INTRODUCTION

Hello guyz, this is my first blog, so it maybe still some mistakes. Please help me by follow and give me some comment. I will help you too.

For the A2's member, I've already follow all the blog that written on the class's blog. I don't know if you've change the site, so if you do please tell me. Leave me your new address via comment, if I have time I will respond to it, OKAY!!

Sorry for the late introduction, i forgot to make it. ^o^V

Thank You. God Bless You All~~

Meteor Shower

A meteor shower is a celestial event in which a number of meteors are observed to radiate from one point in the night sky. These meteors are caused by streams of cosmic debris called meteoroids entering Earth's atmosphere at extremely high speeds on parallel trajectories. Most meteors are smaller than a grain of sand, so almost all of them disintegrate and never hit the Earth's surface. Fragments that do survive impact with Earth's surface are called meteorites. Intense or unusual meteor showers are known as meteor outbursts and meteor storms, which may produce greater than 1,000 meteors an hour.

Meteoroid

A meteoroid is a sand- to boulder-sized particle of debris in the Solar System. The visible path of a meteoroid that enters Earth's (or another body's) atmosphere is called a meteor, or colloquially a shooting star or falling star. If a meteor reaches the ground and survives impact, then it is called a meteorite. Many meteors appearing seconds or minutes apart are called a meteor shower. The root word meteor comes from the Greek meteōros, meaning "high in the air".

Comet

A comet is a relatively small Solar System body. Comet nuclei are loose collections of ice, dust, and small rocky particles, ranging from a few hundred meters to tens of kilometers across. When a comet is close enough to the Sun, it displays a thin, fuzzy, temporary atmosphere called a coma, and sometimes also has a tail. These phenomenon are the result of the solar radiation and the solar wind interacting with the comet nucleus. Comets have been observed since ancient times and have historically been considered bad omens. Particularly bright or notable examples are called "Great Comets".

Comets have a wide range of orbital periods, ranging from a few years to hundreds of thousands of years. Short-period comets originate in the Kuiper Belt, or its associated scattered disc, which lie beyond the orbit of Neptune. Longer-period comets are thought to originate in the Oort Cloud, a cloud of icy bodies in the outer Solar System that were left behind during the condensation of the solar nebula. Long-period comets plunge towards the Sun from the Oort Cloud because of gravitational perturbations caused by either the massive outer planets of the Solar System (Jupiter, Saturn, Uranus, and Neptune), or passing stars. Rare hyperbolic comets pass once through the inner Solar System before being thrown out into interstellar space along hyperbolic trajectories.

Comets are distinguished from asteroids by the presence of a coma or a tail. However, extinct comets that have passed close to the Sun many times have lost nearly all of their volatile ices and dust, and may come to resemble small asteroids. Asteroids are thought to have a different origin from comets, having formed inside the orbit of Jupiter rather than in the outer Solar System. These have somewhat blurred the distinction between asteroids and comets (see centaurs and asteroid terminology).

As of May 2009 there are a reported 3,648 known comets of which about 1,500 are Kreutz Sungrazers and about 400 are short-period. This number is steadily increasing. However, this represents only a tiny fraction of the total potential comet population: the reservoir of comet-like bodies in the outer solar system may number one trillion. The number visible to the naked eye averages roughly one per year, though many of these are faint and unspectacular.

Meteorite

A meteorite is a natural object originating in outer space that survives impact with the Earth's surface.Meteorites can be big or small. Most meteorites derive from small astronomical objects called meteoroids, but they are also sometimes produced by impacts of asteroids. When it enters the atmosphere, impact pressure causes the body to heat up and emit light, thus forming a fireball, also known as a meteor or shooting/falling star. The term bolide refers to either an extraterrestrial body that collides with the Earth, or to an exceptionally bright, fireball-like meteor regardless of whether it ultimately impacts the surface.

More generally, a meteorite on the surface of any celestial body is a natural object that has come from elsewhere in space. Meteorites have been found on the Moon and Mars.

Meteorites that are recovered after being observed as they transited the atmosphere or impacted the Earth are called falls. All other meteorites are known as finds. As of February 2010, there are approximately 1,086 witnessed falls having specimens in the world's collections. In contrast, there are over 38,660 well-documented meteorite finds.

Meteorites have traditionally been divided into three broad categories: stony meteorites are rocks, mainly composed of silicate minerals; iron meteorites are largely composed of metallic iron-nickel; and, stony-iron meteorites contain large amounts of both metallic and rocky material. Modern classification schemes divide meteorites into groups according to their structure, chemical and isotopic composition and mineralogy

DOOMSDAY is NEAR?!?! : Duren Sawit Meteorite

Watch Out! The DOOMSDAY is coming up!!

A shocking event happened at Duren Sawit, East Jakarta. A small meteorite fell at Delima Street, Duren Sawit that made three houses broken. This happened at Thursday, 29'th April 2010.

A witness said that he saw some flash of lights hit the houses. He firstly thought that it was a lightning. But after that, he heard some hard sound like bomb's blast.

Main scientist of Astronomy-Astrophysics Lembaga Penerbangan dan Antariksa Nasional (LAPAN), Bandung, Thomas Djamaluddin explained that the meteorite came from south-west with high speed and temperature, more than hundred degree of Celsius.

Is this sign of nearer DOOMSDAY? It would be a warning from GOD. For some people who already watch "2012", it can be imagined to happened. Thought that it just a "Small Meteorite" which can destroy 3 houses at suddenly, you can imagine if that is bigger meteorite and made a MASSIVE EXPLOSION which can destroy the Earth.

So, prepare yourself, DO A GOOD THING AND KEEP PRAY TO 'HIM'.

Watch Out!

Solar System

The Solar System consists of the Sun and those celestial objects bound to it by gravity, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. Of the retinue of objects that orbit the Sun, most of the mass is contained within eight relatively solitary planets whose orbits are almost circular and lie within a nearly-flat disc called the ecliptic plane. The four smaller inner planets, Mercury, Venus, Earth and Mars, also called the terrestrial planets, are primarily composed of rock and metal. The four outer planets, Jupiter, Saturn, Uranus and Neptune, also called the gas giants, are composed largely of hydrogen and helium and are far more massive than the terrestrials.

The Solar System is also home to two regions populated by smaller objects. The asteroid belt, which lies between Mars and Jupiter, is similar to the terrestrial planets as it is composed mainly of rock and metal. Beyond Neptune's orbit lie trans-Neptunian objects composed mostly of ices such as water, ammonia and methane. Within these two regions, five individual objects, Ceres, Pluto, Haumea, Makemake and Eris, are recognized to be large enough to have been rounded by their own gravity, and are thus termed dwarf planets. In addition to thousands of small bodies in those two regions, various other small body populations, such as comets, centaurs and interplanetary dust, freely travel between regions.

The solar wind, a flow of plasma from the Sun, creates a bubble in the interstellar medium known as the heliosphere, which extends out to the edge of the scattered disc. The hypothetical Oort cloud, which acts as the source for long-period comets, may also exist at a distance roughly a thousand times further than the heliosphere.

Six of the planets and three of the dwarf planets are orbited by natural satellites, usually termed "moons" after Earth's Moon. Each of the outer planets is encircled by planetary rings of dust and other particles.

Neptune

Neptune is the eighth and farthest planet from the Sun in our Solar System. Named for the Roman god of the sea, it is the fourth-largest planet by diameter and the third-largest by mass. Neptune is 17 times the mass of Earth and is slightly more massive than its near-twin Uranus, which is 15 Earth masses and not as dense. On average, Neptune orbits the Sun at a distance of 30.1 AU, approximately 30 times the Earth-Sun distance. Its astronomical symbol is Astronomical symbol for Neptune., a stylized version of the god Neptune's trident.

Discovered on September 23, 1846, Neptune was the first planet found by mathematical prediction rather than by empirical observation. Unexpected changes in the orbit of Uranus led Alexis Bouvard to deduce that its orbit was subject to gravitational perturbation by an unknown planet. Neptune was subsequently observed by Johann Galle within a degree of the position predicted by Urbain Le Verrier, and its largest moon, Triton, was discovered shortly thereafter, though none of the planet's remaining 12 moons were located telescopically until the 20th century. Neptune has been visited by only one spacecraft, Voyager 2, which flew by the planet on August 25, 1989.

Neptune is similar in composition to Uranus, and both have compositions which differ from those of the larger gas giants Jupiter and Saturn. Neptune's atmosphere, while similar to Jupiter's and Saturn's in that it is composed primarily of hydrogen and helium, along with traces of hydrocarbons and possibly nitrogen, contains a higher proportion of "ices" such as water, ammonia and methane. Astronomers sometimes categorize Uranus and Neptune as "ice giants" in order to emphasize these distinctions. The interior of Neptune, like that of Uranus, is primarily composed of ices and rock. Traces of methane in the outermost regions in part account for the planet's blue appearance.

In contrast to the relatively featureless atmosphere of Uranus, Neptune's atmosphere is notable for its active and visible weather patterns. At the time of the 1989 Voyager 2 flyby, for example, the planet's southern hemisphere possessed a Great Dark Spot comparable to the Great Red Spot on Jupiter. These weather patterns are driven by the strongest sustained winds of any planet in the Solar System, with recorded wind speeds as high as 2,100 km/h. Because of its great distance from the Sun, Neptune's outer atmosphere is one of the coldest places in the Solar System, with temperatures at its cloud tops approaching −218 °C (55 K). Temperatures at the planet's centre, however, are approximately 5,400 K (5,000 °C). Neptune has a faint and fragmented ring system, which may have been detected during the 1960s but was only indisputably confirmed in 1989 by Voyager 2.

Uranus

Uranus is the seventh planet from the Sun, and the third-largest and fourth most massive planet in the Solar System. It is named after the ancient Greek deity of the sky Uranus (Ancient Greek: Οὐρανός) the father of Cronus (Saturn) and grandfather of Zeus (Jupiter). Though it is visible to the naked eye like the five classical planets, it was never recognized as a planet by ancient observers because of its dimness and slow orbit. Sir William Herschel announced its discovery on March 13, 1781, expanding the known boundaries of the Solar System for the first time in modern history. Uranus was also the first planet discovered with a telescope.

Uranus is similar in composition to Neptune, and both have different compositions from those of the larger gas giants Jupiter and Saturn. As such, astronomers sometimes place them in a separate category, the "ice giants". Uranus's atmosphere, while similar to Jupiter and Saturn's in its primary composition of hydrogen and helium, contains more "ices" such as water, ammonia and methane, along with traces of hydrocarbons. It is the coldest planetary atmosphere in the Solar System, with a minimum temperature of 49 K (–224 °C). It has a complex, layered cloud structure, with water thought to make up the lowest clouds, and methane thought to make up the uppermost layer of clouds. In contrast the interior of Uranus is mainly composed of ices and rock.

Like the other giant planets, Uranus has a ring system, a magnetosphere, and numerous moons. The Uranian system has a unique configuration among the planets because its axis of rotation is tilted sideways, nearly into the plane of its revolution about the Sun. As such, its north and south poles lie where most other planets have their equators. Seen from Earth, Uranus's rings can sometimes appear to circle the planet like an archery target and its moons revolve around it like the hands of a clock, though in 2007 and 2008 the rings appeared edge-on. In 1986, images from Voyager 2 showed Uranus as a virtually featureless planet in visible light without the cloud bands or storms associated with the other giants. However, terrestrial observers have seen signs of seasonal change and increased weather activity in recent years as Uranus approached its equinox. The wind speeds on Uranus can reach 250 meters per second (900 km/h, 560 mph).

Saturn

Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Saturn, along with Jupiter, Uranus and Neptune, is classified as a gas giant. Together, these four planets are sometimes referred to as the Jovian, meaning "Jupiter-like", planets.

Saturn is named after the Roman god Saturn, equated to the Greek Cronus (the Titan father of Zeus) the Babylonian Ninurta and to the Hindu Shani. Saturn's symbol represents the god's sickle (Unicode: ♄).

The planet Saturn is composed of hydrogen, with small proportions of helium and trace elements. The interior consists of a small core of rock and ice, surrounded by a thick layer of metallic hydrogen and a gaseous outer layer. The outer atmosphere is generally bland in appearance, although long-lived features can appear. Wind speeds on Saturn can reach 1,800 km/h, significantly faster than those on Jupiter. Saturn has a planetary magnetic field intermediate in strength between that of Earth and the more powerful field around Jupiter.

Saturn has a prominent system of rings, consisting mostly of ice particles with a smaller amount of rocky debris and dust. Sixty-one known moons orbit the planet, not counting hundreds of "moonlets" within the rings. Titan, Saturn's largest and the Solar System's second largest moon (after Jupiter's Ganymede), is larger than the planet Mercury and is the only moon in the Solar System to possess a significant atmosphere.

Jupiter

Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with a mass slightly less than one-thousandth of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn, Uranus and Neptune. Together, these four planets are sometimes referred to as the Jovian planets.

The planet was known by astronomers of ancient times and was associated with the mythology and religious beliefs of many cultures. The Romans named the planet after the Roman god Jupiter. When viewed from Earth, Jupiter can reach an apparent magnitude of −2.94, making it on average the third-brightest object in the night sky after the Moon and Venus. (Mars can briefly match Jupiter's brightness at certain points in its orbit.)

Jupiter is primarily composed of hydrogen with a quarter of its mass being helium; it may also have a rocky core of heavier elements. Because of its rapid rotation, Jupiter's shape is that of an oblate spheroid (it possesses a slight but noticeable bulge around the equator). The outer atmosphere is visibly segregated into several bands at different latitudes, resulting in turbulence and storms along their interacting boundaries. A prominent result is the Great Red Spot, a giant storm that is known to have existed since at least the 17th century when it was first seen by telescope. Surrounding the planet is a faint planetary ring system and a powerful magnetosphere. There are also at least 63 moons, including the four large moons called the Galilean moons that were first discovered by Galileo Galilei in 1610. Ganymede, the largest of these moons, has a diameter greater than that of the planet Mercury.

Jupiter has been explored on several occasions by robotic spacecraft, most notably during the early Pioneer and Voyager flyby missions and later by the Galileo orbiter. The most recent probe to visit Jupiter was the Pluto-bound New Horizons spacecraft in late February 2007. The probe used the gravity from Jupiter to increase its speed. Future targets for exploration in the Jovian system include the possible ice-covered liquid ocean on the moon Europa.

Mars

Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance. Mars is a terrestrial planet with a thin atmosphere, having surface features reminiscent both of the impact craters of the Moon and the volcanoes, valleys, deserts, and polar ice caps of Earth. Mars’ rotational period and seasonal cycles are likewise similar to those of Earth. Mars is the site of Olympus Mons, the highest known mountain in the Solar System, and of Valles Marineris, the largest canyon. The smooth Borealis basin in the northern hemisphere covers 40% of the planet and may be a giant impact feature. Unlike Earth, Mars is now geologically and tectonically inactive.

Until the first flyby of Mars occurred in 1965, by Mariner 4, many speculated about the presence of liquid water on the planet's surface. This was based on observed periodic variations in light and dark patches, particularly in the polar latitudes, which appeared to be seas and continents; long, dark striations were interpreted by some as irrigation channels for liquid water. These straight line features were later explained as optical illusions, yet of all the planets in the Solar System other than Earth, Mars is the most likely to harbor liquid water, and thus to harbor life. Geological evidence gathered by unmanned missions suggest that Mars once had large-scale water coverage on its surface, while small geyser-like water flows may have occurred during the past decade. In 2005, radar data revealed the presence of large quantities of water ice at the poles, and at mid-latitudes. The Phoenix Lander directly sampled water ice in shallow martian soil on July 31, 2008.

Mars has two moons, Phobos and Deimos, which are small and irregularly shaped. These may be captured asteroids, similar to 5261 Eureka, a Martian Trojan asteroid. Mars is currently host to three functional orbiting spacecraft: Mars Odyssey, Mars Express, and the Mars Reconnaissance Orbiter. On the surface are the two Mars Exploration Rovers (Spirit and Opportunity) and several inert landers and rovers, both successful and unsuccessful. The Phoenix Lander completed its mission on the surface in 2008. Observations by NASA's now-defunct Mars Global Surveyor show evidence that parts of the southern polar ice cap have been receding.

Mars can easily be seen from Earth with the naked eye. Its apparent magnitude reaches −2.91, a brightness surpassed only by Venus, the Moon, and the Sun, although most of the time Jupiter will appear brighter to the naked eye than Mars. Mars has an average opposition distance of 78 million km but can come as close as 55.7 million km during a close approach, such as occurred in 2003.

Earth

Earth (or the Earth) is the third planet from the Sun, the fifth-largest and the densest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets. It is sometimes referred to as the World, the Blue Planet, or by its Latin name, Terra.

Home to millions of species including humans, Earth is the only place in the universe where life is known to exist. The planet formed 4.54 billion years ago, and life appeared on its surface within a billion years. Since then, Earth's biosphere has significantly altered the atmosphere and other abiotic conditions on the planet, enabling the proliferation of aerobic organisms as well as the formation of the ozone layer which, together with Earth's magnetic field, blocks harmful solar radiation, permitting life on land. The physical properties of the Earth, as well as its geological history and orbit, have allowed life to persist during this period. Without intervention, the planet could be expected to continue supporting life for between 0.5 to 2.3 billion years, after which the rising luminosity and expansion of the Sun – as a result of the gradual but inexorable depletion of its hydrogen fuel – would eventually eliminate the planet's biosphere.

Earth's outer surface is divided into several rigid segments, or tectonic plates, that gradually migrate across the surface over periods of many millions of years. About 71% of the surface is covered with salt water oceans, the remainder consisting of continents and islands which together have many lakes and other sources of water contributing to the hydrosphere. Liquid water, necessary for all known life, is not known to exist on any other planet's surface. Earth's poles are mostly covered with solid ice (Antarctic ice sheet) or sea ice (Arctic ice cap). The planet's interior remains active, with a thick layer of relatively solid mantle, a liquid outer core that generates a magnetic field, and a solid iron inner core.

Earth interacts with other objects in space, especially the Sun and the Moon. At present, Earth orbits the Sun once for every roughly 366.26 times it rotates about its axis. This is a sidereal year, which is equal to 365.26 solar days. The Earth's axis of rotation is tilted 23.4° away from the perpendicular to its orbital plane, producing seasonal variations on the planet's surface with a period of one tropical year (365.24 solar days). Earth's only known natural satellite, the Moon, which began orbiting it about 4.53 billion years ago, provides ocean tides, stabilizes the axial tilt and gradually slows the planet's rotation. Between approximately 3.8 billion and 4.1 billion years ago, numerous asteroid impacts during the Late Heavy Bombardment caused significant changes to the greater surface environment.

Both the mineral resources of the planet, as well as the products of the biosphere, contribute resources that are used to support a global human population. These inhabitants are grouped into about 200 independent sovereign states, which interact through diplomacy, travel, trade, and military action. Human cultures have developed many views of the planet, including personification as a deity, a belief in a flat Earth or in Earth as the center of the universe, and a modern perspective of the world as an integrated environment that requires stewardship.

Venus

Venus is the second-closest planet to the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows. Because Venus is an inferior planet from Earth, it never appears to venture far from the Sun: its elongation reaches a maximum of 47.8°. Venus reaches its maximum brightness shortly before sunrise or shortly after sunset, for which reason it is often called the Morning Star or the Evening Star.

Classified as a terrestrial planet, it is sometimes called Earth's "sister planet" because they are similar in size, gravity, and bulk composition. Venus is covered with an opaque layer of highly reflective clouds of sulfuric acid, preventing its surface from being seen from space in visible light. Venus has the densest atmosphere of all the terrestrial planets, consisting mostly of carbon dioxide, as it has no carbon cycle to lock carbon back into rocks and surface features, nor organic life to absorb it in biomass. A younger Venus is believed to have possessed Earth-like oceans, but these totally evaporated as the temperature rose, leaving a dusty dry desertscape with many slab-like rocks. The water has most likely dissociated, and, because of the lack of a planetary magnetic field, the hydrogen has been swept into interplanetary space by the solar wind. The atmospheric pressure at the planet's surface is 92 times that of the Earth.

Venus's surface was a subject of speculation until some of its secrets were revealed by planetary science in the twentieth century. It was finally mapped in detail by Project Magellan in 1990–91. The ground shows evidence of extensive volcanism, and the sulfur in the atmosphere may indicate that there have been some recent eruptions. However, the absence of evidence of lava flow accompanying any of the visible caldera remains an enigma. The planet has few impact craters, demonstrating that the surface is relatively young, approximately half a billion years old. There is no evidence for plate tectonics, possibly because its crust is too strong to subduct without water to make it less viscous. Instead, Venus may lose its internal heat in periodic massive resurfacing events.

Mercury

Mercury is the innermost and smallest planet in the Solar System, orbiting the Sun once every 87.969 days. The orbit of Mercury has the highest eccentricity of all the Solar System planets, and it has the smallest axial tilt. It completes three rotations about the axis for every two orbits. The perihelion of Mercury's orbit precesses around the Sun at an excess of 43 arcseconds per century; a phenomenon that was explained in the 20th century by Albert Einstein's General Theory of Relativity. Mercury is bright when viewed from Earth, ranging from −2.3 to 5.7 in apparent magnitude, but is not easily seen as its greatest angular separation from the Sun is only 28.3°. Since Mercury is normally lost in the glare of the Sun, unless there is a solar eclipse, Mercury can only be viewed in morning or evening twilight.

Comparatively little is known about Mercury; ground-based telescopes reveal only an illuminated crescent with limited detail. The first of two spacecraft to visit the planet was Mariner 10, which mapped about 45% of the planet’s surface from 1974 to 1975. The second is the MESSENGER spacecraft, which mapped a further 30% during its flyby of January 14, 2008. MESSENGER's last flyby took place in September 2009 and it is scheduled to attain orbit around Mercury in 2011, where it will begin mapping the rest of the planet.

Mercury is similar in appearance to the Moon: it is heavily cratered with regions of smooth plains, has no natural satellites and no substantial atmosphere. However, unlike the moon, it has a large iron core, which generates a magnetic field about 1% as strong as that of the Earth. It is an exceptionally dense planet due to the large relative size of its core. Surface temperatures range from about 90 to 700 K (−183 °C to 427 °C, −297 °F to 801 °F), with the subsolar point being the hottest and the bottoms of craters near the poles being the coldest.

Recorded observations of Mercury date back to at least the first millennium BC. Before the 4th century BC, Greek astronomers believed the planet to be two separate objects: one visible only at sunrise, which they called Apollo; the other visible only at sunset, which they called Hermes. The English name for the planet comes from the Romans, who named it after the Roman god Mercury, which they equated with the Greek Hermes (Ἑρμῆς). The astronomical symbol for Mercury is a stylized version of Hermes' caduceus.

Sun

The Sun is the star at the center of the Solar System. It has a diameter of about 1,392,000 kilometers (865,000 mi) (about 109 Earths), and its mass (about 2 × 1030 kilograms, 330,000 times that of Earth) accounts for about 99.86% of the total mass of the Solar System; the remainder consists of the planets (including Earth), dwarf planets, satellites, small Solar System bodies and dust in orbit. About three-quarters of the Sun's mass consists of hydrogen, while most of the rest is helium. Less than 2% consists of other elements, including iron, oxygen, carbon, neon, and others.

The Sun's color is white, although from the surface of the Earth it may appear yellow because of atmospheric scattering. Its stellar classification, based on spectral class, is G2V, and is informally designated a yellow star, because the majority of its radiation is in the yellow-green portion of the visible spectrum. In this spectral class label, G2 indicates its surface temperature of approximately 5,778 K (5,505 °C; 9,941 °F), and V (Roman five) indicates that the Sun, like most stars, is a main sequence star, and thus generates its energy by nuclear fusion of hydrogen nuclei into helium. In its core, the sun fuses 430–600 million tons of hydrogen each second. Once regarded by astronomers as a small and relatively insignificant star, the Sun is now presumed to be brighter than about 85% of the stars in the Milky Way galaxy, most of which are red dwarfs. The absolute magnitude of the Sun is +4.83; however, as the star closest to Earth, the Sun is the brightest object in the sky with an apparent magnitude of −26.74. The Sun's hot corona continuously expands in space creating the solar wind, a hypersonic stream of charged particles that extends to the heliopause at roughly 100 astronomical units. The bubble in the interstellar medium formed by the solar wind, the heliosphere, is the largest continuous structure in the Solar System.

The Sun is currently traveling through the Local Interstellar Cloud in the Local Bubble zone, within the inner rim of the Orion Arm of the Milky Way galaxy. Of the 50 nearest stellar systems within 17 light-years from Earth, the Sun ranks 4th in mass. The Sun orbits the center of the Milky Way at a distance of approximately 24,000–26,000 light years from the galactic center, completing one clockwise orbit, as viewed from the galactic north pole, in about 225–250 million years.

The mean distance of the Sun from the Earth is approximately 149.6 million kilometers (1 AU), though this varies as the Earth moves from perihelion in January to aphelion in July. At this average distance, light travels from the Sun to Earth in about 8 minutes and 19 seconds. The energy of this sunlight supports almost all life on Earth by photosynthesis, and drives Earth's climate and weather. The enormous effect of the Sun on the Earth has been recognized since prehistoric times, and the Sun has been regarded by some cultures as a deity. An accurate scientific understanding of the Sun developed slowly, and as recently as the 19th century prominent scientists had little knowledge of the Sun's physical composition and source of energy. This understanding is still developing; there are a number of present-day anomalies in the Sun's behavior that remain unexplained.