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The Universe’s Stellar Baby Boom

By David Reneke

Dave Reneke’s wrap-up of space and astronomy news.

Observations with the Atacama Large Millimetre Array (ALMA) in northern Chile, which celebrated its inauguration on 13 March, show that the most vigorous bursts of star birth in the cosmos took place much earlier than previously thought.

The most intense bursts of star birth are thought to have occurred in the early universe in massive, bright galaxies. These starburst galaxies convert vast reservoirs of cosmic gas and dust into new stars at a furious pace – many hundreds of times faster than in stately spiral galaxies like our own galaxy, the Milky Way.

By looking at galaxies so distant that their light has taken billions of years to reach us, astronomers can observe this busy period in the universe’s youth. “The more distant the galaxy, the further back in time we’re looking, so by measuring their distances we can piece together a timeline of how vigorously the universe was making new stars at different stages of its 13.7 billion year history,” said Joaquin Vieira of the California Institute of Technology, who led an international team of researchers.

The team discovered these distant starburst galaxies and used ALMA to zoom in on them to explore the stellar baby boom in the young universe. On average, these bursts of star birth took place 12 billion years ago, when the universe was just under two billion years old – one billion years earlier than previously thought.

Two of these galaxies are the most distant of their kind ever seen. Furthermore, water is among the molecules detected, marking the most distant observations of water in the cosmos.

The astronomers were using only a partial array of 16 of ALMA’s full complement of 66 giant antennas. When complete, ALMA will be even more sensitive, and will be able to detect even fainter galaxies.

For now, astronomers targeted the brighter ones using gravitational lensing, where light from a distant galaxy is distorted by the gravitational influence of a nearer foreground galaxy. Acting like a lens, it makes the distant source appear brighter.

The beautiful pictures from ALMA show the background galaxies warped into multiple arcs of light known as Einstein rings that encircle the foreground galaxies. Analysis of the distortion reveals that some of the distant star-forming galaxies are as bright as 40 trillion suns.

Auroras Outside Our Solar System

Planetary scientists have found new evidence suggesting that auroras, similar to the Earth’s Aurora Borealis, occur on bodies outside our solar system.

Auroras occur on several planets within our solar system, and the brightest, on Jupiter, are 100 times brighter than those on Earth. However, no auroras have yet been observed beyond Neptune.

A new study led by Dr Jonathan Nichols of the University of Leicester has shown that processes strikingly similar to those that power Jupiter’s auroras could be responsible for radio emissions detected from a number of objects outside our solar system.

In addition, the radio emissions are powerful enough to be detectable across interstellar distances, meaning that auroras could provide an effective way of observing new objects outside our solar system.

Auroras occur when charged particles in an object’s magnetosphere collide with atoms in its upper atmosphere, causing them to glow. However, before hitting the atmosphere these particles also emit radio waves into space. The study shows that this phenomenon is not limited to our solar system.

“We have recently shown that beefed-up versions of the auroral processes on Jupiter are able to account for the radio emissions observed from certain "ultracool dwarfs" – bodies which comprise the very lowest mass stars – and "brown dwarfs" – “failed stars” which lie in between planets and stars in terms of mass,” Nichols said.

“These results strongly suggest that auroras do occur on bodies outside our solar system, and the auroral radio emissions are powerful enough – 100,000 times brighter than Jupiter’s – to be detectable across interstellar distances.”

The results could have major implications for the detection of planets and objects outside our solar system that could not be discovered with other methods. Furthermore, the radio emission could provide us with key information about the length of the planet’s day, the strength of its magnetic field, how the planet interacts with its parent star and even whether it has any moons.

Nichols is now part of a group that has recently been awarded time on the Low Frequency Array (LOFAR), which is the largest connected radio telescope ever built. Using a new concept based on a vast array of omni-directional antennas, LOFAR is centred in The Netherlands but has stations across a number of countries in northern Europe.

The group will now use LOFAR try to observe auroras on exoplanets, and is confident it will get interesting results soon.

David Reneke is an astronomy lecturer and teacher, a feature writer for major Australian newspapers and magazines, and a science correspondent for ABC and commercial radio. Subscribe to David’s free Astro-Space newsletter at www.davidreneke.com