The Universe

The Universe How everything began with a bang

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Contents

02 A loud Beginning 04 The Milky Way 06 The Sun 08 Mercury 10 Venus 13 Earth 15 Plate Tectonics 18 The Red Planet 20 Jupiter 22 Saturn 24 Uranus 28 Neptune 31 Black Holes 36 Cosmic Rays 39 Nasa 41 The iss

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A Loud Beginning starting from a singularity

The Big Bang theory is the prevailing cosmological model for the universe from the earliest known periods during its subsequent large-scale evolution.

The model accounts for the fact that the universe expanded from a very high density and high temperature state, and offers a comprehensive explanation for a broad range of observed phenomena, including the abundance of light elements, the cosmic microwave background, large scale structure, and Hubble’s— Law. If the known laws of physics are extrapolated beyond where they are valid, there is a singularity.

Modern measurements place this moment at approximately 13.8 billion years ago, which is thus considered the age of the universe. After the initial expansion, the universe cooled sufficiently to allow the formation of subatomic particles, and later simple atoms. Giant clouds of these primordial elements later coalesced with gravity to form stars and galaxies.

Since Georges LemaĂŽtre first noted, in 1927, that an expanding universe might be traced back in time to an originating single point, scientists have built on his idea of cosmic expansion.

Our Galaxy

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Like a rapidly expanding balloon, it swelled from a size smaller than an electron to nearly its current size within a tiny fraction of a second.

While the scientific community was once divided between supporters of two different expanding universe theories, the Big Bang and the Steady State theory, accumulated empirical evidence provides strong support for the former.

In 1929, from analysis of galactic redshifts, Edwin Hubble concluded that galaxies are drifting apart, important observational evidence consistent with the hypothesis of an expanding universe. In 1964, the cosmic microwave background radiation was discovered,

which was crucial evidence in favor of the Big Bang model, since that theory predicted the existence of background radiation throughout the universe before it was discovered. Recently, measurements of the redshifts of supernovae indicate that the expansion of the universe is accelerating, an observation attributed to dark energy’s existence. The known physical laws of nature can be used to calculate the characteristics of the universe in detail back in timeto an initial state of extreme density and temperature.

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The Milky Way

Our Galaxy

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The Milky Way The Milky Way is the galaxy that contains our Solar System. Its name “milky” is derived from its appearance as a dim glowing band arching across the night sky whose individual stars cannot be distinguished by the naked eye. The term “Milky Way” is a translation of the Latin via lactea, from the Greek (galaxías kýklos, “milky circle”).From Earth the Milky Way appears as a band because its disk-shaped structure is viewed from within. Galileo Galilei first resolved the band of light into individual stars with his telescope in 1610. Until the early 1920s most astronomers thought that the Milky Way contained all the stars in the Universe.

Following the 1920 Great Debate between the astronomers Harlow Shapley and Heber Curtis, observations by Edwin Hubble

showed that the Milky Way is just one of many galaxies—now known to number in the billions. The Milky Way is a barred spiral galaxy that has a diameter usually considered to be roughly 100,000–120,000 light-years but may be 150,000–180,000 light-years instead.

The Milky Way is estimated to contain 100–400 billion stars, although this number may be as high as one trillion. There are probably at least 100 billion planets in the Milky Way. The Solar System is located within the disk, about 27,000 light-years from the Galactic Center, on the inner edge of one of the spiral-shaped concentrations of gas and dust. called the Orion Arm.

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The Sun The Sun is by far the largest object in the solar system. It contains more than 99.8% of the total mass of the Solar System (Jupiter contains most of the rest).

It is often said that the Sun is an “ordinary” star. That’s true in the sense that there are many others similar to it. But there are many more smaller stars than larger ones; the Sun is in the top 10% by mass.

The median size of stars in our galaxy is probably less than half the mass of the Sun. How big is the sun? The Sun is personified in many mythologies: the Greeks called it Helios and the Romans called it Sol. The Sun is, at present, about 70% hydrogen and 28% helium by mass everything else (“metals”) amounts to less than 2%.

This changes slowly over time as the Sun converts hydrogen to helium in its core.

The outer layers of the Sun exhibit differential rotation: at the equator the surface rotates once every 25.4 days; near the poles

it’s as much as 36 days. This odd behavior is due to the fact that the Sun is not a solid body like the Earth. Similar effects are seen in the gas planets. The differential rotation extends considerably down into the interior of the Sun but the core of the Sun rotates as a solid body.

Conditions at the Sun’s core (approximately the inner 25% of its radius) are extreme. The temperature is 15.6 million Kelvin and the pressure is 250 billion atmospheres. At the center of the core the Sun’s density is more than 150 times that of water.

The Sun’s power (about 386 billion billion mega Watts) is produced by nuclear fusion reactions. Each second about 700,000,000 tons of hydrogen are converted to about 695,000,000 tons of helium and 5,000,000 tons (=3.86e33 ergs) of energy in the form of gamma rays. As it travels out toward the surface, the energy is continuously absorbed and re-emitted at lower and lower temperatures so that by the time it reaches the surface, it

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Our Solar System is primarily visible light. For the last 20% of the way to the surface the energy is carried more by convection than by radiation.

The surface of the Sun, called the photosphere, is at a temperature of about 5800 K. Sunspots are “cool” regions, only 3800 K (they look dark only by comparison with the surrounding regions). Sunspots can be very large, as much as 50,000 km in diameter. Sunspots are caused by complicated and not very well understood interactions with the Sun’s magnetic field.

A small region known as the chromosphere lies above the photosphere. The highly rarefied region above the chromosphere, called the corona, extends millions of kilometers into space but is visible only during a total solar eclipse (left). Temperatures in the corona are over 1,000,000 K.

The Sun’s power (about 386 billion billion mega Watts) is produced by nuclear fusion reactions It just happens that the Moon and the Sun appear the same size in the sky as viewed from the Earth. And since the Moon orbits the Earth in approximately the same plane as the Earth’s orbit around the Sun sometimes the Moon comes directly between the Earth and the Sun. This is called a solar eclipse; if the alignment is slighly imperfect then the Moon covers only part of the Sun’s disk and the event is called a partial eclipse. When it lines up perfectly the entire solar disk is blocked and it is called a total eclipse of the Sun. Partial eclipses are visible over a wide area of the Earth but the region from which a total eclipse is visible, called the path oft totality, is very narrow, just a few kilometers (though it is usually thousands of kilometers long). Eclipses of the Sun happen once or twice a year.

If you stay home, you’re likely to see a partial eclipse several times per decade. But since the path of totality is so small it is very unlikely

that it will cross you home. So people often travel half way around the world just to see a total solar eclipse. For a few precious minutes it gets dark in the middle of the day. The stars come out. The animals and birds think it’s time to sleep. And you can see the solar corona. It is well worth a major journey.

Some facts about the Sun:

One million Earths could fit inside the Sun: If a hollow Sun was filled up with spherical Earths then around 960,000 would fit inside. On the other hand if these Earths were squished inside with no wasted space then around 1,300,000 would fit inside. The Sun’s surface area is 11,990 times that of the Earth’s.

Eventually, the Sun will consume the Earth: When all the Hydrogen has been burned, the Sun will continue for about 130 million more years, burning Helium, during which time it will expand to the point that it will engulf Mercury and Venus and the Earth. At this stage it will have become a red giant The Sun will one day be about the size of Earth: After its red giant phase, the Sun will collapse, retaining its enormous mass, but containing the approximate volume of our planet. When this happens, it will be called a white dwarf.

In addition to heat and light, the Sun also emits a low density stream of charged particles (mostly electrons and protons) known as the solar wind which propagates throughout the solar system at about 450 km/sec. The solar wind and the much higher energy particles ejected by solar

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Mercury flares can have dramatic effects on the Earth ranging from power line surges to radio interference to the beautiful aurora borealis.

Further study of the solar wind will be done by Wind, ACE and SOHO spacecraft from the dynamically stable vantage point directly between the Earth and the Sun about 1.6 million km from Earth.ecthe 17th century called the Maunder Minimum. It coincides with an abnormally cold period in northern Europe sometimes known as the Little Ice Age. Since the formation of the solar system the Sun’s output has increased by about 40%.

The Sun is about 4.5 billion years old.

Since its birth it has used up about half of the hydrogen in its core. It will continue to radiate “peacefully” for another 5 billion years or so (although its luminosity will approximately double in that time). But eventually it will run out of hydrogen fuel.

It will then be forced into radical changes which, though commonplace by stellar standards, will result in the total destruction of the Earth (and probably the creation of a planetary nebula).

The Sun’s satellites There are eight planets and a large number of smaller objects orbiting the Sun. (Exactly which bodies should be classified as planets and which as “smaller objects” has been the source of some controversy, but in the end it is really only a matter of definition. Pluto is no longer officially a planet but we’ll keep it here for history’s sake.)

In Roman mythology Mercury is the god of commerce, travel and thievery, the Roman counterpart of the Greek god Hermes, the messenger of the Gods. The planet probably received this name because it moves so quickly across the sky.

Mercury has been known since at least the time of the Sumerians (3rd millennium BC). It was sometimes given separate names for its apparitions as a morning star and as an evening star. Greek astronomers knew, however, that the two names referred to the same body. Heraclitus even believed that Mercury and Venus orbit the Sun, not the Earth.

Since it is closer to the Sun than the Earth, the illumination of Mercury’s disk varies when viewed with a telescope from our perspective. Galileo’s telescope was too small to see Mercury’s phases but he did see the phases of Venus.

Mercury has been now been visited by two spacecraft, Mariner 10 and Messenger.

Marriner 10 flew by three times in 1974 and 1975. Only 45% of the surface was mapped (and, unfortunately, it is too close to the Sun to be safely imaged by HST). Messenger was launched by NASA in 2004 and has been in orbit Mercury since 2011. Its first flyby in Jan 2008 provided new high quality images of some of the terrain not seen by Mariner 10. Since then Messenger has taken over 250,000 photographs coving the entire planet. Global Mosaics.

The mission has provided support for the hypothesis that water ice and other volatiles do exist in the polar regions in permanent shadow.

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Our Solar System

Mercury In Roman mythology Mercury is the god of commerce, travel and thievery, the Roman counterpart of the Greek god Hermes, the messenger of the Gods. The planet probably received this name because it moves so quickly across the sky.

Mercury has been known since at least the time of the Sumerians (3rd millennium BC). It was sometimes given separate names for its apparitions as a morning star and as an evening star. Greek astronomers knew, however, that the two names referred to the same body.

Heraclitus even believed that Mercury and Venus orbit the Sun, and not the Earth.

Temperature variations on Mercury are the most extreme in the solar system ranging from 90 K to 700 K. The temperature on Venus is slightly hotter but very stable.

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Venus Venus, the second planet from the sun, is named for the Roman goddess of love and beauty. The planet — the only planet named after a female — may have been named for the most beautiful deity of her pantheon because it shone the brightest of the five planets known to ancient astronomers.

In ancient times, Venus was often thought to be two different stars, the evening star and the morning star — that is, the ones that first appeared at sunset and sunrise.

In Latin, they were respectively known as Vesper and Lucifer. In Christian times, Lucifer, or “light-bringer,” became known as the name of Satan before his fall.The planet — the only planet named after a female — may have been named for the most beautiful deity of her pantheon because it shone the brightest of the five planets known to ancient astronomers.

In ancient times, Venus was often thought to be two different stars, the evening star and the morning star — that is, the ones

that first appeared at sunset and sunrise.

In Latin, they were respectively known as Vesper and Lucifer. In Christian times, Lucifer, or “light-bringer,” became known as the name of Satan before his fall.

Venus and Earth are often called twins because they are similar in size, mass, density, composition and gravity. However, the similarities end there.

Venus is the hottest world in the solar system. Although Venus is not the planet closest to the sun, its dense atmosphere traps heat in a runaway version of the greenhouse effect that warms Earth. As a result, temperatures on Venus reach 870 degrees Fahrenheit (465 degrees Celsius), more than hot enough to melt lead. Probes that scientists have landed there have survived only a few hours before being destroyed. Venus has a hellish atmosphere as well, consisting mainly of carbon dioxide with clouds of sulfuric acid, and scientists have only detected trace amounts of water in the atmosphere.

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Our Solar System

The atmosphere is heavier than that of any other planet, leading to a surface pressure 90 times that of Earth. The surface of Venus is extremely dry. During its evolution, ultraviolet rays from the sun evaporated water quickly, keeping it in a prolonged molten state. There is no liquid water on its surface today because the scorching heat created by its ozone-filled atmosphere would cause any to boil away. Roughly two-thirds of the Venusian surface is covered by flat, smooth plains that are marred by thousands of volcanoes, some which are still active today, ranging from about 0.5 to 150 miles (0.8 to 240 kilometers) wide, with lava flows carving long, winding canals up to more than 3,000 miles (5,000 km) in length, longer than on any other planet.

Six mountainous regions make up about one-third of the Venusian surface.

One mountain range, called Maxwell, is about 540 miles (870 km) long and reaches up to some 7 miles (11.3 km) high, making

it the highest feature on the planet.Venus also possesses a number of surface features unlike anything on Earth. For example, Venus has coronae, or crowns — ringlike structures that range from roughly 95 to 360 miles (155 to 580 km) wide. Scientists believe these formed when hot material beneath the crust rises up, warping the planet’s surface.

Venus also has tesserae, or tiles — raised areas in which many ridges and valleys have formed in different directions.

With conditions on Venus that could be described as infernal, the ancient name for Venus — Lucifer — seems to fit. However, this name did not carry any fiendish connotations; Lucifer means “light-bringer,” and when seen from Earth, Venus is brighter than any other planet or even any star in the night sky because of its highly reflective clouds and its closeness to our planet.

Venus takes 243 Earth days to rotate on its axis, by far the slowest of any of the major planets, and because of this sluggish spin, its metal core cannot generate a magnetic field similar to Earth’s.

Orbital characteristics

“There is good evidence that Venus once had liquid water and a much thinner atmosphere, similar to Earth billions of years ago. But today the surface of Venus is dry as a bone, hot enough to melt lead, there are clouds of sulfuric acid that reach a hundred miles high and the air is so thick it’s like being 900 meters deep in the ocean.”

-Bill Nye

If viewed from above, Venus rotates on its axis the opposite way that most planets rotate. That means on Venus, the sun would appear to rise in the west and set in the east.

On Earth, the sun appears to rise in the east and set in the west.

The Venusian year — the time it takes to orbit the sun — is about 225 Earth days long.

Normally, that would mean that days on Venus would be longer than years. However, because of Venus’ curious retrograde rotation, the time from one sunrise to the next is only about 117 Earth days long.

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Climate The very top layer of Venus’ clouds zip around the planet every four Earth days, propelled by hurricane-force winds traveling roughly 224 mph (360 kph). This super-rotation of the planet’s atmosphere, some 60 times faster than Venus itself rotates, may be one of Venus’ biggest mysteries. The winds at the planet’s surface are much slower, estimated to be just a few miles per hour.

The Venus Express spacecraft, which the European Space Agency launched in 2005, intriguingly found evidence of lightning on the planet. This lightning is unique from that found on the other planets in the solar system, in that it is not associated with water clouds. Instead, on Venus, the lightning is associated with clouds of sulfuric acid. Scientists are excited by these electrical discharges, because they can break molecules into fragments that can then combine with other fragments in unexpected ways.

A long-lived cyclone on Venus, first observed in 2006, remains in constant flux, with elements constantly breaking apart and reforming. The clouds also carry signs of meteorological events known as gravity waves, caused when winds blow over geological features, causing rises and falls in the layers of air.

Unusual stripes in the upper clouds of Venus are dubbed “blue absorbers” or “ultraviolet absorbers” because they strongly absorb light in the blue and ultraviolet wavelengths. These are soaking up a huge amount of energy — nearly half of the total solar energy the planet absorbs.

As such, they seem to play a major role in keeping Venus as hellish as it is. Their exact composition remains uncertain.

Research & exploration

The United States, Soviet Union and European Space Agency have deployed many spacecraft to Venus, more than 20 in all so far. NASA’s Mariner 2 came within 21,600 miles (34,760 km) of Venus in 1962, making it the first planet to be observed by a passing spacecraft. The Soviet Union’s Venera 7 was the first spacecraft to land on another planet, and Venera 9 returned the first photographs of the Venusian surface. The first Venusian orbiter, NASA’s Magellan, generated maps of 98 percent of the planet’s surface using radar, showing details of features as small as 330 feet (100 meters) across.

The European Space Agency’s Venus Express spent eight years in orbit around Venus with a large variety of instruments, and has confirmed the presence of lightning there. In August 2014, as the satellite began wrapping up its mission, controllers engaged in a month-long maneuver that plunged it into the outer layers of the planet’s atmosphere. Venus Express survived the daring journey, then moved into a higher orbit, where it will spend several months until it runs out of fuel. By December 2014, controllers expect to send the craft plunging to its death through the planet’s atmosphere.

The next mission to Venus, Japan’s Akatsuki, was launched in 2010, but its main engine died during a pivotal orbit-insertion burn, sending the craft hurling into space. Using smaller thrusters, the Japanese team successfully performed a burn to correct the spacecraft’s course. In November 2015, the team hopes to once again use the thrusters to put it back in orbit around Venus, with planets to probe the hot planet’s cloud layers.

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Our Solar System

Earth “It suddenly struck me that that tiny pea, pretty and blue, was the Earth.

I put up my thumb and shut one eye, and my thumb blotted out the planet Earth. I didn’t feel like a giant. I felt very, very small.”

–Neil Armstrong

The first era in which the Earth existed is what is known as the Hadean Eon. This name comes from the Greek word “Hades” (underworld), which refers to the condition of the planet at the time. This consisted of the Earth’s surface being under a continuous bombardment by meteorites and intense volcanism, which is believed to have been severe due to the large heat flow and geothermal gradient dated to this era.

Outgassing and volcanic activity produced the primordial atmosphere, and evidence exists that liquid water existed at this time, despite the conditions on the surface. Condensing water vapor, augmented by ice delivered by comets, accumulated in the atmosphere and cooled the molten exterior of the planet to form a solid crust and produced the oceans.

It was also during this eon – roughly 4.48 billion years ago (or 70–110 million years after the start of the Solar System) – that the Earth’s only satellite, the Moon, was formed. The most common theory, known as the “giant impact hypothesis” proposes that the Moon originated after a body the size of Mars (sometimes named Theia) struck the proto-Earth a glancing blow.

It is believed that 4.4 billion years ago, a celestial body (Theia) slammed into Earth and produced the Moon. It is believed that 4.4 billion years ago, a celestial body (Theia) slammed into Earth and produced the Moon. Image Credit: NASA/JPL-Caltech The collision was enough to vaporize some of the Earth’s outer layers and melt both bodies, and a portion of the mantle material

14. was ejected into orbit around the Earth. The ejecta in orbit around the Earth condensed, and under the influence of its own gravity, became a more spherical body: the Moon.

The Hadean Eon ended roughly 3.8 billion years ago with the onset of the Archean age. Much like the Hadean, this eon takes it name from a ancient Greek word, which in this case means “beginning” or “origin.”

This refers to the fact that it was during this period that the Earth had cooled significantly and life forms began to evolve.

Most life forms today could not have survived in the Archean atmosphere, which lacked oxygen and an ozone layer.

Nevertheless, it is widely understood that it was during this time that most primordial life began to take form, though some scientists argue that many lifeforms may have occurred even sooner during the late Hadean.

At the beginning of this Eon, the mantle was much hotter than it is today, possibly as high as 1600 °C (2900 °F). As a result, the planet was much more geologically active, processes like convection and plate tectonics occurred much faster, and subduction zones were more common. Nevertheless, the presence of sedimentary rock date to this period indicates an abundance of rivers and oceans.

The super-continent Pangea during the Permian period (300 – 250 million years ago).

The super-continent Pangea during the Permian period (300 – 250 million years ago). Credit: NAU Geology/Ron Blakey The first larger pieces of continental crust are also dated to the late Hadean/early Achean Eons. What is left of these first small continents are called cratons, and these pieces of crust form the cores around which today’s continents grew. As the surface continually reshaped itself over the course of the ensuing eons, continents formed and broke up.

The continents migrated across the surface, occasionally combining to form a supercontinent. Roughly 750 million years ago, the earliest-known supercontinent called Rodinia began to break apart, then recombined 600 – 540 million years ago to form Pannotia, then finally Pangaea.

This latest supercontinent broke apart 180 million years ago, eventually settling on the configuration that we know today.

Since that time, a mere blip on the geological time scale, all the events that we consider to be “recent history” took place.

The dinosaurs ruled and then died, mammals achieved ascendancy, hominids began to slowly evolve into the species we know as homo sapiens, and civilization emerged.

And it all began with a lot of dust, fire, and some serious impacts. From this, the Sun, Moon, Earth, and life as we know it were all created.

Our Solar System

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Plate Tectonics The study of the lithosphere, the outerportion of the earth consisting of the crust and part of the upper mantle. The lithosphere is divided into about a dozen large plates which move and interact with one another to create earthquakes, mountain ranges, volcanic activity, ocean trenches and many other features. Continents and ocean basis are moved and changed in shape as a result of these plate movements.

The image ontop show how a large supercontinent, known as Pangaea was then

fragmented into several pieces, each being part of a mobile plate of the lithosphere. These pieces were to become Earth’s current continents.

In the early 1900s Alfred Wegener proposed the idea of Continental Drift. His ideas centered around continents moving across the face of the earth. The idea was not quite correct – compared to the plate tectonics theory of today – but his thinking was on the proper track.

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Water on planet Earth is an abundant resource and is the essential ingredient for life. According to scientists, the existance of water on earth may have arrived on Earth by meteorites during the early days of its formation.

Lake Louise: Image from Pinterest.

Our Solar System

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Mars

The Red Planet Mars is the fourth planet from the sun.

Befitting the red planet’s bloody color, the Romans named it after their god of war.

The Romans copied the ancient Greeks, who also named the planet after their god of war, Ares. Other civilizations also typically gave the planet names based on its color — for example, the Egyptians named it “Her Desher,” meaning “the red one,” while ancient Chinese astronomers dubbed it “the fire star.”

Physical characteristics RegolithThe bright rust color Mars is known for is due to iron-rich minerals in its regolith — the loose dust and rock covering its surface. The soil of Earth is a kind of regolith, albeit one loaded with organic content. According to NASA, the iron minerals oxidize, or rust, causing the soil to look red.

Geology The cold, thin atmosphere means liquid water currently cannot exist on the Martian surface for any length of time. This means that although this desert planet is just half the diameter of Earth, it has the same amount of dry land.

The red planet is home to both the highest mountain and the deepest, longest valley in the solar system. Olympus Mons is roughly 17 miles (27 kilometers) high, about three times as tall as Mount Everest, while the Valles Marineris system of valleys — named after the Mariner 9 probe that discovered it in 1971 — can go as deep as 6 miles (10 km) and runs east-west for roughly 2,500 miles (4,000 km), about onefifth of the distance around Mars and close to the width of Australia or the distance from Philadelphia to San Diego. Mars has

Our Solar System the largest volcanoes in the solar system, including Olympus Mons, which is about 370 miles (600 km) in diameter, wide enough to cover the entire state of New Mexico.

It is a shield volcano, with slopes that rise gradually like those of Hawaiian volcanoes, and was created by eruptions of lavas that flowed for long distances before solidifying.

Mars also has many other kinds of volcanic landforms, from small, steep-sided cones to enormous plains coated in hardened lava.

Some minor eruptions might still occur on the planet.

Scientists think the Valles Marineris formed mostly by rifting of the crust as it got stretched. Individual canyons within the system are as much as 60 miles (100 km) wide. They merge in the central part of the Valles Marineris in a region as much as 370 miles (600 km) wide. Large channels emerging from the ends of some canyons and layered sediments within suggest the canyons might once have been filled with liquid water.

Channels, valleys, and gullies are found all over Mars, and suggest that liquid water might have flowed across the planet’s surface in recent times. Some channels can be 60 miles (100 km) wide and 1,200 miles (2,000 km) long. Water may still lie in cracks and pores in underground rock.

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Many regions of Mars are flat, low-lying plains. The lowest of the northern plains are among the flattest, smoothest places in the solar system, potentially created by water that once flowed across the Martian surface. The northern hemisphere mostly lies at a lower elevation than the southern hemisphere, suggesting the crust may be thinner in the north than in the south. This difference between the north and south might be due to a very large impact shortly after the birth of Mars.

The number of craters on Mars varies dramatically from place to place, depending on how old the surface is. Much of the surface of the southern hemisphere is extremely old, and so has many craters — including the planet’s largest, 1,400-mile-wide (2,300 km) Hellas Planitia — while that of northern hemisphere is younger and so has fewer craters. Some volcanoes have few craters, which suggests they erupted recently, with the resulting lava covering up any old craters. Some craters have unusual-looking deposits of debris around them resembling solidified mudflows, potentially indicating that impactor hit underground water or ice.

NASA: The martian landscape

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Jupiter Jupiter is the largest planet in the solar system. It is approximately 143,000 kilometers (about 89,000 miles) wide at its equator. Jupiter is so large that all of the other planets in the solar system could fit inside it. More than 1,000 Earths would fit inside Jupiter.

Jupiter is like a star in composition.

If Jupiter had been about 80 times more massive, it would have become a star rather than a planet.

Jupiter is the fifth planet from the sun. Jupiter’s average distance from the sun is 5.2 astronomical units, or AU. This distance is a little more than five times the distance from Earth to the sun. When viewed from Earth, it is usually the second brightest planet in the sky, after Venus.

The planet is named after Jupiter, the king of the Roman gods.

What Is Jupiter Like?

Jupiter is a giant gas planet. Its atmosphere is made up of mostly hydrogen gas and helium gas, just like the sun. The planet’s surface is covered in thick red, brown, yellow and white clouds.

One of Jupiter’s most famous features is the Great Red Spot. It is a giant spinning storm, resembling a hurricane. At its widest point, the storm is about three-and-a-half times the diameter of Earth. Jupiter is a very windy planet. Winds range from 192 mph to more than 400 mph.

Jupiter has three thin rings. The rings were discovered in 1979 by NASA’s Voyager 1 spacecraft. Jupiter’s rings are made up mostly of tiny dust particles.

Jupiter rotates, or spins, faster than any other planet. One rotation equals one day.

Our Solar System Jupiter’s day is only about 10 hours long.

Jupiter’s orbit is elliptical, or oval-shaped.

It takes 12 Earth years for Jupiter to make one revolution around the sun, so a year on Jupiter is equal to 12 years on Earth.

The temperature in the clouds of Jupiter is about minus 145 degrees Celsius (minus 234 degrees Fahrenheit). The temperature near the planet’s center is much, much hotter.

The core temperature may be about 24,000 degrees Celsius (43,000 degrees Fahrenheit).

That’s hotter than the surface of the sun!

If a person could stand on the clouds at the top of Jupiter’s atmosphere, the force of gravity he or she would feel would be about 2.4 times the force of gravity on the surface of Earth. A person who weighs 100 pounds on Earth would weigh about 240 pounds on Jupiter.

Jupiter has an extremely powerful magnetic field, like a giant magnet. Deep under Jupiter’s clouds is a huge ocean of liquid metallic hydrogen. As Jupiter spins, the swirling liquid metal ocean creates the strongest magnetic field in the solar system.

At the tops of the clouds (tens of thousands of kilometers above where the field is created), Jupiter’s magnetic field is 20 times stronger than the magnetic field on Earth.

How Many Moons Does Jupiter Have?

Jupiter has 62 known moons.

Image taken by NASA

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The most recent moons were discovered in 2003. The planet’s four largest moons are Io (eye-OH), Europa (yur-O-puh), Ganymede (GAN-i-meed) and Callisto (kuh-LIS-toe).

These four moons are called the Galilean satellites. Italian astronomer Galileo Galilei discovered these moons in 1610.

The largest of Jupiter’s moons is Ganymede. It is the largest moon in the solar system. Ganymede is larger than the planet Mercury and three-fourths the size of Mars. Ganymede is the only moon in the solar system known to have its own magnetic field. Ganymede and Callisto have many craters and appear to be made of ice and rocky material.

Io has many active volcanoes. The volcanoes produce gases containing sulfur. The yellow-orange surface of Io is most likely made of sulfur from the volcanic eruptions.

Europa is the smallest of the Galilean satellites. Europa’s surface is mostly water ice.

Beneath the ice may be an ocean of water or slushy ice. Europa is thought to have twice as much water as Earth.

How Is NASA Exploring Jupiter Today?

A new spacecraft named Juno is on its way to Jupiter. NASA’s Juno spacecraft launched in August of 2011 and will arrive at Jupiter in 2016. The goal of Juno is to help scientists better understand the origin and evolution of Jupiter and how planets form.

Juno will orbit closer to Jupiter than any previous spacecraft. It will use Jupiter’s magnetic field, gravity field and naturally occurring radio waves to study the mysterious interior of the giant planet. Juno also will take the first pictures of Jupiter’s polar regions and study the huge aurora that lights up Jupiter’s north and south poles.

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Saturn Saturn is the most distant of the five planets known to ancient stargazers. In 1610, Italian Galileo Galilei was the first astronomer to gaze at Saturn through a telescope. To his surprise, he saw a pair of objects on either side of the planet, which he later drew as “cup handles” attached to the planet on each side. In 1659, Dutch astronomer Christiaan Huygens announced that this was a ring encircling the planet. In 1675, Italian-born astronomer Jean Dominique Cassini discovered a gap between what are now called the A and B rings.

Like Jupiter, Uranus, and Neptune, Saturn is a gas giant. It is made mostly of hydrogen and helium. Its volume is 755 times greater than Earth’s. Winds in the upper atmosphere reach 500 meters per second in the equatorial region. (In contrast, the strongest hurricane-force winds on Earth top out at about 110 meters

per second.) These super-fast winds, combined with heat rising from within the planet’s interior, cause the yellow and gold bands visible in its atmosphere.

Saturn’s ring system is the most extensive and complex in our solar system; it extends hundreds of thousands of kilometers from the planet. In fact, Saturn and its rings would just fit in the distance between Earth and the Moon.

In the early 1980s, NASA’s two Voyager spacecraft revealed that Saturn’s rings are made mostly of water ice, and they found “braided” rings, ringlets and “spokes” dark features in the rings that seem to circle the planet at a different rate from that of the surrounding ring material.

Some of the small moons orbit within the ring system as well. Material in the rings ranges in size from a few micrometers to several tens of meters.

Our Solar System

Saturn has 31 known natural satellites (moons). The largest, Titan, is a bit bigger than the planet Mercury. Titan is shrouded in a thick nitrogen-rich atmosphere that might be similar to what Earth’s was like long ago. Further study of this moon promises to reveal much about planetary formation and, perhaps, about the early days of Earth as well.

In addition to Titan, Saturn has many smaller “icy” satellites. From Enceladus, which shows evidence of surface changes, to Iapetus, with one hemisphere darker than asphalt and the other as bright as snow, each of Saturn’s satellites is unique.

Saturn’s ring system is the most extensive and complex in our solar system; it extends hundreds of thousands of kilometers from the planet.

Image taken by National Geographic

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Saturn, the rings, and many of the satellites lie totally within Saturn’s enormous magnetosphere, the region of space in which the behavior of electrically charged particles is influenced more by Saturn’s magnetic field than by the solar wind. Recent images by NASA’s Hubble Space Telescope show that Saturn’s polar regions have aurorae similar to Earth’s Northern and Southern Lights.

Aurorae occur when charged particles spiral into a planet’s atmosphere along magnetic field lines.

The next chapter in our knowledge of Saturn is already under way, as the CassiniHuygens spacecraft began its journey to Saturn in October 1997 and will arrive on July 1, 2004. The Huygens probe will descend through Titan’s atmosphere in late November 2004 to collect data on the atmosphere and surface of the moon.

Cassini will orbit Saturn more than 70 times during a four-year study of the planet, its moons, rings and magnetosphere. CassiniHuygens is a joint NASA/European Space Agency mission.

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Uranus Uranus is the seventh planet from the Sun and is the third largest in the solar system.

It was discovered by William Herschel in 1781. It has an equatorial diameter of 51,800 kilometers (32,190 miles) and orbits the Sun once every 84.01 Earth years. It has a mean distance from the Sun of 2.87 billion kilometers (1.78 billion miles). It rotates about its axis once every 17 hours 14 minutes. Uranus has at least 22 moons.

The two largest moons of Uranus, Titania and Oberon, were discovered by William Herschel in 1787. The atmosphere of Uranus is composed of 83% hydrogen, 15% helium, 2% methane and small amounts of acetylene and other hydrocarbons.

Methane in the upper atmosphere absorbs red light, giving Uranus its blue-green color.

The atmosphere is arranged into clouds running at constant latitudes, similar to

the orientation of the more vivid latitudinal bands seen on Jupiter and Saturn. Winds at mid-latitudes on Uranus blow in the direction of the planet’s rotation. These winds blow at velocities of 40 to 160 meters per second (90 to 360 miles per hour). Radio science experiments found winds of about 100 meters per second blowing in the opposite direction at the equator.

Uranus is distinguished by the fact that it is tipped on its side. Its unusual position is thought to be the result of a collision with a planet-sized body early in the solar system’s history. Voyager 2 found that one of the most striking influences of this sideways position is its effect on the tail of the magnetic field, which is itself tilted 60 degrees from the planet’s axis of rotation.

The magnetotail was shown to be twisted by the planet’s rotation into a long corkscrew

Our Solar System shape behind the planet. The magnetic field source is unknown; the electrically conductive, super-pressurized ocean of water and ammonia once thought to lie between the core and the atmosphere now appears to be nonexistent. The magnetic fields of Earth and other planets are believed to arise from electrical currents produced in their molten cores.

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There may be a large number of narrow rings, or possibly incomplete rings or ring arcs, as small as 50 meters (160 feet) in width. The individual ring particles were found to be of low reflectivity. At least one ring, the epsilon, was found to be gray in color. The moons Cordelia and Ophelia act as shepherd satellites for the epsilon ring.

Uranus’ Rings In 1977, the first nine rings of Uranus were discovered. During the Voyager encounters, these rings were photographed and measured, as were two other new rings and ringlets. Uranus’ rings are distinctly different from those at Jupiter and Saturn. The outermost epsilon ring is composed mostly of ice boulders several feet across. A very tenuous distribution of fine dust also seems to be spread throughout the ring system.

Image from American Life Wire

Its unusual position is thought to be the result of a collision with a planetsized body early in the solar system’s history.

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The planet Uranus and Earth. Uranus is a giant ball of gas and scientists believe that this was caused by a collision with another smaller planet during the early days of our solar system causing Uranus to explode.

However, the powerful gravitational force of the planet was able to hold Uranus together.

Our Solar System

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Image by Nasa

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Neptune Neptune is the outermost planet of the gas giants. It has an equatorial diameter of 49,500 kilometers (30,760 miles). If Neptune were hollow, it could contain nearly 60 Earths. Neptune orbits the Sun every 165 years. It has eight moons, six of which were found by Voyager. A day on Neptune is 16 hours and 6.7 minutes. Neptune was discovered on September 23, 1846 by Johann Gottfried Galle, of the Berlin Observatory, and Louis d’Arrest, an astronomy student, through mathematical predictions made by Urbain Jean Joseph Le Verrier. The first two thirds of Neptune is composed of a mixture of molten rock, water, liquid ammonia and methane. The outer third is a mixture of heated gases comprised of hydrogen, helium, water and methane. Methane gives Neptune its blue cloud color.

Neptune is a dynamic planet with several large, dark spots reminiscent of Jupiter’s hurricane-like storms. The largest spot, known as the Great Dark Spot, is about the size of the earth and is similar to the Great Red Spot on Jupiter. Voyager revealed a small, irregularly shaped, eastward-moving cloud scooting around Neptune every 16 hours or so. This scooter as it has been dubbed could be a plume rising above a deeper cloud deck.

Long bright clouds, similar to cirrus clouds on Earth, were seen high in Neptune’s atmosphere. At low northern latitudes, Voyager captured images of cloud streaks casting their shadows on cloud decks below.

The strongest winds on any planet were measured on Neptune. Most of the winds

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Our Solar System there blow westward, opposite to the rotation of the planet. Near the Great Dark Spot, winds blow up to 2,000 kilometers (1,200 miles) an hour.

Neptune has a set of four rings which are narrow and very faint. The rings are made up of dust particles thought to have been made by tiny meteorites smashing into Neptune’s moons. From ground based telescopes the rings appear to be arcs but from Voyager 2 the arcs turned out to be bright spots or clumps in the ring system. The exact cause of the bright clumps is unknown.

The magnetic field of Neptune, like that of Uranus, is highly tilted at 47 degrees Canvas painting of Uranus

from the rotation axis and offset at least 0.55 radii (about 13,500 kilometers or 8,500 miles) from the physical center. Comparing the magnetic fields of the two planets, scientists think the extreme orientation may be characteristic of flows in the interior of the planet and not the result of that planet’s sideways orientation or of any possible field reversals at either planet.

Uranus turns on its axis once every 17 hours, 14 minutes:

The planet rotates in a retrograde direction, opposite to the way Earth and most other planets turn.

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The black hole teaches us that space can be crumpled like a piece of paper into an infinitesimal dot, that time can be extinguished like a blown-out flame, and that the laws of physics that we regard as ‘sacred,’ as immutable, are anything but.

-John Wheeler (1911–2008):

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Black Holes

BLACK HOLES What Is a Black Hole?

An artist’s drawing a black hole named Cygnus X-1. It formed when a large star caved in.

This black hole pulls matter from blue star beside it.

A black hole is a place in space where gravity pulls so much that even light can not get out.

The gravity is so strong because matter has been squeezed into a tiny space. This can happen when a star is dying.

Because no light can get out, people can’t see black holes. They are invisible. Space telescopes with special tools can help find black holes. The special tools can see how stars that are very close to black holes act differently than other stars.

Black holes can be big or small.

Scientists think the smallest black holes are as small as just one atom.

These black holes are very tiny but have the mass of a large mountain.

Mass is the amount of matter, or “stuff,” in an object.

Another kind of black hole is

called “stellar.” Its mass can be up to 20 times more than the mass of the sun.

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A black hole is a place in space where gravity pulls so much that even light can not get out. The gravity is so strong because matter has been squeezed into a tiny space. This can happen when a star is dying.

Because no light can get out, people can’t see black holes. They are invisible.

Space telescopes with special tools can help find black holes. The special tools can see how stars that are very close to black holes act differently than other stars in the universe.

Black holes can be big or small.

Scientists think the smallest black holes are as small as just one atom.

These black holes are very tiny but have the mass of a large mountain. Mass is the amount of matter, or “stuff,” in an object.

Another kind of black hole is called

“stellar.” Its mass can be up to 20 times more than the mass of the sun. There may be many, stellar

mass black holes in Earth’s galaxy.

Earth’s galaxy is called the Milky Way.

The largest black holes are called “supermassive.” These black holes have masses that are more than 1 million suns together. Scientists have found proof that every large galaxy contains a supermassive black hole at its center.

The supermassive black hole at the center of the Milky Way galaxy is called Sagittarius A. It has a mass equal to about 4 million suns and would fit inside a very large ball that could hold a few million Earths. Scientists think the smallest black holes formed when the universe began.

Could a Black Hole Destroy Earth?

Black holes do not go around in space eating stars, moons and planets.

Earth will not fall into a black hole because no black hole is close enough to the solar system for Earth to do that.

These black holes have masses that are more than 1 million suns together.

Black Holes

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The Crab Nebula – A beautiful look at what remains after a star explodes and goes supernova. According to scientists, the expansion rate of the nebula was accelerating. This discovery led to the 2012 Physics Nobel Prize.

When a star explodes, it releases a huge amount of cosmic radiation.

Black Holes

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COSMIC RAYS If recent measurements of cosmic ray particles are correct, then we may have the first evidence that the universe as we know it is really a giant computer simulation.

Humans have explored the laws of our universe for many years now, and it’s not uncommon to hear people talk about how amazing it is that certain fundamental values are just right for life to exist. Some people have wondered if that’s because the whole universe is actually some kind of sandbox simulation, and we’re merely characters in some cosmic game of The Sims.

If that’s true, then there should be a point where we start to bump up against the edges of the simulator, like Jim Carrey’s character escaping from The Truman Show -- and now a team of physicists think that a particular measurement of some cosmic ray particles might be the first such indication of one of those edges.

The idea that we might be living in an artificial reality constructed by something higher than ourselves has been a recurring philosophical hypothesis for centuries.

Plato’s Allegory of the Cave, Descartes’ evil demon, Putnam’s brain in a vat -- these are all variants of justifications for solipsism, a philosophical idea that says it’s impossible to know with any certainty whether the world as we experience it is “real” or a simulation projected by some external entity.

Keanu Reeves’ character Neo in The Matrix opts for a dose of reality when he chooses to take the red pill, but figuring out whether our universe is “real” or not is a touch more complicated than that.

It shouldn’t be surprising that simulating the universe would take up a lot of processing power, since the universe is exceedingly large (and then some). Currently, if we wanted to simulate quantum chromodynamics -- the rules which give rise to the strong nuclear force, which binds protons and neutrons together in atomic nuclei -we can only manage it on the scale of femtometres (millionths of a nanometre). That’s not even close to the level of detail needed for even the smallest microorganisms, let alone planets, stars and galaxies.

What we do know, though, is that when we create such a simulator, there’s some kind of underlying lattice that holds everything together like a kind of framework. Think of it as the smallest scale at which a simulator runs -- like the way a grid divides up the playable space in a chess game. You can’t move a piece less than one grid space.

Gizmag: Cosmic Rays

The universe as we know it is really a giant computer simulation.

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Cosmic Rays If we were living in a simulator, we’d expect to find evidence of that lattice if we looked close enough to the edges of the observable universe -- and that’s what Sila Beane from the University of Bonn and colleagues have calculated, in a paper published in arXiv. As cosmic particles fly through the universe, they lose energy and change direction and spread out across a spectrum of energy values. There’s a known limit to how much energy those particles have, though, and Beane and his colleagues have calculated that this seemingly arbitrary cliff in the spectrum is consistent with the kind of boundary that you’d find if there was an underlying lattice governing the limits of a simulator.

It should also, if present, scatter the particles in a certain way as they come up against it, and we should be able to investigate whether that’s the case.

If such an investigation does look consistent with a simulator lattice, then that could mean several things. It could show us that there’s a boundary out there consistent with Beane et al’s hypothesis, and it works a bit like the one we’d expect if we were living inside a simulator based on the same principles as one we would also build.

It could be, though, that we’re incorrectly interpreting evidence of certain fundamental laws we are as yet unfamiliar with. It could even be that this isn’t evidence at all for a simulator, as a real lattice might work in a different way to how we would envision it.

Frankly, we don’t know yet. It’s a bit like sitting really close to the TV when you’re a kid and being able to pick out all the pixels -- we just have to hope the universe doesn’t have a retina display.

It’s a bit like sitting really close to the TV when you’re a kid and being able to pick out all the pixels

The magnetic field of eath acts as a shield against the solar wind and harmful rays of the sun.

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NASA

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NASA NASA is designing and building capabilities to send humans farther into the solar system than ever before, including to an asteroid and Mars. On this Journey to Mars, NASA is developing the most advanced rocket and spacecraft ever designed. NASA’s Orion spacecraft will carry four astronauts to missions beyond the moon, launched from Florida aboard the Space Launch System (SLS) – an advanced heavy-lift rocket that will provide an entirely new national capability for human exploration beyond Earth’s orbit.

To help test other spaceflight capabilities to meet the goal of sending humans to Mars, including advanced propulsion and spacesuits, NASA is developing the Asteroid Redirect Mission first-ever mission to identify, capture and redirect a near-Earth asteroid to a stable orbit around the moon, where astronauts will explore it in the 2020s, returning with samples that will be analysed further.

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International Space Station The human Journey to Mars begins some 250 miles overhead, as astronauts aboard the International Space Station are working off the Earth for the Earth. The space station’s microgravity environment makes research possible that can’t be achieved on Earth, leading to breakthroughs in understanding Earth, space and physical and biological sciences.

By studying astronauts living in space for six months or more, NASA is learning how future crews can thrive on longer missions into the solar system, including round-trip journeys to an asteroid and Mars. The space station also is a test bed for exploration technologies like autonomous refueling of spacecraft, advanced life support systems and human/robotic interfaces.

A portion of the space station has been designated a national laboratory and NASA is committed to using this unique resource for wide-ranging scientific research. A new generation of U.S. commercial spacecraft and rockets are supplying cargo to the space station and soon launch astronauts once again from U.S. soil, allowing NASA to focus on building new capabilities for deep space exploration. As a blueprint for international cooperation, the space station enables a U.S.-led multinational partnership and advances shared goals in space exploration.

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The ISS

The ISS The International Space Station is a unique place – a convergence of science, technology and human innovation that demonstrates new technologies and makes research breakthroughs not possible on Earth.

It is a microgravity laboratory in which an international crew of six people live and work while traveling at a speed of five miles per second, orbiting Earth every 90 minutes.

The space station has been continuously occupied since November 2000. In that time, more than 200 people from 15 countries have visited.

Crew members spend about 35 hours each week conducting research in many disciplines to advance scientific knowledge in Earth, space, physical, and biological sciences for the benefit of people living on our home planet.

The station facilitates the growth of a robust commercial market in low-Earth orbit, operating as a national laboratory for scientific research and facilitating the development of U.S. commercial cargo and commercial crew space transportation capabilities. More than an acre of solar arrays provide power to the station, and also make it the next brightest object in the night sky after the moon. You don’t even need a telescope to see it zoom over your house and we’ll even send you a text message or email alert to let you know when (and where) to look up, spot the station, and wave!

It is the blueprint for global cooperation – one that enables a multinational partnership and advances shared goals in space exploration.

The Universe

How everything began with a bang