"Places in The Hitchhiker's Guide to the Galaxy This is a list of places featured in Douglas Adams's science fiction series ""The Hitchhiker's Guide to the Galaxy"". The series is set in a fictionalised version of the Milky Way galaxy and thus, while most locations are pure invention, many are based on ""real world"" settings such as Alpha Centauri, Barnard's Star and various versions of the Earth. ""The Galaxy"" is our home galaxy, the Milky Way, though it is referred to exclusively as ""the Galaxy"" in the series. Apart from a very brief moment during the first radio series, when"
"Galaxy A galaxy is a gravitationally bound system of stars, stellar remnants, interstellar gas, dust, and dark matter. The word galaxy is derived from the Greek """" (), literally ""milky"", a reference to the Milky Way. Galaxies range in size from dwarfs with just a few hundred million () stars to giants with one hundred trillion () stars, each orbiting its galaxy's center of mass. Galaxies are categorized according to their visual morphology as elliptical, spiral, or irregular. Many galaxies are thought to have supermassive black holes at their centers. The Milky Way's central black hole, known as Sagittarius A*,"
"of the Milky Way. The ESA spacecraft ""Gaia"" provides distance estimates by determining the parallax of a billion stars and is mapping the Milky Way with four planned releases of maps in 2022. Milky Way The Milky Way is the galaxy that contains our Solar System. The name describes the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye. The term ""Milky Way"" is a translation of the Latin ', from the Greek (', ""milky circle""). From Earth, the Milky Way appears as"
"Location of Earth Knowledge of the location of Earth has been shaped by 400 years of telescopic observations, and has expanded radically in the last century. Initially, Earth was believed to be the center of the Universe, which consisted only of those planets visible with the naked eye and an outlying sphere of fixed stars. After the acceptance of the heliocentric model in the 17th century, observations by William Herschel and others showed that the Sun lay within a vast, disc-shaped galaxy of stars. By the 20th century, observations of spiral nebulae revealed that our galaxy was one of billions"
"hypothesis is not falsifiable. Location of Earth Knowledge of the location of Earth has been shaped by 400 years of telescopic observations, and has expanded radically in the last century. Initially, Earth was believed to be the center of the Universe, which consisted only of those planets visible with the naked eye and an outlying sphere of fixed stars. After the acceptance of the heliocentric model in the 17th century, observations by William Herschel and others showed that the Sun lay within a vast, disc-shaped galaxy of stars. By the 20th century, observations of spiral nebulae revealed that our galaxy"
"other galaxies, along with ""Destiny"", which was sent out after the ""seed ships"" to further investigate a pattern discovered in the Cosmic Background Microwave Radiation (Stargate Universe). Among the planets they settled was Earth, which they called ""Terra"". The status of Earth in the Ancients' empire is currently unknown. However, as the planet's original Stargate, eventually discovered by SG-1 in Antarctica, was the oldest gate ever encountered, and being the eventual birthplace of the second evolution of humanity, Earth was probably one of their oldest, if not the first world, they settled upon arriving in this galaxy. Also the nine-chevron"
"Milky Way The Milky Way is the galaxy that contains our Solar System. The name describes the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye. The term ""Milky Way"" is a translation of the Latin ', from the Greek (', ""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"
"Tadpole Galaxy The Tadpole Galaxy is a disrupted barred spiral galaxy located 420 million light-years from Earth in the northern constellation Draco. Its most dramatic feature is a massive trail of stars about 280,000 light-years long; the size of the galaxy has been attributed to a merger with a smaller galaxy that is believed to have occurred about 100 million years ago. The galaxy is filled with bright blue star clusters. It is hypothesized that a more compact intruder galaxy crossed in front of the Tadpole Galaxy—from left to right from the perspective of Earth—and was slung around behind the"
"the western spiral arm of the galaxy. It is home to a number of planets, including Earth and Rupert. Earth is ""an utterly insignificant little blue-green planet far out in the uncharted backwaters of the unfashionable end of the western spiral arm of the galaxy"". The sapient life-forms on Earth are, in descending order of intelligence, mice, dolphins and humans, the lattermost of whom may or may not be descended from a race of Golgafrinchan telephone-sanitisers, hairdressers, management consultants, and documentary film producers."" These Golgafrinchans arrived in a space ark which crashed into the planet circa 2 mya, promptly christening"
"Comet Galaxy The Comet Galaxy, a spiral galaxy located 3.2 billion light-years from Earth, in the galaxy cluster Abell 2667, was found with the Hubble Space Telescope. This galaxy has slightly more mass than our Milky Way. It was detected on 2 March 2007. This unique spiral galaxy, which is situated 3.2 billion light-years from the Earth, has an extended stream of bright blue knots and diffuse wisps of young stars. It rushes at 3.5 million km/h through the cluster Abell 2667 and therefore, like a comet, shows a tail, with a length of 600,000 light-years. The Сomet Galaxy is"
"in the image, with bits going to the right and more significant digits below. Earth The solar system, showing the Sun and the planets in the order of their position from the Sun: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto. (Pluto has since been reclassified as a dwarf planet by the International Astronomical Union, but it was still considered a planet at the time the message was transmitted.) The Earth is the third planet from the Sun; its graphic is shifted up to identify it as the planet from which the signal was sent. Additionally, the human"
"Earth (Noon Universe) The Noon Universe is the setting of a series of science-fiction books written by Boris and Arkady Strugatsky. Earth is one of the planets populated by humans in this setting, and is implied to be their origin. ""Noon"" Earth is identical in concept to real-life Earth, but set in an alternate future, with the story taking place in the 22nd century. Earth is described in detail in """", which serves as the first in the ""Noon Universe"" series. While humans also inhabit other planets in the Noon Universe, the humans of Earth and make up the most"
"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. The Milky Way is a barred spiral galaxy with a diameter between 150,000 and 200,000 light-years (ly). It is estimated to contain 100–400 billion stars and more than 100 billion planets. The Solar System is located at a radius of 26,490 (± 100) light-years from the Galactic Center, on the inner edge of the Orion Arm, one of the spiral-shaped concentrations"
"Pinwheel Galaxy The Pinwheel Galaxy (also known as Messier 101, M101 or NGC 5457) is a face-on spiral galaxy distanced 21 million light-years (six megaparsecs) away from Earth in the constellation Ursa Major. First discovered by Pierre Méchain on March 27, 1781, it was communicated to Charles Messier who verified its position for inclusion in the ""Messier Catalogue"" as one of its final entries. On February 28, 2006, NASA and the European Space Agency released a very detailed image of the Pinwheel Galaxy, which was the largest and most detailed image of a galaxy by Hubble Space Telescope at the"
"According to Plato, the Earth was a sphere, stationary at the center of the universe. The stars and planets were carried around the Earth on spheres or circles, arranged in the order (outwards from the center): Moon, Sun, Venus, Mercury, Mars, Jupiter, Saturn, fixed stars, with the fixed stars located on the celestial sphere. In his ""Myth of Er"", a section of the ""Republic"", Plato describes the cosmos as the Spindle of Necessity, attended by the Sirens and turned by the three Fates. Eudoxus of Cnidus, who worked with Plato, developed a less mythical, more mathematical explanation of the planets'"
"the inner planets, the asteroid belt, and the outer planets. The inner terrestrial planets consist of Mercury, Venus, Earth, and Mars. The outer gas giant planets are Jupiter, Saturn, Uranus, and Neptune. Beyond Neptune lies the Kuiper Belt, and finally the Oort Cloud, which may extend as far as a light-year. The planets were formed 4.6 billion years ago in the protoplanetary disk that surrounded the early Sun. Through a process that included gravitational attraction, collision, and accretion, the disk formed clumps of matter that, with time, became protoplanets. The radiation pressure of the solar wind then expelled most of"
"that other galaxies apart from the Milky Way therefore existed. By 1925, Edwin Hubble had confirmed that many objects previously thought to be clouds of dust and gas and classified as ""nebulae"" were actually galaxies beyond the Milky Way. When astronomers realized that starlight can be absorbed by clouds of gas and dust, infrared radiation was used to penetrate the dust clouds. Estimates dating after 2000 locate our solar system within the range from the Galactic Center of the Milky Way galaxy. Galactocentrism In astronomy, Galactocentrism is the theory that the Milky Way Galaxy, home of Earths Solar System, is"
"NGC 6397 NGC 6397, also known as Caldwell 86, is a globular cluster in the constellation Ara. It is located about 7,800 light-years from Earth, making it one of the two nearest globular clusters to Earth (the other one being Messier 4). The cluster contains around 400,000 stars, and can be seen with the naked eye under good observing conditions. NGC 6397 is one of the at least 20 globular clusters of the Milky Way Galaxy that have undergone a core collapse, meaning that the core has contracted to a very dense stellar agglomeration. In 2004, a team of astronomers"
"Galactocentrism In astronomy, Galactocentrism is the theory that the Milky Way Galaxy, home of Earths Solar System, is at or near the center of the Universe. Observations by William Herschel in 1785 suggested that the Milky Way was a disk-shaped galaxy with the sun in a central position. Although heliocentric, Herschel's observations were the first attempt at an observational cosmology. Herschel's heliocentric theory was overthrown by astronomer Harlow Shapley's work on globular clusters in 1918. Shapley's research marked the transition from heliocentrism to galactocentrism, placing the Galactic Center of the Milky Way Galaxy far away from the sun, towards Sagittarius."
"by mutual gravitational attraction. As the Earth is located within the dusty outer arms, there are large portions of the Milky Way that are obscured from view. In the center of the Milky Way is the core, a bar-shaped bulge with what is believed to be a supermassive black hole at its center. This is surrounded by four primary arms that spiral from the core. This is a region of active star formation that contains many younger, population I stars. The disk is surrounded by a spheroid halo of older, population II stars, as well as relatively dense concentrations of"
"Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. According to radiometric dating and other sources of evidence, Earth formed over 4.5 billion years ago. Earth's gravity interacts with other objects in space, especially the Sun and the Moon, Earth's only natural satellite. Earth revolves around the Sun in 365.26 days, a period known as an Earth year. During this time, Earth rotates about its axis about 366.26 times. Earth's axis of rotation is tilted with respect to its orbital plane, producing seasons on Earth. The gravitational interaction between Earth and"
"Discovery and exploration of the Solar System Discovery and exploration of the Solar System is observation, visitation, and increase in knowledge and understanding of Earth's ""cosmic neighborhood"". This includes the Sun, Earth and the Moon, the major planets including Mercury, Venus, Mars, Jupiter, Saturn, Uranus, and Neptune, their satellites, as well as smaller bodies including comets, asteroids, and dust. For many thousands of years, astronomers maintained a geocentric world view and did not recognize the existence of a Solar System. Most believed Earth was stationary at the center of the Universe and categorically different from the divine or ethereal objects"
"Sombrero Galaxy The Sombrero Galaxy (also known as Messier Object 104, M104 or NGC 4594) is a spiral galaxy in the constellation Virgo located from Earth. The galaxy has a diameter of approximately 15kpc (50,000 light-years), 30% the size of the Milky Way. It has a bright nucleus, an unusually large central bulge, and a prominent dust lane in its inclined disk. The dark dust lane and the bulge give this galaxy the appearance of a sombrero. Astronomers initially thought that the halo was small and light, indicative of a spiral galaxy, but the Spitzer Space Telescope found that the"
"universe is composed of two spheres: one—the Earth—is solid and the other—the ""sphere of stars"", often called the firmament— is hollow. The constellations are fixed in the firmament; the Earth is stationary and the firmament revolves around it, explaining the movements of the stars. The planets, the moon, and the Sun also revolve around the Earth in the vast space between its surface and the edge of the firmament. Because the Earth is in the center of the universe, it is equidistant from the firmament and is thus not compelled to ""fall"" in any specific direction. According to Manilius, the"
"the Earth, between and . HD 34445 HD 34445 is a 7th-magnitude G-type main-sequence star located in the constellation Orion. Parallax measurements made by Gaia put the star at about 148 light-years (45.4 parsecs) away. At an age of 8.5 billion years, this star is larger, hotter, brighter, and more massive than our Sun. Also its metal content is roughly 40% greater than the Sun. In 2004, a gas giant planet was found in orbit around the star, but it was not until 2009 that this planet was confirmed. In 2017, five more planets were found. All have minimum masses"
"it much later. Two other possibilities are a collision with the Milky Way before the Andromeda Galaxy arrives or an ejection out of the Local Group. Triangulum Galaxy The Triangulum Galaxy is a spiral galaxy approximately 3 million light-years (ly) from Earth in the constellation Triangulum. It is catalogued as Messier 33 or NGC 598. The Triangulum Galaxy is the third-largest member of the Local Group of galaxies, behind the Milky Way and the Andromeda Galaxy. It is one of the most distant permanent objects that can be viewed with the naked eye. The galaxy is the smallest spiral galaxy"
"by the then-thriving custom planet industry of Magrathea to run a ten-million-year program in which organic life would play a major role. Slartibartfast, a Magrathean designer, was involved in the project and signed his name among the fjords of Norway (an area that won him an award). Earth is also home to Arthur Dent and Trillian. Earth is located in Galactic Sector ZZ9 Plural Z Alpha. ""The Hitchhiker's Guide to the Galaxy"" originally described Earth as """"harmless"""" (the entry is short because of the limited amount of space the Guide possessed, what with the sheer size and content of the"
"billion Earth-sized planets orbiting in the habitable zones of sun-like stars and red dwarf stars within the Milky Way Galaxy. 11 billion of these estimated planets may be orbiting sun-like stars. Since there are about 100 billion stars in the galaxy, this implies is roughly 0.4. The nearest planet in the habitable zone is Proxima Centauri b, which is as close as about 4.2 light-years away. The consensus at the Green Bank meeting was that had a minimum value between 3 and 5. Dutch science journalist Govert Schilling has opined that this is optimistic. Even if planets are in the"
"from the original solar nebula. The Solar System has four terrestrial planets: Mercury, Venus, Earth, and Mars. Only one terrestrial planet, Earth, is known to have an active hydrosphere. During the formation of the Solar System, there were probably many more terrestrial planetesimals, but most merged with or were ejected by the four terrestrial planets. Dwarf planets, such as Ceres, Pluto and Eris, and small Solar System bodies are similar to terrestrial planets in the fact that they do have a solid surface, but are, on average, composed of more icy materials (Ceres, Pluto and Eris have densities of 2.17,"
"Galactic Empire (Isaac Asimov) The Galactic Empire is an interstellar empire featured in Isaac Asimov's ""Robot"", ""Galactic Empire"", and ""Foundation"" series. The Empire is spread across the Milky Way galaxy and consists of almost 25 million planets settled exclusively by humans. It had a total population of 500 quintillion. For over 12 millennia the seat of imperial authority was located on the ecumenopolis of Trantor, whose population exceeded 40 billion, until it was sacked in the year 12,328. The official symbol of the empire is the Spaceship-and-Sun. Cleon II was the last Emperor to hold significant authority. The fall of"
"Gaia (Foundation universe) Gaia is a fictional planet described in the book ""Foundation's Edge"" (1982) and referred to in ""Foundation and Earth"" (1986), both by Isaac Asimov. The name is derived from the Gaia hypothesis, which is itself eponymous to Gaia, the Earth Goddess. In this fictional universe, Gaia is located in the Sayshell Sector, about ten parsecs (32 light years) from the system Sayshell itself. It orbits a G-4 class star, and has one natural satellite (50 km or 31 miles in diameter). Its axial inclination is 12°, and a Gaian day lasts 0.92 Galactic Standard Days. In its"
"the solar system. In turn, the natural history of the Earth caused parts of this planet to have differing concentrations of the elements. The mass of the Earth is approximately 5.98 kg. In bulk, by mass, it is composed mostly of iron (32.1%), oxygen (30.1%), silicon (15.1%), magnesium (13.9%), sulfur (2.9%), nickel (1.8%), calcium (1.5%), and aluminium (1.4%); with the remaining 1.2% consisting of trace amounts of other elements. The bulk composition of the Earth by elemental-mass is roughly similar to the gross composition of the solar system, with the major differences being that Earth is missing a great deal"
"unmapped. There are also ongoing studies of the region between Mercury and the Sun. Objects may yet be discovered in the Solar System's uncharted regions. Currently, the furthest known objects, such as Comet West, have aphelia around 70,000 AU from the Sun, but as the Oort cloud becomes better known, this may change. The Solar System is located in the Milky Way, a barred spiral galaxy with a diameter of about 100,000 light-years containing about 100 billion stars. The Sun resides in one of the Milky Way's outer spiral arms, known as the Orion–Cygnus Arm or Local Spur. The Sun"