October is an ideal month for stargazing. The Sun is setting earlier so you don’t have to wait as long to head outdoors, yet, for much of the country, nighttime temperatures are still pleasant. That provides great conditions for watching Pegasus, the flying horse, soar high across the sky, or to pick out the subtle glow of M31 (and perhaps even M33). Jupiter and Saturn remain in view in the western evening sky, while Mars just peeks into view in the morning sky by month’s end.
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In the Sky This Month
October 20: Lingering Summer
A pair of astronomical markers of the summer season is still in view. As twilight begins to fade, look toward the southwest for the sinuous outline of Scorpius, the scorpion, with teapot-shaped Sagittarius to its upper left.
October 21: Last-Quarter Moon
The Moon is at last-quarter today. It lines up at a right angle to the line between Earth and the Sun, so sunlight illuminates half of the hemisphere that faces our way. The Moon is now three-fourths of the way through its month-long cycle of phases.
October 22: Moon and Regulus
Look for the Moon high in the sky at first light tomorrow. The bright star Regulus, which represents the heart of Leo, the lion, will stand below it.
October 23: AU Microscopii
The faint constellation Microscopium is low in the south at nightfall. One of its members, AU Microscopium, is a newborn red-dwarf star. The faint light is encircled by a disk of dust that could provide the raw materials for making planets.
October 24: Georgian Stars
Sandwiched between the big constellations Taurus, Cetus, and Eridanus is a small, extinct constellation that honored England’s King George II. Its brightest star, known today as Omicron 2 Eridani, is really three stars bound by gravity.
October 25: Moon and Mars
Mars is creeping into view in the early morning. It’s quite low in the east as twilight begins to paint the sky and looks like a moderately bright star. It will be easier to pick out tomorrow because it will stand just below the crescent Moon.
October 26: Time Travel
The star Aldebaran is low in the east by 10 p.m. It’s 65 light-years away, so the light we see from Aldebaran tonight left the star 65 years ago. The Pleiades star cluster is above Aldebaran. We see it as it looked near the start of the 17th century.