Talk:Gravitational microlensing

message: Well, the article is not very well descibed, but it is my first Wiki article. The previous article (stating that a planet magnifies the light of its host star) was just good-old wrong, since it is the planet around the lens causing a deviation in the lightcurve!
There are plenty of potential issues to add: Microlensing is a tool producing many papers every month, so there is plenty of potential subjects to cover.
--Christianvinter 14:56, 12 July 2005 (UTC)

message: The NASA figure illustrating the effect of microlensing is technically wrong: The gravitational
field of the lens star does not focus the light of the observed source star like a convex lens.
Instead, light rays closer to the lens star experience a stronger bending (rather than a weaker one). Can this figure be replaced? I have contacted NASA JPL on this issue.
Martin Dominik, 21 February 2006
There are plenty of good illustrations about microlensing floating around on the web, but I don't know how to get around the copyright restrictions.  David s graff 13:13, 20 March 2006 (UTC)
thread_title:  Illustration of microlensing 

message: I felt like this page needed a new start, so I did a major overhall.  Rather than adding my own work to some of the previous work, I included nearly all the pre-existing links and ideas to my own description.  I've introduced many sections, currently blank, to be filled in later, but done some major overhall on the links to collaborations.  My apologies to the previous contributors if I've left something out.
I don't know why, but it seems to me that Astronomy articles lag behind other technical fields in Wikipedia.  Perhaps Astronomers are less likely to use Wikipedia than computer scientists.  Perhaps its just because as an Astronomer, my expectations are higher.  Or perhaps the neglect of this article reflects how the once red-hot field of microlensing has passed its glory. David s graff 10:35, 21 March 2006 (UTC)
thread_title:  Fresh Start 

message: in the second paragraph, it says: "When a nearby object passes in front of a distant star or quasar, the gravity of the nearby object magnifies the distant star. By detecting that magnification, astronomers can study the near star."
Don't we want that last word to be "object," not "star"? Because before we were talking about some object that might not be a star. Am I right? If so, could someone change it? Thanks.
:You are right. Changed. Christianvinter 15:43, 5 February 2007 (UTC)
replies: text: In fact, 'nearby object' is technically wrong. The probability for (phometric) microlensing tends to zero as the lens object gets close to the observer. A lens object half-way between source and observer is ideal. I took that opportunity to rephrase some other paragraphs. When I find some time, I should make further edits with respect to the historic developments. Maybe someone could send me a reminder? MD:astronomer 23:17, 10 February 2007 (UTC)
thread_title:  2nd paragraph 

message: Anyone seen comments along the lines of anywhere we are seeing something through a gravitational lens they (if anyone is there) are seeing us? Just looking for refs....--Smkolins (talk) 03:13, 22 March 2008 (UTC)
replies: text: You mean the Sun-Earth system, the whole solar system or what? If someone was observing the Solar System -- no matter almost which way -- if they were lucky enough to see any planets, it would be completely dominated by Jupiter. Anyway, yes there are papers touching on this subject, and it is relevant to this article at some point. Christianvinter (talk) 10:02, 27 March 2008 (UTC)
replies: text: There's a fair bit of chatter in the news of forth coming efforts specifically to identify Earth-type planets and I think micro-lensing was mentioned too. I'd presume in a microlensing environment any place we find could see us- certainly picking up Jupiter first but if they have an equivalent scope then they should be able to see Earth. If they are there and watching of course. I suppose that pattern is true of non-microlensing situations too (looking at our system with big enough scopes etc. but I thought of it in the microlensing situation first because it has some extreme distances it covers if you then look at the larger scale lensing. I've not seen references to it yet and would like refs if they are public.--Smkolins (talk) 11:07, 27 March 2008 (UTC)
replies: text: Microlensing is generally used to study the *lens*, not the *source*, and in particular planet detections are always planets around the lens. When we see a source get lensed, we're studying the object between us and the source, not the source itself. If someone at the source were looking back at us, they could see our sun get lensed, but it wouldn't be especially useful for, say, detecting planets around our sun. Cosmologicon (talk) 23:02, 2 April 2008 (UTC)
replies: text:  Thats not true.  Microlensing has been used to study the source stars, and has the potential to search for planets around source stars as well.  For example, and as detailed in http://spiff.rit.edu/classes/phys440/lectures/limb/limb.html , microlensing has been used to study limb darkening in source stars and is the only technique to study the surface of single stars besides the Sun and Betelgeuse.  I've written a paper describing the use of microlensing to look for planets around source stars: Graff & Gaudi, Astrophysical Journal 2000  David s graff (talk) 19:25, 31 October 2008 (UTC)
thread_title:  reversing the lens? 

message: This page seems pretty dead, which is too bad.  I'll start bugging my microlensing buddies to help out with it.  I've recently added some more text on other observables theta_E and r_E tilde/pi_E, and a new section of discussion of some other effects.
The introduction promises a discussion of how microlensing can be used to study a huge range of phenomena such as cosmic strings.  Either we should put in links to papers proposing these different ideas, or discuss them here in the article.  David s graff (talk) 16:55, 19 May 2009 (UTC)
thread_title: More work to be done

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thread_title:  External links modified 

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thread_title:  External links modified (January 2018) 

message: Regarding this paragraph in the lede:
:"Microlensing by an isolated object was first detected in 1989. Since then, microlensing has been used to constrain the nature of the dark matter, detect exoplanets, study limb darkening in distant stars, constrain the binary star population, and constrain the structure of the Milky Way's disk. Microlensing has also been proposed as a means to find dark objects like brown dwarfs and black holes, study starspots, measure stellar rotation, and probe quasars[1][2] including their accretion disks.[3][4][5][6] Microlensing was used in 2018 to detect Icarus, the most distant star ever observed.[7][8]"
If you read the sources, you can see that microlensing can be used to enable astronomers to constrain certain otherwise unknown aspects of an investigation ... say an upper limit of some variable.   But to say the microlensing can "constrain the structure of the Milky Way's disk", is perhaps overstating the power of gravitational lensing ...  The astronomer can use the data obtained to "constrain" their understanding of the thing under investigation, but certainly not the object itself.  
I think a preferable word would simply be "understand".   Since then, microlensing has been used to understand the nature of the dark matter, etc.
Since this is in the lede, I didn't want to wade in there and rewrite without getting other opinions, in case this use of the word is somehow normal for the subject matter.   I'll take a stab at it if I do not hear any objections in the month or so.
Bobsd (talk) 18:36, 13 January 2022 (UTC)
replies: text: Yes, it's a jargonistic usage in physics and some other sciences. It applies to the range of possibilities, in which theoreticians imagine what might be, and more detailed study shows that some part of that range cannot be. For example, we are in a ship and want to know how deep the water is. We know the whole planet can't be water, so it's less than 7000 km deep. We look down, and decide we are seeing 10 meters down and it's all just water. So, it's somewhere in the range of ten meters to 5000 km. We use a sounding weight on a kilometer of rope, and don't hit bottom, so now we have further "constrained" the depth to be between one and 7000 kilometers deep. Similarly, are detectable microlenses more numerous or less numerous, than stars? If we have found that they cannot be less numerous, or cannot be more numerous, we have "constrained" the range of possibilities. This bit of jargon is well understood among practitioners, but we're not writing for practitioners; we're writing for outsiders who are unfamiliar with the jargon of this trade. Jim.henderson (talk) 14:15, 16 January 2022 (UTC)
replies: text: I think that means we are in agreement.  Jargon is often used to avoid the need to be specific.  The only current usage in the lede that is specific enough to add any information to the article is "constrain the binary star population" since it points to population, a value that could have some limit.  But to use it for "nature" and "structure" is just too broad.  I just retired as a software quality engineer, so yeah ... jargon.  I'll sleep on making the changes.  Thanks for the input.  Bobsd (talk) 17:09, 20 January 2022 (UTC)
thread_title:  Use of the term "constrain"