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Galactic ‘hailstorm’ in the early Universe

Astronomy News - 16 January 2015 - 8:04am

Two teams of astronomers led by researchers at the University of Cambridge have looked back nearly 13 billion years, when the Universe was less than 10 percent its present age, to determine how quasars – extremely luminous objects powered by supermassive black holes with the mass of a billion suns – regulate the formation of stars and the build-up of the most massive galaxies.

Using a combination of data gathered from powerful radio telescopes and supercomputer simulations, the teams found that a quasar spits out cold gas at speeds up to 2000 kilometres per second, and across distances of nearly 200,000 light years – much farther than has been observed before.

How this cold gas - the raw material for star formation in galaxies - can be accelerated to such high speeds had remained a mystery. Detailed comparison of new observations and supercomputer simulations has only now allowed researchers to understand how this can happen: the gas is first heated to temperatures of tens of millions of degrees by the energy released by the supermassive black hole powering the quasar. This enormous build-up of pressure accelerates the hot gas and pushes it to the outskirts of the galaxy.

The supercomputer simulations show that on its way out of the parent galaxy, there is just enough time for some of the hot gas to cool to temperatures low enough to be observable with radio telescopes. The results are presented in two separate papers published today (16 January) in the journals Monthly Notices of the Royal Astronomical Society and Astronomy & Astrophysics.

Quasars are amongst the most luminous objects in the Universe, and the most distant quasars are so far away that they allow us to peer back billions of years in time. They are powered by supermassive black holes at the centre of galaxies, surrounded by a rapidly spinning disk-like region of gas. As the black hole pulls in matter from its surroundings, huge amounts of energy are released.

“It is the first time that we have seen outflowing cold gas moving at these large speeds at such large distances from the supermassive black hole,” said Claudia Cicone, a PhD student at Cambridge’s Cavendish Laboratory and Kavli Institute for Cosmology, and lead author on the first of the two papers. “It is very difficult to have matter with temperatures this low move as fast as we observed.”

Cicone’s observations allowed the second team of researchers specialising in supercomputer simulations to develop a detailed theoretical model of the outflowing gas around a bright quasar.

“We found that while gas is launched out of the quasar at very high temperatures, there is enough time for some of it to cool through radiative cooling – similar to how the Earth cools down on a cloudless night,” said Tiago Costa, a PhD student at the Institute of Astronomy and the Kavli Institute for Cosmology, and lead author on the second paper. “The amazing thing is that in this distant galaxy in the young Universe the conditions are just right for enough of the fast moving hot gas to cool to the low temperatures that Claudia and her team have found.”

Working at the IRAM Plateau De Bure interferometer in the French Alps, the researchers gathered data in the millimetre band, which allows observation of the emission from the cold gas which is the primary fuel for star formation and main ingredient of galaxies, but is almost invisible at other wavelengths.

The research was supported by the UK Science and Technology Facilities Council (STFC), the Isaac Newton Trust and the European Research Council (ERC). The computer simulations were run using the Computer Cluster DARWIN, operated by the University of Cambridge High Performance Computing Service, as part of STFCs DiRAC supercomputer facility.

Inset image: Comparison of observation and simulations. Credit: Tiago Costa

Astronomers have been able to peer back to the young Universe to determine how quasars – powered by supermassive black holes with the mass of a billion suns – form and shape the evolution of galaxies.

While gas is launched out of the quasar at very high temperatures, there is enough time for some of it to cool through radiative cooling – similar to how the Earth cools down on a cloudless nightTiago CostaTiago CostaIllustration of the outflow (red) and gas flowing in to the quasar in the centre (blue). The cold clumps shown in the inset image are expelled out of the galaxy in a 'galactic hailstorm'

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NASA’s New Horizons Spacecraft Begins First Stages of Pluto Encounter

Astronomy News - 15 January 2015 - 9:58pm

NASA's New Horizons spacecraft recently began its long-awaited, historic encounter with Pluto. The spacecraft is entering the first of several approach phases that culminate July 14 with the first close-up flyby of the dwarf planet, 4.67 billion miles (7.5 billion kilometers) from Earth.

Huygens: the top 10 discoveries at Titan

Astronomy News - 15 January 2015 - 3:23pm
Ten years ago, ESA's Huygens probe entered the history books by descending to the surface of Titan, Saturn’s largest moon. Humanity's first successful attempt to land a probe on another world in the outer Solar System took place at 13:34 CET (12:34 GMT) on 14 January 2005.

Galactic zombies roam the cosmos and refuse to die

Astronomy News - 14 January 2015 - 7:50pm

Cannibalism plays a big part in the life cycle of galaxies, but some rise from the dead as zombies – including one on a collision course with our own






New Exoplanet-hunting Telescopes on Paranal

Astronomy News - 14 January 2015 - 11:10am
The Next-Generation Transit Survey (NGTS) has achieved first light at ESO’s Paranal Observatory in northern Chile. This project will search for transiting exoplanets — planets that pass in front of their parent star and hence produce a slight dimming of the star’s light that can be detected by sensitive instruments. The telescopes will focus on discovering Neptune-sized and smaller planets, with diameters between two and eight times that of Earth.

Huge circle in Antarctic ice hints at meteorite impact

Astronomy News - 9 January 2015 - 7:14pm
A 2-kilometre-wide circle of deformed ice discovered in Antarctica may be a site of a large meteorite impact from 2004






‘Bent time’ tips pulsar out of view

Astronomy News - 9 January 2015 - 5:46pm

One of deep space's spinning "lighthouses" fades from view as it warps space-time, tilting its radio beams away from Earth.

'Planet' Pluto comes into view

Astronomy News - 9 January 2015 - 3:48pm

The little world is finally about to come into view

Saturn pinpointed to within one mile

Astronomy News - 9 January 2015 - 11:52am

Astronomers measure Saturn’s position with unprecedented accuracy thanks to a continent-wide radio telescope.

Mercury may be sole survivor of planetary pile-up

Astronomy News - 8 January 2015 - 6:28pm
Our solar system may have started out with several planets packed closer to the sun than Mercury, much like the planets we see around other stars






Jupiter's eroding core may already be just a husk

Astronomy News - 8 January 2015 - 1:51pm

The lump of ice and rock at the planet's centre is dissolving like salt in water, and the latest calculations say it's happening twice as fast as we thought






Bright black hole may have blasted early Earth life

Astronomy News - 8 January 2015 - 12:14pm

The black hole at the centre of our galaxy may have been more active in the past, hurling X-rays at ancient life forms