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The distance modulus is a way of expressing distances that is often used in astronomy. It describes distances on a logarithmic scale based on the astronomical magnitude system . Definition
The cosmic distance ladder (also known as the extragalactic distance scale) is the succession of methods by which astronomers determine the distances to celestial objects. A direct distance measurement of an astronomical object is possible only for those objects that are "close enough" (within about a thousand parsecs ) to Earth.
Distance measures are used in physical cosmology to give a natural notion of the distance between two objects or events in the universe.They are often used to tie some observable quantity (such as the luminosity of a distant quasar, the redshift of a distant galaxy, or the angular size of the acoustic peaks in the cosmic microwave background (CMB) power spectrum) to another quantity that is ...
This is known as the distance modulus, where d is the distance to the star measured in parsecs, m is the apparent magnitude, and M is the absolute magnitude. If the line of sight between the object and observer is affected by extinction due to absorption of light by interstellar dust particles , then the object's apparent magnitude will be ...
Knowing the apparent magnitude (m) and absolute magnitude (M) of the star, one can calculate the distance (d, in parsecs) of the star using = (/) (see distance modulus). The true distance to the star may be different than the one calculated due to interstellar extinction. [3] The method ultimately derives from the spectroscopic studies of ...
Distance description for orbital and non-orbital parameters: d - distance d - in km = kilometer; d - in mi = mile; d - in AU = astronomical unit; d - in ly = light-year; d - in pc = parsec; d - in kpc = kiloparsec (1000 pc) D L - luminosity distance, obtaining an objects distance using only visual aspects
The comoving distance from an observer to a distant object (e.g. galaxy) can be computed by the following formula (derived using the Friedmann–Lemaître–Robertson–Walker metric): = ′ (′) where a(t′) is the scale factor, t e is the time of emission of the photons detected by the observer, t is the present time, and c is the speed of ...
In astronomy, the Tully–Fisher relation (TFR) is a widely verified empirical relationship between the mass or intrinsic luminosity of a spiral galaxy and its asymptotic rotation velocity or emission line width. Since the observed brightness of a galaxy is distance-dependent, the relationship can be used to estimate distances to galaxies from ...