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RASC St. John's Centre Monthly Meeting
November 17, 2004
Location: Chemistry/Physics Building, MUN
Time: 8:00 pm
Chris welcomed everyone and gave a brief overview of the society. It is
important to note that free parking is available from 7-11 at area 5 behind
the building. Calendars are now on sale for $15. We also have some odds and
ends left over from the GA, such as pins.
John is a graduate student of Dr. John Lewis. Here is a brief summary of the
topics of the talk:
- Open (Galactic) Clusters.
- Consist of Population I stars.
- Usually 1-20 parsecs in radius.
- Globular Clusters
- Usually 100,000 to 1,000,000's of stars. Many more than an open cluster.
- Age about the same as the universe.
- 5-15 parsecs.
- Globular clusters are a sort of laboratory for stellar evolution, and the age of the universe.
- What is spectral analysis?
- Stars emit blackbody radiation.
- Absorption lines.
- Spectral types.
- Distance Measurement.
- Parallax or "Standard Candles".
- RR Lyrae variable stars.
- Sub-dwarfs (but very faint). Some recent work indicates their distance scale could be as much as 10% off.
- Hertzsprung-Russell (HR) Diagram.
- Car analogy. (Fast, slow, compact, sports car, etc.)
- 90% are on the main sequence burning Hydrogen to Helium.
- HR diagram of a Globular Cluster.
- Characteristics of a Globular.
- Share age, distance, and chemistry.
- Mass is really the one variable.
- So, we can have a better experimental comparison with our models of stellar evolution.
- Three formation models: before, during, or after host galaxy. Was the cluster pre-enriched or self-enriched with metals?
- Dynamics: The King Model.
- How to model a Globular.
- Some problems:
- Eventual equipartition of the energy of the ensemble of particles.
- Core collapse.
- Tidal forces (from host galaxy) ignored.
- Some improvements on the King Model.
- Age of the Universe.
- Over the last 10 years we believe we have a much better handle on the age of the universe. No longer do we have the embarrassment of the age of some globulars exceeding the predicted age of the universe.
- Globular Cluster age determination.
- Age of M4 cluster (about 12-13 billion years).
- Chris: Sun. Aurora.
- Randy: Aurora.
- Florence: Green Aurora from vehicle on Foxtrap Highway.
- The lunar eclipse was clouded out. This was Garry Dymond's fault.
Planets are mostly morning objects except Saturn (and Uranus/Neptune). Leonids
are this week. Geminids on December 15. Occultation on December 7. A possible
good comet may be C/2004 Q2 (Machholz) later on.
Randy noted a good deal on the Celestron Nexstar 80GTL can be had at Costco.
These go for $285 at Costco, but "non-L" version typically goes for $449 or
more on the mainland. For a slightly better scope, you are saving over $150.
There are also Bushnell 10x40's. If you are interested in binoculars the
Birdshop has offerings as well.
Gary went to the Geocentre and Chapters. The Geocentre has a number of
astronomical gifts, mainly for the younger set. Chapters has some of the best
range he has seen in a long while. Gary has a detailed list which he passed
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