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Riding the light

universefinder.com — fly the route at universefinder.com
Name:Date:

Big idea: light takes time to travel. When we look at something far away, we see it as it was, not as it is. One light-year is how far light travels in a year.

Stop 1 — Sirius, the brightest star in the night sky

  1. Search for Sirius. How far away is it? light-years
  2. The light you see tonight left Sirius in the year . What is one thing you remember from that year?

Stop 2 — Betelgeuse, a dying giant

  1. Fly to Betelgeuse. Its light left about 500 years ago — before the telescope was invented. Betelgeuse is about how many times wider than the Sun?
  2. Betelgeuse will one day explode as a supernova. If it exploded today, in about what year would people on Earth find out?

Stop 3 — the Orion Nebula, where stars are born

  1. Visit the Orion Nebula. What is a nebula?

Stop 4 — the Andromeda Galaxy, beyond the Milky Way

  1. Fly to the Andromeda Galaxy. How far is it? light-years
  2. Was there anyone on Earth to see the light leave? Explain.

Think about it

  1. Why do astronomers say a telescope is a time machine?
  2. Put in order from nearest to farthest: Andromeda Galaxy · Sirius · the Sun · Betelgeuse
  3. If you could fly the map to any one object, what would it be, and why?
Universe Finder — an independent, free educational site. No account needed; distances are best-known estimates from published catalogues (see universefinder.com/references.html).