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## The earliest stars

This story caught my attention recently, it pertains to the earliest stars in the Universe. These earliest stars have not yet been directly observed, this story is about observations of unusual stars in our own Galaxy which are believed to be formed from the first generation of stars.

In the early Universe, the only elements created were hydrogen and helium. All the elements heavier than hydrogen and helium have been formed in the interior of stars, and more recent generations of stars contain these heavier elements along with hydrogen and helium formed in the early Universe. As the earliest stars would have been formed from only hydrogen and helium, and because of the absence of an effect called “line blanketing”, this earliest generation of stars could form with masses much greater than subsequent generations. Theoreticians believe that masses beyond 100 solar masses were possible in the first generation of stars.

Theoretical models also suggest that such super-massive stars would have ended their lives in something called a pair-instabiliuty supernova, which is different from the supernova which signals the end of the high mass stars we see around us today. In a pair-instabiliuty supernova, the models suggest that no neutron star or black hole is left at the centre, instead all of the material in the exploding star is sent back into the interstellar medium.

Researchers using the Japanese Subaru telescope in Hawaii have been taking spectra of stars in our Galaxy which show a particularly low level of iron, a level which is about 1,000 times less than in our Sun. Such a low iron level suggests that the stars belong to an earlier generation than our Sun, which is believed to be a third-generation star. The stars they have been observing are not first generation stars, but probably second generation. They have found one star, named SDSS J0018-0939 (it was found to be low in iron by the Sloan Digital Sky Survey) to have a very unusual spectrum. The ratio of the abundance of various elements in the star’s spectrum suggests that it could have been formed from a pair-instabiliuty supernova, and thus be the direct descendent of a first generation star.

The original paper, entitled “A chemical signature of first-generation very massive stars” can be found here.

## Jumièges abbey

In the Seine valley just to the west of Rouen is a beautiful abbey in a small town called Jumièges.

The abbey in Jumièges

The abbey was founded in 654, but most of what one sees today was built in the late 10th and early 11th Century. The Abbey was consecrated in the presence of William the Conqueror in 1067, who was also Duke of Normandy.

## All Right Now – Free (song)

At number 21 in BBC Radio 2’s list of the 100 greatest guitar riffs is “All Right Now” by Free.

At number 21 in BBC Radio 2’s list of the 100 greatest guitar riffs is “All Right Now” by Free.

The song was released in May 1970 and got to number 2 in the Disunited Kingdom singles charts, and to number 4 in the US singles charts.

Whoa-oh-oh-oh-woha
There she stood in the street
Smilin’ from her head to her feet;

I said, “Hey, what is this?
Now maybe, baby,
Maybe she’s in need of a kiss.”

I said, “Hey, what’s your name?
Maybe we can see things the same.

“Now don’t you wait, or hesitate.
Let’s move before they raise the parking rate.”

All right now, baby, it’s a-all right now.
All right now, baby, it’s a-all right now.

(Let me tell you now)
I took her home to my place,
Watchin’ every move on her face;

She said, “Look, what’s your game?
Are you tryin’ to put me to shame?”

I said “Slow, don’t go so fast, don’t you think that love can last?”

She said, “Love, Lord above,
Now you’re tryin’ to trick me in love.”

All right now, baby, it’s a-all right now.
All right now, baby, it’s a-all right now

Here is a video of this song. Enjoy!

## Bayeux Cathedral

Bayeux is, of course, most famous for its wonderful tapestry, which is well worth a visit. But, it is also a beautiful town (city?), and has a wonderful cathedral. The present cathedral was consecrated in 1077, some 11 years after William the Conqueror had killed Harold at the Battle of Hastings.

The cathedral in Bayeux, consecrated in 1077

Another claim to fame for Bayeux is that it was the first town to be liberated by the Allies after the D-Day landings. Only one day after the landings on the 6th of June 1944, Bayeux was liberated by the Allied forces.

## The 10 best Bob Dylan songs – number 2 – A Hard Rain’s A-Gonna Fall

At number 2 in Rolling Stone Magazine’s 10 best Bob Dylan songs is “A Hard Rain’s A-Gonna Fall” which Dylan recorded in December 1962. It was released on his 1963 album “The Freewheelin’ Bob Dylan”, and is the 6th (and last) track on the first side.

At number 2 in Rolling Stone Magazine’s 10 greatest Bob Dylan songs is “A Hard Rain’s A-Gonna Fall”

The lyrics to this song are available here on Bob Dylan’s official website, as well as short audio clips of the original album version and other, alternative, versions on other albums. I find it hard to believe that Dylan was only 21 when he wrote this song, it has such dark and foreboding lyrics it seems to me like the work of a much older person.

Oh, where have you been, my blue-eyed son?
Oh, where have you been, my darling young one?
I’ve stumbled on the side of twelve misty mountains
I’ve walked and I’ve crawled on six crooked highways
I’ve stepped in the middle of seven sad forests
I’ve been out in front of a dozen dead oceans
I’ve been ten thousand miles in the mouth of a graveyard
And it’s a hard, and it’s a hard, it’s a hard, and it’s a hard
And it’s a hard rain’s a-gonna fall

Oh, what did you see, my blue-eyed son?
Oh, what did you see, my darling young one?
I saw a newborn baby with wild wolves all around it
I saw a highway of diamonds with nobody on it
I saw a black branch with blood that kept drippin’
I saw a room full of men with their hammers a-bleedin’
I saw a white ladder all covered with water
I saw ten thousand talkers whose tongues were all broken
I saw guns and sharp swords in the hands of young children
And it’s a hard, and it’s a hard, it’s a hard, it’s a hard
And it’s a hard rain’s a-gonna fall

And what did you hear, my blue-eyed son?
And what did you hear, my darling young one?
I heard the sound of a thunder, it roared out a warnin’
Heard the roar of a wave that could drown the whole world
Heard one hundred drummers whose hands were a-blazin’
Heard ten thousand whisperin’ and nobody listenin’
Heard one person starve, I heard many people laughin’
Heard the song of a poet who died in the gutter
Heard the sound of a clown who cried in the alley
And it’s a hard, and it’s a hard, it’s a hard, it’s a hard
And it’s a hard rain’s a-gonna fall

Oh, who did you meet, my blue-eyed son?
Who did you meet, my darling young one?
I met a young child beside a dead pony
I met a white man who walked a black dog
I met a young woman whose body was burning
I met a young girl, she gave me a rainbow
I met one man who was wounded in love
I met another man who was wounded with hatred
And it’s a hard, it’s a hard, it’s a hard, it’s a hard
It’s a hard rain’s a-gonna fall

Oh, what’ll you do now, my blue-eyed son?
Oh, what’ll you do now, my darling young one?
I’m a-goin’ back out ’fore the rain starts a-fallin’
I’ll walk to the depths of the deepest black forest
Where the people are many and their hands are all empty
Where the pellets of poison are flooding their waters
Where the home in the valley meets the damp dirty prison
Where the executioner’s face is always well hidden
Where hunger is ugly, where souls are forgotten
Where black is the color, where none is the number
And I’ll tell it and think it and speak it and breathe it
And reflect it from the mountain so all souls can see it
Then I’ll stand on the ocean until I start sinkin’
But I’ll know my song well before I start singin’
And it’s a hard, it’s a hard, it’s a hard, it’s a hard
It’s a hard rain’s a-gonna fall

Here is a live version of this amazing song from 1963. Enjoy!

## The Origin of the Elements – part 1

One of the outstanding problems in astrophysics in the 1940s was how were the elements created. In the 1920s it was realised by Cecilia Payne-Gaposchkin in her PhD work that the Sun was mainly composed of hydrogen. Then, spectral analysis of others stars and the gases of the interstellar medium led astrophycisits to realise that the Universe was composed mainly of hydrogen (about $75\%$), with the remainder being helium (about $24\%$), and only $1\%$ or so being all the other elements (oxygen, nitrogen, carbon etc.)

In the mid 1940s Russian-American physicist George Gamow started thinking about how the elements originated, and he developed a theory with his student Ralph Alpher that they were all created in the early Universe when, he argued, it would have been hotter and denser than it currently is. He published his famous paper “The Origin of Chemical Elements” in Physical Review in 1948, adding renowned physicist Hans Bethe’s name to the author list as a joke so that the paper would have the author list Alpher, Bethe, Gamow (alpha,beta, gamma, geddit? There is also a story that he tried to get his post-doctoral researcher Bob Herman to change his last name to “Delta” 😛 )

The famous Alpher, Bethe, Gamow paper, “The Origin of Chemical Elements”, which appeared in Physical Review in 1948.

In fact, Bethe played no part in writing the paper, but he was happy for Gamow to include his name for Gamow’s little joke. In this paper, Gamow and Alpher argued that all the elements were created in the early Universe. However, when others went through the details it was realised that the numbers did not add up, the Universe expanded and cooled too quickly for all the elements to be created in this way. Although it was possible for hydrogen and helium to be created in the first few minutes of the Universe, by the time the Universe was a few minutes old it had become too cool and the density too low to form the heavier elements beyond helium. Part of the reason for heavier elements not being built up in these first few minutes was due to something called the deuterium bottleneck, which I will explain in a future blog.

In the 1950s an alternative theory for the origin of the elements was put forward by Fred Hoyle and his collaborators Willy Fowler and Geoffrey and Margaret Burbidge. In a series of papers they argued that the elements had been built up in the interior of stars, the most famous of this series of papers was a 1957 paper entitled “Synthesis of the Elements in Stars” which appeared in Reviews of Modern Physics. Hoyle was the main advocate of a theory called the Steady State Theory which he had first proposed in 1948. This was a competing theory to the hot big bang theory, and so of course Hoyle did not believe any elements had been formed in a hot, dense early Universe as he did not believe such a Universe ever existed.

The first page of Burbidge teal.’s famous paper “Synthesis of the Elements in Stars” published in Reviews of Modern Physics in 1957

Again, as with Alpher and Gamow’s theory, detailed calculations found flaws in the Burbidge etal. theory. Although it could explain the creation of elements beyond helium, it was not possible to create enough helium in stars to account for the approximately $25\%$ found to be present in the Universe today. In part 2 of this blog, I will explain what our current understanding is of the origin of the elements in the proportions we observe in the Universe, and what the deuterium bottleneck is and why it is important.

## Cotentin windmill, Normandy

Recently my wife and I went to Normandy. Whilst winding through the backroads of Normandy from Cherbourg to le Mont Saint Michel (we got off the motorway on purpose), we stumbled across this lovely windmill – moulin à vent du Cotentin, which has recently been restored.

The moulin à vent du Cotentin

Of course it helped that we had beautiful weather with cloudless skies, but if you get the chance to visit this lovely building it is well worth it.