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Creat de pri3st3ss, 13 Aprilie 2007, 21:07:59

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0 Membri şi 1 Vizitator vizualizează acest subiect.


am sa postez aici tot ce iese din sfera Hubble, SPITZER , precum si noi afirmatii privind planetele care nu au propriul lor topic :lol:

eclipse of a supermassive black hole

April 12, 2007: NASA's Chandra X-ray Observatory has observed a remarkable eclipse of a supermassive black hole, allowing a disk of hot matter swirling around the hole to be measured for the first time.

The supermassive black hole is located in NGC 1365, a spiral galaxy 60 million light years from Earth. It contains a so-called active galactic nucleus, or AGN. Scientists believe that a black hole at the center of the AGN is fed a steady stream of material from a surrounding disk. Matter just about to fall into a black hole should be heated to millions of degrees before passing over the event horizon, or point of no return. This super-heated disk material glows brightly in the X-ray part of the electromagnetic spectrum where Chandra can see it. ( fig 1)

The disk of gas around the central black hole in NGC 1365 is much too small to resolve directly with a telescope. However, the disk was eclipsed by an intervening cloud. By recording the time taken for the disk to go in and out of eclipse, scientists were able to estimate the diameter of the disk.

"For years we've been struggling to confirm the size of this X-ray structure," said Guido Risaliti of the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass, and the Italian Institute of Astronomy (INAF). "A serendipitous eclipse enabled us to make this breakthrough."

The Chandra team directly measured the diameter of the X-ray source as about seven times the distance between the Sun and the Earth or 7 AU (astronomical units). For comparison, if such a disk were placed in our own solar system, it would swallow all the planets out to Mars and most of the asteroid belt as well.(fig 2)
According to these measurements, the source of X-rays is about 2 billion times smaller than the host galaxy NGC 1365 and only about 10 times larger than the estimated size of the black hole's event horizon. This is consistent with theoretical predictions.

"Thanks to this eclipse, we were able to probe much closer to the edge of this black hole than anyone has been able to before," said co-author Martin Elvis from CfA. "Material this close in will likely cross the event horizon and disappear from the universe in about a hundred years, a blink of an eye in cosmic terms."

In addition to measuring the size of this disk of material, Risaliti and his colleagues were also able to estimate the location of the dense gas cloud that eclipsed the X-ray source and central black hole. The Chandra data show that this cloud is one hundredth of a light year from the black hole's event horizon--much closer than anyone expected. So this is a bit of a puzzle.

"AGN [are among] the brightest objects in the cosmos and they are powerful probes of the early history of the Universe. It's vital we understand their basic structure," said Risaliti. "It turns out that we still have work to do to understand these monsters."

fig 3: An artist's concept (not to scale) of Chandra observing the black hole eclipse
Ii invat si ei se indeparteaza,
Ascult si ei se se apropie....
Puterea mea, este tacerea mea.


Space shield to block radiation

British scientists are planning to see whether a Star Trek-style deflector shield could be built to protect astronauts from radiation.
They argue that magnetic shields could be deployed around spacecraft and on the surfaces of planets to deflect harmful energetic particles.
Several countries' space agencies have announced their intentions to resume human exploration of the Solar System.
Scientists hope to mimic the magnetic field which protects the Earth.
Details have been presented at the Royal Astronomical Society's National Astronomy Meeting in Preston, UK.

There are a variety of risks facing future space explorers, not least of which is the cancer-causing radiation from cosmic rays and solar flares that astronauts will encounter when they venture beyond the Earth's protective magnetic envelope, or magnetosphere.    
The Earth's magnetosphere deflects many of the energetic particles from space; others are largely absorbed by the atmosphere.

Between 1968 and 1973, the Apollo astronauts were only in space for about 10 days at a time.
They were simply lucky not to have been in space during a major eruption on the Sun that would have flooded their spacecraft with deadly radiation.
Crew members on the International Space Station can retreat to a thick-walled room during times of increased solar radiation.

Stable field

But these protective shelters would not be practical on long-duration space journeys, since the "drip-drip" of energised particles is thought to be as harmful to the health of astronauts as large solar storms.
Potentially damaging solar activity is hard to predict
The harmful particles come from the Sun, in the form of the solar wind, and from sources outside our Solar System.
To create the deflector shield around a spacecraft or on the surface of a planet or moon, scientists need to generate a magnetic field and then fill it with ionised gas called plasma.
The plasma would held in place by a stable magnetic field (without the magnetic field, the plasma would simply drift away). This shield could be deployed around a spacecraft or around astronauts on the surface of a planetary body such as the Moon.
As energetic particles interact with the plasma, energy is sapped away from them and they slow down.
"You don't need much of a magnetic field to hold off the solar wind. You could produce the shield 20-30 kilometres away from the spacecraft," explained Dr Ruth Bamford, from the Rutherford-Appleton Laboratory in Didcot, UK, one of the scientists on the team.
Dr Mike Hapgood, from the Didcot-based research centre, told BBC News: "The nice thing is that magnet technology is really quite evolved here on Earth. The question is can you take it into space?'"
The team from Rutherford-Appleton plans to build an artificial magnetosphere in the laboratory. They would eventually like to fly a test satellite which would test the technology in space.

'Shields on'

The idea has been likened to the deflector shields which protect the USS Enterprise and other spacecraft in Star Trek. Like their fictional counterparts, these shields could also be switched on and off.
The planned moon base will be exposed to solar radiation
An artificial magnetosphere could come in handy anywhere in the Solar System where humans would need to be for long durations.
A permanent Moon base, of the type Nasa plans to build, could be buried under lunar soil to protect the occupants and equipment from space radiation. But inhabitants will still be vulnerable when venturing outside in their spacesuits.
"Our warning systems aren't very good [for solar flares]. You might be able to say: 'this is a dangerous period in terms of solar activity', but you might be on red alert for weeks," said Dr Hapgood.
"If you've got a problem, you might not want to wait a week to fix it. You might want a device to deploy on the surface as a shield that would blunt the effect of a flare at ten minutes' notice, it adds an extra level of safety."
The idea for the shields draws on technology pioneered in experimental nuclear fusion reactors. Nuclear fusion is not yet a mature technology.
It works on the principle that energy can be released by forcing together atomic nuclei rather than by splitting them, as in the case of the fission reactions that drive existing nuclear power stations.
At the Jet experimental fusion facility at Culham in the UK, magnetic fields were used to keep plasma away from the interior wall of the reactor.
This represents a reversal of that technology: "We want to use the same technique to keep an object in the middle away from plasma that's on the outside," said Dr Bamford.
But the plasma needed to protect against particles from the solar wind and elsewhere would actually be weaker than that generated in experimental fusion reactors like Jet.
Ii invat si ei se indeparteaza,
Ascult si ei se se apropie....
Puterea mea, este tacerea mea.


Pipe organ' plays above the Sun

Immense coils of hot, electrified gas in the Sun's atmosphere behave like a musical instrument, scientists say.
These "coronal loops" carry acoustic waves in much the same way that sound is carried through a pipe organ.
Solar explosions called micro-flares generate sound booms which are then propagated along the coronal loops.
"The effect is much like plucking a guitar string," Professor Robert von Fay-Siebenbuergen told BBC News at the National Astronomy Meeting in Preston.
The corona is an atmosphere of hot, electrically-charged gas - or plasma - that surrounds the Sun. The temperature of the corona should drop the further one moves from the Sun.
But, in fact, the coronal temperature is up to 300 times hotter than the Sun's visible surface, or photosphere. And no one can explain why.

Fiery fountains

The coronal loops arch hundreds of thousands of kilometres above the Sun's surface like huge fiery fountains, and are generated by the Sun's magnetic field.
As solar plasma travels from the photosphere into the loops, it is heated from about 6,000 Kelvin (5,700C) to upwards of one million Kelvin.
Solar explosions called micro-flares can release energy equivalent to millions of hydrogen bombs.
These blasts can send immensely powerful acoustic waves hurtling through the loops at tens of kilometres per second, creating cosmic "organ music".
"These loops can be up to 100 million kilometres long and guide waves and oscillations in a similar way to a pipe organ," said Dr Youra Taroyan, from the Solar Physics and Space Plasma Research Centre (SP2RC) at the University of Sheffield.
The sound booms decay in less than an hour and dissipate in the very hot solar corona.
Professor von Fay-Siebenbuergen, who is director of SP2RC, said that studying how plasma is heated to such high temperatures in coronal loops could speed up the technological development of industrial-scale nuclear fusion on Earth.

'Star on Earth'

Nuclear fusion is the same process which powers the Sun and other stars. Unlike the burning of fossil fuels, fusion reactions produce no carbon dioxide, the greenhouse gas blamed by scientists for warming the planet.
Fusion works on the principle that energy can be released by forcing together atomic nuclei rather than by splitting them, as in the case of the fission reactions that drive existing nuclear power stations.
In the core of the Sun, huge gravitational pressure allows this to happen at temperatures of around 10 million Celsius.
At the much lower pressure that is possible on Earth, temperatures to produce fusion need to be much higher - above 100 million Celsius
In nuclear fusion experiments, powerful magnetic fields can be used to isolate hot plasma from the walls of a containment vessel.
This reduces the conductive heat loss, allowing the electrified gas to be heated to high temperatures.
The most promising magnetic confinement systems are ring-shaped; called a torus.
Professor von Fay-Siebenbuergen said a coronal loop could give clues to improving nuclear fusion because it could be regarded as a half-torus.

http://news.bbc.co.uk/2/hi/science/nature/6574059.stm    ascultati muzica universului!!!!!!
Ii invat si ei se indeparteaza,
Ascult si ei se se apropie....
Puterea mea, este tacerea mea.


unde esti,priestess,ne lasi in urma cu  stirile??

Today NASA released stunning new images of Jupiter and its moons taken by the New Horizons spacecraft. Views include a movie of a volcanic eruption on Jupiter's moon Io; a nighttime shot of auroras and lava on Io; a color photo of the "Little Red Spot" churning in Jupiter's cloudtops; images of small moons herding dust and boulders through Jupiter's faint rings--and much more: gallery.

"We'll be analyzing these data for months to come," says Science Mission Directorate Associate Administrator and New Horizons Principal Investigator Alan Stern of NASA Headquarters. "We have collected spectacular scientific products as well as evocative images."


Planeta cu "gheata calda"

Observatorul spatial elvetian OFXB a confirmat descoperirea unei exoplanete, situata la 30 de ani-lumina de Terra, compusa in principal din "gheata calda" ultracomprimata, stare fizica inexistenta pe Pamant.
Denumita GJ436b, planeta este de 22 de ori mai mare decat Terra, fiind compusa in principal din apa. Ea are un nucleu din roca si se presupune ca este inconjurata de hidrogen.

cine mi-a dus dorul sa ridice mana :lol:
i`m back,reloaded
Ii invat si ei se indeparteaza,
Ascult si ei se se apropie....
Puterea mea, este tacerea mea.


Astronomers using NASA's Hubble Space Telescope have discovered a ghostly ring of dark matter that formed long ago during a titanic collision between two massive galaxy clusters. The ring's discovery is among the strongest evidence yet that dark matter exists. Astronomers have long suspected the existence of the invisible substance as the source of additional gravity that holds together galaxy clusters. Such clusters would fly apart if they relied only on the gravity from their visible stars. Although astronomers don't know what dark matter is made of, they hypothesize that it is a type of elementary particle that pervades the universe.

This Hubble composite image shows the ring of dark matter in the galaxy cluster Cl 0024+17. The ring-like structure is evident in the blue map of the cluster's dark matter distribution. The map was derived from Hubble observations of how the gravity of the cluster Cl 0024+17 distorts the light of more distant galaxies, an optical illusion called gravitational lensing. Although astronomers cannot see dark matter, they can infer its existence by mapping the distorted shapes of the background galaxies. The map is superimposed on a Hubble Advanced Camera for Surveys image of the cluster taken in November 2004.

This Hubble Space Telescope composite image shows a ghostly "ring" of dark matter in the galaxy cluster Cl 0024+17.

The ring-like structure is evident in the blue map of the cluster's dark matter distribution. The map is superimposed on a Hubble image of the cluster. The ring is one of the strongest pieces of evidence to date for the existence of dark matter, an unknown substance that pervades the universe.
The map was derived from Hubble observations of how the gravity of the cluster Cl 0024+17 distorts the light of more distant galaxies, an optical illusion called gravitational lensing. Although astronomers cannot see dark matter, they can infer its existence by mapping the distorted shapes of the background galaxies. The mapping also shows how dark matter is distributed in the cluster.

Astronomers suggest that the dark-matter ring was produced from a collision between two gigantic clusters.

Dark matter makes up the bulk of the universe's material and is believed to make up the underlying structure of the cosmos.

The Hubble observations were taken in November 2004 by the Advanced Camera for Surveys (ACS). Thanks to the exquisite resolution of the ACS, astronomers saw the detailed cobweb tracery of gravitational lensing in the cluster.

Object Names: CL0024+17, ZwCl 0024+1652

Image Type: Astronomical

Credit: NASA,

si un ghid util pt iunie        http://hubblesite.org/explore_astronomy/tonights_sky/june/2007/play
isn`t it amasing!!! :-o
Ii invat si ei se indeparteaza,
Ascult si ei se se apropie....
Puterea mea, este tacerea mea.


pri3st3ss,cred ca toti ti-am dus dorul ,fara posturile tale rufonul este rece, fara suflet.Ai facut tu ce ai facut si ne-ai prezentat pana si o planeta de "GHEATA CALDA"
Cei care; ziua dorm si noaptea se odihnesc, cand oare mai au curiozitatea sa vada cum este sa fii trezit la "realitate" ?


hehe,doar sunt RADIO COSMOS,nu? :lol:

uite,pentru ca ti-a fost dor de mine, iti ofer un cadou...sunt de fel generoasa :wink:

Five-Star" Rated Gravitational Lens

NASA's Hubble Space Telescope has captured the first-ever picture of a group of five star-like images of a single distant quasar.
The multiple-image effect seen in the Hubble picture is produced by a process called gravitational lensing, in which the gravitational field of a massive object — in this case, a cluster of galaxies — bends and amplifies light from an object — in this case, a quasar — farther behind it.

Although many examples of gravitational lensing have been observed, this "quintuple quasar" is the only case so far in which multiple quasar images are produced by an entire galaxy cluster acting as a gravitational lens.
The background quasar is the brilliant core of a galaxy. It is powered by a black hole, which is devouring gas and dust and creating a gusher of light in the process. When the quasar's light passes through the gravity field of the galaxy cluster that lies between us and the quasar, the light is bent by the space-warping gravity field in such a way that five separate images of the object are produced surrounding the cluster's center. The fifth quasar image is embedded to the right of the core of the central galaxy in the cluster. The cluster also creates a cobweb of images of other distant galaxies gravitationally lensed into arcs.

pt poza 3 - Globular Cluster with Multiple Stellar Populations

This Hubble telescope image of a dense swarm of stars shows the central region of the globular cluster NGC 2808.

Astronomers were surprised when Hubble spied three generations of cluster stars. The discovery is far different from the standard picture of a globular cluster. For decades, astronomers thought that cluster stars formed at the same time, in the same place, and from the same material, and have co-evolved for billions of years.

Globular clusters are the homesteaders of our Milky Way Galaxy, born during our galaxy's formation. They are compact swarms of typically hundreds of thousands of stars held together by gravity.

All the stars in NGC 2808 were born within 200 million years very early in the life of the 12.5-billion-year-old massive cluster. Of the about 150 known globular clusters in our Milky Way Galaxy, NGC 2808 is one of the most massive, containing more than 1 million stars.

pt im 4--Comet Galaxy' Being Ripped Apart By Galaxy Cluster
Space Telescope, in collaboration with several other ground- and space- based telescopes, has captured a galaxy being ripped apart by a galaxy cluster's gravitational field and harsh environment.

The finding sheds light on the mysterious process by which gas-rich spiral-shaped galaxies might evolve into gas-poor irregular- or elliptical-shaped galaxies over billions of years. The new observations also reveal one mechanism for forming the millions of "homeless" stars seen scattered throughout galaxy clusters.
Ii invat si ei se indeparteaza,
Ascult si ei se se apropie....
Puterea mea, este tacerea mea.


Citat din: pri3st3ss din  20 Mai 2007, 21:32:16
Planeta cu "gheata calda"

cine mi-a dus dorul sa ridice mana :lol:
i`m back,reloaded

i missed ya,girly!
Citat din: lylyt_ice din  20 Mai 2007, 23:44:47
pri3st3ss,cred ca toti ti-am dus dorul ,fara posturile tale rufonul este rece, fara suflet.Ai facut tu ce ai facut si ne-ai prezentat pana si o planeta de "GHEATA CALDA"
de acord cu lylyt si uite,ridic labuta :lol:

welcome back!!!


Andromeda Galaxy (M31):
A New Look at a Close Neighbor

The Andromeda Galaxy is a large spiral galaxy very similar to our own Galaxy, the Milky Way. Also known as Andromeda Galaxy (M31), the Andromeda Galaxy is over 65,000 light years in diameter and approximately 2.9 million light years from Earth.

Andromeda, the nearest major galaxy to the Milky Way, is shown here in this wide-field optical image from Kitt Peak. The central region of Andromeda is shown in a composite image, with X-rays from NASA's Chandra X-ray Observatory (blue) combined with the optical image. Astronomers believe that Andromeda, also known as Andromeda Galaxy (M31), and the Milky Way will merge in a few billion years.

In the composite image, hot, X-ray bright gas is seen to envelop the central region of Andromeda. Point sources are also prominent, mostly from pairs of stars that are interacting with each other.
Many of these double stars are thought to include white dwarfs that are pulling large amounts of material away from a companion star. When the amount of gas being dumped onto the white dwarf gets too high a thermonuclear explosion occurs on the surface of the white dwarf, emitting bright X-rays.

By taking multiple observations of these so-called novae with Chandra and ESA's XMM-Newton observatories, a team of astronomers studied how long the burst of X-ray emission lasts. They found that several novae are bright in X-rays for surprisingly short periods of time, suggesting that the corresponding nova explosions were missed in earlier
observations. Such short periods of bright X-ray emission, according to theoretical calculations, indicate that the white dwarfs have relatively high masses. This makes them good candidates for progenitors of Type Ia supernovas, where a white dwarf reaches a mass limit and undergoes a thermonuclear explosion and is completely destroyed. The high masses suggested by the short X-ray outbursts suggests that the white dwarfs do not have to gain very much mass before reaching their limit and being destroyed. A long-running goal in stellar astrophysics has been to identify the elusive stars that explode as Type Ia supernovas.

SN 2006gy:
NASA's Chandra Sees Brightest Supernova Ever
- imaginea 4

According to observations by NASA's Chandra X-ray Observatory and ground-based optical telescopes, the supernova SN 2006gy is the brightest and most energetic stellar explosion ever recorded and may be a long-sought new type of explosion. The top panel of this graphic is an artist's illustration that shows what SN 2006gy may have looked like   
if viewed at a close distance. The fireworks-like material in white shows the explosion of an extremely massive star. This debris is pushing back two lobes of cool, red gas that were expelled in a large eruption from the star before it exploded. The green, blue and yellow regions in these lobes shows where gas is being heated in a shock front as the explosion material crashes into it and pushes it backwards. Most of the optical light generated by the supernova is thought to come from debris that has been heated by radioactivity, but some likely comes from the shocked gas.
Ii invat si ei se indeparteaza,
Ascult si ei se se apropie....
Puterea mea, este tacerea mea.


Blue Moon over North America

May 30, 2007: At 9:04 pm Eastern Daylight Time on May 31st, the full moon over North America will turn blue.

Not really. But it will be the second full moon of May and, according to folklore, that makes it a Blue Moon.If you told a person in Shakespeare's day that something happens "once in a Blue Moon" they would attach no astronomical meaning to the statement. Blue moon simply meant rare or absurd, like making a date for "the Twelfth of Never."

But "meaning is a slippery substance," writes Philip Hiscock of the Dept. of Folklore, Memorial University of Newfoundland. "The phrase 'Blue Moon' has been around a long time, well over 400 years, and during that time its meaning has shifted

The modern definition sprang up in the 1940s. In those days the Maine Farmer's Almanac offered a definition of Blue Moon so convoluted even professional astronomers struggled to understand it. It involved factors such as ecclesiastical dates of Easter and Lent, tropical years, and the timing of seasons according to the dynamical mean sun. Aiming to explain blue moons to the layman, Sky & Telescope published an article in 1946 entitled "Once in a Blue Moon." The author James Hugh Pruett (1886-1955) cited the 1937 Maine almanac and opined that the "second [full moon] in a month, so I interpret it, is called Blue Moon
Surveying the last four centuries of literature and folklore, "I have counted six different meanings which have been carried by the term," recounts Hiscock. In song, for instance, Blue Moons are a symbol of loneliness; when love conquers all, the Blue Moon turns gold. (See old Elvis records for more information.) "This makes discussion of the term a little complicated," he says.

I had never paid any real attention to the term 'Blue Moon' until one October evening in 2003," he recalls. "I had my telescope set up in the backyard and the moon began rising in the east with a strange blue tint I had not seen before."

The cause of the blue was probably tiny droplets of water in the air. "The air was damp and heavy with moisture," notes King. When water droplets are about 1 micron (one millionth of a meter) in diameter, they strongly scatter red and green light while allowing other colors to pass. A white moonbeam passing through such a misty cloud turns blue.

Clouds of ice crystals, fine-grained sand, volcanic ash or smoke from forest fires can have the same effect. "The key," notes atmospheric optics expert Les Cowley, "is that the airborne particles should all be of very similar size, a micron or so in diameter." Only then do they scatter the correct wavelengths of moonlight and act as a blue filter.

There are other reasons for blue Moons, he notes. "Our eyes have automatic 'white balances' just like digital cameras. Go outdoors from a cozy cabin lit by an oil lamp (yellow light) and the Moon will appear blue until your eyes adjust."

im 1. The first full moon of May 2007, photographed May 2nd by Tony Wilder of Wisconsin. May's second full Moon on May 31st will probably look as gray as this one, although according to folklore, it is "blue."
Ii invat si ei se indeparteaza,
Ascult si ei se se apropie....
Puterea mea, este tacerea mea.


Wow, interesant! Nu stiam ca exista asa ceva in realitate (ca luna se poate vedea in albastru), credeam ca e doar imaginatia mea.  :mrgreen:
Nu tot ce zboară şi este necunoscut este extraterestru.
All warfare is based on deception. -- Sun Tzu, 600 BC

All types of knowledge, ultimately mean self knowledge. -- Bruce Lee


nici eu nu stiam...
stiam ca in popor se numeste asa,dar ca de fapt e gri,dar vad ca tipul asta din texas a fotografiat-o albastra... o fi  fost ceva in atmosfera?!

What about Europe? Because of time zones, this week's full Moon occurs over Europe on June 1st rather than May 31st. In Europe, therefore, it is the month of June which has two full Moons, and a Blue Moon on June 30th
Ii invat si ei se indeparteaza,
Ascult si ei se se apropie....
Puterea mea, este tacerea mea.


More info:

Although the full moon occurring Thursday, May 31, 2007, will look like an ordinary full moon, it will actually be a bit extraordinary—a blue moon.

What is a Blue Moon?
There are in fact two definitions for a blue moon. According to the more recent definition, a blue moon is the second full moon in a calendar month. For a blue moon to occur, the first of the full moons must appear at or near the beginning of the month so that the second will fall within the same month (the average span between two moons is 29.5 days). May 2007 will have two full moons: the first on May 2, the second on May 31—that second full moon is called the blue moon.

Note that the May 31 date applies to most of the Western Hemisphere, including the United States. In the Eastern Hemisphere, the full moon in question will occur on June 1. For that half of the world, the blue moon will be on June 30, 2007.

The Other Kind of Blue Moon
An older definition for the blue moon is recorded in early issues of the Maine Farmer's Almanac. According to this definition, the blue moon is the third full moon in a season that has four full moons. Why would one want to identify the third full moon in a season of four full moons? The answer is complex, and has to do with the Christian ecclesiastical calendar.

Some years have an extra full moon—thirteen instead of twelve. Since the identity of the moons was important in the ecclesiastical calendar (the Paschal Moon, for example, used to be crucial for determining the date of Easter), a year with a thirteenth moon skewed the calendar, since there were names for only twelve moons. By identifying the extra, thirteenth moon as a blue moon, the ecclesiastical calendar was able to stay on track.

For a fuller explanation see http://www.inconstantmoon.com/cyc_blue.htm. For more background information on the controversy over the two definitions of blue moon, see the Sky and Telescope article, "What's a Blue Moon?" In it they explain how the two different definitions of a blue moon came about—including their own role in introducing the second, modern definition.

A Star Rating for the Modern Blue Moon
Although Sky & Telescope calls the modern blue moon definition "trendy" and a "mistake," the fact that there is an older, preexisting (and more complicated) definition does not necessarily make it the more interesting or meaningful definition. Charting the "third full moon in four full moons" in a season isn't everyone's idea of an fascinating enterprise. The modern, "trendy" definition, however, points to an intriguing astronomical phenomenon—every so often two moons can manage to position themselves in the same month. Given that full moons occur once every 29.5 days, this is quite an accomplishment!

How Often Does a Blue Moon Occur?
Over the next twenty years there will be a total of 17 blue moons, with an almost equal number of both types of blue moons occurring. No blue moon of any kind will occur in the years 2006, 2011, 2014, and 2017.

The more recent phenomenon, where the blue moon is considered to be the second full moon in a calendar month, last occurred on July 31, 2004. Two full moons in one month may occur in any month out of the year except for February, which is shorter than the lunar cycle.

The other, older blue moon event, which happens when there are four full moons in a season, last occured in August 2005. Since this type of blue moon is reckoned according to the seasons, it can only occur in February, May, August, or November, about a month before the equinox or the solstice.

Twice in a Blue Moon
The rare phenomenon of two blue moons (using the more recent definitition) occurring in the same year happens approximately once every 19 years. 1999 was the last time a blue moon appeared twice, in January and March.

The months of the double blue moons are almost always January and March. That is because the short month that falls in between them, February, is a key ingredient in this once-every-nineteen-year phenomenon. For January and March to each have two full moons, it's necessary for February to have none at all. Since February is usually 28 days long, and the average span between full moons is 29.5 days, if a full moon occurs at the end of January, it's possible for the next full moon to skip February entirely and fall in the beginning of March.

Once in a Blue Moon
"Blue moon" appears to have been a colloquial expression long before it developed its calendrical senses. According to the Oxford English Dictionary, the first reference to a blue moon comes from a proverb recorded in 1528:

If they say the moon is blue,
We must believe that it is true.

Saying the moon was blue was equivalent to saying the moon was made of green (or cream) cheese; it indicated an obvious absurdity. In the 19th century, the phrase until a blue moon developed, meaning "never." The phrase, once in a blue moon today has come to mean "every now and then" or "rarely"—whether it gained that meaning through association with the lunar event remains uncertain.

Sursa: http://www.infoplease.com/spot/bluemoon1.html

alte info:

Nu tot ce zboară şi este necunoscut este extraterestru.
All warfare is based on deception. -- Sun Tzu, 600 BC

All types of knowledge, ultimately mean self knowledge. -- Bruce Lee


Venus Flyby

The spacecraft is MESSENGER, and the planet is Venus. On June 5, 2007, MESSENGER will fly past Venus just 338 km above the planet's surface--and it will shoot a 20 Watt laser into the clouds.
MESSENGER is on a mission to Mercury, not Venus. But the spacecraft must pass by Venus for a gravity assist en route. In passing, researchers hope to learn a few things about Earth's "evil twin," an Earth-sized world with sulfuric acid clouds, a choking carbon dioxide atmosphere, and a surface hot enough to melt lead.

"We are treating the Venus flyby as a full dress rehearsal for the first flyby of Mercury in January 2008," says Sean Solomon, the mission's principal investigator at the Carnegie Institution of Washington. "All of the spacecraft's science instruments will be turned on during the flyby."

Of particular interest is the laser experiment, which aims to measure the location of Venus' cloud decks. "It could either fizzle or be a major result," says Ralph McNutt, MESSENGER's project scientist at the Johns Hopkins University Applied Physics Lab. "We've never sent a laser to Venus before. This could give us some unique information about the planet's clouds."

In addition to the laser, MESSENGER will scrutinize Venus using high-resolution cameras, a suite of spectrometers ranging in wavelength from infra-red to gamma-rays, an energetic particle counter and a magnetometer. Data from these instruments may shed new light on the chemistry of Venus' atmosphere and how it interacts with the solar wind.

Unlike Earth, Venus has no global magnetic field to protect it from solar wind. A gale of charged particles traveling 300 km/s (almost a million mph) hits Venus with full force, and to some degree this erodes the planet's atmosphere.

Cold object delights astronomers

Astrophysicists have found a star-like object with a surface temperature just one tenth that of the Sun.
The cold object is known as a brown dwarf: a "failed" star that never achieved the mass required to begin nuclear fusion reactions in its core.
This one - called J0034-00 - is thought to have a surface temperature of just 600-700 Kelvin (up to 430C/800F).
It is the coldest solitary brown dwarf ever seen, according to the British team that discovered it.
This find further tests the boundary between high-mass gas planets, like Jupiter, and the smallest brown dwarfs.

'Needle in a haystack'

"Physically, stars, brown dwarfs and the gas planets are all the same thing - they're just blobs of gas with different mass," said Dr Steve Warren, of Imperial College London, who led the project.
"And as this work progresses, we're going to start finding things between the stars which have the masses of planets, and what are we going to call them?"
Te brown dwarf was first spotted by his colleague Dr Daniel Mortlock.
"Identifying an object like J0034-00 is a more challenging version of finding a needle in a haystack," he said.
"In this case it was like looking for a piece of slightly reddish straw rather than a nice shiny needle."
It has a mass of just 15-30 times that of Jupiter and a similar diameter.
It was spotted in the early stages of the world's deepest ever near-infrared sky survey - using the UKIRT telescope in Hawaii.
Using four filters, the telescope produces 2,000 images a night - a vast amount of material to sift through.
The reason for the filters is to get an idea of the colour of objects in the sky.

'Billion times nearer'

Dr Mortlock had been looking for distant quasars when he found the brown dwarf.
"One of the interesting objects that turned up there didn't have quite the right colours for a quasar, and that was J0034-00," he said.
"The peculiar thing was it was a billion times nearer than the quasars we were actually looking for, and it looks almost identical in terms of the colours," added Dr Warren.
More observations, made at the Gemini South Telescope in Chile, were needed to work out its temperature and likely mass.
It is still too early to say exactly how far away it is from Earth, but the research team believes it could be about 50 light-years.
And that is not so far, compared with the distance from some of the stars that can be seen with the naked eye.

planeta Venus, fotografiata de Galileo in 1990
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