Astronomy

Two NASA astronauts will venture outside the International Space Station today (June 13), and you can watch the action live.

Most neutron stars spin rapidly, completing a rotation in seconds or even a fraction of a second. But astronomers have found one that takes its time, completing a rotation in 54 minutes. What compels this odd object to spin so slowly?

When a massive supergiant star explodes as a supernova, it leaves a collapsed core behind. The extreme pressure forces protons and electrons to combine into neutrons. Since they’re made almost entirely of neutrons, we call them neutron stars. These stellar remnants are extremely small and extremely dense. Only black holes have greater density.

Due to the conservation of angular momentum, neutron stars start to spin rapidly, often rotating as fast as several hundred times per second. Astronomers have found more than 3,000 radio-emitting neutron stars, and out of all of them, only a very small number rotate slowly.

We usually detect neutron stars by their electromagnetic radiation and call them pulsars. Astrophysicists also call the ones with slow rotations long-period radio transients. There’s uncertainty around their slow rotation speeds and if they’re even neutron stars, and the most recently discovered one isn’t helping remove the uncertainty.

In new research in Nature Astronomy, a team of researchers presented the discovery of ASKAP J1935+2148, a long-period radio transient about 16,000 light-years away. The paper is “An emission-state-switching radio transient with a 54-minute period.” The lead author is Dr. Manisha Caleb from the University of Sydney in Australia.

“Long-period radio transients are an emerging class of extreme astrophysical events of which only three are known,” the paper’s authors write. “These objects emit highly polarized, coherent pulses of typically a few tens of seconds duration, and minutes to approximately hour-long periods.”

Researchers have proposed different explanations for these long-period objects, including highly-magnetic white dwarfs and highly-magnetic neutron stars called magnetars. But the research community hasn’t reached a consensus.

ASKAP J1935+2148 has an extremely long period of 53.8 minutes and three distinct emission states. Its bright pulse state lasts between 10 and 50 seconds, and its weaker pulse state, 26 times dimmer, lasts about 370 milliseconds. It also exhibits what’s called a “quenched state” with no pulses.

This image took six hours to acquire and shows the new object close to the magnetar SGR 1935+2154. The six hours of observations revealed the object’s long-period emissions. Image Credit: Caleb, M., Lenc, E., Kaplan, D.L. et al. An emission-state-switching radio transient with a 54-minute period. Nat Astron (2024). CC 4.0

Astronomers discovered the puzzling object accidentally while observing an unrelated gamma-ray burst with the Australian Square Kilometre Array Pathfinder (ASKAP) telescope in October 2022. The observations revealed ASKAP J1935+2148’s bright pulses of radio emissions. In about six hours of observations, the object emitted four bright pulses lasting from 10 to 50 seconds. Light curve inspections and follow-up observations with the MeerKAT radiotelescope revealed the object’s entire pulsing pattern.

“This discovery relied on the combination of the complementary capabilities of ASKAP and MeerKAT telescopes as well as the ability to search for these objects on timescales of minutes while studying how their emission changes from second to second! Such synergies are allowing us to shed new light on how these compact objects evolve,” said Dr. Kaustubh Rajwade, paper co-author and an Astronomer at the University of Oxford.

The three emission states, each different from the others, are puzzling. The researchers needed to verify that each signal from each state came from the same point in the sky. The fact that each signal had the same time of arrival (TOA), as determined by both ASKAP and MeerKAT observations, indicates a single source.

“What is intriguing is how this object displays three distinct emission states, each with properties entirely dissimilar from the others. The MeerKAT radio telescope in South Africa played a crucial role in distinguishing between these states. If the signals didn’t arise from the same point in the sky, we would not have believed it to be the same object producing these different signals.”

ASKAP detected the object’s strong, bright pulse mode, while MeerKAT detected its fainter, weak pulse mode. Both telescopes detected the quiescent mode.

This figure from the research shows the light curves detected by ASKAP and MeerKAT. A critical part of the results is that the ASKAP and MeerKAT arrived in phase with one another. Image Credit: Caleb, M., Lenc, E., Kaplan, D.L. et al. An emission-state-switching radio transient with a 54-minute period. Nat Astron (2024). CC 4.0

“In the study of radio-emitting neutron stars, we are used to extremes, but this discovery of a compact star spinning so slowly and still emitting radio waves was unexpected,” said paper co-author Ben Stappers, Professor of Astrophysics at the University of Manchester. “It is demonstrating that pushing the boundaries of our search space with this new generation of radio telescopes will reveal surprises that challenge our understanding.”

The nature of the emissions and the rate of change of the spin periods strongly suggest that ASKAP J1935+2148 is a neutron star. However, the researchers say they can’t rule out a highly magnetized white dwarf. Since astrophysicists think that white dwarfs become highly magnetized as binaries, and there are no other white dwarfs nearby, the neutron star explanation is more likely.

The object’s radius also doesn’t conform to our understanding of white dwarfs. “However, the implied radius is ~0.8? solar radii, leading us to conclude that this source cannot be expected by standard white-dwarf models,” the researchers explain. White dwarfs are only slightly larger than Earth, which seems to eliminate one as the potential source.

Only follow-up observations and more dedicated studies can reveal the object’s true nature. Either way, whether it’s a white dwarf or a neutron star, the object will open another window into the extreme physics of either type of object. Our understanding of both objects is only decades old, so there’s bound to be lots left to discover.

“It is important that we probe this hitherto unexplored region of the neutron-star parameter space to get a complete picture of the evolution of neutron stars, and this may be an important source to do so,” the authors conclude.

The post Astronomers Find the Slowest-Spinning Neutron Star Ever appeared first on Universe Today.

Watch a new clip from director Eli Roth's upcoming live-action video game adaptation, "Borderlands."

Magnificent spiral galaxy

As the winner of the Longitude prize on antimicrobial resistance is announced, chair of the prize committee Martin Rees, the UK's Astronomer Royal, explains why it pays to reward ideas

As the winner of the Longitude prize on antimicrobial resistance is announced, chair of the prize committee Martin Rees, the UK's Astronomer Royal, explains why it pays to reward ideas

The FDA has authorized just one type of avian flu test, and it is only available to livestock workers

The third episode of "The Acolyte" is a long flashback that adds more layers to both the story being told and the Star Wars universe as a whole.

Earth observations are one of the most essential functions of our current fleet of satellites. Typically, each satellite specializes in one kind of remote sensing – monitoring ocean levels, for example, or watching clouds develop and move. That is primarily due to the constraints of their sensors – particularly the radar. However, a new kind of sensor undergoing development could change the game in remote Earth sensing, and it recently received a NASA Institute for Advanced Concepts (NIAC) grant to further its development.

That new sensor technology is known as a Rydberg sensor, and it uses quantum theory to detect a broad band of radar signals all at once. The grant went to Darmindra Arumugam of NASA’s Jet Propulsion Laboratory, who specializes in remote sensing and has worked with the technology for years. So why are Rydberg sensors so special?

In a typical remote sensing application, a sensor is launched on a satellite that is very good at detecting a particular frequency of light. In radar terms, these are broken up into several different “bands,” each covering anywhere from a few megahertz to a few gigahertz. Some are more familiar than others, such as UHF (ultra-high frequency—300-1000 MHz), but some are more esoteric, such as the Ku band from 12-18 GHz.

Here’s a presentation on the topic Dr. Arumugam gave to NC State’s Electrical and Computer Engineering Department
Credit – NC State ECE

Each of these bands is good at monitoring one particular system back on Earth. For example, NASA uses the VHF (30-300 MHz) to study Earth’s tomography and the UHF band to study snow and rainfall. However, each of these frequencies would require its own specially designed antenna to detect, so any system that would attempt to have detection capabilities over a wide range of frequencies, and thereby be monitoring a wide range of different systems, would get more and more expensive as additional bands were added to the system.

That’s where Rydberg sensors come in. They are a novel type of sensor that uses the quantum state of a single atom to detect a broad band of different electromagnetic waves. For example, a single Rydberg sensor could detect signals from the HF band all the way up through the Ka-band at the faster end of the radar spectrum. This would allow a satellite with a single sensor to monitor all the different systems that radar can detect remotely.

Explaining the functioning of a Rydberg sensor requires a relatively complete understanding of quantum mechanics. Rydberg sensors are named after a quantum state known as the Rydberg state, which is extraordinarily sensitive to its environment. To get to the Rydberg state, engineers have to zap a single atom of Rubidium or Cesium with a laser to make it grow to an extraordinarily large state – almost to the size of a bacteria. They then optically monitor changes in the atom, which is affected by signals in the radar bands previously mentioned. The supporting optical system then analyzes the changes in the atom and can correlate those changes to changes in the signal at a particular frequency band.

In this AstronomyCast episodes, Fraser and Pamela discuss why remote sensing is so useful.

Several proofs of concepts have already been shown, such as those provided by the National Institutes of Standards and Technology. But they have yet to be applied to space – and that is where Dr. Arumugam’s research comes in. His NIAC-funded project is to develop a Rydberg sensor that can be launched on a satellite and detect a broad band of radar signals, including those that monitor the cryosphere, where ice and snow are present on land. With a single Rydberg sensor, Dr. Arumugam hopes to capture all the data for a complete picture of how Earth’s glaciers, snow melt, and ice pack change over time. 

That is still a long way off, as rides into space aren’t well known for being gentle, and so far, Rydberg sensors have only ever been shown to work in a lab. But, given that the technology is only ten years old, there is much potential room for improvement, which is precisely what NIAC grants are for. As Dr. Arumugam says at the end of his proposal write-up, this technology “[has great] potential to generate interest within NASA, the public, and industry…” If it works how theorists expect it to, he will be proven right.

Learn More:
Darmindra Arumugam – Crysopheric Rydberg Radar
UT – Mapping Lava Tubes on the Moon and Mars from Space
UT – Satellite Images Can Help Predict When Underwater Volcanos are About to Erupt
UT – Satellites can Track Microplastics From Space

Lead Image:
Graphical depiction of Rydberg sensing radars.
Credit – Darmindra Arumugam

The post How a Single Atomic Sensor Can Help Track Earth’s Glaciers appeared first on Universe Today.

The waning gibbous Moon is pictured above Earth from the International Space Station as it soared into an orbital nighttime 260 miles above the Atlantic Ocean near the northeast coast of South America on Sept. 30, 2023.

By looking at Earth as an exoplanet, astronomers hope to search for similar fingerprints coming from planets around other stars, which would be a potential sign of intelligent life.

After a lifetime of avoidance, avid baker Catherine de Lange discovers that puff pastry isn't hard to make –you just need a bit of time

After a lifetime of avoidance, avid baker Catherine de Lange discovers that puff pastry isn't hard to make –you just need a bit of time

The Leftovers follows those left behind after 140 million people vanish, unaccountably, in The Departure. The parallels with the covid-19 pandemic are obvious in this jewel of a TV show, says Bethan Ackerley

The Leftovers follows those left behind after 140 million people vanish, unaccountably, in The Departure. The parallels with the covid-19 pandemic are obvious in this jewel of a TV show, says Bethan Ackerley

These stunning photographs are some of the winners of this year’s Milky Way Photographer of the Year competition

Hunt for the Oldest DNA, the story of Eske Willerslev, a Danish evolutionary geneticist reconstructing ecosystems from ancient DNA, is as compelling as his scientific discoveries

These stunning photographs are some of the winners of this year’s Milky Way Photographer of the Year competition

Hunt for the Oldest DNA, the story of Eske Willerslev, a Danish evolutionary geneticist reconstructing ecosystems from ancient DNA, is as compelling as his scientific discoveries

Nine years after hackers targeted Ashley Madison, the dating site for wannabe adulterers, many people still don't grasp what was truly chilling about the scandal, says Annalee Newitz