Posted on by Fraser Cain

Storm Compressed the Earth’s Magnetosphere

Image credit: ESA

The European Space Agency’s Cluster spacecraft were perfectly positioned to watch the effect of the recent solar storms on the Earth’s magnetosphere. Normally the magnetosphere bubbles out in front of the Earth by about 64,000 km, but during the storm it was down to only 43,000 km. The speed at which the magnetosphere compressed will help scientists calculate the power of the storm, and make more accurate predictions for what will happen in future storms.

On the 24th of October 2003, the SOHO spacecraft registered a huge Coronal Mass Ejection (CME), emitted by the Sun. Several hours later this eruption reached the Earth and was detected by a number of spacecraft including Cluster.

The ACE spacecraft, situated along the Sun/Earth direction, was situated about 1 500 000 km upstream from the Earth, monitoring the solar wind. At about 14:49 UT, ACE recorded a sharp increase on the proton velocity, which jumped from about 450 kms-1 to more than 600 km-1 . The proton density, which was about 3 to 4 particles cm-3 , increased to more than 20. The proton temperature in the solar wind at this instant was also multiplied by a factor of 8.

The four Cluster spacecraft were in the southern magnetospheric lobe, inbound towards their perigee. Note that the Sun, ACE, Cluster and the Earth were almost aligned when the CME was ejected from the Sun. Cluster was situated close to the inner magnetosphere (near to the ring current region) when it detected the effects of the solar wind pressure on the magnetosphere: The sudden increase of the solar wind pressure registered by ACE arrived at the Earth?s magnetosphere about 40 minutes later. It provoked a huge compression of the dayside magnetosphere. The Cluster spacecraft detected this compression by getting suddenly out of the southern magnetospheric lobe into the Magnetosheath. They thus detected the Magnetopause, moving earthward, at about 15:25 UT. They remained into the Magnetosheath until about 17:00 UT, when they were only at a 6.8 RE (Earth radii) distance from the Earth. The transition between the lobes and the Magnetosheath was characterised by an important ion density increase (from close to 0 in the lobe to more than 160 particles cm-3 in the Magnetosheath) as well as a very clear signature in the velocity components, as measured by the CIS experiment onboard Cluster (P.I: Henri R?me).

This is a very unusual position for the Magnetopause, which on the average is standing ahead of the Earth at about 10 to 11 RE. Such compressions can have dramatic space weather effects, particularly to geostationnary satellites which are orbiting the Earth at a distance of about 6.6 RE. Further analysis of the four spacecraft data will tell us at what speed the magnetopause moved which will give information on the strength of the CME.

Original Source: ESA News Release

Posted on by Fraser Cain

Hubble Sees a Huge Star Forming Region

Image credit: ESA

The Hubble Space Telescope was recently used to peer into a star forming region that’s a million times more active than the Orion Nebula. The Lynx Arc contains a million blue-white stars (the Orion Nebula has four) which are twice as hot as similar stars in our own Milky Way galaxy; but this cluster is located 12 billion light-years away, and seen when the Universe was only 2 billion years old. This discovery will help astronomers understand how some of the first stars formed shortly after the Big Bang.

A mysterious arc of light found behind a distant cluster of galaxies has turned out to be the biggest, brightest and hottest star-forming region ever seen in space.

The so-called Lynx Arc is one million times brighter than the well-known Orion Nebula, a nearby prototypical ?starbirth? region visible with small telescopes. The newly identified super-cluster contains a million blue-white stars that are twice as hot as similar stars in our Milky Way galaxy. It is a rarely glimpsed example of the early days of the Universe where furious firestorms of starbirth blazed across the skies. The spectacular cluster?s opulence is dimmed when seen from Earth only by the fact that it is 12 000 million light years away.

The discovery of this unique and tantalising object was the result of a systematic study of distant clusters of galaxies carried out with major X-ray, optical and infrared telescopes, including the NASA/ESA Hubble Space Telescope, ROSAT and the Keck Telescopes. Bob Fosbury, of the European Space Agency?s Space Telescope-European Coordinating Facility in Germany, and a team of international co-authors report the discovery in the 20 October 2003 issue of the Astrophysical Journal.

The mega-cluster of stars appears as a puzzling red arc behind a distant galaxy cluster 5400 million light-years away in the northern constellation of Lynx. The arc is the stretched and magnified image of a mysterious celestial object about 12 000 million light-years away (at a redshift of 3.36), far beyond the cluster of galaxies. This means that the remote source existed when the Universe was less than 2000 million years old.

Fosbury and colleagues first tried to identify the arc by analysing the light from the object, but the team was not able to recognise the pattern of colours in the spectral signature of the remote object. While looking for matches with the colour spectrum, Fosbury realised that the light was related to that of the nearby Orion Nebula, a star-forming region in our own Milky Way. However where the Orion Nebula is powered by only four hot and bright blue stars, the Lynx Arc must contain around a million such stars!

Furthermore, the spectrum shows that the stars in the Lynx Arc are more than twice as hot as the Orion Nebula?s central stars, with surface temperatures up to 80 000?C. Though there are much bigger and brighter star-forming regions than the Orion Nebula in our local Universe, none are as bright as the Lynx Arc, nor do they contain such large numbers of hot stars.

Even the most massive, normal nearby stars are no hotter than around 40 000?C. However, stars forming from the original, pristine gas in the early Universe can be more massive and consequently much hotter – perhaps up to 120 000?C. The earliest stars may have been as much as several hundred solar masses, but the chemical make-up of the Universe today prevents stars from forming beyond about 100 solar masses. Such ?primordial? super-hot stars are thought to be the first luminous objects to condense after the Big Bang cooled. Astronomers believe that these first ?monster? stars formed considerably earlier than the Lynx Arc ? up to 1800 million years earlier. ?This remarkable object is the closest we have come so far to seeing what such primordial objects might look like when our telescopes become powerful enough to see them,? says Fosbury. The desire to find and study the first luminous objects in the Universe is the main scientific drive behind the construction of the NASA/ESA/CSA James Webb Space Telescope, scheduled for launch in 2011.

Original Source: ESA News Release

Posted on by Fraser Cain

Solar Storm Buffets the Earth

Image credit: SOHO

It started as the largest flare ever seen by the SOHO spacecraft, and only 19 hours later, the associated solar storm reached the Earth. The storm arrived as a G-5, the largest they get on the NOAA space weather scale. There was little disruption on Earth, however, with only some communications disrupted, and it appears that the Japanese might have lost contact with one of their satellites. Beautiful auroras were visible from many parts of the world, as far south in North America as Texas and Florida. People in Scotland reported that the aurora had already started when the Sun went down, and it was still going past midnight.

Forecasters at the NOAA Space Environment Center in Boulder, Colo., said that a powerful geomagnetic storm emitted from the sun sped though space at 5 million mph and reached Earth Wednesday 1:13 a.m. EST. NOAA space weather forecaster Larry Combs said, ?It took the geomagnetic storm just 19 hours to reach Earth after it occurred on the sun. That?s one of the fastest traveling solar storms this cycle.? The storm came in as a G-5 or extreme geomagnetic storm on the NOAA space weather scales, which run 1 to 5. (Click here to view larger image from the SOHO spacecraft of the intense solar activity on the sun taken Oct. 28, 2003, at 5:24 p.m. EDT. Click here to view high resolution version, which is a large file. Click here to view latest images. Please credit ?SOHO.?)

The solar flare caused an S-4 radiation event, which is the fourth largest in history since NOAA began keeping records in 1976. It?s also the second largest radiation event during this cycle of the sun.

Combs said, ?The geomagnetic storm is expected affect the Earth for the next 12 to 24 hours, but NOAA is forecasting that further major eruptions in these active regions of the sun will continue for the next week.?

Reports received by NOAA indicate that power grids in the northern United States and Canada are feeling the effects of the extreme geomagnetic storm. Utilities are experiencing power surges and are closely monitoring their systems. NOAA received a report that the Aurora Borealis, or northern lights, were visible as far south as El Paso, Texas.

?The NOAA Space Environment Center is home to the nation?s early warning system for solar activities that directly affect people and equipment?, explained retired Navy Vice Admiral Conrad Lautenbacher, undersecretary of commerce for oceans and atmosphere and NOAA administrator. ?Big solar storms like the current one can create brilliant northern lights but can also threaten with increased exposure to X-rays, damage and disrupt communications, energy delivery systems and aviation operations. SEC?s 24 hour-a-day, 7 day-a-week operations are critical to protecting space and ground-based assets.?

Through the NOAA Space Environment Center, NOAA and the U.S. Air Force jointly operate the space weather operations center that continuously monitors, analyzes and forecasts the environment between the sun and Earth. In addition to the data gathered from NOAA and NASA satellites, the center receives real-time solar and geophysical information from ground based-observatories around the world. The NOAA space weather forecasters use the data to predict solar and geomagnetic activity and issue worldwide alerts of extreme events.

The NOAA Space Environment Center plays a leadership role in the space weather community and helps foster a space weather services industry.

NOAA is dedicated to enhancing economic security and national safety through the prediction and research of weather and climate-related events and providing environmental stewardship of the nation?s coastal and marine resources. NOAA is part of the U.S. Department of Commerce.

Original Source: NOAA

Posted on by Fraser Cain

Green Minerals on Mars Say it’s Dry

Image credit: NASA

Astronomers have uncovered a green mineral on Mars called olivine that could indicate that the planet has been completely dry for at least a billion years, since the mineral was exposed to the Martian air. Olivine is found in many rocks on Earth, and it’s highly susceptible to chemical weathering. If liquid water was present at any time in the past, the olivine would have altered into other materials – but this hasn’t happened. The areas will be further investigated in 2005 by the upcoming Mars Reconnaissance Orbiter, which has 100 times the resolution of the Mars Global Surveyor.

The presence of a common green mineral on Mars suggests that the Red Planet could have been cold and dry since the mineral has been exposed, which may have been more than a billion years ago, according to new research appearing in the Oct. 24 edition of Science.

Todd Hoefen, a Denver-based U.S. Geological Survey (USGS) geophysicist, led a team of researchers from USGS, Arizona State University and NASA, that found abundant quantities of olivine on Mars at least locally. They based their conclusions on data obtained from a Thermal Emission Spectrometer (TES) carried by NASA’s Mars Global Surveyor (MGS) spacecraft.

Olivine, a transparent, green-colored mineral found in many rocks containing magnesium and iron (mafic igneous rocks), is highly susceptible to chemical weathering and readily alters to other minerals in the presence of liquid water (minerals such as iddingsite, goethite, serpentine, chlorite, smectite, maghemite and hematite). Except for trace amounts of hematite, which gives Mars its red color, none of these other weathering products have been detected at kilometer scales on Mars.

The team detected a 30,000 square kilometer (18,720 square mile) area rich in olivine, in the Nili Fossae region of Mars, which makes up ~ 0.02 % of the planet by area. Nili Fossae has been interpreted as a complex of grabens (long depressions between geologic faults) and fractures related to the formation of the Isidis impact basin, where post-impact faulting most plausibly exposed the locally abundant olivine. They have also found smaller deposits of olivine all over the planet, all indicating a surface at least regionally dominated by volcanic processes.

The fact that so much olivine is exposed at the surface in the Nili Fossae region indicates that there has been little to no weathering due to water, thus no liquid water-mineral chemical reactions. The absolute age of the surface is somewhat uncertain but is probably over 3 billion years old, on the basis of our best current estimates. If, however, such surfaces have been more recently exposed, one would not expect for the olivine to have been chemically altered due to the current environmental conditions on Mars (cold, dry).

It took approximately three years for the MGS spacecraft and the TES instrument to gather the data for the analysis, and another year for scientists to analyze and fully interpret the results. The MGS spacecraft is healthy and continues to map Mars.

“The detection of minerals such as olivine that serve as fingerprints of the geological processes responsible for forming the Martian surface we are exploring today is a vital part of the overall Mars Exploration Program science strategy,” stated Dr. Jim Garvin, NASA’s Lead Scientist for Mars at NASA Headquarters. “The provocative findings by Hoefen and his team will be further investigated when NASA’s 2005 Mars Reconnaissance Orbiter turns its hyperspectral imaging spectrometer, with 100 times the spatial resolution of the MGS TES instrument, on these olivine-rich regions in a few years,” continues Garvin.

The USGS serves the nation by providing reliable scientific information to describe and understand the Earth; minimize loss of life and property from natural disasters; manage water, biological, energy, and mineral resources; and enhance and protect our quality of life.

Original Source: NASA News Release

Posted on by Fraser Cain

New Space Plane Could Be Put on Hold

Key members of the United States Congress are asking NASA to postpone further work on the Orbital Space Plane until the government decides what its next steps in space are going to be. Expected to cost $13 billion over the next 5 years, the OSP would provide a new way to transfer crews to and from the International Space Station. Two contractor teams, Boeing and Lockheed Martin/Grumman/Orbital Sciences, are competing to build the OSP – the winning team would be selected by this summer. NASA acknowledged the request, but they haven’t said if they’re going to comply yet.

Posted on by Fraser Cain

SMART-1 Update: One Month in Orbit

Image credit: ESA

The European Space Agency’s SMART-1 spacecraft has been orbiting the Earth for a full month now, and has made 64 complete orbits. Engineers have been wary this week about firing its ion engine with the increased solar activity. There have been a few problems: the engine unexpectedly turned off, but worked fine on the next firing; its star tracker had difficulty orienting the spacecraft but upgrades to the software resolved that. It’s still on track to reach the Moon by March 2005.

The spacecraft is now in its 64th orbit and has been flying in space for one month! The main activity of the last week was to continue the thrust firings of the electric propulsion engine in order to boost the spacecraft orbit. This operation was limited due to problems with the local radiation environment as a result of the recent, high intensity solar activity. The engine has now generated thrust for a total cumulated time of about 300 hours.

Despite the rather short thrusting phase, the electric propulsion engine performance has been periodically monitored as usual by means of the telemetry data transmitted by the spacecraft and by radio-tracking by the ground stations. We noticed that the EP performance is still improving. From the original expected underperformance of about 3%, we went to last week?s slight over-performance of about 0.5% and we now have an engine that gives about 1% higher thrust than expected. This confirms our confidence in the excellent conditions of the electric propulsion system.

In this period we have also experienced an autonomous shut-down, or flame-out, of the engine. This happened on 26 October 2003 at 19:23 UTC, a few hours before a scheduled switch-off. The engine then re-ignited autonomously at the next scheduled thrusting restart without problems. The experts are investigating the problems. One curious coincidence is that at exactly the same time the radiation monitors on two ESA scientific spacecraft in highly elliptical orbits (XMM and Integral) had detected considerable radiation coming probably from a solar flare. This event was so large and potentially dangerous that one instrument on board Integral stopped operations and switched itself in to safe mode.

The electric power provided by the solar arrays has been according to predictions – about 1850 W for this phase of the mission. The power degradation, due to the radiation environment, was also less than expected at 1-1.5 Watts per day. Recently however, starting from October 20, we noticed a sharper degradation of the power, probably due to the increased radiation environment.

The communication, data handling and on-board software subsystems have been performing according to expectations so far. We are also detecting signs of an increase in the local radiation environment. An onboard counter records the number of hits produced by charged particles, like protons or ions, which cause a single bit in the digital circuits of the computer memory to change state, known as a Single Event Upset. We noticed a sharp increase in the count rate from 23 October onwards. This is currently attributed to the increased solar activity.

The thermal subsystem continues to perform well and all the temperatures are as expected. During the last period the spacecraft systems coped very well with a partial lunar eclipse, where the Moon obscured about 70% of the solar disk for around 80 minutes. Although the average spacecraft equipment temperature has not changed much during the mission, some equipment is experiencing temperature fluctuations due to changes in both the spacecraft’s attitude along its orbit and the Sun’s position. The angle between the Sun direction and the orbit line of apses (the line joining the perigee and the apogee) has changed considerably during the mission. It has varied from about 16 degrees at the beginning of the mission to a current value of 35 degrees. This change could be responsible for the increase of the star tracker optical head temperature during part of the orbit. As the Sun gets further away from the line of apses, this effect should be attenuated and the star tracker conditions should improve.

The attitude control subsystem continues to work, in general, very well. The main area of concern in this period has been the star tracker. This advanced autonomous star mapper has failed in the last two weeks to provide good attitude information in a few cases during different parts of the orbit. We have now found the explanation for all cases. It is due to a combination of several effects. The dominant effect is the increased background radiation level, especially protons to which the star tracker CCD is sensitive. This effect, combined with the temperature increase of the star tracker optical head in some parts of the orbit, created ‘hot spots’ in the CCD which were mistakenly interpreted as stars. This problem has been corrected by a software change uploaded to the star tracker computer.

Another problem was caused by the high star richness of some areas of the galaxy where the star tracker is pointing during part of the orbit. Too many stars require a computer processing time in excess of the allocated slot and cause ‘drops’ of attitude determination. The third problem was the blinding that the Earth disk produces to the optical head. These problems have been corrected by modifications to the software of the star tracker, which has been successfully updated onboard. Since these corrections have been made, the star tracker has been working very well and no further drops in attitude determination have been observed.

Original Source: ESA News Release

Posted on by Fraser Cain

Palomar Isn’t at Risk From Fire Yet

Image credit: Caltech

The terrible wild fires in Southern California have destroyed thousands of homes, killed more than 16 people and are still out of control in many areas. The Palomar observatory is in the area, but its operators feel that the 200-inch telescope isn’t at risk. The observatory was built with two layers of concrete and steel, dead trees and underbrush have been removed from a significant area, and it boasts a large water tank and volunteer fire fighting team. Smoke and ash have put a temporary halt to observations, though.

The tragic fires that continue to affect San Diego County remind us all just how fragile life and property can be. Currently fires are slowly approaching the area of Palomar Mountain, home to the California Institute of Technology’s historic Palomar Observatory.

Smoke and ash from the fires have put a temporary end to the Observatory’s nightly observations, but the Observatory itself is not threatened. In fact the dome of the 200-inch telescope is a safe place for and has been selected as an evacuation point for the Palomar Mountain Community .

“The builders of Palomar realized the potential fire danger and designed the 200-inch Hale Telescope to survive a fire. It is constructed with two layers of concrete and steel. Also, in recent months our maintenance staff along with foresters have removed dead and dying trees from the Observatory grounds. We are prepared for the worst,” says Palomar Observatory’s superintendent, Bob Thicksten. It doesn’t hurt that the Observatory has its own million gallon water tank, an array of fire hydrants and staff members who double as volunteer firefighters as well. Thicksten has worked tirelessly to maintain a working relationship with the local fire department, the United States Forest Service and the California Department of Forestry (CDF), which has its own fire station less than half a mile from the Observatory’s main gate.

The Palomar Observatory will issue further press statements as necessary.

Original Source: Palomar Observatory

Posted on by Fraser Cain

Did You See an Aurora?

So, did you see an aurora? I got an email from my Dad at 4:00 am PST letting me know that he could see white ribbons of light directly overhead (Southwestern Canada). John Chumack was in Ohio and sent in the picture you see beside this story – they look like a red curtain against the horizon. He saw them twice at 4:30 am and 5:40 am.

The bulk of the storm hit us this morning, but the aurora should be visible for another day or two. So, have another try tonight and see if you can get lucky. If you’re in the Northern Hemisphere, look towards the north, and if you’re in the Southern Hemisphere, look south.

If you did see an aurora, let me know, I want to hear all about it. Send in pictures if you took them. If I get enough letters, I’ll put them into a story tomorrow, so be vivid in your description of what you saw. Just reply to this newsletter, or send me an email at [email protected].

Good luck!

Fraser Cain
Publisher
Universe Today

Posted on by Fraser Cain

Book Review: Entanglement

Entanglement is the unusual behavior of elementary particles where they become linked so that when something happens to one, something happens to the other; no matter what the distance. Two entangled particles could be separated by the entire distance of the Universe and yet they can still communicate instantly with each other. Confused? Well, you’re in good company – this stuff is hard, and weird, and it defies common sense. In his latest book, “Entanglement”, Amir D. Aczel hopes to shed some light on this puzzling behavior.

With Entanglement, Aczel covers a pretty tough topic – the bizarre behavior of particles that become inextricably linked together; what Einstein called “spooky action at a distance.” In order to set the groundwork, the book begins with a series of one-chapter biographies, covering each of the major players in the research to uncover the nature of quantum entanglement, from Thomas Young (1773 – 1829) to physicists who only did their experiments in the last couple of years.

The book then moves into a detailed description of the major experiments that physicists have done to push the field of quantum theory forward. Some of these experiments will blow your mind when you consider the amazing stuff that’s going on in the world of the very small. Each time we encounter the concepts of entanglement, Aczel tries to present them differently hoping something will eventually stick in the reader’s mind.

The test of a good science writer is the ability of walk the line when including difficult concepts, and it’s here that Aczel really excels – he can explain complex scientific and mathematic concepts without baffling you; but also without dumbing it down too much. My eyes glazed over some of the formulae, but most of the time I could follow the points that Aczel was trying to get across.

I’ve got a special place in my heart for quantum theory; I really feel that it encapsulates what’s great about science. Here’s a field of study that defies common sense at every turn. Every advancement was made through experimentation, studying the results, and then working out the math to help describe what’s going on. The human mind can’t really conceive of what’s going on, and yet the science keeps uncovering more and more details about how the universe seems to work on the smallest scale. I wish other disciplines could leave their preconceived notions at the door like the quantum scientists. Nature seems to give up her secrets more willingly when we don’t try to force them one way or the other. (That’s a quantum pun there… )

I’ll warn you in advance, I’ve got some university math under my belt and I’ve read my share of quantum theory books, so the concepts were a little more accessible to me. This isn’t an introduction to quantum theory, but it’s not overly complex either; a nice compromise in my opinion. If this kind of thing interests you, then I recommend you give “Entanglement” a read – you won’t be disappointed.

Here’s more information from Amazon.com – Amazon.co.uk

Posted on by Fraser Cain

Sloan Builds 3D Map of the Universe

Image credit: SDSS

Astronomers from the Sloan Digital Sky Survey have gathered data to build a precise 3-dimensional map that details the clusters of galaxies and dark matter. The map includes images of 200,000 galaxies up to 2 billion light-years away, accounting for six percent of the sky. The SDSS team – 200 astronomers in 13 countries – measured the Universe to contain 70% dark energy (a mysterious force that repels galaxies apart), 25% dark matter, and 5% normal matter.

Astronomers from the Sloan Digital Sky Survey (SDSS) have made the most precise measurement to date of the cosmic clustering of galaxies and dark matter, refining our understanding of the structure and evolution of the Universe.

“From the outset of the project in the late 80’s, one of our key goals has been a precision measurement of how galaxies cluster under the influence of gravity”, explained Richard Kron, SDSS’s director and a professor at The University of Chicago.

SDSS Project spokesperson Michael Strauss from Princeton University and one of the lead authors on the new study elaborated that: “This clustering pattern encodes information about both invisible matter pulling on the galaxies and about the seed fluctuations that emerged from the Big Bang.”

The findings are described in two papers submitted to the Astrophysical Journal and to the Physical review D; they can be found on the physics preprint Web site, www.arXiv.org, on October 28.

MAPPING FLUCTUATIONS
The leading cosmological model invokes a rapid expansion of space known as inflation that stretched microscopic quantum fluctuations in the fiery aftermath of the Big Bang to enormous scales. After inflation ended, gravity caused these seed fluctuations to grow into the galaxies and the galaxy clustering patterns observed in the SDSS.

Images of these seed fluctuations were released from the Wilkinson Microwave Anisotropy Probe (WMAP) in February, which measured the fluctuations in the relic radiation from the early Universe.

“We have made the best three-dimensional map of the Universe to date, mapping over 200,000 galaxies up to two billion light years away over six percent of the sky”, said another lead author of the study, Michael Blanton from New York University. The gravitational clustering patterns in this map reveal the makeup of the Universe from its gravitational effects and, by combining their measurements with that from WMAP, the SDSS team measured the cosmic matter to consist of 70 percent dark energy, 25 percent dark matter and five percent ordinary matter.

The SDSS is two separate surveys in one: galaxies are identified in 2D images (right), then have their distance determined from their spectrum to create a 2 billion lightyears deep 3D map (left) where each galaxy is shown as a single point, the color representing the luminosity – this shows only those 66,976 our of 205,443 galaxies in the map that lie near the plane of Earth’s equator. (Click for high resolution jpg, version without lines.)
They found that neutrinos couldn’t be a major constituent of the dark matter, putting among the strongest constraints to date on their mass. Finally, the SDSS research found that the data are consistent with the detailed predictions of the inflation model.

COSMIC CONFIRMATION
These numbers provide a powerful confirmation of those reported by the WMAP team. The inclusion of the new SDSS findings helps to improve measurement accuracy, more than halving the uncertainties from WMAP on the cosmic matter density and on the Hubble parameter (the cosmic expansion rate). Moreover, the new measurements agree well with the previous state-of-the-art results that combined WMAP with the Anglo-Australian 2dF galaxy redshift survey.

“Different galaxies, different instruments, different people and different analysis – but the results agree”, says Max Tegmark from the University of Pennsylvania, first author on the two papers. “Extraordinary claims require extraordinary evidence”, Tegmark says, “but we now have extraordinary evidence for dark matter and dark energy and have to take them seriously no matter how disturbing they seem.”
The new SDSS results (black dots) are the most accurate measurements to date of how the density of the Universe fluctuates from place to place on scales of millions of lightyears. These and other cosmological measurements agree with the theoretical prediction (blue curve) for a Universe composed of 5% atoms, 25% dark matter and 70% dark energy. The larger the scales we average over, the more uniform the Universe appears. (Click for high resolution jpg, no frills version.)

“The real challenge is now to figure what these mysterious substances actually are”, said another author, David Weinberg from Ohio State University.

SDSS LARGE-SCALE UNDERTAKING
The SDSS is the most ambitious astronomical survey ever undertaken, with more than 200 astronomers at 13 institutions around the world.

“The SDSS is really two surveys in one”, explained Project Scientist James Gunn of Princeton University. On the most pristine nights, the SDSS uses a wide-field CCD camera (built by Gunn and his team at Princeton University and Maki Sekiguchi of the Japan Participation Group) to take pictures of the night sky in five broad wavebands with the goal of determining the position and absolute brightness of more than 100 million celestial objects in one-quarter of the entire sky. When completed, the camera was the largest ever built for astronomical purposes, gathering data at the rate of 37 gigabytes per hour.

On nights with moonshine or mild cloud cover, the imaging camera is replaced with a pair of spectrographs (built by Alan Uomoto and his team at The Johns Hopkins University). They use optical fibers to obtain spectra (and thus redshifts) of 608 objects at a time. Unlike traditional telescopes in which nights are parceled out among many astronomers carrying out a range of scientific programs, the special-purpose 2.5m SDSS telescope at Apache Point Observatory in New Mexico is devoted solely to this survey, to operate every clear night for five years.

The first public data release from the SDSS, called DR1, contained about 15 million galaxies, with redshift distance measurements for more than 100,000 of them. All measurements used in the findings reported here would be part of the second data release, DR2, which will be made available to the astronomical community in early 2004.

Strauss said the SDSS is approaching the halfway point in its goal of measuring one million galaxy and quasar redshifts.

“The real excitement here is that disparate lines of evidence from the cosmic microwave background (CMB), large-scale structure and other cosmological observations are all giving us a consistent picture of a Universe dominated by dark energy and dark matter”, said Kevork Abazajian of the Fermi National Accelerator Laboratory and the Los Alamos National Laboratory.

Original Source: Sloan Digital Sky Survey News Release