Don’t overlook Ophiuchus – the 13th sign of the zodiac

Greetings, stargazers.

I am really happy with the recent rain and will gladly trade a few good observing nights for a reduced fire danger. Please ignore me if I try to predict the weather, but sometimes these monsoon afternoon thunderstorms do clear off at night for some pleasant evenings.

The ecliptic is the path of the sun through the sky throughout the year. It is tilted with respect to the celestial equator because the Earth’s axis is tilted. We experience our Northern Hemisphere summer when the sun is on the part of the ecliptic that is the farthest north. This places the sun closer to overhead during the daytime.

When the northern half of the ecliptic is overhead in the daytime, the part that is farthest south is in the sky at night. This means that the moon, the planets and constellations that are along the ecliptic during summer nights are closer to the southern horizon than at any other time of year. The summertime full moon will always be very low in the southern sky, and above the horizon for a much shorter time than a winter full moon.

The zodiac is the band of sky on either side of the ecliptic. Even if you couldn’t pick them out in the night sky, many of you can name most of the constellations along the zodiac. The 12 astrology signs for your horoscope correspond to 12 constellations and 12 months. But they are associated with where the sun is, which is why the constellations of “summer” signs like Gemini and Cancer are visible in the winter, and the constellations of the “winter” signs like Sagittarius and Capricorn are visible now.

The ecliptic actually passes through 13 constellations, not 12. Ophiuchus is often called the 13th sign of the zodiac. Because the sky has shifted significantly since the original astrological dates were set, these dates have little to do with what is where and when, so don’t expect any reorganizations of published horoscopes.

Ophiuchus is an often-overlooked constellation, but it is worth discussing, even if it isn’t your “sign.” The name means serpent bearer, but my imagination isn’t quite good enough to see a man holding a snake. Possibly because of its proximity to the teapot of Sagittarius, I see a coffee pot when you connect the dots as shown on most star charts.

Ophiuchus is a rather large constellation, but none of the stars are brighter than second magnitude. Like other constellations in the direction of the galactic center it has many globular clusters. Seven are prominent enough to have Messier identification numbers – M9, M10, M12, M14, M19, M62 and M107 – so these are easily visible with small telescopes. A bit of trivia is that Voyager 1 is heading toward of Ophiuchus.

This month

Ophiuchus is in the southern sky right after dark and will reach its highest point about 11 p.m. You can find it right above Scorpius, and just to the right of Sagittarius and the brightest part of the Milky Way. Because none of the stars are prominent, a star-finder app should help you identify it.

The first scientific results from the James Webb Space Telescope should be released next week. These should just be an appetizer for a main course that should last for years.

The full moon is on July 13. Look for it to cross the sky near the southern horizon.

The planets are still mostly morning objects, but Saturn is rising by 11 p.m. The line of planets that also includes Mars, Jupiter and Venus will continue to spread out over the next few months and be visible in the evening sky this fall.

Charles Hakes teaches in the physics and engineering department at Fort Lewis College and is the director of the Fort Lewis Observatory. Reach him at hakes_c@fortlewis.edu.