The Ellensburg, WA sky for the week of August 19, 2023

Saturday: “The sky is black (or light polluted), the stars are white (or red or orange or yellow or blue), the whole world gazes upon the sight (except where there are too many city lights or people are lazy.” Wow. It is difficult to write a flowing set of lyrics when there are so many parenthetical thoughts. Most people think of the sky’s blackness as a lack of stars. But dark patches in the Milky Way are actually massive clouds of dust that are blocking the stars behind them. Two of the most prominent are dark nebulae B142 and B143 in the constellation Aquila the eagle. These are easy to find and enjoy with binoculars. First find the bright white star Altair, five fists held upright and at arm’s length above due south at 11:00 p.m. Then move your binoculars up a little bit to the next bright star Tarazed, about one fifth as bright. B142 and B143 are to the upper right of Tarazed. They make an “E” shape in the sky; fitting because American astronomer E. E. Barnard first proposed that these were dust clouds and not simply big spaces between the stars. For more information about dark nebulae, including many more to look at with binoculars, go to https://goo.gl/9tiqdh.  

Sunday: Arcturus is two and a half fists above due west at 10:00 p.m. This star, whose name means bear watcher, is the brightest in the sky’s northern hemisphere. It follows Ursa Major, the Great Bear, around the North Star. Arcturus is the closest giant star to Earth. It is one of the few stars whose diameter can be measured directly rather than being inferred from its density and mass, which themselves are derived from other parameters. 

Monday: Mars is a half a fist above the western horizon at 8:30 p.m.

Tuesday: Deneb is straight overhead at 11:30 p.m. When you look at Deneb, you are seeing light that left Deneb about 2,600 years ago.

Wednesday: All stars rotate. Our Sun takes a little less than one Earth month to rotate once on its axis. Astronomers studied the relationship between mass, stellar rotation, and planetary formation by aiming NASA’s recently retired Kepler space telescope toward the Pleiades open star cluster. All 1,000 stars in this group are nearly the same age, 125 million years old. Since all of the stars are the same age and formed from the same set of materials, astronomers have the ideal “laboratory” to isolate the role star mass plays on star rotation and evolution. Read more about the findings at http://goo.gl/osijIY. See the Pleiades for yourself, nearly one fist above the east-northeastern horizon at 11:30 p.m.

Thursday: At 11:00 p.m., Saturn is two and a half fists above the southeastern horizon and Jupiter is one fist above the eastern horizon.

Friday: Seventeenth century astronomers documented the appearance of a new star, or “nova”, in 1670. However, as modern astronomers studied the records of the star, called Nova Vulpeculae 1670, they realized it didn’t have the characteristics of a typical nova because it didn’t repeatedly brighten and dim. It brightened twice and disappeared for good. Turning their telescopes to the region, they discovered the chemical signature to be characteristic of a very rare collision of two stars. For more information about this discovery, go to http://goo.gl/rJnC2G. Nova Vulpeculae 1670 is right below the binary star system Alberio, the head of Cygnus the swan. Alberio is five fists above due south at 10:30 p.m.

The positional information in this column about stars and planets is typically accurate for the entire week. For up to date information about the night sky, go to https://nightsky.jpl.nasa.gov/planner.cfm.