"Planets Billions of Years Older Than Earth May Exist in the Milky Way"
- Billions of years older?? Wonder what human life would be like in a
Sent: 6/18/2013 6:03:28 P.M. Eastern Daylight Time
Subj: The Daily Galaxy: News from Planet Earth & Beyond
_The Daily Galaxy: News from Planet Earth & Beyond_
_"Planets Billions of Years Older Than Earth May Exist in the Milky Way"
Posted: 18 Jun 2013 09:48 AM PDT
Building a _terrestrial planet_
(http://en.wikipedia.org/wiki/Terrestrial_planet) requires raw materials that weren't available in the early history
of the universe. The Big Bang filled space with hydrogen and helium.
Chemical elements like silicon and oxygen - key components of rocks - had to be
cooked up over time by stars. But how long did that take? How many of such
_heavy elements_ (http://en.wikipedia.org/wiki/Heavy_metal_(chemistry)) do
you need to form planets?Studies have shown that Jupiter-sized gas giants
tend to form around stars containing more heavy elements than the Sun.
However, research by a team of astronomers completed last year found that planets
smaller than Neptune are located around a wide variety of stars,
including those with fewer heavy elements than the Sun. As a result, rocky worlds
like Earth could have formed earlier than expected in the universe's
"This work suggests that terrestrial worlds could form at almost any time
in our galaxy's history," said Smithsonian astronomer David Latham
(_Harvard-Smithsonian Center for Astrophysics_
Smithsonian%20Center%20for%20Astrophysics)&t=h) ). "You don't need many earlier generations
of stars." Latham played a lead role in the study, which was led by Lars A.
Buchhave from the _University of Copenhagen_
(University%20of%20Copenhagen)&t=h) published in the journal Nature.
Astronomers call chemical elements heavier than hydrogen and helium
"metals." They measure the metal content, or metallicities, of other stars using
the Sun as a benchmark. Stars with more heavy elements are considered
_metal-rich_ (http://en.wikipedia.org/wiki/Metallicity) while stars with fewer
heavy elements are considered metal-poor.
Latham and his colleagues examined more than 150 stars known to have
planets, based on data from NASA's _Kepler spacecraft_ (http://kepler.nasa.gov/)
. They measured the stars' metallicities and correlated that with the sizes
of the associated planets. Large planets tended to orbit stars with solar
metallicities or higher. Smaller worlds, though, were found around
metal-rich and metal-poor stars alike.* "_Giant planets_
(http://en.wikipedia.org/wiki/Gas_giant) prefer metal-rich stars. Little ones don't," explained
They found that terrestrial planets form at a wide range of metallicities,
including systems with only one-quarter of the Sun's metal content.
Their discovery supports the "core accretion" model of _planet formation_
(http://en.wikipedia.org/wiki/Nebular_hypothesis) . In this model, primordial
dust accumulates into mile-sized planetesimals that then coalesce into
full-fledged planets. The largest, weighing 10 times Earth, can then gather
surrounding hydrogen and become a gas giant.
A gas giant's core must form quickly since hydrogen in the protoplanetary
disk dissipates rapidly, swept away by stellar winds in just a few million
years. Higher metallicities might support the formation of large cores,
explaining why we're more likely to find a gas giant orbiting a metal-rich
star."This result fits with the core accretion model of planet formation in a
natural way," said Latham.
The Daily Galaxy via Harvard-Smithsonian Center for Astrophysics Related
Planets of Red Dwarf Stars --"If Life is Discovered There It May Be Older &
(http://www.dailygalaxy.com/my_weblog/2013/05/alien-planet-chemistry-fundamentally-diiferent-than-earth.html) _Alien Planet Chemistry --A Diamond and
Graphite Surface (Weekend Feature)_
) _Planets Born Before the Formation of the Milky Way --8 Billion Years
Earlier than Earth (Weekend Feature)_
(http://www.dailygalaxy.com/my_weblog/2013/06/alien-planet-discovery-a-puzzle-accepted-theory-says-it-cant-exist.html) _Alien Planet Discovery a
Puzzle --Accepted Theory Says "It Can't Exist"_
Kepler! --The Mission That Changed Our View of the Probability of Life in
Planet" --New Method Using Theory of Relativity Detects Its First Alien
(http://www.sci-news.com/astronomy/article01129-exoplanet-kelt-saturn.html) _Astronomy Student Discovers Saturn-like Exoplanet KELT-6b_
_Galaxy Starbursts Triggered by Dark Matter --A Herschel Space Observatory
Posted: 18 Jun 2013 07:42 AM PDT
Most of the mass of any galaxy is expected to be "dark matter," the
elusive X Factor that has yet to be detected but which astronomers believe must
exist to provide sufficient gravity to prevent galaxies ripping themselves
apart as they rotate. But _ESA_
(http://maps.google.com/maps?ll=48.8482,2.3042&spn=1.0,1.0&q=48.8482,2.3042 (European%20Space%20Agency)&t=h) ’s Herschel
space observatory has discovered a population of dust-enshrouded galaxies
that do not need as much "dark matter" as previously thought to collect gas
and burst into star formation.With the end of Europe's _Herschel Space
Telescope_ (http://herschel.esac.esa.int/) (ground controllers put the
Herschel Observatory in sleep mode yesterday), turning off the infrared
observatory, we thought it would be appropriate to feature one of the observatory's
“Herschel is showed us that we don’t need quite so much dark matter as we
thought to trigger a starburst,” says _Asantha Cooray_
(http://en.wikipedia.org/wiki/Asantha_Cooray) , _University of California, Irvine_
41667 (University%20of%20California,%20Irvine)&t=h) . Current models of
the birth of galaxies start with the accumulation of large amounts of dark
matter believed to reside in a considerably larger assembly, or halo. Its
gravitational attraction drags in ordinary atoms. If enough atoms accumulate,
a ‘starburst’ is ignited, in which stars form at rates 100–1000 times
faster than in our own galaxy does today.
Dark matter halos are, according to the most commonly accepted theory for
the formation of cosmic structure, the sites where galaxies take shape. In
this theory, tiny fluctuations in the early Universe grew, under the
attractive effect of gravity, into a complex network of dark matter sheets and
filaments - the so-called _cosmic web_
(http://en.wikipedia.org/wiki/Observable_universe) ; later, gas accumulating in the densest knots of the cosmic
web began to cool, giving rise to clumps where the first stars formed and
which would later assemble into galaxies.
Since the cosmic web constitutes the skeleton supporting the later
emergence of stars and galaxies, the distribution of galaxies is expected to
follow, and thus trace, that of the dark matter. Whereas the growth of dark
matter structures is only regulated by gravity, a number of additional
phenomena affect star and galaxy formation, resulting in two different clustering
trends. Astronomers refer to this by saying that galaxies are biased tracers
of the dark matter distribution.
An interesting feature in this context is that all galaxies are to be
found within dark matter halos, with one or more galaxies inhabiting a halo,
but not all halos are expected to harbour a galaxy.
"The formation of a galaxy is simply not efficient enough in halos with
masses that are either too large or too small," explains Asantha Cooray from
the University of California, Irvine, USA, who directed the study based on
Herschel data that has revealed new details about the most efficient sites
for galaxy formation.
This dark matter discovery was made by analyzing infrared images taken by
Herschel’s SPIRE (Spectral and Photometric Imaging Receiver) instrument at
wavelengths of 250, 350, and 500 microns. These are roughly 1000 times
longer than the wavelengths visible to the human eye and reveal galaxies that
are deeply enshrouded in a fog of dust.
“With its very high sensitivity to the far-infrared light emitted by these
young, enshrouded starburst galaxies, Herschel allows us to peer deep into
the Universe and to understand how galaxies form and evolve,” says Göran
Pilbratt, the ESA Herschel project scientist.
The team of astronomers used HerMES observations of two fields, the
_Lockman Hole_ (http://en.wikipedia.org/wiki/Lockman_Hole) (see below) and the
GOODS North. "With its large telescope and its unprecedented resolution and
sensitivity at these far-infrared wavelengths, Herschel is a unique facility
that has now made it possible to scrutinize the CIB fluctuations down to
scales that reveal really interesting information about the emergence of
starburst galaxies around the peak of the star formation history of the
Universe," comments Goran Pilbratt, Herschel Project Scientist at ESA.
The galaxies in the Hershel images are not distributed randomly but follow
the underlying pattern of dark matter in the Universe, and so the fog has
a distinctive pattern of light and dark patches.
Analysis of the brightness of the patches in the SPIRE images has shown
that the star-formation rate in the distant infrared galaxies is 3–5 times
higher than previously inferred from visible-wavelength observations of
similar, very young galaxies by the _Hubble Space Telescope_
(http://hubble.nasa.gov/) and other telescopes.
Further analysis and simulations have shown that this smaller mass for the
galaxies is a sweet spot for star formation. Less massive galaxies find it
hard to form more than a first generation of stars before fizzling out. At
the other end of the scale, more massive galaxies struggle because their
gas cools rather slowly, preventing it from collapsing down to the high
densities needed to ignite star formation.
But at this newly identified ‘just-right’ mass of a few hundred billion
solar masses, galaxies can make stars at prodigious rates and thus grow
“This is the first direct observation of the preferred mass scale for
igniting a starburst,” says Dr Cooray.
The image below shows the patch of the sky known as the 'Lockman Hole', as
observed by the SPIRE instrument on board Herschel. Located in northern
constellation of Ursa Major, The Great Bear, the 'Lockman Hole' is a field on
the sky almost devoid of foreground contamination and thus ideally suited
for observations of galaxies in the distant Universe.
Almost every dot in the image is an entire galaxy, each containing
billions of stars and appearing as they did 10-12 billion years ago, when the
Universe was only a couple of billion years old. The blue, green and red
colours represent the three far-infrared wavelengths used for Herschel's
observations: 250, 350 and 500 micron, respectively.
The galaxies shown below in white have equal intensity in all three
wavebands and are the ones forming the most stars. Detecting these galaxies
individually is particularly challenging, as they are both extremely faint and
numerous, so many of them overlap in Herschel's images. This creates a fog
of infrared radiation known as the _Cosmic Infrared Background_
(http://en.wikipedia.org/wiki/Cosmic_infrared_background) (CIB), which reflects the
clustering pattern of the galaxies responsible for this fog. Studying the CIB
and its fluctuations is thus an extremely powerful tool to explore the way
galaxies tend to be grouped on both small and large scales.
Models of galaxy formation can now be adjusted to reflect these new
results, and astronomers can take a step closer to understanding how galaxies –
including our own –came into being.
The image at the top of the page shows dwarf galaxy _NGC 1569_
(http://en.wikipedia.org/wiki/NGC_1569) undergoing a burst of star forming activity,
thought to have begun over 25 million years ago. The resulting turbulent
environment is fed by supernova explosions as the cosmic detonations spew out
material and trigger further star formation. Two massive star clusters -
youthful counterparts to globular star clusters in our own spiral Milky Way
galaxy - are seen left of center in the gorgeous Hubble Space Telescope
image. The above picture spans about 8,000 light-years across NGC 1569. A mere
11 million light-years distant, this relatively close starburst galaxy
offers astronomers an excellent opportunity to study stellar populations in
rapidly evolving galaxies.
The Daily Galaxy via ESA and APOD Related articles
(http://www.dailygalaxy.com/my_weblog/2013/05/astronomers-probe-1st-large-scale-structures-produced-by-dark-matter.html) _Astronomers Probe 1st
Large-scale Structures Produced by Dark Matter_
(http://www.dailygalaxy.com/my_weblog/2013/05/galaxy-evolution-fueled-by-giant-cosmic-webs.html) _Galaxy Evolution Fueled By Giant Cosmic Webs_
ml) _"The Great Attractor" --Is Something is Pulling Our Region of the
Universe Towards a Colossal Unseen Mass?_
(http://www.dailygalaxy.com/my_weblog/2013/06/cosmic-flows-mapping-the-movements-of-the-galaxies.html) _"Cosmic Flows" --Mapping the Movements of the
(http://www.dailygalaxy.com/my_weblog/2013/05/massive-missing-link-galaxy-discovered-10-times-size-of-milky-way.html) _Massive "Missing-Link" Galaxy
Discovered --10 Times Size of Milky Way_
(http://www.dailygalaxy.com/my_weblog/2013/06/500-billion-a-universe-of-galaxies-some-older-than-milky-way.html) _500 Billion --A Universe of
Galaxies: Some Older than Milky Way_
(http://www.dailygalaxy.com/my_weblog/2013/06/dwarf-galaxy-found-with-only-1000-stars-bound-by-dark-matter.html) _Dwarf Galaxy Found with Only 1,000
Stars Bound by Dark Matter_
(http://www.space.com/21508-dark-matter-atoms-disks.html) _New Kind of
Dark Matter Could Form 'Dark Atoms'_
_Herschel telescope now off_
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