Pluto is most known for its famous debate: Is it a planet or not? As of 2006, Pluto is known as Dwarf Planet. A Dwarf Planet is a celestial body that orbits the Sun just like a regular planet; however a dwarf planet lacks a clear orbital path, sharing it with other objects. Pluto’s size is also wildly different that the other 8 planets, being smaller than the moon! Pluto was originally considered a planet because the term “planet” hadn’t specified its definition until more recent years with the help of new technology.
According to NASA, our Sun is a 4.5 billion year old yellow dwarf star composed of Helium and Hydrogen. It is the largest object in the Solar System with a diameter of about 1.4 million kilometers. The hottest part of the Sun is its core with a peak temperature around 15 million °C. Meanwhile, its surface – the photosphere – is significantly cooler in comparison with a temperature of only 5,500 °C. The Sun is the lifeblood of our solar system as it is the star’s gravitational pull that holds the Solar System together, keeping everything in its orbit. Additionally, without this star’s energy, life on Earth would not exist. The Sun’s importance is further demonstrated with how its presence also drives the seasons, ocean currents, and climate of Earth.
We have learned about radioactivity in class, and we hear about it in the news, but many do not have direct experience with radiation. It is a scary word that elicits a lot of fear in most; for example, concerns about safety have stopped nuclear power from gaining dominance despite otherwise being a superior source of electricity.
However, we are actually exposed to radiation on a daily basis. Radon in the air and ground is the source of most of our radiation exposure, and when buying a house it is very common to get a radon test (some places require it) to ensure the radiation exposure is not too high. There is also an amount that we get from cosmic rays, high-energy particles that originate from outside our solar system that make it down into our atmosphere. Something that we also may not think about are airplane flights, which actually expose us to a marginal amount of radiation. Finally, medical imaging studies are also a major source of radiation.
Radiation safety is highly regulated in most countries, and while it may sound scary and is certainly something to be mindful of, radiation is also all around us. Indeed, Carbon-14 is common enough for us to do radiometric dating, a useful tool in studying astronomy and many other fields of science.
Around 4.6 billion years ago, the sun formed along with the planets surrounding it due to the collapse of the solar nebula. When this supernova explosion took place, the collapsed cloud began to spin around in a circle, ultimately getting pulled by gravity to create the center (the Sun). The excess material smashed together making planets and their moons. The gas and dust leftover cleared once solar wind began due to the Sun beginning to release plasma into the atmosphere. From there, the leftover material formed the now asteroid belt. It took the solar system hundreds of millions of years to officially form.
The words “climate change” and “global warming” are thrown around in politics and science, but what is “climate change” and what is causing it? There are actually four causes of climate change: solar brightening, changes in reflectivity, changes in axial tilt, and changes in greenhouse gas abundance.
Solar Brightening is the change in energy the Sun radiates to the Earth. The Sun gradually becomes brighter over time, increasing the amount of sunlight, which causes the Earth to become warmer. However, this is a minor contributor to climate change, as the Sun becomes brighter at a very slow rate.
The change in reflectivity refers to how much sunlight is reflected in the space. Light is reflected due to the atmosphere, clouds, ice covers, and use of land (plants absorb sunlight, cities are darker which causes more light absorption). The more sunlight is reflected, the cooler the Earth becomes as it absorbs less energy.
The change in axial tilt determines the extremity of seasons (the higher the tilt, the more extreme the seasons are) as the amount of sunlight the planet at a location receives is more varied.
The topic that is widely talked about regarding climate change is the change in greenhouse gas abundance. Greenhouse gasses, which are gasses that are transparent to visible light but absorb infrared radiation (such as water vapor, carbon dioxide, and methane), scatter infrared light, which causes the surface and lower atmosphere to absorb more light, causing an increase in temperature. Human activity such as burning fossil fuels or mass deforestation (to name a few) increases greenhouse gasses in the air which causes the planet to become warmer. This is the most relevant in climate change to humans as the other three are generally less controlled by humans.
Now when you hear scientists or politicians talk about climate change, you are now informed what they are talking about.
In total, Saturn has a total of 146 moons! The most out of any planet in our solar system. These moons vary significantly in terms of terrain and position around Saturn. Some hold huge oceans and some are rocky worlds that seem to be out of Star Wars. There’s also a few moons that are considerably larger than the average moon in our solar system such as Titan (which is also the only moon to contain an atmosphere). Other moons orbiting Saturn include Rhea, Dione, Enceladus, Iapetus, and Mimas.
Whats even more interesting is that more than 60 of the current moons orbiting Saturn were discovered just last year!
Asteroids are a really interesting part of the solar system, but is strangely absent from most models of the solar system. So what exactly is the Asteroid Belt?
The Asteroid Belt is a ring of asteroids between Mars and Jupiter and is made up of millions of them. They vary in size, with some being about as big as a large boulder and some are a few thousand feet across. The biggest object in the belt is Ceres, a dwarf planet. Despite how many asteroids there are, the amount of total mass actually in the belt is about 3% of Earth’s Moon, and the diagram is pretty exaggerated for visual effect. Each asteroid is also an average of nearly 1,000,000 km apart from each other, so those Sci-Fi depictions of compact fields of rocks is just fiction.
On to some of the history of the Asteroid Belt, it was formed while the solar system was also still forming there was a lot of space dust floating around. While most of it formed into planets, some of it wasn’t able to and ended up turning into the asteroid belt. An asteroid belt is also not unique to our solar system, scientists have found a star called Zeta Leporis that also has a cloud of dust surrounding it that resembles our own belt, and one can imagine many more have one.
Nuclear fusion is the process that creates the massive amount of energy needed to power the sun. In the sun’s core 4 Hydrogen atoms collide to create 1 Helium atom, 2 electrons, 2 neutrinos, and 2 gamma ray photons. The amount of Helium created is less than the overall mass of Hydrogen used to create the helium. This creates a small amount of energy because of Einstein’s equation: E=mc^2. Since the mass of the atom is lowering, the energy must increase to keep it equivalent. Although only a small amount of energy is created, this is happening at such a fast rate at all times that an incredible amount of energy is created every second. The sun has a tremendous amount of Hydrogen, enough to have powered it for the last 4.5 billion years and will keep powering it for the next 4.5 billion years.
Stars like the Sun have been powering themselves through the use of nuclear fusion for billions of years, and the Sun is expected to be powered for billions more before it runs out of its source of hydrogen fuel through the proton-proton chain. As outlined on my previous blog post, one second of energy created by the Sun could power planet Earth for over 25,000 years, but harnessing energy through nuclear fusion on Earth is (and has proven to be) much more challenging. Fusion reactions are being studied, but the difficulties are associated with sustaining the immense pressure and temperature needed to combine nuclei (as opposed to, in fission, splitting them). The promise of nuclear fusion, though, is immense as, through it, Earth could be provided nearly limitless, clean nuclear energy without the radioactive waste associated with nuclear fission (Office of Nuclear Energy). By 2020, around 80% of the world’s energy supply came from fossil fuels (Environmental and Energy Study Institute), which further warrants the need to continue intensive research on alternative, clear, and more renewable sources of energy.
Achieving the necessary conditions for fusion on Earth requires extremely cutting-edge technology. Projects such as the International Thermonuclear Experimental Reactor are leading the way in fusion research, promising devices, tools or facilities that will be “capable of creating a ‘little star’ on Earth” (ITER). While currently in construction, the Tokamak (ITER’s fusion device) (Image 1) aims to demonstrate that controlled fusion can be a viable energy source. Different than the cores of stars, gases on Earth need to be heated to more than 10 times the temperature of the Sun: 150,000,000º Kelvin. Since there are no known materials which can contain the extremely hot plasma required to create the conditions, a “magnetic cage” is used suspend the particles and keep them from touching the reactor walls (Eurofusion). On top of this, for energy production, the conditions must be sustained for a long-enough period for fusion. Alternative methods exist, but the Tokamak seems to be the most advanced and promising route.
In order for stars to generate the enormous amounts of energy that they do, a very specific, energy-intensive process is needed: nuclear fusion. It is this process that allows stars to shine brightly for billions of years. But how exactly does nuclear fusion work? In short, in the cores of stars, temperatures reach the millions of degrees and the pressure is immense. Inside the core of the Sun, for example, nuclei of hydrogen atoms are so hot– about 15,000,000º K (Space.com)– that they move at tremendous speeds. Even though two positively charge hydrogen protons would naturally repel each other, the extreme heat provides enough energy to overpower the repulsion and allow them to collide. Under these conditions, something called the proton-proton cycle becomes possible, allowing stars to convert hydrogen to helium, releasing tremendous amounts of energy in the process. Although there are different paths that this cycle can follow, between the temperatures of 10 to 18 million degrees Kelvin, the dominant is the proton-proton I branch (Image 1).
When two hydrogen-1 protons collide at these speeds, they form a hydrogen-2 nucleus and emit a positron (a positive electron) and a neutrino. helium nucleus and, as a byproduct, releasing huge amounts of energy. In extremely dense and hot places– such as the cores of stars– these hydrogen-2 nuclei will then quickly collide with another hydrogen-1 proton and form a helium-3 nucleus and emit a gamma ray. For the next step, the helium-3 nucleus has to collide with another helium-3 nucleus (that will have undergone the same process, will have consumed the same 3 helium-1 protons, and emitted the same 1 neutrino and 1 positron). When these two helium-3 nuclei collide, they form a helium-4 nucleus and release 2 hydrogen-1 nuclei.
The complete chain produces a total 26.732 million electron-volts (MeV) (Proton-Proton Chain Wikimedia), which is not a lot of energy by itself: only equivalent to 1.6022 * 10-13 joules (J). On the other hand, the proton-proton chain happens around 9.2 * 1037 times per second (Canada Energy Education) in the Sun, meaning that the Sun produces an estimated (considering the rough estimates and generalizations outlined above) 1.474 * 1025 J per second. For comparison, below is the amount of energy that the entire planet uses in one year (The World Counts):
Energy output of the Sun per second = 14,740,000,000,000,000,000,000,000 joules Entire planet energy usage per year = 580,000,000,000,000,000,000 joules
This means that, IN A SINGLE SECOND, the Sun produces 25,400 times more energy that the entire planet uses in a year. This means that, given a non-changing usage of energy, if the entire energy of the Sun could be harnessed, 1 second of its energy could power the planet for over 25,000 years.
