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- Units of measurement in astronomy

Jupiter radius

The Jupiter radius or Jovian radius (RJ or RJup) has a value of 71,492 km (44,423 mi), or 11.2 Earth radii (REarth) (one Earth radius equals 0.08921 RJ). The Jupiter radius is a unit of length used in

Billion years

A billion years or giga-annum (109 years) is a unit of time on the petasecond scale, more precisely equal to 3.16×1016 seconds (or simply 1,000,000,000 years). It is sometimes abbreviated Gy, Ga ("gig

Planetary mass

In astronomy, planetary mass is a measure of the mass of a planet-like astronomical object. Within the Solar System, planets are usually measured in the astronomical system of units, where the unit of

Earth mass

An Earth mass (denoted as or , where ⊕ is the standard astronomical symbol for Earth), is a unit of mass equal to the mass of the planet Earth. The current best estimate for the mass of Earth is M⊕ =

Crab (unit)

A Crab is a standard astrophotometrical unit for measurement of the intensity of Astrophysical X-ray sources. One Crab is defined as the intensity of the Crab Nebula at the corresponding X-ray photon

Kyr

The abbreviation kyr means "thousand years". Kyr was formerly common in some English language works, especially in geology and astronomy, for the unit of 1,000 years or millennium. The "k" is the unit

Zodi

The zodi is a unit of zodiacal dust. One zodi is the amount of interplanetary dust in the inner Solar System. This dust absorbs light from the Sun and re-radiates it as thermal radiation. The luminosi

Lunar distance (astronomy)

The instantaneous Earth–Moon distance, or distance to the Moon, is the distance from the center of Earth to the center of the Moon. Lunar distance (LD or ), or Earth–Moon characteristic distance, is a

Astronomical system of units

The astronomical system of units, formerly called the IAU (1976) System of Astronomical Constants, is a system of measurement developed for use in astronomy. It was adopted by the International Astron

Earth radius (unit)

No description available.

Solar mass

The solar mass (M☉) is a standard unit of mass in astronomy, equal to approximately 2×1030 kg. It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxies an

Light-year

A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (9.46×1012 km), or 5.88 trillion mi

Jupiter mass

Jupiter mass, also called Jovian mass, is the unit of mass equal to the total mass of the planet Jupiter. This value may refer to the mass of the planet alone, or the mass of the entire Jovian system

Solar flux unit

The solar flux unit (sfu) is a convenient measure of spectral flux density often used in solar radio observations, such as the F10.7 solar activity index: 1 sfu = 104 Jy = 10−22 W⋅m−2⋅Hz−1 = 10−19 erg

Astronomical unit

The astronomical unit (symbol: au, or AU or AU) is a unit of length, roughly the distance from Earth to the Sun and approximately equal to 150 million kilometres (93 million miles) or 8.3 light-minute

Parsec

The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System, approximately equal to 3.26 light-years or 206,000 astronomical units

Astronomical constant

An astronomical constant is any of several physical constants used in astronomy. Formal sets of constants, along with recommended values, have been defined by the International Astronomical Union (IAU

Jansky

The jansky (symbol Jy, plural janskys) is a non-SI unit of spectral flux density, or spectral irradiance, used especially in radio astronomy. It is equivalent to 10−26 watts per square metre per hertz

Light-second

The light-second is a unit of length useful in astronomy, telecommunications and relativistic physics. It is defined as the distance that light travels in free space in one second, and is equal to exa

Magnitude (astronomy)

In astronomy, magnitude is a unitless measure of the brightness of an object in a defined passband, often in the visible or infrared spectrum, but sometimes across all wavelengths. An imprecise but sy

Torino scale

The Torino scale is a method for categorizing the impact hazard associated with near-Earth objects (NEOs) such as asteroids and comets.It is intended as a communication tool for astronomers and the pu

Solar luminosity

The solar luminosity (L☉), is a unit of radiant flux (power emitted in the form of photons) conventionally used by astronomers to measure the luminosity of stars, galaxies and other celestial objects

Population index

The population index, or r-value, indicates the magnitude distribution of a meteor shower. Values below 2.5 correspond to distributions where bright meteors are more frequent than average, while value

Myr

The abbreviation Myr, "million years", is a unit of a quantity of 1,000,000 (i.e. 1×106) years, or 31.556926 teraseconds.

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