Wednesday, November 7, 2007

Big Chunk Of The Universe Is Missing -- Again


Not only has a large chunk of the universe thought to have been found in 2002 apparently gone missing again but it is taking some friends with it, according to new research at The University of Alabama in Huntsville (UAH). The new calculations might leave the mass of the universe as much as ten to 20 percent lighter than previously calculated.

The same UAH group that found what was theorized to be a significant fraction of the "missing mass" that binds together the universe has discovered that some x-rays thought to come from intergalactic clouds of "warm" gas are instead probably caused by lightweight electrons.

If the source of so much x-ray energy is tiny electrons instead of hefty atoms, it is as if billions of lights thought to come from billions of aircraft carriers were found instead to come from billions of extremely bright fireflies.

"This means the mass of these x-ray emitting clouds is much less than we initially thought it was," said Dr. Max Bonamente, an assistant professor inUAH's Physics Department. "A significant portion of what we thought was missing mass turns out to be these 'relativistic' electrons."Traveling at almost the speed of light (and therefore "relativistic"), these feather weight electrons collide with photons from the cosmic microwave background. Energy from the collisions converts the photons from low-energy microwaves to high-energy x-rays.

"The discovery was made while trying to analyze the makeup of warm, x-ray emitting gas at the center of galaxy clusters - the largest cosmological structures in the universe. In 2002 the UAH team reported finding large amounts of extra "soft" (relatively low-energy) x-rays coming from the vast space in the middle of galaxy clusters. This was in addition to previously-discovered "hot" gas in that space, which emits higher energy"hard" x-rays.

Although the soft x-ray-emitting atoms were thought to be spread thinly through space (less than one atom per cubit meter), they would have filled billions of billions of cubic light years. Their cumulative mass was thought to account for as much as ten percent of the mass and gravity needed to hold together galaxies, galaxy clusters and perhaps the universe itself.

When Bonamente and his associates looked at data gathered by several satellite instruments, including the Chandra X-ray Observatory, from a galaxy cluster in the southern sky, however, they found that energy from those additional soft x-rays doesn't look like it should."We have never been able to detect spectral emission lines associated with those detections," he explained. "If this 'bump' in the data were due to cooler gas, it would have emission lines.

"The best, most logical explanation seems to be that a large fraction of the energy comes from electrons smashing into photons instead of from warm atoms and ions, which would have recognizable spectral emission lines.Finding these electrons, however, is like finding "the tip of the iceberg,"said Bonamente, because they would not be limited to emitting only the soft x-ray signal. The signal from these electrons would also make up part of the previously observed harder X-rays, which would reduce the amount of mass thought to make up the hot gas at the center of galaxy clusters.

To further complicate the issue, the energy from these electrons might also"puff up" the cluster. Previously, astrophysicists used the energy coming from inside these clusters to calculate how much mass is needed to reach the equilibrium seen there; too much mass and the cloud would collapse; too little and the hot gas cloud would expand.Since the energy coming from these hot clouds can be accurately measured, it was thought the mass could be calculated with reasonable confidence - for astrophysics.Instead, says Bonamente, if a significant portion of the total x-ray energy comes from fast electrons, "that could trick us into thinking there is more gas than is actually there.""It means we need to revise how we calculate both the gas mass and the total mass," he said. "We have to follow the evidence and, if that leads us to confusion, well that's OK."If part of the hard x-ray energy comes from electrons and photons, it might also shift what we think is the mix of elements in the universe.

Outside of the excess soft x-rays, the x-ray energy coming from galaxy clusters has emission lines which are especially prominent around iron and other metals.Non-thermal x-rays from electrons colliding with photons might mask those emission lines, like thick snow can mask the height of fence posts."This is also telling us there is fractionally more iron and other metals than we previously thought," said Bonamente. "Less mass but more metals."

Space Mission Xeus Probes Origins Of The Universe


A new mission seeks to study the origins of the universe. Professor Martin Turner of the Department of Physics and Astronomy is Co-Principal Investigator on XEUS - a next-generation X-ray space observatory.

XEUS, which stands for X-ray Evolving Universe Spectroscopy, aims to study the fundamental laws of the Universe. With unprecedented sensitivity to the hot, million-degree universe, XEUS will explore key areas of contemporary astrophysics: growth of supermassive black holes, cosmic feedback and galaxy evolution, evolution of large-scale structures, extreme gravity and matter under extreme conditions, the dynamical evolution of cosmic plasmas and cosmic chemistry.

Professor Turner is also Chair of the XEUS International Steering committee. He said: “XEUS is an X-ray observatory 30-50 times more sensitive than XMM-Newton, which will be placed 1.5 million km from Earth, beyond the Moon, at the second Lagrangian point, a quiet stable location where the instruments can observe the universe undisturbed.

“Because it is so large, the observatory has two spacecraft. The five-metre diameter X-ray lens is in one, and the instruments in another. The two spacecraft fly together, 35 metres apart, to keep the instruments at the focus of the lens.

“XEUS has been selected for study by ESA as part of its Cosmic Vision programme. If the study outcome is successful it will be launched on Ariane 5 from Kourou in 2018.

"We have been developing the XEUS concept for an advanced X-ray observatory, for many years. This acceptance by ESA is a major step forward for X-ray astronomers all over the world."

"The million degree universe, where gravity is the main source of energy, is the finest physics laboratory we have. XEUS will help us find out about the behaviour of matter under extreme conditions of temperature, pressure, and gravity. It will also let us study the influence of black holes on the formation of galaxies and stars; and ultimately planets and ourselves."

Dr Richard Willingale, of the University of Leicester and chairman of the XEUS telescope working group said.

“XEUS will use new lightweight silicon optics to make the lens, the same material used to make silicon chips; one of the instruments has sensors cooled to within a tiny fraction of absolute zero to study the chemistry and physics of matter surrounding black holes.”

Various international Space Agencies have expressed interest in cooperation in XEUS and discussions will start by the end of the year to ensure the earliest involvement in study work.

All the candidate missions are now competing in an assessment cycle which ends in 2011. Before the end of the cycle, there will be an important selection foreseen in 2009. At the end of this process, two missions will be proposed for implementation to ESA's Science Programme Committee, with launches planned for 2017 and 2018 respectively.

The selected missions fit well within the themes of ESA's Cosmic Vision 2015-2025 plan. The themes range from the conditions for life and planetary formation, to the origin and formation of the Solar System, the fundamental laws of our cosmos and the origin, structure and evolution of the Universe.

“The maturity of most of the proposals received demonstrates the excellence of the scientific community in Europe. This made the task of the SSAC very difficult but we believe that the set of selected missions will shape the future of European space science,” said Tilman Spohn, chairperson of the SSAC (German Aerospace Center, Berlin). “The next decade will indeed be very exciting for the scientific exploration of space.”

According to the chair of the Astronomy Working Group (AWG), Tommaso Maccacaro, (INAF – Osservatorio Astronomico di Brera) “The chosen candidates for astronomy missions show very promising and broad scientific return and have received excellent recommendations also from external referees.”

“Technical feasibility and potential for successful cooperation with other agencies are two factors which are clearly evident in the Solar System missions that have been chosen,” added Nick Thomas at the Physikalisches Institut, Universit├Ąt Bern, chair of the Solar System Working Group.

In 2004, Professor Turner was honoured with a CBE for services to X-ray astronomy. Paying tribute to his colleague, Professor George Fraser, Director of the Space Research Centre, said at the time: “The award of a CBE to Martin Turner is very well-deserved recognition of a tremendous contribution to the field of X-ray Astronomy in a career of over thirty years here at Leicester. Martin has, perhaps uniquely, led the development of three major instruments in the field -launched on the EXOSAT (1983), Ginga (1987) and XMM-Newton (1999) –of which he is Principal Investigator- satellites. The last of these - the EPIC camera -has now performed flawlessly in orbit for four years. Martin, nothing daunted, is also heavily involved in the initial design stages of the successor to XMM, a giant European observatory called XEUS.”

Fifth Planet Found Orbiting 55 Cancri


Our Solar System has 8 planets, but another, 55 Cancri, is catching up fast. Astronomers today announced the discovery of a 5th planet in the system, located 41 light-years away. This newly discovered planet weighs in with 45 times the mass of the Earth, and might look similar to Saturn in composition and appearance. But the news gets better, it's in the star's habitable zone, and could have water-covered moons.

The discovery of a 5th planet around 55 Cancri was made by astronomers from UC Berkeley, and several other collaborating universities, with funding from NASA and the National Science Foundation. Their research will appear in an upcoming issue of the Astrophysical Journal.

Astronomers used the radial velocity technique to find the planets. This is where the velocity of the star is carefully measured. Periodic changes in this velocity mean that a large planet's gravity is yanking the star back and forth. In this case, the discovery was even more difficult, because there were already known planets in the system, polluting the data.

"It is amazing to see our ability to detect extrasolar planets growing," said Alan Stern, associate administrator for the Science Mission Directorate at NASA Headquarters, Washington. "We are finding solar systems with a richness of planets and a variety of planetary types comparable to our own."

Perhaps the coolest part of this whole discovery: the planet orbits its parent star once every 260 days. This places it within its star's habitability zone, where liquid water can be present. It's a little closer than our Earth is to the Sun, but its star is also a little fainter, so it all evens out.

Obviously, this rules out the planet itself, but it could have a collection of moons, just like Saturn. Instead of Saturn's icy moons, this 5th planet of 55 Cancri could have ocean moons.

Finding this planet was an enormous challenge. The discoverers have been making observations of 55 Cancri for 18 years, before the first extra solar planets were ever found. They had to make more than 320 velocity measurements to disentangle the 5 planets from the data.

First Look at the Orion Crew Module


The Constellation program will continue the US human spaceflight efforts, eventually bringing people back to the Moon. As part of the program, workers at NASA unveiled a mockup of the Orion crew module.

The lifesize Orion crew module was build by engineers at NASA's Dryden Flight Research Center's Fabrication Branch. No, this aluminum mockup won't actually be flying. It won't even be used for aerodynamic testing. It's just going to help engineers figure out how to cram everything in.

As the engineers are developing the various avionics systems, instrumentation, wire harness routing, etc, they'll want a life-size mockup of the module to test how things fit together. Eventually, you can imagine future astronauts crawling inside, and giving engineers their feedback on the placement of the instrumentation, the feel of the controls, and cushiness of the seats.

This mockup will help engineers until the first abort flight test vehicle, called "Boilerplate 1" arrives for testing. This next testing vehicle is a flying simulator that will mimic the flight characteristics of the actual vehicle. Boilerplate 1 will have the same mass, dimensions, and aerodynamic properties of the Orion capsule, so it can be tested in wind tunnels and atop rockets.

NASA is planning two pad abort, and four ascent tests of the launch abort system as early as 2008, and continuing on through 2011.