The sky gets a makeover

eye @As if reflecting April’s magical mutations, the sky also undergoes a radical makeover this month. The brilliant winter constellations now plummet into the west, consumed by the crepuscular fires of ever-later sunsets.

With dusk advancing rapidly, and the stars marching into the west four minutes earlier per night, it was forever destined that the two opposing armies would meet headlong each spring. The effect of this lopsided confrontation is to plunge Orion and his friends into the western twilight like lemmings.

April opens with Orion conspicuous at nightfall, but ends with the ancient Hunter low and setting. In his place stand the dim constellations of spring: a murkiness caused by our orientation away from the plane of the Milky Way. We now peer into the yawning nothingness of intergalactic space.

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Because our galaxy is pancake-flat – only some 600 light-years thick by a whopping 100,000 light-years long – there’s not much to see when we look through the thin section, as we do when gazing up these nights.

Just two bright stars call the spring sky their home. Both are easily found by following the Big Dipper’s handle – itself easy to find because the Dipper now hovers at its highest of the year: virtually overhead in the early part of each night. You “Arc to Arcturus,” as the old saying goes, and then follow that arc much farther to dimmer blue Spica of Virgo. This year, two bright planets add a bit of gaiety: At nightfall, Mars is bright and orange in the southeast, while even-brighter Jupiter dominates the west as the most brilliant “star” in the sky. This is truly astronomy made easy.

Mars happens to mark the direction to the nearest major group of galaxies, some 50 million light-years away: It’s the famous Virgo Cluster. Whenever you see striking photos of spiral galaxies, there’s a good chance that it’s an official card-carrying member of that grouping of 5,000 galaxies. Despite these thousands of cities of suns in that region of the April heavens, the area merely shows up as a dark patch of celestial real estate. Those who can find it – centered near but far behind Mars – have an excellent week for telescopic observations, as the Moon doesn’t rise these nights until after midnight.

So, pushing up from the earth, crocuses and tulips are bathed each night by faint photons of light that have traveled for eons from faraway empires. Too weak to nourish the emerging life of spring, they give the gift of wonder to the handful of humans who point telescopes into that darkest district of the April heavens.

Want to know more? To read Bob Berman’s previous “Night Sky” columns, visit our Almanac Weekly website at HudsonValleyAlmanacWeekly.com.

 

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