Question

In: Physics

1). A star with an absolute magnitude of 4.5 is located 50 pc from Earth. Ignoring...

1). A star with an absolute magnitude of 4.5 is located 50 pc from Earth. Ignoring the dimming effect of the interstellar medium, its apparent magnitude will be...

Question 38 options:

54.5

8.0

1.0

4.5

-7.5

2). The absolute magnitude of a star is 2.6, but its apparent magnitude viewed from Earth is 8.9. How far away from Earth is the star?

Question 37 options:

182 pc

18.2 pc

1995 kpc

1995 pc

19.95 kpc

3). Two stars have the same radius, but surface temperatures star A is 3,000 K and the surface temperature of star B is 12,000 K. How much more luminous is star B than star A?

16 times more luminous.

256 times more luminous.

4 times more luminous.

9000 times more luminous.

This cannot be determined from the information given.

4). A star has an absolute magnitude of 2.84. What is its luminosity in solar units?

Question 40 options:

6.3 times more luminous than the Sun

0.16 times as luminous as the Sun

2.5 times more luminous than the Sun

0.40 times as luminous as the Sun

97 times more luminous than the Sun

Please help. Thanks

Solutions

Expert Solution

1) Apparent magnitude,

Explanation: Conversion formula for absolute and apparent magnitude is as follows,

where  = apparent magnitude, = absolute magnitude and =distance between star and earth.

2) Distance, =182 pc

Explanation: as we know that the formula for distance is,

where is the luminocity difference and given by , and is the magnitude difference between apparent and absolute magnitudes.  

3) 256 times more luminous

Explanation: Luminicity is directly proportional to and .

4) Luminisity in solar units= 0.16 times as luminous as the sun

Explanation: from the formula

where and are the luminisity of the Star and Sun respectively and and are the absolute masses of the star and sun respectively.


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