One of the units used in Astronomy is Magnitude (or brightness). It tells us about the brightness of stars or other astronomical objects.
Magnitude is actually divided in two types, apparent and absolute.
1. Apparent Magnitude tells us how bright a star is as seen from Earth. And its inversely proportional to the square of distance.
The measurement of apparent brightness is called photometry.
Image Credit: www.windows2universe.org
If we assume that stars are at same distance from us then we can compare their brightness. And that's what absolute magnitude tells us.
2. Absolute Magnitude gives us the brightness of stars as seen from 10 parsecs (32.6 light years).
Greek Astronomer Hipparchus categorized the stars according to their brightness more than 2000 years ago. According to him the brightest stars were of first magnitude and faintest were of sixth magnitude.
The first magnitude stars were two times brighter than second magnitude stars.
Later, as the instruments became more sensitive, astronomers found that the magnitude scale was not accurate.
But instead of abandoning it, they refined it.
In the Modern Magnitude System, first magnitude stars are about 2.512 times brighter than second magnitude stars. And second magnitude stars are (2.512)^2 times brighter than third magnitude stars.
So faint stars have bigger magnitude.
For example let's take two stars of Orion constellation, Rigel and Betelgeuse.
1. Rigel
Apparent magnitude (m) = +0.12
2. Betelgeuse
m = +0.50
The difference between their magnitude is
0.50 - 0.12 = 0.38
So Rigel is about (2.512)^0.38 times brighter (apparent brightness) than Betelgeuse.
Absolute magnitude, apparent magnitude and distance are interrelated. So if two are known, another can be calculated.
To study brightest stars (as seen from Earth) BRITE (BRIght Target Explorer) a set of 6 nano satellites were launched in 2013.
Out of six, two satellites UniBRITE-1 and TUGSAT-1 (BRITE-Austria) were launched by PSLVC-20 on February 25, 2013 from ISRO's Satish Dhawan Space Centre, Sriharikota, Andhra Pradesh.
Image credit : ww.isro.gov.in
Magnitude is actually divided in two types, apparent and absolute.
1. Apparent Magnitude tells us how bright a star is as seen from Earth. And its inversely proportional to the square of distance.
The measurement of apparent brightness is called photometry.
Image Credit: www.windows2universe.org
If we assume that stars are at same distance from us then we can compare their brightness. And that's what absolute magnitude tells us.
2. Absolute Magnitude gives us the brightness of stars as seen from 10 parsecs (32.6 light years).
Greek Astronomer Hipparchus categorized the stars according to their brightness more than 2000 years ago. According to him the brightest stars were of first magnitude and faintest were of sixth magnitude.
The first magnitude stars were two times brighter than second magnitude stars.
Later, as the instruments became more sensitive, astronomers found that the magnitude scale was not accurate.
But instead of abandoning it, they refined it.
In the Modern Magnitude System, first magnitude stars are about 2.512 times brighter than second magnitude stars. And second magnitude stars are (2.512)^2 times brighter than third magnitude stars.
So faint stars have bigger magnitude.
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| https://en.m.wikipedia.org/wiki/Luminosity |
For example let's take two stars of Orion constellation, Rigel and Betelgeuse.
1. Rigel
Apparent magnitude (m) = +0.12
2. Betelgeuse
m = +0.50
The difference between their magnitude is
0.50 - 0.12 = 0.38
So Rigel is about (2.512)^0.38 times brighter (apparent brightness) than Betelgeuse.
Absolute magnitude, apparent magnitude and distance are interrelated. So if two are known, another can be calculated.
To study brightest stars (as seen from Earth) BRITE (BRIght Target Explorer) a set of 6 nano satellites were launched in 2013.
 |
| www.brite-constellation.at |
Out of six, two satellites UniBRITE-1 and TUGSAT-1 (BRITE-Austria) were launched by PSLVC-20 on February 25, 2013 from ISRO's Satish Dhawan Space Centre, Sriharikota, Andhra Pradesh.
Image credit : ww.isro.gov.in
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