Welcome to the February 2014 STARS Newsletter
This is the first year STARS has done the Holyoke Winter Carnival.
Our club outreach programs are the life blood of the club. First they are fun to do; second it is a chance to get new members. There will be a report on the
event in next month’s newsletter. Photo by Alan Rifkin.
The purpose of the newsletter is to communicate information about the club and astronomical events and topics. It is also a place where members can contribute articles, comment on STARS activities and give suggestions for the club and for this newsletter. Email them to me at email@example.com and a copy to the STARS president Alan Rifkin at firstname.lastname@example.org. If you don’t use email, then please talk with me at a future meeting. I’m the guy with a beard, probably sitting near the first row.
Looking for member contributions! What did you think of the last meeting? See anything special in the night sky recently? Get a new telescope? Do you have a photo to grace our Welcome page? Please share with your fellow members!
Here is one of Dr. Ethan Siegel’s recent blogs: Are we running out of Helium? https://medium.com/starts-with-a-bang/6757fcdaa283
Index to this Newsletter:
3) Some Upcoming Events
4) Future Speaker Lists for STARS and SOS (Stars Over Springfield)
5) Contact Info Supplied by Board Members and Officers
6-9) Spectroscopy: Balmer Series
10-12) Ethan Siegel’s Article: A Two-Toned Wonder from the Saturnian Outskirts
Because of the bad weather for the holiday party and the resulting reduced attendance, there is a make-up party on Saturday March 29th at Nippon Grill, near Kohl's at the Riverdale Shops in West Springfield at 6 PM.
More info on Nippon Grill at the web site
Northeast Astronomy Forum April 12-13 http://www.rocklandastronomy.com/neaf/
The Pioneer Valley Outdoor Festival is Saturday April 26 http://www.valleyplanning.com/
This is the second year we are doing the outdoor festival at Holyoke Community College. We are in a much nicer and bigger space this year
I am looking for volunteers to sit at the table and be outside baby-sitting scopes if it is sunny.
And Don’t Forget!
Amanda’s monthly astronomy articles (AKA “Reach for the Stars”): http://www.reflector.org/amanda/index.php
Here is a link to “Reach for the Stars” columns posted by Masslive. It's in chronological order starting with the most recent, and going back as far as July, 2011. The columns before that date would still have to be accessed through the Stars Club website. If you want to see the more recent ones as they appeared in the paper and on Masslive, with photos and all, you can view the more recent ones through this link.
Speakers and Topics for Upcoming STARS Meetings
Feb. 25: Kevin Collins - Report on Arunah Hill Solar Observatory and other Arunah Hill projects.
The Arunah Hill website: http://www.arunah.org/
March 25: David Wexler - Time and Space
April 22: Jack Megas and Kevin Kopchynski - Star of your Birth (expanded version of prior talk)
May 27: To be decided: Alan Rifkin will try to get a well-known speaker such as Jay Pasachoff
Speakers and Topics for Upcoming SOS (Stars Over Springfield)
March 7: Paul Cardone
April 4: Rich Sanderson
May 2: Jack Megas - Summer Observing
Updated Contact Info for Board Members and Officers
(Attention Board Members: it's important for board members and club members to be able to communicate with one another, and we can't do this if we don't have contact info, at least email. Thanks to those that have provided information!)
President: Alan Rifkin email@example.com 413-519-9393
Vice-President: Mike Kozicki
Secretary/Treasurer: Richard Sanderson 413-263-6800 Ext 318
Website: Mike Kozicki
Amanda Jermyn firstname.lastname@example.org 413-567-7425
Dr. David Wexler
Alan added,” I have room for new board members and board advisors. A board advisor is someone, not necessarily a club member, who is invited to Board of Directors’ meetings to help out.”
THE BALMER SERIES
Compiled by Barlow Bob
( AKA Robert Godfrey email@example.com )
The February 2014 issue of Astronomy magazine contained an article about the fate of the Sun. There was an illustration showing the differences between the various types of dark Fraunhofer absorption lines in the spectrum of the Sun, a hot blue star and a white dwarf star.
The solar spectrum consisted of many thin dark lines of different elements. The hot blue star spectrum consisted of only thin dark lines of the Balmer Series of hydrogen. The white dwarf spectrum also contained only the Balmer Series lines. In the white dwarf spectrum, however, these lines were very thick.
(continued on next page)
The spectrum of the Sun, a white dwarf, and blue giant. Image taken from: pasthorizonspr.com/index.php/archives/06/2012/stellar-archaeology-traces-milky-ways-history
Reference books and articles about spectroscopy state that the Fraunhofer lines in the spectrum of hot stars with a high-pressure atmosphere are thin. The lines of cool stars with a low-pressure atmosphere are thick. Why does a white dwarf with an extremely high-pressure atmosphere have wide Fraunhofer lines in its spectrum?
Sue French provided the explanation below, which is reprinted here with permission.
“It’s a question of density and pressure differences between the different luminosity classes of stars. Hydrogen lines broaden from luminosity class I (luminous supergiant) to luminosity class V (main sequence). The lines are generated by collisions in a star’s photosphere. Close-passing atoms can slightly disturb an electron’s energy level such that the electron can absorb at a wavelength that is a bit offset from the center of the line. Whole bunches of these interactions put together broaden the line, and higher photospheric density (class V) promotes more interactions. For example, a B5V star and a B5I star would have about the same photospheric temperature, but the lines would be broader in the former because of its higher photospheric density. Thus for the white dwarf, where the photospheric density is very high, the lines are broadened with respect to stars of similar photospheric temperature.”
From 1859 until his death at age 73, Johann Jakob Balmer (1825-1898) was a high school teacher at a girl’s school in Basel, Switzerland. His primary academic interest was geometry, but in the middle 1880’s he became fascinated with four numbers: 6,562.10, 4,860.74, 4,340.1, and 4,101.2. These are not pretty numbers, but for the mathematician Balmer, they became an intriguing puzzle. Was there a pattern to the four numbers that could be represented mathematically? The four numbers Balmer chose were special because these numbers pertained to the spectrum of the hydrogen atom. By the time Balmer became interested in the problem, the spectra of many chemical elements had been studied and it was clear that each element gave rise to a unique set of spectral lines. Balmer was a devoted Pythagorean: he believed that simple numbers lay behind the mysteries of the universe. His interest was not directed toward spectra, which he knew little about, nor was it directed toward the discovery of some hidden physical mechanism inside the atom that would explain the observed spectra. Balmer was intrigued by the numbers themselves.
In the mid-1880’s, Balmer began his examination of the four numbers associated with the hydrogen spectrum. At his disposal were the four numbers measured by Anders Jonas Angström (1814-1874): 6,562.10, 4,860.74, 4,340.1, and 4,101.2. These numbers represented the wavelengths, in units of Angströms, of the four visible spectral lines in the hydrogen atom spectrum.
The Balmer Series for hydrogen. Image taken from en.wikipedia.org/wiki/Balmer_series
In 1885, Balmer published a paper in which his successful formulation was communicated to the scientific world. Balmer showed that the four wavelengths could be obtained with the formula that bears his name: wavelength = B x (m2)/(m2-n2), with B = 3645.6 Angströms. He had found a simple mathematical formula that expressed a law by which the hydrogen wavelengths could be represented with striking precision. He further suggested that there might be additional lines in the hydrogen spectrum. Other spectral lines with their own wavelengths were predicted by Balmer and later found by other scientists. Angström measured the wavelengths of the spectral lines of hydrogen, but Balmer showed that the wavelengths of the spectral lines are not arbitrary. The values of the wavelengths are the expression of a single mathematical formula – and this Balmer Series equation altered how scientists thought about spectral lines. Before Balmer published his results, scientists drew an analogy between spectral lines and musical harmonies. They assumed that there were simple harmonic ratios between the frequencies of spectral lines. After Balmer’s work, all scientists recognized that spectral wavelengths could be represented by simple numerical relationships.
Balmer disappeared from the ranks of working scientists and continued his classroom work teaching young ladies mathematics. Neither he nor his students recognized that his paper on the spectrum of hydrogen would bring him scientific immortality. The spectral lines of hydrogen that were the focus of Balmer’s attention are now known as the Balmer Series.
Article from NASA:
A Two-Toned Wonder from the Saturnian Outskirts
By Dr. Ethan Siegel
Although Saturn has been known as long as humans have been watching the night sky, it's only since the invention of the telescope that we've learned about the rings and moons of this giant, gaseous world. You might know that the largest of Saturn's moons is Titan, the second largest moon in the entire Solar System, discovered by Christiaan Huygens in 1655. It was just 16 years later, in 1671, that Giovanni Cassini (for whom the famed division in Saturn's rings—and the NASA mission now in orbit there—is named) discovered the second of Saturn's moons: Iapetus. Unlike Titan, Iapetus could only be seen when it was on the west side of Saturn, leading Cassini to correctly conclude that not only was Iapetus tidally locked to Saturn, but that its trailing hemisphere was intrinsically brighter than its darker, leading hemisphere. This has very much been confirmed in modern times!
In fact, the darkness of the leading side is comparable to coal, while the rest of Iapetus is as white as thick sea ice. Iapetus is the most distant of all of Saturn's large moons, with an average orbital distance of 3.5 million km, but the culprit of the mysterious dark side is four times as distant: Saturn's remote, captured moon, the dark, heavily cratered Phoebe!
Orbiting Saturn in retrograde, or the opposite direction to Saturn's rotation and most of its other Moons, Phoebe most probably originated in the Kuiper Belt, migrating inwards and eventually succumbing to gravitational capture. Due to its orbit, Phoebe is constantly bombarded by micrometeoroid-sized (and larger) objects, responsible for not only its dented and cavity-riddled surface, but also for a huge, diffuse ring of dust grains spanning quadrillions of cubic kilometers! The presence of the "Phoebe Ring" was only discovered in 2009, by NASA's infrared-sensitive Spitzer Space Telescope. As the Phoebe Ring's dust grains absorb and re-emit solar radiation, they spiral inwards towards Saturn, where they smash into Iapetus—orbiting in the opposite direction—like bugs on a highway windshield. Was the dark, leading edge of Iapetus due to it being plastered with material from Phoebe? Did those impacts erode the bright surface layer away, revealing a darker substrate?
In reality, the dark particles picked up by Iapetus aren't enough to explain the incredible brightness differences alone, but they absorb and retain just enough extra heat from the Sun during Iapetus' day to sublimate the ice around it, which resolidifies preferentially on the trailing side, lightening it even further. So it's not just a thin, dark layer from an alien moon that turns Iapetus dark; it's the fact that surface ice sublimates and can no longer reform atop the leading side that darkens it so severely over time. And that story—only confirmed by observations in the last few years—is the reason for the one-of-a-kind appearance of Saturn's incredible two-toned moon, Iapetus!
Learn more about Iapetus here: http://saturn.jpl.nasa.gov/science/moons/iapetus.
See images on next page!
Images credit: Saturn & the Phoebe Ring (middle) - NASA / JPL-Caltech / Keck; Iapetus (top left) - NASA / JPL / Space Science Institute / Cassini Imaging Team; Phoebe (bottom right) - NASA / ESA / JPL / Space Science Institute / Cassini Imaging Team.
End of the February 2014 Newsletter
Copyright © Art Meyer