As the weather changes into the cooler evenings of autumn, the stars slowly transition toward the bright winter stars. One familiar group, known as the Big Dipper in North America, lies low in the northwestern sky during the early evening hours of October. More, formally known as the Great Bear (Ursa Major), the stars can be found in the northern sky throughout the year. In autumn they start the evening low in the northern sky; they are likely blocked by the trees or the neighbor’s house.
An interesting pair of stars, Mizar and Alcor, is at the bend of the dipper’s handle. Mizar is the brighter star with dimmer Alcor nearby. If you cannot see the close pair, use binocular. While not physically connected in a binary star system, their close proximity makes them appear together. Mizar is about 100 light years away with Alcor perhaps another light year away from its brighter neighbor.
This chart shows the positions for the visible planets as seen from north of the solar system. Notice that Earth is between Jupiter and the sun. Venus, Mercury, and Saturn appear near the sun. Earth is slowly moving up to catch Mars.
Always difficult to locate, Mercury appears near Venus in late October. As the sky darkens on October 28, look for the moon and the reddish star Antares. Look farther to the right of the moon for bright Venus and below it for Mercury. You’ll need a good horizon. Binoculars will help locate Mercury.
Mars is a morning star rising after 1 a.m. throughout the month. Early in the month, it appears near the Beehive Cluster. (See the separate article about this event.) The moon serves as a good guide to Mars on October 21 and 22 as displayed in the chart above. The star Regulus serves as a marker of the sun’s annual path and the plane of the solar system. Look for Mars each morning and note how its orbital motion is carrying it closer to Regulus. Of course, the two are not close; Regulus is much farther away than Mars. Mars will appear to pass Regulus next month.