Nav: Home

NASA missions explore a 'TIE Fighter' active galaxy

August 25, 2020

Not so long ago, astronomers mapped a galaxy far, far away using radio waves and found it has a strikingly familiar shape. In the process, they discovered the object, called TXS 0128+554, experienced two powerful bouts of activity in the last century.

Around five years ago, NASA's Fermi Gamma-ray Space Telescope reported that TXS 0128+554 (TXS 0128 for short) is a faint source of gamma rays, the highest-energy form of light. Scientists have since taken a closer look using the Very Long Baseline Array (VLBA) and NASA's Chandra X-ray Observatory.

"After the Fermi announcement, we zoomed in a million times closer on the galaxy using the VLBA's radio antennas and charted its shape over time," said Matthew Lister, a professor of physics and astronomy at Purdue University in West Lafayette, Indiana. "The first time I saw the results, I immediately thought it looked like Darth Vader's TIE fighter spacecraft from 'Star Wars: A New Hope.' That was a fun surprise, but its appearance at different radio frequencies also helped us learn more about how active galaxies can change dramatically on decade time scales."

A paper describing the findings, led by Lister, was published in the Aug. 25 issue of the Astrophysical Journal and is now available online.

TXS 0128 lies 500 million light-years away in the constellation Cassiopeia, anchored by a supermassive black hole around 1 billion times the Sun's mass. It's classified as an active galaxy, which means all its stars together can't account for the amount of light it emits.

An active galaxy's extra energy includes excess radio, X-ray, and gamma-ray light. Scientists think this emission arises from regions near its central black hole, where a swirling disk of gas and dust accumulates and heats up because of gravitational and frictional forces.

Around one-tenth of active galaxies produce a pair of jets, beams of high-energy particles traveling at nearly the speed of light in opposite directions. Astrophysicists think these jets produce gamma rays. In some cases, collisions with tenuous intergalactic gas eventually slow and halt the outward motion of jet particles, and the material starts to flow back toward the galaxy's center. This results in broad regions, or lobes, filled with fast-moving particles spiraling around magnetic fields. The particle interactions create bright radio emission.

Fermi has identified over 3,000 active galaxies using its Large Area Telescope, which surveys the entire sky every three hours. Nearly all of them are aligned so that one jet points almost directly at Earth, which boosts their signals. TXS 0128, however, is around 100,000 times less powerful than most of them. In fact, even though it's relatively nearby, Fermi needed to accumulate five years of data from the galaxy before reporting it as a gamma-ray source in 2015.

Researchers then added the galaxy to a long-running survey conducted by the VLBA, a network of radio antennas operated by the National Radio Astronomy Observatory stretching from Hawaii to the U.S. Virgin Islands.

The array's measurements provide a detailed map of TXS 0128 at different radio frequencies. The radio structure they revealed spans 35 light-years across and tilts about 50 degrees out of our line of sight. This angle means the jets aren't pointed directly at us and may explain why the galaxy is so dim in gamma rays.

"The real-world universe is three-dimensional, but when we look out into space, we usually only see two dimensions," said Daniel Homan, a co-author and professor of astronomy at Denison University in Granville, Ohio. "In this case, we're lucky because the galaxy is angled in such a way, from our perspective, that the light from the farther lobe travels dozens more light-years to reach us than the light from the nearer one. This means we're seeing the farther lobe at an earlier point in its evolution."

If the galaxy was aligned so the jets and lobes were perpendicular to our line of sight, all the light would reach Earth at the same time. We would see both sides at the same stage of development, which they are in reality.

The galaxy's apparent shape depends on the radio frequency used. At 2.3 gigahertz (GHz), about 21 times greater than the maximum broadcast frequency of FM radio, it looks like an amorphous blob. The TIE fighter shape emerges at 6.6 GHz. Then, at 15.4 GHz, a clear gap in the radio emission appears between the galaxy's core and its lobes.

Lister's team suspects a lull in TXS 0128's activity created this gap. The galaxy's jets appear to have started around 90 years ago, as observed from Earth, and then stopped about 50 years later, leaving behind the unconnected lobes. Then, roughly a decade ago, the jets turned on again, producing the emission seen closer to the core. What caused the sudden onset of these active periods remains unclear.

The radio emission also sheds light on the location of the galaxy's gamma-ray signal. Many theorists predicted that young, radio-bright active galaxies produce gamma rays when their jets collide with intergalactic gas. But in TXS 0128's case, at least, the particles in the lobes don't produce enough combined energy to generate the detected gamma rays. Instead, Lister's team thinks the galaxy's jets produce gamma rays closer to the core, like the majority of active galaxies Fermi sees.

The team observed the galaxy in X-rays using Chandra, looking for evidence of an enveloping cocoon of ionized gas. While their measurements couldn't confirm the presence or absence of a cocoon, there has been evidence for such structures in other active galaxies, like Cygnus A. The observations do indicate the galaxy has a large amount of dust and gas surrounding its core, which is consistent with a highly inclined viewing angle.

"This galaxy reminds us of the importance of multiwavelength observations, looking at objects across a wide range of the electromagnetic spectrum," said Elizabeth Hays, the Fermi project scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "Fermi, the VLBA, and Chandra each add a layer to our growing picture of this object, revealing their own surprises."

The Fermi Gamma-ray Space Telescope is an astrophysics and particle physics partnership managed by NASA's Goddard Space Flight Center in Greenbelt, Maryland. Fermi was developed in collaboration with the U.S. Department of Energy, with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden, and the United States.

NASA's Marshall Space Flight Center manages the Chandra program. The Smithsonian Astrophysical Observatory's Chandra X-ray Center controls science and flight operations from Cambridge and Burlington, Massachusetts.

NASA/Goddard Space Flight Center

Related Science Articles:

75 science societies urge the education department to base Title IX sexual harassment regulations on evidence and science
The American Educational Research Association (AERA) and the American Association for the Advancement of Science (AAAS) today led 75 scientific societies in submitting comments on the US Department of Education's proposed changes to Title IX regulations.
Science/Science Careers' survey ranks top biotech, biopharma, and pharma employers
The Science and Science Careers' 2018 annual Top Employers Survey polled employees in the biotechnology, biopharmaceutical, pharmaceutical, and related industries to determine the 20 best employers in these industries as well as their driving characteristics.
Science in the palm of your hand: How citizen science transforms passive learners
Citizen science projects can engage even children who previously were not interested in science.
Applied science may yield more translational research publications than basic science
While translational research can happen at any stage of the research process, a recent investigation of behavioral and social science research awards granted by the NIH between 2008 and 2014 revealed that applied science yielded a higher volume of translational research publications than basic science, according to a study published May 9, 2018 in the open-access journal PLOS ONE by Xueying Han from the Science and Technology Policy Institute, USA, and colleagues.
Prominent academics, including Salk's Thomas Albright, call for more science in forensic science
Six scientists who recently served on the National Commission on Forensic Science are calling on the scientific community at large to advocate for increased research and financial support of forensic science as well as the introduction of empirical testing requirements to ensure the validity of outcomes.
World Science Forum 2017 Jordan issues Science for Peace Declaration
On behalf of the coordinating organizations responsible for delivering the World Science Forum Jordan, the concluding Science for Peace Declaration issued at the Dead Sea represents a global call for action to science and society to build a future that promises greater equality, security and opportunity for all, and in which science plays an increasingly prominent role as an enabler of fair and sustainable development.
PETA science group promotes animal-free science at society of toxicology conference
The PETA International Science Consortium Ltd. is presenting two posters on animal-free methods for testing inhalation toxicity at the 56th annual Society of Toxicology (SOT) meeting March 12 to 16, 2017, in Baltimore, Maryland.
Citizen Science in the Digital Age: Rhetoric, Science and Public Engagement
James Wynn's timely investigation highlights scientific studies grounded in publicly gathered data and probes the rhetoric these studies employ.
Science/Science Careers' survey ranks top biotech, pharma, and biopharma employers
The Science and Science Careers' 2016 annual Top Employers Survey polled employees in the biotechnology, biopharmaceutical, pharmaceutical, and related industries to determine the 20 best employers in these industries as well as their driving characteristics.
Three natural science professors win TJ Park Science Fellowship
Professor Jung-Min Kee (Department of Chemistry, UNIST), Professor Kyudong Choi (Department of Mathematical Sciences, UNIST), and Professor Kwanpyo Kim (Department of Physics, UNIST) are the recipients of the Cheong-Am (TJ Park) Science Fellowship of the year 2016.
More Science News and Science Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: The Power Of Spaces
How do spaces shape the human experience? In what ways do our rooms, homes, and buildings give us meaning and purpose? This hour, TED speakers explore the power of the spaces we make and inhabit. Guests include architect Michael Murphy, musician David Byrne, artist Es Devlin, and architect Siamak Hariri.
Now Playing: Science for the People

#576 Science Communication in Creative Places
When you think of science communication, you might think of TED talks or museum talks or video talks, or... people giving lectures. It's a lot of people talking. But there's more to sci comm than that. This week host Bethany Brookshire talks to three people who have looked at science communication in places you might not expect it. We'll speak with Mauna Dasari, a graduate student at Notre Dame, about making mammals into a March Madness match. We'll talk with Sarah Garner, director of the Pathologists Assistant Program at Tulane University School of Medicine, who takes pathology instruction out of...
Now Playing: Radiolab

What If?
There's plenty of speculation about what Donald Trump might do in the wake of the election. Would he dispute the results if he loses? Would he simply refuse to leave office, or even try to use the military to maintain control? Last summer, Rosa Brooks got together a team of experts and political operatives from both sides of the aisle to ask a slightly different question. Rather than arguing about whether he'd do those things, they dug into what exactly would happen if he did. Part war game part choose your own adventure, Rosa's Transition Integrity Project doesn't give us any predictions, and it isn't a referendum on Trump. Instead, it's a deeply illuminating stress test on our laws, our institutions, and on the commitment to democracy written into the constitution. This episode was reported by Bethel Habte, with help from Tracie Hunte, and produced by Bethel Habte. Jeremy Bloom provided original music. Support Radiolab by becoming a member today at     You can read The Transition Integrity Project's report here.