Upcoming Highlights
March 9, 2000 7:30 P.M. - Reading Public Museum
Come one come all, to the BCAAS Talent Show. Be a participant and show us your stuff, or just sit back and enjoy! It should be a fun night for all.
See you there!
April 13, 2000 7:30 P.M. - Reading Planetarium
This month we meet in the Planetarium for a wonderful show entitled "Clouds of Fire". Mark promises us an exciting evening "under the stars".
Pegasus Deadline: In order to have the Pegasus, one week prior to the Thursday meeting, the deadline for receipt of submissions will be the last Sunday of the month preceding the publication date. This should make more people aware of the upcoming meeting.
Thank you, Bob Capone Editor
In this issue:
| 1.
President's Message 2. BCAAS Talentfest 3. BCAAS History 4. Club Officers |
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
Well, it looks like we all have survived the Winter’s worst. The snows have come and gone, and we can start thinking about milder weather and star watches. Our first public event will be at Nolde Forest March 10, at 7 PM. Following in April (8th) will be our Astronomy Day event at the Museum, and in May our Spring star watch at the Heritage Center on the 12th at 7:30 PM. I look forward to seeing many of you there as we share the wonders of the heavens with the public. Think clear skies!
-Barry L. Shupp, Pres.
There is still time to enter the talent program at the March meeting. A suggestion was made that not everybody’s talent is something that can be done in front of a group in a short amount of time. For instance, if your talent is craft work, you probably will not want to bring your entire woodworking shop to the Museum to make something while we watch (and heckle!). But you could bring something to the meeting that you have already made to show it off and impress us all with your skill. So, if your talent is more along these lines, please feel free to bring something you made. There will be no winners and no losers - just a time of sharing.
Just a quick reminder to any and all members, especially the founding-fathers, of the my intent to collect club memorabilia, articles, newspaper clippings, and so forth. I would welcome personal insights to the growth and development of the club over the past 26 years in order to accumulate an ongoing historical legacy of the "where we are and where we were". Please submit to Joanne Reigle-Capone either in person at the next club assembly, or by internet to BobCl957@netcarrier.com. I thank those who have offered some person information, and encourage other longtime members to take a few minutes and write done some personal memories of your own.
| President...................................... Vice President............................. Secretary...................................... Treasurer...................................... Pegasus Editor............................ Home Page Editor....................... Public Observing Coordinator..... Public Event Coordinator............. Program Coordinator................... |
Barry Shupp Ron Kunkle Dan Davidson Linda Sensenig Bob and Joanne Capone Michael Bashore Betty Perry Paul Becker Barry Shupp/ George Babel |
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 4, The Hertzsprung-Russell Diagram
In prior articles we discussed stellar brightness (magnitude) and color (surface temperature). In this article we’ll look at a population plot of absolute magnitude versus color for a large group of stars. From the Hertzsprung-Russell diagram, or H-R diagram, we shall be able to discern various types of stars and begin to make generalizations about their evolution.
The H-R diagram below, is a population plot of magnitude versus color (temperature) for a group of stars. Each dot represents a star whose absolute magnitude and color (temperature) have been determined. Inspection of the plot shows that stars do not form a continuum of magnitude and temperature. Rather they form very specific subgroups, which to a first order are indicative of their size, or more specifically their color.
The most obvious feature of the H-R plot is the diagonal band, called the Main Sequence, across the corners of the plot. 90% of all stars are M-S type stars, with the majority populating the low temperature, low brightness end of the M-S band. Extensive study by astronomers has determined that this band does not represent the evolutionary path of a single star, but rather an evolutionary stage for stars of varying mass. Low mass, low brightness stars populate the M corner and high mass, high brightness stars populate the 0 corner. In fact, astronomers now realize that everything which appears to distinguish one star from another, namely it’s magnitude, color, size, and life cycle, are all determined almost entirely by one factor, the star’s mass.
The life time of a star on the M-S is determined by the mass of the star. Lower mass star’s, those with masses less than the sun, live considerable longer times on the M-S than higher mass stars. It is also known that stars, on the M-S represent the very stable and long lived hydrogen burning phase of energy production for stars with masses varying from about 0.5 solar masses (red, M class stars) to masses in excess of 100 solar masses (white, 0 class stars). In a future article we will discuss the hydrogen burning phase of energy production for M-S stars.
Two other groupings of stars in the H-R diagram are labeled Giants and Supergiants. These groupings represent another evolutionary stages in the life cycle of some stars and in fact represent the end of the Main Sequence, M-S stage of hydrogen burning for many of the more massive stars. Giants, typically Red Giants, are cool stars but because of their large size have high brightness or absolute magnitude. Not labeled, but within the Giants are a subgroup of variable stars called Cepheid variables. Cepheid vanabfes; as will be discussed in an later article since they are very useful for measuring stellar and galactic distances. The group labeled Supergiants is also cool stars, and because of their extremely large size have even higher brightness. The grouping labeled White Dwarfs represents the final stages of stellar evolution for solar mass stars. Although they are extremely hot, because of their extremely small size, they have low brightness. What is not shown on the H-R diagram is the final stage of stellar evolution for the stars more massive than the sun. High mass stars, greater than 10 solar masses, after evolving off the M-S become Neutron stars and stars more massive than 30 solar masses evolve into Black Holes. Since neither of these end state objects emit much visible light, principally because of their ultra small size, they cannot be classified by the method of brightness and temperature shown on the H-R diagram. We will discuss these stages of stellar evolution in subsequent articles.
The next article is this series will discuss the formation of a Main Sequence star from a cloud of dust and gas into a star. We will learn what technically determines when a star becomes a star.
MYTHOLOGY OF THE NIGHT SKY - GEMINI
Double your pleasure, double your fun. On a cold, clear night you can look up at the stars and see not one hero, but TWO! The idea that this part of the sky contained twins has been universal from remote antiquity, but the Latin title of Gemini dates only back to classical time. While on earth, prior to their being transferred to the sky by Jupiter in reward for their brotherly love , Castor and Pollux were sons of the goddess Leda . This is attested to by Dante, who wrote of their location as "the Nest of Leda". Cowley, a contemporary of Milton called them the Ledaean Stars.
In India they were known as the Horsemen, a name also found in other parts of the sky for other Hindu twin deities. The Buddhist zodiac (BUDDHIST zodiac!?) had in their place a woman holding a golden cord. Most Jews called the stars Simeon and Levi (2 brothers of Jacob that went on to become two of the 12 tribes). Other Judeo-Christian scholars called the constellation the Twin Sons of Rebecca (Jacob and Esau, two famous Biblical twins which makes more sense than using Simeon and Levi who were two brother that were NOT twins). The Arabians also saw twins in that part of the sky. And the Persians also called this constellation the Twins - only in Persian.
There are numerous symbols used in classical times to represent Gemini. The ancient Romans pictured the stars as a pile of bricks! So, were the twins, perchance, masons? Actually, the bricks refer to the building of the first city and the brothers Romulus and Remus. So this constellation was very significant to the Romans. In fact, they believed Jupiter appointed Gemini to be the guardians of Rome. The sailors of Rome also saw the Twins as protectors, which can be verified by a passage in the Bible! Acts 28:11 - Paul is sailing on a Roman ship, and it reads: After three months we departed in a ship of Alexandria which had wintered in the isle, whose sign was Castor and Pollux.
GALILEO MISSION LIVES ON
On February 22nd, the Galileo spacecraft made its third and closest flyby of Jupiter’s volcanically active moon Ia. At 14:32 Universal Time (9:32 a.m. EST), the spacecraft passed only 199 kilometers above Io’s surface. Images and data will be transmitted and analyzed over the coming weeks.
Although battered by Jupiter’s strong radiation, Galileo continues to provide useful imagery and other data. While it isn’t completely official, the Galileo spacecraft is now operating under its second mission extension. The first extension, called the Galileo Europa Mission, ostensibly ended on January 31st, following a flyby of Europa on January 3rd. As long as Galileo works, researchers hope to continue using it. Its future schedule includes another lo flyby on February 20th, flybys of Ganymede on May 20th and December 28th, and joint observations of Jupiter with the Cassini spacecraft at the end of the year.
NEW QUASAR DISTANCE RECORD
Astronomers have found a new record holder for most distant quasar. Daniel Stern (Jet Propulsion Laboratory) and his colleagues uncovered the object using the 5-meter Hale Telescope atop Palomar Mountain and the 4-meter Mayall Telescope at Kitt Peak. The quasar’s spectrum was subsequently obtained at Hawaii’s Keck Observatory. The calculated redshift of 5.5 means that the recessional velocity of the quasar is stretching the wavelengths of light 6.5 times, implying that the light was emitted when the universe was perhaps about a billion years old. The researchers’ results will appear in an upcoming issue of Astrophysical Journal Letters. Although this is the most-distant quasar known so far, it is not the absolute distance record holder. To date, that honor is held by a galaxy with a redshift of 6.68.
YUKON METEORITE BEING TESTED
According to the Anchorage Daily News a piece of the fireball that exploded over western Canada has been recovered and is undergoing tests at NASA’s Johnson Space Center. A 6 ounce chunk was found on a snow-covered lake. The interplanetary debris slammed into Earth’s atmosphere on January 18th exploding 25 kilometers in the air just south of Whitehorse, Yukon Territory.
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