# Astrophysics Help!

1. May 16, 2005

### faisal

Show that 1600 light years is equal to a distance of 1.5x10exp19 ?
The black Hole was detected because of its effects on its neighbouring star. why do astromers have to rely on indirect evidence for looking at stars?
A star has a a radius of 9x10exp7 calculate its lumanosity
4X3.14X2.025EXP15=2.54X10EXP16
Help would be very welcomed.
thank you

2. May 16, 2005

### Staff: Mentor

A "light year" is a measure of distance, not time. You calculated the number of seconds in 1600 years, which is not the question. How far does light travel in one year? What's the speed of light?

3. May 16, 2005

### faisal

How far is a light year? 10 trillion kilometers -its a guess-

Last edited: May 16, 2005
4. May 16, 2005

### Staff: Mentor

Why guess? Either look it up or look up the speed of light and calculate how far it travels in a year. Distance = speed X time.

5. May 16, 2005

### faisal

1600x9.5exp12=1.52exp16

6. May 16, 2005

### faisal

7. May 16, 2005

### Staff: Mentor

You were the one who said "it's a guess".

8. May 16, 2005

### faisal

the speed of light = 299 792 458 m / s

9. May 16, 2005

### Curious3141

No of meters light travels in a second = 299,792,458 (approximately)
No of seconds in a year = ? (work it out)
Hence no of meters light travels in a year = ? (this is one light year, measured in meters)

Hence 1600 light years = ? meters

10. May 3, 2010

### kathykoo9

if your entire mass were to be converted to pure energy, how long could you proviede a MegaW (10^6 W) of energy to help in solving our energy crisises?

11. May 3, 2010

### kathykoo9

help!!!!

how much more or less would you weigh (same as force) at the surface of the sun than on earth?