India's largest radio telescope key to detecting the universe's vibrations

 India's Giant Metrewave Radio Telescope (GMRT) was one of the world's six large telescopes that played a key role in finding the first direct evidence for the relentless vibrations of the fabric of the universe, caused by ultra-low frequency gravitational waves.

"We are within a whisker of achieving such a dynamic range where one can finally listen to the bass sections in this cosmic gravitational-wave-symphony," said Pratik Tarafdar of The Institute of Mathematical Sciences, Chennai.

Such waves are expected to originate from a large number of dancing monster black hole pairs, several million times heavier than the Sun, the scientists said.

"It is fantastic to see our unique uGMRT data being used for the ongoing international efforts on gravitational wave astronomy," said Yashwant Gupta, Centre Director at National Centre for Radio Astrophysics (NCRA), Pune, which operates the GMRT.

The team's results are considered as a crucial milestone in opening a new, astrophysically-rich window in the gravitational wave spectrum.

Scientists of the European Pulsar Timing Array in collaboration with the Indo-Japanese colleagues of the InPTA arrived at the findings after analysing pulsar data collected over 25 years with six of the world's largest radio telescopes.

This includes more than three years of very sensitive data collected using the unique low radio frequency range and the flexibility GMRT, which underwent significant upgrades in 2019.

"The results reported by the EPTA+InPTA collaboration are tantalisingly close to the discovery of nano-hertz gravitational waves and are the culmination of many years of efforts by many scientists including early career researchers and undergraduate students," said Prof. Shantanu Desai of IIT, Hyderabad.

The InPTA experiment involved researchers from NCRA (Pune), TIFR (Mumbai), IIT (Roorkee), IISER (Bhopal), IIT (Hyderabad), IMSc (Chennai) and RRI (Bengaluru) along with their colleagues from Kumamoto University, Japan.

The 100-m Effelsberg radio telescope in Germany, the Lovell Telescope of the Jodrell Bank Observatory in the United Kingdom, the Nancay Radio Telescope in France, the Sardinia Radio Telescope in Italy and the Westerbork Synthesis Radio Telescope in the Netherlands were used for observations.

India's Giant Metrewave Radio Telescope (GMRT) was one of the world's six large telescopes that played a key role in finding the first direct evidence for the relentless vibrations of the fabric of the universe, caused by ultra-low frequency gravitational waves.

Such waves are expected to originate from a large number of dancing monster black hole pairs, several million times heavier than the Sun, the scientists said.

The results are considered a crucial milestone in opening a new, astrophysically-rich window in the gravitational wave spectrum.

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Astrophysicist discusses new evidence of gravitational waves

 Astronomers around the world have spent decades observing dozens of pulsars—the super-dense remains of exploded stars that emit regular pulses of radio waves as they spin at ludicrous speeds, like runaway lighthouses. 

Last week, dozens of physicists began promising to reveal findings from these observations that could, in time, change our understanding of the universe.

On the evening of June 28, several research groups announced that they had found evidence of low-frequency gravitational waves: fantastically long ripples in the fabric of spacetime that alter the timing of the pulsars' flashing signals by minuscule amounts. 

With further research, the network of pulsars may act as a galaxy-scale telescope for glimpsing the sources of those waves, potentially providing clues about the evolutions of millions of galaxies across the universe.

"Investigating the origins of these gravitational waves may help us tell the narrative history of how galaxies are born, how they grow, and how they die," said Stanford's Roger Blandford, who answered some questions on the significance of the announcement for Stanford News.

This announcement is the culmination of many years of collecting data from pulsars across our neighborhood of the Milky Way. What sets these findings apart from those that came before?

A couple of years ago, there was an announcement of a signal of what these astrophysicists were looking for, but they hadn't confirmed the signature of low-frequency gravitational waves rather than just some general signal out there. Now, they are starting to see a telltale signature of the gravitational waves themselves. There's still some doubt—there should be—but it's looking like a pretty careful measurement to me.

Where do astrophysicists think these gravitational waves might have come from?

What they're looking at is a background of gravitational radiation from many undifferentiated sources—like looking through a fog, as it were, seeing a sort of diffuse light rather than a single source. However, when their sensitivity improves, they should start to see the nearby, individual sources making up that background fog.

 How long it takes to get to that point depends on how the pulsar observation techniques improve and on what sources of gravitational radiation are actually out there. The leading candidate for the source of what they're detecting now is a population of merging, massive black holes.

What's significant about investigating the origins of gravitational waves?

It may tell us a lot about the life histories of galaxies. A large part of that is how they merge together.

The basic interpretation is that, long ago, we had smaller galaxies merging together to become bigger galaxies, and the black holes in those galaxies' centers also merged. But we haven't had strong evidence that black holes merge, or how, because if you actually look for these paired black holes, they're rather shy. 

So if the idea that these gravitational waves come from merging black holes is borne out by subsequent observations—and it's certainly on the right track to do that—then we will have one key part of the story of how galaxies merge. This is more like doing paleontology or archaeology more than like doing physics experiments.

What do you think is most important for people to understand about the scientific process involved in a discovery of this scale?

It's a collaboration. You have people who are experts in signal processing, people who are experts in using telescopes, and more. And it's an international enterprise: there's NANOGrav observing pulsars from the U.S., but there are five other teams out there, too. 

They're going to combine their signals and try and get a stronger result, and it will get even better in the future because they will observe even more pulsars over longer periods of time. They all have to compete, cooperate and collaborate. 

It's complicated! And it all has to be paid for—the National Science Foundation should be credited for sticking with this research for 15 years. There's a lot of work that's gone into this, and I'd be very surprised if there's any serious flaw in it. We seem to be opening up a new window on the universe.

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Pune’s GMRT becomes first Indian facility to detect gravitational waves

 In a major breakthrough, an international team of astronomers Thursday announced scientific evidence confirming the presence of gravitational waves using pulsar observations.

Operated by the National Centre for Radio Astrophysics (NCRA), India’s Giant Metrewave Radio Telescope (GMRT) located in Pune was among the six of the world’s largest radio telescopes that paved the way for this discovery of nano-hertz gravitational waves.

This major announcement has come eight years after the first detection of gravitational waves which was proposed by Physicist Albert Einstein a century ago.

In two different studies published on Thursday, radio astronomers representing the Indian Pulsar Timing Array (InPTA) and European Pulsar Timing Array (EPTA) shared that a time aberration was observed in the signals emerging from these pulsars.

Nicknamed as cosmic clocks, pulsars are rapidly spinning neutron stars that send out radio signals at regular intervals which are seen as bright flashes from the Earth. As these signals are accurately timed, there is a great interest in studying these pulsars and to unravel the mysteries of the Universe. In order to detect gravitational wave signals, scientists explore several ultra-stable pulsar clocks randomly distributed across our Milky Way galaxy and create an ‘imaginary’ galactic-scale gravitational wave detector.

There are several signals travelling through spacetime of the Universe. But, the presence of gravitational waves influences the arrival of these signals when detected from Earth. It was noticed that some signals arrive early while others, with a slight delay (less than a millionth of a second).

These nano-hertz signals were heard as humming from the Universe. These were caused due to the presence of gravitational waves and due to signal irregularities emerging from pulsars, said the scientists.

“These irregularities showcased consistent effects on the resultant emanating gravitational waves at ultra-low frequency,” said Bhal Chandra Joshi, senior NCRA scientist and the man behind forming InPTA.

It is expected that ultra-low frequency gravitational waves, also known as nano-hertz gravitational waves, emerge from a colliding pair of very large ‘monster’ black holes, many crores of times heavier than our Sun. Such ‘monster’ black holes are believed to be located in the centre of colliding galaxies. The signals or ripples that emerge from within these blackholes are known as nano-hertz gravitational waves. Their wavelengths can be many lakhs of crores of kilometres and oscillate with a periodicity anywhere between a 1 year to 10 years. When there is continuous arrival of these nano-hertz gravitational waves, it creates a consistent humming in our Universe, which gets detected using powerful radio telescopes from the Earth.

In all, six of the world’s most powerful and large radio telescopes – uGMRT, Westerbork Synthesis Radio Telescope, Effelsberg Radio Telescope, Lovell Telescope, Nançay Radio Telescope and Sardinia Radio Telescope — were deployed to study 25 pulsars over a period of 15 years. In addition to data from these facilities, highly sensitive uGMRT data of more than three years were analysed too. It has been concluded that radio flashes from these pulsars were affected by the nano-hertz gravitational waves believed to emerge from ‘monster’ black holes.

Along with scientists from NCRA, the InPTA comprises experts from Indian Institute of Science Education and Research, Bhopal, Raman Research Institute (RRI), Bengaluru, IIT-Roorkee, IIT-Hyderabad, Institute of Mathematical Sciences, Chennai.

Even though the Laser Interferometer Gravitational Observatory (LIGO) captured these waves lasting over a few seconds, PTAs observed these signals in a different frequency range.

“But our galaxy-sized PTA could sense a permanent vibration of the gravitational wave background in nano-hertz frequencies,” said Prof. A Gopakumar from Tata Institute of Fundamental Research (TIFR), Mumbai.

According to Joshi, Albert Einstein had stated that gravitational waves change the arrival times of these radio flashes, and thereby affect the measured ticks of our cosmic clocks.

“As these changes are tiny, astronomers need sensitive telescopes like uGMRT and a collection of radio pulsars to separate these changes from other disturbances. Such slow variations of the signal have meant that it takes decades to look for these elusive nano-hertz gravitational signals,” Joshi said.

Yashwant Gupta, centre director, NCRA, said, “The whiteband receiver systems designed and built for the uGMRT played a crucial role in obtaining high quality data from low frequency radio bandwidth.”

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Wanted: Gravity-Busting Detectives! Scientists seek your help hunting kilonovae among space oddities

 Gravitational Wave Detectors register the collisions between the most exotic objects in the universe, including neutron stars, black holes and white dwarfs. However, it actually see these events, astronomers have to observe them in electromagnetic frequencies.

 A new citizen science project invites the general public to spot the optical counterparts of events registered by gravitational wave detectors.

The Gravitational-wave Optical Transient Observer (GOTO) are a pair of telescopes on opposite sides of the world, one at the Siding Spring Observatory in Australia, and the other at Roque de Los Muchachos Observatory on La Palma island in the Canary Islands. 

Together, the two instruments complement the observations of gravitational wave detectors such as LIGO, VIRGO and KAGRA, and identify the electromagnetic counterparts of the gravitational wave sources.

Kilonovae are produced by a neutron star colliding with another neutron star or a black hole. Once LIGO, VIRGO or KAGRA detectors register a source of gravitational waves, they alert GOTO about the general region in the sky of the event. 

Within 30 seconds of the alert, GOTO is configured to scan the skies to identify the electromagnetic counterpart, or the same event as visible in optical frequencies. The captured images are analysed by scientists, and also sent over to the Kilonova Seekers citizen science project.

The GOTO telescopes capture massive amounts of data, and scientists cannot possibly visually inspect all the images. The Kilonova Seekers citizen science project allows anyone to participate in cutting edge multimessenger astronomy, working with images that have not been seen by anyone before. 

While there is a brief orientation, there are no special skills necessary to participate in the project, or a deep knowledge of science. The choices of the volunteers will also be used to train machine learning algorithms that can then autonomously hunt down kilonovae.

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Science news this week: Gravitational waves and a winged Medusa medal

 Space is the place for science news it seems, with a number of astounding discoveries from the cosmic realm getting us all starry-eyed this week.

The main headlines were the groundbreaking discovery of gravitational waves rippling in the cosmic background, and the first map of the Milky Way made with matter, not light, by tracing the galactic origins of thousands of "ghost particles," or neutrinos. However, we also had distortions in space-time putting Einstein's theory of relativity to the test, carbon compounds crucial to life found in star system 1,000 light-years from Earth, rare streaks of light above the U.S. signaling the fast-approaching solar maximum, and an alien planet hiding in our solar system — and it’s not "Planet X."

Back on Earth, we learned that the the world's largest crocodile living in captivity has passed a medical with flying colors, we saw an incredible video of a 28-year-old lab chimp seeing the open sky for the first time, and watched a shapeshifting eel with a “remarkably full tummy” swim in the deep sea. Sadly, we also found out that White Gladis, the orca that likely started the attacks on boats in Iberian waters, may have been pregnant at the time of her first strike, and was so hellbent on stopping boats that she neglected her calf once born.

Outside of the animal kingdom, we found a silver medal with a winged Medusa at a Roman fort near Hadrian's Wall, some enigmatic Anglo-Saxon ivory rings, and a 2,000-year-old fresco in Pompeii that is definitely not a pizza (although it does offer a mouthwatering taste of the Roman diet).

Of course there is more, from controversial vaginal seeding to Yellowstone’s supervolcano, honey bee origins to collapsing mountain peaks, it has certainly been a busy one, so be sure to check back for the latest science news. Visit the site daily, follow us on Facebook, Twitter and Instagram, and sign up to our daily newsletter using the form below to stay up to date.

The James Webb Space Telescope (JWST) has become synonymous with jaw-dropping, full-color photos of some of the most compelling cosmic landscapes in the universe (if you don’t believe us, here are a few of our favorites). But, as new photos of Saturn reveal, even JWST's unprocessed black-and-white images are stunning.

JWST captured the new images of the ringed planet between June 24 and 25 as part of a project to study the planet's rings, moons and atmospheric composition.

Currently, the pictures are in stark — and somewhat eerie — black and white, which represent the number of photons JWST's Near Infrared Camera collects. Later, scientists will process and colorize the images into something more instantly recognizable. For now, they remain a ghostly and rarely seen portrait of the planet's icy rings.

Point your telescope to the sky on Monday (July 3) to get a view of the beautiful Buck moon, the first supermoon of the year. Not only will the moon be closer to Earth than it typically is, but for most observers, the moon will also remain lower in the sky than at any other time this year.

The Earth-facing side of the moon will be fully lit by the sun at 6:40 a.m. EDT on Monday, but it will be best viewed at moonrise the previous evening as it appears in the southeastern sky. It will be in the constellation Sagittarius, and will appear bright and full on the nights of July 2 and 4 as well.

Of course, you don’t need a telescope to look at the moon, but if you’re interested in getting one, here’s our pick of the best, as well as our guide on the different types of telescope.

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Dying Stars’ Cocoons: A New Unexpected Source of Gravitational Waves

 So far, gravitational waves have been only detected by astrophysicists from binary systems – the fusion of either two black holes, two neutron stars, or one of each. In theory, it should be possible to detect gravitational waves emanating from a solitary, non-binary source, but such elusive signals have yet to be discovered.

Researchers from Northwestern University now propose that these elusive signals could be sought in a novel, unexpected, and entirely unexplored area: The turbulent, energetic cocoons of debris that surround dying massive stars.

For the first time ever, the researchers have used state-of-the-art simulations to show that these cocoons can emit gravitational waves. And, unlike gamma-ray burst jets, cocoons’ gravitational waves should be within the frequency band that the Laser Interferometer Gravitational-Wave Observatory (LIGO) can detect.

“As of today, LIGO has only detected gravitational waves from binary systems, but one day it will detect the first non-binary source of gravitational waves,” said Northwestern’s Ore Gottlieb, who led the study. “Cocoons are one of the first places we should look to for this type of source.”

Gottlieb recently presented the research during a virtual press briefing at the 242nd meeting of the American Astronomical Society.

As a jet escapes from a collapsed star, it punches into a cocoon of stellar debris. Credit: Ore Gottlieb/CIERA/Northwestern University

So far, gravitational waves have been only detected by astrophysicists from binary systems – the fusion of either two black holes, two neutron stars, or one of each. In theory, it should be possible to detect gravitational waves emanating from a solitary, non-binary source, but such elusive signals have yet to be discovered.

Researchers from Northwestern University now propose that these elusive signals could be sought in a novel, unexpected, and entirely unexplored area: The turbulent, energetic cocoons of debris that surround dying massive stars.

For the first time ever, the researchers have used state-of-the-art simulations to show that these cocoons can emit gravitational waves. And, unlike gamma-ray burst jets, cocoons’ gravitational waves should be within the frequency band that the Laser Interferometer Gravitational-Wave Observatory (LIGO) can detect.

“As of today, LIGO has only detected gravitational waves from binary systems, but one day it will detect the first non-binary source of gravitational waves,” said Northwestern’s Ore Gottlieb, who led the study. “Cocoons are one of the first places we should look to for this type of source.”

Gottlieb recently presented the research during a virtual press briefing at the 242nd meeting of the American Astronomical Society.

The new source was ‘impossible to ignore’

To conduct the study, Gottlieb and his collaborators used new state-of-the-art simulations to model the collapse of a massive star. When massive stars collapse into black holes, they may create powerful outflows (or jets) of particles traveling close to the speed of light. Gottlieb’s simulations modeled this process — from the time the star collapses into a black hole until the jet escapes.

Initially, he wanted to see whether or not the accretion disk that forms around a black hole could emit detectable gravitational waves. But something unexpected kept emerging from his data.

“When I calculated the gravitational waves from the vicinity of the black hole, I found another source disrupting my calculations — the cocoon,” Gottlieb said. “I tried to ignore it. But I found it was impossible to ignore. Then I realized the cocoon was an interesting gravitational wave source.”

As jets collide into collapsing layers of the dying star, a bubble, or a “cocoon,” forms around the jet. Cocoons are turbulent places, where hot gases and debris mix randomly and expand in all directions from the jet. As the energetic bubble accelerates from the jet, it perturbs space-time to create a ripple of gravitational waves, Gottlieb explained.

“A jet starts deep inside of a star and then drills its way out to escape,” Gottlieb said. “It’s like when you drill a hole into a wall. The spinning drill bit hits the wall and debris spills out of the wall. The drill bit gives that material energy. Similarly, the jet punches through the star, causing the star’s material to heat up and spill out. This debris forms the hot layers of a cocoon.”

Call to action to look at cocoons

If cocoons do generate gravitational waves, then LIGO should be able to detect them in its upcoming runs, Gottlieb said. Researchers have typically searched for single-source gravitational waves from gamma-ray bursts or supernovae, but astrophysicists doubt that LIGO could detect those.“Both jets and supernovae are very energetic explosions,” Gottlieb said. 

“But we can only detect gravitational waves from a higher frequency, asymmetrical explosions. Supernovae are rather spherical and symmetrical, so spherical explosions do not change the balanced mass distribution in the star to emit gravitational waves. Gamma-ray bursts last dozens of seconds, so the frequency is very small — lower than the frequency band that LIGO is sensitive to.”

Instead, Gottlieb asks astrophysicists to redirect their attention to cocoons, which are both asymmetrical and highly energetic.

“Our study is a call to action to the community to look at cocoons as a source of gravitational waves,” he said. “We also know cocoons emit electromagnetic radiation, so they could be multi-messenger events. By studying them, we could learn more about what happens in the innermost part of stars, the properties of jets, and their prevalence in stellar explosions.”

Reference: “Jetted and Turbulent Stellar Deaths: New LVK-detectable Gravitational-wave Sources” by Ore Gottlieb, Hiroki Nagakura, Alexander Tchekhovskoy, Priyamvada Natarajan, Enrico Ramirez-Ruiz, Sharan Banagiri, Jonatan Jacquemin-Ide, Nick Kaaz and Vicky Kalogera, 10 July 2023, The Astrophysical Journal Letters.

Gottlieb is a CIERA Fellow at Northwestern’s Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA). Northwestern co-authors of the study include professors Vicky Kalogera and Alexander Tchekovskoy, postdoctoral associates Sharan Banagiri and Jonatan Jacquemin-Ide and graduate student Nick Kaaz.

The study was supported by the National Science Foundation, NASA, and the Fermi Cycle 14 Guest Investigator program. These advanced simulations were made possible by the Department of Energy’s Oak Ridge National Laboratory supercomputer Summit and National Energy Research Scientific Computing Center’s supercomputer Perlmutter through the ASCR Leadership Computing Challenge computational time award.

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