One of the most important stellar parameters is the total energy production of a star in each second which is known as the luminosity. It is difficult to determine a star's luminosity from the Earth since we receive only a fraction of the star's energy. Astronomers can determine the <1> (or apparent brightness) which is the star's luminosity spread out over the area of a <2> whose radius is the star's distance from the Earth.
To make expressing the star's apparent brightness more convenient, Astronomer's make use of the apparent magnitude (m) system originated by Hipparchus. This system puts the apparent brightness on a logarythmic system which yields much more convenient values. Hipparchus called the brightest stars in the sky apparent magnitude <3> and the faintest stars magnitude <4>. Today the system encompasses a greater range of values including approximately <5> for the moon and <6> for the faintest object detected by the HST.
To remove the distance dependence of the magnitude system, astronomer's define absolute magnitude M: the apparent magnitude of a star moved to a distance of <7> parsecs. If the quantity m-M (known as the <8>) is <9>, the object must be closer than 10 parsecs.
Velocity is another important stellar parameter. There are two distinct components to velocity: the <10> velocity which is determined from the doppler shift and the <11> velocity which is related to proper motion. The two components can be combined with the pythagorean theorm to determine the <12> velocity.
@ qu.1.1.blank.1=intensity, magnitude, peak wavelength, photonic power@ qu.1.1.blank.2=sphere, cylinder, circle, square@ qu.1.1.blank.3=1,6,10,15@ qu.1.1.blank.4=6,1,10,15@ qu.1.1.blank.5=-13,-26, 6, 30@ qu.1.1.blank.6= 30, 6, -13, -26@ qu.1.1.blank.7=10, 5, 50, 100@ qu.1.1.blank.8=distance modulus, proper motion, reference magnitude, intensity@ qu.1.1.blank.9=negative, positive, zero@ qu.1.1.blank.10=radial, tangential, space@ qu.1.1.blank.11=tangential, radial, space@ qu.1.1.blank.12=space, tangential, radial@ qu.1.1.grader.1=menu@ qu.1.1.grader.2=menu@ qu.1.1.grader.3=menu@ qu.1.1.grader.4=menu@ qu.1.1.grader.5=menu@ qu.1.1.grader.6=menu@ qu.1.1.grader.7=menu@ qu.1.1.grader.8=menu@ qu.1.1.grader.9=menu@ qu.1.1.grader.10=menu@ qu.1.1.grader.11=menu@ qu.1.1.grader.12=menu@ qu.1.2.mode=Blanks@ qu.1.2.editing=useHTML@ qu.1.2.name=Stellar Parameters@ qu.1.2.question=One of the most important stellar parameters is the total energy production of a star in each second which is known as the luminosity. It is difficult to determine a star's luminosity from the Earth since we receive only a fraction of the star's energy. Astronomers can determine the <1> (or apparent brightness) which is the star's luminosity spread out over the area of a <2> whose radius is the star's distance from the Earth.
To make expressing the star's apparent brightness more convenient, Astronomer's make use of the apparent magnitude (m) system originated by Hipparchus. This system puts the apparent brightness on a logarythmic system which yields much more convenient values. Hipparchus called the brightest stars in the sky apparent magnitude <3> and the faintest stars magnitude <4>. Today the system encompasses a greater range of values including approximately <5> for the sun and <6> for the faintest object detected by the HST.
To remove the distance dependence of the magnitude system, astronomer's define absolute magnitude M: the apparent magnitude of a star moved to a distance of <7> parsecs. If the quantity m-M (known as the <8>) is <9>, the object must be farther away than 10 parsecs.
Velocity is another important stellar parameter. There are two distinct components to velocity: the <10> velocity which is related to proper motion and the <11> velocity which is determined from doppler shifts. The two components can be combined with the pythagorean theorm to determine the <12> velocity.
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