Upcoming Highlights
May 11, 2000 7:30P.M.- Reading Public Museum
Inge Heyer of the Space Telescope Science Institute will present a combined program on Extra- Solar Planets, and an update on the Hubble Space Telescope. The program will run approximately 90 minutes in the Planetarium.
June 8, 2000 7:30P.M.- Reading Public Museum
This month we will break into 3-4 small groups to discuss a variety of topics. Each group will have a leader with some expertise in the subject. Topics to be announced later.
Presidents message:
As we welcome the warming breezes of Spring, we are already well into our public starwatch season with Astronomy Day, and several smaller starwatches already completed ( Thanks to all who helped! ), and with this month's Heritage Center Starwatch rapidly approaching on May 12 . We already have starwatches scheduled for campers at French Creek State Park in July and August, and the Hawk Mt. starwatch will probably be in late July. The Muhlenberg Middle School starwatch will be Friday August 4 at Stoudt's Ferry. I hope to see many of you at these events. On another matter, I overlooked including Dave Brown in last issue's list of club special officers. Dave is BCAAS' Public Relations Coordinator as well as the Observing Chairman for club starwatches. Sorry for the omission, and many Thanks! Dave for all your efforts. I look forward to an exciting and enjoyable Spring and Summer of observing!
IN MEMORIUM
I regret to inform you of the passing of our member Phil Klein near the end of March. Phil lived at The Highlands and while he did not attend our meetings, he renewed his membership faithfully every year, enjoying being a part of our club. Our thoughts and prayers are with the family.
In this issue:
| 1.
Upcoming Highlights 2. Video Astronomy 3. Telescope Review Website 4. Buzz Aldrin Preemts BCAAS |
6. A Layman’s Guide to Stellar
Evolution |
Pegasus is a bimonthly publication of the Berks County Amateur Astronomical Society
Editor/Desktop publisher: Bob and Joanne Capone
E-Mail submissions may be made to: BobC1957@netcarrier.com
VIDEO ASTRONOMY COURSE AVAILABLE
Would you like to know more about the universe? You can go to school in the comfort of your own livingroom with the video course: "Understanding The Universe - An Introduction to Astronomy". Put out by The Teaching Company, this is a very comprehensive course consisting of 40 lectures of 45 minutes in length. The teacher is Professor Alex Filippenko of the University of California at Berkeley. In December 1998, "Science" magazine credited Professor Filippenko and his internation-al team of astronomers with the "Science Breakthrough of 1998" for research on supernovae, showing that the universe is expanding at an accelerating rate. You do not need to have extensive knowledge of physics or math. If you are interested, the cost of this course, including shipping and handling, is about $500. However - if you order before June 1, you SAVE $300!!! It will only cost about $200. You can order toll-free by calling 1-800-832-2412. If you want more information before you decide, I have the brochure that lists what all 40 lectures are about. I did not take this course, however I have just completed another course with The Teaching Company that was fantastic!
I have found one of the most comprehensive telescope review websites. It contains detailed review of 69 telescopes, eyepiece review, beginner’s advice column, and many more interesting items. If you are interested, go to: www.scopereviews.com.
You might have noticed that at the April meeting two officers were conspicuously missing-at least we hope we were missed! What could have been happening that was more important than a BCAAS meeting? Buzz Aldrin! Second man to walk on the moon! In READING!
Linda was lucky enough to get to the dinner for FREE - of course, the dinner was put on by the Caron Foundation and she happens to work there. Still, most other employees had to pay for their meal. One of the women from the New York office had purchased a table of eight then found out that she couldn't make it, so she opened those eight seats to any employee who wanted to go. A random drawing was held and Linda won!
Dan had no such luck and had to purchase his meal. The funds go to a very worthy cause and getting the chance to meet Dr. Aldrin doesn't hurt either. After seeing a short video on the famous flight of Apollo 11, Buzz Aldrin was introduced. Now you have to understand something about the Caron Foundation annual fund raising dinner - they always invite somebody REALLY famous, but the subject of the talk always revolves around chemical addiction because that is what the Foundation is all about. So, Dr. Aldrin spoke a little about our space program, but mostly talked about what happened to him after he left NASA. After a lifetime of always working and striving to be the very best with the eventual culmination of being the second man to walk on the moon, Buzz slipped into a deep depression leading to alcoholism. He explained that after leading such a structured and regimented life, always working toward the next goal and then coming to the realization of "what's next" after the moon landing left him for the first time in his life lost. Dr. Aldrin testified to the great help of institutions like the Caron Foundation that helped him put his life back on track. He now owns his own company designing boosters to be used in future planetary exploration and travels the country touting the need for a strong space program.
The REALLY exciting part didn't happen till after the dinner was over! We headed toward the stage hoping to get just one quick, close look at Buzz - and discovered that people were lining up to go onstage and meet him. Linda and Dan were able to get his picture, his autograph, a handshake and were even able to ask him a few questions. The experience of being able to meet living history will forever remain one of the most exciting and memorable events of our lifetime.
Linda Sensenig and Dan Davidson
A Layman’s Guide to Stellar Evolution
This article is part of a series dealing with stellar evolution. The articles are written by a layman to convey that understanding to others. To that extent, errors and omissions should be excused. The series will cover the formation of stars, their energy production, assemblages, and their deaths. For comments, please contact the author.
Article 5, Formation of Main Sequence Stars
In the prior article we discovered that the most prominent feature of the Hertzsprung-Russell diagram was the band of stars diagonally across the corners of the plot, called the Main Sequence. The M-S band represents stars in the long lived and stable hydrogen burning phase of their life cycle. In this article we will describe how a M-S star forms.
Stars are formed by gravitational attraction of dust and gases from large clouds of interstellar material. The materials in these clouds, often called molecular clouds, are primarily hydrogen and helium but are sprinkled with many of the heavier elements from prior stars. As a cloud of gas and dust contracts under the force of gravity, the materials in the cloud heat up by fiction (refer to the diagram, initial gravitation collapse)and begin to emit some light Since the collapsing cloud typically has some spin associated with it, a flattened disk with a bulge forms in the center. The central bulge continues to collapse under its own gravity and continues to heat up. This central object is typically referred to as a protostar. During this phase of formation, heat (in the form of red and infrared light) and materials are being emitted by the protostar. The source of this energy is frictional heating, driven by the gravitational collapse. At some point, the temperature in the core of the collapsing protostar, becomes hot enough, e.g. 10 million degrees, such that a new energy process, nuclear fusion, start producing energy. The onset of fusion reactions heralds the birth of the star and its arrival onto the Main-Sequence (refer to short horizontal line on H-R diagram.) Prior to the onset of fusion, all energy production and emission by the protstar, was due to the fictional heating associated with the gravitational collapse. While in the Main-Sequence, the source of energy is nuclear fusion. A stars position along the Main-Sequence is determined by the amount of mass that has collapsed to form the star. The example sketched is for a star similar in mass to our sun. The collapse phase of a solar mass star occurs relatively rapidly, on the order of a 10’s millions of years. For larger mass stars, greater than 10 solar masses, the collapse phase is even more rapid, a few 100,000 years.
The Main-Sequence stage represents the longest lived stage of a star and it is the period of time during which the star produces its energy by the fusion of Hydrogen into Helium. The fusion reaction process will be explained in more detail in future article. Suffice it to say that this phase of the stars life cycle is typically very long lived and very stable. A star of the mass of our sun will typically exist for about 10 billion years on the Main-Sequence. During this time is will move very lithe in the H-R diagram, e.g. an indication of it’s stability. It will slowly move vertically across the thickness of the Main-Sequence band, slowing producing slightly more energy as the core slowly shrinks and heats up as it uses up it’s Hydrogen supply. 90% of all observed stars are Main-Sequence stars, simply because the typical star spends about 90% of it’s life in this phase of it’s evolution.
If the amount of mass collapsed during the formation of the star is less than one solar mass, it’s position on the Main-Sequence will be to the lower right of the sun’s position on the Main-Sequence. These stars spend a considerably longer time on Main-Sequence on the order of 100’s of billions years. These stars are called Red Dwarfs (not labeled on the H-R diagram) and are the most common type of star formed, as evidenced by their large numbers at this end of the Main-Sequence. Stars of this low mass have not existed long enough since the universe was formed to have used up their Hydrogen fuel and thus they have not yet evolved off the Main-Sequence.
Not all protostars make it to the Main-Sequence. Some do not have enough mass and thus do not get hot enough in their cores to begin the Hydrogen fusing process. Such failed stars are referred to as Brown Dwarfs. The energy output of these failed stars, e.g. energy produced by the frictional heating associated with the gravitation collapse, diminishes rapidly and the star cools and becomes essentially undetectable. The Brown Dwarf class of stars is not shown on the H-R diagram, but would be the newly designated class L if included. Typically stars with mass less than 0.08 solar mass will become Brown Dwarfs, e.g. failed stars. Ironically, Brown Dwarfs may be the most common type of star in the galaxy, although they have been impossible to detect except when located within about 20 light years of the sun.
Higher mass stars are located above and to the left of the sun on the Main-Sequence. As we progress up the Main-Sequence, the stars increase in mass and each spends a shorter and shorter periods of time on the Main-Sequence because each uses up it’s Hydrogen fuel at faster and faster rates. A 10 solar mass star may exist a few 10’s of millions of years on the Main-Sequence. A 30 solar mass star may exist only a million years on the Main-Sequence before using up it’s supply of Hydrogen and then progressing to the next phase of stellar evolution. While these massive stars are on the Main-Sequence they exhibit a brightness many thousands of times more than the sun, indicative of their very high rates of energy production.
In the next article we shall discuss in more detail the process of Hydrogen fusion, and discover why the lifetime of a star on the Main-Sequence is so strongly dependent upon it’s mass.
MYTHOLOGY OF THE NIGHT SKY -
SERPENS AND OPHIUCHUS (REVISITED)
There sure are a lot of squiggly creatures in the night sky! Cetus, Drago, Hydra, and Serpens. Serpens is exactly what its name implies - a snake! While it is listed as a separate constellation, in western mythology it is always connected with Ophiuchus. In fact, the two constellations adjoin and if you were to creatively DRAW your star chart as they did before star charts just became nothing more than boring dots, you would draw Ophiuchus holding the Serpent in his on hand.
There is a real interesting story connected with Ophiuchus and while I already wrote about this constellation in September of 1996, some of you were not members at that time, so you don’t know the story. Ophiuchus was identified with Aesculapius who was a medicine man who afterwards was made a god. (We have a number of doctors who are members of BCAAS, so this constellation is for you!) The worship of Aesculapius was always associated with the use of snakes as symbols of the power of discovering healing herbs. Aesculapius was the earliest of his profession; he was supposed to have been raised either by Apollo or by the Centaur Chiron. He was the ship’s surgeon on the famous voyage of the Argos. He became very famous for his abilities to heal. In fact he became so good at his profession that it was said that he could even bring the dead to life again.
While this made him very beloved by all the many people he healed and/or brought back to life, it made for him a very dangerous enemy in Pluto, god of the underworld, who was not too happy about this doctor snatching dead people out of his kingdom! So he induced Jupiter to strike Aesculapius with a thunderbolt and put him among the constellations.
One of our members, Timothy Siminski took this great shot of the North American nebula. He submitted it to Sky and Telescope to be shone in the photo gallery. this was the response he received
Tim, Nice shot of the North America nebula and surrounding starfield — we’ll consider it for a future Gallery.
Regards,
Dennis di Cicco
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