The Ellensburg, WA sky for the week of March 16, 2024

 Saturday: 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, a few 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 already 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.

Sunday: Mercury is about a half a fist held upright and at arm’s length above the western horizon at 8:00 p.m.

Monday: Pollux is about a thumb width above the moon and Castor is about a first to the upper right of the moon at 10:00 pm. They are more than six fists above the southwestern horizon at this time.

Tuesday: 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 8:00 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 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”.

Wednesday: Many artists have sung the song “Blue Moon”. But few have sung the song “Blue Planet”. It goes, in part “Blue Planet, you saw me standing with 28 others. Rolling around like a barrel. Without close sisters or brothers.” It’s about the planet Uranus, which orbits the Sun in a rolling motion and has 28 moons. 25 of Uranus’ moons are named after characters in works by William Shakespeare and three are from the poem “The Rape of the Lock” by Alexander Pope.

Typically, Uranus is difficult to find. For the next few weeks, Uranus will be moving towards the much brighter Jupiter. Tonight, Uranus is a half a fist above Jupiter. View these two bodies for the next few nights. Jupiter is easy to identify. If the dimmer point of light you are looking at moves compared to the neighboring dim points of light, you are looking at Uranus.

Thursday: 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.

Friday: If you know exactly where to look in the sky, you can see a few bright planets when the Sun is out. The Solar and Heliospheric Observatory, or SOHO, is always watching the sky when the Sun is out… because it is always watching the Sun! Most of the SOHO images are filtered images of the Sun’s photosphere, the top of the visible layer. But two images, the LASCO C2 and C3, place a mask over the Sun in order to observe the Sun’s corona as well as solar system objects that pass near the Sun. For the next few days, For more about using SOHO to observe Solar System objects, go to https://skyandtelescope.org/astronomy-news/planets-and-comets-cant-hide-from-sohos-eye/.

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.