Author: Edward
Outer Planets
The Outer Planets are Jupiter, Saturn, Uranus, and Neptune. The following Table indicates the spacecraft that have been sent to the planets, the most recent is at the top of the list. More information on each planet is given below…..
| Jupiter | Saturn | Uranus | Neptune |
| space craft successfully sent to the Planets; | |||
| New Horizons
Cassini Ulysses Galileo Voyager 2 Voyager 1 Pioneer 11 Pioneer 10 |
Cassini-Huygens
Voyager 2 Voyager 1 Pioneer |
Voyager 2 | Voyager 2 |
| USA (NASA) | European Space Agency | China | India | Japan | Russia |
Jupiter
Description
Gas giant. The largest planet in our solar system. The visible clouds are mostly ammonia. The atmosphere is mostly hydrogen and helium and extends down to a point where the pressure forms liquid hydrogen. At a depth about two-third’s of the radius, the liquid hydrogen becomes metallic due to the high atmospheric pressure. At the center there is thought to be a rock-ice core about the size of earth.
Jupiter has 49 officially named Moons and many more identified with a number only. The four largest moons are planet sized and were discovered by Galileo with his small primitive telescope. These moons are shown in the photo in this order:
| Io – most volcanically active body in the solar system with an atmosphere of sulfur dioxide. No water present. Third largest of Jupiter’s satellites. 262,000 miles from Jupiter. | |
| Europa – size of our moon, covered with an ocean of salty water with it’s surface frozen. It has an atmosphere of oxygen. It could support simple life forms. 420,000 miles from Jupiter. | |
| Ganymede – The largest moon in the solar System. It may have a liquid water ocean beneath it’s crust of water ice and rocks. It may also have a thin oxygen atmosphere. 625,000 miles from Jupiter. | |
| Callisto – Many Impact craters. No volcanoes and no geologic activity. It is a dead planet, thought to have the oldest landscape in the solar system….4 million years old.. Second largest of Jupiter’s satellites. 1,170,000 miles from Jupiter. |
Imagine for a moment that you were on Io at night, when Io was between the Sun and Jupiter. Since Jupiter is so large, and Io is so close to Jupiter, you can imagine that Jupiter would fill the night sky and reflect a great deal of light!
Weather
It’s very interesting to think of how to describe the weather on Jupiter. If you were standing on the rocky core, you’d be encased in metallic hydrogen….I suppose that would qualify for no weather at all! If on the other hand you were above the metallic hydrogen and the liquid hydrogen, it would be windy, rainy (liquid hydrogen), and very cold. If you were higher in the ammonia clouds you would experience very high winds. It would be cold. The good news is there would be no dust and no dirt!
Viewing
Jupiter can be easily seen with the naked eye. The moons of Jupiter can be seen with a small telescope.
Visitors
(Names in Bold are still operational, strikethrough were not successful, blue are future.)
| Europa Astrobiology Lander. Proposed for 2036 to land on the moon Europa. | |
| Juno. In development for 2016. This space craft will study the gravity field, magnetic field and atmosphere of Jupiter. | |
| Prometheus One. Proposed for 2015. To orbit three of Jupiter’s moons | |
| New Horizons – February 27, 2007. Single fly-by. Photos of Callisto. | |
| Cassini-Huygens – 2000. Single fly-by. Continued on to orbit Saturn. | |
| Ulysses – February 8, 1992. ESA. Made 3 passes (Flybys) studying the atmosphere and fields of Jupiter. Continued on to orbit the Sun. | |
| Galileo – December 7, 1995. Mapping and atmospheric measurements. Released a probe to study the atmosphere, which lasted 58 minutes as it was consumed by the high pressures, intense radiation, and high winds. At the end of its mission in 2003, the space craft was intentionally crashed into Jupiter. | |
| Voyager 2 – July 9, 1979. Images of Io, Europe, and Ganymede. Headed for Interstellar space via Saturn. | |
| Voyager 1 – March 5, 1979. Single fly-by. Headed for Interstellar space via Saturn. | |
| Pioneer 11 – December 2, 1974. Single fly-by to take photos, atmospheric measurements. Contact lost in 1995. | |
| Pioneer 10 – December 3, 1973. Single fly-by to take photos and magnetosphere measurements. Continues the mission to exit the solar system. |
Saturn
Description
Gas giant. Atmosphere is 97% Hydrogen and 3% helium
Saturn has 52 moons with Titan being the largest. Titan’s atmosphere is dominated by Nitrogen, similar to Earth, Earth is 78% N2 while Titan is 95% N2. Although much smaller than Earth, Titan’s atmospheric pressure is about 50% greater than Earth. The temperature is around -290oF. Frozen water forms the land and liquid ethane and methane form the lakes, rivers, and rain……a strange land indeed.
Weather
Saturn
Viewing
Visitors
(Names in Bold are still operational, strikethrough were not successful, blue are future.)
| Future Flybys to be launched in 2015 will include several probes to be released into the planets atmosphere. | |
| Cassini-Huygens. Inserted into Saturn orbit on July 1, 2004. The Huygens probe was released on December 24, 2004 in the vicinity of the moon Titan and landed on Titan 2 weeks later on January 14, 2005. The spacecrafts orbit brings it in close proximity to the moons of Saturn where it is able to make measurements of the atmosphere and surface of the moons. | |
| Voyager 2. August 26, 1981 Flyby with the closest approach to Saturn at 62,000 miles above Saturn. It took photos of Saturn and several of its moons before departing to Uranus. It currently is traveling toward interstellar space and is continues to be operational. | |
| Voyager 1. November 11, 1980 Flyby with the closest approach to Saturn at 77,000 miles. Voyager 1 took hi-resolution photos of Saturn and its Moon Titan. It currently is traveling toward interstellar space and is continues to be operational. | |
| Pioneer 11. First spacecraft to visit Saturn. September 1, 1979 Flyby. Pioneer 11 took photos of Saturn and then continued on to eventually leave the solar System. All contact with the spacecraft was lost in November 1995, however the craft continues to travel towards interstellar space. |
Uranus
Description
Uranus is very odd planet in that it spins on it’s side relative to its orbit around the Sun. It is a true Gas giant in that there is no solid rocky core, however it does have a condensed liquid core made up of water, ammonia, and methane. The atmosphere consists of hydrogen and helium, as well as methane and traces of water and ammonia. It’s blue-green color comes from the methane in the atmosphere.
Uranus has 27 known moons and 11 rings.
Weather
Cold and dark. The surface is covered with liquid so you will need a flotation device
Viewing
Visitors
(Names in Bold are still operational, strikethrough were not successful.)
| Voyager 2. January 24, 1986. Single Flyby to study atmosphere and the magnetic field. |
Neptune
Description
Named after the Roman God of the Sea. Atmosphere of hydrogen and methane. Neptune also has rings consisting of small rocks and ice. It is thought that Neptune has an earth-sized rocky core covered with water and other melted ices from the atmosphere. The deep blue color is due to methane and another element which currently remains a mystery.
Neptune has 13 moons including Triton, the largest of Neptune’s moons and one of just a few moons in the Solar System which has active geysers.
Weather
Cold and dark. Sustained winds can be a couple hundred miles per hour. If you are on the surface you will need a boat as the surface is covered with liquid water, hydrogen, and methane
Viewing
Too small to see with the unaided eye.
Visitors
Only 1 visitor to Neptune…
| Voyager 2 – August 24, 1989. Single fly-by. Measured physical characteristics of Neptune and its moon Triton. Continued on to interstellar space. |
No current or future missions in development.
Pluto
Description
Way too cold. Sorry, not a regular planet anymore. It is the first object to be classified as a Dwarf Planet, a new category. It is the smallest of the planets, having a diameter of just over 1400 miles….it would fit nicely in the Gluf of Mexico.
Pluto has 3 moons
| Charon (KARE-on) approximayely half the size of Pluto | |
| Nix – very small. Little is known of this moon | |
| Hydra – very small. Little is known of this moon. |
Weather
Cold, no wind, no rain, no clouds….basically no weather, however it does have a very thin atmosphere discovered in 1988.
Viewing
Impossible to see with the naked eye.
Visitors
| New Horizons. Currently enroute for arrival in 2016. Single Flyby of 150 days |
Inner Planets
The Inner Planets are Mercury, Venus, Earth, and Mars. The following Table indicates the spacecraft that have been sent to the planets, the most recent is at the top of the list. More information on each planet is given below……
| Mercury | Venus | Earth | Mars |
| space craft successfully sent to the Planets; | |||
| BepiColomboMessenger
Mariner
|
Venus ExpressGalileo
Magellan Vega 2 Vega 1 Mariner 10 Mariner 5 Mariner 2
|
Hubble Telescope
|
Recon. Orbiter Opportunity
Spirit Phoenix Mars Express Beagle 2 Odyssey Pathfinder Global surveyor Viking 2 Viking 1 Mariner 9 Mariner 7 Mariner 6 Mariner 4 Mars Series |
| USA (NASA) | European Space Agency | China | India | Japan | Russia |
Mercury
Description
Twice as close to the Sun as the Earth, it is about the size of our moon. Mercury is a highly cratered planet, similar to the Moon. It has a solid inner core, a liquid outer core, and a crust, just like the Earth. However, Mercury is more dense, consisting of predominantly the heavier elements, like iron. The recent flyby of the spacecraft Messenger October 2008, has revealed active volcanoes. It has essentially no atmosphere, what little there is is thought to be helium.
There are no moons.
Weather
Closest to the Sun….and way too hot! The mean surface temperature is 347F. During the day the temperature can reach 800F. Although you could settle in one of the few places near the poles that are always in shadow, where the temperature may never exceed -300F..that’s minus 300 degrees! Otherwise, there is no atmosphere, so no wind, no rain, no clouds…..no weather!
Viewing
If you are to have any chance of seeing it, it’ll have to be right after the sun sets, or just before the sun rises, and only at select times during the year. When visible, it can be seen fairly easily but will be close to the horizon, due to the fact that it is close to the sun.
Visitors
(Names in Bold are still operational)
| BepiColombo – future. The European Space Agency has named a future Spacecraft planned for Mercury exploration … scheduled to arrive at Mercury in 2011 and set up orbit around the planet. | |
| Messenger – January 2008. Messenger flew pass Mercury in January, 2008. Only the second craft to explore Mercury since Mariner 10 in 1975, Messenger will settle into orbit around Mercury in 2011, 3 years from now, and begin the real exploration of this hot, barren planet. |
Messenger = MErcury Surface Space ENvironment, GEochemistry, and Ranging. (yes indeed…kind of clumsy.)
| Mariner 10 was the first Spacecraft to visit the planet in 1974 and 1975. It made 3 fly-bys to map less than half of it’s surface. |
Venus
Description
Venus is totally covered in clouds and cannot be directly seen with our eyes. However radar scans from several space probes have revealed most of the surface features to us. The planet has many impact craters and is also covered with volcanic rock and lava flows from the active volcanoes on the planet. It is thought that the lava flows have erased the evidence of older impact craters. Also, as result of the volcanoes, the atmosphere consists of carbon dioxide (96%) and sulfuric acid. This results in a very dense atmosphere with very high pressure on the surface of the planet. As beautiful as it is from Earth, it is not a very hospital place.
There are no moons. As a possibility however, some scientists believe that Mercury may have been a moon of Venus in the early days of the solar system. Take a look at the relative sizes….I suppose it could have been a moon of Venus at some time.
Weather
Venus is in a global warming situation. The atmosphere is mostly Carbon dioxide and as a result is much like a Greenhouse….very warm indeed. The mean surface temperature is 847F, which means it gets a lot hotter than that on a summer day! Note that it is warmer on Venus than on Mercury which is closer to the sun, due of course to the Greenhouse gases. The upper atmosphere does contain water vapor which creates sulfuric acid. This acid however does not reach the surface since the water evaporates due to the high temperature. The weather for Venus is hot and cloudy, with the possibility of very heavy winds, and no rain in sight.
Viewing
My favorite planet……the “morning star”, or, “evening star” depending on when it’s visible. Very easy to spot after sunset or before sunrise…it is the brightest object in the sky, after the sun and moon of course and looks like a diamond in the sky. Most people will think it is the landing lights on a commercial jet plane far in the distance. Actually Venus is fairly close to us….equivalent to 1,000 times around the earth.
Visitors
(Names in Bold are still operational, strikethrough were not successful missions.)
| Venus Express – April 11, 2006. European Space agency. Currently in orbit. Atmospheric studies | |
| Galileo – 1990. Single flyby at 10,000 miles on way to Jupiter. | |
| Magellan – August 10, 1990 – Established orbit around Venus and radar-mapped 98% of the surface. Remained operational for over 4 years. | |
| Vega 2 – June 15, 1985. USSR landing on Venus and analyzed soil sample. | |
| Vega 1 – June, 1985. USSR landing on surface and two weather balloons. Lander functioned for 56 minutes. Balloons operated for 46 hours. | |
| Mariner 10 – February 5 1974 single flyby at 3,600 miles. Studied atmosphere and photos. Continued on to Mercury. | |
| Mariner 5 – October 19, 1965 single flyby at 2,400 miles. Studied atmosphere. | |
| Mariner 2 – December 14, 1962 single flyby at 20,000 miles for 42 minutes. First successful Interplanetary mission. | |
| Mariner 1 – July 22, 1962. Destroyed at launch. |
Mars
Description
Mars may have had water on the surface 3 to 4 million years ago. Since water is considered essential to life, the presence of water on Mars would increase the likelihood that life had existed there in the distant past …. and the occurrence of life twice in one solar system would then indicate that maybe life is common in the cosmos. The surface of Mars is rocky with impact craters and there is evidence of erosion from past water floods. As can be noted below, we have sent many space craft to explore Mars. It will be the first Planet to be visited by man. All of this because it has water and will be the easiest to adapt to.
Mars has two moons, Phobos and Deimos, among the smallest moons in the solar system.
Weather
The atmosphere is very thin so that winds, although high in speed, do not pack much of a force. Dust storms are common. No free water so no rain. The maximum temperature is 98F and the minimum is -190F. Cooler than Earth, no clouds, and no rain.
Viewing
Pretty easy to spot…it is reddish in color.
Visitors
Mars is the most often visited planet by mankind. A total of 20 space craft have been successfully sent to Mars. (Names in Bold are still operational, strikethrough were not successful missions.)
| Mars Reconnaissance Orbiter – March 10, 2006. Look for water and dust in Mars atmosphere and for evidence of ancient seas and climate changes. | |
| Opportunity – January 24, 2004. Sister rover to Spirit but on the other side of Mars. | |
| Spirit – January 3, 2004. Rover. Geologic survey from microscopic examination to panoramic views looking for evidence of water. | |
| Phoenix – May 25, 2008. Mars Lander intended to look for water beneath the surface and also analyzer the soil for organic matter. The Lander was successful and creased operation on November 10, 2008 nearly 3 months beyond it’s design life. | |
| Mars Express – December 24, 2003. European Space Agency, successfully inserted into orbit and is currently operating to study the geology and atmosphere. | |
| Beagle 2 -December 24, 2003. United Kingdom Lander onboard the Mars Express. The Lander lost contact after landing. Failed. | |
| Mars Odyssey – October 24, 2001. Mission is to map the surface and search for signs of water. It is still operational as of 2008 | |
| Deep Space 2 – December 3, 1999. This was a microprobe which was onboard the Polar Lander intended to look for water beneath the polar ice cap. It was lost when the Polar Lander crashed. | |
| Mars Polar Lander – December 3, 1999. The Lander apparently crashed on the surface of Mars due to premature engine shutdown during the landing. | |
| Mars Climate Orbiter – September 23, 1999. The Orbiter failed to be inserted into orbit due to inconsistent use of Metric and English units. | |
| Nozomi – July 3, 1998. Japan’s first interplanetary space craft intended to orbit Mars. It failed to achieve orbit around Mars. | |
| Mars Pathfinder – July 4, 1997. Pathfinder was a low-cost Lander with the first wheeled rover. It obtained geology data and performed soil analysis. It lasted 3 months, several times beyond its design life and performed beyond expectations. | |
| Mars Global surveyor – September 11, 1997. It’s planned 2-year mission was delayed for 1 year due to solar array deployment problems. However, it operated for 9 productive years giving data on the geology and atmosphere of Mars. | |
| Mars Observer – August 22, 1993. Launched to carry out long term wave and particle investigation into the geology, atmosphere, and climate of Mars. The Observer fell silent just two days before reaching Mars. | |
| Fobos 1 – 1988. USSR. Two space craft were launched to orbit Mars and to put a Lander on the moon Phobos. Fobos 1 failed enroute due to a programming error. | |
| Viking 2 – August 7, 1976. Orbiter and Lander. Also flew within 10 miles of one of the moons, Deimos. | |
| Viking 1 – June 19, 1976. Orbiter and Lander. Sampled soil and atmosphere. Also flew within 50 miles of one of the moons, Phobos. High resolution photos. | |
| Mariner 9 – November 14, 1971. Orbit for 1 year taking photographs. | |
| Mariner 7 – August 5, 1969. Single flyby to photograph 10% of surface. | |
| Mariner 6 – July 31, 1969. Single flyby to photo graph 10% of surface. | |
| Mariner 4 – July 15, 1965. Single flyby to photograph and take field measurements. | |
| Mars Series by the USSR. From the 1960’s to the 1990’s the USSR sent 15 space craft to Mars….only 1 was successful and 4 were partially successful. |
Earth
Earth was formed approximately 4.5 Billion years ago….. 4,500 million years ago. It consisted entirely of molten rock with a hot dry gaseous atmosphere. A significant portion of uranium was present and the heat from its decay contributed to the molten environment. 100 million years later enough cooling had occurred that water vapor condensed, forming free water. Water vapor is thought to have initially arrived with meteorites and accumulated over millions of years. During this period earth was bombarded with countless meteorites. Oxygen and CO2 formed thick clouds and heavy rain continued for millions of years.
After 400 million years of water accumulation, over 90% of the earth was ocean and it remained this way for 500 million years. The atmosphere was dense and surface temperature was just below the boiling point of water…around 200F. The ocean and the sky were a dirty, dark color. It was a very inhospitable place.
At 3.4 Billion years ago…3,400 million years….volcanoes appeared and brought with them granite which was lighter than the mantel material and therefore floated on the mantel and began to form the continents.
(…….to be completed)
Solar System
Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto
0.4 0.7 1 1.5 5 10 20 30 40
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My Very Educated Mother Just Served Us Nachos
Of course the major elements of our solar system are the 8 major planets, listed above. It was 9 planets but Pluto is no longer considered a full fledged Planet, rather it has been downgraded to a new classification…..a Dwarf Planet. More on that later. For now it is important to know that the planets, which we are so familiar with, are only part of the story. In addition to the Planets, there are three other categories of objects in our Solar System…..moons, Dwarf Planets, and Small Solar System Bodies.
Planets
Initially, all lights in the sky were thought to be from a similar source, until early astronomers began to notice that a few of the lights behaved differently than the others. As these lights were discovered and studied they were named Planets. Today we know there are other kinds of bodies in our solar system and some are similar to the 8 major planets. In 2006, the International Astronomical Union (IAU) defined a Planet as: (1) in orbit around the sun, and (2) enough mass for gravity to have drawn it into a round shape, and (3) enough mass to have cleared out everything else in it’s orbital path. Because of this new definition, Pluto was no longer a Planet since it did not clear out everything else in its orbit. However, the term Dwarf Planet was given to Pluto (see below). However, this did not end the discussion…the debate continues, but officially Pluto is a Dwarf Planet for now. There are 8 Planets and there will not be any new planets in our Solar System simply because we’ve looked and there aren’t any new objects that meet the criteria above.
The diagram at the top of this page is not to scale in regard to distance from the Sun. The Planets are actually spread out much more than indicated. Note the numbers below the Planet names…these numbers represent the distance from the sun, in terms of the Earths distance. For example. Mars is one and half times further from the sun than the Earth. A couple of things can be noticed right away:
Mercury, Venus, Earth, and Mars are tucked in pretty close to the Sun (all within 1½ earth distances), compared to Jupiter, Saturn, Uranus, and Neptune . For this reason, these planets are referred to as the Inner Planets, and the latter Planets are referred to as the Outer Planets.
If we had a scale model of the Solar system on our desk and the earth was positioned 1 inch from the sun, the inner planets would be within the first 1½ inches…..and Neptune would be 30 inches away! If you think about this for a minute you soon realize that the planets are well spread out.
There’s another thing to notice that has some astronomers thinking…..each Planet seems to be about 1 to 1½ times further from the Sun then the previous Planet….except for Jupiter. There seems to be a missing planet between Mars and Jupiter. Now this on it’s own might seem to be a bit academic however there is one other curious thing….right about where this missing Planet might be expected, there’s a ring of debris!….the asteroid belt! See the discussion below…The Exploding Planet Theory.
Planet…..a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighborhood around its orbit.
Satellites (moons)
Any of the above objects can have a satellite, which is basically defined as an object circling a celestial body. Satellites around objects other than stars are also commonly called moons, however strictly speaking the Moon is actually the name of Earth’s satellite. But for ease of use we’ll call all the satellites moons, which is common anyway. Several of the planets have moons. There are at least 144 moons circling 6 planets in our Solar System…6 planets because Mercury and Venus don’t have moons (surprised that there 144 moons?….see the Inner planets and the Outer Planets). However, as noted above, moons are not limited to the Planets alone. The Dwarf Planets have moons, as well as some of the larger asteroids.
Moons have become especially important today because of their diverse character and make-up. Many are very different in many ways, for example, some have volcanoes and are active geologically, some have substantial atmospheres, some have hydrocarbon lakes, some are heavily cratered, some are icy, and some rotate very slowly. A few seem to have the conditions that might support life of some elementary form
Dwarf Planets
The Dwarf Planet is a relatively new classification of objects in our Solar System. It was defined in 2006 by the International Astronomical Union (IAU) as those objects which are large enough to be round but are not one of the current 8 Planets. One of the characteristics is that the object must be large enough to become round. How many round objects are there in the Solar System that are not planets or moons? Maybe in the order of 200 when current surveys are completed. However, officially the IAU has only identified 5 objects as Dwarf Planets, as of 2008…..Ceres (an asteroid in the Asteroid Belt); Pluto (recently demoted); Makemake, Haumea, and Eris.
There is another term, Minor Planets, which has been used in the past to refer to asteroids in the Asteroid Belt. This term has never been fully accepted by the astronomical community. It often is used interchangeably with the term asteroid, although usually applied to the larger asteroids. I believe its use has now been largely discontinued as a result of the new definition of Dwarf planet, however you may still find it in some of the literature. Don’t get too excited about it…I’d just ignore it’s use.
Dwarf Planet….A celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has not cleared the neighborhood around its orbit.
Within the category of Dwarf Planet, there is a classification known as Plutoid. A Plutoid is basically a Dwarf Planet beyond the orbit of Neptune. Currently there are 4 Plutoids. The first was named in June of 2007 and is, oddly enough, Pluto. The others are Makemake, Haumea, and Eris. All of these are located in the Trans-Neptunian region where Pluto orbits. What about Dwarf Planets that are located within the orbit of Neptune? Do they have a separate classification? No. There is currently only one Dwarf Planet in this area, Ceres, and it is located in the Asteroid Belt. It is possible that a future classification will be named if more Dwarf Planets are found within the orbit of Neptune. But for now there is no further classification, Ceres is simply called a Dwarf Planet.
Small Solar System Bodies
Small Solar System Bodies are all the other objects not in the Planet or Dwarf Planet category. They include asteroids (between Mars and Jupiter), comets, near Earth Objects, and Kupier Belt Objects/ Oort Cloud objects (in and beyond the area of Pluto’s orbit).
Asteroids
Asteroids are small rocky and icy objects of irregular shape. They can be a few meters in size to several thousand meters in size.
Between Mars and Jupiter there is the Asteroid Belt, in which there are hundreds of thousands of asteroids ranging from less than 1km in diameter to over 200km in diameter. There are 26 asteroids over 200km in diameter. Nearly all of the asteroids in excess of 100 km have been cataloged. Over half of the asteroids between 10km and 100km have been cataloged. Why are these asteroids here….in a nice orbit around the sun, between Mars and Jupiter? Actually, there is some conjecture that this Asteroid Belt is the remnants of a previously existing Planet which exploded! This mystery Planet has been given the name Planet V to indicate it would have been the fifth planet from the sun.
……did you say exploding planet??
The Exploding Planet Theory. Yes, there is sufficient evidence to suggest that a planet did explode. It is not understood how a planet can explode, i.e.. the process by which that could happen has not been proposed, but there are conditions in our solar system today which make the exploding planet idea plausible…..
a gap between Mars and Jupiter which seems to cry out “missing planet”
debris in this gap, i.e., the Asteroid Belt
water on Mars in the past. Did it arrive from the nearby large Planet V when it exploded?
Saturn’s moon Iapetus seems coated on one side with a dark carbonaceous material which may have accompanied the shock wave of an exploding planet. Iapetus has a very slow rotation (80 days) so one side only could easily have been exposed to a sudden bombardment of finer debris from the initial blast, thereby coating only one side with the blast of finer material. Other moons, with quicker rotations, show evidence of a black material scattered over their entire surface.
calculated orbits of comets and some minor planets (asteroids) seem to suggest that they all originated from a common point at a single time in the Solar system. This supports the exploding planet theory as the source of the comets and minor planets.
In any event, the origins of the asteroids will continue to be debated until further evidence points the way. This is a good example of observations and measurements from which scientists develop theories to fit the measurements. As additional information is discovered, the theories are refined…or dropped as the case may be.
Comets
Comets are basically asteroids which are in highly elliptical orbits around the sun. Because their orbits bring them close to the sun they heat up and give off gases which result in long spectacular tails as they approach the sun.
In contrast to the Exploding Planet Theory for the source of comets, the conventional thinking is that there is a cloud of material a great distance beyond Pluto (several thousand times the distance from the Sun – this is a huge distance away!) which is the source of the comets. This is the Oort Cloud. If disturbed for some reason one of these objects could be set off towards the Sun and become what we see as Comets. These comets from the Oort Cloud have extremely long orbits so that any given generation here on earth would only see them once. The theory actually considers that 1000’s of these comets have been setoff on their journeys but we see only a few.
In addition to the Oort Cloud there is another source for comets known as the Kuiper Belt, (pronounced Ki-per). The Kuiper Belt is located just beyond the orbit of Pluto. The Kuiper Belt is populated with thousands of icy objects and approximately 1000 have been identified. These objects are called Kupier Belt Objects (KBO) or Trans-Neptunian Objects (TNO). Because they are so much closer than the Oort Cloud Objects, once disturbed to begin their orbit of the sun their orbital periods are much shorter and therefore a generation here on earth may see them repeatedly.
Cosmic Events
| The Big Bang | Life cycle of a Star | Quasars | Colliding Galaxies |
The Cosmic Events discussed here are a few of those major events that shape the universe…”the movers and shakers” of the universe. They are not the comets that occasionally pass our way, nor the asteroids that threaten our life…although those are the issues that have the greatest direct impact on us. The ‘movers and shakers” of this universe are those events which define the path for the development of this universe. Some of these major events are discussed here and consist of the following:
| the start of the universe….The Big Bang; | |
| followed by the initial formation of stars; | |
| then the death of stars, which allowed many other events to take place, like the formation of planets and Black Holes; | |
| and finally, colliding Galaxies. |
Of course there are many other cosmic events which have important effects on the universe but the above seem to have a common thread between them which fundamentally defines how our universe has developed.
| Some background physics (you can skip this if you like)
It is interesting to note that there are three fundamental concepts from physics that I like to think of as instrumental to the development of the universe as we know it….gravity, conservation of angular momentum, and temperature: Gravity. We are well aware of the effects of gravity. It is the universal attraction between all objects…always has been, always will be (except, of course, for love). Conservation of Angular Momentum. Ever notice how everything in the universe is rotating? Moons around planets, planets around suns, suns around galaxies, galaxies around other galaxies…even asteroids and comets rotate around suns. How does that happen? Conservation of angular momentum! …..in the beginning, when gravity first had that little tug of one particle to another, there was a slight hint of rotation or a slight differential of the velocity component perpendicular to the line of gravity. No matter how slight it was, there was that small, insignificant velocity component. That velocity component is conserved as the particles are drawn closer through the action of gravitational force…as the distance gets smaller, the rotation gets faster. Remember the well known example of the spinning ice skater….begin a spin with outstretched arms and the rotation will increase to a blazing fast spin as the arms and legs are brought into the body. From this law of physics we end up today with a host of spinning structures….and it is because of that we don’t go flying off into oblivion, or, crashing into the sun Temperature. It is also interesting to note that temperature plays an essential role in the occurrence of the events listed above. Consider this sequence of events:
All of this is dependent on the temperature of the material.
|
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The Big Bang – the First “Cosmic Event”
The universe is expanding. We know this because we can measure the rate at which all major structures in the universe are moving away from one another. It is a well studied and easily measured property of our universe (see Astronomers, Edwin Hubble). By going back in time, astronomers and physicists can identify the sequence of events leading to today’s universe. Most astronomers and physicists see the Big Bang theory as the logical beginning based on observations to date. By observing, measuring, and analyzing data collected over the past hundreds of years, scientists have developed a logical sequence of events leading backwards to a Big Bang event.
The beginning of the universe is now generally accepted as described by the Big Bang Theory. What is the Big Bang? Current science considers the Big Bang to be the beginning ….the First Moment… when all the substance of the universe consisted only of sub-atomic and atomic particles……and lots of energy, at a temperature of trillions of degrees! All the material of today’s universe evolved from a single point of pure energy! Think of it….no material, no stable matter. Nothing to put your hands on! Just elementary particles and an energy field! …a huge energy field….and at a very high temperature. It is hard to imagine such a time and place! From that moment, all we know of today evolved in accordance with the physical laws we know of or have theorized. It is important also to note that the Big Bang Theory requires an infinite density and temperature, which is consistent with Einstein’s General Theory of Relativity.
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| Cooling of the Universe immediately after the Big Bang. Today’s temperature is -270°C The Yellow portion signifies the period in which all the matter of the Universe was in the form of a plasma. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
The above chart shows the timeline currently held by today’s astrophysicists and scientists. The chart covers essentially the first 100 seconds after the Big Bang (the last little bit of the chart goes on to 380,000 years but only because nothing much changed between 100 seconds old and 380,000 years! (other than the universe got a lot bigger). You are probably wondering right about now….”How the hell do they know that?” Good question. The answer lies in the experiments that these scientists have performed. The tools they use are big, expensive, and exotic….Particle Colliders. In order to test what happens in very hot, very dense environments, the scientists must create very hot, very dense environments. That is what the Particle Colliders do. The workhorse to date has been the Relativistic Heavy Ion Collider (RHIC). With this instrument, conditions approaching those that are thought to exist about 2 microseconds (μsec) after the Big Bang are created. Yes…at atomic nuclei levels, pressures as high as 15×1030 PSIG and temperatures of several trillions of degrees have been attained. The particles which exist at these conditions can be created and their properties measured. How to go further back in time to that Big Bang? Build bigger and better Colliders. The new Large Hadron Collider (LHC), located in France and Switzerland, is just the instrument. It is expected to reach densities several times larger than the RHIC and temperatures in excess of 10 trillion degrees. If successful this will allow scientists to investigate the conditions existing just 0.3 of a μsec after the Big Bang! Yes…this is definitely exotic science!
However, some physicists have recently developed the concept that there was a time before the Big Bang. This concept involves the idea that there was a universe before this one that had collapsed in on itself, to the point where the entire universe occupied a single, finite point in time and space at which point a “big bang” occurred. This alternate theory may be thought of as the Big Bounce. In this scenario the previous universe imploded to a point of finite density, at a given point in time and space, and then explodes to begin the expansion all over. The underlying basis for this concept is that a single point of infinite density (as required by the Big Bang Theory) is not possible, even though Einstein’s General Theory of Relativity requires it. Contrary to the General Theory of Relativity, recent theories of quantum theory of gravity provide for a limit to the density of energy and matter. This limit would then require the present universe to have begun with a finite beginning. The relevant question then is “how did this energy and matter get to that point?”. One possible answer would suggest some sort of process for the accumulation of material, such as a collapse of a previous universe. So expect more theories and adjustments to define this initial state for the Big Bang.
In any event, the universe we know of began with a bang…..and it proceeded to expand and continues to this day. There is a fine point of the Big Bang theory regarding the expansion of the universe…..from the first moment, the universe expanded…it did not expand into something, rather the universe itself simply expanded. There was no edge to the universe as it expanded, nor was there a central point from which the expansion began. The universe simply was the universe and it expanded itself. Yes, this concept is a bit mind-bending because it requires one to visualize a space not only empty (in the truest sense of the word) but also a place which is not a place…..irrelevant! I don’t know about you, but I’ve got a little problem getting my mind around that concept….
So the Big Bang occurred…as some very smart people tell us. Within the first 20 minutes, ¼ of the matter in the universe was converted to helium nuclei. Why helium and not hydrogen?
It was simply too hot for an electron to stick to a single proton, or any proton-neutron nuclei. But the formation of Helium was perfectly suited for this environment! In rapid succession, as the universe cooled slightly in the first few minutes, a proton and a neutron formed, then 2 protrons and a neutrons, then finally 2 protrons and 2 neutrons….a helium nucleus. After some 300,000 years the universe cooled sufficiently for this helium nucleus to attract an electron and the first hydrogen atom was formed.
This is predicted by nuclear physics and confirmed by observations – even today ¼ of the universe is helium. The universe expanded and cooled for the next hundreds of thousands of years and not much changed. After half a million years or so, the temperature had dropped to 3,000°K and this allowed hydrogen to form… the stuff stars are made out of. This opened the door for the existence of molecules as stable matter and allowed the formation of stars and galaxies at a later date. And the formation of stars provided, for the first time, the means to produce elements heavier than hydrogen and helium, through the process of nuclear fusion.
Life cycle of a Star
Stars are born in the enormous gas clouds which occupy the universe. Once born they live their long lives in nuclear fusion and then die. However, even in death the process continues with the remnants of the star…smaller stars, like our sun, leave behind a white dwarf….a white hot mass consisting of mainly carbon, hydrogen, and helium. It will about the size of earth, have no nuclear reactions, and will slowly cool over a period of several thousand million years. Larger stars, greater than 8 solar masses, explode in huge explosions called supernova and leave behind a neutron star, a mass so dense that a teaspoon portion would weigh thousands of tons. It has no nuclear reactions taking place, but emits a narrow beam of electromagnetic radiation which is how the neutron star is detected.
A Star is born…….
Stars depend on fusion of hydrogen for the creation of energy. The hydrogen comes from the abundant supply within the massive gas clouds in the Universe. As these gas clouds cool and condense the atoms come under the influence of gravity and begin to collect and grow in size. As this clump grows larger it attracts, by gravity, more and more hydrogen gas atoms and other, smaller, gas clumps. The increase in mass results in higher gravitational forces, which in turn results in the attraction of more mass, resulting in ever higher gravitational forces. and a continuing cycle. As the mass increases the temperature increases. When the mass is great enough to generate high enough temperatures – 10 million degrees – nuclear fusion results, converting the hydrogen to helium. The helium created is left in the core and the fusion reaction continues from the inside out. Extra large stars (see below) will continue the fusion process to produce heavier and heavier elements. This process takes billions of years. The quantity of hydrogen is so large that the conversion to helium takes a very long time, in spite of the continuous fusion reaction.
Take a moment and appreciate the tremendous process that is taking place in our own Sun. We have all seen the video of a hydrogen bomb detonation…..this is a relatively small amount of material that creates a huge amount of energy in an instant. In our Sun this same process has been going on continuously for 5,000 million years, and will continue for another 5,000 million years!
A Star dies…..
Stars come in different sizes….pretty much divided into 4 groups….small, medium, large, and massive. The massive stars are capable of producing the heavier elements. Each of these groups have a unique characteristic of their death, they behave differently depending on their size. But for each group the first step in the death of a star is he same…they become a …….Red Giant.
The first step in the death…. a Red Giant. As the hydrogen runs out and the fusion reaction slows, the star begins to collapse upon itself. This collapse continues until the temperature rises (due to the collapse) and then the star expands outward to many times its original size. For our sun this Red Giant phase will last for several thousand million years and will encompass the Inner planets. It stays this way for millions of years, slowly shedding layers of helium…
For low-mass stars….less than 0.4 times the mass of our sun…..as the Red Giant cools the core this star will collapse to a white dwarf. Its size shrinks to several thousand miles in diameter and remains that way for 1,000,000 million years, eventually losing all it’s mass to the space around. Note that the life of a low-mass star can be longer than the age of the universe as we know it. Therefore, it may be said that no low-mass stars have completed their life.
For medium-mass stars…. between 0.4 and 1.4 times the mass of the sun…..just as with a low-mass star, it will expand over a period of 100 million years to become a Red Giant, encompassing the Inner Planets. Then, over a period of 0.1 million years, it will shed it’s outer layers until only a white hot core (30,000 degrees) remains, a white dwarf, about the size of earth. It is very dim but has a very high surface temperature. It remains that way for thousands of millions of years, eventually cooling to a cold, cold object in space.
For large-mass stars... from 1.5 to 8 times the mass of the sun….. the completion of burning the hydrogen fuel does not result directly in a Red Giant. Rather, it will contract slightly, the core temperature will increase (100 million degrees) and additional fusion will occur, converting helium into carbon. The star will continue to expand towards the red super giant phase. At this point the physics is not certain but it is expected that thermonuclear processes continue, temperatures decrease as fuel runs out, collapse occurs resulting in an explosion during which huge amounts of energy are released within seconds as the star destroys itself (except for the super-dense core). The super-dense remnants make-up a neutron star in which the density, and therefore gravity is so great that electrons and protons are combined to neutrons. The size of the neutron star is very small….on the order of 10 km!
For massive stars…greater than 8 times the mass of our sun (and up to 20 times the mass) these stars may become Black Holes. The massive stars do not live as long as our Sun and the other smaller stars, maybe 10 million years before running out of nuclear fuel, but they burn brighter and hotter. Because they are hotter they can generate the internal temperatures (over a billion degrees) necessary to sustain successive nuclear reactions which produce heavier elements. This is how the heavier elements, such as gold, lead, and uranium, are formed. Note that all heavy elements found on earth were formed in the successive nuclear reactions within these massive stars.
As these massive stars progress through successive stages of nuclear reactions they balloon to enormous size until they eventually run out of fuel at which point gravity takes over and they suddenly collapse, in a matter of seconds. During the sudden collapse the core becomes more and more dense, it reaches a point where the material rebounds and explodes outward to become a Supernova, exploding in a huge flash and shining as brightly as 10 million of our Sun, if only for a short time….a matter of weeks. The remaining core is usually a neutron star or small, Stellar mass Black Hole. It is during this Supernova process when the interstellar space is littered with the heavier elements.
While many Supernovas are observed each year, only five (5) Supernovas have been observed with the unaided eye…..4 in our galaxy and 1 in the nearby galaxy, Large Magellanic Cloud. A Supernova is a rare sight, but one which can be seen with the unaided eye…so consider yourself fortunate indeed should you one night suddenly see a much brighter than normal object in the sky.
Quasars
Quasars are currently a theory. They are sources of tremendous amounts of energy from the core of galaxies. The central engine of a Quasar is theorized to be a super massive Black hole which is actively consuming material at a tremendous rate. (Note that most galaxies are thought to contain a super massive Black Hole but most do not actively consume large amounts of material, as in the case of a Quasar.) As the Super massive Black Hole consumes material, the objects reach tremendous temperatures (millions of degrees) and extreme speeds before entering the Black Hole and, in the process, give up large quantities of energy in the form of x-rays and visible light, which can be detected here on earth. Quasars are millions of times more massive than our sun and would contain most of a galaxy’s nucleus. At the end of their life they would remain Black Holes.
Colliding Galaxies
Galaxies do collide…..and result in a new galaxy of larger size.