Planck mission results shake cosmology’s basics

Image: Artist's concept: Planck spacecraft. Credit: ESA/NASA
Artist’s concept: Planck spacecraft. Credit: ESA/NASA

WASHINGTON — The Planck space mission has released the most accurate and detailed map ever made of the oldest light in the universe, revealing new information about its age, contents and origins.

The map results suggest the universe is expanding more slowly than scientists thought, and is 13.8 billion years old, 100 million years older than previous estimates. The data also show there is less dark energy and more matter, both normal and dark matter, in the universe than previously known. Dark matter is an invisible substance that only can be seen through the effects of its gravity, while dark energy is pushing our universe apart. The nature of both remains mysterious.

The map, based on the mission’s first 15.5 months of all-sky observations, reveals tiny temperature fluctuations in the cosmic microwave background, ancient light that has traveled for billions of years from the very early universe to reach us. The patterns of light represent the seeds of galaxies and clusters of galaxies we see around us today.

The findings also test theories describing inflation, a dramatic expansion of the universe that occurred immediately after its birth. In far less time than it takes to blink an eye, the universe blew up by 100 trillion trillion times in size. The new map, by showing that matter seems to be distributed randomly, suggests that random processes were at play in the very early universe on minute “quantum” scales. This allows scientists to rule out many complex inflation theories in favor of simple ones.

The newly-estimated expansion rate of the universe, known as Hubble’s constant, is 67.15 plus or minus 1.2 kilometers/second/megaparsec. A megaparsec is roughly 3 million light-years. This is less than prior estimates derived from space telescopes, such as NASA’s Spitzer and Hubble, using a different technique. The new estimate of dark matter content in the universe is 26.8 percent, up from 24 percent, while dark energy falls to 68.3 percent, down from 71.4 percent. Normal matter now is 4.9 percent, up from 4.6 percent.

Planck launched in 2009 and has been scanning the skies ever since, mapping the cosmic microwave background, the afterglow of the theorized big bang that created our universe. Complete results from Planck, which still is scanning the skies, will be released in 2014.

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From a NASA/JPL News Release, 3/21/2013


From Hubble: a grand new view of M9

Photo: M9 globular star cluster. Hubble image by NASA & ESA.
The stars of the M9 globular cluster. Photo credit: NASA & ESA.

The NASA/ESA Hubble Space Telescope has produced the most detailed image so far of Messier 9 (M9), a globular star cluster located close to the center of the galaxy. This ball of stars is too faint to see with the naked eye, yet Hubble can see over 250,000 individual stars shining in it.

M9, pictured here is a roughly spherical swarm of stars that lies around 25,000 light-years from Earth, near the center of the Milky Way, so close that the gravitational forces from the galactic center pull it slightly out of shape. Globular clusters are thought to harbor some of the oldest stars in our galaxy, born when the Universe was just a small fraction of its current age. As well as being far older than the Sun —around twice its age— the stars of M9 also have a markedly different composition, and are enriched with far fewer heavier elements than the Sun.

In particular, the elements crucial to life on Earth, like oxygen and carbon, and the iron that makes up our planet’s core, are very scarce in M9 and clusters like it. This is because the Universe’s heavier elements were gradually formed in the cores of stars, and in supernova explosions. When the stars of M9 formed, there were far smaller quantities of these elements in existence.

M9, as its name suggests, was discovered by the great French comet hunter Charles Messier in 1764. Even through the most advanced telescopes of the day, none of the stars in the cluster could be seen individually. Messier, seeing only a faint smudge, therefore classified the object as a nebula –or “cloud” in Latin– and put it on his list of objects that looked like but were not comets. It was only later in the 18th century that astronomers, most notably William Herschel, began to spot stars within the cluster.

The contrast between Messier’s equipment and the tools at the disposal of today’s astronomers is stark. Hubble’s image, the highest resolution image yet made of M9, is able to resolve individual stars, right into the crowded center of the cluster. Over 250,000 of them are neatly focused on the detector of Hubble’s Advanced Camera for Surveys, in an image which covers an area of sky no bigger than the size of the head of a pin held at arm’s length.

As well as showing the individual stars, Hubble’s image clearly shows the different colors of the stars. A star’s color is directly related to its temperature — counter-intuitively, perhaps, the redder it is, the cooler it is; and the bluer it is, the hotter. The wide range of stellar temperatures here is clearly displayed by the broad palette of colors visible in Hubble’s image of M9.