June 2009 Volume 15 Number 12 Page 1

Star Gazer News

Newsletter of the Delmarva Stargazers www.delmarvastargazers.org

Upcoming Events: Meeting ! Jun 2nd 7PM Mallard Lodge Observing ! Jun 19th Dusk Equestrian Cntr

Please attend the June Meeting of the Delmarva Stargazers.

Come out and show your support and appreciation for your Officers

The following are just a few of the events for this meeting:

Elections of Officers for the 2009/2010 Season. Exit speech from Tim Milligan (Tim joins a small elite group of Past Presidents)

A few (?) Inaugural comments from Don Surles as he takes office, once again, as club president.

This is our last meeting before the summer break.

Galactic Jewels Tom Koonce Antelope Valley Astronomy Club Lancaster, California What inspired your earliest interest in amateur astronomy? Was it your first telescopic views of the Moon’s cra-ters or your first view of Saturn’s rings? Perhaps it was watching the night sky for satellites passing overhead on a sum-mer’s night. Whatever inspired you to pursue astronomy as a hobby, it has probably been deep sky views of galaxies, nebulae, and beautiful star clusters that have kept your interest focused. For many of us, motivation has come from globular clusters appearing like spheres of sparkling jewels in the heavens. Among the oldest objects in our galaxy, globular clusters have an abundance of older, metal-poor, redder stars.

Formed billions years ago, all of the stars in these cluster were born at approximately the same time from a common cloud of interstellar dust. Astronomers have determined the age of the clusters by measuring the concentrations of heavy elements con-tained within them and comparing these amounts with the other stars in the galactic disk. As generation after generation of stars pass and stars die, supernovae release heavy elements out into space, so the next generations of stars in globular clusters ap-pear to have less heavy elements than other stars. I’ll never forget the night when a fellow amateur astrono-mer showed me my first high power view of the rich pool of stars within the globular cluster M13. It was an awe-inspiring sight to see hundreds of thousands of stars orbiting around each other, packed into a spherical volume just 145 light years across. Pic-tures like the one here just don’t do it justice. Now, each time I swing the telescope into the constellation Hercules and find M13, I still feel that sense of wonder and amazement.

(See Jewel on page 3)

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How to Join the Delmarva Stargazers: Anyone with an interest in any aspect of astronomy is welcome NAME________________________________________________________________________________________ ADDRESS_____________________________________________________________________________________ CITY, STATE & ZIP______________________________________________________________________________ E-MAIL ADDRESS (If any)_________________________________________________________________________ Do you need the newsletter snail mailed to you (Y/N)?___________________________________________________ Please attach a check for $15 made payable to Delmarva Stargazers and mail to Kathy Sheldon, 20985 Fleatown Rd, Lincoln, DE 19960. Call club President Tim Milligan at 410-841-9853 for more information.

Some Additional Astronomy History Airy – the man and disk

Don Surles We have all read and talked about diffraction limited optics, diffraction rings or circles, and Airy disks. These terms relate to the quality of our optics and the behavior of light as it passes through or is reflected by them. Wikipedia’s definition for diffraction is: “diffraction is normally taken to refer to various phenomena which occur when a wave encounters an obstacle”. The Airy disk and Airy pattern are descriptions of the best focussed spot of light that a perfect lens with a circular aperture can make, limited by the diffraction of light. The diffraction pattern’s bright region in the center is known as the Airy disk. This disk, together the series of concentric bright rings around it is called the Airy pattern. If you haven’t seen these circles with your scope you may want to reduce the aperture and pump up the power while looking at a star…or you may want to shoot your scope. Both the disk and the pattern of concentric circles are named after George Biddell Airy, who first described the phenomenon. George Biddell Airy (1801-1892) was an interesting character. First he lived a long life…91 years when the av-erage life span was in the mid forties – quite an accomplishment without the aid of today’s medicines, clean air, clean water, central HVAC, horseless transportation, etc. No sanitary sewers (isn’t “sanitary sewer” an oxymoron?), no refrig-erated food, all heat came from wood, peat, or coal (smoke!). And animal waste in the streets…chamber pots had to be emptied each morning…somewhere. Talk about funk! This was the age of the Victorians; Victorians brought order to everything - scientific research included. George Biddell Airy was Astronomer Royal at the Royal Observatory in Greenwich from 1835 to 1881 – a 46 year reign. During his administration Airy transformed the observatory. New and advanced astronomical instruments were installed. He increased the both staff and workload. Did I mention that Victorians were organizers? Some of Airy’s changes were: • Staff had to clock-in and clock-out • Airy produced step-by-step instructions for each function • Reducing errors:

“It was not only the observers and the instruments that introduced errors to the measurements made. Once the observations had been made, the measurements would be handed over to the computers or clerks, who in Airy's day, worked at the Observatory from 8 in the morning until 8 at night. Their job was to turn the raw data into use-ful tables. To ensure that as few errors were made as possible, Airy devised a form to fill out, taking the com-puter through every step of the calculation. This production line method meant that errors might be reduced or at least be easily traceable. It also meant that someone relatively inexperienced could carry out quite complex cal-culations.” Wikipedia

• BTW…the computers were the peons of the Observatory. The Royal Observatory’s main purpose in the 1800’s was to aid navigation…remember England was a seafaring nation and it’s wealth depended on ocean-going ships making their journeys safely. Airy's drive to make the Observa-tory carry out its job of aiding navigation more efficiently led to the installation of the timeball in 1833. The purpose of the timeball was/is to calibrate the ships’ clocks. To this day it falls at 1pm every day to signal to navigators on the Thames the time at Greenwich. Airy changed the drop from manual to automatic. This function should probably be ceased in light of GPS navigation. Airy also had the Airy Transit Circle installed in 1850; it was first used on January 4, 1851. This instrument sits on the north-south line, which today marks longitude 0°. This Prime Meridian, signals the start of the Universal day for the entire world. The world’s time begins here. A transit instrument is always lined up with a north-south line, or merid-ian. When a star passes over the meridian, the transit instrument can be used to measure the angle at which this hap-pens. When this happens, an extremely accurate clock, called a regulator, is used to measure the time it occurs. (Do you remember the “REGULATOR” school clocks?) These two measurements give the co-ordinates of that star, which

(See Airy on page 4)

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Your 2008-2009 Officers Office Officer Phone President Tim Milligan 410-841-9853 President-elect Don Surles 302-653-9445 Secretary Michael Lecuyer 302-284-3734 Treasurer Kathy Sheldon 302-422-4695 Past President Tom Pomponio 302-736-0157 Editor Pj Riley 302-738-5366

Unlike our Sun, globular clusters are located in the halo of the Milky Way, the ‘fog’ of stars and matter that orbit the center of the galaxy above and below the plane of the galactic disk, with a significant concentration toward the Ga-lactic Center. Our galaxy is associated with about two hundred globulars. Try imagining what it might be like to stand on the surface of a planet circling a star just inside of a globular clus-ter… Surrounded by stars brighter than the planet Venus, perhaps two main concentrations of stars would be visible to you; one very large area of the sky towards the center of the globular cluster would be visible as a region more closely packed with stars; and perhaps opposite this, a view of the central bulge of stars of the Milky Way could be seen promi-nently in the night sky. The sky might be so dazzling at night that the subtlety of faint nebulae might be completely over-whelmed in the light. With so many bright stars surrounding you, your view of other galaxies might be severely limited. In fact your location within the Milky Way could be a limiting factor in your very understanding of the universe, a tradeoff between beauty and knowledge.

Sir Edmund Halley discovered M13 in 1714 and it was logged as a nebula by Charles Messier when he added it to his famous listing fifty years later. By the 1920 debate on the size of the universe between Harlow Shapley and Heber Curtis, globular clusters (including M13) featured prominently in Shapley’s rough determination of the shape of the Milky Way. Since globulars are essentially spherical in shape, can be seen from great distances and are appear to be evenly distributed around the galaxy, they were a natural choice for Shapley’s research. Globular clusters exist in most other galaxies too. The Hubble Space Telescope was used to detect approximately thirteen thousand (!) globulars associated with the galactic giant galaxy M87, indicating that globulars will remain an important focus of astronomical re-search into galactic evolution for years to come. If you haven’t observed M13 yet, get out your binoculars or at least a 3 inch telescope and you’ll be able to resolve stars within the cluster, but you’ll be able to see hundreds of stars and details of its structure using an eight inch telescope at about two hundred power. More details become visible as you add aperture so this cluster never gets boring. M13 is located one third of the way between the stars Eta and Zeta Hercules on an imaginary line connecting them. Through the eyepiece, stars will fill the field of view from edge to edge. Use fairly low power to see the overall structure of the cluster and then switch to much higher power to peer deeper into the depths of the globular, to see dust lanes and the tendrils of star chains. The view is worth the work of finding M13 and adding it to your ‘star party favorites’ list. It’s 25,100 light years away and contains between hundreds of thousands to one million stars. One esti-mate put the age of M13 between 12 and 14 billion years old, making it certainly one of the oldest objects in our galaxy. For M13’s part in galactic history, perhaps none is more interesting and unusual than the fact that in 1974 it was selected as the target for one of Earth’s first intentional radio mes-sages to be beamed to the stars. The message was designed as a ‘First Contact’ message to possible extra-terrestrial intelligent races and sent by SETI using the Arecibo Observatory. The message will take about 25,100 years to reach the cluster, so that an answer cannot be expected for over fifty thousand years. You can relax, there’s still time to go out and observe M13 through your telescope while you’re waiting! As you gaze upon the galactic jewels in the globular cluster M13 and are imagining the view from a planet orbiting a star nestled within, also try to imagine what possible crea-

tures living there might think upon receiving this message in another 25,065 years. Hopefully our species will be around to get the answer. Clear Skies, Tom References: The Munich Astro Archive: http://www.maa.clell.de/Messier/E/m013.html

SETI Institute: http://www.seti.org/Page.aspx?pid=1241

(Jewel from page 1)

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Magazine Subscriptions As a paid member of DMSG, you can sign up/renew your S&T or Astronomy mags through the club for a discount over private rate. S&T, reg. $42.95, is $32.95 thru DMSG, Astronomy, reg. $44, is $34. See Michael Lecuyer for details.

The Sky in June From

Half-Hours with the Stars

RICHARD A. PROCTOR, F.R.A.S. (Published 1911) The Great Bear (Ursa Major) is in the mid-heavens toward the northwest, the Pointers not far from the horizontal

position. They direct us to the Pole Star (α of the Little Bear, Ursa Minor). The line from this star to the Guardians of the Pole, ß and γ , is in about the position of the minute hand of a clock 2 minutes before an hour. The Dragon (Draco) curls over the Little Bear, curving upward on the east, to where its head, high up in the northeast, is marked by the gleaming eyes, ß and γ . Under the Little Bear, the Camelopard has at last come upright.

Low down in the west the Lion (Leo) is setting. The point of the "Sickle in the Lion" is turned toward the horizon; the handle (marked by α and η) is nearly horizontal. Above the Lion's tail is Berenice's Hair (Coma Berenices); and between that and the Great Bear's tail our chart shows a solitary star of the Hunting Dogs (Canes Venatici). The Crow (Corvus) is low down in the southwest, the Cup (Crater) beside it, partly set, on the right. Above is Virgo, the Virgin. Still higher in the southwest—in fact, with head close to the point overhead—is the Herdsman (Boötes), the Crown (Corona Borealis) near his southern shoulder marking what was once the Herdsman's uplifted arm.

Low down between the south and southwest we find the head and shoulders of the Centaur (Centaurus), who holds the Wolf (Lupus) due south. Above the Wolf are the Scales (Libra), and above these the Serpent (Serpens), his head in the south, stretching toward the Crown. In the mid-sky, toward the southeast, we find the Serpent Bearer (Ophiuchus—one star of the Serpent lies east of him). Below the Serpent Bearer we find the Scorpion (Scorpio), now fully risen, and showing truly scorpionic form. Beside the Scorpion is the Archer (Sagittarius), low down in the southeast. To his left we see, low down, two stars marking the head of the Sea Goat (Capricornus), and one belonging to the Water Bearer (Aquarius). Above the Sea Goat flies the Eagle (Aquila), with the bright star Altair; and above, near the point overhead, is the kneeling Hercules. Due east, we see part of the Winged Horse (Pegasus); above that, the little Dolphin (Delphinus), and higher, the Swan (Cygnus) and the Lyre (Lyra), with the beautiful bluish-white star Vega.

Lastly, low down, between north and northeast, we find the Seated Lady (Cassiopeia); and above, somewhat east-wardly, the inconspicuous constellation Cepheus, Cassiopeia's royal husband. (Use a planisphere or chart on pg. 7 to help guide you—Ed.)

can be used to make a star chart - and star position tables to aid navigation. The production of these tables, published annually to this day, along with the Nautical Almanac, was fundamental to the founding duty of the Observatory, which was to improve navigation. An ex-employee once said “if Airy wiped his pen on a piece of blotting paper he would duly endorse the blotting paper with the date and particulars of its use, and file it away amongst his papers”. Another anecdote describes Airy as having spent an entire afternoon labeling empty boxes 'empty'. More information can be found here: • Greenwich Observatory, vol 1, by Eric G. Forbes (London, 1975) • Greenwich Observatory, vol 2, by A. J. Meadows (London, 1975) • Greenwich Observatory, vol 3, by Derek Howse (London, 1975) • The History of the Airy Transit Circle by Gilbert Satterthwaite (MSc Dissertation at University of London, 1995) • The Royal Observatory, Greenwich by E Walter Maunder (London, 1900) • Autobiography of Sir George Biddell Airy edited by Wilfrid Airy (Cambridge University Press, 1896) • The Victorian Amateur Astronomer, Wiley-Paxis by Allan Chapman (Chichester, 1998)

(Airy from page 2)

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Swift Sets Distance Record Jerry Truitt We often tout our telescopes as “Time Machines” with the ability to look back millions of years in time as we ex-amine ancient light. But we don’t come close to NASA’s Swift gamma-ray burst satellite, which smashed the cosmic dis-tance record just before Dr. Neil Gehrels spoke to us at the Star Gaze XV star Party on April 25. We’ve known gamma-ray burst existed but for a long time had no clue what caused them. Thanks to the quick acting Swift we now know that gamma-ray bursts longer than two seconds are caused by the detonation of a massive star at the end of its life For those who missed his presentation Dr. Neil Gehrels is the lead scientist for Swift at NASA’s Goddard Space Flight Center in Greenbelt Maryland. He gave us a great presentation on the work of Swift and had mentioned the dis-covery found the day our star party had started Thursday April 23. The data was preliminary at the time but he had said it looked like a record distant burst. According to NASA’s account “At 3:55 a.m. EDT on April 23, Swift detected a ten-second-long gamma-ray burst of modest brightness. It quickly pivoted to bring its ultraviolet/optical and X-ray telescopes to observe the burst location. Swift saw a fading X-ray afterglow but none in visible light.” The lack of light in the visible spectrum suggests it is a very distant object. This was most likely the demise of a massive star exploding and forming a black hole. But this star was one of the first generations of stars, at only 630 mil-lion years old, the most distant explosion ever seen. The expansion of the universe shifts visible light into longer infrared light, ultraviolet on the other hand stretches to visible but the hydrogen gas from the early universe was abundant and absorbs it. So if you go back far enough you will see no visible light. One of the main things Swift does is notify telescopes on Earth who quickly turn their attention to a new gamma-ray burst, the universe’s most luminous explosions. Prior to Swift the opportunity to observe these burst were missed or only caught at the very end. Now the Swift alert system has enabled us to study the afterglow with not only it’s on board telescopes but from the ground too before it fades. Telescope on Mauna Kea, Hawaii quickly slewed to view the burst GRB 090423 and obtained images of the afterglow in the Infrared. The images showed the source in longer wavelength but absent in the shortest 1 micron wavelength. The drop out tells sci-entist that the distance of this object was about 13 billion light-years. Meanwhile telescopes at La Palma in the Canary Islands gathered nearly simultaneous observations with European South-ern Observatory’s Very Large Telescope on Cerro Paranal, Chile and found a red shift of 8.2; this translates to a gamma-ray burst that exploded 13.035 billion light-years away. For more information on this burst go to: http://www.nasa.gov/mission_pages/swift/bursts/cosmic_record.html To learn more about Swift and to keep abreast of the latest Swift finds go to: http://heasarc.gsfc.nasa.gov/docs/swift/swiftsc.html

This image merges data from Swift's Ultraviolet/Optical (blue, green) and X-Ray (orange, red) tele-scopes. No visible light accompanied the burst, which hints at great distance. The image is 6.3 arcminutes wide. Credit: NASA/Swift/Stefan Immler

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Moondark for June: What's Up for Summer? Doug Miller I’m just getting caught up after being away for a long weekend. So what’s up—in the news, in our sky, and ahead for this summer? “High fives!” for the Atlantis astronauts: they have just bid farewell to the over-hauled Hubble Space Telescope. My news reader was stuffed with headlines marking the progress of the five space walks as well as some frustrations in revitalizing Hubble for at least five more years of cutting edge science and stunning photos. So when will the refurbished space telescope be visible in our sky? Check out Heavens Above's and Space Weather’s online pass predictors. In other space exploration news: the Mars rover Spirit has five wheels stuck in a ferric-sulfate salt sand. So far, 2009 has been a challenging year, with memory glitches and dusty solar panels. On the other side of the Red Planet, Opportunity rolls onward toward Endeavour Crater. And last week, the ESA launched two space telescopes. The Herschel Space Observatory’s 3.5-m diameter primary mirror is the largest ever sent into space and is designed for the study of newly forming stars and galaxies at far infra-red wavelengths not available to ground-based telescopes. Planck Surveyor is a micro-wave telescope that will scan the whole sky to map the cosmic background radiation at parts per million levels. The polarization of the CMB photons will also be measured to shed light on inflation of the early universe. Both telescopes are on their way to the L2 point 1.5 million miles from the us directly opposite the Sun. To avoid swamping their sensitive detectors, both telescopes must be located far away from radiation emitted by Earth. Much closer to home and as close as the Delaware Bay shoreline, it’s time for the annual spawning of the horseshoe crabs. This too is an astronomical phenomenon: spawning and egg laying are precisely timed to the spring tides of early summer. You’ll find the nesting horseshoe crabs, as well as volunteers counting them, on the nocturnal high tides around the full moon on June 7th and new moon on the 22nd. Both hurricane season and meteorological summer begin on the first of June. Astronomically, the summer starts on the solstice as the Sun (eerily quiet so far this year) reaches its northernmost point in the sky on June 21st in the middle of our night, 01:45 EDT to be precise. Earth is farthest from the Sun, just over 152 x 106 kilometers on July 3rd. And we miss all three eclipses this summer: two slight penumbral lunar eclipses on either side of the longest total solar eclipse of the century on July 22nd; In-dia, China and the western Pacific Ocean are favored locations. For the early summer, Saturn is the only bright planet visible, easy to find as soon as night falls, located below Leo’s hindquarters. But this planet’s most distinguish-ing figure, its rings are shrinking and will all but disappear as summer closes. Ring-plane crossing is on September 4th, just ahead of its conjunction with the Sun on the 17th. Jupiter reaches opposition in mid August and is brilliant and visible all night long. How many of you will try again for the Perseid meteor shower? The moon is near last quarter, but the meteor-optimists project greater than average activity. For my part, I’m afraid the spectacular displays a decade ago have spoiled me forever. Instead, how about a nice summertime comet, like Hyakutake in 1996? Summer is a time to relax, put up your feet and enjoy the warm evenings under the Milky Way. Let the mind wander and wonder about the infinitesimal difference in refraction of light, red a bit less and blue slightly more, that creates a rainbow following a thundershower. Dispersion also accounts for the green flash and colors of twinkling stars. Ponder why the sky is blue? Or why are there no green stars? Or consider the near coincidence of moon and sun’s angular size, one-half a degree, leading to rare and spectacular eclipses and comparable tidal effects, spring tides and neap tides, on the sea as well. And don’t forget the bug spray. Summer comes to a close with the No Frill Star Party followed immediately by the equinox on September 22. It’s just thirteen weeks long, only 93.65 days. How did you spend your 2009 summer vacation? Moondark is written by Douglas C. Miller, published at the Moondark web site, and printed in the Delmarva Star Gazers' Star Gazer News. This document was last revised on 21 May 2009. Text and graphics on this web page are free for non-commercial use with attribution under a Creative Commons Attribution-Non-commercial 3.0 License. Ask Doug about other uses.