Pegasus is one of the best-known autumn constellations. Depicting the winged horse that Perseus used to rescue Princess Andromeda from the clutches of Cetus the Sea Monster, Pegasus flies high in our southern sky during October and November evenings.

Pegasus is usually drawn upside down in our sky, with four stars – Alpheratz (Alpha [α] Andromedae), Scheat (Beta [β] Pegasi), Markab (Alpha [α] Pegasi), and Algenib (Gamma [γ] Pegasi) -- marking the corners of a great square that frames the horse's torso. (Although always shown as marking the northeast corner of the Great Square of Pegasus, Alpheratz is technically assigned to the neighboring constellation Andromeda. In fact, Alpheratz is Alpha (α) Andromedae.)

A line of three stars – Homam (Zeta [ζ] Pegasi) Baham (Theta [θ] Pegasi), and Enif (Epsilon [ε] Pegasi) -- hooking to the southwest of Markab is usually shown as the horse's neck and head, with Enif marking its nose.

Unfortunately, this means that poor Pegasus is flying upside down from a Northern Hemisphere perspective. To make matters worse, we only see the front half of the horse; its hindquarters are nowhere to be found (there is a political joke in here somewhere, but I'll leave that to you).

Rather than strain to see a horse flying across the sky, planetarium lecturers often tell their audiences that the Great Square marks a baseball diamond, a perfect allusion for this month’s World Series. In our cosmic baseball diamond, Scheat and Alpheratz, both 2nd magnitude, mark home plate and first base, respectively. The remaining two stars, Algenib and Markab, both 3rd-magnitude stars, are second and third base, respectively.

Let's fill in the rest of the team players out in the field. Pitching today's game is number 71; 5.3-magnitude 71 Pegasi, that is. It looks like he's about to be joined on the mound by 4.4-magnitude catcher Upsilon (υ) Pegasi and team manager Tau (υ) Pegasi, at magnitude 4.6. It would also appear that the home plate ump, 4.8-magnitude 56 Pegasi, is heading out to see what's going on. With a time-out called, the batter, 3.5-magnitude Mu (μ) Pegasi has headed back to the on-deck circle to talk to Lambda (λ) Pegasi, at magnitude 4.0, who is next at bat.

Meanwhile, at first base, we have Psi (ψ) Pegasi, a 4.7-magnitude sun that appears to be playing in as if looking for the batter to bunt. Second baseman Chi (χ) Pegasi, at magnitude 4.8, is playing in the hole between first and second. Shortstop Phi (φ) Pegasi, at magnitude 5.1, and third baseman 70 Pegasi (magnitude 4.6) round out the infield, while HD 216489 is the 5.6-magnitude third base coach.

Depending on the darkness and transparency of your observing site, you may be able to see the full complement of players on our cosmic ball field, or possibly just the four bases. From dark, rural sites, however, the infield looks to be overrun by fans racing in from the stands, as if this must have been the final game of the World Series and the game has just ended.

Stars within the Great Square of Pegasus

How many stars can you count inside the Great Square? The table above lists the number of stars visible in half-step increments beginning at magnitude 5.0, while the corresponding panels in the chart above plot the locations of those stars.

Wait for the Great Square to reach culmination, its greatest altitude above the horizon, before attempting a star count.  That occurs at about 10 PM local standard time (11 PM local daylight saving time) on October 1 and 8 PM local standard time (9 PM local daylight saving time) on November 1.

Post your result in this column’s discussion forum. Or contact me directly through my web site.

Until next month, remember that half of the fun is the thrill of the chase. Game on!