The Ellensburg WA sky for the week of March 14, 2020

Saturday:  Avast ye matey. Swab the poop deck. Pirates love astronomy. In fact, the term “poop” in poop deck comes from the French word for stern (poupe) which comes for the Latin word Puppis. Puppis is a constellation that represents the raised stern deck of Argo Navis, the ship used by Jason and the Argonauts in Greek mythology. Argo Nevis was an ancient constellation that is now split into the constellations Puppis, Vela and Carina. The top of Puppis is two fists above due south and about a fist and a half to the left of the bright star Sirius at 9:30 p.m. Zeta Puppis, the hottest, and thus the bluest, naked eye star in the sky at 40,000 degrees Celsius, is about a half a fist above due south at this time..

Sunday: Venus is more than three fists above the western horizon at 8:00 p.m.

Monday: Ask someone which day in March has the same duration day and night. Go ahead, ask someone. Why are you still reading this? I can wait. If that person said the first day of spring, they are wrong. Today, four days before the first day of spring, is the date in which day and night are closest in duration in central Washington. There are two main reasons for this. First, the atmosphere acts like a lens, bending light from the Sun above the horizon when the Sun is actually below the horizon. This makes the Sun appear to rise before it actually rises and appear to set after it actually sets. Second, spring starts when the center of the Sun passes through the point called the vernal equinox. But, the Sun is not a point. The upper edge of the Sun rises about a minute before the center of the Sun and the lower edge sets a minute after the center of the Sun. Thus, even if we didn’t have an atmosphere that bends the sunlight, daytime on the first day of spring would still be longer than 12 hours.

Tuesday: “Oooo, they’re little runaways. Orion’s stars moved fast. Tried to make a getaway. Ooo-oo, they’re little runaways,” sang Bon Jovi in his astronomical hit “Runaway.  At least that’s what I hear when I listen to the song. After all, it fits the recently calculated trajectory of AE Aurigae, Mu Columbae, and 53 Arietis. Extrapolating the actual motion of these three stars back in time, they were all in the location of the star-forming region called the Orion Nebula a few million years ago. What kicked these stars out? Not paying rent? Excessive partying? No, it was simply gravitational interactions with near-by stars. Find out more about the eviction at http://goo.gl/UeLwKQ. The Orion Nebula is visible with the naked eye from a very dark site, about three fists above the southwestern horizon at 9:00 p.m.

Wednesday: The southeastern sky is crowded with Solar System objects this morning at 6:00. Most noticeable is the waning crescent Moon, a fist above the southeastern horizon. The bright planet Jupiter is less than a half a fist above the Moon. Mars is about a finger width to the right of Jupiter. Saturn is a little more than a half a fist to the left of the Moon.

Thursday: Look up in the sky. It’s a plane. It’s a bird. No, it’s the vernal equinox. The vernal equinox!? Spring starts at 8:54 p.m. Pacific Daylight Time. The first day of spring is often called the vernal equinox. This label for the day is misleading. The vernal equinox is actually the point in the sky where the Sun’s apparent path with respect to the background stars (called the ecliptic) crosses the line that divides the stars into northern and southern celestial hemispheres (called the celestial equator). This point is in the constellation Pisces the fishes. At the vernal equinox, the Sun is moving from the southern region of background stars to the northern region. 

Because the Earth slowly wobbles like a spinning top, the vernal equinox is slowly moving into the constellation Aquarius. By the year 2597, the vernal equinox will reach the constellation Aquarius and the “Age of Aquarius” will begin. Until then, we’ll be in “the age of Pisces”.

Friday: If you want to put somebody off, tell her or him to wait until Deneb sets. At Ellensburg’s latitude of 47 degrees, Deneb is a circumpolar star meaning it never goes below the horizon. At 9:45 p.m., it will be as close as it gets to the horizon, about two degrees above due north. Watch it reach this due north position about 4 minutes earlier each night.

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.