We all know the controversy that Pluto causes. Should it be a planet? Should it not be one? Why should or shouldn’t it be?
Although astronomers and other scientists claim that Pluto should not be considered a planet, some researches believe that this decision was unfair and incorrect and that we should reconsider Pluto to be a planet in our solar system.
So why isn’t Pluto considered a planet? Well, according to Tom Metcalfe, a Planet must have three requirements: 1. Must be spherical, 2. Must orbit the sun, and 3. Must have gravitationally “cleared its orbit” of others planets. Pluto fulfills 2/3 of these requirements, but it does not fulfill the last requirement. Pluto shares its orbit with other objects (“plutinos”).
So if this is true, and Pluto does not fulfill the requirements for having the title of a planet, then why do researchers believe that Pluto should be considered a planet again? These researchers state that a previous definition, created in the 16th century, of a planet being “any geological active body in space”. But if this definition was used to classify “planets” rather than the previous three requirements, this would mean that over 150 objects in our solar system would be our “planets”.
So many things need to be considered before making this decision. Will Pluto become our 9th planet again, or will it stay outcasted as just a Dwarf Planet?
In class, we learned about various categories of exoplanets, including Super-Earths, terrestrials, ice giants, gas giants, and hot Jupiters. One other category that was mentioned was “water worlds,” an ill-defined and not entirely proven category of planets. This category would describe planets that are on the border between terrestrials and ice giants, or terrestrial worlds right near the frost line.
I did some more research into water worlds and found the Wikipedia page for “ocean worlds.” However, this isn’t necessarily exactly what I was looking for–the page describes a planet that contains a significant amount of water in the form of oceans, either subsurface or on the surface of the planet. This is not a very narrow definition–it includes Earth, with our surface oceans, and some icy satellites, like Europa and Enceladus. While the latter two are exciting prospects for life due to the presence of water and recent geological activity, they don’t fit the definition of water worlds that I was looking for.
I read on and found a more narrow discussion of one type of ocean worlds. To preface, water accounts for only 0.05% of Earth’s mass. Imagine an exoplanet with a much higher percentage of water–if the ocean is deeper and denser, the pressure could be extremely high at the bottom. Think about how much pressure you feel in your ears when you swim to the bottom of a diving well–that’s about 12 feet. Earth’s ocean gets to almost 7 miles deep. The exoplanets Kepler-138 c and Kepler-138 d appear to have oceans 1,000 miles deep.
An illustration comparing the interior of Earth, with its thin oceans, to the potential interior of Kepler-138 d, with its predicted thicker oceans. (Source)
At such immense pressures, ice could exist, even at the high temperatures of a planet’s interior. One form of ice that can form under these conditions is ice V (read “ice five”), a specific crystalline phase of water with a notably complicated molecular structure. Ganymede is thought to have such ice at the base of its potential liquid water ocean. Ice V could make up the mantles of such ocean worlds.
The structure of ordinary ice, ice XI. (Source)The structure of ice V. (Source)
Taking this a step further, what if the ocean world is close enough to its star that water reaches its boiling point? The water would become a supercritical fluid, which means that it is at a temperature and pressure above its critical point but below the pressure required to compress it into a solid, and thus distinct liquid and gas phases do not exist. The exoplanet would lack a well-defined surface. The atmosphere would be thick and mostly water vapor, leading to a greenhouse effect.
The pressure vs. temperature graph for water, showing the supercritical phase at high temperature and pressure. (Source)
Such exoplanets must not be very massive or must be close to their star. Otherwise, they would have retained a thick atmosphere of hydrogen and helium, making them more similar to their cousins–ice giants like Uranus and Neptune.
While this line was a comical hit in the box-office hit “The Martian,” it also emphasizes a particular problem that we are experiencing as we explore new worlds. It is very heavy, cumbersome, and expensive to send all the food we need on space missions, and for a prolonged colonization mission, it just isn’t feasible. Therefore, the strategy is to use the field of astro-botany to farm food for the colonization missions.
There are a number of problems with farming in space, whether it be on space stations or on other planets. Firstly, in conditions where gravity is absent or extremely low, water behaves in funky ways. Cohesion and adhesion has more power relative to the force of gravity. (See this video to see an example). It’s difficult to provide the plants with the correct amount of water if water isn’t behaving in a predictable manner, so specialized irrigation techniques are necessary.
Another problem is that plants are evolved to Earth. They have not developed in the lower gravity’s of other planets, nor the lack of gravity of space. This may not be a huge problem, or it may cause plants to lack effective development, affecting their methods of gravitropism. Current tests in the ISS are looking at genetic modification of these plants to change their levels of lignin, which gives plants their stiffness. Ultimately, it remains to be seen if this will cause significant problems on our celestial plants.
There are even more problems with obtaining the necessary resources for growing plants. Sunlight, water, atmosphere, and nutrients are all needed. Firstly, plants are evolved to receive specific wavelengths on Earth. Different types of light reach planets’ surfaces in different quantities due to the varying compositions of their atmospheres. But this likely isn’t too big of a problem, especially with the use of artificial light or greenhouse roofs that screen the excessive harmful wavelengths.
A bigger problem is our old friend dihydrogen monoxide. Water is difficult to obtain, as it is far too dense to take into large quantities into space. Currently, the ISS uses recycled water from the urine, sweat, and showers, but since that is just being used for drinking and other small tasks, it is extremely cyclical with very little being removed from the system. But plants need lots of water, so they would be a massive drain on the cycle. Thus, we’d need to produce more water than we bring to a new frontier in space. This can be done in several ways: first of all, the ISS is trying out a new advanced Sabatier system. This will turn the hydrogen and carbon dioxide waste of the space station into methane and water, which will help the ISS to reduce waste and provide more water for the astronauts. On a planet like Mars, this is an option, but there is another one as well. The soil is about 3% frozen water, with more ice content being found below the surface. This ice can be extracted and turned to liquid water for human (and plant) use.
For soil nutrition, scientists have been developing new ways to garner the necessary nutrients for the plants on other worlds. Like water, it isn’t feasible to send tons of Earth dirt to other planets, so we have to use the soil we find there. The problem is, most of these soils lack any “nutritional” value. Soil without any nutrients can not provide support for plants. Furthermore, Martian soil, for example, has toxic chemicals like perchlorates which can even be harmful if we can consume, posing another barrier to effective farming. Yet we have made some headway. Cyanobacteria were shown to be able to survive harsh radiation from space, similar to what they’d experience on Mars. Their interaction with regolith on Mars could provide nutrients for the plants in the same soil.
Astrobotany is an emerging science as we approach our goal of colonizing Mars. Having the ability to grow crops on another planet frees up room on a rocket for other equipment and supplies, as well as bringing a more balanced diet to the astronauts. It is certainly very interesting the ways that space explorations makes us think of possibilities we had never before thought of.
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I used measurements from Halley’s Comet for the impact homework, so I wanted to learn more about it. It certainly has name recognition, but I wanted to learn more about it. I found some great information from NASA that I figured I would share.
Halley’s Comet is named after an astronomer by the name of Edmond Halley. He figured out by using theories of Isaac Newton along with previous orbits of comets in 1531, 1607, and 1682 that the comets were one comet. Under this assumption, he predicted it would next be visible in 1758. His prediction was correct which resulted in the comet being named after him.
This marked the first time that a correct prediction was made for the return of a comet. This turning point in understanding comets made Halley’s Comet even more notable.
Halley’s comet is set to return in 38 years, 3 months, and 19 days from now given its orbit period of about 76 years and its latest appearance being in 1986. The image below shows the comet which is rather dark given its lack of reflectivity. This image is special in that it was the first spacecraft encounter with the comet which occurred by the Giotto spacecraft.
Image Credit: Halley Multicolor Camera Team (1986), Giotto Project, ESA, from NASA Photojournal
Interestingly, this comet has be orbiting for at least 16,000 years, and while a comet’s lifetime normally extends to 1,000 trips, Halley’s Comet does not appear to be reducing in size meaning we can expect it to be around for quite a while.
When I was in 6th grade, I participated in a summer engineering competition called Zero Robotics through MIT. The objective was to create a code that would allow for droids aboard the International Space Station (ISS) to take pictures of research targets the most efficiently. In the process, however, we also got the opportunity to learn about what life is like aboard the ISS for these astronauts and we even got to Skype and hear their own accounts as well.
As you can imagine, there are many obstacles that these astronauts face by living far above the Earth’s biosphere and in a place with significantly reduced gravitational force. One of these principal caveats to the privilege of doing research in space is disruptions to normal bone density.
The human skeleton has two primary cellular mechanisms to maintain bone density. Osteoblasts and Osteoclasts. The former generates new bone tissue while the latter breaks the old tissue down. In order for Osteoblasts to continue their production of normal Osteocytes (typical bone cells), they must be subjected to pressure and weight: the kind they’d receive from the strain of gravitation on the body during everyday life on the surface of the earth.
However, as aforementioned, the forces of gravity at the altitude of the ISS are not nearly as strong as at the surface. See the law of gravitation here to understand the mechanics and mathematics of why exactly this is. This means that Osteoblasts are not receiving the normal amount of stimuli that trigger the continuity of bone cell generation. The Osteoclasts on the other hand, still continue their typical function of breaking down osseous matter. Leading to approximately a 1.5% bone density loss for every month spent in space, according to NASA.
To compensate for this, scientists researching aboard the ISS take “Bisphosphonate”: a medication used to treat bone density disorders such as Osteoporosis, in conjunction with calcium and mineral supplements. But one of their most used methods of maintaining their bone density is one used on Earth: exercise. The astronauts which we got to speak with on Skype at my engineering competition showed us several pieces of exercise equipment, variations of ellipticals and/or treadmills being some if I am remembering correctly. The strain from rigorous exercise the astronauts participate in helps to stall bone degeneration but this technique is not just for space people, a healthy exercise regimen provides the same benefits on the blue planet’s surface as well.
Pluto, known as the ninth planet of the solar system, was reclassified as a dwarf planet in 2006. Pluto is one of the most interesting objects to study in our solar system. In this blog test, I will discuss the biggest moon Charon and the discoveries of the New Horizons spacecraft.
One fabulous thing about Pluto is that it has five moons but I will be only talking about the biggest one—Charon. Astronomer James Christy found Charon in 1978; it is Pluto’s biggest moon and the largest known satellite in terms of its parent planet. Christy spotted oddly elongated photos of Pluto and found that the elongation cycled back and forth over 6.39 days, which is the length of Pluto’s spin. Other photos of Pluto from years earlier that supported his discovery of the first known moon of Pluto were later uncovered by him. The fact that Charon is approximately half the size of Pluto and that their surfaces always face one another is known as mutual tidal locking. Every 6.4 Earth days, Charon orbits Pluto, and like Uranus, Pluto, and Charon are also tipped on their side. Pluto and Charon were captured by the Hubble Space Telescope in 1994. This telescope showed that they have different surface compositions and structures.
Additionally, further secrets about Pluto were revealed in 2015 when the New Horizons spacecraft passed by the planet and took detailed pictures and data about it. It showed Pluton surface characteristics: large ice mountains and an area with a heart-shaped form. Also, the presence of cryovolcanoes and a potential subterranean ocean was further evidence of active geology discovered by the probe.
Hello (again), and welcome (back) to my Astronomy Blog! Today’s post is about the Kuiper Belt and its objects.
What is the Kuiper Belt?
The Kuiper (Kai-per) Belt is a donut-shaped region beyond the orbit of Neptune. Within the Kuiper Belt, it is estimated that millions of icy objects (or even trillions of these objects, according to some estimates) orbit the Sun from a distance of 30-55 astronomical units. (One astronomical unit–or 1 AU–is the distance from the Earth to the Sun.) And although this region was first proposed by Gerard Kuiper in 1951, it was not confirmed until Dave Jewitt and Jane Luu discovered an object beyond Pluto’s orbit (44 AU) in 1992. Some of the best-known Kuiper Belt Objects (KBOs) include several dwarf planets, like Pluto and its moon, Charon. Other well-known KBOs include short-period comets (those with orbital periods less than 200 years) like Halley’s Comet.
Studies of the Kuiper Belt, and the objects within it, are incredibly important because they help inform and expand scientific understanding of planetary formation and our solar system’s formation. Presently, the Kuiper Belt is thought to include remnants of the early solar system and was formed approximately 4.6 billion years ago. Additionally, astronomers believe the objects in the Kuiper Belt could have become a planet in the absence of Neptune’s gravitational influence.
A quick note regarding terminology
Although the Asteroid and Kuiper Belts share many similarities, it is important to know that the objects comprising the respective belts have different compositions and names. Objects orbiting in the asteroid belt–roughly located between Mars and Jupiter–are primarily made of rocks and metals; we generally call these objects asteroids. KBOs, in contrast, are predominantly comprised of ice–including methane, ammonia, and water ice.
Stay tuned for the next post to learn more about how the New Horizons mission has enabled us to gather data about Pluto and the Kuiper Belt.
The shimmering curtains of color that make up the Northern Lights are incredibly fascinating. For many (myself included), it is a life goal to get to witness this phenomenon in person.
The name Aurora Borealis has its roots in classical mythology. Famous astronomer Galileo Galilei combined the Roman goddess of the dawn, Aurora, with the god of the northern wind, Boreas. The lights also find themselves as playing in important role in oral history for many different cultures; for example, the Dene people believed that reindeers originated in the Aurora Borealis.
Despite this shroud of mythology and curiosity, scientists are confident in the cause of the Northern Lights!
Rather than the calm before the storm, aurora is the light show after the storm in space.
The sun is incredibly volatile (shocker, I know), and its chaos can create some disturbances that affect Earth’s magnetic field. These disturbances pull on the field like its a rubber band, and the recoil that results from the pull being released creates powerful ripples called Alfven Waves. These waves, created 80,000 miles from the ground, accelerate towards the Earth’s surface. Electrons ride Alfven Waves until they hit the thin upper atmosphere, where they collide with Nitrogen and Oxygen particles, get excited, and eventually calm down and release light. These resulting light emissions are what we know as the Aurora!
Your best chance of seeing these lights in person is close to one of Earth’s magnetic poles (different than the North and South geographic poles) when there is high visibility and it’s dark out. Have you ever been lucky enough to see Aurora in person? If you’re like me and you haven’t, I hope that someday you do!
Comet NEOWISE near Mt Washington in 2021 (from the New York Times)
The terms ‘asteroid’ and ‘comet’ are often used interchangeably, but in reality there are important differences between the two! The primary difference is in their composition; asteroids are rocky because they formed in the inner Solar System, and comets are more icy because they formed beyond the frost line!
Comets are visible every few years and appear with long, streaking tails. I, for one, did not realize how common comets actually were, but in doing my research for this blog post I found dozens of articles from the last few years about different sightings. I had only known about comets because that was my high school mascot!
Comets have played an important role in different cultures throughout history. The Babylonian “Epic of Gilgamesh” believed a comet to be the harbinger of tragedies, and ancient Mongolian legend thought that destruction was bound to accompany comets. Specifically in Hinduism, they played a dual role, representing not only good and regularity but also evil and disruption.
There has been an incredibly interesting and exciting discovery made recently! The James Webb telescope has discovered and photographed an exoplanet and collected data to validate its existence as an exoplanet. An exoplanet is an astronomical object that classifies as a planet but orbits a star other than our lovely Sun! This discovery and validation is not only interesting for the fact that it exists outside our solar system, it is incredibly similar to our own Earth in size. The Webb found that this exoplanet, professionally labelled as LHS 475 b, is 99% the size of Earth in diameter, and it is a rocky world much like our own. Very unlike our Earth, however, this exoplanet has an orbital period of 2 days around its star! The Webb distanced this exoplanet at about 41 million light years away, so it is very cool that such a similarly sized planet is so close!
Unfortunately for followers of the question of if there is another livable planet out there, this one is not looking too habitable. It has not been ruled out, but its atmosphere seems to be very methane-based like Saturn’s moon Titan!
I certainly did not know all this! I was taught a lot of this by NASA!
