The Gloucester Area Astronomy Club

High-energy Spy

By Dr. Martin C. Weisskopf

The idea for the Chandra X-Ray Observatory was born only one year after Riccardo Giacconi discovered the first celestial X-ray source other than the Sun. In 1962, he used a sounding rocket to place the experiment above the atmosphere for a few minutes. The sounding rocket was necessary because the atmosphere blocks X-rays. If you want to look at X-ray emissions from objects like stars, galaxies, and clusters of galaxies, your instrument must get above the atmosphere. 

Giacconi’s idea was to launch a large diameter (about 1 meter) telescope to bring X-rays to a focus. He wanted to investigate the hazy glow of X-rays that could be seen from all directions throughout the sounding rocket flight.  He wanted to find out whether this glow was, in fact, made up of many point-like objects. That is, was the glow actually from millions of X-ray sources in the Universe. Except for the brightest sources from nearby neighbors, the rocket instrument could not distinguish objects within the glow.

Giacconi’s vision and the promise and importance of X-ray astronomy was borne out by many sounding rocket flights and, later satellite experiments, all of which provided years-, as opposed to minutes-, worth of data.

By 1980, we knew that X-ray sources exist within all classes of astronomical objects. In many cases, this discovery was completely unexpected. For example, that first source turned out to be a very small star in a binary system with a more normal star. The vast amount of energy needed to produce the X-rays was provided by gravity, which, because of the small star’s mass (about equal to the Sun’s) and compactness (about 10 km in diameter) would accelerate particles transferred from the normal star to X-ray emitting energies. In 1962, who knew such compact stars (in this case a neutron star) even existed, much less this energy transfer mechanism?

X-ray astronomy grew in importance to the fields of astronomy and astrophysics. The National Academy of Sciences, as part of its “Decadal Survey” released in 1981, recommended as its number one priority for large missions an X-ray observatory along the lines that Giacconi outlined in 1963. This observatory  was eventually realized as the Chandra X-Ray Observatory, which launched in 1999.

The Chandra Project is built around a high-resolution X-ray telescope capable of sharply focusing X-rays onto two different X-ray-sensitive cameras. The focusing ability is of the caliber such that one could resolve an X-ray emitting dime at a distance of about 5 kilometers! 

The building of this major scientific observatory has many stories.

Learn more about Chandra at www.science.nasa.gov/missions/chandra .  Take kids on a “Trip to the Land of the Magic Windows” and see the universe in X-rays and other invisible wavelengths of light at spaceplace.nasa.gov/magic-windows.

Dr. Weisskopf is project scientist for NASA's Chandra X-ray Observatory. This article was provided by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

Image Caption: Composite image of DEM L50, a so-called superbubble found in the Large Magellanic Cloud. X-ray data from Chandra is pink, while optical data is red, green, and blue. Superbubbles are created by winds from massive stars and the shock waves produced when the stars explode as supernovas.

Our June 14 meeting is rapidly approaching, and it's going to be a dandy. We're holding the meeting in the Visitor's Center at Halibut Point State Park, with a star party immediately following (weather permitting).

At the meeting, amateur astronomer Jim Koerth will show us what's going to be up in the sky to look at and how to find it, and afterwards we'll go out onto the grounds of the park and observe everything we just heard about in Jim's presentation. Some objects to look forward to include the moon and Saturn, as well as bright galaxies and star clusters.

The meeting will be on Friday the 14th regardless of weather, although if the weather doesn't cooperate the observing portion will have a cloud date of the next night, Saturday 6/15 at sunset. As a rule of thumb, if you can see the moon and some stars, we'll be out there.

The meeting will start promptly at 8:00 as always. Here's a map: http://bit.ly/16SLCjd

Please park in the paved lot on Gott Avenue and walk up the gravel drive to the Visitor's Center.

Present: Patrick, Dick L, and myself, along with several couples who visited for awhile.

Best transparency in a long time, very dry (no dew at all until long after the moon was up), and great seeing. Only downside was that deep sky viewing time was cut short, but I drove myself night blind absorbing colors and features of the waning moon at 300x.

Also at 300x, could detect subtle color difference between Saturn and rings, and between outer and inner rings:

http://www.practicalspace.com/saturn/images/hubble-saturn-1.jpg

Found what I've dubbed The Little Hercules Cluster (near the Great Cluster, and also sits at the apex of a triangle formed with two stars):

http://www.astro.uni-bonn.de/~mischa/gallery_ccd/ngc6229.jpg

Visited my old favorite binary, though I just learned it's actually a triple star system. The distance between primary and secondary is 55 AU's (astronomical unit = distance between earth and sun):

http://jumk.de/astronomie/big-stars/ras-algethi.shtml

And only heard two mosquitos all night. Probably the last bug-free viewing before the fall.

Alan

Nu Scorpii – A “Double-double” Challenge in Scorpius
by Glenn Chaple

I first met nu Scorpii in the summer of 1971. Using a 3-inch f/10 reflector and magnifying power of 60X, I saw the same wide (41 arc-second) magnitude 4.2 and 6.6 double star that the German astronomer Christian Mayer had discovered nearly two centuries earlier. At the time, I had no idea there was more to be seen.

Neither did the American astronomer Ormsby M. Mitchel (who would later become a decorated Civil War general) when, in 1846, he eyed nu Scorpii with the 11-inch refractor at the Cincinnati Observatory. He was able to split the fainter star into its magnitude 6.6 and 7.2 components, which were 1.1 arc-seconds apart at the time. In 1873, the eagle-eyed double star observer S. W. Burnham outdid Mitchel by detecting the duplicity of the brighter star when its magnitude 4.4 and 5.3 components were a mere 0.3 arc-seconds apart. This was an amazing visual accomplishment, as Burnham made the discovery using a 6-inch refractor!

In the ensuing decades, these two pairs (designated Mitchel 2 and Burnham 120) widened and, by the early 1900s, were within reach of medium aperture scopes. In 1905, Agnes Clerke wrote that nu Scorpii is “perhaps the most beautiful quadruple group in the heavens.” Other astronomers likened it to the better-known “Double-double” epsilon Lyrae.

Today, the two binary stars that comprise the nu Scorpii system are wider than ever – 2.4 arc-seconds for Mitchel 2 and 1.3 arc-seconds for Burnham 120. Splitting them will still require planning and patience. Because of its southerly declination, you’ll have to wait until nu Scorpii is as high above the horizon as possible (around 10pm on a mid-June evening). Optimum seeing conditions are a must, and you’ll need an optically sound telescope of at least 6-inch aperture and a 200X-plus magnifying power.

Was Agnes Clerke’s assessment of nu Scorpii accurate? Does it actually outrank the celebrated epsilon Lyrae in visual splendor? You won’t know unless you give each a telescopic examination.
 

Triple Treat

By Dr. Ethan Siegel

The solar system is a busy place, with five wandering planets visible to the naked eye alone. When any two pass close by each other from our point of view, we see an astronomical conjunction, but on very rare occasions, three planets will find themselves grouped together: a triple conjunction. Towards the end of May, Mercury, Venus and Jupiter will treat us to the best triple conjunction in years.

During the nights of May 26th-27th, all three planets are visible immediately after sunset within the same 3° field of view, with the triple conjunction peaking in a triangular shape on the 26th. (For scale, the full Moon subtends about 1/2°.) The three planets appear close together for a few days more, making a line in the sky on the 30th/31st.

How does this happen? Mercury and Venus race around the Sun far faster than Earth, with Mercury completing more than four revolutions around the Sun for each one that Earth makes. At the same time, Jupiter is far slower, taking 12 years to orbit just once around the Sun. Jupiter’s been high in the sky during the early parts of the night, but steadily lowers throughout May as Earth continues to move away from it, approaching its maximum distance from Earth. Mercury and Venus, meanwhile, begin to move out from behind the Sun during May: Venus at the beginning of the month and Mercury in the middle.

Thus, during this triple conjunction, all three planets will be on the far side of the Sun, something that happens just 25% of the time in triple conjunctions involving Mercury and Venus! If you telescopically resolve these planets into disks, you’ll see our inner worlds in a nearly-full gibbous phase. Jupiter will appear largest in terms of angular diameter, followed by Venus and lastly by Mercury.

Just a year ago, during its now-famous transit, Venus took up more than a full arc-minute in the sky; during this conjunction, it will just one-sixth that angular size and less than a third the apparent diameter of Jupiter. Nevertheless, Venus will still be more than six times as bright as Jupiter during this time, outshining all night-sky objects other than the Moon. Closer conjunctions of two naked-eye planets are frequent, but getting three or more like this happens just once or twice per decade, so don’t miss your chance to see it.

And speaking of occultations, The Space Place has a great kid-friendly explanation of the Venus transit and solar eclipses of 2012 at spaceplace.nasa.gov/venus-transit.

Dr. Ethan Siegel, a theoretical astrophysicist, is a professor at the University of Portland (OR) and Lewis & Clark College.

Picture Caption: The image shows the configuration of Mercury, Venus, and Jupiter in the western sky just after sunset on May 26, 2013. Insets show the relative size appearance of the planets on that date.

Exploring the Water World

In some ways, we know more about Mars, Venus and the Moon than we know about Earth. That’s because 70% of our solar system’s watery blue planet is hidden under its ocean. The ocean contains about 98% of all the water on Earth. In total volume, it makes up more than 99% of the space inhabited by living creatures on the planet.

As dominant a feature as it is, the ocean—at least below a few tens of meters deep—is an alien world most of us seldom contemplate. But perhaps we should.

The ocean stores heat like a “fly wheel” for climate. Its huge capacity as a heat and water reservoir moderates the climate of Earth. Within this Earth system, both the physical and biological processes of the ocean play a key role in the water cycle, the carbon cycle, and climate variability.

This great reservoir continuously exchanges heat, moisture, and carbon with the atmosphere, driving our weather patterns and influencing the slow, subtle changes in our climate.

The study of Earth and its ocean is a big part of NASA’s mission. Before satellites, the information we had about the ocean was pretty much “hit or miss,” with the only data collectors being ships, buoys, and instruments set adrift on the waves.

Now ocean-observing satellites measure surface topography, currents, waves, and winds. They monitor the health of phytoplankton, which live in the surface layer of the ocean and supply half the oxygen in the atmosphere. Satellites monitor the extent of Arctic sea ice so we can compare this important parameter with that of past years. Satellites also measure rainfall, the amount of sunlight reaching the sea, the temperature of the ocean’s surface, and even its salinity!

Using remote sensing data and computer models, scientists can now investigate how the oceans affect the evolution of weather, hurricanes, and climate. In just a few months, one satellite can collect more information about the ocean than all the ships and buoys in the world have collected over the past 100 years!

NASA’s Earth Science Division has launched many missions to planet Earth. These satellites and other studies all help us understand how the atmosphere, the ocean, the land and life—including humans—all interact together.

Find out more about NASA’s ocean studies at http://science.nasa.gov/earth-science/oceanography. Kids will have fun exploring our planet at The Space Place, http://spaceplace.nasa.gov/earth.

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

Image Caption:

This image from September 2012, shows that the Arctic sea is the smallest recorded since record keeping began in 1979. This image is from  NASA’s Scientific Visualization Studio at Goddard Space Flight Center.

See this Boston night sky?

It's coming this way, incrementally, bit by bit, light by light. Please make plans to attend this month's very important GAAC meeting, with Dr. Mario Motta speaking on the dangers to our dark Cape Ann skies and even to our health posed by the encroaching lights.

If you want your children to be able to look up and see the milky way stretching overhead, come to this month's meeting, 8:00, Friday night April 12 and hear about the problem and what we can do about it. Like all GAAC meetings it will be fun, informative and free, with lots of good things to eat and great conversation.

See you there!

Messier 101 – Spiral Galaxy in Ursa Major
by Glenn Chaple

One of the best examples of a star-hop is the one that takes us from Mizar (the middle star in the Handle of the Big Dipper) to the face-on spiral galaxy M101. It’s a fortuitous situation because, were it isolated, M101 might be one of the more difficult Messier objects to locate. M101 has a listed at magnitude of 7.9, but the light is spread over a roughly circular area just under one-half degree across. The situation mirrors that of M33, another elusive face-on spiral.

While there is no major star-hop path to M33, there is one to help us locate M101.Bridging the 5 degree gap between Mizar and M101 is a chain of stellar steppingstones madeup of 81, 83, 84, and 86 Ursae majoris. Mizar’s naked eye partner Alcor (80 UMa) conveniently points the way from Mizar to 81 UMa, and from there you’re on your way.

Viewed with small-aperture scopes, M101 is a diffuse circular glow about ¼ degree across. An 8-inch scope will begin to reveal traces of the spiral arms, while a large Dob will capture knots within the arms – H II regions and stellar associations bright enough to have their own NGC designations.

Four supernovae have been observed in M101 since 1900. The most recent reached 10th magnitude in September 2011. This is indeed a galaxy worthy of our attention.

  Chart from www.astrosurf.com      photo by Mario Motta M.D.