GAAC December 12 Program Note -- Come to our Party!

Our Holiday Party is this coming Friday night at 8:00 at the Lanesville Community Center. Come join us -- we'll have a terrific time, eating all kinds of seasonal goodies and visiting with all our astronomy friends both new and old, and we have an outstanding program to help us celebrate.

To get us started, Steve K will fill us in on all the noteworthy visitors moving into our winter skies; there's plenty to look forward to. I'm willing to bet Mercury is in there someplace, but we'll just have to wait and see. Will Steve wear the Santa hat? Stay tuned.

The main attraction this month is Elaine K's research on an astronomer who deserves to be much better known -- Henrietta Swan Leavitt, who discovered that a particular type of star can act as a cosmic milepost, telling us exactly how far away it and it's neighborhood are. All kinds of wonderful discoveries resulted from her figuring this out. This is fascinating stuff. How do we know where the Andromeda galaxy is, or where we're situated in our own galaxy? This is how.

Come in for a truly fascinating tale of professional astronomy, fame and ignominy, clouds and galaxies, a peculiar type of star that announces how far away it is with every blink, and the woman who figured it all out.

The festivities begin at 8:00 Friday December 12, at the Lanesville Community Center, 8 Vulcan Street Gloucester.  See our Contact page for directions.

We'll see you there!

NASA Spaceplace Partners' Article, November 2014

Where the Heavenliest of Showers Come From
By Dr. Ethan Siegel

You might think that, so long as Earth can successfully dodge the paths of rogue asteroids and comets that hurtle our way, it's going to be smooth, unimpeded sailing in our annual orbit around the sun. But the meteor showers that illuminate the night sky periodically throughout the year not only put on spectacular shows for us, they're direct evidence that interplanetary space isn't so empty after all!

When comets (or even asteroids) enter the inner solar system, they heat up, develop tails, and experience much larger tidal forces than they usually experience. Small pieces of the original object—often multiple kilometers in diameter—break off with each pass near the sun, continuing in an almost identical orbit, either slightly ahead-or-behind the object's main nucleus. While both the dust and ion tails are blown well off of the main orbit, the small pieces that break off are stretched, over time, into a diffuse ellipse following the same orbit as the comet or asteroid it arose from. And each time the Earth crosses the path of that orbit, the potential for a meteor shower is there, even after the parent comet or asteroid is completely gone!

This relationship was first uncovered by the British astronomer John Couch Adams, who found that the Leonid dust trail must have an orbital period of 33.25 years, and that the contemporaneously discovered comet Tempel-Tuttle shared its orbit. The most famous meteor showers in the night sky all have parent bodies identified with them, including the Lyrids (comet Thatcher), the Perseids (comet Swift-Tuttle), and what promises to be the best meteor shower of 2014: the Geminids (asteroid 3200 Phaethon). With an orbit of only 1.4 years, the Geminids have increased in strength since they first appeared in the mid-1800s, from only 10-to-20 meteors per hour up to more than 100 per hour at their peak today! Your best bet to catch the most is the night of December 13th, when they ought to be at maximum, before the Moon rises at about midnight.

The cometary (or asteroidal) dust density is always greatest around the parent body itself, so whenever it enters the inner solar system and the Earth passes near to it, there's a chance for a meteor storm, where observers at dark sky sites might see thousands of meteors an hour! The Leonids are well known for this, having presented spectacular shows in 1833, 1866, 1966 and a longer-period storm in the years 1998-2002. No meteor storms are anticipated for the immediate future, but the heavenliest of showers will continue to delight skywatchers for all the foreseeable years to come!

What’s the best way to see a meteor shower? Check out this article to find out: http://www.nasa.gov/jpl/asteroids/best-meteor-showers.

Kids can learn all about meteor showers at NASA’s Space Place: http://spaceplace.nasa.gov/meteor-shower

Image credit: NASA / JPL-Caltech / W. Reach (SSC/Caltech), of Comet 73P/Schwassman-Wachmann 3, via NASA's Spitzer Space Telescope, 2006.

Sky Object of the Month – November 2014

NGC 40 – Planetary Nebula in Cepheus
by Glenn Chaple

Our November deep-sky target, NGC 40, could be featured any month of the year. Just 17.5 degrees from the North Celestial Pole, it’s circumpolar from mid-northern latitudes. But it’s during mid autumn that NGC 40’s parent constellation Cepheus rides highest above the northern horizo after sunset.

NGC 40 was discovered by Sir William Herschel on November 25, 1788, and bears the Herschel Catalog designation H IV-58 (his 58th Class IV [Planetary Nebulae] entry). A more recent designation, C2, reflects its inclusion in Sir Patrick Caldwell-Moore’s 1995 Caldwell Catalog – his compilation of the finest 109 non-Messier deep-sky objects. NGC 40 is also nick-named the Bow-Tie Nebula, a moniker it shares with the planetary nebula NGC 2440 in Puppis and the Hubble-imaged protoplanetary nebula PGC 3074547 in Centaurus.

Finding NGC 40 is problematic, as it lies in a star-poor region of Cepheus. The accompanying Telrad chart shows it location about one-third of the way from gamma (() Cephei (labeled Errai) to kappa (() Cassiopeiae. Center your finderscope on the area and begin a low-power search (about 50X should suffice) until you come to what looks like an out-of-focus 12th magnitude star midway between and slightly west of a pair of 9th magnitude stars. NGC 40 can be glimpsed with a 4-inch scope under dark skies, but you’ll need twice that aperture to capture significant detail. Magnifications of 150X and up will reveal a slightly oval 35 X 38 arc second haze surrounding a star of 11.6 magnitude.

If you gaze at NGC 40’s central star, the surrounding nebulosity seems to disappear. Look to the side, and the nebulosity pops into view. The effect mirrors that of NGC 6826 (the “Blinking Planetary” in Cygnus. At a distance of 3500 light years, NGC 40 is about one light year in diameter.

Cosmic Concert Saturday October 11, 7:00

The Gloucester Area Astronomy Club (GAAC) proudly presents a public concert by composer and pianist Bruce Lazarus featuring his major astronomy-themed solo piano work, Musical Explorations of the Messier Catalogue of Star Clusters and Nebulae, Saturday October 11, 2014, 7:00pm, at St Paul Lutheran Church in Lanesville, Massachusetts. Admission is $5.

Musical Explorations of the Messier Catalogue is a series of fourteen pieces inspired by the compilation of astronomical objects of French astronomer Charles Messier (1730-1817). Comet hunter Messier identified, with his small telescope, 110 celestial objects that resembled but were not comets, an extensive numerical "catalogue" of stunning beauty widely used by astronomers of the present day. Composer Lazarus writes of his 45-minute collection, composed between 2004 and 2011:

"Recent Hubble telescope photos of Charles Messier’s list of fuzzy objects in the clear night sky (now known as nebulae, star clusters, galaxies, and immense patches of interstellar gas) reveal vistas of extraordinary beauty and also great variation in energy patterning – spiraling, floating, exploding, diffusing – which suggest musical variations in rhythm, texture, formal design, and melodic elements. I decided to compose a series of musical descriptions of the fourteen most iconic images of these objects: starting with the familiar Andromeda Galaxy (Messier 31), and later moving on to the Orion Nebula (M42), The Pleiades (M45), the most impressive of the globular clusters (M13), the Eagle Nebula with its majestic ‘pillars of star creation,’ and double stars, star clusters, novas and supernovas.

"Following the six-year process of composing my major opus, I switched roles to that of concert pianist recording a CD of the entire cycle, and performing these difficult but very personal scores in public. I am most grateful to GAAC for the opportunity to perform my Messier pieces in Lanesville.”

For directions and a map, click here: https://goo.gl/maps/JQz6F

GAAC’s October 11 live Messier performance will be accompanied by projected images of the individual objects. For more information on the Messier pieces, read Bruce Lazarus’ article on the Messier pieces in GAAC’s affiliated eJournal, The Galactic Inquirer.

NASA Spaceplace Partners' Article, September 2014

Twinkle, twinkle, variable star

By Dr. Ethan Siegel

As 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: http://www.nasa.gov/mission_pages/galex/20070815/v.html

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

Images credit: 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).

September 12 GAAC Meeting Program Note

At our Sept 12 meeting we have a distinguished guest with a great program on how giant, monster galaxies came to be, back at the beginning of everything. This is an important question, one at the forefront of current Hubble discoveries (see image, left).

New ideas on the emergence of these galactic monsters have astronomers rethinking what the very young Universe looked like.

On September 12 Professor Danilo Marchesini of Tufts University will take us back to these primordial times -- and introduce us to the beasts that lit the night skies back then.

Mark your calendars, folks, this will be  a terrific night with an absolutely outstanding presentation by an expert on the subject.

We meet on the second Friday of every month except August, at 8:00 in the Lanesville Community Center. See our Contact page for directions.

And don't forget: we'll see you at the 9/5 HPSP star party!

Sky Object of the Month – September 2014

Messier 22  – Globular Cluster in Sagittarius
by Glenn Chaple

On early evenings in September, the constellation Sagittarius arches above the southern horizon, its rich deep-sky treasures accessible to those of us who inhabit mid-northern latitudes. One of the more spectacular of these cosmic splendors is the globular cluster M22 Its discovery is attributed to the German astronomer Abraham Ihle, who came across it on August 26, 1665 while observing Saturn.

Among globular clusters, M22 is exceeded in brightness and apparent size only by omega Centauri and 47 Tucanae. Much of its grandeur results from its nearness to the earth. At a distance of 10,500 light years, it’s over two times closer than the much-heralded M13. In reality, M13 is half again as large and contains several hundred thousand stars, compared to M22’s estimated 70.000.

I’ve always been a proponent of small telescopes for backyard astronomy, but had to admit that large aperture scopes are the way to go should you want to resolve the stars in a globular cluster. M22 is an exception. I’ve resolved it quite nicely with a 4-inch f/4 RFT (an Edmund Astroscan) and a magnifying power of just 74X.

Naturally, to view M22 in all its glory you’ll want to use a large instrument and 2 or 3 times that magnification.M22 is relatively easy to locate, if you use the “Teapot” of Sagittarius as a guide. In binoculars and finderscopes, it appears as a 5th magnitude smudge just 2 ½ degrees northeast of Kaus Borealis (Lambda [] Sagittarii) - a 3rd magnitude star that forms the top of the Teapot’s lid. Next time you’re visiting M13, drop southward and give M22 a look-see. Which do you prefer?

Chart credit: freestarcharts.com photo by Mario Motta, MD

NASA Spaceplace Partners' Article, August 2014

Droughts, Floods and the Earth's Gravity, by the GRACE of NASA
By Dr. Ethan Siegel

When you think about gravitation here on Earth, you very likely think about how constant it is, at 9.8 m/s2 (32 ft/s2). Only, that's not quite right. Depending on how thick the Earth's crust is, whether you're slightly closer to or farther from the Earth's center, or what the density of the material beneath you is, you'll experience slight variations in Earth's gravity as large as 0.2%, something you'd need to account for if you were a pendulum-clock-maker.

But surprisingly, the amount of water content stored on land in the Earth actually changes the gravity field of where you are by a significant, measurable amount. Over land, water is stored in lakes, rivers, aquifers, soil moisture, snow and glaciers. Even a change of just a few centimeters in the water table of an area can be clearly discerned by our best space-borne mission: NASA's twin Gravity Recovery and Climate Experiment (GRACE) satellites.

Since its 2002 launch, GRACE has seen the water-table-equivalent of the United States (and the rest of the world) change significantly over that time. Groundwater supplies are vital for agriculture and provide half of the world's drinking water. Yet GRACE has seen California's central valley and the southern high plains rapidly deplete their groundwater reserves, endangering a significant portion of the nation's food supply. Meanwhile, the upper Missouri River Basin—recently home to severe flooding—continues to see its water table rise.

NASA's GRACE satellites are the only pieces of equipment currently capable of making these global, precision measurements, providing our best knowledge for mitigating these terrestrial changes. Thanks to GRACE, we've been able to quantify the water loss of the Colorado River Basin (65 cubic kilometers), add months to the lead-time water managers have for flood prediction, and better predict the impacts of droughts worldwide. As NASA scientist Matthew Rodell says, "[W]ithout GRACE we would have no routine, global measurements of changes in groundwater availability. Other satellites can’t do it, and ground-based monitoring is inadequate." Even though the GRACE satellites are nearing the end of their lives, the GRACE Follow-On satellites will be launched in 2017, providing us with this valuable data far into the future. Although the climate is surely changing, it's water availability, not sea level rise, that's the largest near-term danger, and the most important aspect we can work to understand!

Learn more about NASA’s GRACE mission here: http://www.nasa.gov/mission_pages/Grace/

Kids can learn al about launching objects into Earth’s orbit by shooting a (digital) cannonball on NASA’s Space Place website. Check it out at: http://spaceplace.nasa.gov/how-orbits-work/

Image credit: NASA Earth Observatory image by Jesse Allen, using GRACE data provide courtesy of Jay Famigleitti, University of California Irvine and Matthew Rodell, NASA Goddard Space Flight Center. Caption by Holli Riebeek.