Whats Up in the Sky September, 2006

Autumn Constellations

I always look forward to this time of year (at least now that I’m retired from teaching) because the conditions for backyard observing are good. Cool nights, clear skies, and a variety of interesting objects often combine for a fun night of sky watching. And, since the planets are not well-placed for viewing, we can concentrate on some other things

I often tell people that a good place to begin in amateur astronomy is to identify the major constellations just using the naked eye. Go out about an hour after sunset, when the brightest stars are beginning to appear. Face south and look straight up. You will see the bright star Vega (VEE ga) which is in the constellation Lyra and is one of the stars in the Summer Triangle. At 27 light years (LY) distant it is one of the closest bright stars.

To the left and a little above Vega is Deneb (DEN ebb), the tail of Cygnus, the swan. Deneb is one of the most luminous stars known, 60,000 times brighter than the sun. If it were as close to us as Alpha Centauri (our nearest stellar neighbor at 4.4 LY) we could read by its light. It is the second star in the Summer Triangle.

Directly below these two stars is the third member of the Summer Triangle, Altair, in the constellation Aquila, the eagle. According to legend, Aquila belonged to Zeus, the king of the gods, who rewarded the bird for all his years of faithful service with a place among the stars.

Continue down to the southern horizon and look for Sagittarius. This constellation resembles a teapot with its spout pointing to the right (west) and tipped down. On a dark, moonless night you can see the Milky Way rising from the teapots spout and arching overhead.

Turn now toward the northwest and look for the Big Dipper just over the treetops. Its handle arches to the left (west) and the bowl is on the right (north). Follow the two northernmost bowl stars up to Polaris, the North Star, which is the end star in the handle of the Little Dipper. Returning to the handle, look closely at the middle star, Mizar, and see if you can spot its faint companion, Alcor.

Follow the arc formed by the three stars down and left to Arcturus, the bright star near the western horizon. Arcturus is at the bottom of the constellation Bootes, the herdsman, which looks like a tall, slanted house or kite extending up from the horizon.

It will be helpful to identify these stars and constellations if you use a star chart which can easily be found online or in several popular astronomy magazines. This will aid your exploration of all the cool things up in the sky.

This month in history:

Sept. 1: Pioneer 11 first spacecraft to fly past Saturn – 1979
Sept. 3: Viking 2 lands on Mars – 1976
Sept. 5: Voyager 1 launched – 1977
Sept. 8: Star Trek premiers – 1966
Sept. 12: Gemini 11 launched – 1966
Sept. 15: Lost in Space premiers – 1965
Sept. 22: Pioneer 10 leaves the solar system – 1990
Sept. 23: The Jetsons premiers – 1962
Sept. 30: Daily communication with Pioneer 11 ends – 1995

Here are this months viewing highlights:

Planets this month: Jupiter is very low in the SW evening sky. Venus close to horizon in ENE before dawn – look 45 min. before sunrise. Saturn can be found 10° to the upper right of Venus.
Sept. 4: Uranus is at opposition.
Sept. 6: Venus less than 1° from the star Regulus.
Sept. 7: Closest Full Moon (222,000 mi.)of the year.
Sept. 11-12: Binoculars show Jupiter about one moon diameter from the star Zubenelgenubi.
Sept. 14: Last-quarter Moon.
Sept. 22: New Moon.
Sept. 23: Autumnal Equinox – 12:03 a.m.
Sept. 30: First quarter Moon.

Peter Burkey – SAAA President

Whats Up in the Sky August, 2006

A Tribute to the Instruments of Space Exploration?

Do you remember the Top-40 single that was named after a satellite? I was reminded of it when I saw the Space Shuttle on the news recently. Remember when we knew the names of satellites and spacecraft because they were in the news?

The most famous satellite is probably Sputnik 1 because it was the first human-made object to orbit the earth. Other spacecraft, such as Mercury, Apollo, Voyager, and the Hubble Space Telescope are fairly well known, but lately a bevy of less familiar spacecraft have been making some amazing discoveries.

For example, the Galileo spacecraft studied the planet Jupiter and its moons for over 14 years, making many discoveries. Ulysses studied the polar regions of the sun and was the first spacecraft sent out of the plane of the earths orbit. The Mars Global Surveyor has studied the entire surface of Mars and has sent back more data about the red planet than all other previous missions combined. Mars is also currently being studied by the 2001 Mars Odyssey and the two tremendously successful Mars Exploration Rovers, Spirit and Opportunity. These two workhorses have all but confirmed the theory that ancient surface water once flowed on the planet.

Cassini-Huygens, with a record number of twelve instruments, has been studying Saturn since June 2004. Discoveries include ice geysers on one of Saturns moons, and details of the atmosphere of Titan, its largest moon, on which the Huygens probe successfully landed. Even distant Pluto will soon (2015) be visited by the New Horizons probe.

The Stardust spacecraft rendezvoused with comet Wild-2, passed through the comets coma where it collected cometary dust, and returned the sample last January, an amazing accomplishment! We’ve even landed a spacecraft (NEAR Shoemaker) on an asteroid (Eros).

The aforementioned Hubble Space Telescope has been joined by the Chandra X-ray Observatory, the Spitzer Space telescope, and the Compton Gamma Ray Observatory. Known as NASAs Great Observatories Program, the instruments are designed to cover the majority of the electromagnetic spectrum.

All of these instruments, and more, have contributed greatly to our understanding of everything from the formation of planets to the fate of the universe. We’ve learned quite a bit since Telstar.

I recently wrote about observing phenomena involving the moons of Jupiter. On the evening of Sunday, August 6, start observing Jupiter (low in the southwest) as soon as it gets dark. Three of its moons are easily visible, but a fourth one, Europa, is probably not visible because it is in front of Jupiter and lost in its glare. A little after 11:00 p.m. it emerges into view along the left-hand side of the planet (as viewed in most telescopes) just as its shadow is entering the planets disc from the lower right. Meanwhile, Io, the lone moon on the right side of the planet, moves closer and closer until it, too, crosses in front. You will need a good telescope and a clear view of the horizon to do this observation.

Here are this months viewing highlights:

Planets this month: Jupiter is still visible in the SW evening sky. Venus low in ENE before dawn, lower at end of month. Venus is joined first by Mercury, then by Saturn in the predawn sky.

August 2: First-quarter Moon.
August 2: Venus is 5.5° above Mercury – look near the eastern horizon one hour before sunrise.
August 9: Full Moon.
August 10: Mercury now only 2° below Venus.
August 12: Waning gibbous moon spoils peak of Perseid meteor shower.
August 15: Last-quarter Moon.
August 22: Use binoculars to see Mercury, Saturn, and Venus next to thin crescent moon 30 minutes before sunrise.
August 23: New Moon.
August 26: Venus and Saturn separated by about one full moon diameter.
August 31: First quarter Moon just below star Antares, low in SSW one
hour after sunset.

Peter Burkey – SAAA President

Whats Up in the Sky July, 2006

The Milky Way Galaxy

This is the season of the summer vacation. Many of us are probably planning a camping trip up north, a beach vacation, or perhaps a tour of western national parks. Whatever your destination, some moonless night you may want to take a side trip to a dark location far from the glare of city lights where you can enjoy one of the most spectacular objects in the night sky, our own galaxy, the Milky Way.

Our sun, along with about 200 billion other stars, is a member of this galaxy, a giant spinning pinwheel of stars, gas, and dust. In fact, every star we can see is a member of the Milky Way. We see the Milky Way edge-on from the inside, so it appears as a faint band of diffuse light which, at this time of year, stretches from Sagittarius and Scorpius in the south high across the eastern sky to Cassiopeia in the north.

Its name dates back to antiquity, long before its true nature was known, and is purely descriptive. In fact, the word “galaxy” comes from the Greek “gala”, which means “milk”. It is associated with many ancient legends and has been described over the centuries as a great celestial river, a path to the stars, a giant serpent, and the “backbone of the night”. It wasn’t until the winter of 1609-1610 when Galileo turned his telescope to the sky that this flowing stream of milk was resolved into stars.

The number of stars in the Galaxy is so enormous as to be beyond our comprehension but the following may help. It’s been estimated that a typical box of salt contains about a million grains, so 200,000 boxes contain as many salt grains as there are stars in the Milky Way. If you tried to model the Galaxy by spreading all those grains out over a giant circle, the average distance between grains would be 7 miles!

The Milky Way is about 100,000 light years across, which means it would take a beam of light 100,000 years to traverse its entire diameter. We are located about 30,000 light years from the center, or nucleus, where the concentration of stars is the greatest. If you look toward the constellation Sagittarius (known as the “teapot”), located near the southern horizon, you are looking directly toward the nucleus of the Galaxy. But dense clouds of gas and dust in the plane of the Galaxy obscure our view and create great dark regions seemingly devoid of stars. These dark dust lanes add beauty and structure and are themselves interesting to observe.

The region above the spout of the teapot is one of my favorite parts of the sky. Scan this area with binoculars or a small telescope and you can find many interesting objects including huge clouds of glowing gas, open clusters of stars, and very distant globular clusters. With binoculars or the naked eye, observing the Milky Way is fascinating and fun. It’s easy to imagine the wonder and awe of the ancients and Galileo as they viewed this part of what’s up in the sky.

Here are this month’s viewing highlights:
Planets this month: Saturn and Mars are fading in west at dusk. Jupiter dominates southern evening sky. Venus is brilliant morning “star” in east before dawn.
July 2: Venus is 4° north of the star Aldebaran.
July 3: First-quarter Moon.
July 9: Month’s southernmost moonset in SW before dawn.
July 10: Full Moon.
July 16-22: Use binoculars to see Mars close in on the star Regulus low in west at dusk.
July 17: Last-quarter Moon.
July 20: Crescent moon passes very close to the Pleiades, covering some stars in the cluster in the predawn sky (3-5 am).
July 25: New Moon.
July 28: Peak of Southern Delta Aquarid meteor shower before dawn.

Peter Burkey – SAAA President