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Artist’s impression of the gas surrounding a young galaxy in the distant
universe. The gas, shown as red streams on the left, is actually
invisible, and the starlight from the galaxy is too faint for
astronomers to see directly. Instead, the gas is seen in silhouette
against a bright, background quasar. Molecules in the gas imprint a
shadow, or absorption line, onto the quasar light at a very specific
color, as seen on the right, and astronomers can detect this shadow. Image credits: ESO/L. Calçada/ESA/AOES Medialab, Swinburne Astronomy Productions - Hi-res image5.10 MB JPEG
An international team of astronomers has discovered that gas around
young galaxies is almost barren, devoid of the seeds from which new
stars are thought to form—molecules of hydrogen.
Without starlight to see them directly, the team, which includes Dr. Regina Jorgenson of the Institute for Astronomy at the University of Hawaii at Manoa—observed the young galaxies’ outskirts in silhouette.
They searched for telltale signs of hydrogen
molecules absorbing the light from background objects called
quasars—supermassive black holes sucking in surrounding material—that
glow very brightly.
“Previous experiments led us to expect
molecules in about 10 of the 90 young galaxies we observed, but we
just one case,” said Associate Professor Michael Murphy from Swinburne
University of Technology in
Australia. He co-led the study with
Astronomers believe that stars begin to form in cold gas that is rich
in molecules. The team observed galaxies at a time when the Universe
was most actively forming stars, about 12 billion years ago.
“This is a little mystery. This is when most
stars are born, and we think this gas forms stars eventually, but it
lacks the key ingredient—molecules—to do so,” Murphy said.
The team believes that location and time are the key.
“The gas we observe in silhouette probably lies too far from the galaxies to form stars,” Jorgenson said.
“It’s got lots of potential, but it hasn’t
had time to fall into the richer, denser parts of the galaxies which
might be better stellar nurseries.”
The researchers made new observations of more than 50 quasars for this study using the 6.5-meter Magellan telescopes in Chile.
It was conducted by researchers from the
University of Hawaii at Manoa, Swinburne University of Technology, the
University of Cambridge and the University of Arizona.
This image from the Hubble Space Telescope shows the galaxy cluster
MACSJ0416.1-2403, one of six being studied by the Hubble Frontier Fields
program, which analyzes the mass distribution in these huge clusters
and uses them, combined with a process known as gravitational lensing,
to peer even deeper into the distant universe. A team of researchers
used almost 200 images of distant galaxies, whose light has been bent
and magnified by this huge cluster, combined with new Hubble data, to
measure the total mass of this cluster more precisely than ever before.Credit:ESA/Hubble,NASA,HST Frontier Fields.
Acknowledgement: Mathilde Jauzac (Durham University, UK and
Astrophysics & Cosmology Research Unit, South Africa) and Jean-Paul
Kneib (École Polytechnique Fédérale de Lausanne, Switzerland).(32.7 Mb TIFFor10.5 Mb JPEG)
Figure 2: This image shows the galaxy MACSJ0416.1-2403,
one of six clusters targeted by the Hubble Frontier Fields program. The
varying intensity of the blue haze in this image is a mass map created
by using new Hubble observations combined with the magnifying power of a
process known as gravitational lensing. Strong lensing gives a much
more precise indication of the mass at the cluster’s core, while weak
lensing provides valuable information about the mass surrounding the
cluster core. Credit:ESA/Hubble, NASA, HST Frontier Fields.
Acknowledgement: Mathilde Jauzac (Durham University, UK and
Astrophysics & Cosmology Research Unit, South Africa) and Jean-Paul
Kneib (École Polytechnique Fédérale de Lausanne, Switzerland).(23.4 Mb TIFFor10.0 Mb JPEG)
An international team of astronomers, including Dr. Harald Ebeling of
the University of Hawaii at Manoa Institute for Astronomy, has used the
Hubble Space Telescope to map the mass within a galaxy cluster,
originally discovered with Maunakea telescopes, more precisely than ever before.
Clusters of galaxies are the most massive
objects in the universe, comprising hundreds to thousands of galaxies
and also enormous amounts of invisible dark matter. They grow through
collisions in which smaller clusters merge into ever more massive
systems, a process that can temporarily lead to highly complex mass
Ebeling specializes in finding the rarest,
most extreme clusters that are the most rewarding targets for detailed
studies of the formation and evolution of cosmic structure. One of the
clusters discovered by Ebeling’s team in the course of the Massive
Cluster Survey (MACS), which used several telescopes on Maunakea, goes
by the unpoetic name of MACSJ0416.1-2403.
It was found to be so massive that the
cluster was selected for extremely deep observations with the Hubble
Space Telescope as part of the Frontier Fields program. The resulting Hubble data show the galaxy distribution within the cluster in stunning detail (Figure 1).
The new, ultra-deep observations also reveal a multitude of distorted
images of galaxies that are in fact far behind the cluster, bent and
often appearing multiple times within the Hubble image of MACSJ0416 due
to an effect called gravitational lensing, in which the mass of a
foreground object magnifies and distorts more distant objects.
Gravitational lensing by mass concentrations
in space comes in two varieties: so-called “strong lensing,” which
creates the highly elongated, almost linear images of distant background
galaxies visible near the center of the cluster (as predicted by
Einstein’s theory of relativity), and “weak lensing,” pioneered by IfA’s
Nick Kaiser in the 1990s, which causes much less perceptible, faint,
statistical distortions of hundreds of background galaxies viewed at
larger distances from the cluster core.
The spectacular images collected of MACSJ0416
during the Frontier Fields program were recently analyzed by members of
the team led by Mathilde Jauzac (Durham University, UK. and
Astrophysics & Cosmology Research Unit, South Africa). They used
both strong- and weak-lensing techniques to infer the cluster mass
distribution that creates the many lensing features identified in these
Their meticulous search for even the faintest
gravitationally lensed images was unprecedentedly successful, resulting
in the identification of four times as many lensed background galaxies
as were previously known in this system. The result is a mass map of
MACSJ0416 that is more precise than any ever derived for any galaxy
cluster, showing the highly elongated distribution of dark matter in
this merging cluster in great detail and over an enormous range of
scales (Figure 2).
The study also established MACSJ0416 as a huge cluster indeed, with a
measured mass of 160 trillion times the mass of the sun.
“Our analysis of the Frontier Fields data
demonstrates impressively how detailed studies of the extremely massive
clusters found by MACS can advance our understanding not only of the
complexity of cluster formation but in fact of the distant universe
behind these powerful gravitational lenses,” explains Ebeling.
Further investigations of MACSJ0416 are
underway, combining the Frontier Fields images with deep X-ray
observations of the hot gas within the cluster and with spectroscopic
redshifts of the cluster galaxies, measured by Ebeling as part of the
follow-up work conducted by the MACS team using Maunakea facilities.
Primary goal: to deduce the merger history of this extreme cluster by
establishing its three-dimensional geometry and the trajectories of the
clusters involved in the collision.
The results of the study will be published in
Monthly Notices of the Royal Astronomical Society in July 2014.
Artist's rendering of a possible exoplanetary system with a gas-giant
planet orbiting close to his parent star which is more massive than our
Artwork by Lynette Cook
Credit: Gemini Observatory/AURA. Full ResolutionTIFF(6MB) | Full ResolutionJPEG(2MB) | Medium ResolutionJPEG(296KB)
Gemini Observatory’s Planet-Finding Campaign finds that, around many
types of stars, distant gas-giant planets are rare and prefer to cling
close to their parent stars. The impact on theories of planetary
formation could be significant.
Finding extrasolar planets has become so commonplace that it seems
astronomers merely have to look up and another world is discovered.
However, results from Gemini Observatory’s recently completed
Planet-Finding Campaign – the deepest, most extensive direct imaging
survey to date – show the vast outlying orbital space around many types
of stars is largely devoid of gas-giant planets, which apparently tend
to dwell close to their parent stars.
“It seems that gas-giant exoplanets are like clinging offspring,” says
Michael Liu of the University of Hawaii’s Institute for Astronomy and
leader of the Gemini Planet-Finding Campaign. “Most tend to shun orbital
zones far from their parents. In our search, we could have found gas
giants beyond orbital distances corresponding to Uranus and Neptune in
our own Solar System, but we didn’t find any.” The Campaign was
conducted at the Gemini South telescope in Chile, with funding support
for the team from the National Science Foundation and NASA. The
Campaign’s results, Liu says, will help scientists better understand how
gas-giant planets form, as the orbital distances of planets are a key
signature that astronomers use to test exoplanet formation theories.
Eric Nielsen of the University of Hawaii, who leads a new paper
about the Campaign’s search for planets around stars more massive than
the Sun, adds that the findings have implications beyond the specific
stars imaged by the team. "The two largest planets in our Solar System,
Jupiter and Saturn, are huddled close to our Sun, within 10 times the
distance between the Earth and Sun,” he points out. “We found that this
lack of gas-giant planets in more distant orbits is typical for nearby
stars over a wide range of masses."
Two additional papers from the Campaign will be published soon and
reveal similar tendencies around other classes of stars. However, not
all gas-giant exoplanets snuggle so close to home. In 2008, astronomers
using the Gemini North telescope and W.M. Keck Observatory on Hawaii’s
Mauna Kea took the first-ever direct images
of a family of planets around the star HR 8799, finding gas-giant
planets at large orbital separations (about 25-70 times the Earth-Sun
distance). This discovery came after examining only a few stars,
suggesting such large-separation gas giants could be common. The latest
Gemini results, from a much more extensive imaging search, show that
gas-giant planets at such distances are in fact uncommon.
Liu sums up the situation this way: “We’ve known for nearly 20 years
that gas-giant planets exist around other stars, at least orbiting
close-in. Thanks to leaps in direct imaging methods, we can now learn
how far away planets can typically reside. The answer is that they
usually avoid significant areas of real estate around their host stars.
The early findings, like HR 8799, probably skewed our perceptions.”
The team’s second new paper explores systems where dust disks around
young stars show holes, which astronomers have long suspected are
cleared by the gravitational force of orbiting planets. “It makes sense
that where you see debris cleared away that a planet would be
responsible, but we did not know what types of planets might be causing
this. It appears that instead of massive planets, smaller planets that
we can’t detect directly could be responsible,” said Zahed Wahhaj of the
European Southern Observatory and lead author on the survey’s paper on
dusty disk stars. Finally, the third new paper from the team looks at
the very youngest stars close to Earth. “A younger system should have
brighter, easier to detect planets,” according to the lead author Beth
Biller of the Max Planck Institute for Astronomy.
“Around other stars, NASA's Kepler telescope has shown that planets
larger than the Earth and within the orbit of Mercury are plentiful,”
explains Biller. “The NICI Campaign demonstrates that gas-giant planets
beyond the distance of the orbit of Neptune are rare.” The
soon-to-be-delivered Gemini Planet Imager will begin to bridge this gap
likely revealing, for the first time, how common giant planets are in
orbits similar to the gas-giant planets of our own Solar System.
The observations for the Campaign were obtained with the Gemini
instrument known as NICI, the Near-Infrared Coronagraphic Imager, which
was the first instrument for an 8-10 meter-class telescope designed
specifically for finding faint companions around bright stars. NICI was
built by Doug Toomey (Mauna Kea Infrared), Christ Ftaclas, and Mark Chun
(University of Hawai‘i), with funding from NASA.
The first two papers from the Campaign have been accepted for publication in The Astrophysical Journal (Nielsen et al. and Wahhaj et al.), and the third paper (Biller et al.) will be published later this summer.
The NICI Campaign team is composed of PI Michael Liu, co-PI Mark Chun
(University of Hawaii), co-PI Laird Close (University of Arizona), Doug
Toomey (Mauna Kea Infrared), Christ Ftaclas (University of Hawaii),
Zahed Wahhaj (European Southern Observatory), Beth Biller (Max Planck
Institute for Astronomy), Eric Nielsen (University of Hawaii), Evgenya
Shkolnik (DTM, Carnegie Institution of Washington), Adam Burrows
(Princeton University), Neill Reid (Space Telescope Science Institute),
Niranjan Thatte, Matthias Tecza, Fraser Clarke (University of Oxford),
Jane Gregorio Hetem, Elisabete De Gouveia Dal Pino (University of Sao
Paolo), Silvia Alencar (University of Minas Gerais), Pawel Artymowicz
(University of Toronto), Doug Lin (University of California Santa Cruz),
Shigeru Ida (Tokyo Institute of Technology), Alan Boss (DTM, Carnegie
Institution of Washington), and Mark Kuchner (NASA Goddard), Tom Hayward
and Markus Hartung (Gemini Observatory), Jared Males, and Andy Skemer
(University of Arizona).
Hilo, HI 96720
Office: +1 (808) 974-2510
Cell: +1 (808) 936-6643 firstname.lastname@example.org
Institute for Astronomy
University of Hawaii at Manoa
Honolulu, HI 96822
Office: +1 (808) 956-6235 email@example.com
Institute for Astronomy
University of Hawaii at Manoa
Honolulu, HI 96822
Office: +1 (808) 956-6666 firstname.lastname@example.org
Institute for Astronomy
University of Hawaii at Manoa
Honolulu, HI 96822
Office: +1 (808) 956-9841
Cell: 408 394-4582 email@example.com
Credit: ESA/Hubble & NASA Acknowledgement: M. Novak
A dying star’s final moments are captured in this image from the
NASA/ESA Hubble Space Telescope. The death throes of this star may only
last mere moments on a cosmological timescale, but this star’s demise is
still quite lengthy by our standards, lasting tens of thousands of
The star’s agony has culminated in a wonderful planetary nebula known as NGC 6565, a cloud of gas that was ejected from the star after strong stellar winds
pushed the star’s outer layers away into space. Once enough material
was ejected, the star’s luminous core was exposed and it began to
produce ultraviolet radiation, exciting the surrounding gas to varying
degrees and causing it to radiate in an attractive array of colours.
These same colours can be seen in the famous and impressive Ring Nebula (heic1310), a prominent example of a nebula like this one.
Planetary nebulae are illuminated for around 10 000 years before the central star begins to cool and shrink to become a white dwarf.
When this happens, the star’s light drastically diminishes and ceases
to excite the surrounding gas, so the nebula fades from view.
A version of this image was entered into the Hubble’s Hidden Treasures basic image competition by contestant Matej Novak.
Identification of Exoplanet Host Star OGLE-2005-BLG-169 (Artist's Illustration)
This graphic illustrates how a star can magnify and brighten the light
of a background star when it passes in front of the distant star. If
the foreground star has planets, then the planets may also magnify the
light of the background star, but for a much shorter period of time
than their host star. Astronomers use this method, called gravitational
microlensing, to identify planets. Credit:NASA,ESA, and A. Feild (STScI)
NASA's Hubble Space Telescope and the W. M. Keck Observatory in
Hawaii have made independent confirmations of an exoplanet orbiting far
from its central star. The planet was discovered through a technique
called gravitational microlensing.
This finding opens a new piece of discovery space in the extrasolar
planet hunt: to uncover planets as far from their central stars as
Jupiter and Saturn are from our sun. The Hubble and Keck Observatory
results will appear in two papers in the July 30 edition of The
The large majority of exoplanets cataloged so far are very close to
their host stars because several current planet-hunting techniques
favor finding planets in short-period orbits. But this is not the case
with the microlensing technique, which can find more distant and colder
planets in long-period orbits that other methods cannot detect.
Microlensing occurs when a foreground star amplifies the light of a
background star that momentarily aligns with it. If the foreground star
has planets, then the planets may also amplify the light of the
background star, but for a much shorter period of time than their host
star. The exact timing and amount of light amplification can reveal
clues to the nature of the foreground star and its accompanying
The system, cataloged as OGLE-2005-BLG-169, was discovered in 2005 by
the Optical Gravitational Lensing Experiment (OGLE), the Microlensing
Follow-Up Network (MicroFUN), and members of the Microlensing
Observations in Astrophysics (MOA) collaborations — groups that search
for extrasolar planets through gravitational microlensing.
Without conclusively identifying and characterizing the foreground
star, however, astronomers have had a difficult time determining the
properties of the accompanying planet. Using Hubble and the Keck
Observatory, two teams of astronomers have now found that the system
consists of a Uranus-sized planet orbiting about 370 million miles from
its parent star, slightly less than the distance between Jupiter and
the sun. The host star, however, is about 70 percent as massive as our
"These chance alignments are rare, occurring only about once every 1
million years for a given planet, so it was thought that a very long
wait would be required before the planetary microlensing signal could
be confirmed," said David Bennett of the University of Notre Dame,
Indiana, the lead of the team that analyzed the Hubble data.
"Fortunately, the planetary signal predicts how fast the apparent
positions of the background star and planetary host star will separate,
and our observations have confirmed this prediction. The Hubble and
Keck Observatory data, therefore, provide the first confirmation of a
planetary microlensing signal."
In fact, microlensing is such a powerful tool that it can uncover
planets whose host stars cannot be seen by most telescopes. "It is
remarkable that we can detect planets orbiting unseen stars, but we'd
really like to know something about the stars that these planets
orbit," explained Virginie Batista of the Institut d'Astrophysique de
Paris, France, leader of the Keck Observatory analysis. "The Keck and
Hubble telescopes allow us to detect these faint planetary host stars
and determine their properties."
Planets are small and faint compared to their host stars; only a few
have been observed directly outside our solar system. Astronomers often
rely on two indirect techniques to hunt for extrasolar planets. The
first method detects planets by the subtle gravitational tug they give
to their host stars. In another method, astronomers watch for small
dips in the amount of light from a star as a planet passes in front of
Both of these techniques work best when the planets are either
extremely massive or when they orbit very close to their parent stars.
In these cases, astronomers can reliably determine their short orbital
periods, ranging from hours to days to a couple years.
But to fully understand the architecture of distant planetary
systems, astronomers must map the entire distribution of planets around
a star. Astronomers, therefore, need to look farther away from the
star-from about the distance of Jupiter is from our sun, and beyond.
"It's important to understand how these systems compare with our
solar system," said team member Jay Anderson of the Space Telescope
Science Institute in Baltimore, Maryland. "So we need a complete census
of planets in these systems. Gravitational microlensing is critical in
helping astronomers gain insights into planetary formation theories."
The planet in the OGLE system is probably an example of a
"failed-Jupiter" planet, an object that begins to form a Jupiter-like
core of rock and ice weighing around 10 Earth masses, but it doesn't
grow fast enough to accrete a significant mass of hydrogen and helium.
So it ends up with a mass more than 20 times smaller than that of
Jupiter. "Failed-Jupiter planets, like OGLE-2005-BLG-169Lb, are
predicted to be more common than Jupiters, especially around stars less
massive than the sun, according to the preferred theory of planet
formation. So this type of planet is thought to be quite common,"
Microlensing takes advantage of the random motion of stars, which are
generally too small to be noticed without precise measurements. If one
star, however, passes nearly precisely in front of a farther
background star, the gravity of the foreground star acts like a giant
lens, magnifying the light from the background star.
A planetary companion around the foreground star can produce a
variation in the brightening of the background star. This brightening
fluctuation can reveal the planet, which can be too faint, in some
cases, to be seen by telescopes. The duration of an entire microlensing
event is several months, while the variation in brightening due to a
planet lasts a few hours to a couple of days.
The initial microlensing data of OGLE-2005-BLG-169 had indicated a
combined system of foreground and background stars plus a planet. But
due to the blurring effects of our atmosphere, a number of unrelated
stars are also blended with the foreground and background stars in the
very crowded star field in the direction of our galaxy's center.
The sharp Hubble and Keck Observatory images allowed the research
teams to separate out the background source star from its neighbors in
the very crowded star field in the direction of our galaxy's center.
Although the Hubble images were taken 6.5 years after the lensing
event, the source and lens star were still so close together on the sky
that their images merged into what looked like an elongated stellar
Astronomers can measure the brightness of both the source and
planetary host stars from the elongated image. When combined with the
information from the microlensing light curve, the lens brightness
reveals the masses and orbital separation of the planet and its host
star, as well as the distance of the planetary system from Earth. The
foreground and background stars were observed in several different
colors with Hubble's Wide Field Camera 3 (WFC3), allowing independent
confirmations of the mass and distance determinations.
The observations, taken with the Near Infrared Camera 2 (NIRC2) on
the Keck 2 telescope more than eight years after the microlensing
event, provided a precise measurement of the foreground and background
stars' relative motion. "It is the first time we were able to
completely resolve the source star and the lensing star after a
microlensing event. This enabled us to discriminate between two models
that fit the data of the microlensing light curve," Batista said.
The Hubble and Keck Observatory data are providing proof of concept
for the primary method of exoplanet detection that will be used by
NASA's planned, space-based Wide-Field Infrared Survey Telescope
(WFIRST), which will allow astronomers to determine the masses of
planets found with microlensing.
WFIRST will have Hubble's sharpness to
search for exoplanets using the microlensing technique. The telescope
will be able to observe foreground, planetary host stars approaching
the background source stars prior to the microlensing events, and
receding from the background source stars after the microlensing
"WFIRST will make measurements like we have made for
OGLE-2005-BLG-169 for virtually all the planetary microlensing events
it observes. We'll know the masses and distances for the thousands of
planets discovered by WFIRST," Bennett explained.
Some of the most breathtaking views in
the Universe are created by nebulae — hot, glowing clouds of gas. This
new NASA/ESA Hubble Space Telescope image shows the centre of the Lagoon
Nebula, an object with a deceptively tranquil name. The region is
filled with intense winds from hot stars, churning funnels of gas, and
energetic star formation, all embedded within an intricate haze of gas
and pitch-dark dust.
Nebulae are often named based on their key characteristics — particularly beautiful examples include the Ring Nebula (heic1310), the Horsehead Nebula (heic1307) and the Butterfly Nebula (heic0910). This new NASA/ESA Hubble Space Telescope image shows the centre of the Lagoon Nebula, otherwise known as Messier 8, in the constellation of Sagittarius (The Archer).
The inspiration for this nebula’s name may not be immediately obvious
— this is because the image captures only the very heart of the nebula.
The Lagoon Nebula’s name becomes much clearer in a wider field view (opo0417i) when the broad, lagoon-shaped dust lane that crosses the glowing gas of the nebula can be made out.
Another clear difference between this new image and others is that this image combines both infrared and optical light rather than being purely optical(heic1015).
Infrared light cuts through thick, obscuring patches of dust and gas,
revealing the more intricate structures underneath and producing a
completely different landscape .
However, even in visible light, the tranquil name remains misleading as the region is packed full of violent phenomena.
The bright star embedded in dark clouds at the centre of this image is known as Herschel 36.
This star is responsible for sculpting the surrounding cloud, stripping
away material and influencing its shape. Herschel 36 is the main source
of ionising radiation for this part of the Lagoon Nebula.
This central part of the Lagoon Nebula contains two main structures
of gas and dust connected by wispy twisters, visible in the middle third
of this image (opo9638).
These features are quite similar to their namesakes on Earth — they are
thought to be wrapped up into their funnel-like shapes by temperature
differences between the hot surface and cold interior of the clouds. The
nebula is also actively forming new stars, and energetic winds from
these newborns may contribute to creating the twisters.
Artist's conception of a very young, still-forming brown dwarf, with a disk of material orbiting it, and jets of material ejected outward from the poles of the disk. Credit: Bill Saxton, NRAO/AUI/NSF
Astronomers using the Karl G. Jansky Very Large Array (VLA) have
discovered jets of material ejected by still-forming young brown dwarfs.
The discovery is the first direct evidence that brown dwarfs,
intermediate in mass between stars and planets, are produced by a
scaled-down version of the same process that produces stars.
astronomers studied a sample of still-forming brown dwarfs in a
star-forming region some 450 light-years from Earth in the constellation
Taurus, and found that four of them have the type of jets emitted by
more-massive stars during their formation. The jets were detected by
radio observations with the VLA. The scientists also observed the brown
dwarfs with the Spitzer and Herschel space telescopes to confirm their
status as very young objects.
"This is the first time that such
jets have been found coming from brown dwarfs at such an early stage of
their formation, and shows that they form in a way similar to that of
stars," said Oscar Morata, of the Institute of Astronomy and
Astrophysics of the Academia Sinica in Taiwan. "These are the
lowest-mass objects that seem to form the same way as stars," he added.
dwarfs are less massive than stars, but more massive than giant planets
such as Jupiter. They have insufficient mass to produce the
temperatures and pressures at their cores necessary to trigger the
thermonuclear reactions that power "normal" stars. Theorists suggested
in the 1960s that such objects should exist, but the first unambiguous
discovery of one did not come until 1994.
A key question has been
whether brown dwarfs form like stars or like planets. Stars form when a
giant cloud of gas and dust in interstellar space collapses
gravitationally, accumulating mass. A disk of orbiting material forms
around the young star, and eventually planets form from the material in
that disk. In the early stages of star formation, jets of material are
propelled outward from the poles of the disk. No such jets mark planet
Previous evidence strongly suggested that
brown dwarfs shared the same formation mechanism as their larger
siblings, but detecting the telltale jets is an important confirmation.
Based on this discovery, "We conclude that the formation of brown dwarfs
is a scaled-down version of the process that forms larger stars,"
Morata led an international team of astronomers with
members from Asia, Europe, and Latin America. They reported their
findings in the Astrophysical Journal.
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The chemical element lithium has been
found for the first time in material ejected by a nova. Observations of
Nova Centauri 2013 made using telescopes at ESO’s La Silla Observatory,
and near Santiago in Chile, help to explain the mystery of why many
young stars seem to have more of this chemical element than expected.
This new finding fills in a long-missing piece in the puzzle
representing our galaxy’s chemical evolution, and is a big step forward
for astronomers trying to understand the amounts of different chemical
elements in stars in the Milky Way.
The light chemical element lithium
is one of the few elements that is predicted to have been created by
the Big Bang, 13.8 billion years ago. But understanding the amounts of
lithium observed in stars around us today in the Universe has given
astronomers headaches. Older stars have less lithium than expected , and some younger ones up to ten times more .
Since the 1970s, astronomers have speculated that much of the extra lithium found in young stars may have come from novae
— stellar explosions that expel material into the space between the
stars, where it contributes to the material that builds the next stellar
generation. But careful study of several novae has yielded no clear
result up to now.
A team led by Luca Izzo (Sapienza University of Rome, and ICRANet, Pescara, Italy) has now used the FEROS instrument on the MPG/ESO 2.2-metre telescope at the La Silla Observatory, as well the PUCHEROS spectrograph on the ESO 0.5-metre telescope at the Observatory of the Pontificia Universidad Catolica de Chile in
Santa Martina near Santiago, to study the nova Nova Centauri 2013
(V1369 Centauri). This star exploded in the southern skies close to the
bright star Beta Centauri in December 2013 and was the brightest nova so
far this century — easily visible to the naked eye .
The very detailed new data revealed the clear signature of lithium
being expelled at two million kilometres per hour from the nova . This is the first detection of the element ejected from a nova system to date.
Co-author Massimo Della Valle (INAF–Osservatorio Astronomico di
Capodimonte, Naples, and ICRANet, Pescara, Italy) explains the
significance of this finding: “It is a very important step forward.
If we imagine the history of the chemical evolution of the Milky Way as a
big jigsaw, then lithium from novae was one of the most important and
puzzling missing pieces. In addition, any model of the Big Bang can be
questioned until the lithium conundrum is understood.”
The mass of ejected lithium in Nova Centauri 2013 is estimated to be
tiny (less than a billionth of the mass of the Sun), but, as there have
been many billions of novae in the history of the Milky Way, this is
enough to explain the observed and unexpectedly large amounts of lithium
in our galaxy.
Authors Luca Pasquini (ESO, Garching, Germany) and Massimo Della
Valle have been looking for evidence of lithium in novae for more than a
quarter of a century. This is the satisfying conclusion to a long
search for them. And for the younger lead scientist there is a different
kind of thrill:
"It is very exciting,” says Luca Izzo, “to find something that was predicted before I was born and then first observed on my birthday in 2013!”
 The lack of lithium in older stars is a long-standing puzzle. Results on this topic include these press releases: eso1428, eso1235 and eso1132.
 More precisely, the terms
“younger” and “older” are used to refer to what astronomers call
Population I and Population II stars. The Population I category includes
the Sun; these stars are rich in heavier chemical elements and form the
disc of the Milky Way. Population II stars are older, with a low
heavy-element content, and are found in the Milky Way Bulge and Halo,
and globular star clusters. Stars in the “younger” Population I class
can still be several billion years old!
 These comparatively small
telescopes, equipped with suitable spectrographs, are powerful tools for
this kind of research. Even in the era of extremely large telescopes
smaller telescopes dedicated to specific tasks can remain very valuable.
 This high velocity, from the nova
towards the Earth, means that the wavelength of the line in the
absorption in the spectrum due to the presence of lithium is
significantly shifted towards the blue end of the spectrum.
This research was presented in a paper entitled “Early optical spectra
of Nova V1369 Cen show presence of lithium”, by L. Izzo et al.,
published online in the Astrophysical Journal Letters.
The team is composed of Luca Izzo (Sapienza University of Rome, and
ICRANet, Pescara, Italy), Massimo Della Valle (INAF–Osservatorio
Astronomico di Capodimonte, Naples; ICRANet, Pescara, Italy), Elena
Mason (INAF–Osservatorio Astronomico di Trieste, Trieste, Italy),
Francesca Matteucci (Universitá di Trieste, Trieste, Italy), Donatella
Romano (INAF–Osservatorio Astronomico di Bologna, Bologna, Italy), Luca
Pasquini (ESO, Garching bei Munchen, Germany), Leonardo Vanzi
(Department of Electrical Engineering and Center of Astro Engineering,
PUC-Chile, Santiago, Chile), Andres Jordan (Institute of Astrophysics
and Center of Astro Engineering, PUC-Chile, Santiago, Chile), José
Miguel Fernandez (Institute of Astrophysics, PUC-Chile, Santiago,
Chile), Paz Bluhm (Institute of Astrophysics, PUC-Chile, Santiago,
Chile), Rafael Brahm (Institute of Astrophysics, PUC-Chile, Santiago,
Chile), Nestor Espinoza (Institute of Astrophysics, PUC-Chile, Santiago,
Chile) and Robert Williams (STScI, Baltimore, Maryland, USA).
ESO is the foremost intergovernmental astronomy organisation in
Europe and the world’s most productive ground-based astronomical
observatory by far. It is supported by 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”.
When two different sized galaxies smash together, the larger galaxy
stops the smaller one making new stars, according to a study of more
than 20,000 merging galaxies.
The research, published today, also found that when two galaxies of
the same size collide, both galaxies produce stars at a much faster
Astrophysicist Luke Davies, from The University of Western Australia
node of the International Centre for Radio Astronomy Research (ICRAR),
says our nearest major galactic neighbour, Andromeda, is hurtling on a
collision course with the Milky Way at about 400,000 kilometres per
“Don’t panic yet, the two won’t smash into each other for another four billion years or so,” he says.
“But investigating such cosmic collisions lets us better understand how galaxies grow and evolve.”
Previously, astronomers thought that when two galaxies smash into
each other their gas clouds—where stars are born—get churned up and seed
the birth of new stars much faster than if they remained separate.
However Dr Davies’ research, using the Galaxy and Mass Assembly
(GAMA) survey observed using the Anglo-Australian Telescope in regional
New South Wales, suggests this idea is too simplistic.
He says whether a galaxy forms stars more rapidly in a collision, or
forms any new stars at all, depends on if it is the big guy or the
little guy in this galactic car crash.
“When two galaxies of similar mass collide, they both increase their stellar birth rate,” Dr Davies says.
“However when one galaxy significantly outweighs the other, we have
found that star formation rates are affected for both, just in different
“The more massive galaxy begins rapidly forming new stars, whereas the smaller galaxy suddenly struggles to make any at all."
“This might be because the bigger galaxy strips away its smaller
companion’s gas, leaving it without star-forming fuel or because it
stops the smaller galaxy obtaining the new gas required to form more
The study was released today in the journal Monthly Notices of the
Royal Astronomical Society, published by Oxford University Press.
So what will happen in four billion years to the Milky Way and Andromeda?
Dr Davies says the pair are like “cosmic tanks”—both relatively large and with similar mass.
“As they get closer together they will begin to affect each other’s
star formation, and will continue to do so until they eventually merge
to become a new galaxy, which some call ‘Milkdromeda’,” he says.
ICRAR is a joint venture between Curtin University and The University of
Western Australia with support and funding from the State Government of
Fig 1:Two ultra-dense galaxies(insets) have been discovered orbiting larger host galaxies. The
compact systems are thought to be the remnants of once normal galaxies
that were swallowed by the host, a process that removed the fluffy outer
parts of the systems, leaving the dense centers behind. Image credit:
A. Romanowsky (SJSU), Subaru, Hubble Legacy Archive
Fig 3.Reconstructed spectrum of lightfrom the ultracompact galaxies M59-UCD3, as seen by the SOAR telescope
(top) and M85-HCC1, as seen by the Sloan Digital Sky Survey (bottom).
Dark bands are the fingerprints of atoms and molecules in the
atmospheres of the stars in the galaxy. These bands reveal the
compositions and ages of the stars as well as the velocities of the
Fig 4. Computer animated movie showing the formation of an ultra-dense
galaxy: the giant host galaxy disrupts the smaller galaxy, removing its
fluffy outer parts, and the dense center is left behind. The animation
then zooms in to a possible embedded planet and supermassive black hole.
Click for thefull version. Credit: M. Sandoval, A. Romanowsky (SJSU).
Two undergraduates at San José State University have discovered two
galaxies that are the densest known. Similar to ordinary globular star
clusters but a hundred to a thousand times brighter, the new systems
have properties intermediate in size and luminosity between galaxies and
The first system discovered by the investigators, M59-UCD3, has a
width two hundred times smaller than our own Milky Way Galaxy and a
stellar density 10,000 times larger than that in the neighborhood of the
Sun. For an observer in the core of M59-UCD3, the night sky would be a
dazzling display, lit up by a million stars. The stellar density of the
second system, M85-HCC1, is higher still: about a million times that of
the Solar neighborhood. Both systems belong to the new class of galaxies
known as ultracompact dwarfs (UCDs).
The study, led by undergraduates Michael Sandoval and Richard Vo,
used imaging data from the Sloan Digital Sky Survey, the Subaru
Telescope, and Hubble Space Telescope, as well as spectroscopy from the
Goodman Spectrograph on the Southern Astrophysical Research Telescope
(SOAR), located on the Cerro Tololo Inter-American Observatory site. The
National Optical Astronomy Observatory (NOAO) is a SOAR partner. The
SOAR spectrum was used to show that M59-UCD3 is associated with a larger
host galaxy, M59, and to measure the age and elemental abundances of
the galaxy’s stars.
“Ultracompact stellar systems like these are easy
to find once you know what to look for. However, they were overlooked
for decades because no one imagined such objects existed: they were
hiding in plain sight”, said Richard Vo. “When we discovered one UCD
serendipitously, we realized there must be others, and we set out to
The students were motivated by the idea that all it takes to initiate
a discovery is a good idea, archival data, and dedication. The last
element was critical, because the students worked on the project on
their own time. Aaron Romanowsky, the faculty mentor and coauthor on the
study, explained, “The combination of these elements and the use of
national facilities for follow up spectroscopy is a great way to engage
undergraduates in frontline astronomical research, especially for
teaching universities like San José State that lack large research
budgets and their own astronomical facilities.”
The nature and origins of UCDs are mysterious – are they the remnant
nuclei of tidally stripped dwarf galaxies, merged stellar
super-clusters, or genuine compact dwarf galaxies formed in the smallest
peaks of primordial dark matter fluctuations?
Michael Sandoval favors the tidally stripped hypothesis. “One of the
best clues is that some UCDs host overweight supermassive black holes.
This suggests that UCDs were originally much bigger galaxies with normal
supermassive black holes, whose fluffy outer parts were stripped away,
leaving their dense centers behind. This is plausible because the known
UCDs are found near massive galaxies that could have done the
An additional line of evidence is the high abundance of heavy
elements such as iron in UCDs. Because large galaxies are more efficient
factories to make these metals, a high metal content may indicate that
the galaxy used to be much larger.
To test this hypothesis, the team will investigate the motions of
stars in the center of M59-UCD3 to look for a supermassive black hole.
They are also on the hunt for more UCDs, to understand how commonly they
occur and how diverse they are.
“Hiding in plain sight: record-breaking compact
stellar systems in the Sloan Digital Sky Survey,” Michael A. Sandoval,
Richard P. Vo, Aaron J. Romanowsky et al. 2015, Astrophysical Journal Letters, 808, L32. (Preprint:http://arxiv.org/abs/1506.08828)
NOAO is operated by Association of Universities for Research in
Astronomy Inc. (AURA) under a cooperative agreement with the National
Science Contact Dr. Aaron Romanowsky Department of Physics and Astronomy San José State University One Washington Square San Jose, CA 95192 USA 408-924-5225 E-mail:email@example.com
Beneath the vivid hues of this eye-shaped cloud, named Abell 78, a
tale of stellar life and death is unfolding. At the centre of the
nebula, a dying star – not unlike our Sun – which shed its outer layers
on its way to oblivion has, for a brief period of time, come back to
echo its past glory.
Releasing their outer shells is the usual
fate for any star with a mass of 0.8–8 times that of the Sun. Having
exhausted the nuclear fuel in their cores after burning for billions of
years, these stars collapse to become dense, hot white dwarf stars.
Around them, the ejected material strikes the ambient gas and dust,
creating beautiful clouds known as ‘planetary nebulas’. This curious
name was adopted by 18th-century astronomers who discovered these
‘puffing’ stars and thought their round shape similar to that of
However, the resurgence to life seen in this image is an
exceptional event for a planetary nebula. Only a handful of such
born-again stars have been discovered, and here the intricate shape of
the cloud’s glowing material gives away its turbulent history.
nuclear burning of hydrogen and helium had ceased in the core of the
dying star, causing it to collapse under its own weight and its envelope
to expand into a bubble, some of the star’s outer layers became so
dense that fusion of helium resumed there.
The renewed nuclear
activity triggered another, much faster wind, blowing more material
away. The interplay between old and new outflows has shaped the cloud’s
complex structure, including the radial filaments that can be seen
streaming from the collapsing star at the centre.
between slow and fast winds gusting in the environment of Abell 78
heated the gas to over a million degrees, making it shine brightly in
X-rays. Astronomers detected this hot gas with ESA’s XMM-Newton space
observatory, revealing striking similarities with another born-again
planetary nebula, Abell 30.
three-colour image combines X-ray data collected in 2013 by XMM-Newton
(blue) with optical observations obtained using two special filters that
reveal the glow of oxygen (green) and helium (red). The optical data
were gathered in 2014 with the Andalusian Faint Object Spectrograph and
Camera at the Nordic Optical Telescope on La Palma, in the Canary
Islands. A study of the X-ray emission from Abell 78 is presented in a paper by J.A. Toalá et al. 2015.
An infrared image of the Orion Nebula; the circled area shows the region where shocks and emission from molecular oxygen are found.
Oxygen is the third most abundant element in the universe (after hydrogen and helium) and of course it is important: all known life forms require liquid water and its oxygen content. For over thirty years, astronomers have been searching for molecular oxygen, O2, as part of an accounting of cosmic oxygen atoms. Despite early predictions that O2 should be abundant in the molecular clouds that form new stars and planetary systems, it is virtually absent. Only two locations have convincing O2 detections, a region of shocks near the Orion Nebula, and a cloud in the constellation of Ophiuchus. The theory is clearly wrong. What is not clear is whether O2 is missing (with dramatic implications for its abundance and the chemistry of molecular clouds), is in some less detectable form (perhaps frozen onto dust grains), or has been taken up to form water, carbon monoxide, or other oxygen-bearing molecules.
The launch of the Herschel Space Observatory enabled much more sensitive searches for O2, and prompted updated chemical modeling for molecular clouds and their oxygen. CfA astronomer Gary Melnick and his colleague improved the models to take into account the role of ultraviolet radiation in modifying the chemical and physical conditions in shocks. Their goal was to explain the strength and proportions of the line emission in Orion, and to understand what made the Orion environment so special.
The scientists report that when UV illuminates the region of a shock, the width and temperature of the shocked region changes, and enhances the O2 in two ways: by knocking oxygen off dust grains and breaking apart some molecules, thus increasing the number of free atoms before the shock, and by breaking apart water in the post-shock gas so that more O2 can form. The new model also successfully resolves the outstanding puzzle about its limited detection, finding that the detectability is very sensitive to the size and geometry of the emitting region. The paper provides the first self-consistent treatment of preshock, shock, and postshock regions under the influence of UV fields, and explains why O2 detections are so rare.
"O2 Emission toward Orion H2 Peak 1 and the Role of FUV-illuminated C-shocks," Gary J. Melnick and Michael J. Kaufman,ApJ 806, 227, 2015.
A snapshot image from a computer simulation of a star disrupted by a supermassive black hole. The red-orange plumes show the debris of the star after its passage near the black hole (located close to the bottom left corner of the image). About half of the disrupted star moves in elliptical orbits around the black hole and forms an accretion disc which eventually shines brightly in optical and X-ray wavelengths. Credit: J. Guillochon (Harvard University) and E. Ramirez-Ruiz (University of California).
Andrea Merloni and members of his team, from the Max-Planck Institute for Extraterrestrial Physics
(MPE) in Garching, near Munich, were exploring the huge archive of the
Sloan Digital Sky Survey (SDSS) in preparation for a future X-ray
satellite mission. The SDSS has been observing a large fraction of the
night sky with its optical telescope. In addition, spectra
(where light is dispersed across wavelengths, allowing astronomers to
deduce properties like composition and temperature) have been taken of
distant galaxies and black holes.
For a variety of reasons, the spectra of some objects were taken more
than once. And when the team was looking at one of the objects with
multiple spectra, they were struck by an extraordinary change in one of
the objects under study, with the catalogue number SDSS J0159+0033, a
galaxy in the constellation of Cetus. The huge distance to the galaxy means that we see it as it was 3.5 billion years ago.
“Usually distant galaxies do not change significantly over an
astronomer’s lifetime, i.e. on a timescale of years or decades,”
explains Andrea Merloni, “but this one showed a dramatic variation of
its spectrum, as if the central black hole had switched on and off.”
This happened between 1998 and 2005, but nobody had noticed the odd
behaviour of this galaxy until late last year, when two groups of
scientists preparing the next (fourth) generation of SDSS surveys
independently stumbled across these data.
Luckily enough, the two flagship X-ray observatories, the ESA-led
XMM-Newton and the NASA-led Chandra took snapshots of the same area of
the sky close in time to the peak of the flare, and again about ten
years later. This gave the astronomers unique information about the
high-energy emission that reveals how material is processed in the
immediate vicinity of the central black hole.
Gigantic black holes are at home in the nuclei of large galaxies all
around us. Most astronomers believe that they grew to the enormous sizes
that we can observe today by feeding mostly on interstellar gas from
their surroundings, which is unable to escape the immense gravitational
pull. Such a process takes place over a very long time (tens to hundreds
of millions of years), and is capable of turning a small black hole
created in the explosion of a heavy star into the super-heavyweight monsters that lurk at the centre of galaxies.
However, galaxies also contain a huge number of stars. Some unlucky
ones may happen to pass too close to the central black hole, where they
are destroyed and eventually swallowed by the black hole. If this is
compact enough, the strong, tidal gravitational forces tear the star
apart in a spectacular way. Subsequently bits and pieces swirl into the
black hole and thus produce huge flares of radiation that can be as
luminous as all of the rest of the stars in the host galaxy for a period
of a few months to a year. These rare events are called Tidal
Disruption Flares (TDF).
Merloni and his collaborators quite quickly realised that 'their'
flare matched almost perfectly all the expectations of this model.
Moreover, because of the serendipitous nature of the discovery, they
realised that this was an even more peculiar system than those which had
been found through active searches until now. With an estimated mass of
100 million solar masses, this is the biggest black hole caught in the
act of star-tearing so far.
However, the sheer size of the system is not the only intriguing
aspect of this particular flare; it is also the first one for which
scientists can assume with some degree of certainty that the black hole
was on a more standard 'gas diet' very recently (a few tens of thousands
of years). This is an important clue to finding out which sort of food
black holes mostly live on.
"Louis Pasteur said: 'Chance favours the prepared mind' - but in our
case, nobody was really prepared," marvels Merloni. "We could have
discovered this unique object already ten years ago, but people did not
know where to look. It is quite common in astronomy that progress in our
understanding of the cosmos is helped by serendipitous discoveries. And
now we have a better idea of how to find more such events, and future
instruments will greatly expand our reach."
This computer simulation of the disruption of a star by a black hole
shows the formation of an accretion disk of stellar material spiralling
into the black hole. This sequence shows an early stage in the
formation of the disk. The stellar material is coloured according to its
temperature, with red being colder and purple hotter. Credit: J.
Guillochon and E. Ramirez Ruiz
In less than two years’ time a new powerful X-ray telescope eROSITA,
which is currently being built at MPE, will be put into orbit on the
Russian-German SRG satellite. It will scan the entire sky with the right
cadence and sensitivity needed to discover hundreds of new tidal
disruption flares. Big optical telescopes are also being designed and
built with the goal of monitoring the variable sky, and will greatly
contribute to solving the mystery of black hole eating habits.
Astronomers will have to be prepared to catch these dramatic last acts
of a star's life. But however prepared they’ll be, the sky will be full
of new surprises.
Media contact Dr Hannelore Hämmerle Pressesprecherin Max-Planck-Institut für extraterrestrische Physik Garching Germany Tel: +49 (0)89 30000 3980 firstname.lastname@example.org
Science contact Dr Andrea Merloni Max-Planck-Institut für extraterrestrische Physik Garching Germany Tel: +49 (0)89 30000-3893 email@example.com
The other group, who independently discovered the strange light
curve of this object, was Stephanie Lamassa (Yale) and her
collaborators. They were the fastest to alert the community about this
object, but did not explore the stellar disruption interpretation for
Tidal Disruption Flares are very rare, with perhaps one occurring
every few tens of thousands of year in any given galaxy. In addition,
because they do not last very long, they are very hard to find. Only
about twenty of them have been studied so far, but with the advent of
larger telescopes designed to survey large areas of the sky in a short
time, more and more dedicated searches are being carried out, and the
pace of discovery is rapidly increasing.
Notes for editors
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