NASA Space Place – Twinkle, Twinkle, Variable Star

Poster’s Note: One of the many under-appreciated aspects of NASA is the extent to which it publishes quality science content for children and Ph.D.’s alike. NASA Space Place has been providing general audience articles for quite some time that are freely available for download and republishing. Your tax dollars help promote science! The following article was provided for reprinting in September, 2014.

By Dr. Ethan Siegel

2013february2_spaceplaceAs bright and steady as they appear, the stars in our sky won’t shine forever. The steady brilliance of these sources of light is powered by a tumultuous interior, where nuclear processes fuse light elements and isotopes into heavier ones. Because the heavier nuclei up to iron (Fe), have a greater binding energies-per-nucleon, each reaction results in a slight reduction of the star’s mass, converting it into energy via Einstein’s famous equation relating changes in mass and energy output, E = mc2. Over timescales of tens of thousands of years, that energy migrates to the star’s photosphere, where it’s emitted out into the universe as starlight.

There’s only a finite amount of fuel in there, and when stars run out, the interior contracts and heats up, often enabling heavier elements to burn at even higher temperatures, and causing sun-like stars to grow into red giants. Even though the cores of both hydrogen-burning and helium-burning stars have consistent, steady energy outputs, our sun’s overall brightness varies by just ~0.1%, while red giants can have their brightness’s vary by factors of thousands or more over the course of a single year! In fact, the first periodic or pulsating variable star ever discovered—Mira (omicron Ceti)—behaves exactly in this way.

There are many types of variable stars, including Cepheids, RR Lyrae, cataclysmic variables and more, but it’s the Mira-type variables that give us a glimpse into our Sun’s likely future. In general, the cores of stars burn through their fuel in a very consistent fashion, but in the case of pulsating variable stars the outer layers of stellar atmospheres vary. Initially heating up and expanding, they overshoot equilibrium, reach a maximum size, cool, then often forming neutral molecules that behave as light-blocking dust, with the dust then falling back to the star, ionizing and starting the whole process over again. This temporarily neutral dust absorbs the visible light from the star and re-emits it, but as infrared radiation, which is invisible to our eyes. In the case of Mira (and many red giants), it’s Titanium Monoxide (TiO) that causes it to dim so severely, from a maximum magnitude of +2 or +3 (clearly visible to the naked eye) to a minimum of +9 or +10, requiring a telescope (and an experienced observer) to find!

Visible in the constellation of Cetus during the fall-and-winter from the Northern Hemisphere, Mira is presently at magnitude +7 and headed towards its minimum, but will reach its maximum brightness again in May of next year and every 332 days thereafter. Shockingly, Mira contains a huge, 13 light-year-long tail — visible only in the UV — that it leaves as it rockets through the interstellar medium at 130 km/sec! Look for it in your skies all winter long, and contribute your results to the AAVSO (American Association of Variable Star Observers) International Database to help study its long-term behavior!

Check out some cool images and simulated animations of Mira here: www.nasa.gov/mission_pages/galex/20070815/v.html

Kids can learn all about Mira at NASA’s Space Place: spaceplace.nasa.gov/mira/en/.

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Caption: NASA’s Galaxy Evolution Explorer (GALEX) spacecraft, of Mira and its tail in UV light (top); Margarita Karovska (Harvard-Smithsonian CfA) / NASA’s Hubble Space Telescope image of Mira, with the distortions revealing the presence of a binary companion (lower left); public domain image of Orion, the Pleiades and Mira (near maximum brightness) by Brocken Inaglory of Wikimedia Commons under CC-BY-SA-3.0 (lower right).

This article was provided by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

About NASA Space Place

The goal of the NASA Space Place is “to inform, inspire, and involve children in the excitement of science, technology, and space exploration.” More information is available at their website: http://spaceplace.nasa.gov/

Star Party Announcement: Mountains of Stars Amateur Astronomers Weekend, 24-26 October 2014

Greetings fellow astrophiles!

The following announcement came through our website recently. For those not considering a drive South to attend the Kopernik AstroFest that same weekend, consider a drive East for a long weekend under high, dark (hopefully) skies!

First Annual – Mountains of Stars Amateur Astronomers Weekend – In The White Mountains

The Appalachian Mountain Club and the Carthage Institute of Astronomy announce the first annual Mountains of Stars Amateur Astronomers Weekend, to be held October 24th to 26th 2014 at the Appalachian Mountain Club’s Highland Center in Bretton Woods, New Hampshire. Surrounded by the White Mountain National Forest, the Highland Center is a wonderful place to enjoy dark skies. Less than a day’s drive from one-quarter of the US population, the location offers outstanding hiking and outdoor activities, and the area is wonderful for families. Bring your telescopes and observing gear – and several facility telescopes will also be available. The Mountains of Stars Weekend will include opportunities for presentations and short talks, and two nights of dark sky observing around New Moon.

Please contact AMC Reservations at 603-466-2727 or amclodging@outdoors.org for more information or to make a reservation.

The Carthage Institute of Astronomy is a branch of Carthage College, a liberal arts college founded in 1847 and located in Kenosha, WI. The Institute conducts research in astronomy and astrophysics, operates the Griffin Observatory, offers courses in physics and astronomy, and delivers outreach and education programs. The institute’s director is astrophysicist Dr. Douglas Arion, who will be the host of the Mountains of Stars Weekend. He also heads the Galileoscope program, which has delivered more than 200,000 high quality, low cost telescopes for education and outreach to over 106 countries.

Founded in 1876, the Appalachian Mountain Club is America’s oldest conservation and recreation organization. With more than 100,000 members, advocates, and supporters in the Northeast and beyond, the nonprofit AMC promotes the protection, enjoyment, and understanding of the mountains, forests, waters, and trails of the Appalachian region. The AMC supports natural resource conservation while encouraging responsible recreation, based on the philosophy that successful, long-term conservation depends upon first-hand enjoyment of the natural environment.

The Mountains of Stars event is part of an NSF-funded joint Carthage/AMC astronomy outreach and education program, bringing astronomy and nature education to the public.

CNYO Observing Log: Beaver Lake Nature Center, 18 September 2014

Greetings fellow astrophiles,

After a double wash-out for our scheduled August 8/15 event, CNYO made a triumphant return to Beaver Lake Nature Center for one last end-of-Summer public viewing session. While the local meteorologists and the Clear Sky Clock predicting clear, dark skies for the entire evening, the observing itself was still a bit touch-and-go until about 9:00 p.m., when the whole sky finally opened up.

Despite a small snafu with the Beaver Lake events calendar (or, specifically, our lack of presence on it for this rescheduled event), we still managed 10 attendees (and passed the word along to several people there for an event earlier in the evening – I’m also happy to report that Patricia’s attendance justified our meetup group event scheduling!). With four CNYO’ers (Bob Piekiel, Larry Slosberg, Christopher Schuck, and myself) and three scopes present (including Bob Piekiel’s Celestron NexStar 11, Larry Slosberg’s 12” New Moon Telescope Dob, and my 12.5” NMT Dob) this was a great chance for several of the new observers to ask all kinds of questions, learn all the mechanics of observing through someone else’s scope, and, of course, take in some great sights at their own pace.

The 7:00 p.m. setup started promising, with otherwise overcast conditions gradually giving way to clearings to the Northwest. That all changed for the worse around 8:00 p.m. (when everyone showed up), when those same NW skies closed right up again, gradually devouring Arcturus, Vega, and any other brighter stars one might align with. The next hour was goodness-challenged, giving us plenty of time to host a Q+A, show the scope workings, remark on the amount of reflected light from Syracuse, and swing right around to objects within the few sucker holes that opened. And when all looked lost (or unobservable), the 9:00 p.m. sky finally cleared right up to a near-perfect late Summer sky, complete with a noticeable Milky Way band, bright Summer Triangle, and a host of satellites, random meteors, and bright Summer Messiers.

As has been the case for nearly every public viewing session this year, all the new eyes were treated to some of the best the Summer and Fall have to offer. These include:

M13 – The bright globular (“globe” not “glob”) cluster in Hercules
M31/32 – The Andromeda Galaxy (and its brighter, more separated satellite M32)
M57 – The Ring Nebula in Lyra
Herschel’s Garnet Star – To show very clearly that many stars have identifiable colors when magnified
Albireo – To reinforce the color argument above and to show one of the prominent doubles in the Night Sky, right at the tip of Cygnus.
Alcor/Mizar – Did you know that Alcor/Mizar is actually a sextuple star system? Alcor is its own double, each in Mizar is a double, and recent data reveals that the Alcor pair is gravitationally bound to the Mizar quartet.

To the observing list was added a discussion of how to begin learning the constellations. As we’ve discussed at several sessions, the best place to start is due North, committing the circumpolar constellations to memory FIRST. For those unfamiliar, these are the six constellations that never set below the horizon from our latitude (Ursa Minor (Little Dipper), most or Ursa Major (Big Dipper), Cassiopeia, Cepheus, Draco, and Camelopardalis (and if you can find Camelopardalis, you’re ready for anything). We’ve even consolidated all of this material into one of our introductory brochures for your downloading and printing pleasure:

CNYO Guide For New Observers

To my own observing list was added a treat thanks to Bob’s perfect position on the rise of the Beaver Lake parking circle, as he managed to catch Uranus low on the Eastern horizon just before we packed up for the evening. Even with Syracuse’s glow dimming the view, Uranus is a clear sight either in a scope (as a slightly blue-green disc) or through a low-power finder scope.

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Closing at Beaver Lake (including one low-flyer).

We offer special thanks to the Beaver Lake staff, who were fine with us staying as late as we liked (although we still finished up around 10) and who found *all* the light switches for the parking lot. I suspect our next Beaver Lake event won’t happen until the Spring, meaning we hope to see you at one of Bob Piekiel’s Baltimore Woods sessions during the winter – unless we all get inspired to throw extra layers on and organize another winter observing session somewhere, in which case we hope to see you there as well!