# 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?

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?

SpaceTiger
Staff Emeritus
Gold Member
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?

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
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
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.