Suppose a star has a luminosity of 7.0x1026 watts and an apparent brightness of 4.0x10-12 watt/m?. How far away is it? Give your answer in both kilometers and light-years.

If a star has a surface temperature of 3000 K but a luminosity 150 times greater than our Sun, what size is this star? Give your answer in units of the solar radius, R.

This star has a mass of 3.3 MSun. What is the main sequence lifetime of this star? You may assume that the lifetime of the sun is 1010 yr.

Compute the distance to the following stars using the luminosity-distance relationship: m-M=5 log (d) - 5 Name: X Ari App. Mag. (m): 9.95 Abs. Mag. (M): 0.75 O 693.23 690.43 692.56 691.83

A star has an apparent magnitude of 10 and an absolute magnitude of 2.5. How far is it?

14 Suppose you see two main-sequence stars of the same spectral type. Star 1 is dimmer in apparent brightness than Star 2 by a factor of 100. What can you conclude? (Neglect any effects that might be caused by interstellar dust and gas.) A B C D Star 1 is 10 times more distant than Star 2. The luminosity of Star 1 is a factor of 100 less than the luminosity of Star 2. Star 1 is 100 times nearer than Star 2. Star 1 is 100 times more distant than Star 2. E Without first knowing the distances to these stars, you cannot draw any conclusions about how their true luminosities compare to each other.

Using the center-of-mass equations or the Center of Mass Calculator (under Binary-Star Basics, above), you will investigate a specific binary-star system. Assume that Star 1 has m₁ = 3.4 solar masses, Star 2 has m₂ = 1.4 solar masses, and the total separation of the two (R) is 52 AU. (One AU is Earth's average distance from the Sun.) (a)What is the distance, d₁, (in AU) from Star 1 to the center of mass? AU (b)What is the distance, d2, (in AU) from Star 2 to the center of mass? AU

Question 32 Consider three Main Sequence stars, an O tar, an F star and a K star, each with an apparent magnitude of 2. Which star is the most luminous? They're all the same luminosity. The O star The F star The K star Question 33 Consider three Main Sequence stars, an O star, an F star and a K star, each with an apparent magnitude of 2. Which star appears the brightest in the night sky? The O star The F star O The K star O They all appear the same. Please answer both

How about 11518 light-years? how many sig figs are there?

The hydrogen lines in spectral type A stars   a. are most narrow for supergiants.   b. are most narrow for main-sequence stars.   c. cannot be used to estimate the luminosity of the star.   d. are very weak and difficult to see.   e. are useful in determining the apparent magnitude of the star.