Pegasus

Volume XXVIII Issue 6


November / December 2002


In this issue:

1. Presidents message
2. Did You Know?
3. Upcoming Events
4. Mythology of the Night Sky - Aries
5. Treasurer's Corner - Astronomy Wall Calendar
6. Treasurer's Corner - In Memorium
7. A Brief Sound Bite from the History of Astronomy
8. My Travels throuhg 30 Years of the Space Program
9. Star Orbiting Massive MilkyWay Center
10. The Structure of the Milkyway Galaxy

President’s message

Hello fellow BCAASers,

We’re finally getting into some crisper, clearer skies for our observing sessions. Don’t miss the opportunity to get out and observe some of fall’s sky splendors such as Saturn, the Orion Nebulae, and the Pleiades. While October’s meteor shower was washed out by the Moon, November’s Leonids are predicted to be a storm despite the Moon’s presence. Perhaps we can arrange a club activity for the shower. The peak for us will be around 5:30 AM on the nineteenth. Let’s hope for clear skies!!

Well it’s hard for me to believe, but this will be my final president’s message. After serving for three years, I have decided not to run for another term. It’s time to get some new, and different ideas into the mix, and I will open the way for vice president Ron to take the reins of the club. I have thoroughly enjoyed serving as your president. You are a great group of people to work with. I hope to continue to influence the club in other ways by helping with selection of the programs, and writing for the club newsletter.

I feel we’ve accomplished much over the last three years strengthening the club by putting good people in key positions such as Program coordinator, and Pegasus editor.

Kathy Matisko, and now, Barb Geigle are excellent Secretaries, and Linda Sensenig has always done a great job as Treasurer. Ron Kunkel has done a superb job as Vice President helping me when my schedule required me to miss an occasional meeting, but especially at club, and some public starwatches that I could not attend. Thanks to all officers, and committee chairpersons who have been of great assistance to me, and without whom I could not have done the job.

We’ve had many good programs with speakers Inge Heyer (STScI), Dr. Jacob Trombka (Goddard -NASA), and Dr. Dana Backman (F&M College) as well as talks by local speakers Pete Detterline, and Gary Becker, and our own Ron Kunkel (Virtual Messier Marathon). Thanks to Ryan for an excellent job. I think that we had several good public starwatches despite some being rained or clouded out, and I would like to thank Melody Gardner for scheduling sometimes conflicting requests for programs.

I look forward to working with all of you in the new year, as we continue to progress as a club, enjoying the night skies together, and presenting astronomy to the public.

Barry L. Shupp, Pres. BCAAS


Did You Know?

Isaac Newton dropped out of school when he was a teenager, at his mother's request.

She hoped he would become a successful farmer.

I hope she forgave him for sleeping under the apple trees when he should have been working!

Sorry, Mom!


Pegasus is a bimonthly publication of the Berks County Amateur Astronomical Society

Editor/Desktop publisher: Melody Gardner

E-Mail submissions may be made to: dblhlx@rcn.com


Upcoming BCAAS Events

Friday, November 1st @ dusk: Club starparty at the Flying Field (r.d. Nov. 2nd)

Sunday, November 3rd: LVAAS 45th Anniversary Banquet, Allentown

Saturday, November 9th @ dusk: Starparty for Cub Scouts at Daniel Boone Homestead

Thursday, November 14th @ 7:30pm: BCAAS general meeting, presentation "Astronomy in Hawaii" by Ryan Hannahoe

Monday, November 18th – Wednesday, November 20th: Leonid Meteor Shower — potential meteor STORM on the 19th!!!

Thursday, November 28th: Happy Turkey Day!!

Thursday, December 12th @ 7:30pm: General Meeting—Elections and PARTY!!!!
Please bring a dish to share and all your Holiday Spirit!!!

Thursday, Dec. 12th—Saturday, Dec. 14th: Geminid Meteor Shower

Friday, Dec. 20th—Saturday, Dec. 21st: Ursid Meteor Shower

Saturday, Dec. 21st: Winter Solstice

Wednesday, December 25th: Merry Christmas!!!

(Watch out for the mistletoe at the Christmas party!)

Wednesday, December 31st: Happy New Year!!


Mythology of the night sky—Aries

It’s a very dim part of the night sky. Of course, from where I live, every part of the night sky is dim. However, I suspect this part of the sky to be dim even at star watch locations because the book actually gives it’s PRECISE location as west of the Pleiades, 6 degrees north of the ecliptic, 20 degrees north of the celestial equator and 20 degrees due south from Gamma Andromedae. (Just give it’s right ascension and declination, please, and you could probably find it even from my house!)

The Greeks used this faint area of the night sky to commemorate a tragic event. Phrixus, the hero-son of Athamas, was fleeing on the back of a Ram with his sister, Helle (no, I didn’t forget the "n"), to escape the wrath of their wicked stepmother. On the way, Helle fell off the Ram into the sea, which henceforth was known as the Hellespont. When Phrixus reached his destination, he sacrificed the Ram and hung its fleece in the Grove of Ares where it turned to gold. Yep! The famous golden fleece which connects this legend to the legendary voyage of Jason and the Argonauts.

One would think the name of this constellation would have been Phrixus since he is, after all, a hero. And if you were an ancient Greek, you would be right. But we take our name of this constellation from the Romans, who for some dumb reason decided to name it after the Ram, Aries, who becomes more important in legend AFTER he was dead.

Linda Sensenig, Treasurer


Treasurer’s Corner

ASTRONOMY WALL CALENDAR.

If you ordered Astronomy calendars, they should be at the November meeting. If you missed the boat, it’s still not too late. Even small orders you save significantly. Instead of a 50% discount, you get a 45% discount.

Linda Sensenig, Treasurer

IN MEMORIUM

ADELAIDE CAPONE

It was only about six months ago that we lost our long time member Tony Capone. Sadly, we have now lost is wife, Adelaide. I didn’t know her as well as I knew Tony, however she accompanied him to our meetings and it was evident how much they loved each other. She was the quiet one, content to be the one behind the scene providing love and support for her husband, secure in knowing how very much he loved and supported her.

It is a devastating experience to lose a parent, however Bob and his brother and sisters lost both of their parents within a short period of time. They all need our love and our prayers.


It is with great sorrow that I announce that Bill Eyrich's son has died. So far the cause is unknown but it came very suddenly. We would like to express sympathy for the Bill Eyrich Family.

Linda Sensenig, Treasurer


 

A BRIEF SOUND-BITE FROM THE HISTORY OF ASTRONOMY

The theory that matter is made up of small particles called atoms is very old. Greeks speculated on it hundreds of years before Christ. The man who finally set the theory of atoms on a scientific footing was born September 6, 1766. John Dalton was fortunate that his parents were Quakers. Members of this Christian sect insisted that their children be taught to read at a time when only one British child in 215 knew how. From childhood, John worked hard to eke out a living. At 12, he ran a school but had a hard time controlling the bullies bigger than himself. What set him on the path to his atomic discoveries was his interest in weather. Trying to explain heat, dew points, atmospheric pressure and evaporation, he studied gas mixtures and combinations of elements. Although atoms are too tiny to see, he recognized that their weights could be compared to one another because, being individual units, they combine as whole units. This was a revolutionary finding and led directly to the periodic table, putting chemistry on a scientific basis. John was a regular Quaker who faithfully attended religious services twice each Sunday and often served as a representative in Quaker councils.

(from the on- line newsletter of Christian History Institute, September 6, 2002).


My Travels Through 30 Years of the Space Program

In the early 70s, as minor character in the Apollo Program, I worked in the Vehicle Assembly Building at KSC. Stepping into the VAB, I felt like the incredible shrinking woman. The space inside accommodated six 45-story office towers with vast open spaces to spare. In the vertical spaces between the office towers, the 363-foot high Saturn Vs were assembled.

From my third floor office in one tower, I often delivered documents to higher flo ors in other towers. Between riding the stomach-dropping glass elevators and dashing across to other towers on narrow, open catwalks at the 28th or 44th floor levels, I soon overcame my fear of heights.

On these excursions, I would see the Saturn Vs come together in the 500-foot high bays. After hundreds of engineers and technicians had toiled around the clock for months, the morning of high-bay rollout would arrive. Slowly, the Crawler Transporter would bear forth the Mobile Launch Platform and the majestic Saturn V rocket. The morning sun reflecting off its gle aming white form would take my breath away.

The last Apollo mission was 30 years ago. As the Apollo program ended, some thought human missions to the Moon, Mars, and beyond would continue apace. Though they didn't continue, the Apollo program remains a single, large step in our technological evolution as a species. It is a great tribute to the intelligence, ingenuity, and dedication of the people responsible for the Apollo missions that they were so successful and the disasters so few. NASA's program today continues to build on the technological and managerial legacy bequeathed us by Apollo.

And just where are we now? Among its other tasks, the International Space Station is teaching people to live in space for long periods. Robotic space missions are studying issues like land use and global warming and discovering the wonders of the universe, its history, and our place in it. With humanity's many other pressing needs, such quests must be done efficiently.

Part of NASA's mission is to develop the technologies to do cost-effectively what has never been done before at all. NASA's New Millennium Program develops and validates new technologies for space. Missions such as Deep Space 1 and Earth Observing 1 carry and test multiple new technologies (such as ion propulsion and advanced imaging instruments) previously untried in space. And, unlike the Saturn V, the ultimate gas-guzzling muscle car of the 70s, the new technologies must be the "zero emission" vehicles of the 21st century-small, efficient, and capable beyond anything done before.

Many of the New Millennium technologies are described for adults at nmp.nasa.gov and for children at The Space Place, spaceplace.nasa.gov.

Diane K. Fisher is the developer and writer for The Space Place web site.


A Late Breaking Astronomical Development

Star Orbiting Massive Milky Way Center Approaches to within 17 Light-Hours

An international team of astronomers has directly observed at the infrared wavelengths an otherwise normal star orbiting the super massive black hole at the center of the Milky Way Galaxy. Ten years of painstaking measurements have been crowned by a series of unique images obtained by the Adaptive Optics instrument on the 8.2-m VLT YEPUN telescope at the ESO Paranal Observatory. It turns out that earlier this year the star approached the central Black Hole to within 17 light-hours - only three times the distance between the Sun and planet Pluto - while traveling at no less than 5000 km/sec.

Previous measurements of the velocities of stars near the center of the Milky Way and variable X-ray emission from this area have provided the strongest evidence so far of the existence of a central Black Hole in our home galaxy and, implicitly, that the dark mass concentrations seen in many nuclei of other galaxies probably are also super massive black holes. However, it has not yet been possible to exclude several alternative configurations.

In a break-through paper appearing in the research journal Nature on October 17th, 2002, the present team reports their exciting results, including high-resolution images that allow tracing two-thirds of the orbit of a star designated "S2". It is currently the closest observable star to the compact radio source and massive black hole candidate "SgrA*" ("Sagittarius A") at the very center of the Milky Way. The orbital period of the star around the black hole is just over 15 years.

The new measurements exclude with high confidence that the central dark mass consists of a cluster of unusual stars or elementary particles, and leave little doubt of the presence of a super massive black hole at the center of the galaxy in which we live.

The center of our Milky Way galaxy is located in the southern constellation Sagittarius and is "only" 26,000 light-years away. On high resolution images, it is possible to discern thousands of individual stars within the central, one light-year wide region (this corresponds to about one-quarter of the distance to "Proxima Centauri", the star nearest to the solar system). Over the last decade, using the motions of these stars to probe the gravitational field, various observatories had shown that a mass of about 3 million times that of the Sun is concentrated within a radius of only 10 light-days of the compact radio and X-ray source SgrA* at the center of the star cluster.

This means that SgrA* is the most likely counterpart of the putative black hole and, at the same time, it makes the Galactic Center the best piece of evidence for the existence of such super massive black holes. However, those earlier investigations could not exclude several other, non-black hole configurations.

Combining prior VLT infrared images with high-resolution radio data, the team was able to determine - during a ten-year period - very accurate positions of about one thousand stars in the central area with respect to the compact radio source SgrA*. When they included the latest VLT data in the analysis in May 2002, they could not believe their eyes. The star S2, which is the one currently closest to SgrA*, had just performed a rapid swing-by near the radio source. They suddenly realized that they were actually witnessing the motion of a star in orbit around the central black hole, taking it incredibly close to that mysterious object".

No event like this one has ever been recorded. These unique data show unambiguously that S2 is moving along an elliptical orbit around SgrA* . The superb data also allow a precise determination of the orbital parameters (shape, size, etc.). It turns out that S2 reached its closest distance to SgrA* in the spring of 2002, at which moment it was only 17 light-hours away from the radio source, or just 3 times the Sun-Pluto distance. It was then moving at more than 5000 km/s, or nearly two hundred times the speed of the Earth in its orbit around the Sun. The orbital period is 15.2 years. The orbit is rather elongated - the eccentricity is 0.87 - indicating that S2 is about 10 light-days away from the central mass at the most distant orbital point.

Astronomer are now able to demonstrate with certainty that SgrA* is indeed the location of the central dark mass. Even more important, the new data have "shrunk" by a factor of several thousand the volume within which those several million solar masses are contained". In fact, model calculations now indicate that the best estimate of the mass of the Black Hole at the center of the Milky Way is 2.6 0.2 million times the mass of the Sun. The "event horizon" radius for a 2.6 0.2 million solar masses black hole (as the one at the center of the Milky Way galaxy) is about 7.7 million km (26 light-seconds).

S2 is an otherwise "normal" star, but some 15 times more massive and 7 times larger than the Sun. Its orbit around the Black Hole is comparatively stable. Even though it moves relatively close to the Black Hole in the present orbit, S2 would have to be at least 70 times closer (about 16 light-minutes from the Black Hole) before it would risk being disrupted by tidal forces.

Submitted by Ron Kunkel,

Reference: Surfing a Black Hole (ESO Press Release 17/02)
Date: Wed, 16 Oct 2002 22:00:07 +0200
From: esonews-html@eso.org


The Structure of the Milkyway Galaxy submitted by R I Kunkel

The island of stars in which we live is called the Milkyway Galaxy . It was not until about 1924 that Edwin Hubble deduced that we lived in an island of stars, later to be called a galaxy, and that many, many other such islands of stars exist in the universe. Prior to Hubble it was believed that we lived in a universe consisting of stars distributed more or less uniformly ad infinitum with an occasional "nebulae".

Thanks to Hubble’s insight, many of these "nebulae" are now recognized as galaxies, and that our star, the sun, resides in one of these "nebulae". Galaxies come in three types of structures, spiral, elliptical, or irregular. Our Milkyway Galaxy is a spiral galaxy. Spiral galaxies typically reside in the more isolated reaches of space, e.g. they do not reside in what are called galactic clusters, large groupings of galaxies in a relatively small region of space. Galactic clusters are typically the home of the elliptical type of galaxy. And the irregular galaxies, so called because their structure is neither of the more organized spiral or elliptical structures, reside in both galactic clusters and in the isolated reaches of space.

The Milkyway Galaxy is a spiral galaxy, actually a grand spiral galaxy containing an estimated 300 billion stars. As spiral galaxies go the Milkyway is atypically large. It so happens, that the nearest "large" neighboring galaxy to the Milkyway, the Andromeda galaxy, is also a grand spiral galaxy and it is actually nearly twice as large as the Milkyway. There are other galaxies closer to the Milkway than Andromeda, but these are all very small irregular galaxies, containing only few 100,000’s of stars. The Large and Small Magellanic Clouds, and various dwarf spheroidal galaxies are technically our closest neighboring galaxies.

The structure of a spiral galaxy consists of six major components, disk, core, black hole, halo stars, globular clusters, and dark matter halo. The most obvious component of a spiral is the DISK which contains the spiral arms which identifies this type of galaxy. The disk of the Milkyway is about 100,000 light years (l.y.) across, but only about 2000 l.y. thick. Our sun resides in this disk of stars, about two-thirds of the way from the center, or about 28,000 l.y. from the center. The stars in the disk or organized into arms which appear to wind around the center of the galaxy. The disk of the galaxy typically contains younger stars and it also contains much gas and dust. This is the material continually forming stars thus the reason why most younger stars reside in the disk. Stellar densities in the disk are typically a few light years between starts.

After the disk, the next most obvious component of the galaxy would be the galactic bulge or CORE. Until the last decade, the core of the Milkyway galaxy was thought to be a spherical distribution of stars. Recently it has been determined that our core is really elongated, being about twice as long in one direction as the other. This structure is called a bar, and technically makes our galaxy a barred spiral. The bar in our galaxy appears to be of relatively recent origin, having come into existence in the last 3 to 6 billion years, while the overall age of our galaxy is estimated to be 12 – 15 billion years. The stars that reside in the core are generally aged "reddish" stars, and there is very little gas and dust for forming new stars in this region of the galaxy. Stellar densities in the core are much higher than in the disk and stars are typically only about one-quarter light year apart on average. Numerous stellar mass black holes from aged stars reside in the core. The core of the Milkyway galaxy is not visible to the eye due to the fact that our sun is in the disk and the dust and gas in the disk prevents visible light from the core from reaching us. The core and opposite side of the disk are observable via radio waves and Infrared telescopes.

Inside the barred core of the Milkyway galaxy is a BLACK HOLE, specifically a galactic size black hole. Galactic size black holes differ from the more familiar and more common stellar back holes simply by their mass size. Galactic black holes are now believed to reside inside nearly all galactic cores. The size of these galactic black holes varies from galaxy to galaxy, but recently a very consistent relationship has been discovered about the mass of these black holes – the mass of the black hole is 0.5% of the mass of the core of stars that surrounds it. For the Milkyway our black hole has been determined to have a mass of about 3 million suns. The black hole in the Milkyway is not an active black hole in that it is not actively swallowing much material. The size of our black hole relative to the size of the galaxy is really an infinitesimally small spot. It is estimated to be about only about the size of our solar system, e.g. 9 light hours, versus 100,000 light years, but it contains about 3 million times the mass of our solar system in this tiny region of space.

Beyond the disk and the core with it’s resident black hole is a large SPHERICAL HALO of stars that surrounds both the disk and core. Stars are very sparsely distributed in this spherical halo. Stellar distances are measured in 10’s to 100’s of light years between halo stars. Also in this spherical halo of stars resides the fifth component of the Milkyway, GLOBULAR CLUSTERS. Globular cluster are dense balls of stars, gravitation bound into a very dense cluster of stars which then orbit the Milkyway as an singular object. Globular clusters typically have between 100,000 and 1,000,000 stars. About 150 globular clusters have been identified orbiting the galaxy. It was the distribution of globular clusters around our sun that enable Hubble to conclude that our sun resided in an island of stars and that we were offset from the center.

The remaining sixth and last component of the Milkyway galaxy is its DARK MATTER HALO. The other five components of the galaxy were all light producing objects. From the motion of these visible parts of the galaxy, it is apparent that there is much more mass in the galaxy than what is visible and that this mass exists in a vast spherical halo that stretches halfway to the neighboring Andromeda galaxy. Astronomers do not know what makes up the bulk of the mass of this dark matter halo, but they know it’s there due to its gravitational effects on the visible components of the galaxy. Minor percentages of the dark matter halo have been identified to be faint white dwarf stars, stellar mass black holes, and large clouds of nearly undetectable hydrogen gas. But the nature of the bulk of the dark matter halo is unknown.

In summary. We live in an island of stars called the Milkyway Galaxy. It is a grand spiral galaxy, a barred spiral, and its major components are the disk, core, black hole, halo stars. globular clusters, and the dark matter halo.


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