sunset astronomical society the sunset gaze tte · 1 year - $34.00 + membership 2 year - $60.00 +...
TRANSCRIPT
Volume 6, Issue 2
T h e S u n s e t Gaze t t e Serving the Tri -Cit ies s ince 1975
Sunset Astronomical Society
Meeting information
Meetings are generally in the theater in the Delta College Planetarium in Bay City. The meetings will usually be on the 2nd Friday of each month at 7:00 PM. Watch the newsletter for changes in dates and times. See Page 4 for this month’s meeting site.
Membership Information
Student / Senior: (17 years & younger, 65+ years)
1 year - $15
2 year - $20
Regular: (18+ years)
1 year - $20
2 year - $30
Family: 1 year - $25
2 year - $40
New Members receive a New Mem-ber Observing Kit at their first meeting, courtesy of SAS,
Subscription Information
Subscription prices available at club rate with the purchase of individual or family membership.
“Sky and Telescope” Magazine: 1 year - $32.95 + Membership
2 year - Not available
“Astronomy” Magazine:
1 year - $34.00 + Membership
2 year - $60.00 + Membership
Call Jenifer Robb to Join: 989-843-6223
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October, 2008
First Impressions from the
Great Lake Star Gaze 6 Left: Thursday, 25th 5 pm. The registra-tion for the sixth Great Lake Star Gaze has finally and officially opened its gates! In the picture you see the registration and hospitality tent.
Right: Robert Burta with his 6 inch APO refractor inclusive CCD camera. Robert is later going to win the Astrophoto contest! Well done Robert!
Right into the tube of a 260 mm Cassegrain: If you look carefully you can see the editor up-side down.
Late Friday afternoon sunset: the telescopes awaiting eagerly the coming of the night. Friday was going to be a fantastically clear night!
PAGE 2 THE SUNSET GAZETTE VOLUME 6 , I SSUE 2
Left: Last preparations by Norbert Vance before the rocket launch Saturday morning 10 am (this should wake up the even the most sleepy astronomers!)
Right: A big crowd was gathering in high anticipation of the coming launch.
5...4...3...2...1...Zero
And lift off!
Parachute successfully opened!
This year we had the lux-ury of a ven-dor on the hill which was open form 8 am to 8 pm in the evening. Great food by the way!
Telescopes, telescopes everywhere!
PAGE 3 THE SUNSET GAZETTE VOLUME 6 , I SSUE 2
Greetings Fellow Star Gazers,
I must admit that I haven't taken as much advantage of the multitude of observing opportunities due to clear night skies this Summer. But I have done far more observing than usual. In particular I've tried out my latest telescope, a Meade 5" refractor that provides eye-popping views of Jupiter and the other planets. I hope that we don't have to 'pay the price' in bad weather this winter for all the good weather we had this summer. But on a positive note maybe the clear skies will continue!
Those who attended the September 12th SAS meeting were treated to an overview of "Space Weather" by Eric Jylha. Eric's explanations of the Sun and its interaction with the Earth were clearly illustrated by spectacular dome projections of SOHO and other spacecraft and enlightening graphics provided by Bill Mitchell and Garry Beckstrom.
Our next SAS meeting on October 10th will feature the accomplished Astronomer, Joe Bruessow, who will present "How to Observe". Bring your planisphere and receive a free red LED flashlight to use while comparing it to the night sky projected in the Planetarium dome. Joe will also present other tools used to find objects in the sky and how to plan and document an ob-serving session.
We are looking for volunteers to be Treasurer and 2nd Vice President of the Sunset Astronomical Society. Steve VanTol and I are covering these duties on a temporary basis. Please call or e-mail me if you have questions about your membership or subscriptions.
Peg and I are going on a vacation (from retirement??) in Hawaii starting Monday so Steve VanTol will host the October 10th meeting which starts at 7 pm sharp. I'll be thinking of you as we tour the 18 different climates of the 'Big Island'. We hope to see Greg Wirth, Secretary of SAS in the early 80s, when we visit the Keck Headquarters in Waimea. He gave us a complete and memorable tour of the twin 10-meter scopes and facilities in 2003. But that tour is the subject of a future meeting presen-tation.
Clear Skies - Bill
President's Message Corner
Left: Critical eyes were studying the pictures for the best Astrophoto contest.
Right: As every year the swap meet is a great oppor-tunity to go through one’s closet to sell off the odd eye-piece or other equipment and have a look what’s new and what’s hot on this year astro-market!
By Martin Grasmann. This is the sixth part of an extended summary of a lecture about Astrobiology that Dana Bachmann, SETI Institute/SOFIA-Ames gave on Wednesday, March 26th at the CMU.
In our journey through our solar sytem and search for potential places to find live outside from Earth we have reached the Jupiter system and visited Io and Europa. Before we leave the Jupiter system and venture into the outer reaches of the solar system we will make a stop at the two outer Galilean moons Ganymede and Callisto.
Jupiter moon Ganymede and Callisto:
Ganymede is the largest moon in the Solar System (diameter: 5268 km) and even larger in diameter than the planet Mercury but has only about half its mass. Ganymede completes an orbit in a little more than seven days which is also the time of its revolution because Ganymede’s orbit is tidally locked (= it always shows the same hemisphere towards Jupiter).
Ganymede is com-posed of an iron sul-fate–iron core, a sili-cate-rock mantle and an outer ice mantle. Ganymede is the only satellite in the Solar System known to possess a magneto-sphere. The exis-tence of a liquid, iron-rich core provides a natural explanation for the intrinsic magnetic field of Ganymede detected by the space craft Galileo. Similar to Earth, the convection in the liquid iron which has high electrical conductivity, is the most reasonable model of magnetic field
generation. The permanent magnetic moment creates a tiny magnetosphere inside the giant magnetosphere of Jupiter and so far it is the only moon in the Solar System known to possess the feature. In addition to the permanent magnetic field a second induced magnetic moment was discovered by Galileo in 2000. This additional magnetic moment is strong evidence a saltwater ocean in its interior. This saltwater ocean is believed to exist nearly 200 km below Ganymede's surface, sandwiched between layers of ice. Similar subsurface oceans are also present in the other icy Galilean moons, Europa and Callisto. The existence of the ocean can be made more likely if an antifreeze is dissolved in the water. The best candidates are ammonia and various salts like sulfates and chlorides. Ammonia, for instance, can depress the melting temperature to as low as 175 K. In many respects the ganymedian ocean is similar to that of Callisto (see below).
But there are important differences with Europa’s ocean, which is much closer to the surface and may be in direct contact with hydrothermal systems (black smokers, see previous SAS newsletter issue) on its seafloor. Ganymede's ocean lays much deeper and is sandwiched between layers of ice, has thus been seen as a less likely location for extraterrestrial life. Research suggests that interior magmatic activity might still generate pockets of melted water that would supply the ocean with nutrients, possibly sus-taining a biosphere.
A very thin oxygen atmosphere was found by the Hubble Space Telescope (HST) in 1995. The HST actually observed airglow of atomic oxygen in the far-ultraviolet. An airglow is generated when molecular oxygen is dissociated by electron impacts probably from charged particles from Jupiter’s magnetosphere. Thus is evidence of a significant neutral atmosphere composed predomi-nantly of O2 molecules. However the oxygen is not evidence of life; it is thought to be produced when water ice on Ganymede's surface is split into hydrogen and oxygen by radiation, with the hydrogen then being more rapidly lost due to its low atomic mass. The airglow observed over Ganymede seems to be concentrated in two spots (probably polar auroras) located in the northern and southern hemispheres, near ± 50° latitude, which is exactly the boundary between the open and closed field lines of the gany-median magnetosphere.
ARE WE ALONE? or
“The discovery of one-cell organisms on a distant planet in our solar system
PAGE 4 THE SUNSET GAZETTE VOLUME 6 , I SSUE 2
Callisto is the outermost of the four Galilean moons of Jupiter and like its inner counterparts, its rotation is locked to be syn-chronous with its orbit. Therefore a Callistoan day is of the length of its orbital period, about 16.7 Earth days. Because of its great distance to Jupiter it has probably never participated in the orbital resonance that affects the three inner Galilean satellites Io, Europa and Ganymede. This dynamical isolation of Callisto means that it has probably never been tidally heated, which has had im-portant consequences for its internal structure and evolution. The average density of Callisto is quite low (1.83 g/cm3). This sug-gests a composition of approximately equal parts water ice and rocky material probably mixed with some ammonia (see picture below). Callisto's battered surface (brown) lies on top of a cold, stiff, and icy lithosphere (light blue) hat is between 80 and 150 kilometers thick. Indicated by studies of the magnetic fields around Jupiter and its moons by Galileo, a salty ocean between 50 – 200 kilometers deep may lie beneath the crust (blue). Galileo found that Callisto responds to Jupiter's varying background mag-netic field like a perfectly conducting sphere; that means that the field cannot penetrate inside the moon. This suggests a layer of
highly con-ductive fluid (salt water?) within it with a thickness of at least 10 km. Like with Ganymede the existence of an ocean is more likely if water contains a small amount of ammonia or other antifreeze. If this is the case the ocean can be as thick as 250–300 km! If there is no ocean the icy lithosphere may be somewhat thicker, up to about 300 km.
As already mentioned like with Europa and Ganymede extraterres-trial microbial life may exist in a salty ocean under the Callistoan sur-face. However, like Ganymede the conditions for life appear to be less favorable on Callisto than on Europa. The principal reasons are: the lack of contact with rocky material and the lower heat flux from the interior of Callisto: Callisto's ocean is only being heated by radioactive elements, whereas Europa has tidal energy in addition from its greater proximity to Jupiter.
Colonization of Callisto? In 2003 NASA conducted a con-ceptual study called the "Human Outer Planets Explora-tion" (HOPE) regarding the future human exploration of the outer solar system and Callisto was studied in greater detail. As can be seen by an artist picture on the right a surface base being build on Callisto could produce fuel by electrochemical splitting the abundant water in hydrogen and oxygen for further exploration of the solar system. Ad-vantages of this localization include the large distance from Jupiter which means much lower radiation than on the other Galilean moons and Callisto's geological stability. A base there could either promote remote exploration of Europa or the other moons, or it could be a and ideal jump board for spacecrafts who would venture into the outer reaches of the Solar System, for example by using gravity assisted fly-by’s of Jupiter.
Want to know more about the Moons of Saturn and the outer Solar System? Then watch this space! The next parts
of this gripping story of ‘Are We Alone?’ will follow in the next issues of the S u n s e t Gaze t t e !
PAGE 5 THE SUNSET GAZETTE VOLUME 6 , I SSUE 2
Martin Grasmann Secretary - SAS 6108 Summerset Drive Midland, MI 48640
SUNSET ASTRONOMICAL SOCIETY THE SUNSET GAZETTE SERVING THE TRI- CITIES SINCE 1975 http://sunsetastronomicalsociety.com
President, Bill Albe
2nd Vice-President, Steve VanTol
Secretary, Newsletter Editor, Martin Grasmann
UPCOMING MEETINGS
7:00 Welcome, new members
Dale Sisson’s
Constellation of the Month: ‘Cepheus’
Break: Refreshments served
Joe Bruessow presents:
"How to Observe".
Don’t forget to bring your planisphere!
Don’ t forget to bring your tele-scopes for some Sidewalk Astron-omy after the meeting (weather permitting).
Observable Planets in February: Venus shines low in the west-
November 21: Public Telescope show: Bring in your Telescope. Planetarium show “Explore space with us”
December 12: Planetarium Show. To be announced
January 9: Bill Albe "Experience a Solar Eclipse in South America"
February 13: Telescope Workshop: "How to Use the Telescope You Got for Christmas" including "Collimate and Use Your Telescope"
March 13: Messier Marathon prepara-tion.
April 10: "Astronomical Tutorial" / NASA Lunar Sample training
SAS Elections
April 24: Messier Marathon with the AU
May 8: “The Lunar Landings” Dick Van Effen
May 1 - 31: Possible Star Party at the 30” Observatory of Garry Beckstrom. Weather permitting on short notice.
If you are interested in presenting to our club, please contact Bill Albe:
(989) 835-4142
Oct 1: Watch out for the thin crescent
Moon at the west-southwest horizon. Look
5 - 6° below Venus.
Oct 7: 1st quarter Moon.
Oct 14: Full Moon
Oct 17: Watch the Moon passing through
the Pleiades early this morning.
Oct 17 - 30: Best change to see Mercury
in the dawn for 2008 shining brightly more
than 5° above the eastern horizon 45 min
before sunrise.
Oct 21: Last quarter Moon
Oct 21: Watch out for the Orion shower.
Should peak this morning, but moonlight
will interfere.
Oct 25 - 26: Venus is passing 3.5° north of
Antares low in the southwest in bright
twilight.
Oct 24: Fish Lake Star Party!
Oct 28: New Moon.
UPCOMING EVENTS SAS Meeting
October 10, 2008
Delta College Planetarium Theater