Bill Murray and Jay Schwartz on the cover of US 1. February 29, 2012
If you missed the print edition, the full article is available online at: US1, February 29, 2012
Rosette Nebula. Credit: Brian Van Liew
Astrophotography – An Inside Look
Years ago I had offered interested members a SIG (special interest group) on getting into astrophotography. Over the last year, I have not been active in imaging. Well, as it is starting to warm up, I would like to start this again. I am currently using a DSLR as my imaging camera and would like to share what I use to image with in both hardware and software.
Since this meeting would take place at my home in Belle Mead, NJ, I can only open it up to a few at a time. Once I see how much interest there is in this, I will notify the respondents a date and time that works best. I’m thinking some time in late March or in April. So if you would like to have an inside look at what it takes to image, contact me at brian@princetonastronomy.org.
Brian Van Liew
compiled by Bryan Hubbard
NASA’S Chandra Finds Fastest Wind from Stellar-Mass Black Hole
Published: Tuesday, February 21, 2012 – 16:33 in Astronomy & Space
Astronomers using NASA’s Chandra X-ray Observatory have clocked the fastest wind yet discovered blowing off a disk around a stellar-mass black hole. This result has important implications for understanding how this type of black hole behaves. The record-breaking wind is moving about 20 million mph, or about 3 percent of the speed of light. This is nearly 10 times faster than had ever been seen from a stellar-mass black hole.
Stellar-mass black holes are born when extremely massive stars collapse. They typically weigh between five and 10 times the mass of the Sun. The stellar-mass black hole powering this super wind is known as IGR J17091-3624, or IGR J17091 for short.
For the full story go to – Fastest wind from stellar-mass black hole
Scientists Discover a Saturn-Like Ring System Eclipsing a Sun-Like Star
Published: Wednesday, January 11, 2012 – 14:35 in Astronomy & Space
A team of astrophysicists from the University of Rochester and Europe has discovered a ring system in the constellation Centaurus that invites comparisons to Saturn. The scientists, led by Assistant Professor of Physics and Astronomy Eric Mamajek of Rochester and the Cerro Tololo Inter-American Observatory, used data from the international SuperWASP (Wide Angle Search for Planets) and All Sky Automated Survey (ASAS) project to study the light curves of young sun-like stars in the Scorpius-Centaurus association — the nearest region of recent massive star formation to the Sun.
The basic concept of the research is straightforward. Imagine yourself sitting in a park on a sunny afternoon and a softball passes between you and the sun. The intensity of light from the sun would appear to weaken for just a moment. Then a bird then flies by, causing the intensity of the sunlight to again weaken — more or less than it did for the baseball, depending on the size of the bird and how long it took to pass. That’s the principle that allowed the researchers to discover a cosmic ring system.
For the full story go to – Saturn-Like Ring System
Discovery of the Smallest Exoplanets: The Barnard’s Star Connection
Published: Wednesday, January 11, 2012 – 17:36 in Astronomy & Space
The discovery of the three smallest planets yet orbiting a distant star, which was announced January 11 at the annual meeting of the American Astronomical Society, has an unusual connection to Barnard’s star, one of the Sun’s nearest neighbors. The discovery was made by a scientific team led by astronomers at the California Institute of Technology (Caltech) that included three members from Vanderbilt. The team used data from NASA’s Kepler mission combined with additional observations of a single star, called KOI-961, to determine that it possesses three planets that range in size from 0.57 to 0.78 times the radius of Earth. This makes them the smallest of the more than 700 exoplanets confirmed to orbit other stars.
In their investigation of KOI-961, which is about 130 light years away in the Cygnus constellation, the astronomers found that it is nearly identical to Barnard’s star, which is only six light years away in the constellation Ophiuchus. This similarity allowed them to use information about Barnard’s star, which was discovered in 1916 by Vanderbilt astronomer E.E. Barnard, to determine the mass, size and luminosity of the distant star. These values, in turn, were used to determine the size of the three new exoplanets.
For the full story go to – The Barnard’s star connection
UCLA Astronomers Solve Mystery of Vanishing Electrons
Published: Sunday, January 29, 2012 – 17:31 in Astronomy & Space
UCLA researchers have explained the puzzling disappearing act of energetic electrons in Earth’s outer radiation belt, using data collected from a fleet of orbiting spacecraft. In a paper published Jan. 29 in the advance online edition of the journal Nature Physics, the team shows that the missing electrons are swept away from the planet by a tide of solar wind particles during periods of heightened solar activity.
“This is an important milestone in understanding Earth’s space environment,” said lead study author Drew Turner, an assistant researcher in the UCLA Department of Earth and Space Sciences and a member of UCLA’s Institute for Geophysics and Planetary Physics (IGPP). “We are one step closer towards understanding and predicting space weather phenomena.”
The complete article may be found at Vanishing Electrons
By John Church
Some years ago I analyzed the objective lens of the AAAP’s historic 6-1/4-inch Hastings-Byrne (H-B) refractor and published the results in Sky & Telescope magazine, along with a history of the telescope1. The readers of Sidereal Times might be interested in knowing how the basic concepts of geometrical optics apply to this fine old instrument.
Geometrical optics starts with the idea that light consists of thin rays whose paths through transparent media can be treated by relatively simple mathematics. This approach is oversimplified in that it ignores the whole field of physical optics, where light is treated as waves rather than rays and which allows us to account for phenomena such as interference and diffraction. Diffraction causes the series of rings we see around the telescopic images of stars, with larger apertures giving smaller rings and therefore better resolution. The mathematics of physical optics is more complex than the relatively simple algebra and trigonometry we use for geometrical optics. But when it comes to lens design and optimization, geometrical optics actually works very well.
Another simplification is often used in the preliminary design of a lens, where we assume that the elements are thin in comparison with their focal lengths. This assumption is actually better than it sounds, as refractor lenses at typical f/ratios are actually thin as compared with their focal lengths. Also, the two components needed to make a color-corrected achromat are close to one another, sometimes in actual contact.
The above approach neglects color correction as well as the important field aberrations such as spherical aberration, coma, and the like. When the design of complex lenses gets farther along, we often use trigonometric ray-tracing to optimize achromatism and the actual shapes and surface curvatures of the lens elements. But for the common case of doublet refractor objectives slower than about f/10, such as the H-B lens at nearly f/15, a computer program can give excellent design results with correction of all the significant aberrations. However, this is getting away from our main story.
A converging lens is one that is thicker in the middle than at the edge. It could be either biconvex or have one surface convex and the other concave, as long as it’s thicker in the middle. Such lenses will bring light to a focus and form a real image. On the other hand, a lens that is thicker at the edge than in the middle is a diverging lens. It could be either biconcave or have one surface concave and the other convex, as long as the edge is thicker than the middle. It cannot bring light to a definite focus by itself, but in combination with a converging lens of the right focal length, it can make a lens that does form a real image. All two-element refractor lenses are like this. The H-B lens is made up of one converging and one diverging lens made of different kinds of glass, in order to provide achromatism (color correction).
The focal length of a thin lens is given by the well-known “lens-maker’s formula”:
FL = 1/[(n – 1) (1/R1 – 1/R2>)]
where n is the refractive index of the glass, R1 is the radius of curvature of the first surface that the light encounters, and R2 is the radius of curvature of the rear surface where the light emerges. With the usual convention that light goes from left to right, a radius is considered positive if its center of curvature is to the right, and negative if to the left. Thus, for a typical biconvex lens such as the front (crown) element of the H-B objective, R1 is positive and R2 is negative.
The values of these radii as determined by my measurements with a spherometer are R1 = + 1,336 mm and R2 = – 606 mm. For light near the middle of the visible spectrum, at a wavelength of 561.4 nm, the refractive index of this glass (according to measurements by Hastings) is 1.516673. Thus, applying the lens maker’s formula, the focal length of the crown element is 807 mm for light of this wavelength.
The “power” of a lens is the inverse of its focal length. Thus, a lens with a long focal length has low power, i.e. it converges light only weakly. For the H-B crown element, the power is 1/807 = 0.001239 inverse mm. In eyeglass lenses, power is given in units of inverse meters (called “diopters”) instead of inverse mm. So the H-B crown element has a power of 1.239 diopters, which is comparable to the power of weak ordinary reading glasses.
The concept of power is useful with compound lenses such as the H-B achromat, because the power of a thin combination is simply the sum of the individual powers of the elements. The final focal length will then be the inverse of the total power. (It’s important not to confuse the power of a lens with the magnifying power of a telescope with an eyepiece in place, which is the focal length of the objective divided by the focal length of the eyepiece.)
For the flint element of the H-B objective, we have the following radii and refractive index (again for the same wavelength of light): n = 1.616333, R1 = – 625 mm, and R2 = – 3,435 mm. It’s a diverging lens, because it’s thicker at the edge than in the middle. Rounding off the results to 4 figures, its focal length comes out to – 1,240 mm and its power is – 0.0008067 inverse mm, or – 0.8067 diopters. Adding up the powers of the two elements, we get a total power of 0.0004323 inverse mm (0.4323 diopters), and a focal length of 2,313 mm, or 91.1 inches.
This is fine, but what about a direct measurement of the focal length? I experimentally determined this by two methods. First, I made a direct-objective color slide during a total lunar eclipse when the moon’s diameter was known to be 30’13” and measured the image diameter at 0.801 inches with a micrometer. The focal length came out to 91.1 inches. I also set up a 30-foot long optical bench in my back yard and meas-ured the focal length by the conjugate focus method, casting the image of a penlight bulb on a screen and getting the same result. Calculating the focal length via trigonometric ray tracing, taking into account the actual glass thicknesses and separation of the elements, gives the same value to within the limits of rounding-off errors. So for a long-focus refractor with relatively thin elements, simple theory will give excellent results for the actual focal length.
One might still ask, how does a lens designer determine in advance the relative shapes of the two elements of an achromatic lens? For a given pair of glasses, many different combinations of radii could give the same total focal length for a given wavelength of light as well as acceptable color correction. I plan to discuss this in a later article, as well as how we further determine the proper element shapes in order to minimize spherical aberration and coma.
1 J. Church, Sky & Telescope, March 1979, p. 294-300.
2 J. Church, Sky & Telescope, November 1984, p. 450-451.
by Dr. Ken Kremer
NASA’s resilient Opportunity robot has begun her ninth year roving around beautiful Earth-like Martian terrain where potentially life sustaining liquid water once flowed billions of years ago. Opportunity celebrated her eighth anniversary on the red planet gazing at the foothills of the vast crater named Endeavour that promises a “mother lode” of water related science – an unimaginable circumstance since the nail biting landing on the hematite rich plains of Meridiani Planum on 24 January 2004. She is now 99 months into the three month mission, that’s 33 times beyond the designers’ expectation.
Mars Rover Opportunity. Credit: NASA/JPL/Cornell/ASU/Marco Di Lorenzo/Kenneth Kremer
NASA’s endearing robot is simultaneously carrying out an ambitious array of ground breaking science experiments this winter providing insight into the mysterious nature of the Martian core while sitting stationary until the energy augmenting rays of the springtime sun shower down on her from the heavens above.
“Milestones like eight years on Mars always make me look forward rather than looking back,” Rover Principal Investigator Prof. Steve Squyres of Cornell University told me for this article commemorating Opportunity’s landing. “We’ve still got a lot of exploring to do, but we’re doing it with a vehicle that was designed for a 90-sol mission. That means that every sol is a gift at this point.”
Opportunity has driven more than 21 miles across the red planet’s surface during what is truly human-kind’s first overland expedition on another planet. NASA’s twin rovers Spirit and Opportunity blasted off for Mars atop a pair of Delta II rockets in the summer of 2003 with a mission “warranty” of just 90 Martian days, or Sols.
The robot will remain parked at Endeavour for the winter on a slope at the north end of the crater rim segment called Cape York with an approximate 15-degree northerly tilt towards the life-giving sun to maximize solar energy production. The park-site is at an outcrop dubbed “Greeley Haven”, named in honor of Ronald Greeley, a beloved and recently deceased science team member.
This is the first winter that Opportunity did not have sufficient power to continue roving across the surface, because of the thick layer of dust on the solar arrays. Since Opportunity is just south of the Martian equator, the daylight hours for solar power generation are growing shorter until the southern Mars winter solstice occurs on March 30, 2012.
The rover science team is ingeniously using the lack of movement to their advantage, and Opportunity is still vigorously hard at work doing breakthrough research every day. From her stationary position, Op-portunity is conducting her first radio-science, Doppler tracking measurements to support geo-dynamic investigations and to elucidate the unknown structure of the Martian interior and core. The team was eager for the long awaited chance to carry out the radio tracking experiment with the High Gain Antenna (HGA) and determine if Mars’ core is liquid or solid. Months of data collection are required while the rover stays stationary.
“This winter science campaign will feature two-way radio tracking with Earth to determine the Martian spin axis dynamics – thus the interior structure, a long-neglected aspect of Mars,” Ray Arvidson told me. Arvidson, of Washington University in St. Louis, is the Deputy Rover Principal Investigator.
A few months after the Martian southern winter solstice, the team will drive her off the outcrop and fur-ther explore Cape York in search of further evidence of the gypsum mineral veins like “Homestake” – indicative of ancient water flow – previously discovered at Cape York. Then Opportunity will rove further south to investigate deposits of phyllosilicates, the clay minerals which stem from an earlier epoch when liquid water flowed on Mars and which may have been more favorable to sustaining life.
Meanwhile, NASA’s Curiosity Mars Science Laboratory rover is rocketing through space and on course for a pinpoint touchdown inside the layered terrain of Gale Crater on August 6, 2012. Curiosity is now America’s last planned Mars rover following the Obama administration’s cancellation of the joint NASA/ESA ExoMars rover mission.
Check Ken’s Mars features online at Universe Today and the February 2012 issue of Spaceflight magazine:
Opportunity Phones Home Dusty Self-Portraits and Ground Breaking Science
A Penny for your Curiosity on Mars
Experts React to Obama Slash to NASA’s Mars and Planetary Science Exploration
Spirit Lander – 1st Color Image from Mars Orbit
NASA’s Resilient Rover Opportunity Begins Year 9 On Mars with Audacious Science Ahead
Astronomy Outreach by Ken Kremer
Rockland Astronomy Club RAC, Rockland Community College, Suffern, NY, Mar 16, 8 PM, “NASA’s Year of the Solar System: Mars, Moon, Mercury, Vesta, Jupiter, Comets and Beyond (plus 3-D”). Website: http://www.rocklandastronomy.com/
New Jersey Astronomical Association NJAA- Vorhees State Park: High Bridge, NJ, March 24, Sat., 8 PM “Atlantis, the End of America’s Shuttle Program and What’s Beyond for NASA”. Website: http://www.njaa.org/
Ken Kremer: Spaceflight magazine & Universe Today
Ken has a selection of his Shuttle photos and Mars mosaics for sale as postcards and frameable prints.
Please contact Ken for more info or science outreach presentations:
Email: kremerken@yahoo.com website: www.kenkremer.com
http://www.universetoday.com/author/ken-kremer/
by Ludovico D’Angelo, Director AAA
We had a very productive Board of Trustee’s meeting on January 25th. Thanks to all that attended. It was crowded, but I was very pleased to have so much input into the club’s future.
On November 5, 1962, a group of astronomy enthusiasts formed the AAAP at their first meeting. This year will mark the 50th year of astronomical discovery, research, and knowledge. I am happy to be part of this club and grateful that it exists. It supplies anyone with an interest in astronomy the chance to learn and grow in knowledge through our regular meetings and guest speakers, And also through our observatories where we can observe the night sky. Read the club history online by accessing the pull down in the upper right corner of the webpage. It will give a good perspective on our 50 years.
The Board is agreed that there will be many activities that promote our club and astronomy enthusiasm in Princeton and its local surroundings as part of our 50th year. To accomplish these things, we need your participation. Activities that we have in mind are a presence at Princeton’s Communiversity in April, Super Science Day at the Trenton State Planetarium (also in April), and weekly or monthly sidewalk astronomy in Princeton throughout the year, starting in March.
We are trying to arrange a location for a public event to view the Transit of Venus, which occurs this year on June 5th. The location at this point will be Baldpate Mountain. It will be the last time to view this event from the earth for more than 100 years. Suffice to say, none of us will be here at the next occurrence.
We also had plans to show a movie “The City Dark” (which premiered in New York a few weeks ago) and have sidewalk astronomy afterwards. As it happens, the film “The City Dark” will be shown at the Princeton Public Library on February 11th at 7 pm. We will set up some scopes by the library after the movie. The director of the film, Ian Cheney, is scheduled to speak afterwards in a Q&A session along with Michael Lemonick, who spoke to our club in the fall of 2009. Go to http://www.princetonlibrary.org for details on the Princeton Environmental Film Festival.
A dinner party to celebrate the club in lieu of our November meeting has been suggested. Stay tuned for more info on this. If you would like to help plan and pick the location, please speak up!
A process is underway to create a Facebook page to expanding our presence on the web, to communicate and announce special events, and to be connected in general. It needs some help to organize, so if any of you have experience setting up a page for an organization, please contact me.
Other activities discussed at the Board meeting were trips to any one of numerous dark sky sites, to the Navel Observatory in Washington, DC, and to the Southwest. Plus there are several outreach events coming up, and some great speakers for the rest of our current season! We are just a flurry of activity (without the actual snow flurries).
If any of you should have more suggestions, please bring them to the next meeting, and also please attend the next meeting where our guest speaker will be Dr. Paul Stenhardt of Princeton University. Please stay afterwards for the discussion on planning our future astronomy events.
See you all in Peyton Hall on February 14th (Happy Valentine’s Day!) at 8 p.m.
Ken Levy, Program Chair
AAAP Enjoys Dr. Shara’s Talk Credit: Ken Levy
Many thanks to Dr. Michael Shara who provided a fascinating talk on the structure and evolution of novae and supernovae as well as a focus on his current exhibit at the American Museum of Natural History, Beyond Planet Earth: The Future of Space Exploration. I encourage all members to visit the exhibit, now on view through August 12th. If you missed the lecture or would like to review it, please go to the following link for a complete MP3 of the talk: files.me.com/kenetics/97phzg.mp3
Dr. Michael Shara Credit: Ken Levy
This month we’re proud to have Dr. Paul Steinhardt. Dr. Steinhardt is the Albert Einstein Professor in Science and Director of the Princeton Center for Theoretical Science at Princeton University, where he’s also on the faculty of both the Department of Physics and the Department of Astrophysical Sciences.
Dr. Steinhardt is the author of over 200 refereed articles, five patents, three technical books, numerous popular articles. In 2007, he co-authored Endless Universe: The Big Bang and Beyond, a popular book on contemporary theories of cosmology.
Dr. Paul Steinhardt. Courtesy: Embry-Riddle Aeronautical University
He is one of the co-discoverers of the first natural quasicrystal and recently organized a geological expedition to Chukotka in Far Eastern Russia to find new information about its origin and search for more samples. Dr. Steinhardt will be speaking on the controversial topic “Inflationary Cosmology on Trial” from his recently published article in Scientific American; another not to miss lecture, on Valentine’s Day, Tuesday February 14th. Bring someone you love!
by David Letcher, Outreach Chair
So far this 2012 season has seen us scheduled for three star parties. January 26th was to be our first of the season at Antheil School in Ewing, NJ, but very cloudy weather put a damper on that one. The next one was a very successful but chilly evening at the Lawrenceville Elementary School on Friday, January 27th. Thanks go to members Gene Ramsey, Jeff Bernardis, Victor Davis, Darryl Foyuth, and yours truly. Many children and their parents enjoyed seeing the waxing crescent moon, Jupiter, double stars, clusters and the Great Nebula in Orion.
Our next scheduled star party will be held at the Hopewell Elementary School on the evening of Friday, March 16th. Let me know if you are interested in volunteering and helping out. I’ll be sending reminder emails to our membership in the near future.
Lastly, I received a request from Ms. Emily Blackman of the D&R Greenway Land Trust in Princeton about the possibility of co-hosting an event this summer. She states that they are sched-uling a trail walk and meteor shower watching event for Sunday August 12th from 8-9:30 pm. This event will be held on Cider Mill Preserve in East Amwell. (I hope the Perseids will be visible. I’ll have to tell them that late night hours are best for seeing meteor showers.) We are asked if we would be interested in co-hosting and bringing along some telescopes for attendees to use. August is a bit into the future but keep this event in mind. That’s all for now!
Larry Kane, Secretary
The meeting was called to order by Director Ludy D’Angelo.
Larry Kane, Secretary
The meeting was called to order by Director Ludy D’Angelo.
Amateur Astronomers Association of Princeton 