While the Green Bank Observatory celebrates its one-year anniversary in October, the location itself (Green Bank) is celebrating a much longer relationship with radio astronomy. Green Bank, West Virginia, was the first home of the National Radio Astronomy Observatory (NRAO) and we are celebrating 60 years of research and discovery this year!
The Milky Way is chock-full of star clusters. Some contain just a few tens-to-hundreds of young stars. Others, known as globular clusters, are among the oldest objects in the Universe and contain up to a million ancient stars.
Some globular clusters are thought to be fragments of our galaxy, chiseled off when the Milky Way was in its infancy. Others may have started life as standalone dwarf galaxies before being captured by the Milky Way during its formative years.
Regardless of their origins, many globular clusters reside either in or behind the dusty regions of our galaxy. For ground- and space-based optical telescopes, however, this poses a challenge. Though it is possible to observe the cluster as a whole, the dust hinders astronomers’ efforts to study the motions of individual stars. If astronomers could track the motions of individual stars, they could see how “lumpy” the globular cluster is or if it contains something really dense, like a giant black hole at its center.
Fortunately, radio waves — like those emitted by pulsars — are unhindered by galactic dust. So rather than tracing the motions of the stars, astronomers should be able to map the motions of pulsars instead. But, of course, things are never that simple. Though globular clusters are brimming with stars, they contain far fewer pulsars.
“That’s what makes Terzan 5 such an important target of study; it has an unprecedented abundance of pulsars – a total of 37 detected so far, though only 36 were used in our study,” said Brian Prager, a Ph.D. candidate at the University of Virginia in Charlottesville and lead author on a paper appearing in the Astrophysical Journal. “The more pulsars you can observe, the more complete your dataset and the more details you can discern about the interior of the cluster.”
The Terzan 5 cluster is about 19,000 light-years from Earth, just outside the central bulge of our galaxy.
For their research, the astronomers used the National Science Foundation’s (NSF) Green Bank Telescope (GBT) in West Virginia. The GBT is an amazingly efficient instrument for pulsar detection and observation. It has exquisitely sensitive electronics, some specifically optimized for this task, and a 100-meter dish, the largest of any fully steerable radio telescope.
Pulsars are neutron stars – the fantastically dense remains of supernovas — that emit beams of radio waves from their magnetic poles. As a pulsar rotates, its beams of radio light sweep across space in a cosmic version of a lighthouse. If the beams shine in the direction of Earth, astronomers can detect the exquisitely steady pulses from the star.
As the pulsars in Terzan 5 move in relation to Earth – drawn in different directions by the varying density of the cluster — the Doppler effect comes into play. This effect adds a tiny delay to the timing if the pulsar is moving away from Earth. It also shaves off the tiniest fraction of a millisecond if the pulsar is moving toward us.
In the case of Terzan 5, astronomers are particularly interested in a class of pulsars known as millisecond pulsars. These pulsars rotate hundreds of times each second with a regularity that rivals the precision of atomic clocks on Earth.
Pulsars achieve these remarkable speeds by siphoning off matter from a nearby companion star. The infalling matter hits the edge of the neutron star at an angle, increasing the pulsar’s rate of spin in much the same way that a basketball balanced on the tip of a finger can be spun up by striking its side.
Millisecond pulsars are a particular boon to astronomers because they make it possible to detect almost infinitesimally small changes in the timing of the radio pulses.
“Pulsars are amazingly precise cosmic clocks,” said Scott Ransom, an astronomer with the National Radio Astronomy Observatory (NRAO) in Charlottesville, Virginia, and coauthor on the paper. “With the GBT, our team was able to essentially measure how each of these clocks is falling through space toward regions of higher mass. Once we have that information, we can translate it into a very precise map of the density of the cluster, showing us where the bulk of the ‘stuff’ in the cluster resides.”
Previously, astronomers thought that Terzan 5 might be either a warped dwarf galaxy gobbled up by the Milky Way or a fragment of the galactic bulge. If the cluster were a captured dwarf galaxy, it might also harbor a central supermassive black hole, which is one of the hallmarks of all large galaxies and can be found in many dwarf galaxies as well.
The new GBT data, however, show no obvious signs that a single, central black hole is lurking in Terzan 5. “However, we can’t yet say for sure if a smaller, intermediate mass black hole resides there. The new observations also provide better evidence that Terzan 5 is a true globular cluster born in the Milky Way rather than the remains of a dwarf galaxy,” said Ransom.
Future observations using more sophisticated acceleration models may better constrain the origin of Terzan 5.
Animation showing locations of millisecond pulsars inside the globular cluster Terzan 5. Pulsars represented in blue are accelerating toward observers on Earth; those in red are accelerating away. These relative accelerations were derived by measuring minute changes in the speed of rotation of the pulsars.
Credit: B. Saxton (NRAO/AUI/NSF); GBO/AUI/NSF; NASA/ESA Hubble, F. Ferraro
Video describing how astronomers traced the motions of 36 rapidly rotating pulsars inside Terzan 5 – a massive, ancient star cluster near the center of the Milky Way — to get a clearer picture of the cluster’s interior and likely birthplace.
Credit: B. Saxton (NRAO/AUI/NSF); GBO/AUI/NSF; NASA/ESA Hubble
The Green Bank Observatory (GBO) is a facility of the National Science Foundation operated under a cooperative agreement by Associated Universities, Inc.
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This research is presented in a paper titled “Using Long-term Millisecond Pulsar Timing to Obtain Physical Characteristics of the Bulge Globular Cluster Terzan 5,” B. Prager et al., published in the Astrophysical Journal.
Contact: Mike Holstine
As the public prepares for the upcoming eclipse, astronomers have released a striking new radar view of the Moon. Researchers from the Smithsonian’s National Air and Space Museum are using radio telescopes at the Arecibo Observatory and Green Bank Observatory to map the Moon with radar. The radar signals, transmitted from the Arecibo telescope and received at the Robert C. Byrd Green Bank Telescope, can probe many meters below the surface of the Moon, just like ground-piercing radar on Earth. They reveal Lunar structures that can’t be seen in optical images because they’re hidden from view under the layer of dust and rubble that covers the Moon’s surface. The scientists are searching for unseen structures of Lunar geology such as lava flow complexes and buried craters.
This is a radar view of the Moon’s southeastern highlands, showing the densely cratered surface formed as the result of more than 4 billion years of meteorite impacts. The radar can distinguish the age of some craters. Younger impact craters have enhanced radar return showing bright floors and surrounding areas due to rocky material that has not yet been worn away by very small meteorites.
In this image North is up, and the bright crater at the upper right is Theophilus. The dark ring in the image is due to the pattern formed by the transmitting and receiving antennas.
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contact: Michael Holstine
Business Manager, Green Bank Observatory
A very happy Fourth of July to everyone, and I hope your summer is as filled with fun science and education as ours is here in Green Bank. Our summer hires have, as usual, added an additional 50% to the overall staff here, and span the range from people painting the telescope, interns with our plant maintenance program, tour guides, cafeteria and café workers, and students taking part in co-ops, interns, and Research Experience for Undergraduates (REU) positions on site. Our other summer visitors include participants in our undergraduate radio astronomy course, PING (Physics Inspiring the Next Generation) campers, Pulsar Search Collaboratory participants, West Virginia Science teachers taking part in the Earth/Space Science Passport development program, Chautauqua, StarQuest, and Southeastern Association for Research in Astronomy (SARA) attendees, and the annual undergraduate Arecibo Legacy Fast ALFA (ALFALFA) workshop participants. The 6th annual Space Race Rumpus also took place here the weekend of June 9-11, and attracted a record 170 participants from the eastern United States who biked, danced, and learned a little astronomy on the side.
Within the next 1-2 months we anticipate the release of the draft Environmental Impact Statement (EIS) report. Once the draft EIS report is released, a 45 day window will open for comments on the document, including 1-2 onsite meetings. Announcement of the report, information on how to provide comments, and the dates/times for the scheduled meetings will be release on the NSF website [nsf.gov]. A link to this information will also be provided on the Green Bank Observatory website.
Looking forward, we have a number of items coming up in the next few months. In addition to our annual open house which is taking place September 10, and another observer training workshop the following week, we also plan on attending the upcoming URSI (Union Radio Scientifique Internationale) General Assembly in Montreal this August. After that, we will begin preparations for our 60th birthday celebrations being held in October.
Enjoy your summer!
Dr. Karen O’Neil,
Director, Green Bank Observatory
The Green Bank Observatory (GBO) invites scientists to participate in the GBO’s 2018A Semester Call for Proposals for the Green Bank Telescope (GBT). The entire proposal call can be found on our proposals page.
The submission deadline for Semester 2018A proposals is Tuesday, 1 August 2017, at 17:00 EDT (21:00 UTC).
The GBO wishes to remind proposers of continuing opportunities for joint observations with the Chandra X-ray Observatory, the Hubble Space Telescope, the Swift Gamma-Ray Burst Mission and the Fermi Gamma-ray Space Telescope
Jansky Lecture – Jacqueline van Gorkom (Columbia University)
The 2016 Jansky Lecture — Gas and Galaxy Evolution — will be given on July 31 at 7:00 PM in the Science Center Auditorium by Dr. Jacqueline van Gorkom of Columbia University. It is free and open to the public. The Jansky Lectureship is an honor established by the trustees of AUI to recognize outstanding contributions to the advancement of radio astronomy.
Professor van Gorkom is a longtime radio astronomer, specializing in studies of neutral hydrogen, the most abundant element in the Universe. Her observations have focused on the distribution and dynamics of hydrogen in and around nearby galaxies of varied types and in widely different environments, and how the gas affects the evolution of the galaxies. She currently leads an important Very Large Array observing project aimed at learning how these properties change over time by observing hydrogen at greater cosmic distances.
The Jansky Lectureship has been awarded annually since 1966. It is named in honor of the man who first detected radio waves from a cosmic source in 1932.
Have you heard?! The Green Bank Observatory in Green Bank, WV is hosting a Great American Eclipse viewing party. Don’t miss out on this rare event. It’s been 26 years since a partial solar eclipse was visible from West Virginia! West Virginians will be able to see a 90% partial eclipse this August. So join us from 11:00 a.m. until 4:00 p.m. for a day of food, fun, and education!
Hands-on Activities from 11 a.m.- 12 p.m.
Lunch and Exhibits from 12 p.m. – 1 p.m.
Safe eclipse viewing through telescopes and projections. Plus live streaming video of the eclipse provided by NASA.
We would love to know if you’re joining us! Visit our Great American Eclipse event page and let us know you’re attending today!
Green Bank Open House and Family Science Day
The Green Bank Science Center hosts our annual Open House and Family Science Day event. With past attendance reaching over 700 guests, this is the most popular way for our visitors to enjoy hands-on experiments and get to know the Green Bank Observatory.
Where else can you… build and launch a rocket, test your engineering skills, learn about liquid nitrogen, and see some of the biggest telescopes all in one day? Public site tours are available as well as rare peeks into the GBT Control Room. Each year, the Valley Aerospace Team builds custom launch pads, helps participants build their rockets, and even brings a few of their own custom rockets to launch. This event is free and fun for all ages. Plan to come early! Rocket kits are first come, first serve.
Observer Training Workshop
September 18 – 22
The Green Bank Observatory will host the next GBT observer training workshop September 18-22 2017. The workshop will provide an introduction to general radio astronomical techniques as well as onsite training for GBT observers. We especially encourage high frequency observers (i.e. those interested in observing at 8 GHz and above) to attend in preparation for the winter season. The workshop will include dedicated time for general purpose training on the GBT in a compact, one week workshop and includes training to become qualified to observe remotely. For further information, please see the event page.
Transformative Science Workshop Updates
October 16 – 20
Big Questions, Large Programs, and New Instruments: With new instruments and excellent performance, the 100m Green Bank Telescope is only just reaching its full potential. On this 60th anniversary of the ground breaking for the Green Bank Observatory, we are holding a workshop looking toward the next 10, 20, and even 60 years of the Green Bank Observatory, and invite the community to attend and aid us in planning the future. For more information, please see the event page.
60th Anniversary of the Green Bank Observatory
On October 17 2017, the Green Bank Observatory turns 60 years old, and we would like to invite you to help us celebrate! The celebration will take place on site the afternoon and evening of October 17, and will include tours, talks, discussions, and, of course, food. Information on the gathering will be posted online by mid-August.
Ammonia in Orion – Star Formation Press Release
A team of astronomers has unveiled a striking new image of the Orion Molecular Cloud (OMC) – a bustling stellar nursery teeming with bright, young stars and dazzling regions of hot, glowing gas.
The researchers used the National Science Foundation’s (NSF) Green Bank Telescope (GBT) in West Virginia to study a 50 light-year long filament of star-forming gas that is wending its way through the northern portion of the OMC known as Orion A.
Previously released – Read the full press release.
Latest commissioning observations with the Focal L-band Array for the GBT (FLAG) and the real-time beamformer
Following a successful test of the FLAG phased-array feed on the GBT in March, a team of astronomers and engineers from Brigham Young University (BYU) and West Virginia University (WVU) came to Green Bank in late May to work with National Radio Astronomy Observatory (NRAO) and GBO engineers in commissioning the broadband beamformer funded by a NSF ATI grant. All three modes of the beamformer were tested: a 150 MHz, coarse resolution mode for calibration, a 150 MHz real-time beamforming mode for pulsar timing and transient surveys, and a narrow-band, 10 MHz, spectral-line mode. The tests confirmed the excellent Tsys/η = 28 K at 1350 MHz, equivalent to the existing single pixel feed and with good sensitivity across the entire 30′ field of view. The FLAG beamformer system will be seven times faster for mapping projects than the current single pixel receiver.
Tests of the real-time beamformer included observations of the pulsar B1937+21 in the central beam, where individual giant pulses were detected (see figure). Multiple bright galaxies were observed using On/Off single-pointing maps in spectral line mode, but these data are still being processed.
Final commissioning observations will take place in August, including tests of the commensal spectral line and real-time transient detection mode, with the hope that the instrument will be available for shared-risk observing in the near future.
Beamformer Team: Brian Jeffs, Karl Warnick, Richard Black, Mitchell Burnett, Mark Rudzindana (BYU); Duncan Lorimer, Maura McLaughlin, D.J. Pisano, Nick Pingel, Kaustubh Rajwade (WVU); Richard Prestage, Paul Marganian, Thomas Chamberlin, Vereese van Tonder, Luke Hawkins, Jason Ray (GBO) and more.
The work of the FLAG (Phased Array Feed) Team is also acknowledged for the development of the new, low-noise cryogenic phased array feed receiver (PAF), including: D. Anish Roshi, William Shillue, J.R. Fisher, Matt Morgan, Jason Castro, Wavley Groves, Tod Boyd (NRAO); Bob Simon, Steve White, J.D. Nelson (GBO) and many others. The successful PAF commissioning was reported on in the April 2017 newsletter.
During the first week of June the Green Bank Observatory welcomed 22 students from the GBO and NRAO for an annual summer student workshop. Young scientists and engineers enrolled in the Research Experience for Undergraduates (REU), Physicists Inspiring the Next Generation (PING), and the National Astronomy Consortium (NAC), as well as summer graduate students, gathered to prepare for summer research through talks, observing projects, team-building exercises, and behind the scenes tours of the observatory. The workshop also gives summer students from across AUI the chance to meet face-to-face and provides career development opportunities. This year’s students were treated to a historical site tour, hands on observing with the GBO’s 40-foot radio telescope, and a special science talk on fast radio bursts by Prof. Duncan Lorimer of West Virginia University. The workshop continues a long tradition of excellence in student education at GBO.
GBO Machine Shop Gives Atacama Large Millimeter/submillimeter Array (ALMA) a Lift
To perform routine receiver service and upgrades on ALMA’s 66 antennas, supercooled “Front End” containers that house the receivers and electronics for each antenna must be carefully removed. To handle that removal and transport, ALMA uses Front End Handling Vehicles (FEHV), which are large lift carts specifically designed to transport the ALMA Front Ends.
Each Front End package weighs approximately 750 kilograms (1,600 lbs) and must be lifted over 5 feet above the floor inside the highly confined receiver room of each antenna. FEHVs were designed specifically to make that task safer, quicker, and more routine.
The GBO Machine shop is in the midst of fabricating new FEHV chassis to help out ALMA North America.
Because of the weight and instrumentation these FEHVs need to carry, rigorous certification processes are being followed. Congratulations to Pat Schaffner, who successfully obtained an American Welding Society (AWS) structural welding certification on his first try, which was a prerequisite to proceeding with the work. The AWS representative that conducted the certification review reported that Pat did a “great job. Usually 1 out of 3 test samples will break at the weld but none of Pat’s did.”
The first chassis has been assembled, certified by an external inspector, and shipped to Chile where it will be integrated into a full handling vehicle for acceptance. The Machine Shop has been given the go ahead to proceed with the fabrication of three additional units.
Thanks to Pat, Roger Dickenson, Mike Hedrick and everyone in the Shop for the great work, and to Butch Wirt, Todd Wright, and the Maintenance team for building a custom shipping crate.
Want to plan your visit? The new Green Bank Observatory Reservation System (GBORS) is now live! Our visitors can now create an account to track and manage all reservations from overnight stays and meal planning to meeting room requests and group visits. This tool makes visiting a cinch for our GBT users.
As always, please feel free to contact our reservationist for support at email@example.com or 304-456-2011. The new reservation tool is live now.
GBT Joins Goldstone and Allen Telescope Array in Radar Test
Use of the GBT as a radar receiver is a commonplace activity for Green Bank, but recently we participated in an interesting experiment with a bit of a different twist. We were contacted by the Advanced Physics Lab at Johns Hopkins to participate the Advanced Space Radar Experiment (ASRE) as a monitoring and recording station. The project tested the ability of the Allen Telescope Array (ATA) to receive X-Band signals bounced off commercial satellites in geosynchronous orbit. While the ATA used sets of antennas to correlate into multiple beams, the GBT used the JPL radar backend to receive all of the signals as a reference for the post-experiment analysis.
The ASRE project purchased six hours of GBT time to conduct the experiment using four different satellites as targets and varying radar transmission waveforms. One other interesting feature of the test was the use of three Deep Space Network (DSN) antennas with their radar transmitters phased together into a single higher power beam at the target. You may be familiar with a similar system long, long, ago.
After initial data analysis, the experiment appears to be a success and the GBT systems performed flawlessly. It is unclear if any follow-on experiments are planned, but a request for additional funds for the experiment is underway. Test participants included: Jet Propulsion Lab, SRI, GBO, Aerospace, MITRE, MIT Lincoln Laboratory, JHU/APL
The Frank Drake Lectureship
Dr. Frank Drake has had a long and distinguished career that began at the Observatory in Green Bank West Virginia in 1958. His scientific achievements include discovery of the radiation belts of Jupiter, some of the earliest measurements of pulsars, contributions to our understanding of the high surface temperature of Venus, and characterization of the radio sources at the center of the Milky Way.
In 1960, using a radio telescope at Green Bank, Dr. Drake made the first modern search for radio signals from extraterrestrial civilizations. He thus began an area of scientific research that has continued and is flourishing today, engaging creative minds worldwide. The Drake equation, first introduced in Green Bank in 1961, has caught the public imagination and continues to draw audiences around the world to discuss and learn about science and astronomy.
In recognition of the work Dr. Drake has done, the Frank Drake Lectureship was created to recognize individuals from the sciences, arts or humanities in recognition of their contributions to advancing human knowledge and creativity in the scientific realm.
The Frank Drake Lectureship is awarded to one individual annually. The recipient of this award will present the annual Frank Drake Lecture in Green Bank, West Virginia. The public lecture will promote scientific knowledge or literacy. All costs associated with the awardee’s travel will be covered through the lecture series, as well a dinner, held in the awardee’s honor. The awardee will receive both a plaque honoring his/her award and a $1,000 honorarium.
Nominations for the 2017 Frank Drake Lectureship are now open, and should be sent to: firstname.lastname@example.org
Venus is hot!
Frank Drake is famous for having done the first SETI search, using the 85-foot Tatel telescope at Green Bank, in 1961. About the same time, he also used the 85-foot telescope to measure microwave radiation from some of the planets at a wavelength of 3 cm.
The radiation from most planets is due to the temperature of the surface of the planet. Previous work by others measured the optical and near infrared radiation from the planets from which one can estimate the temperature. It was expected that the radio radiation would indicate the same temperature as the infra-red.
But Venus was quite a surprise – the 3 cm radiation indicated a temperature much higher than expected, about 600 degrees Kelvin (curiously, when you convert that to Fahrenheit, it is also near 600 degrees).
Venus has a very thick atmosphere which prevents seeing the surface of the planet in the optical and near infrared; the infrared temperature is from the upper part of the atmosphere. On the other hand, the microwave radiation at 3 cm and longer wavelengths comes from the solid surface unhindered by the atmosphere.
The conclusion was that the surface of Venus was very hot, much hotter than the top of her atmosphere. How can that be?
The answer was worked out by Carl Sagan, who calculated how the atmosphere can provide a “greenhouse effect”. Energy from the Sun comes through the atmosphere at a wavelength of a few microns and warms up the surface. The surface radiates the energy back up at longer infrared wavelengths but the radiation is absorbed by the water vapor in the atmosphere and kept near the surface. Whatever oceans Venus may have had in the past have evaporated and formed the thick atmosphere of mostly water vapor. This keeps the surface of Venus uncomfortably hot.
The Earth’s atmosphere also has a greenhouse effect, but much less extreme than on Venus, due to the Earth being somewhat farther from the Sun. Although we worry about the Earth warming up too much, we depend on the effect to keep the Earth comfortable. Without any water vapor and other greenhouse gases, the Earth’s average temperature would be around -20 C (or -2 F).
In 1962, the US launched the first spacecraft to fly by Venus, Mariner 2. An article in “The Observer” (reprinted in “But It Was Fun”, page 83) noted that Mariner 2 measurements got similar results to those that had been found earlier at Green Bank by Dr. Frank Drake with the 85-1. But, of course, Mariner 2 cost enormously more than the observations done at Green Bank.
The Observatory had “scooped” the space mission at very low cost!
Reference: Physics Today, April 1961, page 30
We are seeking an enthusiastic and energetic scientist to join the staff of the Green Bank Observatory in Green Bank, West Virginia.
Duties will include providing support for GBT observers as well as developing thorough theoretical and practical knowledge of the microwave holography system which is used for measurement and improvement of the GBT primary surface, working in the area of data reduction and post-processing mathematical analysis. The applicant would eventually assume primary responsibility in this area. Over time, the successful applicant will join other projects, potentially including the development and commissioning of new instrumentation on the telescope, working with the engineering staff to improve the overall telescope performance, and aiding with the data reduction pipelines needed for the GBT.
The Green Bank Observatory employs 100 people on a year round basis, and an additional 40 people in the summer time. We are committed to a diverse and inclusive work place culture that accepts and appreciates all individuals.
Please check out all our current listings.