O Universo: Como funcionam as Galáxias

Como funcionam as Galáxias

Quando você observa o céu noturno, especialmente no verão,
percebe uma faixa indistinta de estrelas espalhadas pela
porção central do céu. Esse grupo de estrelas constitui a
nossa galáxia, a Via Láctea.
O Sol é apenas uma das 200 bilhões de estrelas da Via
Láctea, que é apenas uma das bilhões de galáxias do
universo. Uma galáxia é um amplo sistema de estrelas,
gases (principalmente hidrogênio), poeira e matéria
escura que orbita um ponto central comum e é mantido
unido pela gravidade. Já foram descritas como
"universos-ilha" e apresentam diferentes formas e
tamanhos. Sabemos que são muito antigas e se formaram no
começo da evolução do Universo, mas a maneira como se
formaram e evoluíram para as diferentes formas que
exibem continua a ser um mistério.
Como funcionam as Galáxias

* A Atlantis *

Atlantis Lifts Off!
Photographers crowd around the countdown clock to capture the successful launch of Space Shuttle Atlantis from Launch Pad 39A. The shuttle is delivering a new segment to the starboard side of the International Space Station's backbone, known as the truss. Three spacewalks are planned to install the S3/S4 truss segment, deploy a set of solar arrays and prepare them for operation. STS-117 is the 118th space shuttle flight, the 21st flight to the station, the 28th flight for Atlantis and the first of four flights planned for 2007. Image credit: NASA/Jim Grossmann

As Cores de Saturno

The Colors of Saturn
This delightfully detailed false color image of Saturn is a combination of three images taken in January 1998 by the Hubble Space Telescope and shows the ringed planet in reflected infrared light. Different colors indicated varying heights and compositions of cloud layers generally thought to consist of ammonia ice crystals. The eye-catching rings cast a shadow on Saturn's upper hemisphere, while the bright stripe seen within the left portion of the shadow is infrared sunlight streaming through the large gap in the rings known as the Cassini Division. Two of Saturn's many moons have also put in an appearance (in the full resolution version), Tethys just beyond the planet's disk at the upper right, and Dione at the lower left. Image credit: NASA/E. Karkoschka (University of Arizona)

Estrela de Misteriosa Luz

Light Echoes From a Red Supergiant
This Hubble Space Telescope image of the star V838 Monocerotis reveals dramatic changes in the illumination of surrounding dusty cloud structures. The effect, called a light echo, unveiled never-before-seen dust patterns when the star suddenly brightened for several weeks in early 2002.A light echo is light from a stellar explosion echoing off dust surrounding the star that produces enough energy in a brief flash to illuminate surrounding dust. The star presumably ejected the illuminated dust shells in previous outbursts. Light from the latest outburst travels to the dust and then is reflected to Earth.The phenomena is similar to that of a nova. A typical nova is a normal star that dumps hydrogen onto a compact white-dwarf companion star. The hydrogen piles up until it spontaneously explodes by nuclear fusion -- like a titanic hydrogen bomb -- exposing a searing stellar core with a temperature of hundreds of thousands of degrees Fahrenheit.By contrast, V838 Monocerotis did not expel its outer layers. Instead, it grew enormously in size. Its surface temperature dropped to temperatures that were not much hotter than a light bulb. This behavior of ballooning to an immense size, but not losing its outer layers, is very unusual and completely unlike an ordinary nova explosion.The outburst may representtransitory stage in a star's evolution that is rarely seen. The star has some similarities to highly unstable aging stars called eruptive variables, which suddenly and unpredictably increase in brightness.V838 Monocerotis is located about 20,000 light-years away from Earth in the direction of the constellation Monoceros, placing the star at the outer edge of our Milky Way galaxy.Image credit: NASA, ESA, and

STEREO's First View of the Sun
Loops of highly charged particles burst from the sun's surface in this image, taken on Dec. 4, 2006. Among the first images taken by STEREO, the image shows the sun's roiling surface and atmosphere at temperatures around one million Kelvin (1.8 million degrees Fahrenheit).

The charged particles, mostly extremely hot protons and electrons, create a strong magnetic field that pulls the particles into the loops seen here. Over time, magnetic stress builds in the sun's atmosphere until the energy is released in a massive explosion. The explosion sends a giant cloud of charged particles (a coronal mass ejection) and x-ray solar flares hurtling into space with a force comparable to a billion megaton nuclear bombs. When the charged particles and x-rays bombard the Earth, they can disrupt
communications and power systems and are a threat to satellites and astronauts in space. Understanding the difference between harmful and harmless coronal mass ejections is one of the biggest questions that scientists studying the face of the sun. Currently, scientists only see ejections in one dimension. To understand how solar storms travel through the solar systems, scientists need a three-dimensional view of the storms. STEREO, launched on Oct. 25, 2006, consists of observation systems orbiting the sun in front of and behind the Earth. Just as our two eyes give us a three-dimensional view of the world, the views provided by each STEREO system can be combined to provide a three-dimensional view of the sun. Though the first STEREO images were taken in early December, the two systems won't be in position to give three dimensional images until April 2007. Image credit: NASA

* Estrela de Misteriosa Lúz *

Star's Mysterious Light
In January 2002, a dull star in an obscure constellation suddenly became 600,000 times more luminous than our sun, temporarily making it the brightest star in our Milky Way galaxy. The mysterious star has long since faded back to obscurity, but observations by NASA's Hubble Space Telescope of a phenomenon called a "light echo" have uncovered remarkable new features. These details promise to provide astronomers with a CAT-scan-like probe of the three-dimensional structure

* É na Lua Mesmo...

Lunar Grand Prix
The Lunar Roving Vehicle (LRV) gets a high-speed workout by astronaut John W. Young in the "Grand Prix" run during the third Apollo 16 extravehicular activity at the Descartes landing site. This view is a frame from motion picture film exposed by a 16mm Maurer camera held by astronaut Charles M. Duke, Jr. While astronauts Young and Duke, lunar module pilot, descended onto the lunar surface to explore the Descartes highlands region of the moon, command module pilot Thomas K. Mattingly remained with the Command and Service Modules in lunar orbit. Image credit: NASA

* O Universo *

Cosmic Pearls
Two decades ago, astronomers spotted one of the brightest exploding stars in more than 400 years. Since that first sighting, the doomed star, called Supernova 1987A, has continued to fascinate astronomers with its spectacular light show. NASA's Hubble Space Telescope is one of many observatories that has been monitoring the blast's aftermath. The supernova is located 163,000 light-years away in the Large Magellanic Cloud. This image shows the entire region surrounding the supernova, the most prominent feature of which is a ring with dozens of bright spots, shining like cosmic pearls. Unleashed by the stellar blast, this material is slamming into regions along the ring's inner regions, heating them up, and causing them to glow. The ring, about a light-year across, was likely shed by the star about 20,000 years before it exploded. This image was taken in December

* O Universo Infinito *

A Ghostly Presence
This composite image shows Z Camelopardalis, or Z Cam, a double-star system. The Z Cam system features a collapsed, dead star, called a white dwarf, and its companion star, as well as a ghostly shell around the system. The massive shell provides evidence of lingering material ejected during, and swept up by, a powerful explosion that occurred a few thousand years ago.The image combines data gathered from the far-ultraviolet and near-ultraviolet detectors on NASA's Galaxy Evolution Explorer on Jan. 25, 2004. The orbiting observatory first began imaging Z Cam in 2003.Z Cam is the largest white object in the image, located near the center. Parts of the shell are seen as a wispy, yellowish feature below and to the right of Z Cam, and as two large, whitish, perpendicular lines on the left.Z Cam was one of the first known recurrent dwarf nova, meaning it erupts in a series of small, hiccup-like blasts, unlike classical novae, which undergo a massive explosion.
Image credit: NASA/JPL-Caltech

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Como funcionam as Galáxias

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* A Atlantis *

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