Sky & Telescope - February 2023 - 77

MIDDLE AGES ATLAS: LEIDEN UNIVERSITY CATALOGUE / PUBLIC DOMAIN;
BAYER ATLAS: JOHANN BAYER / PUBLIC DOMAIN
and Taurus, the Bull, are good examples
of Bayer's methodical approach.
But as always there are exceptions.
Let's take another look at our friend
Orion, the way Bayer portrays him
(below right). First, the good news -
you'll note that he oriented the figure
the way we see the Hunter in the night
sky. Also, brighter stars appear larger
than fainter stars, so Bayer used different-size
symbols to illustrate this. You'll
note that Bayer drew two stars much
larger than the others: Betelgeuse (the
shoulder) and Rigel (the foot). See the
Greek letters by those two star symbols?
Yup, they're Alpha and Beta. The only
problem is that the Beta star (Rigel) is,
in fact, slightly brighter than the Alpha
star (Betelgeuse). The same fate befell
nearby Gemini, where Pollux - the
brightest star - bears the Beta designation,
whereas his dimmer twin Castor
carries the Alpha label. One of the more
popular explanations is that Bayer may
have assigned the letters according to the
order in which the stars popped above
the horizon as they rose in the east.
To properly denote stars' names
using Bayer's system, you'll also need
Greek Alphabet
β
α
Alpha
η
Eta
ν
Nu
τ
Tau
Beta
θ
Theta
ξ
Xi
υ
Upsilon
γ
Gamma
ι
Iota
ο
Omicron
φ
Phi
to know Latin grammar - a star's
complete designation consists of the
Greek letter followed by the constellation's
genitive case. Let's look at
Betelgeuse, the Alpha star in Orion:
Its Bayer name is Alpha Orionis. The
good news is you don't need to memorize
all this - a useful resource is at
https://is.gd/SandT_constellations.
Regular readers of this magazine will
notice that in our observing articles
and columns we include the symbol for
the Greek letter in parentheses thus:
δ
Delta
κ
Kappa
π
Pi
χ
Chi
ε
Epsilon
λ
Lamda
ρ
Rho
ψ
Psi
ζ
Zeta
μ
Mu
σ
Sigma
ω
Omega
Alpha (α) Orionis. This helps you easily
identify which star we're discussing
when you refer to the finder chart in
the article (or the central star chart).
You can snap a photo of the handy
table above so you always have it with
you (or you can look for a similar version
online).
So when you study the central star
chart or peruse our Pocket Sky Atlas you
can thank a meticulous German celestial
cartographer for systematically
organizing the night sky for us. ¢
ORION IN THE MIDDLE AGES AND BY BAYER Left: A plate from an astronomical treatise from the 800s shows the mythological hunter Orion,
but not as we'd recognize him today. For starters, we're seeing him from the back. And the star symbols are all presented the same size as if they
were all the same brightness, which is clearly not the case. Right: Johann Bayer introduced the Greek lettering system to label stars, adopted the
world over. By introducing this convention, he instilled order and method in star charts and atlases. Today we tend to use larger symbols for the Greek
letters, but look closely and you should spot them in the chart below. Refer to the table above to learn the letters' names.
sk yand tele scope .o r g * FEBRUARY 2023 77

https://www.is.gd/SandT_constellations http://skyandtelescope.org

Sky & Telescope - February 2023

Table of Contents for the Digital Edition of Sky & Telescope - February 2023