مدیران انجمن: parse, javad123javad
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اماتور
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Omega Centauri
A new discovery has resolved some of the mystery surrounding Omega Centauri, the largest and brightest
globular cluster in the sky. Images obtained with the Advanced Camera for Surveys onboard the NASA/ESA
Hubble Space Telescope and data obtained by the GMOS spectrograph on the Gemini South telescope in Chile
show that Omega Centauri appears to harbour an elusive intermediate-mass black hole in its centre.
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A bizarre cosmic rarity
This new Hubble image shows a peculiar galaxy known as NGC 660, located around 45 million light-years
away from us.
NGC 660 is classified as a "polar ring galaxy", meaning that it has a belt of gas and stars around its centre that
it ripped from a near neighbour during a clash about one billion years ago. The first polar ring galaxy was
observed in 1978 and only around a dozen more have been discovered since then, making them something
of a cosmic rarity.Unfortunately, NGC 660’s polar ring cannot be seen in this image, but has plenty of other
features that make it of interest to astronomers – its central bulge is strangely off-kilter and, perhaps more
intriguingly, it is thought to harbour exceptionally large amounts of dark matter. In addition, in late 2012
astronomers observed a massive outburst emanating from NGC 660 that was around ten times as bright as a
supernova explosion. This burst was thought to be caused by a massive jet shooting out of the supermassive
black hole at the centre of the galaxy.
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اماتور
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M74
In the new Hubble image of the galaxy M74 we can also see a smattering of bright pink regions decorating
the spiral arms. These are huge, relatively short-lived, clouds of hydrogen gas which glow due to the strong
radiation from hot, young stars embedded within them; glowing pink regions of ionized hydrogen (hydrogen
that has lost its electrons). These regions of star formation show an excess of light at ultraviolet wavelengths
and astronomers call them HII regions
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اماتور
عضویت : پنجشنبه ۱۳۹۰/۱۲/۲۵ - ۱۲:۴۳
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cosmos
An image of a galaxy cluster taken by the NASA/ESA Hubble Space Telescope gives a remarkable
cross-section of the Universe, showing objects at different distances and stages in cosmic history. They
range from cosmic near neighbours to objects seen in the early years of the Universe. The 14-hour
exposure shows objects around a billion times fainter than can be seen with the - eye.
Hubble’s images might look flat, but this one shows a remarkable depth of field that lets us see more than
halfway to the edge of the observable Universe. Most of the galaxies visible here are members of a huge
cluster called CLASS B1608+656, which lies about five billion light-years away. But the field also contains
other objects, both significantly closer and far more distant, including quasar QSO-160913+653228 which
is so distant its light has taken nine billion years to reach us, two thirds of the time that has elapsed
since the Big Bang.
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NGC 4522
Hubble's Advanced Camera for Surveys (ACS) allows astronomers to study an interesting and
important phenomenon called ram pressure stripping that is so powerful, it is capable of mangling
galaxies and even halting their star formation. NGC 4522 is a spectacular example of a spiral
galaxy that is currently being stripped of its gas content. The galaxy is part of the Virgo galaxy cluster
and its rapid motion within the cluster results in strong winds across the galaxy as the gas within
is left behind. Scientists estimate that the galaxy is moving at more than 10 million kilometres per
hour. A number of newly formed star clusters that developed in the stripped gas can be seen in the
Hubble image. The stripped spiral galaxy is located some 60 million light-years away from Earth.
Even though it is a still image, Hubble's view of NGC 4522 practically swirls off the page with apparent
movement. It highlights the dramatic state of the galaxy with an especially vivid view of the ghostly
gas being forced out of it. Bright blue pockets of new star formation can be seen to the right and
left of centre.