| |
| Risultati della ricerca nelle immagini - "GALEX" |
GALEX Portrait-PIA03295.jpgPortrait of the Universe56 visiteFrom sparkling blue rings to dazzling golden disks, Galaxy Evolution Explorer (Galex) scientists are handing out a collection of their finest galactic treasures at the January 2006 American Astronomical Society meeting in Washington, D.C.
Mined from the mission's Survey of Nearby Galaxies data, these cosmic gems were collected with the telescope's sensitive ultraviolet instruments. The gallery of galaxies has been made into a poster for meeting attendees visiting the mission's booth. Organized from far-ultraviolet to near-ultraviolet bright galaxies, this poster encapsulates the heart of the mission to study how galaxies and star formation rates have changed over the past 10 billion years.
Events in space take millions or billions of years to unfold, which means that astronomers can't watch individual galaxies and stars age over time. Luckily, because the physics of light travel dictates that the farther away an object is from Earth, the longer it takes for its light to travel to us, the universe can be thought of as a time machine. By building telescopes sensitive enough to capture objects that are 10 billion light-years away, astronomers can essentially see an object the way it looked 10 billion years ago. Galex astronomers are using this phenomenon to their advantage by taking snapshots of different galaxies at various distances in space. By comparing portraits of numerous objects at various times in the universe's history, the team can begin to piece together the life cycle of stars and galaxies.
For the poster, Galex scientists organized 196 different nearby galaxies in bins of increasing ultraviolet color. By placing the various snapshots side by side, astronomers can see how galaxies age differently. When viewed in ultraviolet, active star-forming regions in galaxies can be seen as glittering blue structures, while a soft, golden glow indicates the presence of older stars.
The 196 galaxies represented in the poster were selected from more than 1,000 galaxies in the "Ultraviolet Atlas of Nearby Galaxies." So far, the Galex mission has surveyed more than 100 million galaxies.
|
|
M-081-4.jpgM 81: Feeding a Black Hole54 visite"...L'unico "trend" che gli Istituti dediti ai Sondaggi ed alle Statistiche si sono dimenticati di misurare è quello che io chiamo "Trend Umanistico". Ed è l'unico trend che misura e dimostra, in maniera inquivocabile, che l'Umanità, nel suo complesso - e fatte salve le ovvie ed inevitabili (e Benedette!) eccezioni -, di giorno in giorno diventa sempre più instabile, violenta, egoista ed ignorante..."
P.C. Floegers - "Conversations"
MareKromium
|
|
Mira-PIA09958-0.jpgMira soars through the Sky!56 visiteNew ultraviolet images from NASA's Galaxy Evolution Explorer shows a speeding star that is leaving an enormous trail of "seeds" for new solar systems. The star, named Mira (pronounced my-rah) after the latin word for "wonderful," is shedding material that will be recycled into new stars, planets and possibly even life as it hurls through our galaxy.
In figure 1, the upper panel shows Mira's full, comet-like tail as seen only in shorter, or "far" ultraviolet wavelengths, while the lower panel is a combined view showing both far and longer, or "near" ultraviolet wavelengths. The close-up picture at bottom gives a better look at Mira itself, which appears as a pinkish dot, and is moving from left to right in this view. Shed material appears in light blue. The dots in the picture are stars and distant galaxies. The large blue dot on the left side of the upper panel, and the large yellow dot in the lower panel, are both stars that are closer to us than Mira.
The Galaxy Evolution Explorer discovered the strange tail during part of its routine survey of the entire sky at ultraviolet wavelengths. When astronomers first saw the picture, they were shocked because Mira has been studied for over 400 years yet nothing like this has ever been documented before.
Mira's comet-like tail stretches a startling 13 light-years across the sky. For comparison, the nearest star to our sun, Proxima Centauri, is only about 4 light-years away. Mira's tail also tells a tale of its history -- the material making it up has been slowly blown off over time, with the oldest material at the end of the tail being released about 30,000 years ago (figure 2).
Mira is a highly evolved, "red giant" star near the end of its life. Technically, it is called an asymptotic giant branch star. It is red in color and bloated; for example, if a red giant were to replace our sun, it would engulf everything out to the orbit of Mars. Our sun will mature into a red giant in about 5 billion years.
Like other red giants, Mira will lose a large fraction of its mass in the form of gas and dust. In fact, Mira ejects the equivalent of the Earth's mass every 10 years. It has released enough material over the past 30,000 years to seed at least 3,000 Earth-sized planets or 9 Jupiter-sized ones.
While most stars travel along together around the disk of our Milky Way, Mira is charging through it. Because Mira is not moving with the "pack," it is moving much faster relative to the ambient gas in our section of the Milky Way. It is zipping along at 130 kilometers per second, or 291,000 miles per hour, relative to this gas.
Mira's breakneck speed together with its outflow of material are responsible for its unique glowing tail. Images from the Galaxy Evolution Explorer show a large build-up of gas, or bow shock, in front of the star, similar to water piling up in front of a speeding boat. Scientists now know that hot gas in this bow shock mixes with the cooler, hydrogen gas being shed from Mira, causing it to heat up as it swirls back into a turbulent wake. As the hydrogen gas loses energy, it fluoresces with ultraviolet light, which the Galaxy Evolution Explorer can detect.
Mira, also known as Mira A, is not alone in its travels through space. It has a distant companion star called Mira B that is thought to be the burnt-out, dead core of a star, called a white dwarf. Mira A and B circle around each other slowly, making one orbit about every 500 years. Astronomers believe that Mira B has no effect on Mira's tail.
Mira is also what's called a pulsating variable star. It dims and brightens by a factor of 1,500 every 332 days, and will become bright enough to see with the naked eye in mid-November 2007. Because it was the first variable star with a regular period ever discovered, other stars of this type are often referred to as "Miras."
Mira is located 350 light-years from Earth in the constellation Cetus, otherwise known as the whale. Coincidentally, Mira and its "whale of a tail" can be found in the tail of the whale constellation.
These images were between November 18 and December 15, 2006.
MareKromium
|
|
Mira-PIA09958-1.jpgMira: anatomy of a "Celestial Shooting Star"...59 visiteA close-up view of a star racing through space faster than a speeding bullet can be seen in this image from NASA's Galaxy Evolution Explorer. The star, called Mira (pronounced My-rah), is traveling at 130 kilometers per second, or 291,000 miles per hour. As it hurls along, it sheds material that will be recycled into new stars, planets and possibly even life.
In this image, Mira is moving from left to right. It is visible as the pinkish dot in the bulb shape at right. The yellow dot below is a foreground star. Mira is traveling so fast that it's creating a bow shock, or build-up of gas, in front of it, as can be seen here at right.
Like a boat traveling through water, a bow shock forms ahead of the star in the direction of its motion. Gas in the bow shock is heated and then mixes with the cool hydrogen gas in the wind that is blowing off Mira. This heated hydrogen gas then flows around behind the star, forming a wake.
Why is the wake of material glowing? When the hydrogen gas is heated, it transitions into a higher-energy state, which then loses energy by emitting ultraviolet light - a process called fluorescence. The Galaxy Evolution Explorer has special instruments that can detect this ultraviolet light.
A similar fluorescence process is responsible for the Northern Lights -- a glowing, green aurora that can be seen from northern latitudes. However, in that case nitrogen and oxygen gas are fluorescing with visible light.
Streams and a loop of material can also be seen coming off Mira. Astronomers are still investigating what these streams are, but they suspect that they are denser parts of Mira's wind perhaps flowing out of the star's poles.
This image consists of data captured by both the far- and near-ultraviolet detectors on the Galaxy Evolution Explorer between November 18 and December 15, 2006. It has a total exposure time of about 3 hours.
MareKromium
|
|
Mira-PIA09959.jpgMira: anatomy of a "Celestial Shooting Star"...58 visiteA close-up view of a star racing through space faster than a speeding bullet can be seen in this image from NASA's Galaxy Evolution Explorer. The star, called Mira (pronounced My-rah), is traveling at 130 kilometers per second, or 291,000 miles per hour. As it hurls along, it sheds material that will be recycled into new stars, planets and possibly even life.
In this image, Mira is moving from left to right. It is visible as the pinkish dot in the bulb shape at right. The yellow dot below is a foreground star. Mira is traveling so fast that it's creating a bow shock, or build-up of gas, in front of it, as can be seen here at right.
Like a boat traveling through water, a bow shock forms ahead of the star in the direction of its motion. Gas in the bow shock is heated and then mixes with the cool hydrogen gas in the wind that is blowing off Mira. This heated hydrogen gas then flows around behind the star, forming a wake.
Why is the wake of material glowing? When the hydrogen gas is heated, it transitions into a higher-energy state, which then loses energy by emitting ultraviolet light - a process called fluorescence. The Galaxy Evolution Explorer has special instruments that can detect this ultraviolet light.
A similar fluorescence process is responsible for the Northern Lights -- a glowing, green aurora that can be seen from northern latitudes. However, in that case nitrogen and oxygen gas are fluorescing with visible light.
Streams and a loop of material can also be seen coming off Mira. Astronomers are still investigating what these streams are, but they suspect that they are denser parts of Mira's wind perhaps flowing out of the star's poles.
This image consists of data captured by both the far- and near-ultraviolet detectors on the Galaxy Evolution Explorer between November 18 and December 15, 2006. It has a total exposure time of about 3 hours.
MareKromium
|
|
Mira-PIA09961.jpgMira's Tail57 visiteCaption NASA:"NASA's Galaxy Evolution Explorer discovered an exceptionally long comet-like tail of material trailing behind Mira -- a star that has been studied thoroughly for about 400 years.
So, why had this tail gone unnoticed for so long? The answer is that nobody had scanned the extended region around Mira in ultraviolet light until now.
As this composite demonstrates, the tail is only visible in ultraviolet light (top), and does not show up in visible light (bottom). Incidentally, Mira is much brighter in visible than ultraviolet light due to its low surface temperature of about 3000 Kelvin (about 5000° Fahrenheit)".MareKromium
|
|
NGC-0055-PIA04923.jpgNGC 55 - Spiral Galaxy54 visite"...Credo che il giusto è un istrion beffardo,
E nel viso e nel cuor,
Che tutto è in lui bugiardo:
Lagrima, bacio, sguardo,
Sacrificio ed onor..."
Arrigo Boito - "Otello"
|
|
NGC-0253_-_PIA08646.jpgNGC 253 - The (Dusty) "Silver Dollar Galaxy"55 visite"...Anche se non c'è nessuno ad ascoltare, quando un albero cade, in una qualsiasi foresta del Mondo, un rumore viene comunque prodotto..."
(anonimo)
|
|
NGC-0404-PIA11393-1.jpgNGC 404 - The 'Ghost of Mirach' rears its Spooky Head58 visiteThe "Ghost of Mirach" Galaxy is shown in visible light on the left, and in UltraViolet as seen by NASA's Galaxy Evolution Explorer on the right. The fields of view are identical in both pictures, with the Ghost of Mirach — a galaxy also known as NGC 404 — seen as the whitish spot in the center of the images.
Mirach is a Red Giant star that looms large in visible light. Because NGC 404 is lost in the glare of this star, it was nicknamed the "Ghost of Mirach".
But when the galaxy is viewed in ultraviolet light, it comes to "life", revealing a never-before-seen ring. This ring, seen in blue in the picture on the right, contains new stars — a surprise considering that the galaxy was previously thought to be, essentially, dead.
The field of view spans 55.000 Light Years across. The Ghost of Mirach is located 11 MLY from Earth. The star Mirach is very close in comparison — since it is only 200 LY away and is visible with the naked eye.
The visible data come from the Digitized Sky Survey of the Space Telescope Science Institute in Baltimore, Md.MareKromium
|
|
NGC-1510_and_NGC-1512-PIA08646.jpgNGC 1510 and NGC 1512 - Interacting Galaxies56 visite"...Though leaves are many, the root is one:
Through all the lying days of my Youth
I swayed my leaves and flowers in the Sun;
Now I may wither into the Truth..."
W.B. Yeats (1865 - 1939) - "The coming of Wisdom with Time" (1910)
|
|
NGC-5560-5566_and_5569-PIA08646.jpgNGC 5560, 5566 and 5569 - Galactic "Trio" in the Virgo Galaxy Cluster69 visite"...Non ci può essere Gloria ed Immortalità per alcun Uomo il quale non sia disposto, per esse, dentro di esse e nel loro nome, ad annientarsi.
Come una scintilla che sfugge al fuoco, si libra nell'aria per un istante e poi, gettata un'ultima gemma di luce negli occhi della notte, si estingue, così è l'Eroe: libero, luminoso ed effimero..."
P.C. Floegers - "Conversations for Tomorrow"
|
|
|
| 11 immagini su 1 pagina(e) |
|
|
|
