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Saturday, December 1, 2018

is there life outside our galaxy ~ whether and how near ? - Andromeda !!


In ‘Crazy thieves in Palavakkam’ drama – a middle class family (in 1970s) would build a small house in the outskirts of Chennai in an area called Palavakkam (now a richman’s place)  - they would be gleeful when they see another house in distance and more so, when an odd man walks on the street ! ~  who lives next door ? 0r whether there is life nearby has always a great curiosity of mankind !!

So is there life nearby ! – in the nearest gruha (not as nearby home but nearby galaxy !) .. ..  a  Galaxy is a gravitationally bound system of stars, stellar remnants, interstellar gas, dust, and dark matter.  The word galaxy is derived from the Greek galaxias, literally "milky", a reference to the Milky Way. Galaxies range in size from dwarfs with just a few hundred million (108) stars to giants with one hundred trillion  stars, each orbiting its galaxy's center of mass.  Galaxies are categorized according to their visual morphology as elliptical,  spiral, or irregular.  Many galaxies are thought to have supermassive black holes at their centers. The Milky Way's central black hole, known as Sagittarius A*, has a mass four million times greater than the Sun.

Assembled from a total of 7,398 exposures taken over 411 individual pointings of the telescope, this image of our nearest major galactic neighbor, M31, is the largest Hubble mosaic to date. The 1.5 billion pixels in the mosaic reveal over 100 million stars and thousands of star clusters embedded in a section of the pancake-shaped disk of M31, also known as the Andromeda galaxy. Though the galaxy is over 2 million light-years away, Hubble is powerful enough to resolve individual stars in this 61,000-light-year-long stretch of the disk. It’s like photographing a beach and resolving individual grains of sand !!

ஸ்ரீ வைஷ்ணவ நெறி ஆழ்வார்கள் பற்றி, ஸ்ரீரங்கத்து பெண்களை பற்றி, காவேரி கொள்ளிடத்தை பற்றி, மாட வீதியில் கடை வைத்துஇருந்தவர் பற்றி,  சைக்கிள் முதல் ஆகாய விமானம் ஓட்டுவது பற்றி, ஸ்ரீரங்கத்து கிரிக்கெட் மேட்ச் முதல் ஸ்ரீகாந்த் டெபு டெஸ்ட் பற்றி, அறிவியல்,  விஞ்ஞானம், சரித்திரம், பொது அறிவு, கூடவே, குடும்பம், அப்பா, காதல், கணினி - என சுஜாதா படைப்புகள் அளவேயில்லாமல் வியக்க வைக்கும். 

"திசை கண்டேன் வான் கண்டேன்" - ஒரு அறிவியல் அற்புதம். கதைக்களம் மெரினா பீச் முதல் வாஷிங்டன் வரை ! - சாதாரண மனிதர்களும், வேற்று கிருஹத்துவாசிகளும் உண்டு.  ஆண்ட்ரமீடா காலக்ஸியில் உள்ள மிகவும் முன்னேறிய கிரகம் நோரா. அக்கிரகத்தினர் இன்டர் காலக்ஸி ரூட்டில் ஒரு மேம்பாலம் கட்டத் திட்டமிடுகிறார்கள். அதற்கு இடைஞ்சலாகக் குறுக்கிடும் பூமி கிரகத்தை அழிப்பதென்று முடிவெடுக்கிறார்கள். ஐக்கிய காலக்ஸி விதிகளின்படி எந்தக் கிரகத்தையும் அழிக்கும் முன் அந்தக் கிரகத்தின் தலைமைக்குச் செய்தி சொல்லவேண்டியது அவசியம். எனவே பூமியின் தலைமையகம் ஐ.நாவுக்கு தகவல் சொல்லி எச்சரிக்கை விடுக்க, நோரா கிரகத்தின் பிரஜை பாரி என்பவன் பூமிக்குப் புறப்படுகிறான். பேசும், பாடும், கவிதை சொல்லும் இயந்திர வாகனம் 121, மார்ஃப் என்கிற எந்த வடிவத்தையும் எடுக்கக்கூடிய சக்தி, பணத்தை உருவாக்கும் ரெப்ளிக்கேட்டர், ஆக்ஸிஜன் போல் ரிப்ரெஷ் அளிக்கும் ஆர்க்கான் குச்சிகள், நோராவில் அரசு மான்யத்தில் ஜீவிக்கும் உப தெய்வங்கள் என்று சுஜாதாவுக்கே உரித்தான கற்பனை உச்சத்தில் அட்டகாசமான, ஆர்ப்பாட்டமான நகைச்சுவை விஞ்ஞானக் கதை.

.. .. that story kindled me to read something about ‘Andormeda galaxy’,  also known as Messier 31, a spiral galaxy approximately 780 kiloparsecs (2.5 million light-years) from Earth, and the nearest major galaxy to the Milky Way. With an apparent magnitude of 3.4, the Andromeda Galaxy is among the brightest of the Messier objects making it visible to the naked eye on moonless nights when viewed from areas with moderate light pollution.  Its name stems from the area of the sky in which it appears, the constellation of Andromeda.  The 2006 observations by the Spitzer Space Telescope revealed that the Andromeda Galaxy contains approximately one trillion stars,  more than twice the number of the Milky Way's estimated 200 to 400 billion stars.  It’s  mass is estimated to be around 1.76 times that of the Milky Way Galaxy .

To make us fear, the Milky Way and Andromeda galaxies are expected to collide in ~4.5 billion years, merging to form a giant elliptical galaxy or a large disc galaxy.  Getting back to that photo – that is the  largest NASA Hubble Space Telescope image ever assembled, this sweeping bird’s-eye view of a portion of the Andromeda galaxy (M31) is the sharpest large composite image ever taken of our galactic next-door neighbor.  Never before have astronomers been able to see individual stars inside an external spiral galaxy over such a large contiguous area. Most of the stars in the universe live inside such majestic star cities, and this is the first data that reveal populations of stars in context to their home galaxy.

Somewhat recently, a  signal detected from the neighboring Andromeda galaxy may indicate presence of the mysterious dark matter – the elusive substance that is believed to make up most of our universe – NASA said.  The signal is similar to one seen by the NASA’s Fermi Gamma-ray Space Telescope at the centre of our own Milky Way galaxy in 2014. Gamma rays are the highest-energy form of light, produced by the universe’s most energetic phenomena. They are common in galaxies like the Milky Way because cosmic rays, particles moving near the speed of light, produce gamma rays when they interact with interstellar gas clouds and starlight.

                       Surprisingly, the latest Fermi data shows the gamma rays in Andromeda – are confined to the galaxy’s centre instead of spread throughout. To explain this unusual distribution, scientists are proposing that the emission may come from several undetermined sources. One of them could be dark matter, an unknown substance that makes up most of the universe.  Another possible source for this emission could be a rich concentration of pulsars in M31’s centre. These spinning neutron stars weigh as much as twice the mass of the sun and are among the densest objects in the universe. One teaspoon of neutron star matter would weigh a billion tons on Earth.

The similar discovery in both the Milky Way and M31 means scientists can use the galaxies as models for each other when making difficult observations.  Recently, a group of astronomers have taken the first steps to looking for alien life in the Andromeda galaxy as part of new research.  The project is called the Trillion Planet Survey, and it’s being run by the University of California, Santa Barbara. The idea is that if there’s a civilization out there that’s purposely sending out signals, it might be possible to spot them. The team are looking for transmissions from a civilization of “similar or higher class than ours trying to broadcast their presence using an optical beam,” noted Andrew Stewart from Emory University in a statement. This is known as Optical SETI (Search for Extraterrestrial Intelligence). Based on a 2016 paper from Philip Lubin, who’s leading the new project, the team are searching on the idea that there’s another civilization out there that doesn’t know we’re here, but is trying to make contact.

With photonics, they say it could be possible to create a bright light that could be seen across the universe. The team are now surveying Andromeda  to get what they call “the pipeline” up and running to look for such a light. Using an array of images taken by telescopes of the Andromeda galaxy, they’re going to create a single image of the galaxy. They will compare that image to another control image of the galaxy, which shows no “transient signals” – events that operate on relatively short time frames measured in years or less. If there’s a difference between their survey photo and the control photo, it could indicate that there is some sort of signal being transmitted. Their software is designed to remove interference from satellites and other nearby sources.

It may all be for naught – we could be alone, or any signals could be undetectable. But as is often said, if we don’t try then we’ll never know.  Interesting !!

With regards – S. Sampathkumar
28th Nov. 2018.




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