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 PISGAH ASTRONOMICAL RESEARCH INSTITUTE Dr. Bob Hayward Astronomer/Educator Graphics from TheSky Software Bisque
Mountain Skies April 3, 2017 MARS AND MERCURY LOW IN THE WEST IN EARLY APRIL The Planets: Well, the switch is complete. Venus, which has been our brilliant “evening star” since last summer, passed by through inferior conjunction with the sun on March 25 and has moved into our morning skies to become our “morning star.” Jupiter, on the other hand, which has been in the pre-­dawn skies as our “morning star” since October is now low in the east just after sunset and will be our “evening star” into late September. This giant planet passes through opposition on Friday when it will be exactly opposite the sun in the sky and, thus, rises as the sun sets and sets as the sun rises. About an hour after midnight the beautiful ringed planet Saturn will rise and, by dawn, when Jupiter is setting in the west, Saturn will be visible high in the south. The beautiful rings of Saturn are tilted at 26°, nearly the maximum, to our line of sight and, thus, present a beautiful picture through a telescope. Mars, as it has been doing since last June, is still hanging in there low in the west at sunset. It has been involved in an interesting situation where its eastward motion through the zodiac has just about matched the westward motion of the zodiac due to the revolution of the earth around the sun. Thus, Mars has changed its position in our evening skies very little since late summer 2016. For the coming week, it is joined by Mercury. Mercury is the closest planet to the sun and is spotted only low in the west after sunset or low in the east before sunrise depending on where it is in its orbit. In April, we get a chance at both views. Tonight, as the sky darkens, it is in the west below Mars. But, recall that Mercury, because it is so close to the sun, moves very rapidly. Thus, we will have a favorable view of this elusive planet for only the next week or so. Then, Mercury will dive into the sunset to pass through inferior conjunction on April 20. And, just as Venus did in late March, in late April Mercury will reappear low in the morning twilight, joining the much brighter Venus. The stars: Early evening in April catches us betwixt and between the prominent constellations of the receding winter skies and those of the quickly rising spring skies. In the former, the great hunter Orion can still be seen in the west. But now, as the sky darkens, he is leaning over looking downward as he follows the bull Taurus towards the horizon. The Gemini twins Castor and Pollux stand to the north of their mentor as they follow him across the sky. Two bright stars mark their heads. Following these folks as the sky turns are the two dogs. The Dog Star Sirius, the brightest star in the nighttime sky, is in the southwest. Above Sirius is the lesser or little dog consisting of only two naked eye stars, Procyon and the much dimmer Gomiesa. Meanwhile, to the east we find the springtime constellations becoming more apparent. Leo the lion is standing high in the east. The front or western portion of the lion has traditionally been called the sickle and can be found labeled as such on some star charts. It consists of an almost complete circle of stars with the bright star Regulus lying below it. In more modern times, we view this pattern as a coat hanger or a backward question mark with Regulus as the dot below the question mark. The hindquarters and tail of the lion are found in a triangle to the east of the sickle. Between the twins and the lion is Cancer the crab, basically an open area without any bright stars. In the middle of Cancer is a pretty cluster of stars popularly known as Praesepe or the “Beehive Cluster” since, with a pair of binoculars or a small telescope, it looks like a swarm of celestial bees. To the astronomer this cluster is known as M44 for Messier 44. Since the Beehive lies close to the zodiac, it is often occulted, i.e., covered up, by the moon. The planets can appear to pass through this swarm of bees as well as they follow their own orbits in front of Praesepe. Celestial Calendar: April 3, 2:39 p.m. EDT – First Quarter Moon April 7, 6 p.m. EDT – Jupiter at opposition. Visible all night long. April 11, 2:08 a.m. EDT – Full Moon April 12 – The sun in its apparent annual path around the sky moves from the constellation of Pisces the fish into Aries the ram.