The Last Week of Winter

Figure 1. Looking NE, 9:00 PM March 13, 2010

By Dave Grosvold

This coming week is the last week of the Winter season in the northern hemisphere, and is marked by the appearance of fiery Arcturus (Ark-TUR-es) in the evening Eastern Sky. Arcturus (Alpha Boötis,) is by definition the brightest star in the constellation Boötes (pronounced Boh-OH-teez.) The Ancient Greek name Arcturus means “Guardian of the Bear,” and is appropo considering its proximity to Ursa Major and Ursa Minor, the Great and Small Bears. The orange giant star's celestial appearance was supposed to portend tempestuous weather in Ancient Greece, and that certainly seems true in our millennium as well! Looking northeast in the evenings this week, you will find the Big Dipper (part of Ursa Major) tipping back on its handle until the water spills out the back of the bowl, which is another ancient sign of stormy weather ahead.

Following the handle from the bowl in an arc along the handle stars will lead you to Arcturus (see Figure 1.) Arcturus, being the third brightest star in the sky after Sirius and Canopus is a mere 36.7 light years from Earth. This places it in the same vicinity in the Orion Arm of the Milky Way galaxy as Earth — a very close neighbor in astronomical terms.

Venus is very low in the southwest just after sunset this week, but will be rising higher and higher each evening. If you look carefully, you might just find the thinnest sliver of the New Moon below and to the right of Venus during the last of the sunset on Tuesday, March 16th. By Wednesday, the now-visible waxing crescent Moon will be higher than Venus in the west-southwest.

Figure 2. Looking southwest just after sunset on Wednesday, March 17, 2010

Saturn is getting higher in the night sky this week and is nearing opposition, which falls on March 21 this year. Look for Saturn low in the east after sunset, higher in the southeast in late evening, and at its highest in the south at 1:00 AM this week. The rings are tilted nearly edge-on now, and will reach their most edge-on position in May.

Mercury is hidden in the glare of the Sun. Jupiter is now rising as a morning star, but hidden deep in the surrounding glow of the Solar disk. Uranus and Neptune are also both hidden in the glare of the Sun.

The Spring Equinox occurs at 12:32 PM Central Daylight Time on Saturday, March 20, and marks the beginning of Spring in the Northern Hemisphere. That evening, we will see a special treat. The Moon will be right next to the Pleiades (PLEE-a-deez) that evening, and will present a spectacular sight — especially in binoculars! The Moon will be so close that it will occult some of the fainter outlying stars of the Pleiades cluster.

An occultation is the covering of one celestial object by another as the first object passes in front of the second. The best observing time for this is 9:00 or 9:30 PM on Saturday, March 20th. Be sure to mark your calendar! This event will be the last occultation of the Pleiades by the Moon visible from North America until 2023.

Figure 3. Looking SW, 9:00 PM, Saturday, March 20 2010

The International Space Station will not be visible this week, but there will be a couple of bright Iridium Flares, if the weather cooperates. We have a shot at a VERY bright one (mag -8.0) at 6:23 AM on Sunday morning, March 14th, when Iridium 72 passes nearly directly overhead. Look directly North at an altitude of 46° to catch this flare.

Another bright Iridium Flare will occur early on Friday evening at 7:53 PM. Iridium 25 will only reach magnitude -2.0, and will be visible in the south-southeast at an altitude of 49° above the horizon. You might also want to try to catch Iridium 62 at 6:17 AM on Monday, March 13th in the North at an altitude of 44°, or Iridium 22 at 7:59 PM on Thursday, March 18th in the SSE at an altitude of 47. These two flares will only reach magnitude -0.0 and -1.0, respectively.