NASA Chandra Image: A Surprisingly Bright Superbubble

Credits: X-ray: NASA/CXC/U.Mich./S.Oey, IR: NASA/JPL, Optical: ESO/WFI/2.2-m

This composite image shows a superbubble in the Large Magellanic Cloud (LMC), a small satellite galaxy of the Milky Way located about 160,000 light years from Earth.

Many new stars, some of them very massive, are forming in the star cluster NGC 1929, which is embedded in the nebula N44, so named because it is the 44th nebula in a catalogue of such objects in the Magellanic Clouds.

The massive stars produce intense radiation, expel matter at high speeds, and race through their evolution to explode as supernovas.

The winds and supernova shock waves carve out huge cavities called superbubbles in the surrounding gas. X-rays from NASA's Chandra X-ray Observatory (blue) show hot regions created by these winds and shocks, while infrared data from NASA's Spitzer Space Telescope (red) outline where the dust and cooler gas are found.

The optical light from the 2.2-m Max-Planck-ESO telescope (yellow) in Chile shows where ultraviolet radiation from hot, young stars is causing gas in the nebula to glow.

A long-running problem in high-energy astrophysics has been that some superbubbles in the LMC, including N44, give off a lot more X-rays than expected from models of their structure.

These models assume that hot, X-ray emitting gas has been produced by winds from massive stars and the remains of several supernovas.

A Chandra study published in 2011 showed that there are two extra sources of N44's X-ray emission not included in these models: supernova shock waves striking the walls of the cavities, and hot material evaporating from the cavity walls.

The Chandra observations also show no evidence for an enhancement of elements heavier than hydrogen and helium in the cavities, thus ruling out this possibility as a third explanation for the bright X-ray emission.

Only with long observations making full use of the capabilities of Chandra has it now become possible to distinguish between different sources of the X-rays produced by superbubbles.

STFC UK: Hawaii Telescope Closure is Blue News for UK Astronomers

Astronomers have welcomed a partial reprieve granted to the UK’s northern hemisphere telescopes, but have described the closure of two major facilities in Hawaii as a “sad day for British astronomy”.

A Science and Technology Facilities Council (STFC) prioritisation exercise in 2009 recommended the closure of its island-based telescopes by the end of this year, prompting an outcry from astronomers about the loss of all UK access to optical and infrared telescopes in the northern hemisphere.

On the advice of its science board, however, the STFC has now decided to continue funding for the Isaac Newton Group of Telescopes on La Palma in the Canary Islands until March 2015 while discussions continue with Spain and the Netherlands about sharing running costs.

Meanwhile, the James Clerk Maxwell Telescope (JCMT) and the United Kingdom Infrared Telescope (UKIRT), both in Hawaii, will be kept open until their current experiments are finished. After that, they will be transferred to another operator or decommissioned, with the loss of 40 jobs.

The board of the latter facility says in a statement that it is “very disappointed” and mystified by the STFC’s decision to end its funding in September 2013, arguing that another year of operation would cost less than £100,000.

Prof. David Southwood, president of the Royal Astronomical Society and leading light in ESA, agreed that the Hawaiian telescopes were doing “front-rank” work and described their closure as “a sad day for British astronomy”.

Their loss would “further reduce the capacity of UK astronomers to carry out world-leading science” and damage the UK’s reputation as a “credible” partner in large international projects such as the Square Kilometre Array, whose construction in South Africa and Australia was confirmed last week.

But Professor Southwood, a senior research investigator at Imperial College London, said he had resisted pressure from some astronomers to “jump up and down” on the STFC because he recognised that its hands were tied by the constraints on its budget.

He commended its efforts to minimise the damage to current projects, which represented a partial victory for the society’s lobbying.

He viewed the closures as part of a general move in astronomy towards large international facilities that would continue “as long as scientists say they want bigger and bigger facilities”.

Professor Southwood admitted that the lack of “flexibility” inherent in international collaborations could be frustrating, and, in an ideal world, access would be preserved to national “back-up” facilities.

“But for astronomers in the UK at the moment, we are not living in an ideal world,” he said.