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Let’s Talk about Aliens
I don’t know about you, but thinking of aliens brings up images of UFOs and bright green skin, bulbous heads and an echo of “Take me to your leader.” However, this representation of extraterrestrial life is simply something made up by Hollywood and pop culture. As far as we know, Earth has never been visitedContinue reading "Let’s Talk about Aliens"
Posted in Aliens
Tagged astro2110, blog6, drakeequation, extraterrestrials, fermiparadox
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An Important Musician In Astronomy
Many will remember William Herschel as the one who found planet Uranus. This founding was shocking and revolutionary. After all, Uranus was the first star found by humans for a long time. Nevertheless, there are many more interesting things one can say about William Herschel. For one, he did not train to be an astronomer. His father was a musician for army, and William Herschel followed his father’s footsteps to be a musician. His early life was tumultuous as he had to feel his fatherland of Germany to England. His talent in music allowed to him to quickly to earn a career in England. However, his curiosity pushed him further. William Herschel started to be interested in telescopes and observations of the sky. He did not satisfy himself with simply observing objects that were close to the Earth. Instead, he was determined to see further. Therefore, he began to make his own telescopes. After much effort, he was able to make telescopes that were more powerful than some observatories. With a superior size, his telescope offered him higher resolution and more magnifications. It was this telescope that enabled him to find Uranus. He thus decided to become a professional astronomer at the age of 43. His dedication for astronomy was unparalleled. He tried to observe every night. When weather conditions were not optimal, he asked a watch man to wake him up as soon as weather cleared. Such dedication combined with his ability to make high quality telescopes allowed him to record abundant data. Therefore, besides finding Uranus, Herschel also observed binary star systems. He spent much time watching star nebulae and proposed ideas of star clusters and island universes. He was indeed a very important figure in the history of astronomy.
Source:https://www.britannica.com/biography/William-Herschel
Posted in Class, Historical
Tagged astro2110, blog5, history
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Extremophiles, and What They Mean For Life in Space
Extremophiles are organisms on Earth that thrive in extreme environment that most other organisms wouldn’t be able to survive in. They are found in places that at a glance, seem unlivable, places like inside volcanoes, or deep in the ocean under extreme pressures. So why do these extremophiles matter when thinking about space? The idea of biological organisms surviving in intense conditions changes how we think both about the possibility of life in our universe, and life in general. Recently, scientists in Ontario have extracted water samples that they believe to have not been changed in around two billion years. As they examine this water, one of the prime things they will look for is extremophiles, to determine either how something could survive, or trying to determine if there is an “antibiotic line,” or conditions which simply no life can survive. When thinking about extremophiles in space, it’s interesting to see the possibilities. Scientists have exposed extremophiles to the vacuum of space, and they have survived, which was a shocking development, and expands where we think life could be. Different moons on Jupiter and Saturn that previously we might have assumed couldn’t sustain life, we now realize have a higher chance, since it’s been proven that some life can exist even in extreme conditions. Extremophiles are at the cutting edge of how life can exist, and thus have huge implications for what life could look like in our own solar system.
Posted in Class, Galaxies, Moons, Stars
Tagged astro2110, blog6, jupiter, life, life in space, planets, pluto, Solar System, space, Uncategorized
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So Where Are the Aliens?
Our galaxy should be teeming with civilizations, but where are they? If we imagine that we would be able to survive long enough to become interstellar travelers, and that we begin to colonize habitable planets around nearby star systems, we would have dozens of outposts around nearby stars within a few centuries. We would be spread out to hundreds of light-years beyond Earth in 10,000 years and become a galactic civilization within a few million. With this idea, we are then led to an astonishing conclusion: there should already be a galactic civilization, yet we have found no evidence of such a civilization thus far.
This is the Fermi’s paradox, named after Nobel Prize-winning physicist Enrico Fermi, that highlights the apparent contradiction between the lack of evidence for extraterrestrial intelligence and various high estimates for their probability. If we decide that the chances of a civilization arising around a star are about 1 in a million, about the same as one’s odds of winning the lottery, then with a low estimate of 100 million billion stars in the Milky Way Galaxy, this would mean around 100,000 civilizations in our galaxy alone. Additionally, stars and planetary systems like our own could have formed billions of years ago, so even at the slow pace of currently envisioned interstellar travel (this doesn’t matter as any halfway reasonable assumption about how fast colonization could take place still ends up profoundly shorter than the age of the galaxy), most these civilizations would be millions or billions of years ahead of us.
Broadly speaking, there are three possible solutions to this paradox: 1) we are alone – there is no galactic civilization because it is extremely rare and our civilization is a remarkable achievement, perhaps even the first in the universe, which makes humanity all the more precious. 2) civilizations are common, but no one has colonized the galaxy. This could be due to a number of reasons, but if thousands of civilizations before us failed to achieve interstellar travel on a larger scale then what hope do we have? 3) there is a galactic civilization, but it has not yet revealed its existence to us. This solution seems to be the most intriguing as we could be the newcomers on the scene of a galactic civilization and when the time is right, be invited to join. However, we must be able to survive long enough, as it is only then can the possibilities be almost limitless.
The Drake Equation
The Drake equation, also known as the Green Bank equation, is used to yield the number of technically advanced civilizations in the Milky Way Galaxy. The equation uses astronomical, biological, and psychological factors to determine this number. The formula was first discussed in 1961 at a conference on the “search of extraterrestrial intelligence”, formulated largely in part by astrophysicist Frank Drake.
The formula states: N = R*fpneflfifcL.
R* is the mean rate of star formation in the galaxy; fp is the fraction of stars with planetary systems.; ne represents the number of planets in such systems that are ecologically suitable for the origin of life; fl is the fraction of such planets on which life in fact develops; fi shows the fraction of such planets on which life evolves to an intelligent form; fc is the fraction of such worlds in which the intelligent life form invents high technology capable at least of interstellar radio communication; and L, shows the average lifetime of such advanced civilizations.
The correct number for each factor is poorly known, and the uncertainty of each variable only grows across the equation. However, the most widely quoted values for each factor are R* = 10/yr, fp = 0.5, ne = 2, fl = 1, fi fc = 0.01. According to these numbers, N should equal 10. Following this, if civilizations destroy themselves within the decade of achieving radio astronomy, then there are no other intelligent life forms in the galaxy with whom we can communicate.
Comets: where do they come from?
A comet is made of a nucleus (inner core), coma (cloudy envelope around the nucleus), and then a tail. Where exactly do these beautiful, fast-moving cosmic snowballs come from? Scientists are able to trace comets that we see in the inner solar system by retracing their orbits. Through this, scientists believe that comets come from two distinct reservoirs: long-period comets from the Oort Cloud and short-period comets from Kuiper Belt. (A long-period comet is one that takes more than 200 years to complete an orbit around the sun and a short-period comet is one that takes less than 200 years).
The Oort cloud is a theoretical gigantic cloud – found at the outer edges of the solar system beyond Pluto – made of icy planetesimals. Scientists have stated that there could be more than a trillion comets within this cloud. Because of this, it may make up a significant portion of our solar system’s mass. Furthermore, we do not have direct evidence that this cloud exists because it is so far away. Our fastest space probe, Voyager 1, will reach the cloud in ~300 years and it will take another 30,000 years to travel through it!
The second home of comets, the Kuiper belt, is a circumstellar disc that is past the orbit of Neptune. Pluto was actually the first object that was discovered in the Kuiper Belt! The belt contains a vast number of icy bodies which become comets. It is far away, but the Oort Cloud is even further!
How Life Could Start and Exist on Europa
Although our understanding of the evolutionary process is deep, the exact time and process through which the first life forms on Earth arose is still not entirely clear. The panspermia hypothesis speculates that life exists throughout the universe and is distributed through asteroids, comets, and space dust, and that life on Earth was brought from somewhere else. Though this is nearly impossible to prove, the presence of organic compounds on asteroids and interstellar dust show that at the very least, these building blocks could have been brought to Earth from outer space. The prevailing theory, however, is abiogenesis; how we transitioned from organic compounds to life that is self-replicating. In 1952, Stanley Miller and Harold Urey ran an experiment in which a spark (serving as lightning) was conducted through simulated conditions thought to be present on the early Earth. This resulted in 11 (later found to be 20) amino acids were formed through this process, showing that complex molecules can spontaneously form through the addition of external energy.
We already know that extremophiles can be found deep in Antarctica’s lakes, which is the nearest comparison to Europa’s 100-km deep liquid ocean that we can find on Earth. If there are already organisms that exists on this moon (and are possibly similar to the archaea on Earth), how could angiogenesis be possible? Since there is no atmosphere on Europa, the same electric energy simulated by the spark would not be possible – or could it? Jupiter’s electric field is so large that it reaches its moons, and Europa displays a frozen record of strikes by Jupiter’s thunderbolts in the recent past. The gas giant’s thunderbolts prefer to run across the surface of its moon rather than through the near-vacuum of space. Additionally, research from 2000 found that sparks ran through conditions that simulate Europa yield adenine and guanine, as well as a simple set of amino acids dominated by glycine. We are far away from sending a probe into the liquid ocean of Europa, but hopefully when we do, at least some microorganisms will be waiting for us.
How Big Can a Planet Get?
Jupiter is big. Not only is it the biggest planet in our solar system, but it is large enough to fit all the other planets in the solar system inside of it. However, Jupiter is not as dense as Earth, and even though it can fit about 1,300 Earths inside of it, it is approximately 318 times as massive as Earth. Is Jupiter’s size – or more importantly its mass – pushing the boundary for what is considered a planet? This question is complicated. Scientists believe that the mass requirement for deuterium fusion, in which a deuterium nucleus (a hydrogen nucleus with a neutron) and a proton combine to form a helium-3 nucleus, is about 13 times the mass of Jupiter. Celestial objects that are this large are classified as “brown dwarfs,” and are unable to sustain nuclear fusion of ordinary hydrogen to helium in their cores. For this to occur, a star must have a mass 65-75 times that of Jupiter.
Planets that are below brown dwarf size are referred to as sub-brown dwarfs or planetary-mass brown dwarfs. Observationally, it is difficult to distinguish between a sub-brown dwarf and a massive exoplanet (sometimes called a super-Jupiter), but they are formed through different processes; sub-brown dwarfs are formed through the collapse of a gas cloud like brown dwarfs and other stars, while super-Jupiters follow classical gas giant formation. The most massive sub-brown dwarf that has been observed (and is very unlikely to be a brown dwarf) is OTS 44 located 550 light-years away from us. It is eleven and a half times as massive as Jupiter, and likely has a circumstellar disk of dust and particles of rock and ice that is about ten times as massive as Earth. Based on NASA’s exoplanet archive, the largest super-Jupiter observed so far is HD 100546 b, an exoplanet 320 light years away from us who’s radius is 6.9 times that of Jupiter.
Life on Europa?
When considering the likeliest hosts for extraterrestrial life in our very own system, Europa surely is near the top of possible candidates. One of Jupiter’s 79 (!) moons, it possesses the smoothest surface of any celestial body in the solar system. Because of this and imaging from probes, scientists have hypothesized that Europa has a vast subsurface saltwater ocean about 100km thick covering the entire planet. This has led to discussion about the strong possibility of life evolving here; life could exist in a manner similar to deep sea hydrothermal vents on Earth. Additionally, clay-like minerals have been found on Europa which are strongly connected to the proliferation of organic life. The multiple contributing factors to the possibility of life on Europa have led to countless different theories on the nature of life on Europa. Could it be hydrothermal vent dwelling organisms? Or perhaps plankton-like creatures closer to the surface? Or maybe an entirely new form of life that has arisen from processes extremely different to those on Earth? The exciting possibilities of Europa’s ocean has ensured funding for many missions in the near future, which hopefully will provide us with more answers.
Why isn’t Pluto a planet?
Contrary to what Jerry Smith says in Rick and Morty, Pluto is not a planet. But why did Pluto lose this designation in 2006? The International Astronomical Union has 3 main criteria to determine what is a planet and what is not. These three criteria are: having an orbit around the sun, having sufficient mass to maintain a hydrostatic equilibrium (creating a round shape), and clearing out the space around its orbit. The main reason why Pluto is now considered a dwarf planet is because Pluto only meets two of the three criteria. While Pluto does orbit around the sun, and has enough mass to assume a spherical shape, it has not cleared out the space around its orbit. To clear out space around a planet, it must become gravitationally dominant. When a planet becomes gravitationally dominant in an area of space, it means that there are no other objects of comparable mass in the area other than a planet’s satellites. In Pluto’s case, there are objects in the Kuiper belt within Pluto’s vicinity called plutinos that are also comparable in mass. Because of the discovery of these plutinos, Pluto was downgraded to the status of dwarf planet.
Picture Source: Business Insider