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Gravitational Lensing by Galaxy in Cluster IRC 0218
Credit:NASA,ESA, K.-V. Tran (Texas A&M University), and K. Wong (Academia Sinica Institute of Astronomy & Astrophysics). Release Images
Astronomers using NASA's Hubble Space Telescope have unexpectedly
discovered the most distant cosmic magnifying glass, produced by a
monster elliptical galaxy. Seen here as it looked 9.6 billion years ago,
this monster elliptical galaxy breaks the previous record holder by 200
million years. These "lensing" galaxies are so massive that their
gravity bends, magnifies, and distorts light from objects behind them, a
phenomenon called gravitational lensing.
The object behind the cosmic lens is a tiny spiral galaxy undergoing a
rapid burst of star formation. Its light has taken 10.7 billion years
to arrive here. Seeing this chance alignment at such a great distance
from Earth is a rare find.
Locating more of these distant lensing galaxies will offer insight
into how young galaxies in the early universe built themselves up into
the massive dark-matter-dominated galaxies of today. Dark matter cannot
be seen, but it accounts for the bulk of the universe's matter.
"When you look more than 9 billion years ago in the early universe,
you don't expect to find this type of galaxy-galaxy lensing at all,"
explained lead researcher Kim-Vy Tran of Texas A&M University in
College Station. "It's very difficult to see an alignment between two
galaxies in the early universe. Imagine holding a magnifying glass close
to you and then moving it much farther away. When you look through a
magnifying glass held at arm's length, the chances that you will see an
enlarged object are high. But if you move the magnifying glass across
the room, your chances of seeing the magnifying glass nearly perfectly
aligned with another object beyond it diminishes."
Team members Kenneth Wong and Sherry Suyu of Academia Sinica
Institute of Astronomy & Astrophysics (ASIAA) in Taipei, Taiwan,
used the gravitational lensing from the chance alignment to measure the
giant galaxy's total mass, including the amount of dark matter, by
gauging the intensity of its lensing effects on the background galaxy's
light. The giant foreground galaxy weighs 180 billion times more than
our Sun and is a massive galaxy for its epoch. It is also one of the
brightest members of a distant cluster of galaxies, called IRC 0218.
"There are hundreds of lens galaxies that we know about, but almost
all of them are relatively nearby, in cosmic terms," said Wong, first
author on the team's science paper. "To find a lens as far away as this
one is a very special discovery because we can learn about the
dark-matter content of galaxies in the distant past.
By comparing our
analysis of this lens galaxy to the more nearby lenses, we can start to
understand how that dark-matter content has evolved over time."
Although the elliptical galaxy is hefty, it is not as massive as many
of today's galaxies. Our Milky Way galaxy, for example, is three to
four times more massive than the elliptical galaxy. Most of the Milky
Way's mass is locked up in dark matter. The lensing galaxy, however, is
underweight in terms of its dark-matter content.
"The unusually small amount of dark matter in this massive,
elliptical, lensing galaxy is very surprising," Suyu said. "Other
elliptical galaxies that are closer to us have much more dark matter
and have inventories of stars that appear to be different from this
super-distant lensing galaxy."
The team suspects that the lensing galaxy will continue to grow over
the next 9 billion years, gaining stars and dark matter by
cannibalizing neighboring galaxies. "Recent studies suggest that these
massive galaxies gain more dark matter than stars as they continue to
grow," Tran explained. "Astronomers had assumed that dark matter and
normal matter build up equally in a galaxy over time. But now we know
that the ratio of dark matter to normal matter changes with time. Our
lensing galaxy will eventually become much more massive than the Milky
Way and definitely will have more dark matter, too."
Tran and her team were studying star formation in two distant galaxy
clusters, including IRC 0218, when they stumbled upon the gravitational
lens. While analyzing spectrographic data from the W.M. Keck
Observatory in Hawaii, Tran spotted a strong detection of hot hydrogen
gas that appeared to arise from a massive, bright elliptical galaxy. The
detection was surprising because hot hydrogen gas is a clear signature
of star birth. Previous observations had shown that the giant
elliptical was an old, sedate galaxy that had stopped making stars a
long time ago. Another puzzling discovery was that the young stars were
at a much farther distance than the massive elliptical. "I was very
surprised and worried," Tran recalled. "I thought we had made a major
mistake with our observations."
The astronomer soon realized she hadn't made a mistake when she
looked at the Hubble images taken in blue wavelengths, which revealed
the glow of fledgling stars. The images, taken by the Advanced Camera
for Surveys and the Wide Field Camera 3, revealed a blue,
eyebrow-shaped object next to a smeared blue dot around the big
elliptical. Tran recognized the unusual features as the distorted,
magnified images of a more distant galaxy behind the elliptical galaxy,
the signature of a gravitational lens. But some team members were not
convinced. They speculated that the two objects could be a nearby
galaxy pair being shredded during a galaxy collision. Tran, however,
only had a partial fingerprint; she needed conclusive evidence.
To confirm the gravitational-lens hypothesis, collaborator Ivelina
Momcheva of Yale University, New Haven, Connecticut, analyzed Hubble
spectroscopic data from the 3D-HST survey, a near-infrared
spectroscopic survey taken with the Wide Field Camera 3. She compared
that data with images from the Cosmic Assembly Near-infrared Deep
Extragalactic Legacy Survey (CANDELS), a large Hubble deep-sky program.
To paint an even more detailed picture of the system, Momcheva also
added archival Hubble observations of the galaxy cluster. The data
turned up another fingerprint of hot gas connected to the more distant
"We discovered that light from the lensing galaxy and from the
background galaxy were blended in the ground-based data, which was
confusing us," Momcheva said. "The Keck spectroscopic data hinted that
something interesting was going on here, but only with Hubble's
high-resolution spectroscopy were we able to separate the lensing galaxy
from the more distant background galaxy and determine that the two
were at different distances. The Hubble data also revealed the telltale
look of the system, with the foreground lens in the middle, flanked by
a bright arc on one side and a faint smudge on the other — both
distorted images of the background galaxy. We needed the combination of
imaging and spectroscopy to solve the puzzle."
The distant galaxy is too small and far away for Hubble to resolve
its structure. Team members, therefore, reconstructed and analyzed the
distribution of light in the object to infer its spiral shape. In
addition, spiral galaxies are more plentiful during those early times.
The Hubble images also reveal at least one bright compact region near
the center. The team suspects that the bright region is due to a flurry
of star formation and is most likely composed of hot hydrogen gas
heated by massive young stars.
Team members calculated the lensing galaxy's mass, including its
dark-matter content, by first measuring the amount of light emitted by
its stars. From that measurement, the astronomers obtained the mass of
all the stars, which equals the amount of normal matter. Next, the team
estimated the total mass by measuring how much the galaxy's gravity
bends and distorts light from the distant background galaxy. The
astronomers then subtracted the stellar mass from the total mass to
determine the amount of dark matter in the galaxy.
As Tran continues her star-formation study in galaxy clusters, she
will be hunting for more signatures of gravitational lensing. "I'm
definitely going to keep an eye out for more lensing galaxies, but
they're so rare that you would normally have to survey hundreds of
clusters for them," Tran said. "That's why finding this one in such a
small area of space was a complete shock."
The team's results appeared in the July 10 issue of The Astrophysical Journal Letters.
Astronomers using the Atacama Large
Millimeter/submillimeter Array (ALMA) have found wildly misaligned
planet-forming gas discs around the two young stars in the binary system
HK Tauri. These new ALMA observations provide the clearest picture ever
of protoplanetary discs in a double star. The new result also helps to
explain why so many exoplanets — unlike the planets in the Solar System —
came to have strange, eccentric or inclined orbits. The results will
appear in the journal Nature on 31 July 2014.
Unlike our solitary Sun, most stars form in binary pairs — two stars
that are in orbit around each other. Binary stars are very common, but
they pose a number of questions, including how and where planets form in
such complex environments.
“ALMA has now given us the best view yet of a binary star system
sporting protoplanetary discs — and we find that the discs are mutually
misaligned!” said Eric Jensen, an astronomer at Swarthmore College in Pennsylvania, USA.
The two stars in the HK Tauri system, which is located about 450 light-years from Earth in the constellation of Taurus (The
Bull), are less than five million years old and separated by about 58
billion kilometres — this is 13 times the distance of Neptune from the
The fainter star, HK Tauri B, is surrounded by an edge-on protoplanetary disc
that blocks the starlight. Because the glare of the star is suppressed,
astronomers can easily get a good view of the disc by observing in visible light, or at near-infrared wavelengths.
The companion star, HK Tauri A, also has a disc, but in this case it
does not block out the starlight. As a result the disc cannot be seen in
visible light because its faint glow is swamped by the dazzling
brightness of the star. But it does shine brightly in
millimetre-wavelength light, which ALMA can readily detect.
Using ALMA, the team were not
only able to see the disc around HK Tauri A, but they could also measure
its rotation for the first time. This clearer picture enabled the
astronomers to calculate that the two discs are out of alignment with
each other by at least 60 degrees. So rather than being in the same
plane as the orbits of the two stars at least one of the discs must be
“This clear misalignment has given us a remarkable look at a young binary star system,” said Rachel Akeson of the NASA Exoplanet Science Institute at the California Institute of Technology in the USA. “Although
there have been earlier observations indicating that this type of
misaligned system existed, the new ALMA observations of HK Tauri show
much more clearly what is really going on in one of these systems.”
Stars and planets form out of vast clouds of dust and gas. As
material in these clouds contracts under gravity, it begins to rotate
until most of the dust and gas falls into a flattened protoplanetary
disc swirling around a growing central protostar.
But in a binary system like HK Tauri things are much more complex.
When the orbits of the stars and the protoplanetary discs are not
roughly in the same plane any planets that may be forming can end up in
highly eccentric and tilted orbits .
“Our results show that the necessary conditions exist to modify
planetary orbits and that these conditions are present at the time of
planet formation, apparently due to the formation process of a binary
star system,” noted Jensen. “We can’t rule other theories out, but we can certainly rule in that a second star will do the job.”
Since ALMA can see the otherwise invisible dust and gas of
protoplanetary discs, it allowed for never-before-seen views of this
young binary system. “Because we’re seeing this in the early stages
of formation with the protoplanetary discs still in place, we can see
better how things are oriented,” explained Akeson.
Looking forward, the researchers want to determine if this type of
system is typical or not. They note that this is a remarkable individual
case, but additional surveys are needed to determine if this sort of
arrangement is common throughout our home galaxy, the Milky Way.
Jensen concludes: “Although understanding this mechanism is a big
step forward, it can’t explain all of the weird orbits of extrasolar
planets — there just aren’t enough binary companions for this to be the
whole answer. So that’s an interesting puzzle still to solve, too!”
 If the two stars and their discs
are not all in the same plane, the gravitational pull of one star will
perturb the other disc, making it wobble or precess, and vice versa. A
planet forming in one of these discs will also be perturbed by the other
star, which will tilt and deform its orbit.
The Atacama Large Millimeter/submillimeter
Array (ALMA), an international astronomy facility, is a partnership of
Europe, North America and East Asia in cooperation with the Republic of
Chile. ALMA is funded in Europe by the European Southern Observatory
(ESO), in North America by the U.S. National Science Foundation (NSF) in
cooperation with the National Research Council of Canada (NRC) and the
National Science Council of Taiwan (NSC) and in East Asia by the
National Institutes of Natural Sciences (NINS) of Japan in cooperation
with the Academia Sinica (AS) in Taiwan. ALMA construction and
operations are led on behalf of Europe by ESO, on behalf of North
America by the National Radio Astronomy Observatory (NRAO), which is
managed by Associated Universities, Inc. (AUI) and on behalf of East
Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint
ALMA Observatory (JAO) provides the unified leadership and management
of the construction, commissioning and operation of ALMA.
This research was presented in a paper entitled “Misaligned
Protoplanetary Disks in a Young Binary Star System”, by Eric Jensen and
Rachel Akeson, to appear in the 31 July 2014 issue of the journal Nature.
The team is composed of Eric L. N. Jensen (Dept. of Physics &
Astronomy, Swarthmore College, USA) and Rachel Akeson (NASA Exoplanet
Science Institute, IPAC/Caltech, Pasadena, USA).
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”.
New observations of M4 have studied the binary stars in this cluster.
globular cluster is a roughly spherical ensemble of stars, as many as
several million of them, gravitationally bound together in groups whose
diameters can be as small as only tens of light-years. To sense the
dramatic implications of this dense packing, consider that the nearest
star to the Sun, Proxima Centauri, is about four light-years away.
Messier 4 (M4) is the closest globular cluster to Earth at a distance of
about six thousand light-years, and a puzzle to astronomers. Normal
gravitational effects should, over time, redistribute the stars in a
globular cluster until they are more numerous towards the center, but
while M4 shows a central concentration of stars it does not show
evidence for a steep central cusp even though astronomers think enough
time has passed.
To understand what is going on in this globular cluster, and to help
understand how these clusters evolve in general, CfA astronomer Maureen
van den Berg and her collaborators have undertaken a large and
unprecedented set of deep images of M4 with the Hubble Space Telescope
to look for binary stars, that is stars with companions. The dynamical
interactions between the densely crowded stars in a globular cluster
should disrupt many such binaries, but for reasons that are not
understood about fifteen percent of the stars in M4 are binaries, at
least based on monitoring brightness variations (a more typical number
is two percent). Whether or not this unusual abundance is connected to
the lack of a central cusp in stellar density is also not understood.
The astronomers set out to use Hubble to study the binary star
population in M4 looking at both brightness variations and stellar
wobble (astrometric) variations, in particular due to binaries with a
massive, faint, and evolved companion like a white dwarf or neutron
star. The team was able to find and characterize a much more complete
set of binaries, including thirty-six new variables. They note in
passing that, as part of the search process, any stars with massive "hot
Jupiter" exoplanet companions would probably also have been detected,
but that none were. The extensive results are still being analyzed, but
the improved statistics will make the conclusions much more reliable.
M 4 Core Project with HST – III. Search for Variable Stars in the
Primary Field," V. Nascimbeni, L. R. Bedin, D. C. Heggie, M. van den
Berg, M. Giersz, G. Piotto, K. Brogaard, A. Bellini, A. P. Milone, R. M.
Rich, D. Pooley, J. Anderson,, L. Ubeda, S. Ortolani, L. Malavolta, A.
Cunial1, and A. Pietrinferni, MNRAS 442, 2381, 2014
indicate the density of interstellar helium near Earth and its
enhancement in a downstream cone as the neutral atoms respond to the
sun's gravity (blue is low density, red is high). Also shown are the
observing angles for DXL and ROSAT. Image Credit: NASA's Goddard Space Flight Center.Hi-Res Image
New findings from a NASA-funded instrument have resolved a decades-old
puzzle about a fog of low-energy X-rays observed over the entire sky.
Thanks to refurbished detectors first flown on a NASA sounding rocket in
the 1970s, astronomers have now confirmed the long-held suspicion that
much of this glow stems from a region of million-degree interstellar
plasma known as the local hot bubble, or LHB.
At the same time, the study also establishes upper limits on the
amount of low-energy, or soft, X-rays produced within our planetary
system by the solar wind, a gusty outflow of charged particles emanating
from the sun.
"Interactions between the solar wind and neutral atoms in comets, the
outer atmospheres of planets, and even interstellar gas produce soft
X-rays," explained team member Steve Snowden, an astrophysicist at
NASA's Goddard Space Flight Center in Greenbelt, Maryland. "We need to
account for these processes because the X-rays they produce complicate
our observations of the wider universe."
Decades of mapping the sky in X-rays with energies around 250
electron volts -- about 100 times the energy of visible light --
revealed strong emission precisely where it shouldn't be. This glow,
known as the soft X-ray diffuse background, is surprisingly bright in
the gas-rich central plane of our galaxy, where it should be strongly
absorbed. This suggested the background was a local phenomenon, arising
from a bubble of hot gas extending out a few hundred light-years from
the solar system in all directions. Improved measurements also made it
increasingly clear that the sun resides in a region where interstellar
gas is unusually sparse. Taken together, the evidence suggests our solar
system is moving through a region that may have been blasted clear by
one or more supernova explosions during the past 20 million years.
In the 1990s, a six-month all-sky survey by the German X-ray
observatory ROSAT provided improved maps of the diffuse background, but
it also revealed that comets were an unexpected source of soft X-rays.
As scientists began to understand this process, called solar wind charge
exchange, they realized it could occur anywhere neutral atoms
interacted with solar wind ions.
the last decade, some scientists have been challenging the LHB
interpretation, suggesting that much of the soft X-ray diffuse
background is a result of charge exchange," said F. Scott Porter, a
Goddard astrophysicist also participating in the study. "The only way to
check is to design an instrument and make measurements."
Led by Massimiliano Galeazzi, a professor of physics at the
University of Miami in Coral Gables, Florida, an international
collaboration developed a mission to do just that. The team includes
scientists from NASA, the University of Wisconsin -- Madison, the
University of Michigan at Ann Arbor, the University of Kansas at
Lawrence, Johns Hopkins University in Baltimore, Maryland, the French
National Center for Scientific Research (CNRS), headquartered in Paris,
and other institutions.
Galeazzi and his colleagues rebuilt, tested, calibrated, and adapted
X-ray detectors originally designed by the University of Wisconsin and
flown on sounding rockets in the 1970s. Components from another
instrument flown on space shuttle Endeavour in 1993 also were given new
life. The mission was named DXL, for Diffuse X-ray emission from the
On Dec. 12, 2012, DXL launched from White Sands Missile Range in New
Mexico atop a NASA Black Brant IX sounding rocket, reaching a peak
altitude of 160 miles (258 km) and spending five minutes above Earth's
atmosphere. The mission design allowed the instrument to observe a
worst-case scenario involving charge exchange with interstellar gas.
The solar system is currently passing through a small cloud of cold
interstellar gas as it moves through the galaxy. The cloud’s neutral
hydrogen and helium atoms stream through the planetary system at about
56,000 mph (90,000 km/h). While hydrogen atoms quickly ionize and
respond to numerous forces, the helium atoms travel paths largely
governed by the sun's gravity. This creates a "helium focusing cone"
downstream from the sun that crosses Earth's orbit and is located high
in the sky near midnight in early December.
"This helium focusing creates a region with a much greater density of
neutral atoms and a correspondingly enhanced charge exchange rate,"
The solar wind is accelerated in the sun's corona, the hottest part
of its atmosphere, so its atoms have been ionized -- stripped of many of
their electrons. When a neutral atom collides with a solar wind ion,
one of its electrons often jumps to the charged particle. Once captured
by the ion, the electron briefly remains in an excited state, then emits
a soft X-ray and settles down at a lower energy. This is solar wind
charge exchange in action.
To establish a baseline for the soft X-ray background, the
researchers used data captured by the ROSAT mission in September 1990 in
a direction looking along, rather than into, the helium focusing cone.
The results, published online in the journal Nature on July 27, indicate
that only about 40 percent of the soft X-ray background originates
within the solar system.
"We now know that the emission comes from both sources but is
dominated by the local hot bubble,” said Galeazzi. "This is a
significant discovery. Specifically, the existence or nonexistence of
the local bubble affects our understanding of the area of the galaxy
close to the sun, and can, therefore, be used as a foundation for future
models of the galaxy structure."
Galeazzi and his collaborators are already planning the next flight
of DXL, which will include additional instruments to better characterize
the emission. The launch is currently planned for December 2015.
"The DXL team is an extraordinary example of cross-disciplinary
science, bringing together astrophysicists, planetary scientists, and
heliophysicists," added Porter. "It’s unusual but very rewarding when
scientists with such diverse interests come together to produce such
The Milky Way Galaxy as seen in infrared light. The pink shaded region is not visible from the
Northern Hemisphere, so has not been studied previously by the SDSS. The new phase of the SDSS
will see the entire galaxy.
Credit: The SDSS collaboration, Galaxy image credit: Two Micron All Sky Survey / Infrared Processing
and Analysis Center / Caltech & University of Massachusetts
MaNGA galaxy plate, showing the holes for the MaNGA IFUs and sky fibers.
(credit: D.R. Law)
SDSS images of the galaxies observed during the March 2014 MaNGA commissioning run at the Apache Point Observatory.
(credit: K. Bundy)
At the beginning of July, the Sloan Digital Sky Survey started a new phase with three major new programmes.
eBOSS will work to extend precision cosmological measurements to a critical early phase of cosmic history;
APOGEE-2 will expand the survey of the Galaxy across both the northern and southern hemispheres, and MaNGA
(with participation of the Max Planck Institute for Astrophysics) will for the first time be using the Sloan
spectrographs to make spatially resolved maps of individual galaxies. SDSS-IV will run from 2014 to 2020.
Building on its past successes, the Sloan Digital Sky Survey (SDSS) has launched a major new program
that will expand its census of the Universe into new areas it had been unable to explore before:
- Exploring the compositions and motions of stars across the entire Milky Way in unprecedented detail,
using a telescope in Chile.
- Making detailed maps of the internal structure of thousands of nearby galaxies to determine how they
have grown and changed over billions of years, using a cutting-edge measurement device.
-Measuring the expansion of the Universe in a poorly-understood five-billion-year period of the Universe's
history, using a new set of galaxies and quasars
The new survey is a collaboration of more than 200 astronomers at more than 40 institutions on four
continents, and incorporates telescopes in both the Northern and Southern Hemispheres. With these two
telescopes, the SDSS will be able to see the entire sky for the first time.
This new phase of the SDSS will provide a vast new database of observations that will significantly
expand our understanding of the nature of the Universe at all scales, from our own galaxy to the distant
universe. In our galaxy, the new SDSS will see hundreds of thousands of individual stars, including stars
that were born at the birth of the Milky Way and stars that were born yesterday. Measuring the
compositions, positions, and motions of individual stars will reveal how the Galaxy evolved from the
distant past to today.
In addition to the Sloan Foundation 2.5-meter Telescope in New Mexico, SDSS-IV will use the 2.5-meter
Irenee du Pont Telescope at Las Campanas Observatory in La Serena, high in the Chilean Andes and home
to the clearest skies on the planet. In addition to providing a 360-degree view of the Milky Way, the
new telescope will also observe stars in the nearby Magellanic Clouds, giving astronomers a better
understanding of the Milky Way's celestial environment.
But the Milky Way is far from the only galaxy that the new SDSS will examine. The new survey will employ
innovative new technology to make detailed maps of thousands of nearby galaxies. Unlike nearly all previous
astronomy surveys, which looked only at small areas in the centers of other galaxies, the new SDSS will
measure light from all over. These better maps are made possible through a new technique of bundling sets
of fiber optic cables into tightly-packed arrays. Those collect light from across the entire face of a galaxy,
enabling detailed spectral measurements of more than 10,000 nearby galaxies in less than one-twentieth of
MPA scientist Guinevere Kauffmann was heavily involved in planning the "Mapping Nearby Galaxies at APO" (MaNGA)
survey right from the beginning. MaNGA's goal is to understand the "life cycle" of present day galaxies
from imprinted clues of their birth and assembly, through their ongoing growth via star formation and merging,
to their death from quenching at late times.
"MaNGA will be key to disentangling the physical processes important in the lives of galaxies," Guinevere Kauffmann
points out. "In particular, we need to understand which aspects of galaxies are set by cosmological initial
conditions and which are set by black holes."
And the new SDSS will continue to improve our understanding of the Universe as a whole. It will precisely
measure the expansion history of the universe through 80% of cosmic history, back to when the Universe was
less than three billion years old. These new detailed measurements will help to improve constraints on
the nature of dark energy, the most mysterious experimental result in modern physics.
The new cosmology measurements will include a survey of nearly all the quasars, which will allow for
precision measurements of the history of the Universe's expansion in ways never before possible. Other
programs within the new SDSS will follow up on galaxies seen by prior X-ray surveys, and will conduct
the first systematic spectral study of variable objects, yielding a critical resource astronomers can
use to identify the nature of many types of time-varying light sources discovered in previous surveys.
SDSS Press Officer:
Jordan Raddick, SDSS-III Public Information Officer, Johns Hopkins University
Email:email@example.com Phone: 1-410-516-8889
Contact at MPA:
Max-Planck-Institut für Astrophysik
Phone: 089 30000-2013
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Max-Planck-Institut für Astrophysik
Tel: +49 (89) 30 000 3980
ABOUT THE SLOAN DIGITAL SKY SURVEY
Funding for the Sloan Digital Sky Survey IV has been provided by the Alfred P. Sloan Foundation
and the Participating Institutions. SDSS-IV acknowledges support and resources from the Center
for High-Performance Computing at the University of Utah. The SDSS web site iswww.sdss.org.
SDSS-IV is managed by the Astrophysical Research Consortium for the Participating Institutions
of the SDSS Collaboration including the Carnegie Institution for Science, Carnegie Mellon University,
the Chilean Participation Group, Harvard-Smithsonian Center for Astrophysics, Instituto de Astrofisica
de Canarias, The Johns Hopkins University, Kavli Institute for the Physics and Mathematics of the
Universe (IPMU) / University of Tokyo, Lawrence Berkeley National Laboratory, Leibniz Institut für
Astrophysik Potsdam (AIP),Max-Planck-Institut für Astrophysik (MPA Garching), Max-Planck-Institut
für Extraterrestrische Physik (MPE), Max-Planck-Institut für Astronomie (MPIA Heidelberg), National
Astronomical Observatory of China, New Mexico State University, New York University, The Ohio State
University, Pennsylvania State University, Shanghai Astronomical Observatory, United Kingdom
Participation Group, Universidad Nacional Autonoma de Mexico, University of Arizona, University of
Colorado Boulder, University of Portsmouth, University of Utah, University of Washington, University
of Wisconsin, Vanderbilt University, and Yale University.
this artist's conception, the atmosphere of an Earth-like planet
displays a brownish haze - the result of widespread pollution. New
research shows that the upcoming James Webb Space Telescope potentially
could detect certain pollutants, specifically CFCs, in the atmospheres
of Earth-sized planets orbiting white dwarf stars. Credit: Christine Pulliam (CfA). High Resolution (jpg)-Low Resolution (jpg)
Cambridge, MA -Humanity
is on the threshold of being able to detect signs of alien life on
other worlds. By studying exoplanet atmospheres, we can look for gases
like oxygen and methane that only coexist if replenished by life. But
those gases come from simple life forms like microbes. What about
advanced civilizations? Would they leave any detectable signs?
They might, if they spew industrial pollution into the atmosphere.
New research by theorists at the Harvard-Smithsonian Center for
Astrophysics (CfA) shows that we could spot the fingerprints of certain
pollutants under ideal conditions. This would offer a new approach in
the search for extraterrestrial intelligence (SETI).
"We consider industrial pollution as a sign of intelligent life, but
perhaps civilizations more advanced than us, with their own SETI
programs, will consider pollution as a sign of unintelligent life since
it's not smart to contaminate your own air," says Harvard student and
lead author Henry Lin.
"People often refer to ETs as 'little green men,' but the ETs
detectable by this method should not be labeled 'green' since they are
environmentally unfriendly," adds Harvard co-author Avi Loeb.
The team, which also includes Smithsonian scientist Gonzalo Gonzalez
Abad, finds that the upcoming James Webb Space Telescope (JWST) should
be able to detect two kinds of chlorofluorocarbons (CFCs) --
ozone-destroying chemicals used in solvents and aerosols. They
calculated that JWST could tease out the signal of CFCs if atmospheric
levels were 10 times those on Earth. A particularly advanced
civilization might intentionally pollute the atmosphere to high levels
and globally warm a planet that is otherwise too cold for life.
There is one big caveat to this work. JWST can only detect pollutants
on an Earth-like planet circling a white dwarf star, which is what
remains when a star like our Sun dies. That scenario would maximize the
atmospheric signal. Finding pollution on an Earth-like planet orbiting a
Sun-like star would require an instrument beyond JWST -- a
The team notes that a white dwarf might be a better place to look for
life than previously thought, since recent observations found planets
in similar environments. Those planets could have survived the bloating
of a dying star during its red giant phase, or have formed from the
material shed during the star's death throes.
While searching for CFCs could ferret out an existing alien
civilization, it also could detect the remnants of a civilization that
annihilated itself. Some pollutants last for 50,000 years in Earth's
atmosphere while others last only 10 years. Detecting molecules from the
long-lived category but none in the short-lived category would show
that the sources are gone.
"In that case, we could speculate that the aliens wised up and
cleaned up their act. Or in a darker scenario, it would serve as a
warning sign of the dangers of not being good stewards of our own
planet," says Loeb.
This work has been accepted for publication in The Astrophysical Journal and is available online.
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.
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Mass map of galaxy cluster MCS J0416.1–2403 using strong and weak lensing
Stunning new observations from Frontier Fields
Astronomers using the NASA/ESA Hubble
Space Telescope have mapped the mass within a galaxy cluster more
precisely than ever before. Created using observations from Hubble's
Frontier Fields observing programme, the map shows the amount and
distribution of mass within MCS J0416.1–2403, a massive galaxy cluster
found to be 160 trillion times the mass of the Sun. The detail in this
mass map was made possible thanks to the unprecedented depth of data
provided by new Hubble observations, and the cosmic phenomenon known as
strong gravitational lensing.
Measuring the amount and distribution of mass within distant objects
in the Universe can be very difficult. A trick often used by astronomers
is to explore the contents of large clusters of galaxies by studying
the gravitational effects they have on the light from very distant
objects beyond them. This is one of the main goals of Hubble's Frontier Fields,
an ambitious observing programme scanning six different galaxy clusters
— including MCS J0416.1–2403, the cluster shown in this stunning new
Large clumps of mass in the Universe warp and distort the space-time
around them. Acting like lenses, they appear to magnify and bend light
that travels through them from more distant objects .
Despite their large masses, the effect of galaxy clusters on their
surroundings is usually quite minimal. For the most part they cause what
is known as weak lensing,
making even more distant sources appear as only slightly more
elliptical or smeared across the sky. However, when the cluster is large
and dense enough and the alignment of cluster and distant object is
just right, the effects can be more dramatic. The images of normal
galaxies can be transformed into rings and sweeping arcs of light, even
appearing several times within the same image. This effect is known as strong lensing,
and it is this phenomenon, seen around the six galaxy clusters targeted
by the Frontier Fields programme, that has been used to map the mass
distribution of MCS J0416.1–2403, using the new Hubble data.
"The depth of the data lets us see very faint objects and has
allowed us to identify more strongly lensed galaxies than ever before,"
explains Mathilde Jauzac of Durham University, UK, and Astrophysics
& Cosmology Research Unit, South Africa, lead author of the new
Frontier Fields paper. "Even though strong lensing magnifies the
background galaxies they are still very far away and very faint. The
depth of these data means that we can identify incredibly distant
background galaxies. We now know of more than four times as many
strongly lensed galaxies in the cluster than we did before."
Using Hubble's Advanced Camera for Surveys,
the astronomers identified 51 new multiply imaged galaxies around the
cluster, quadrupling the number found in previous surveys and bringing
the grand total of lensed galaxies to 68. Because these galaxies are
seen several times this equates to almost 200 individual strongly lensed
images which can be seen across the frame. This effect has allowed
Jauzac and her colleagues to calculate the distribution of visible and
dark matter in the cluster and produce a highly constrained map of its
"Although we’ve known how to map the mass of a cluster using
strong lensing for more than twenty years, it’s taken a long time to get
telescopes that can make sufficiently deep and sharp observations, and
for our models to become sophisticated enough for us to map, in such
unprecedented detail, a system as complicated as MCS J0416.1–2403," says team member Jean-Paul Kneib.
By studying 57 of the most reliably and clearly lensed galaxies, the
astronomers modelled the mass of both normal and dark matter within MCS
J0416.1-2403. "Our map is twice as good as any previous models of this cluster!" adds Jauzac.
The total mass within MCS J0416.1-2403 — modelled to be over 650 000
light-years across — was found to be 160 trillion times the mass of the
Sun. This measurement is several times more precise than any other
cluster map, and is the most precise ever produced .
By precisely pinpointing where the mass resides within clusters like
this one, the astronomers are also measuring the warping of space-time
with high precision.
"Frontier Fields' observations and gravitational lensing
techniques have opened up a way to very precisely characterise distant
objects — in this case a cluster so far away that its light has taken
four and a half billion years to reach us," adds Jean-Paul Kneib. "But,
we will not stop here. To get a full picture of the mass we need to
include weak lensing measurements too. Whilst it can only give a rough
estimate of the inner core mass of a cluster, weak lensing provides
valuable information about the mass surrounding the cluster core."
The team will continue to study the cluster using ultra-deep Hubble
imaging and detailed strong and weak lensing information to map the
outer regions of the cluster as well as its inner core, and will thus be
able to detect substructures in the cluster's surroundings. They will
also take advantage of X-ray measurements of hot gas and spectroscopic
redshifts to map the contents of the cluster, evaluating the respective
contribution of dark matter, gas and stars .
Combining these sources of data will further enhance the detail of
this mass distribution map, showing it in 3D and including the relative
velocities of the galaxies within it. This paves the way to
understanding the history and evolution of this galaxy cluster.
The results of the study will be published online in Monthly Notices of the Royal Astronomical Society on 24 July 2014.
 The cluster is also known as MACS J0416.1–2403.
 The warping of space-time by large objects in the
Universe was one of the predictions of Albert Einstein’s theory of
 Gravitational lensing is one of the few methods
astronomers have to find out about dark matter. Dark matter, which makes
up around three quarters of all matter in the Universe, cannot be seen
directly as it does not emit or reflect any light, and can pass through
other matter without friction (it is collisionless). It interacts only
by gravity, and its presence must be deduced from its gravitational
 The uncertainty on the measurement is only around
0.5%, or 1 trillion times the mass of the sun. This may not seem
precise but it is for a measurement such as this.
 NASA's Chandra X-ray Observatory
was used to obtain X-ray measurements of hot gas in the cluster and
ground based observatories provide the data needed to measure
Notes for editors
The Hubble Space Telescope is a project of international cooperation between ESA and NASA.
The international team of astronomers in this study consists of M. Jauzac (Durham University, UK and Astrophysics & Cosmology Research Unit, South Africa);
B. Clement (University of Arizona, USA); M. Limousin (Laboratoire
d’Astrophysique de Marseille, France and University of Copenhagen,
Denmark); J. Richard (Université Lyon, France); E. Jullo (Laboratoire
d’Astrophysique de Marseille, France); H. Ebeling (University of Hawaii,
USA); H. Atek (Ecole Polytechnique Fédérale de Lausanne, Switzerland);
J.-P. Kneib (Ecole Polytechnique Fédérale de Lausanne, Switzerland and
Laboratoire d’Astrophysique de Marseille, France); K. Knowles
(University of KwaZulu-Natal, South Africa); P. Natarajan (Yale
University, USA); D. Eckert (University of Geneva, Switzerland); E.
Egami (University of Arizona, USA); R. Massey (Durham University, UK);
and M. Rexroth (Ecole Polytechnique Fédérale de Lausanne, Switzerland).
Credit: ESA/Hubble & NASA Acknowledgement: Nick Rose
The thin, glowing streak slicing across this image cuts a lonely
figure, with only a few foreground stars and galaxies in the distant
background for company.
However, this is all a case of perspective; lying out of frame is
another nearby spiral. Together, these two galaxies make up a pair,
moving through space together and keeping one another company.
The subject of this Hubble image is called NGC 3501, with NGC 3507
as its out-of-frame companion. The two galaxies look very different —
another example of the importance of perspective. NGC 3501 appears
edge-on, giving it an elongated and very narrow appearance. Its partner,
however, looks very different indeed, appearing face-on and giving us a
fantastic view of its barred swirling arms.
While similar arms may not be visible in this image of NGC 3501, this
galaxy is also a spiral — although it is somewhat different from its
companion. While NGC 3507 has bars cutting through its centre, NGC 3501
does not. Instead, its loosely wound spiral arms all originate from its
centre. The bright gas and stars that make up these arms can be seen
here glowing brightly, mottled by the dark dust lanes that trace across
This is an artistic illustration of the gas giant planet HD 209458b
(unofficially named Osiris) located 150 light-years away in the
constellation Pegasus. This is a "hot Jupiter" class planet. Estimated
to be 220 times the mass of Earth. The planet's atmosphere is a
seething 2,150 degrees Fahrenheit. It orbits very closely to its bright
sunlike star, and the orbit is tilted edge-on to Earth. This makes the
planet an ideal candidate for the Hubble Space Telescope to be used to
make precise measurements of the chemical composition of the giant's
atmosphere as starlight filters though it. To the surprise of
astronomers, they have found much less water vapor in the atmosphere
than standard planet-formation models predict. Credit:NASA,ESA, and G.Bacon (STScI)
This graph compares observations with modeled infrared spectra of
three hot-Jupiter-class exoplanets that were spectroscopically observed
with the Hubble Space Telescope. The red curve in each case is the
best-fit model spectrum for the detection of water vapor absorption in
the planetary atmosphere. The blue circles and error bars show the
processed and analyzed data from Hubble's spectroscopic observations. Credit:NASA, ESA, N. Madhusudhan (University of Cambridge), and A. Feild and G. Bacon (STScI)
Astronomers using NASA's Hubble Space Telescope have gone looking for
water vapor in the atmospheres of three planets orbiting stars similar
to the Sun — and have come up nearly dry.
The three planets, HD 189733b, HD 209458b, and WASP-12b, are between
60 and 900 light-years away. These giant gaseous worlds are so hot,
with temperatures between 1,500 and 4,000 degrees Fahrenheit, that they
are ideal candidates for detecting water vapor in their atmospheres.
However, to the surprise of the researchers, the planets surveyed
have only one-tenth to one one-thousandth the amount of water predicted
by standard planet-formation theories.
"Our water measurement in one of the planets, HD 209458b, is the
highest-precision measurement of any chemical compound in a planet
outside the solar system, and we can now say with much greater
certainty than ever before that we've found water in an exoplanet,"
said Dr. Nikku Madhusudhan of the Institute of Astronomy at the
University of Cambridge, United Kingdom, who led the research.
"However, the low water abundance we are finding is quite astonishing."
Madhusudhan said that this finding presents a major challenge to
exoplanet theory. "It basically opens a whole can of worms in planet
formation. We expected all these planets to have lots of water in them.
We have to revisit planet formation and migration models of giant
planets, especially 'hot Jupiters', and investigate how they're formed."
He emphasizes that these results, though found in these large hot
planets close to their parent stars, may have major implications for
the search for water in potentially habitable Earth-sized exoplanets.
Instruments on future space telescopes may need to be designed with a
higher sensitivity if target planets are drier than predicted. "We
should be prepared for much lower water abundances than predicted when
looking at super-Earths (rocky planets that are several times the mass
of Earth)," Madhusudhan said.
Using near-infrared spectra of the planets observed with Hubble,
Madhusudhan and his collaborators from the Space Telescope Science
Institute, Baltimore, Maryland; the University of Maryland, College
Park, Maryland; the Johns Hopkins University, Baltimore, Maryland; and
the Dunlap Institute at the University of Toronto, Ontario, Canada,
estimated the amount of water vapor in the planetary atmospheres based
on sophisticated computer models and statistical techniques to explain
The planets were selected because they orbit relatively bright stars
that provide enough radiation for an infrared-light spectrum to be
taken. Absorption features from the water vapor in the planet's
atmosphere are superimposed on the small amount of starlight that
glances through the planet's atmosphere.
Detecting water is almost impossible for transiting planets from the
ground because Earth's atmosphere has a lot of water in it that
contaminates the observation. "We really need the Hubble Space
Telescope to make such observations," said Nicolas Crouzet of the
Dunlap Institute at the University of Toronto and co-author of the
The currently accepted theory on how giant planets in our solar
system formed is known as core accretion, in which a planet is formed
around the young star in a protoplanetary disk made primarily of
hydrogen, helium, and particles of ices and dust composed of other
chemical elements. The dust particles stick to each other, eventually
forming larger and larger grains. The gravitational forces of the disk
draw in these grains and larger particles until a solid core forms.
This core then leads to runaway accretion of both solids and gas to
eventually form a giant planet.
This theory predicts that the proportions of the different elements
in the planet are enhanced relative to those in their star, especially
oxygen that is supposed to be the most enhanced. Once the giant planet
forms, its atmospheric oxygen is expected to be largely encompassed
within water molecules. The very low levels of water vapor found by
this research raises a number of questions about the chemical
ingredients that lead to planet formation, say researchers.
"There are so many things we still don't know about exoplanets, so
this opens up a new chapter in understanding how planets and solar
systems form," said Drake Deming of the University of Maryland, who led
one of the precursor studies. "The problem is that we are assuming the
water to be as abundant as in our own solar system. What our study has
shown is that water features could be a lot weaker than our
The findings are being published on July 24 in The Astrophysical Journal Letters.
Space Telescope Science Institute, Baltimore, Md.
Institute of Astronomy, University of Cambridge, United Kingdom
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data from NASA's Kepler and Spitzer Space Telescopes, scientists have
made the most precise measurement ever of the size of a world outside
our solar system, as illustrated in this artist's conception.Image Credit: NASA/JPL-Caltech.Full image and caption
to NASA's Kepler and Spitzer Space Telescopes, scientists have made the
most precise measurement ever of the radius of a planet outside our
solar system. The size of the exoplanet, dubbed Kepler-93b, is now known
to an uncertainty of just 74 miles (119 kilometers) on either side of
the planetary body.
The findings confirm Kepler-93b as a "super-Earth" that is about
one-and-a-half times the size of our planet. Although super-Earths are
common in the galaxy, none exist in our solar system. Exoplanets like
Kepler-93b are therefore our only laboratories to study this major class
With good limits on the sizes and masses of super-Earths, scientists
can finally start to theorize about what makes up these weird worlds.
Previous measurements, by the Keck Observatory in Hawaii, had put
Kepler-93b's mass at about 3.8 times that of Earth. The density of
Kepler-93b, derived from its mass and newly obtained radius, indicates
the planet is in fact very likely made of iron and rock, like Earth.
"With Kepler and Spitzer, we've captured the most precise measurement
to date of an alien planet's size, which is critical for understanding
these far-off worlds," said Sarah Ballard, a NASA Carl Sagan Fellow at
the University of Washington in Seattle and lead author of a paper on
the findings published in the Astrophysical Journal.
"The measurement is so precise that it's literally like being able to
measure the height of a six-foot tall person to within three quarters
of an inch -- if that person were standing on Jupiter," said Ballard.
Kepler-93b orbits a star located about 300 light-years away, with
approximately 90 percent of the sun's mass and radius. The exoplanet's
orbital distance -- only about one-sixth that of Mercury's from the sun
-- implies a scorching surface temperature around 1,400 degrees
Fahrenheit (760 degrees Celsius). Despite its newfound similarities in
composition to Earth, Kepler-93b is far too hot for life.
To make the key measurement about this toasty exoplanet's radius, the
Kepler and Spitzer telescopes each watched Kepler-93b cross, or
transit, the face of its star, eclipsing a tiny portion of starlight.
Kepler's unflinching gaze also simultaneously tracked the dimming of the
star caused by seismic waves moving within its interior. These readings
encode precise information about the star's interior. The team
leveraged them to narrowly gauge the star's radius, which is crucial for
measuring the planetary radius.
Spitzer, meanwhile, confirmed that the exoplanet's transit looked the
same in infrared light as in Kepler's visible-light observations. These
corroborating data from Spitzer -- some of which were gathered in a
new, precision observing mode -- ruled out the possibility that Kepler's
detection of the exoplanet was bogus, or a so-called false positive.
Taken together, the data boast an error bar of just one percent of
the radius of Kepler-93b. The measurements mean that the planet,
estimated at about 11,700 miles (18,800 kilometers) in diameter, could
be bigger or smaller by about 150 miles (240 kilometers), the
approximate distance between Washington, D.C., and Philadelphia.
Spitzer racked up a total of seven transits of Kepler-93b between
2010 and 2011. Three of the transits were snapped using a "peak-up"
observational technique. In 2011, Spitzer engineers repurposed the
spacecraft's peak-up camera, originally used to point the telescope
precisely, to control where light lands on individual pixels within
Spitzer's infrared camera.
The upshot of this rejiggering: Ballard and her colleagues were able
to cut in half the range of uncertainty of the Spitzer measurements of
the exoplanet radius, improving the agreement between the Spitzer and
"Ballard and her team have made a major scientific advance while
demonstrating the power of Spitzer's new approach to exoplanet
observations," said Michael Werner, project scientist for the Spitzer
Space Telescope at NASA's Jet Propulsion Laboratory, Pasadena,
JPL 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.
NASA's Ames Research Center in Moffett Field, California, is
responsible for Kepler's ground system development, mission operations
and science data analysis. JPL managed Kepler mission development. Ball
Aerospace & Technologies Corp. in Boulder, Colorado, developed the
Kepler flight system and supports mission operations with the Laboratory
for Atmospheric and Space Physics at the University of Colorado in
Boulder. The Space Telescope Science Institute in Baltimore archives,
hosts and distributes Kepler science data. Kepler is NASA's 10th
Discovery Mission and was funded by the agency's Science Mission
For more information about the Kepler mission, visit: