19.08.2019 : Of periodic tables..

Carl Sagan,  one of  the most  charismatic figures  of later-twentieth century Astrophysics,  has been the first  to inform the common  man that - "Our Sun is a second-  or  third-generation star.  All  of  the rocky  and  metallic material we stand on, the iron in our blood, the calcium in our teeth, the carbon  in our genes  were produced billions  of years ago  in the interior of  a red giant star.  We are made of  star-stuff (The Cosmic Connection: An Extraterrestrial Perspective, 1973)".

Yes, starstuff. Quite literally. According to the currently accepted cosmological models, the Universe started in an incredibly hot and dense state, about 14 billion years ago in a singular event known as the `Big Bang'. As the Universe expanded, it cooled and within the first three minutes matter, as we know it, formed. However, it was mostly hydrogen (76%) and helium  (24%), with a rather small fraction of other material like lithium etc.  It was not till the first stars were born that heavier elements could be formed through fusion of lighter elements in a process now known as 'stellar nucleosynthesis'.

Even though this appears to be rather obvious now, there was considerable uncertainty regarding stellar nucleosynthesis in the early part of the twentieth century when scientists were not sure if stellar interiors were hot enough for such fusion processes. Eventually, the day was won and Arthur Eddington proclaimed from Cambridge - "We do not argue  with the critic who urges that the stars are not hot enough for this  process; we tell him to go and find a hotter place (The Internal Constitution of Stars, 1926)". The story would be completed a couple of decades later by another Cambridge man, Sir Fred Hoyle, when he and his collaborators would work out the details of stellar nucleosynthesis in the celebrated BBFH (Burbidge, Burbidge, Fowler, Hoyle, 1957) paper.

However, stellar nucleosynthesis goes only as far as iron and nickel. Manufacturing elements heavier than iron require other more energetic processes like - a supernova explosion or merger of neutron stars. Jennifer A. Johnson of Ohio State University has now created a rather clever 'astrophysical' periodic table to indicate the origin of all the elements we commonly (or not so commonly) encounter around us.

But this is just for the show. :) In reality, astrophysicists mostly refer to another, far less complex version of the periodic table. Because, we basically deal with only three elements - Hydrogen, Helium and everything else. And in an ingenuous fashion this 'everything else' is called 'metal'. This is not as crazy as it sounds. This 'astrophysical' periodic table actually reflects the composition of the Universe, the fractional amount of a particular elements being proportional to the area under its symbol.

Dmitri Ivanovich Mendeleev, father of the periodic table, used a balloon to ascend above the cloud cover to observe an eclipse on this day in 1887. I am sure, when he dabbled in his passion for Astronomy, he had no inclination that one day his periodic table would become such a favourite of Astronomers. :)

24.06.2019 : Remembering Sir Fred..

Thirty years ago I spent the better part of a summer night reading a science fiction story. Nothing remarkable about that. Next morning though, I faced the said author's disciple, chairing an interview panel for PhD admission and asking me questions about our Solar System. The interview didn't work for me but I got that particular question right because of my extra-curricular reading the previous night. The interviewer was Prof. Jayant Vishnu Narlikar and the author of the book was none other than his PhD advisor Sir Fred Hoyle, who found time to write science-fiction stories besides being a prolific and brilliant astrophysicist.

Sir Fred, born on this day (24 June 1915) in early twentieth century England, spent most of his working life in Cambridge (1945-1973), except for his service to Britain's radar project during the war years. Apparently, discussions with some of his (physicist) colleagues during this radar phase was responsible for leading him towards astrophysics, which ultimately resulted in him formulating the theory of stellar nucleosynthesis in the 1950s.

His pioneering work on nucleosynthesis (creation of the nuclei of heavier material from fusion of lighter nuclei through nuclear fusion) taking place in stable stars and during supernova explosions has laid the foundation for the entire paradigm of stellar nucleosynthesis. This work would be followed by a comprehensive paper in 1957, authored by Margaret Burbidge, Geoffrey Burbidge, William Fowler and Fred Hoyle. Famously known as B2FH, this would go on to become the most influential paper in this area of nuclear astrophysics.

In 1983, Fowler would win the Nobel prize (with S. Chandrasekhar) for his work on nucleosynthesis and generate considerable controversy about Hoyle's exclusion. Controversy, of course, was a constant companion to Sir Fred. Though the story of 1974 Nobel (discovery of the first neutron star) is well known now, it was Sir Fred who first remarked about Jocelyn Bell's non-inclusion (the Nobel was awarded to her PhD advisor Anthony Hewish).

That has not been all, however. He held controversial views about a number of purely scientific issues too. In particular, he was opposed to the "Big  Bang" (a term coined by him on a BBC radio show) theory, in which the Universe itself begins its existence at some time in the past. Instead, he believed the Universe to be in a "steady state" and went on to formulate the Steady State theory. Though his theory did conform with the observations available then, it could not explain later observations.

Nevertheless, Sir Fred remained one of the most influential modern astrophysicists, mentoring several important figures like Leon Mestel, Jayant Narlikar, Donald Clayton.. He was also instrumental in establishing the Institute of Theoretical Astronomy (later rechristened as the Institute of Astronomy, Cambridge) which enjoys being one of the finest astrophysics research centres till date.

Sir Fred Hoyle with his Indian (academic) family : IUCAA, Pune

Sir Fred's story remains incomplete without mentioning his Indian family. It seems this month we are in the business of claiming kinship to legends. The man of our house traces his academic lineage directly to Sir Fred, through the Hoyle-->Narlikar-->Padmanabhan route. 😁 In fact, Sir Fred has left quite a large Indian family of astrophysicists, acquired through Prof. Narlikar. The accompanying photograph bears testimony to a happy family gathering (about three decades ago) showing Sir Fred with his student, a number of grand-students and very many great-grand-students (courtesy Debi Prasad Duari ).

04.02.2019 : Billboards on the Sky

Astronomy, because of its very nature, has been one of the ancient branches of knowledge. The sky has guided humans on their daily endeavours since the dawn of civilisation (perhaps even before) and we have looked up at the sky in wonder pondering about our own origin and that of the Universe. That sense of wonder has given rise to this vibrant field of study today. Unfortunately, that early beginning is also the reason the practitioners find it difficult to disentangle their scientific study from the soothsaying practise of Astrology in popular perception.

The trouble does not end there. Astronomy is the only physical science where it is not possible to set up one's own laboratory experiment. Instead we must make do with the information coming from the sky in the form of electromagnetic waves (and the awfully-difficult-to-detect gravitational waves). It takes the whole of known physics (and then some) to decode these signals. Also, we can only 'see' the visible light and the radio waves from our ground-based observatories, everything else (X-ray, gamma-ray..) gets completely messed up by our atmosphere.

Optical (visible light) Astronomy has become progressively difficult with the advent of big cities. Light pollution has ended the career of many a research observtories of yesteryear, relegating them to the status of outreach or student project instruments.

And now the sky is up for sale. It is the next frontier for the advertising world. Coca-cola and McDonald would now jostle for space up there. The children of future would have to take a space shuttle to the orbit to get his/her first glimpse of the Orion or the Great Bear. The new age grandmothers and mothers would no longer tell their young ones the story of the seven sages that mark the constellation of 'Saptarshi' (as Great Bear is known in India) - stories connecting the sky to the mytholoical beginning of human culture. Astronomy is going to change; so is our cultural perspective. 😔

Picture Courtesey : Daily Mail, UK