# SOLAR SYSTEM

## UNIVERSE

### COMETS

 Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
What does magnitude tell about a comet?
 A size B brightness C shape of orbit D color
Explanation:

Detailed explanation-1: -The brighter an object appears, the lower the value of its magnitude, with the brightest objects reaching negative values. Astronomers use two different definitions of magnitude: apparent magnitude and absolute magnitude.

Detailed explanation-2: -Their brightness varies roughly as the inverse cube of their distance from the sun, meaning that if a comet’s distance from the sun is halved, it will become eight times as bright. This means that the peak brightness of a comet depends significantly on its distance from the sun.

Detailed explanation-3: -Hughes Department of Physics, The University, Sheffield, S3 7RH, UK. Summary The absolute magnitude is one of the main parameters in the expression for the brightness of a comet. It is defined as the apparent magnitude a comet would have if it was observed when at a distance of 1 AU from both the Earth and the Sun.

Detailed explanation-4: -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-5: -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.

Detailed explanation-6: -Astronomers measure the brightness of a star in the sky using a magnitude scale. On this scale, the brightest objects have the SMALLEST number and the faintest objects have the LARGEST numbers. It’s a ‘backwards’ scale that astronomers inherited from the ancient Greek astronomer Hipparchus.

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