Kepler-452b is an exoplanet about 15 light-years away from us. It is notable because it is the most Earth-like planet that has been discovered so far. It is 60% larger than Earth, which is certainly significant, but it has an orbit that lasts 385 Earth-days, and it orbits only 5% further from its star than Earth. For the Kepler mission, this represents a tremendous amount of success in its effort to find Earth-like planets, but it is far from the only one. Just in the Kepler-452 system, there are other planets that attracted some attention, like Kepler-452h. No matter the ultimate result of any of these individual planets, the fact that multiple planets can be found in individual systems near ours alludes to a universe rich in the kinds of habitats and materials life is made of.
Aside from being named after Jupiter’s progenitors rather than his offspring or contemporaries, Uranus has the obvious distinction from having its axis be almost horizontal, meaning it rotates on its side like a wheel rather than like a top, possibly due to a drastic collision it suffered while forming that it never bothered to correct.
This unique movement pattern comes with some interesting climate patterns. The poles only experience one day per Uranian year, meaning there’s 42 Earth years of consecutive light followed by 42 years of darkness. Seasons on Uranus essentially mean whether or not you get sunlight at all.
Shown above is from the National Ignition Facility, where scientists successfully produced (and reproduced) a nuclear fusion reaction that had more energy output than input. The underlying math behind this lies in E=mc2, which shows that Mass (m) can be converted into a large amount of energy at the sacrifice of just a small amount of matter, as the multiplier of the speed of light squared takes the small amount of matter and creates a large amount of energy produced.
Nuclear fusion usually takes place in the Sun, where incredible pressure and temperature battle the repulsive forces between the nuclei of atoms, eventually winning and combining the two. Often in nuclear fusion reactions, two Hydrogen atoms (who’s nuclei have just 1 proton) combine, creating a deuterium and releasing a positron and neutrino, then a Hydrogen ion (a proton) fuses with that deuterium to create Helium-3 and releasing a photon. After that Helium-4 is created by the fusing of two Helium-3 nuclei, necessarily releasing two protons.
Gamma ray photons eventually make their way from the inside the Sun to its surface and are emitted from the celestial object as sunlight.
Gravitational forces are the standard for nuclear fusion reactions, as it is by far the most common natural occurrence of conditions needed (high temperature and pressure). Because the Sun is so massive, the gravitational pull towards its center is also much stronger than any other celestial object in our Solar System, meaning that it is able to create the conditions necessary for nuclear fusion to take place.
In the case of ignition on Earth as performed by the NIF, gravitational pressure was substituted for powerful lasers that create a similar environment (in terms of pressure and temperature) for frozen hydrogen isotopes. Ultimately, they were able to create such great pressure and temperature that fusion took place, and more energy was produced than was put into the system, a historic achievement.
Stars like our Sun are considered “ordinary” and quite common. They produce energy through hydrogen fusion. A weirder type of star is a white dwarf. These are stars that at one point produced energy through hydrogen fusion, but have run out of hydrogen, and do not have the mass to carry out fusion energy reactions with heavier elements. Instead, these white stars sit idle, cooling down for billions of years. A white dwarf star has about the mass of our sun, with about the diameter of earth. The atoms within a white star are packed so tightly together that they exert an outward degeneracy pressure, as the particles are packed as tightly together as the laws of quantum mechanics allow.
Another type of weird star is the neutron star. Created by the collapse of a star’s core during a supernova, these stars are only 10 km across, but with a mass greater than the sun. They are made almost entirely of neutrons, as protons and electrons within it are so closely packed that they combine into neutrally charged neutrons. In fact, if a 10km wide neutron star appeared in Nashville, it would condense the entire earth into a size no thicker than your thumb. Really crazy!
Stars like our Sun are considered “ordinary” and quite common. They produce energy through hydrogen fusion. A weirder type of star is a white dwarf. These are stars that at one point produced energy through hydrogen fusion, but have run out of hydrogen, and do not have the mass to carry out fusion energy reactions with heavier elements. Instead, these white stars sit idle, cooling down for billions of years. A white dwarf star has about the mass of our sun, with about the diameter of earth. The atoms within a white star are packed so tightly together that they exert an outward degeneracy pressure, as the particles are packed as tightly together as the laws of quantum mechanics allow.
Another type of weird star is the neutron star. Created by the collapse of a star’s core during a supernova, these stars are only 10 km across, but with a mass greater than the sun. They are made almost entirely of neutrons, as protons and electrons within it are so closely packed that they combine into neutrally charged neutrons. In fact, if a 10km wide neutron star appeared in Nashville, it would condense the entire earth into a size no thicker than your thumb. Really crazy!
Black holes are undetectable by telescopes because no light can escape from them; However, they can be detected through their interactions with nearby matter. For example, when a star gets too close to a black hole it can be broken apart, and as the gas from the star falls into the black hole, it heats up and emits X-rays and radio waves that can be detected by astronomers. Here’s a visual of how that may look like:
Additionally, the gravitational influence of black holes can affect the orbits of objects around them, which provides further evidence for their presence.
Black holes vary in size, from small (just a few times the mass of the Sun) to supermassive (millions or even billions of times the mass of the Sun). Some of these massive black holes can reside at the centers of galaxies, like our Milky Way.
Telescopes laid the foundation for everything we know about space, but they can only get you so far. If you don’t particularly feel like removing the planet’s entire atmosphere to get a better view, spacecrafts do a pretty good job of getting a closer look.
Flyby spacecraft are the simplest and least expensive; they can be light as long as they can withstand the trip to space. The lack of air friction up there also saves on fuel. Flybies, as the name implies, move past planets and transmit images of them back to Earth, essentially serving as a long range cameras and spectrographs. Orbiters are more specialized, being built to stay in a celestial body’s orbit, in turn allowing a more sustained stream of data. Landers and probes go the extra mile and land on the celestial bodies, allowing for an even closer look. Probably the most elaborate type of data retrieval spacecraft is the type that literally retrieves data and bring it back to Earth: sample return crafts, which have already been used to collect comet dust and are aiming for Mars next.
The solar system began to form from a giant molecular cloud of gas and dust particles about 4.6 billion years ago. This cloud most likely experienced a shock wave from a nearby supernova, which could have made it collapse under its own gravity. It then began to spin and flatten into a disk shape due to conservation of angular momentum. Most of the material in this nebula was pulled towards the center, in which formed our Sun. Within the spinning disk, the process of accretion had tiny grains of dust colling that caused them to stick and form larger particles called planetesimals. These planetesimals continued to collide and accumulate to form planets. Close to the Sun, where it is hotter, only rocky materials could condense, leading to the formation of 4 inner terrestrial planets: Mercury, Venus, Earth, and Mars. As you go more towards the outside, the cooler, icy materials are able to condense, allowing for the formation of the outer gas giants: Jupiter, Saturn, Uranus, and Neptune. As the planets formed, they cleared out their paths of orbit, by gravitational attraction. However, some debris remained which led to the formation of asteroids and comets. Asteroids are rocky remnants from the early solar system that never formed into planets, primarily found in the asteroid belt between Mars and Jupiter. Comets are icy bodies composed of dust, rock, and ice that originate from the outer solar system and sometimes head closer to the Sun.
As I was growing up, I never truly understood what the sun exactly was. I had understood that it emitted light and eventually I learned that it was basically a big ball of really really REALLY hot gasses. However I never understood the intricacies behind the Sun’s structure. The most interesting part of the sun’s structure to me is its core. Within the core, we can learn how the sun produces massive amounts of energy output that results from the extremely high temperatures and densities created by the surrounding gas. In the process of nuclear fusion, hydrogen atoms slam into one another creating the energy that escapes the sun and is seen as visible light by us on Earth. This process is extremely interesting as it is balanced by the inward gravitational pull of the star. Knowing the different layers of the sun have different levels of pressure and how the core creates a unique process of fusion is extremely fascinating to me and will have me looking a little differently at that great ball of fire we see in our sky every day.
The northern lights, or aurora borealis, is a display of natural light that occurs in the Earth’s sky. What you might not know is that there is another light show on Earth called aurora australis, which occurs in the southern hemisphere. So, what causes these natural and captivating lights? Solar winds are a stream of charged particles given off by the sun. During a coronal mass ejection, these winds are stronger and have more energy when they reach Earth. When a solar wind approaches Earth, it is funneled toward the poles by Earth’s magnetic field. The charged particles then collide with the atoms and molecules in the atmosphere and excite them. This causes the molecules to release photons, which we see in the sky as the colored lights. The color of the lights depends on what type of gas is excited by the solar particles because each gas has its own emission spectrum. What is also interesting is that the altitude of the gas also impacts the color. For example, oxygen at high altitudes gives off a red color, while at lower altitudes, it gives off a green one. Other planets give off auroras too! Any planet with an atmosphere and a magnetic field can emit an aurora. Auroras on Jupiter and Saturn have been documented.
