It’s long been a mystery for astronomers: why aren’t galaxies bigger? What regulates their rates of star formation and keeps them from just becoming even more chock-full-of-stars than they already are? Now, using a worldwide network of radio telescopes, researchers have observed one of the processes that was on the short list of suspects: one supermassive black hole’s jets are plowing huge amounts of potential star-stuff clear out of its galaxy.
Astronomers have theorized that many galaxies should be more massive and have more stars than is actually the case. Scientists proposed two major mechanisms that would slow or halt the process of mass growth and star formation — violent stellar winds from bursts of star formation and pushback from the jets powered by the galaxy’s central, supermassive black hole.
“With the finely-detailed images provided by an intercontinental combination of radio telescopes, we have been able to see massive clumps of cold gas being pushed away from the galaxy’s center by the black-hole-powered jets,” said Raffaella Morganti, of the Netherlands Institute for Radio Astronomy and the University of Groningen.
The scientists studied a galaxy called 4C12.50, nearly 1.5 billion light-years from Earth. They chose this galaxy because it is at a stage where the black-hole “engine” that produces the jets is just turning on. As the black hole, a concentration of mass so dense that not even light can escape, pulls material toward it, the material forms a swirling disk surrounding the black hole. Processes in the disk tap the tremendous gravitational energy of the black hole to propel material outward from the poles of the disk.
At the ends of both jets, the researchers found clumps of hydrogen gas moving outward from the galaxy at 1,000 kilometers per second. One of the clouds has much as 16,000 times the mass of the Sun, while the other contains 140,000 times the mass of the Sun.
The larger cloud, the scientists said, is roughly 160 by 190 light-years in size.
“This is the most definitive evidence yet for an interaction between the swift-moving jet of such a galaxy and a dense interstellar gas cloud,” Morganti said. “We believe we are seeing in action the process by which an active, central engine can remove gas — the raw material for star formation — from a young galaxy,” she added.
The researchers published their findings in the September 6 issue of the journal Science.
An ancient passing between two nearby galaxies appears to have left the participants connected by a tenuous “bridge” of hydrogen gas, according to findings reported Monday, June 11 by astronomers with the National Radio Astronomy Observatory (NRAO).
Using the National Science Foundation’s Green Bank Telescope in West Virginia — the world’s largest fully-steerable radio telescope — astronomers have confirmed the existence of a vast bridge of hydrogen gas streaming between the Andromeda galaxy (M31) and the Triangulum galaxy (M33), indicating that they likely passed very closely billions of years ago.
The faint bridge structure had first been identified in 2004 with the 14-dish Westerbork Synthesis Radio Telescope in the Netherlands but there was some scientific dispute over the findings. Observations with the GBT confirmed the bridge’s existence as well as revealed the presence of six large clumps of material within the stream.
Since the clumps are moving at the same velocity as the two galaxies relative to us, it seems to indicate the bridge of hydrogen gas is connecting them together.
“We think it’s very likely that the hydrogen gas we see between M31 and M33 is the remnant of a tidal tail that originated during a close encounter, probably billions of years ago,” said Spencer Wolfe of West Virginia University. “The encounter had to be long ago, because neither galaxy shows evidence of disruption today.”
A special project to search for pulsars has bagged the first student discovery of a millisecond pulsar – a super-fast spinning star, and this one rotates about 324 times per second. The Pulsar Search Collaboratory (PSC) has students analyzing real data from the National Radio Astronomy Observatory’s (NRAO) Robert C. Byrd Green Bank Telescope (GBT) to find pulsars. Astronomers involved with the project said the discovery could help detect elusive ripples in spacetime known as gravitational waves.
“Gravitational waves are ripples in the fabric of spacetime predicted by Einstein’s theory of General Relativity,” said Dr. Maura McLaughlin, from West Virginia University. “We have very good proof for their existence but, despite Einstein’s prediction back in the early 1900s, they have never been detected.”
Four other pulsars have been discovered by high school students participating in this project.
“When you discover a pulsar, you feel like you’re walking on air! It is the best experience you can ever have,” said student co-discoverer Jessica Pal of Rowan County High School in Kentucky. “You get to meet astronomers and talk to them about your experience. I still can’t believe I found a pulsar. It is wonderful to know that there is something out there in space that you discovered.”
The other student involved in the discovery was Emily Phan of George C. Marshall High School in Virginia, who along with Pal found the millisecond pulsar on January 17, 2012. It was later confirmed by Max Sterling of Langley High School, Sydney Dydiw of Trinity High School, and Anne Agee of Roanoke Valley Governor’s School, all in Virginia.
“I am considering pursuing astronomy as a career choice,” said Agee. “The Pulsar Search Collaboratory has opened my eyes to how fun astronomy can be!”
Once the pulsar candidate was reported to NRAO, a followup observing session was scheduled on the giant, 17-million-pound telescope. On January 24, 2012, observations confirmed that the pulsar was real.
Pulsars are spinning neutron stars that sling “lighthouse beams” of radio waves around as they rotate. A neutron star is what is left after a massive star explodes at the end of its “normal” life. With no nuclear fuel left to produce energy to offset the stellar remnant’s weight, its material is compressed to extreme densities. The pressure squeezes together most of its protons and electrons to form neutrons; hence, the name “neutron star.” One tablespoon of material from a pulsar would weigh 10 million tons.
The object that the students discovered is a special class of pulsars called millisecond pulsars, which are the fastest-spinning neutron stars. They are highly stable and keep time more accurately than atomic clocks.
Astronomers don’t know much about them, however. But because of their stability, these pulsars may someday allow astronomers to detect gravitational waves.
Millisecond pulsars, however, could hold the key to that discovery. Like buoys bobbing on the ocean, pulsars can be perturbed by gravitational waves.
“Gravitational waves are invisible,” said McLaughlin. “But by timing pulsars distributed across the sky, we may be able to detect very small changes in pulse arrival times due to the influence of these waves.”
Millisecond pulsars are generally older pulsars that have been “spun up” by stealing mass from companion stars, but much is left to discover about their formation.
“This latest discovery will help us understand the genesis of millisecond pulsars,” said Dr. Duncan Lorimer, who is also part of the project. “It’s a very exciting time to be finding pulsars!”
The PSC is a joint project of the National Radio Astronomy Observatory and West Virginia University, funded by a grant from the National Science Foundation. The PSC includes training for teachers and student leaders, and provides parcels of data from the GBT to student teams. The project involves teachers and students in helping astronomers analyze data from the GBT.
Approximately 300 hours of the observing data were reserved for analysis by student teams. These students have been working with about 500 other students across the country. The responsibility for the work, and for the discoveries, is theirs. They are trained by astronomers and by their teachers to distinguish between pulsars and noise.
The PSC will continue through the 2012-2013 school year. Teachers interested in participating in the program can learn more at this link. The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.
The pop culture-rich Very Large Array has been updated with state-of-the-art technology and to befit the VLA’s new capabilities, the National Radio Astronomy Observatory (NRAO) has given it a new name. Recall, back in October 2011, the NRAO asked for the public’s help in choosing a new name, and 17,023 people from 65 different countries responded by sending 23,331 suggestions.
The new name for the world’s most famous radio telescope is the “Karl G. Jansky Very Large Array” to honor the founder of radio astronomy. Radio astronomy enables the study of the Universe via radio waves naturally emitted by objects in space.
The VLA has been part of movie plots, is on album covers, in comic books and video games. It has now been transformed from its original 1970s-vintage technology with the latest equipment, and the NRAO says that the upgrades will greatly increase the VLA’s technical capabilities and scientific impact.
The new name was announced at the American Astronomical Society’s meeting in Austin, Texas. The new name will become official at a re-dedication ceremony at the VLA site in New Mexico on March 31, 2012.
Karl Guthe Jansky (1905-1950) joined Bell Telephone Laboratories in 1928, and was assigned the task of studying radio waves that interfered with the recently-opened transatlantic radiotelephone service.
He designed and built advanced, specialized equipment, and made observations over the entire year of 1932 that allowed him to identify thunderstorms as major sources of radio interference, along with a much weaker, unidentified radio source. Careful study of this “strange hiss-type static” led to the conclusion that the radio waves originated from beyond our Solar System, and indeed came from the center of our Milky Way Galaxy.
His discovery was reported on the front page of the New York Times on May 5, 1933, and published in professional journals. Janksy thus opened an entirely new “window” on the Universe. Astronomers previously had been confined to observing those wavelengths of light that our eyes can see.
NRAO officials say the new name recognizes the VLA’s dramatic new capabilities and its promise for important scientific discoveries in the future.
“When Karl Jansky discovered radio waves coming from the center of the Milky Way Galaxy in 1932, he blazed a scientific trail that fundamentally changed our perception of the Universe. Now, the upgraded VLA will continue that tradition by equipping scientists to address outstanding questions confronting 21st-Century astronomy,” said NRAO Director Fred K.Y. Lo.
“It is particularly appropriate that the upgraded Very Large Array honor the memory and accomplishments of Karl Jansky,” Lo explained, adding that “the new Jansky VLA is by far the most sensitive such radio telescope in the world, as was the receiver and antenna combination that Jansky himself painstakingly developed 80 years ago.”
Lo said they deeply appreciate all the suggestions for a new name, as well as the strong public interest in the VLA and in astronomy. “There was a tremendous amount of thought and creativity that went into the numerous submissions,” he said. “In the end, we decided it was most appropriate to name the telescope after a genuine pioneer who took the first step on the road that led to this powerful scientific facility,” he said.
The Jansky VLA is more than ten times more sensitive to faint radio emission than the original VLA, and covers more than three times more radio frequency range. It will provide astronomers the capability to address key outstanding scientific questions, ranging from the formation of stars and planets in the Milky Way and nearby galaxies, to mapping magnetic fields in galaxies and clusters, and imaging the gas that forms the earliest galaxies.
In the constellation of Ophiuchus, above the disk of our Milky Way Galaxy, there lurks a stellar corpse spinning 30 times per second — an exotic star known as a radio pulsar. This object was unknown until it was discovered last week by three high school students. These students are part of the Pulsar Search Collaboratory (PSC) project, run by the National Radio Astronomy Observatory (NRAO) in Green Bank, WV, and West Virginia University (WVU).
The pulsar, which may be a rare kind of neutron star called a recycled pulsar, was discovered independently by Virginia students Alexander Snider and Casey Thompson, on January 20, and a day later by Kentucky student Hannah Mabry. “Every day, I told myself, ‘I have to find a pulsar. I better find a pulsar before this class ends,'” said Mabry.
When she actually made the discovery, she could barely contain her excitement. “I started screaming and jumping up and down.”
Thompson was similarly expressive. “After three years of searching, I hadn’t found a single thing,” he said, “but when I did, I threw my hands up in the air and said, ‘Yes!’.”
Snider said, “It actually feels really neat to be the first person to ever see something like that. It’s an uplifting feeling.”
As part of the PSC, the students analyze real data from NRAO’s Robert C. Byrd Green Bank Telescope (GBT) to find pulsars. The students’ teachers — Debra Edwards of Sherando High School, Leah Lorton of James River High School, and Jennifer Carter of Rowan County Senior High School — all introduced the PSC in their classes, and interested students formed teams to continue the work.
Even before the discovery, Mabry simply enjoyed the search. “It just feels like you’re actually doing something,” she said. “It’s a good feeling.”
Once the pulsar candidate was reported to NRAO, Project Director Rachel Rosen took a look and agreed with the young scientists. A followup observing session was scheduled on the GBT. Snider and Mabry traveled to West Virginia to assist in the follow-up observations, and Thompson joined online.
“Observing with the students is very exciting. It gives the students a chance to learn about radio telescopes and pulsar observing in a very hands-on way, and it is extra fun when we find a pulsar,” said Rosen.
Snider, on the other hand, said, “I got very, very nervous. I expected when I went there that I would just be watching other people do things, and then I actually go to sit down at the controls. I definitely didn’t want to mess something up.”
Everything went well, and the observations confirmed that the students had found an exotic pulsar. “I learned more in the two hours in the control room than I would have in school the whole day,” Mabry said.
Pulsars are spinning neutron stars that sling lighthouse beams of radio waves or light around as they spin. A neutron star is what is left after a massive star explodes at the end of its normal life. With no nuclear fuel left to produce energy to offset the stellar remnant’s weight, its material is compressed to extreme densities. The pressure squeezes together most of its protons and electrons to form neutrons; hence, the name neutron star. One tablespoon of material from a pulsar would weigh 10 million tons — as much as a supertanker.
The object that the students discovered is in a special class of pulsar that spins very fast – in this case, about 30 times per second, comparable to the speed of a kitchen blender.
“The big question we need to answer first is whether this is a young pulsar or a recycled pulsar,” said Maura McLaughlin, an astronomer at WVU. “A pulsar spinning that fast is very interesting as it could be newly born or it could be a very old, recycled pulsar.”
A recycled pulsar is one that was once in a binary system. Material from the companion star is deposited onto the pulsar, causing it to speed up, or be recycled. Mystery remains, however, about whether this pulsar has ever had a companion star.
If it did, “it may be that this pulsar had a massive companion that exploded in a supernova, disrupting its orbit,” McLaughlin said. Astronomers and students will work together in the coming months to find answers to these questions.
The PSC is a joint project of the National Radio Astronomy Observatory and West Virginia University, funded by a grant from the National Science Foundation. The PSC, led by NRAO Education Officer Sue Ann Heatherly and Project Director Rachel Rosen, includes training for teachers and student leaders, and provides parcels of data from the GBT to student teams. The project involves teachers and students in helping astronomers analyze data from the GBT, a giant, 17-million-pound telescope.
Some 300 hours of observing data were reserved for analysis by student teams. Thompson, Snider, and Mabry have been working with about 170 other students across the country. The responsibility for the work, and for the discoveries, is theirs. They are trained by astronomers and by their teachers to distinguish between pulsars and noise. The students’ collective judgment sifts the pulsars from the noise.
All three students had analyzed thousands of data plots before coming upon this one. Casey Thompson, who has been with the PSC for three years, has analyzed more than 30,000 plots.
“Sometimes I just stop and think about the fact that I’m looking at data from space,” Thompson said. “It’s really special to me.”
In addition to this discovery, two other astronomical objects have been discovered by students. In 2009, Shay Bloxton of Summersville, WV, discovered a pulsar that spins once every four seconds, and Lucas Bolyard of Clarksburg, WV, discovered a rapidly rotating radio transient, which astronomers believe is a pulsar that emits radio waves in bursts.
Those involved in the PSC hope that being a part of astronomy will give students an appreciation for science. Maybe the project will even produce some of the next generation of astronomers. Snider, surely, has been inspired.
“The PSC changed my career path,” confessed Thompson. “I’m going to study astrophysics.”
Snider is pleased with the idea of contributing to scientific knowledge. “I hope that astronomers at Green Bank and around the world can learn something from the discovery,” he said.
Mabry is simply awed. “We’ve actually been able to experience something,” she said.
The PSC will continue through 2011. Teachers interested in participating in the program can learn more at this link.