Astro2110 – The Solar System | Aggregating the class blogs of Astro2110 at Vanderbilt

The Future Spacecraft

Posted on March 6, 2023 by reachforthestarsbysam

With countless spacecraft having been launched throughout a long history of space exploration, what is next for NASA?

Pictured above is a computer-rendered image of NASA’s Orion Spacecraft

Looking to shoot beyond the Moon and delve into the nearly untapped knowledge of Mars, the Orion project is what’s next on NASA’s agenda, as they prepare to send a series of Orion shuttles into space to build up to a manned mission to Mars.

The Orion mission has the ultimate goal of exploring Mars like never before, using the science and technology of satellites and spacecraft past while also containing some of the newest technology available.

The Orion craft is first set to launch under the title Artemis I and spend about six weeks shooting thousands of miles past the Moon. The Artemis I mission is in place to test the spacecraft, its technology, its aborting capabilities, and its capability of returning home safely. This check, while also collecting data from space, will ensure that the next mission Artemis II, is safe for humans to ride on and venture farther into space than any human has gone before.

Posted in Class | Tagged astro2110, blog 3, observing, space exploration, spacecraft | Comments Off

Hohmann Transfer Orbit

Posted on March 5, 2023 by aaronxu041009

In Andy Weir’s The Martian, NASA plans to send a supply probe to Mars to save the stranded astronaut Mark Watney through what’s called the ‘Hohmann Transfer Orbit‘. What exactly is the Hohmann transfer orbit? And when the carrying capacity of rockets is limited, why does a probe following this orbit saves limited and precious fuel?

This maneuver is proposed by German scientist Walter Hohmann in his 1925 book The Attainability of Celestial Bodies. This orbital maneuver requires two thrusts to bring a probe from a lower orbit to a higher orbit (see Figure 1 below). The initial thrust is Δv, which is preferably applied when the probe is at its periapsis (lowest point of its orbit). This initial thrust raises the apoapsis (highest point) of its orbit, and sends the probe to an elliptical transfer orbit. The second thrust Δv’ raises the periapsis of its orbit, allowing the probe to match and enter the desired, higher orbit.

Figure 1. Diagram for a Hohmann transfer orbit

If we wish to let the probe intercept an object at the higher orbit (in our case Earth and Mars), we have to take the relative positions of Earth and Mars, and the typical travel time of the transfer into account. For Earth and Mars, the window for the Hohmann transfer opens once every 26 months, and a spacecraft following this orbit takes 9 months to reach Mars.

Hohmann transfer orbits are typically applied when the amount of fuel a spacecraft can take is limited. If time is of the essence, a probe can reach Mars much faster if it is capable of producing more thrust. In reality, the Hohmann transfer orbit requires less thrust when considering the gravitational effects of the planets at the initial and final positions, as maneuvering through the gravitational well of a planet conserves momentum and saves fuel. Also, the Hohmann transfer orbit can be applied backwards, sending a spacecraft to a lower orbit around a common central object by reversing the direction of the thrust.

I am excited to see how space agencies will apply this maneuver when we decide to send people to Mars! Here are some links to the Hohmann transfer orbit and the Oberth effect (powered flyby).

Posted in Class | Tagged astro2110, blog4 | Comments Off

Earth and Us

Posted on March 5, 2023 by cuia2

I’ve always wondered how rare it is for Earth to exist and support life on it, and now I know that out of the billions of solar systems, Earth is the only planet we know of to support life on it currently. Earth had to be at just the right distance from the Sun for water vapor to condense and fall to the surface as rain. Earth had to be just big enough for volcanism and outgassing to produce an atmosphere and for its gravity to keep atmospheric gasses from escaping. Earth had to rotate just fast enough for wind and other weather to exist. Even with all that, we would still not be able to exist on Earth if it wasn’t for the fact that Earth is the only planet out of all terrestrial worlds to be shaped primarily by ongoing plate tectonics, which means we have a stable climate to live in. All in all, I would consider ourselves very lucky to be alive.

Posted in Class, Terrestrials | Tagged astro2110, blog3, earth, plate tectonics, Solar System | Comments Off

Chelyabinsk event

Posted on March 5, 2023 by andrewccascio

On the morning of February 15, 2013, an undetected meteor the size of a six-story building exploded over the city of Chelyabinsk, Russia. At 20 meters long, it reached speeds of 60,000 km/h before detonating with the force of a 500-kiloton nuclear bomb. Witnesses saw a flash brighter than the Sun before hearing a delayed seismic blast that tore down walls, shattered glass up to a hundred miles away, and injured over a thousand. Eye damage and burns from the intense ultraviolet radiation was also reported.

To put the blast into perspective, Fat Man, the nuclear bomb dropped over Nagasaki, had a blast yield of 21 kilotons. Were the meteor to make contact with the surface, the resulting damage would have been catastrophic.

This begs the question: Why wasn’t this meteoroid detected? According to NASA, the meteoroid was relatively small, and its path of impact came towards Earth out of the Sun. Asteroid telescopes have a brightness magnitude limit of +24, a scale such that higher magnitudes represent dimmer objects. The Sun has a magnitude of -27, for example. Together, these factors suggest that the meteoroid would not have been visible until only two hours before impact.

Posted in Class, Small SS Objects | Tagged astro2110, blog4, meteor | Comments Off

Blog 3 – Nuclear Fusion

Posted on March 5, 2023 by kevkoppa123

Nuclear fusion is the process of combining, or fusing, two or more small nuclei into a larger one, creating energy as a byproduct. Stars like the Sun constantly emit energy through nuclear fusion because their cores are filled with high-speed, hot plasma. More specifically, the Sun’s extremely hot core of 15 million K allows for nearly 10³⁸ fusion reactions to take place in the form of proton-proton chains where 4 hydrogen protons are converted into 1 helium, 2 protons, 2 positrons, and gamma rays. This reaction is only possible because the hot, high-speed plasma in the Sun’s core forces protons to fuse together to form a proton-neutron pair, employing the Strong Force and overwhelming the electromagnetic forces that separate positively charged particles. Nuclear fusion is different from nuclear fission, the process used by nuclear reactors to generate energy, because fission separates larger nuclei into smaller nuclei.

In the Sun, nuclear fusion combines deutrium with helium-3.

Posted in Class, Science | Tagged astro2110, blog3, nuclear fusion | Comments Off

Olympus Mons

Posted on March 5, 2023 by andrewccascio

Currently the largest known volcano in the Solar System, Olympus Mons stands at a remarkable 25 km high, which is almost 3 times the height of Mount Everest, and is wide as Arizona. Compared to the largest active volcano on Earth, Mauna Loa, Olympus Mons is 100 times larger in volume, a seemingly odd feat considering Mars is just over half the size of Earth.

Olympus Mons is a shield volcano. It was formed by “runny” lava that spread a far distance before solidifying, which caused very shallow slopes. This lava is a consequence of volcanism, the process in which underground molten rocks are pushed to the surface by surrounding higher density rock and internally trapped gasses. Similar to other volcanoes in the Tharsis region, Olympus Mons was able to amass a great size compared to volcanoes on Earth due to lower gravity and higher eruption rates. Mars also has limited plate movement when compared to Earth, meaning erupted lava tends to stay in a single spot.

The surface of Olympus Mons is relatively smooth compared to the rest of Mars. We can conjecture that the volcano must be somewhat young then, which supports the possibility that it may erupt again in the future. It also isn’t unique; there are three other similar sized behemoths neighboring Olympus Mons, collectively known as Tharsis Montes.

Posted in Class, Terrestrials | Tagged astro2110, blog3, Mars, olympus mons | Comments Off

The Moon Illusion

Posted on March 5, 2023 by sydneyastr2110

We saw a really cool picture of the Moon during class that was taken when it was near the horizon with an ancient Greek temple in front of it. The Moon looked unusually large, and I wanted to know more. The reason for the Moon appearing much larger when it is rising and setting is a result of an optical illusion. Its width is constant, but our brains essentially trick us into thinking that it is much larger when it is near the horizon. As stated in an article by NASA about this illusion, “it’s all in your head…an actual illusion, rather than an effect of our atmosphere or some other physics.” The article also talks about how to prove that the Moon is an illusion.

Interestingly, there is not really an explanation for why humans experience this illusion. Given how long humans have studied the Moon, this may seem like an unbelievable answer. However, there is a general idea which has to do with how far away our brains expect objects to be. According to the above NASA article, “our brains don’t know that the Moon’s distance doesn’t change that much no matter where it is in the sky on a given night.” These is also the potential explanation that the foreground along the horizon has to do with this which is described by the Ponzo illusion. For now, we will just have to be content with these partial explanations while still acknowledging that there is more to the story. The below picture shows how the Ponzo illusion relates to the Moon showing that with two identical objects, one can appear bigger due to a human’s sense of distance.

Image Credit: Time and Date, The Ponzo Illusion

Another noticeable feature of the Moon nearer to the horizon is the change in color. This is not an illusion, but rather a result of the distance the light illuminating the Moon has to travel through the Earth’s atmosphere. The longer the light has to travel, the more of the short wavelengths of light which are scattered. The longer distance is experienced at the horizon. Since blue has a shorter wavelength, it is scattered meaning the longer wavelengths which are redder will be left. This results in the Moon being orangish or yellowish closer to the horizon.

Posted in Class, Light, Observables | Tagged astro2110, blog4, earth, Moon, Solar System: Moons | Comments Off

All About Aurorae

Posted on March 5, 2023 by 7smessier45

As the title suggests, our topic for today is Earth’s aurorae (pronounced auh-ror-eye). These stunning displays generally occur in two symmetrical oval rings about the planet’s far northern and southern regions–Earth’s magnetic north and south poles. When they happen in the north, aurorae are often referred to as the northern lights or Aurora Borealis. Likewise, southern aurorae are called the southern lights or Aurora Australis.

(Southern) Auroral Oval, from NASA Image Library

How are they formed?

Coronal mass ejections, solar flares, and other features of solar weather can violently hurl electrically charged plasma into the void of space at speeds up to 2000 km/sec. Sometimes these ejections travel on a collision course with Earth which, in extreme cases, can wreak havoc on electrical and telecommunications systems. (Interested in learning more? Check out NOAA’s article on the 1859 Carrington Event.)

Fortunately, though, the Earth has a magnetosphere–shaped in part by the interaction of Earth’s magnetic field and solar wind–that protects the matter below from the effects of all but the most severe solar weather. Earth’s magnetosphere–like those of Mercury and the outer giant planets–occurs due to material spinning within its hot molten core. These conditions essentially turn the planet into a large electromagnet. Charged particles become trapped in the magnetic field lines and race along them to the poles (1), where they then interact with gasses in our atmosphere to produce aurorae.

Solar Weather and Aurorae, from NASA Image Library

Wait, what about the colors?

When the charged particles from the sun mingle with the gasses in Earth’s atmosphere, their interaction induces excitation. During this process, electrons impart energy to the gaseous atoms. When the electrons of the gaseous atoms return to a lower state, they release energy in the form of a photon–a particle of light. The color of the emitted light depends on the amount of energy released and the type of gas that was exited. In large concentrations–such as during aurora events–these emissions can be seen with the naked eye. The greenish-yellow hue that characterizes typical aurorae results from the oxygen in our atmosphere. Emissions from high-altitude oxygen create vibrant red aurorae. And nitrogen emissions cause blue and purple-hued aurorae.

Aurora Borealis as seen from the ISS, from NASA Image Library

Closing

If you made it to the end, congratulations! I’m aware of my aversion to short descriptions–it’s a problem that’s exacerbated when I’m excited about a topic. But I hope this post was informational! If you want to learn more or get involved in some citizen science, NASA operates aurorasaurus, where you can help filter and classify real tweets as (non)sightings of aurorae. Zooniverse’s aurora zoo is another cool citizen science opportunity where you can help classify features of auroral images and videos for use in further scientific research. (It’s also a great way to procrastinate while still feeling productive!) Let me know if you’ve ever seen the aurorae in person or if you decide to participate in either aurorasaurus or aurora zoo.

Until next time,

7smessier45

Posted in Class, Historical, Observables | Tagged astro2110, atmospheres, blog3, earth, Magnetosphere, NASA, Solar System | Comments Off

Will The City of Angels Join The Angels? (Los Angeles Tectonics)

Posted on March 4, 2023 by Alex Diefenbach

Image Source: https://images.app.goo.gl/ndxgiuzkinyLpxyZ8

The media, especially in recent years, has depicted that in the foreseeable future Los Angeles might break off of California and sink into the Pacific Ocean. Not only that but they also allude to the idea that this doomsday for the City of Angels may be completely impromptu as well.

It is no secret to most people that California is infamous for its earthquakes. This is because California itself actually lies on top of different tectonic plates: The North American plate and the Pacific Plate. Due to Earth’s volatile and hot interior, these tectonic plates on its surface are very active and tend to shift around, unlike those on colder planets and satellites.

There actually is a somewhat visible boundary between the Pacific and North American plates. It is a fault line whose name you likely have already heard from the 2015 flick, “San Andreas”. When these two plates shift against one another, their friction causes seismic disturbances which humans experience as earthquakes.

Tectonic plates can shift in an array of different fashions. So the notion that Los Angeles may end up 20,000 leagues under is not completely unfounded in science but it fails to take into account the actual directions California’s two particular plates are heading which is the crux of the issue.

Image Source: https://images.app.goo.gl/331WTdfdsM1yQXKN6

California’s two plates are shifting roughly parallel to one another. Not only is this evidenced by earthquakes being its primary form of seismic activity but also scientists have measured it to be so. Both plates are moving northwest, but the Pacific Plate is doing so at a higher rate; said scientific measurements have revealed that the movement along the San Andreas fault is approximately 1-2 inches each year.

This means that provided that no global calamities happen before, in 16 million years, Los Angeles and San Francisco will be adjacent to one another. That’s going to be some megatropolis.

Posted in Physics, Universe | Tagged astro2110, blog3, me | Comments Off

The Intersection of Religion and Science: God’s Plan

Posted on March 4, 2023 by Alex Diefenbach

Image Source: https://images.app.goo.gl/ED9iiXG9qQeWhL3K7

Throughout history and into today the theories of religion and science have clashed, however, there is an idea about humanity that is bipartisan. While religion and science typically have different explanations of what may be working to create it, both dispute the existence of a free will. According to the theories of both divinity and the Big Bang, the natural world has a script of sorts that it will follow from its beginning to end.

The majority of theistic religions have somewhere in their gospels that the creator is the ultimate puppeteer of the natural world. These schools of divine thought usually also state that humans have the ability to do as they wish at their disposal but their respective deity is omnipotent. This means that from the very beginning of the creation, god knew how everything was going to pan out from start to finish. And although branches of divinity such as Deism may propose that god took a hands-off approach after the creation was finished, this does not signify that god was oblivious to what was to happen afterward. It just means god created a machine with a set of instructions on how it should maneuver the marionettes and now god is watching sitting back to watch the play.

In the realm of science, the Big Bang is thought to have ejected colossal amounts of matter and energy out all over space and all events that have ensued in the history of the universe have been a result of this incident. Some of these effects of the Big Bang are more immediately attributable to the beginning, such as the apparent expansion of the universe, while others are more complex, such as how the exact conditions needed to form life became co-present.

The idea of free will likely evolved from humans’ inability to perceive the results of their actions over immense periods of time. Especially since succeeding events appear to be the result of collective actions; not just the sole influence of the individual actor in question.

But regardless of whoever or whatever the Geppetto of the natural world may be, what we know about physics— the programming language of our universe’s fabric, alludes to the idea of our time’s arrow being cast and having a definitive trajectory.

Posted in Physics, Universe | Tagged astro2110, blog4 | Comments Off