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- https://phys.libretexts.org/Bookshelves/College_Physics/College_Physics_1e_(OpenStax)/34%3A_Frontiers_of_Physics/34.04%3A_Dark_Matter_and_ClosureThe motion of stars in galaxies and the motion of galaxies in clusters imply that there is about 10 fold more mass as in the luminous objects we can see. The indirectly observed non-luminous matter is...The motion of stars in galaxies and the motion of galaxies in clusters imply that there is about 10 fold more mass as in the luminous objects we can see. The indirectly observed non-luminous matter is called dark matter. Why is dark matter a problem? For one thing, we do not know what it is. It may well be 90% of all matter in the universe, yet there is a possibility that it is of a completely unknown form -- a stunning discovery if verified. Dark matter has implications for particle physics.
- https://phys.libretexts.org/Bookshelves/Astronomy__Cosmology/Big_Ideas_in_Cosmology_(Coble_et_al.)/12%3A_Gravitational_Lenses/12.02%3A_Lensing_by_Point_MassesYou will understand how the lensing effect depends on the relative positions of the source, lens and observer and understand that the mass of the lens can be determined using gravitational lensing. Yo...You will understand how the lensing effect depends on the relative positions of the source, lens and observer and understand that the mass of the lens can be determined using gravitational lensing. You will understand that objects such as dim stars, brown dwarfs, and stellar remnants (white dwarfs, neutron stars, black holes) can act as gravitational lenses - collectively called MACHOs.
- https://phys.libretexts.org/Bookshelves/Astronomy__Cosmology/Supplemental_Modules_(Astronomy_and_Cosmology)/Cosmology/Astrophysics_(Richmond)/33%3A_Limb_DarkeningIn the closeup of this diagram below, you can see the estimated angular size of the source star (green circle) as it moves past the second and third caustic crossings (events B and C in the light curv...In the closeup of this diagram below, you can see the estimated angular size of the source star (green circle) as it moves past the second and third caustic crossings (events B and C in the light curve). The limb-darkening parameters are primarily determined by the behavior of the light curve between the time the source edge enters the caustic and the time the source center enters the caustic (and the inverse of this process as the source leaves the caustic).
