StarWatch: Moravian College Astronomy

StarWatch for the greater Lehigh Valley

JULY 2011

JULY STAR MAP | STARWATCH INDEX | MOON PHASE CALENDAR

Print Large Sky Charts For 10 p.m. EDT: NORTH | EAST | SOUTH | WEST | ZENITH

Current Solar X-rays:
Current Geomagnetic Field:

Status

Current Moon Phase

776 JULY 3, 2011: Globular Clusters and the Milky Way: Globular clusters are aggregates or glob-like groupings of stars which range in size from 10,000 members to assemblages of a million luminaries. They represent some of the oldest members of our Milky Way, dating back nearly 13 billion years when galaxy formation in our young universe was rampant. The Milky Way currently contains 152 of them, but some globulars are not original associates of our fraternity. They were born in other galaxies which over eons of time have been successfully cannibalized by the Milky Way, leaving behind some of their globulars to begin orbiting our galaxy. The reason for their longevity and survival during galactic collisions results from their compactness which produces the large gravitational forces necessary to hold them together. Since galaxies collide with the Milky Way in random directions, globulars are also left to wheel around the Milky Way in random directions and with varying orbital parameters. They kamikaze through the galactic plane where we live in periods of hundreds of millions of years, churning up the interstellar medium, which in turn, creates new stars. During these gravitational interactions some of their outer members escape to orbit the galaxy on their own to form a kind of galactic haze or halo which surrounds the Milky Way to distances as far as 200,000 light years from its center. Unfortunately for us, the best two globular clusters, Omega Centauri and 47 Tucanae, are best positioned for the southern hemisphere. Third on the list, M13 in Hercules the Strongman, is squarely a northern hemispheric object, best seen on clear moonless evenings in the early summer sky. It contains about 300,000 stars and is found just over 25,000 light years from Earth. Use the map found in the web edition of this week’s StarWatch along with binoculars to locate this cotton ball-like jewel.

777 JULY 10, 2011: What's Happening to the Sun?: I am a proponent of global warming which is an accepted model being advocated by a majority of individuals in the scientific community. Even if this theory is proven wrong, it makes no sense to me to continue to pump pollutants into the atmosphere which are known to trap heat—heat that will cause our planet to warm. One aspect of global warming or cooling, however, is not within our control. Solar physicists have noted that the sun’s varying activity can be understood by looking at sunspot numbers. Sunspots are intense areas of solar magnetism which slow the ability of the sun to transport energy to its surface. Intuitively, it seems that many dark, cool spots covering the sun should produce a lower energy output than when the sun is spotless. An interesting ideas—yes; a correct idea—no! The sun actually overcompensates by funneling greater energy outflow in regions called faculae near the spots. A spotless sun is less luminous than when Sol is heavily spotted. This means that when a sunspot cycle bottoms, the Earth cools ever so slightly and warms in a similar fashion when activity is high. Sunspot numbers vary in periods which average 11 years, but groupings of cycles seem to show periodicity also; and sometimes the cycles cease to occur for decades. This happened from 1645 to 1715 and to a lesser extent from 1790 to 1830. In both instances, the Earth’s temperature cooled significantly, producing colder winters and cooler summers. A similar situation may be occurring now. We are just emerging from the longest solar minimum in a century and a weak solar maximum has been predicted for 2013, three years later than originally calculated. Forecasts for the following solar maximum envision even less activity, due to a weaker circulation of solar plasma. If this proves correct, we may get an extra decade or two to sort out our global warming issues.

778 JULY 17, 2011: Saturn Exits, Jupiter Debuts: Back in July of 2000 when I was New Mexico helping with the National Parks’ burgeoning night sky program, I remember the vivid appearance made by the close encounter of Jupiter and Saturn in the early morning July sky. The two rose almost like a pair of sentient eyes starring down into Chaco Canyon where I was stationed. Now 11 years later, those eyes are almost as separated as they can get. I have been watching Saturn in the west at dusk, using it as a locator “star” to align my computerized mount. By the time it gets dark, it stands about one third of the distance from the horizon to the zenith in the WSW. Don’t get it confused with the bright blue-white star Spica which is nearby and to Saturn’s left. They are both at the same altitude above the horizon and at the same brightness. Binoculars will reveal that Saturn possesses a warmer hue and that it also shines with a steadier light. Binoculars won’t reveal Saturn’s ring system which is close to edge-on, but a small telescope will show a thin line extending on either side of the god of the Harvest, as well as Saturn’s largest moon, Titan. Binoculars will also reveal a star just to Saturn’s right, Porrima of Virgo the Virgin visible to the unaided eye from suburban locales. While Saturn will be shortly exiting the heavens, Jupiter is making its debut, but don’t expect to see this giant world easily until dawn. Saturn sets just after midnight, and Jupiter rises an hour later. Best views will come around 4 a.m. when brilliant Jupiter is highest in the east, about 30 degrees above the horizon. That’s still low by astronomical standards, but its altitude can be judged by looking at Saturn’s height above the horizon when it first gets dark. If you’re hesitant to check upon Jupiter in the a.m., then simply give it a couple more months. By bitterly cold January, you’ll be able to catch it at 7 p.m., mid-sky in the south. Yes, you’re right; there is no winning in astronomy.

779 JULY 24, 2011: Magnets, Trains, and the Universe: Magnetism plays a fundamental role in astronomy as well as in our daily lives. From the creation of stars, the operation of electric motors and the turbines which generate electricity, to the force that binds electrons to the nuclei of atoms, magnetism is found all around us. In fact without magnetism, the elements and compounds that compose our universe would simply fly apart. The cosmos would be immersed in a subatomic haze. Earth’s magnetic field, created by the flow of electrons in the outer liquid core, can be visible to the unaided eye when large auroral outbursts occur. As a train-loving aficionado, I’ve always been a supporter of using magnetism in high-speed rail transportation. The environmental impact as well as the community living impact of passenger rail service is far-reaching. One of the most important developments in recent years regarding train travel has been the concept of maglevs or magnetic levitation. These trains use like magnetic fields in a C-shaped track which repel each other to allow the train to hover above the track, creating a virtually frictionless and smooth ride. Air resistance is still a factor. An electric current supplied to coils in the guideway walls is constantly alternating to push and pull the train forward. The first commercial maglev train system was opened in Britain in 1984, and it was such a success that the technology has since seen widespread use elsewhere in the developed world. The US, however, has not yet invested in any maglev technology. Transportation by magnetism, however, may be a key player when colonizing the moon or other planets like Mars. Bodies in space without much of an atmosphere would allow maglev trains to incur little or no air resistance, meaning that magnetic transportation would be the quickest and most efficient way to carry people and goods to and from cities on many future habitable worlds.
--Rudy Garbely, Moravian College Astronomy, for www.astronomy.com...

780 JULY 31, 2011: Perseids Fly Early This Year: Perseid meteors will be flying earlier this year. In fact, you can see them now. No, there has not been a change in the orbital path of the dross left behind by Comet Swift-Tuttle making it intersect Earth’s orbit earlier. It’s simply due to the moon’s brightness which will be near its full phase throughout the peak days of this shower and full on the morning of greatest activity, August 13. On the evening of the 12th, the moon rises about 8 p.m. and does not set until 6 a.m. on the 13th. There is a positive side to this lunar conspiracy. Perseid rates rise gradually over a two week span until the 13th, than rapidly decrease over the next week. There is also the tendency to see brighter meteors before maximum night than after. In older streams like the Perseids, the pressure from sunlight has time to segregate particle sizes leaving the larger ones less affected. Earth intersects the bigger dross first. If you are planning to see Perseids this year, watch during the morning hours, especially after the moon has reached first quarter on August 6. Rates will be depressed, 5-15 meteors per hour, but the meteors will be brighter. Face towards the northeast, and always try to keep the moon away from your field of vision. Recline on an air mattress or a bedroll and look directly overhead which is normally the darkest part of the sky. A plastic tarp to help protect you from dew will also prove handy. Perseid meteors tend to be “groupies.” If you see one, another or more may follow in the next 30 seconds or so. Then there will be a lull in activity for five or 10 minutes before the next set happens. This is not an absolute rule for Perseid behavior, but many observers have noticed this bunching tendency. Perseids are swift and diverge from a point near the top of the constellation of the Hero making their identification a no-brainer. Much success despite the moonlight and summer haze!

[July Star Map]

[July Moon Phase Calendar]