200,000 Degree Star Found at Center of NGC 6302

Astronomers at The University of Manchester's Jodrell Bank Centre for Astrophysics have discovered one of the hottest stars in the Galaxy - with a surface temperature of around 200,000 degrees, it is 35 times hotter than the Sun. Despite numerous attempts by astronomers across the world, the mysterious dying star at the heart of NGC 6302, the Butterfly nebula - one of the brightest and most beautiful of the planetary nebulae - has never been seen before. NGC 6302 lies within our Milky Way galaxy, roughly 3,800 light-years away in the constellation Scorpius. The glowing gas is the star's outer layers, expelled over about 2,200 years. The "butterfly" stretches for more than two light-years, which is about half the distance from the Sun to the nearest star, Alpha Centauri.The central star, which up to now could not be seen because it is hidden within a doughnut-shaped ring of dust, appears as a dark band pinching the nebula in the center. The thick dust belt constricts the star's outflow, creating the classic "bipolar" or hourglass shape displayed by some planetary nebulae.

The star's surface temperature is estimated to be about 200,000 degrees Fahrenheit, making it one of the hottest known stars in our galaxy. Spectroscopic observations made with ground-based telescopes show that even the gas surrounding the star is roughly 36,000 degrees Fahrenheit, which is unusually hot compared to typical planetary nebulae."This star was so hard to find because it is hidden behind a cloud of dust and ice in the middle of the nebula.

Using the recently refurbished Hubble Space Telescope (HST), a team of astronomers have shed new light on the nebula with a set of spectacular images. The images were taken to show off the new improved HST after it began work again in September this year. The Manchester astronomers were amazed to find that the images unexpectedly revealed the missing central star.

Astronomer's said "It's extremely important to understand planetary nebulae such as the Bug Nebula, as they are crucial to understanding our own existence on Earth". That is because the elements necessary for life, especially carbon, are created inside stars, and ejected into space as part of these planetary nebulae. Planets such as the Earth form from small dust particles, which also form within planetary nebulae. The cloud of dust and ice in the Bug Nebula contains the seeds of a future generation of planets." Finding the star was made possible by the Space Shuttle's final servicing mission of the HST, earlier this year. During the mission, astronauts installed the new Wide Field Camera 3 which was used to take these images. "How a star ejects a nebula like this is still a mystery. It seems most stars, including the Sun, will eject as much as 80 per cent of their mass when they finally run out of nuclear fuel at the end of their lives. Material that then goes on to help form the next generation of stars and planets.

These observations have shown that the star at the heart of the Bug Nebula is only about 2/3 as heavy as the Sun, but was several times heavier before it threw off its outer layers to form the nebula which had previously hidden it from our view.

Something Big is Lurking Beyond the Visible Edge of Our Universe

Using data from NASA's Wilkinson Microwave Anisotropy Probe (WMAP), scientists have identified an unexpected motion in distant galaxy clusters. The cause, they suggest, is the gravitational attraction of matter that lies beyond the observable universe.

"The clusters show a small but measurable velocity that is independent of the universe's expansion and does not change as distances increase, We never expected to find anything like this."

Hot X-ray-emitting gas in a galaxy cluster scatters photons from the cosmic microwave background. Clusters don't precisely follow the expansion of space, so the wavelengths of scattered photons change in a way that reflects each cluster's individual motion.

This results in a minute shift of the microwave background's temperature in the cluster's direction. Astronomers refer to this change as the kinematic Sunyaev-Zel'dovich (SZ) effect.

A related distortion, known as the thermal SZ effect, has been observed in galaxy clusters since the 1980s. But the kinematic version is less than one-tenth as strong and has not been detected in any cluster.

In 2000, Kashlinsky and Fernando Atrio-Barandela from the University of Salamanca, Spain, showed that astronomers could, in essence, amplify the effect isolating the kinematic SZ term. The trick, they found, is to study large numbers of clusters.

The astronomers teamed to identify some 700 X-ray clusters that could be used to find the subtle spectral shift. This sample includes objects up to 6 billion light-years -- or nearly half of the observable universe -- away.

Using the cluster catalog and WMAP's three-year view of the microwave background, the astronomers detected bulk cluster motions of nearly 2 million miles per hour. The clusters are heading toward a 20-degree patch of sky between the constellations of Centaurus and Vela.

What's more, this motion is constant out to at least a billion light-years. "Because the dark flow already extends so far, it likely extends across the visible universe,"

The finding flies in the face of predictions from standard cosmological models, which describe such motions as decreasing at ever greater distances.

Cosmologists view the microwave background - a flash of light emitted 380,000 years after the big bang - as the universe's ultimate reference frame. Relative to it, all large-scale motion should show no preferred direction.

Big-bang models that include a feature called inflation offer a possible explanation for the flow. Inflation is a brief hyper-expansion early in the universe's history. If inflation did occur, then the universe we can see is only a small portion of the whole cosmos.

WMAP data released in 2006 support the idea that our universe experienced inflation. Kashlinsky and his team suggest that their clusters are responding to the gravitational attraction of matter that was pushed far beyond the observable universe by inflation.

The next step is to narrow down uncertainties in the measurements.