A Plethora of Un-Earthly Delights

A Plethora of Un-Earthly Delights

It helps to draw pictures to model the fantastic structures we learn about when we study astronomy and cosmology (the study of the origins of the Universe). Draw colorful pictures to illustrate the descriptions of objects we see in the Universe below.

1. At least half of all the stars in the night sky (and within our galaxy the Milky Way) are binary stars. Binary means double. In other words what looks like one star to our eye is really two! It takes a binocular or a telescope to split the pair. Algol in the constellation Perseus is called the “winking eye” of the Medussa because it’s an eclipsing binary where one dimmer star passes in front of the brighter star every three days! Draw the picture of an eclipsing binary on page 615 in the textbook.

2. Stars tend to cluster together under their combined gravity into clusters. The Pleiades (the seven sisters) is an example of an open cluster. Open clusters tend to have younger stars with lots of gasses forming new stars. Globular clusters look like a pile of spilled salt and tend to contain much older stars and contain many more stars than open clusters. You can see the Pleiades right now if you can find Orion which is nearby and to the right in the sky. You’ll recognize it when you see it! You need a binocular or telescope to enjoy globular clusters but they are worth the trouble to find. Draw the globular cluster and the open cluster (the Pleiades) on page 616 in the textbook.

3. Major galaxies (up to 300 billion star!) are spirals (or versions of spirals). Our galaxy, the Milky Way and our nearest neighbor, the Andromeda galaxy at 2.5 million light years (every photograph you will ever see of the Milky Way is actually Andromeda…) are spiral galaxies. Draw the structure of the Milky Way below (both pictures) on page 619 in the textbook.

Turn this page over now!

There are other galaxies with other shapes. Elliptical galaxies look like massive globular clusters (although they contain billions not just millions of stars). And irregular and spheroidal dwarf galaxies (not mentioned in your book!) are smaller and contain younger stars and lots of gas. The Milky Way is surrounded by about a dozen of these types of galaxies and they are the closest galaxies to us. One hypothesis is that these nearby smaller galaxies are probably the remains of more massive galaxies that the Milky Way cannibalized billions of years ago. Draw the spiral, elliptical and irregular galaxies on page 618 in the textbook.

Finally galaxies cluster together under their mutual gravity (like star clusters!) and make up the super-structure of the Universe. The Milky Way and Andromeda are members of the Local Group (about 35 galaxies) which in turn are part of the Virgo Supercluster of about 100 other galaxy groups that measure 110 million light years across! And remember that there are other Superclusters of galaxies in any direction you can point extending billions of light years in all directions! Draw the Virgo Supercluster on page 621 in your binder.

Answer the question. Astronomers use the constellations as boundaries on a map of the sky for locating objects like stars, star clusters. Where would you look to find the Andromeda galaxy? Where would you look to find the Virgo Supercluster?