RSSArchive for July, 2014

Mysterious dance of dwarfs may force a cosmic rethink

THE DISCOVERY THAT many small galaxies throughout the universe do not ‘swarm’ around larger ones as bees do but ‘dance’ in orderly orbits is a challenge to our understanding of how the universe formed and evolved.

The finding, by an international team of astronomers, including Professor Geraint Lewis of the University of Sydney, was published in the prestigious science journal Nature today.

“Early in 2013 we announced our startling discovery that half of the dwarf galaxies surrounding the Andromeda Galaxy are orbiting it in an immense plane” said Professor Lewis. “This plane is more than a million light years in diameter, but is very thin, with a width of only 300,000 light years.”

The universe contains billions of galaxies. Some, such as the Milky Way, are immense, containing hundreds of billions of stars. Most galaxies, however, are dwarfs, much smaller and with only a few billion stars.

Many of the larger galaxies have dwarf galaxies circling around them. Astronomers call them satellite galaxies.

Result contradicts standard understandings

For decades astronomers have used computer models to predict how these dwarf galaxies should orbit the large galaxies, and they’d always found that the dwarfs should be scattered randomly.

“Our Andromeda discovery did not agree with expectations, and we felt compelled to explore if it was true of other galaxies throughout the universe,” said Professor Lewis.

Using the Sloan Digital Sky Survey, a remarkable resource of colour images and 3-D maps covering more than a third of the sky, the researchers dissected the properties of thousands of nearby galaxies.

An artist's impression of the orbit of dwarf galaxies about a large galaxy

An artist’s impression of the orbit of dwarf galaxies about a large galaxy. Credit Geraint Lewis. The Hubble Image Archive was used as a source of the galaxies used in this illustration.

They were surprised to find that a large proportion of pairs of satellite galaxies are travelling in opposite directions if they are on opposite sides of larger galaxy hosts, said lead author Neil Ibata of the Lycée International in Strasbourg, France. And each of the dwarfs seemed to orbiting in the same plane, or angle, around the parent galaxy.

“Everywhere we looked we saw this strangely coherent co-ordinated motion of dwarf galaxies,” said Professor Lewis. From this the astronomers have extrapolated that this phenomenon is widespread in the universe, and seen in about 50 percent of galaxies.

“This is a big problem that contradicts our standard cosmological models. It challenges our understanding of how the universe works including the nature of dark matter,” said Professor Lewis.

Keeping an open mind

The researchers think the explanation might lie in some currently unknown physical process that governs how gas flows in the universe, although, as yet, there is no obvious mechanism that can guide dwarf galaxies into narrow planes.

Some experts, however, have made more radical suggestions, including bending and twisting the laws of gravity and motion.

“Throwing out seemingly established laws of physics is unpalatable,” said Professor Lewis, “but if our observations of nature are pointing us in this direction, we have to keep an open mind. That’s what science is all about.”

Adapted from information issued by the University of Sydney.

Watch NASA’s celebrations of the Apollo 11 landing

NASA’s APOLLO 11 CREW landed on the Moon July 20, 1969 (July 21 in Australia). The world watched 45 years ago as astronauts Neil Armstrong and Buzz Aldrin set their lunar module Eagle down in the Sea of Tranquility, while crewmate Michael Collins orbited above in the command module Columbia.

The agency is commemorating Armstrong’s “one giant leap for mankind” through a number of events, as well as on the agency’s website and NASA Television.

Buzz Aldrin stands next the lunar module Eagle on the surface of the Moon, July 1969.

Buzz Aldrin stands next the lunar module Eagle on the surface of the Moon, July 1969.

On July 21 at 12:39pm Monday, Eastern Australian time, (Sunday at 10:39pm, US EDT), which was the time 45 years ago when Armstrong opened the spacecraft hatch to begin the first spacewalk on the Moon, NASA TV will replay the restored footage of Armstrong and Aldrin’s historic steps on the lunar surface.


On Tuesday at 12:15am, Eastern Australian time (Monday, July 21 at 10:15am, US EDT), from the agency’s Kennedy Space Centre in Florida, NASA TV will air live coverage of the renaming of the centre’s Operations and Checkout Building in honour of Armstrong, who passed away in 2012.

The renaming ceremony will include NASA Administrator Charles Bolden, Kennedy Centre Director and former space shuttle pilot Robert Cabana, as well as Apollo 11’s remaining crewmembers, Collins and Aldrin, and astronaut Jim Lovell, who was the mission’s back-up commander.

International Space Station NASA astronauts Steve Swanson, who is the current Station commander, and Reid Wiseman, also will take part in the ceremony from their orbiting laboratory 415 kilometres above Earth.

Launch of Apollo 11.

Launch of Apollo 11.

The Apollo 11 crew: Neil Armstrong, Michael Collins and Edwin 'Buzz' Aldrin.

The Apollo 11 crew: Neil Armstrong, Michael Collins and Edwin ‘Buzz’ Aldrin.

Armstrong and Aldrin on the Moon.

Armstrong and Aldrin on the Moon.

Kennedy’s Operations and Checkout Building has played a vital role in NASA’s spaceflight history. It was used during the Apollo program to process and test the command, service and lunar modules. Today, the facility is being used to process and assemble NASA’s Orion spacecraft, which the agency will use to send astronauts to an asteroid in the 2020s and Mars in the 2030s.

On Friday at 8:00am, Eastern Australian time (Thursday, July 24 at 6:00pm US EDT), which is the 45th anniversary of Apollo 11’s return to Earth, the agency will host a panel discussion – called NASA’s Next Giant Leap – from the Comic-Con International in San Diego, California.

Moderated by actor Seth Green, the panel will include Aldrin, NASA Planetary Science Division Director Jim Green, JPL systems engineer Bobak Ferdowsi (the man seen with the unique haircut in mission control during the landing of the Curiosity rover on Mars), and NASA astronaut Mike Fincke, who will talk about Orion and the Space Launch System rocket, which will carry humans on America’s next great adventure in space.

Adapted from information issued by NASA.