Talk:Astrophysics/Archive 1

Overlap ?
There seems to be a lot of overlap in this field: there's Astronomy, History of astronomy, Observational astronomy (which has almost nothing in it), and Theoretical astrophysics.

In my head, astronomy is the obselete word for any study of the vacuum called space: historical, amateur or professional;  while astrophysics is the scientific field of study. The OED calls astrophysics "That branch of astronomy which treats of the physical or chemical properties of the celestial bodies." So perhaps this page should primarily deal with the scientific discoveries and theories of the cosmos, and link to the astronomy and history of astronomy pages? --Screetchy cello 00:58, 6 Jun 2004 (UTC)

I agree, there is too much overlap. Astronomy is the scientific study of objects in space, astrophysics is the study of the physical science of objects in space. Unless life is discovered in space, or the definition of science is expanded, all astronomical science is physical science, and so astronomy and astrophysics are the same thing. Indeed the terms are used interchangeably. I think the two entries should be merged. Also I wonder whether history, observational and theoretical really need to be separate entries.

(There is vague notion that astrophysics is more rigorous or quantitative than astronomy; all this means in practice is if you're an astronomer and you're out to impress you call yourself an astrophysicist, whereas if you want to avoid freaking out people out you say you're an astronomer.) --Rkundalini 10:29, 8 Jun 2004 (UTC)


 * I think the Astronomy wiki has it quite right: Observations are understood as the main work of 'Astronomers,' and the explanation of astronomical objects through theoretical work is what an 'Astrophysicist' does. So, let's concentrate on the physical concepts of Astronomy, here. Awolf002 23:37, 9 Jun 2004 (UTC)

I think Obervational Astronomy is a bit redundant; that's what astronomy is, the observation of the universe. And shouldn't Einstein's contibutions (i.e. Relativity) be included in the history?Trevor macinnis 23:04, 10 Jun 2004 (UTC)

Astronomy literally means the laws of celestial objects, not just the observation of them. But ok I will buy the assertion that in common usage it has come to be associated with observational astronomy, while theoretical astronomy tends to be called astrophysics. Is this a big enough difference to justify two different pages, instead of sections within a single page? I would opt for the latter. Certainly the entries for individual objects should cover both observational and theoretical aspects (imagine having a page on say, star (observational) saying a star is a bright dot on the sky with such and such a spectral energy distribution, and another entry star (theoretical) saying a star is a self-gravitating object undergoing nuclear fusion or so... would be strange!). So it seems weird to divide the field at the top level and not at the bottom level. But ok if people do want separate astronomy and astrophysics pages, can we at least do away with the observational section of the astrophysics entry? And if we do have separate entries, how do we better organise linking structure from each of these entries to objects on specific celestial phenomena/objects? Rkundalini 13:13, 11 Jun 2004 (UTC)

-- Astrophysics isn't just the theoretical side. Astrophysics is the scientific study of the cosmos, both theoretical and observational. Astronomy is more general; you could say, for example, the people who built Stonehenge did astronomy. So I think it's reasonable to have a distinction between astronomy, which is a word for *any* observation or study of the heavens, and astrophysics, which is science.

I envision this page as talking about current scientific theories in astrophysics (the theoretical side), and how scientists observe the cosmos (the observational side).

Some ideas for this page:
 * Big Bang, obviously (this could discuss the cosmic microwave background and red shifting as evidence for why scientists believe this took place.)
 * Stellar formation
 * Large-scale structure - galaxies, etc
 * Tools of the trade - visible observing, but also radio and infrared, and space-based telescopes. Spectroscopy.

Crikey, just in writing this, I'm realizing my astrophysics history is ruuuusty. I need to do some research. Screetchy cello 18:12, Jun 13, 2004 (UTC)

That sounds like a pretty good solution to me. Rkundalini 07:47, 14 Jun 2004 (UTC)


 * When I created the page like three years ago I called it "Astronomy and astrophysics" for close to the reasons the Rkindalini cites: most of the work done in astronomy is astrophysics, with celestial mechanics essentially complete and astrometry still done, but not by so many people as once was done. Astrophysics is a 20th century creation, but has taken over most of astronomy. The name of the departments in universities in many places has to do more with history than with what they do, so the old departments are called "astronomy department", while the newer ones "astronomy and astrophysics", or some just "astrophysics". But, someone disagreed with me not so long ago and decided to rename the page to "astronomy", what made necessary to create this one. I didn't try to fight back, as most of the links one makes in other articles will be to "astronomy", not "astronomy and astrophysics". I disagree that "astronomy" is not science while "astrophysics" is. Of course astronomy is science!, otherwise we would have to include "astrology" with astronomy. It simply happens to be that astronomy is older than physics, and for a while it was not understood that all physics as studied on earth applies to the objects that astronomy studies. As late as late XIX century the was one philosopher (Comte, I think, but not sure) telling that astronomers would never know the chemical composition of the starts, and they had to limit themselves to observe positions and brightnesses (or something like that). So the realizing that you could, in fact, study the physics of objects revoluzionited astronomy, and expanded it. But that didn't "detach" astrophysics, as this new discipliene was called, from the rest of astronomy, it simply gave more depth to it. In short, yes, it is problematic to see what to put here. If there is not duplication with the astronomy page, there will be things missing. If there is duplication, well, there will be duplication. But, as I didn't create this mess (a relative term, as many won't think this is a mess at all), I won't try to solve it, and I exit the discussion having given my opinion...--AstroNomer 05:24, Jun 15, 2004 (UTC)

What happened in the 18th century in astrophysics? -- Karada 14:18, 10 Jun 2004 (UTC)


 * Not a lot. Astrophysics didn't become distinct from astronomy until people began studying the spectra of celestial objects in the 19th century.  By the way, I've been trying to learn (or coin?) the name of a branch of astrophysics (I think), dealing with the rate at which more massive chemical elements are created and dispersed over time: see Talk:Kinetics. --Arkuat 02:12, 2005 July 17 (UTC)

Vote
I agree with recombining. If it is too long, there must be a better way to split it. How about making history of astronomy one page and astronomy and astrophysics the other. Or if not that, then before and after the year 1900. That sort of corresponds to the modern physics period. --David R. Ingham 21:54, 9 August 2005 (UTC)

Galileo
", but in astronomy his observation did not have astrophysical significance." You mean his laws of motion experiments didn't yet. They contributed to classical mechanics, and therefore to explaining Kepler's laws. --David R. Ingham 21:21, 9 August 2005 (UTC)

Images
The usage of the image of a galaxy doesn't seem right to me.. While it might be on the cover of an astrophysics textbook, it doesn't illustrate the concept of astrophysics at all. IMO, images of the cosmos belong in Astronomy, diagrams and things belong in astrophysics. &mdash;Snargle 01:31, 6 September 2005 (UTC)

Stellar structure
One of the biggest astrophysical topics that seems to be almost completely missing from this page is the very successful model of stellar structure for main sequence stars. The model includes hydrostatic equilibrium, thermal equilibrium, opacity, energy transport (conduction, convection, and radiation), and, of course, energy production. The Stellar structure page only has a weak coverage of this topic. Thanks. :) &mdash; RJH 17:43, 9 September 2005 (UTC)

Astrodynamics; choice of topics?
I feel as though celestial mechanics is classified as a branch of Astrophysics. Regarding to this, I don't understand why it should have its own section; also the article should be formulas-free as this is supposed to be an introductory article.

I think that a good thing to do would be to create a 'research topics', listing the most prominent topics that are object of theoretical research, linked to the appropriate page and divided in four main chunks. ie: Lipschitz 17:26, 7 January 2006 (UTC)
 * Star and stellar populations: Stellar evolution, Stellar structure, Variable stars, Globular clusters, Pulsars, Extrasolar planets...
 * Extragalactic: Galaxy formation, Galaxy evolution, Galactic dynamics, AGN, Cluster of galaxies...
 * Cosmology: Universe models, CMB, Dark matter, Dark energy...

I think that astrodynamics (celestial mechanics) is not just a branch of astrophysics. i have taken upper-level courses in both and neither even overlap material.

Dpu2002 17:42, 5 June 2006 (UTC)

GA nomination
I took this article off the good article nominations page as I feel it fails the criteria - it omits major facets of the topic by being extremely brief. The theoretical astrophysics section, for example, consists of one sentence and a list. Worldtraveller 21:40, 22 April 2006 (UTC)

Pre-Aristarchus?
"This idea had been around, though, for nearly 2000 years when Aristarchus first suggested it, but not in such a nice mathematical model." -- tantalizing, but no citation. Can someone be more specific? David Brooks 02:54, 24 June 2006 (UTC)

Inappropriate Content
The paragraph in the 'Theoretical Astrophysics' section Within the astronomical community, theorists are widely caricatured as being mechanically inept and unlucky for observational efforts. Having a theorist at an observatory is considered likely to jinx an observation run and cause machines to break inexplicably or to have the sky cloud over is in my opinion inappropriate for an encyclopedia and should be removed. Thomas —The preceding unsigned comment was added by 81.107.80.92 (talk) 10:18, 6 December 2006 (UTC).

Merge notice
Please see the discussion at Wikipedia Talk:WikiProject Astronomy. Dr. Submillimeter 23:00, 14 June 2007 (UTC)

In my humble opinion, the statement that "To become a classic research astronomer (someone who runs a telescope, analyzes data, publishes papers), astrophysicists need to get a Ph.D. degree." stands at the same level as the statement "To conduct a masss it is necessary to have been ordinated as a priest." I also think it is false. The author presents an interesting historical review where most of the people had not PhD degrees. —Preceding unsigned comment added by 72.222.155.206 (talk) 23:25, 28 June 2008 (UTC)

Turn into redirect for astronomy
It looks like this could be turned into a redirect for astronomy at this point. Most of the useful non-duplicative material was moved to astronomy. I will do this on 25 Jun 2007 unless I receive strong objections. Dr. Submillimeter 13:44, 22 June 2007 (UTC)


 * Good idea. Until(1 == 2) 14:16, 22 June 2007 (UTC)


 * I know this is somewhat late, but historically the fusion of astronomy with astrophysics is rather recent, since astrophysics itself (as a field of study) is of much more recent origin than astronomy. The history of astronomy extends back into prehistory, but the history of astrophysics is rooted in the discovery of spectral lines by Fraunhofer and others.  From that time, only 200 years ago or so, until the development of quantum mechanics only 75 years ago, the fields were completely distinct.  I think a short separate article about the subject matter that has historically been specific to astrophysics and distinguished from astronomy as a whole might be better than a simple redirect.  There is a distinction to be drawn, even now, and the specifically astrophysical content tends to get lost in the (already very large) article on astronomy.   I propose reverting the redirect, and shortening and simplifying the article on astrophysics as it stood at the time the redirect was made.  --arkuat (talk) 08:01, 21 July 2007 (UTC)

Actually, it could be argued that the fusion of astronomy with astrophysics started with Isaac Newton, whose theories of physics were first applied to the motions of the planets. This assessment above is therefore incorrect. Moreover, the astronomy and astrophysics articles contained mostly redundant information anyway, so merging the articles made sense. Furthermore, this was extensively discussed in several locations (including Wikipedia Talk:WikiProject Astronomy before action was taken; reverting this would be disruptive. Finally, may I ask whether arkuat is a professional astronomer like I am?  Is he really familiar with the field?   If not, then perhaps he or she should rely on the professional advice of others.  Dr. Submillimeter 08:25, 21 July 2007 (UTC)

November 2007
This merge looks as if it has not worked. With over 50 other languages still having separate articles for Astrophysics, and over 500 articles linking here, it looks as if there is not really a consensus for the redirect and that a large number of people see a distinction. Moreover, it has contaminated the Astronomy article, which now contains a POV description of why they could (implying should) be considered equivalent. The leading proponent of the redirect has left Wikipedia, making it difficult to discuss, so I think we should try restoring the earlier version and see whether this leads to an improvement. --Rumping 23:23, 11 November 2007 (UTC)

February 2008
The merge did work. The referenced information in astronomy clearly indicates that astrophysics is frequently used interchangably with astronomy. Moreover, a consensus was built up both here and at Wikiproject Astronomy that the merge should go ahead.

The revert, however, did not work. The reverted article still contained no references to back up any of its statements about what it defined as astronomy. Anonymously, I left a tag indicating that the introduction (which could be considered controversial) was unreferenced. Nothing happened.

I also do not think that the astrophysics articles in other langauges (which are often poorly referenced or copies of the English-langauge Wikipedia) are a justification for keeping a factually incorrect article here. I also have not seen any discussion here or any effort by Rumping to discuss the reversion.

Therefore, I am reverting this article back to a redirect. Next time, please discuss the issue first, and please discuss the meaning of astrophysics with a professional astrophysicist. Dr. Submillimeter (talk) 18:25, 6 February 2008 (UTC)


 * I did raise it here on the talk page, on 11 November. The anon redirect was reverted in December, not by me, suggesting you are nowhere near a consensus. Even your own paragraphs give references showing that astrophysics is a branch of astronomy.  And if neither the early history of astronomy nor modern amateur observational astronomy are astrophysics and there are a huge number of incoming links to Astrophysics then there really is not a good reason to merge, . --Rumping (talk) 09:55, 9 February 2008 (UTC)

Please come join the discussion over on the astronomy project page. WilliamKF (talk) 18:02, 13 February 2008 (UTC)

March 2008 and later
Also, I have put a subsection in the Wikipedia talk:WikiProject Astronomy article under the Essence of astronomy section that tries to clarify the distinction for incoming readers:


 * Relation to astrophysics


 * The subjects of astronomy and astrophysics are very large and closely related, too overlaid and intertwined in almost all their branches for either to be considered subordinate to the other. Astronomy is the ancient subject, concerning the observations of bodies beyond the Earth (and also with timekeeping and calendar maintenance), together with the meaning of those observations and our understanding of the nature of those bodies. Astrophysics is much more recent. The basic understanding of the movement of celestial bodies, and its essential connection with earthly natural science, or physics, dates from the work of Galileo and Isaac Newton. The realization that the light of stars could be analyzed for clues about their physical nature, such as mass, size, temperature, composition, age, and evolution, began with the development of optical spectroscopy in the mid-19th century.


 * Thus uninterpreted observation may be considered as closest to pure astronomy, whereas physical modeling of the Universe, from comets and asteroids to the Sun, planets and stars, to cosmology and the Big Bang, becomes more nearly "pure astrophysics" (if indeed such a subject exists apart from speculation) the more it is concerned with laboratory and theoretical physics, and the more detached from observation. As astronomy has taught us a great deal about physics, so has physics (and its related fields, from mathematics to chemistry, and perhaps soon to include biology) proved essential to our understanding of astronomy.

I worry that at least some sourcing is needed, for though I do happen to be "a professional astrophysicist" in some sense, this is not really enough. But consensus among other editors that it is at least going in the right direction would help. It seems to me that the definition given in this Astrophysics intro is fairly good. Wwheaton (talk) 00:00, 17 March 2008 (UTC)


 * That's a beautifully written pair of paragraphs, and I'm particularly fond of the nice succinct summary of the historical aspects at the end of the first paragraph. --arkuat (talk) 06:28, 26 June 2008 (UTC)

Scientific Discussion - Astrophysics
http://www.intellecttoday.com/

IntellectToday is a place to discuss Astrophysics, as well as other scientific and philosophical subjects. IntellectToday has an extensive database related to Astrophysics and Astronomy, and considers it one of it's primary points of focus. —Preceding unsigned comment added by 71.181.181.118 (talk) 22:48, 27 March 2008 (UTC)

Who discovered laws of planetary motion?
The history section has the following:

Later that century, Isaac Newton bridged the gap between Kepler's laws and Galileo's dynamics, discovering that the same laws that rule the dynamics of objects on Earth rule the motion of planets and the moon. Celestial mechanics, the application of Newtonian gravity and Newton's laws to explain Doplers's laws of planetary motion, was the first unification of astronomy and physics.

At 23:37, 6 July 2008, someone with the I.P. address I have today made the change from "Kepler's laws" to "Dopler's laws". I beleive "Kepler's" is correct, and it is Kepler, not Dopler that is mentioned earlier in the paragraph. 206.53.197.24 (talk) 16:49, 6 August 2008 (UTC)


 * You are correct, and I undid the edit in question. Thanks.  -- Coneslayer (talk) 17:40, 6 August 2008 (UTC)

Allegedly unsourced statements in the history section
An IP editor just deleted quite a lot of material from the history section, for being unverifiable or for being sourced from YouTube. All the material in those paragraphs is meant to be supported by the reference given at the end of each one: I'm not arguing that the paragraphs are good interpretations of those sources, but the information is (meant to be) sourced. The YouTube videos are of lectures by an accepted authority in the field, George Saliba, which would seem to be appropriate sources. Then again, I would happily support deleting almost the entire history section, as it is not about astrophysics and it is all repeated from other articles. Perhaps all that appears to be about astrophysics is the very last paragraph; the rest is just astronomy. All the best. –Syncategoremata (talk) 22:55, 29 May 2010 (UTC)

Please revert vandalism
Someone with the powers, please revert the article to 20:57, 2 July 2010 asap. Keeping my manually reverted revision would not do much harm, but a nice, clear revision revert would be more appropriate. -- Nameless Undead (talk) 13:22, 10 July 2010 (UTC)

Experimental and Computational Astrophysics Sections Needed
Experimental Astrophysics: Experimental astrophysics is at the intersection of astronomy, engineering, and physics, in other words, research specializing in the design and construction of astronomical instrumentation. Experimentalists find astronomical problems that demand technical innovation for their solution, problems that cannot be solved using existing techniques or instruments. The development of new detector technologies, new instruments, and new concepts for future astrophysics space missions open up new possibilities for discovery.

Computational Astrophysics: Astrophysical processes are extremely nonlinear and computers are essential to understanding them. This involves building on analytical models, desktop calculations, and high-quality observations to conduct large-scale parallel computations with detailed, testable predictions. Computational astrophysicists do not merely run public domain codes‭,‬ but rather lead efforts to develop‭, ‬implement, ‬and test new state-of-the-art algorithms in many areas‭. ‬

--72.193.73.84 (talk) 19:11, 1 January 2012 (UTC)

Inaccurate history section
The history section inaccurately expounds too much on pre-modern astronomy. Modern physics essentially started with Galileo, Newton, Boyle, Halley and some few more, but evolved slowly until the 19th century, when stellar dynamics and spectroscopy was emerging. We almost don't need the extensive text on antique and medieval cosmology, which is almost off-topical, since premodern astronomy could be said to be pre-physics science. Rursus dixit. ( m bork3 !) 10:55, 1 June 2012 (UTC)
 * It doesn't seem so much that the pre-modern section is inaccurate, but that it is inappropriate. According to the OED, the terms astrophysics and astrophysicist first appeared in 1870 and 1869, respectively.  The oldest texts where these words appear refer to their concern with the "luminous spectra of the heavenly bodies" and "the influences which pressure and temperature exercise on the nature of the spectrum of luminous gases."  In sum, the original meaning of the term was concerned with the use of spectral information to determine the composition of celestial bodies and gases.  Since, then, astrophysics has expanded to consider the physical processes within the stars and in the interstellar medium.


 * As it stands, this article expands the meaning of astrophysics to include the early celestial mechanics of Newton's Principia; Galileo's discovery of the moons of Jupiter, and even a wide range of early discussions of the cause of the tides. If this article were to consider the history of the composition of the celestial bodies before the Nineteenth Century, it would probably be appropriate to discuss the various concepts that celestial bodies were made of a different kind of material, as advanced by Plato (Fire) and Aristotle (Aether) and Galileo's arguments to the contrary that celestial bodies were Earthlike in their nature.  Such a historical narrative leads more naturally to the use of spectra to identify earthlike elements in the stars, than does the article's present one.


 * I'd welcome comments from astronomers about what kind of historical treatment would reflect the modern scope of astrophysics. SteveMcCluskey (talk) 21:16, 12 June 2013 (UTC)


 * After looking further at the historical treatment, It seems appropriate to delete most of the discussion of pre-modern cosmology, replacing it with a brief discussion of the material nature of the Aristotelian cosmos. SteveMcCluskey (talk) 19:33, 17 June 2013 (UTC)

Assessment comment
Substituted at 14:17, 1 May 2016 (UTC)

Information and references
I've been looking at this article and feel that there is much to be improved. For an article on such a weighty scientific field, it seems to be lacking in sufficient references, furthermore, the introduction does not set out the basics and principles of astrophysics as clearly as it should. I'm by no means an expert on the topic and merely fascinated by it, as such I feel my contributions to the page would be limited. Nonetheless, for those who are more well-learnt on the topic I just wanted to raise the issue. I've inserted a small number of sources to the introduction and have added an additional sentence which, I feel and hope, flows decently within the intro (please review it if you wish).

Kind regards,

--&#38;レア (talk) 00:44, 20 December 2013 (UTC)

Taught in Engineering Departments?
There is a long-standing claim that astrophysics is taught in engineering departments. Three sources were recently added to support this claim.

After checking all three sources I find that the closest they come to discussing engineering is to indicate that some engineering coursework may be taken as part of a degree program (or minor) in astronomy, astrophysics, or interdisciplinary studies or that astrophysics is part of the general development of education in Science, Technology, Engineering, and Mathematics (STEM). Since these sources do not support the claim made, I intend to delete the claim and the sources shortly. --SteveMcCluskey (talk) 16:01, 28 February 2014 (UTC)


 * I have deleted the claim discussed above. Sorry I missed an edit description :( SteveMcCluskey (talk) 13:51, 1 March 2014 (UTC)

Was Carl Sagan an astrophysicist?
A recent edit added a section listing prominent astrophysicists, among them Carl Sagan. I deleted Sagan's name since he is a noted planetary astronomer, not an astrophysicist.

Since my edit was reverted I took a quick check of the title's of Sagan's 645 publications listed in the NASA ADS. Starting with his oldest listed publication, The Production of Organic Molecules in Planetary Atmospheres, Astronomical Journal, Vol. 65, (1960) p. 499, Sagan's scientific work has focused on planetary astronomy; I saw no scientific papers on astrophysics. Lacking evidence that Sagan was an astrophysicist I intend to delete his name again. --SteveMcCluskey (talk) 04:35, 22 December 2014 (UTC)


 * You might want to check his article at Carl Sagan before you blunder and change the status quo of this article a second time. Joys and Happy Holidays to you and yours! –  Paine Ellsworth    07:58, 22 December 2014 (UTC)


 * Okay, this is just weird. I'm not sure what status quo is, since I went back six months and did not find Sagan's name in the article.  Now it seems that it is not only you, SteveMcCluskey, who does not think that Sagan was a respected astrophysicist – Tetra quark just reverted my reversion with the edit summary, "There is no edit war. I just undid his revision once on a mistake. His revision is ok."  His revision is not okay.  Even if we separate the man from the PhD (the one in astrophysics he achieved in 1960), Sagan was both notable and respected, and an astrophysicist.  So I don't understand why his name should be removed from that article section.  Please explain it to me as if I were a six-year-old. –  Paine Ellsworth    23:21, 22 December 2014 (UTC)


 * Okay, you've made me dig a little deeper. First, Sagan's dissertation was granted by the Department of Astronomy and Astrophysics at the University of Chicago but that doesn't really resolve the question of whether it's a dissertation on astronomy, astrophysics, or both.  It's title, however, "Physical Studies of Planets" clearly points in the direction of planetary astronomy, rather than astrophysics (which focuses on the nature of the stars and bodies beyond the solar system).  Confirming that reading of the title is David Morrison's biographical note on Sagan published by the National Academy of Sciences: "Sagan continued at Chicago for graduate work, receiving his doctorate in astronomy in 1960 with Gerard P. Kuiper as advisor." By the time Sagan was his student, Kuiper's work was focusing on solar system astronomy.  In sum, Sagan wrote a dissertation on planetary astronomy with an advisor who was working in the same field; his training was clearly that of a planetary astronomer, not of an astrophysicist.
 * Turning to his later research, I went beyond my subjective reading of the titles of his papers to see where he published them. He published 106 papers in Icarus, a leading journal of solar system studies; 18 in the Astronomical Journal, and 19 in the Astrophysical Journal.  His publications in Astrophysical Journal mainly concern aspects of his work on planetary astronomy.
 * In sum, Sagan is a significant astronomer, but he does not represent the mainstream of astrophysics and thus shouldn't appear in this article as an exemplar of what astrophysics is about. --SteveMcCluskey (talk) 02:36, 23 December 2014 (UTC)


 * So then, you seem to be saying that these two articles do not give the correct information to readers? There is nothing in this article that restricts astrophysics' focus to the .  The first section of Sagan's article tells us that he received his PhD in astronomy and astrophysics in 1960.  Whether or not the focus of his articles was "planetary astronomy" is not the point.  The point is that everything he wrote was from the perspective of a trained astronomer and astrophysicist.  So your text above appears to fail to explain why Sagan cannot be considered a respected and notable astrophysicist.  Even his studies of planetary astronomy such as Venus included details that went beyond astronomy into the areas of chemistry and physics.  Only his detractors (and he had many for whatever reasons) would try to squelch his accomplishments in the physical studies of the universe.  What exactly is it about Carl Sagan's major gifts to humanity that you don't like? –  Paine Ellsworth    14:17, 23 December 2014 (UTC)


 * You're right, the articles you mention do mislead the reader, but then Wikipedia is not a reliable source.


 * As to the two articles you cite, the Carl Sagan article's description that Sagan has a degree in astronomy and astrophysics has been around since this unsourced edit ten years ago. The sources presently cited describe his degree as in "astronomy and astrophysics" but with no further detail.  The source I cite above describes it as a "doctorate in astronomy" from Chicago's Department of Astronomy and Astrophysics.  I would let the title of Sagan's dissertation speak for itself.


 * My central concern, however, is not with Sagan but with this article, which has long presented a confusing view of astrophysics. Until recent edits, it included everything in which physics was applied to astronomy, including such elements as Newtonian planetary dynamics.  This is historically unrealistic, as astrophysics emerged in the late nineteenth century with the use of spectroscopic methods to understand the physical nature of the stars and interstellar media.  Personally, I have on my to do list a rewrite of the article to clarify  the scope of astrophysics, but I haven't seen any sources that concisely define its scope.  The best sources I have seen are the contents of astrophysics textbooks and online syllabi of courses.  A few (far too long) examples follow:


 * Bradley W. Carroll and Dale A. Ostlie, An Introduction to Modern Astrophysics (2nd Edition) Addison Wesley, 2006: The Tools of Astronomy: The Celestial Sphere, Celestial Mechanics, The Continuous Spectrum of Light, The Theory of Special Relativity, The Interaction of Light and Matter, Telescopes; The Nature of Stars: Binary Systems and Stellar Parameters, The Classification of Stellar Spectra, Stellar Atmospheres, The Interiors of Stars, The Sun, The Process of Star Formation, Post-Main-Sequence Stellar Evolution, Stellar Pulsation, Supernovae, The Degenerate Remnants of Stars, Black Holes, Close Binary Star Systems; Planetary Systems: Physical Processes in the Solar System, The Terrestrial Planets, The Jovian Worlds, Minor Bodies of the Solar System, The Formation of Planetary Systems; Galaxies and the Universe: The Milky Way Galaxy, The Nature of Galaxies, Galactic Evolution, The Structure of the Universe, Active Galaxies, Cosmology, The Early Universe; Astronomical and Physical Constants, Unit Conversions Between SI and cgs, Solar System Data, The Constellations, The Brightest Stars, The Nearest Stars, Stellar Data, The Messier Catalog.


 * Lang, Kenneth R. Essential Astrophysics Springer, 2012:  Preface.- Observing the Universe.- Radiation.- Gravity.- Cosmic Motion.- Moving Particles.- Detecting Atoms in Stars.- Transmutation of the Elements.- What Makes the Sun Shine?.- The Extended Solar Atmosphere.- The Sun Amongst the Stars.- The Material Between the Stars.- Formation of the Stars and their Planets.- Stellar End States.- A Larger, Expanding Universe.- Origin, Life and Destiny of the Observable Universe.


 * Prof. Paul Schechter, Course at MIT, Modern Astrophysics (Spring 2006): Description: This course explores the applications of physics (Newtonian, statistical, and quantum mechanics) to fundamental processes that occur in celestial objects. The list of topics includes Main-sequence Stars, Collapsed Stars (White Dwarfs, Neutron Stars, and Black Holes), Pulsars, Supernovae, the Interstellar Medium, Galaxies, and as time permits, Active Galaxies, Quasars, and Cosmology. Observational data is also discussed.


 * My point is that discussions of the planets either do not appear at all or play a very minor role in astrophysics courses, while they play a major role in Sagan's studies, from his PhD dissertation to the end of his life. Sagan does occasionally draw on the findings of astrophysics, as when he said we're all made of star stuff, but astrophysics, as defined above, does not play a sufficiently significant role in his work to call him an astrophysicst.  Inclusion of the planetary astronomer Sagan in a discussion of prominent astrophysicists further confuses the focus of this, presently ill-focused, article. --SteveMcCluskey (talk) 16:09, 23 December 2014 (UTC)


 * No, sorry, you have not made this case. Since I'm not an astrophysicist, I cannot speak to how ill-focused is this article.  However, inclusion of Carl Sagan in any discussion of (quoting this article) "respected" and "notable" astrophysicists, if anything, monumentally adds to and improves this article beyond words!  Sagan received his bachelors degree in physics.  He received his masters degree in physics.  Then he received his doctorate in astronomy and astrophysics.  This says to me that everything he did, everything he studied and all that he wrote after that must have been colored with his training in both astronomy and astrophysics.  It is unconcionable that you or anybody else could possibly think otherwise with or without ulterior motive.  You seem to be judging him as a scientist by today's standards of what it is now to be an astrophysicist.  In reality, Sagan was a pioneer who helped shaped astrophysics and bring it to what it is today, and you have not shown otherwise.  His name belongs here. –  Paine Ellsworth    18:48, 23 December 2014 (UTC)
 * OK, we'll continue to work to improve the article's discussion of astrophysics. If you can provide sources documenting how Sagan contributed to astrophysics, please do so.  I will continue to challenge unsourced material in this article.  It seems to me that we've both said about all we have to say about Sagan and astrophysics.  I welcome others to add their two cents worth to this discussion. SteveMcCluskey (talk) 20:10, 23 December 2014 (UTC)
 * OK, we'll continue to work to improve the article's discussion of astrophysics. If you can provide sources documenting how Sagan contributed to astrophysics, please do so.  I will continue to challenge unsourced material in this article.  It seems to me that we've both said about all we have to say about Sagan and astrophysics.  I welcome others to add their two cents worth to this discussion. SteveMcCluskey (talk) 20:10, 23 December 2014 (UTC)

RfC: Should Carl Sagan be included as a prominent, notable and respected astrophysicist?
Carl Sagan was recently removed from the "Notable astrophysicists" section of this article. Since it is difficult to determine exactly what is "status quo", Sagan's name has not been returned to the article. Should Sagan be returned to that section or should his name continue to be omitted based upon the above discussion? –  Paine Ellsworth   17:08, 28 December 2014 (UTC)


 * I'd like to raise two points in addition to my discussions above:
 * First, to the extent that Sagan's education is at issue, his dissertation provides contradictory indications. On the Title Page (and the corresponding University form) it says it was submitted to the Department of Astronomy and Astrophysics.  On Page ii it is described as "submitted in partial fulfillment of the  require­ments for the degree of Doctor of  Philosophy in the Department of Astron­omy, University of Chicago, June, 1960."   I would take the title page and the form as reflecting the administrative organization of the University rather than Sagan's academic interests; he was an astronomer not an astrophysics.
 * Secondly, at the time he wrote his dissertation, Planetary Studies were emerging as a new discipline. One of the contributing areas was the work of Sagan and his dissertation director, Gerard Kuiper, on Physical Studies of Planets. Kuiper at that time was President of the International Astronomical Union's Commission on "Physical Study of Planets and Satellites".
 * The underlying question here is the relationship between planetary astronomy and astrophysics. If planetary astronomy fits within the framework of astrophysics, then Sagan is an astrophysicist and should be included in a list of notable astrophysicists.  If, however, planetary astronomy is a separate discipline distinct from astrophysics, the inclusion of Sagan would confuse the focus of the article and he should not be included.
 * Input from editors with expertise in astrophysics and its historical development may shed some light on this issue. --SteveMcCluskey (talk) 18:24, 28 December 2014 (UTC)


 * Support as nom. If Sagan was an astronomer who was involved in "physical studies of planets and satellites", then isn't he more than a planetary astronomer?  Doesn't "physical studies" show that his planetary studies must have also involved his background in physics?  (bachelors in physics, masters in physics, PhD in astronomy and astrophysics)  Sagan saw everything through the eyes of a trained astronomer and physicist; therefore he should continue to be included along with Professor Stephen Hawking and Neil DeGrasse Tyson as a respected and prominent astronomer and physicist in the "Notable astrophysicists" section of this article. –  Paine Ellsworth    23:26, 28 December 2014 (UTC)
 * Oppose. The argument supporting Sagan's inclusion seems to be that Sagan studied physics and Sagan applied his physical knowledge to astronomy; therefore Sagan was an astrophysicist.  This argument fails on several grounds.
 * First, almost all astronomers have extensive training in physics and much of their research employs physical principles, but not all astronomers are astrophysicsts.
 * Second, including astronomers who applied physics to the study of the heavens could (and until recent edits did) lead to the inappropriate inclusion in this article of people like Galileo, Newton, Kepler, and many others who used physical principles to understand celestial bodies.
 * Third, it ignores the particular focus and historical development of the discipline of astrophysics—which is really what this article should be about.
 * Lacking substantial evidence regarding Sagan's work in astrophysics and/or his active participation in the astrophysical community, I oppose his inclusion in a section on prominent astrophysicists. --SteveMcCluskey (talk) 19:49, 29 December 2014 (UTC)


 * Comment Wikipedia does not rely on what editors think, WP relies on Reliable Sources WP:RS, that may include his body of work but isnt exclusive to that. Adding or removing a name from a list, if the action disagrees with reliable sources is Original Research WP:OR. The question should be, is Carl Sagan listed as a notable astrophysicist in reliable sources? A quick search leads me to believe that in reliable sources, he is. That he may have gone into other areas is besides the point.  AlbinoFerret  04:28, 9 January 2015 (UTC)
 * Support. Sagan (unlike Galileo, Newton and Kepler) made significant contributions to astrophysics as defined in the first sentence of the article. Maproom (talk) 01:55, 1 January 2015 (UTC)
 * Support & Comment. As others, most recently AlbinoFerret, pointed out, That he may have gone into other areas is beside the point. My degree was in entomology. I spent nearly my whole professional career in various roles as a computer consultant. In some contexts I describe myself as a biologist,in some as an entomologist, in some as a consultant in any of several aspects of computer work. In all I have encountered various levels of assessment ranging from approbation to opprobrium; what I have not encountered is any client or colleague saying: "Ah, but you are not REALLY a..." whatever the discipline in question happened to be. And yet, neither I, nor any other practitioner in any of those fields could claim to be fully competent in every aspect of the field. IOW it is useful to define a competent practitioner inclusively in terms of his skills and activities, but to define him exclusively as falling outside a given professional category requires some type of formal, generally statutory, standard, such as we can say that though I have certain (admittedly limited and informal) medically significant skills, some of which are unusual among medical doctors, I emphatically am not a medical doctor; this can be demonstrated in any first-world country by showing (correctly) that I have never (and never will have) appeared on any medical register. At the same time many such a medical register will include professionals that are suitably qualified, but never do any direct medical practice, but are administrators, technicians, lab workers and the like. They might thoroughly validly be called medical doctors, but don't try phoning them for a medical emergency at midnight! (Personal experience, trying to find an honest to goodness doctor in a strange city by working through the medical pages in the directory.) Now, this Sagan-exclusion thing not only is nit-picking, it is nit-inventing. Some participants in the discussion are trying to invent, or quote inventors of, a discipline they call astrophysics. More health to them, but their only basis is the convenience of certain authors and tertiary courses, and not even internally consistent, let alone mutually consistent sources at that. To try to limit "astrophysics" to what goes on in stars makes about as much sense as trying to limit "astronomy" to the naming of stars ("astro-" plus "-nomy", right?) not studying anything that happens inside stars, which would include two extra (and mutually exclusive) disciplines, astrophysics and astrochemistry, and certainly not anything to do with what happens between stars such as between binary pulsars or (Horrors!) planets orbiting stars. I am sure you can see where this gets you. 1: Lets not waste everybody's time niggling. 2: If you want to eliminate Sagan from the ranks of astrophysicists, you need to do better than point out that he did more of work other than the narrowly- and arbitrarily-defined astrophysics of a few textbooks and university prospectuses. 3: If you wish to argue that he was not notable, enjoy, but it will take some special pleading. JonRichfield (talk) 06:49, 1 January 2015 (UTC)
 * SNOW support Sagan's credentials in the area of astrophysics, and especially his relevance to popularizing topics within it, are about as well-attested as you're going to get, but that being said, aside from AlbinoFerret's comments, most everyone (well reasoned as their arguments have generally been) has been missing the point as regards the factors that influence a content-policy decision here; as AF states it's not how we regard him but how the sources do, and multiple sources do indeed reference him as an expert in the field in question.  S n o w  talk 16:21, 8 January 2015 (UTC)
 * Support per AlbinoFerret and Snow. The article should reflect what reliable sources say, not what editors think, and reliable sources appear to say that he was an astrophysicist. Ca2james (talk) 00:52, 10 January 2015 (UTC)
 * Yes Carl Sagan was a notable Astrophysicist. My only concern is whether we should even have the List of Notable Astrophysicist as a subsection of this article. Is there a guideline on such things? I propose that we work the names into the prose of the article and delete the section. Anyone interested in a draft? --Adam in MO Talk 21:07, 19 January 2015 (UTC)
 * Comment Good point.  I agree that discussion of the nature of individuals' contributions to astrophysics should best be included within the body of the article (perhaps in the history section) rather than having a separate list in the article. --SteveMcCluskey (talk) 02:43, 20 January 2015 (UTC)
 * It does sound like a good idea to integrate the names of notable astrophysicists into other sections of the article. The three mentioned before this RfC, Professor Stephen Hawking, Neil DeGrasse Tyson and Carl Sagan were in the article both because they are prominent and to be representative examples of "Several astrophysicists (who) have become prominently well known culturally for modern science education."  It wouldn't hurt the article if those three and other notable astronomers who are also physicists were to be summarized throughout the article.  Until that can be done in an encyclopedic manner, it would still be a good idea to reinsert Sagan's name back into the section from where it was extracted. – Paine Ellsworth</b>C LIMAX ! 06:16, 21 January 2015 (UTC)
 * I think this would be the best way to go. I'll leave it to those who are experts in this area to take care of the execution. I don't have the time to give it the attention it deserves.--Adam in MO Talk 15:24, 21 January 2015 (UTC)


 * Oppose/Comment As an article on a scientific topic, name-dropping of practitioners should be done sparingly and mainly in the history section. The history section could use a brief precis about black holes and condensed-matter stars, in which Schwartzchild and Hawking would be due mentions. While Sagan and Tyson are astrophysicists and are notable, they are not notable as astrophysicists. They get their due at Popular science. Rhoark (talk) 17:22, 30 January 2015 (UTC)

Expansion of the History section
As mentioned above, apart from the "notable astrophysicists" issue, I think the history section could do with expansion about the development of knowledge of stellar lifecycles. Here's some candidate text - unsourced at the moment, but the linked pages could easily be looted for citations


 * Classification of stars by spectrum and luminosity led to the creation of the Hertzsprung-Russell Diagram and identification of the Main Sequence, the first steps toward understanding of stellar evolution. Arthur Eddington presented in 1926 an explanatory model for stars' positions on the diagram based on stellar structure and the Kelvin-Helmholtz mechanism, which was believed at the time to be the primary source of energy in stars. In 1938, Hans Bethe and Charles Critchfield explained solar radiation as a product of nuclear fusion, enabling the prediction of stars' transitions through phases of the diagram. The theory of stellar nucleosynthesis of heavier elements was developed by Fred Hoyle in 1946.


 * When a star is depleted of fusible elements, it will collapse into one of several possible remnant objects, depending on the star's mass. The majority of stars will become a white dwarf and resist further collapse via electron degeneracy pressure, a process explained by Ralph H. Fowler in 1926. Stars more massive than the Chandrasekhar limit may overcome electron degeneracy pressure to become a neutron star composed of neutron degenerate matter, a type of object predicted by Walter Baade and Fritz Zwicky in 1934. The first neutron star to be identified as such was observed by Jocelyn Bell in 1967. Particularly massive stars can collapse into a black hole, a region whose gravitational pull cannot be escaped. Black holes were described in terms of the Einstein field equations by Karl Schwarzchild in 1915.

I got stumped at how to concisely describe the contributions of Penrose and Hawking. It could also benefit from a further paragraph about the development of ideas around novae, nebulae, and solar system formation. Rhoark (talk) 05:12, 3 February 2015 (UTC)


 * I agree that the history section needs expansion. Among other things, it would illustrate what questions astrophysics addresses and how it is done. Since its a bit outside my detailed historical study (which pretty much ends after Newton) I did some bibliographic searches that might provide useful starting points.:
 * Longair, Malcolm. 2013.  The Cosmic Century: A History of Astrophysics and Cosmology. Cambridge University Press.
 * Becker, Barbara. 2011. Unravelling Starlight: William and Margaret Huggins and the Rise of the New Astronomy. Cambridge University Press.
 * From the reviews (haven't had time to get the books) Longair presents a scientist's history of the development of astrophysics while Becker presents a historians' study drawing on both manuscripts and published materials. SteveMcCluskey (talk) 14:43, 3 February 2015 (UTC)
 * Belated thanks for the suggestions. I'd personally find it more congenial to find the necessary bits in finely focused monographs. No time to ruminate. If you come across a relevant book passage though, it could help to note the page number. Rhoark (talk) 20:26, 17 March 2015 (UTC)

I'd like to move forward with this, but I realized I misinterpreted Eddington's position with respect to the Kelvin-Helmholz mechanism. I'm going to see if I can parse the issue better out of this, if no one else works it out in the meantime. Rhoark (talk) 20:21, 17 March 2015 (UTC)

Section about notables
The section about notable astrophysicists is in need of change and expansion as noted in past discussions. While I could just make the following edits, I would prefer to first propose them here as follows:

== Growth == (rather than "Notable astrophysicists")

The two separate sciences of astronomy and physics first began to combine together as a single discipline due to the work of Tycho Brahe, Galileo and Johannes Kepler. Kepler used Brahe's naked eye observations to make the astounding discovery that the orbits of the planets were not perfect circles but instead are elliptical shapes! In modern times, astrophysics, astronomy and cosmology have been popularized by notable educators such as prominent professors Subrahmanyan Chandrasekhar, Stephen Hawking, Hubert Reeves, Carl Sagan, Neil deGrasse Tyson and others. Their efforts have attracted and continue to draw young people to study astrophysics.

With the above, there is still room and need for expansion of this section, but I wonder if it might be considered an improvement? – <b style="font-size:85%;color:darkblue;font-family:Segoe Script">Paine</b> 14:23, 17 July 2015 (UTC)


 * I think your edit goes in the wrong direction, as it seems to bring back the confusion between the physics of planetary motion (inaugurated by Kepler et al.) and astrophysics, which deals with the physical nature of the celestial bodies. This has been discussed previously on the talk page.
 * The new science of astrophysics is generally held to have emerged in the mid to late nineteenth century. As James Keeler defined it in 1897 in an article in vol. 6 of the new Astrophysical Journal, which he co-edited, Astrophysics "seeks to ascertain the nature of the heavenly bodies, rather than their positions or motions in space–what they are, rather than where they are."  That quotation is currently buried in footnote 1; perhaps I should move it into the article somewhere.
 * Adding Brahe, Galileo, and Kepler doesn't really advance the discussion. --SteveMcCluskey (talk) 14:45, 18 July 2015 (UTC)
 * Thank you for your comments! Didn't realize that past discussions had actually removed Kepler from the history of astrophysics.  The fact remains that, just as astronomy has its roots in astrology, astrophysics has its roots in 17th century astronomy, not just Galileo's great work, but also Brahe's and Kepler's.  In my opinion, it's the very same type of argument people have used to say that Carl Sagan wasn't a "real" astrophysicist.  Historical facts should not be denied.  There is nothing in my brief rendering above that denies that a modern science of astrophysics actually began to take shape in the 19th century – that would be the "young sapling tree".  But the firm "roots" or foundation was laid more subtly by Brahe's viewings and by Kepler's excruciatingly difficult conclusions he drew from those naked-eye observations.  There is still room for "growth" in that section, and while nobody is saying that Kepler's work was "astrophysics", it certainly was at least one of the first building blocks of the science. – <b style="font-size:85%;color:darkblue;font-family:Segoe Script">Paine</b>  15:02, 18 July 2015 (UTC)
 * I'd be careful about the aspects of the work of 17th century astronomy that relate to astrophysics. Their concern with the position and motion of the planets really points back to the earlier astronomical work of Ptolemy and his predecessors rather than forward to astrophysics.  Their concern with the physical nature of the celestial bodies themselves, and to a lesser extent their insistence that the same laws operate on them as on Earth does relate -- in a general way -- to the later development of astrophysics.  In this regard I would rank Galileo, Descartes, and Newton as more important to the development of astrophysics than Kepler. --SteveMcCluskey (talk) 15:25, 18 July 2015 (UTC)
 * Well, they all lived in the midst of a change of perspective from retrograde astronomy, which asserted that the various laws were once well known and lost and just had to be rediscovered, and progressive astronomy, of which Kepler was an avid and important supporter and which maintained that "modern" astronomy (of their time) had slowly grown out of the infant Babylonian, Greek and Chinese astronomies, that there was no "lost" astronomy. As I said and implied, none of them were astrophysicists, but they all played an important role in the eventual flowering of astronomy, cosmology and astrophysics.  The rest is just your and my personal opinions of their contributions, an area in which we evidently, and sadly, disagree. – <b style="font-size:85%;color:darkblue;font-family:Segoe Script">Paine</b>  17:52, 18 July 2015 (UTC)
 * I'm a bit puzzled about what you mean by the rediscovery of lost astronomies — Newton sometimes maintained that he was merely presenting the wisdom of the ancients but Galileo and Descartes were certain they were doing something innovative.
 * Since you maintain that Kepler contributed to the flowering of astrophysics (astronomy and cosmology aren't really relevant to this article) feel free to spell out the nature of that contributions to later understanding of the physical nature of the heavenly bodies — in Keeler's phrase, "what they are."
 * Incidentally, thanks for the Descartes ref., I gave away my Descartes when I retired. --SteveMcCluskey (talk) 20:20, 18 July 2015 (UTC)
 * I feel very certain that you have read at least as much about Kepler as I have read, so I see no need to expound on his excellent math and physics prowesses in addition to his greatness in astronomy. Like Galileo, Kepler was both an astronomer and a physicist, so in my opinion they were both quintessential astrophysicists long before the actual term came into being.  Astronomers today have done all they can to distance themselves from astrology, and rightly so, since astrology is by no means a scientific endeavor (only a "popular" one).  In addition to Kepler being a great astronomer, physicist and mathematician, he also liked to give the occasional astrology reading to friends and acquaintances, much as did Tycho Brahe.  And I think that may be why Kepler and Brahe are swept under the rug today by many science lovers.  Just as astronomers cannot deny astronomy's historical connection to astrology, those who would extract Kepler from the history of astrophysics still cannot deny his work in astronomy and physics that played a role in the foundation and construction of astrophysics as a true science.  To deny the facts, whether scientific or historical facts, isn't really a very scientific attitude, is it?  Kepler did not have the tools to study "what they are", so he had to settle for "what were their orbits like?" instead.  His 25-year study of the orbit of Mars plus all the data he'd received from Brahe led him to a conclusion that, in his own words, almost drove him mad.  Kepler was a bit of a mystic (I know - just one more notch on your pistol), and his greatest and dearest belief and faith was in God, a creator who made a "perfect" universe.  And for hundreds, perhaps thousands of years that perfect universe, Platonic/Ptolemeic if you will, included planetary orbits that were perfect circles.  Try to imagine the agony Kepler endured when he could not match the eight data points he took of Mars' orbital path to a circular Martian orbit!  Lesser men, men who are not true scientists, would have discarded the data and stuck to the age-old tenets – not Kepler!  Kepler chose to go with the data and realized that the planetary orbits were ellipses, not perfect circles.  I'm just amazed that the Church didn't do to him what they did to Galileo.  Heck, Newton was a hero, almost a "god", in his country, Kepler was a distinguished man in his country, and Galileo was a criminal in his country.  What was up with that?  So the point is (and aren't you happy that I'm finally getting to it) scientists today should pay more attention to "what is right" rather than to "who is right".  The Kepler/astrology connection should not be used to deny his mega-contributions to science.  He, like Galileo, the Galileo who loathed both Kepler and astrology, was one of the fathers of modern astronomy and astrophysics.  The historical facts are "out there"! (and cannot be denied). – <b style="font-size:85%;color:darkblue;font-family:Segoe Script">Paine</b>  23:43, 18 July 2015 (UTC)
 * PS. As to the Descartes ref., it's a pleasure! And so sorry – I guess I could go on and on about all this.  Speaking of the separation of astronomy and astrology, how about the separation of church and science?  That's even more important than the separation of church and state – and yet nobody seems to hold Newton's faith against him.  Heck, Newton confided to a friend that, since he could find no cause of gravity after an exhaustive scientific search, he must conclude that gravity is caused by the creator.  "God did it!" was the best he could come up with.  Today, we know little more about gravity, but at least our scientists are still looking for a valid scientific explanation, not "God did it!".  Sorry, again. PS added by – <b style="font-size:85%;color:darkblue;font-family:Segoe Script">Paine</b>

Thanks for bringing up Kepler again. As Bruce Stephenson pointed out in his Kepler's Physical Astronomy, Kepler was very much in the tradition (going back at least to Aristotle) of trying to provide a physical explanation for celestial motions. (For the long history of this problem see the Wikipedia article on Dynamics of the celestial spheres, to which I contributed a substantial part.) It's interesting that Newton was also trying to relate, albeit with more mathematical rigor than any of his predecessors, dynamical theory to the observed motions of the celestial bodies. I would point out, however, that Kepler's and Newton's celestial physics, which is concerned with how the planets move and hence finding where they are is not astrophysics, which is concerned with finding what they are. Keeler's important distinction is why I don't see either Kepler's work or Newton's as astrophysics. --SteveMcCluskey (talk) 00:10, 19 July 2015 (UTC)
 * Under that definition of astrophysics, no none of the class of 17th are true astrophysicists – nobody could deny that. And I certainly never meant to imply that they were astrophysicists in that strictest sense.  It's the "history" and "growth" of astrophysics that should concern us both, and histories contain roots as well as stems, trunks, leaves and flowers.  The class of 17th are part of the roots of astrophysics, since very basically they began to combine astronomy and physics.  So they all, Descartes, Newton, Galileo, Kepler, and other men who in the end gave their all to science and truth, should continue to be seen as giants upon whose shoulders we all stand, and stand tall. – <b style="font-size:85%;color:darkblue;font-family:Segoe Script">Paine</b>  00:47, 19 July 2015 (UTC)
 * OK, I see where you're coming from, but if I were to trace the historical roots of astrophysics, I would look at the early answers to the questions raised by modern astrophysicists. What did early thinkers have to say about the physical nature of celestial objects?  In that regard, Aristotle's theory that they were made of Aether and Plato's rival theory that they were made of Fire provides early answers analogous to the modern astrophysicists' answer that stars are made primarily of Hydrogen and Helium.
 * When teaching Aristotle's science I used to use the discovery of Helium to illustrate the scientific nature of Aristotle's reasoning. Aristotle observed that the stars and planets moved with unchanging circular motion unlike the ordinary elements found on Earth, therefore they must be made of an element not found on Earth whose natural motion was circular; he called that element Aether.  Norman Lockyer observed that the spectra of the Sun and stars displayed absorption lines not found on any element on Earth, therefore they must be made of a different element not found on Earth which absorbs those wavelengths; he called that element Helium. Of course, all that is WP:OR and doesn't belong in the article.
 * Best, SteveMcCluskey (talk) 01:31, 19 July 2015 (UTC)
 * Agreed. That article you linked is a good read btw.  I have to leave now, and I'll try to massage the above tomorrow.  Not happy with the subheader, "Growth", for one thing.  Joys! – <b style="font-size:85%;color:darkblue;font-family:Segoe Script">Paine</b>  01:57, 19 July 2015 (UTC)

Second stab
== Popularization == (rather than "Notable astrophysicists" or "Growth")

The roots of astrophysics can be found in the seventeenth century emergence of a unified physics, in which the same laws applied to the celestial and terrestrial realms. There were scientists who were qualified in both physics and astronomy who laid the firm foundation for the current science of astrophysics. In modern times, young students continue to be drawn to astrophysics due to its popularization by notable educators such as prominent professors Subrahmanyan Chandrasekhar, Stephen Hawking, Hubert Reeves, Carl Sagan, Neil deGrasse Tyson and others. The efforts of the early, late, and present scientists continue to attract young people to study the history and science of astrophysics.

Please let me know what you think about this "second stab" as an improvement to the section now titled "Notable astrophysicists". – <b style="font-size:85%;color:darkblue;font-family:Segoe Script">Paine</b> 21:56, 20 July 2015 (UTC)


 * Some quick thoughts, the merger of physics and astronomy doesn't resolve the difference between celestial mechanics, to which the developments of the seventeenth century made major contributions, and the development of a unified physics of the celestial and terrestrial realms, which emerged at the same time. I think its the latter that we should be talking about here.  Maybe it could be done by rewriting the opening as follows:
 * "The roots of astrophysics can be found in the seventeenth century emergence of a unified physics, in which the same laws applied to the celestial and terrestrial realms. "


 * Okay, great! Thank you, very much, SteveMcCluskey, I've merged it in above.  The section seems to be shaping up! – <b style="font-size:85%;color:darkblue;font-family:Segoe Script">Paine</b>  00:04, 22 July 2015 (UTC)
 * Looks ready to go; nice job.--SteveMcCluskey (talk) 01:20, 22 July 2015 (UTC)
 * Thank you! I'm sure it could use some tweaks and more detail, yet it looks to me to be a good start. – <b style="font-size:85%;color:darkblue;font-family:Segoe Script">Paine</b>  01:32, 22 July 2015 (UTC)

Draft outline
There is a draft for an outline on this topic at WikiProject Outlines/Drafts/Outline of astrophysics if anyone is interested. There is also a RM request on the talk page related to moving it out of the WikiProject Outlines space to draftspace. -- Ricky81682 (talk) 08:33, 23 June 2016 (UTC)

astrophysics
Its importance in the uni8 Seethaangadi (talk) 13:15, 20 December 2016 (UTC)

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Request for comment: Plasma (physics)
There is a request for comment on the lede of Rfc Plasma (physics) that might interest astrophysics editors. Attic Salt (talk) 13:59, 14 October 2017 (UTC)

The article is also being considered for demotion from "good article" status:. Please consider weighing in. Attic Salt (talk) 14:53, 20 October 2017 (UTC)

Navbox clutter
The recent addition of the Science template to this article raises the total number of navigation templates to four; two sidebars (part of a series templates): Science and General physics and two horizontal navboxes: Branches of physics and Astronomy subfields. This seems to be a case of WP:NAVBOXCREEP.

I recommend deleting the two sidebars; the sidebar Science is too general for this specialized article, and the sidebar General physics overlaps significantly with the horizontal navbox Branches of physics. This should clean up the article while still facilitating navigation to related articles. --SteveMcCluskey (talk) 01:19, 10 January 2018 (UTC)