Published on May 30, 2016
Weather permitting, the first GAAC star party of the year is set for Saturday night, June 4, from sunset to 10 pm. All are invited, and of course there is no cost. We'll have telescopes set up next to the Vistor Center to view Mars, Jupiter, galaxies, nebulae, colorful double stars, and more!
Please park in the paved lot off of Gott Ave and walk up the hill to the Visitor Center. We'll see you there!
Published on Mar 11, 2016
Gravitational Wave Astronomy Will Be The Next Great Scientific Frontier
By Ethan Siegel
Imagine a world very different from our own: permanently shrouded in clouds, where the sky was never seen. Never had anyone see the Sun, the Moon, the stars or planets, until one night, a single bright object shone through. Imagine that you saw not only a bright point of light against a dark backdrop of sky, but that you could see a banded structure, a ringed system around it and perhaps even a bright satellite: a moon. That's the magnitude of what LIGO (the Laser Interferometer Gravitational-wave Observatory) saw, when it directly detected gravitational waves for the first time.
An unavoidable prediction of Einstein's General Relativity, gravitational waves emerge whenever a mass gets accelerated. For most systems -- like Earth orbiting the Sun -- the waves are so weak that it would take many times the age of the Universe to notice. But when very massive objects orbit at very short distances, the orbits decay noticeably and rapidly, producing potentially observable gravitational waves. Systems such as the binary pulsar PSR B1913+16 [the subtlety here is that binary pulsars may contain a single neutron star, so it’s best to be specific], where two neutron stars orbit one another at very short distances, had previously shown this phenomenon of orbital decay, but gravitational waves had never been directly detected until now.
When a gravitational wave passes through an objects, it simultaneously stretches and compresses space along mutually perpendicular directions: first horizontally, then vertically, in an oscillating fashion. The LIGO detectors work by splitting a laser beam into perpendicular “arms,” letting the beams reflect back and forth in each arm hundreds of times (for an effective path lengths of hundreds of km), and then recombining them at a photodetector. The interference pattern seen there will shift, predictably, if gravitational waves pass through and change the effective path lengths of the arms. Over a span of 20 milliseconds on September 14, 2015, both LIGO detectors (in Louisiana and Washington) saw identical stretching-and-compressing patterns. From that tiny amount of data, scientists were able to conclude that two black holes, of 36 and 29 solar masses apiece, merged together, emitting 5% of their total mass into gravitational wave energy, via Einstein's E = mc2.
During that event, more energy was emitted in gravitational waves than by all the stars in the observable Universe combined. The entire Earth was compressed by less than the width of a proton during this event, yet thanks to LIGO's incredible precision, we were able to detect it. At least a handful of these events are expected every year. In the future, different observatories, such as NANOGrav (which uses radiotelescopes to the delay caused by gravitational waves on pulsar radiation) and the space mission LISA will detect gravitational waves from supermassive black holes and many other sources. We've just seen our first event using a new type of astronomy, and can now test black holes and gravity like never before.
Image credit: Observation of Gravitational Waves from a Binary Black Hole Merger B. P. Abbott et al., (LIGO Scientific Collaboration and Virgo Collaboration), Physical Review Letters 116, 061102 (2016). This figure shows the data (top panels) at the Washington and Louisiana LIGO stations, the predicted signal from Einstein's theory (middle panels), and the inferred signals (bottom panels). The signals matched perfectly in both detectors.
Published on Nov 22, 2015
Wow, do we ever have an amazing treat for you at our December 11 GAAC holiday party.
We'll have all kinds of goodies to eat and drink, of course, and lots of good company and conversation, of course, but the big news is all about who we've got speaking: Babak Tafreshi, the creator of "The World At Night," will discuss his work and present a stunning program of his unique astrophotographs. Babak is an internationally known photographer and a tireless advocate for astronomy and the preservation of dark skies.
Here is just a small section of his official Bio from http://www.twanight.org/:
"TWAN founder and leader, Babak Tafreshi is an award winning photographer working with the National Geographic, Sky&Telescope magazine, and the European Southern Observatory (ESO). Babak is also a freelance science journalist and astronomy communicator using all media. Born in 1978 in Tehran he is based in Boston, United States, but could be anywhere on the planet, from the Sahara to the Himalayas or Antarctica. He is a board member of Astronomers Without Borders organization, an international organization to bridge between cultures and connect people around the world through their common interest to astronomy. He received the 2009 Lennart Nilsson Award, the world’s most recognized award for scientific photography, for his global contribution to night sky photography."
Holy cow, you'll want to come early for this one. The joint will be packed. This will be a GAAC party to remember. See our Contact page for directions; see our home page for other club details.
Published on Nov 12, 2015
Our November meeting will be held on Friday November 13, at 8:00 pm, at the Lanesville Community Center. Old friend Jim Koerth will host a profound, colorful exposition on the human investigation into the origin of all things. When and how did the universe begin? As we peer farther and farther back in time with our giant telescopes, a global group of astronomers wants to answer that question by looking as far back as a large telescope will let us see.
Jim will introduce us all, via DVD, to a prime mover in the creation of the Giant Magellan Telescope, now under construction in South America. Share in the bold vision about the discoveries the GMT could possibly make about our universe. A Q&A and discussion session will follow the brief video.
Come in and enjoy the fall musings of GAACsters from far and wide, and become part of the conversation. There will be pie.
The club meets at 8:00 pm on the second Friday of every month at the Lanesville Community Center. See our Contact page for a map and driving directions. Parking is free, there are no dues or fees, and everyone is welcome. Come on in -- you'll have a great time!
Published on Oct 3, 2015
The Gloucester Area Astronomy Club registered the domain name gaac.us on October 13 2003, which makes the Friday October 9 meeting our twelfth anniversary! Come on in and help us celebrate, along with some of our accomplished stable of astrophotographers as they each show off examples of their most recent work, including some shots they've been saving for just this occasion.
We'll see a bunch of terrific pictures, and hear the how's and why's as well, as each photographer explains each image, its significance, and some details of the hunt that produced it.
This will be a colorful, entertaining and elucidating night of astrophotography, science, friends, coffee and cake, and of course lots of great conversation to boot. Don't miss it!
GAAC meets at 8:00 on the second Friday of every month at the Lanesville Community Center, 8 Vulcan Street Gloucester. See our Contact page for directions. There is no cost, and parking is free. For more info on the club, see our Facebook page, http://www.facebook.com/gaacpage, or follow us on Twitter @gaacster. All are welcome, and no prior knowledge of astronomy is needed to have a great time!
Published on Sep 3, 2015
S Cepheii – Carbon Star in Cepheus
by Glenn Chaple
This past August 15th, I presented a talk on carbon stars at the Stellafane Convention. The library at the McGregor Observatory, which served as the setting, hosts a typical audience of 12 to 20. This time, more than 30 Stellafaners showed up. The topic was obviously one of intense interest!
The reason is obvious to anyone who has ever looked at a carbon star like R Leporis (“Hind’s Crimson Star”), T Lyrae, or V Aquilae. At certain times, they can appear red – drop-of- blood red!
Popular fare for backyard astronomers over a century ago, carbon stars have enjoyed a resurgence in popularity, particularly with individuals seeking a change from the usual deep-sky fare of nebulae. clusters, and galaxies. They have become so popular that the Astronomical League recently initiated a carbon star observing program that lists 100 of these cosmic rubies.
Like its kindred carbon stars, of which nearly 7000 have been catalogued, S Cephei is a red supergiant with a 
‘sooty” carbon-laced outer atmosphere that enhances its ruddy appearance. Typical of its stellar class, it varies in brightness, ranging from 7th to 11th magnitude in a period averaging 485 days.
Lest I be accused of false advertisement, I should point out that not all carbon stars are ruby red. The color you see will depend on your vision, the nature of binocular or telescope used, sky conditions, and the star’s magnitude (carbon stars tend to be reddest when near minimum brightness). At the very least, a carbon star will shine with a rich golden yellow hue.
The accompanying finder charts point the way to S Cephei. A line from gamma (γ) to the wide pair rho (ρ) and 28 Cephei and extended an equal distance beyond brings you to a triangle of 7th magnitude stars perched atop a 6th magnitude star labeled 59 (its magnitude without decimals) on Chart B. Chart C will help you star-hop from the triangle to S Cephei. Magnitudes of surrounding stars are added (decimals omitted).
You’ll find more information on S Cephei at www.aavso.org/lcotw/s-cephei. The Astronomical League’s Carbon Star Program is described at www.astroleague.org/content/carbon-star-observing-program.
Finder Charts A (www.constellation-guide.com); Finder Chart B. (AAVSO); Finder Chart C. (AAVSO)
Published on Aug 12, 2015
Solar Wind Creates—and Whips—a Magnetic Tail Around Earth
By Ethan Siegel
As Earth spins on its axis, our planet's interior spins as well. Deep inside our world, Earth's metal-rich core produces a magnetic field that spans the entire globe, with the magnetic poles offset only slightly from our rotational axis. If you fly up to great distances, well above Earth's surface, you'll find that this magnetic web, called the magnetosphere, is no longer spherical. It not only bends away from the direction of the sun at high altitudes, but it exhibits some very strange features, all thanks to the effects of our parent star.
The sun isn't just the primary source of light and heat for our world; it also emits an intense stream of charged particles, the solar wind, and has its own intense magnetic field that extends much farther into space than our own planet's does. The solar wind travels fast, making the 150 million km (93 million mile) journey to our world in around three days, and is greatly affected by Earth. Under normal circumstances, our world's magnetic field acts like a shield for these particles, bending them out of the way of our planet and protecting plant and animal life from this harmful radiation.
But for every action, there's an equal and opposite reaction: as our magnetosphere bends the solar wind's ions, these particles also distort our magnetosphere, creating a long magnetotail that not only flattens and narrows, but whips back-and-forth in the onrushing solar wind. The particles are so diffuse that collisions between them practically never occur, but the electromagnetic interactions create waves in Earth's magnetosphere, which grow in magnitude and then transfer energy to other particles. The charged particles travel within the magnetic field toward both poles, and when they hit the ionosphere region of Earth’s upper atmosphere, they collide with ions of oxygen and nitrogen causing aurora. Missions such as the European Space Agency and NASA Cluster mission have just led to the first accurate model and understanding of equatorial magnetosonic waves, one such example of the interactions that cause Earth's magnetotail to whip around in the wind like so.
The shape of Earth's magnetic field not only affects aurorae, but can also impact satellite electronics. Understanding its shape and how the magnetosphere interacts with the solar wind can also lead to more accurate predictions of energetic electrons in near-Earth space that can disrupt our technological infrastructure. As our knowledge increases, we may someday be able to reach one of the holy grails of connecting heliophysics to Earth: forecasting and accurately predicting space weather and its effects. Thanks to the Cluster Inner Magnetosphere Campaign, Van Allen Probes, Mars Odyssey Thermal Emission Imaging System, Magnetospheric Multiscale, and Heliophysics System Observatory missions, we're closer to this than ever before.
Kids can learn about how solar wind defines the edges of our solar system at NASA Space Place. http://spaceplace.nasa.gov/interstellar
Image credit: ESA / C. T. Russell (L), of Earth's magnetic tail and its cause: the solar wind; Southwest Research Institute / IBEX Science Team (R), of the first image of the plasma sheet and plasmasphere created around Earth by the solar wind.
Published on Jun 29, 2015
Xi (ξ) Scorpii (Σ1998) – Double Star in Scorpius
by Glenn Chaple
Our cosmic wanderings take us 93 light years away to the triple star xi (ξ) Scorpii (Σ1998), 
located in the Scorpion’s northwest corner. A 60mm refractor magnifying 60X will reveal two stars (xi Scorpii A and C), of magnitudes 4.9 and 7.3 and separated by 7.0”. If the seeing is extremely steady, check out the brighter star with a larger scope (minimum aperture of 4 inches) and magnification of 150X or more.
You should capture a magnitude 5.2 companion (xi Scorpii B) just 1.1” away. Xi Scorpii A and B are a binary pair with an orbital period of 46 years. As the diagram shows, they are currently near greatest separation.
When I first viewed xi Scorpii with a 3-inch reflecting telescope in the summer of 1971, I was surprised to see a faint double star in the same field. I had “discovered” Σ1999 (magnitudes 7.5 and 8.1; separation 11.8”. Although nearly 5 minutes of arc separate Σ1999 from xi Scorpii, the two have the same common proper motion and are likely gravitationally bound.
When viewing xi Scorpii and Σ1999, pay close attention to the colors of their component stars. Xi Scorpii A and B are F-type stars, while C is a cooler G8 dwarf. Both Σ1999 stars have K spectral classes. What colors do you see?