StarWatch: Moravian College Astronomy

StarWatch for the greater Lehigh Valley

FEBRUARY 2014

FEBRUARY STAR MAP | MOON PHASE CALENDAR | STARWATCH INDEX | NIGHT SKY NOTEBOOK

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911 FEBRUARY 2, 2014: “Death Star” Rocks Nearby Galaxy: A brilliant supernova has rocked a bright galaxy in Ursa Major (Big Dipper) called M82. The discovery was made on January 21 by an astronomer at University of London Observatory, located within the bright city limits, who was scrambling to image the galaxy for his students as weather conditions rapidly deteriorated. The undergraduates had chosen M82 because it was located in one of the few remaining clear patches of sky. While adjusting the position of the 14-inch, automated telescope, teaching fellow, Dr. Stephen J. Fossey, noticed a new star overlaid on the M82 photo which he did not recognize from previous observations. Checking online pictures of M82 against his new image of the galaxy revealed that the star was indeed a supernova blasting its way into visibility through the dusty lanes of this cigar-shaped galaxy. M82 is really strange. At a close distance of 12 million light years, M82 is interacting with another nearby galaxy, M81. The gravitational disruptions to M82 have caused an enormous amount of star formation in the galaxy’s center, about 10 times greater than is occurring in our own Milky Way, giving the irregular galaxy a scruffy appearance as galaxies go. In the central, starburst region, supernovas occur at the rate of about one every decade. Ironically, the new supernova blew far outside this active region. Spectrographic analysis of the exploding star revealed it to be a Type Ia event originating from a carbon-oxygen rich white dwarf, the core of a dead star. In one scenario, hydrogen from a companion star in a contact binary system accretes onto the white dwarf. As the white dwarf gains more mass, temperatures and pressures exerted on its core increase, eventually triggering a runaway thermonuclear event which blows the star apart, creating the supernova. SN 2014J, as it is named, will continue to brighten for about one more week. The fun is just beginning.

912 FEBRUARY 9, 2014: Winter Group Rides High: If you can bear the cold of February, now is the best time to step outdoors right after dark, face to the south, and view the winter group of star patterns. Without a doubt, the ringleader and finest of the lot is Orion the Hunter, a magnificent assemblage of blue giant and supergiant stars with one red supergiant thrown in for good measure. If you cannot imagine Mintaka, Alnitak, and Alnilam, the three belt stars girding his waist, the breadth of Orion’s shoulders outlined by ruddy Betelgeuse and the Amazon, Bellatrix, and Orion’s “Richard Burton” knees created by sparkling blue supergiant Rigel, and more demure, azure Saiph, then there can be no astronomy merit badge for you. Beneath Orion’s diamond belt are three, less conspicuous “stars” which form his sword. The top and bottom luminaries are actually small clusters of stars, but the center looks fuzzy, and is the famous Orion Nebula. Through binoculars it flowers into a wing shaped diaphanous cloud, even under brighter suburban skies. The youngest stars known in our part of the Milky Way Galaxy, just 300,000 years in age, are found here. Follow Orion’s belt downward to Sirius the Dog Star, brightest luminary of the night and the nose of the Big Dog, Canis Major, one of Orion’s two hunting dogs. The hungry dog is begging for food from the Hunter, but Orion has been too encumbered in his battle with the Bull, Taurus, to feed him. Follow the stars of Orion’s belt upward, and your line of sight will pass just under orangey Aldebaran. That’s the blood-curdling eye of the bull. If you look harder or use binoculars, you’ll notice that Aldebaran is the brightest star of a “V” which represents Taurus’ head. By allowing the eye to continue just a bit farther, another gossamer area will be perceived, the Pleiades or Seven Sisters. Both the head of Taurus, minus Aldebaran (the Hyades), and the Pleiades are two more star clusters which are visible to the unaided eye.

913 FEBRUARY 16, 2014: Grazing the Winter Sky: This is the time of the year to see the winter constellations dominating the early evening sky right after dark. Orion with its three belt stars pointing southward to Sirius, the brightest star of the night and northward towards Aldebaran, the orangey eye of Taurus the Bull, are only part of the cyclic mix. Winter star patterns lie above and to the left of this anchor assembly. Begin with the left shoulder of Orion (reddish Betelgeuse) and his right knee (blue Rigel). Let them guide you upward to a truly dazzling planet, Jupiter, which outshines Sirius by almost threefold, some 40 degrees below. Binoculars, correctly focused, should reveal at least two of Jupiter’s four bright Galilean moons if they are far enough away from the planet. However, don’t stop at Jove. Continue onward and you will pass just right of two first magnitude stars, Castor and Pollux, the heads of the fabled Gemini Twins. Castor was mortal, and Pollux was immortal. Their bodies demonstrate this nicely with Castor’s stretched arms and abdomen, accented awkwardly by his short stubby legs. Pollux, on the other hand, stands straight and tall except for his slight bowlegged appearance. From brighter suburban locales, the Twins may look more like a rectangular box than two brothers supporting each other. Below Pollux sits Procyon, the alpha star of Canis Minor, the Little Dog. One winter constellation which lies to Gemini’s right and above is Auriga the Charioteer. Capella, its most famous star and the six brightest luminary of the night, is near the zenith by 8 p.m. Four other stars, about the brightness of the Big Dipper, complete what looks like the body of a chariot. To Auriga’s right are the “leftover” stars of autumn while left of Gemini are the fresh, newbie stars of the spring sky, heralding warmer, much longer days ahead. A star map can be found online at www.astronomy.org. Click on the StarWatch button when the page loads.

914 FEBRUARY 23, 2014: Serious about Sirius: I once posed a web question regarding the brightest star of the night. There were just over 2000 respondents, and 51 percent of them choose the North Star. Ten percent of the viewers answered correctly. It was Sirius, the Dog Star of Canis Major, which incidentally is about 23 times brighter than Polaris. In fact, its name is Greek and means “searing” or “scorching.” I picked Sirius to write about this week because with the deep snow on the ground, you don’t even have to go outdoors to see it. All you need is a room with a window facing south. Turn off the room lights around 8 p.m. and peer out into the night. Sirius is due south about 30 degrees above the horizon and usually twinkling noticeably. Forty degrees above Sirius is the planet Jupiter which is nearly three times brighter than Sirius, but shining with a steady light. Don’t get the two confused. Most of the dazzling stars of the night sky are actually much, much brighter than the sun, but Sirius is just a little different. Yes, Sirius in absolute terms is more luminous than the sun, but if you moved the Dog Star to the standard distance that astronomers use to compare stars to one another, 32.6 light years, Sirius would be just a little brighter than the brightest stars of the Big Dipper, while the sun would only be faintly apparent in even the darkest sky. Sirius has a companion, a white dwarf that is just a little more massive than our sun. White dwarfs are the helium rich or carbon-oxygen rich cores of dead stars. They once were normal hydrogen-burning stars, then become red giants as they struggled to fuse helium into heavier elements. Finally, during an instability period, they ejected a substantial part of their mass to evolve into a white dwarf. Sirius’ companion as a normal star was brighter than Sirius, but when it became a red giant, it would have been hundreds of times more luminous than Sirius is today. What a sight that would have been from your window!

[February Star Map]

[February Moon Phase Calendar]