GENERAL KNOWLEDGE

GK

THE UNIVERSE

Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
How bright a star appears in the night sky relative to other stars seen there is called its
A
luminosity
B
spectral class
C
absolute magnitude
D
apparent magnitude
Explanation: 

Detailed explanation-1: -Apparent magnitude (m) is a measure of the brightness of a star or other astronomical object observed from Earth. An object’s apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object’s light caused by interstellar dust along the line of sight to the observer.

Detailed explanation-2: -Apparent magnitude m of a star is a number that tells how bright that star appears at its great distance from Earth. The scale is “backwards” and logarithmic. Larger magnitudes correspond to fainter stars. Note that brightness is another way to say the flux of light, in Watts per square meter, coming towards us.

Detailed explanation-3: -One magnitude = 2.512 times brighter So a 1st-magnitude star is 100 times brighter than a 6th-magnitude star. Or, conversely, a 6th-magnitude star is 100 times dimmer than a 1st-magnitude star. So a difference of 1 magnitude corresponds to a brightness factor of about 2.512 times.

Detailed explanation-4: -The brightest star in the sky is Sirius, also known as the “Dog Star” or, more officially, Alpha Canis Majoris, for its position in the constellation Canis Major. Sirius is a binary star dominated by a luminous main sequence star, Sirius A, with an apparent magnitude of-1.46.

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