Nearby Stars

small D = 000004 Alpha CentauriIn this segment of our “How far away is it” video book, we take a look at our stellar neighborhood and how we know how far away these nearby stars are.

We cover the first stellar parallax measurement form the star Cygni 61. Then we examine our stellar neighborhood including: Proxima Centauri, Alpha Centauri, Barnard’s Star with its Proper Motion, Wolf 359, Lalande 21185, Sirius A & B, 61 Cygni, Altair, Fomalhaut with its planet, and Vega.

small D = 000025 Vega copyA deeper look into what we mean by ‘luminosity’ is outlined. We point out that it is measured in watts just like a light bulb and that its value over distance from a point source follows the ‘inverse square law’. We use our Sun as an example and introduce Einstein’s famous “energy = mass time the speed of light squared” formula.

We then cover some more stars including: Pollux, Arcturus, GJ1214, Capella, and Castor. Having reached the limits of ground based telescopes to measure parallax, we discuss the European Space Agency’s Hipparcos satellite and the more distant stars it helped fined small D = 000042 Capella copyparallax for including: HD 189733, Aldebaran, Mizar, Spica, Mira, Polaris, and Antares. Along the way, we cover how a star’s mass is calculated from the motion of binary stars, and then we build the mass vs. luminosity empirical graph.

We end by pointing out that parallax only takes us to a small percentage of stars in the Milky Way and that we’ll need to know more about light to go any further.