The Solar System

Our solar system consists of an average star we call the Sun, the planets Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto. It includes: the satellites of the planets; numerous comets, asteroids, and meteoroids; and the interplanetary medium. The Sun is the richest source of electromagnetic energy (mostly in the form of heat and light) in the solar system. The Sun's nearest known stellar neighbor is a red dwarf star called Proxima Centauri, at a distance of 4.3 light years away. The whole solar system, together with the local stars visible on a clear night, orbits the center of our home galaxy, a spiral disk of 200 billion stars we call the Milky Way. The Milky Way has two small galaxies orbiting it nearby, which are visible from the southern hemisphere. They are called the Large Magellanic Cloud and the Small Magellanic Cloud. The nearest large galaxy is the Andromeda Galaxy. It is a spiral galaxy like the Milky Way but is 4 times as massive and is 2 million light years away. Our galaxy, one of billions of galaxies known, is traveling through intergalactic space.

The planets, most of the satellites of the planets and the asteroids revolve around the Sun in the same direction, in nearly circular orbits. When looking down from above the Sun's north pole, the planets orbit in a counter-clockwise direction. The planets orbit the Sun in or near the same plane, called the ecliptic. Pluto is a special case in that its orbit is the most highly inclined (18 degrees) and the most highly elliptical of all the planets. Because of this, for part of its orbit, Pluto is closer to the Sun than is Neptune. The axis of rotation for most of the planets is nearly perpendicular to the ecliptic. The exceptions are Uranus and Pluto, which are tipped on their sides.

Composition Of The Solar System

The Sun contains 99.85% of all the matter in the Solar System. The planets, which condensed out of the same disk of material that formed the Sun, contain only 0.135% of the mass of the solar system. Jupiter contains more than twice the matter of all the other planets combined. Satellites of the planets, comets, asteroids, meteoroids, and the interplanetary medium constitute the remaining 0.015%. The following table is a list of the mass distribution within our Solar System.

• Sun: 99.85%
• Planets: 0.135%
• Comets: 0.01% ?
• Satellites: 0.00005%
• Minor Planets: 0.0000002% ?
• Meteoroids: 0.0000001% ?
• Interplanetary Medium: 0.0000001% ?

Interplanetary Space

Nearly all the solar system by volume appears to be an empty void. Far from being nothingness, this vacuum of "space" comprises the interplanetary medium. It includes various forms of energy and at least two material components: interplanetary dust and interplanetary gas. Interplanetary dust consists of microscopic solid particles. Interplanetary gas is a tenuous flow of gas and charged particles, mostly protons and electrons -- plasma -- which stream from the Sun, called the solar wind.

The solar wind can be measured by spacecraft, and it has a large effect on comet tails. It also has a measurable effect on the motion of spacecraft. The speed of the solar wind is about 400 kilometers (250 miles) per second in the vicinity of Earth's orbit. The point at which the solar wind meets the interstellar medium, which is the "solar" wind from other stars, is called the heliopause. It is a boundary theorized to be roughly circular or teardrop-shaped, marking the edge of the Sun's influence perhaps 100 AU from the Sun. The space within the boundary of the heliopause, containing the Sun and solar system, is referred to as the heliosphere.

The solar magnetic field extends outward into interplanetary space; it can be measured on Earth and by spacecraft. The solar magnetic field is the dominating magnetic field throughout the interplanetary regions of the solar system, except in the immediate environment of planets which have their own magnetic fields.

The Terrestrial Planets

The terrestrial planets are the four innermost planets in the solar system, Mercury, Venus, Earth and Mars. They are called terrestrial because they have a compact, rocky surface like the Earth's. The planets, Venus, Earth, and Mars have significant atmospheres while Mercury has almost none. The following diagram shows the approximate distance of the terrestrial planets to the Sun.

The Jovian Planets

Jupiter, Saturn, Uranus, and Neptune are known as the Jovian (Jupiter-like) planets, because they are all gigantic compared with Earth, and they have a gaseous nature like Jupiter's. The Jovian planets are also referred to as the gas giants, although some or all of them might have small solid cores. The following diagram shows the approximate distance of the Jovian planets to the Sun.

Solar System Animation

• Formation of the Solar System.

Views of the Solar System

Our Milkyway Galaxy
This image of our galaxy, the Milky Way, was taken with NASA's Cosmic Background Explorer's (COBE) Diffuse Infrared Background Experiment (DIRBE). This never-before-seen view shows the Milky Way from an edge-on perspective with the galactic north pole at the top, the south pole at the bottom and the galactic center at the center. The picture combines images obtained at several near-infrared wavelengths. Stars within our galaxy are the dominant source of light at these wavelengths. Even though our solar system is part of the Milky Way, the view looks distant because most of the light comes from the population of stars that are closer to the galactic center than our own Sun. (Courtesy NASA)
Our Milky Way Gets a Makeover
Like early explorers mapping the continents of our globe, astronomers are busy charting the spiral structure of our galaxy, the Milky Way. Using infrared images from NASA's Spitzer Space Telescope, scientists have discovered that the Milky Way's elegant spiral structure is dominated by just two arms wrapping off the ends of a central bar of stars. Previously, our galaxy was thought to possess four major arms.

This artist's concept illustrates the new view of the Milky Way, along with other findings presented at the 212th American Astronomical Society meeting in St. Louis, Mo. The galaxy's two major arms (Scutum-Centaurus and Perseus) can be seen attached to the ends of a thick central bar, while the two now-demoted minor arms (Norma and Sagittarius) are less distinct and located between the major arms. The major arms consist of the highest densities of both young and old stars; the minor arms are primarily filled with gas and pockets of star-forming activity.

The artist's concept also includes a new spiral arm, called the "Far-3 kiloparsec arm," discovered via a radio-telescope survey of gas in the Milky Way. This arm is shorter than the two major arms and lies along the bar of the galaxy.

Our sun lies near a small, partial arm called the Orion Arm, or Orion Spur, located between the Sagittarius and Perseus arms. (Courtesy NASA/JPL-Caltech)
Spiral Galaxy, NGC 4414
The majestic galaxy, NGC 4414, is located 60 million light-years away. Like the Milky Way, NGC 4414 is a giant spiral-shaped disk of stars, with a bulbous central hub of older yellow and red stars. The outer spiral arms are considerably bluer due to ongoing formation of young, blue stars, the brightest of which can be seen individually at the high resolution provided by the Hubble camera. The arms are also very rich in clouds of interstellar dust, seen as dark patches and streaks silhouetted against the starlight. (Courtesy NASA/STSCI)
Obliquity of the Eight Planets
This illustration shows the obliquity of the eight planets. Obliquity is the angle between a planet's equatorial plane and its orbital plane. By International Astronomical Union (IAU) convention, a planet's north pole lies above the ecliptic plane. By this convention, Venus, Uranus, and Pluto have a retrograde rotation, or a rotation that is in the opposite direction from the other planets. (Copyright 2008 by Calvin J. Hamilton)
The Solar System
During the past three decades a myriad of space explorers have escaped the confines of planet Earth and have set out to discover our planetary neighbors. This picture shows the Sun and all nine planets of the solar system as seen by the space explorers. Starting at the top-left corner is the Sun followed by the planets Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto. (Copyright 1998 by Calvin J. Hamilton)
Sun and Planets
This image shows the Sun and nine planets approximately to scale. The order of these bodies are: Sun, Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto. (Copyright Calvin J. Hamilton)
Jovian Planets
This image shows the Jovian planets Jupiter, Saturn, Uranus and Neptune approximately to scale. The Jovian planets are named because of their gigantic Jupiter-like appearance. (Copyright Calvin J. Hamilton)
The Largest Moons and Smallest Planets
This image shows the relative sizes of the largest moons and the smallest planets in the solarsystem. The largest satellites pictured in this image are: Ganymede (5262 km), Titan (5150 km), Callisto (4806 km), Io (3642 km), the Moon (3476 km), Europa (3138 km), Triton (2706 km), and Titania (1580 km). Both Ganymede and Titan are larger than planet Mercury followed by Io, the Moon, Europa, and Triton which are larger than the planet Pluto. (Copyright Calvin J. Hamilton)
Diagram of Portrait Frames
On February 14, 1990, the cameras of Voyager 1 pointed back toward the Sun and took a series of pictures of the Sun and the planets, making the first ever "portrait" of our solar system as seen from the outside. This image is a diagram of how the frames for the solar system portrait were taken. (Courtesy NASA/JPL)
All Frames from the Family Portrait
This image shows the series of pictures of the Sun and the planets taken on February 14, 1990, for the solar system family portrait as seen from the outside. In the course of taking this mosaic consisting of a total of 60 frames, Voyager 1 made several images of the inner solar system from a distance of approximately 6.4 billion kilometers (4 billion miles) and about 32° above the ecliptic plane. Thirty-nine wide angle frames link together six of the planets of our solar system in this mosaic. Outermost Neptune is 30 times further from the Sun than Earth. Our Sun is seen as the bright object in the center of the circle of frames. The insets show the planets magnified many times. (Courtesy NASA/JPL)
Portrait of the Solar System
These six narrow-angle color images were made from the first ever "portrait" of the solar system taken by Voyager 1, which was more than 6.4 billion kilometers (4 billion miles) from Earth and about 32° above the ecliptic. Mercury is too close to the Sun to be seen. Mars was not detectable by the Voyager cameras due to scattered sunlight in the optics, and Pluto was not included in the mosaic because of its small size and distance from the Sun. These blown-up images, left to right and top to bottom are Venus, Earth, Jupiter, Saturn, Uranus, and Neptune. (Courtesy NASA/JPL)

Sun and Planet Summary

The following table lists statistical information for the Sun and planets:

	Distance (AU)	Radius (Earth's)	Mass (Earth's)	Rotation (Earth's)	# Moons	Orbital Inclination	Orbital Eccentricity	Obliquity	Density (g/cm3)
Sun	0	109	332,800	25-36*	9	---	---	---	1.410
Mercury	0.39	0.38	0.05	58.8	0	7	0.2056	0.1°	5.43
Venus	0.72	0.95	0.89	244	0	3.394	0.0068	177.4°	5.25
Earth	1.0	1.00	1.00	1.00	1	0.000	0.0167	23.45°	5.52
Mars	1.5	0.53	0.11	1.029	2	1.850	0.0934	25.19°	3.95
Jupiter	5.2	11	318	0.411	16	1.308	0.0483	3.12°	1.33
Saturn	9.5	9	95	0.428	18	2.488	0.0560	26.73°	0.69
Uranus	19.2	4	17	0.748	15	0.774	0.0461	97.86°	1.29
Neptune	30.1	4	17	0.802	8	1.774	0.0097	29.56°	1.64
Pluto	39.5	0.18	0.002	0.267	1	17.15	0.2482	119.6°	2.03

* The Sun's period of rotation at the surface varies from approximately 25 days at the equator to 36 days at the poles. Deep down, below the convective zone, everything appears to rotate with a period of 27 days.

Extinct Species

Sophora Toromiro

Cosmos Atrosanguineus

Saint Helena Olive

Cooksonia

seventymph

pvorchirds

Enviromental Destruction 4

Pollution is the introduction of contaminants into an environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms. Pollution can take the form of chemical substances or energy, such as noise, heat, or light. Pollutants, the elements of pollution, can be foreign substances or energies, or naturally occurring; when naturally occurring, they are considered contaminants when they exceed natural levels. Pollution is often classed as point source or nonpoint source pollution. The Blacksmith Institute issues annually a list of the world's worst polluted places. In the 2007 issues the ten top nominees are located in Azerbaijan, China, India, Peru, Russia, Ukraine and Zambia.

The major forms of pollution are listed below along with the particular pollutants relevant to each of them:

• Air pollution, the release of chemicals and particulates into the atmosphere. Common gaseous air pollutants include carbon monoxide, sulfur dioxide, chlorofluorocarbons (CFCs) and nitrogen oxides produced by industry and motor vehicles. Photochemical ozone and smog are created as nitrogen oxides and hydrocarbons react to sunlight. Particulate matter, or fine dust is characterized by their micrometre size PM₁₀ to PM_2.5.

• Water pollution, by the release of waste products and contaminants into surface runoff into river drainage systems, leaching into groundwater, liquid spills, wastewater discharges, eutrophication and littering.
• Soil contamination occurs when chemicals are released by spill or underground leakage. Among the most significant soil contaminants are hydrocarbons, heavy metals, MTBE, herbicides, pesticides and chlorinated hydrocarbons.
• Littering
• Radioactive contamination, resulting from 20th century activities in atomic physics, such as nuclear power generation and nuclear weapons research, manufacture and deployment. (See alpha emitters and actinides in the environment.)
• Noise pollution, which encompasses roadway noise, aircraft noise, industrial noise as well as high-intensity sonar.
• Light pollution, includes light trespass, over-illumination and astronomical interference.
• Visual pollution, which can refer to the presence of overhead power lines, motorway billboards, scarred landforms (as from strip mining), open storage of trash or municipal solid waste.
• Thermal pollution, is a temperature change in natural water bodies caused by human influence, such as use of water as coolant in a power plant.

Air pollution

A government committee has estimated that 12,000 to 24,000 people in the UK die every year from the acute effects of air pollution. More die from chronic effects. Air pollution is therefore a major health issue.

In many parts of West London our air is not fit to breathe. The main source of air pollution is traffic emissions. Significant amounts also come from residential and commercial gas use, industry, construction sites and emissions from outside London. A particularly large and concentrated source of air pollution is Heathrow. Indeed, it is the biggest single source of pollution in Western Europe.

Water pollution

The quality of the water in our rivers and canals is generally not too good. They are not fit for us to swim in and they are often not too good for wildlife either. There have been improvements in recent years, but they are still far from what we would wish to see.

The Environment Agency is the government body responsible for water quality. It does some admirable work, but it suffers from the failing of most public bodies - it is not really prepared to take on those parties who are polluting our water. A notable instance has been heavy pollution of water bodies by Heathrow Airport. Nothing was being done about it by the Environment Agency until a concerted campaign was launched by local residents.

A particular class of pollutants which can get into water and which threaten our health and our wildlife are pesticides. 31,000 tonnes of pesticides are used in the UK every year. Overuse, careless use and incorrect disposal of pesticides mean that a range of dangerous chemicals get into our watercourses. Water companies have to constantly test for pesticides and removing them drinking water costs us - consumers of water - large sums of money.





Contaminated land and pollution of groundwater

There are significant areas of contaminated land in West London. This is the legacy of earlier industrial activity, at a time when looking after the environment and cleaning up after one had finished were not even considered.

There is now legislation that requires local authorities to identify contaminated land and, if necessary, make it safe. However, it has to be said that this is very low in the government's set of priorities.




Noise pollution

Noise is a common problem in modern-day life and it represents a serious threat to our quality of life. A recent survey showed that the biggest problems in London are, in order of priority:

• Traffic noise
• Aircraft noise
• Neighbour noise
• Construction noise
• Railway noise

Enviromental Destructions 3

A flash flood is a rapid flooding of geomorphic low-lying areas - washes, rivers, dry lakes and basins. It may be caused by heavy rain associated with a storm, hurricane, or tropical storm or meltwater from ice or snow flowing over icesheets or snowfields. Flash floods can also occur after the collapse of an ice dam, debris dam or a human structure, such as a dam, for example, the Johnstown Flood of 1889. Flash floods are distinguished from a regular flood by a timescale less than six hours. The temporary availability of water is often utilised by plants with rapid germination and short growth cycle, and by specially adapted animal life.

Flash flooding occurs when a barrier holding back water fails or when water falls too quickly on saturated soil or dry soil that has poor absorption ability. The runoff collects in low-lying areas and rapidly flows downhill. Flash floods most often occur in normally dry areas that have recently received precipitation, but may be seen anywhere downstream from the source of the precipitation, even dozens of miles from the source. In areas on or near volcanoes, flash floods have also occurred after eruptions, when glaciers have been melted by the intense heat.

Pictures

A "slump" landslide in San Mateo County, California in January 1997

Enviromental Destruction 3

A landslide or landslip is a geological phenomenon which includes a wide range of ground movement, such as rock falls, deep failure of slopes and shallow debris flows, which can occur in offshore, coastal and onshore environments. Although the action of gravity is the primary driving force for a landslide to occur, there are other contributing factors affecting the original slope stability. Typically, pre-conditional factors build up specific sub-surface conditions that make the area/slope prone to failure, whereas the actual landslide often requires a trigger before being released.

Landslides occur when the stability of a slope changes from a stable to an unstable condition. A change in the stability of a slope can be caused by a number of factors, acting together or alone. Natural causes of landslides include:

• groundwater (porewater) pressure acting to destabilize the slope
• Loss or absence of vertical vegetative structure, soil nutrients, and soil structure (e.g. after a wildfire)
• erosion of the toe of a slope by rivers or ocean waves
• weakening of a slope through saturation by snowmelt, glaciers melting, or heavy rains
• earthquakes adding loads to barely-stable slopes
• earthquake-caused liquefaction destabilizing slopes (see Hope Slide)
• volcanic eruptions

landslides are aggravated by human activities, Human causes include:deforestation, cultivation and construction, which destabilize the already fragile slopes

• vibrations from machinery or traffic
• blasting
• earthwork which alters the shape of a slope, or which imposes new loads on an existing slope
• in shallow soils, the removal of deep-rooted vegetation that binds colluvium to bedrock
• Construction, agricultural or forestry activities (logging) which change the amount of water which infiltrates the soil.

Enviromental Destructions 2

Soil erosion by water, wind and tillage affects both agriculture and the natural environment. Soil loss, and its associated impacts, is one of the most important (yet probably the least well-known) of today's environmental problems (BBC 2000; Guardian 2004).

"The threat of nuclear weapons and man's ability to destroy the environment are really alarming. And yet there are other almost imperceptible changes - I am thinking of the exhaustion of our natural resources, and especially of soil erosion - and these are perhaps more dangerous still, because once we begin to feel their repercussions it will be too late." (p144 of The Dalai Lama's Little Book of Inner Peace: 2002, Element Books, London)

It isn't easy to find comprehensive information on erosion, however. To a large extent this is because soil erosion does not fit neatly under any one heading: it is studied by geomorphologists, agricultural engineers, soil scientists, hydrologists and others; and is of interest to policy-makers, farmers, environmentalists and many other individuals and groups.

Despite the global nature of the problem of erosion by water, even today we do not have good information regarding the global extent of erosion by water. Data on the severity of erosion is also often limited.

The GLASOD study estimated that around 15 per cent of the Earth's ice-free land surface is afflicted by all forms of land degradation. Of this, accelerated soil erosion by water is responsible for about 56 per cent and wind erosion is responsible for about 28 per cent.

This means that the area affected by water erosion is, very roughly, around 11

million square km., and the area affected by wind erosion is around 5.5 million square km.

The area affected by tillage erosion is currently unknown.

Because soil is formed slowly, it is essentially a finite resource. The severity of the global erosion problem is only now becoming widely appreciated.

ENVIROMENTALISME

Environmentalism is a broad philosophy and social movement regarding concerns for environmental conservation and improvement of the state of the environment. Environmentalism and environmental concerns are often represented by the colour green.

Environmentalism can also be defined as a social movement that seeks to influence the political process by lobbying, activism, and education in order to protect natural resources and ecosystems. In recognition of humanity as a participant in ecosystems, the environmental movement is centered on ecology, health, and human rights.

An environmentalist is a person who may advocate stewardship of the natural environment and the sustainable management of its resources through changes in public policy or individual behavior by supporting practices such as recycling. In various ways (for example, grassroots activism and protests), environmentalists and environmental organizations seek to give the natural world a stronger voice in human affairs.

In recent years environmentalism has frequently been called, or compared to, a religion by its detractors. This is usually done at the same time as pointing out what are perceived as extremist viewpoints or actions of self-identified environmentalists or groups.

Enviromental Movement

The environmental movement (a term that sometimes includes the conservation and green movements) is a diverse scientific, social, and political movement. In general terms, environmentalists advocate the sustainable management of resources, and the protection (and restoration, when necessary) of the natural environment through changes in public policy and individual behavior. In its recognition of humanity as a participant in ecosystems, the movement is centered around ecology, health, and human rights. Additionally, throughout history, the movement has been incorporated into religion. The movement is represented by a range of organizations, but has a younger demographic than is common in other social movements (see green seniors). Because of its large membership, varying and strong beliefs, the movement is not entirely united. Some argue that an environmental ethic of at least some sort is so urgently needed in all quarters and that the broader the movement is the better. Conversely, others assert that disunity can be a weakness in the face of strong opposition from unsympathetic political and industrial forces.

Free Market Enviromentalism
Free market environmentalism is a theory that argues that the free market, property rights, and tort law provide the best tools to preserve the health and sustainability of the environment. It considers environmental stewardship to be natural, as well as the expulsion of polluters and other aggressors through individual and class action.

Preservation and Conservation
Environmental preservation in the United States is viewed as the setting aside of natural resources to prevent damage caused by contact with humans or by certain human activities, such as logging, mining, hunting, and fishing, only to replace them with new human activities such as tourism and recreation. Regulations and laws may be enacted for the preservation of natural resources.

Organizations and Conferences
Environmental organizations can be global, regional, national or local; they can be government-run or private (NGO). Despite a tendency to see environmentalism as an American or Western-centered pursuit, almost every country has its share of environmental activism. Moreover, groups dedicated to community development and social justice may also attend to environmental concerns.

There are some volunteer organizations. For example Ecoworld, which is about the environment and is based in team work and volunteer work. Some US environmental organizations, among them the Natural Resources Defense Council and the Environmental Defense Fund, specialize in bringing lawsuits (a tactic seen as particularly useful in that country). Other groups, such as the US-based National Wildlife Federation, the Nature Conservancy, and The Wilderness Society, and global groups like the World Wide Fund for Nature and Friends of the Earth, disseminate information, participate in public hearings, lobby, stage demonstrations, and may purchase land for preservation. Smaller groups, including Wildlife Conservation International, conduct research on endangered species and ecosystems. More radical organizations, such as Greenpeace, Earth First!, and the Earth Liberation Front, have more directly opposed actions they regard as environmentally harmful. While Greenpeace is devoted to nonviolent confrontation as a means of bearing witness to environmental wrongs and bringing issues into the public realm for debate, the underground Earth Liberation Front engages in the clandestine destruction of property, the release of caged or penned animals, and other criminal acts. Such tactics are regarded as unusual within the movement, however.

On an international level, concern for the environment was the subject of a UN conference in Stockholm in 1972, attended by 114 nations. Out of this meeting developed UNEP (United Nations Environment Programme) and the follow-up United Nations Conference on Environment and Development in 1992. Other international organizations in support of environmental policies development include the Commission for Environmental Cooperation (NAFTA), the European Environment Agency (EEA), and the Intergovernmental Panel on Climate Change (IPCC).

For more information, please click Enviroment Portal