Skywatch Line for Friday, May 3 through Sunday, May 5, 2019

This is Dudley Observatory’s Skywatch Line for Friday, May 3 through Sunday, May 5, written by Sam Salem.

On Friday, the Sun rises at 5:48am and sets at 7:58pm. On Saturday, new Moon occurs at 6:46pm.

Mercury continues to brighten in the first part of this month before being lost to morning twilight around mid-month. Venus remains low in the morning sky, gradually losing separation from the Sun. Venus, at magnitude –3.9, and much fainter Mercury, at magnitude –0.3, are both very low in the brightening dawn. Try to locate Venus just above the due-east horizon about 20 minutes before sunrise. Then use binoculars or a wide-field telescope to look for little Mercury about 6 to 8 degrees to its lower left.

Mars, at magnitude +1.6, lies in constellation Taurus. Mars glows in the west during and after dusk, lower every week now. Spot Mars about 20 degrees to the right of brighter, Mars-colored Betelgeuse, the topmost bright star of constellation Orion. Mars sets around 11:15pm. Jupiter is becoming more dominant in the late evening through overnight. Jupiter rises around 11pm. Saturn, now in retrograde motion in constellation Sagittarius, is visible for more than half the night. Saturn rises around 1am.

On any moon-free night this month, let the blue-white star Spica guide you to the Omega Centauri globular star cluster. You can see this cluster with the unaided eye, if your sky is dark enough. Omega Centauri looks like a faint fuzzy star. To find Omega Centauri, first find Spica, the brightest star in the constellation Virgo, the Maiden. Spica climbs to its highest point in the sky around 12pm in early May. You can use the Big Dipper to find Spica. Just “follow the arc” in the Big Dipper’s handle to the bright orange star Arcturus, then “drive a spike”, or keep extending that arc to Spica. Spica and Omega Centauri transit due south at the same time. Look for Omega Centauri about 35 degrees directly below Spica. A fist at arm’s length is about 10 degrees. Globular clusters are large, symmetrically shaped groupings of stars, fairly evenly distributed around the core of our Milky Way galaxy. Omega Centauri is the largest and finest globular star cluster visible to the eye alone.

This moon-free weekend is a good time for watching the annual Eta Aquariid meteor shower. Watch for these meteors to streak across the sky before dawn the next several mornings. The peak of the Eta Aquariid meteor shower, when the most meteors are visible, should happen before dawn this Sunday, according to Bill Cooke, lead of NASA’s Meteoroid Environment Office. In theory, rates this year can reach up to 40 meteors per hour during that time. The shower is of medium brightness, and the darker your skies the more you’ll see. The Moon will not interfere with the peak this year. The meteors appear to originate from Eta Aquarii, one of the brighter stars in the constellation Aquarius. The point meteors appear to come from is called the radiant. Unfortunately, for our area, north of 40

degrees north latitude, the meteors tend to be sparse and few between. The radiant won’t be very high in the sky, for people in mid-northern latitudes. Therefore, you’ll need a dark-sky site with a relatively clear southern horizon to make the most of the meteors. Observers near the equator will have the best views. Even as far north as Miami, the view will be much better than it will be from New York or San Francisco. Every year, Earth crosses the orbital path of Halley’s comet in late April and May. Pieces from this comet light up the nighttime as Eta Aquariid meteors. The comet dust smashes into Earth’s upper atmosphere at nearly 150,000 miles per hour. Roughly half of these swift-moving meteors leave persistent trains, ionized gas trails that glow for a few seconds after the meteor has passed. Earth also crosses the orbital path of Halley’s comet in late October, giving rise to the Orionid meteor shower, which is usually at its best in the predawn hours around October 21.

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