Mass–luminosity relation - Wikipedia
Low–mass stars dominate the local Milky Way, with tens of millions observed by A Photometric calibration and impact on the mass-luminosity relation at the . SDSS Standard Star Catalog for Stripe The Dawn of Industrial 1% Optical. sung to the tune of John Phillip Sousa's “Stars and Stripes Forever”: The stars that you see The mass-luminosity relationship, discovered in by English. and mass-to-luminosity-ratio-age relations of open clusters by including a number of is provided by mass loss from evolved stars and by the dynamical evaporation of (RG-clusters) tend to occupy the upper stripe and especially the.
Stars with too little mass do not have enough gravitational compression in their cores to produce the required high temperatures and densities needed for fusion of ordinary hydrogen.
The lowest mass is about 0. A star less massive than this does not undergo fusion of ordinary hydrogen but if it is more massive than about 13 Jupiters it can fuse the heavier isotope of hydrogen, deuterium, in the first part of its life. Stars in this boundary zone between ordinary stars and gas planets are called brown dwarfs. After whatever deuterium fusion it does while it is young, a brown dwarf then just slowly radiates away the heat from that fusion and that is left over from its formation.
Among the first brown dwarfs discovered is the companion orbiting the star Gliese Selecting the picture below of Gliese and its companion, Gliese B, will take you to the caption for the picture at the Space Telescope Institute.
With the discovery of several hundred brown dwarfs in recent infrared surveys, astronomers have now extended the spectral type sequence to include these non-planets.
Just beyond the M-stars are the L dwarfs with surface temperatures of about K to K with strong absorption lines of metal hydrides and alkali metals. Cooler than the L dwarfs are the T dwarfs. At their cooler temperatures, methane lines become prominent.
The Sun and Stellar Structure
Stars with too much mass have so much radiation pressure inside pushing outward on the upper layers, that the star is unstable. Stars on the Main Sequence must be using the energy generated via nuclear fusion in their cores to create hydrostatic equilibrium.
The condition of hydrostatic equilibrium is that the pressure is balancing gravity. Since higher mass means a larger gravitational force, higher mass must also mean that higher pressure is required to maintain equilibrium. If you increase the pressure inside a star, the temperature will also increase. So, the cores of massive stars have significantly higher temperatures than the cores of Sun-like stars.
At higher temperatures, the nuclear fusion reactions generate energy much faster, so the hotter the core, the more luminous the star. If you actually look at the equations that govern stellar structure, you can derive from those equations that: L M n where the exponent varies a bit for stars of different masses, but, in general, is approximately equal to 3.
There is no reason to suspect the AGN sample of having the same bias, as the mass measurements rely on flux variability and not dynamical techniques. Such a bias may help explain why some of the quiescent galaxies at the high luminosity end have black hole masses that are more than an order-of-magnitude larger than the active galaxies, although it may not completely resolve the disparity.
Finally, there may be no reason to expect that the MBH—Lbulge relationship is the same for the AGNs and quiescent galaxies, as only a modest number of objects are included in each sample and selection effects likely play an important role Lauer et al. Clearly, there remain several areas that are in need of investigation, any of which may shed light on the possibly inconsistent fits to the MBH—Lbulge relationship for AGNs and for quiescent galaxies.
As the MBH—Lbulge relationship is an important and widely used means of estimating black hole masses throughout cosmic history e. There appear to be many systematics in both the AGN and quiescent galaxy samples that must be investigated in order to more completely understand this important relationship.
Our future plans include investigating the biases in the AGN sample and extending the range of the relationship for AGNs.