Thursday, September 23, 2010

Light Echoes From Red Supergiant Star

The earliest beginning of a star is called a nebula. A nebula is a cloud of hydrogen and a few helium atoms hanging in space. Sometimes a nebula just stays at this point, but if the cloud gets thick enough, with enough hydrogen atoms close enough together, it can become a brown dwarf. A brown dwarf is a small star that is not quite big enough, so there is not enough gravity to start the nuclear fusion process. Brown dwarf stars hardly shine at all, but they're not very common either. 

If the brown dwarf succeeds in attracting enough hydrogen atoms and packing them tightly enough together, then it turns into a main-sequence star - an ordinary star like our sun. Nine out of every ten stars you can see from Earth are main-sequence stars. Inside a main-sequence star, the pressure of gravity pushes hydrogen atoms together so they become helium atoms, and the extra energy released by this fusion process shoots out of the star and become heat and sunlight.
The red giant star Betelgeuse
(thanks to Hubble Space Telescope)
A main-sequence star usually doesn't change for several billion years, but eventually it runs out of hydrogen atoms to turn into helium atoms, like a car running out of gas. When this happens, the main-sequence star turns into a supergiant star. These supergiants, or "red giants", are much bigger and cooler than regular stars. Two examples of supergiant stars are Antares and Betelgeuse. Supergiant stars still have nuclear fusion going on inside them, but they change helium atoms into carbon, or carbon into oxygen. A supergiant lasts about one-tenth as long as the main-sequence star did.  (Read more at History for kids)

Monday, August 23, 2010

Spiral Galaxies


A spiral galaxy is a certain kind of galaxy originally described by Edwin Hubble in his 1936 work The Realm of the Nebulae[1] and, as such, forms part of the Hubble sequence. Spiral galaxies consist of a flat, rotating disk containing stars, gas and dust, and a central concentration of stars known as the bulge. These are surrounded by a much fainter halo of stars, many of which reside in globular clusters.

Monday, August 9, 2010

Saturn Aurora


These images reveal the dynamic nature of Saturn's auroras. Viewing the planet's southern polar region for several days, NASA's Hubble Space Telescope snapped a series of photographs of the aurora dancing in the sky. The snapshots show that Saturn's auroras differ in character from day to day, as they do on Earth, moving around on some days and remaining stationary on others. But compared with Earth, where auroral storms develop in about 10 minutes and may last for a few hours, Saturn's auroral displays always appear bright and may last for several days.
The observations, made by Hubble and the Cassini spacecraft, while enroute to the planet, suggest that Saturn's auroral storms are driven mainly by the pressure of the solar wind — a stream of charged particles from the Sun — rather than by the Sun's magnetic field.

The aurora's strong brightening on Jan. 28, 2004 corresponds with the recent arrival of a large disturbance in the solar wind. The image shows that when Saturn's auroras become brighter (and thus more powerful), the ring of light encircling the pole shrinks in diameter.

Seen from space, an aurora appears as a ring of glowing gases circling a planet's polar region. Auroral displays are initiated when charged particles in space collide with a planet's magnetic field. The charged particles are accelerated to high energies and stream into the upper atmosphere. Collisions with the gases in the planet's atmosphere produce flashes of glowing energy in the form of visible, ultraviolet, and infrared light.

Sunday, July 25, 2010

Cats Eye Nebula

From Wikipedia

The Cat's Eye Nebula (NGC 6543) is a planetary nebula in the constellation of Draco. Structurally, it is one of the most complex nebulae known, with high-resolution Hubble Space Telescope observations revealing remarkable structures such as knots, jets, bubbles and sinewy arc-like features. In the center of the Cat's Eye there is a bright and hot star, which around 1000 years ago lost its outer envelope producing the nebula.
It was discovered by William Herschel on February 15, 1786, and was the first planetary nebula whose spectrum was investigated by the English amateur astronomer William Huggins in 1864. The results of the latter investigation demonstrated for the first time that planetary nebulae consist of hot gases, but not stars. Currently the nebula have been observed across the full electromagnetic spectrum, from far-infrared to X-rays.
Modern studies reveal several mysteries. The intricacy of the structure may be caused in part by material ejected from a binary central star, but as yet, there is no direct evidence that the central star has a companion. Also, measurements of chemical abundances reveal a large discrepancy between measurements done by two different methods, the cause of which is uncertain. Hubble Telescope observations revealed a number of faint rings around the Eye, which are spherical shells ejected by the central star in the distant past. The exact mechanism of those ejections, however, is unclear.

The Pleiades

From Wikipedia
In astronomy, the Pleiades, or Seven Sisters (Messier object 45), is an open star cluster containing middle-aged hot B-type stars located in the constellation of Taurus. It is among the nearest star clusters to Earth and is the cluster most obvious to the naked eye in the night sky. Pleiades has several meanings in different cultures and traditions.

NASA Fixes Hubble Telescope

Explanation: What is that astronaut doing? Fixing the Hubble Space Telescope. During the fourth servicing mission to upgrade and fix Hubble, astronaut Michael Good can be seen attached to the shuttle's robotic arm, working in an open panel of Hubble. Far below, the terminator between day and night can be seen across planet Earth. Since Hubble was captured by the space shuttle Atlantis last Wednesday, five long space-walks have been used to fix and upgrade the aging telescope. One of the more ambitious orbital missions yet taken, the toiling astronauts have upgraded the Wide Field Camera, fixed the Advanced Camera for Surveys, repaired the Space Telescope Imaging Spectrograph, and replaced COSTAR with the Cosmic Origins Spectrograph. Numerous other general repairs included replacing batteries, gyroscopic sensors, and insulation panels. Hubble will now undergo testing as Atlantis prepares to return to Earth later this week.

Hubble Finds Carbon Dioxide On An Extra Solar Planet

Variable Star Eta Carinae

WFPC2 image of the variable star Eta Carinae

Hubble Space Telescope image showing Eta Carinae and the bipolar Homunculus Nebula which surrounds the star. The Homunculus was partly created in an eruption of Eta Carinae, the light from which reached Earth in 1843. Eta Carinae itself appears as the white patch near the center of the image, where the 2 lobes of the Homunculus touch.

Dying Star

A Dying Star Shrouded by a Blanket of Hailstones Forms the Bug Nebula (NGC 6302)

The Hubble Telescope

 "Since the earliest days of astronomy, since the time of Galileo, astronomers have shared a single goal — to see more, see farther, see deeper.  The Hubble Space Telescope's launch in 1990 sped humanity to one of its greatest advances in that journey. Hubble is a telescope that orbits Earth. Its position above the atmosphere, which distorts and blocks the light that reaches our planet, gives it a view of the universe that typically far surpasses that of ground-based telescopes.  Hubble is one of NASA's most successful and long-lasting science missions. It has beamed hundreds of thousands of images back to Earth, shedding light on many of the great mysteries of astronomy. Its gaze has helped determine the age of the universe, the identity of quasars, and the existence of dark energy."