Timeline for Theoretical measure of distance to black hole?
Current License: CC BY-SA 3.0
10 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| May 13, 2017 at 22:59 | comment | added | ProfRob | @tarzan How would knowing the radius of something tell you how far away it is? | |
| May 13, 2017 at 9:27 | comment | added | oarsome | @RobJeffries Since the radius can be estimated through a spectra feature, then knowing the mass (through some other measurement, e.g. lensing or orbital period in a binary), would one not be able to estimate the distance? Since there cannot be a parallax measurement that would provide another way of estimating distances. | |
| May 11, 2017 at 18:23 | comment | added | ProfRob | @Tarzan I don't understand what you are asking or how it could lead to a distance estimate. Estimating the physical emission radius can be done from a spectrum, yes. | |
| May 11, 2017 at 17:37 | comment | added | oarsome | @RobJeffries I understand that the angular resolution of current instruments don't allow for such measurements, but if I understand correctly spectrum line widths are used for velocity dispersion measurements. In this case there is no "line" or velocity but I was wondering whether there is a spectral feature (e.g. the slope at a certain wavelength) that could be used to estimate how much of the radiation is emitted from the near side. I gather from your answer that there is no such technique, but is that theoretically possible? | |
| May 10, 2017 at 13:22 | comment | added | ProfRob | @tarzan You need both the redshift and a measurement of angular size. The latter cannot be done at present. | |
| May 10, 2017 at 11:32 | comment | added | oarsome | @RobJeffries Would you not be able to estimate the radius based on that variation? | |
| May 10, 2017 at 11:29 | vote | accept | oarsome | ||
| May 8, 2017 at 21:14 | comment | added | ProfRob | @FlorinAndrei If you are simply arguing that this is a difficult measurement; well actually it is impossible at the moment. Doppler shift measurements accurate to 1 part in a million are routine these days., so measurements "close" to the black hole are not required. It is just getting an accurate angular measurement that is difficult. For example, we can easily measure M/R for a white dwarf from GR redshift, but the angular radii of white dwarfs are unreachable. The principle is exactly the same for a black hole. | |
| May 8, 2017 at 19:12 | comment | added | Florin Andrei | Isn't the sharp variation of redshift close to a BH a major impediment and source of errors in practice? Normally you want a function that varies more smoothly to perform such measurements. | |
| May 8, 2017 at 19:10 | history | answered | ProfRob | CC BY-SA 3.0 |