The Gloucester Area Astronomy Club

NGC 1501 – Planetary Nebula in Camelopardalis
by Glenn Chaple

While Go-to technology has gained popularity with backyard astronomers who like to key their telescopes on a sky object with the push of a button, I prefer the no-frills star-hop mode of cosmic travel. Star-hopping lets me see enjoy celestial scenery I’d miss by traveling Go-to. I’ll demonstrate my point with a star-hop to the planetary nebula NGC 1501 in Camelopardalis.

Camelopardalis isn’t very kind to star-hoppers. This sprawling north circumpolar constellation contains just four stars brighter than 5th magnitude. A star-hop to any sky destination in Camelopardalis usually begins with a bright star in an adjacent constellation. To find NGC 1501, we begin at gamma () Persei and trace a 12o path between a pair of 4th magnitude stars to Kemble’s Cascade (refer to the finder charts on the right).Kemble’s Cascade is a stunning 2 ½ o chain comprised of some 20 magnitude 7 to 9 stars.

At its southwest end is the pretty open cluster NGC 1502, punctuated at the center with the eye-pleasing 7th magnitude twins that make up the double star Struve 485. A 1 ½ o push south of NGC 1502 brings us to NGC 1501. Think of it – if we’d traveled to NGC 1501 via Go-to technology, we’d have missed three delightful celestial showpieces!

NGC 1501 is a magnitude 11.5 planetary nebula located about 5000 light-years away. Its slightly oval disk, just under an arc-minute across, can be glimpsed (barely) in a 3-inch scope, but twice that aperture will be needed for a definite sighting.  With a 12-inch scope and dark-sky conditions, you should be able to make out the nebula’s bluish hue and magnitude 14.5 central star.

Minor mergers have massive consequences for black holes
By Dr. Ethan Siegel

When you think of our sun, the nearest star to our world, you think of an isolated entity, with more than four light years separating it from its next nearest neighbor. But it wasn't always so: billions of years ago, when our sun was first created, it very likely formed in concert with thousands of other stars, when a giant molecular cloud containing perhaps a million times the mass of our solar system collapsed. While the vast majority of stars that the universe forms—some ninety-five percent—are the mass of our sun or smaller, a rare but significant fraction are ultra-massive, containing tens or even hundreds of times the mass our star contains. When these stars run out of fuel in their cores, they explode in a fantastic Type II supernova, where the star's core collapses. In the most massive cases, this forms a black hole.

Over time, many generations of stars—and hence, many black holes—form, with the majority eventually migrating towards the centers of their host galaxies and merging together. Our own galaxy, the Milky Way, houses a supermassive black hole that weighs in at about four million solar masses, while our big sister, Andromeda, has one nearly twenty times as massive. But even relatively isolated galaxies didn't simply form from the monolithic collapse of an isolated clump of matter, but by hierarchical mergers of smaller galaxies over tremendous timescales. If galaxies with large amounts of stars all have black holes at their centers, then we should be able to see some fraction of Milky Way-sized galaxies with not just one, but multiple supermassive black holes at their center!

It was only in the early 2000s that NASA's Chandra X-ray Observatory was able to find the first binary supermassive black hole in a galaxy, and that was in an ultra-luminous galaxy with a double core. Many other examples were discovered since, but for a decade they were all in ultra-massive, active galaxies. That all changed in 2011, with the discovery of two active, massive black holes at the center of the regular spiral galaxy NGC 3393, a galaxy that must have undergone only minor mergers no less than a billion years ago, where the black hole pair is separated by only 490 light years! It's only in the cores of active, X-ray emitting galaxies that we can detect binary black holes like this. Examples like NGC 3393 and IC 4970 are not only confirming our picture of galaxy growth and formation, but are teaching us that supermassive relics from ancient, minor mergers might persist as standalone entities for longer than we ever thought!

Check out some cool images and artist reconstructions of black holes from Chandra: http://chandra.harvard.edu/photo/category/blackholes.html

Kids can learn all about Black Holes from this cool animation at NASA’s Space Place: http://spaceplace.nasa.gov/black-holes.

Images credit: NGC 3393 in the optical (L) by M. Malkan (UCLA), HST, NASA (L); NGC 3393 in the X-ray and optical (R), composite by NASA / CXC / SAO / G. Fabbiano et al. (X-ray) and NASA/STScI (optical).

Struve 817 (STF 817, 817) – Double Star in Orion
by Glenn Chaple

I’m a big fan of “off-the-beaten-path” sky objects. One of my favorites is the little-known double star Struve 817 - the 817th double star catalogued by the German-born Russian astronomer F. G. W. Struve during a survey conducted between 1824 and 1827. I wrote about this little gem in my first “Object of the Month” column 5 years ago. It’s time for a return visit!

According to a measure made in 2010 and posted in the Washington Double Star Catalog (available online at ad.usno.navy.mil/proj/WDS), Struve 817 consists of near-twin magnitude 8.68 and 8.93 stars separated by 18.7 arc-seconds in a position angle of 73o. The separation and P.A. differ little from what Struve himself measured around the time of discovery. Astronomers describe stellar partnerships that show little orbital motion as being “relatively fixed.” If the component stars of Struve 817 form a true binary pair, their orbital period must encompass many centuries.

What gives this relatively obscure double star a special allure is its location just 20 arc-minutes south of the red supergiant Betelgeuse. To find Struve 817, simply aim your telescope at Betelgeuse. A medium power eyepiece (75 to 100X works well) should capture this delicate pair shining just outside the dazzling rays of ruddy Betelgeuse. It’s a startling sight. The Washington Catalog lists the spectra of Struve 817’s components as A5 and K. Can you make out a color contrast between the two?

Some years ago, I wrote a four-part seasonal series for Deep Sky Magazine in which I introduced my favorite 100 double stars. Included with such celebrated pairs as Mizar, Albireo, and the “Double-double” epsilon Lyrae was Struve 817. On the next crisp winter night when Orion beckons you to visit his magnificent Nebula, take a minute to travel a road less taken and try for this delightful double star.

      
Image credits: constellation-guide.com (courtesy IAU and Sky and Telescope) Betelgeuse and Struve 817. 3-inch f/10 reflector at 60X; ½ degree field.

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!

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.

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.

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.

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).