# Could someone check these answers?

1. Given that Arcturus has an apparent magnitude of -0.06 and an Absolute magnitude of -0.30, calculate its distance in parsec in light-years.
Answer = 11.17 parsecs & 36.4 light years

2. Given that Sirius has an apparent magnitude of -1.47 and a distance of 2.67 parsecs, what is the Absolute magnitude?
Answer = 1.39

3. Assume that a star has an Absolute Magnitude of -11.7 and a distance of 17-5 parsecs from our solar system, what would be the apparent magnitude as seen from Earth?
Answer = 22.86

## Answers and Replies

SpaceTiger
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Science Advisor
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astronomystudent said:
3. Assume that a star has an Absolute Magnitude of -11.7 and a distance of 17-5 parsecs from our solar system, what would be the apparent magnitude as seen from Earth?
Answer = 22.86

The others are fine, but this one looks way off. Did you mean to type "17-5" parsecs?

No, sorry I typed it wrong. It's supposed to be: 1705. Thanks for catching that. Here are the rest of my answers, are the others correct?

1.) distance - 11.17 parsecs
36.41 light -years

2.) m = 1.39

3.) M = 22.86

4.) distance - 46.08 parsecs
150.302 light-years

5.) 2401 times greater than that of the Sun's using L = M^4

SpaceTiger
Staff Emeritus
Science Advisor
Gold Member
astronomystudent said:
3.) M = 22.86

Try this one again. The SDSS survey can see -11th magnitude objects at much more than 1.7 kpc and its limiting magnitudes are usually in the low 20s.

4.) distance - 46.08 parsecs
150.302 light-years

5.) 2401 times greater than that of the Sun's using L = M^4

Don't know what the questions were for these last two.

3.) m = -.54137808

Here are the other questions:

4.) If the Hubble Space Telescope measure a parallax angle of 0.0217 arcsec for a given star, how far away from us is it in parsecs and light-years?

5.) If a star has a mass seven times greater than our Sun, what is the luminosity of the star compared to our Sun?

SpaceTiger
Staff Emeritus
Science Advisor
Gold Member
astronomystudent said:
3.) m = -.54137808

Here are the other questions:

4.) If the Hubble Space Telescope measure a parallax angle of 0.0217 arcsec for a given star, how far away from us is it in parsecs and light-years?

5.) If a star has a mass seven times greater than our Sun, what is the luminosity of the star compared to our Sun?

They all look right, but in general, it's a bad idea to quote a lot of significant digits in astronomy. On that last problem, in particular, the mass-luminosity relationship is very approximate.