How many stars are there in our galaxy?
There are many ways you can use “AstroCappella 2.0”. The lesson plans can stand alone, helping you teach your students about convection, how radio telescopes and remote sensing work, what the surfaces of our nearest-neighbor planets are like, what scientists learn by looking for X-rays from the skies, and more. Or you can just use the music CD as a starting point for classroom activities. The songs cover the full spectrum, from radio astronomy, through optical observations with the orbiting Hubble Space Telescope, to the powerful pulsars, black holes and quasars of high-energy X-ray astronomy. And they provide a springboard for you and your students to explore the Sun and Moon, the nine planets, and the nearest stars. You can use the songs as a soundtrack to a science skit written and performed by students, as a vocabulary exercise, or as a review tool. But we believe AstroCappella works best when you use the music and activities together. You might want to begin a lesson by playing a
We know the answer is roughly 400 billion stars, even though there may be, realistically, as few as half or as many as double this number. What’s interesting is that about 90% of all of the stars in the Milky Way are relatively cool and small, like our Sun (types F, G, K, and M below). Most are a little smaller (something like 80% are only a fraction of the Sun’s mass), but there are plenty of stars that are very comparable to the Sun in mass, brightness, and composition. This means that of the 400 billion stars in our galaxy, about 10% of them are similar enough to our Sun that they could reasonably have planets around them that support life. This means our galaxy has about 40 billion chances to have another planet like Earth in it. So the next step, now that we know how many good stars there are, is to ask how many of them have planets that could support life on them? It turns out, as far as we can tell, that most stars actually do have planets orbiting them. Although we’ve only disc
