COMPOSITION OF STARS !!! ✨
What you think about the composition of the star?
The star
Star is an astronomical object consisting of a luminous spheroid of plasma held together by its own gravity. the nearest star to earth Is our beautiful star " the sun ". many other stars are visible to the naked eye from Earth during the night, appearing as a multitude of fixed luminous points in the sky due to their immense distance from earth. a star shines due to thermonuclear fusion of hydrogen into helium in its core, releasing energy that traverses the star's interior and then radiates into outer space. the observable universe contains an estimated 1 x 10^24 stars, but most are invisible to the naked eye from the earth, including all stars outside our galaxy, The Milky Way.
The element
The following are emission line spectra of five-element ( hydrogen, helium, oxygen, calcium, and sodium from top to bottom ). these are not actually laboratory data but constructed from atomic data and software at NIST.
Star classification
The stars are classified by their spectra ( the element that they absorb ) and their temperature. there are seven main types of stars. in the order of decreasing temperature, O, B, A, F, G, K, and M.
O and B stars are uncommon but very bright; M star is common but dim.....
an easy mnemonic for remembering these is :
" Oh Be A Fine Guy/Girl, Kiss Me "
Hertzsprung - Russell Diagram
The Hertzsprung -Russell ( H-R ) Diagram is a graph that plots stars color ( spectral type or surface temperature ) vs. its luminosity. ( intrinsic brightness or absolute magnitude ). on it, astronomers plot stars color, temperature, luminosity, spectral type, and evolutionary stage.
Spectroscopy of star
The composition of stars is determined through spectroscopy. spectroscopy is the study of something using spectra. the electromagnetic radiation chapter that a spectrum is what results when you spread starlight out into its individual colors. by noting what absorption line is present and their strength, you can find out a tremendous amount of information. stars have absorption lines pattern similar to the sun. this means that they are composed mostly of hydrogen and helium with traces of other elements.
Stars composition
1. Structure of stars :
From the simple fact that you see the absorption line in most stellar spectra, you know that the stars must have a hot dense part that produces a continuous spectrum and an outer layer or atmosphere, made of cooler, low-density gas. the general trend is the density and temperature of the stars decrease as the distance from the star's center increases. the hot dense part is also gaseous because of the extreme temperature. star has no molten rock in them like the interiors of some of the planets.
the next two things have already been noted elsewhere but they are important enough to state again.
2. The universality of physical laws :
The same pattern of hydrogen lines is seen in the spectra of the star, stars, distant galaxies, and quasars. this is a sensitive test of whether or not the laws of physics used in the structure of atoms work everywhere in the universe. even slight difference in the rules of quantum mechanics that govern the interaction of the protons, electron, and neutrons or differences in the strengths of the fundamental forces of nature from that observed on the earth would produce noticeable changes in the spacing and strength of the spectral lines. if the subatomic particle had a different amount of charge or mass, the pattern of lines would be different than what you see on the earth.
3. The permanence of physical laws :
Since light has a finite speed and the distance is vast, the light received from very distant galaxies and quasars has been traveling for billions of years. the light from those remote regions tells us about the ways of the physical laws back then. the spectra seen can be explained with the same physical law in operation here on earth at the present time. physical laws are the same throughout time!
Chemical composition of stars
In the early day of astrophysics, scientists thought that the stars were probably similar to the earth in chemical composition. when they passed starlight through a prism and absorption lines of many elements common here on earth. for example, here's a position of the spectrum of Arcturus ( taken from a paper by Hinkle, Wallace, and Livingstone, PASP 107, 1024, 1995 ):
Does this mean that the chemical composition of stars varies wildly? initially, scientists thought the answer was " yes ".
In the nineteen-twenties, Cecilia Payne studied the spectra of stars and devised away to figure out the temperature and true chemical composition of stars. she concluded that the atmospheres of stars were
* NOT made up of the same mix of elements as the earth
* NOT wildly variable in composition but in fact,
* almost entirely hydrogen, in almost all-stars
this was so surprising that scientists ignored or rejected the idea for several years. eventually, after further study confirmed Payne's work, the astronomical community had to concede that the stars were, in fact, very different from the earth. they appeared to be made up of
* 90% hydrogen
* 10% helium
* tiny traces of heavy elements
so now what you think about the composition of stars after reading this blog?
Reference
my astrophysics teacher Celeste Carbonell
my astrophysics teacher Katy Rodriguez Wimberly
book, essential astrophysics, by Kenneth R Lang
By: Pradyumn Kumar Sharma
Tags: Astrophysics, astronomy, NASA, ESA, space science, space exploration, stars, telescopes
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