A Pattern, Not a Group

Nothing but Light · Page 1 of 4

Name Date
DIRECTIONS: Fill in how far away each star of Orion is, using the list. Then answer.
BetelgeuseRigelBellatrixMintakaAlnilamAlnitakSaiphdot size = how bright it LOOKS from here
#StarHow far away, in light years
1.Betelgeuse550 ± 100Like this
2.Rigel
3.Bellatrix
4.Mintaka
5.Alnilam
6.Alnitak
7.Saiph
Star catalogue — Orion, A to Z (light years): Alnilam 2,000 ± 300 · Alnitak 1,260 · Bellatrix 250 · Betelgeuse 550 ± 100 · Mintaka 1,200 · Rigel 860 · Saiph 650
  1. Are the three belt stars at similar distances from us? Give the three numbers.

The Picture the Sky Cannot Show You

Nothing but Light · Page 2 of 4

DIRECTIONS: The same seven stars, placed by how far away they are.
05001,0001,5002,000light years from us0BellatrixBetelgeuseSaiphRigelMintakaAlnitakAlnilam
Alnilam, the middle belt star, is about 2,000 light years away and Bellatrix is about 250 — one is roughly 8 times further than the other.
  1. Say what a constellation actually is, given the two pictures on this sheet.
  2. A constellation is a direction rather than a place. Explain what would happen to the shape of Orion if you could travel a long way sideways and look again.
  3. Betelgeuse is written as "about 550 light years, give or take 100". Say why an astronomer would print a rough figure rather than a precise one, and why that is more honest than rounding it neatly.

Except the Plow Is Different

Nothing but Light · Page 3 of 4

DIRECTIONS: Is every constellation an accident like Orion? Fill in the Plow and check.
#Star of the PloughHow far away, in light years
12.Dubhe123Like this
13.Merak
14.Phecda
15.Megrez
16.Alioth
17.Mizar
18.Alkaid
Star catalogue — the Plow, A to Z (light years): Alioth 81 · Alkaid 104 · Dubhe 123 · Megrez 81 · Merak 79 · Mizar 83 · Phecda 84
For Orion, the furthest star divided by the nearest is about 8.0.
  1. What is the furthest-divided-by-nearest for the Plough? How does it compare with Orion's?
  2. Five of these seven really are traveling through the galaxy together, having formed in the same place. Say what that means for the sentence "constellations are not real groups".

The Dates Have Moved

Nothing but Light · Page 4 of 4

DIRECTIONS: Read, then answer.
Through the year the sun passes in front of twelve named constellations, on dates written down about 2,000 years ago. Since then the earth's axis has slowly swung round, so the dates are now out by about one month: born in late March, the calendar says Aries, but the sun is in front of Pisces. The same wobble took Thuban's job as pole star and will one day give Polaris's to Vega.
  1. The dates were written down about 2,000 years ago and are now out by about a month. Say what changed — the stars, the sun, the calendar, or the earth.
  2. Polaris has not always been the pole star and will not always be. Using the same wobble, say why.