COMING EVENTS Public Observing

Post-Band Concerts Wed. June 01, 2011

Wed. June 15

Wed. June 29

Wed. July 13 South Park - West

9:00 PM

President Rick Heschmeyer

rcjbm@sbcglobal.net

University Advisor Dr. Bruce Twarog btwarog@ku.edu

Webmaster

Gary Webber gwebber@ku.edu

Observing Clubs

Doug Fay dfay@ku.edu

Report from the Officers: Summer is here and we now switch to public observing every other Wed. evening at South Park, west side of Mass. St. Sessions take place starting at ~9:00 PM (it takes a while for it to get really dark), after the Band Concerts in the Park. The complete schedule is on the left, with the first session set for June 1, the first day of the month. The May 26 event fell victim to the never-ending rainy weather. If you can help, as always, please let Rick know so we can schedule people efficiently. Summer is a great time to get out and relax under the warm dark skies (assuming you are willing to wait for it to get dark!). There are a number of regional events for observing over the summer that may be of interest. Two big

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Volume 37 Number 06 JUNE 2011

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INSIDE THIS ISSUE

Amateur Astronomy (cont.) 2

Blue Stragglers in Bulge 3

NASA Space Place 4

Blue Stragglers (continued) 5

Crystal Rain 6

Historic Star 7

Crystal Rain (continued) 8

Historic Star (continued) 9

Historic Star (continued) 10

Amateur Astronomy – a solitary activity… best done with friends

by Bill Pellerin, Houston Astronomical Society, GuideStar editor

An amateur astronomer is one person, with one telescope, observ-ing under clear, dark skies, right? It's you, your telescope, and the sky. Much of my observing is like that, but not all. You can (and you should) connect with fellow amateur astronomers because these

connections can significantly enhance your observing program and your appreciation of the night sky.

Recently, I had dinner with one of my long-time astronomy friends. We were chatting about the issues he was having with his research-grade instrument and control sys-tem and about my equatorially mounted setup. We talked about how the control sys-tems model the sky, the accuracy of pointing systems, the benefits of adding soft-ware that improves pointing, and so on.

I talked about my variable star photometry program (measuring the brightness of stars) and how some of my unguided images have tracking errors and had to be dis-carded from the image stacking process. Then, he mentioned the PEC (periodic error correction) capability of my mount and asked if I was using it. Uh, no, I haven't been. This is one of those 'duh' moments when you realize that you have a capability and you're not taking advantage of it. So, I'm going to work with my mount's PEC capabil-ity, learn it thoroughly, and see what it can do to improve tracking. Sometimes, you need a friend to remind you of the obvious.

Another friend, at a star party, wasn't getting good alignment of his computer con-trolled telescope mount. After we talked about it for a while, he realized that he had selected Castor as an alignment star but had incorrectly pointed his telescope at Pol-lux instead of Castor. Oops.

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About the Astronomy Associates of Lawrence

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The club is open to all people interested in sharing their love for astronomy. Monthly meetings are typically on the second Fri-day of each month and often feature guest speakers, presentations by club members, and a chance to exchange amateur as-tronomy tips. Approximately the last Sunday of each month we have an open house at the Prairie Park Nature Center. Periodic

star parties are scheduled as well. For more information, please contact the club officers:our president, Rick Heschmeyer at rcjbm@sbcglobal.net, our webmaster, Gary Webber, at gwebber@ku.edu, or our faculty advisor, Prof. Bruce Twarog at

btwarog@ku.edu. Because of the flexibility of the schedule due to holidays and alternate events, it is always best to check the Web site for the exact Fridays and Sundays when events are scheduled. The information about AAL can be found at

http://www.ku.edu/~aal. Copies of the Celestial Mechanic can also be found on the web at

http://www.ku.edu/~aal/celestialmechanic

ones are: (a) Rocky Mountain Star Stare, Starry Meadows, Gardner CO, June 29. RMSS is held annually under some of the darkest skies in the Rocky Mountain region. Four days of camping under the stars on the Colorado Springs Astronomical Society's private land, 3.5 miles north of Gardner, CO. Speakers, kid's events, catered dinners, and dark skies combine to make RMSS one of the pre-mier events in the country! See www.rmss.org for more information or to register; (b) NEBRASKA STAR PARTY, July 31 - August 5th, 2011, Snake Campground, Merritt Reservoir, 27 Miles South of Valentine, NE. The astronomical views from Merritt Reservoir's Snake Campground are fabulous, and there are plenty of recreational oppor-tunities to keep the entire family entertained all week long at the 18th annual Nebraska Star Party. For more info, check out the NSP web site at http://www.nebraskastarparty.org/ For the more adventurous, don’t forget ALCON 2011 in Bryce Canyon National Park, Utah from June 29 - July 2, 2011. For more details, check out http://alcon.astroleague.org/ All AAL members are also Astronomical League members. Any suggestions for improving the club or newsletter are always welcome. Have a great week.

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It's not often the case that I get all the knowledge I need from a conversation with another observer, but it is often that I get pointed in the right direction – I walk away from the discussion knowing what I need to look into, what I need to learn. This isn't always about equipment or operating the equipment, sometimes it's about the science of astronomy. (Did Edwin Hubble see the expansion of the universe by measuring the red shift of the Andromeda Galaxy? No, because the Andromeda Galaxy is moving toward us, so it isn't redshifted at all, it's blueshifted.)

There are plenty of opportunities for sharing. A star party is all about sharing the view. Do you have an object in your eyepiece that is worth sharing? Do it. It's fascinating how different telescopes provide different views of the same object. They can all be great views, but they have a different character. For example, a wide field telescope view of the Veil Nebula under dark skies is amazing. Think of it; you're looking at a supernova remnant from a star that exploded 10,000 years ago. A larger, narrow field telescope will show you parts of the nebula in far greater detail. You will be amazed by the structure in the Veil.

We're a diverse group, and we all don't look at the same kinds of objects in the sky. The large telescope crowd is often looking for galaxies or other objects on the edge of their ability to detect. I'm using a relatively small refractor, so I'm looking at brighter objects, not because that's all I can see but because these objects are interesting to me. The point is, you should see the universe through someone else's eyepiece sometime. You may find a class of objects that you've overlooked in the past. You may better appreciate the objects you can see in your telescope when you understand how other objects fit into the scheme of things.

Astronomy clubs – What a great resource these are. Clubs vary in size and in resources and activities, but the members share a common love of astronomy and, usually, observing. Many clubs either have a dedicated observing site or have observing locations on public lands that they use. A weekend outing to one of these sites is similar to a small star party. Everyone is there to observe, share, and learn. Clubs can offer other resources, such as lectures or loaner telescopes. Imagine that… everything you need to get started in amateur astronomy for the cost of a club membership. Need to find a club? Look at the Astronomical League web site, www.astroleague.org, under 'Member Societies'.

How about on-line astronomy friends? Just like looking at a photo of the Crab Nebula is never as exciting as seeing the object through an eyepiece, being connected to people online is not quite the same as being connected to them in person. That said, there is a lot of value in online connections. An online connection can be a supplement to a personal connection and can help maintain the friendship. Sometimes, we have come to the limit of our ability to solve a problem and we post a question on an online discussion group. This almost always results in an answer and often results in a conversation among interested astronomers in the group. The answer may just point you in a direction you hadn't thought about.

So, if you're a solitary observer with your own observing site, make the effort to engage with other amateur and professional astrono-mers. You can help each other with discussions of equipment, techniques, and the science of astronomy.

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NASA'S HUBBLE FINDS RARE 'BLUE STRAGGLER' STARS IN MILKY WAY'S HUB HST Press Release

NASA's Hubble Space Telescope has found a rare class of oddball stars called blue stragglers in the hub of our Milky Way, the first detected within our galaxy's bulge. Blue stragglers are so named because they seemingly lag behind in the aging process, appearing younger than the population from which they formed. While they have been detected in

many distant star clusters, and among nearby stars, they never have been seen inside the core of our galaxy.

It is not clear how blue stragglers form. A common theory is that they emerge from binary pairs. As the more massive star evolves and expands, the smaller star gains material from its companion. This stirs up hydrogen fuel and causes the growing star to undergo nuclear fusion at a faster rate. It burns hotter and bluer, like a massive, young star. The findings support the idea that the Milky Way's central bulge stopped making stars billions of years ago. It now is home to aging sun-like stars and cooler red dwarfs. Giant blue stars that once lived there have long since exploded as super-novae. The results have been accepted for publication in an upcoming issue of the Astrophysical Journal. Lead author Will Clarkson of Indiana University in Bloomington and the University of California in Los Angeles, discussed them at the American Astronomical Society meeting in Boston.

"Although the Milky Way bulge is by far the closest galaxy bulge, several key aspects of its formation and subsequent evolution remain poorly understood," Clarkson said. "Many details of its star-formation history remain controversial. The

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This is an artist's concept of a close binary pair of stars that are merging to form a blue-straggler-class star. Blue strag-glers are so named because they seem to be lagging behind in their rate of aging compared with the population from which they formed. The merger stirs up hydrogen fuel and causes the resulting more massive star to undergo nuclear fusion at a faster rate, causing it to burn hotter and bluer. Probing the star-filled, ancient hub of our Milky Way, the Hub-ble Space Telescope has found blue stragglers for the first time within our galaxy's bulge.

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Milky Way Safari by Dauna Coulter & Dr. Tony Phillips

Safari, anyone? Citizen scientists are in-vited to join a hunt through the galaxy. As

a volunteer for Zooniverse's Milky Way Project, you'll track down exotic creatures like mysterious gas bubbles, twisted green knots of dust and gas, and the notorious “red fuzzies.” “The project began about four months ago,” says astrophysi-cist Robert Simpson of Oxford University. “Already, more than 18,000 people are scouting the Milky Way for these quarry.”

The volunteers have been scrutinizing infrared images of the Milky Way's inner regions gathered by NASA’s Spitzer Space Telescope. Spitzer's high resolution in infrared helps it pierce the cloaking haze of interstellar gas and dust, revealing strange and beautiful structures invisible to conventional telescopes. The Milky Way Project is helping astronomers cata-logue these intriguing features, map our galaxy, and plan future research.

“Participants use drawing tools to flag the objects,” explains Simpson. “So far they've made over a million drawings and classified over 300,000 images.” Scientists are especially interested in bubble-like objects believed to represent areas of active star formation. “Every bubble signifies hundreds to thousands of young, hot stars. Our volunteers have circled al-most 300,000 bubble candidates, and counting,” he says.

Humans are better at this than computers. Computer searches turn up only the objects precisely defined in a program, missing the ones that don't fit a specified mold. A computer would, for example, overlook partial bubbles and those that are skewed into unusual shapes.

“People are more flexible. They tend to pick out pat-terns computers don't pick up and find things that just look interesting. They're less precise, but very comple-mentary to computer searches, making it less likely we'll miss structures that deserve a closer look. And just the sheer numbers of eyes on the prize mean more comprehensive cover-age.” Along the way the project scientists distill the

volunteers' data to eliminate repetitive finds (such as different people spotting the same bubbles) and other distortions.

The project's main site (http://www.milkywayproject.org ) includes links to a blog and a site called Milky Way Talk. Here “hunters” can post comments, chat about images they've found, tag the ones they consider especially intriguing, vote for their favorite images (see the winners at http://talk.milkywayproject.org/collections/CMWS00002u ), and more. Zooniverse invites public participation in science missions both to garner interest in science and to help scientists achieve their goals. More than 400,000 volunteers are involved in their projects at the moment. If you want to help with the Milky Way Project, visit the site, take the tutorial, and … happy hunting!

You can get a preview some of the bubbles at Spitzer’s own web site, http://www.spitzer.caltech.edu/. Kids will enjoy look-ing for bubbles in space pictures while playing the Spitzer concentration game at http://spaceplace.nasa.gov/spitzer-concentration/. This article was provided by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

Volunteers study infrared images of our galaxy from the Spitzer Space Telescope, identify-ing interesting features using the special tools of the Milky Way Project, part of the Citizen Science Alliance Zooniverse web site.

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extent of the blue straggler population detected provides two new constraints for models of the star-formation history of the bulge."

The discovery followed a seven-day survey in 2006 called the Sagittarius Window Eclipsing Extrasolar Planet Search (SWEEPS). Hubble peered at 180,000 stars in the crowded central bulge of our galaxy, 26,000 light-years away. The survey was intended to find hot Jupiter-class planets that orbit very close to their stars. In doing so, the SWEEPS team also uncovered 42 oddball blue

stars with bright-ness and tempera-tures typical for stars much younger than ordinary bulge stars. The observa-tions clearly indicate that if there is a young star popula-tion in the bulge, it is very small. It was not detected in the SWEEPS program. Blue stragglers long have been sus-pected to be living in the bulge, but had not been observed because younger stars in the disk of our galaxy lie along the line-of-sight to the core, confusing and contaminating the view.

Astronomers used Hubble to distin-guish the motion of the core population from foreground stars in the Milky Way. Bulge stars orbit the galactic center at a different speed than fore-ground stars. Plot-ting their motion required returning to the SWEEPS target region with Hubble two years after the first observations were made. The blue stragglers were

identified as moving along with the other stars in the bulge.

"The size of the field of view on the sky is roughly that of the thickness of a human fingernail held at arm's length, and within this region, Hubble sees about a quarter million stars toward the bulge," Clarkson said. "Only the superb image quality and stability of Hubble allowed us to make this measurement in such a crowded field." From the 42 candidate blue stragglers, the investigators estimate 18 to 37 are likely genuine. The remainder could be a mix of foreground objects and, at most, a small population of genuinely young bulge stars.

"The SWEEPS program was designed to detect transiting planets through small light variations," said Kailash Sahu, the principal investigator of the SWEEPS program. "Therefore the program could easily detect the variability of binary pairs, which was crucial in confirming these are indeed blue stragglers."

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Peering deep into the star-filled, ancient hub of our Milky Way (left), the Hubble Space Telescope has found a rare class of oddball stars called blue stragglers, the first time such objects have been detected within our galaxy's bulge. Blue stragglers — so named because they seem to be lagging behind in their rate of aging compared with the population from which they formed — were first found inside ancient globular star clus-ters half a century ago. This discovery is a spin-off from a seven-day-long survey conducted in 2006 called the Sagittarius Window Eclipsing Extrasolar Planet Search (SWEEPS). Hubble peered at and obtained vari-ability information for 180,000 stars in the crowded central bulge of our galaxy, 26,000 light-years away. The picture at right shows the 42 blue straggler candidates circled in green.

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Spitzer Sees Crystal 'Rain' in Outer Clouds of Infant Star Tiny crystals of a green mineral called olivine are falling down like rain on a burgeoning star, according to observations from NASA's Spitzer Space Telescope.

This is the first time such crystals have been observed in the dusty clouds of gas that col-lapse around forming stars. Astronomers are still debating how the crystals got there, but the most likely culprits are jets of gas blasting away from the embryonic star. "You need tempera-tures as hot as lava to make these crystals," said Tom Megeath of the University of Toledo in Ohio. He is the principal investigator of the re-search and the second author of a new study appearing in Astrophysical Journal Letters. "We propose that the crystals were cooked up near the surface of the forming star, then carried up into the surrounding cloud where temperatures are much colder, and ultimately fell down again like glitter."

Spitzer's infrared detectors spotted the crystal rain around a distant, sun-like embryonic star, or protostar, referred to as HOPS-68, in the constellation Orion.

The crystals are in the form of forsterite. They belong to the olivine family of silicate minerals and can be found everywhere from a periodot gemstone to the green sand beaches of Hawaii to remote galaxies. NASA's Stardust and Deep Impact missions both detected the crystals in their close-up studies of comets.

"If you could somehow transport yourself inside this protostar's collapsing gas cloud, it would be very dark," said Charles Poteet, lead author of the new study, also from the University of Toledo. "But the tiny crystals might catch what-ever light is present, resulting in a green sparkle against a black, dusty backdrop."

Forsterite crystals were spotted before in the swirling, planet-forming disks that surround young stars. The discovery of the crystals in the outer collapsing cloud of a proto-star is surpris-ing because of the cloud's colder temperatures, about minus 280 degrees Fahrenheit (minus 170 degrees Celsius). This led the team of as-tronomers to speculate the jets may in fact be transporting the cooked-up crystals to the chilly

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This image from NASA's Spitzer Space Telescope shows what lies near the sword of the constellation Orion -- an active stellar nursery containing thousands of young stars and developing protostars. Many will turn out like our sun. Some are even more massive. These massive stars light up the Orion nebula, which is seen here as the bright region near the center of the image. To the north of the Orion nebula is a dark filamentary cloud of cold dust and gas, over 5 light-years in length, containing ruby red protostars that jewel the hilt of Orion's sword. These are the newest generation of stars in this stellar nursery, and include the protostar HOPS 68, where Spitzer spotted tiny green crystals in a surrounding cloud of gas.

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Hubble Views the Star that Changed the Universe Though the universe is filled with billions upon billions of stars, the discovery of a single variable star in 1923 altered the course of modern astronomy. And, at least one famous astronomer of the time lamented that the discovery had shattered his world view. The star goes by the inauspicious name of Hubble variable number one, or V1, and resides in the outer regions of the neighboring Andromeda galaxy, or M31. But in the early 1900s, most astronomers considered the Milky Way a single "island universe" of stars, with nothing observable beyond its boundaries. Andromeda was cataloged as just one of many faint, fuzzy patches of light astronomers called "spiral nebulae."

Were these spiral nebulae part of the Milky Way or were they independent island universes lying outside our galaxy? As-tronomers didn't know for sure, until Edwin Hubble found a star in Andromeda that brightened and faded in a predictable pattern, like a lighthouse beacon, and identified it as V1, a Cepheid variable. This special type of star had already been proven to be a reliable distance marker within our galaxy. The star helped Hubble show that Andromeda was beyond our galaxy and settled the debate over the status of the spiral nebulae. The universe became a much bigger place after Hubble's discovery, much to the dismay of astronomer Harlow Shapley, who believed the fuzzy nebulae were part of our Milky Way.

Nearly 90 years later, V1 is in the spotlight again. Astronomers pointed Edwin Hubble's namesake, NASA's Hubble Space Telescope, at the star once again, in a symbolic tribute to the legendary astronomer's milestone observation. Astronomers with the Space Telescope Science Institute's Hubble Heritage Project partnered with the American Association of Variable Star Observers (AAVSO) to study the star. AAVSO observers followed V1 for six months, producing a plot, or light curve, of the rhythmic rise and fall of the star's light. Based on this light curve, the Hubble Heritage team scheduled telescope time to capture images of the star.

"V1 is the most important star in the history of cosmology," says astronomer Dave Soderblom of the Space Telescope Sci-ence Institute (STScI) in Baltimore, Md., who proposed the V1 observations. "It's a landmark discovery that proved the uni-verse is bigger and chock full of galaxies. I thought it would be nice for the Hubble telescope to look at this special star dis-covered by Hubble, the man."

But Hubble Heritage team member Max Mutchler of the STScI says that this observation is more than just a ceremonial nod to a famous astronomer. "This observation is a reminder that Cepheids are still relevant today," he explains. "Astronomers are using them to measure distances to galaxies much farther away than Andromeda. They are the first rung on the cosmic distance ladder."

The Hubble and AAVSO observations of V1 were presented at a press conference May 23 at the American Astronomical Society meeting in Boston, Mass. Ten amateur astronomers from around the world, along with AAVSO Director Arne Henden, made 214 observations of V1 between July 2010 and December 2010. They obtained four pulsation cycles, each of which lasts more than 31 days. The AAVSO study allowed the Hubble Heritage team to target Hubble observations that would capture the star at its brightest and dimmest phases.

The observations were still tricky, though. "The star's brightness has a gradual decline followed by a sharp spike upward, so if you're off by a day or two, you could miss it," Mutchler explains. Using the Wide Field Camera 3, the team made four ob-servations in December 2010 and January 2011.

"The Hubble telescope sees many more and much fainter stars in the field than Edwin Hubble saw, and many of them are some type of variable star," Mutchler says. "Their blinking makes the galaxy seem alive. The stars look like grains of sand, and many of them have never been seen before." For Soderblom, the Hubble observations culminated more than 25 years of promoting the star. Shortly after Soderblom arrived at the Institute in 1984, he thought it would be fitting to place a me-mento of Edwin Hubble's aboard the space shuttle Discovery, which would carry the Hubble Space Telescope into space.

"At first, I thought the obvious artifact would be his pipe, but [cosmologist] Allan Sandage [Edwin Hubble's protégé] sug-gested another idea: the photographic glass plate of V1 that Hubble made in 1923," Soderblom recalls. He made 15 film copies of the original 4-inch-by-5-inch glass plate. Ten of them flew onboard space shuttle Discovery in 1990 on the Hubble deployment mission. Fittingly, two of the remaining five film copies were part of space shuttle Atlantis's cargo in 2009 for NASA's fifth servicing mission to Hubble. One of those copies was carried aboard by astronaut and astronomer John Gruns-feld, now the STScI's deputy director.

Prior to the discovery of V1 many astronomers thought spiral nebulae, such as Andromeda, were part of our Milky Way gal-axy. Others weren't so sure. In fact, astronomers Shapley and Heber Curtis held a public debate in 1920 over the nature of these nebulae. During the debate, Shapley championed his measurement of 300,000 light-years for the size of the Milky Way. Though Shapley overestimated its size, he was correct in asserting that the Milky Way was much larger than the com-monly accepted dimensions. He also argued that spiral nebulae were much smaller than the giant Milky Way and therefore must be part of our galaxy. But Curtis disagreed. He thought the Milky Way was smaller than Shapley claimed, leaving room for other island universes beyond our galaxy.

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outer cloud.

The findings might also explain why comets, which form in the frigid outskirts of our solar sys-tem, contain the same type of crystals. Comets are born in regions where water is frozen, much colder than the searing temperatures needed to form the crystals, approximately 1,300 degrees Fahrenheit (700 degrees Celsius). The leading theory on how comets ac-quired the crystals is that ma-terials in our young solar sys-tem mingled together in a planet-forming disk. In this scenario, materials that formed near the sun, such as the crys-tals, eventually migrated out to the outer, cooler regions of the solar system.

Poteet and his colleagues say this scenario could still be true but speculate that jets might have lifted crystals into the collapsing cloud of gas sur-rounding our early sun before raining onto the outer regions of our forming solar system. Eventually, the crystals would have been frozen into comets.

The Herschel Space Observa-tory, a European Space Agency-led mission with im-portant NASA contributions, also participated in the study by characterizing the forming star.

"Infrared telescopes such as Spitzer and now Herschel are providing an exciting picture of how all the ingredients of the cosmic stew that makes plane-tary systems are blended to-gether," said Bill Danchi, sen-ior astrophysicist and program scientist at NASA Headquar-ters in Washington.

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NASA's Spitzer Space Telescope detected tiny green crystals, called olivine, thought to be raining down on a devel-oping star. This graphic illustrates the process, beginning with a picture of the star and ending with an artist's con-cept of what the crystal "rain" might look like. The top picture was taken in infrared light by NASA's Spitzer Space Telescope. An arrow points to the embryonic star, called HOPS-68. The middle panel illustrates how the olivine crystals are suspected to have been transported into the outer cloud around the developing star, or protostar. Jets shooting away from the protostar, where temperatures are hot enough to cook the crystals, are thought to have transported them to the outer cloud, where temperatures are much colder. Astronomers say the crystals are raining back down onto the swirling disk of planet-forming dust circling the star, as depicted in the final panel.

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To settle the debate, astronomers had to establish reliable distances to the spiral nebulae. So they searched for stars in the nebulae whose intrinsic brightness they thought they understood. Knowing a star's true brightness allowed astronomers to calculate how far away it was from Earth. But some of the stars they selected were not dependable milepost markers.

For example, Andromeda, the largest of the spiral nebulae, presented ambiguous clues to its distance. Astronomers had observed different types of exploding stars in the nebula. But they didn't fully understand the underlying stellar processes, so they had difficulty using those stars to calculate how far they were from Earth. Distance estimates to Andromeda, therefore, varied from nearby to far away. Which distance was correct? Edwin Hubble was determined to find out.

The astronomer spent several months in 1923 scanning Andromeda with the 100-inch Hooker telescope, the most powerful telescope of that era, at Mount Wilson Observatory in California. Even with the sharp-eyed telescope, Andromeda was a

monstrous target, about 5 feet long at the telescope's focal plane. He therefore took many exposures covering dozens of photographic glass plates to capture the whole nebula. He concentrated on three regions. One of them was deep inside a spiral arm. On the night of Oct. 5, 1923, Hubble began an observing run that lasted until the early hours of Oct. 6. Under poor viewing conditions, the astronomer made a 45-minute exposure that yielded three suspected novae, a class of explod-ing star. He wrote the letter "N," for nova, next to each of the three objects.

Later, however, Hubble made a startling discovery when he compared the Oct. 5-6 plate with previous exposures of the

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AAL Astronomy Associates of Lawrence

University of Kansas Malott Hall 1251 Wescoe Hall Dr, Room 1082 Lawrence, KS 66045-7582

Celestial Mechanic JUNE 2011

novae. One of the so-called novae dimmed and brightened over a much shorter time period than seen in a typical nova. Hubble obtained enough observations of V1 to plot its light curve, determining a period of 31.4 days, indicating the object was a Cepheid variable. The period yielded the star's intrinsic brightness, which Hubble then used to calculate its dis-tance. The star turned out to be 1 million light-years from Earth, more than three times Shapley's calculated diameter of the Milky Way. Taking out his marking pen, Hubble crossed out the "N" next to the newfound Cepheid variable and wrote "VAR," for variable, followed by an exclamation point. For several months the astronomer continued gazing at Andro-meda, finding another Cepheid variable and several more novae. Then Hubble sent a letter along with a light curve of V1 to Shapley telling him of his discovery. After reading the letter, Shapley was convinced the evidence was genuine. He reportedly told a colleague, "Here is the letter that destroyed my universe." By the end of 1924 Hubble had found 36 vari-able stars in Andromeda, 12 of which were Cepheids. Using all the Cepheids, he obtained a distance of 900,000 light-years. Improved measurements now place Andromeda at 2 million light-years away.

"Hubble eliminated any doubt that Andromeda was extragalactic," says Owen Gingerich, professor emeritus of Astron-omy and of the History of Science at Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. "Basically, as-tronomers didn't know the distance to novae, so they had to make a rough estimate as to where they were and therefore what their absolute luminosity was. But that is on very treacherous ground. When you get a Cepheid that's been reasona-bly calculated, the period will tell you where it sits on the luminosity curve, and from that you can calculate a distance."

Shapley and astronomer Henry Norris Russell urged Hubble to write a paper for a joint meeting of the American Astro-nomical Society and American Association for the Advancement of Science at the end of December 1924. Hubble's pa-per, entitled "Extragalactic Nature of Spiral Nebulae," was delivered in absentia and shared the prize for the best paper. A short article about the award appeared in the Feb. 10, 1925, issue of The New York Times. Gingerich says Hubble's discovery was not big news at the meeting because the astronomer had informed the leading astronomers of his result months earlier. Edwin Hubble's observations of V1 became the critical first step in uncovering a larger, grander universe. He went on to find many galaxies beyond the Milky Way. Those galaxies, in turn, allowed him to determine that the uni-verse is expanding.

Could Hubble ever have imagined that nearly 100 years later, technological advances would allow amateur astronomers to perform similar observations of V1 with small telescopes in their backyards? Or, could Hubble ever have dreamed that a space-based telescope that bears his name would continue his quest to precisely measure the universe's expansion rate?

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