Okay I Know That I Love Black Holes But Buddy Why Don’t You Not Come Here?

This basically sums it up.

Well, it doesn’t show the other things stars can be after their deaths. But it was a nice video :)

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For a star to be born, there is one thing that must happen: a gaseous nebula must collapse. So collapse. Crumble. This is not your destruction. This is your birth.

Zoe Skylar

(via the-wolf-and-moon)

Everything that is created comes from destruction, that’d just how our universe works.

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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 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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That’s how I want the world to end

better than us all getting killed by a pandemic or a nuke

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On November 12, 1833, there was such an intense meteor shower that it was possible to see up to 100,000 meteors crossing the sky every hour. At the time, many thought it was the end of the world, so much that inspired this wood engraving by Adolf Vollmy.

Escape velocity!!!!!!!

I.e. the velocity that an object must attain before being able to resist an object’s gravitational pull and escape it’s influence.

Please get this.

This is why I’m so excited for the supernova chapter ehehe

It’s so amazing that this little dot growing a bit but still being little is a supernova! 

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This is the galaxy Messier 85! 🌌🌌🌌

Just last month, scientists found a supernova taking place! The event is named SN 2020nlb and has been continuously getting brighter. It is classified as a Type Ia supernova, which results from a white dwarf exploding within a binary star system. The brightness of this supernova can be used to calculate the distance to the galaxy! 🤩🤩🤩

Taken by me (Michelle Park) using the Slooh Canary Two telescope.

Yeah Earth is such a narcissist

But TESS is a great satellite (it launched in 2018 by SpaceX - so thanks guys!)

The study of exoplanets has never been my main thing in astrophysics (sorry, my heart belongs to black holes and cosmology!) but I think it’s a really cool and important field. And, for everyone who says that the vastness of space just shows our insignificance, know that the odds of us finding other intelligent life are extremely small. I think we’re pretty special.

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SpaceX successfully launched TESS yesterday! We’re going to discover so many new exoplanets.

In a sense cosmology contains all subjects because it is the story of everything, including biology, psychology and human history.

Peter Theodore Landsberg

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Just so you guys know, the Galilean Moons aren’t Jupiter’s only moons. It has 79 confirmed moons.

Hey, at least they’re not all lonely.

Also, fun-fact, the Moon Europa is a big candidate for a “2nd Earth,” having an ocean under a shell of ice.

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Over the span of a few hours, I collected images of Jupiter and its Galilean Moons. I labelled each one and you can see them move in their orbits! 🪐🪐🪐

Taken by me (Michelle Park) using the Slooh Canary Two telescope on June 3rd, 2020.