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The Galaxy NGC 4151 called the, ‘Eye of Sauron’ due to its similarity to the eye in the film Lord of the Rings. The image shows the supermassive black hole, which is still active, that is to say that it engulfs gas and dust clouds from its surroundings. In this process, it emits ultraviolet radiation, which heats the ring-shaped dust cloud that orbits around the black hole at a distance and this causes the dust cloud to emit infrared radiation. Credit: NASA
MAUNA KEA, Hawaii — A team of scientists, led by Dr. Sebastian Hoenig from the University
of Southampton, has accurately
measured the distance to the nearby NGC4151 galaxy, using the W. M. Keck
Observatory Interferometer. The team employed a new technique they developed,
which allows them to measure precise distances to galaxies tens of
millions of light years away. The
research was published today in the journal Nature.
new technique is similar to that used by land surveyors on earth, who measure
both the physical
and angular – or ‘apparent’ – size of a distant
object, to calculate its distance from Earth.
reported distances to NGC 4151, which contains a supermassive black hole, ranged
from 4- to 29-megaparsecs, but using this new, more accurate method, the
researchers calculated the distance to the supermassive black hole as 19
galaxy NGC415 is dubbed the ‘Eye of Sauron’ by astronomers for the similarity to its
namesake in the film trilogy The Lord of the Rings. As in the famous saga, a ring plays a crucial role in this
new measurement. All big galaxies in the universe host a supermassive black
hole in their center and in about 10 percent of all galaxies, these
supermassive black holes are growing by swallowing huge amounts of gas and dust
from their surrounding environments. In this process, the material heats up and
becomes very bright — becoming the most energetic sources of emission in the
universe known as active galactic nuclei (AGN).
This hot dust forms a ring around the supermassive black hole and
emits infrared radiation, which the researchers used as the ruler. However, the
apparent size of the Eye of Sauron’s ring is so small, the observations were
carried out using the Keck Interferometer, which combines Keck Observatory’s
twin 10-meter telescopes — already the largest telescopes on Earth — to achieve
the resolving power of an 85m telescope.
To measure the physical size of the dusty ring, the researchers measured
the time delay between the emission of light from close to the black hole and
the more distant infrared emission. The distance from the center to the hot
dust is simply this delay divided by the speed of light.
By combining the physical size of the dust ring with the apparent size
measured with the Keck Interferometer, the researchers were able to determine a
distance to NGC 4151.
“One of the key findings is that the
distance determined in this new
fashion is quite precise — with 90
percent accuracy,” Hoenig said.
“In fact, this method, based on simple geometrical principles, gives the
precise distances for remote galaxies. Moreover, it can be readily used
more sources than current methods. Such distances are key in pinning
down the cosmological parameters that characterize our universe or in
accurately measuring black hole masses. Indeed,
NGC 4151 is a key to calibrating various techniques of estimating black
masses. Our new distance implies that these masses may have been
underestimated by 40 percent.”
Hoenig, together with colleagues in Denmark and Japan, is currently
setting up a new program to extend their work to many more AGN. The goal is to
establish precise distances to a dozen galaxies using this technique and use
them to constrain cosmological parameters to within few per cent. Combined with
other measurements, this will provide a better understanding of the history of
expansion of our universe.
The W. M. Keck Observatory operates the most scientifically productive telescopes on Earth. The two, 10-meter
optical/infrared telescopes near the summit of Mauna Kea on the Island of
Hawaii feature a suite of advanced instruments including imagers, multi-object
spectrographs, high-resolution spectrographs, integral-field spectrographs and
world-leading laser guide star adaptive optics systems.
Interferometer began construction in 1997, and finished its mission in
2012. It was funded by NASA and managed by JPL. JPL is managed by
Caltech for NASA.
Keck Observatory is a private 501(c) 3
non-profit organization and a scientific partnership of the California
Institute of Technology, the University of California and NASA.
The galaxy cutting dramatically across the frame of this NASA/ESA Hubble Space Telescope image is a slightly warped dwarf galaxy
known as UGC 1281. Seen here from an edge-on perspective, this galaxy
lies roughly 18 million light-years away in the constellation of
Triangulum (The Triangle).
The bright companion to the lower left of UGC 1281 is the small
galaxy PGC 6700, officially known as 2MASX J01493473+3234464. Other
prominent stars belonging to our own galaxy, the Milky Way, and more
distant galaxies can be seen scattered throughout the sky.
The side-on view we have of UGC 1281 makes it a perfect candidate for studies into how gas is distributed within galactic halos
— the roughly spherical regions of diffuse gas extending outwards from a
galaxy’s centre. Astronomers have studied this galaxy to see how its
gas vertically extends out from its central plane, and found it to be a
quite typical dwarf galaxy. However, it does have a slightly warped
shape to its outer edges, and is forming stars at a particularly low
A version of this image was entered into the Hubble's Hidden Treasures image processing competition by contestant Luca Limatola.
Panning across the colourful star cluster NGC 3532
The MPG/ESO 2.2-metre telescope at ESO’s
La Silla Observatory in Chile has captured a richly colourful view of
the bright star cluster NGC 3532. Some of the stars still shine with a
hot bluish colour, but many of the more massive ones have become red
giants and glow with a rich orange hue.
NGC 3532 is a bright open cluster located some 1300 light-years away in the constellation of Carina (The
Keel of the ship Argo). It is informally known as the Wishing Well
Cluster, as it resembles scattered silver coins which have been dropped
into a well. It is also referred to as the Football Cluster, although
how appropriate this is depends on which side of the Atlantic you live.
It acquired the name because of its oval shape, which citizens of
rugby-playing nations might see as resembling a rugby ball.
This very bright star cluster is easily seen with the naked eye from
the southern hemisphere. It was discovered by French astronomer Nicolas Louis de Lacaille
whilst observing from South Africa in 1752 and was catalogued three
years later in 1755. It is one of the most spectacular open star
clusters in the whole sky.
NGC 3532 covers an area of the sky that is almost twice the size of
the full Moon. It was described as a binary-rich cluster by John
Herschel who observed “several elegant double stars” here during his
stay in southern Africa in the 1830s. Of additional, much more recent,
historical relevance, NGC 3532 was the first target to be observed by
the NASA/ESA Hubble Space Telescope, on 20 May 1990.
This grouping of stars is about 300 million years old. This makes it middle-aged by open star cluster standards .
The cluster stars that started off with moderate masses are still
shining brightly with blue-white colours, but the more massive ones have
already exhausted their supplies of hydrogen fuel and have become red
giant stars. As a result the cluster appears rich in both blue and
orange stars. The most massive stars in the original cluster will have
already run through their brief but brilliant lives and exploded as
supernovae long ago. There are also numerous less conspicuous fainter
stars of lower mass that have longer lives and shine with yellow or red
hues. NGC 3532 consists of around 400 stars in total.
The background sky here in a rich part of the Milky Way is very
crowded with stars. Some glowing red gas is also apparent, as well as
subtle lanes of dust that block the view of more distant stars. These
are probably not connected to the cluster itself, which is old enough to
have cleared away any material in its surroundings long ago.
This image of NGC 3532 was captured by the Wide Field Imager instrument at ESO’s La Silla Observatory in February 2013.
 Stars with masses
many times greater than the Sun have lives of just a few million years,
the Sun is expected to live for about ten billion years and low-mass
stars have expected lives of hundreds of billions of years — much
greater than the current age of the Universe.
ESO is the foremost intergovernmental
astronomy organisation in Europe and the world’s most productive
ground-based astronomical observatory by far. It is supported by 15
countries: Austria, Belgium, Brazil, the Czech Republic, Denmark,
France, Finland, Germany, Italy, the Netherlands, Portugal, Spain,
Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious
programme focused on the design, construction and operation of powerful
ground-based observing facilities enabling astronomers to make
important scientific discoveries. ESO also plays a leading role in
promoting and organising cooperation in astronomical research. ESO
operates three unique world-class observing sites in Chile: La Silla,
Paranal and Chajnantor. At Paranal, ESO operates the Very Large
Telescope, the world’s most advanced visible-light astronomical
observatory and two survey telescopes. VISTA works in the infrared and
is the world’s largest survey telescope and the VLT Survey Telescope is
the largest telescope designed to exclusively survey the skies in
visible light. ESO is the European partner of a revolutionary
astronomical telescope ALMA, the largest astronomical project in
existence. ESO is currently planning the 39-metre European Extremely
Large optical/near-infrared Telescope, the E-ELT, which will become “the
world’s biggest eye on the sky”.
are millimeter-sized constituents of primitive meteorites that formed
in brief heating events in the young solar nebula. Scientists have
succeeded in determining the ancient magnetic field strength by
measuring the field recorded in chondrules like this one containing the
mineral olivine. The scale shows a length of 0.2 millimeters.Credit: Wu et al.
observations of young protostars indicate that early planetary systems
evolved from the dust in a protoplanetary disk very quickly - in under
five million years. Such short timescales require very efficient
mechanism(s) to transport material inward towards the central star, but
the mechanism(s) that do this are uncertain. Several have been invoked,
however, in which magnetic fields play a key role, either in the
stellar wind or in the disk itself.
Astronomers cannot currently directly measure magnetic field
strengths in planet-forming regions, but experiments on meteoritic
materials in our own Solar system can potentially constrain the strength
of early Solar nebular magnetic fields. Chondrules are
millimeter-sized constituents of primitive meteorites that formed in
brief heating events in the young solar nebula. They probably constitute
a significant fraction of the mass of asteroids and even of terrestrial
planet precursors. The formation of chondrules, therefore, very likely
occurred during a key stage in the evolution of the early solar system.
If a stable field was present during their cooling off phase, they
should themselves have become slightly magnetized. Determining their
magnetic fields should therefore not only constrain models of their
formation, but of the disk's evolution as well.
Among the most pristine known meteorites is one called Semarkona. It
contains chondrules of crystalline olivine which, due to their unique
compositional and magnetic properties, can retain their primitive
magnetization even over the eons since they formed and despite their
subsequent histories in the solar system. CfA astrophysicists Xue-Ning
Bai and Ron Walsworth, and their collaborators, isolated eight olivine
chondrules from the Semarkona meteorite; they are tiny, less than a
millimeter in size. Using newly perfected techniques that take advantage
of cryogenic quantum measurements developed in Walsworth's laboratory,
the team was able to detect magnetic fields in these minuscule crystal
samples, and to conclude that the primitive nebula in which these
chondrules formed had a field strength corresponding to about double the
Earth’s current magnetic field (at its surface). The scientists
conclude that the evidence supports the model of chondrules forming in
shocks or collisions between larger bodies, rather than any of the
stellar wind formation theories. They also conclude that the nebular
magnetic fields were large enough to account for the measured rates of
mass transport in the early evolutionary stages. Not least, the result
is an impressive application of newly perfected quantum measuring
Nebula Magnetic Fields Recorded in the Semarkona Meteorite," Roger R.
Fu, Benjamin P. Weiss, Eduardo A. Lima, Richard J. Harrison, Xue-Ning
Bai, Steven J. Desch, Denton S. Ebel, Clement Suavet, Huapei Wang, David
Glenn, David Le Sage, Takeshi Kasama, Ronald L. Walsworth, Aaron T.
Kuan, Science, in press, 2014
Copyright Credit: NASA/ESA/Hubble Heritage Team (STScI/AURA). Acknowledgment: W. Sparks (STScI) & R. Sahai (JPL)
This colourful image shows a cosmic lighthouse known as the Egg
Nebula, which lies around 3000 light-years from Earth. The image, taken
with the NASA/ESA Hubble Space Telescope, has captured a brief but
dramatic phase in the life of a Sun-like star.
The Egg Nebula is a
‘preplanetary nebula’. These objects occur as a dying star’s hot
remains briefly illuminates material it has expelled, lighting up the
gas and dust that surrounds it.
These objects will one day develop
into planetary nebulas which, despite the name, have nothing at all to
do with planets. They gained their rather misleading title because when
they were discovered in the 18th century they resembled planets in our
Solar System when viewed through a telescope.
Although the dying
star is hidden behind the thick dust lane that streaks down the centre
of this image, it is revealed by the four lighthouse-like beams clearly
visible through the veil of dust that lies beyond the central lane.
light beams were able to penetrate the central dust lane due to paths
carved out of the thick cloud by powerful jets of material expelled from
the star, although the cause of these jets is not yet known.
concentric rings seen in the less dense cloud surrounding the star are
due to the star ejecting material at regular intervals – typically every
hundred years – during a phase of the star’s evolution just prior to
this preplanetary nebula phase. These dusty shells are not usually
visible in these nebulas, but when they are it provides astronomers with
a rare opportunity to study their formation and evolution.
fleeting nature of this phase in a star’s life – which occupies only a
few thousand of the star’s few billion years of existence – and the fact
that they are fairly faint make it rare to capture them in action. In
fact, the Egg Nebula, the first of its kind to be identified, was
discovered only 40 years ago.
This image was taken with Hubble’s
Advanced Camera for Surveys. Artificial colours are used to represent
how the light from the star reflects off the dust – this can tell
scientists about the physical properties of the dust.
combines observations with three different polarising filters, each
showing light vibrating at a specific orientation. The three filters
have been coloured red, blue and green, and all three observations were
made at a wavelength of 0.606 microns. The image spans 1.2 light-years.
North is to the right and east is up.
Credit: ESO/S. Ramstedt (Uppsala University, Sweden) & W. Vlemmings (Chalmers University of Technology, Sweden)
Studying red giant stars
tells astronomers about the future of the Sun — and about how previous
generations of stars spread the elements needed for life across the
Universe. One of the most famous red giants in the sky is called Mira A,
part of the binary system Mira which lies about 400 light-years from Earth. In this image ALMA reveals Mira’s secret life.
A is an old star, already starting to throw out the products of its
life’s work into space for recycling. Mira A’s companion, known as Mira B, orbits it at twice the distance from the Sun to Neptune.
A is known to have a slow wind which gently moulds the surrounding
material. ALMA has now confirmed that Mira’s companion is a very
different kind of star, with a very different wind. Mira B is a hot,
dense white dwarf with a fierce and fast stellar wind.
observations show how the winds from the two stars have created a
fascinating, beautiful and complex nebula. The remarkable heart-shaped
bubble at the centre is created by Mira B’s energetic wind inside Mira
A’s more relaxed outflow. The heart, which formed some time in the last
400 years or so, and the rest of the gas surrounding the pair show that
they have long been building this strange and beautiful environment
By looking at stars like Mira A and Mira B scientists
hope to discover how our galaxy’s double stars differ from single stars
in how they give back what they have created to the Milky Way’s stellar
ecosystem. Despite their distance from one another, Mira A and its
companion have had a strong effect on one another and demonstrate how
double stars can influence their environments and leave clues for
scientists to decipher.
Other old and dying stars also have
bizarre surroundings, as astronomers have seen using both ALMA and other
telescopes. But it’s not always clear whether the stars are single,
like the Sun, or double, like Mira. Mira A, its mysterious partner and
their heart-shaped bubble are all part of this story.
The new observations of Mira A and its partner are presented in this paper.
dwarf galaxy Markarian 177 (center) and its unusual source SDSS1133
(blue) lie 90 million light-years away. The galaxies are located in the
bowl of the Big Dipper, a well-known star pattern in the constellation
Ursa Major. Image Credit: Sloan Digital Sky Survey
the Keck II telescope in Hawaii, researchers obtained high-resolution
images of Markarian 177 and SDSS1133 using a near-infrared filter. Twin
bright spots in the galaxy's center are consistent with recent star
formation, a disturbance that hints this galaxy may have merged with
another. Image Credit: Credit: W. M. Keck Observatory/M. Koss (ETH Zurich) et al. Unlabeled version
(bright spot, lower left) has been a persistent source for more than 60
years. This sequence of archival astronomical imagery, taken through
different instruments and filters, shows that the source is detectable
in 1950 and brightest in 2001. Image Credit: NASA's Goddard Space Flight Center/M. Koss (ETH Zurich)
An international team of researchers analyzing decades of observations
from many facilities, including NASA's Swift satellite, has discovered
an unusual source of light in a galaxy some 90 million light-years away.
object's curious properties make it a good match for a supermassive
black hole ejected from its home galaxy after merging with another giant
black hole. But astronomers can't yet rule out an alternative
possibility. The source, called SDSS1133, may be the remnant of a
massive star that erupted for a record period of time before destroying
itself in a supernova explosion.
"With the data we have in hand, we can't yet distinguish between
these two scenarios," said lead researcher Michael Koss, an astronomer
at ETH Zurich, the Swiss Federal Institute of Technology. "One exciting
discovery made with NASA's Swift is that the brightness of SDSS1133 has
changed little in optical or ultraviolet light for a decade, which is
not something typically seen in a young supernova remnant."
In a study published in the Nov. 21 edition of Monthly Notices of the
Royal Astronomical Society, Koss and his colleagues report that the
source has brightened significantly in visible light during the past six
months, a trend that, if maintained, would bolster the black hole
interpretation. To analyze the object in greater detail, the team is
planning ultraviolet observations with the Cosmic Origins Spectrograph
aboard the Hubble Space Telescope in October 2015.
Whatever SDSS1133 is, it's persistent. The team was able to detect it in astronomical surveys dating back more than 60 years.
The mystery object is part of the dwarf galaxy Markarian 177, located
in the bowl of the Big Dipper, a well-known star pattern within the
constellation Ursa Major. Although supermassive black holes usually
occupy galactic centers, SDSS1133 is located at least 2,600 light-years
from its host galaxy's core.
In June 2013, the researchers obtained high-resolution near-infrared
images of the object using the 10-meter Keck II telescope at the W. M.
Keck Observatory in Hawaii. They reveal the emitting region of SDSS1133
is less than 40 light-years across and that the center of Markarian 177
shows evidence of intense star formation and other features indicating a
"We suspect we're seeing the aftermath of a merger of two small
galaxies and their central black holes," said co-author Laura Blecha, an
Einstein Fellow in the University of Maryland's Department of Astronomy
and a leading theorist in simulating recoils, or "kicks," in merging
black holes. "Astronomers searching for recoiling black holes have been
unable to confirm a detection, so finding even one of these sources
would be a major discovery."
The collision and merger of two galaxies disrupts their shapes and
results in new episodes of star formation. If each galaxy possesses a
central supermassive black hole, they will form a bound binary pair at
the center of the merged galaxy before ultimately coalescing themselves.
Merging black holes release a large amount of energy in the form of
gravitational radiation, a consequence of Einstein's theory of gravity.
Waves in the fabric of space-time ripple outward in all directions from
accelerating masses. If both black holes have equal masses and spins,
their merger emits gravitational waves uniformly in all directions. More
likely, the black hole masses and spins will be different, leading to
lopsided gravitational wave emission that launches the black hole in the
The kick may be strong enough to hurl the black hole entirely out of
its home galaxy, fating it to forever drift through intergalactic space.
More typically, a kick will send the object into an elongated orbit.
Despite its relocation, the ejected black hole will retain any hot gas
trapped around it and continue to shine as it moves along its new path
until all of the gas is consumed.
If SDSS1133 isn't a black hole, then it might have been a very
unusual type of star known as a Luminous Blue Variable (LBV). These
massive stars undergo episodic eruptions that cast large amounts of mass
into space long before they explode. Interpreted in this way, SDSS1133
would represent the longest period of LBV eruptions ever observed,
followed by a terminal supernova explosion whose light reached Earth in
The nearest comparison in our galaxy is the massive binary system Eta
Carinae, which includes an LBV containing about 90 times the sun's
mass. Between 1838 and 1845, the system underwent an outburst that
ejected at least 10 solar masses and made it the second-brightest star
in the sky. It then followed up with a smaller eruption in the 1890s.
In this alternative scenario, SDSS1133 must have been in nearly
continual eruption from at least 1950 to 2001, when it reached peak
brightness and went supernova. The spatial resolution and sensitivity of
telescopes prior to 1950 were insufficient to detect the source. But if
this was an LBV eruption, the current record shows it to be the longest
and most persistent one ever observed. An interaction between the
ejected gas and the explosion's blast wave could explain the object's
steady brightness in the ultraviolet.
Whether it's a rogue supermassive black hole or the closing act of a
rare star, it seems astronomers have never seen the likes of SDSS1133
NGC 986 is found in the constellation of Fornax (The Furnace), located in the southern sky. NGC 986 is a bright, 11th-magnitude
galaxy sitting around 56 million light-years away, and its golden
centre and barred swirling arms are clearly visible in this image.
Barred spiral galaxies are spiral galaxies with a central
bar-shaped structure composed of stars. NGC 986 has the characteristic
S-shaped structure of this type of galactic morphology. Young blue stars
can be seen dotted amongst the galaxy’s arms and the core of the galaxy
is also aglow with star formation.
To the top right of this image the stars appear a little
fuzzy. This is because a gap in the Hubble data was filled in with data
from ground-based telescopes. Although the view we see in this filled in
patch is accurate, the resolution of the stars is no match for Hubble’s
clear depiction of the spiral galaxy.
Hubble observations cast further doubt on how globular clusters formed
Thanks to the NASA/ESA Hubble Space
Telescope, some of the most mysterious cosmic residents have just become
even more puzzling. New observations of globular clusters in a small
galaxy show they are very similar to those found in the Milky Way, and
so must have formed in a similar way. One of the leading theories on how
these clusters form predicts that globular clusters should only be
found nestled in among large quantities of old stars. But these old
stars, though rife in the Milky Way, are not present in this small
galaxy, and so, the mystery deepens.
— large balls of stars that orbit the centres of galaxies, but can lie
very far from them — remain one of the biggest cosmic mysteries. They
were once thought to consist of a single population of stars that all
formed together. However, research has since shown that many of the
Milky Way's globular clusters had far more complex formation histories
and are made up of at least two distinct populations of stars.
Of these populations, around half the stars are a single generation
of normal stars that were thought to form first, and the other half form
a second generation of stars, which are polluted with different
chemical elements. In particular, the polluted stars contain up to
50-100 times more nitrogen than the first generation of stars.
The proportion of polluted stars found in the Milky Way's globular
clusters is much higher than astronomers expected, suggesting that a
large chunk of the first generation star population is missing. A
leading explanation for this is that the clusters once contained many
more stars but a large fraction of the first generation stars were
ejected from the cluster at some time in its past.
This explanation makes sense for globular clusters in the Milky Way,
where the ejected stars could easily hide among the many similar, old
stars in the vast halo, but the new observations, which look at this type of cluster in a much smaller galaxy, call this theory into question.
"We knew that the Milky Way's clusters were more complex than was
originally thought, and there are theories to explain why. But to
really test our theories about how these clusters form we needed to know
what happened in other environments," says Søren Larsen of Radboud University in Nijmegen, the Netherlands, lead author of the new paper. "Before
now we didn’t know whether globular clusters in smaller galaxies had
multiple generations or not, but our observations show clearly that they
The astronomers' detailed observations of the four Fornax clusters
show that they also contain a second polluted population of stars 
and indicate that not only did they form in a similar way to one
another, their formation process is also similar to clusters in the
Milky Way. Specifically, the astronomers used the Hubble observations to
measure the amount of nitrogen in the cluster stars, and found that
about half of the stars in each cluster are polluted at the same level
that is seen in Milky Way's globular clusters.
This high proportion of polluted second generation stars means that
the Fornax globular clusters' formation should be covered by the same
theory as those in the Milky Way.
Based on the number of polluted stars in these clusters they would
have to have been up to ten times more massive in the past, before
kicking out huge numbers of their first generation stars and reducing to
their current size. But, unlike the Milky Way, the galaxy that hosts
these clusters doesn't have enough old stars to account for the huge
number that were supposedly banished from the clusters.
"If these kicked-out stars were there, we would see them — but we don't!" explains Frank Grundahl of Aarhus University in Denmark, co-author on the paper. "Our
leading formation theory just can't be right. There's nowhere that
Fornax could have hidden these ejected stars, so it appears that the
clusters couldn't have been so much larger in the past."
This finding means that a leading theory on how these mixed
generation globular clusters formed cannot be correct and astronomers
will have to think once more about how these mysterious objects, in the
Milky Way and further afield, came to exist.
The new work is detailed in a paper published today, 20 November 2014, in The Astrophysical Journal.
 The Milky Way’s gravity keeps Fornax orbiting around us as a satellite galaxy.
 The clusters studied were named
Fornax 1, 2, 3, and 5. Fornax 1, 3, and 5 are made up of approximately 40% first generation stars to 60% polluted second generation ones, while
Fornax 2 contains around 60% first generation and 40% second generation.
Notes for editors
The Hubble Space Telescope is a project of international cooperation between ESA and NASA.
The international team of astronomers in this study consists of S.
Larsen (Radboud University, the Netherlands), J. P Brodie (University of
California, USA), F. Grundahl (Aarhus University, Denmark), and J.
Strader (Michigan State University, USA).
Image credit: NASA, ESA, S. Larsen (Radboud University, the Netherlands)
Figure 1:Color composite images of seven LAEs found in
this study as they appeared 13.1 billion years ago. This represents the
combination of three filter images from Subaru Telescope. Red objects
between two white lines are the LAEs. The LAEs of 13.1 billion years ago
have a quite red color due to the effects of cosmic expansion on their
component wavelengths of light. (Credit: ICRR, University of Tokyo)
Figure 2:This shows evolution of the Lyman-alpha
luminosities of the galaxies. The yellow circle at 1 billion years after
the Big Bang is used for normalization. The yellow circles come from
previous studies, and the yellow dashed line shows the expected
evolutionary trend of the luminosity. The current finding is shown by a
red circle, and we can see that the galaxies appear suddenly when the
universe was 700 million years old. This indicates that the neutral
hydrogen fog was suddenly cleared, allowing the galaxies to shine out,
as indicated by the backdrop shown for scale and illustration. Clickhere to see the diagram without the labels inside. (Credit: ICRR, University of Tokyo; Hubble Space Telescope/NASA/ESA)
A team of astronomers using the Subaru Telescope's Suprime-Cam to
perform the Subaru Ultra-Deep Survey for Lyman-alpha Emitters have
looked back more than 13 billion years to find 7 early galaxies that
appeared quite suddenly within 700 million years of the Big Bang (Note 1).
The team, led by graduate student Akira Konno and Dr. Masami Ouchi
(Associate Professor at the University of Tokyo's ICRR) was looking for a
specific kind of galaxy called a Lyman-alpha emitter (LAE), to
understand the role such galaxies may have played in an event called
"cosmic reionization". (Figure 1)
LAE galaxies are illuminated by strong hydrogen excitation (called Lyman-alpha emission) (Note 2).
The team's discovery of these LAEs at a distance of 13.1 billion
light-years suggests that LAE galaxies appeared rather suddenly in the
The universe was born in the Big Bang some 13.8
billion years ago. In its earliest epochs, it was filled with a hot
"soup" of charged protons and electrons. As the newborn universe
expanded, its temperature decreased uniformly. When the universe was
400,000 years old, conditions were cool enough to allow the protons and
electrons to bond and form neutral hydrogen atoms. That event is called
"recombination" and resulted in a universe filled with a "fog" of these
Eventually the first stars and galaxies began to
form, and their ultraviolet light ionized (energized) the hydrogen
atoms, and "divided" the neutral hydrogen into protons and electrons
again. As this occurred, the "fog" of neutrals cleared. Astronomers call
this event "cosmic reionization" and think that it ended about 12.8
billion years ago (about a billion years after the Big Bang). The timing
of this event – when it started and how long it lasted – is one of the
big questions in astronomy.
To investigate this cosmic reionization, the Subaru
team searched for early LAE galaxies at a distance of 13.1 billion light
years. Although Hubble Space Telescope has found more distant LAE
galaxies, the discovery of seven such galaxies at 13.1 billion
light-years represents a distance milestone for Subaru Telescope (Note 3).
Mr. Konno, the graduate student heading the analysis
of the data from the Subaru Telescope pointed out the obstacles that
Subaru had to overcome to make the observations. "It is quite difficult
to find the most distant galaxies due to the faintness of the galaxies."
he said. "So, we developed a special filter to be able to find a lot of
faint LAEs. We loaded the filter onto Suprime-Cam and conducted the
most distant LAE survey with the integration time of 106 hours."
That extremely long integration time was one of the
longest ever performed at Subaru Telescope. It allowed for unprecedented
sensitivity and enabled the team to search for as many of the most
distant LAEs as possible. According to Konno, the team expected to find
several tens of LAEs. Instead they only found seven.
"At first we were very disappointed at this small
number," Konno said. "But we realized that this indicates LAEs appeared
suddenly about 13 billion years ago. This is an exciting discovery. Figure 2
shows how the luminosities of LAEs changed based on this study. We can
see that the luminosities suddenly brightened during the 700-800 million
years after the Big Bang. What would cause this?
According to the team's analysis, one reason that
LAEs appeared very quickly is cosmic reionization. LAEs in the epoch of
cosmic reionization became darker than the actual luminosity due to the
presence of the neutral hydrogen fog. In the team's analysis of their
observations, they suggest the possibility that the neutral fog filling
the universe was cleared about 13.0 billion years ago and LAEs suddenly
appeared in sight for the first time."
"However, there are other possibilities to explain
why LAEs appeared suddenly," said Dr. Ouchi, who is the principal
investigator of this program. "One is that clumps of neutral hydrogen
around LAEs disappeared. Another is that LAEs became intrinsically
bright. The reason of the intrinsic brightening is that the Lyman-alpha
emission is not efficiently produced by the ionized clouds in a LAE due
to the significant escape of ionizing photons from the galaxy. In either
case, our discovery is an important key to understanding cosmic
reionization and the properties of the LAEs in early universe."
Dr. Masanori Iye, who is a representative of the
Thirty Meter Telescope (TMT) project of Japan, commented on the
observations and analysis. "To investigate which possibility is correct,
we will observe with HSC (Hyper Suprime-Cam) on Subaru Telescope, which
has a field of view 7 times wider than Suprime-Cam, and TMT currently
being built on the summit of Mauna Kea in Hawaii in the future. By
these observations, we will clarify the mystery of how galaxies were
born and cosmic reionization occurred."
This research is published in the November 20, 2014
issue of The Astrophysical Journal. The work was supported by the
Carnegie Observatory, World Premier International Research Center
Initiative (WPI Initiative), MEXT, Japan, and KAKENHI (23244025)
Grant-in-Aid for Scientific Research (A) through Japan Society for the
Promotion of Science (JSPS).
The values of the cosmic age and distance in this press release are
based on the latest Planck results. Planck observes the cosmic microwave
background. A previous press release on this subject used values based
on the cosmological parameters derived from the measurements by WMAP
(Wilkinson Microwave Anisotropy Probe). The parameters used here are
H_0=67.1 km/s/Mpc, Ω=0.317, Λ=0.683 instead of the ones used in the past
articles at Subaru Telescope's website H_0=71, Ω=0.27, Λ=0.73.
Lyman-alpha emission line is a spectral line of hydrogen, with a
wavelength of 121.6 nm (1nm is one billionth of a meter), and is in the
ultraviolet portion of the spectrum. Galaxies illuminated by strong
Lyman-alpha line are called "Lyman-alpha emitting galaxies" (LAEs).
In previous studies, astronomers have found hundreds of LAEs
existing 12.9 billion years ago, which corresponds to the epoch when
cosmic reionization finally ended.
Artist's impression of mysterious alignment of quasar rotation axes
VLT reveals alignments between supermassive black hole axes and large-scale structure
New observations with ESO’s Very Large
Telescope (VLT) in Chile have revealed alignments over the largest
structures ever discovered in the Universe. A European research team has
found that the rotation axes of the central supermassive black holes in
a sample of quasars are parallel to each other over distances of
billions of light-years. The team has also found that the rotation axes
of these quasars tend to be aligned with the vast structures in the
cosmic web in which they reside.
galaxies with very active supermassive black holes at their centres.
These black holes are surrounded by spinning discs of extremely hot
material that is often spewed out in long jets along their axes of
rotation. Quasars can shine more brightly than all the stars in the rest
of their host galaxies put together.
A team led by Damien Hutsemékers from the University of Liège in Belgium used the FORS instrument on the VLT
to study 93 quasars that were known to form huge groupings spread over
billions of light-years, seen at a time when the Universe was about one
third of its current age.
“The first odd thing we noticed was that some of the quasars’
rotation axes were aligned with each other — despite the fact that these
quasars are separated by billions of light-years,” said Hutsemékers.
The team then went further and looked to see if the rotation axes
were linked, not just to each other, but also to the structure of the
Universe on large scales at that time.
When astronomers look at the distribution of galaxies on scales of
billions of light-years they find that they are not evenly distributed.
They form a cosmic web of filaments and clumps around huge voids where
galaxies are scarce. This intriguing and beautiful arrangement of
material is known as large-scale structure.
The new VLT results indicate that the rotation axes of the quasars
tend to be parallel to the large-scale structures in which they find
themselves. So, if the quasars are in a long filament then the spins of
the central black holes will point along the filament. The researchers
estimate that the probability that these alignments are simply the
result of chance is less than 1%.
“A correlation between the orientation of quasars and the
structure they belong to is an important prediction of numerical models
of evolution of our Universe. Our data provide the first observational
confirmation of this effect, on scales much larger that what had been
observed to date for normal galaxies,” adds Dominique Sluse of the Argelander-Institut für Astronomie in Bonn, Germany and University of Liège.
The team could not see the rotation axes or the jets of the quasars directly. Instead they measured the polarisation
of the light from each quasar and, for 19 of them, found a
significantly polarised signal. The direction of this polarisation,
combined with other information, could be used to deduce the angle of
the accretion disc and hence the direction of the spin axis of the
“The alignments in the new data, on scales even bigger than
current predictions from simulations, may be a hint that there is a
missing ingredient in our current models of the cosmos,” concludes Dominique Sluse.
This research was presented in a paper
entitled “Alignment of quasar polarizations with large-scale
structures“, by D. Hutsemékers et al., to appear in the journal Astronomy & Astrophysics on 19 November 2014.
The team is composed of D. Hutsemékers (Institut d’Astrophysique et
de Géophysique, Université de Liège, Liège, Belgium), L. Braibant
(Liège), V. Pelgrims (Liège) and D. Sluse (Argelander-Institut für
Astronomie, Bonn, Germany; Liège).
ESO is the foremost intergovernmental astronomy organisation in
Europe and the world’s most productive ground-based astronomical
observatory by far. It is supported by 15 countries: Austria, Belgium,
Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy,
the Netherlands, Portugal, Spain, Sweden, Switzerland and the United
Kingdom. ESO carries out an ambitious programme focused on the design,
construction and operation of powerful ground-based observing facilities
enabling astronomers to make important scientific discoveries. ESO also
plays a leading role in promoting and organising cooperation in
astronomical research. ESO operates three unique world-class observing
sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO
operates the Very Large Telescope, the world’s most advanced
visible-light astronomical observatory and two survey telescopes. VISTA
works in the infrared and is the world’s largest survey telescope and
the VLT Survey Telescope is the largest telescope designed to
exclusively survey the skies in visible light. ESO is the European
partner of a revolutionary astronomical telescope ALMA, the largest
astronomical project in existence. ESO is currently planning the
39-metre European Extremely Large optical/near-infrared Telescope, the
E-ELT, which will become “the world’s biggest eye on the sky”.
A labeled panel of images showing different views of Supernova Remnant 1987A
Left Panel: SNR1987A as seen by the Hubble Space
Telescope in 2010.Middle Panel: SNR1987A as seen by the Australia
Telescope Compact Array (ATCA) in New South Wales and the Atacama Large
Millimeter/submillimeter Array (ALMA) in Chile. Right Panel: A computer
generated visualisation of the remnant showing the possible location of a
Pulsar. Credit: ATCA & ALMA Observations & data - G.
Zanardo et al. / HST Image: NASA, ESA, K. France (University of
Colorado, Boulder), P. Challis and R. Kirshner (Harvard-Smithsonian
Center for Astrophysics).Labeled image-No labels image
A mosaic of images showing the latest observations of Supernova remnant 1987A at radio frequencies to the far infrared.
Images below 100 GHz are from observations made with the ATCA telescope (NSW, Australia), and images above 100 GHz are from the ALMA telescope (Chile). The map on the bottom right of the mosaic is obtained by combining five images. This is used to investigate whether there is a pulsar wind nebula inside the remnant.
Credit: G. Zanardo, ICRAR-UWA
An outline of the equatorial ring and inner debris,
as seen with the Hubble Space Telescope (green/blue contours), on top of
ALMA observations of the remnant at 345 GHz (red/orange, with
rendering). Credit: G. Zanardo, ICRAR-UWA
A simulated still showing components of Supernova Remnant 1987A.
A video compilation showing Supernova Remnant 1987A as seen by the Hubble Space Telescope in 2010, and by radio telescopes located in Australia and Chile in 2012. The piece ends with a computer generated visualisation of the remnant showing the possible location of a Pulsar.
A visualisation showing how Supernova1987A evolves between May of 1989 and July of 2014
Credit: Dr Toby Potter, ICRAR-UWA, Dr Rick Newton, ICRAR-UWA
In research published today in the Astrophysical Journal, an
Australian led team of astronomers has used radio telescopes in
Australia and Chile to see inside the remains of a supernova.
The supernova, known as SN1987A, was first seen by observers in the
Southern Hemisphere in 1987 when a giant star suddenly exploded at the
edge of a nearby dwarf galaxy called the Large Magellanic Cloud.
In the two and a half decades since then the remnant of Supernova
1987A has continued to be a focus for researchers the world over,
providing a wealth of information about one of the Universe’s most
PhD Candidate Giovanna Zanardo at The University of Western
Australia node of the International Centre for Radio Astronomy Research
led the team that used the Atacama Large Millimetre/submillimeter Array
(ALMA) in Chile’s Atacama Desert and the Australia Telescope Compact
Array (ATCA) in New South Wales to observe the remnant at wavelengths
spanning the radio to the far infrared.
"By combining observations from the two telescopes we’ve been able
to distinguish radiation being emitted by the supernova’s expanding
shock wave from the radiation caused by dust forming in the inner regions of the remnant,” said
Giovanna Zanardo of the International Centre for Radio Astronomy
Research (ICRAR) in Perth, Western Australia.
"This is important because it means we’re able to separate out the
different types of emission we’re seeing and look for signs of a new
object which may have formed when the star's core collapsed. It's like
doing a forensic investigation into the death of a star."
“Our observations with the ATCA and ALMA radio telescopes have
shown signs of something never seen before, located at the centre or the
remnant. It could be a pulsar wind nebula, driven by the spinning
neutron star, or pulsar, which astronomers have been searching for since
1987. It’s amazing that only now, with large telescopes like ALMA and
the upgraded ATCA, we can peek through the bulk of debris ejected when
the star exploded and see what’s hiding underneath."
More research published recently in the Astrophysical Journal also
attempts to shine a light on another long-standing mystery surrounding
the supernova remnant. Since 1992 the radio emission from one side of
the remnant has appeared ‘brighter’ than the other.
In an effort to solve this puzzle, Dr Toby Potter, another
researcher from ICRAR’s UWA node has developed a detailed
three-dimensional simulation of the expanding supernova shockwave.
“By introducing asymmetry into the explosion and adjusting the gas
properties of the surrounding environment, we were able to reproduce a
number of observed features from the real supernova such as the
persistent one-sidedness in the radio images”, said Dr Toby Potter.
The time evolving model shows that the eastern (left) side of the
expanding shock front expands more quickly than the other side, and
generates more radio emission than its weaker counterpart. This effect
becomes even more apparent as the shock collides into the equatorial
ring, as observed in Hubble Space Telescope images of the supernova.
"Our simulation predicts that over time the faster shock will move
beyond the ring first. When this happens, the lop-sidedness of radio
asymmetry is expected to be reduced and may even swap sides.”
“The fact that the model matches the observations so well means
that we now have a good handle on the physics of the expanding remnant
and are beginning to understand the composition of the environment
surrounding the supernova – which is a big piece of the puzzle solved in
terms of how the remnant of SN1987A formed.”
The animation and images below are available for download fromthislink.
Original publication details:
‘Spectral and Morphological Analysis of the Remnant of Supernova
1987a with ALMA & ATCA’ G. Zanardo, L. Staveley-Smith, R. Indebetouw
et al. Published in the in the Astrophysical Journal November 10th,
2014. Pre-print paper available at: http://arxiv.org/abs/1409.7811 and http://iopscience.iop.org/0004-637X/796/2/82 after 8am EST, November 10th.