Hot gas, dust and magnetic fields mingle in a colorful swirl in
this new map of our Milky Way galaxy. The image is part of a new
and improved data set from Planck, a European Space Agency mission
in which NASA played a key role.
Planck spent more than four years observing relic radiation
left over from the birth of our universe, called the cosmic
microwave background. The space telescope is helping scientists
better understand the history and fabric of our universe, as well
as our own Milky Way.
"Planck can see the old light from our universe's birth, gas
and dust in our own galaxy, and pretty much everything in between,
either directly or by its effect on the old light", said Charles
Lawrence, the U.S. project scientist for the mission at NASA's Jet
Propulsion Laboratory in Pasadena, California.
The new data include
observations made during the entire mission. The Planck team says
these data are refining what we know about our universe, making
more precise measurements of matter, including dark matter, and
how it is clumped together. Other key properties of our universe
are also measured with greater precision, putting theories of the
cosmos to ever more stringent tests.
One cosmic property appears to have changed with this new batch
of data: the length of time in which our universe remained in
darkness during its infant stages. A preliminary analysis of the
Planck data suggests that this epoch, a period known as the Dark
Ages that took place before the first stars and other objects
ignited, lasted more than 100 million years or so longer than
thought. Specifically, the Dark Ages ended 550 million years after
the Big Bang that created our universe, later than previous
estimates by other telescopes of 300 to 400 million years.
Research is ongoing to confirm this finding.
The Planck data also support the idea that the mysterious force
known as dark energy is acting against gravity to push our
universe apart at ever-increasing speeds. Some scientists have
proposed that dark energy doesn't exist. Instead, they say that
what we know about gravity, as outlined by Albert Einstein's
general theory of relativity, needs refining. In those theories,
gravity becomes repulsive across great distances, eliminating the
need for dark energy.
"So far Einstein is looking pretty good", said Martin White, a
U.S. Planck team member from University of California, Berkeley. "The dark energy hypothesis is holding up very well, but this is
not the end of the story".
What's more, the new Planck catalog of images now has more than
1,500 clusters of galaxies observed throughout the universe, the
largest catalog of this type ever made. It is archived at the
European Space Agency and, in the U.S., at NASA's Infrared
Processing and Analysis Center at the California Institute of
Technology in Pasadena. These galaxy clusters act as beacons at
the crossroads of huge filamentary structures in a cosmic web. They help scientists trace our recent cosmic evolution.
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A new analysis by the Planck team of more than 400 of these galaxy
clusters gives us a new look at their masses, which range between 100 to
1,000 times that of our Milky Way galaxy. In one of the
first-of-its-kind efforts, the Planck team obtained the cluster masses
by observing how the clusters bend background microwave light. The
results narrow in on the overall mass of hundreds of clusters, a huge
step forward in better understanding dark matter and dark energy.
How can so much information about our universe, in both its
past and current states, be gleaned from the Planck data? Planck,
like its predecessor missions, captured ancient light that has
traveled billions of years to reach us. This light, the cosmic
microwave background, originated 370,000 years after the Big Bang,
during a time when the flame of our universe cooled enough that
light was no longer impeded by charged particles and could travel
freely.
Planck's splotchy maps of this light show where matter had just
begun to clump together into the seeds of the galaxies we see
around us today. By analyzing the patterns of clumps, scientists
can learn how conditions even earlier in the universe, just
moments after its birth, set the clumping process in motion. What's more, the scientists can study how the ancient light has
changed during its long journey to reach us, learning about the
entire history of the cosmos.
"The cosmic microwave background light is a traveler from far
away and long ago", said Lawrence. "When it arrives, it tells us
about the whole history of our universe".
A big challenge for Planck scientists is sifting through all
the long-wavelength light in our universe to pick out the
signature from just the ancient cosmic microwave background. Much
of our galaxy gives off light of the same wavelength, blocking our
view of the relic radiation. But what might be one scientist's
trash is another's treasure, as illustrated in the new map of the
Milky Way released today. Light generated from within our galaxy,
the same light subtracted from the ancient signal, comes to life
gloriously in the new image. Gas, dust and magnetic field lines
make up a frenzy of activity that shapes how stars form.
More papers analyzing the data are expected to come out later.
James Bartlett, a U.S. Planck team member from JPL, said: "The
kind of questions we ask now we never would have thought possible
to even ask decades ago, long before Planck".
Planck launched in 2009 and completed its mission 4.5 years
later in 2013. NASA's Planck Project Office is based at JPL. JPL
contributed mission-enabling technology for both of Planck's
science instruments. European, Canadian and U.S. Planck scientists
work together to analyze the Planck data.
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Polarized Dust
Lights Up Milky Way
Our Milky Way galaxy is ablaze with dust in this new all-sky map
from Planck, a European Space Agency mission with important NASA
contributions. The towers of fiery colors are actually dust in
the galaxy and beyond that has been polarized. The data show
light of 353 gigahertz or 0.85-millimeter wavelengths, which is
longer than what we see with our eyes.
When light reflects off surfaces or particles it can become
polarized, which means that its electric fields − normally oriented
in all directions − line up together in the same direction.
Polarized sunglasses reduce glare by blocking polarized light.
Planck has special detectors that can pick up polarized light.
Most of it comes from dust within our galaxy, but a very tiny
fraction travels to us from the dawn of time, from billions of
light-years away. That ancient polarized light holds clues about the
birth of our universe, and its explosive period of growth called
inflation.
Researchers are sifting through data from Planck and other
telescopes, in an effort to isolate this faint polarized signal.
In particular, they are searching for a "curly" pattern of polarized
light called B-modes, thought to have originated in the very first
moments after our universe was born. One of their biggest
challenges is separating these ancient B-modes from those that
originated in our Milky Way galaxy. This map helps illustrate
the daunting task at hand: our galaxy is teeming with polarized
light, masking the feeble signal from billions of years ago.
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