Stars over Sisters 5/11/2021

As the spring season continues to progress toward summer, the frequency of warmer temperatures and clearer skies will increase. Take advantage of the last full month of spring to appreciate the still-dark night skies in our Sisters community, because with light pollution still on the increase the magnificent star-studded sight may not last forever.

With the arrival of dusk during May, our featured constellation will slowly materialize nearly overhead. Positioned about 10 degrees below the handle of the Big Dipper, Canes Venatici (the two Hunting Dogs of Boötes the Herdsman) belongs to the ten-member family of Ursa Major constellations. Devoid of any bright stars in this region of the sky, the constellation is only recognized by catching sight of third magnitude Cor Caroli and fourth magnitude Chara.

Sir Charles Scarborough is credited with naming the constellation’s brightest star Cor Caroli (‘heart of Charles’) in memory of King Charles I, the unseated king of Britain. Cor Caroli also happens to be a fine double star that is easily resolved in most backyard-sized telescopes. It is 110 light-years from earth. The dimmer Chara is only 27 light-years away.

What Canes Venatici lacks in the way of luminous stars is more than compensated for in the department of deep sky objects. No fewer than five Messier objects are found there, and all but one of them are galaxies. The lone exception is M3, a large and bright globular star cluster. While several other galaxies also populate the constellation, none are more visually striking than M51, the famous Whirlpool Galaxy.

M51 is the first galaxy found to show a spiral form, the result of Lord Rosse’s work in 1845. Its graceful, winding arms are comprised of long lanes of stars and gas laced with interstellar dust. Photos made by the Hubble Space Telescope show that NGC 5195, a small, yellowish galaxy, is passing behind M51. The Whirlpool Galaxy lies at a distance of 31 million light-years from the earth.

The Eta Aquariids meteor shower peaked on the morning of May 5. Between 4 a.m. and dawn, observers in the southern portion of the U.S. saw approximately 20 meteors per hour; observers in the Southern Hemisphere were treated to three times that many. The meteors result from the earth intercepting debris from Halley’s Comet.

Evening skies were darkest in early to mid-May because of the waning moon. This was the perfect time to view those faint star clusters and galaxies without interfering moonlight. Officially, new moon occurred on the 11th.

But this month it’s the full moon that steals the show, pulling off a three-act performance. At 4:14 a.m. PDT on May 26 the Full Flower Moon arrives on the scene. It will also be within a day of its closest approach to earth, making it the second of three supermoons in 2021. The main event, however, is a total lunar eclipse.

Because the sun, earth and moon will be oriented in nearly a straight line, the sun will cast earth’s shadow upon the moon. The moon will be fully eclipsed for a period of 15 minutes beginning at 4:11 a.m.

Mercury and Venus spend quality time together nearly all month. They will appear closest together on May 28 in the western sky. Mars in Gemini stands above them both. The solar system’s two biggest gas giants continue to roam the morning sky, Saturn rising at about 2:30 a.m. local time, Jupiter popping up 45 minutes later.

Dark skies at night and having the ability to see the Milky Way is becoming increasingly rare, and as a community our collective actions add up to preserve this precious natural resource.

Luckily, reducing and preventing light pollution is easy for each of us to influence by following four simple actions. We urge you to:

1. Shield all your outdoor lights so the light is only pointing where you intend it to be.

2. Dim your lights when possible.

3. Turn off your outdoor lights when you can, or put them on a motion sensor.

4. Use warm-colored bulbs (<2700 Kelvins).

Each month students from the Sisters High School astronomy club, who volunteer to write articles for the Stars over Sisters column, will bring you more information about how and why to prevent light pollution and protect our dark night skies.