Lookin’ Good!

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.

THE LIFE OF A STAR: A STAR IS BORN

All you need to make a star is dust, gravity, and time.

        Stars form from nebulae's molecular clouds - which are "clumpy, with regions containing a wide range of densities—from a few tens of molecules (mostly hydrogen) per cubic centimetre to more than one million." Stars are only made in the densest regions - cloud cores - and larger cloud cores create more massive stars. Stars also form in associations in these cores. Cores with higher percentages of mass used only for star formation will have more stars bound together, while lower percentages will have stars drifting apart. 

        These cloud cores rotate very slowly and its mass is highly concentrated in its center - while also spinning and flattening into a disk (Britannica: Star Formation). This concentration is caused by gravity. As the mass of the clump increases - it is very cold and close to absolute zero, which increases density and causes atoms to bind together into molecules such as CO and H2 - it's gravity increases and at a certain point, it will collapse under it (Uoregon). The pressure, spinning, and compressing create kinetic energy which continues to heat the gas and increase density.

        Finally, there's the last ingredient: time. The process of these molecular clouds clumping, spinning, concentrating, and collapsing takes quite a while. From start (the cloud core-forming) to finish (the birth of a main-sequence star) - the average time is at about a cool 10 million years (yikes). Of course, this differs with density and mass, but this is the time for a typical solar-type star (StackExchange).

        The next stage in a star's life - after the nebulae - is a protostar.

        After one clump separates from the cloud core, it develops its own identity and gravity, and loose gas falls into the center. This releases more kinetic energy and heats the gas, as well as the pressure. This clump will collapse under gravity, grow in density in the center. and trap infrared light inside (causing it to become opaque) (Uoregon).

        A protostar looks like a normal star - emitting light - but it's just a baby star. Protostars' cores are not hot enough to undergo nuclear fusion and the light they emit (instead of coming from the release of photons after the fusion of atoms) comes from the heat of the protostar as it contracts under gravity. By the time this is formed, the spinning and gravity have flattened the dust and gas into a protostellar disk. The rotation also generates a magnetic field - which generates a protostellar wind - and sometimes even streams or jets of gas into space (LCO).    

        This protostar, which is not much bigger than Jupiter, continues to grow by taking in more dust and gas. The light emitted absorbs dust and is remitted over and over again, resulting in a shift to longer wavelengths and causing the protostar to emit infrared light. The growth of the star is halted as jets of material stream out from the poles - the cause of this has been unidentified, although theories suggest that strong magnetic fields and rotation "act as whirling rotary blades to fling out the nearby gas." (Britannica: Star Formation)

        The "infall" of stars stops by pressure, and the protostar becomes more stable. Eventually, the temperature grows so hot (a few million kelvins) that thermonuclear fusion begins - usually in the form of deuterium (a heavier form of hydrogen), lithium, beryllium, and boron - which radiates light and energy. This starts the pre-main-sequence star phase - also called T Tauri stars - which includes lots of surface activity in the form of flares, stellar winds, opaque circumstellar disks, and stellar jets. In this phase, the star begins to contract - it can lose almost 50% of its mass - and the more massive the star, the shorter the T Tauri phase (Uoregon).

        Eventually, when the star's core becomes hot enough (in some cases, we'll touch on this later), it will begin to fuse hydrogen. This will produce "an outward pressure that balances with the inward pressure caused by gravity, stabilizing the star." (Space.com)

        This will either create an average-sized star or a massive star.

        Nuclear fusion marks the beginning of the main sequence star. A star is born.

        But it isn't always.

        Now that we've discussed the transition from nebulae to main-sequence star, we'll be talking about what happens when hydrogen fusion doesn't occur. Those are called Brown Dwarfs.

        Brown Dwarfs are those stars that form much too small - less than 0.08 the sun's mass - and as a result, they cannot undergo hydrogen fusion (Space.com).

        Brown Dwarfs, are, bigger than planets. They are roughly between the size of Jupiter and our sun. Like protostars, brown dwarfs start by fusing deuterium, and their cores contract and increase in heat as they do so. Brown Dwarfs, however, cannot contract to the size required to heat the core enough to fuse hydrogen. Their cores are dense enough to hold themselves up with pressure. They are much colder compared to main-sequence stars, ranging from 2,800 K to 300 K (the sun is 5,800 K). They are called "Brown Dwarfs" because objects below 2,200 often cold too much and develop minerals in their atmosphere, turning a brown-red color (Britannica: Brown Dwarf).

        Once Brown Dwarfs have fused all of their deuterium, they glow infrared, and the force of gravity overcomes internal pressure (the internal force of nuclear fusion used to keep it stable) as it slowly collapses. They eventually cool down and become dark balls of gas - black dwarfs (NRAO).

        Now that we've covered how stars form - and what happens in certain cases where they are not - we'll be moving to the actual life of a star. Before we talk about the end of a star's life (arguably - my favorite part) we need to discuss main-sequence, cycles, mass, heat, pressure, structure, and more. This is to understand how a star died the way it did.

        Because - when it comes to the menu of star death - stars have a few options to choose from.

First -  Chapter 1: An Introduction

Previous -  Chapter 3: Star Nurseries

Next -  Chapter 5: A Day in the Life

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CMB!!!

Aka the cosmic microwave background, which is a huge piece of evidence for the Big Bang Theory of cosmology, a remnant from the early universe.

Also my favorite superhero is Spiderman.

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I am omnipresent

It’s been two years, and I’ll never forget him.

I remember when I was little and I loved space, but I was worried that I would be too bored of the astrophysics area. Then I read Mr. Hawking’s book a Brief History of Time, and I fell in love.

Thanks, Stephie.

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The world lost an amazing thinker today. Celebrated world-renowned physicist Stephen Hawking passed away in Cambridge on March 14th, 2018 (Pi Day), at age 76. Somehow, I think he would have found this to be very poetic.

Stephen William Hawking CH CBE FRS FRSA was an English theoretical physicist, cosmologist, author and Director of Research at the Centre for Theoretical Cosmology within the University of Cambridge.

I love supermassive black holes!!!

Expect this in the chapter about black holes lol

The relationship between SBHs and their host galaxies are so cool!

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AAS NOVA

A Young Population of Hidden Jets

By Susanna Kohler

Looking for a fireworks show this 4th of July? Try checking out the distant universe, where powerful jets flung from supermassive black holes slam into their surroundings, lighting up the sky.

Though these jets are hidden behind shrouds of gas and dust, a new study has now revealed some of these young powerhouses.

A Galaxy–Black-Hole Connection

In the turbulent centers of active galaxies (active galactic nuclei, or AGN), gas and dust rains onto supermassive black holes of millions to billions of solar masses, triggering dramatic jets that plow into the surrounding matter and light up across the electromagnetic spectrum.

The growth of a supermassive black hole is thought to be closely tied to the evolution of its host galaxy, and feedback like these jets may provide that link. As the jets collide with the gas and dust surrounding the galaxy’s nucleus, they can trigger a range of effects — from shock waves that drive star formation, to gas removal that quenches star formation.

To better understand the connections between supermassive black holes and their host galaxies, we’d especially like to observe AGN at a time known as Cosmic Noon. This period occurred around 10 billion years ago and marks a time when star formation and supermassive black hole growth was at its strongest.

The Hidden World of Cosmic Noon

But there’s a catch: around Cosmic Noon, galaxies were heavily shrouded in thick gas and dust. This obscuring material makes it difficult for us to observe these systems in short wavelengths like optical and X-ray. Instead, we have to get creative by searching for our targets at other wavelengths.

Since AGN emission is absorbed by the surrounding dust and re-radiated in infrared, we can use infrared brightness to find obscured but luminous sources. To differentiate between hidden clumps of star formation and hidden AGN, we also look for a compact radio source — a signature that points to a jet emitted from a central black hole.

A team of scientists led by Pallavi Patil (University of Virginia and the National Radio Astronomy Observatory) has now gone on the hunt for these hidden sources at Cosmic Noon.

Newly-Triggered Jets Caught in the Act

Patil and collaborators observed a sample of 155 infrared-selected sources, following up with high-resolution imaging from the Jansky Very Large Array to identify compact radio sources. From their observations and modeling of the jets, the authors estimate these sources’ properties.

The authors find bright luminosities, small sizes, and high jet pressures — all of which suggest that we’ve caught newly-triggered jets in a short-lived, unique phase of AGN evolution where the jets are still embedded in the dense gas reservoirs of their hosts. The jets are expanding slowly because they have to work hard to push through the thick clouds of surrounding material. Over time, the jets will likely expand to larger scales and clear out the surrounding matter, causing the sources to evolve into more classical looking radio galaxies.

What’s next? The authors are currently working on a companion study to further explore the shapes of the jets and their immediate environments. These young, hidden sources will provide valuable insight into how supermassive black holes evolve alongside their host galaxies.

Citation “High-resolution VLA Imaging of Obscured Quasars: Young Radio Jets Caught in a Dense ISM,” Pallavi Patil et al 2020 ApJ 896 18. doi:10.3847/1538-4357/ab9011

TOP IMAGE….Artist’s impression of a galaxy forming stars, as powerful jets that are flung from its central black hole collide with the surrounding matter. [ESO/M. Kornmesser]

CENTRE IMAGE….This composite image of Centaurus A shows an example of large-scale jets launched from an AGN, which can eventually extend far beyond the galaxy, as seen here. [ESO/WFI (Optical); MPIfR/ESO/APEX/A.Weiss et al. (Submillimetre); NASA/CXC/CfA/R.Kraft et al. (X-ray)]

LOWER IMAGE….The redshift distribution of the authors’ sample, based on spectroscopic redshifts of 71 sources. The sources span the period of peak star formation and black hole fueling around Cosmic Noon. [Patil et al. 2020]

BOTTOM IMAGE….The JVLA 10 GHz radio continuum observations for four sources in the authors’ sample. The cyan plus symbol marks the infrared-obtained source position. The color bars indicate flux in mJy/beam. [Adapted from Patil et al. 2020]

Can you kill a star with iron?

Since the energy required to fuse iron is more than the energy that you get from doing it, could you use iron to kill a star like our sun?

I read this article when answering a question on quotev and it’s fascinating!

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Favorite color?

It changes almost every day ~ but I’ve always really liked purple :D

Update on The Life of a Star, Chapter 7

So I’m a little over halfway done (I should be ready for some editing on Saturday) with this chapter and I think this might be my one longest yet! My current longest is Chapter 6, with 1,245 words. I’m currently at around 700 words with this one, and I’ve got at least 400 more to go. Anyway, I’m really excited for this one. We’ll be touching on nebulae again, and finally addressing our first ending for a star. 

We’ve only got three more chapters left, plus a possible one for additional topics. I’ll be sad to end this one, but I’m starting to gather ideas for the next book. Maybe on the methods of observing the universe? Maybe on random astrophysics topics? Perhaps one on galaxies? Cosmology? The Four Fundamental Forces? Haven’t decided yet xD

I think you’ll all really like these last chapters I have planned, or at least I hope you do. Thanks for reading :)

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Omg particles are such players - JUST CHOOSE ONE!!!

But yeah wave-particle duality is kinda confusing sometimes lol

Like, how is it both? I dunno! Maybe I’ll read up on that later ...

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Photons : Hello I’m a particle . Oh yeah but i behave like a wave too , isn’t that beautiful !!

Okay, that is really funny lol

Also - I’m back from my self-imposed vacation! I’m drafting the next chapter and starting my post schedule tomorrow, so look forward to new content coming soon!

I hope you’re all doing well :)

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Here’s some physics.