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Friday, April 1, 2022

Earendel ~the farthest Star identified !!

Life in concrete jungle, especially small apartments has taken much away .. .. till a few decades ago, people loved open spaces, night time dinner used to be group-family affairs in moonlight. No longer !  - as you look up to sky, one could gaze the Moon and ‘Stars’ !

Perhaps the first English poem, known to us – which we confidently sung was ‘Twinkle, Twinkle, Little Star’ .. .. (Sivaji in Thanga pathakkam !)

Stars are the most widely recognized astronomical objects, and represent the most fundamental building blocks of galaxies. The age, distribution, and composition of the stars in a galaxy trace the history, dynamics, and evolution of that galaxy. Moreover, stars are responsible for the manufacture and distribution of heavy elements such as carbon, nitrogen, and oxygen, and their characteristics are intimately tied to the characteristics of the planetary systems that may coalesce about them. Consequently, the study of the birth, life, and death of stars is central to the field of astronomy.

A star is an astronomical object comprising a luminous spheroid of plasma held together by its gravity. The nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night, but their immense distance from Earth makes them appear as fixed points of light in the sky. The most prominent stars have been categorised into constellations and asterisms, and many of the brightest stars have proper names. Astronomers have assembled star catalogues that identify the known stars and provide standardized stellar designations. The observable universe contains an estimated 1022 to 1024 stars. Still, most are invisible to the naked eye from Earth, including all individual stars outside our galaxy, the Milky Way.

A star's life begins with the gravitational collapse of a gaseous nebula of material composed primarily of hydrogen, along with helium and trace amounts of heavier elements. The total mass is the main factor determining its evolution and eventual fate. A star shines for most of its active life due to the thermonuclear fusion of hydrogen into helium in its core. This process releases energy that traverses the star's interior, radiating into outer space. At the end of a star's lifetime, its core becomes a stellar remnant: a white dwarf, a neutron star, or—if it is sufficiently massive—a black hole.

The closest star to Earth is a triple-star system called Alpha Centauri. The two main stars are Alpha Centauri A and Alpha Centauri B, which form a binary pair. They are about 4.35 light-years from Earth, according to NASA. The third star is called Proxima Centauri or Alpha Centauri C, and it is about 4.25 light-years from Earth, making it the closest star other than the sun. According to NASA, Alpha Centauri A and B are on average about 23 astronomical units (AU) from each other — a little more than the distance between the sun and Uranus. (An astronomical unit is the average distance between Earth and the sun, which equals 92,955,807 miles or 149,597,870 kilometers.) The closest the two stars ever come to each other is 11 astronomical units, according to NASA, and the two stars orbit a common center of gravity every 80 years.

This is no post on Alpha Centauri  but on the farthest star. Named Earendel (Morning Star) – has been now identified as most  distant star.

Earendel's discovery by the Hubble Space Telescope was reported on 30.3.2022.    The star is found due to gravitational lensing of a galaxy cluster in front, amplifying the light from the star significantly. Computer simulations of the lensing effect suggest that Earendel's brightness was magnified between one- and forty-thousand times. This discovery also demonstrate a possible combination of lensing effects: a main gravitational lensing from galaxy clusters and further gravitational microlensing caused by heavy objects inside.

The star was nicknamed Earendel by the discoverers, derived from Old English name for "Morning Star" or "Rising Light". Eärendil is also the name of a half-elven character in J.R.R. Tolkien's book The Silmarillion who travelled through the sky with a radiant jewel that appeared as bright as a star to the inhabitants of Tolkien's Middle-earth; NASA astronomer Michelle Thaller confirmed that the reference to Tolkien was intentional.

The James Webb Space Telescope will then follow-up the star's observations. The telescope's higher sensitivity will analyze the Earendel's stellar spectra and determine for certain whether it was actually a single star.  The spectra analysis would reveal the presence of elements heavier than hydrogen and helium, if any.  The light detected from Earendel was emitted 900 million years after the Big Bang. The star is now 28 billion light-years away. Earendel reported has  between 50–100 solar masses, considerably more than average.  Due to its large mass, the star likely exploded as a supernova just a few million years after emerging !

"Twinkle, Twinkle, Little Star" is a popular English lullaby, taken from an early-19th-century English poem written by Jane Taylor, "The Star".  The poem, which is in couplet form, was first published in 1806 in Rhymes for the Nursery, a collection of poems by Taylor and her sister Ann. It is sung to the tune of the French melody "Ah! vous dirai-je, maman", which was published in 1761 and later arranged by several composers, including Mozart and has many variations as found in domain.

With regards – S. Sampathkumar
1st Apr 2022. 

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