The Sky Tonight, April 17th, 2018

The sky tonight for April 17, 2018 without narration. A version of this video will follow with full narration by Dr. James Daly of Astronomy For Change. This is the first video in our weekly tour of the night sky. Each installment will be seasonal and timely, designed to take our guests on a quick tour of the evening sky.

We open with Venus following the setting sun flanked by the one-day old waxing crescent moon. Zooming in on Venus, we note its phase approaching what could be described as “waxing gibbous”. The phases of Venus were first observed by Galileo over 400 years ago, providing empirical evidence for the heliocentric model of the solar system first proposed by Copernicus almost 100 years earlier; this observation presented quite a conundrum for those who continued to adhere to a geocentric or Earth centered model. The only way Venus can appear to go through phases is if it were closer to the sun, as it is, and if the sun were at the center.

Make sure you have a clear view of the western sky, otherwise you would miss Venus. The planet is so bright that it is often referred to as either an evening star or a morning star.

If we look to the east, we take note of the beautiful Pleiades, the seven sisters, an open cluster of young, bright stars in Taurus the bull. With a pair of binoculars, the cluster takes on a whole new look and, under dark skies, a thin misty veil can be seen, the very gas and dust left over from the stars formation. Taurus is marked by a stellar V with the red giant star Aldebaran marking his right eye.

Taurus is a prominent winter constellation and, since spring is already upon us, we note that it is high in the west at twilight with Orion, the mighty centurion and another winter constellation, further to the east. With each day, these winter constellations will be further and further west, eventually setting with the sun by mid-summer.

If we gaze a bit north from Orion’s sword, we immediately note his three belt stars. It’s striking the number of bright stars visible in this part of the sky. Orion is marked out by the glittering sapphire, Betelgeuse, his right shoulder and a red supergiant star that is expected to explode very soon in a spectacular supernova. His left shoulder, Bellatrix, and his knees marked by Saiph and brilliant blue-white Rigel, another supernova candidate. Returning to the belt and drawing a line due east takes us directly to the brightest star in the sky, Sirius, the dog star and the head of Orion’s faithful celestial companion, Canis Major seen standing upright and facing him.

In this first installment, we zoom in on four notable objects in the three constellation we explore tonight, Taurus, the Bull, Orion, the mighty Centurion and his faithful celestial companion, Canis Major, the Great Dog.

Three of these objects are delightful in a modest pair of binoculars: The Pleiades otherwise known as the Seven Sisters, the Great Nebula in Orion, Messier-42 (M-42), located in his sword and a veritable stellar nursery where we’re observing active star formation, and an open cluster of stars in Canis Major known as Messier-41 (M-41), a beautiful sight in binoculars. We “zoom in” on all these objects, first providing an “expanded view”, followed by a telescopic view for three of the four objects, images courtesy of the author. The fourth object is the remnant of a supernova, known as the Crab Nebula, a “new star” first observed by Chinese astronomers in the constellation Taurus on July 4th, 1054. We know today that a supernova isn’t a “new star” at all but the death of a high-mass star where, in one of the most spectacular and elegant processes in all of nature, the exploding star enriches the interstellar medium with the raw materials for new worlds and new life.

Please check back frequently for the latest installment of The Sky Tonight!