The Gloucester Area Astronomy Club

Messier 78 – Reflection Nebula in Orion
by Glenn Chaple

In his guidebook The Messier Objects, author Stephen James O’Meara confides, “Before beginning this book, I had looked at M78 only once.” Yours truly hasn’t fared much better. Prior to writing this column, I had seen M78 on three occasions –first in the late 1970s when I viewed all of the Messier objects with a 3-inch reflector, and more recently during two Messier Marathons.

It’s understandable that M78 should be overlooked by backyard astronomers. Not far away is the much brighter, much more easily found, and much, much more spectacular M42 - the Orion Nebula. This deep-sky masterpiece was spectacular even through the eyepiece of my 3-inch scope. M78, on the other hand, was a faint blob that seemed to sport an off-center nucleus.

At a recent star party, I had the opportunity to look at M78 with a 16-inch Dobonian-mounted reflector. The view was amazing! Two “eyes” (a pair of 10th magnitude stars that illuminate the nebula) peering out of a misty patch of light took on the ominous form of a cosmic ghost! The eerie visual effect was repeated when I made a follow-up observation with my 10-inch scope.

The accompanying finder chart shows the location of M78 relative to Orion’s Belt. At 8th magnitude, it covers an area 6’ by 8’ and is best seen with magnifications of 100X or more. A scan of the immediate area will pick up several other nebulas, including NGC 2071 situated 15’ NNE of M78.  M78 was discovered by Pierre Mechain early in 1780. He was the first to see it – why not be the latest?

M78 Photo by Mario Motta/Chart by Bill O'Donnell

Tackling the Really BIG Questions
By Diane K. Fisher

How does NASA get its ideas for new astronomy and astrophysics missions?  It starts with a Decadal Survey by the National Research Council, sponsored by NASA, the National Science Foundation, and the Department of Energy. The last one, New Worlds, New Horizons in Astronomy and Astrophysics was completed  in 2010. It defines the highest-priority research activities in the next decade for astronomy and astrophysics that will “set the nation firmly on the path to answering profound questions about the cosmos.” It defines space- and ground-based research activities in the large, midsize, and small budget categories.

The recommended activities are meant to advance three science objectives:

Deepening understanding of how the first stars, galaxies, and black holes formed,

Locating the closest habitable Earth-like planets beyond the solar system for detailed study, and

Using astronomical measurements to unravel the mysteries of gravity and probe fundamental physics.

For the 2012-2021 period, the highest-priority large mission recommended is the Wide-field Infrared Survey Telescope (WFIRST). It would orbit the second Lagrange point and perform wide-field imaging and slitless spectroscopic surveys of the near-infrared sky for the community. It would settle essential questions in both exoplanet and dark energy research and would advance topics ranging from galaxy evolution to the study of objects within the galaxy and within the solar system.

Naturally, NASA’s strategic response to the recommendations in the decadal survey must take budget constraints and uncertainties into account.

The goal is to begin building this mission in 2017, after the launch of the James Webb Space Telescope. But this timeframe is not assured. Alternatively, a different, less ambitious mission that also address the Decadal Survey science objectives for WFIRST would remain a high priority.

The Astrophysics Division is also doing studies of moderate-sized missions, including: gravitational wave mission concepts that would advance some or all of the science objectives of the Laser Interferometer Space Antenna (LISA), but at lower cost; X-ray mission concepts to advance the science objectives of the International X-ray Observatory (IXO), but at lower cost; and mission concept studies of probe-class missions to advance the science of a planet characterization and imaging mission.

For a summary of NASA’s plans for seeking answers to the big astrophysics questions and to read the complete Astrophysics Implementation Plan (dated December 2012), see http://science.nasa.gov/astrophysics/.  For kids, find lots of astrophysics fun facts and games on The Space Place, http://spaceplace.nasa.gov/menu/space/.

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

Picture Caption:
Clusters of galaxies collide in this composite image of “Pandora's Cluster.” Data (in red) from NASA's Chandra X-ray Observatory show gas with temperatures of millions of degrees. Blue maps the total mass concentration (mostly dark matter) based on data from the Hubble Space Telescope (HST), the European Southern Observatory's Very Large Telescope (VLT), and the Japanese Subaru telescope. Optical data from HST and VLT also show the constituent galaxies of the clusters. Such images begin to reveal the relationship between concentration of dark matter and the overall structure of the universe.

The Gloucester Area Astronomy Club March meeting has been postponed to Friday March 15th. The program will be "An Introduction to Amateur Astronomy"!

We'll feature presentations on the rewards of the hobby, what the different types of telescopes are, how they work, how to buy one, how much to spend, what to look at, you name it. Everything you need to know to get started, or to up your game. Bring your questions! The public is warmly invited; as always, there are no dues or fees, and presentations are geared toward the general public.

If you have an unused telescope in your closet, or would like to get started in the hobby, this night is for you! See you there!

We'll meet at 8:00 pm at the Lanesville Community Center. See our Contact page for directions.

40 Eridani – Triple Star in Eridanus
by Glenn Chaple

This month, we travel 16.5 light years to the remarkable triple star 40 Eridani (aka Keid and omicron2 Eridani). This system merits must-see status by virtue of the fact that one of its members is the most easily-seen white dwarf in the night sky. Trekkies would add that the primary, a K1 dwarf not unlike our sun, is orbited by the planet Vulcan - homeworld of the starship Enterprise’s first officer Spock.

A small-aperture telescope and magnification of 50-60X shows two stars – the yellowish 4th  magnitude primary (designated 40 Eridani A) and a faint 9th magnitude companion (40 Eridani B) some 83 arc-seconds away. This ordinary-looking speck is a white dwarf with half the mass of the sun packed into a body whose diameter is only half again that of the earth. One cubic inch of its matter would weigh 4 tons!

The white dwarf has a companion of its own, located about 9 arc-seconds away. Discovered by William Herschel in 1783, 40 Eridani C is an 11th magnitude main sequence red dwarf which can be glimpsed with a 6-inch telescope and magnification of 150X or more. Viewed with a large-aperture Dob, the colors – yellow for A, white for B, and pale red for C – are amazing!

40 Eridani B and C are separated by an average distance of 35 Astronomical Units (slightly less than the gap between the sun and Neptune) and orbit each other in a 252 year cycle.  They lie 400 Astronomical Units (about 37 billion miles) from 40 Eridani A, circling this star in a period estimated to exceed 7000 years.

You may not have the starship Enterprise to transport you to the 40 Eridani star system, but a good backyard telescope will put you in the neighborhood.  Would you like to get even closer? A wonderful piece of artwork by Andrew Taylor takes us to the surface of a planet (Vulcan, perhaps?) orbiting 40 Eridani A. View it online at fineartamerica.com/featured/the-triple-star-system-40-eridani-andrew-taylor.html.

The Art of Space Imagery
By Diane K. Fisher

When you see spectacular space images taken in infrared light by the Spitzer Space Telescope and other non-visible-light telescopes, you may wonder where those beautiful colors came from? After all, if the telescopes were recording infrared or ultraviolet light, we wouldn’t see anything at all. So are the images “colorized” or “false colored”?

No, not really. The colors are translated. Just as a foreign language can be translated into our native language, an image made with light that falls outside the range of our seeing can be “translated” into colors we can see. Scientists process these images so they can not only see them, but they can also tease out all sorts of information the light can reveal. For example, wisely done color translation can reveal relative temperatures of stars, dust, and gas in the images, and show fine structural details of galaxies and nebulae.

Spitzer’s Infrared Array Camera (IRAC), for example, is a four-channel camera, meaning that it has four different detector arrays, each measuring light at one particular wavelength. Each image from each detector array resembles a grayscale image, because the entire detector array is responding to only one wavelength of light. However, the relative brightness will vary across the array.

So, starting with one detector array, the first step is to determine what is the brightest thing and the darkest thing in the image. Software is used to pick out this dynamic range and to re-compute the value of each pixel. This process produces a grey-scale image. At the end of this process, for Spitzer, we will have four grayscale images, one for each for the four IRAC detectors.

Matter of different temperatures emit different wavelengths of light. A cool object emits longer wavelengths (lower energies) of light than a warmer object. So, for each scene, we will see four grayscale images, each of them different.

Normally, the three primary colors are assigned to these gray-scale images based on the order they appear in the spectrum, with blue assigned to the shortest wavelength, and red to the longest. In the case of Spitzer, with four wavelengths to represent, a secondary color is chosen, such as yellow. So images that combine all four of the IRAC’s infrared detectors are remapped into red, yellow, green, and blue wavelengths in the visible part of the spectrum.

Download a new Spitzer poster of the center of the Milky Way. On the back is a more complete and colorfully-illustrated explanation of the “art of space imagery.” Go to spaceplace.nasa.gov/posters/#milky-way.

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

Photo Caption: 
This image of M101 combines images from four different telescopes, each detecting a different part of the spectrum. Red indicates infrared information from Spitzer’s 24-micron detector, and shows the cool dust in the galaxy. Yellow shows the visible starlight from the Hubble telescope. Cyan is ultraviolet light from the Galaxy Evolution Explorer space telescope, which shows the hottest and youngest stars. And magenta is X-ray energy detected by the Chandra X-ray Observatory, indicating incredibly hot activity, like accretion around black holes.

NGC 7662 – Planetary Nebula in Andromeda, the “Blue Snowball”
by Glenn Chaple

What could be a more appropriate telescopic destination for a wintry night in January than the “Blue Snowball?” More formally known as NGC 7662, the Blue Snowball is a beautiful planetary nebula located in Andromeda. Discovered by William Herschel in 1784, it sports as the nickname implies a circular form and eye-pleasing bluish hue.

To capture NGC 7662, point your telescope towards the Y-shaped asterism known as “Frederick’s Glory” - a quartet of 4th and 5th magnitude stars in the northwest part of Andromeda (look in the upper right-hand corner of the accompanying finder chart). From iota Andromedae (the base of the Y), move 2 degrees westward until 6th magnitude 13 Andromedae is centered in the finderscope field. With your telescope and an eyepiece that captures a chunk of sky at least a degree across and magnifies 40X to 50X, scan the surrounding area. If you spot what appears to be a tiny out-of-focus star about one-half degree to the southwest of 13 Andromedae, you’ve found NGC 7662.

An 8th magnitude object with an apparent diameter comparable to that of Saturn, the Blue Snowball can be viewed with telescopes of all sizes. I’ve glimpsed it with a 3-inch f/10 reflector and magnifying power of just 60X. Its dazzling hue and intricate detail mandate larger telescopes and magnifications exceeding 200X. Whether you own a common 60mm refractor or a huge Dob, look for the Blue Snowball on the next clear January evening.

Finder chart for NGC 7662 From Mag-7 Star Atlas (Copyright Andrew L. Johnson)

Partnering to Solve Saturn’s Mysteries

By Diane K. Fisher

From December 2010 through mid-summer 2011, a giant storm raged in Saturn’s northern hemisphere. It was clearly visible not only to NASA’s Cassini spacecraft orbiting Saturn, but also astronomers here on Earth—even those watching from their back yards. The storm came as a surprise, since it was about 10 years earlier in Saturn’s seasonal cycle than expected from observations of similar storms in the past. Saturn’s year is about 30 Earth years. Saturn is tilted on its axis (about 27° to Earth’s 23°), causing it to have seasons as Earth does.
But even more surprising than the unseasonal storm was the related event that followed.

First, a giant bubble of very warm material broke through the clouds in the region of the now-abated storm, suddenly raising the temperature of Saturn’s stratosphere over 150 °F. Accompanying this enormous “burp” was a sudden increase in ethylene gas. It took Cassini’s Composite Infrared Spectrometer instrument to detect it.

According to Dr. Scott Edgington, Deputy Project Scientist for Cassini,  “Ethylene [C2H4] is normally present in only very low concentrations in Saturn’s atmosphere and has been very difficult to detect. Although it is a transitional product of the thermochemical processes that normally occur in Saturn’s atmosphere, the concentrations detected concurrent with the big ‘burp’ were 100 times what we would expect.”

So what was going on?

Chemical reaction rates vary greatly with the energy available for the process. Saturn’s seasonal changes are exaggerated due to the effect of the rings acting as venetian blinds, throwing the northern hemisphere into shade during winter. So when the Sun again reaches the northern hemisphere, the photochemical reactions that take place in the atmosphere can speed up quickly. If not for its rings, Saturn’s seasons would  vary as predictably as Earth’s.

But there may be another cycle going on besides the seasonal one. Computer models are based on expected reaction rates for the temperatures and pressures in Saturn’s atmosphere, explains Edgington. However, it is very difficult to validate those models here on Earth. Setting up a lab to replicate conditions on Saturn is not easy!
Also contributing to the apparent mystery is the fact that haze on Saturn often obscures the view of storms below. Only once in a while do storms punch through the hazes. Astronomers may have previously missed large storms, thus failing to notice any non-seasonal patterns.

As for atmospheric events that are visible to Earth-bound telescopes, Edgington is particularly grateful for non-professional astronomers. While these astronomers are free to watch a planet continuously over long periods and record their finding in photographs, Cassini and its several science instruments must be shared with other scientists. Observation time on Cassini is planned more than six months in advance, making it difficult to immediately train it on the unexpected. That’s where the volunteer astronomers come in, keeping a continuous watch on the changes taking place on Saturn.

Edgington says, “Astronomy is one of those fields of study where amateurs can contribute as much as professionals.”

Go to http://saturn.jpl.nasa.gov/ to read about the latest Cassini discoveries. For kids, The space Place has lots of ways to explore Saturn at http://spaceplace.nasa.gov/search/cassini/.

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

Photo Caption:
This false-colored Cassini image of Saturn was taken in near-infrared light on January 12, 2011. Red and orange show clouds deep in the atmosphere. Yellow and green are intermediate clouds. White and blue are high clouds and haze. The rings appear as a thin, blue horizontal line.

Gamma (γ) Arietis – Double Star in Aries
by Glenn Chaple

I’m a double star aficionado; my sky gazing motto is “double stars are twice the fun!” Unlike the “faint fuzzies” most backyard astronomers prefer, double stars aren’t hidden by light pollution or bright moonlight.

They aren’t the exclusive property of big-scope owners. In fact, many showpiece doubles are within reach of small-aperture instruments. The common 60mm refractor with its crisp stellar images delivers exquisite views of double stars - especially twin systems.

Case in point – gamma (γ) Arietis, properly known as Mesartim. It’s comprised of two stars, magnitudes 4.5 and 4.6, separated by 7.5 seconds of arc. Their spectral types –

F9 and A1 - are also nearly identical. What you see when you gaze into the eyepiece are two gleaming pure-white specks, eerily evocative of the eyes of some cosmic creature gazing back. The sight is mesmerizing!

Double stars are at their visual best when viewed with a magnifying power sufficient enough to allow for a comfortable split. Too little magnification, and the pair is unresolved; too much and the visual appeal is lost. In the case of gamma Arietis, you’ll want to try 50-75X.