Well TECHNICALLY It’s A Helium-4 Nucleus

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

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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

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.

Woah :O

COOOOOLLL

I’ve never gotten to see a full solar eclipse, just a partial one that happened a few years ago. 

Maybe I’ll have better luck in the future?

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Traveling for 4 days, Just to See 30 Seconds of The Full Annular Eclipse! It Was worth All the Effort!

via reddit

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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Aw, now that’s a smart kitty

Also - what’s the meaning of life and death - good question. Cat please explain lol

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Upvote me so that I can post on r/science too.

Omg yes this is it - this is the unified theory of everything - Einstein was just a lion the whole time!

It does explain the hair though

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The physics lion

Max Planck, you absolute boss

Btw there’s always something left in physics to discover. Going from nothing left to discover to quantum theory is a huge leap though, because quantum has PLENTY to figure out.

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Oof

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.

Today's Moon Phase!

Keep track of the Moon on MoonGiant as it does it's monthly dance around the Earth

Tonight’s a New Moon!

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