Releases from NASA, NASA's Galex, NASA's Goddard Space Flight Center, HubbleSite, Spitzer, Cassini, ESO, ESA, Chandra, HiRISE, Royal Astronomical Society, NRAO, Astronomy Picture of the Day, Harvard-Smithsonian Center For Astrophysics, Max Planck Institute for Astrophysics, Gemini Observatory, Subaru Telescope, W. M. Keck Observatory, Fermi Gamma-ray Space Telescope, JPL-Caltech, etc
Within the swaddling dust of the Serpens
Cloud Core, astronomers are studying one of the youngest collections of
stars ever seen in our galaxy. Image credit: NASA/JPL-Caltech/2MASS.Full image and caption
Stars that are just beginning to coalesce out of cool swaths of dust
and gas are showcased in this image from NASA's Spitzer Space Telescope
and the Two Micron All Sky Survey (2MASS). Infrared light has been
assigned colors we see with our eyes, revealing young stars in orange
and yellow, and a central parcel of gas in blue. This area is hidden in
visible-light views, but infrared light can travel through the dust,
offering a peek inside the stellar hatchery.
The dark patch to the left of center is swaddled in so much dust,
even the infrared light is blocked. It is within these dark wombs that
stars are just beginning to take shape.
Called the Serpens Cloud Core, this star-forming region is located
about 750 light-years away in Serpens, or the "Serpent," a constellation
named after its resemblance to a snake in visible light. The region is
noteworthy as it only contains stars of relatively low to moderate mass,
and lacks any of the massive and incredibly bright stars found in
larger star-forming regions like the Orion nebula. Our sun is a star of
moderate mass. Whether it formed in a low-mass stellar region like
Serpens, or a high-mass stellar region like Orion, is an ongoing
The inner Serpens Cloud Core is remarkably detailed in this image. It
was assembled from 82 snapshots representing a whopping 16.2 hours of
Spitzer observing time. The observations were made during Spitzer's
"warm mission," a phase that began in 2009 after the observatory ran out
of liquid coolant, as planned.
Most of the small dots in this image are stars located behind, or in front of, the Serpens nebula.
The 2MASS mission was a joint effort between the California Institute
of Technology, Pasadena; the University of Massachusetts, Amherst; and
NASA's Jet Propulsion Laboratory, also in 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. For more information about
Credit: ESA/Hubble & NASA Acknowledgements: R. Sahai (Jet Propulsion Laboratory), Serge Meunier
This new Hubble image shows IRAS 14568-6304, a young star that is
cloaked in a haze of golden gas and dust. It appears to be embedded
within an intriguing swoosh of dark sky, which curves through the image
and obscures the sky behind.
This dark region is known as the Circinus molecular cloud. This cloud
has a mass around 250 000 times that of the Sun, and it is filled with
gas, dust and young stars. Within this cloud lie two prominent and
enormous regions known colloquially to astronomers as Circinus-West and
Circinus-East. Each of these clumps has a mass of around 5000 times that
of the Sun, making them the most prominent star-forming sites in the
Circinus cloud. The clumps are associated with a number of young stellar
objects, and IRAS 14568-6304, featured here under a blurry fog of gas
within Circinus-West, is one of them.
IRAS 14568-6304 is special because it is driving a protostellar jet,
which appears here as the "tail" below the star. This jet is the
leftover gas and dust that the star took from its parent cloud in order
to form. While most of this material forms the star and its accretion
disc — the disc of material surrounding the star, which may one day form
planets — at some point in the formation process the star began to
eject some of the material at supersonic speeds through space. This
phenomenon is not only beautiful, but can also provide us with valuable
clues about the process of star formation.
IRAS 14568-6304 is one of several outflow sources in the
Circinus-West clump. Together, these sources make up one of the
brightest, most massive, and most energetic outflows ever reported.
Scientists have even suggested calling Circinus-West the "nest of
molecular outflows" in tribute to this activity.
A version of this image was entered into the Hubble's Hidden Treasures image processing competition by contestant Serge Meunier.
A false-color imageof the Smith Cloud made with data from the Green Bank Telescope
(GBT). New analysis indicates that it is wrapped in a dark matter halo.
Like a bullet wrapped in a full metal jacket, a high-velocity hydrogen
cloud hurtling toward the Milky Way appears to be encased in a shell of
dark matter, according to a new analysis of data from the National
Science Foundation’s Robert C. Byrd Green Bank Telescope (GBT).
Astronomers believe that without this protective shell, the
high-velocity cloud (HVC) known as the Smith Cloud would have
disintegrated long ago when it first collided with the disk of our
If confirmed by further observations, a halo of dark
matter could mean that the Smith Cloud is actually a failed dwarf
galaxy, an object that has all the right stuff to form a true galaxy,
just not enough to produce stars.
“The Smith Cloud is really
one of a kind. It’s fast, quite extensive, and close enough to study in
detail,” said Matthew Nichols with the Sauverny Observatory in
Switzerland and principal author on a paper accepted for publication in
the Monthly Notices of the Royal Astronomical Society. “It’s also
a bit of a mystery; an object like this simply shouldn’t survive a trip
through the Milky Way, but all the evidence points to the fact that it
Previous studies of the Smith Cloud revealed that it
first passed through our Galaxy many millions of years ago. By
reexamining and carefully modeling the cloud, astronomers now believe
that the Smith Cloud contains and is actually wrapped in a substantial
“halo” of dark matter -- the gravitationally significant yet invisible
stuff that makes up roughly 80 percent of all the matter in the
“Based on the currently predicted orbit, we show that
a dark matter free cloud would be unlikely to survive this disk
crossing,” observed Jay Lockman, an astronomer at the National Radio
Astronomy Observatory in Green Bank, West Virginia, and one of the
coauthors on the paper. “While a cloud with dark matter easily survives
the passage and produces an object that looks like the Smith Cloud
The Milky Way is swarmed by hundreds of high-velocity
clouds, which are made up primarily of hydrogen gas that is too rarefied
to form stars in any detectable amount. The only way to observe these
objects, therefore, is with exquisitely sensitive radio telescopes like
the GBT, which can detect the faint emission of neutral hydrogen. If it
were visible with the naked eye, the Smith Cloud would cover almost as
much sky as the constellation Orion.
Most high-velocity clouds
share a common origin with the Milky Way, either as the leftover
building blocks of galaxy formation or as clumps of material launched by
supernovas in the disk of the galaxy. A rare few, however, are
interlopers from farther off in space with their own distinct pedigree. A
halo of dark matter would strengthen the case for the Smith Cloud being
one of these rare exceptions.
Currently, the Smith Cloud is
about 8,000 light-years away from the disk of our Galaxy. It is moving
toward the Milky Way at more than 150 miles per second and is predicted
to impact again in approximately 30 million years.
to have dark matter this would in effect be a failed galaxy,” said
Nichols. “Such a discovery would begin to show the lower limit of how
small a galaxy could be.” The researchers believe this could also
improve our understanding of the Milky Way's earliest star formation.
An international team of astronomers, led by Dr.
Tae-Soo Pyo (Subaru Telescope, NAOJ), has revealed a complicated outflow
structure in the binary UY Aur (Aurigae). The team observed the binary
using the Gemini North's NIFS (Near-Infrared Integral Field
Spectrometer) with the Altair adaptive optics system (Note 1). The team found that the primary star has a wide, open outflow, while the secondary star has a well-collimated jet.
Because many stars form together as companions in
binary or multiple systems, investigating these systems is essential for
understanding star and planet formation. Although jets (i.e., narrow
bright streams of gas) and outflows (i.e., less collimated flows of gas)
from single young stars are ubiquitous, only a few observations have
shown jets or outflows from multiple, low-mass young stars. Therefore,
the current team chose to examine the outflow structure of binary UY
Aur, which is a close binary system composed of young stars separated by
less than an arcsecond (0".89).
To better understand this system, the team began by
trying to identify the driving source of the receding jets. To separate
the binary stars and distinguish their driving sources, they used Gemini
North's NIFS with its adaptive optics system to observe this close
binary system in the 1-micrometer infrared wavelength region. Since
ionized iron gas ([Fe II]) traces shocked gas in jets and outflows very
well, the team used iron gas emissions to examine the emission gas
distribution. They found that [Fe II] is associated with both the
primary and the secondary stars (Figure 1).
Figure 1:Emission images of UY Aur. The large plus
marks indicate the primary star, located in the upper portion of each
panel and designated as "A" in the continuum image. The smaller plus
marks indicate the secondary star, located below the primary star and
labeled as "B" in the continuum panel. Large tick marks correspond to
measures of 1 arcsecond (140 Astronomical Unit). The filled circles at
the bottom right corners show the spatial resolution (=0.12"). (Credit:
In addition, they found that the shape of the gas
distribution conformed to simulations of gas streaming between the
primary and secondary stars. However, the high velocity of the gas (100
km/s or > 20,000 mile/h) indicated that it emanated from the close
vicinity of stars rather than arose in the disk gas around the two
Further investigation of the emission structure involved separation of the receding and approaching emissions (Figure 1).
The team found that the distribution of gas was different for each of
the stars. While the approaching gas was widely spread in an outflow
from the primary star and slightly connected with the secondary star,
the receding gas was spread widely toward the secondary star and flowing
beyond it (Figure 1).
Redshifted and blueshifted outflows. The primary star (A) shows wide,
open, redshifted and blueshifted outflows as well as a redshifted jet
(in solid red), while the secondary star (B) shows a blueshifted jet (in
solid blue). Redshifted jets from B might be within the solid red
outflow area from A. (Credit NAOJ).
Right: Model of the UY Aur binary
and its outflows and jets, showing the wide redshifted and blueshifted
outflows of the primary star (A) and the blueshifted jet from the
secondary star (B). The dotted red lines indicate where the redshifted
jets from the secondary star might be. (Credit: NAOJ)
What explains this difference? The team analyzed the
system in terms of bipolar outflows, i.e., each star has a disk and
ejects both blueshifted (approaching) and redshifted (receding) outflows
or jets. The primary ejects wide,open bipolar outflows. Its redshifted
(receding) outflow overlaps with the secondary. In contrast, the
approaching gas from the secondary is distributed in a well-collimated
bipolar jet, with its blueshifted flow tilted toward the wide, open wind
from the primary (Figure 2).
It is known from mid-infrared (wavelength of ~10 micrometer)
observations that the circumstellar disk of the secondary is not aligned
with the plane of the circumbinary disk. This misalignment is
consistent with the jet from the secondary tilted toward the wide, open
outflow from the primary star.
Two jets from a binary system can be explained if the
jets emanate from each of the star-disk systems. Some binaries show
only one jet or outflow. A larger sample of [Fe II] gas distribution
toward binary and multiple young-star systems can clarify how typical
the outflow structure of the UY Aur system is.
Figure 3:Artist's rendition of UY Aur's probable outflow system (Credit: NAOJ)
The observations were conducted as part of the Subaru/Gemini Time
Exchange Program, during which astronomers from each telescope's
community can mutually access some of each telescope's unique
Active, supermassive black holes at the
hearts of galaxies tend to fall into two categories: those that are
hidden by dust, and those that are exposed. Image credit:
NASA/JPL-Caltech.Full image and caption
This infographic explains a popular theory
of active supermassive black holes, referred to as the unified model --
and how new data from NASA's Wide-field Infrared Survey Explorer, or
WISE, is at conflict with the model. Image credit:
NASA/JPL-Caltech/NOAO/AURA/NSF/ESO.Full image and caption - enlarge image
A survey of more than 170,000 supermassive black holes, using NASA's
Wide-field Infrared Survey Explorer (WISE), has astronomers reexamining a
decades-old theory about the varying appearances of these interstellar
The unified theory of active, supermassive black holes, first
developed in the late 1970s, was created to explain why black holes,
though similar in nature, can look completely different. Some appear to
be shrouded in dust, while others are exposed and easy to see.
The unified model answers this question by proposing that every black
hole is surrounded by a dusty, doughnut-shaped structure called a
torus. Depending on how these "doughnuts" are oriented in space, the
black holes will take on various appearances. For example, if the
doughnut is positioned so that we see it edge-on, the black hole is
hidden from view. If the doughnut is observed from above or below,
face-on, the black hole is clearly visible.
However, the new WISE results do not corroborate this theory. The
researchers found evidence that something other than a doughnut
structure may, in some circumstances, determine whether a black hole is
visible or hidden. The team has not yet determined what this may be, but
the results suggest the unified, or doughnut, model does not have all
"Our finding revealed a new feature about active black holes we never
knew before, yet the details remain a mystery," said Lin Yan of NASA's
Infrared Processing and Analysis Center (IPAC), based at the California
Institute of Technology in Pasadena. "We hope our work will inspire
future studies to better understand these fascinating objects."
Yan is the second author of the research accepted for publication in
the Astrophysical Journal. The lead author is a post-doctoral
researcher, Emilio Donoso, who worked with Yan at IPAC and has since
moved to the Instituto de Ciencias Astronómicas, de la Tierra y del
Espacio in Argentina. The research also was co-authored by Daniel Stern
at NASA's Jet Propulsion Laboratory in Pasadena, California, and Roberto
Assef of Universidad Diego Portales in Chile and formerly of JPL.
Every galaxy has a massive black hole at its heart. The new study
focuses on the "feeding" ones, called active, supermassive black holes,
or active galactic nuclei. These black holes gorge on surrounding gas
material that fuels their growth.
With the aid of computers, scientists were able to pick out more than
170,000 active supermassive black holes from the WISE data. They then
measured the clustering of the galaxies containing both hidden and
exposed black holes -- the degree to which the objects clump together
across the sky.
If the unified model were true, and the hidden black holes are simply
blocked from view by doughnuts in the edge-on configuration, then
researchers would expect them to cluster in the same way as the exposed
ones. According to theory, since the doughnut structures would take on
random orientations, the black holes should also be distributed
randomly. It is like tossing a bunch of glazed doughnuts in the air --
roughly the same percentage of doughnuts always will be positioned in
the edge-on and face-on positions, regardless of whether they are
tightly clumped or spread far apart.
But WISE found something totally unexpected. The results showed the
galaxies with hidden black holes are more clumped together than those of
the exposed black holes. If these findings are confirmed, scientists
will have to adjust the unified model and come up with new ways to
explain why some black holes appear hidden.
"The main purpose of unification was to put a zoo of different kinds
of active nuclei under a single umbrella," said Donoso. Now, that has
become increasingly complex to do as we dig deeper into the WISE data."
Another way to understand the WISE results involves dark matter. Dark
matter is an invisible substance that dominates matter in the universe,
outweighing the regular matter that makes up people, planets and stars.
Every galaxy sits in the center of a dark matter halo. Bigger halos
have more gravity and, therefore, pull other galaxies toward them.
Because WISE found that the obscured black holes are more clustered
than the others, the researchers know those hidden black holes reside in
galaxies with larger dark matter halos. Though the halos themselves
would not be responsible for hiding the black holes, they could be a
clue about what is occurring.
"The unified theory was proposed to explain the complexity of what
astronomers were seeing," said Stern. "It seems that simple model may
have been too simple. As Einstein said, models should be made 'as simple
as possible, but not simpler.'"
Scientists still are actively combing public data from WISE, which
was put into hibernation in 2011 after scanning Earth's entire sky
twice. WISE was reactivated in 2013, renamed NEOWISE, and given a new
mission to identify potentially hazardous near-Earth objects.
Astar in a distant galaxyexplodes as a supernova: while observing a galaxy known as UGC 9379 (left; image from the Sloan Digital Sky Survey; SDSS) located about 360 million light years away from Earth, the team discovered a new source of bright blue light (right, marked with an arrow; image from the 60-inch robotic telescope at Palomar Observatory). This very hot, young supernova marked the explosive death of a massive star in that distant galaxy.
A detailed study of the spectrum (the distribution of colors composing
the light from the supernova) using a technique called “flash
spectroscopy” revealed the signature of a wind blown by the aging star
just prior to its terminal explosion, and allowed scientists to
determine what elements were abundant on the surface of the dying star
as it was about to explode as a supernova, providing important
information about how massive stars evolve just prior to their death,
and the origin of crucial elements such as carbon, nitrogen and oxygen.
The Palomar 48 inch telescope
Photo by: Iair Arcavi, Weizmann Instiute of Science
Berkeley Lab Researchers Help Catch a Wolf-Rayet Hours After it Goes Supernova
Our Sun may seem pretty impressive: 330,000 times as massive as
Earth, it accounts for 99.86 percent of the Solar System’s total mass;
it generates about 400 trillion trillion watts of power; and it has a
surface temperature of about 10,000 degrees Celsius. Yet for a star,
it’s a lightweight.
For the first time ever, scientists have direct confirmation that a
Wolf-Rayet star—sitting 360 million light years away in the Bootes
constellation—died in a violent explosion known as a Type IIb supernova.
Using the iPTF pipeline, researchers at Israel’s Weizmann Institute of Science
led by Avishay Gal-Yam caught supernova SN 2013cu within hours of its
explosion. They then triggered ground- and space-based telescopes to
observe the event approximately 5.7 hours and 15 hours after it
self-destructed. These observations are providing valuable insights into
the life and death of the progenitor Wolf-Rayet.
“Newly developed observational capabilities now enable us to study
exploding stars in ways we could only dream of before. We are moving
towards real-time studies of supernovae,” says Gal-Yam, an
astrophysicist in the Weizmann Institute’s Department of Particle
Physics and Astrophysics. He is also the lead author of a recently
published Nature paper on this finding.
“This is the smoking gun. For the first time, we can directly point to
an observation and say that this type of Wolf-Rayet star leads to this
kind of Type IIb supernova,” says Peter Nugent, who heads Berkeley Lab’s Computational Cosmology Center (C3) and leads the Berkeley contingent of the iPTF collaboration.
“When I identified the first example of a Type IIb supernova in 1987,
I dreamed that someday we would have direct evidence of what kind of
star exploded. It’s refreshing that we can now say that Wolf-Rayet stars
are responsible, at least in some cases,” says Alex Filippenko,
Professor of Astronomy at UC Berkeley. Both Filippenko and Nugent are
also co-authors on the Nature paper.
Elusive Signatures Illuminated in a Flash of Light
Some supermassive stars become Wolf-Rayets in the final stages of
their lives. Scientists find these stars interesting because they enrich
galaxies with the heavy chemical elements that eventually become the
building blocks for planets and life.
“We are gradually determining which kinds of stars explode, and why,
and what kinds of elements they produce,” says Filippenko. “These
elements are crucial to the existence of life. In a very real sense, we
are figuring out our own stellar origins.”
All stars—no matter what size—spend their lives fusing hydrogen atoms
to create helium. The more massive a star, the more gravity it wields,
which accelerates fusion in the star’s core, generating energy to
counteract gravitational collapse. When hydrogen is depleted, a
supermassive star continues to fuse even heavier elements like carbon,
oxygen, neon, sodium, magnesium and so on, until its core turns to iron.
At this point, atoms (even subatomic particles) are packed in so
closely that fusion no longer releases energy into the star. It is now
solely supported by electron degeneracy pressure—the quantum mechanical
law that prohibits two electrons from occupying the same quantum state.
When the core is massive enough, even electron degeneracy won’t
support the star and it collapses. Protons and electrons in the core
merge, releasing a tremendous amount of energy and neutrinos. This, in
turn, powers a shockwave that tears through the star ejecting its
remains violently into space as it goes supernova.
The Wolf-Rayet phase occurs before the supernova. As nuclear fusion
slows, the heavy elements forged in the star’s core rise to the surface
setting off powerful winds. These winds shed a tremendous amount of
material into space and obscure the star from prying telescopes on
“When a Wolf-Rayet star goes supernova, the explosion typically
overtakes the stellar wind and all information about the progenitor star
is gone,” says Nugent. “We got lucky with SN 2013cu—we caught the
supernova before it overtook the wind. Shortly after the star exploded,
it let out an ultraviolet flash from the shock wave that heated and lit
up the wind. The conditions that we observed in this moment were very
similar to what was there before the supernova.”
Before the supernova debris overtook the wind, the iPTF team managed
to capture its chemical light signatures (or spectra) with the
ground-based Keck telescope
in Hawaii and saw the telltale signs of a Wolf-Rayet star. When the
iPTF team performed follow-up observations 15 hours later with NASA’s Swift satellite,
the supernova was still quite hot and strongly emitting in the
ultraviolet. In the following days, iPTF collaborators rallied
telescopes around the globe to watch the supernova crash into material
that had been previously ejected from the star. As the days went by, the
researchers were able to classify SN 2013cu as a Type IIb supernova
because of the weak hydrogen signatures and strong helium features in
the spectra that appeared after the supernova cooled.
“With a series of observations, including data I took with the Keck-I
telescope 6.5 days after the explosion, we could see that the
supernova’s expanding debris quickly overtook the flash-ionized wind
that had revealed the Wolf-Rayet features. So, catching the supernova
sufficiently early is hard—you’ve got to be on the ball, as our team
was,” says Filippenko.
“This discovery was totally shocking, it opens up a whole new
research area for us,” says Nugent. “With our largest telescopes you
might have a chance of getting a spectrum of a Wolf-Rayet star in the
nearest galaxies to our Milky Way, perhaps 4 million light years away.
SN 2013cu is 360 million light years away—further by almost factor of
And because the researchers caught the supernova early—when the
ultraviolet flash lit up the progenitor’s stellar wind—they were able to
take several spectra. “Ideally, we’d like to do this again and again
and develop some interesting statistics, not just for supernovae with
Wolf-Rayet progenitors but other types as well,” says Nugent.
Pipeline Upgrade Leads to Unexpected Discoveries
Since February 2014, the iPTF survey has been scanning the sky
nightly with a robotic telescope mounted on the 48-inch Samuel Oschin
Telescope at Palomar Observatory in Southern California. As soon as
observations are taken, the data travel more than 400 miles to NERSC in
Oakland via the National Science Foundation’s High Performance Wireless
Research and Education Network and the Department of Energy’s ESnet. At
NERSC, the Real-Time Transient Detection Pipeline sifts through the
data, identifies events to follow up on and sends an alert to iPTF
scientists around the globe.
The survey was built on the legacy of the Palomar Transient Factory
(PTF), designed in 2008 to systematically chart the transient sky by
using the same camera at Palomar Observatory. Last year Nugent and
colleagues at Caltech and UC Berkeley made significant modifications to
the transient detection pipeline for the iPTF project. Working with
NERSC staff, Nugent upgraded the pipeline’s computing and storage
hardware. The iPTF team also made improvements to the machine learning
algorithms at the heart of the detection pipeline and incorporated the Sloan Digital Star Survey III star and galaxy catalogs so the pipeline could immediately reject known variable stars.
They even added an asteroid rejection feature to the automated
workflow, which calculates the orbit of every known asteroid at the
beginning of the night, determines where the asteroids are in an
individual image, and then rejects them.
“All of our modifications significantly sped up our real-time
transient detection; we now send high quality supernova alerts to
astronomers all around the globe in less than 40 minutes after taking an
image at Palomar,” says Nugent. “In the case of SN 2013cu, that made
all the difference.”
The automated real-time detection pipeline was created under the DOE
Office of Science’s Scientific Discovery through Advanced Computing
(SciDAC) program and through additional support from NASA.
provided the storage and systems infrastructure. NERSC and ESnet are
also supported by the DOE Office of Science.
Led by Shri Kulkarni of Caltech, iPTF has discovered more than 2000
supernovae during its four and a half years of observations, including
many rare and exotic types of cosmic outbursts. The iPTF survey is a
scientific collaboration among Caltech, Los Alamos National Laboratory,
the University of Wisconsin, Milwaukee, the Oskar Klein Center, the
Weizmann Institute of Science, the TANGO Program of the University
System of Taiwan, and the Kavli Institute for the Physics and
Mathematics of the Universe.
This research was supported by the I-CORE Program “The Quantum
Universe” of the Planning and Budgeting Committee and The Israel Science
Foundation; grants from the ISF, BSF, GIF, Minerva, the FP7/ERC, and a
Kimmel Investigator award; support from the Hubble and
Carnegie-Princeton Fellowships; support from the Arye Dissentshik career
development chair and a grant from the Israeli MOST; support from the
NSF; support from an NSF Postdoctoral Fellowship; support from the
TABASGO Foundation, the Christopher R. Redlich Fund, and NSF grant
AST-1211916. Some of the data were obtained at the W. M. Keck
Observatory, which was made possible by the generous financial support
of the W. M. Keck Foundation.
stars, entirely speculative entities for now, are hypothesized to form
in the early cosmos when dark matter condenses and associated particle
annihilation reactions heat up the matter, perhaps disrupting the
formation of normal stars. The image shows one result from a new
simulation of the birth of the first stars: the left panel shows normal
stars forming when no annihilating dark matter is present and the right
panel shows one instance of what happens when dark stars form and
disrupt the process.Credit: A. Stacey
vast majority of matter is the universe, about eighty-five percent of
it, is so-called "dark matter." It consists not of ordinary atoms, but
of some still unknown kind of particle. Understanding this ubiquitous
yet mysterious substance is a prime goal of modern astrophysics. Dark
matter is detected via its gravitational influence on stars and other
normal matter, and some astronomers speculate that it might have another
other property besides gravity in common with ordinary matter: It
might come in two forms, matter and anti-matter, that annihilate on
contact emitting high energy radiation.
Several hundred million years after the big bang, the first stars
began to form as gravity gradually condensed the primordial material and
heated it to temperatures able to trigger nuclear burning. Scientists
have speculated that something roughly similar might also have occurred
to dark matter: Gravity condensed it into cores that ultimately ignite,
not with nuclear burning – dark matter is not atomic and has no (normal)
nuclei – but rather via annihilation radiation. These so-called "dark
stars" might have shone for some time as more and more dark matter
accreted onto them, powering ongoing annihilation. They may even have
heated up their environment in a way that inhibited the growth of the
first generation of normal stars.
CfA astronomer Avi Loeb and three of his colleagues used computer
simulations of dark matter in the early universe to investigate if and
how dark matter might influence the development of normal stars. The
details are complex, in part because the growing clumps of matter tend
to fragment into clusters within which they then scatter off one
another. The scientists tested their simulations under a variety of
assumptions, and found in one of the more sophisticated versions that
the annihilating dark matter was considerably less effective in forming a
dark star (or disrupting normal stars) than had been thought because of
the disruption from scattering. They conclude that dark stars may never
have existed, and hence that the formation of normal stars may not have
been retarded. They caution, however, that further research is needed
to refine these conclusions, not least to determine nature of the
mysterious dark matter itself. Astronomers are optimistic that some of
the first stars in the universe will actually be detected in this
decade; some proposed space missions (like the Japanese WISH mission)
set this as their primary goal. These new simulations provide a basis
for interpreting those detections.
"The Mutual Interaction Between Population III Stars and Self-Annihilating Dark Matter," Athena Stacy, Andreas H. Pawlik, Volker Bromm and Abraham Loeb, MNRAS 441, 822, 2014.
Astronomers have found cosmic clumps so
dark, dense and dusty that they throw the deepest shadows ever recorded.
Image credit: NASA/JPL-Caltech/University of Zurich.Full image and caption
Astronomers have found cosmic clumps so dark, dense and dusty that
they throw the deepest shadows ever recorded. Infrared observations from
NASA's Spitzer Space Telescope of these blackest-of-black regions
paradoxically light the way to understanding how the brightest stars
The clumps represent the darkest portions of a huge, cosmic cloud of
gas and dust located about 16,000 light-years away. A new study takes
advantage of the shadows cast by these clumps to measure the cloud's
structure and mass.
The dusty cloud, results suggest, will likely evolve into one of the
most massive young clusters of stars in our galaxy. The densest clumps
will blossom into the cluster's biggest, most powerful stars, called
O-type stars, the formation of which has long puzzled scientists. These
hulking stars have major impacts on their local stellar environments
while also helping to create the heavy elements needed for life.
"The map of the structure of the cloud and its dense cores we have
made in this study reveals a lot of fine details about the massive star
and star cluster formation process," said Michael Butler, a postdoctoral
researcher at the University of Zurich in Switzerland and lead author
of the study, published in The Astrophysical Journal Letters.
The state-of-the-art map has helped pin down the cloud's mass to the
equivalent of 7,000 suns packed into an area spanning about 50
light-years in diameter. The map comes courtesy of Spitzer observing in
infrared light, which can more easily penetrate gas and dust than
short-wavelength visible light. The effect is similar to that behind the
deep red color of sunsets on smoggy days -- longer-wavelength red light
more readily reaches our eyes through the haze, which scatters and
absorbs shorter-wavelength blue light. In this case, however, the
densest pockets of star-forming material within the cloud are so thick
with dust that they scatter and block not only visible light, but also
almost all background infrared light.
Observing in infrared lets scientists peer into otherwise inscrutable
cosmic clouds and catch the early phases of star and star cluster
formation. Typically, Spitzer detects infrared light emitted by young
stars still shrouded in their dusty cocoons. For the new study,
astronomers instead gauged the amount of background infrared light
obscured by the cloud, using these shadows to infer where material had
lumped together within the cloud. These blobs of gas and dust will
eventually collapse gravitationally to make hundreds of thousands of new
Most stars in the universe, perhaps our sun included, are thought to
have formed en masse in these sorts of environments. Clusters of
low-mass stars are quite common and well-studied. But clusters giving
birth to higher-mass stars, like the cluster described here, are scarce
and distant, which makes them harder to examine.
"In this rare kind of cloud, Spitzer has provided us with an
important picture of massive star cluster formation caught in its
earliest, embryonic stages," said Jonathan Tan, an associate professor
of astronomy at the University of Florida, Gainesville, and co-author of
The new findings will also help reveal how O-type stars form. O-type
stars shine a brilliant white-blue, possess at least 16 times the sun's
mass and have surface temperatures above 54,000 degrees Fahrenheit
(30,000 degrees Celsius). These giant stars have a tremendous influence
on their local stellar neighborhoods. Their winds and intense radiation
blow away material that might draw together to create other stars and
planetary systems. O-type stars are short-lived and quickly explode as
supernovas, releasing enormous amounts of energy and forging the heavy
elements needed to form planets and living organisms.
Researchers are not sure how, in O-type stars, it is possible for
material to accumulate on scales of tens to 100 times the mass of our
sun without dissipating or breaking down into multiple, smaller stars.
"We still do not have a settled theory or explanation of how these
massive stars form," said Tan. "Therefore, detailed measurements of the
birth clouds of future massive stars, as we have recorded in this study,
are important for guiding new theoretical understanding."
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.
Hubble Space Telescope image of the center
of the newly-confirmed JKCS 041 galaxy cluster, located at a distance of
9.9 billion light years. The galaxies located in the cluster are
circled. Blue circles show the few galaxies that continue to form new
stars, while yellow circles show those that have already entered
quiescence. A larger version is availablehere.
Pasadena, CA - The structures and star populations of
massive galaxies appear to change as they age, but much about how these
galaxies formed and evolved remains mysterious. Many of the oldest and
most massive galaxies reside in clusters, enormous structures where
numerous galaxies are found concentrated together. Galaxy clusters in
the early universe are thought to be key to understanding the lifecycles
of old galaxies, but to date astronomers have located only a handful of
these rare, distant structures.
New research from a team led by Carnegie’s Andrew Newman has
confirmed the presence of an unusually distant galaxy cluster, JKCS 041.
It is published by The Astrophysical Journal.
“Our observations make this galaxy cluster one of the best-studied structures from the early universe,” Newman said.
Although the team began studying JKCS 041 in 2006, it has taken years
of observing with many of the world’s most powerful telescopes to
finally confirm its distance. The team used the Hubble Space Telescope
to capture sharp images of the distant cluster and split the starlight
from the galaxies into its constituent colors, a technique known as
spectroscopy. They found 19 galaxies at precisely the same great
distance of 9.9 billion light years, the tell-tale sign of an early
A previous study using the Chandra X-ray Observatory discovered X-ray emissions in the location of JKCS 041.
“These X-rays likely originate from hot gas in JKCS 041, which has
been heated to a temperature of about 80 million degrees by the gravity
of the massive cluster,” said team member Stefano Andreon of the
Osservatorio Astronomico di Brera, who led a companion paper published
by Astronomy & Astrophysics.
Today the largest and oldest galaxies are found in clusters, but
there is a mystery about when and why these giant galaxies stopped
forming new stars and became dormant, or quiescent. Peering back to a
time when the galaxies in JKCS 041 were only 1 billion years old---or 10
percent of their present age---the team found that most had already
entered their quiescent phase.
“Because JKCS 041 is the most-distant known cluster of its size, it
gives us a unique opportunity to study these old galaxies in detail and
better understand their origins,” Newman said.
Once massive galaxies enter their quiescent phase, they continue
expanding in overall size. This is thought to occur as galaxies collide
with one another and evolve into a new, larger galaxy. Early clusters
are suspected to be prime locations for these collisions, but to the
team’s surprise they found that the galaxies in JKCS 041 were growing at
nearly the same rate as non-cluster galaxies.
The international team included Newman, Andreon, Ginevra Trinchieri
of the Osservatorio Astronomico di Brera, Richard Ellis of Caltech,
Tommaso Treu of the University of California at Santa Barbara, and Anand
Raichoor of the Observatorie di Paris.
This work was based on observations made with the NASA/ESA Hubble
Space Telescope, obtained at the Space Telescope Science Institute,
which is operated by the Association of Universities for Research in
Astronomy, Inc., under NASA contract NAS 5-26555. These observations are
associated with program number GO-12927, which was supported under NASA
contract NAS 5-26555. The work was also supported by the agreement
ASI-INAF I/009/10/0 and the Osservatorio Astronomico di Brera.
The Astrophysical Journal paper is available here.
The Astronomy & Astrophysics sister paper is available here.
This colourful new image from the MPG/ESO
2.2-metre telescope at ESO's La Silla Observatory in Chile shows the
star cluster NGC 3590. These stars shine brightly in front of a dramatic
landscape of dark patches of dust and richly hued clouds of glowing
gas. This small stellar gathering gives astronomers clues about how
these stars form and evolve — as well as giving hints about the
structure of our galaxy's pinwheeling arms.
NGC 3590 is a small open cluster of stars around 7500 light-years
from Earth, in the constellation of Carina (The Keel). It is a gathering
of dozens of stars loosely bound together by gravity and is roughly 35
million years old.
This cluster is not just pretty; it is very useful to astronomers. By
studying this particular cluster — and others nearby — astronomers can
explore the properties of the spiral disc of our galaxy, the Milky Way.
NGC 3590 is located in the largest single segment of a spiral arm that
can be seen from our position in the galaxy: the Carina spiral feature.
The Milky Way has multiple spiral arms, long curved streams of gas
and stars stretching out from the galactic centre. These arms — two
major star-filled arms, and two less populated minor arms — are each
named after the constellations in which they are most prominent .
The Carina spiral feature is seen from Earth as a patch of sky heavily
populated with stars, in the Carina-Sagittarius minor arm.
The name of this arm — Carina, or The Keel — is quite appropriate.
These spiral arms are actually waves of piled up gas and stars sweeping
through the galactic disc, triggering sparkling bursts of star formation
and leaving clusters like NGC 3590 in their wake. By finding and
observing young stars like those in NGC 3590, it is possible to
determine the distances to the different parts of this spiral arm,
telling us more about its structure.
Typical open clusters can contain anything from a few tens to a few
thousands of stars, and provide astronomers with clues about stellar
evolution. The stars in a cluster like NGC 3590 are born at around the
same time from the same cloud of gas, making these clusters perfect test
sites for theories on how stars form and evolve.
This image from the Wide Field Imager (WFI) on the MPG/ESO 2.2-metre
telescope at La Silla, shows the cluster and the gas clouds surrounding
it, which glow in orange and red hues due to the radiation coming from
nearby hot stars. WFI's large field of view also captures a colossal
number of background stars.
To obtain this image, multiple observations were made using different
filters to capture the different colours of the scene. This image was
created by combining images taken in the visible and infrared parts of
the spectrum, and a special filter that collected only light coming from
 These four arms are named the Carina-Sagittarius, Norma, Scutum-Centaurus, and Perseus arms.
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”.
Artist's impression of a galaxy that is releasing material via two
strong jets (shown in red/orange) as well as via wide-angle outflows
(shown in gray/blue). Both jets and outflows are being driven by the
black hole located at the galaxy's centre.
Black holes, which lurk
unseen at the centres of almost all galaxies, are regarded as one of
the keys to understanding galaxy formation and evolution. Copyright: ESA/AOES Mediala. Hi-Res (JPG)
Stacked telescope mirrors of ESA's current XMM-Newton
Curved mirrors stacked within one of three optical modules of ESA's
XMM-Newton telescope. Each one contains 58 mirrors with a total
telescope optical surface of more than 120 m2 – bigger than a tennis
court. Copyright: ESA
Silicon pore optics mirror stack
A silicon pore optics mirror stack consisting of 35 mirror plates.
The plates are made of silicon wafers. Hundreds of pores allow the
X-rays to propagate through the mirror stack and be reflected on the
coated stripes. Copyright: cosine Research.Hi-Res (JPG)
A silicon pore optics mirror module is mounted in a test adapter for
vibration tests. Acceleration sensors are connected to the module to
measure the vibration levels. Copyright: ESA
A new idea to use super-polished silicon wafers as the heart of a
telescope is set to reveal more of the hot, high-energy Universe,
peering back into its turbulent history.
Invisible X-rays tell us about the very hot matter in the Universe –
black holes, supernovas and superheated gas clouds. Today’s X-ray
observatories, ESA’s XMM-Newton and NASA’s Chandra, were launched in the
last century, and are still delivering world-class science. But they
are starting to age.
To replace them, ESA is planning a much more capable X-ray observatory
for launch in 2028, which would probe 10 to 100 times deeper into the
Universe than the current generation of X-ray telescopes.
“This demands a whole new type of X-ray mirror,” explains Marcos Bavdaz,
leading the technology push for ESA’s future science missions. “To
reach the kind of size needed, this new mission’s mirrors will have to
be 10 times lighter than XMM’s, while delivering even sharper images.”
The problem is that energetic X-rays do not behave like typical light
waves – try to reflect them with a standard mirror and they are absorbed
inside. Instead, X-rays can only be reflected at shallow angles, like
stones skimming along water.
That means multiple mirrors must be stacked together to build a
large-enough telescope. XMM has 174 gold-plated nickel mirrors, nested
inside one another like Russian dolls.
But to reach the performance required for ESA’s next X-ray mission, tens
of thousands of densely packed mirror plates will be needed. How can
this be done?
A new approach is required. ‘Silicon pore optics’, developed by ESA,
draws on high-tech equipment and materials from the semiconductor
“We make use of industrial silicon wafers, normally used to manufacture
microprocessors,” adds Eric Wille, optical system engineer for the X-ray
“We take advantage of their stiffness and super-polished surface,
stacking a few dozen at a time together to form a single ‘mirror
Many hundreds of these modules will be fitted together to form the optics of the X-ray mission.
Grooves are cut into the wafers, leaving stiffening ribs and paper-thin
mirrors, which are then covered with reflective metal. For maximum
accuracy, semiconductor manufacturing techniques are applied for the
“Stacking is done by a specially designed robot, aiming for micron-scale
precision,” Eric describes. “We’ve seen big jumps in quality as the
“All the stacking takes place in a cleanroom, since tiny dust particles risk large deformations in the mirror stack.
“The semiconductor industry is improving the quality of silicon wafers, which will further improve the mirror quality in future.
Credit:NASA, ESA Acknowledgement: J. Nichols (University of Leicester)
Astronomers using the NASA/ESA Hubble Space Telescope have captured
new images of the dancing auroral lights at Saturn’s north pole. Taken
from Hubble’s perspective in orbit around the Earth, these images
provide a detailed look at Saturn’s stormy aurorae — revealing
previously unseen dynamics in the choreography of the auroral glow.
The cause of the changing patterns in Saturn's aurorae is an ongoing
mystery in planetary science. These ultraviolet images, taken by
Hubble’s super-sensitive Advanced Camera for Surveys,
add new insight by capturing moments when Saturn’s magnetic field is
affected by bursts of particles streaming out from the Sun.
Saturn has a long, comet-like magnetic tail known as a magnetotail — as do Mercury, Jupiter, Uranus, Neptune and Earth . This magnetotail is present around planets that have a magnetic field, caused by a rotating core of magnetic elements.
It appears that when bursts of particles from the Sun hit Saturn, the
planet’s magnetotail collapses and later reconfigures itself, an event
that is reflected in the dynamics of its aurorae.
Some of the bursts of light seen shooting around Saturn’s polar
regions travelled at over three times faster than the speed of the gas
The new images also formed part of a joint observing campaign between Hubble and NASA's Cassini spacecraft,
which is currently in orbit around Saturn itself. Between them, the two
spacecraft managed to capture a 360-degree view of the planet’s aurorae
at both the north and south poles. Cassini also used optical imaging to
delve into the rainbow of colours seen in Saturn’s light shows. On
Earth, we see green curtains of light with flaming scarlet tops.
Cassini’s imaging cameras reveal similar auroral veils on Saturn, that
are red at the bottom and violet at the top.
 A magnetosphere is the area of space around an
astronomical object in which charged particles are controlled by that
object’s magnetic field. The magnetosphere is compressed on the side of
the sun, and on the other side it extends far beyond the object. It is
this extended region of the magnetosphere that is known as the
This sequence of images was taken by the
Ultraviolet/Visible/Near-Infrared spectrometer (VIRTIS) on board ESA’s
Venus Express spacecraft between 12 and 19 April 2006, during the first
orbit (capture orbit) around the planet.
The images were obtained
at six different time slots and different distances from the planet (top
left: 12 April, from 210 000 kilometres; top centre: 13 April, from 280
000 kilometres; top right: 14 April, from 315 000 kilometres; bottom
left:16 April, from 315 000 kilometres; bottom centre: 17 April, from
270 000 kilometres; bottom right: 19 April, from 190 000 kilometres),
while the spacecraft moved along a long ellipse around Venus. The
separate images can be downloaded here [ VOI_1_12_04_2006_b, VOI_2_13_04_2006_b, VOI_3_14_04_2006_b, VOI_4_16_04_2006_b, VOI_5_17_04_2006_b, VOI_6_19_04_2006].
image is the composite of the day side of Venus (left, in blue, taken
in visible light at 380 nanometres) and the night side (right, in a red
colour scheme, taken in infrared light at 1.7 microns).
visible part shows solar radiation reflected by the atmosphere. The
infrared part shows complex cloud structures, revealed by the thermal
radiation coming up from different atmospheric depths. Venus Express can
resolve these structures by use (for the first time from orbit) of the
so so-called ‘infrared windows’ present in the atmosphere of Venus. In
fact, if observed at certain wavelengths, it is possible to detect
thermal radiation leaking from the deepest atmospheric layers, revealing
what lies beneath the dense cloud curtain situated at about 60
In the colour scheme of the presented infrared images, the brighter the
colour, the more radiation comes up from the lower layers.
This image shows galaxy NGC 4485 in the constellation of Canes
Venatici (The Hunting Dogs). The galaxy is irregular in shape, but it
hasn’t always been so. Part of NGC 4485 has been dragged towards a
second galaxy, named NGC 4490 — which lies out of frame to the bottom
right of this image.
Between them, these two galaxies make up a galaxy pair
called Arp 269. Their interactions have warped them both, turning them
from spiral galaxies into irregular ones. NGC 4485 is the smaller galaxy
in this pair, which provides a fantastic real-world example for
astronomers to compare to their computer models of galactic collisions.
The most intense interaction between these two galaxies is all but over;
they have made their closest approach and are now separating. The trail
of bright stars and knotty orange clumps that we see here extending out
from NGC 4485 is all that connects them — a trail that spans some 24
Many of the stars in this connecting trail could never have
existed without the galaxies’ fleeting romance.
When galaxies interact
hydrogen gas is shared between them, triggering intense bursts of star
formation. The orange knots of light in this image are examples of such
regions, clouded with gas and dust.
A version of this image was entered into the Hubble’s
Hidden Treasures image processing competition by contestant Kathy van
Pelt, and won sixth prize in the “basic image searching” category.
Photo Credit:NASA,ESA, and A. Simon (Goddard Space Flight Center). Acknowledgment: C. Go, H. Hammel (Space Science Institute andAURA), and R. Beebe (New Mexico State University). Science Credit: A. Simon
(Goddard Space Flight Center), G. Orton (Jet Propulsion Laboratory), J.
Rogers (University of Cambridge, UK), and M. Wong and I. de Pater
(University of California, Berkeley)
Jupiter's monster storm, the Great Red Spot, was once so large that
three Earths would fit inside it. But new measurements by NASA's Hubble
Space Telescope reveal that the largest storm in our solar system has downsized significantly.
Jupiter's trademark Great Red Spot — a swirling anticyclonic storm
feature larger than Earth — has shrunken to the smallest size ever
measured. Astronomers have followed this downsizing since the 1930s.
"Recent Hubble Space Telescope observations confirm that the Great
Red Spot (GRS) is now approximately 10,250 miles across, the smallest
diameter we've ever measured," said Amy Simon of NASA's Goddard Space
Flight Center in Greenbelt, Md. Historic observations as far back as the
late 1800s gauged the GRS to be as big as 25,500 miles on its long
axis. The NASA Voyager 1 and Voyager 2 flybys of Jupiter in 1979
measured the GRS to be 14,500 miles across.
Starting in 2012, amateur observations revealed a noticeable increase
in the spot's shrinkage rate. The GRS's "waistline" is getting smaller
by 580 miles per year. The shape of the GRS has changed from an oval to a
circle. The cause behind the shrinking has yet to be explained.
"In our new observations it is apparent that very small eddies are
feeding into the storm," said Simon. "We hypothesized that these may be
responsible for the accelerated change by altering the internal dynamics
and energy of the Great Red Spot."
Simon's team plans to study the motions of the small eddies and also
the internal dynamics of the GRS to determine if these eddies can feed
or sap momentum entering the upwelling vortex.
In the comparison images one Hubble photo was taken in 1995 when the
long axis of the GRS was estimated to be 13,020 miles across. In a 2009
photo, the GRS was measured at 11,130 miles across.
The Hubble Space Telescope is a project of international cooperation
between NASA and the European Space Agency. NASA's Goddard Space Flight
Center in Greenbelt, Md., manages the telescope. The Space Telescope
Science Institute (STScI) in Baltimore conducts Hubble science
operations. STScI is operated for NASA by the Association of
Universities for Research in Astronomy, Inc., in Washington, DC.
Flying through the young star cluster Westerlund 1 (artist's impression)
Magnetars are the bizarre super-dense
remnants of supernova explosions. They are the strongest magnets known
in the Universe — millions of times more powerful than the strongest
magnets on Earth. A team of European astronomers using ESO’s Very Large
Telescope (VLT) now believe they’ve found the partner star of a magnetar
for the first time. This discovery helps to explain how magnetars form —
a conundrum dating back 35 years — and why this particular star didn’t
collapse into a black hole as astronomers would expect.
When a massive star collapses under its own gravity during a supernova explosion it forms either a neutron star or black hole. Magnetars
are an unusual and very exotic form of neutron star. Like all of these
strange objects they are tiny and extraordinarily dense — a teaspoon of
neutron star material would have a mass of about a billion tonnes — but
they also have extremely powerful magnetic fields. Magnetar surfaces
release vast quantities of gamma rays when they undergo a sudden
adjustment known as a starquake as a result of the huge stresses in their crusts.
The Westerlund 1 star cluster ,
located 16 000 light-years away in the southern constellation of Ara
(the Altar), hosts one of the two dozen magnetars known in the Milky
Way. It is called CXOU J164710.2-455216 and it has greatly puzzled
“In our earlier work (eso1034) we showed that the magnetar in the cluster Westerlund 1 (eso0510)
must have been born in the explosive death of a star about 40 times as
massive as the Sun. But this presents its own problem, since stars this
massive are expected to collapse to form black holes after their deaths,
not neutron stars. We did not understand how it could have become a
magnetar,” says Simon Clark, lead author of the paper reporting these results.
Astronomers proposed a solution to this mystery. They suggested that
the magnetar formed through the interactions of two very massive stars
orbiting one another in a binary system so compact that it would fit
within the orbit of the Earth around the Sun. But, up to now, no
companion star was detected at the location of the magnetar in
Westerlund 1, so astronomers used the VLT to search for it in other
parts of the cluster. They hunted for runaway stars
— objects escaping the cluster at high velocities — that might have
been kicked out of orbit by the supernova explosion that formed the
magnetar. One star, known as Westerlund 1-5 , was found to be doing just that.
“Not only does this star have the high velocity expected if it is
recoiling from a supernova explosion, but the combination of its low
mass, high luminosity and carbon-rich composition appear impossible to
replicate in a single star — a smoking gun that shows it must have
originally formed with a binary companion,” adds Ben Ritchie (Open University), a co-author on the new paper.
This discovery allowed the astronomers to reconstruct the stellar
life story that permitted the magnetar to form, in place of the expected
black hole .
In the first stage of this process, the more massive star of the pair
begins to run out of fuel, transferring its outer layers to its less
massive companion — which is destined to become the magnetar — causing
it to rotate more and more quickly. This rapid rotation appears to be
the essential ingredient in the formation of the magnetar’s ultra-strong
In the second stage, as a result of this mass transfer, the companion
itself becomes so massive that it in turn sheds a large amount of its
recently gained mass. Much of this mass is lost but some is passed back
to the original star that we still see shining today as Westerlund 1-5.
“It is this process of swapping material that has imparted the
unique chemical signature to Westerlund 1-5 and allowed the mass of its
companion to shrink to low enough levels that a magnetar was born
instead of a black hole — a game of stellar pass-the-parcel with cosmic
consequences!” concludes team member Francisco Najarro (Centro de Astrobiología, Spain).
It seems that being a component of a double star may therefore be an
essential ingredient in the recipe for forming a magnetar. The rapid
rotation created by mass transfer between the two stars appears
necessary to generate the ultra-strong magnetic field and then a second
mass transfer phase allows the magnetar-to-be to slim down sufficiently
so that it does not collapse into a black hole at the moment of its
 The open cluster Westerlund 1 was
discovered in 1961 from Australia by Swedish astronomer Bengt
Westerlund, who later moved from there to become ESO Director in Chile
(1970–74). This cluster is behind a huge interstellar cloud of gas and
dust, which blocks most of its visible light. The dimming factor is more
than 100 000, and this is why it has taken so long to uncover the true
nature of this particular cluster.
Westerlund 1 is a unique natural laboratory for the study of extreme
stellar physics, helping astronomers to find out how the most massive
stars in the Milky Way live and die. From their observations, the
astronomers conclude that this extreme cluster most probably contains no
less than 100 000 times the mass of the Sun, and all of its stars are
located within a region less than 6 light-years across. Westerlund 1
thus appears to be the most massive compact young cluster yet identified
in the Milky Way galaxy.
All the stars so far analysed in Westerlund 1 have masses at least
30–40 times that of the Sun. Because such stars have a rather short life
— astronomically speaking — Westerlund 1 must be very young. The
astronomers determine an age somewhere between 3.5 and 5 million years.
So, Westerlund 1 is clearly a newborn cluster in our galaxy.
 The full designation for this star is Cl* Westerlund 1 W 5.
 As stars age, their nuclear reactions change
their chemical make-up — elements that fuel the reactions are depleted
and the products of the reactions accumulate. This stellar chemical
fingerprint is first rich in hydrogen and nitrogen but poor in carbon
and it is only very late in the lives of stars that carbon increases, by
which point hydrogen and nitrogen will be severely reduced — it is
thought to be impossible for single stars to be simultaneously rich in
hydrogen, nitrogen and carbon, as Westerlund 1-5 is.
The research presented in this ESO Press Release will soon appear in the research journal Astronomy and Astrophysics (“A
VLT/FLAMES survey for massive binaries in Westerlund 1: IV.Wd1-5 binary
product and a pre-supernova companion for the magnetar CXOU J1647-45” by J. S. Clark et al.). The same team published a first study of this object in 2006 (“A Neutron Star with a Massive Progenitor in Westerlund 1” by M. P. Muno et al., Astrophysical Journal, 636, L41).
The team is composed of Simon Clark and Ben Ritchie (The Open
University, UK), Francisco Najarro (Centro de Astrobiología, Spain),
Norbert Langer (Universität Bonn, Germany, and Universiteit Utrecht, the
Netherlands) and Ignacio Negueruela (Universidad de Alicante, Spain).
The astronomers used the FLAMES instrument on ESO’s Very Large
Telescope at Paranal, Chile to study the stars in the Westerlund 1
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”.