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This image shows something spectacular: a galaxy cluster so massive
that it is warping the space around it! The cluster, whose heart is at
the centre of the frame, is named RCS2 J2327, and is one of the most
massive clusters known as its distance or beyond.
Massive objects such as RCS2 J2327 have such a strong influence on
their surroundings that they actually warp the space around them — this
effect is known as gravitational lensing,
and can cause light from more distant objects to be bent, distorted,
and amplified, allowing us to see galaxies that would otherwise be far
too distant for us to detect. Gravitational lensing is one of the
predictions of Albert Einstein's General Theory of Relativity and can be observed in three different regimes: strong lensing, weak lensing, and microlensing. Unlike strong lensing, which produces stunning images of distorted galaxies, sweeping arcs, and phenomena known as Einstein rings, weak gravitational lensing is mostly studied statistically — but offers a way to measure the masses of cosmic objects, as shown here.
Using the slider a mass map becomes visible, showing the amount of
mass thought to be contained within each part of the cluster. The
creation of the map was only possible due to the exact measurements on
the amount of gravitational lensing in the different areas of the
Different scenarios for the aftermath of the collision of two neutron stars. At left (in the short gamma-ray burst [SGRB] scenario), a jet of material moving at nearly the speed of light is propelled from the collision site into a sphere of material initially blown out by the resulting explosion. If viewed from an angle away (off-axis) from the center of the jet, the long-term emission of X-rays and radio waves would be getting weaker. At right, the jet cannot punch out of the shell of explosion debris, but instead sweeps up material into a broad "cocoon," which absorbs the jet's energy and emits X-rays and radio waves over a wider angle. In this case, such emission is still growing in intensity, as now observed with both radio and X-ray telescopes.
Credit: NRAO/AUI/NSF: D. Berry.Hi-Res File
months of observations with the National Science Foundation’s Karl G.
Jansky Very Large Array (VLA) have allowed astronomers to zero in on the
most likely explanation for what happened in the aftermath of the
violent collision of a pair of neutron stars in a galaxy 130 million
light-years from Earth. What they learned means that astronomers will be
able to see and study many more such collisions.
On August 17, 2017, the LIGO and VIRGO gravitational-wave
observatories combined to locate the faint ripples in spacetime caused
by the merger of two superdense neutron stars. It was the first
confirmed detection of such a merger and only the fifth direct detection
ever of gravitational waves, predicted more than a century ago by
The gravitational waves were followed by outbursts of gamma rays,
X-rays, and visible light from the event. The VLA detected the first
radio waves coming from the event on September 2. This was the first
time any astronomical object had been seen with both gravitational waves
and electromagnetic waves.
The timing and strength of the electromagnetic radiation at different
wavelengths provided scientists with clues about the nature of the
phenomena created by the initial neutron-star collision. Prior to the
August event, theorists had proposed several ideas — theoretical models —
about these phenomena. As the first such collision to be positively
identified, the August event provided the first opportunity to compare
predictions of the models to actual observations.
Astronomers using the VLA, along with the Australia Telescope Compact
Array and the Giant Metrewave Radio Telescope in India, regularly
observed the object from September onward. The radio telescopes showed
the radio emission steadily gaining strength. Based on this, the
astronomers identified the most likely scenario for the merger’s
“The gradual brightening of the radio signal indicates we are seeing a
wide-angle outflow of material, traveling at speeds comparable to the
speed of light, from the neutron star merger,” said Kunal Mooley, now a
National Radio Astronomy Observatory (NRAO) Jansky Postdoctoral Fellow
hosted by Caltech.
The observed measurements are helping the astronomers figure out the
sequence of events triggered by the collision of the neutron stars.
The initial merger of the two superdense objects caused an explosion,
called a kilonova, that propelled a spherical shell of debris outward.
The neutron stars collapsed into a remnant, possibly a black hole, whose
powerful gravity began pulling material toward it. That material formed
a rapidly-spinning disk that generated a pair of narrow, superfast jets
of material flowing outward from its poles.
If one of the jets were pointed directly toward Earth, we would have
seen a short-duration gamma-ray burst, like many seen before, the
“That clearly was not the case,” Mooley said.
Some of the early measurements of the August event suggested instead
that one of the jets may have been pointed slightly away from Earth.
This model would explain the fact that the radio and X-ray emission were
seen only some time after the collision.
“That simple model — of a jet with no structure (a so-called top-hat
jet) seen off-axis — would have the radio and X-ray emission slowly
getting weaker. As we watched the radio emission strengthening, we
realized that the explanation required a different model,” said
Alessandra Corsi, of Texas Tech University.
The astronomers looked to a model published in October by Mansi
Kasliwal of Caltech, and colleagues, and further developed by Ore
Gottlieb, of Tel Aviv University, and his colleagues. In that model, the
jet does not make its way out of the sphere of explosion debris.
Instead, it gathers up surrounding material as it moves outward,
producing a broad “cocoon” that absorbs the jet’s energy.
The astronomers favored this scenario based on the information they
gathered from using the radio telescopes. Soon after the initial
observations of the merger site, the Earth’s annual trip around the Sun
placed the object too close to the Sun in the sky for X-ray and
visible-light telescopes to observe.
For weeks, the radio telescopes
were the only way to continue gathering data about the event.
“If the radio waves and X-rays both are coming from an expanding
cocoon, we realized that our radio measurements meant that, when NASA’s
Chandra X-ray Observatory could observe once again, it would find the
X-rays, like the radio waves, had increased in strength,” Corsi said.
Mooley and his colleagues posted a paper with their radio
measurements, their favored scenario for the event, and this prediction
online on November 30. Chandra was scheduled to observe the object on
December 2 and 6.
“On December 7, the Chandra results came out, and the X-ray emission
had brightened just as we predicted,” said Gregg Hallinan, of Caltech.
“The agreement between the radio and X-ray data suggests that the
X-rays are originating from the same outflow that’s producing the radio
waves,” Mooley said.
“It was very exciting to see our prediction confirmed,” Hallinan
said. He added, “An important implication of the cocoon model is that we
should be able to see many more of these collisions by detecting their
electromagnetic, not just their gravitational, waves.”
Mooley, Hallinan, Corsi, and their colleagues reported their findings in the scientific journal Nature.
The National Radio Astronomy Observatory is a facility of the
National Science Foundation, operated under cooperative agreement by
Associated Universities, Inc.
first and only spatially-resolved strongly lensed Type Ia Supernova,
iPTF16geu, discovered by Goobar et al. (2017). Left: HST image taken on
28 October 2016, showing four images of the same source around the
foreground galaxy. Middle and right: Two different reconstructions from
lens mass models of the system by More, Suyu, Oguri et al. (2017). From More, Suyu et al.
Unravelling Enigmas of Type Ia SuperUnravelling Enigmas of Type Ia Supernova Progenitors and Cosmology through Strong Lensingnova Progenitors and Cosmology through Strong Lensing
End of November, the European Research Council announced that Sherry
Suyu, research group leader at the Max Planck Institute for Astrophysics
and member of the Max-Planck@TUM programme, is one of the awardees of
the 2017 ERC Consolidator Grants. With this funding, Suyu can expand her
group to study gravitationally lensed supernovae and find out more
about their progenitors. Strongly lensed supernovae also provide an
independent way of measuring the Hubble constant, which tells scientists
about the rate of expansion of the Universe.
lensing of the Type Ia Supernova iPTF16geu. The spacetime between the
supernova (marked with a star symbol) and the observer (on Earth) is
disturbed by the gravity of the lensing galaxy (in orange). The observer
will see the host galaxy of the supernova form a ring-like structure in
the background, and the supernova split into four images. As Type Ia
Supernovae have a distinct light-curve shape, the time delay between the
four images can easily be determined (bottom image).
Illustration: Chien-Hsiu Lee/Subaru Telescope
The LENSNOVA project proposed by Sherry Suyu plans to capitalize on
her experience in the field of strong lensing time delays. With the aid
of lensing, SNe can be observed in their entirety with unprecedented
temporal sampling. Observations of the beginning of SN explosions are
key to revealing SN progenitors that have been under debate for decades.
Strongly lensed SNe Ia also allow an independent measurement of the
Hubble constant (H0) that sets the cosmic expansion rate. The
independent measurement is important to ascertain the possible need of
new physics beyond the standard cosmological model, given the tensions
in current H0 measurements. Thus, the LENSNOVA project will
shed light on the natures of SNe Ia progenitors and dark energy, two of
the greatest puzzles in the present era.
The advent of new, powerful telescopes such as the Large Synoptic
Survey Telescope and the Euclid mission makes LENSNOVA particularly
timely for building the first sample of a handful of strongly lensed SNe
Ia. The ERC grant now enables Sherry Suyu to recruit further
researchers for her team and to acquire the computing resources needed
to capitalise on the new data. Thus, the project could potentially
revolutionise both the fields of stellar physics and cosmology.
reconstructed surface brightness distribution of the supernova host
galaxy in Fig 1 from the best lens model. The location of the supernova
is indicated with a blue star. From More, Suyu et al
The ERC Consolidator Grants are awarded to outstanding researchers of
any nationality and age in any field of research, with at least seven
and up to twelve years of experience after PhD, and a scientific track
record showing great promise. Research must be conducted in a public or
private research organisation located in one of the EU Member States or
Associated Countries. The funding (maximum of €2 million per grant), is
provided for up to five years and mostly covers the employment of
researchers and other staff to consolidate the grantees' teams.
Proposals are evaluated by selected international peer reviewers who
assess them on the basis of excellence as the sole criterion.
Acknowledgement: S. Djorgovski (Caltech) and F. Ferraro (University of Bologna)
It’s beginning to look a lot like Christmas in this NASA/ESA Hubble
Space Telescope image of a blizzard of stars, which resembles a swirling
storm in a snow globe.
These stars make up the globular cluster Messier 79, located about 40 000 light-years from Earth in the constellation of Lepus (The Hare).
Globular clusters are gravitationally bound groupings of up to one
million stars. These giant “star globes” contain some of the oldest
stars in our galaxy. Messier 79 is no exception; it contains about 150
000 stars, packed into an area measuring just roughly 120 light-years
This 11.7-billion-year-old star cluster was first discovered by French astronomer Pierre Méchain in 1780. Méchain reported the finding to his colleague Charles Messier, who included it in his catalogue of non-cometary objects: The Messier catalogue. About four years later, using a larger telescope than Messier’s, William Herschel was able to resolve the stars in Messier 79 and described it as a “globular star cluster.”
In this sparkling Hubble image, Sun-like stars appear yellow-white
and the reddish stars are bright giants that are in the final stages of
their lives. Most of the blue stars sprinkled throughout the cluster are
aging “helium-burning” stars, which have exhausted their hydrogen fuel
and are now fusing helium in their cores.
radio image from the NSF’s Karl G. Jansky Very Large Array showing the
center of our galaxy. The mysterious radio filament is the curved line
located near the center of the image, & the supermassive black hole
Sagittarius A* (Sgr A*), is shown by the bright source near the bottom
of the image.NSF/VLA/UCLA/M. Morris et al.Captions/Credits
Cambridge, MA -The
center of our Galaxy has been intensely studied for many years, but it
still harbors surprises for scientists. A snake-like structure lurking
near our galaxy’s supermassive black hole is the latest discovery to
In 2016, Farhad Yusef-Zadeh of Northwestern University reported the
discovery of an unusual filament near the center of the Milky Way Galaxy
using the NSF’s Karl G. Jansky Very Large Array (VLA). The filament is
about 2.3 light years long and curves around to point at the
supermassive black hole, called Sagittarius A* (Sgr A*), located in the
Now, another team of astronomers has employed a pioneering technique
to produce the highest-quality image yet obtained of this curved object.
“With our improved image, we can now follow this filament much closer
to the Galaxy’s central black hole, and it is now close enough to
indicate to us that it must originate there,” said Mark Morris of the
University of California, Los Angeles, who led the study. “However, we
still have more work to do to find out what the true nature of this
The researchers have considered three main explanations for the
filament. The first is that it is caused by high-speed particles kicked
away from the supermassive black hole. A spinning black hole coupled
with gas spiraling inwards can produce a rotating, vertical tower of
magnetic field that approaches or even threads the event horizon, the
point of no return for infalling matter. Within this tower, particles
would be sped up and produce radio emission as they spiral around
magnetic field lines and stream away from the black hole.
The second, more fantastic, possibility is that the filament is a
cosmic string, theoretical, as-yet undetected objects that are long,
extremely thin objects that carry mass and electric currents.
Previously, theorists had predicted that cosmic strings, if they exist,
would migrate to the centers of galaxies. If the string moves close
enough to the central black hole it might be captured once a portion of
the string crosses the event horizon.
The final option is that the position and the direction of the
filament aligning with the black hole are merely coincidental
superpositions, and there is no real association between the two. This
would imply it is like dozens of other known filaments found farther
away from the center of the Galaxy. However, such a coincidence is quite
unlikely to happen by chance.
“Part of the thrill of science is stumbling across a mystery that is
not easy to solve,” said co-author Jun-Hui Zhao of the
Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. “While
we don’t have the answer yet, the path to finding it is fascinating.
This result is motivating astronomers to build next generation radio
telescopes with cutting edge technology.”
Each of the scenarios being investigated would provide intriguing
insight if proven true. For example, if the filament is caused by
particles being ejected by Sgr A*, this would reveal important
information about the magnetic field in this special environment,
showing that it is smooth and orderly rather than chaotic.
The second option, the cosmic string, would provide the first
evidence for a highly speculative idea with profound implications for
understanding gravity, space-time and the Universe itself.
Evidence for the idea that particles are being magnetically kicked
away from the black hole would come from observing that particles
further away from Sgr A* are less energetic than those close in. A test
for the cosmic string idea will capitalize on the prediction by
theorists that the string should move at a high fraction of the speed of
light. Follow-up observations with the VLA should be able to detect the
corresponding shift in position of the filament.
Even if the filament is not physically tied to Sgr A*, the bend in
the shape of this filament is still unusual. The bend coincides with,
and could be caused by, a shock wave, akin to a sonic boom, where the
blast wave from an exploded star is colliding with the powerful winds
blowing away from massive stars surrounding the central black hole.
“We will keep hunting until we have a solid explanation for this
object,” said co-author Miller Goss, from the National Radio Astronomy
Observatory in Socorro, New Mexico. “And we are aiming to next produce
even better, more revealing images.”
A paper describing these results appeared in the December 1st, 2017 issue of The Astrophysical Journal Letters.
in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics
(CfA) is a collaboration between the Smithsonian Astrophysical
Observatory and the Harvard College Observatory. CfA scientists,
organized into six research divisions, study the origin, evolution and
ultimate fate of the universe.
For more information, contact: Megan Watzke Harvard-Smithsonian Center for Astrophysics +1 617-496-7998 email@example.com
Image of the quasar host galaxy from the UC San Diego research team’s data. The distance to this quasar galaxy is ~9.3 billion light years. The four-color image shows findings from use of the Keck Observatory and ALMA. As seen from Keck Observatory, the green colors highlight the energetic gas across the galaxy that is being illuminated by the quasar. The blue color represents powerful winds blowing throughout the galaxy. The red-orange colors represent the cold molecular gas in the system as seen from ALMA. The supermassive black hole sits at the center of the bright red-orange circular area slightly below the middle of the image. Credit: A. Vayner and Team
Hawaii– Stars forming in galaxies
appear to be influenced by the supermassive black hole at the center of the
galaxy, but the mechanism of how that happens has not been clear to astronomers
black holes are captivating,” says lead author Shelley Wright, a University
of California San Diego Professor of Physics. “Understanding why and
how galaxies are affected by their supermassive black holes is
an outstanding puzzle in their formation.”
In a study published today in The Astrophysical Journal, Wright, graduate student Andrey Vayner, and their
colleagues examined the energetics surrounding the powerful winds
generated by the bright, vigorous supermassive black hole (known as a “quasar”)
at the center of the 3C 298 host galaxy, located approximately 9.3 billion
light years away.
study supermassive black holes in the very early universe when they are
actively growing by accreting massive amounts of gaseous material,” says
Wright. “While black holes themselves do not emit light, the gaseous material
they chew on is heated to extreme temperatures, making them the most luminous
objects in the universe.”
The UC San Diego team’s
research revealed that the winds blow out through the entire galaxy and impact
the growth of stars.
is remarkable that the supermassive black hole is able to impact stars forming
at such large distances,” says Wright.
neighboring galaxies show that the galaxy mass is tightly correlated with the
supermassive black hole mass. Wright’s and Vayner’s research indicates that 3C
298 does not fall within this normal scaling relationship between nearby
galaxies and the supermassive black holes that lurk at their center. But, in
the early universe, their study shows that the 3C 298 galaxy is 100 times less
massive than it should be given its behemoth supermassive black hole mass.
implies that the supermassive black hole mass is established well before the
galaxy, and potentially the energetics from the quasar are capable of
controlling the growth of the galaxy.
conduct the study, the UC San Diego researchers utilized multiple
state-of-the-art astronomical facilities. The first of these was Keck
Observatory’s instrument OSIRIS (OH-Suppressing
Infrared Imaging Spectrograph) and its advanced adaptive optics (AO)
system. An AO system allows ground-based telescopes to achieve higher quality
images by correcting for the blurring caused by the Earth’s atmosphere. The
resulting images are as good as those obtained from space.
second major facility was the Atacama Large Millimeter/submillimeter Array,
known as “ALMA,” an international observatory in Chile that is able to detect
millimeter wavelengths using up to 66 antennae to achieve high-resolution
images of the gas surrounding the quasar.
most enjoyable part of researching this galaxy has been putting together all
the data from different wavelengths and techniques,” said Vayner. “Each new
dataset that we obtained on this galaxy answered one question and helped us put
some of the pieces of the puzzle together. However, at the same time, it created
new questions about the nature of galaxy and supermassive black hole
agreed, saying that the data sets were “tremendously gorgeous” from both Keck Observatory
and ALMA, offering a wealth of new information about the universe.
findings are the first results from a larger survey of distant quasars and
their energetics’ impact on star formation and galaxy growth. Vayner and the team
will continue developing results on more distant quasars using the new facilities
and capabilities from Keck Observatory and ALMA.
The OH-Suppressing Infrared
Imaging Spectrograph (OSIRIS) is one of W. M. Keck Observatory’s "integral
field spectrographs." The instrument works behind the adaptive optics
system, and uses an array of lenslets to sample a small rectangular patch of
the sky at resolutions approaching the diffraction limit of the 10-meter Keck
Telescope. OSIRIS records an infrared spectrum at each point within the patch
in a single exposure, greatly enhancing its efficiency and precision when
observing small objects such as distant galaxies. It is used to characterize
the dynamics and composition of early stages of galaxy formation.
About W.M. Keck Observatory
The W. M. Keck Observatory telescopes are
among the most scientifically productive on Earth. The two, 10-meter
optical/infrared telescopes on the summit of Maunakea on the Island of Hawaii
feature a suite of advanced instruments including imagers, multi-object
spectrographs, high-resolution spectrographs, integral-field spectrometers, and
world-leading laser guide star adaptive optics systems.
Some of the data presented herein were
obtained at Keck Observatory, which is a private 501(c) 3 non-profit organization
operated as a scientific partnership among the California Institute of
Technology, the University of California, and the National Aeronautics and
Space Administration. The Observatory was made possible by the generous
financial support of the W. M. Keck Foundation.
The authors wish to
recognize and acknowledge the very significant cultural role and reverence that
the summit of Maunakea has always had within the indigenous Hawaiian
community. We are most fortunate to have the opportunity to conduct
observations from this mountain.
Latest findings using the W. M. Keck Observatory on Maunakea,
Hawaii increase scientific understanding of how powerful winds generated
by supermassive black
holes impact and regulate the growth of 3C 298 Quasar Host Galaxy.
An innovative interpretation of X-ray data from a galaxy cluster could help scientists understand the nature of dark matter, as described in our latest press release.
The finding involves a new explanation for a set of results made with
NASA's Chandra X-ray Observatory, ESA's XMM-Newton and Hitomi, a
Japanese-led X-ray telescope. If confirmed with future observations,
this may represent a major step forward in understanding the nature of
the mysterious, invisible substance that makes up about 85% of matter in the Universe.
The image shown here contains X-ray
data from Chandra (blue) of the Perseus galaxy cluster, which has been
combined with optical data from the Hubble Space Telescope (pink) and
radio emission from the Very Large Array (red). In 2014, researchers detected an unusual spike of intensity,
known as an emission line, at a specific wavelength of X-rays (3.5 keV)
in the hot gas within the central region of the Perseus cluster. They
also reported the presence of this same emission line in a study of 73
other galaxy clusters.
In the subsequent months and years, astronomers have tried to confirm
the existence of this 3.5 keV line. They are eager to do so because it
may give us important clues about the nature of dark matter. However, it
has been debated in the astronomical community exactly what the
original and follow-up observations have revealed.
Credit: NASA/CXC/M. Weiss
A new analysis of Chandra data by a team from Oxford University,
however, is providing a fresh take on this debate. The latest work shows
that absorption of X-rays at an energy of 3.5 keV is detected when
observing the region surrounding the supermassive black hole
at the center of Perseus. This suggests that dark matter particles in
the cluster are both absorbing and emitting X-rays (see our artist's
impression above for a diagram
helping to explain this behavior, where 3.5 keV X-rays are shown). If
the new model turns out to be correct, it could provide a path for
scientists to one day identify the true nature of dark matter. For next
steps, astronomers will need further observations of the Perseus cluster
and others like it with current X-ray telescopes and those being
planned for the next decade and beyond.
A paper describing these results was published in Physical Review D on December 19, 2017 and a preprint is available online.
The authors of the paper are Joseph Conlon, Francesca Day, Nicolas
Jennings, Sven Krippendorf and Markus Rummel, all from Oxford University
in the UK. NASA's Marshall Space Flight Center in Huntsville, Alabama,
manages the Chandra program for NASA's Science Mission Directorate in
Washington. The Smithsonian Astrophysical Observatory in Cambridge,
Massachusetts, controls Chandra's science and flight operations.
Astronomers using ESO’s Very Large
Telescope have for the first time directly observed granulation patterns
on the surface of a star outside the Solar System — the ageing red
giant π1 Gruis. This remarkable new image from the PIONIER instrument
reveals the convective cells that make up the surface of this huge star,
which has 350 times the diameter of the Sun. Each cell covers more than
a quarter of the star’s diameter and measures about 120 million
kilometres across. These new results are being published this week in
the journal Nature.
Located 530 light-years from Earth in the constellation of Grus (The Crane), π1 Gruis is a cool red giant. It has about the same mass as our Sun, but is 350 times larger and several thousand times as bright . Our Sun will swell to become a similar red giant star in about five billion years.
An international team of astronomers led by Claudia Paladini (ESO) used the PIONIER instrument on ESO’s Very Large Telescope to observe π1
Gruis in greater detail than ever before. They found that the surface
of this red giant has just a few convective cells, or granules, that are
each about 120 million kilometres across — about a quarter of the
star’s diameter . Just one of these granules would extend from the Sun to beyond Venus. The surfaces — known as photospheres — of many giant stars are obscured by dust, which hinders observations. However, in the case of π1 Gruis, although dust is present far from the star, it does not have a significant effect on the new infrared observations .
When π1 Gruis ran out of hydrogen to burn long
ago, this ancient star ceased the first stage of its nuclear fusion
programme. It shrank as it ran out of energy, causing it to heat up to
over 100 million degrees. These extreme temperatures fueled the star’s
next phase as it began to fuse helium into heavier atoms such as carbon
and oxygen. This intensely hot core then expelled the star’s outer
layers, causing it to balloon to hundreds of times larger than its
original size. The star we see today is a variable red giant. Until now, the surface of one of these stars has never before been imaged in detail.
By comparison, the Sun’s photosphere contains about two
million convective cells, with typical diameters of just 1500
kilometres. The vast size differences in the convective cells of these
two stars can be explained in part by their varying surface gravities. π1
Gruis is just 1.5 times the mass of the Sun but much larger, resulting
in a much lower surface gravity and just a few, extremely large,
While stars more massive than eight solar masses end their lives in dramatic supernovae explosions, less massive stars like this one gradually expel their outer layers, resulting in beautiful planetary nebulae. Previous studies of π1
Gruis found a shell of material 0.9 light-years away from the central
star, thought to have been ejected around 20 000 years ago. This
relatively short period in a star's life lasts just a few tens of
thousands of years – compared to the overall lifetime of several billion
– and these observations reveal a new method for probing this fleeting
red giant phase.
Notes  π1 Gruis is named following theBayer designation system. In 1603 the German astronomer Johann Bayer classified 1564
stars, naming them by a Greek letter followed by the name of their
parent constellation. Generally, stars were assigned Greek letters in
rough order of how bright they appeared from Earth, with the brightest
designated Alpha (α). The brightest star of the Grus constellation is
π1 Gruis is one of an attractive pair of stars
of contrasting colours that appear close together in the sky, the other
one naturally being named π2 Gruis. They are bright enough to be well seen in a pair of binoculars. Thomas Brisbanerealised in the 1830s that π1 Gruis was itself also a much closer binary star system.Annie Jump Cannon, credited with the creation of theHarvard Classification Scheme, was the first to report the unusual spectrum of π1 Gruis in 1895.
 Granules are patterns ofconvectioncurrents in the plasma of a star. As plasma heats up at the centre of
the star it expands and rises to the surface, then cools at the outer
edges, becoming darker and more dense, and descends back to the centre.
This process continues for billions of years and plays a major role in
many astrophysical processes including energy transport, pulsation,
stellar wind and dust clouds on brown dwarfs.
 π1 Gruis is one of the brightest members of the rareS classof stars that was first defined by the American astronomer Paul W.
Merrill to group together stars with similarly unusual spectra. π1 Gruis, R AndromedaeandR Cygnibecame prototypes of this type. Their unusual spectra is now known to be the result of the “s-process” or “slow neutron capture process” — responsible for the creation of half theelements heavier than iron.
This research was presented in a paper “Large granulation cells on the surface of the giant star π1 Gruis”, by C. Paladini et al., published in the journal Nature on 21 December 2017.
The team is composed of C. Paladini (Institut d’Astronomie
et d’Astrophysique, Université libre de Bruxelles, Brussels, Belgium;
ESO, Santiago, Chile), F. Baron (Georgia State University, Atlanta,
Georgia, USA), A. Jorissen (Institut d’Astronomie et d’Astrophysique,
Université libre de Bruxelles, Brussels, Belgium), J.-B. Le Bouquin
(Université Grenoble Alpes, CNRS, IPAG, Grenoble, France), B. Freytag
(Uppsala University, Uppsala, Sweden), S. Van Eck (Institut d’Astronomie
et d’Astrophysique, Université libre de Bruxelles, Brussels, Belgium),
M. Wittkowski (ESO, Garching, Germany), J. Hron (University of Vienna,
Vienna, Austria), A. Chiavassa (Laboratoire Lagrange, Université de Nice
Sophia-Antipolis, CNRS, Observatoire de la Côte d’Azur, Nice, France),
J.-P. Berger (Université Grenoble Alpes, CNRS, IPAG, Grenoble, France),
C. Siopis (Institut d’Astronomie et d’Astrophysique, Université libre de
Bruxelles, Brussels, Belgium), A. Mayer (University of Vienna, Vienna,
Austria), G. Sadowski (Institut d’Astronomie et d’Astrophysique,
Université libre de Bruxelles, Brussels, Belgium), K. Kravchenko
(Institut d’Astronomie et d’Astrophysique, Université libre de
Bruxelles, Brussels, Belgium), S. Shetye (Institut d’Astronomie et
d’Astrophysique, Université libre de Bruxelles, Brussels, Belgium), F.
Kerschbaum (University of Vienna, Vienna, Austria), J. Kluska
(University of Exeter, Exeter, UK) and S. Ramstedt (Uppsala University,
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 16 countries:
Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland,
Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden,
Switzerland and the United Kingdom, along with the host state of Chile
and by Australia as a strategic partner. 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 and its
world-leading Very Large Telescope Interferometer as well as two survey
telescopes, VISTA working in the infrared and the visible-light VLT
Survey Telescope. ESO is also a major partner in two facilities on
Chajnantor, APEX and ALMA, the largest astronomical project in
existence. And on Cerro Armazones, close to Paranal, ESO is building the
39-metre Extremely Large Telescope, the ELT, which will become “the
world’s biggest eye on the sky”.
Artistic impression of a habitable planet (centre) near a pulsar
(right). Such a planet must have an enormous atmosphere that convert the
deadly X-rays and high energy particles of the pulsar into heat. (c)
Institute of Astronomy, University of Cambridge. Hi-res image
It is theoretically possible that habitable planets exist around
pulsars. Such planets must have an enormous atmosphere that convert the
deadly X-rays and high energy particles of the pulsar into heat. That is
stated in a scientific paper by astronomers Alessandro Patruno and
Mihkel Kama, working in the Netherlands and the United Kingdom. The
paper appears today in the journal Astronomy & Astrophysics.
Pulsars are known for their extreme conditions. They are neutron stars
of only 10 to 30 kilometers in diameter. They have enormous magnetic
fields, they accrete matter and they regularly burst out large amounts
of X-rays and other energetic particles. Nevertheless, Alessandro Patruno (Leiden
University and ASTRON) and Mihkel Kama (Leiden University and Cambridge
University) suggest that there could be life in the vicinity of these
It is the first time that astronomers try to calculate so-called
habitable zones near neutron stars. The calculations show that the
habitable zone around a neutron star can be as large as the distance
from our Earth to our Sun. An important premise is that the planet must
be a super-Earth with a mass between one and ten times of our Earth. A
smaller planet will lose its atmosphere within a few thousand years.
Furthermore, the atmosphere must be a million times as thick as that of
the Earth. The conditions on the pulsar planet surface might resemble
those of the deep sea at Earth.
The astronomers studied the pulsar PSR B1257+12 about 2300 light-years
away in the constellation Virgo. They used the Chandra space telescope
that is specially made to observe X-rays. Three planets orbit the
pulsar. Two of them are super-Earths with a mass of four to five times
our Earth. The planets orbit close enough around the pulsar to warm up.
Patruno: "According to our calculations, the temperature of the planets
might be suitable for the presence of liquid water on their surface.
Though, we don't know yet if the two super-Earths have the right,
extremely dense atmosphere."
In the future, the astronomers would love to observe the pulsar in more
detail and compare it with other pulsars. The ALMA telescope of the
European Southern Observatory would be able to show dust discs around
neutron stars. Such disks are good predictors of planets.
Probably our Milky Way contains about 1 billion neutron stars of which
about 200,000 pulsars. So far, 3000 pulsars have been studied and only 5
pulsar planets have been found. PSR B1257+12 is a much-studied pulsar.
In 1992, the first exoplanets ever were discovered around this object.
Galaxies glow like fireflies in this spectacular NASA/ESA Hubble Space Telescope
image! This flickering swarm of cosmic fireflies is a rich cluster of
galaxies called Abell 2163. Abell 2163 is a member of the Abell catalogue, an all-sky catalogue of over 4000 galaxy clusters. It is particularly well-studied because the material sitting at its core (its intracluster medium) exhibits exceptional properties, including a large and bright radio halo and extraordinarily high temperatures and X-ray luminosities. It is the hottest cluster in the catalogue! Observing massive clusters like Abell 2163 can contribute to the study of dark matter, and provide a new perspective on the distant Universe via phenomena such as gravitational lensing.
illustration depicts charged particles from a solar storm stripping away
charged particles of Mars' atmosphere, one of the processes of Martian
atmosphere loss studied by NASA's MAVEN mission, beginning in 2014.
Unlike Earth, Mars lacks a global magnetic field that could deflect
charged particles emanating from the Sun. Image credit: NASA/GSFC.› Full image and caption
To receive the same amount of starlight as Mars receives from our Sun, a
planet orbiting an M-type red dwarf would have to be positioned much
closer to its star than Mercury is to the Sun. Image credit: NASA/GSFC.› Full image and caption
How long might a rocky, Mars-like planet be habitable if it were
orbiting a red dwarf star? It's a complex question but one that NASA's Mars
Atmosphere and Volatile Evolution mission can help answer.
"The MAVEN mission tells us that Mars lost substantial
amounts of its atmosphere over time, changing the planet's habitability,"
said David Brain, a MAVEN co-investigator and a professor at the Laboratory for
Atmospheric and Space Physics at the University of Colorado Boulder. "We
can use Mars, a planet that we know a lot about, as a laboratory for studying
rocky planets outside our solar system, which we don't know much about yet."
At the fall
meeting of the American Geophysical Union on Dec. 13, 2017, in New Orleans,
Louisiana, Brain described how insights from the MAVEN mission could
be applied to the habitability of rocky planets orbiting other stars.
MAVEN carries a suite of instruments that have been measuring Mars'
atmospheric loss since November 2014. The studies indicate that Mars has lost
the majority of its atmosphere to space over time through a combination of
chemical and physical processes. The spacecraft's instruments were chosen to
determine how much each process contributes to the total escape.
In the past three years, the Sun has gone through periods of higher
and lower solar activity, and Mars also has experienced solar storms, solar
flares and coronal mass ejections. These varying conditions have given MAVEN
the opportunity to observe Mars' atmospheric escape getting cranked up and
Brain and his colleagues started to think about applying these
insights to a hypothetical Mars-like planet in orbit around some type of
M-star, or red dwarf, the most common class of stars in our galaxy.
The researchers did some preliminary calculations based on the
MAVEN data. As with Mars, they assumed that this planet might be positioned at
the edge of the habitable zone of its star. But because a red dwarf is dimmer
overall than our Sun, a planet in the habitable zone would have to orbit much
closer to its star than Mercury is to the Sun.
The brightness of a red dwarf at extreme ultraviolet (UV)
wavelengths combined with the close orbit would mean that the hypothetical
planet would get hit with about 5 to 10 times more UV radiation than the real
Mars does. That cranks up the amount of energy available to fuel the processes
responsible for atmospheric escape. Based on what MAVEN has learned, Brain and
colleagues estimated how the individual escape processes would respond to
having the UV cranked up.
Their calculations indicate that the planet's atmosphere could
lose 3 to 5 times as many charged particles, a process called ion escape. About
5 to 10 times more neutral particles could be lost through a process called
photochemical escape, which happens when UV radiation breaks apart molecules in
the upper atmosphere.
Because more charged particles would be created, there also would
be more sputtering, another form of atmospheric loss. Sputtering happens when
energetic particles are accelerated into the atmosphere and knock molecules
around, kicking some of them out into space and sending others crashing into
their neighbors, the way a cue ball does in a game of pool.
Finally, the hypothetical planet might experience about the same
amount of thermal escape, also called Jeans escape. Thermal escape occurs only
for lighter molecules, such as hydrogen. Mars loses its hydrogen by thermal
escape at the top of the atmosphere. On the exo-Mars, thermal escape would
increase only if the increase in UV radiation were to push more hydrogen to the
top of the atmosphere.
Altogether, the estimates suggest that orbiting at the edge of the
habitable zone of a quiet M-class star, instead of our Sun, could shorten the
habitable period for the planet by a factor of about 5 to 20. For an M-star
whose activity is amped up like that of a Tasmanian devil, the habitable period
could be cut by a factor of about 1,000 -- reducing it to a mere blink of an
eye in geological terms. The solar storms alone could zap the planet with
radiation bursts thousands of times more intense than the normal activity from
However, Brain and his colleagues have considered a particularly
challenging situation for habitability by placing Mars around an M-class star.
A different planet might have some mitigating factors -- for example, active
geological processes that replenish the atmosphere to a degree, a magnetic
field to shield the atmosphere from stripping by the stellar wind, or a larger
size that gives more gravity to hold on to the atmosphere.
"Habitability is one of the biggest topics in astronomy, and
these estimates demonstrate one way to leverage what we know about Mars and the
Sun to help determine the factors that control whether planets in other systems
might be suitable for life," said Bruce Jakosky, MAVEN's principal
investigator at the University of Colorado Boulder.
MAVEN's principal investigator is based at the University of
Colorado's Laboratory for Atmospheric and Space Physics, Boulder. The
university provided two science instruments and leads science operations, as
well as education and public outreach, for the mission. NASA's Goddard Space
Flight Center in Greenbelt, Maryland, manages the MAVEN project and provided
two science instruments for the mission. NASA's Jet Propulsion Laboratory, a
division of Caltech in Pasadena, California, manages the Mars Exploration
Program for NASA's Science Mission Directorate, Washington.
The OmegaCAM camera on ESO’s VLT Survey
Telescope has captured this glittering view of the stellar nursery
called Sharpless 29. Many astronomical phenomena can be seen in this
giant image, including cosmic dust and gas clouds that reflect, absorb,
and re-emit the light of hot young stars within the nebula.
The region of sky pictured is listed in the Sharpless catalogue of H II regions: interstellar clouds of ionised gas, rife with star formation. Also known as Sh 2-29, Sharpless 29 is located about 5500 light-years away in the constellation of Sagittarius (The Archer), next door to the larger Lagoon Nebula. It contains many astronomical wonders, including the highly active star formation site of NGC 6559, the nebula at the centre of the image.
This central nebula is Sharpless 29’s most striking
feature. Though just a few light-years across, it showcases the havoc
that stars can wreak when they form within an interstellar cloud. The
hot young stars in this image are no more than two million years old and
are blasting out streams of high-energy radiation. This energy heats up
the surrounding dust and gas, while their stellar winds
dramatically erode and sculpt their birthplace. In fact, the nebula
contains a prominent cavity that was carved out by an energetic binary star system. This cavity is expanding, causing the interstellar material to pile up and create the reddish arc-shaped border.
When interstellar dust and gas are bombarded with
ultraviolet light from hot young stars, the energy causes them to shine
brilliantly. The diffuse red glow permeating this image comes from the emission of hydrogen gas, while the shimmering blue light is caused by reflection and scattering off small dust particles. As well as emission and reflection, absorption
takes place in this region. Patches of dust block out the light as it
travels towards us, preventing us from seeing the stars behind it, and
smaller tendrils of dust create the dark filamentary structures within
The rich and diverse environment of Sharpless 29 offers
astronomers a smorgasbord of physical properties to study. The triggered
formation of stars, the influence of the young stars upon dust and gas,
and the disturbance of magnetic fields can all be observed and examined
in this single area.
But young, massive stars live fast and die young. They will
eventually explosively end their lives in a supernova, leaving behind
rich debris of gas and dust. In tens of millions of years, this will be
swept away and only an open cluster of stars will remain.
Sharpless 29 was observed with ESO’s OmegaCAM on the VLT Survey Telescope
(VST) at Cerro Paranal in Chile. OmegaCAM produces images that cover an
area of sky more than 300 times greater than the largest field of view
imager of the NASA/ESA Hubble Space Telescope,
and can observe over a wide range of wavelengths from the ultraviolet
to the infrared. Its hallmark feature is its ability to capture the very
red spectral line H-alpha, created when the electron inside a hydrogen
atom loses energy, a prominent occurrence in a nebula like Sharpless 29.
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 16 countries: Austria, Belgium, Brazil, the
Czech Republic, Denmark, France, Finland, Germany, Italy, the
Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United
Kingdom, along with the host state of Chile and by Australia as a
strategic partner. 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 a
major partner in ALMA, the largest astronomical project in existence.
And on Cerro Armazones, close to Paranal, ESO is building the 39-metre
Extremely Large Telescope, the ELT, which will become “the world’s
biggest eye on the sky”.
Where do most of the elements essential for life on Earth come from?
The answer: inside the furnaces of stars and the explosions that mark
the end of some stars' lives.
Astronomers have long studied exploded stars and their remains — known as "supernova remnants" — to better understand exactly how stars produce and then disseminate many of the elements observed on Earth, and in the cosmos at large.
Due to its unique evolutionary status, Cassiopeia A (Cas A) is one of
the most intensely studied of these supernova remnants. A new image
from NASA's Chandra X-ray Observatory shows the location of different
elements in the remains of the explosion: silicon (red), sulfur
(yellow), calcium (green) and iron (purple). Each of these elements
within narrow energy ranges, allowing maps of their location to be
created. The blast wave from the explosion is seen as the blue outer
Location of elements in Cassiopeia A.
X-ray telescopes such as Chandra are important to study supernova
remnants and the elements they produce because these events generate
extremely high temperatures — millions of degrees — even thousands of
years after the explosion. This means that many supernova remnants,
including Cas A, glow most strongly at X-ray wavelengths that are
undetectable with other types of telescopes.
Chandra's sharp X-ray vision allows astronomers to gather detailed
information about the elements that objects like Cas A produce. For
example, they are not only able to identify many of the elements that
are present, but how much of each are being expelled into interstellar
The Chandra data indicate that the supernova that produced Cas A has
churned out prodigious amounts of key cosmic ingredients. Cas A has
dispersed about 10,000 Earth masses worth of sulfur alone, and about
20,000 Earth masses of silicon. The iron in Cas A has the mass of about
70,000 times that of the Earth, and astronomers detect a whopping one
million Earth masses worth of oxygen being ejected into space from Cas
A, equivalent to about three times the mass of the Sun. (Even though
oxygen is the most abundant element in Cas A, its X-ray emission is
spread across a wide range of energies and cannot be isolated in this
image, unlike with the other elements that are shown.)
Astronomers have found other elements in Cas A in addition to the
ones shown in this new Chandra image. Carbon, nitrogen, phosphorus and
hydrogen have also been detected using various telescopes that observe
different parts of the electromagnetic spectrum. Combined with the
detection of oxygen, this means all of the elements needed to make DNA,
the molecule that carries genetic information, are found in Cas A.
Periodic Table of Elements
Credit: NASA/CXC/K. Divona
Oxygen is the most abundant element in the human body
(about 65% by mass), calcium helps form and maintain healthy bones and
teeth, and iron is a vital part of red blood cells that carry oxygen
through the body. All of the oxygen in the Solar System comes from exploding massive stars.
About half of the calcium and about 40% of the iron also come from
these explosions, with the balance of these elements being supplied by
explosions of smaller mass, white dwarf stars.
While the exact date is not confirmed (PDF),
many experts think that the stellar explosion that created Cas A
occurred around the year 1680 in Earth's timeframe. Astronomers estimate
that the doomed star was about five times the mass of the Sun just
before it exploded. The star is estimated to have started its life with a
mass about 16 times that of the Sun, and lost roughly two-thirds of
this mass in a vigorous wind blowing off the star several hundred
thousand years before the explosion.
Earlier in its lifetime, the star began fusing hydrogen and helium in
its core into heavier elements through the process known as "nucleosynthesis."
The energy made by the fusion of heavier and heavier elements balanced
the star against the force of gravity. These reactions continued until
they formed iron in the core of the star. At this point, further
nucleosynthesis would consume rather than produce energy, so gravity
then caused the star to implode and form a dense stellar core known as a
As it nears the end of its evolution, heavy elements produced by nuclear
fusion inside the star are concentrated toward the center of the star.
Illustration Credit: NASA/CXC/S. Lee
The exact means by which a massive explosion is produced after the
implosion is complicated, and a subject of intense study, but eventually
the infalling material outside the neutron star was transformed by
further nuclear reactions as it was expelled outward by the supernova
NASA's Marshall Space Flight Center in Huntsville, Alabama, manages
the Chandra program for NASA's Science Mission Directorate in
Washington. The Smithsonian Astrophysical Observatory in Cambridge,
Massachusetts, controls Chandra's science and flight operations.