Chapter 18

Find the distance in parsecs to the star Altair, which has an annual parallax of 0.20 arcsec.

The bright star Sirius has a parallax angle of 0.38 arcsec. Find the distance in parsecs and in lightyears.

Calculate the number of seconds in a year ( 365 days). Express your answer in standard exponential notation, with three significant figures.

The red supergiant star in Orion is called Betelgeuse, and its distance is 640 ly. What is the distance in parsecs?

The famous Pleiades star cluster is about 140 parsecs distant. How many light- years is that?

How many times brighter is a Cepheid variable of absolute magnitude - 3 than a white dwarf of absolute magnitude \(+7 ?\)

How many times dimmer is a star with magnitude +1 compared with the planet Venus with a magnitude of \(-4 ?\)

A galaxy cluster in Ursa Major has a recessional velocity of \(15,000 \mathrm{km} / \mathrm{s}\). Using the best estimate for Hubble-Lemaitre constant, find the distance to the galaxy cluster.

The Hydra supercluster has a distance of about \(800 \mathrm{Mpc}\). Using the Hubble-Lemaitre law, determine the recessional velocity to this cluster.

Suppose that the Hubble constant had a value of \(H=100 \mathrm{km} / \mathrm{s} / \mathrm{Mpc}\). What would be the age of the universe? What if \(H\) had a value of \(50 \mathrm{km} / \mathrm{s} / \mathrm{Mpc}\) ?