Astronomy, TRA-WHY
Human beings have long been fascinated by the celestial sphere above, whose twinkling lights have inspired not only scientific theories but also many artistic endeavors. Humankind's fascination with the world beyond Earth has led to many landmark moments in history, as when space exploration took a giant step forward with the advent of technology that allowed humans to successfully travel to the Moon and to build spacecraft capable of exploring the rest of the solar system and beyond.
Astronomy Encyclopedia Articles By Title
Transition Region and Coronal Explorer
Transition Region and Coronal Explorer (TRACE), U.S. satellite designed to study the solar corona. It was launched......
Triangulum
Triangulum, constellation in the northern sky at about 2 hours right ascension and 30° north in declination. Its......
Triangulum Australe
Triangulum Australe, constellation in the southern sky at about 16 hours right ascension and 65° south in declination.......
Trifid Nebula
Trifid Nebula, (catalog numbers NGC 6514 and M 20), bright, diffuse nebula in the constellation Sagittarius, lying......
Triton
Triton, largest of Neptuneâs moons, whose unusual orbital characteristics suggest that it formed elsewhere in the......
Trojan asteroid
Trojan asteroid, any one of a number of asteroids that occupy a stable Lagrangian point in a planetâs orbit around......
Trumpler, Robert Julius
Robert Julius Trumpler was a Swiss-born U.S. astronomer who, in his extensive studies of galactic star clusters,......
TRW Inc.
TRW Inc., major American industrial corporation providing advanced-technology products and services primarily in......
Tsiolkovsky, Konstantin
Konstantin Tsiolkovsky was a Russian research scientist in aeronautics and astronautics who pioneered rocket and......
Tucana
Tucana, constellation in the southern sky at about 0 hour right ascension and 60° south in declination. Its brightest......
Turner, Herbert Hall
Herbert Hall Turner was an English astronomer who pioneered many of the procedures now universally employed in......
TuĂąn, PháșĄm
PháșĄm TuĂąn is a Vietnamese pilot and cosmonaut, the first Vietnamese citizen in space. TuĂąn joined the Vietnam Peopleâs......
Tycho
Tycho, conspicuous impact crater resulting from an impact event and lying at the centre of the most extensive system......
Tychonic system
Tychonic system, scheme for the structure of the solar system put forward in 1583 by the Danish astronomer Tycho......
Tychoâs Nova
Tychoâs Nova, one of the few recorded supernovas in the Milky Way Galaxy. The Danish astronomer Tycho Brahe first......
Tyson, Neil deGrasse
Neil deGrasse Tyson is an American astronomer who popularized science with his books and frequent appearances on......
U Geminorum star
U Geminorum star, any of a class of irregular variable stars that display sudden increases in brightness so great......
UBV system
UBV system, system of classifying stars by spectral type, based on photometric measurements of the ultraviolet......
Ultraviolet astronomy
Ultraviolet astronomy, study of the ultraviolet spectra of astronomical objects. Ultraviolet radiation comes from......
Ultraviolet telescope
Ultraviolet telescope, telescope used to examine the ultraviolet portion of the electromagnetic spectrum, between......
Ulysses
Ulysses, joint European-U.S. space probe launched in 1990 that was the first spacecraft to fly over the poles of......
Umbra
Umbra, that part of a shadow in which all light from a given source is excluded. The shadow from a point source......
Umbriel
Umbriel, third nearest of the five major moons of Uranus and the one having the darkest and oldest surface of the......
Understanding Keplerâs Laws of Planetary Motion
In the early 17th century, German astronomer Johannes Kepler postulated three laws of planetary motion. His laws......
unidentified flying object
unidentified flying object (UFO), any aerial object or optical phenomenon not readily identifiable to the observer.......
Unidentified Flying Objects: What We Know
Everything we know (and only what we know) about the phenomenon of UFOs. Companion, UFO, UFOs, flying saucers,......
United States Naval Observatory
United States Naval Observatory (USNO), in Washington, D.C., an official source, with the U.S. National Institute......
Universe
Universe, the whole cosmic system of matter and energy of which Earth, and therefore the human race, is a part.......
Urania
Urania, in Greek religion, one of the nine Muses, patron of astronomy. In some accounts she was the mother of Linus......
Uraniborg
Uraniborg, observatory established in 1576 by the Danish astronomer Tycho Brahe. It was the last of the primitive......
Uranus
Uranus, seventh planet in distance from the Sun and the least massive of the solar systemâs four giant, or Jovian,......
Urey, Harold C.
Harold C. Urey was an American scientist awarded the Nobel Prize for Chemistry in 1934 for his discovery of the......
Ursa Major
Ursa Major, in astronomy, a constellation of the northern sky, at about 10 hours 40 minutes right ascension and......
Ursa Minor
Ursa Minor, in astronomy, a constellation of the northern sky, at about 15 hours right ascension and 80° north......
Utopia Planitia
Utopia Planitia, northern lava plain on the planet Mars that was selected as the landing site of the U.S. Viking......
Valles Marineris
Valles Marineris, vast system of interconnected canyons on the planet Mars. The system was discovered during, and......
Vanguard
Vanguard, any of a series of three uncrewed U.S. experimental test satellites. Vanguard 1, launched March 17, 1958,......
Varahamihira
Varahamihira was an Indian philosopher, astronomer, and mathematician, author of the Pancha-siddhantika (âFive......
Variable star
Variable star, any star whose observed light varies notably in intensity. The changes in brightness may be periodic,......
Vastitas Borealis
Vastitas Borealis, nearly level lowland plain that surrounds the north pole of the planet Mars and extends southward......
Vega
Vega, brightest star in the northern constellation Lyra and fifth brightest in the night sky, with a visual magnitude......
Vela
Vela, any of a series of 12 unmanned U.S. reconnaissance satellites developed to detect radiation from nuclear......
Vela
Vela, constellation in the southern sky at about 10 hours right ascension and 50° south in declination. Its brightest......
Velikovsky, Immanuel
Immanuel Velikovsky was an American writer, proponent of controversial theories of cosmogony and history. Educated......
Venera
Venera, any of a series of unmanned Soviet planetary probes that were sent to Venus. Radio contact was lost with......
Venus
Venus, second planet from the Sun and sixth in the solar system in size and mass. No planet approaches closer to......
Venus Express
Venus Express, European Space Agency spacecraft that orbited the planet Venus. The design of Venus Express was......
Verbiest, Ferdinand
Ferdinand Verbiest was a Dutch Jesuit missionary and astronomer who became an influential official in the Chinese......
Vernal equinox
Vernal equinox, two moments in the year when the Sun is exactly above the Equator; also, either of the two points......
Very Large Array
Very Large Array (VLA), radio telescope system situated on the plains of San Agustin near Socorro, New Mexico,......
Very Large Telescope
Very Large Telescope (VLT), observatory located on the mountain Cerro Paranal (2,635 metres [8,645 feet]) in Chile......
Vesta
Vesta, second largestâand the brightestâasteroid of the asteroid belt and the fourth such object to be discovered,......
Viehböck, Franz
Franz Viehböck is an Austrian electrical engineer and cosmonaut, the first Austrian to go into space. Viehböck......
Viking
Viking, either of two robotic U.S. spacecraft launched by NASA for extended study of the planet Mars. The Viking......
Virgo
Virgo, in astronomy, zodiacal constellation lying in the southern sky between Leo and Libra, at about 13 hours......
Virgo cluster
Virgo cluster, the closest large cluster of galaxies. The Virgo cluster is located at a distance of about 5 Ă 107......
Vogel, Hermann Karl
Hermann Karl Vogel was a German astronomer who discovered spectroscopic binariesâdouble-star systems that are too......
Volans
Volans, constellation in the southern sky at about 8 hours right ascension and 70° south in declination. Its brightest......
Volkov, Alexander
Alexander Volkov is a Russian pilot and cosmonaut, the first cosmonaut whose son also went into space. Volkov graduated......
Volkov, Sergey
Sergey Volkov is a Russian military pilot and cosmonautâthe first second-generation cosmonaut, following his father,......
Volkov, Vladislav Nikolayevich
Vladislav Nikolayevich Volkov was a Soviet cosmonaut, participant in the Soyuz 7 and 11 missions of 1969 and 1971,......
Voskhod
Voskhod, second series of manned Soviet spacecraft. Following the triumph of the Vostok launchings that had put......
Vostok
Vostok, any of a series of manned Soviet spacecraft, the initial flight of which carried the first human being......
Voyager
Voyager, in space exploration, either of a pair of robotic U.S. interplanetary probes launched to observe and to......
Voyager 1
Voyager 1, robotic U.S. interplanetary probe launched in 1977 that visited Jupiter and Saturn and was the first......
Vulpecula
Vulpecula, constellation in the northern sky at about 20 hours right ascension and 25° north in declination. It......
VÀisÀlÀ, Yrjö
Yrjö VÀisÀlÀ was a Finnish meteorologist and astronomer noted for developing meteorological measuring methods and......
Wakata, Koichi
Koichi Wakata is a Japanese astronaut who accumulated a number of records during his career. Among them, he spent......
Was the Big Bang Actually an Explosion?
The big-bang theory was first proposed by Georges LemaĂźtre in 1927 sans its contemporary name, which was coined......
Was the Moon Landing Fake?
The Apollo project was one of humanityâs greatest achievements. For the first time, people walked on another world.......
Watkins, Jessica
Jessica Watkins is an American astronaut who spent six months aboard the International Space Station (ISS) in 2022......
Weather satellite
Weather satellite, any of a class of Earth satellites designed to monitor meteorological conditions (see Earth...
Wee Worlds: Our 5 (Official) Dwarf Planets
There was much outrage and confusion in 2006 when Pluto lost its status as our solar systemâs ninth planet. But......
weight
weight, gravitational force of attraction on an object, caused by the presence of a massive second object, such......
Weiss, Rainer
Rainer Weiss was a German-born American physicist who was awarded the 2017 Nobel Prize for Physics for his work......
What are the phases of the Moon?
The Moon goes through a cycle of eight distinct phases as it orbits Earth, each offering a unique view of its illuminated......
What are the rings of Saturn made of?
Saturnâs rings are made of billions of particles, chiefly composed of water ice and small amounts of rock and dust.......
What Causes Lunar and Solar Eclipses?
An eclipse happens when one astronomical body blocks light from or to another. In a lunar eclipse, the Moon moves......
What causes tides in the ccean?
The main cause of tides in the ocean are the gravitational forces exerted by the Moon and the Sun on Earth. When......
What color is the universe?
Not black, despite what the night sky may suggest. The vast expanse of the universe that separates stars and galaxiesâspace......
What Have We Left on the Moon?
In July 1969 Neil Armstrong and Buzz Aldrin made history as the first human beings to land on the Moonâs surface.......
What is dark matter?
Although dark matter is not well understood, it is clearly a crucial component of the universe. Because it is electromagnetically......
What is the difference between comets and asteroids?
Comets and asteroids differ primarily in their composition, origin, and orbits within the solar system. Comets......
What is the difference between mass and weight?
Mass is a fundamental property of an object that quantifies the amount of matter it contains by measuring its inertia.......
Whatâs the Difference Between a Meteoroid, a Meteor, and a Meteorite?
Itâs a cool night, and you look up at the stars twinkling and serene in the dark sky. Then a light streaks across......
Whatâs the Difference Between a Solstice and an Equinox?
You may know that the solstices and equinoxes signal the changing of the seasons on Earth, but do you remember......
Whatâs the difference between planets and stars?
Stars burn bright and hot due to nuclear fusion reactions occurring in their cores. This process involves the fusion......
Where Did the Moon Come From?
The largest and most familiar sight in the night sky is the Moon. Its presence has likely bewitched observers since......
White dwarf star
White dwarf star, any of a class of faint stars representing the endpoint of the evolution of intermediate- and......
White, Edward H., II
Edward H. White II was the first U.S. astronaut to walk in space. White graduated from the U.S. Military Academy,......
Whiting, Sarah Frances
Sarah Frances Whiting was an American physicist and astronomer who advanced the scientific education of women in......
Whitney, Mary Watson
Mary Watson Whitney was an American astronomer who built Vassar Collegeâs research program in astronomy into one......
Whitson, Peggy
Peggy Whitson is an American biochemist and astronaut, who was the first female commander of the International......
Who was the first cat in space?
On October 18, 1963, FĂ©licetteâa black-and-white tuxedo cat who hailed from Franceâwas the first cat to be sent......
Who won the space race?
The United States is generally considered to have won the Space Race. The Space Race was a fierce rivalry between......
Why Are Planets Round?
The Sun and all eight planets of the solar system are round. Why? The gravitational force of a planetâs mass pulls......
Why are some stars brighter than others?
Stars vary in brightness because of their intrinsic luminosity and because of their distance from us. More massive......
Why are stars different colors?
Red giants. White dwarfs. Stars come in different colors. The reason they come in different colors is because they......
Why do stars twinkle?
Light emitted from stars does not actually twinkle but only appears to twinkle when viewed from Earth. As starlight......
Why does the Earth rotate?
The Earth rotates because of the conservation of angular momentum acquired from the rotation of the solar nebula,......