James Webb Space Telescope may have spotted the most distant and the oldest known galaxy till date

 

Image of Glass-z13 galaxy captured by JWST

Glass-z13 is the name of the galaxy that has been spotted by Nasa's James Webb Space Telescope (JWST), which scientists believe to be the most distant galaxy known to mankind to date. From a preliminary study, it is estimated that the galaxy was formed 13.5 billion years ago, which is around 300 million years after the Big bang (Big Bang occurred 13.8 billion years ago). This is an improvement of around 100 million years from the farthest known galaxy previously. 

Here we are gazing at the most distant starlight that any human has ever seen. The more distant the body, the more time it takes for the light to reach us. So looking farther deep into space means we are looking back in time. So we are not only looking at the farthest starlight but also these are the oldest photons to reach us. We are practically looking at the galaxy as it was 13.5 billion years ago!! Isn't it amazing!! Thus rightly said by Einstein, "The most comprehensible thing about the universe is that it is incomprehensible!!"

The observation was made in the "early release" data from the observatory's main infrared imager called NIRcam, but the result was not made public in the first set of publications of JWST. It needed some time to translate the data from infrared to visible spectrum, where the galaxy appeared as a blob of red with white in its center. The farther an object is situated from the observer, the farther the light has to travel, and due to the expansion of the universe, the light wavelength is stretched from the visible to the infrared region of the spectrum. This is where JWST specializes. It is well equipped with infrared detectors that are suitable to make observations of very distant objects right till the big bang with unprecedented clarity.

Two separate teams of astronomers, one headed by Mr. Naidu and the other by Marco Castellano have independently taken the observations, analyzed the data, and reached the same conclusions. This is why they are confident about the results they have obtained. Currently, the study is under peer-review in a scientific journal and posted publicly on a preprint server.

The team of scientists believes that they have to conduct a detailed spectroscopic analysis of the data they have obtained to confirm their claim and also extract more knowledge about the galaxy. As of now, they know that the galaxy has a mass of billion suns, which is really surprising considering how soon after the big bang it formed. They also need to confirm the distance of the galaxy that they have claimed. The spectroscopic analysis will also reveal some detailed properties of the galaxy. 

Along with GLASS z-13 they have also found the signature of another galaxy known as GLASS z-11, which is not as ancient as the former but around a similar time scale. JWST is expected to open a new era of astronomy, with records being broken with each observation. We have started to see the results already!! We hope that JWST outperforms its expectations and helps us to reveal the deep-lying secrets of the universe. As of now, our fingers are crossed!!

PC:  NASA/ESA/CSA

By

Prabir Rudra

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Black Hole: The monster of the Universe

 

A black hole is a region in spacetime where the gravitational pull is so strong, that no matter can escape from it. The gravity in such a region is of such magnitude that not even electromagnetic radiation (light) can escape from it. Theoretically, black holes were predicted from the solutions of the field equations of general relativity, as regions in spacetime with infinite curvature, such that gravity in the region becomes extremely large.

The boundary of a black hole is called the event horizon, which has great significance for a particle falling into the black hole. The event horizon is basically a point of no return for the infalling bodies, because once a particle crosses the event horizon it does not have any possibility of making it back, and is destined to be engulfed by the black hole. For an external observer, the infalling body will appear to fall into the black hole for eternity due to time dilation near the black hole. Time dilation is caused by the extreme gravity of the black hole and the flow of time is slowed down drastically. The object that is falling into the black hole will appear to fall very slowly to an external observer and the event of falling will seem to occur for eternity.

Using quantum field theory in curved spacetime famous cosmologist Stephen Hawking predicted that a particular type of radiation is emitted from the event horizon of a black hole. This radiation is called the Hawking radiation, whose temperature is inversely proportional to the mass. This temperature is of the order of a billionth of a kelvin for stellar black holes due to which it is almost impossible to detect it directly.

Black hole as a Mathematical entity

In 1916,  Karl Schwarzschild derived the first solution of the Einstein's equations of general relativity which directly showed the presence of a black hole theoretically. For a long time black holes just remained a mathematical curiosity with no physical reality associated with it. With the discovery of neutron stars by Jocelyn Bell Burnell in 1967, new interest was generated in the field of gravitationally collapsing bodies. 

Formation of a black hole

A star at the end of its lifetime undergoes gravitational collapse and forms a white dwarf which is a compact astronomical object. Further collapse from this state will occur if the mass of the white dwarf exceeds 1.4 solar mass (Chandrasekhar limit) and the resulting object will be a highly compact neutron star. If this state is not in equilibrium, then further collapse is a possibility, which will result in a singularity. If the singularity is shrouded by an event horizon, then it is a black hole. The first black hole known to us was Cygnus X-1 identified in 1971.

After the formation of a black hole

After a black hole is formed it can grow by absorbing the surrounding mass due to its immense gravitational pull. Supermassive black holes (millions of solar masses) can absorb stars or even other black holes. The presence of a black hole is generally inferred by the way it interacts with the surrounding matter and electromagnetic radiation. Any infalling matter in the black hole forms an accretion disk which is enormously heated due to friction. Stars which are in the close vicinity of a black hole will be shredded and engulfed by it, whereas stars which are at a considerable distance will orbit the black hole. The mass of the black hole and its location can be inferred from the orbit of these stars. It is believed that supermassive black holes exists at the centres of most galaxies. There is a radio source at the heart of our galaxy Milky Way known as the Sagittarius A*. It is believed that it houses a supermassive black hole of 4.3 million solar masses.

Recent Advancement

On February 11, 2016 gravitational waves due to a black hole merger was recorded by the LIGO and Virgo scientific collaboration. On April 10, 2019 the first direct image of a black hole was recorded by the Event Horizon telescope. It was situated in the M87 galaxy around 50 million lightyears away from us. Till date gravitational lensing is possibly the best method to infer the presence of a black hole. Although only around 20 black holes have been detected so far, it is expected that there are hundreds of millions of such monsters roaming in the universe. Having an encounter with such a thing is not going to be a pleasant experience at all!!

By

Prabir Rudra

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NASA releases the first image taken by the James Webb Space Telescope : The farthest that humanity has ever seen

PC:  NASA, ESA, CSA

Finally, the moment has arrived!! Nasa has released the first image taken by the James Webb Space Telescope (JWST). The deepest and the sharpest infrared image is known as Webb's First Deep Field. The image focuses on the galaxy cluster SMACS J0723.3-7327 which lies around 4.6 billion light-years away from us. Since the mass of the galaxy cluster is huge, it distorts spacetime in such a way that objects behind the cluster are magnified. As a result, some distant galaxies lying behind these clusters are visible in the image. That's the aura of gravitational lensing!!

This is the farthest that humanity has ever seen-the deepest and the sharpest view of the cosmos till date. Each bright dot in the image, barring the very bright ones, represents a galaxy. The slice of the vast universe focused in the image, covers a patch of sky approximately the size of a grain of sand held at arm's length by someone on the ground!! Isn't it amazing!!! Intimidating indeed!!

The image was the result of a day-long observation with the JWST. US President Joe Biden unveiled the image during an event in the White House on Monday, July 11, 2022. This image surpasses all previous records held by the images from Hubble Space Telescope. But the scientists believe that this is just the beginning of a new era in infrared astronomy-The JWST era. 

By

Prabir Rudra

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The wait is coming to an end: NASA is all set to release its James Webb Space Telescope's first images on 12th July, 2022

Nasa is going to release its James Webb Space Telescope's (JWST) first full-colour images on 12th July 2022. This will mark a new dawn in space science with this revolutionary apparatus going online. We will get enhanced eyes through which we will be able to look deep into space and peer deep into time, right to the dawn of the universe. A time to rejoice for everybody associated with space science!! A time to thrill and wait for the release.

It will be just like an unveiling in an exhibition, drawing the curtain in a photo gallery. All the fine-tuning and adjustment that was necessary have been done and the device is all set to give results in some hours. Nasa will not only release the pictures of different astronomical subjects which are currently being studied by JWST but also give us spectroscopic data from the newly operational observatory.

Nasa has released a list of five celestial subjects which will be studied by JWST as its debut assignment. This list is populated by two nebulae (gas clouds that form nurseries for new stars) and two galaxy clusters. The idea is to look far and look back in time!! Among the data to be published, there is also the spectroscopic analysis of the atmosphere of an exoplanet. This exoplanet is 1100 lightyears away from Earth and roughly half the mass of Jupiter.  

Although all the subjects listed above have been known to us for a long time, there is an expectation of a different level with JWST. JWST will study its subject in the infrared spectrum and it is believed that its results will be 100 times more sensitive than its predecessor, the Hubble space telescope. 

Considering all these, it is expected that JWST will revolutionize astronomy providing us the first glimpse of the infant galaxies which date back to just 100 million years after the Big Bang, 13.8 billion years ago. The creation of the universe might just be in front of our eyes!! The very thought gives goosebumps indeed!!! 

So the countdown has begun and it is just a wait for a few more hours before JWST starts revealing before us some of the deep secrets of the universe. The live broadcast begins at 10.30 a.m. EDT on Tuesday, July 12, 2022, from the Goddard Space fight center in Greenbelt, Maryland. The released images will be simultaneously made available on various social media sites and also on Nasa's website at  https://www.nasa.gov/webbfirstimages.

From 10.30 a.m. EDT, the live coverage of the image release broadcast will air on NASA TV, the NASA app, and also on NASA's website. The public can also watch this live on various social media sites like Facebook, Twitter, YouTube, Twitch, and Daily Motion. At 12 p.m. following the live broadcast, NASA and its partners (ESA & CSA) will hold a joint briefing at NASA Goddard. The briefing will be live-streamed on NASA TV, the NASA app, and the NASA's website.

By,

Prabir Rudra

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Dark Matter: An Unsolved Mystery

 

As the name suggests, dark matter is an invisible form of matter that is supposed to fill a substantial part of the universe and is responsible for driving some critical cosmological events. One thing is certain, it is not in the form of stars or planets that we can see around us. From the observations, it is estimated that 85 % of the total matter content of the universe must be dark matter. Along with dark energy, it forms 95 % of the total mass-energy content.

Why is it dark?

Dark matter seems to have no interactions with the electromagnetic field, which implies that it does not emit, reflect or absorb light. This is the reason why it is totally invisible to us and hence aptly termed dark matter.

Then how is it detected and what role does it play in the dynamics of the universe?

Observations from the evolution of galaxies suggest that the galaxy dynamics would be quite different if it is governed by the presence of the matter that we see in the universe (visible matter). The galaxy rotation curves (path of motion) would be quite different if gravitational interaction emerged from visible matter only. Many galaxies would never have formed if it was only due to the contributions of normal matter. Simply we need more matter to generate the necessary gravity such that the observed galaxy dynamics can be explained!! To put it in another way, we need around 27 % of matter to explain the observations, but the normal matter is far less than that.

So it is quite understandable that there is a missing link in the picture. Either our observations are faulty or there is some form of matter that is totally eluding our vision, but playing a significant role in the structure formation and evolution of galaxies. This invisible form of matter that generates sufficient gravitational interaction to sustain the galaxy dynamics is dark matter. We cannot see it, but we can feel its presence due to the role played by it. There are other scientific pieces of evidence of the presence of dark matter such as gravitational lensing (bending of light in a gravitational field), Cosmic microwave background radiation (which is a relic of the Big Bang), etc.

What is dark matter made of?  

It is now well known that dark matter has minimal interactions with visible matter & radiation, which is the basic reason behind its mysterious nature. It remains secluded without intermingling with other components of the universe but reveals its presence only through gravitational interaction. So naturally, a question arises regarding the chemical composition of dark matter. In simpler terms, one would like to know what is dark matter made of. This question is not yet answered by the scientific community, but extensive research is underway. It is believed that dark matter is made up of some new kind of elementary particle that is yet to be discovered. 

 

Speculations:

Dark matter is sometimes argued to be some form of antimatter (matter composed of antiparticles of the corresponding particles in the ordinary matter), but this is not correct. The reason is, that we do not see the unique gamma rays that are supposed to form when matter annihilates with antimatter. Some people argue that dark matter can be black holes, which are themselves mysterious invisible objects, and share some common properties. But this is not true either, because black holes are centers of gravitational lensing due to their enormous gravitational pull. If dark matter was present in the form of black holes we would have seen far more gravitational lensing phenomena than we actually see in the universe. As of now, we believe that dark matter must be made up of some exotic particles which are yet to find their places in the periodic table and, about which our knowledge is extremely limited.

By Prabir Rudra

#darkmatter #galaxy #galaxyrotationcurve #cosmology #blackhole #darkenergy #visiblematter #gravitationallensing #CMBR #bigbang #spacetime #spacetimerecipe #gravity #astrophysics

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Dark Energy: The greatest puzzle of modern cosmology

 

At the turn of the last century, observations from Supernova Type Ia confirmed the fact that our universe has entered a phase of accelerated expansion. Two separate teams respectively working on the Supernova cosmology project and the high-Z supernova search team reached this result independently in 1998. They were respectively headed by Saul Perlmutter and Brian P. Schmidt & Adam Riess.  This came as a shocking discovery to the scientific community since the outcome defied our orthodox understanding of the dynamics of the universe.

It is clearly known that gravitational interaction is attractive in nature. So an expanding universe that originated from the Big Bang would tend to slow down due to gravity interacting between the objects such as planets, stars, galaxies, etc. Thus a decelerated expansion of the universe will slowly bring the universe to a halt before the contraction phase sets in. But the discovery of accelerated expansion totally defies this idea, and we are left wondering about the mechanism that is responsible for this strange phenomenon.

It was clear to the scientific community that in order to explain this phenomenon theoretically, we will have to introduce a repulsive (anti-gravitational) interaction, which will counterbalance and even dominate the attractive gravitational interaction. But this repulsion will not jump out of nowhere, and there should be some source for it. So what is needed is basically a matter field that can sustain a repulsive interaction. This matter field is exactly what we term Dark Energy which is a hypothetical matter fluid with negative pressure.

Observations suggest that our universe is basically filled with three major components, namely normal or visible matter, dark energy, and dark matter. It is really very strange that normal matter (which includes all the visible entities around us) accounts for the smallest portion of the universe, which is around 6 %. Around 26 % of the universe is considered to be dark matter and the rest around 68% is dark energy. So it is evident that the present universe is dominated by dark energy and its queer exotic properties affect the universe at the cosmological scales, thus driving the accelerated expansion.

The density of dark energy is very low, estimated at around 7 x 10^ (-30) gm per cubic cm. This is considerably low compared to that of visible matter and dark matter, but still, it plays a major role in shaping the dynamics of the universe due to its uniformity across space. From the general relativistic point of view, Einstein’s field equations become inconsistent with the observations at the cosmological scales. This basically means that general relativity in its original form cannot account for the accelerated expansion of the universe in its framework. So we need to introduce modifications to the field equations in order to address this issue. The right-hand side of Einstein’s field equations comprises the matter fields, which can be modified by introducing dark energy. Such modifications have been attempted and found to be consistent with the observations.

There are basically two broadly proposed forms of dark energy, the cosmological constant and the scalar fields such as quintessence. The cosmological constant represents the constant vacuum energy density filling the space homogeneously, whereas scalar fields involve dynamic quantities, whose energy densities vary in space and time.

Cosmological inflation is an enormous and exponential expansion that took place just after the Big Bang. Dark energy can not only explain the dynamics of the late-time accelerated expansion of the universe but can also satisfactorily account for the early-time inflationary evolution of the universe. Alan Guth and Alexei Starobinsky in 1980 proposed that a matter field with negative pressure (similar to that of dark energy) can drive the cosmic inflationary mechanism in the early universe.

In physical cosmology, dark energy is studied extensively to explain cosmological observations and derive a proper cosmological model of the universe. This will ultimately help us get a description of the large-scale structure and the dynamics of the universe. Proper knowledge of dark energy will help us answer critical questions regarding the origin, structure, evolution, and ultimate fate of the universe. As of now we are still shrouded by the darkness of dark energy and trying to find our way out of the puzzle.

By Prabir Rudra

#darkenergy #cosmology #universe #cosmicexpansion #gravity #relativity #spacetime #spacetimerecipe #darkmatter #cosmicinflation

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