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(Artist concept) Far beyond the orbit of Neptune,
the solar wind and the interstellar medium interact to create a region
known as the , bounded on the inside by the termination
shock, and on the outside by the heliopause. Credits: NASA/IBEX/Adler Planetarium
This simulation shows the origin of ribbon
particles of different energies or speeds outside the heliopause
(labeled HP). The IBEX ribbon particles interact with the interstellar
magnetic field (labeled ISMF) and travel inwards toward Earth,
collectively giving the impression of a ribbon spanning across the sky.Credits: SwRI/Zirnstein
The new paper is based on one particular theory of the origin of the
IBEX ribbon, in which the particles streaming in from the ribbon are
actually solar material reflected back at us after a long journey to the
edges of the sun’s magnetic boundaries. A giant bubble, known as the
heliosphere, exists around the sun and is filled with what’s called
solar wind, the sun’s constant outflow of ionized gas, known as plasma.
When these particles reach the edges of the heliosphere, their motion
becomes more complicated.
“The theory says that some solar wind protons are sent flying back
towards the sun as neutral atoms after a complex series of charge
exchanges, creating the IBEX ribbon,” said Eric Zirnstein, a space
scientist at the Southwest Research Institute in San Antonio, Texas, and
lead author on the study. “Simulations and IBEX observations pinpoint
this process – which takes anywhere from three to six years on average –
as the most likely origin of the IBEX ribbon.”
Outside the heliosphere lies the interstellar medium, with plasma
that has different speed, density, and temperature than solar wind
plasma, as well as neutral gases. These materials interact at the
heliosphere’s edge to create a region known as the inner heliosheath,
bounded on the inside by the termination shock – which is more than
twice as far from us as the orbit of Pluto – and on the outside by the
heliopause, the boundary between the solar wind and the comparatively
dense interstellar medium.
Some solar wind protons that flow out from the sun to this boundary
region will gain an electron, making them neutral and allowing them to
cross the heliopause. Once in the interstellar medium, they can lose
that electron again, making them gyrate around the interstellar magnetic
field. If those particles pick up another electron at the right place
and time, they can be fired back into the heliosphere, travel all the
way back toward Earth, and collide with IBEX’s detector. The particles
carry information about all that interaction with the interstellar
magnetic field, and as they hit the detector they can give us
unprecedented insight into the characteristics of that region of space.
“Only Voyager 1 has ever made direct observations of the interstellar
magnetic field, and those are close to the heliopause, where it’s
distorted,” said Zirnstein. “But this analysis provides a nice
determination of its strength and direction farther out.”
The directions of different ribbon particles shooting back toward
Earth are determined by the characteristics of the interstellar magnetic
field. For instance, simulations show that the most energetic particles
come from a different region of space than the least energetic
particles, which gives clues as to how the interstellar magnetic field
interacts with the heliosphere.
For the recent study, such observations were used to seed simulations
of the ribbon’s origin. Not only do these simulations correctly predict
the locations of neutral ribbon particles at different energies, but
the deduced interstellar magnetic field agrees with Voyager 1
measurements, the deflection of interstellar neutral gases, and
observations of distant polarized starlight.
However, some early simulations of the interstellar magnetic field
don’t quite line up. Those pre-IBEX estimates were based largely on two
data points – the distances at which Voyagers 1 and 2 crossed the
“Voyager 1 crossed the termination shock at 94 astronomical units, or
AU, from the sun, and Voyager 2 at 84 AU,” said Zirnstein. One AU is
equal to about 93 million miles, the average distance between Earth and
the sun. “That difference of almost 930 million miles was mostly
explained by a strong, very tilted interstellar magnetic field pushing
on the heliosphere.”
But that difference may be accounted for by considering a stronger
influence from the solar cycle, which can lead to changes in the
strength of the solar wind and thus change the distance to the
termination shock in the directions of Voyager 1 and 2. The two Voyager
spacecraft made their measurements almost three years apart, giving
plenty of time for the variable solar wind to change the distance of the
“Scientists in the field are developing more sophisticated models of the time-dependent solar wind,” said Zirnstein.
The simulations generally jibe well with the Voyager data.
TheIBEX ribbonis a relatively narrow strip of
particles flying in towards the sun from outside the heliosphere. A new
study corroborates the idea that particles from outside the heliosphere
that form the IBEX ribbon actually originate at the sun – and reveals
information about the distant interstellar magnetic field. Credits: SwRI
“The new findings can be used to better understand how our space
environment interacts with the interstellar environment beyond the
heliopause,” said Eric Christian, IBEX program scientist at NASA’s
Goddard Space Flight Center in Greenbelt, Maryland, who was not involved
in this study. “In turn, understanding that interaction could help
explain the mystery of what causes the IBEX ribbon once and for all.”
The Southwest Research Institute leads IBEX with teams of national
and international partners. NASA Goddard manages the Explorers Program
for the agency’s Heliophysics Division within the Science Mission
Directorate in Washington.
Credit:ESA/Hubble & NASA Acknowledgement: Judy Schmidt
Sparkling at the centre of this beautiful NASA/ESA Hubble Space Telescope image is a Wolf–Rayet star known as WR 31a, located about 30 000 light-years away in the constellation of Carina (The Keel).
The distinctive blue bubble appearing to encircle WR 31a, and its uncatalogued stellar sidekick, is a Wolf–Rayet nebula — an interstellar cloud of dust, hydrogen, helium and other gases. Created when speedy stellar winds
interact with the outer layers of hydrogen ejected by Wolf–Rayet stars,
these nebulae are frequently ring-shaped or spherical. The bubble —
estimated to have formed around 20 000 years ago — is expanding at a
rate of around 220 000 kilometres per hour!
lifecycle of a Wolf–Rayet star is only a few hundred thousand years —
the blink of an eye in cosmic terms. Despite beginning life with a mass
at least 20 times that of the Sun, Wolf–Rayet stars typically lose half
their mass in less than 100 000 years. And WR 31a is no exception to
this case. It will, therefore, eventually end its life as a spectacular supernova, and the stellar material expelled from its explosion will later nourish a new generation of stars and planets.
An international team led by researchers at the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA) has used a new infrared imaging technique to reveal dramatic moments in star and planet formation. These seem to occur when surrounding material falls toward very active baby stars, which then feed voraciously on it even as they remain hidden inside their birth clouds. The team used the HiCIAO (High Contrast Instrument for the Subaru Next-Generation Adaptive Optics) camera on the Subaru 8-meter Telescope in Hawaii to observe a set of newborn stars. The results of their work shed new light on our understanding of how stars and planets are born (Figure 1).
Figure 1:Circumstellar structures revealed by
Subaru-HiCIAO. The scale bars are shown in AUs (astronomical units). One
AU is the average distance from the sun to the earth. The gas and dust
surrounding baby stars (their food) are significantly more extended than
our solar system. Here we show the first observations of such complex
structures around active young stars. Figure without the labels is
linked here. (Credit: Science Advances, H. B. Liu.)
The Process of Star Birth
Stars are born when giant clouds of dust and gas collapse under the pull
of their own gravity. Planets are believed to be born at nearly the
same time as their stars in the same disk of material. However, there
are still a number of mysteries about the detailed physical processes
that occur as stars and planets form (Figure 2).
Figure 2:A schematic diagram of star and planet formation based on Green (2001)
The giant collections of dust and gas where stars form are called
"molecular clouds" because they are largely made up of molecules of
hydrogen and other gases. Over time, gravity in the densest regions of
these clouds gathers in the surrounding gas and dust, via a process
called "accretion". It is often assumed that this process is smooth and
continuous (Figure 2).
However, this steady infall explains only a small fraction of the final
mass of each star that is born in the cloud. Astronomers are still
working to understand when and how the remaining material is gathered in
during the process of star and planet birth.
A few stars are known to be associated with a sudden and violent
"feeding" frenzy from inside their stellar nursery. When they gluttonize
on the surrounding material, their visible light increases very
suddenly and dramatically, by a factor of about a hundred. These sudden
flareups in brightness are called "FU Orionis outbursts" because they
were first discovered toward the star FU Orionis.
Not many stars are found to be associated with such outbursts — only a
dozen out of thousands. However, astronomers speculate that all baby
stars may experience such outbursts as part of their growth. The reason
we only see FU Ori outbursts toward a few newborn stars is simply
because they are relatively quiet most of the time.
One key question about this mysterious facet of starbirth is "What
are the detailed physical mechanisms of these outbursts?" The answer
lies in the region surrounding the star. Astronomers know the optical
outbursts are associated with a disk of material close to the star,
called the "accretion disk". It becomes significantly brighter when the
disk gets heated up to temperatures similar to those of lava flows here
on Earth (around 700 to 1200 C or 1292 to 2182 F) like the one flowing
from Kilauea volcano area in the island of Hawaii. Several processes
have been proposed as triggers for such outbursts and astronomers have
been investigating them over the past few decades.
Finding a Mechanism for FU Ori Outbursts
An international team lead by Drs. Hauyu Baobab Liu and Hiro Takami,
two researchers at ASIAA, used a novel imaging technique available at
the Subaru Telescope to tackle this issue. The technique – imaging
polarimetry with coronagraphy – has tremendous advantages for imaging
the environments in the disks. In particular, its high angular
resolution and sensitivity allow astronomers to "see" the light from the
disk more easily. How does this work?
Circumstellar material is a mixture of gas and dust. The amount of
dust is significantly smaller than the amount of gas in the cloud, so it
has little effect on the motion of the material. However, dust
particles scatter (reflect) light from the central star, illuminating
all the surrounding material. The HiCIAO camera mounted on the Subaru
8.2-meter telescope, one of the largest optical and near-infrared (NIR)
telescopes in the world, is well-suited to observing this dim
circumstellar light. It successfully allowed the team to observe four
stars experiencing FU Ori outbursts.
Details of Four FU Ori Outbursts
The team's target stars are located 1,500-3,500 light-years from our
solar system. The images of these outbursting newborns were surprising
and fascinating, and nothing like anything previously observed around
young stars (Figure 1).
Three have unusual tails. One shows an "arm", a feature created by the
motion of material around the star. Another shows odd spiky features,
which may result from an optical outburst blowing away circumstellar gas
and dust. None of them match the picture of steady growth shown in Figure 2. Rather, they show a messy and chaotic environment, much like a human baby eating food.
To understand the structures observed around these newborn stars,
theorists on the team extensively studied one of several mechanisms
proposed to explain FU Ori outbursts. It suggests that gravity in
circumstellar gas and dust clouds creates complicated structures that
look like cream stirred into coffee (Figure 3,
left). These oddly shaped collections of material fall onto the star at
irregular intervals. The team also conducted further computer
simulations for scattered light from the outburst. Although more
simulations are required to match the simulations to the observed
images, these images show that this is a promising explanation for the
nature of FU Ori outbursts (Figure 3).
Figure 3:Images made from computer simulations based
on one theory for violent growth of a star. (Left) Simulations of the
motion of circumstellar materials falling onto a baby star. (Middle and
right). Models of how we would observe the structure in scattered light,
seen from two different angles.
(Credit: Science Advances, H. B. Liu.)
Studying these structures may also reveal how some planetary systems
are born. Astronomers know some exoplanets (planets around other stars)
are found extremely far away from their central stars. Sometimes they
orbit more than a thousand times the distance between the Sun and Earth,
and significantly larger than the orbit of Neptune (which is about 30
times the distance between the Sun and Earth). These distances are also
much larger than orbits explained by standard theories of planet
formation. Simulations of complicated circumstellar structures like the
ones seen in the HiCIAO views also predict that some dense clumps in the
material may become gas giant planets. This would naturally explain the
presence of exoplanets with such large orbits.
In spite of these exciting new results, there is a still great deal
more work to do to understand the mechanisms of star and planet birth.
More detailed comparisons between observation and theory are needed.
Further observations, particularly with the Atacama Large
Millimeter/Submillimeter Array, will take our gaze more deeply into
circumstellar gas and dust clouds. The array allows observations of the
surrounding dust and gas with unprecedented angular resolution and
sensitivity. Astronomers are also planning to construct telescopes
significantly larger than Subaru in the coming decades – including the
Thirty Meter Telescope (TMT) and the European Extremely Large Telescope.
These should allow detailed studies of regions very close to newborn
Astronomical Unit (AU) is a unit of distance. 1 AU corresponds to the average distance between the Earth and the Sun.
Paper and Research Team:
This research was supported by the Ministry of Science and Technology
(MoST) of Taiwan (Grant Nos. 103-2112-M-001-029 and
104-2119-M-001-018). E.I.V. acknowledges the support from the Russian
Ministry of Education and Science Grant 3.961.2014/K and RFBR grant
14-02-00719. R.D. was supported by Hubble Fellowship. M.M.D.
acknowledges support from the Submillimeter Array through an SMA
Postdoctoral Fellowship. These observational results were published
by Liu et al. as "Circumstellar Disks of the Most Vigorously Accreting
Young Stars" in the Science Advances on February 5, 2016.
This research was conducted by:
Hauyu Baobab Liu (Academia Sinica Institute of Astronomy and Astrophysics, Taiwan / European Southern Observatory, EU)
Michihiro Takami (Academia Sinica Institute of Astronomy and Astrophysics, Taiwan)
Tomoyuki Kudo (Subaru Telescope, National Astronomical Observatory of Japan, USA)
Jun Hashimoto (National Astronomical Observatory of Japan, Japan)
Ruobing Dong (Academia Sinica Institute of Astronomy and
Astrophysics, Taiwan / Hubble Fellow / Department of Astronomy, UC
Eduard I. Vorobyov (Department of Astrophysics, University of
Vienna, Austria / Research Institute of Physics, Southern Federal
Tae-Soo Pyo (Subaru Telescope, National Astronomical Observatory of Japan, USA)
Misato Fukagawa (National Astronomical Observatory of Japan, Japan)
Motohide Tamura (National Astronomical Observatory of Japan, Japan /
Department of Astronomy, Graduate School of Science, The University of
Thomas Henning (Max-Planck-Institut für Astronomie, Germany)
Michael M. Dunham (Harvard-Smithsonian Center for Astrophysics, USA)
Jennifer Karr (Academia Sinica Institute of Astronomy and Astrophysics, Taiwan)
Nobuhiko Kusakabe (National Astronomical Observatory of Japan, Japan)
Toru Tsuribe (College of Science, Ibaraki University, Japan)
An international team of scientists using a combination of radio and
optical telescopes identified the distant location of a fast radio burst
(FRB) for the first time. This discovery has allowed them to confirm
the current cosmological model of the distribution of matter in the
The fast radio burst was detected on April 18, 2015 by the
Commonwealth Scientific and Industrial Research Organisation (CSIRO)'s
64-meter Parkes radio telescope in Australia. That observation triggered
an international alert to other telescopes to follow up with their
observations. Within a few hours, CSIRO's Australian Telescope Compact
Array (ATCA), as well as other facilities around the world were looking
for the signal.
FRBs are mysterious bright radio flashes generally lasting only a few
milliseconds. Their cause is still unknown and there is a long list of
phenomena potentially associated with them. FRBs are very difficult to
detect; before this discovery only 16 had been observed.
"In the past, FRBs have been found by sifting through data months or
even years later. By that time it is too late to do follow up
observations," said Dr. Evan Keane, Project Scientist at the Square
Kilometre Array Organisation (SKAO) and the lead scientist behind the
study. To remedy this, the team developed its own observing system at
Swinburne University of Technology in Australia to detect FRBs within
seconds, and to immediately alert other telescopes while there is still
time to search for more evidence in the aftermath of the initial flash (Figure 1).
Figure 1:This image shows the field of view of the
Parkes radio telescope on the left. On the right are successive zoom-ins
in on the area where the signal came from (cyan circular region). The
image at the bottom right shows the Subaru Telescope's image of the FRB
galaxy, with the superimposed elliptical regions showing the location of
the fading 6-day afterglow seen with ATCA. Image Credit: D. Kaplan
(UWM), E. F. Keane (SKAO).
Catching a Flash
Thanks to the ATCA's six 22-meter dishes and their combined
resolution, the team was able to pinpoint the location of the signal
with much greater accuracy than has been possible in the past. The
observations revealed a radio afterglow that lasted for around six days
before fading away. This afterglow enabled astronomers to pinpoint the
location of the FRB about a thousand times more precisely than for
previous observed events (Figure 1).
The team members from the University of Tokyo (UTokyo), the National
Astronomical Observatory of Japan (NAOJ), and Konan University next
examined an optical image of the FRB taken a day after the first flash
by the NAOJ's 8.2-meter Subaru Telescope in Hawaii. The image revealed a
possible source: an elliptical galaxy some 6 billion light-years away.
Follow-up spectroscopic observations by the Subaru Telescope yielded a
redshift measurement for the source, which allowed astronomers to
calculate its distance. (Redshift is the speed at which the galaxy is
moving away from us due to the expansion of the universe). "For the
first time, we have identified the host galaxy and measured the distance
to a fast radio burst," said Dr. Tomonori Totani, professor at the
UTokyo Department of Astronomy, who led the optical observation effort.
Doing Cosmology with an FRB
FRBs show a frequency-dependent dispersion (Figure 2),
a delay in the radio signal caused by how much material it has gone
through. "Until now, the dispersion measure is all we had. By also
having a distance we can now measure how dense the material is between
the point of origin and Earth, and compare that with the current model
of the distribution of matter in the universe" explained Dr. Simon
Johnston, of CSIRO's Astronomy and Space Science division. "Essentially,
this lets us weigh the universe, or at least the normal matter it
In the current model, the universe is believed to be made of 70% dark
energy, 25% dark matter and 5% 'ordinary' matter, the matter that
makes up everything we see. However, through observations of stars,
galaxies and hydrogen, astronomers have only been able to account for
about half of the ordinary matter, the rest cannot be seen directly and
so has been referred to as 'missing.'
"The good news is our observations and the model match. We have found
the missing matter" explained Dr. Keane. "It's the first time a fast
radio burst has been used to conduct a cosmological measurement."
Finding the Cause of FRBs
Still, the origin of FRBs is a mystery. The fact that the host galaxy
is an elliptical galaxy, which is not actively forming young stars,
implies that it takes a long time for a stellar system to evolve into an
FRB. This favors scenarios like compact binary star mergers, but there
is no direct evidence yet.
Future observations of FRBs in a variety of wavebands may well reveal
more details about this enigmatic astronomical phenomenon. Optical
observations are essential as demonstrated by the present study.
Instruments such as the Subaru Telescope and the upcoming Thirty Meter
Telescope (TMT) in future will play major roles as FRBs occur.
Even more tantalizing is the idea that FRBs could also be sources of
gravitational waves, leading to collaboration between FRB search
projects and gravitational wave observations. These could make valuable
contributions to the new era of gravitational wave astronomy begun by
the recent discovery of a black hole binary merger by the LIGO
Figure 2:This image shows the increased delay in the
arrival time of the Fast Radio Burst as a function of the frequency. The
delay in the signal is caused by the material it goes through between
its point of origin and Earth. Image Credit: E. F. Keane (SKAO).
The study was published in Nature on February 24, 2016, titled "The host galaxy of a fast radio burst"
by Keane et al. This research is supported in part by a Grant-in-Aid
for the Scientific Research (No. 15K05018) by the Japan Society for the
Promotion of Science.
Comparison of the central part of the Milky Way at different wavelengths
A spectacular new image of the Milky Way
has been released to mark the completion of the APEX Telescope Large
Area Survey of the Galaxy (ATLASGAL). The APEX telescope in Chile has
mapped the full area of the Galactic Plane visible from the southern
hemisphere for the first time at submillimetre wavelengths — between
infrared light and radio waves — and in finer detail than recent
space-based surveys. The pioneering 12-metre APEX telescope allows
astronomers to study the cold Universe: gas and dust only a few tens of
degrees above absolute zero.
Atacama Pathfinder EXperiment telescope, is located at 5100 metres above
sea level on the Chajnantor Plateau in Chile’s Atacama region. The ATLASGAL
survey took advantage of the unique characteristics of the telescope to
provide a detailed view of the distribution of cold dense gas along the
plane of the Milky Way galaxy . The new image includes most of the regions of star formation in the southern Milky Way .
The new ATLASGAL maps cover an area of sky 140 degrees long and 3 degrees wide, more than four times larger than the first ATLASGAL release.
The new maps are also of higher quality, as some areas were re-observed
to obtain a more uniform data quality over the whole survey area.
The ATLASGAL survey is the single most successful APEX large
programme with nearly 70 associated science papers already published,
and its legacy will expand much further with all the reduced data
products now available to the full astronomical community .
At the heart of APEX are its sensitive instruments. One of these, LABOCA
(the LArge BOlometer Camera) was used for the ATLASGAL survey. LABOCA
measures incoming radiation by registering the tiny rise in temperature
it causes on its detectors and can detect emission from the cold dark
dust bands obscuring the stellar light.
The new release of ATLASGAL complements observations from ESA's Planck satellite .
The combination of the Planck and APEX data allowed astronomers to
detect emission spread over a larger area of sky and to estimate from it
the fraction of dense gas in the inner Galaxy. The ATLASGAL data were
also used to create a complete census of cold and massive clouds where
new generations of stars are forming.
“ATLASGAL provides exciting insights into where the next
generation of high-mass stars and clusters form. By combining these with
observations from Planck, we can now obtain a link to the large-scale
structures of giant molecular clouds,” remarks Timea Csengeri from
the Max Planck Institute for Radio Astronomy (MPIfR), Bonn, Germany, who
led the work of combining the APEX and Planck data.
The APEX telescope recently celebrated
ten years of successful research on the cold Universe. It plays an
important role not only as pathfinder, but also as a complementary
facility to ALMA,
the Atacama Large Millimeter/submillimeter Array, which is also located
on the Chajnantor Plateau. APEX is based on a prototype antenna
constructed for the ALMA project, and it has found many targets that
ALMA can study in great detail.
Leonardo Testi from ESO, who is a member of the ATLASGAL team and the
European Project Scientist for the ALMA project, concludes: “ATLASGAL
has allowed us to have a new and transformational look at the dense
interstellar medium of our own galaxy, the Milky Way. The new release of
the full survey opens up the possibility to mine this marvellous
dataset for new discoveries. Many teams of scientists are already using
the ATLASGAL data to plan for detailed ALMA follow-up.”
 The map was constructed from individual APEX observations of radiation with a wavelength of 870 µm (0.87 millimetres).
 The northern part of the Milky Way had already been mapped by the James Clerk Maxwell Telescope (JCMT)
and other telescopes, but the southern sky is particularly important as
it includes the Galactic Centre, and because it is accessible for
detailed follow-up observations with ALMA.  The first data release covered an
area of approximately 95 square degrees, a very long and narrow strip
along the Galactic Plane two degrees wide and over 40 degrees long. The
final maps now cover 420 square degrees, more than four times larger.
 The Planck data cover the full
sky, but with poor spatial resolution. ATLASGAL covers only the Galactic
plane, but with high angular resolution. Combining both provides
excellent spatial dynamic range.
More Information ATLASGAL is a collaboration between the Max Planck Institute for
Radio Astronomy (MPIfR), the Max Planck Institute for Astronomy (MPIA),
ESO, and the University of Chile.
APEX is a collaboration between the Max Planck Institute for Radio
Astronomy (MPIfR), the Onsala Space Observatory (OSO) and ESO. Operation
of APEX at Chajnantor is carried out by ESO.
ALMA is a partnership of the ESO, the U.S. National Science
Foundation (NSF) and the National Institutes of Natural Sciences (NINS)
of Japan in cooperation with the Republic of Chile. ALMA is funded by
ESO on behalf of its Member States, by NSF in cooperation with the
National Research Council of Canada (NRC) and the National Science
Council of Taiwan (NSC) and by NINS in cooperation with the Academia
Sinica (AS) in Taiwan and the Korea Astronomy and Space Science
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. 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 European Extremely Large Telescope, the E-ELT,
which will become “the world’s biggest eye on the sky”.
A Hubble Space Telescope image of distant, bright radio galaxies being gravitationally lensed by a very large foreground galaxy cluster. The red contours show the radio emission of these galaxies, which date from an epoch about three billion years after the big bang. A team of X-ray astronomers used these lensed radio galaxies to identify and study distant galaxies with active supermassive black hole nuclei. Credit: NASA HST, and van Weeren et al.
A lensing cluster is a gravitationally bound collection of galaxies, hundreds or even thousands, whose mass acts as a gravitational lens to collect and reimage the light of more distant objects. These lensing clusters make excellent targets for astronomical research into the early universe because they magnify the faint radiation from more distant galaxies seen behind them, making these remote objects accessible to our telescopes. Most searches in "lensed galaxies" have so far been done at optical, near infrared or submillimeter wavelengths, and the latter have been successful at identifying luminous dusty galaxies from earlier cosmic epochs that are powered by bursts of star formation that were more common back then.
X-ray astronomers study the powerful jets and high energy particles around supermassive black holes at the nuclei of active galaxies (AGN). X-rays are also seen in galaxies dominated by star formation, but they are much dimmer than those seen from AGN and so are difficult to study when these galaxies are at cosmological distances. Even finding distant examples in lensing searches can be challenging, and when the star formation activity is modest they are not even expected to show up in infrared lensing searches. But in galactic nuclei, the same fast-moving particles that emit at X-ray wavelengths also emit at radio wavelengths. A search for lensed radio emission, therefore, is a way to study distant, faint galaxies and their black hole nuclei.
CfA astronomers Reinout van Weeren, G. Ogrean, Christine Jones, Bill Forman, Felipe Andrade-Santos, E. Bulbul, Lawrence David, Ralph Kraft, Steve Murray (deceased), Paul Nulsen, Scott Randall, and Alexey Vikhlinin and their colleagues have completed a radio survey of the large cluster known as MACS J0717.5+3745. This group of galaxies, one of the largest and most complex known with the equivalent of over ten thousand Milky Way-sized galaxies, is located about five billion light-years away.
The astronomers used the Jansky Very Large Array to hunt for lensed radio sources in this cluster, and detected fifty-one compact galaxies -- seven whose light seems to be magnified by the cluster by more than factor of two and as much as a factor of nine. The scientists infer from the radio fluxes that most of these seven are forming new stars at a modest rate, ten to fifty per year, and date from an epoch about three billion years after the big bang. Two are also detected in X-rays by the Chandra X-ray Observatory, and so host AGN, each one radiating about as much light in X-rays as a billion Suns. The two AGN are interesting in themselves, but finding them both in this one region suggests that, like bright star forming galaxies, these AGN were more common back then too.
"The Discovery of Lensed Radio and X-ray Sources Behind the Frontier Fields Cluster MACSJ0717.5+3745 with the JVLA and Chandra," R. J. van Weeren, G. A. Ogrean, C. Jones, W. R. Forman, F. Andrade-Santos, A. Bonafede, M. Brüggen, E. Bulbul, T. E. Clarke, E. Churazov, L. David, W. A. Dawson, M. Donahue, A. Goulding, R. P. Kraft, B. Mason, J. Merten, T. Mroczkowski, S. S. Murray, P. E. J. Nulsen, P. Rosati, E. Roediger, S. W. Randall, J. Sayers, K. Umetsu, A. Vikhlinin, and A. Zitrin, ApJ 817, 98, 2016.
Credit: ESA/Hubble & NASA Acknowledgement: Judy Schmidt
Surrounded by an envelope of dust, the subject of this NASA/ESA Hubble Space Telescope image is a young pre-main-sequence star
known as HBC 1. The star is in an immature and adolescent phase of
life, hence its classification — most of a Sun-like star’s life is spent
in a stage comparable to human adulthood dubbed the main sequence.
In this view, HBC 1 illuminates a wispy reflection nebula known as IRAS 00044+6521. Formed from clouds of interstellar dust,
reflection nebulae do not emit any visible light of their own and
instead — like fog encompassing a lamppost — shine via the light from
the stars embedded within. Though nearby stars cannot ionise the nebula’s non-gaseous contents, as with brighter emission nebulae, scattered starlight can make the dust visible.
What makes this seemingly ordinary reflection nebula more interesting are three nearby Herbig–Haro objects
known as HH 943, HH 943B and HH 943A — which are not visible in this
image — located within IRAS 00044+6521 itself. Herbig–Haro objects are
small patches of dust, hydrogen, helium and other gases that form when narrow jets
of gas ejected by young stars such as HBC 1 collide with clouds of gas
and dust. Lasting just a few thousand years, these objects rapidly move
away from their parent star before dissipating into space.
This is an illustration of a planet that is four times the mass of
Jupiter and orbits 5 billion miles from a brown-dwarf companion (the
bright red object seen in the background). The rotation rate of this
"super-Jupiter" has been measured by studying subtle variations in the
infrared light the hot planet radiates through a variegated, cloudy
atmosphere. The planet completes one rotation every 10 hours — about
the same rate as Jupiter. Because the planet is young, it is still
contracting under gravity and radiating heat. The atmosphere is so hot
that it rains molten glass and, at lower altitudes, molten iron.
2M1207, 2MASS J12073346-3932539 [Left] — This is a Hubble Space Telescope near-infrared-light
image of a brown dwarf located 170 light-years away from Earth. The
object is no more than 30 times the mass of Jupiter, making it too
small to sustain nuclear fusion to shine as a star.
[Right] — When the glow of the brown dwarf is subtracted from
the image, a smaller and fainter companion object becomes visible. No
more that four times the mass of Jupiter, this companion is dubbed a
"super-Jupiter." It has an estimated diameter as big as 40 percent
greater than Jupiter's diameter. The world is 5 billion miles from the
brown dwarf, nearly twice the distance between our sun and the planet
Because the planet is only 10 million years old, it is so hot it may
rain molten glass and iron in its atmosphere. Hubble has measured
fluctuations in the planet's brightness that suggests the planet has
patchy clouds as it completes one rotation every 10 hours.Credit:NASA, ESA, and Y. Zhou (University of Arizona)
This graph plots small changes in the infrared brightness of a
super-Jupiter as measured by the Hubble Space Telescope. The S-shaped
curve is extrapolated from the data points. Its sinusoidal shape
suggests that brightness changes are a result of a 10-hour rotation
period (horizontal axis). The vertical axis shows small changes in
brightness. This would mean that the planet likely has patchy clouds
that influence the amount of infrared radiation observed as the planet
rotates. At a distance of 170 light-years from Earth, the planet is too
far away for Hubble to actually resolve atmospheric structure. Credit:NASA,ESA, Y. Zhou (University of Arizona), and P. Jeffries (STScI)
Astronomers using NASA's Hubble Space Telescope have measured the
rotation rate of an extreme exoplanet by observing the varied
brightness in its atmosphere. This is the first measurement of the
rotation of a massive exoplanet using direct imaging.
"The result is very exciting," said Daniel Apai of the University of
Arizona in Tucson, leader of the Hubble investigation. "It gives us a
unique technique to explore the atmospheres of exoplanets and to
measure their rotation rates."
The planet, called 2M1207b, is about four times more massive than
Jupiter and is dubbed a "super-Jupiter." It is a companion to a failed
star known as a brown dwarf, orbiting the object at a distance of 5
billion miles. By contrast, Jupiter is approximately 500 million miles
from the sun. The brown dwarf is known as 2M1207. The system resides
170 light-years away from Earth.
Hubble's image stability, high resolution, and high-contrast imaging
capabilities allowed astronomers to precisely measure the planet's
brightness changes as it spins. The researchers attribute the
brightness variation to complex clouds patterns in the planet's
atmosphere. The new Hubble measurements not only verify the presence of
these clouds, but also show that the cloud layers are patchy and
Astronomers first observed the massive exoplanet 10 years ago with
Hubble. The observations revealed that the exoplanet's atmosphere is
hot enough to have "rain" clouds made of silicates: vaporized rock that
cools down to form tiny particles with sizes similar to those in
cigarette smoke. Deeper into the atmosphere, iron droplets are forming
and falling like rain, eventually evaporating as they enter the lower
levels of the atmosphere.
"So at higher altitudes it rains glass, and at lower altitudes it
rains iron," said Yifan Zhou of the University of Arizona, lead author
on the research paper. "The atmospheric temperatures are between about
2,200 to 2,600 degrees Fahrenheit."
The super-Jupiter is so hot that it appears brightest in infrared
light. Astronomers used Hubble's Wide Field Camera 3 to analyze the
exoplanet in infrared light to explore the object's cloud cover and
measure its rotation rate. The planet is hot because it is only about
10 million years old and is still contracting and cooling. For
comparison, Jupiter in our solar system is about 4.5 billion years old.
The planet, however, will not maintain these sizzling temperatures.
Over the next few billion years, the object will cool and fade
dramatically. As its temperature decreases, the iron and silicate
clouds will also form lower and lower in the atmosphere and will
eventually disappear from view.
Zhou and his team have also determined that the super-Jupiter
completes one rotation approximately every 10 hours, spinning at about
the same fast rate as Jupiter.
This super-Jupiter is only about five to seven times less massive
than its brown-dwarf host. By contrast, our sun is about 1,000 times
more massive than Jupiter. "So this is a very good clue that the 2M1207
system we studied formed differently than our own solar system," Zhou
explained. The planets orbiting our sun formed inside a circumstellar
disk through accretion. But the super-Jupiter and its companion may
have formed throughout the gravitational collapse of a pair of separate
"Our study demonstrates that Hubble and its successor, NASA's James
Webb Space Telescope, will be able to derive cloud maps for exoplanets,
based on the light we receive from them," Apai said.
super-Jupiter is an ideal target for the Webb telescope, an infrared
space observatory scheduled to launch in 2018. Webb will help
astronomers better determine the exoplanet's atmospheric composition
and derive detailed maps from brightness changes with the new technique
demonstrated with the Hubble observations.
Results from this study will appear in the Feb. 18, 2016, edition of The Astrophysical Journal.
This video shows an artist's impression of the super-Earth 55 Cancri e
moving in front of its parent star. During these transits astronomers
were able to gather information about the atmosphere of the exoplanet.
The Scientists were able to retrieve the spectrum of 55 Cancri e
embedded in the light of its parent star. The analysis showed that the atmosphere of 55 Cancri e consists mainly of helium and hydrogen with hints of hydrogen cyanide.Credit: ESA/Hubble, M. Kornmesser
For the first time astronomers were able
to analyse the atmosphere of an exoplanet in the class known as
super-Earths. Using data gathered with the NASA/ESA Hubble Space
Telescope and new analysis techniques, the exoplanet 55 Cancri e is
revealed to have a dry atmosphere without any indications of water
vapour. The results, to be published in the Astrophysical Journal,
indicate that the atmosphere consists mainly of hydrogen and helium.
The international team, led by scientists from
University College London (UCL) in the UK, took observations of the
nearby exoplanet 55 Cancri e, a super-Earth with a mass of eight
Earth-masses . It is located in the planetary system of 55 Cancri, a star about 40 light-years from Earth.
Using observations made with the Wide Field Camera 3
(WFC3) on board the NASA/ESA Hubble Space Telescope, the scientists
were able to analyse the atmosphere of this exoplanet. This makes it the
first detection of gases in the atmosphere of a super-Earth. The
results allowed the team to examine the atmosphere of 55 Cancri e in
detail and revealed the presence of hydrogen and helium, but no water
These results were only made possible by exploiting a
newly-developed processing technique.
“This is a very exciting result because
it’s the first time that we have been able to find the spectral
fingerprints that show the gases present in the atmosphere of a
super-Earth,” explains Angelos Tsiaras, a PhD student at UCL,
who developed the analysis technique along with his colleagues Ingo
Waldmann and Marco Rocchetto. “The observations of 55 Cancri
e’s atmosphere suggest that the planet has managed to cling on to a
significant amount of hydrogen and helium from the nebula from which it
Super-Earths like 55 Cancri e are thought to be the
most common type of planet in our galaxy. They acquired the name
‘super-Earth’ because they have a mass larger than that of the Earth but
are still much smaller than the gas giants in the Solar System. The
WFC3 instrument on Hubble has already been used to probe the atmospheres
of two other super-Earths, but no spectral features were found in those
previous studies .
55 Cancri e, however, is an unusual super-Earth as it
orbits very close to its parent star. A year on the exoplanet lasts for
only 18 hours and temperatures on the surface are thought to reach
around 2000 degrees Celsius. Because the exoplanet is orbiting its
bright parent star at such a small distance, the team was able to use
new analysis techniques to extract information about the planet, during
its transits in front of the host star.
Observations were made by scanning the WFC3 very quickly across
the star to create a number of spectra.
By combining these observations
and processing them through analytic software, the researchers were
able to retrieve the spectrum of 55 Cancri e embedded in the light of
its parent star.
“This result gives a first insight into
the atmosphere of a super-Earth. We now have clues as to what the planet
is currently like and how it might have formed and evolved, and this
has important implications for 55 Cancri e and other super-Earths,” said Giovanna Tinetti, also from UCL, UK.
Intriguingly, the data also contain hints of the presence of hydrogen cyanide, a marker for carbon-rich atmospheres.
“Such an amount of hydrogen cyanide would indicate an atmosphere with a very high ratio of carbon to oxygen,”
said Olivia Venot, KU Leuven, who developed an atmospheric chemical
model of 55 Cancri e that supported the analysis of the observations.
“If the presence of hydrogen cyanide and other
molecules is confirmed in a few years time by the next generation of
infrared telescopes, it would support the theory that this planet is
indeed carbon rich and a very exotic place,” concludes Jonathan Tennyson, UCL. “Although hydrogen cyanide, or prussic acid, is highly poisonous, so it is perhaps not a planet I would like to live on!”
 55 Cancri e has previously been dubbed the
“diamond planet” because models based on its mass and radius have led to
the idea that its interior is carbon-rich.
 Hubble observed the
super-Earths GJ1214b and HD97658b in 2014, using the transit method. The
observations did not show any spectral features, indicating an
atmosphere covered by thick clouds made of molecular species much
heavier than hydrogen.
The Hubble Space Telescope is a project of international cooperation between ESA and NASA.
The results were summarized by Tsiaras et al. in the
paper “Detection of an atmosphere around the super-Earth 55 Cancri e”
which is going to be published in the Astrophysical Journal.
The team of astronomers in this study consists of A.
Tsiaras (UCL, UK), M. Rocchetto (UCL, UK), I. P. Waldmann (UCL, UK), O.
Venot (Katholieke Universiteit Leuven, Belgium), R. Varley (UCL, UK), G.
Morello (UCL, UK), G. Tinetti (UCL, UK), E. J. Barton (UCL, UK), S. N.
Yurchenko (UCL, UK), J. Tennyson (UCL, UK).
University College London was founded in 1826. It was the first
English university established after Oxford and Cambridge, the first to
open up university education to those previously excluded from it, and
the first to provide systematic teaching of law, architecture and
medicine. UCL is among the world’s top universities, as reflected by
performance in a range of international rankings and tables. UCL
currently has over 35 000 students from 150 countries and over 11 000
A jet from a very distant black hole being illuminated by the leftover glow from the Big Bang, known as the cosmic microwave background (CMB), has been found as described in our latest press release.
Astronomers using NASA's Chandra X-ray Observatory discovered this
faraway jet serendipitously when looking at another source in Chandra's
field of view.
Jets in the early Universe such as this one, known as B3 0727+409,
give astronomers a way to probe the growth of black holes at a very
early epoch in the cosmos. The light from B3 0727+409 was emitted about
2.7 billion years after the Big Bang when the Universe was only about
one fifth of its current age.
This main panel graphic shows Chandra's X-ray data
that have been combined with an optical image from the Digitized Sky
Survey. (Note that the two sources near the center of the image do not
represent a double source, but rather a coincidental alignment of the
distant jet and a foreground galaxy.)
The inset shows more detail of the X-ray emission from the jet detected by Chandra. The length of the jet in 0727+409 is at least 300,000 light years.
Many long jets emitted by supermassive black holes have been detected
in the nearby Universe, but exactly how these jets give off X-rays has
remained a matter of debate. In B3 0727+409, it appears that the CMB is
being boosted to X-ray wavelengths.
Scientists think that as the electrons in the jet fly from the black
hole at close to the speed of light, they move through the sea of CMB
radiation and collide with microwave photons. This boosts the energy of
the photons up into the X-ray band to be detected by Chandra. If this is
the case, it implies that the electrons in the B3 0727+409 jet must
keep moving at nearly the speed of light for hundreds of thousands of
The significance of this discovery is heightened because astronomers
essentially stumbled across this jet while observing a galaxy cluster in
the field. Historically, such distant jets have been discovered in
radio waves first, and then followed up with X-ray observations to look
for high-energy emission. If bright X-ray jets can exist with very faint
or undetected radio counterparts, it means that there could be many
more of them out there because astronomers haven't been systematically
looking for them.
A paper describing these results was published in the 2016 January 1st issue of The Astrophysical Journal Letters and is available online.
The authors are Aurora Simionescu (Institute of Space and Astronautical
Science, Kanagawa, Japan), Lukasz Stawarz (Jagiellonian University,
Kraków, Poland), Yuto Ichinohe (Institute of Space and Astronautical
Science, Kanagawa, Japan), Teddy Cheung (Naval Research Laboratory,
Washington, DC), Marek Jamrozy (Jagiellonian University, Kraków,
Poland), Aneta Siemiginowska (Harvard-Smithsonian Center for
Astrophysics, Cambridge, MA), Kouichi Hagino (Institute of Space and
Astronautical Science, Kanagawa, Japan), Poshak Gandhi (University of
Southampton, Southampton, UK) and Norbert Werner (Stanford University,
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.
Fast Facts for B3 0727+409:
Scale: Main image is 10 arcmin across (16 million light years); Inset image is 46 arcsec across (1.23 million light years)
An international team of researchers led by Aaron Romanowsky of San
José State University has used the Subaru Telescope to identify a faint
dwarf galaxy disrupting around a nearby giant spiral galaxy. The
observations provide a valuable glimpse of a process that is fleeting
but important in shaping galaxies.
"The outer regions of giant galaxies like our own Milky Way appear to
be a jumble of debris from hundreds of smaller galaxies that fell in
over time and splashed into smithereens," said Romanowsky. "These dwarfs
are considered building blocks of the giants, but the evidence for
giants absorbing dwarfs has been largely circumstantial. Now we have
caught a pair of galaxies in the act of a deadly embrace." (Figure 1)
The two objects in the study are NGC 253, also called the Silver
Dollar galaxy, and the newly discovered dwarf NGC 253-dw2. They are
located in the Southern constellation of Sculptor at a distance of 11
million light years from Earth, and are separated from each other by
about 160 thousand light years. The dwarf has an elongated appearance
that is the hallmark of being stretched apart by the gravity of a larger
The dwarf has been trapped by its giant host and will not survive
intact for much longer," said team member Nicolas Martin, of the
Strasbourg Observatory. "The next time it plunges closer to its host, it
could be shredded into oblivion. However, the host may suffer some
damage too, if the dwarf is heavy enough."
The interplay between the two galaxies may resolve an outstanding
mystery about NGC 253, as the giant spiral shows signs of being
disturbed by a dwarf. The disturber was previously unseen and presumed
to have perished, but now the likely culprit has been found. "This looks
like a case of galactic stealth attack," said Gustavo Morales of
Heidelberg University. "The dwarf galaxy has dived in from the depths of
space and barraged the giant, while remaining undetected by virtue of
its extreme faintness."
The discovery of NGC 253-dw2 has an unusual pedigree. It began with a
digital image of the giant galaxy taken by astrophotographer Michael
Sidonio using a 30 centimeter (12 inch) diameter amateur telescope in
Australia. Other members of the international team noticed a faint
smudge in the image and followed it up with a larger, 80 centimeter (30
inch) amateur telescope in Chile, led by Johannes Schedler. The identity
of the object was still not clear, and it was observed with the 8 meter
(27 foot) Subaru Telescope on the summit of Mauna Kea in Hawaii, in
December 2014. "In the first image, we weren't sure if there was really a
faint galaxy or if it was some kind of stray reflection," said David
Martínez-Delgado, also from Heidelberg University. "With the
high-quality imaging of the Suprime-Cam instrument on the Subaru
Telescope, we can now see that the smudge is composed of individual
stars and is a bona fide dwarf galaxy. This discovery is a wonderful
example of fruitful collaboration between amateur and professional
astronomers." (Figure 2)
The findings are in research paper published in the Monthly Notices
of the Royal Astronomical Society Letters by Oxford University Press, as
"Satellite accretion in action: a tidally disrupting dwarf spheroidal
around the nearby spiral galaxy NGC 253" by Romanowsky et al., first
online on January 23, 2016 (http://mnrasl.oxfordjournals.org/lookup/doi/10.1093/mnrasl/slv207).
The research team:
Aaron J. Romanowsky (San José State University and University of California Observatories, USA)
David Martínez-Delgado (Zentrum für Astronomie der Universität Heidelberg, Germany)
Nicolas F. Martin (Université de Strasbourg, France and Max-Planck-Institut für Astronomie, Germany)
Gustavo Morales (Zentrum für Astronomie der Universität Heidelberg, Germany)
Zachary G. Jennings (University of California, USA)
R. Jay GaBany (Black Bird Observatory II, USA)
Jean P. Brodie (University of California Observatories and University of California, USA)
Eva K. Grebel (Zentrum für Astronomie der Universität Heidelberg, Germany)
Johannes Schedler (Cerro Tololo Inter-American Observatory, Chile)