Friday, April 1, 2016

The April Sky, Tonight's Sky for April 1

With the new month of April here, the lengthening of the days will continue at a brisk pace as the equinox is still within recent memory, which means that, for the first time of the new year, staying up late to observe under truly dark skies will become a chore for many. On the good news front, April is usually the first month of the year where the persistent winter clouds and cold finally loosen their grasp after months of winter weather, revealing the stunning celestial sights that had been so often shrouded in clouds for the first 3 months of the year in no longer bone-chilling temperatures.

Cool Constellations
If March was the last time to see many winter constellations under dark sky conditions, April is the last chance to see them, period. So, come sundown, look low in the West-Southwest for Cassiopeia, Cepheus, Perseus, Orion, Canis Major, and Canis Minor. A few later/more Northerly winter constellations, including Auriga, Taurus, Gemini, and the Pleiades are now in that twilight zone where one needs to observe them under dark skies now or miss them for the year. By the time April rolls around, the Big Dipper signpost to the stars is well up for all to see. Starting at the Dipper, follow the arc of the Dipper to bright orange Arcturus, alpha Bootes, and the brightest star in the spring sky. To the left of the kite-shaped Bootes, look for the arc of stars that is Corona, the crown. Next, speed onto blue Spica, alpha Virgo, and one of the brightest spring stars. Next, continue the curve to trapezoidal constellation Corvus, the crow. Finally, conclude in dim Crater the cup. Moving higher in the sky, zodiac constellations Cancer and Leo are well-placed as well. Speaking of Cancer, look just below the cosmic crab for a distinct ring of stars, the head of Hydra, the sky's biggest constellation, which snakes (sorry) through over 120 degrees of sky. For those who like to stay up late (or get up extremely early), there's mythological strongman Hercules and the Summer Triangle high overhead and, to the South, Ophiuchus, Serpens, and Scorpius. However, unlike in previous months, the later time of year will not bring new predawn constellations thanks to the Sun, which is rising ever earlier in the morning.

Planetary Perceptions
On the planet front, the big highlight is Mercury, which is making its best evening appearance of the year mid-month. Visible all month, itself rare, Mercury will peak in apparent height on April 18 in the Western sky just after sunset. How good is this apparition? So good that, even half an hour after sunset, Mercury is still well over 10 degrees above the horizon (hold a fist at arm's length to simulate 10 degrees). Additionally, at its best, Mercury will set almost two hours after the Sun. Moving into the night, Jupiter, which reached opposition on March 8 is still up just about all night. By month's end, Jupiter is just about crossing the Meridian, and is hence at its highest, as the sky finally gets dark. Later in the night, Mars is next to break the horizon, albeit in middle of the night, followed closely by Saturn. An item of note: Mars is still converging with, but not as fast as last month. Still, Mars and Saturn will continue to converge until their closest meeting takes place at month's end. Additionally, Mars will appear stationary mid month, after which it will eventually begin to retrograde and move forward with the stars through June. Moving to the immediate predawn sky, it's now or never (or at least until evening reappearance) to catch Venus, hangs very close to the predawn Eastern horizon and will be nearly impossible to spot by month's end.

Tonight's Sky for April 1: Mercury Rising
Mercury is on the rise and this has nothing to do with the trend of warmer temperatures. Right now, Mercury is low in the Western sky immediately after sunset. However, as the month progresses, Mercury will climb higher and higher in the Western twilight, peaking in height mid month. Still, why not start looking now?

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