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A New Age of Discovery
The last half century has been an exciting time to be an astronomer. The rise of technology has opened up new avenues for study, with inventions like the radio telescope and satellites. Today we are able to observe the universe around us in ways that would have been unimaginable just a century ago. The discoveries that have been made might be a little more complex than the heliocentric solar system, but they are just as exciting!
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Proof of the Big Bang
Immediately after the big bang, the universe was a 10 billion degree soup of protons, neutrons, and all the other fundamental particles. The extreme temperature made it impossible for any of these particles to combine to form any atoms. However, as time went on and the universe cooled, electrons were able to combine with nuclei to form atoms. Before this happened, the universe would have been opaque, since photons would have been scattered by the free electrons floating around. When the universe became suddenly transparent, these photons were now able to travel unimpeded. When the Big Bang theory was first created, it predicted the existence of this afterglow.
In 1965, two scientists working for Bell Labs in New Jersey were confounded by a heavy static that they were picking up on a radio receiver they were building. Arno Penzias and Robert Wilson, trying to get to the bottom of the static, pointed their receiver at different spots in the sky. They found that this radio signal was coming equally from all directions. Miles away at Princeton University, astronomers heard about Penzias' and Wilson's trouble, and immediately realized that they had discovered the Cosmic Microwave Background radiation. This accidental discovery finally put to rest the debate over the Big Bang theory.
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Dark Matter: A Space Age Mystery
For the past few centuries astronomers have been able to predict the movement of heavenly bodies. With better technology, we have started to observe galaxies with more and more detail. While observing the movement of stars in distant galaxies, we have found irregularities in their orbits. From what it looks like, there just isn't enough matter to be holding galaxies together. Instead of throwing out several centuries of science, astronomers believe that there must be matter in these galaxies that we cannot see--Dark matter.
Even more puzzling is the fact that dark matter isn't normal matter as we know it. At first glance, dark matter could just be large glouds of molecular hydrogen that does not emit light like stars. However, clouds of gas actually are visible to us through light that they absorb and then emit as radio signals. This dark matter is made up of something completely alien to us; some new form of matter that reacts only through gravitation. Even more surprising is how much dark matter there is. To fit in with our equations, there must be 5 times as much dark matter in the universe than regular matter. Even with all of our technology, there is still mystery left in the universe.
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Dark Energy: The Mystery Continues
The Big Bang theory predicts that our universe is expanding from an initial explosion billions of years ago. That expansion had been observed as far back as 1925, and for decades the only question was how quickly the force of gravity was slowing it down. In 1998 the Hubble Space Telescope turned astronomy on its head. Observations showed that rather than slowing down, the universe was actually speeding up!
To fix this flaw, the concept of dark energy was created. Dark energy is the energy that would be required to overcome gravity and force the universe to accelerate its expansion. Using the equation E=mc^2, we can relate all the matter and energy in the universe. All tallied up, the universe is made of 70% dark energy, 25% dark matter, and only 5% of the regular matter that you and I are made of. It is still a mystery what exactly dark energy is. Some say its a result of an interpretation of Einstein's theory of gravity called the "cosmological constant". Others say its a kind of fluid-like energy that fills all of space. It could even be that there actually is a flaw in our model of the universe. Regardless, the presence of dark energy was an astounding discovery that asks more questions than it answers.
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The Curious Case of Venus
For a long time Venus was widely considered to be Earth's "sister planet". Early observations showed that it has a similar mass and size, and its high reflectivity implied that it was covered in clouds and had abundant moisture. For some time Venus was pictured as a paradise, teeming with hypothetical life in an Earth-like environment. So when the Space Age got into full swing, it was logical for Venus to be our first stop in the solar system.
In 1962 our first extra-planetary prode, Mariner 2, came within 35,000 kilometers of Venus. Rather than a sister planet, NASA found that Venus has a surface temperature of at least 800 degrees Fahrenheit and a atmospheric pressures between 75 and 100 times the Earth's atmosphere! When the Russians sent the Venera 4 spacecraft and released a lander probe, it was only able to transmit for 93 minutes before it was crushed by high pressures. The Russian probe discovered that the Venerian atmosphere was 95 percent carbon dioxide, and its clouds were actually made of sulfuric acid, rather than water. Our first trip to a neighbor revealed a hellish landscape, rather than the paradise we expected.
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Easily the most controversial new discovery in space has been several new objects in our outer solar system that have come to be known as the Kuiper Belt. This cloud of debris orbits the Sun past Neptune, extending out to around 55 AU. It is composed of around 70,000 balls of rock surrounded by frozen methane and water. In 2005 an astronomer named Mike Brown made a discovery that would rattle the foundations of second grade science classes around the world. In the Kuiper Belt he found an object, named Eris by the International Astronomical Union, that has a diameter of 3,000 kilometers; a full 700 kilometers bigger than Pluto. Around the same time two other objects were discovered: Makemake and Haumea. Astronomers were discovering that there was a whole host of objects out in the Kuiper Belt that were similar to Pluto in size and composition.
Instead of adding a handful of new planets to our solar system, the IAU decided to create a new classification of object: the dwarf planet. These are objects orbiting the Sun that are too small to form a roughly spherical shape and whose gravity is too weak to clear debris in its neighborhood. As it has done several times throughout history, our view of the solar system has once again gone through a transformation. Some people consider this an offense to Pluto, as if it has lost some of its majesty or grandeur. Just remember, people said the same thing when Copernicus said the Earth orbits the Sun.
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The Van Allen Belts
The beginning of the Space Age was a time of awe and wide-eyed discovery. Humans were making the first steps into a completely unexplored frontier that was filled with mystery. One of the first discoveries of this period was a ring of radiation that perpetually surrounds the Earth called the Van Allen Belt. In 1958 the United States launched its first satellite into space, the Explorer I. About 3,000 kilometers above the Earth's surface the Explorer I was bombarded by extreme radiation ranging from 10 to 100 MeV.
The Van Allen Belts, as there are two of them, are areas surrounding the Earth with an abundance of high-energy protons. These protons, most of which probably came from the Sun, have become trapped by the Earth's magnetic field. Typically manned space flight is well below this dangerous radiation, but it is a problem for missions that go further out, like the Apollo Missions. Lucky for us, NASA developed shielding in the 1960s that is adequate for protecting our astronauts, overcoming yet another hurdle in exploring space.
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Van Allen Belts - NASA
Venus - NASA
Galaxy Clusters - Chandra X-ray Observatory
Scattering of Light - NASA