MAY  2009

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The moon, the Pleiades star cluster, and Mercury light up the twilight sky on April 26. If the clouds near the horizon look more like summer, that was because the temperature in Coopersburg, PA had reached into the low 90s earlier in the day, unprecedented warmth for mid-spring. An equatorially mounted Canon 40D camera was used to image this 10 sec., 112mm, F/4.5 exposure of the western horizon. The scene was equally impressive through binoculars. Photography by Gary A. Becker...

Photography by Gary A. Becker...

663    MAY 3, 2009:   Halley's Comet Redux

If you had the opportunity of seeing Halley’s Comet this week, would you take advantage of it? The last time that Halley swung by the Earth was during the spring of 1986. That passage was one of the worst appearances of the comet since it was first recorded by humans in 239 BC. Halley will not again return to the sun until 2061. One of the interesting features about comets is that they lose part of themselves every time they slingshot past our sun. Estimates vary between inches to as much as 10 feet of surface material lost to space per solar passage. Dirty ices evaporate (sublimate) beneath a flimsy, dark surface, forming pockets of pressurized gas and dust. The stressed crust eventually breaks, releasing this material into space. Gas molecules and small dust particles interact with the sun’s light and are swept away to form the familiar tail structure of the comet. Larger pieces of grit remain in the comet’s orbital path, spreading out over tens of thousands of years, to form a dusty tube that the Earth may intersect over time. That is exactly what will be happening this Wednesday morning, May 6, when Earth plows through the dust of Halley’s Comet to produce the Eta Aquarid meteor shower. Start observing about an hour before dawn (4 a.m.) and face east. Look towards the zenith, usually the darkest part of the sky. Any fast moving shooting star that traces itself back to the east will undoubtedly be an Eta Aquarid. Because of the southerly location of Aquarius the Water Bearer, rates are higher in the southern hemisphere, with about 30 meteors visible per hour. Mid-latitude locales north of the equator will find the Eta Aquarids producing about 10 events each hour. Irregardless of rates, if you have seen an Eta Aquarid meteor flash across the predawn sky, you can say that you’ve said “hello” to Halley’s Comet, even in an off year.

664    MAY 10 2009:   Local Group Downsized

In 2004, when I last spoke about our Local Group of galaxies which includes our own Milky Way, the Andromeda Galaxy, and M33, another large galaxy in the star pattern of Triangulum the Triangle, the Local Group’s population numbered about 45. Five years later, that figure is now approaching 50. That does not mean new galaxies have been created during this time, but rather improved techniques of observations are revealing more members. Five years ago, astronomers were boasting that our Milky Way with its 400 billion active stars and 13 satellite members was the most massive constituent of the group. Today, the scales are again tipping ever so slightly in favor of Andromeda with its 600 billion stars and its 14 member satellite system. The Milky Way has about 20 percent less matter according to the newest research. The most startling revelation seems to have been an overestimation of the total mass of the Local Group, perhaps by as much as three times. Presently (2009), all of the Local Group’s inhabitants tip the scale at about 1.9 trillion solar masses, which means that the Local Group contains 1.9 trillion times more “stuff” than our sun. That is less than estimates of the Milky Way alone made in 2004. One event that still seems to be on track is the eventual collision of the Milky Way with the Andromeda Galaxy. Although each galaxy’s bloated envelope of hydrogen may already be in contact, the galaxies themselves don’t start slipping and sliding through one another for another three billion years, a real bummer if you were planning to wait this one out. Eventually, Andromeda and the Milky Way and other members of the Local Group will have cannibalized each other and merged themselves into a super galaxy. Galaxies have probably been doing this since the universe’s beginning, 13.7 billion years ago.

Adapted from Wikipedia...

Adapted from Wikipedia...

665    MAY 17, 2009:   Swing Time for Jupiter and Neptune

I always feel a certain amount of hypocrisy when writing about astronomical events that will be happening in the morning sky. While my enthusiasm is great, my flesh is often weak when the actual moment, let’s say 4 a.m. rolls around, and the alarm wails me into consciousness. I will, however, probably make an attempt to view and photograph what I will be describing in this article because it will be 13 years before this event transpires again. In addition, this particular occurrence takes over one half year to unfold. The waning crescent moon will encounter Jupiter during the predawn hours of Sunday, May 17. The following morning, the moon will be to Jupiter’s left and still farther to the left on May 19. The point of trying to observe the SE sky on one of these three mornings is to locate Jupiter and to become familiar with its position. The last quarter moon and Jupiter, separated by only two and one half degrees on May 17, will be a beautiful sight in itself. Of intriguing note will be the location of Neptune, the last planet in the solar system, less than one degree to the east (left) of Jupiter. During the next week, Jupiter will close on the God of the Oceans, so that by Wednesday, May 27, the giant of the solar system will be less than one half degree to the south of Neptune. Jupiter will pass Neptune, but then by a curious coincidence in geometry, both Jupiter and Neptune will begin to retrograde (move towards the west) as the Earth passes both planets in space. Jupiter will again pass Neptune on July 9 moving off to Neptune’s right and reaching its greatest elongation during the early evening hours of October 13. The King of the Gods returns to its direct motion passing Neptune for a third time on December 21 when Jupiter is positioned just over one half degree from Neptune. An online map is posted with this article.

Jupiter overtakes Neptune on the morning of May 27 at a distance of less than one lunar diameter, the first chapter of a triple conjunction which will see Jupiter passing Neptune again on July 9 and for a third time on December 21. Observe with large binoculars or a small telescope and note that the brightest star on the map, +5.1 magnitude, Mu Capricorni, is about as bright as the four large Galilean satellites of Jupiter, also visible in the drawing. Jupiter will be over 14,000 times brighter than Neptune. Map created by Gary A. Becker using Software Bisque's The Sky...

666    MAY 24, 2009:   Saturn's Rings Play Hide and Seek

I am sitting here at a Saturn dealership waiting for my 2004 Vue to be inspected so that it is deemed worthy to navigate the roadways of Pennsylvania. The brand name “Saturn” really had nothing to do with the sixth planet from the sun, but rather the splendid engineering feat of NASA engineers, led by Wernher von Braun, of the Saturn Ib and Saturn V rockets which powered our astronauts to the moon and back. But as I sit here waiting for my car, I can’t help but think of the planet, still situated below the hind quarters of Leo the Lion, now in the western sky after sundown. See the online map which is included with this article at www.astronomy.org. If you look at yellowish Saturn through a telescope, you will notice that its beautiful ring system is almost missing. Twice during it 29.5 year circuit around the sun, the Earth’s view of the Harvest God slips in and out of Saturn’s ring plane. When we are viewing nearly in the ring plane, like we are currently doing, Saturn’s ring system appears thin and emaciated. The planet’s brightness in the sky is also diminished. During the summer months as we continue revolving around the sun, our view of Saturn’s rings will appear ever more edgewise until the evening of September 3, when the rings will disappear. Unfortunately by that time, Saturn will be nearly impossible to view because of its setting time, just 36 minutes after the sun in a bright sky. This week Saturn sets about 2 a.m., midnight in late June, and 10 p.m. by late July. On August 22, ultra thin ringed Saturn lines up with Mercury and the crescent moon, setting an hour after the sun. Over the next three months, we have a ringside view of the narrowing of Saturn’s rings. During the fall, the rings start becoming more and more open, a trend that will continue for the more than six years into the future.

667    MAY 31, 2009:   One with the Universe

In a few weeks, millions of summer travelers will journey to remote places where they will have the chance to look up and to see a dark sky, to wonder about those stars that twinkle with quiet glory, and to witness their home galaxy, the Milky Way, a suffused glow that can be seen arching across the heavenly vault. Contemplate the Milky Way with its 400 billion active stars. Our sun slowly orbits at 200 miles per second, 28,000 light years from its galactic hub, completing one circuit every 250 million years. Its sheer size, 100,000 light years across, dwarfs our mental grasp. We live, love, and die hardly giving it a second thought. The Hubble Space Telescope has given us fresh insights about our Milky Way and our universe by showing us a different reality than the one that we are used to experiencing. It reveals the stellar tapestry of welling outbursts of energy, dying stars, colliding galaxies, and the flimsy wisps of gas looking like colored streamers at a fair. Billions of light years away from anything remotely familiar, we wonder what these images can do for us. They can make us dream. They can make us imagine that “out there” is another planet, another race of people, beings like us yearning to know and comprehend the comic riddle of why. Who cannot be moved by those photos that are a snapshot of our past, the closest we can get to a visual fingerprint of an infinite being echoing His signature across the cosmos? Perhaps the most amazing consequence of our reality is that we are composed of the very stuff and processes that we seek to understand, for most of the atoms inside of our bodies were once in the belly of a star, a star that died so that we might one day live. We, humankind, are a piece of the universe that has become self-aware. So celebrate your connection to the litany of stars that pulse with the rhythm of your heartbeat too.