If you have participated in observing for class, then you have seen through a telescope the Orion Nebula. Nebulae are star-forming regions that when studied can tell us lots about how stars and solar systems come to be, and the Orion Nebula is no different. When we look at the Orion Nebula through a telescope, four bright stars called the Trapezium are visible. These are relatively young stars that have been formed from the gravitational collapse of dust and gas within the nebula and are very massive at 15-30 times the mass of our sun. However, these are just a small fraction of the stars being formed in the nebula: the nebula is truly massive in scale.
In addition to observing star formation, images of planet-forming regions around stars have been captured in the Orion Nebula. Images such as those shown below help scientists understand how our own solar system was born and to continue to test theories of planet formation.
Protoplanetary disks located inside the Orion Nebula where planetary formation is likely occurring
The Martian originated as a book written by Andy Weir, then was adapted into a movie which was directed by Ridley Scott. The book and the movie prided themselves on being scientifically accurate. In fact, when Andy Weir was first writing the book, he published chapters on his blog, and adjusted them based on the feedback of scientists reading them.
In fairness to the writers, many of the events in the movie, like the gravity assist around Earth and Mars, or Mark being able to survive a brief, partial depressurization of his helmet are all scientifically valid; however, the science breaks down as soon you start looking into the variation of the atmospheric pressure on the planet.
The storm that sparks the initial conflict of the story, while necessary to the plot, is actually impossible in Mars’s thin atmosphere. In fact, the strongest Martian winds amount to a light breeze. Definitely not something strong enough to tip over a spaceship. What’s more, if the Martian atmosphere really was thick enough to cause the damage seen by the storm, then the entire ship modifications used to make Watney’s ascent vehicle would be impossible due to the increased drag it would feel.
Also, Mars has about one tenth the mass of Earth, and therefore gravity is far less on the red planet; however, Watney is rarely shown moving as such in the movie.
Even with these exceptions, both the book and its film adaptation have been praised for their commitment to scientific accuracy. (Wikipedia)
On a personal note, The Martian and its explanation of the scientific concepts behind the story is the main reason that I fell in love with outer space and am pursuing a mechanical engineering degree.
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In discussing how planets and stars form, one will quickly find the nebular hypothesis — an idea that stars and the planets that orbit them were formed from clouds of gas called nebulae. But how was this nebula first formed, where did it come from, and what are the different types of nebulae?
A nebula is simply a cloud of gas with a density of about 100 too 10,000 atoms per cubic centimeter. In comparison, the Earth’s atmosphere has about 2.5×1019 atoms per cubic centimeter (at surface level). Most are composed of hydrogen and sometimes emit a reddish spectrum, but other elements such as oxygen have also been seen (oxygen emits a greenish-blue color depending on temperature).
Nebulae appear from the collapse of stars, or if an extensive amount of time is given, nebulae can form from the clouds of ‘space dust’ that clump together. In the former, not all stars form nebulae in the same way:
Object formed vs. Stellar mass. Depending on the mass of the star collapsing, it can form a variety of stellar remnants.
For a star ranging from about 100 to 250 solar masses, it may be subject to Pair Instability, a phenomena in which electrons and positrons are produced, giving way to the gravitational collapse of the star. If such an event occurs, neither a black hole nor neutron star will be formed, instead, the star will obliterate itself completely, leaving a large nebula behind.
For a nebula to form from cold gas, an immense amount of time is required. These ‘space clouds’ will travel throughout the universe, subject to the gravitational pull of nearby objects, which will sometimes alter the nebula just enough to begin star formation if enough matter has accumulated.
On October 15th, 1997, the rocket carrying the Cassini Spacecraft and its Huygens probe took off from Cape Canaveral. It was sent to the outer solar system to study Saturn, as well as its moons. The Huygens probe was deployed to one of these moons, Titan, recording images and data. In 2017, after running out of fuel 20 years after deployment, the spacecraft was sent into Saturn’s atmosphere to prevent disturbing its moons. Below are some of the images captured by Cassini in its lifetime.
In this picture captured by Cassini in the second half of its mission, Enceladus, a notable moon is in the foreground with Pandora, a smaller moon, in the background.
This image captures Enceladus more than a year later, clearly showing fractures on its surface. Additionally, this picture shows the jets emitted from the surface of the moon.
The creation of our planet, the Earth, was achieved by the forces of gravity over millions of years, melding together different rocks into a sphere. This process, known as accretion, let the Earth grow into the size it is today, with the help of Thea, a large planet that turned into our moon.
These rocks were not all uniform in composition, with some being silicate rocks and others were icy rocks. Some were even metal. During the formation of Earth, the materials inside the planet shifted in a process known as differentiation, where the denser materials shifted down into the core while the less dense materials shifted up to the surface. It is just like oil and water being mixed together then separating after time. This is the reason why we have a rocky surface on the earth and crust, while the core of our planet is composed of denser metals such as iron and nickel.
Example of the effects of differentiation, where denser materials fall closer to the center of the planet due to gravity, credit to Wikipedia
This can also be shown on a larger scale to the solar system. The solar system started out as a cloud of cosmic dust that started to spin, flatten, and heat up. This is the birth of our star, but also the birth of the rocks that will become our planets. In a sense, this collection of mass in a disk is similar to accretion.
Furthermore, the heat near the center of the early solar system is much more intense compared to the outskirts. This causes a difference in what rocks can feasibly condense. Metals and rocks have higher melting temperatures, so they can exist closer to the center of the sun. These metal building blocks can also exist farther away from the sun, but there are also icy rocks and gasses that have cooled to a solid state. This means that the center of the solar system can have planets made of only denser materials, while the outer planets have less dense materials making up their composition. This process, although dictated by temperature and condensation rather than gravity, is very akin to differentiation.
In both cases, the density of the material, which influences relative position from other materials as well as melting temperature, has shaped both our planets’ and solar system’s layout.
While we don’t know a whole lot across the board about super-earths as a whole we do speculate that they can be extremely unique. Here’s a list of some fascinating super-earth exoplanets and some of the predictions surrounding them.
Kepler-452b: the first Earth-size planet discovered around a nearby twin solar system
Kepler-22b: a super-earth thought to be covered in a super ocean
TOI-270b: likely a rocky super-earth 25% larger than earth. This exoplanets orbits its sun every 3.4 days and is 13 times closer to its sun that mercury.
55 Cancri e: only 41 light years away this super-earth orbits its sun every 18 hours and, due to its proximity, has one side considered to be the day-side and one the night-side like our moon. By studying the star with infrared vision with 80 hours, multiple orbits, it was able to be concluded that there was a temperature difference of 1,300 Kelvin from one side to the other with the hottest side nearly 2,700 Kelvin and the cooler side 1,400 Kelvin.
Approx. 13.8 billion years ago, everything we know and love in the universe was formed with The Big Bang. Fast-forwarding 9.2 billion years, we can start to see the formation of our Solar System. 4.6 billion years ago, what we call the Solar System was nothing but a large cloud of debris, gas, and dust in the Milky Way. Gravity starts to pull a chunk of this cloud closer and closer together until it collapses and forms the beginning of our sun. 4.56 billion years ago, the mass that did not become part of the Sun begin to orbit the Sun, and tiny planets start forming. 4.5 billion years ago, Jupiter forms as the first planet, followed by Saturn, Neptune, and Uranus. Then, the sun becomes hot and dense enough to begin nuclear fusion, and the universe is lit up. Starting with Venus and Earth, the inner planets form. A Mars-sized planet called Theia crashes into earth, and the debris forms the Moon. ~4.3 billion years ago, the Sun starts to separate from the other protesters. ~4 billion years ago, water and organics make it to Earth as the Giant planets’ orbits shift. 3-4 billion years ago, the inner planets experience extreme conditions and lots of volcanism. Life begins on earth approx. 3.7 billion years ago, and 3 billion years ago, Mars lost most of its atmosphere and almost all of its water. 2.5 billion years ago, organisms that can perform photosynthesis dominate the earth filling our atmosphere with oxygen. 1 billion years ago, The moon stops its volcanism. Just as complex animals were beginning to be prominent on Earth, the Cambrian Extinction wipes out almost all life. Saturn obtains its rings 100 million years ago. 65 million years ago, a huge astroid strikes earth wiping out the dinosaurs. ~2000 years ago, the first models of the Solar System are created by the Greeks with the Earth as the Center. ~500 years ago, Nicolas Copernicus creates the Heliocentric model of the universe–the first astronomer to claim the Earth to not be the center of the universe. ~300 years ago, Sir William Herschel discovers Uranus. ~200 years ago, John Couch Adams discovers Neptune after finding evidence of ‘dark’ mass in the Solar System. ~100 years ago, Clyde Tombaugh discovers Pluto. ~15 years ago, Pluto is declared to be a dwarf planet.
Space rovers can cost a space program billions of dollars to make; in fact, Perseverance cost NASA 2.7 billion dollars. (Planetary) With that much money, time, and effort being put into a project, it makes sense that those behind it, wish to actually see their hard work successfully operate. For this to happen, the rover must successfully land on the planet that it is meant to explore.
In December of 1999, NASA’s Mars Polar Lander crashed into the southern pole of the planet at around 400 miles an hour, a disastrous failed landing. (SpaceRef) Perseverance used a new, autonomous system to land on Mars. After breaking through the atmosphere, the largest parachute ever used on Mars helped slow its descent. Then the heat shield fell away allowing for the sky crane to deploy. Using thrusters to steer away from the rest of the descent vehicle, the sky crane lowered the rover. Finally, it released the rover off of the cables, and flew away. (Space.com)
The pure ingenuity of the landing was its live adjustments. The landing vehicle was able to capture images of the planet and compare them to satellite photos, making adjusting its course in real time so that it could land as close to its predetermined spot as possible. Additionally, it was able to avoid hazardous locations amidst landing. This allowed for NASA to land the rover much closer to its scientific objectives than any of its previous projects.
With technology like this, astronomical research will continue to expand, allowing us to unlock more of the secrets of the solar system.
An atmosphere consists of the gases surrounding a planet. Atmospheres are created by volcanism (outgassing of volcanoes involves eruptions that take gasses from the earth’s interior and put them into the atmosphere), evaporation (of compounds such as water), and life (outgassing of carbon dioxide and oxygen). Life is an interesting component of an atmosphere as it only exists and contributes to the atmosphere of earth. Despite earth’s clear unique atmospheric composition, the terrestrial planets have similar atmospheres to each other and the gas giants do as well.
Terrestrial planets are known for having gases in their atmospheres such as carbon dioxide, nitrogen, oxygen and argon. The gas giants on the other hand have primarily helium and hydrogen in theirs. Below is a list of all the planets atmospheric attributes:
Mercury: thin, nearly undetectable atmosphere consisting of mainly sodium and potassium gas
Venus: mainly carbon dioxide with minor amounts of nitrogen and trace amounts of helium, neon and argon
Earth: mainly composed of nitrogen and oxygen with smaller amounts of carbon dioxide, ozone, argon and helium
Mars: thin atmosphere, mainly composed of carbon dioxide. Smaller concentration of nitrogen and argon with traces of oxygen and water vapor
Jupiter: mainly helium and hydrogen with trace amounts of water, ammonia, methane and other carbon compounds. Jupiter’s outermost atmosphere contains three layers of clouds with the lowest being made of water/ice, the mid-level clouds of crystals formed by a compound of ammonia and hydrogen sulfide and the highest clouds of ammonia ice
Saturn: mainly composed of helium and hydrogen with smaller amounts of methane and ammonia
Uranus: mainly hydrogen based with small amounts of helium as well as methane. Methane is the basis of most of the clouds seen on Uranus making the planet appear blue (likewise with Neptune) as methane absorbs light of other wavelengths
Neptune: mainly hydrogen and helium with about 2.5-3% of its atmosphere being methane
Black holes have always been a topic that interests me, and this article gives some very cool insight to a possible cause for the formation of these black holes. Most black holes have been found to form as the result of stars collapsing, and then when matter in multiple black holes collides, these black holes grow. This provides a good explanation for the forming of the large black holes, but how supermassive black holes for so rapidly is still not answered. A new thought is that the supermassive black holes might have formed during, and as a result of, the universe cooling from its “hot, dense state“. This would involve the combination of dark matter to have these black holes grow in size. This would’ve occurred before galaxies were formed.
The term supermassive black hole refers to the gigantic black holes that sit at the center of most galaxies. Around these supermassive black holes a particle has been discovered: the ultralight boson. This is thought to be a cause of the universes dark matter and it swirls around these black holes. These particles swirl around each other and explode, possibly expanding the black holes.
