sn1987....Anglo Observatory

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One of the few courses I enjoyed in the 80's, worth saving the materials from was in an Astronomy class. The professor wrote interesting stuff in the text and held a position at an observatory. The material itself is well known and discussed on Sci or History channels ;

"Most of you have picked up a penny from the street..when doing that you are looking at copper atoms that originated from supernovas.." Text went on to describe the type of star needed; the core 'collapsing' in a few tenths of second to produce the outcome. Tremendous gravitational force of layers coming inward, with compression at the center.

sn1987 - observed very well in Australia, that occured roughly 170,000 years ago. The same distance in light years from earth. Various ring pics were seen then and now, and fewer of the combustion. While a vintage car is a beautiful thing..it's worth noting how these metals came to pass at one time and source of.. Enjoy.

sn1987.2.jpg

Serene by comparison
Observatory.jpg

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Supposedly more light output than all stars in it's galaxy for short time.

sn1987.jpg

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Source material... this gives a much improved picture than what I wrote. ( A short exam is given after it, which is optional)

( Professor Stein :
-- Death of stars with Masses between 1.4 and 3 Solar Masses --

The events surrounding a supernova phenomenon are not known with great assurance at the present time. Many theories have appeared over the years. They all have one thing in common. That is, something like 80% of the star is blasted into space as a result of a runaway reaction taking place (quite suddenly) within the star. It is believed that this is brought about by a sudden, catastrophic collapse of the star's core. With support removed from beneath, the outer layers of the star fall onto the collapsed core (in a matter of half-an hour). The heat and high densities caused by the impact allow the hydrogen, helium, carbon, etc. in the outer layers of the star to undergo fusion reactions : In a matter of minutes the nuclear energy of the entire outer shell of the star is released ! The energy is enormous, being nearly equal to all the energy radiated by the sun over the last 4.5 billion years !

The gas in the suddenly heated shell erupts into space at speeds between 5 - 10 thousand kilometers per second, far in excess of escape velocity because of high temperatures generated in the runaway reaction. The shell, comprising 80% of the total mass of the star, rushes to the depths of interstallar space.

The shell is now rich in heavy elements, built up in fierce heat and enormous pressures just after the reaction. These are the elements with nuclei more massive than iron atoms, nuclei that can be built up in no other way.

Find a penny and hold it in your hand. The atoms in that penny were made billions of years ago in supernovae. So, how did they get into the penny ? A supernova ejects a massive shell containing these more massive nuclei. The gas will go on expanding until it merges with dust and gas lying between the stars. Someday it will again be gathered into a nebula from which a new generation of stars will form. These stars (and their planets) will have an extra supply of heavy elements. The legacy of the supernova.

Observed 1054 A.D. by Chinese astronomers. The star was so bright it was visible during daytime and cast shadows at night. The expanding shell contains heavy elements produced during the explosion. ( Crab Nebula )

Crab.jpg


So it is with the copper penny. It is our legacy from a host of massive stars that were born, lived out their lives on the main sequence, and died a firey death of a supernova, long before our sun came into being.

-- Fate of the Remnant --

The fate of the portion of the star > not ejected is of interest too : When the explosion occurs around it, a core is crushed by the enormous forces generated. The shell kicks off into space and the core collapses. In short order, the electrons are called upon to support the weight of the core. Momentum and sheer mass of a collapsing core are too much for the electrons to resist. Electrons are forced to combine with protons to create neutrons. ..There is more room available for it now, so it continues.

Soon the neutrons are packed as tightly as they can be. At this point, when the core is about 50 kilometers in diameter, the collapse halts. We say the star is a neutron degenerate. The 'star' is a ball of hot neutrons having the mass of our sun ! This material is so dense that a piece of it about the size of a grain of table salt would, if brough to the earth, weigh 340 tons !

In the discussion of the conservation of angular momentum, we used the exampe of the figure skater pulling her arms in so that she could spin more rapidly. Like the skater, as the core collapses it spins faster and faster. One of these collapsed cores has been observed to spin as many as 40 times per second on it's axis !

Under the right conditions of geometry and physics a neutron star can be seen, from the Earth, to flash on and off each time it rotates on it's axis. Emitting radiation which acts like a beam from a lighthouse, sweeping around the sky as the star rotates. Each time the beam sweeps past the earth, we see a flash of light. This pulsating has prompted astronomers to call neutron stars displaying this effect, pulsars.

Neutron stars have enormous gravitational fields, of course. The gravity is so strong that to give your weight on a neutron's star's surface would lose all meaning since you could not imagine such incredible weights.
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Grain of salt = 0.000000625 kilograms

160 lb man = 72 kilograms

How much would the man weigh ?

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100 billion stars
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"Many of you I'm sure, have found yourselves far from the city at night. If the sky was clear you would have noticed a vast number of stars visible to the naked eye. You may have remarked, "My God, look at all the stars." Your eye would have been drawn to a hazy, somewhat indistinct, band of light running more or less overhead and down to the horizon on either side of the zenith. This was the Milky Way. With a pair of binoculars, Galileo ( first to see it thus) described it ; ". . .a host of stars are perceived. . . so numerous as almost to surpass belief."

Can you imagine 100 billion stars ?

Get yourself a single grain of sand. If the grain represents a single star, 100 billion of them would fill a cubical box 7.6 feet on a side. Our sun is just one of those.

Within range of our largest telescopes roughly one-hundred billion galaxies can be seen, each containing on average, one-hundred billion stars. One hundred-billion galaxies, of one-hundred billion stars each.


If the number of stars in the observable universe is 100 billion times 100 billion, it is a staggering 10 ^22 stars (that reads 10 sextillion - 10,000,000,000,000,000,000,000 or 10 billion trillion stars. In terms of our sandbox, 10 ^22 grains would fill a box 6.7 [miles] on a side."


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"So the next time that you are thinking you aren't very special..."

Simply for browsing, or entertainment reading:

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"As we have seen, stars in the final death throws eject their outer layers of gas back to the interstellar medium from which they came. Violent events alluded to herein are but one mechanism by which this happens. At first sight it's not clear what any of this has to do with life on other planets, since we expect that, long before ejection mechanisms take place, a star that turns into a red giant would sterilize life. It makes no difference at all to life connected with that star, however for life that will appear among planets yet to form, it makes all the difference in the world.

When the universe was very young it contained atoms of hydrogen and helium. Fine for making stars, but hardly adequate for making living organisms. You for example, contain little if any helium. However, while you contain fair amounts of hydrogen in the molecules of your body, there is a lot of carbon and nitrogen with reasonable amounts of other elements such as phosphorus there as well. In short---a being, such as yourself, would have been impossible to make when the universe was very young.

Where did the heavy elements come from if not there at the beginning? The answer is that they were made in the cores of stars that formed, died, and returned a portion of these elements to the interstellar medium long before our sun and planetary system formed. By the time our sun and planets formed there were plenty of these elements mixed into the hydrogen and helium of the interstellar medium and, since it was an especially dense portion of that medium, they were present in the solar nebula as well.

So the next time that you are thinking you aren't very special, just remember that whole generations of stars had to die to make you possible. Spring blossoms, the sparkling sea, or the sheen of a girl's hair are, in a very real sense, stardust."

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