Appearance of the Constellations

Appearance of the Constellations

The appearance of the Constellations changes not only in space but also in time; not only if we alter our position but also if we merely wait sufficiently long. Sometimes stars move together in a group of cluster; other times a single star may move very rapidly with respect to its fellows. Eventually such stars leave an old constellation and enter a new one.

Occasionally, one member of a double-star system explodes, breaking the gravitational shackles that bound its companion, which then leaps into space at its former orbital velocity, a slingshot in the sky.

In addition, stars are born, stars evolve, and stars die. If we wait long enough, new stars will appear and old stars vanish. The patterns in the sky slowly melt and alter.

Time is important. (quotations from Megan Jorgensen). Image : © Megan Jorgensen (Elena)

Even over the lifetime of the human species – a few million years – constellations have been changing. Consider the present configuration of the Big Dipper, or Great Bear. Our computer can carry us in time as well as in space. As we run the Big Dipper backwords into the past, allowing for the motion of its stars, we find quite a different appearance a million years ago. The Big Dipper then looked quite a bit like a spear. If a time machine dropped you precipitously in some unknown age in the distant past, you could in principle determine the epoch by the configuration of the stars : if the Big Dipper is a spear, this must be the Middle Pleistcene…