Do the terms magnitude and luminosity mean the same thing? Do they both mean brightness of a star? or is there any difference ?pls explain . thanks. (:
2006-09-13 00:29:20 · 7 answers · asked by venkat Subramaniam 2 in Science & Mathematics ➔ Astronomy & Space
You tell us
2006-09-13 00:31:17 · answer #1 · answered by Anonymous · 0⤊ 1⤋
To answer your question is one paragraph: there are three terms, Luminosity, Apparent Magnitude and Absolute MAgnitude. Luminosity and Absolute Magnitude are very close to the same thing. Apparent Magnitude is related, but is affected by distance.
They have related meanings, but they do not mean quite the same thing. Luminosity of a star is a term for how much light the star radiates. L=(4ÏR^2) Ï(T^4) where Ï is the S-Boltz. constant. It takes into account the surface area of the star and the temperature. Obviously the luminosity of a star is brighter if it is hotter, and it is also brighter if it is larger.
Magnitude has two forms. Absolute Magnitude is a scale of brightness that is directly proportional to Luminosity. Absolute Magnitude is how bright a star appears to be from a distance of 10 parsecs. If you know the Absolute Magnitude of a star, you can easily calculate its Luminosity.
Apparent Magnitude is how bright a star appears from the earth. Apparent Magnitude is the same as Absolute Magnitude and Luminosity except that it has the additional factor of distance added in. A star that is dim may appear brigher than a bright star because it is much closer.
Two stars that are the same brightness (read that as Luminosity or Absolute Magnitude) may have different Apparent Magnitudes if they are different distances. If you know the Apparent Magnitude of a star, you can not calculate its Luminosity until you first determine its distance.
I hope this helped.
2006-09-13 01:18:25 · answer #2 · answered by sparc77 7 · 0⤊ 1⤋
Luminosity is a measure of the stars total energy output.
Magnitude is a measure of the stars brightness - how bright it 'appears' to us.
Apparent magnitude is how bright it appears to us on Earth; absolute magnitude is how bright it would appear at a distance of 10 parsecs (about 32 light years).
The magnitude scale is a logarithmic scale, with a difference of 5 magnitudes translating to a factor of 100 brightness.
The lower the magnitude number, the brighter an object appears. For example, the Sun has an apparent magnitude of about -26, whereas the brightest star in the night sky, Sirius, is about -1.5. However, in terms of absolute magnitude, Sirius is +1.5, and the sun is +4.8.
The brightest apparent magnitude object is the sun, and the faintest, as detected with the Hubble Space Telescope is at about +30.
The naked eye can see, with dark skies, down to about +6, although this varies from person to person.
Magnitude also depends on which wavelength band you look.
2006-09-13 01:21:44 · answer #3 · answered by Morgy 4 · 0⤊ 0⤋
Yes, they both mean the brightness of the star, but magnitude is a logarithmic scale while luminosity is linear. A 1st magnitude star is 100 times as luminous as a 6th magnitude star. and 10,000 as luminous as an 11th magnitude star.
2006-09-13 02:40:07 · answer #4 · answered by campbelp2002 7 · 0⤊ 0⤋
No, magnitude and luminosity are not the same thing, although they are related.
LUMINOSITY - the amount of energy escaping from a star's surface each second, usually given in ergs per second
MAGNITUDE - a measure of the amount of light received from a star or other luminous object
2006-09-13 02:08:00 · answer #5 · answered by Chug-a-Lug 7 · 0⤊ 0⤋
'Magnitude' relates to size/ dimensions.
'Luminosity' to the intenseness of light emitted(brightness)
2006-09-13 00:37:10 · answer #6 · answered by kapilbansalagra 4 · 0⤊ 1⤋
Yes. See below.
2006-09-13 00:38:15 · answer #7 · answered by Kristen H 6 · 0⤊ 0⤋