I Am Always Surprised When A Young Man Tells Me He Wants To Work At Cosmology. I Think Of Cosmology As
I am always surprised when a young man tells me he wants to work at cosmology. I think of cosmology as something that happens to one, not something one can choose.
Sir William McCrea
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I swear every-time I see the quadratic formula I get the song stuck in my head
During math tests if you listen closely you can hear me mumbling
“oooooh x equals the opposite of b, plus or minus the square root, b squared minus 4ac all divided by 2a!”
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It was at this moment he knew…….
THE LIFE OF A STAR: CLASSIFICATION
In order to understand the life of a star, we must understand star classification.
And there are SO many different ways to classify a star.
In star classification, understanding the relationship between color and temperature is crucial. The greater the temperature of the star, the bluer they are (at their hottest, around 50,000 degrees Celcius), while red stars are cooler (at their coolest, around 3,000 degrees Celcius). This occurs on a wide range (fun fact: stars only come in red, orange, yellow, white, and blue, because stars are approximately something called a "black body"). For example, our Sun is a yellow star with a surface temperature of 5,500 degrees Celcius (The Life of a Star).
But why is this so? In order to understand that, I'm going to tell you about how stars live at all. This is what will determine the entire life of a star - something we'll be focusing on throughout this series. Two words: nuclear fusion.
Nuclear fusion is "a reaction in which two or more atomic nuclei are combined to form one or more different atomic nuclei and subatomic particles (neutrons or protons). The difference in mass between the reactants and products is manifested as either the release or absorption of energy." (Wikipedia) And this is where nuclear fusion gets REALLY important to stars. Throughout their lives, stars undergo nuclear fusion in their core. This is mostly in the form of fusing two or more hydrogen atoms into one or more helium atoms. This releases energy in the form of light (the pressure of nuclear fusion in the core also prevents the star from collapsing under the weight of gravity, something we'll get to later). The energy transports to the surface of the star and then radiates at an "effective temperature." (Britannica)
Stars are different colors due to differing amounts of energy. This is best explained by Einstein's e=mc2 or the mass-energy equivalence. In other words, the more mass something has, the more energy, and vice versa. Stars with greater mass undergo more nuclear fusion - and as such - emit more energy/temperature. And so, the bigger the star, the greater the temperature, the bluer the star; and the smaller the star, the lower the temperature, the redder the star (Universe Today). Another way to think about this is this: the hotter something is, the shorter frequency of energy it emits. Blue light has a shorter frequency than red light, and so, higher energy/temperature stars are bluer.
Another important classification of a star is its luminosity (or the brightness, or the magnitude of the star). (The Life of a Star)
The most famous diagram classifying stars is the Herzsprung Russell Diagram, shown in this article's picture. The x-axis of the diagram shows surface temperature, hottest left, and coolest right. The y-axis shows brightness, brighter higher, and dimmer lower. There are main groups on the diagram.
Most stars fall in a long band stretching diagonally, starting in the upper left corner and ending in the right lower corner, this is called the main sequence. The main sequence shows stars which mostly use their life going through nuclear fusion. This process takes up most of a star's life. Most stars which are hotter and more luminous fall in the upper left corner of the main sequence and are blue in color. Most stars that have lower-masses are cooler, and redder falls in the lower right. Yellow stars like our Sun fall in the middle.
The group located in the lower-left corner are smaller, fainter, and bluer (hotter) and are called White Dwarfs. These stars are a result of a star like our Sun one day running out of Hydrogen.
The group located right above the righter's main sequence is larger, cooler, brighter, and a more orange-red or red, are called Red Giants. They are also part of the dying process of a star like our sun. Above them in the upper right corner are Red Super Giants, massive, bright, cooler, and much more luminous. To the left of the Red Super Giants are similar stars which are just hotter and bluer and are called the Blue Super Giants.
That explains the most famous star classifying diagram. The important thing to remember is the data on the chart is not what a star will be like it's whole life. A star's position on the chart will change like our Sun will one day do.
In a ThoughtCo. article on the Hertzsprung Russell Diagram, Carolyn Collins Petersen wrote: "One thing to keep in mind is that the H-R diagram is not an evolutionary chart. At its heart, the diagram is simply a chart of stellar characteristics at a given time in their lives (and when we observed them). It can show us what stellar type a star can become, but it doesn't necessarily predict the changes in a star." ( The Hertzsprung-Russell Diagram and the Lives of Stars)
And this will continue to be important in the next chapters. Stars don't just stay in the same position their entire lives: they change in their color, luminosity, and temperature. In this series, we'll be tracking how stars form, live and die - all dependent on these three factors - and nuclear fusion - again - super important :)
Previous - Chapter 1: An Introduction
Next - Chapter 3: Star Nurseries
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So I’m taking AP Calc next year and even though I have an A in Pre Calc I’m really nervous so I’m like frantically summer studying xD
I dunno my teacher seems to think I’ll do fine but everyone makes it sound really intimidating and I’m a worry freak, but I love math so I’m hoping I’ll enjoy it.
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Goregous :O
In the Life of a Star Chapter 11, Additional Topics, I’ve been thinking about putting in a section on solar flares and prominences. Maybe if I have enough room, I do love this photo.
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Dramatic solar activity was going on last night and I was able to create a gif of this solar prominence! 🌞🌞🌞
Solar prominences are different from solar flares since solar prominences are mostly pulled in by the Sun’s gravity, creating a majestic loop like shape! 🤩 🤩🤩
Taken by me (Michelle Park) using the Slooh Canary Five telescope on July 2nd, 2020.
Dark matter is one of my favorite mysteries in Astrophysics, oh I would just love to study it. Some are using particle accelerators to try to study DM and figure out what it is - and it’s so so exciting!!!
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I love this meme format
My favorite YouTube video as of now (I know this doesn’t seem like it’s related to space - but it has a nice discussion about black holes and hawking radiation, which is I love it so much)
Remember kids: be cautious of bouncy castles!
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I love Schrodinger’s Cat memes
I might write something on quantum mechanics in the future, so I’ll probably dedicate an entire chapter to this cat. Maybe with a week’s worth of SC memes? Who knows!
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Erwin doesn’t like that.
Oo
I haven’t done a lot of research on comets. Maybe one day I’ll do an article on one, in the future. They sound so cool xD
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Comet Halley vs Comet SWAN via NASA https://ift.tt/2y0UdFr
The pre-dawn hours of May 3rd were moonless as grains of cosmic dust streaked through southern skies above Reunion Island. Swept up as planet Earth plowed through dusty debris streams left behind periodic Comet 1/P Halley, the annual meteor shower is known as the Eta Aquarids. This inspired exposure captures a bright aquarid meteor flashing left to right over a sea of clouds. The meteor streak points back to the shower’s radiant in the constellation Aquarius, well above the eastern horizon and off the top of the frame. Known for speed Eta Aquarid meteors move fast, entering the atmosphere at about 66 kilometers per second, visible at altitudes of 100 kilometers or so. Then about 6 light-minutes from Earth, the pale greenish coma and long tail of Comet C/2020 F8 SWAN were not to be left out of the celestial scene, posing above the volcanic peaks left of center. Now in the northern sky’s morning twilight near the eastern horizon Comet SWAN has not become as bright as anticipated though. This first time comet made its closest approach to planet Earth only two days ago and reaches perihelion on May 27.
(Published May 14, 2020)
Yeah, Mercury did kinda kick Newton in the balls, didn’t it?
Guess that’s why it’s my favorite planet
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Ah yes, the science
