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How scientists heard hum from the universe?

Friday June 30, 2023 11:45 am

An international team of esteemed astronomers, consisting of scientists from Europe, India and Japan, have made a significant discovery by monitoring pulsars utilizing six of the world’s most sensitive radio telescopes, including upgraded Giant Metrewave Radio Telescope (uGMRT), India’s largest telescope. This is maiden use of uGMRT for detection of gravitational waves.


Using these sensitive radio telescopes scientists got to hear a “humming” or vibrations triggered by ultra-low frequency gravitational waves. These gravitational waves first envisioned by Albert Einstein are generated by dancing monster black hole pairs. These vibrations are being called nano-hertz gravitational waves.


The discovery is a momentous breakthrough in understanding the gravitational wave spectrum, and it has thrown open a new window of exploration in the field of astrophysics. It has also considerably deepened the understanding of the Universe and is a great illustration of the power of international collaboration.

What A Gopakumar said in this regard?

In this regard A Gopakumar, the chair of the Indian Pulsar Timing Array consortium & professor at TIFR, Mumbai said, “The results presented today mark the beginning of a new journey into the Universe to unveil some of these mysteries. More importantly, this is the first time that an Indian telescope’s data is used for hunting gravitational waves.”

How pulsars are monitored?

Pulsars are neutron stars rotating at very high speed. These are remnants of dead stars that emit regular radio beams while rotating. They are monitored using radio telescopes, such as India’s uGMRT.

How gravitational-wave signals get detected?

Onus of detection of gravitational-wave signals is on a collaboration called the Pulsar Timing Array (PTA). Scientists basically utilised pulsars as cosmic beacons for the PTA experiment to detect gravitational-wave signals that are light-year-scale ripples.

Team that made the discovery

The transnational team comprised of members of the European Pulsar Timing Array (EPTA) and Indian Pulsar Timing Array (InPTA) consortium. Both InPTA and EPTA are members of the International Pulsar Timing collaboration (IPTA). InPTA, an Indo-Japanese collaboration that utilises the uGMRT to monitor a sample of nearby millisecond pulsars, is a pulsar timing experiment dedicated to searching for low-frequency nanoHz gravitational waves since 2016.

Gravitational waves first envisioned by Albert Einstein exist

Thursday June 29, 2023 10:11 am

A century ago Albert Einstein had envisioned gravitational waves. Finally astronomers have made a discovery confirming existence of gravitational waves. Background hum of the universe discovered by astronomers is creation of gravitational waves first envisioned by Einstein. This groundbreaking discovery has been made by an international group of scientists. Related report published today says that astrophysicists have been able to hear low frequency gravitational waves that creates universe permeating cosmic background hum. Space is filled with these waves primarily originating from pairs of supermassive black holes spiraling and merging together, indicates the research.

Confirmation of Einstein’s theory

Einstein talked about existence of gravitational waves way back in 1916 but these waves were directly detected by scientists for the first time only in 2016, although scientists had indirect evidence to rely on since 1970s. The recent research relied heavily on pulsars (highly dense remnants of exploded stars spinning at extraordinary speeds). Latest report is based on the data collected by NANOGrav Physics Frontiers Center, comprising over 190 scientists from US and Canada.

Gravitational waves sound like hum

Everybody has heard the hum of large gatherings at some point of time. If you have watched cricket or football match being held in jam packed stadiums on TV then you would have definitely experienced the said hum of large gatherings. On TV hum sound is quiet audible but individual voices are simply not distinguishable. Scientists have discovered that gravitational waves existing in the universe sound similar to hum of large gatherings that are common in cricket, football and tennis stadium or in music concerts or even in auditoriums. This discovery has been made about seven years after initial detection of gravitational waves generated by a pair of distant black holes (black holes are objects so dense with gravity that even light is unable to escape them.

What Jeff Hazbaun has to say about Gravitational waves?

Jeff Hazbaun is an astrophysicist from Oregon State University. He told Reuters, “Gravitational waves are generated by astronomically dense objects in our universe, typically in orbital motion around each other. As these waves travel through space, they physically stretch and compress the fabric of space-time itself.” He said, “We now have compelling evidence of gravitational wave hum in a new frequency range. These frequencies are significantly smaller, around 10-12 orders of magnitude, compared to those detected by LIGO, and they have wavelengths spanning light years.” He also added, “The most straightforward explanation for these gravitational waves involves a collection of supermassive black hole pairs orbiting each other in our cosmic neighbourhood. However, alternative explanations could involve intriguing new physics related to the early stages of the universe, near the Big bang, approximately 13.8 billion years ago.”

Ways to measure distances in universe

Wednesday June 28, 2023 10:47 am

It is not a joke to measure distances in universe. Reason is simple, universe is vast and objects in the universe are usually too far away. Universe is so vast that large part of it is still unobservable. Measuring distances in unobservable universe is out of question and distances can be measured in observable universe only. You will need cosmic distance ladder to measure distances in the universe.

What is cosmic distance ladder?

A ladder consists of succession of steps. Same is the case with cosmic distance ladder. It is the succession of methods used by astronomers to measure distances in the universe. It is not possible to measure all astronomical distances using one method and hence with time ladder analogy developed. Method of direct measurement is at the base of the cosmic distance ladder. Distance of only close objects can be measured directly. Methods of measuring farther objects lie higher on the cosmic distance ladder.

Methods used to measure distances in universe

Direct measurement – Use of radar and parallax to measure distances in universe fall in the category of direct measurement. Radar method of measuring distances of celestial objects involves calculation of time taken by light to reach celestial objects. Velocity of light (300000 km/sec) is known. This multiplied by time taken by light to reach a particular celestial object gives distance of that object. Distance of earth from most planets has been measured using this method. Parallax method is used to measure distance of stars closer than 100 light years.

Standard candles – Parallax method fails if distance of objects in galaxies other than our galaxy is needed. Another method that uses standard candles is useful in such a scenario. Standard candles are astronomical objects whose absolute magnitude is known. Most commonly used standard candles are Cepheid variable stars and RR Lyrae variable stars.

Hubble’s law – For very far away objects none of the aforementioned methods work and astronomers have to rely on theory propounded by Hubble. Hubble claimed in 1929 that universe is expanding. This is known as Hubble’s law.

New method of calculating distances in the universe – A new method of measuring distances using a specific subset of RR Lyrae stars is making news nowadays. RR Lyrae stars used in this method are double-mode RR Lyrae stars. It has been claimed that double-mode RR Lyrae stars are great distance and metallicity indicators.


Newly observed celestial phenomenon – Trail of stars left behind by runway black hole tearing through the universe

Thursday June 8, 2023 11:04 am

Some images from NASA’s Hubble space telescope has helped in discovery of a celestial phenomenon never observed before, trail of stars left behind by a runaway black hole barreling across the cosmos. The said black hole was initially identified as scratches in images from Hubble space telescope but later on was widely accepted as black hole by scientist community. Scientists believe that the black hole in question is tearing across the universe after being thrown out of its own galaxy. Yale university astronomer Pieter van Dokkum has stated that trail of stars seen in the wake of the said black hole is resultant of cooling of gas possible in the wake. Condensation of gas has resulted in formation of stars in the wake of the black hole says Dokkum.

Discovery of the said runaway SMBH (supermassive black hole) and its wake by Pieter van Dokkum was purely serendipitous. Dokkum documented this discovery in his new paper published in ‘The astrophysical journal letters’. The runaway SMBH is tearing across cosmos so fast that its travel from earth to moon in our solar would have ended in 14 minutes. Weight of this SMBH is 20 million times of our sun. It has left behind a 200000 light year long trail of stars, two times the diameter of our galaxy Milky Way. Most likely reason for this celestial incidence is galactic billiards involving three giant black holes. The said runaway SMBH was probably thrown out of its galaxy due to stated galactic billiards. This black hole observation is to be confirmed by observations by Chandra X-ray observatory and James Webb Space Telescope.

The celestial phenomenon that is the subject of this article was definitely not observed before but it is a widely accepted fact that a wake of shocked gas and young stars behind it can be resultant of the interaction of runaway SMBH kicked out of its galaxy with CGM (circumgalactic medium). It is believed that the said runaway SMBH escaped its galaxy on attaining a velocity larger than the escape velocity of the host galaxy. Scientists believe that a binary SMBH was formed due to the merger of two galaxies hosting SMBH and when the third SMBH entered the merger remnant one of the SMBH attained a velocity larger than the escape velocity of the host galaxy formed by an aforementioned merger of galaxies resulting in its expulsion from the host galaxy.  

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