The Official Blog of the Van Vleck Observatory
Central Connecticut is right on the edge of accuweather’s predicted optimal viewing zone for an auroral display on earth tonight. The remains of a solar storm will be sweeping by, hopefully right around sunset on the east coast. Keep an eye on the sky tonight!
Read more here!
Where engineers build their telescopes, astronomers will inevitably come. One of the great perks of having a career path associated with the night sky is the opportunity to visit places where the stars I study shine the brightest. Thanks to Wesleyan University’s newest Assistant Professor of Astronomy, Meredith Hughes, I (Eric Edelman ’13) was able to assist as a student observer at the Submillimeter Array (SMA) on the big island of Hawaii for spring break. Mahalo, Meredith!
The SMA is a telescope array composed of eight individual antennas that specializes in submillimeter, or radio, wavelengths. It is situated near 13,000 feet above sea level, close to the summit of Mauna Kea, one of Hawaii’s inactive volcanoes. This daunting altitude helps the SMA to avoid many atmospheric issues that particularly stymie ground based submillimeter observations. Fortunately, the observing station has an oxygenated control room, so I was able to remain coherent enough during my stay to absorb and document my nights as half guest observer and half gawking, consistently over-impressed tourist.
My five days on the summit gave me a quick glimpse into the many and varied challenges face by ground-based observers. In particular, the weather during my trip was extremely changeable. On my first night at that dark, isolated summit, the starry night sky was clear and vivid enough to drown in. That night, the SMA engineers worked on installing new hardware and the observers set the antennas’ sights on an AGN (active galactic nucleus), which is an extremely luminous galactic nucleus, thought to be caused by large-scale, energetic accretion of matter into the galaxy’s supremely supermassive black hole. However, by my fifth and last observing night, wind and icy snow buffeted the summit, shaded by thick, unmoving clouds, and observing or testing anything was as far from possible as it ever could be. A big portion of an observer’s job is to keep one’s eyes trained on those weather sites in order to adapt accordingly to whatever challenges the fickle weather patterns end up throwing his or her way.
While the sudden snow storm was certainly exciting, I could not enjoy those nights quite as much as I could the clear ones, when actual observing occurred. On those nights, when everything was in working order, every so often I could not help but lean back in my chair in that chilly control room and try and digest the magnitude of this whole operation. Right in front of me, only about ten yards away, was an array of telescopes pointed at and collecting information on an object most likely millions of parsecs away from us. The scale and finesse of observational astronomy has never ceased to impress me, and seeing the SMA in action was a treat to be remembered.
For any readers local to the Wesleyan campus, keep in mind that public observing is held at the campus observatory on clear Wednesday nights from 8:00-9:00pm. We cannot promise you AGNs, but I would still highly recommend a trip to Van Vleck to see the stars if you can make it!
Amy Steele, a first year MA student viewed the solar eclipse of Nov. 13, 2012, from northern Australia and sent along the attached photo. She was part of a team hoping to make measurements during totality but it looks like clouds got in the way. Nonetheless, they were able to see parts of the eclipse and she got a very nice image of a partial phase viewed through the clouds.
Seven students represented Wesleyan at the Fall 2012 Undergraduate Research Symposium of the Keck Northeast Astronomy Consortium (KNAC) held at Middlebury College on Sept. 21. All of them presented talks on their summer research projects to an audience of about 80 students and faculty from the KNAC schools. The presenting students were:
Kerry Klemmer, a senior astronomy major
Lily Zucker, a junior astronomy major
Miche Aaron, a junion E&ES major
Ben Tweed, a senior astronomy major
Eric Edelman, a senior astronomy major
Mark Popinchalk, a senior astronomy major
James Dottin, a senior E&ES major
Congratulations to all of them for their fine contributions to this exciting conference! Also among the pictures find Wesleyan Professor Ed Moran speaking with Prof. Kim McLeod of Wellesley College during one of the coffee breaks.
Without math, astronomers would be pretty lost in space! This Neptoon is a tribute to the man whose work with trigonometry made parallax (and a lot of other astronomy) possible: Pythagoras!
The unique behavior of this “winking star” was discovered in 1995 with the 24 inch (Perkin) telescope at Van Vleck. We continue to follow it at Wesleyan but most data now comes from the SMARTS telescope at Cerro Tololo Interamerican Observatory in Chile. It has been fascinating to see the light curve evolve over the years as precession of the disk has caused various parts of the orbits of the stars to be covered or revealed.
Just recently the star has brightened again, unexpectedly, and it appears that the previously unseen binary component is now peeking out the bottom of the disk. This phase is not shown in the current animation because it was created before we knew this was going to happen.
An interesting aspect of the star is that when it forms a planetary system (IF it forms one!) the planets will probably transit the stars, just like several systems recently discovered by the Kepler satellite, including Kepler 16 (sometimes referred to as Tatooine, after the mythical Star Wars planet orbiting a binary star). KH 15D may, therefore, be described as a proto-Tatooine.
The summer of 2011 was a banner year for Wesleyan students doing research in astronomy. No fewer than SIX of our students obtained competitive REU (Research Experiences for Undergraduates) assistantships sponsored by the National Science Foundation. Alexandra Truebenbach spent the summer in Puerto Rico at the Arecibo Radio Observatory. Phillip Adams and Nora Dumont were in Sunspot, New Mexico at the National Solar Observatory while Alissa Fersch was in Tucson, Arizona at the National Optical Astronomy Observatory. Ben Tweed spent the summer at Colgate University in New York, while David Amrhein split time between Williams College in Massachusetts and Hawaii, where he observed an occultation of Pluto by its moon, Charon.
All of this follows on the heals of a rare experience last year for senior astronomy major Craig Malamut. He joined an expedition to Easter Island to observe a total solar eclipse of the Sun. For more on Craig’s adventures and studies, please see the article about him in the latest issue of the Wesleyan Connection.
If you are a Wesleyan undergraduate interested in astronomy now is the time to start thinking about research for next summer. A good starting place is the Web site of the Keck Northeast Astronomy Consortium. You will find information about KNAC’s REU program and also links to other REU programs across the nation. Also, if you are passing by the poster outside of the classroom in the Observatory, take a look! There are many opportunities available. Application deadlines are approaching, so it is best to start looking now. What better way to spend your summer?!
A pair production between: Holly Capelo and Guy Geyer.
Holly: This fall was an exciting time to be studying special relativity, given that one of the most noteworthy recent science-news headlines was the possible violation of the universal speed limit, c, by superluminal neutrinos. Most of the press coverage on the OPERA report of a neutrino beam traveling through the Earth at a speed greater than light in a vacuum, was some variant on: “Einstein wrong, scientists baffled.” The attitude amongst most scientists I know was more like, “Let’s check the results, what a curiosity!” I myself wondered why Lorentz and Poincare’ weren’t given equal credit for the theory of special relativity.
As the process of investigating the results proceeds, we report on the most convincing evidence that there was no superluminal phenomenon detected, but first discuss what specifically was wrong with a paper that briefly offered the promise to explain the results using special relativity. Relativity can be counter-intuitive at times, so as a sanity check and to enrich the discussion, I have asked a fellow student, Guy Geyer to add his opinion on the same letter (which, according to Denis Overbye’s reporting, has been revised and is now under peer review, following the admission by the author of some of his early mistakes). Guy and I were asked to do a similar exercise at the culmination of a quarter-long course in Relativity taught by Prof. Fred Ellis this fall.
Since the Opera experiment released its results in September it has already received over 140 (and counting) citations from theories trying to justify the findings. Dr. van Elburg of the Department of Artificial Intelligence at the University of Groningen offered up a simple explanation for the recently-observed apparent superluminal motion of neutrinos passing through the Earth between an origin at Gran Sasso Italy to CERN Switzerland. He suggests that the measurement of the time of flight of the neutrino was actually measured from the frame of the GPS satellite, where length contraction would reduce the distance traveled according to the GPS clock, therefore shortening the time of required to cover the distance.
His paper was heavily reported upon, probably because it seems to be a simple solution that invokes special relativity and exactly reproduces the discrepancy in timing reported in the OPERA publication. This is attractive in some respects; after all, it is often a simple oversight that can disrupt a complicated process. Although, the solution may be a little too simple, since in order for special relativity to offer a sufficient explanation, one needs to establish that the Earth and satellite frames are inertial within the accuracy of the experiment – otherwise General Relativity must be invoked. As for the exact value of 64 nanoseconds, the striking similarity to the reported discrepancy may be accidental since the calculations made in the paper are done to very low-order precision.
Here are the elements of the experimental setup to consider:
The general procedure of measuring the neutrino flight time consist of a few procedural steps: 1. Determine the distance of the neutrino flight path baseline using a satellite – referred to as geodesy; 2. Bounce a radio signal originating from CERN off of a satellite towards the Gran Sasso location for the purpose of synchronizing cesium atomic clocks on either end (fiber optic cables running through the Earth were used to very verify the synchronization of the clocks and agreed to within 2 nanoseconds); 3. Having synchronized clocks at the neutrino production and detection sites, measure the distributions of departure and arrival times of the neutrinos in the Earth frame. The steps were carried out roughly in this order, although the geodesic measurements are on-going, as small shifts in the Earth’s crust need to be accounted for.
Guy: Regarding #2, This is the part of the experiment that I thought was most unclear… It isn’t really explained that well how exactly the OPERA clocks were synced. If they accounted for spec. and gen. relativity correctly to sync their clocks to earth frame time, then there shouldn’t be a problem. However, it’s still not clear to me that this is what is happening in their experiment.
Holly: You’re right, the original paper gives a schematic of these elements, but it isn’t entirely clear which calculations were made or how interdependent each of these aspects of the setup really are. Assuming that they are fairly independent, it seems to me that once the clocks are synchronized and the distance determined, then the satellite frame of reference becomes irrelevant to the measurement. Van Elburg defines a “foton” as a particle traveling at light speed, which could refer to either a radio photon used to synchronize clocks or to the neutrino beam itself. In failing to distinguish between these separate sets of events and paths in spacetime, he does not establish the need to consider the GPS frame when making the time measurement of the neutrino’s flight.
Van Elburg maintains that he is not concerned about a mistake in the time synchronization, but that the experiment could have been setup in the GPS clock frame.
Guy: I didn’t take away this impression – maybe there is something that I missed, but I thought he was saying that the mistake CERN made was that they didn’t properly account for how they were synchronizing the clocks.
Holly: Yes, I think that his argument boils down to a problem with the synchronization between clocks, but I ‘m not convinced that HE realizes that. I mean that Van Elburg claimed that the experiment was set up in the satellite frame and then proceeded to make some length contraction calculations of the baseline, but he doesn’t address any of the accompanying problems that come from trying to take coordinated time measurements between stationary and moving clocks. In particular, path- and velocity-dependent time dilation effects and a lack of synchronization with the Earth clocks would ensue.
I think the bottom line is that, although the details of the synchronization were not very explicit, Van Elburg’s premise that the experimenters forgot to change reference frames is easily refuted by looking to the original OPERA paper. The authors of the OPERA paper were conscious of having transformed back to the Earth Frame after measuring the baseline:
“The other fundamental ingredient for the neutrino velocity measurement is the knowledge of the distance between the point where the proton time-structure is measured at CERN and the origin of the underground OPERA detector reference frame at LNGS. The relative positions of the elements of the CNGS beam line are known with millimetre accuracy. When these coordinates are transformed into the global geodesy reference frame by relating them to external GPS benchmarks, they are known within 2 cm accuracy.”
So that would put the experiment back – at rest – on Earth once the baseline has been determined.
Guy and I weren’t the only ones to point out some ambiguities in the van Elburg paper which may have stemmed from the non-explicit nature of the OPERA paper itself. Such missing details make it difficult for outsiders (such as van Elburg or ourselves) to speculate about the experimental setup and any issues it may have had. Experimentally reproducing the results and proving the existence of physically related phenomena are likely to be more definitive tests of the claimed results.
More recently and perhaps more authoritatively, some relative insiders, involved with the sister project to the OPERA group known as ICARUS, have now produced a manuscript to be published in the Physical Review Letters verifying that none of the expected byproducts of superluminal motion were detected. Apart from the specific timing measurements, they considered by analogy one example where particles are known to travel faster than light speed in a given material**, which creates Cherenkov radiation. They argue that since neutrinos decay into additional particles as they lose energy, this energy loss both caps the maximum velocity of the particles and leads to the expectation that the decay products should have been detected. Using the same neutrino beam as the OPERA group, they found no such evidence for the expected decay behavior.
**Note that although the comparison to Cerenkov radiation is by analogy (the neutrino beam was claimed to have traveled faster than the vacuum speed of light) the fact that the particle beam did travel through a medium was lost on some people, leading to an embarrassing gaffe by the Italian Ministry of education, congratulating themselves for contributing to the construction of a “tunnel” between the two detector points (separated by over 500 KM, the longest tunnel in the world is about 20% this distance!) This statement received some cool response here. However, this is not the only tunnel that has been conjured in response to the findings, as dozens of theories evoking quantum behavior have arisen as well.
