Stars over Sisters 6/22/2021


Last updated 6/22/2021 at Noon

courtesy NASA

Lying at a distance of 14,300 light-years, M10 is the brightest star cluster in the constellation of Ophiuchus.

There’s nothing more beautiful than a summer night sky in Sisters. While you’re soaking up the spectacular, starry canopy above, keep an eye out for the snake charmer, er… the snake handler… okay, officially known as Ophiuchus (pronounced of-ee-yoo-kuhs), the Serpent Bearer.

This sprawling constellation is the 11th largest in the sky, and ranges from 14 degrees above the celestial equator at its northernmost extent to 30 degrees below at its southern border. While Ophiuchus is big, it’s not particularly bright. Its brightest star, Rasalhague (Arabic for “the head of the serpent collector”), shines at second magnitude, about as bright as Alkaid, the end star in the handle of the Big Dipper. Rasalhague is about 49 light-years from earth. Look for Ophiuchus in the south-southeast at nightfall.

There are many ancient lores and legends connected to Ophiuchus. One of the best known of them asserts that Ophiuchus was Asclepius, son of Apollo, who had healing abilities that could bring people back from the dead. It is said that Asclepius learned this skill after watching a snake bring healing herbs to another. Afraid that he might render all men immortal, Zeus (king of the gods) slew Asclepius with a thunderbolt and placed him among the stars.

Ophiuchus is home to the famous Barnard’s Runaway Star. It is a low-mass red dwarf star that astronomer Edward Barnard found and measured in 1916 at the Yerkes Observatory in Williams Bay, Wisconsin. After the sun and the three components of the Alpha Centauri system, it is the closest star to Earth, a mere 6.1 light-years away. It is also the fastest moving star known, with an annual proper motion of 10.31 arc-seconds. Unfortunately, at a visual magnitude of 9.5, Barnard’s Star is far too dim to be seen by the unaided eye.

Just like many other large constellations, Ophiuchus has its fair share of deep sky objects. In fact, seven of them are Messier objects and all are globular clusters. The biggest and brightest of these is M10, a compact cluster that spans 83 light-years across and lies approximately 14,300 light-years away. It glows at a magnitude of 6.4.

There are also two open star clusters and one planetary nebula for amateurs to glimpse, but no galaxies.

At 3:27 p.m. PDT on July 5, the earth will reach aphelion, the point in its orbit when it is farthest from the sun. The two bodies will be separated by 94.5 million miles at that time.

While Venus dominates the evening sky, dimmer Mars is there, too, in the twilight. At the beginning of the month, both planets are in Cancer, with Mars in the lead. But the speedier Venus quickly blows by Mars as July progresses, and is well ahead of the Red Planet at month’s end as both cruise into Leo. On July 12 Mars and Venus will be separated by half a degree in the sky. At that time, both planets can be seen together in a telescopic field of view.

Saturn is now an evening object, rising around 10 p.m. local time on July 1. Jupiter is also an evening object, but just barely, rising after 11 p.m. on the first of the month.

Early in July is a good time for evening stargazing as a waning moon will be in play. After new moon on July 9, the moon will gradually become more illuminated until the Full Thunder Moon arrives on July 23. Thereafter, a progressively dimming moon will close out the month.

Here’s this month’s dark-sky awareness tip to help fight light pollution here in Sisters: Please consider changing out your cool-colored light bulbs with warmer-colored white and yellow ones. Lights that have a Kelvin rating greater than 2,700 should be replaced with bulbs that are 2,300 Kelvin or lower. Encourage you neighbors to do likewise.


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