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'''Gravitational microlensing''' is an [[astronomical]] [[phenomenon]] due to the [http://en.wikipedia.org/wiki/Gravitational_lens gravitational lens] effect. It can be used to detect objects ranging from the [[mass]] of a [[planet]] to the mass of a [[star]], regardless of the light they emit. Typically, astronomers can only detect bright objects that emit lots of light (stars) or large objects that block background light (clouds of gas and dust). These objects make up only a tiny [[fraction]] of the mass of a galaxy. Microlensing allows the [[study]] of objects that emit little or no light.

'''Gravitational microlensing''' is an [[astronomical]] [[phenomenon]] due to the [https://en.wikipedia.org/wiki/Gravitational_lens gravitational lens] effect. It can be used to detect objects ranging from the [[mass]] of a [[planet]] to the mass of a [[star]], regardless of the light they emit. Typically, astronomers can only detect bright objects that emit lots of light (stars) or large objects that block background light (clouds of gas and dust). These objects make up only a tiny [[fraction]] of the mass of a galaxy. Microlensing allows the [[study]] of objects that emit little or no light.

When a distant [[star]] or [http://en.wikipedia.org/wiki/Quasar quasar] gets sufficiently aligned with a massive compact foreground object, the bending of [[light]] due to its gravitational field, as discussed by [[Einstein]] in 1915, leads to two [[distorted]] unresolved images resulting in an observable magnification. The time-scale of the transient brightening depends on the mass of the foreground object as well as on the [[relative]] proper motion between the background 'source' and the foreground 'lens' object.

When a distant [[star]] or [https://en.wikipedia.org/wiki/Quasar quasar] gets sufficiently aligned with a massive compact foreground object, the bending of [[light]] due to its gravitational field, as discussed by [[Einstein]] in 1915, leads to two [[distorted]] unresolved images resulting in an observable magnification. The time-scale of the transient brightening depends on the mass of the foreground object as well as on the [[relative]] proper motion between the background 'source' and the foreground 'lens' object.

Since microlensing [[observations]] do not rely on [[radiation]] received from the [[lens]] object, this effect therefore allows astronomers to study massive objects no matter how faint. It is thus an [[ideal]] [[technique]] to study the galactic population of such faint or dark objects as [http://en.wikipedia.org/wiki/Brown_dwarfs brown dwarfs], [http://en.wikipedia.org/wiki/Red_dwarfs red dwarfs], [[planets]], [http://en.wikipedia.org/wiki/White_dwarfs white dwarfs], [http://en.wikipedia.org/wiki/Neutron_stars neutron stars], [[black holes]], and [http://en.wikipedia.org/wiki/Massive_compact_halo_object Massive Compact Halo Objects]. Moreover, the microlensing effect is wavelength-independent, allowing study of source objects that emit any kind of [[electromagnetic]] [[radiation]].

Since microlensing [[observations]] do not rely on [[radiation]] received from the [[lens]] object, this effect therefore allows astronomers to study massive objects no matter how faint. It is thus an [[ideal]] [[technique]] to study the galactic population of such faint or dark objects as [https://en.wikipedia.org/wiki/Brown_dwarfs brown dwarfs], [https://en.wikipedia.org/wiki/Red_dwarfs red dwarfs], [[planets]], [https://en.wikipedia.org/wiki/White_dwarfs white dwarfs], [https://en.wikipedia.org/wiki/Neutron_stars neutron stars], [[black holes]], and [https://en.wikipedia.org/wiki/Massive_compact_halo_object Massive Compact Halo Objects]. Moreover, the microlensing effect is wavelength-independent, allowing study of source objects that emit any kind of [[electromagnetic]] [[radiation]].

Microlensing by an isolated object was first detected in 1989. Since then, microlensing has been used to constrain the nature of the [http://en.wikipedia.org/wiki/Dark_matter dark matter], detect [http://en.wikipedia.org/wiki/Extrasolar_planets extrasolar planets], study [http://en.wikipedia.org/wiki/Limb_darkening limb darkening] in distant stars, constrain the [http://en.wikipedia.org/wiki/Binary_star 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 [http://en.wikipedia.org/wiki/Quasars quasars] including their [http://en.wikipedia.org/wiki/Accretion_disks accretion disks].[http://en.wikipedia.org/wiki/Microlensing]

Microlensing by an isolated object was first detected in 1989. Since then, microlensing has been used to constrain the nature of the [https://en.wikipedia.org/wiki/Dark_matter dark matter], detect [https://en.wikipedia.org/wiki/Extrasolar_planets extrasolar planets], study [https://en.wikipedia.org/wiki/Limb_darkening limb darkening] in distant stars, constrain the [https://en.wikipedia.org/wiki/Binary_star 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 [https://en.wikipedia.org/wiki/Quasars quasars] including their [https://en.wikipedia.org/wiki/Accretion_disks accretion disks].[https://en.wikipedia.org/wiki/Microlensing]

[[Category: Astronomy]]

[[Category: Astronomy]]