Can I Go To Lake Thetis? Damn.

Okay I love the Big Bang Theory (as in the actual scientific theory about the start of our universe) but also the TV show.

(Sheldon was my favorite)

Anyway I didn’t know there was a full version of the theme song and I really like it :)

WANT MORE? GET YOUR HEAD STUCK IN THE STARS AT MY BLOG!

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 :)

WANT MORE? GET YOUR HEAD STUCK IN THE STARS AT MY BLOG!

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

WANT MORE? GET YOUR HEAD STUCK IN THE STARS AT MY BLOG!

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.

WANT MORE? GET YOUR HEAD STUCK IN THE STARS AT MY BLOG!

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.

THE LIFE OF A STAR: STAR NURSERIES

How did this "star stuff" come to exist? The life of stars is a cycle: a star's birth came from a star's death. When it comes to star birth, the star nebulae reigns supreme.

        A Nebula (take a look at pictures, they're some of the most beautiful things in the universe) is a giant cloud of dust and gas. This is the region where new stars are formed. Nebulae live in the space in between stars and between galaxies - called interstellar space (or the interstellar medium) - and are often formed by dying stars and supernovas (NASA). 

        This cloud of particles and gases is mostly made of hydrogen (remember - stars mostly fuse hydrogen!). These appear as patches of light (emission, reflection, or planetary-types) or a dark region against a brighter background (dark-type). This depends on whether "... it reflects light from nearby stars, emits its own light, or re-emits ultraviolet radiation from nearby stars as visible light. If it absorbs light, the nebula appears as a dark patch ..." (The Free Dictionary). 

        There are four main types of nebulae: emission, reflection, dark, and planetary nebulae.

        Emission nebulae are a high-temperature gathering of particles, of which are energized by a nearby ultra-violent-light-emitting star. These particles release radiation as they fall to lower energy states (for more information on electrons moving to energized states and falling back to lower states, read this). This radiation is red because the spectra/wavelength of photons emitted by hydrogen happens to be shifted to the red-end of the visible light spectrum. There are more particles than hydrogen in the nebulae, but hydrogen is the most abundant.

        Next up is the reflection nebulae - which reflect the light of nearby stars. As opposed to emission nebulae, reflection are blue, because "the size of the dust grains causes blue light to be reflected more efficiently than red light, so these reflection nebulae frequently appear blue in color ...." The Reddening Law of Nebula describes that the interstellar dust which forms nebulae affects shorter wavelength light more than longer-wavelengths (CalTech).

        Then there's the "emo" nebulae: dark nebulae. These are, very simply, nebulae which block light from any nearby sources. The lack of light can cause dark nebulae to be very cold and dark (hence their name), and the heat needed for star formation comes in the form of cosmic rays and gravitational energy as dust gathers. Many stars near dark nebulae emit high levels of infrared light (this type is much more intricate then I've explained, but that summary will do for now. If you're interested in learning more, read this).

        Finally, there are planetary nebulae. And these aren't nebulae made of planets. These nebulae are formed when stars (near the ends of their life) throw out a shell of dust. The result is a small, spherical shape, which looks like a planet (hence their name) (METU).

        Nebulae themselves are essentially formed by gas and dust particles clumping together by the attractive force of gravity. The clumps increase in density until they form areas where the density is great enough to form massive stars. These massive stars emit ultraviolet radiation, which ionizes surrounding gas and causes photon emissions, allowing us to see nebulae (like we discussed in the types of nebulae). Universe Today said, "Even though the interstellar gas is very dispersed, the amount of matter adds up over the vast distances between the stars. And eventually, and with enough gravitational attraction between clouds, this matter can coalesce and collapse to forms stars and planetary systems."

        Britannica notes the structure of nebulae in terms of density and chemical composition: "Various regions exhibit an enormous range of densities and temperatures. Within the Galaxy’s spiral arms about half the mass of the interstellar medium is concentrated in molecular clouds, in which hydrogen occurs in molecular form (H2) and temperatures are as low as 10 kelvins (K). These clouds are inconspicuous optically and are detected principally by their carbon monoxide (CO) emissions in the millimeter wavelength range. Their densities in the regions studied by CO emissions are typically 1,000 H2 molecules per cubic cm. At the other extreme is the gas between the clouds, with a temperature of 10 million K and a density of only 0.001 H+ ion per cubic cm." The composition of nebulae also aligns with what we see with the rest of the universe, mostly being made of hydrogen and the rest being other particles, particularly helium (this matches up with the composition of stars!).

        Fun-fact: supernova can create nebulae, but also destroy them. Possibly the most famous nebulae, the "Pillars of Creation," the Eagle Nebula, is hypothesized to have been destroyed by the shockwave of a supernova 6,000 years ago. Since it takes light 7,000 years to travel from that nebulae to the Earth, we won't know for another 1,000 years (Spitzer). If you're wondering how exactly we could know how far nebulae are, check out this article about a new way to measure that distance using the "surface brightness-radius relation", and other distance measurements (such as the parallax measurement).

        Now, why did I just explain the intricacies of nebulae in 900 words when this series is supposed to be about stars? Well, when we talk about the birth of a star (and the death sometimes, too), nebulae become important. Take note of what we've discussed in this article: formation, chemical composition, and density. It'll be important in our next chapter (and nuclear fusion, but when is that not important?).

First -  Chapter 1: An Introduction

Previous -  Chapter 2: Classification

Next -  Chapter 4: A Star is Born

WANT MORE? GET YOUR HEAD STUCK IN THE STARS AT MY BLOG!

I love that

After my Life of Stars series I’ve been wanting to do one on galaxies. Maybe I will hmmmmm

WANT MORE? GET YOUR HEAD STUCK IN THE STARS AT MY BLOG!

Galaxies: Types and morphology

A galaxy is a gravitationally bound system of stars, stellar remnants, interstellar gas, dust, and dark matter. Galaxies range in size from dwarfs with just a few hundred million (108) stars to giants with one hundred trillion (1014) stars, each orbiting its galaxy’s center of mass.

Galaxies come in three main types: ellipticals, spirals, and irregulars. A slightly more extensive description of galaxy types based on their appearance is given by the Hubble sequence. 

Since the Hubble sequence is entirely based upon visual morphological type (shape), it may miss certain important characteristics of galaxies such as star formation rate in starburst galaxies and activity in the cores of active galaxies.

Ellipticals

The Hubble classification system rates elliptical galaxies on the basis of their ellipticity, ranging from E0, being nearly spherical, up to E7, which is highly elongated. These galaxies have an ellipsoidal profile, giving them an elliptical appearance regardless of the viewing angle. Their appearance shows little structure and they typically have relatively little interstellar matter. Consequently, these galaxies also have a low portion of open clusters and a reduced rate of new star formation. Instead they are dominated by generally older, more evolved stars that are orbiting the common center of gravity in random directions.

Spirals

Spiral galaxies resemble spiraling pinwheels. Though the stars and other visible material contained in such a galaxy lie mostly on a plane, the majority of mass in spiral galaxies exists in a roughly spherical halo of dark matter that extends beyond the visible component, as demonstrated by the universal rotation curve concept.

Spiral galaxies consist of a rotating disk of stars and interstellar medium, along with a central bulge of generally older stars. Extending outward from the bulge are relatively bright arms. In the Hubble classification scheme, spiral galaxies are listed as type S, followed by a letter (a, b, or c) that indicates the degree of tightness of the spiral arms and the size of the central bulge.

Barred spiral galaxy

A majority of spiral galaxies, including our own Milky Way galaxy, have a linear, bar-shaped band of stars that extends outward to either side of the core, then merges into the spiral arm structure. In the Hubble classification scheme, these are designated by an SB, followed by a lower-case letter (a, b or c) that indicates the form of the spiral arms (in the same manner as the categorization of normal spiral galaxies). 

Ring galaxy

A ring galaxy is a galaxy with a circle-like appearance. Hoag’s Object, discovered by Art Hoag in 1950, is an example of a ring galaxy. The ring contains many massive, relatively young blue stars, which are extremely bright. The central region contains relatively little luminous matter. Some astronomers believe that ring galaxies are formed when a smaller galaxy passes through the center of a larger galaxy. Because most of a galaxy consists of empty space, this “collision” rarely results in any actual collisions between stars.

Lenticular galaxy

A lenticular galaxy (denoted S0) is a type of galaxy intermediate between an elliptical (denoted E) and a spiral galaxy in galaxy morphological classification schemes. They contain large-scale discs but they do not have large-scale spiral arms. Lenticular galaxies are disc galaxies that have used up or lost most of their interstellar matter and therefore have very little ongoing star formation. They may, however, retain significant dust in their disks.

Irregular galaxy

An irregular galaxy is a galaxy that does not have a distinct regular shape, unlike a spiral or an elliptical galaxy. Irregular galaxies do not fall into any of the regular classes of the Hubble sequence, and they are often chaotic in appearance, with neither a nuclear bulge nor any trace of spiral arm structure.

Dwarf galaxy

Despite the prominence of large elliptical and spiral galaxies, most galaxies in the Universe are dwarf galaxies. These galaxies are relatively small when compared with other galactic formations, being about one hundredth the size of the Milky Way, containing only a few billion stars. Ultra-compact dwarf galaxies have recently been discovered that are only 100 parsecs across.

Interacting

Interactions between galaxies are relatively frequent, and they can play an important role in galactic evolution. Near misses between galaxies result in warping distortions due to tidal interactions, and may cause some exchange of gas and dust. Collisions occur when two galaxies pass directly through each other and have sufficient relative momentum not to merge.

Starburst

Stars are created within galaxies from a reserve of cold gas that forms into giant molecular clouds. Some galaxies have been observed to form stars at an exceptional rate, which is known as a starburst. If they continue to do so, then they would consume their reserve of gas in a time span less than the lifespan of the galaxy. Hence starburst activity usually lasts for only about ten million years, a relatively brief period in the history of a galaxy.

Active galaxy

A portion of the observable galaxies are classified as active galaxies if the galaxy contains an active galactic nucleus (AGN). A significant portion of the total energy output from the galaxy is emitted by the active galactic nucleus, instead of the stars, dust and interstellar medium of the galaxy.

The standard model for an active galactic nucleus is based upon an accretion disc that forms around a supermassive black hole (SMBH) at the core region of the galaxy. The radiation from an active galactic nucleus results from the gravitational energy of matter as it falls toward the black hole from the disc. In about 10% of these galaxies, a diametrically opposed pair of energetic jets ejects particles from the galaxy core at velocities close to the speed of light. The mechanism for producing these jets is not well understood.

The main known types are: Seyfert galaxies, quasars, Blazars, LINERS and Radio galaxy.

source

images: NASA/ESA, Hubble (via wikipedia)

What a cool illustration :D

It’s true though

WANT MORE? GET YOUR HEAD STUCK IN THE STARS AT MY BLOG!

Art by Emanuele Fais

Honestly I don’t really understand why they didn’t call the APOLLO missions the ARTEMIS missions! Artemis is the greek goddess of the moon, not Apollo xD

Dat rocket does look cool though. I prefer posting about astrophysics, but I’m having a lazy day and rockets are easy to find and cool to look at. Apologies for anyone expecting another post on stars or memes.

WANT MORE? GET YOUR HEAD STUCK IN THE STARS AT MY BLOG!

NASA Attaches First of 4 RS-25 Engines to Artemis I Rocket Stage : Engineers and technicians at NASA’s Michoud Assembly Facility in New Orleans have structurally mated the first of four RS-25 engines to the core stage for NASA’s Space Launch System (SLS) rocket that will help power the first Artemis mission to the Moon. (via NASA)

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!”

WANT MORE? GET YOUR HEAD STUCK IN THE STARS AT MY BLOG!

It was at this moment he knew…….

This was such a pretty poem that I had to reblog :)

But really, it’s 100% accurate. We are star-stuff.

WANT MORE? GET YOUR HEAD STUCK IN THE STARS AT MY BLOG!