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It might look like a spoked wheel or even a "Chakram" weapon wielded
by warriors like "Xena," from the fictional TV show, but this ringed
galaxy is actually a vast place of stellar life. A newly released image
from NASA's Spitzer Space Telescope shows the galaxy NGC 1291. Though
the galaxy is quite old, roughly 12 billion years, it is marked by an
unusual ring where newborn stars are igniting.
"The rest of the galaxy is done maturing," said Kartik Sheth of the
National Radio Astronomy Observatory of Charlottesville, Virginia. "But
the outer ring is just now starting to light up with stars."
NGC 1291 is located about 33 million light-years away in the
constellation Eridanus. It is what's known as a barred galaxy, because
its central region is dominated by a long bar of stars (in the new
image, the bar is within the blue circle and looks like the letter "S").
The bar formed early in the history of the galaxy. It churns material
around, forcing stars and gas from their original circular orbits into
large, non-circular, radial orbits. This creates resonances -- areas
where gas is compressed and triggered to form new stars. Our own Milky
Way galaxy has a bar, though not as prominent as the one in NGC 1291.
Sheth and his colleagues are busy trying to better understand how
bars of stars like these shape the destinies of galaxies. In a program
called Spitzer Survey of Stellar Structure in Galaxies, or S4G, Sheth
and his team of scientists are analyzing the structures of more than
3,000 galaxies in our local neighborhood. The farthest galaxy of the
bunch lies about 120 million light-years away -- practically a stone's
throw in comparison to the vastness of space.
The astronomers are documenting structural features, including bars.
They want to know how many of the local galaxies have bars, as well as
the environmental conditions in a galaxy that might influence the
formation and structure of bars.
"Now, with Spitzer we can measure the precise shape and distribution
of matter within the bar structures," said Sheth. "The bars are a
natural product of cosmic evolution, and they are part of the galaxies'
endoskeleton. Examining this endoskeleton for the fossilized clues to
their past gives us a unique view of their evolution."
In the Spitzer image, shorter-wavelength infrared light has been
assigned the color blue, and longer-wavelength light, red. The stars
that appear blue in the central, bulge region of the galaxy are older;
most of the gas, or star-making fuel, there was previously used up by
earlier generations of stars. When galaxies are young and gas-rich,
stellar bars drive gas toward the center, feeding star formation.
Over time, as the fuel runs out, the central regions become quiescent
and star-formation activity shifts to the outskirts of a galaxy. There,
spiral density waves and resonances induced by the central bar help
convert gas to stars. The outer ring, seen here in red, is one such
resonance area, where gas has been trapped and ignited into star-forming
NASA's Jet Propulsion Laboratory, Pasadena, California, manages the
Spitzer Space Telescope mission for NASA's Science Mission Directorate,
Washington. Science operations are conducted at the Spitzer Science
Center at the California Institute of Technology in Pasadena. Spacecraft
operations are based at Lockheed Martin Space Systems Company,
Littleton, Colorado. Data are archived at the Infrared Science Archive
housed at the Infrared Processing and Analysis Center at Caltech.
Caltech manages JPL for NASA.
This neat little galaxy is known as NGC 4526. Its dark lanes of dust
and bright diffuse glow make the galaxy appear to hang like a halo in
the emptiness of space in this new image from the NASA/ESA Hubble Space
Although this image paints a picture of serenity, the galaxy is anything but. It is one of the brightest lenticular galaxies
known, a category that lies somewhere between spirals and ellipticals.
It has hosted two known supernova explosions, one in 1969 and another in
1994, and is known to have a colossal supermassive black hole at its
centre that has the mass of 450 million Suns.
NGC 4526 is part of the Virgo cluster of galaxies. Ground-based
observations of galaxies in this cluster have revealed that a quarter of
these galaxies seem to have rapidly rotating discs of gas at their
centres. The most spectacular of these is this galaxy, NGC 4526, whose
spinning disc of gas, dust, and stars reaches out uniquely far from its
heart, spanning some 7% of the galaxy's entire radius.
This disc is moving incredibly fast, spinning at more than 250
kilometres per second. The dynamics of this quickly whirling region were
actually used to infer the mass of NGC 4526’s central black hole — a
technique that had not been used before to constrain a galaxy’s central
This image was taken using Hubble’s Wide Field Planetary Camera 2.
A version of this image was entered into the Hubble’s Hidden Treasures image
processing competition by contestant Judy Schmidt. Hidden Treasures was
an initiative to invite astronomy enthusiasts to search the Hubble
archive for stunning images that have never been seen by the general
in the atmosphere of Titan, large patches of two trace gases glow near
the north pole, on the dusk side of the moon, and near the south pole,
on the dawn side. Brighter colors indicate stronger signals from the two
gases, HNC (left) and HC3N (right); red hues indicate less pronounced
signals.Image Credit: NRAO/AUI/NSF
maps of Saturn’s moon Titan reveal large patches of trace gases shining
brightly near the north and south poles. These regions are curiously
shifted off the poles, to the east or west, so that dawn is breaking
over the southern region while dusk is falling over the northern one.
The pair of patches was spotted by a NASA-led international team of
researchers investigating the chemical make-up of Titan’s atmosphere.
“This is an unexpected and potentially groundbreaking discovery,”
said Martin Cordiner, an astrochemist working at NASA’s Goddard Space
Flight Center in Greenbelt, Maryland, and the lead author of the study.
“These kinds of east-to-west variations have never been seen before in
Titan’s atmospheric gases. Explaining their origin presents us with a
fascinating new problem.”
The mapping comes from observations made by the Atacama Large
Millimeter/submillimeter Array (ALMA), a network of high-precision
antennas in Chile. At the wavelengths used by these antennas, the
gas-rich areas in Titan’s atmosphere glowed brightly. And because of
ALMA’s sensitivity, the researchers were able to obtain spatial maps of
chemicals in Titan’s atmosphere from a “snapshot” observation that
lasted less than three minutes.
Titan’s atmosphere has long been of interest because it acts as a
chemical factory, using energy from the sun and Saturn’s magnetic field
to produce a wide range of organic, or carbon-based, molecules. Studying
this complex chemistry may provide insights into the properties of
Earth’s very early atmosphere, which may have shared many chemical
characteristics with present-day Titan.
In this study, the researchers focused on two organic molecules, hydrogen isocyanide (HNC) and cyanoacetylene (HC3N),
that are formed in Titan’s atmosphere. At lower altitudes, the two
molecules appear concentrated above Titan’s north and south poles. These
findings are consistent with observations made by NASA’s Cassini
spacecraft, which has found a cloud cap and high concentrations of some
gases over whichever pole is experiencing winter on Titan.
The surprise came when the researchers compared the gas
concentrations at different levels in the atmosphere. At the highest
altitudes, the gas pockets appeared to be shifted away from the poles.
These off-pole locations are unexpected because the fast-moving winds in
Titan’s middle atmosphere move in an east–west direction, forming zones
similar to Jupiter’s bands, though much less pronounced. Within each
zone, the atmospheric gases should, for the most part, be thoroughly
The researchers do not have an obvious explanation for these findings yet.
“It seems incredible that chemical mechanisms could be operating on
rapid enough timescales to cause enhanced ‘pocket’' in the observed
molecules,” said Conor Nixon, a planetary scientist at Goddard and a
coauthor of the paper, published online today in the Astrophysical
Journal Letters. “We would expect the molecules to be quickly mixed
around the globe by Titan’s winds.”
At the moment, the scientists are considering a number of potential
explanations, including thermal effects, previously unknown patterns of
atmospheric circulation, or the influence of Saturn’s powerful magnetic
field, which extends far enough to engulf Titan.
Further observations are expected to improve the understanding of the
atmosphere and ongoing processes on Titan and other objects throughout
the solar system.
NASA’s Astrobiology Program supported this work through a grant to
the Goddard Center for Astrobiology, a part of the NASA Astrobiology
Institute. Additional funding came from NASA’s Planetary Atmospheres and
Planetary Astronomy programs. ALMA, an international astronomy
facility, is funded in Europe by the European Southern Observatory, in
North America by the U.S. National Science Foundation in cooperation
with the National Research Council of Canada and the National Science
Council of Taiwan, and in East Asia by the National Institutes of
Natural Sciences of Japan in cooperation with the Academia Sinica in
Artist’s impression of exocomets around Beta Pictoris
Biggest census ever of exocomets around Beta Pictoris
The HARPS instrument at ESO’s La Silla
Observatory in Chile has been used to make the most complete census of
comets around another star ever created. A French team of astronomers
has studied nearly 500 individual comets orbiting the star Beta Pictoris
and has discovered that they belong to two distinct families of
exocomets: old exocomets that have made multiple passages near the star,
and younger exocomets that probably came from the recent breakup of one
or more larger objects. The new results will appear in the journal
Nature on 23 October 2014.
is a young star located about 63 light-years from the Sun. It is only
about 20 million years old and is surrounded by a huge disc of material —
a very active young planetary system where gas and dust are produced by
the evaporation of comets and the collisions of asteroids.
Flavien Kiefer (IAP/CNRS/UPMC), lead author of the new study sets the scene: “Beta Pictoris is a very exciting target! The detailed observations of its exocomets give us clues to help understand what processes occur in this kind of young planetary system.”
For almost 30 years astronomers have seen subtle changes in the light
from Beta Pictoris that were thought to be caused by the passage of
comets in front of the star itself. Comets are small bodies of a few
kilometres in size, but they are rich in ices, which evaporate when they
approach their star, producing gigantic tails of gas and dust that can
absorb some of the light passing through them. The dim light from the
exocomets is swamped by the light of the brilliant star so they cannot
be imaged directly from Earth.
The researchers selected a sample of 493 different exocomets. Some
exocomets were observed several times and for a few hours. Careful
analysis provided measurements of the speed and the size of the gas
clouds. Some of the orbital properties of each of these exocomets, such
as the shape and the orientation of the orbit and the distance to the
star, could also be deduced.
This analysis of several hundreds of exocomets in a single
exo-planetary system is unique. It revealed the presence of two distinct
families of exocomets: one family of old exocomets whose orbits are
controlled by a massive planet ,
and another family, probably arising from the recent breakdown of one
or a few bigger objects. Different families of comets also exist in the
The exocomets of the first family have a variety of orbits and show a
rather weak activity with low production rates of gas and dust. This
suggests that these comets have exhausted their supplies of ices during
their multiple passages close to Beta Pictoris .
The exocomets of the second family are much more active and are also on nearly identical orbits .
This suggests that the members of the second family all arise from the
same origin: probably the breakdown of a larger object whose fragments
are on an orbit grazing the star Beta Pictoris.
Flavien Kiefer concludes: “For the first time a statistical study
has determined the physics and orbits for a large number of exocomets.
This work provides a remarkable look at the mechanisms that were at work
in the Solar System just after its formation 4.5 billion years ago.”
 A giant planet, Beta Pictoris b,
has also been discovered in orbit at about a billion kilometres from
the star and studied using high resolution images obtained with adaptive optics.
 Moreover, the orbits of these comets (eccentricity and orientation) are exactly as predicted for comets trapped in orbital resonance
with a massive planet. The properties of the comets of the first family
show that this planet in resonance must be at about 700 million
kilometres from the star — close to where the planet Beta Pictoris b
This research was presented in a paper
entitled "Two families of exocomets in the Beta Pictoris system" which
will be published in the journal Nature on 23 October 2014.
The team is composed of F. Kiefer (Institut d’astrophysique de Paris
[IAP], CNRS, Université Pierre & Marie Curie-Paris 6, Paris,
France), A. Lecavelier des Etangs (IAP), J. Boissier (Institut de
radioastronomie millimétrique, Saint Martin d’Hères, France), A.
Vidal-Madjar (IAP), H. Beust (Institut de planétologie et
d'astrophysique de Grenoble [IPAG], CNRS, Université Joseph
Fourier-Grenoble 1, Grenoble, France), A.-M. Lagrange (IPAG), G. Hébrard
(IAP) and R. Ferlet (IAP).
ESO is the foremost intergovernmental astronomy organisation in
Europe and the world’s most productive ground-based astronomical
observatory by far. It is supported by 15 countries: Austria, Belgium,
Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy,
the Netherlands, Portugal, Spain, Sweden, Switzerland and the United
Kingdom. ESO carries out an ambitious programme focused on the design,
construction and operation of powerful ground-based observing facilities
enabling astronomers to make important scientific discoveries. ESO also
plays a leading role in promoting and organising cooperation in
astronomical research. ESO operates three unique world-class observing
sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO
operates the Very Large Telescope, the world’s most advanced
visible-light astronomical observatory and two survey telescopes. VISTA
works in the infrared and is the world’s largest survey telescope and
the VLT Survey Telescope is the largest telescope designed to
exclusively survey the skies in visible light. ESO is the European
partner of a revolutionary astronomical telescope ALMA, the largest
astronomical project in existence. ESO is currently planning the
39-metre European Extremely Large optical/near-infrared Telescope, the
E-ELT, which will become “the world’s biggest eye on the sky”.
NASA's Fermi Gamma-ray Space Telescope detected a rapid-fire "storm" of
high-energy blasts from a highly magnetized neutron star, also called a
magnetar, on Jan. 22, 2009. Now astronomers analyzing this data have
discovered underlying signals related to seismic waves rippling
throughout the magnetar.
rupture in the crust of a highly magnetized neutron star, shown here in
an artist's rendering, can trigger high-energy eruptions. Fermi
observations of these blasts include information on how the star's
surface twists and vibrates, providing new insights into what lies
beneath. Image Credit: NASA's Goddard Space Flight Center/S. Wiessinger.Related multimedia from NASA Goddard's Scientific Visualization Studio
Such signals were first identified during the fadeout of rare giant
flares produced by magnetars. Over the past 40 years, giant flares have
been observed just three times -- in 1979, 1998 and 2004 -- and signals
related to starquakes, which set the neutron stars ringing like a bell,
were identified only in the two most recent events.
"Fermi's Gamma-ray Burst Monitor (GBM) has captured the same evidence
from smaller and much more frequent eruptions called bursts, opening up
the potential for a wealth of new data to help us understand how
neutron stars are put together," said Anna Watts, an astrophysicist at
the University of Amsterdam in the Netherlands and co-author of a new
study about the burst storm. "It turns out that Fermi's GBM is the
perfect tool for this work."
image of NASA's Fermi Gamma-ray Space Telescope, shown here in May 2008
being readied for launch, highlights the spacecraft's instruments. The
Gamma-ray Burst Monitor (GBM) is an array of 14 crystal detectors
sensitive to short-lived gamma-ray blasts. Image Credit: NASA/Jim Grossmann.Unlabeled image
Neutron stars are the densest, most magnetic and fastest-spinning
objects in the universe that scientists can observe directly. Each one
is the crushed core of a massive star that ran out of fuel, collapsed
under its own weight, and exploded as a supernova. A neutron star packs
the equivalent mass of half-a-million Earths into a sphere about 12
miles across, roughly the length of Manhattan Island in New York City.
While typical neutron stars possess magnetic fields trillions of
times stronger than Earth's, the eruptive activity observed from
magnetars requires fields 1,000 times stronger still. To date,
astronomers have confirmed only 23 magnetars.
Because a neutron star's solid crust is locked to its intense
magnetic field, a disruption of one immediately affects the other. A
fracture in the crust will lead to a reshuffling of the magnetic field,
or a sudden reorganization of the magnetic field may instead crack the
surface. Either way, the changes trigger a sudden release of stored
energy via powerful bursts that vibrate the crust, a motion that becomes
imprinted on the burst’s gamma-ray and X-ray signals.
It takes an incredible amount of energy to convulse a neutron star.
The closest comparison on Earth is the 9.5-magnitude Chilean earthquake
of 1960, which ranks as the most powerful ever recorded on the standard
scale used by seismologists. On that scale, said Watts, a starquake
associated with a magnetar giant flare would reach magnitude 23.
The 2009 burst storm came from SGR J1550−5418, an object discovered by
NASA's Einstein Observatory, which operated from 1978 to 1981. Located
about 15,000 light-years away in the constellation Norma, the magnetar
was quiet until October 2008, when it entered a period of eruptive
activity that ended in April 2009. At times, the object produced
hundreds of bursts in as little as 20 minutes, and the most intense
explosions emitted more total energy than the sun does in 20 years.
High-energy instruments on many spacecraft, including NASA's Swift and
Rossi X-ray Timing Explorer, detected hundreds of gamma-ray and X-ray
at the Fifth Fermi International Symposium in Nagoya, Japan, on Oct.
21, Watts said the new study examined 263 individual bursts detected by
Fermi's GBM and confirms vibrations in the frequency ranges previously
seen in giant flares. "We think these are likely twisting oscillations
of the star where the crust and the core, bound by the super-strong
magnetic field, are vibrating together," she explained. "We also found,
in a single burst, an oscillation at a frequency never seen before and
which we still do not understand."
A key element of the research is a new analysis technique developed
by University of Amsterdam researcher Daniela Huppenkothen. Normally
scientists search for oscillations in high-energy data by looking for
variations aligned to a particular frequency. Such methods are best
suited for finding a strong signal with little competition rather than a
faint signal immersed in a bright and rapidly changing environment,
such as a burst.
Huppenkothen likens the problem to detecting ripples from a stone
tossed into a quiet pond. "Now imagine you're in the middle of the North
Atlantic during a storm, searching for those ripples amidst huge waves
in a churning sea," she explained. "Our old methods really weren't
appropriate for this, but I have in effect developed a way of accounting
for the rough sea so we can find ripples even in stormy conditions."
A paper describing the research, which was led by Huppenkothen, appeared in the June 1 edition of The Astrophysical Journal.
While there are many efforts to describe the interiors of neutron
stars, scientists lack enough observational detail to choose between
differing models. Neutron stars reach densities far beyond the reach of
laboratories and their interiors may exceed the density of an atomic
nucleus by as much as 10 times. Knowing more about how bursts shake up
these stars will give theorists an important new window into
understanding their internal structure.
"Right now," added Watts, "we are waiting for more bursts -- and if
we're lucky, a giant flare -- to take advantage of GBM's excellent
Every year, NASA's Chandra X-ray Observatory
looks at hundreds of objects throughout space to help expand our
understanding of the Universe. Ultimately, these data are stored in the Chandra Data Archive,
an electronic repository that provides access to these unique X-ray
findings for anyone who would like to explore them. With the passing of Chandra's 15th anniversary
in operation on August 26, 1999, the archive continues to grow as each
successive year adds to the enormous and invaluable dataset.
To celebrate Chandra's decade and a half in space, and to honor
October as American Archives Month, a variety of objects have been
selected from Chandra's archive. Each of the new images we have produced
combines Chandra data
with those from other telescopes. This technique of creating
"multiwavelength" images allows scientists and the public to see how
X-rays fit with data of other types of light, such as optical, radio,
and infrared. As scientists continue to make new discoveries with the
telescope, the burgeoning archive will allow us to see the high-energy
Universe as only Chandra can.
PSR B1509-58 (upper left)
Pareidolia is the psychological phenomenon where people see recognizable
shapes in clouds, rock formations, or otherwise unrelated objects or
data. When Chandra's image of PSR B1509-58, a spinning neutron star
surrounded by a cloud of energetic particles, was released in 2009,
it quickly gained attention because many saw a hand-like structure in
the X-ray emission. In this new image of the system, X-rays from Chandra
in gold are seen along with infrared data from NASA's Wide-field
Infrared Survey Explorer (WISE) telescope in red, green, and blue.
Pareidolia may strike again in this image as some people report seeing a
shape of a face in WISE's infrared data.
RCW 38 (upper right)
A young star cluster about 5,500 light years from Earth, RCW 38 provides
astronomers a chance to closely examine many young, rapidly evolving
stars at once. In this composite image, X-rays from Chandra are
blue, while infrared data from NASA's Spitzer Space Telescope are orange
and additional infrared data from the 2MASS survey appears white. There
are many massive stars in RCW 38 that will likely explode as supernovas.
Astronomers studying RCW 38 are hoping to better understand this
environment as our Sun was likely born into a similar stellar nursery.
Hercules A (middle left):
Some galaxies have extremely bright cores, suggesting that they contain a
supermassive black hole that is pulling in matter at a prodigious rate.
Astronomers call these "active galaxies,"
and Hercules A is one of them. In visible light (colored red, green and
blue, with most objects appearing white), Hercules A looks like a
typical elliptical galaxy. In X-ray light, however, Chandra detects a
giant cloud of multimillion-degree gas (purple). This gas has been
heated by energy generated by the infall of matter into a black hole at
the center of Hercules A that is over 1,000 times as massive as the one
in the middle of the Milky Way. Radio data (blue) show jets of particles
streaming away from the black hole. The jets span a length of almost
one million light years.
Kes 73 (middle right):
The supernova remnant Kes 73, located about
28,000 light years away, contains a so-called anomalous X-ray pulsar, or
AXP, at its center. Astronomers think that most AXPs are magnetars,
which are neutron stars
with ultra-high magnetic fields. Surrounding the point-like AXP in the
middle, Kes 73 has an expanding shell of debris from the supernova
explosion that occurred between about 750 and 2100 years ago, as seen
from Earth. The Chandra data (blue) reveal clumpy structures along one
side of the remnant, and appear to overlap with infrared data (orange).
The X-rays partially fill the shell seen in radio emission (red) by the
Very Large Array. Data from the Digitized Sky Survey optical telescope
(white) show stars in the field-of-view.
Mrk 573 (lower left):
Markarian 573 is an active galaxy that has two cones of emission streaming away from the supermassive black hole
at its center. Several lines of evidence suggest that a torus, or
doughnut of cool gas and dust may block some of the radiation produced
by matter falling into supermassive black holes, depending on how the
torus is oriented toward Earth. Chandra data of Markarian 573 suggest
that its torus may not be completely solid, but rather may be clumpy.
This composite image shows overlap between X-rays from Chandra (blue),
radio emission from the VLA (purple), and optical data from Hubble
NGC 4736 (lower right):
NGC 4736 (also known as Messier 94) is a spiral galaxy that is unusual
because it has two ring structures. This galaxy is classified as
containing a "low ionization nuclear emission region," or LINER, in its
center, which produces radiation from specific elements such as oxygen and nitrogen.
Chandra observations (gold) of NGC 4736, seen in this composite image
with infrared data from Spitzer (red) and optical data from Hubble and
the Sloan Digital Sky Survey (blue), suggest that the X-ray emission
comes from a recent burst of star formation. Part of the evidence comes
from the large number of point sources near the center of the galaxy,
showing that strong star formation has occurred. In other galaxies,
evidence points to supermassive black holes being responsible for LINER
properties. Chandra's result on NGC 4736 shows LINERs may represent more
than one physical phenomenon.
NASA's Marshall Space Flight Center in Huntsville, Alabama, manages
the Chandra program for NASA's Science Mission Directorate in
Washington, DC. The Smithsonian Astrophysical Observatory in Cambridge,
Massachusetts, controls Chandra's science and flight operations.
image from the Interface Region Imaging Spectrograph (IRIS) shows
emission from hot plasma (T ~ 80,000-100,000 K) in the Sun's transition
region - the atmospheric layer between the surface and the outer corona.
The bright, C-shaped feature at upper center shows brightening in the
footprints of hot coronal loops, which is created by high-energy
electrons accelerated by nanoflares. The vertical dark line corresponds
to the slit of the spectrograph. The image is color-coded to show light
at a wavelength of 1,400 Angstroms. The size of each pixel corresponds
to about 120 km (75 miles) on the Sun. Credit: NASA/IRIS. High Resolution (jpg)-Low Resolution (jpg)
image from the Atmospheric Imaging Assembly on board NASA's Solar
Dynamics Observatory was taken simultaneously with the IRIS
observations. It shows emission from hot coronal loops (T > 5 million
K) in a solar active region. IRIS observed brightenings occurring at
the footpoints of these hot loops. The image is color-coded to show
light at a wavelength of 94 Angstroms. The size of each pixel
corresponds to about 430 km (270 miles) on the Sun. Credit: NASA/SDO.High Resolution (jpg)-Low Resolution (jpg)
Same as above, with a box showing the field of view of the corresponding IRIS image (top).
Cambridge, MA - Why
is the Sun's million-degree corona, or outermost atmosphere, so much
hotter than the Sun's surface? This question has baffled astronomers for
decades. Today, a team led by Paola Testa of the Harvard-Smithsonian
Center for Astrophysics (CfA) is presenting new clues to the mystery of
coronal heating using observations from the recently launched Interface
Region Imaging Spectrograph (IRIS). The team finds that miniature solar
flares called "nanoflares" - and the speedy electrons they produce -
might partly be the source of that heat, at least in some of the hottest
parts of the Sun's corona.
A solar flare occurs when a patch of the Sun brightens dramatically
at all wavelengths of light. During flares, solar plasma is heated to
tens of millions of degrees in a matter of seconds or minutes. Flares
also can accelerate electrons (and protons) from the solar plasma to a
large fraction of the speed of light. These high-energy electrons can
have a significant impact when they reach Earth, causing spectacular
aurorae but also disrupting communications, affecting GPS signals, and
damaging power grids.
Those speedy electrons also can be generated by scaled-down versions
of flares called nanoflares, which are about a billion times less
energetic than regular solar flares. "These nanoflares, as well as the
energetic particles possibly associated with them, are difficult to
study because we can't observe them directly," says Testa.
Testa and her colleagues have found that IRIS provides a new way to
observe the telltale signs of nanoflares by looking at the footpoints of
coronal loops. As the name suggests, coronal loops are loops of hot
plasma that extend from the Sun's surface out into the corona and glow
brightly in ultraviolet and X-rays.
IRIS does not observe the hottest coronal plasma in these loops,
which can reach temperatures of several million degrees. Instead, it
detects the ultraviolet emission from the cooler plasma (~18,000 to
180,000 degrees Fahrenheit) at their footpoints. Even if IRIS can't
observe the coronal heating events directly, it reveals the traces of
those events when they show up as short-lived, small-scale brightenings
at the footpoints of the loops.
The team inferred the presence of high-energy electrons using IRIS
high-resolution ultraviolet imaging and spectroscopic observations of
those footpoint brightenings. Using computer simulations, they modeled
the response of the plasma confined in loops to the energy transported
by energetic electrons. The simulations revealed that energy likely was
deposited by electrons traveling at about 20 percent of the speed of
The high spatial, temporal, and spectral resolution of IRIS was
crucial to the discovery. IRIS can resolve solar features only 150 miles
in size, has a temporal resolution of a few seconds, and has a spectral
resolution capable of measuring plasma flows of a few miles per second.
Finding high-energy electrons that aren't associated with large
flares suggests that the solar corona is, at least partly, heated by
nanoflares. The new observations, combined with computer modeling, also
help astronomers to understand how electrons are accelerated to such
high speeds and energies - a process that plays a major role in a wide
range of astrophysical phenomena from cosmic rays to supernova remnants.
These findings also indicate that nanoflares are powerful, natural
particle accelerators despite having energies about a billion times
lower than large solar flares.
"As usual for science, this work opens up an entirely new set of
questions. For example, how frequent are nanoflares? How common are
energetic particles in the non-flaring corona? How different are the
physical processes at work in these nanoflares compared to larger
flares?" says Testa.
The paper reporting this research is part of a special issue of the journal Science focusing on IRIS discoveries.
in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics
(CfA) is a joint collaboration between the Smithsonian Astrophysical
Observatory and the Harvard College Observatory. CfA scientists,
organized into six research divisions, study the origin, evolution and
ultimate fate of the universe.
For more information, contact:
David A. Aguilar
Director of Public Affairs
Harvard-Smithsonian Center for Astrophysics
Public Affairs Specialist
Harvard-Smithsonian Center for Astrophysics
Figure 1:3D map of the
cosmic web at a distance of 10.8 billion light years from Earth. The map
was generated from imprints of hydrogen gas observed in the spectrum of
24 background galaxies, which are located behind the volume being
mapped. This is the first time that large-scale structures in such a
distant part of the Universe have been mapped directly. The coloring
represents the density of hydrogen gas tracing the cosmic web, with
brighter colors representing higher density.
Credit: Casey Stark (UC Berkeley) and Khee-Gan Lee (MPIA).Larger version for download
Figure 2:Close-up of 3D map
of the distant Universe created by MPIA and UC astronomers. The
filamentary structures seen in this map span distances of millions of
light years, and represent the cosmic web at an earlier stage of cosmic
evolution when the Universe was less than a quarter of its current age.
The region of space seen here is at a distance of 10.8 billion years
from Earth. The coloring represents the density of hydrogen gas tracing
the cosmic web, with brighter colors representing higher density. The
coloring represents the density of hydrogen gas tracing the cosmic web,
with brighter colors representing higher density.
Credit: Casey Stark (UC Berkeley) and Khee-Gan Lee (MPIA).Larger version for download
impression illustrating the technique of Lyman-alpha tomography: as
light from distant background galaxies (yellow arrows) travels through
the Universe towards Earth, hydrogen gas in the foreground leaves a
characteristic imprint ("absorption signature"). From this imprint,
astronomers can reconstruct which clouds the light has encountered as it
traverses the "cosmic web" of dark matter and gas that accounts for the
biggest structures in our universe. By observing a number of background
galaxies in a small patch of the sky, astronomers were able to create a
3D map of the cosmic web using a technique similar to medical computer
tomography (CT) scans. The coloring represents the density of hydrogen
gas tracing the cosmic web, with brighter colors representing higher
density. The rendition of the cosmic web in this image is based on a
supercomputer simulation of cosmic structure formation. Credit: Khee-Gan Lee (MPIA) and Casey Stark (UC Berkeley).Larger version for download
Figure 4:3D map of the cosmic web at a distance of 10.8 billion years from
Earth. The map was generated from imprints of hydrogen gas observed in
the spectrum of 24 background galaxies, which are located behind the
volume being mapped. This is the first time that large-scale structures
in such a distant part of the Universe have been mapped directly. The
coloring represents the density of hydrogen gas tracing the cosmic web,
with brighter colors representing higher density.
Credit: Casey Stark (UC Berkeley) and Khee-Gan Lee (MPIA)
On the largest scales, matter in the Universe is arranged in a vast
network of filamentary structures known as the 'cosmic web', its tangled
strands spanning hundreds of millions of light years. Dark matter,
which emits no light, forms the backbone of this web, which is also
suffused with primordial hydrogen gas left over from the Big Bang.
Galaxies like our own Milky Way are embedded inside this web, but fill
only a tiny fraction of its volume.
Now a team of astronomers led by Khee-Gan Lee, a post-doc at the Max
Planck Institute for Astronomy, has managed to create a
three-dimensional map of a large region of the far-flung cosmic web
nearly 11 billion light years away, when the Universe was just a quarter
of its current age. Similar to a medical CT scan, which reconstructs a
three-dimensional image of the human body from the X-rays passing
through a patient, Lee and his colleagues reconstructed their map from
the light of distant background galaxies passing through the cosmic
web's hydrogen gas.
The use of the combined starlight of background galaxies for this
purpose had been thought to be impossible with current telescopes –
until Lee carried out calculations that suggested otherwise. Lee says: "I
was surprised to find that existing large telescopes should already be
able to collect sufficient light from these faint galaxies to map the
foreground absorption, albeit at a lower resolution than would be
feasible with future telescopes. Still, this would provide an
unprecedented view of the cosmic web which has never been mapped at such
Lee and his colleagues obtained observing time on one of the largest
telescopes in the world: the 10m-diameter Keck I telescope at the W. M.
Keck Observatory on Mauna Kea, Hawaii – but were plagued by a problem
more terrestrial than cosmic. "We were pretty disappointed as the
weather was terrible and we only managed to collect a few hours of good
data. But judging by the data quality as it came off the telescope, it
was already clear to me that the experiment was going to work," says Joseph Hennawi (MPIA), who was part of the observing team.
Although the astronomers only observed for 4 hours, the data they
collected was completely unprecedented. Their absorption measurements
using 24 faint background galaxies provided sufficient coverage of a
small patch of the sky to be combined into a 3D map of the foreground
cosmic web. A crucial element was the computer algorithm used to create
the 3D map: due to the large amount of data, a naïve implementation of
the map-making procedure would have required an inordinate amount of
computing time. Fortunately, team members Casey Stark and Martin White
(UC Berkeley and Lawrence Berkeley National Lab) devised a new fast
algorithm that could create the map within minutes. "We realized we
could simplify the computations by tailoring them to this particular
problem, and thus use much less memory. A calculation that previously
required a supercomputer now runs on a laptop", says Stark.
The resulting map of hydrogen absorption reveals a three-dimensional
section of the universe 11 billions light years away – the first time
the cosmic web has been mapped at such a vast distance. Since observing
to such immense distances is also looking back in time, the map reveals
the early stages of cosmic structure formation when the Universe was
only a quarter of its current age, during an era when the galaxies were
undergoing a major 'growth spurt'. The map provides a tantalizing
glimpse of giant filamentary structures extending across millions of
light years, and paves the way for more extensive studies that should
reveal not only the structure of the cosmic web, but also details of its
function – the ways that pristine gas is funneled along the web into
galaxies, providing the raw material for the growth of galaxies through
the formation of stars and planets.
The work described here will be published as K.G. Lee et al., "Lyα Forest Tomography from Background Galaxies: The first Megaparsec-Resolution Large-Scale Structure Map at z > 2" in the Astrophysical Journal Letters.
The team members are Khee-Gan Lee, Joseph F. Hennawi, and
Anna-Christina Eilers (Max Planck Institute for Astronomy), Casey Stark
and Martin White, (UC Berkeley and Lawrence Berkeley National
Laboratory), J. Xavier Prochaska (University of California at Santa
Cruz, Lick Observatory), David Schlegel (Lawrence Berkeley National
Laboratory), and Andreu Arinyo-i-Prats (Universitat de Barcelona).
This research received financial support from the National Geographic Society/Waitt Grants Program.
Khee-Gan Lee (first author)
Max Planck Institute for Astronomy
Phone: (+49|0) 6221 –528 467
Joe Hennawi (co-author)
Max Planck Institute for Astronomy
Phone: (+49|0) 6221 –528 263
Dr. Markus Pössel (public information officer)
Max Planck Institute for Astronomy
Phone: (+49|0) 6221 –528 261
artist's conception of the planetary system around the nearby solar
analog star, Tau Ceti, showing its five putative planets. Astonomers
using far infrared observations find a debris disk around the star, and
find a model that is consistent with five planets lying within the
disk's inner edge at five astronomical units. Credit: NASA
thousands of exoplanets and hundreds of planetary systems (stars with
multiple exoplanets) are now known, astronomers still don’t know whether
our solar system is typical. The distributions of known planetary
system parameters are strongly affected by observational biases that are
not easy to disentangle from the true distributions. Moreover, our
Solar system’s architecture (small rocky inner planets, large gaseous
outer planets, and an outer debris disc made of many small objects) has
not yet been seen in other systems, most likely due to these same
biases. Long time baselines, for example, are required to discover
planets at greater than a few astronomical units (one AU is the average
distance of the Earth from the Sun) with all techniques except direct
imaging, but direct imaging of planets around mature stars is difficult
due to the low light from planets compared to their host stars.
Debris disks, because they are spread out over large areas, are
easier to see, and structures in debris discs like rings or gaps can
indicate the presence of additional planets. CfA astronomer David
Wilner joined with his colleagues to search for clues of planets in the
debris disc around τ Ceti, a nearby solar-type star located only ten
light-years from the Sun. The infrared excess towards τ Ceti has been
known for nearly three decades and has been attributed to warm dust
particles in a debris disk.
The astronomers used the Herschel Space Telescope to study τ Ceti in
far infrared wavelengths where the dust emission should be strongest.
The carefully processed images reveal evidence for a uniform and
symmetric debris disk with an inner edge about two to three AU from the
star and an outer edge fifty-five AU from the star. For comparison, in
our Solar system the Kuiper Belt of small objects begins at the orbit of
Neptune (about thirty AU from the Sun) and extends out to about fifty
AU (the colder Oort Belt of icy objects and comets extends much farther,
to about fifty thousand AU).
In previous studies of τ Ceti, other astronomers had found
preliminary evidence suggesting the possibility it hosted five planets.
Wilner and his colleagues modeled the stellar system with their
observed debris disk and including these possible planets and a range of
other published observational data, and found that the system was
consistent with the observations and could be stable. The putative
planets would orbit between the debris disk's inner edge and the star.
The scientists conclude by noting that a Jupiter-mass planet could not
be present in this system, making it less than ideal as a Solar system
analog. Future observations should be able to refine the picture
Debris Disc of Solar Analogue τ Ceti: Herschel Observations and
Dynamical Simulations of the Proposed Multiplanet System," S. M. Lawler,
J. Di Francesco, G. M. Kennedy, B. Sibthorpe, M. Booth, B.
Vandenbussche, B. C. Matthews, W. S. Holland, J. Greaves, D. J. Wilner,
M. Tuomi, J. A. D. L. Blommaert, B. L. de Vries, C. Dominik, M.
Fridlund, W. Gear, A. M. Heras, R. Ivison and G. Olofsson, MNRAS 444, 2665, 2014.
Figure 1:CALIFA data example: Top row: Poststamp images of five galaxies. Bottom row: Colour coded gas velocity maps of the same galaxies based on CALIFA IFS data. Credit: Top row: SDSS | Bottom row: CALIFA team
Today, the second large data release of
the CALIFA-Survey has been published to the astronomical community and
the public. It contains an unprecedented amount of data on 200 galaxies
in the local universe allowing astronomers to study in detail numerous
galaxy properties regarding their composition, kinematics, formation
history and evolution.
The Calar Alto Legacy Integral Field Area
survey (CALIFA) is one of the largest surveys of galaxies which is
based on an observing technique called "Integral Field Spectroscopy"
(IFS). Already a single spectrum of an astronomical object provides
important data beyond pure imaging because the light from the source is
split into its wavelength-dependent components and shows characteristic
signatures related to physical, chemical and dynamical properties.
However, using the PMAS Spectrograph at Calar Alto Observatory, the team
of the CALIFA Survey is even able to collect 2000 individual spectra
for each galaxy which are covering the whole surface of each object.
The 2nd CALIFA data release now provides unique data on a
representative sample of 200 galaxies in the local Universe. These
spectra allow studies of the stellar content, ages, star formation
history, as well as gas and dust properties. However, beyond spectral
diagnostics the CALIFA data-cubes allow to study the spatial
distribution of all these properties. Moreover, as a unique feature of
imaging spectroscopy, the kinematic properties, i.e. motions of the
stars and gas over the whole face of a galaxy, enable the inference of
the structure of the galaxy, the formation history, and even the
presence of dark matter.
Compared to the 1st data release in 2012 this 2nd
release presents a much improved preparation of the material. Data is
provided with two spectral setups (in low and high resolution) and for
each galaxy the data cube contains about 2000 individual spectra. In
total this adds up to about 800,000 spectra released in DR2. The data is
freely available for anyone interested.
Artist's impression of the Milky Way. Its hot halo appears to be stripping away the star-forming atomic hydrogen from its companion dwarf spheroidal galaxies. Credit: NRAO/AUI/NSF
Astronomers using the National Science Foundation’s Green Bank Telescope
(GBT) in West Virginia, along with data from other large radio
telescopes, have discovered that our nearest galactic neighbors, the
dwarf spheroidal galaxies, are devoid of star-forming gas, and that our
Milky Way Galaxy is to blame.
These new radio observations,
which are the highest sensitivity of their kind ever undertaken, reveal
that within a well-defined boundary around our Galaxy, dwarf galaxies
are completely devoid of hydrogen gas; beyond this point, dwarf galaxies
are teeming with star-forming material.
The Milky Way Galaxy is
actually the largest member of a compact clutch of galaxies that are
bound together by gravity. Swarming around our home Galaxy is a
menagerie of smaller dwarf galaxies, the smallest of which are the
relatively nearby dwarf spheroidals, which may be the leftover building
blocks of galaxy formation. Further out are a number of similarly sized
and slightly misshaped dwarf irregular galaxies, which are not
gravitationally bound to the Milky Way and may be relative newcomers to
our galactic neighborhood.
“Astronomers wondered if, after
billions of years of interaction, the nearby dwarf spheroidal galaxies
have all the same star-forming ‘stuff’ that we find in more distant
dwarf galaxies,” said astronomer Kristine Spekkens, assistant professor
at the Royal Military College of Canada and lead author on a paper
published in the Astrophysical Journal Letters.
studies have shown that the more distant dwarf irregular galaxies have
large reservoirs of neutral hydrogen gas, the fuel for star formation.
These past observations, however, were not sensitive enough to rule out
the presence of this gas in the smallest dwarf spheroidal galaxies.
bringing to bear the combined power of the GBT (the world’s largest
fully steerable radio telescope) and other giant telescopes from around
the world, Spekkens and her team were able to probe the dwarf galaxies
that have been swarming around the Milky Way for billions of years for
tiny amounts of atomic hydrogen.
“What we found is that there is
a clear break, a point near our home Galaxy where dwarf galaxies are
completely devoid of any traces of neutral atomic hydrogen,” noted
Spekkens. Beyond this point, which extends approximately 1,000
light-years from the edge of the Milky Way’s star-filled disk to a point
that is thought to coincide with the edge of its dark matter
distribution, dwarf spheroidals become vanishingly rare while their
gas-rich, dwarf irregular counterparts flourish.
There are many
ways that larger, mature galaxies can lose their star-forming material,
but this is mostly tied to furious star formation or powerful jets of
material driven by supermassive black holes. The dwarf galaxies that
orbit the Milky Way contain neither of these energetic processes. They
are, however, susceptible to the broader influences of the Milky Way,
which itself resides within an extended, diffuse halo of hot hydrogen
The researchers believe that, up to a certain distance
from the galactic disk, this halo is dense enough to affect the
composition of dwarf galaxies. Within this “danger zone,” the pressure
created by the million-mile-per-hour orbital velocities of the dwarf
spheroidals can actually strip away any detectable traces of neutral
hydrogen. The Milky Way thus shuts down star formation in its smallest
"These observations therefore reveal a great deal
about size of the hot halo and about how companions orbit the Milky
Way," concludes Spekkens.
The brightly glowing plumes seen in this image are reminiscent of an
underwater scene, with turquoise-tinted currents and nebulous strands
reaching out into the surroundings.
However, this is no ocean. This image actually shows part of the
Large Magellanic Cloud (LMC), a small nearby galaxy that orbits our
galaxy, the Milky Way, and appears as a blurred blob in our skies. The
NASA/ESA Hubble Space Telescope has peeked many times into this galaxy,
releasing stunning images of the whirling clouds of gas and sparkling
stars (opo9944a, heic1301, potw1408a).
This image shows part of the Tarantula Nebula's outskirts. This
famously beautiful nebula, located within the LMC, is a frequent target
for Hubble (heic1206, heic1402).
In most images of the LMC the colour is completely different to that
seen here. This is because, in this new image, a different set of
filters was used. The customary R filter, which selects the red light,
was replaced by a filter letting through the near-infrared light. In
traditional images, the hydrogen gas appears pink because it shines most
brightly in the red. Here however, other less prominent emission lines
dominate in the blue and green filters.
This data is part of the Archival Pure Parallel Project (APPP), a project that gathered together and processed over 1000 images taken using Hubble’s Wide Field Planetary Camera 2,
obtained in parallel with other Hubble instruments. Much of the data in
the project could be used to study a wide range of astronomical topics,
including gravitational lensing and cosmic shear,
exploring distant star-forming galaxies, supplementing observations in
other wavelength ranges with optical data, and examining star
populations from stellar heavyweights all the way down to solar-mass
A version of this image was entered into the Hubble’s Hidden Treasures image processing competition by contestant Josh Barrington.
Artist's Illustration of a Giant Cosmic Magnifying Glass
Illustration Credit:NASA,ESA, and Z. Levay (STScI). Science Credit:NASA,ESA, A. Zitrin (Caltech), and J. Lotz, M. Mountain, A. Koekemoer, and the HFF Team (STScI)
Peering through a giant cosmic magnifying glass, NASA's Hubble Space
Telescope has spotted one of the farthest, faintest, and smallest
galaxies ever seen. The diminutive object is estimated to be over 13
billion light-years away.
This new detection is considered one of the most reliable distance
measurements of a galaxy that existed in the early universe, said the
Hubble researchers. They used two independent methods to estimate its
The galaxy appears as a tiny blob that is only a small fraction of
the size of our Milky Way galaxy. But it offers a peek back into a time
when the universe was only about 500 million years old, roughly 3
percent of its current age of 13.7 billion years. Astronomers have
uncovered about 10 other galaxy candidates at this early era. But this
newly found galaxy is significantly smaller and fainter than most of
those other remote objects detected to date.
"This object is a unique example of what is suspected to be an
abundant, underlying population of extremely small and faint galaxies
at about 500 million years after the big bang," explained study leader
Adi Zitrin of the California Institute of Technology in Pasadena. "The
discovery is telling us that galaxies as faint as this one exist, and we
should continue looking for them and even fainter objects so that we
can understand how galaxies and the universe have evolved over time."
The galaxy was detected as part of the Frontier Fields program, an
ambitious three-year effort, begun in 2013, that teams Hubble with
NASA's other Great Observatories — the Spitzer Space Telescope and the
Chandra X-ray Observatory — to probe the early universe by studying
large galaxy clusters. These clusters are so massive that their
gravity deflects light passing through them, magnifying, brightening,
and distorting background objects in a phenomenon called gravitational
lensing. These powerful lenses allow astronomers to find many dim,
distant structures that otherwise might be too faint to see.
In this new discovery, the lensing power of the mammoth galaxy
cluster Abell 2744, nicknamed Pandora's Cluster, produced three
magnified images of the same galaxy. Each magnified image makes the
galaxy appear as much as 10 times larger and brighter than it would
look without the intervening lens.
An analysis of the distant galaxy shows that it measures merely 850
light-years across, 500 times smaller than the Milky Way, and is
estimated to have a mass of only 40 million suns. The galaxy's star
formation rate is about one star every three years (one-third the star
formation rate in the Milky Way). Although this may seem low, Zitrin
said that given its small size and low mass, the tiny galaxy is in fact
rapidly evolving and efficiently forming stars.
"Galaxies such as this one are probably small clumps of matter that
are starting to form stars and shine light, but they don't have a
defined structure yet," Zitrin said. "Therefore, it's possible that we
only see one bright clump magnified due to the lensing, and this is one
possibility as to why it is smaller than typical field galaxies of that
Zitrin's team spotted the galaxy's gravitationally multiplied images
using near-infrared and visible-light photos of the galaxy cluster
taken by Hubble's Wide Field Camera 3 and Advanced Camera for Surveys.
But at first they didn't know how far away it was from Earth.
Normally, astronomers use spectroscopy to determine an object's
distance. The farther away a galaxy, the more its light has been
stretched by the universe's expansion. Astronomers can precisely
measure this effect through spectroscopy, which characterizes an
But the gravitationally lensed galaxy and other objects found at this
early epoch are too far away and too dim for astronomers to use
spectroscopy. Astronomers instead analyze an object's color to estimate
its distance. The universe's expansion reddens an object's color in
predictable ways, which scientists can measure.
Members of Zitrin's team not only performed the color-analysis
technique, but they also took advantage of the multiple images produced
by the gravitational lens to independently confirm their distance
estimate. The astronomers measured the angular separation between the
three magnified images of the galaxy in the Hubble photos. The greater
the angular separation due to lensing, the farther away the object is
from Earth. To test this concept, the astronomers compared the three
magnified images with the locations of several other multiply imaged
objects lensed by Abell 2744 that are not as far behind the cluster.
The angular distance between the magnified images of the closer
galaxies was smaller.
"These measurements imply that, given the large angular separation
between the three images of our background galaxy, the object must lie
very far away," Zitrin explained. "It also matches the distance
estimate we calculated, based on the color-analysis technique. So we
are about 95 percent confident that this object is at a remote distance,
at redshift 10 (a measure of the stretching of space since the big
bang). The lensing takes away any doubt that this might be a heavily
reddened, nearby object masquerading as a far more distant object."
Astronomers have long debated whether such early galaxies could have
provided enough radiation to warm the hydrogen that cooled soon after
the big bang. This process, called "reionization," is thought to have
occurred 200 million to 1 billion years after the birth of the
universe. Reionization made the universe transparent to light, allowing
astronomers to look far back into time without running into a "fog" of
"We tend to assume that galaxies ionized the universe with their
ultraviolet light," Zitrin said. "But we do not see enough galaxies or
light that could do that. So we need to look at fainter and fainter
galaxies, and the Frontier Fields and galaxy cluster lensing can help
us achieve this goal."
The team's results appeared in the Sept. 5 online edition of The Astrophysical Journal Letters.