Minnesota Astronomical Society April 2021 a publication of the Minnesota Astronomical Society Volume 47 Number 2 In the pages of Ode to a Restless Few By Dave Tosteson the Gemini In his book Pale Blue Dot, Carl Sagan, in timeless prose, framed an idea about human nature traceable to our origins. Indeed, in regard to understanding Using the Revolution ImagerTM 2 in our current place at the beginning of the solar system’s physical exploration, the Electronically-Assisted Astronomy concept may be its raison d’etre. The author posits that scarcity of resources By Nelson R. Capes…Page 3 coupled with an inherent wanderlust have fostered a need to explore beyond any present boundary. He ventured that in so doing the survival of our ancestors and MAS Patron Members…Page 6 our collective future were enhanced. The strengths of these traits vary among MAS Board Minutes for January/February individuals. Melville’s hero possessed a higher amount of “an everlasting itch By Trena Johnson, Secretary…Page 6 for things remote,” forging a love “to sail forbidden seas.” Roddenberry’s lure of “new life and new civilizations” led his charges to “explore strange new worlds” A Once-in-Three-Lifetimes Chance: and to “go where no one has gone before.” Certain readers may possess and Viewing Supernova SN 1987A develop such impulses to a greater degree. By Daniel Burbank…Page 7 What, exactly, are we seeking? Is it answers about , astrobiology and possible intelligent life on other worlds? Does it go beyond marveling at Creamy versus Crunchy the universe’s beginning or how myriad circumstances formed into the Planetary Nebulae exquisitely habitable world we are so fortunate to occupy? Is satisfaction in By Charles Blilie…Page 8 understanding the origins of the elements, intricacies of continental synthesis Variable of the Month and subtleties of Darwinian evolution enough to assuage our impulses? Will the By Jim Fox…Page 10 eventually hoped for Theory of Everything regarding fundamental forces satisfy an intellectual craving that complements this need for physical exploration? If MAS 2021 Star Party Schedule…Page 11 history is a teacher, it may not. We are a curious people. AL Con Announcement…Page 12 Why do we move from childhood homes? Is it innate or circumstantial? When I visited relatives in Norway just before the turn of the millennium, their society was steering toward a model of personal independence after adolescence and away from a centuries-old tradition of building a nearby separate home on family land. Times change and cycles renew, exemplified when our neighbor recently split his large lake lot and built a separate home so his son and growing family could all share the beautiful setting together. The pandemic, social unrest and the Stories Wanted: Gemini is written entirely by our members, for our members. Gemini needs financial crisis of 2020 caused our daughter to (temporarily?) return home. We your stories: how you first became interested in are enjoying that closeness for however long it lasts. There seem as many reasons astronomy, how your interest has evolved over the to move as there are movers. , equipment you use, projects or activities you have worked on, star parties or events you’ve attended in this state and elsewhere, how you’ve encouraged others—especially young people—to get involved in this fascinating hobby. Submit your stories to [email protected]

E-mail Update: If your e-mail address has recently changed, chances are your address used for MAS e-mail distribution lists is not current. Please inform the e-mail list administrator of your new e-mail address at [email protected] to update your address for the e-mail distribution lists. Also if your e-mail, phone number or street address has recently changed, please fill out the “Update Member Information” Web form at mnastro.org/ update-member-information to update your contact information in the MAS member records. The Eros, Vesta and Ceres in the asteroid belt. There is a difference between traveling for enjoyment or education and GEMINI INFO for exploration. My wife and I brought Editors our children on many domestic and Brian Litecky and Eugene Brown international trips when they were young, Webmaster and we tried to instill in them a love for MAS Web Committee, learning different places and cultures. chair Merle Hiltner, When resources and time are right, [email protected] they may continue that tradition. Some Forums Administrator of those journeys involved physical Russ Durkee exertion, as in hiking mountains, river rafting and viewing wonders in the Great E-mail List Administrator Barrier Reef, but the most lasting benefit Bob Brose seems an opening of the mind. But it is Monthly Meeting Presenter hard to find a place on this planet that has Coordinator not been visited by many people. Witness Ahmed Reda An astronaut on the surface of the the image of climbers waiting their turn Astronomical League Coordinator to ascend Everest, crowded like sardines (ALCOR) on the Hillary Step; or the years-long wait to raft the Colorado River within the Grand Jerry Jones Canyon. In the distant past being first could have been sparked by something as simple as, “I wonder what’s on the other side of that river?” or “That valley looks as though Outreach Coordinator it could offer protection and food.” It’s almost impossible to be first anymore, at least Lilah Blinkman in regard to finding places on this orb. At some point our planet’s resources will not Gemini is published 6 times annually support its population. We will run out of Planet Earth, so we may need to run off it. by the Minnesota Astronomical Society. We will need space to live and so may need Space to live. Electronic submissions for Exploration that is culturally applicable is different from traveling. Though it can Gemini may be sent to: also be personal, it must involve enlarging a boundary affecting many people. As an [email protected] intentional act, its resultant diaspora of ideas encouraging societal change may be necessary for the continuation of our species. This was Sagan’s eloquence. Though he Hardcopy items should be sent to: Minnesota Astronomical Society was not the first to think of it, he may have said it best: “The appeal, I suspect, has been Attn: Gemini meticulously crafted by natural selection as an essential element in our survival.” He P.O. Box 14931 then states that, because all resources are limited, the future of our species “might be Minneapolis, MN 55414 owed to a restless few, drawn by a craving they can hardly articulate or understand, to undiscovered lands and new worlds.” There is a broader impact to exploration. The effect on the collective imagination MAS Board Members may awaken latent interest in those needing a spark to ignite a fire they only suspected could be lit. Not all can lead, but many can be inspired. A sown seed must be tended, President: Mark Job and followers in any movement of change are tasked with making work what has been E-Mail: [email protected] shown possible. The framework of the future is made of many parts, the importance of Vice President: Valts Treibergs which can rarely be predicted. E-Mail: [email protected] Consider all the advancements of the last one- Treasurer: Matt Dunham hundred years. Relativity, E-Mail: [email protected] quantum mechanics, the Secretary: Trena Johnson expanding universe, dark E-Mail: [email protected] matter, black holes, pulsars, gravitational lensing, planetary Board Member at Large: exploration and dark energy Gunnar Isberg are just the top of the iceberg E-Mail: [email protected]. of knowledge added through Board Member at Large: the creativity and hard work of Conrad Sanders thousands of celestial pioneers. E-Mail: [email protected] I consider my visual observing as a kind of exploration: expanding the limits of what can be seen and constantly incorporating new finds into that fold. I am inspired by what astronomers have done, and I

The Planet Mars. Photo by NASA GEMINI • www.mnastro.org 2 have found that viewing them greatly increases their meaning How will this age be remembered? I hope it is for our joy of and realness. In this pursuit I have learned of many remarkable exploration and the revelation of beauty uncovered that formed things discovered by professionals and amateurs and have and surrounds us. Will unborn generations be inspired by what enjoyed sharing them with others through the eyepiece, writing we have done? The next Magellans, Armstrongs and Sagans and speaking. Brown dwarfs, gravitational lenses, extragalactic may find, in the footsteps of our wanderings, reasons to dedicate supernova remnants, jets from supermassive black holes, high- themselves to what we will all soon need. redshift quasars and even in the Hubble Deep Field are Curiosity inspires. Imagination sustains. all visible in our telescopes and thrilling to see. They are marker buoys on an ocean of hard-won understanding, anchor points from which future voyages may embark.

Astronaut on an untethered space walk

Using the Revolution ImagerTM 2 in As everyone who lives in the Twin Cities metro area knows, Electronically-Assisted Astronomy finding a spot with a dark sky is essentially impossible. Also, By Nelson R. Capes our weather is frequently cloudy. In my opinion, any setup has to be completed within 10 to 15 minutes. There has been many a Electronically Assisted Astronomy (EAA) has been my prime time when the sky is clear, but by the time I am ready to observe, focus for the last couple of years. Perhaps there is no generally clouds have arrived. It is bad enough when this happens on my agreed upon definition of EAA, but the following is helpful: deck, but I do not have the patience to drive to a dark-sky site, go In general, though, the application of any sort of through setup, and then have clouds arrive. technological aid for the enhancement of astronomical viewing I also want to be able to show some great targets to family falls under the EAA umbrella. Devices such as light intensifiers and friends who have a hard time learning to view through an and video cameras both fit into this category. The purpose of the eyepiece with even a lot of relief. With these objectives, I have technological aid is either to increase the observable detail over explored two of many possible EAA setups. what’s possible with a conventional eyepiece, or in some cases to The first setup was to use a ZWOTM ASI290MM Mini camera make it possible for those with vision problems to see anything R at all.1 connected by USB to a laptop computer running Windows and the SharpCapTM image-processing software. However, that This definition captures the two reasons why I got into particular camera’s CMOS chip has a very narrow field of view, EAA about two years ago. First, my home is in one of the making it very difficult to acquire an object even after a very St. Paul suburbs—a Bortle 8 zone. Light in the western sky accurate GoTo. Having to use a computer complicates the setup. from Minneapolis is the major cause of light pollution in my Although the keyboard is backlit, it is obviously necessary to type neighborhood. Fortunately, I live on a cul-de-sac with essentially without gloves, which is a problem in the winter. Furthermore, zero night-time traffic, and the deck faces a small pond, so that in my opinion the SharpCapTM software is far from being easy- ambient light pollution is minimal. Nevertheless, it is next to to-use. After acquiring the object, one has to play with the impossible with the unaided eye to see the outlines of the major histogram to get the proper combination of light and dark and , let alone any but the brightest and a few ideally would have to take a number of dark frames and apply bright asterisms like the Pleiades. them to the captured image. I have even had difficulty getting the My telescope is a Celestron 9.5'' Evolution on an alt-azimuth software to stack frames because it does not see enough stars to computer-controlled mount, thus making it relatively simple to do an alignment. I am sure that others with a larger budget for a “GoTo” a target such as M42 (the Orion ). With a 40mm camera and the time to spend learning SharpCapTM will disagree, Plössl eyepiece at f/6.3, the nebulosity is visible, but it completely but for me this setup did not meet my objectives of quick and lacks detail. I wanted to see more. easy setup. Consequently, I never use this setup anymore. 1 Jim Thompson, “An Introduction to Electronically- My preferred setup is a Revolution Imager™ 2 kit Assisted Astronomy,” https://astronomyconnect.com/ from Orange County Telescope, 2216 N. Main St., Santa Ana, forums/articles/an-introduction-to-electronically- CA 927-6, https://www.revolutionimager.com. The kit is neatly assisted-astronomy-eaa.77/. packaged in an expandable case. I have used my kit a lot, so I cannot show the original packaging, but Fig. 1 shows my kit.

3 April 2021 Fig. 1. Upper compartment: cables, battery, remote control. Lower compartment: monitor, stand, camera (in bag). The kit contains the following components, as shown Fig. 3 Monitor on home-made stand, battery, hand control. in Fig. 2.

Fig. 2. From left to right. Top row: 0.5 focal reducer, analog Fig. 4. Cables from monitor and hand control attached to camera with attached hand control, battery, 7'' color camera, which is inserted in diagonal in place of an monitor. eyepiece. The following figures show the equipment attached The kit also includes a battery charger and the necessary to my telescope. cables for connecting the camera to the monitor and the battery to both the monitor and the camera. The imager is quite easy to set up. Just remove the eyepiece from the diagonal, insert the 1¼-inch diameter camera nosepiece with the optional 0.5 focal reducer. Connect the hand control and cable from the camera to

GEMINI • www.mnastro.org 4 the monitor. Connect the battery to the monitor and camera. The whole process takes about five minutes. Although the setup is simple, capturing an image is more complicated. The supplied analog camera has a very narrow field of view (data is not supplied for this). It is therefore necessary to attach some kind of focal reducer (at least with an f/10 telescope). One can use the supplied 0.5 focal reducer. My preference is to use the Celestron 0.63 focal reducer that attaches to the visual back of the telescope and is therefore usable both for visual and for EAA astronomy. Normally, the accuracy of a GoTo (at least with my telescope) is not enough to center the target in the FOV of the eyepiece (and therefore, of the camera). My procedure is to find a moderately bright star nearby the target, get the star accurately centered in M44 (Beehive Cluster) the eyepiece field of view and accurately focused. My focuser is a Celestron electronic focuser that allows quite precise control of focusing. I have not found that a Bahtinov mask is necessary. I then replace the eyepiece with the camera, which will cause the star to be out of focus and over-amplified but easily visible on the monitor. It will probably be necessary to reduce the amplification. I then focus as accurately as possible on the star. The next step is to do a GoTo on the target. At this point it is necessary to increase the amplification of the camera to allow the target to be visible on the monitor. Usually the object will become visible as the amplification is gradually increased but will not be centered on the monitor, so it will be necessary to use the arrows on the telescope hand control to center the object. It may also be necessary to make some slight adjustment to the focus. Once M13 (Hercules Cluster) all this is done, which may take 10 to 15 minutes, I have found that the tracking capability of the telescope is accurate enough to keep the target visible in the monitor for as long as 15 minutes. I now have (hopefully) a reasonably satisfying image that I can show to others. The usual reaction is awe. A few photos taken of the monitor screen with my smart phone and then enhanced slightly on the phone are shown here. Obviously, these images are not of the quality that would be achieved by using an equatorial mount and guiding continuously for many hours. However, my objectives of quick setup and allowing the user to see something of deep-sky objects even in a light-polluted environment have been achieved. Note: I have purposefully not gone into detail on how to use the Revolution Imager hand control to set the amplification M31 (Andromeda ) and stacking of the camera. These details are available from the seller’s website , https://www.revolutionimager.com.

M42 (Orion Nebula) M57 (Ring Nebula) 5 April 2021 MAS Patron Members Patron memberships are available to those who wish to contribute a little extra to support MAS activities. Patron memberships are established by constitution at 2-1/2 times the Regular membership rate—currently $65 annually for a patron membership. The $39 additional contribution is tax deductible. Patron memberships help fund equipment acquisitions, facility improvements, outreach activities and more. We would like to thank the following patron members as of March 1. Femi Abodunrin Dave Eckblad Greg Hokanson Robert Miller Kristopher Setnes Tom and Arlene Alm Steve Emert Michael Hopfenspirger Scott Morgan Mike Shaw Scott Anderson Kevin Engebretson Ken Hugill Bradley Nasset Jeff Shlosberg Jack Atkins Maram Falk Chris Hunt Brian Nelson Bernie Simmons Steve Baranski David Falkner Ron Hunt Douglas Nelson David Sjogren Greg Baril Robert Farrell Dick Jacobson Jacquelyn Nelson Dennis Sjogren Bradley Beisel Cody Feigum Bharathi Jagadeesan Brady Nesvold Eric Smestad Denise Beusen Allan Ferber Gale Jallen Doug Neverman Andrew Smith Scott Billeadeau Patricia Flugaur Len Jannusch Kenneth Nicholls Katherine Sproll Lilah and Chris Blinkman Robert Foucault Mark Job Tracy Niebeling Kegan Stewart Wayne Boline Andrew Fraser Julie A. Y. Johnson Douglas Oines Bernie Stinger Natalie Broshar Alan Fuller Kurt Johnson Thor Olson Jack Storms Rev. Eugene Brown Paul Gade Trena Johnson Christopher Paola Peter Sullivan Jay Bruesch Jim Gerrity Jerry Jones Joel Papa Tony Thomas Donald Bryan Gregory Gibbons Michael Kauper JJ Plude David Tosteson Stephanie Bue William Glass Bob Kerr Becky Pollack Valts Treibergs Jeff Bullard Martin Godfrey Kenneth Kerrick Chris Polston David Truchot Jonathan Burkhardt Bradley Gordon Sam Khoroosi Aaron Raines Iakovos Tsoukalas Jeff Burrows Martin Gormanson Michael Knowlen Ahmed Reda Hayden Uihlein Earl Bye Steven Grabarkiewicz Jim Knudsen Michael Regouski Steve Ulrich Bill Bynum Antone Gregory Bill Kocken Chaz Rice Bob Vangen Larry Cain Jere Gwin-Lenth David Kocken Stephen Riendl Paul VanNorman Craig Carlson Dale Hagert Shremattie Kokotovich Eric & Rebecca Robinson Balaji Vatsavaya Ken Carlson Jake Hairrell Robert Kowalski Luigi Romolo Lawrence Waite Kurt Casby Nina Hale Parke Kunkle John Rosenberg Joel Waldfogel Stuart Chastain Eric Hall Michael Kutzke James Rowan Paul Walker Mary Chilvers Brandon Hamil Greg Larson Derek Rucker Craig Weinert Cara Clark James Hannon Christine Laughlin Daniel Ruh Mary Williams Deane Clark Ryan Hanson Louis Leichter Theodore Sadler Robert Williams Bruce Coleman Andrew Harwood Michael Lilja Jack Sandberg Neil Worthingham Mark Connolly Greg Haubrich Clayton Lindsey Roy Cameron Sarver Robin Wright Michael Daniels Michael Haydock Edward Malinka James Schenz Gene Yates Gary Davis Jonathan Hayman John Marchetti Ronald Schmit John Zimitsch Mary Beth Smith & Ted Kale Hedstrom Bruce McDonald Steven Schmitt Mark Zimitsch DeMatties Victor Heiner Duane McDonnell Anna Schoeneberger Neal Zimmerman David Dennis Angela Heins Family Zach McGillis Loren Schoenzeit Mark Dietzch John Hill Javier Medrano David Schultz Thomas Dillon Merle Hiltner Rebecca Messer Erica Scott Molly Duffin Lauren Hoen Matt & Jessica Meyer Jon Seilkop Matt Dunham Nadia Hoffman Gerald Miller Collin Semb MAS Board Minutes for January/February February By Trena Johnson, Secretary Attended: Mark J., Valts T., Matt D., Trena J., Conrad S., Gunner I., Jon H., Suresh S., Steve E., Doug S. Membership is January at 609. Site Reports. JJC: Please let us know how the Wi-Fi is Attended: Mark J., Valts T., Matt D., Trena J., Conrad S., working if you have been out there. Metcalf: The committee is Gunner I., Merle H., Dave F. Membership is at 580. Site Reports: exploring options to restore AC power prior to B-SIG events, but JJC-Metcalf: With the assistance of the St. Paul Public School it may be a while. April 24th is the first B-SIG. Check the forum network department, Muska Electric, Belwin staff Josh Leonard, for location, Metcalf or ELO. ELO: Doug presented options to and Merle H. (MAS) Wi-Fi has been extended to the observatory update our cell service/alarm/voicemail. Gunner and Doug will via an underground Ethernet cable. The computer now has a work with Merle on configuring this update. No changes are direct Ethernet connection. Other sites are stable and there are no noted from the other sites. Website/Forum Updates: MAS has updates. Constitution Committee: We welcome Dave Falkner a SLACK site. Many members used it for last ’s Messier as the Constitution Committee chairperson. A YouTube Channel Marathon. We are looking to use this resource as forum posts for the Minnesota Astronomical Society has been created: https:// for ISPs. Bids were requested from four companies with only www.youtube.com/channel/UCs0pH1unWJMOKACuj7RZdIQ. one response to update/create a new website/forum/email Please send new content to [email protected] consolidation. The board reviewed and approved Neuger to start working on this project. It was also noted that 2022 will be the 50th anniversary of MAS.

GEMINI • www.mnastro.org 6 A Once-in-Three-Lifetimes Chance: We returned to Australia, to Melbourne. South of Melbourne Viewing Supernova SN 1987A is Phillip Island. We stayed two nights at Cowes. There I was By Daniel Burbank able to observe the supernova (between clouds). On the night of March 1, I recorded these observations on the back of the Cowes In February 1987 I had the good fortune to embark on a three Anchor Motel room-service menu: week “vacation trip of a lifetime” to Australia and New Zealand with my wife, Kathy, and our kids—Jeff, age 2, and Laura, age 4. Traveling across the Pacific with two small children would have been inconceivable were it not for the fact that Kathy is a planning and packing ninja. Jeff was still in “nappies,” as they are referred to in that part of the world. We flew to Cairns, in Queensland (on the northeast coast of Australia), toured our way to Brisbane by way of the Great Barrier Reef, then flew to Auckland, New Zealand. From there we rented a car, toured north and south islands, and stayed a few days in Christchurch. From Christchurch we flew back to Melbourne, stayed there a few days, and flew back home to Minnesota. As expected, traveling with small children required frequent stops at local parks and playgrounds to let them run off steam. This was a great opportunity to strike up conversations with local people who were doing the same with their own kids. As an amateur astronomer who had never seen the southern sky, I brought along star charts and binoculars, and (uncharacteristically for that point in my life) actually took some notes. This was a good thing, as while we were vacationing in the southern hemisphere a naked-eye supernova appeared in the in the . Before 1987, there had been four naked-eye supernovae in the previous 1,000 years, implying that my chance of seeing one in my roughly 80-year life expectancy was about one in three. So my “once-in- a-lifetime” vacation trip had become a “once-in-three-lifetimes” chance of seeing a supernova. My estimate of the supernova’s visual magnitude as “visually My first opportunity to see the southern sky was in Cairns brighter than Delta Doradus” (magnitude 4.3) agreed fairly well about February 11 in the early morning. I walked out behind with the European Space Agency’s light curve for SN 1987A. our motel, in the parking lot, with binoculars. I was able to see March 1 was about six days after SN 1987A’s appearance. Carina and the Southern Cross, but all in all, observing from Cairns wasn’t that great due to clouds and city lights. In New Zealand, the first place we stayed was Rotorua. Again, the weather did not cooperate. We worked our way south to Wellington, where I missed observing at a public observatory night at the Carter Observatory in the Botanical Gardens by about one week. (The program was held during the fall and winter). Nevertheless, I was invited to poke around the observatory. We were staying across the street from the botanical garden at the Sarella motel. We crossed over to the south island on February 21 and stayed several nights in Nelson. Here my luck improved. I was able to walk a couple blocks to a playing field to get away from lights, and the sky was beautifully clear. I could see the LMC and SMC naked eye (The supernova occurred on February 24 UT or early morning on February 25 NZ time.) It was particularly interesting to see familiar constellations in unfamiliar orientations and places. Orion was standing on its head in the north. Canis Major and Canopus in Carina were directly overhead, and the Pleiades were just 5 degrees off the northern horizon. The southern Milky Way is quite spectacular. The Carina and Southern Cross areas were full of star clusters and nebulosity visible in binoculars. A light curve for SN 1987A. We then trekked to Christchurch, where we stayed for three Source: https://cdn.eso.org/images/large/eso0708c.jpg nights. I contacted Lionel Hussey, president of the Christchurch astronomy club. He offered to have me over to his house to look at some southern stars. However, we were clouded out. 7 April 2021 At the time, I didn’t appreciate what a big deal a “nearby” into space. As SN 1987A was brightening, neutrino researchers (170,000 light years) supernova is for astronomy. A newspaper scoured neutrino counts from their detectors. Two neutrino article in The Weekend Australian provided my first insight into detectors registered a pulse at 7:35 UT on February 23, hours the importance of this event for advancing astrophysics. See the before the first observable brightening of the progenitor star, bold-face text in lower right, next to the photo of the supernova’s later determined to be the blue giant Sanduleak-69 202. location in the Large Magellanic Cloud. Although the Hubble space telescope wasn’t launched until 1990, as soon as it became operational it was used to image (at sub-arcsecond resolution) the interaction of the light pulse from the supernova explosion with the spherical clouds of gas and dust released by the progenitor star prior to the explosion. The time delay to light up these clouds multiplied by the speed of light provides and accurate yardstick for the physical diameter of the cloud features. Knowing the physical diameter and the angular diameter of the illuminated clouds from Hubble enabled a much more accurate determination of the distance to the Large Magellanic Cloud. Many other aspects of this interaction enabled greatly improved models for Type II supernovae.

A very readable account of the many discoveries that resulted from SN 1987A can be found on Wikipedia (https:// en.wikipedia.org/wiki/SN_1987A). The reason SN 1987A has been so important is that it was the first nearby core-collapse, or Type II, supernova that modern astronomers were able to study in great detail. For starters, by 1987 physicists had built several types of neutrino detectors. Theoretical models of a supernova explosion posited that as the last energy-yielding fusion processes end in the core of a massive star (e.g., 20x the mass of the ), radiation pressure would no longer be sufficient to keep gravity from compressing protons and electrons into neutrons and An image of the illuminated gas ring surrounding SN 1987A neutrinos. The rapid collapse leads to the eventual formation Source:https://www.spacetelescope.org/images/ann1111a/ of a neutron star, releasing such stupendous energy so quickly To summarize, I feel pretty lucky to be living in this age of that the resulting shock wave blows the outer layers of the star discovery!

Creamy versus Crunchy Planetary Nebulae By Charles Blilie Years ago, when I got my first decent telescope, among the first deep-sky objects I pointed it at were the Ring Nebula (M57) in Lyra and the Dumbbell Nebula (M27) in Vulpecula. Most readers will be familiar with these. The Ring Nebula, in the eyepiece of a small telescope, looks like a perfectly symmetric smoke ring. The Dumbbell Nebula, in contrast, is irregular and looks sort of like a dumbbell, but in a larger telescope it looks more like a ragged butterfly. Astronomers classify both of these objects as planetary nebulae—so called because they were often mistaken for new planets. Two other Messier objects, the Little Dumbbell Nebula (M76) and the Owl Nebula (M97) are also planetaries; the former is irregular in shape like M27 and the latter is regular like M57. The fact that only four of the Messier objects are planetary nebulae indicates their relative rarity. Some prominent planetaries, such as the Helix Nebula (NGC 7293) in Cat’s Eye Nebula Aquarius, are not in the Messier catalog, either because Messier So here is the question: How is it that M57 can be so perfectly did not see them or because of their southern . symmetric and smooth, while M27 is irregular and structured? GEMINI • www.mnastro.org 8 To make an analogy with peanut butter, why are there “creamy” of the stellar winds; this has been simulated in computer models. and “crunchy” planetary nebulae? Over the past few decades, First of all, as the central star heats up, the stellar winds speed astronomers have made great strides in solving this problem. up, so changes in the of the star are reflected in changes in the nebula, leading to multiple gas shells. Second, the material ejected from the dying star apparently does not come out in a uniform sphere but is often concentrated in jets. This explains the bipolar structure of the Dumbbell Nebula and many other irregular planetaries. To use a bubble-blowing analogy, a “creamy” planetary like the Ring Nebula is one nice round bubble, while a “crunchy” planetary is like a cluster of bubbles. This can be seen in the Cat’s Eye Nebula (NGC 6543) in Draco, although the multiple shells are distinctly visible only in a large telescope. Third, very irregular planetaries may result from binary star systems; this appears to be the case with the Cat’s Eye Nebula. Finally, “creamy” symmetric planetaries may be older than their “crunchy” siblings; the irregularities are washed out as the nebula expands and the various shells merge together. M27 (Dumbbell Nebula) What is a ? Essentially, it is an expanding shell of hot gas thrown off by a dying star. A large star—like Rigel, Deneb, Antares and many other of the first-magnitude stars—will die violently in supernova explosions. But a medium- sized star, like our own Sun, has a quieter destiny. It will expand into a red giant, and then—as the core of the star heats up—will drive away its own atmosphere. The superhot (often over 100,000 degrees ) stellar core ionizes the expanding cloud, which makes the gas shell visible to us. The central star of the planetary nebula is visible only in large telescopes. Eventually, the shell dissipates into interstellar space, leaving behind the stellar core, which cools to become a white dwarf. A planetary nebula is, in astronomical terms, a very short-lived thing, existing for perhaps 10,000 years: it is the transition of a red giant into a white dwarf. This may explain their rarity among deep-sky objects. M57 (Ring Nebula). Photo by NASA We can also understand the differences between “creamy” and “crunchy” planetaries in a rough analogy to the weather. The National Weather Service has an informative page on space weather (https://www.swpc.noaa.gov/) that describes the current conditions of the solar wind and emissions on Earth. If we could measure the space weather within a planetary nebula, the winds would be blowing ever outwards from the central star. For a “creamy” planetary, the winds blow steadily in all directions, perhaps rising over time. But in the “crunchy” planetary, we would experience much more stormy and turbulent space weather. That storminess is reflected in the structure of the nebula.

M27 (Dumbbell Nebula) The model of a planetary nebula as an expanding gas shell lit up by its central star makes it easy to understand “creamy” planetaries like the Ring Nebula. But how do astronomers explain the “crunchy” planetaries? Every star has stellar winds, a stream of material expelled from the stellar surface. For a smallish main-sequence star like the Sun, the stellar wind carries away only a negligible amount of the . But the reverse is true for dying red giants; for them, the winds carry away 50% to 70% of the star. As it turns out, the structure of the “crunchy” M57 (Ring Nebula) planetaries can be explained by the variability and asymmetries

9 April 2021 Variable Star of the Month May – By Jim Fox A variable that you can see this month is V Hydrae in the constellation of the Sea Serpent. Though often bright Editor’s Note: There will be two Variable Star of the Month enough to be seen naked eye from a dark sky site, it is easily entries for each issue of Gemini in 2021. spotted in binoculars, about five degrees south of rd3 magnitude April – R Leonis Nu Hydrae, due to its deep, cherry-red color. This star was known Many, if not most, of the stars we see change brightness over for its very red color even before S.C. Chandler of Harvard periods of time for various reasons. Sometimes a star can dim, announced its variability in 1888. As a semi-regular variable, it brighten and dim again in less than a second. Other stars can take pulsates between magnitudes 5.4 and 8 with a period of about years to complete a cycle of brightness variation. These stars are 530 days. This period is superimposed on a longer period of 18 called “variable stars.” years, where the brightness may drop to magnitude 12, probably One variable star that you can see this month is R Leonis, due to a surrounding disc of obscuring matter. the first variable star identified in the constellation Leo the Lion. The cool red giant V Hydrae is a member of a rare class of When discovered by J.A. Koch of Danzig in 1782, it was only stars known as “Carbon Stars.” This class is so-called because the fourth long-period variable known. You can make your own of the relatively high concentration of carbon in the star’s discovery by looking five degrees (about one binocular field) atmosphere. This excess of carbon is the reason for its deep-red west of the bright star Regulus. R Leonis will be a scarlet-colored color. star forming a small triangle with two nearby yellow stars. Though V Hydrae is not visible naked eye, astronomers have R Leonis is a red that has a radius about the size of observed high speed outflows of material jets. Dubbed “bullets,” the orbit of Mars and is near the end of its life. It varies between these ejections occur every 8.5 years and are thought to be caused magnitude 5 and magnitude 11 over a period of about 310 days. by close approach of a dim companion star in a very elongated Because of low , the outer atmosphere is loosely orbit. bound, forming a shell around the stellar core. Pulsations within the core are believed to send shock waves through this shell, causing the star to vary in brightness. A similar fate may await our Sun but not for another five billion years. For more than 100 years, the American Association of Variable Star Observers (AAVSO) has encouraged the observation and study of variable stars, maintaining databases of all submitted observations. Observing techniques include both visual and photometric (CCD/CMOS, DSLR and photoelectric) and now even spectroscopic. For more information on AAVSO and how you can contribute to astronomical science through variable stars, visit their website at https://www.aavso.org This finder chart for R Leonis will help you estimate its brightness. The image is not inverted, so it is suitable for binoculars. R Leonis is the highlighted circle and magnitudes are in tenths with the decimal point omitted so as not to be confused with a star. So, 50 = 5.0.

This finder chart for V Hydrae will help you estimate its brightness. The image is not inverted so it is suitable for binoculars. V Hydrae is the highlighted circle and magnitudes are in tenths with the decimal point omitted so as not to be confused with a star. So, 52 = 5.2. Chart is courtesy AAVSO.

Chart is courtesy AAVSO.

GEMINI • www.mnastro.org 10 Minnesota Astronomical Society 2021 Star Party Schedule Twilight Completely dark Moon % ELO Public Cherry LLCC Friday Date Sunset ends: from: to: Illuminated Night (Saturday) Grove Weekend Notes March 12 06:17 PM 07:51 PM 07:51 PM 04:50 AM 0% X Messier Marathon Primary weekend CALLED ON/OFF March 20 07:21 PM 09:02 PM 02:53 AM 05:35 AM 41% X Saturday April 3 07:44 PM 09:23 PM 09:23 PM 03:09 AM 58% X Saturday – Venus returns to evening April 9 07:51 PM 09:32 PM 09:32 PM 04:52 AM 6% X X Messier Marathon Secondary weekend April 16 08:00 PM 09:44 PM 12:45 AM 04:38 AM 18% X X April 17 08:01 PM 09:46 PM 01:42 AM 04:35 AM 26% X X Saturday: merc returns to the evening May 1 08:18 PM 10:11 PM 10:11 PM 01:57 AM 74% X Saturday: 3rd quarter May 7 08:25 PM 10:23 PM 10:23 PM 03:53 AM 15% X X Virgo Venture May 14 08:33 PM 10:36 PM 11:37 PM 03:39 AM 8% X X May 15 08:35 PM 10:38 PM 12:30 AM 03:37 AM 14% X X Saturday: Astronomy Day May 29 08:49 PM 11:03 PM 11:03 PM 12:37 AM 87% X Memorial Weekend – Ven, Merc June 4 08:54 PM 11:12 PM 11:12 PM 03:08 AM 28% X June 11 08:58 PM 11:20 PM 11:20 PM 03:02 AM 2% X X June 12 08:59 PM 11:21 PM 11:21 PM 03:02 AM 5% X X X Saturday June 26 09:02 PM 11:25 PM Never dark 96% X Saturday July 2 09:01 PM 11:22 PM 11:22 PM 01:42 AM 42% X X July 9 08:59 PM 11:15 PM 11:15 PM 03:19 AM 0% X X July 17 08:54 PM 11:04 PM 01:05 AM 03:02 AM 50% X Saturday: Pluto opposition July 31 08:39 PM 10:39 PM 10:39 PM 12:28 AM 50% X X Saturday: Saturn opposition August 6 08:31 PM 10:26 PM 10:26 PM 04:08 AM 3% X X August 13 08:21 PM 10:21 PM 11:09 PM 04:21 AM 29% X CWTS: 8/13, 14, 15 August 28 07:57 PM 09:39 PM 09:39 PM 10:54 PM 66% X Saturday: opposition September 1 - 7  This is the proposed time, LLCC has not totally signed off on the date yet. NNSF at LLCC September 3 07:46 PM 09:26 PM 09:26 PM 03:31 AM 11% X X September 10 07:33 PM 09:11 PM 09:38 PM 05:06 AM 17% X X September 11 07:31 PM 09:08 PM 10:09 PM 05:08 AM 26% x X Saturday: Neptune opposition September 25 07:05 PM 08:40 PM 08:40 PM 09:21 PM 80% x Saturday October 1 06:54 PM 08:28 PM 08:28 PM 02:19 AM 23% X X October 8 06:41 PM 08:15 PM 08:15 PM 05:43 AM 7% X X MAS Mini-Messier Marathon (4M) CALLED ON/OFF October 9 06:40 PM 08:13 PM 08:43 PM 05:44 AM 14% X X Saturday: Fall Astronomy Day October 23 06:16 PM 07:51 PM 07:51 PM 07:51 PM 92% X Saturday October 29 06:07 PM 07:42 PM 07:42 PM 01:09 AM 40% X November 5 05:58 PM 07:34 PM 07:34 PM 06:16 AM 1% X X November 6 05:57 PM 07:33 PM 07:33 PM 05:18 AM 5% X X Saturday: Uranus opposition November 26 04:39 PM 06:19 PM 06:19 PM 11:02 PM 57% X X Directions to the Star Party Locations

For maps and further details about the sites, please go to our website at www.mnastro.org/facilities. Eagle Lake Observatory at Baylor Regional Park 10775 County Road 33, Norwood-Young America, MN Cherry Grove Observatory 18781-18861 520th St, Kenyon, MN 55946 Joseph J Casby Observatory at the Belwin Conservancy 1553 Stagecoach Trail S, Afton, MN 55001 Metcalf Field - aka: Metcalf Nature Center Latitude: 44.93734, Longitude: -92.82157 Long Lake Conservation Center 28952 438th Ln, Palisade, MN 56469

11 April 2021 MN ASTRONOMICAL SOCIETY P.O. Box 14931 Minneapolis, MN 55414 a publication of the Minnesota Astronomical Society

How to pay your dues April 2021 Volume 47 Number 2

Your MAS membership expires at the beginning of the month shown on your membership card. You will be notified of your renewal by e-mail two months prior to expiration and by USPS mail the month of your expiration. You may renew by mail or online using PayPal. By mail: Send your payment to the MAS membership coordinator at: Minnesota Astronomical Society, Attn. Membership coordinator, P.O. Box 14931, Minneapolis, MN 55414. Make checks payable to MAS. Current annual membership rates when paying by check are: $26 regular, $13 student, and $65 for patron memberships. You may renew for one year or for two years at a time. Online using PayPal: PayPal charges a fee, so MAS includes a voluntary contribution in the PayPal membership rates to offset that fee. Membership rates using PayPal are $27.50 regular, $13.75 student and $67.25 patron. The membership form and the procedure for joining or renewing using PayPal may be found at www.mnastro.org/members/join/. Sky and Telescope and Astronomy Magazine Subscriptions

MAS members are offered subscriptions to these magazines at an astronomy club discount. Regular Sky & Telescope subscriptions are $54.95 annually. S&T offers astronomy club discount print + digital subscriptions for $43.95 annually. To renew your subscription, go to www.skyandtelescope.org/clubrenew and fill out the web form, paying online using your credit card. For new subscriptions go to www.skyandtelescope.org/clubspecial If you wish to call instead, call S&T customer service at 800-253-0245 and tell them you are a member of MAS. If you wish to pay by check instead of by credit card, you can ask the customer service rep to send you an invoice in the mail. Astronomy magazine regular print subscriptions are $44.95 annually. The Astronomy magazine club discount print or digital subscription is $34 for one year, $60 for two years, or $83 for three years. To subscribe or to renew your current subscription at the astronomy club discount rate, go to www.astronomy.com/clubmember and fill out the web form, paying online using your credit card. You have the choice of a print-only subscription or a digital-only subscription at the above prices, or you can choose a print + digital subscription for $46.00 (one year), $84.00 (two years), or $119.00 (three years). You can also call the Astronomy magazine customer service toll-free number at 1-877-246-4835 to subscribe.

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The MAS uses Web discussion forums and e-mail distribution lists for timely communications. We highly recommend that you subscribe to both the Web forums and the MAS general distribution e-mail list. To join the MAS Web discussion forums, visit mnastro.org/Explore/Discussion Forum and click Register and complete the online registration form. To subscribe to the MAS e-mail list, visit lists.mnastro.org and click on the MAS list link and follow the subscription instructions. There is a general list (MAS), an outreach list and lists for other special purposes.

ALCon Announcement year. In late July or early August, ALCon 2021 will be held virtually, featuring speaker presentations as well as the annual Youth and Recognition award presentations. Complete details John Goss, Astronomical League past president and now AL are still being developed and will be announced at a date in the media officer, sent this message to Jerry Jones: not too distant future. Because of the uncertainty caused by the pandemic, the The Albuquerque Astronomical Society (TAAS) is now Astronomical League will not hold an in-person ALCon this scheduled to host ALCon 2022 instead of 2021.

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