The Ellensburg, WA sky for the week of April 8, 2023

Saturday: The first day of spring was March 20. The most recent full moon was April 6. That means tomorrow is Easter. The standard way to determine the date of Easter for Western Christian churches is that it is the first Sunday after the full moon that occurs on or after the vernal equinox, also known as the first day of spring. Of course, the other standard way is to look for the date of church services celebrating the resurrection of Jesus. There is no Bible story of an “Easter star”. If there were, Spica would be a pretty good choice. The name Spica comes from the Latin “spica virginis” which means “Virgo’s ear of grain”. Spica represents life-giving sustenance rising after a long winter just like the risen Jesus represents life-giving redemption to Christians. Spica is one and a half fists held upright and at arm’s length above the southeastern horizon at 10:00 p.m. To learn how to calculate the exact date of Easter for any year, go to https://www.assa.org.au/edm.

Sunday: For the next few nights, Venus will be moving by The Pleiades open star cluster in the early evening sky. Tonight The Pleiades is about a thumb width to the upper right of very bright Venus. Both are about two fists above the western horizon. Venus will be moving slightly upward with respect to the background stars each night.

Monday: Astronomers are often fascinated with large objects. Planets that could hold 1000 Earths (Jupiter). Stars that would fill up the entire inner Solar System (Betelgeuse). Galaxies with 400 billion stars (Milky Way). But what about the smallest objects? One of the smallest stars is Proxima Centauri, the closest known star other than our Sun. It is about 12% of the mass of the Sun. Earlier this year, astronomers announced the discovery of a possible third planet orbiting Proxima Centauri indicating that even very small stars can have planets. The smallest theoretically possible star would be about 7.5% of the mass of the Sun. Any smaller and it could not support the nuclear reactions characteristic of stars. For more on small stars, go to http://goo.gl/EHBdOX.

Tuesday: Mercury will be as far away from the Sun in the sky as it will get this orbital cycle. This "farthest away" point is known as the planet's greatest elongation. Since Mercury is in the evening sky, it is east of the Sun so this occurrence is called the greatest eastern elongation. This evening will be the best evening to observe Mercury for the next few weeks. Mercury is one fist above the west-northwestern horizon at 8:30 p.m. Over the next few weeks, Mercury will move toward the Sun in the sky. By late May, it will be barely visible in the morning sky.

Wednesday: The Globe at Night April campaign starts today. Globe at night is a citizen science project to quantify the impact of light pollution on our view of the night sky. Go to https://globeatnight.org/campaigns/ to learn more and participate.

Thursday: Mars is four fists above the western horizon at 10:00 p.m.

Friday: The Lyrid meteor shower peaks next weekend. But there will be increased meteor activity in the vicinity of the constellation Lyra until then. The meteors appear to come from a point to the right of the bright bluish star Vega in the constellation Lyra the lyre. This point is about three fists above the east-northeast horizon at midnight and close to straight overhead near dawn. Go to https://earthsky.org/?p=158735 for more information.

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.