I Mean, The Song Really Isn’t Accurate.

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…….

It’s easy to forget that thousands of comets, asteroids, and meteors are near us everyday. They seem like such a rarity.

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Cosmonaut Ivan Vagner obtained this image of the comet NEOWISE a few hours ago from the International Space Station. He says that the dust tail looks very good from there. It is worth enlarging the image.

via reddit

Woah :o

So, basically, like the Mission Space ride at Epcot (that one is my favoriteeeee)?

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Testing and Training on the Boeing Starliner : NASA astronaut Mike Fincke works through a check list inside a mockup of Boeing’s CST-100 Starliner during a simulation at NASA’s Johnson Space Center on Aug. 21, 2019. (via NASA)

INTRODUCTION TO THE LIFE OF A STAR

The yellow dwarf of our Sun is around 4.5 billion years old (NASA).

   This is nothing compared to other stars, the oldest we know of was created 13.2 billion years ago (DISCOVERY OF THE 1523-0901).  Shortly before that, it is theorized the universe was a dense ball of super hot subatomic particles, until it wasn't. 

     For some reason, possibly the amounts of pressure or even the mysterious dark energy, the universe exploded into what it is today, forming crucial atoms and molecules, and continues to expand. These molecules formed clumps and clouds of gas, which eventually collapsed by gravity and created the very first stars. 

    Stars, particularly our Sun, are very important to life and affect the void of space to a great magnitude. They can tell us so much about the early universe, form elements from their deaths, and even create black holes. But how did this come to be?

     By definition, they are "huge celestial bodies made mostly of hydrogen and helium that produce light and heat from the churning nuclear forges inside their cores." (National Geographic) And there are TONS of them. There are stars everywhere we look. In fact, Astrophysicists aren't even sure how many stars there actually ARE in the universe (Space)! That's because they're not sure if the universe is infinite - in which the number of stars would also be infinite. Even so, we may not be able to detect them all, even if the number is finite.

     But they're so much more than a definition or a number. Stars aren't just objects: they're histories. Stars have a life, they are born, fuel themselves on nuclear fusion, and when they can no longer -  there are many ways their deaths can go (in brutal, yet tantalizing ways). They form solar systems, galaxies, galaxy clusters, and might just be the life-blood of the universe. Their light acts as beacons to scientists. Stars are so crucial to us, their deaths through Supernovas form most of the elements on the Periodic Table of the Elements.

    As the brilliant cosmologist, Carl Sagan, once said: "The nitrogen in our DNA, the calcium in our teeth, the iron in our blood, the carbon in our apple pies were made in the interiors of collapsing stars. We are made of star-stuff."

    And if we're made of this stuff, shouldn't we at least try to understand what it actually does?

Next - Chapter 2: Classification

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THE LIFE OF A STAR: WHAT GOES AROUND, COMES AROUND

Previously on The Life of a Star, Chapter 6 ...

"But what happens after the shell is fused? We'll get back to that in Chapter 7, where we'll discuss White Dwarfs and Planetary Nebulae."

        After a low-mass star loses its hydrogen core, it becomes a mighty Red Giant - the star contracts and then heats up again, igniting hydrogen shell fusion and swelling the star to epic proportions. That is, until the hydrogen shell and the helium core and all fused up, in which the helium shell will begin to fuse. Remember the last chapter, when I said that these stars don't have enough pressure to fuse the results of the triple-alpha process? Well, I wasn't lying.

        And unlike the end of hydrogen fusion - where low-mass stars have a "2nd life" and continue fusing the elements - this means the end for our star.  Now, due to the build-up of carbon and oxygen in the core (and the lack of enough pressure to fuse these elements), the star has run out of fuel. This cancels out gas pressure, which breaks the hydrostatic equilibrium. Gravity wins the constant battle within the star, and the core collapses.

        The leftover core - tiny and hot - is called a Wolf-Rayet type star and squeezed into a volume one-millionth the size of the original star (Harvard). Now, why does the star stop here? If gravity overpowers the pressure inside the star, why does it not completely collapse into a black hole? Well, that's due to a little thing called electron degeneracy pressure.  Basically, the Pauli exclusion principle states that "no two electrons with the same spin can occupy the same energy state in the same volume." Due to the core collapse, electrons are forced together. The Pauli exclusion principle predicts that these electrons, once having filled a lower energy state, will move to a higher one and begin to speed up. This creates pressure and prevents the core from further collapse. However, at a certain mass, this becomes impossible to maintain. White dwarfs have something called the Chandrasekhar limit, which states that white dwarfs cannot exist if their original mass is over 1.44 times the mass of the Sun. This is due to mass-radius relationships, something we'll discuss in the next chapter.

        One of my favorite things about stars is the fact that they're a cycle - the death of some stars causes the birth of others. White dwarfs do this, too, by creating something we talked about in Chapter 3: Planetary Nebulae.

        The collapsed Wolf-Rayet type star is extremely small, with high density and temperature. Streams of photons/energy/heat - stellar winds - push out the cooler outer layers of the dead star (Astronomy Notes). The core emits UV radiation, which ionizes the hydrogen and causes it to emit light, forming fluorescent and spherical clouds of gas and dust surrounding the hot white dwarf. These are Planetary Nebulae, which can later be clumped by gravity and spun to create a new star. The cycle continues (Uoregon).

        The leftover core, the White Dwarf, is characterized by a low luminosity (due to the lack of new photons, which the star will start to lose by radiation) and a mass under about 1.44 times that of the Sun.

        Due to the intense gravity, the White Dwarf (despite being very large in mass) has a radius comparable to that of the Earth. If you consult the density equation (d=m/v, which basically means that if you enlarge or shrink either the mass or the volume that the density will increase), White Dwarfs have enormous densities. The core is a compact of carbon and oxygen. Because the star is unable to fuse these elements, they kind of just ... sit there. Surrounding this is a shell of helium and a small hydrogen envelope. Some even have a very thin layer of carbon (Britannica).

        However, the White Dwarf isn't the end for the star. There's one more stage for the star to go through before completely "dying": becoming a Black Dwarf.

        After the core is left behind, there Is no fuel left to burn. That means no new energy production. However, the leftover heat from the contraction remains, and the star will begin to cool down. Higher mass White Dwarfs, due to having a smaller radius, radiate this away slower than the low-mass ones. There are two types of cooling: radiative and neutrino. Radiative cooling is simple: as the star gives off light and energy outward, it loses heat. Neutrino cooling is a bit more complex: at extremely hot temperatures, gamma radiation passes electrons, and this reaction creates a pair of neutrinos. Because neutrinos interact very weakly with matter, they escape the White Dwarf quickly, taking energy with them. It's also possible to have a hunch of crystal in the center of a Black Dwarf: "On the other hand, as a white dwarf cools, the ions can arrange themselves in an organized lattice structure when their temperature falls below a certain point. This is called crystallization and will release energy that delays the cooling time up to 30%." (Uoregon).

        The White Dwarf will become a Black Dwarf after it radiates away all of its heat and becomes a cold, dark shell of its former self. Because it's radiated away all of its heat, it emits no light, hence the name. However, according to theoretical physics, there isn't a single Black Dwarf in the universe. Why? Because it should take at least a hundred million, billion years for a White Dwarf to cool down into a Black Dwarf. Because the universe is predicted to be around 13.7 billion years old, there hasn't been enough time for a single White Dwarf to completely cool down (space.com).

        However, there's one last thing that can happen to a White Dwarf. And that's where things in this book will start to get explosive.

        White Dwarfs in binary star systems (where two stars orbit around a center of mass, we'll touch on it more in Additional Topics) can undergo a Classical Nova. These supernovae occur in systems with one White Dwarf and one main-sequence star. If they orbit close enough, the White Dwarf will begin to pull the hydrogen and helium from the other star in what is called an Accretion Disk, what is to say a disk of plasma and particles which spiral inwards due to gravity and feeds one body off of another. The accretion of this plasma onto the surface of the White Dwarf increases pressure and temperature so much that fusion reactions spark and the outburst of energy ejects the shell in a burst of light - a nova (Cosmos).

        This process doesn't end, however. It can repeat itself again and again in what is called a Recurrent Nova. We know the existence of these based on pictures of the same star system with expanding shells, the aftermath of recurrent novae. Because White Dwarfs are the most common star death in the universe, and most stars are in binary or multiple star systems, novae are fairly common (Uoregon).

        Our discussion of novae will be an excellent transition into our next topic: supernovae! This will be the beginning of the end for the High-mass stars we talked about in Chapter 6, and we’ll even talk a little bit more about White Dwarf collisions and how they are related to supernovae, neutron stars, and more!

        From here on out, stars are going to become much more dramatic - and all the cooler (well, not really)!

First -  Chapter 1: An Introduction

Previous -  Chapter 6: The End (But Not Really)

Next - Chapter 8: Why We’re Literally Made of Star-stuff (unpublished)

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THE LIFE OF A STAR: THE END (BUT NOT REALLY)

In our last chapter, we discussed the main-sequence stage of a star. In this chapter, we'll be discussing when the main-sequence stage ends, and what happens when it does.

        In order to live, stars are required to maintain a hydrostatic equilibrium - which is the balance between the gravitational force and the gas pressure produced from nuclear fusion within the core. If gravity were to be stronger than this pressure, the star would collapse. Likewise, if the pressure were to be stronger than gravity, the star would explode. It's the balance - the equilibrium - between these two forces which keeps a star stable. Stars contain hydrogen - their primary fuel for fusion - in their core, shell, and envelope. The heat and density in the core is the only area in a main-sequence star that has enough pressure to undergo fusion. However, what happens once hydrogen runs out in the core is where things start to get ... explosive.

        For this, we'll be having two discussions: what happens in low-mass stars, versus what happens in high-mass stars.

                                                                      ~ Low-Mass Stars ~

        Low-mass stars are classified as those less than 1.4 times the mass of the sun (NASA). While low-mass stars last a lot longer than their higher-mass counterparts, these stars will eventually have fused all of the hydrogens in their core. Because the core doesn't have enough pressure to fuse helium (as it takes more pressure and heat to fuse heavier elements than less), gas pressure stops and gravity causes the core to contract. This converts gravitational potential energy into thermal energy, which heats up the hydrogen shell until it is hot enough to begin fusing. It also produces extra energy, which overcomes gravity in small amounts and causes the star to swell up a bit. As it expands, the pressure lessens and it cools. The increased energy also causes an increase in luminosity. This is what is now called a Red Giant star (ATNF). 

        Red Giants grow a lot, averagely reaching sizes of 100 million to 1 billion kilometers in diameter, which is 100-1,000 times larger than the sun. The growth of the star causes energy to be more spread out, and so cools it down to only around 3,000 degrees Celsius (still though, pretty hot). Because energy correlates with heat, and the red part of the electromagnetic spectrum is less energized, the stars glow a reddish color. Hence, the name Red Giant. Due to the current size of the sun, we can conclude that it will eventually become a Red Giant. This could be a big problem (literally), as the sun will grow so large that it will either consume Earth or become so close that it would be too hot to live. However, this won't be happening for around 5 billion years, so there's nothing immediately to worry about (Space.com).

        As more hydrogen is fused within the shell of the Red Giant, the produced helium falls down into the core. The increased mass leads to increased pressure, which leads to increased heat. Once the temperature in the core reaches 100 K (at which point the helium produced has enough energy to overcome repulsive forces), helium begins to fuse. This process is called the Triple Alpha Process (as the helium being fused are actually alpha particles, helium-4 nuclei), where three of the helium particles combine to form carbon-12, and sometimes a fourth fuses along to form oxygen-16. Both processes release a gamma-ray photon. In low-mass stars, the Triple Alpha Process spreads so quickly that the entire helium ore is fusing in mere minutes or hours. This is, accurately called, the Helium Flash. 

        After millions of years, the helium in the core will run out. Now the core is made entirely of the products of helium fusion: carbon and oxygen nuclei. As the fusion stops, gas pressure shrinks, and gravity causes the star to contract yet again. The temperature needed to fuse carbon and oxygen is even higher, as heavier elements require more energy to fuse (because, with more protons, there's more Coulombic Repulsion). However, this temperature cannot be reached, because the gravity acting on the core is not strong enough to create enough heat. The core can burn no longer.

        The helium shell of the star begins to fuse, as gravity IS strong enough to do that. The extra energy and gas pressure created causes the star to expand even more so now. The helium shell is not dense enough to cause one single helium flash, so small flashes occur every 10,000-100,000 years (due to the energy released, this is called a thermal pulse). Radiation pressure blows away most of the outer layer of the star, which gravity is not strong enough to contain. The carbon-rich molecules form a cloud of dust which expands and cools, re-emitting light from the star at a longer wavelength (ATNF).

        But what happens after the shell is fused? We'll get back to that in Chapter 7, where we'll discuss White Dwarfs and Planetary Nebulae.

        It's also important to note that not every low-mass star needs to become a Red Giant. Stars that are smaller than half the mass of the Sun (like, Red Dwarfs) are fully convective, meaning that the surface, envelope, shell, and core of star materials all mix. Because of this mixing, there is no helium buildup in the core. This means that there is not enough pressure to fuse the helium in fully convective stars, and so they skip the contraction and expansion phases of Red Giant Stars. Instead, with no gas pressure to counteract gravity, the star collapses in on itself and forms a White Dwarf (Cosmos).

                                                                     ~ High-Mass Stars ~

         High-mass stars are classified as those more than 1.4 times the mass of the sun (NASA). High-Mass Stars, as opposed to their Low-Mass counterparts, use up their hydrogen fast, and as such have much shorter lives. Just like Low-Mass Stars, they'll eventually run out of hydrogen in both their core and their shell, and this will cause the star to contract. Their density and pressure will become so strong that the core becomes extremely hot, and helium fusion starts quickly (there is no helium flash because the process of fusion will begin slowly, rather than in "a flash"). The release of energy will cause it to expand and cool into a Red Supergiant, and will also begin the fusion of the helium shell. 

        Once all of the helium is gone, leaving carbon and oxygen nuclei, the star contracts yet again. The mass (and the gravity squeezing it into a very small space with a very large density) of a high-mass star will be enough to generate the temperatures needed for carbon fusion. This produces sodium, neon, and magnesium. The neon can also fuse with helium (whose nuclei is released in the neon fusion) to create magnesium. Once the core runs out of neon, oxygen fuses. This process keeps going, creating heavier and heavier elements, until it stops at iron. At this point, the supergiant star resembles an onion. It is layered: with the heavier elements being deeper within the star, and the lighter elements closer to the surface (ATNF).

        But what happens after the star finally gets to iron? We'll get back to that in Chapters 8, 9, and 10 - where we'll discuss Supernovae, Neutron Stars, and Black Holes.

        We’re nearing the end of our star’s life, and now it’s time to look into the many ways it can go out.

        If our first five chapters were all about life, these next five will be all about death.

First -  Chapter 1: An Introduction

Previous -  Chapter 5: A Day in the Life

Next - Chapter 7: What Goes Around, Comes Around

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I felt that

I mean they are pretty connected, so even if you choose one you’ll probably have to deal with the other.

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Can I have both?

Calculus Readiness Test - (22 Questions To Find Out If You're Ready)

How To Prepare For Calculus The Right Way. Determine Your Strengths And Weaknesses With Our Calculus Readiness Test. Covering All The Topics You Will Be Expected To Know Before You Enter College Or High School Calculus Courses.

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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The search for another Earth is super cool even if it might never end lol

But like, Aliens.

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Are We Alone? How NASA Is Trying to Answer This Question.

One of the greatest mysteries that life on Earth holds is, “Are we alone?”

At NASA, we are working hard to answer this question. We’re scouring the universe, hunting down planets that could potentially support life. Thanks to ground-based and space-based telescopes, including Kepler and TESS, we’ve found more than 4,000 planets outside our solar system, which are called exoplanets. Our search for new planets is ongoing — but we’re also trying to identify which of the 4,000 already discovered could be habitable.

Unfortunately, we can’t see any of these planets up close. The closest exoplanet to our solar system orbits the closest star to Earth, Proxima Centauri, which is just over 4 light years away. With today’s technology, it would take a spacecraft 75,000 years to reach this planet, known as Proxima Centauri b.

How do we investigate a planet that we can’t see in detail and can’t get to? How do we figure out if it could support life?

This is where computer models come into play. First we take the information that we DO know about a far-off planet: its size, mass and distance from its star. Scientists can infer these things by watching the light from a star dip as a planet crosses in front of it, or by measuring the gravitational tugging on a star as a planet circles it.

We put these scant physical details into equations that comprise up to a million lines of computer code. The code instructs our Discover supercomputer to use our rules of nature to simulate global climate systems. Discover is made of thousands of computers packed in racks the size of vending machines that hum in a deafening chorus of data crunching. Day and night, they spit out 7 quadrillion calculations per second — and from those calculations, we paint a picture of an alien world.

While modeling work can’t tell us if any exoplanet is habitable or not, it can tell us whether a planet is in the range of candidates to follow up with more intensive observations. 

One major goal of simulating climates is to identify the most promising planets to turn to with future technology, like the James Webb Space Telescope, so that scientists can use limited and expensive telescope time most efficiently.

Additionally, these simulations are helping scientists create a catalog of potential chemical signatures that they might detect in the atmospheres of distant worlds. Having such a database to draw from will help them quickly determine the type of planet they’re looking at and decide whether to keep observing or turn their telescopes elsewhere.

Learn more about exoplanet exploration, here. 

Make sure to follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com.

I’m so hype for this telescope though

They say it might be able to see back to when the first stars were born - how exciting!

Eat shit Hubble telescope

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The launch of the James Webb Telescope – the successor of the Hubble Telescope – has been delayed until 2021 but damn it’s going to be awesome.