david-butler 7 jaar geleden
David Butler #Space and Time

How Far Away Is It | 05 - Nearby Stars

In this segment of our 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. This includes the definition of ‘parsec’ and ‘light year’. We then cover the Alpha Centauri system (Proxima Centauri, Alpha Centauri A & B), and use it to show how we calculate the mass of binary star systems. Then we examine our stellar neighborhood including: Barnard’s Star with its Proper Motion, Wolf 359, Lalande 21185, Sirius A & B, 61 Cygni, Altair, Fomalhaut with its planet, and Vega.


A 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, Capella, and Castor. Having reached the limits of ground based telescopes to measure parallax, we discuss the European Space Agency’s (ESA) Hipparcos satellite and the more distant stars it helped fined parallax for including: HD 189733, Aldebaran, Mizar, Spica, Mira, Polaris, and Antares. Along the way, we build the mass vs. luminosity empirical graph.


We then cover the new ESA satellite Gaia that is mapping over a billion stars in the Milky Way and nearby galaxies. We follow that with a look at a few stars too far for Hipparcos but well within the range of Gaia: Betelgeuse, CH Cyg, and Rigel.


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.

David
david-butler
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