Tuesday, April 29, 2008

The History and Future of the Solar System

The Solar System was just sparse amounts of gas 5 billion years ago, Hydrogen and Helium were the main components (Approximately 2% were heavier elements left from another star).  The pre-solar-system nebula collapsed and began to spin.  Then, as more mass condensed at the center, gravity's effects began.  Then, over millions of years, density and energy heated the Sun's core.  Meanwhile, collisions between small, asteroid-like objects formed the first proto-planets.  Then, the Sun's core reached 18 million degrees, and Hydrogen fusion started.  The expulsion of energy and radiation cleared the inner solar system of debris, save the now fairly large proto-planets.  The extra gas ended up orbiting around the outer planets, forming the Gas Giants.  All remaining planetary objects were absorbed by the Gas Giants, turned into tiny moons, propelled back into the soon-to-be asteroid belt, or sent out into the Kuiper Belt or Oort Cloud.  Eventually all planets had "cleared their neighborhood", a term that means to eject all matter form their orbital paths with gravity.  No changes occurred for billions of years afterward, bringing us to the present.

 The Solar System is now 4.6 billion years old.  Every 1.1 billion years, the sun grows slightly larger, and increases by 10% in luminosity.  Within one billion years, the radiation from the Sun will become so powerful that all life on Earth will go extinct, and Mars will be the most habitable planet.  In 5 billion years, the Sun will swell to a red giant and swallow Mercury, Venus, and Earth.  Then, in an explosion the Sun will shed its outer layers into space and become a white dwarf (white dwarfs and other stellar explosions are explained here), and shortly after cool and become a black dwarf.  The frozen planets may orbit into eternity or the explosion of the Sun will send them into space.  Then, the gas from the Sun may help make new stars and planets, maybe for billions of years to come.

Saturday, April 26, 2008

Life in the Solar System

As billions of species come and go on our home planet Earth, we wonder, "Are we alone?"  Outside of our solar system, on extrasolar planets, life could be rare or bountiful.  But locally, here in our solar system, there are still candidates for life.  Recently, evidence of water, and possible evidence of bacteria, and other micro-organisms were revealed in trenches of ancient oceans on Mars, suggesting a habitable climate.  Two gigantic asteroids hit Mars right around the time that the fossils pinpointed the existence of water, leading some people to believe that these asteroids destroyed the magnetic field or some of the atmosphere of Mars.  Therefore, all life on the planet would go extinct, just like an extinction on Earth, but to a greater extent.  

Mercury has no atmosphere, Venus is too hot, the gas giants have no solid surface and objects farther out are too small or cold. So, the moons are the only possibilities left.  Europa, a Galilean moon of Jupiter has an icy surface floating above a freezing ocean, 2 to 100 km deep.  Tides from Jupiter and possible heat from Europa's core, keep this ocean from freezing.  Titan, the only moon in the Solar System with an atmosphere, also holds the ingredients to possible life, save the temperature.  Orbiting freezing Saturn, the only liquid on this moon is liquid nitrogen, collecting in pools on its surface.  Either of these moons could be subject to later spacecraft study, and as our knowledge of technology grows, it is only a matter of time, until we are no longer alone in the Universe...

Tuesday, April 22, 2008

The Oort Cloud and the Kuiper Belt

The Oort cloud is the spherical area of leftover debris from the beginning of the Solar System, including mainly asteroids, and some comets.  The Kuiper belt also contains this debris but it is a lot closer to the Sun, its inner limit being the orbit of Neptune.  In total, millions of asteroid-like bodies have been discovered in these areas, some of which being big enough to be moons, and one, called Eris, is classified as a dwarf planet and is larger than Pluto.  Eris, and a few other relatively large bodies also have moons in orbit around them (one body, discovered in 2003, has two moons!).  Also, comets orbiting elliptically around the sun usually pass through the Kuiper belt.  Periodical comets, ones that orbit continuously around the sun can travel out to the Oort cloud, and some escape the sun's gravity floating free into space.  New Horizons, a spacecraft that flew by Pluto in July 2015, also will explore some objects in the Kuiper belt objects from 2016-2020.  Many secrets of these zones are still waiting to be discovered.

Cosmic Microwave Background Radiation

Cosmic Microwave Background Radiation is the radiation by the Universe in its early stages (here, here and here), shortly after the Photon Epoch, about 400,000 years after the Big Bang or 13.7 billion years ago. Since it was formed close to the Big Bang, it can be used as a "timer" for the age of the Universe (because of light aging).  Today it counts for roughly .00005 of the density of the Universe.  It keeps the average temperature of space around 2.3 Kelvin.  If the CMBR (short for Cosmic Microwave Background Radiation) ever dies out the Universe will end in a Big Freeze.  Microwave instruments detect this Radiation, and it is being studied for a look at the early Universe.

Friday, April 18, 2008

Quasars

A quasar is a supermassive black hole (see here, here, here and here) at the center of a young galaxy.  The farthest are 28 billion light-years away, making them that most distant objects ever observed.  They are so far that the energy they emit to make them visible most be equivalent to over 100 galaxies or a trillion suns.  Over 100,000 quasars have been detected with more on the way.  Some quasars can even be viewed with a small telescope, due to their luminosity with equals around 2 trillion suns.  An average quasar absorbs 10 solar masses (10 times the sun's mass) each year.  The biggest consumption on record being 1000 solar masses per year or 600 Earths per hour!  No quasars are in our supercluster because once they absorb all the mass in their proximity, they die out and become ordinary black holes, leaving a regular galaxy behind.  Quasars are that most powerful objects in our known Universe.

Tuesday, April 15, 2008

Extrasolar Planets

In the past 200 years, people have asked, "Are there other solar systems?"  The answer came in 1992 when an extrasolar planet was discovered.  Due to the distance of these systems, only planets heavier than Earth have been discovered so far, the lightest being 2.6 times the Earth's mass and the most massive outweighing 8 Jupiters!  Extrasolar planets have been found orbiting around giant stars, white dwarfs, brown dwarfs and even pulsars (information on these objects here and here)!  A few systems have been confirmed two planets, and one system holds 6 candidates.  Naturally, most have been gas giants, but some have been seen very close to their parent stars, the closest being only under .05 AU from the star.  Hundreds of these mysterious bodies have been discovered, with hundreds more waiting to be confirmed.  To assist this search, Kelper (named after Johannes Kepler), a spacecraft launched in 2009, has a sole mission to detect these planets.  Who knows what mysteries lie on bodies beyond our solar system?

Sunday, April 13, 2008

Dark Energy

Dark Energy is a hypothetical type of energy believed to be the cause of Universal expansion.  It is believed to fill up about 70% of the Universe.  It exerts a negative pressure on its surroundings which is behind the Universe's expansion.  To explain the acceleration, "vacuum energy", an energy in empty space, was proposed.  As the Universe expands, more vacuum and dark energy are formed in the new space that is created.  This, in turn, adds to the negative pressure that the Universe is exerting.  The Dark Energy's density is nearly unchanged as the Universe expands but the density of Dark Matter decreases.  This steadily increases the domination of this energy. This chain reaction, unless stopped by a different factor will lead the Universe to a Big Freeze or a Heat Death, possibly preceding a Big Rip.  

Tuesday, April 8, 2008

Dark Matter

Dark Matter is a form of invisible matter found in our Universe. It is invisible because it does not interact with electromagnetism. It also does not interact with atoms because unlike most matter, dark matter does not have an interaction with the strong nuclear force. Virtually the only way this matter can be detected is through gravitational effects on ordinary matter or by blocking light through gravitational light bending. Dark matter is believed to be made of neutrinos, axions, and other odd particles. Dark matter makes up a major part of the Universe's mass, and contributed to the beginning of the Universe.

Friday, April 4, 2008

The Tachyon

One well-known exotic particle is the tachyon.  A tachyon is a hypothetical particle that travels faster than the speed of light.  This odd particle seems to defy detection, and many scientists think it might not exist.  If the tachyon did exist it would defy many logical paradoxes.  The tachyon would be able to travel backwards in time, an action that is impossible by the theory of relativity.  But the theory could stay intact if the tachyon couldn't transmit information.  So the tachyon alters the physics of the Universe by itself, proposing three possibilities.  One is the easy way out, just saying that tachyons do not exist.  The second is that, although particles can, information cannot travel faster than the speed of light.  Three, the horrifying choice, is the possibility that the general theory of relativity, even approximately at an larger-than-quantum scale, is false. Scientists have proposed this particle real mass, also defying many previously believed theories, such as the fact that anything with real mass travels at subliminal (below light) speeds. Quantum physics have yet to explain this mysterious particle.

Heat Death of the Universe

This fate of the Universe (note 5) begins 100 trillion years from now when stellar formation has come to a halt.  Over the next 10^30 years, planets, stars, and eventually galaxies will decay gravitationally and start to flow freely in space.  From 10^30 to 10^40 years, all protons will decay and all matter will be converted into photons and gamma rays.  All that remained after this era was black holes.  As the age of the Universe soars to a googol (10^100) years Black holes will evaporate due to Hawking Radiation and all the will remain are gamma rays and the occasional photon.  

Thursday, April 3, 2008

Antiparticles

For most particles, there is an antiparticle.  An antiparticle has the opposite charge and the same mass as its particle partner.  Since particles and antiparticles annihilate each other, it is well-known that there are many more particles than antiparticles.  Antiparticle played apart in the creation of matter in the early Universe.  They also are the cause of Black Hole Evaporation. Because of these unbalanced amounts, antiparticles are not found naturally.  They are engineered in a lab by destroying another particle.  Particles with a quark composition have an antiparticle that contains antiquarks.  Also, two antiprotons, two antineutrons, and two antielectrons (also called the positron) would produce an antihelium atom.  Antiparticles mirror most particles, and they are very similiar with most properties.