The Sun’s Nuclear Fusion

Posted on March 20, 2022 by solarelizabeth
The chemistry behind nuclear fusion.

The Sun has been producing a huge amount of energy for over 4 billion years through nuclear fusion. Nuclear fusion is the process by which the Sun converts mass to energy. Albert Einstein’s equation, E=mc^2, reveals that a little bit of mass has a huge amount of potential energy which indicates why the sun has been able to shine for so long. In fusion, nuclei smash into each other at high speeds and fuse together to form nuclei with higher atomic weights. In this process, some of the mass is converted into energy. 

When the Sun undergoes nuclear fusion, four hydrogen nuclei fuse together to form a Helium nucleus. The Sun’s nuclear fusion process is called the proton-proton chain. This is because two Hydrogen nuclei, which are each a single proton, fuse to form a deuterium nucleus, which is one proton and one neutron. Then, the deuterium nucleus fuses with another Hydrogen proton to form Helium-3. The Helium-3 nucleus fuses with another Helium-3 nucleus to form a Helium nucleus with two protons and two neutrons. The two extra protons are released. In this process, a tiny amount of mass disappears, but it is transformed into a huge amount of energy. The energy is released in the form of gamma rays, neutrinos, and positrons. 


When the sun was forming, the cloud that would become the sun contracted under gravity and became hotter and more dense, setting the stage for nuclear fusion. Nuclear fusion occurs in the Sun’s core because it is the hottest and most dense area, with the core temperature being about 15.6 million K. High temperature and density are required because like charges repel each other, so Hydrogen nuclei would not fuse together to form Helium nuclei otherwise. The point is, the Sun generates its energy because it is massive enough to sustain a hot and dense core, which overcomes repulsion of Hydrogen atoms of the same charge, smashing them together to form Helium. This results in some mass being converted to energy, which we know is an enormous amount because of Einstein’s E=mc^2.

Thanks for reading!! Let me know what fusion processes you think would happen in more massive, hotter stars!

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Blog#4 Dark Energy and Dark Matter

Posted on March 20, 2022 by Irene

Dark Energy and Dark Matter sound both exotic (and yes they absolutely are) but they have very different meanings and opposite effects: One expands our universe while one creates more gravity.

High-z Supernova Search Team was founded in 1994 and in 1998 they found that one investigated supernova is fainter than Hubble’s law predicted. This mismatch could only result from either a wrong prediction or the actual distance of the supernova becomes more distant. After careful research, they claimed that the supernova is accelerating away from us and the Universe is actually expanding and won the 2011 Nobel Prize. What causes the anti-gravity effect is called Dark Energy. Dark Energy bubble out of the vacuum of space, creates a pressure that forces space to expand to an ever-increasing rate, and makes galaxies move faster and faster.

Nonetheless, it is quintessential to know that what is expanding is space-time. Galaxies are like raisins in dough and the dough itself is expanding. 

Artistic Illustration of an Accelerating Universe.

Dark matter was proposed by Fritz Zwicky who was a professor at CalTech in the 1930s. In 1933, he found that galaxies in Coma Cluster moved faster than expected. Therefore, there must have lots of mass we cannot see: 50 times more than the mass we can see. That is to say, 98% of the mass in our Universe is dark. Later the number is reduced to 97%.

Fritz Zwicky

The concept of Dark Matter was further testified by Vera Rabin in 1962. She calculated and graphed stellar curves of the velocities of stars. She found that the velocities didn’t decrease as expected for Keplerian orbits, which means there must be an invisible mass. 

Vera Rabin

Nonetheless, human beings still barely know about dark matter. There is not enough helium in the Universe to make that much mass and there is no evidence for normal stuff to be dark, yet the gravitational lensing proved it existent. We have hypotheses for Dark Matter including Machos (Massive Compact Halo Objects), Axions (cold candidate that made in Big Bang), and WIMPS (weakly interacting massive particles). However, nothing was found. So, are dark energy and dark matter the ether of the 20th and 21st centuries? 

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Blog#3 Radioactive Decay

Posted on March 20, 2022 by Irene

Our world is composed of elements all of which are made of protons, neutrons, and electrons. Protons are positively charged while electrons are negatively charged. Unstable (i.e., radioactive) atomic nuclei can become more stable after the emission of particles and energy, a process called radioactive decay. These emitted particles or energy (the latter emitted as electromagnetic waves) are collectively called radiation.

Illustration of Radioactive Decay. Cr. Wikipedia

There are three types of radioactive decay: α decay, β decay, and γ decay

In the alpha-decay process, a nucleus releases an alpha particle (a helium nucleus formed by two neutrons and two protons) and transforms into a new nucleus with a reduced mass of 4 and a reduced nuclear charge of 2. Alpha radiation releases discrete energy and can be almost completely absorbed by a layer of air several centimeters thick.

In the Beta-decay process, a nucleus releases a beta particle (electron or positron). It releases continuous energy and can be absorbed by a few millimeter aluminum layers. 

Gamma radiation is usually produced along with other forms of radiation, such as alpha radiation and beta radiation. When an atomic nucleus undergoes alpha decay or beta decay, the resulting new nucleus is sometimes in an excited state, at which time the new nucleus leaps to a lower energy level and simultaneously releases gamma particles. This is gamma radiation. It releases discrete energy and has an infinite effective range. Nonetheless, it can be absorbed by about a 10-centimeter lead board. 

During the decay of a radionuclide, the number of nuclei of the nuclide gradually decreases. The number of nuclei that will decay per second is proportional to the number of nuclei at present that has not yet decayed. Therefore, there is an exponential decay equation. The time it takes to decay to only half its original mass is called the half-life of the nuclide. Each radionuclide has a specific half-life, ranging from a few microseconds to several million years. We can use radioactive dating to measure how old an object is.

Exponential Decay and Half-Life. Cr. Wikipedia
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Halley’s Comet

Posted on March 20, 2022 by jesszhang782
Halley’s Comet was the first comet understood to be a periodic comet, or a comet that can pass through the solar system multiple times. The English astronomer Edmund Halley (1656-1742) noticed that the previously recorded orbits of three comets were very similar and suggested that it was actually the same comet returning it its orbit. […]
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Solar Sailing Through The Sea of Space

Posted on March 20, 2022 by josephmaquino9
Figure 1: The Japanese IKAROS solar-powered spacecraft.

As an imaginative mind might ask: can we use the Sun’s light to propel a spacecraft through space? Surprisingly, this avenue of spacecraft propulsion has, and is being, explored. Figure 1 displays the Japanese IKAROS satellite that was deployed on May 21, 2010. The spacecraft was equipped with a 14 m x 14 m solar sail membrane that served as the primary attitude control. Interestinly, the satellite utilized the flow of electricity through the liquid crystal panels in the membrane to steer it in different directions. So, why does this concept work?

Just as it applies in rocketry, conservation of momentum is the driving concept behind a spacecraft with a solar sail. Light is comprised of photons. Although these particles are massless, they have momentum as they travel through space. Thus, when photons reflect off of the sail, momentum is transferred into the spacecraft. The exciting thing about solar sailing through space is that space is a vacuum. This means that there is no drag acting on the spacecraft, and each reflection of a photon increases the vehicle’s velocity. Additionally, the Sun’s light is not going to be extinguished in the very near future, so the solar sail will have a continuous input of light.

Now, you may be asking, “14 m x 14 m is a very large sail, isn’t it?” You would be correct. To keep the mass of the vehicle down, solar sails tend to have a thickness on the magnitude of microns (or 10^-6 m). The IKAROS satellite’s solar sail membrane had a thickness of only 7.5 microns, causing the spacecraft to have a total weight of approximately 310 kg. Since there is continuous light striking the solar sail, the only real negative impact of more mass in space is that it would take the vehicle longer to accelerate (as conservation of momentum considers mass). The main concern with mass is that the spacecraft has to be transported out of the Earth’s atmosphere first before the sails may be utilized. The project would be dead in the water if it was too heavy to be transported.

So, why did the IKAROS satellite use electricity flow throughout its membrane? This is because the liquid crystal panels became reflective when electricity flowed through them, and no electricity made the sunlight pressure more diffuse. When you control the electricity flow through specific portions of the solar sail, you can control where the sunlight mainly impacts, allow the spacecraft to change orientations.

Though the deployment of the IKAROS satellite was only to test the viability of solar sails (as this satellite did not have a specific target destination), it proved that solar sails are a potential method of travelling deeper into space. For example of attainable speeds, The Planetary Society’s LightSail spacecraft is equipped with 32-square-meter solar sail is capable of an acceleration of only 0.058 mm/s^2; however, after only a month’s time of continuous sunlight, the spacecraft will have an increased velocity of 549 km/s (about the same speed as a jet airliner traveling at cruising speed). Issues with more accurate steering abilities and slowing this bullet down remain a concern. Nonetheless, the IKAROS revealed that solar sailing can be an available method of propulsion through space.

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Mercury and its core | blog IV

Posted on March 20, 2022 by clviggiano

Measuring just over one-third of Earth’s diameter, Mercury is the smallest terrestrial planet in the solar system. However, relative to other worlds, Mercury’s core constitutes a very large part of its volume. Despite the vast difference in their scale, “Mercury’s inner core is indeed solid [and] very nearly the same size as Earth’s inner core,” according to NASA’s Goddard Space Flight Center. For comparison, Mercury’s core comprises about 85% of the planet’s volume, while Earth’s only about 15%. The leading theory to explain this discrepancy is that powerful collisions knocked away the majority of Mercury’s outer mantle. This hypothesis suggests that it was originally a larger planet whose core:volume ration was similar to that of other planets. 

There is still relatively little is known about Mercury—in fact, it is the least explored terrestrial planet. However, a joint mission between the European Space Agency and Japan Aerospace Exploration Agency is striving to provide more knowledge about the world. The mission, which launched in October of 2018, is called BepiColombo; it “Comprises two spacecraft: the Mercury Planetary Orbiter (MPO) and the Mercury Magnetospheric Orbiter (Mio).” However, it will be 2025 before MPO or Mio reach Mercury, with the journey from Earth taking more than seven years to complete. It will be well worth the wait: this mission promises to provide insight into our closest-neighboring planet.

NASA/JPL
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Black Holes!

Posted on March 20, 2022 by Emily Bertram

Black holes are regions of spacetime where gravity is so strong that nothing can escape. I have always found the idea of black holes because they can be hard to understand or conceptualize. A weird fact about black holes is how hot they are on the outside and how incredibly freezing they are on the inside. Just outside a black hole the temperature is very high but the interior of the black hole is around one millionth of a degree above absolute zero. 

There are four types of black holes: stellar, intermediate, supermassive, and miniature. They all form in different ways and are all mysterious.

What do you think about black holes?

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Climate Change

Posted on March 20, 2022 by Emily Bertram

We have all heard of climate change but what does it really mean? Climate change can be explained by the change in temperature and weather patterns that are occurring over long periods of time. Humans are at fault for climate change because we continue to burn fossil fuels like oil and coal. Burning fossil fuels leads to greenhouse gases being released into the atmosphere. These greenhouse gases trap the sun’s heat in the atmosphere and raise temperatures on Earth. 

How can we stop global warming? The world need to start cutting emissions. We can do this by switching to renewable energy like solar and wind power. These systems eliminate use of fossil fuels. 

How can YOU help? 

  1. You can walk/bike more. By lowering the use of your car you are lowering your carbon footprint. 
  2. Save energy at home by installing solar power and LED lights around your home. Wash your laundry with cold water and let your clothes air dry instead of using your dryer. 
  3. Eat your vegetables! Eating plant based reduces greenhouse gas emissions and requires less energy.
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The Expanding Universe

Posted on March 20, 2022 by parallaxHubble
The Expanding Universe

The Universe is expanding – and expanding at a rate that is accelerating. Based off simple knowledge of physics, one would assume that this would be the opposite. The Universe should be shrinking over time as gravity slowly pulls billions of galaxy clusters, galaxies, stars, and solar systems towards each other on an inevitable collision course. But this is not the case, proven by measurements of the Hubble Constant and the Cosmic Background Radiation.

The Cosmic Background Radiation

This is the cosmic background radiation. What you are looking at is essentially a map of the entire Universe, with the more dense areas as yellow/orange/red and the less dense as light/dark blue. The CMB originates from a critical moment in time when the Universe was just 300,000 years old. At this time, photons could interact with electrons interchangeably, creating charged ions. But after enough time, after 300,000 years, the Universe had begun to spread and cool so that these photons lacked the energy to jump in and out of electrons. It was at this moment in time that these photons became frozen in time, unable to change back into electrons, floating from that moment in time until the end of the Universe in space. What we are looking at above, more precisely, is an exact image of the Universe’s density almost 14.3 billion years ago, which should closely resemble the density and distribution of matter today as it is the space between galaxies that expands, not the galaxies moving themselves.

The Hubble Constant

Directly above is a diagram demonstrating the Hubble Constant. Charted in the image are Type 1a Supernovae, a special, extremely bright solar entity that occurs when a white dwarf reaches a critical mass and collapses in on itself. The graph demonstrates an extremely linear, positive relationship between distance of the Supernovae and their velocity (measured using Doppler shifts). This chart proves the theory of the expanding Universe as it demonstrates that the further away an entity is, the faster it is moving – and moving away from us. The idea of the expanding Universe stunned astronomers for awhile, as it seemed very counter to what one would assume – wouldn’t gravity be pulling together all the galaxies once the initial energy and momentum of the Big Bang subsided? If this was not the case, then there had to be some other force at play pushing space apart.

Source

The answer is dark energy. Dark energy is mysterious, something that has stifled astronomers and physicists and mathematics for decades. We don’t know very much about what creates it, how it interacts with matter, and what properties it has; however, two things are certain. It is this dark energy that is propelling the universe to expand, and expand at an accelerating rate. This is because the amount of dark energy is actually increasing over time, making up about 68% of all the matter in the entire Universe at this time. Note that dark energy is not actually “dark”, rather the term is used because knowledge about the entity is unknown.

Although it may take several chains of logic and evidence to come to the conclusion, and lots of research, it is quite clearly evident that the Universe is expanding, and accelerating as well – we just don’t know why. For this reason, the origins, details, and principles of the expanding universe is one of the largest questions hovering around astronomers today.

SOURCES:

Source 1

Source 2

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Star Fuel – Nuclear Fusion

Posted on March 20, 2022 by parallaxHubble
The Sun, photo by Western Washington University

The sun has been around for 4.603 billion years, about one third of the entire duration of the universe. With a mass 330,000 times greater than Earth and a radius 108 times larger (source), the sun is a very massive object (though not that large when compared to other stars). Have you ever wondered what powers the sun, what keeps the sun burning bright and able to create heat waves on Earth, 92 million miles away?

The answer is nuclear fusion. You may have heard of nuclear fission, used in nuclear power plants to generate energy. Nuclear fusion is a very different process than nuclear fission. While nuclear fission involves the breakdown of radioactive atoms, nuclear fusion involves the combination of two radioactive atoms (source). Both processes create huge amounts of energy, but fusion is a much more powerful and stable source for the Sun.

Nuclear fusion by Duke Energy

Einstein’s famous equation e=mc^2 highlights how fusion works. Essentially, in a process known as the proton proton chain, protons and neutrons combine to form helium, effectively converting a very small percentage of their mass into energy (source). This is possible because, as Einstein stated, energy equals mass, so at extreme temperatures mass equals energy and vice versa. This is how stars fuel themselves. Eventually, however, a star will run out of mass to convert into energy using the proton proton chain, leading to the creation of a red giant. This will eventually happen to our Sun in 5 billion years.

Photo by NASA.

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