July 2007 (UTC)
