The Interiors of the Giants of the Solar System

The four Jovian planets in the Solar System

The giants of our solar system, other than the Sun of course, are quite different from the terrestrial planets whether it comes to the atmospheres, the surfaces, size, or other planetary features. One key difference is the interior of these giant planets. Terrestrial planets, for context, have a very dense core followed by a rocky mantle and ultimately a thin crust (or surface). When it comes to the giants, or Jovian, planets, the interiors are similar in that they have layers but the compositions are quite different.

The interiors of the four Jovian planets

As you can see in this visual, the layers are present but the compositions are what make these planets distinct from the terrestrials. The cores consist of rock, metals, and different gases. Jupiter and Saturn are similar to one another while Uranus and Neptune resemble one another more.
Jupiter’s and Saturn’s cores are surrounded by layers of hydrogen transforming from a solid to a liquid to a gaseous form. What we see from Earth are the surfaces of the planets which are primarily clouds of gas swirling around as the planets rotate. Uranus’ and Neptune’s inner cores consist of rock and metals while the outer core is made of water, methane, and ammonia. The core is then surrounded by gaseous hydrogen covered by clouds that we see from Earth.
I just wanted to share this with you all since we tend to hear so much about the terrestrial planets. Hopefully, you learned a little something about the Jovian planets and will dig deeper to maybe understand them more.

Back to the Beginning: The Big Bang

The different stages of the Universe following the Big Bang

The Big Bang. It was big and definitely was a bang, but many think that this event just happened and here we are in the same universe billions of years later. In reality, the Universe has been evolving, rapidly at first slowing over time, and it continues to evolve today.

The first stage of evolution was the Planck Era which lasted for about 10-43¬†seconds. There isn’t a theory sufficient enough to describe this time, but we know that the temperatures were extremely high and predict that there was a single, combined force that ruled over nature. Eventually, the temperature dropped allowing for one force, gravity, to separate from the combined forces which lead to the GUT Era (named after the grand unified theories). In this time, gravity and the other combined force (strong, weak, and electromagnetic) operated in nature. Again, there are many theories about this era as well, but we predict it ended when the strong and electromagnetic forces separated as the temperature continued to fall. It is also predicted that in this time, there was a great expansion of the Universe from an atomic nucleus size to that of a solar system.

After these two stages, there was the Electroweak Era where gravity, strong, and “electroweak” (electromagnetic and weak forces were still combined) forces were coexisting in the Universe. Eventually, the Universe cooled even more to about 1015¬†Kelvin which allowed the electromagnetic and weak forces to separate. This era is the first that we have direct evidence of what actually happened. Everything before was theorized with no direct evidence. Following the Electroweak Era was the Particle Era. During this time, very small objects called quarks, antiquarks, electrons, positrons, particles, and antiparticles participated in matter-antimatter collisions swapping masses. As the temperature continued to drop, these collisions slowed and matter, not antimatter, ended up being the winner of the battles since if there were an equal number of matter and antimatter, there wouldn’t be anything in the Universe.

At this point, the Universe is only 0.001 seconds old. The temperatures are still extremely high so fusion is occurring between protons and neutrons to form nuclei, but gamma rays are destroying them at the same time. This stage is known as the Era of Nucleosynthesis. As this went on, the temperature of the Universe was still decreasing and fusion eventually stopped leaving a hydrogen-abundant (75%) Universe with a significant amount of helium (~24.9999%). A smooth transition into the Era of Nuclei consisted of free-floating nuclei without electrons for about 380,000 years. After all of this time, the Universe had cooled enough to where these nuclei could finally capture and keep electrons and photons were able to travel across the Universe.

With fully-formed nuclei, the Era of Atoms began. The Universe was full of neutral atoms and gravity being the force that it is drew free-floating atoms to denser parts of the Universe. As time progressed, these turned into protogalactic clouds, or baby galaxies. About 600,000 years later when the Universe had reached its one-billion-year mark, the first galaxies appeared marking the beginning of the Era of Galaxies. Stars began to form over the billions of years and the Universe came to evolve to more of what we see today.

The Universe has come a long way to be in the Era of Galaxies and the truth is that it will continue evolve as it continues to expand. How? In truth, we do not know and will probably not be around long enough to see any changes, but that doesn’t mean we can’t imagine.

We’re Not the Only Living Ones in the Universe, Kind Of

The various stages of nuclear fusion in a high-mass star

For ages, humans have been questioning the possibility of other life forms in the universe. There are many theories and ideas of evidence of other life forms. For example, there appears to be dry river beds on Mars. It is thought that Mars could at one point retain water on its surface and life could’ve been sustained. There are other similar theories but what many tend to overlook are the seemingly infinite life forms that “twinkle” in our night sky: stars. We may not look like stars but there are similarities. Like humans, stars are born except they’re born out of gas clouds from older stars. Like humans, stars develop and change as they get older as they get more food (energy). Like humans, stars eventually get old and can no longer sustain life. The main difference, and perhaps most important aspect about a star, is the process that it undergoes to remain alive: nuclear fusion. Nuclear fusion is the process of fusing atoms of an element together which gives off energy.

The type of life a star will live, and its nuclear fusion process is determined once the star is born based on its birthweight, or how massive the star is when it starts fusing. If the birthweight is less than 2M, or two solar masses (two times the mass of our Sun), then the star is what we call a low-mass star. The nuclear fusion these stars undergo start out with fusing hydrogen to create helium. Once all of the hydrogen fuel is burned, the star will collapse and then expand to start fusing helium. After all of the helium fuel is fused to create carbon, the core is now primarily carbon but there isn’t enough gravitational energy to start fusing carbon and the core collapses. The outer portions, everything except the core, is blown away in a planetary nebula while the remaining core is left exposed as a white dwarf star.

Any star with a birthweight above 2M will typically have a longer life as a high-mass star. These stars follow the same process of low-mass stars except they continue fusing past carbon. In fact, they fuse each element all the way up to iron. Just like carbon was a low-mass star’s limit, iron is the end of the nuclear fusion process for high-mass stars. Iron can’t fuse into anything because the fusion will not create energy like each preceding fusion did. So, what happens? A supernova! Gravity collapses the core and the temperature rises to billions of Kelvin and then the rest of the star collapse and bounces off the neutron core. The result is a supernova nebula that actually creates the rest of the elements due to the extreme temperatures and abundance of energy.

So stars may not live like humans, but they have life cycles that we can link to our lives in different ways. They are born, they live, they die, and they give birth to other stars and elements. While they aren’t aliens that many want to find, stars are another form of life in our universe that we should no longer overlook as such.

Light: It’s More than We Think

The emission and absorption spectrum for the most abundant element in our Universe: Hydrogen.

Flip a switch. Turn a knob. Push a button. Look in the sky in the day or at night. Each of these actions will allow you to see light, and most people see light as nothing more than an illuminator. Its purpose in the field of astronomy is much more than illuminating the Universe for us to see. Light is the most significant means of measuring just about everything out there. One specific application is figuring out the composition of objects we are looking at.

This is done through spectroscopy, or getting information from spectra, pictured above. An emission spectrum is obtained when a hot, low-density cloud is shone through a prism. Conversely, an absorption spectrum is obtained when a hot light source is shone through a cooler gaseous cloud through a prism. Analyzing the spectra, we see colored lines on a black background or black lines on a continuous spectrum. What does this tell us?

The presence/absence of colors represent a “fingerprint” of an element. In the picture shown, the spectra represent the “fingerprint” of hydrogen. It may seem simple for us then to analyze the composition of objects in the Universe, but the trick comes when objects are made of multiple elements. The spectra would have colored/black lines all over and we’d have to decipher it. Luckily, computer programs aid in this endeavor but nonetheless, it is an application of using light as measurement.

So next time you flip a switch or look at the stars at night, you can think about what elements are present to emit the light you’re seeing. Impossible is the task of knowing, but interesting enough to wonder about.

And We’re Off, To the Past

Looking into the past with light-years

Growing up, I fantasized time travel and if it would ever be possible. I watched cartoons and movies that made time travel seem so real. Of course, I got a little older and realized physical time travel would be a thing of the distant future, if it ever comes to fruition. I let the fantasy go and focused on “real life” as all the adults said. It wasn’t until I learned of the concept of a light-year that I realized a form of time traveling is already upon us.

One light-year is the distance that light can travel in one year. If an object is ten light-years away, then the light from that object will take ten years to reach me. If this distant object emitted light on January 1, 2010, I wouldn’t see the light until January 1, 2020. In a sense, since the light I’m seeing is ten years old, I am looking ten years into the past. Now, this is just a theoretical object. In reality, astronomers have observed plenty of objects (stars, galaxies, etc…) that are at extreme distances.

For example, our closest neighboring galaxy, Andromeda, is around 2.5 million light-years away. The light we observe today from Andromeda was emitted 2.5 million years ago so we’re 2.5 million years into the past! For me, the most interesting concept of light-years is the age of the universe which is estimated to be about 14 billion years old. If we can see to the “edges” of the universe, then we are looking back 14 billion years. Everything between our planet and the edges is known as the observable universe and all of the light we see from the objects is the light of the past. How’s that for time travel?

I may be stuck in the present for now but by looking up at the sky on a clear night to see the multitude of stars and other objects above, I can look back into the past to satisfy my childhood fantasy of time travel.

The Beginning: A Little More of Me

Gateway to the Stars
From https://www.gatewayarch.com/wp-content/uploads/2018/04/Gateway_to_the_Stars.jpg

Welcome to the inaugural post to Jonah’s Astronomy Interests! Just to start, here are some things about me because why not: I’m from St. Louis, Missouri (if you couldn’t tell from the picture above) and I wish I could’ve minored in astronomy but physics wasn’t the move. Another thing to share: I love when I’m driving back home through the plains and can roll down my window, look up and see a clear view of all the stars while simultaneously blasting my favorite playlists. In these moments, I realize how our existence came from the explosion of some star so long ago and has progressed to the that moment in time. While simple, it’s one of the few things I indulge in whenever I can.
Anyways, that’s just an intro into Jonah’s Astronomy Interests. Thanks for stopping by!

PS: Anyone from St. Louis, be sure to check out the St. Louis Astronomical Society’s event calendar at your own convenience for opportunities back home!

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