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Milky Way’s mammoth stars resolved by Hubble

...two of our Galaxy's most massive stars have been scrutinised to reveal a third component of the system...

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More evidence for water reservoir at Enceladus

...geyser like plumes spewing out from Enceladus may be sourced from a warm liquid ocean buried deep within the moon...

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A localised cosmic ray influx

...two nearby regions in space exhibit unusually high readings of cosmic rays...

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Video archive

STS-120 day 2 highlights

Flight Day 2 of Discovery's mission focused on heat shield inspections. This movie shows the day's highlights.


STS-120 day 1 highlights

The highlights from shuttle Discovery's launch day are packaged into this movie.


STS-118: Highlights

The STS-118 crew, including Barbara Morgan, narrates its mission highlights film and answers questions in this post-flight presentation.

 Full presentation
 Mission film

STS-120: Rollout to pad

Space shuttle Discovery rolls out of the Vehicle Assembly Building and travels to launch pad 39A for its STS-120 mission.


Dawn leaves Earth

NASA's Dawn space probe launches aboard a Delta 2-Heavy rocket from Cape Canaveral to explore two worlds in the asteroid belt.

 Full coverage

Dawn: Launch preview

These briefings preview the launch and science objectives of NASA's Dawn asteroid orbiter.

 Launch | Science

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New view of Omega Centauri

Posted: 03 December, 2008

The European Southern Observatory has released a stunning new image of the “glittering giant of the southern skies”, Omega Centauri, the most massive of all our Galaxy’s globular clusters.

Astronomers obtained this image using the Wide Field Imager (WFI) on the 2.2 metre Max-Planck/ESO telescope, located at ESO's La Silla observatory in Chile. The image shows only the central part of the cluster — about the size of the full moon on the sky (half a degree) and is a composite of B, V and I filtered images. Image: ESO/EIS.

Omega Centauri is a magnitude 3.7 globular cluster located roughly 17,000 light years from Earth in the constellation of Centaurus, and is thought to contain some ten million stars. Globular clusters are some of the oldest groupings of stars to be found in the halos that surround galaxies like our own Milky Way, and Omega Centauri itself is thought to be around 12 billion years old. It is also the most massive cluster of stars known in the Milky Way, weighing in at ten times the mass of other big globular clusters, a peculiarity that prompted astronomers to study the giant further.

Indeed, recent research suggests that there is a medium sized black hole lurking at its centre. Observations made with the Hubble Space Telescope and the Gemini Observatory showed that stars at the cluster's centre were moving around at an unusual rate. Astronomers concluded that this unruly behavior was due to the gravitational effect of a black hole boasting a mass roughly 40,000 times that of the Sun. Before this observation, astronomers had only one example of an intermediate mass black hole in the globular cluster G1, in the nearby Andromeda Galaxy.

The discovery of a black hole at the heart of Omega Centauri has led some astronomers to suspect that Omega Centauri is not a globular cluster at all, but a dwarf galaxy stripped of its outer stars during an earlier encounter with the Milky Way. Other evidence points to the several generations of stars present in the cluster — something unexpected in a typical globular cluster, which is thought to contain only stars formed at one time.

Whatever the truth, this dazzling celestial object provides professional and amateur astronomers alike with an incredible view on clear dark nights. Appearing nearly as large as the full moon on the southern night sky, Omega Centauri is visible with the unaided eye from a clear, dark observing site. And even through a modest amateur telescope, the cluster is revealed as an incredible, densely packed sphere of glittering stars.