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Lead author Iair Arcavi, a NASA Einstein postdoctoral fellow at LCO and the University of California Santa Barbara, visiting the Keck Observatory twin 10-meter optical/infrared telescopes on Maunakea, Hawaii. Credit: I. Arcavi
Hawaii – An international team of
astronomers led by Las Cumbres Observatory (LCO) has made a bizarre discovery; a
star that refuses to stop shining.
the explosions of stars, have been observed in the
thousands and in all cases
they marked the death of a star.
in a study published today in the journal Nature, the team discovered a remarkable exception; a star that
exploded multiple times over a period of more than fifty years.
Their observations, which include data from W. M. Keck Observatory on Maunakea, Hawaii, are
challenging existing theories on these cosmic catastrophes.
spectra we obtained at Keck Observatory showed that this supernova looked like
nothing we had ever seen before. This, after discovering nearly 5,000
supernovae in the last two decades,” said Peter Nugent, Senior Scientist and
Division Deputy for Science Engagement in the Computational Research Division
at Lawrence Berkeley National Laboratory who co-authored the study. “While the
spectra bear a resemblance to normal hydrogen-rich core-collapse supernova
explosions, they grew brighter and dimmer at least five times more slowly,
stretching an event which normally lasts 100 days to over two years.”
used the Low Resolution Imaging Spectrometer (LRIS) on the Keck I telescope to
obtain spectrum of the star’s host galaxy, and the Deep Imaging and
Multi-Object Spectrograph (DEIMOS) on Keck II to obtain high-resolution spectra
of the unusual star itself.
The supernova, named
iPTF14hls, was discovered in September of 2014 by the Palomar
Transient Factory. At the time, it looked like an ordinary
supernova. Several months later, LCO astronomers noticed the
supernova was growing brighter again after it had faded.
When astronomers went
back and looked at archival data, they were astonished to
find evidence of an explosion in 1954 at the same
location. This star somehow survived that explosion and exploded
again in 2014.
“This supernova breaks
everything we thought we knew about how they work. It’s
the biggest puzzle I’ve encountered in almost a decade of studying
stellar explosions,” said lead author Iair Arcavi, a NASA Einstein
postdoctoral fellow at LCO and the University of California Santa
The study calculated
that the star that exploded was at least 50 times more massive
than the sun and probably much larger. Supernova iPTF14hls
may have been the most massive stellar explosion ever seen.
The size of this explosion could be the reason that our
conventional understanding of the death of stars failed to explain
Supernova iPTF14hls may be
the first example of a “Pulsational Pair Instability Supernova.”
“According to this theory,
it is possible that this was the result of star so massive and hot that it
generated antimatter in its core,” said co-author Daniel Kasen, an associate
professor in the Physics and Astronomy Departments at UC Berkeley and a
scientist at Lawrence Berkeley Lab. “That would cause the star to go violently
unstable, and undergo repeated bright eruptions over periods of years.”
That process may even repeat
over decades before the star’s large final explosion and collapse to a black
“These explosions were
only expected to be seen in the early universe and should
be extinct today. This is like finding a dinosaur still alive
today. If you found one, you would
question whether it truly was a dinosaur,” said Andy Howell,
leader of the LCO supernova group and co-author of the study.
Indeed, the “Pulsational
Pair Instability” theory may not fully explain all the data
obtained for this event. For example, the energy released by
the supernova is more than the theory predicts. This supernova may be
something completely new.
to monitor iPTF14hls, which remains bright three years after
it was discovered.
“This is one of those head-scratcher type of events,” said Nugent.
“At first we thought it was completely normal and boring. Then it just kept
staying bright, and not changing, for month after month. Piecing it all
together, from our observations at Palomar Transient Factory, Keck Observatory,
LCOGT, and even the images from 1954 in the Palomar Sky Survey, has started to
shed light on what this could be. I would really like to find another one like
The W. M. Keck Observatory telescopes are
among the most scientifically productive on Earth. The two, 10-meter
optical/infrared telescopes on the summit of Maunakea on the Island of Hawaii
feature a suite of advanced instruments including imagers, multi-object
spectrographs, high-resolution spectrographs, integral-field spectrometers, and
world-leading laser guide star adaptive optics systems.
Some of the data presented herein were obtained at
Keck Observatory, which is a private 501(c) 3 non-profit organization operated
as a scientific partnership among the California Institute of Technology, the
University of California, and the National Aeronautics and Space
Administration. The Observatory was made possible by the generous financial
support of the W. M. Keck Foundation.
The authors wish to
recognize and acknowledge the very significant cultural role and reverence that
the summit of Maunakea has always had within the indigenous Hawaiian
community. We are most fortunate to have the opportunity to conduct
observations from this mountain.
Astronomers looked at NGC 4625 in different wavelengths in the hope of solving this cosmic mystery. Observations in the ultraviolet
provided the first hint: in ultraviolet light the disc of the galaxy
appears four times larger than on the image depicted here. An indication
that there are a large number of very young and hot — hence mainly
visible in the ultraviolet — stars forming in the outer regions of the
galaxy. These young stars are only around one billion years old, about
10 times younger than the stars seen in the optical centre. At first
astronomers assumed that this high star formation rate was being
triggered by the interaction with another, nearby dwarf galaxy called NGC 4618.
They speculated that NGC 4618 may be the culprit “harassing”
NGC 4625, causing it to lose all but one spiral arm. In 2004
astronomers found proof for this claim: The gas in the outermost regions
of the dwarf galaxy NGC 4618 has been strongly affected by NGC 4625.
ESO’s HARPS instrument finds Earth-mass exoplanet around Ross 128
A temperate Earth-sized planet has been
discovered only 11 light-years from the Solar System by a team using
ESO’s unique planet-hunting HARPS instrument. The new world has the
designation Ross 128 b and is now the second-closest temperate planet to
be detected after Proxima b. It is also the closest planet to be
discovered orbiting an inactive red dwarf star, which may increase the
likelihood that this planet could potentially sustain life. Ross 128 b
will be a prime target for ESO’s Extremely Large Telescope, which will
be able to search for biomarkers in the planet's atmosphere.
A team working with ESO’s High Accuracy Radial velocity Planet Searcher (HARPS) at the La Silla Observatory in Chile has found that the red dwarf star Ross 128 is orbited by a low-mass exoplanet
every 9.9 days. This Earth-sized world is expected to be temperate,
with a surface temperature that may also be close to that of the Earth.
Ross 128 is the “quietest” nearby star to host such a temperate
“This discovery is based on more than a decade of HARPS
intensive monitoring together with state-of-the-art data reduction and
analysis techniques. Only HARPS has demonstrated such a precision and it
remains the best planet hunter of its kind, 15 years after it began
operations,” explains Nicola Astudillo-Defru (Geneva Observatory –
University of Geneva, Switzerland), who co-authored the discovery paper.
Red dwarfs are some of the coolest, faintest — and most
common — stars in the Universe. This makes them very good targets in the
search for exoplanets and so they are increasingly being studied. In
fact, lead author Xavier Bonfils (Institut de Planétologie et
d'Astrophysique de Grenoble – Université Grenoble-Alpes/CNRS, Grenoble,
France), named their HARPS programme The shortcut to happiness, as it is
easier to detect small cool siblings of Earth around these stars, than
around stars more similar to the Sun .
Many red dwarf stars, including Proxima Centauri,
are subject to flares that occasionally bathe their orbiting planets in
deadly ultraviolet and X-ray radiation. However, it seems that Ross 128
is a much quieter star, and so its planets may be the closest known
comfortable abode for possible life.
Although it is currently 11 light-years from Earth, Ross
128 is moving towards us and is expected to become our nearest stellar
neighbour in just 79 000 years
— a blink of the eye in cosmic terms. Ross 128 b will by then take the
crown from Proxima b and become the closest exoplanet to Earth!
With the data from HARPS, the team found that Ross 128 b
orbits 20 times closer than the Earth orbits the Sun. Despite this
proximity, Ross 128 b receives only 1.38 times more irradiation than the
Earth. As a result, Ross 128 b’s equilibrium temperature is estimated
to lie between -60 and 20°C, thanks to the cool and faint nature of its
small red dwarf host star, which has just over half the surface
temperature of the Sun. While the scientists involved in this discovery
consider Ross 128b to be a temperate planet, uncertainty remains as to
whether the planet lies inside, outside, or on the cusp of the habitable zone, where liquid water may exist on a planet’s surface .
Astronomers are now detecting more and more temperate
exoplanets, and the next stage will be to study their atmospheres,
composition and chemistry in more detail. Vitally, the detection of
biomarkers such as oxygen in the very closest exoplanet atmospheres will
be a huge next step, which ESO’s Extremely Large Telescope (ELT) is in prime position to take .
“New facilities at ESO will first play a critical role in
building the census of Earth-mass planets amenable to characterisation.
In particular, NIRPS,
the infrared arm of HARPS, will boost our efficiency in observing red
dwarfs, which emit most of their radiation in the infrared. And then,
the ELT will provide the opportunity to observe and characterise a large
fraction of these planets,” concludes Xavier Bonfils.
 A planet
orbiting close to a low-mass red dwarf star has a larger gravitational
effect on the star than a similar planet orbiting further out from a
more massive star like the Sun. As a result, this “reflex motion”
velocity is much easier to spot. However, the fact that red dwarfs are
fainter makes it harder to collect enough signal for the very precise
measurements that are needed.
 The habitable zone is
defined by the range of orbits around a star in which a planet can
possess the appropriate temperature for liquid water to exist on the
 This is only possible
for the very few exoplanets that are close enough to the Earth to be
angularly resolved from their stars.
This research was presented in a
paper entitled “A temperate exo-Earth around a quiet M dwarf at 3.4
parsecs”, by X. Bonfils et al., to appear in the journal Astronomy & Astrophysics.
The team is composed of X. Bonfils (Univ. Grenoble Alpes,
CNRS, IPAG, Grenoble, France [IPAG]), N. Astudillo-Defru (Observatoire
de Genève, Université de Genève, Sauverny, Switzerland), R. Díaz (CONICET – Universidad de Buenos Aires, Instituto de Astronomía y Física del Espacio (IAFE), Buenos Aires, Argentina),
J.-M. Almenara (Observatoire de Genève, Université de Genève, Sauverny,
Switzerland), T. Forveille (IPAG), F. Bouchy (Observatoire de Genève,
Université de Genève, Sauverny, Switzerland), X. Delfosse (IPAG), C.
Lovis (Observatoire de Genève, Université de Genève, Sauverny,
Switzerland), M. Mayor (Observatoire de Genève, Université de Genève,
Sauverny, Switzerland), F. Murgas (Instituto de Astrofísica de Canarias,
La Laguna, Tenerife, Spain), F. Pepe (Observatoire de Genève,
Université de Genève, Sauverny, Switzerland), N. C. Santos (Instituto de
Astrofísica e Ciências do Espaço and Universidade do Porto, Portugal),
D. Ségransan (Observatoire de Genève, Université de Genève, Sauverny,
Switzerland), S. Udry (Observatoire de Genève, Université de Genève,
Sauverny, Switzerland) and A. Wü̈nsche (IPAG).
ESO is the foremost intergovernmental astronomy
organisation in Europe and the world’s most productive ground-based
astronomical observatory by far. It is supported by 16 countries:
Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland,
Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden,
Switzerland and the United Kingdom, along with the host state of Chile
and by Australia as a strategic partner. ESO carries out an ambitious
programme focused on the design, construction and operation of powerful
ground-based observing facilities enabling astronomers to make important
scientific discoveries. ESO also plays a leading role in promoting and
organising cooperation in astronomical research. ESO operates three
unique world-class observing sites in Chile: La Silla, Paranal and
Chajnantor. At Paranal, ESO operates the Very Large Telescope and its
world-leading Very Large Telescope Interferometer as well as two survey
telescopes, VISTA working in the infrared and the visible-light VLT
Survey Telescope. ESO is also a major partner in two facilities on
Chajnantor, APEX and ALMA, the largest astronomical project in
existence. And on Cerro Armazones, close to Paranal, ESO is building the
39-metre Extremely Large Telescope, the ELT, which will become “the
world’s biggest eye on the sky”.
The Perseus galaxy cluster, located about 240 million light-years
away, is shown in this composite of visible light (green and red) and
near-infrared images from the Sloan Digital Sky Survey. Unseen here is a
thin, hot, X-ray-emitting gas that fills the cluster. Credit: Robert Lupton and the Sloan Digital Sky Survey Consortium.Hi-res image
Hitomi's Soft X-ray Spectrometer (SXS) instrument
captured data from two overlapping areas of the Perseus galaxy cluster
(blue outlines, upper right) in February and March 2016. The resulting
spectrum has 30 times the detail of any previously captured, revealing
many X-ray peaks associated with chromium, manganese, nickel and iron.
Dark blue lines in the insets indicate the actual X-ray data points and
their uncertainties.Credits: NASA's Goddard Space Flight Center.Hi-res image
Illustration of Hitomi, an X-ray astronomy observatory
Credits: Japan Aerospace Exploration Agency (JAXA).Hi-res image
The Soft X-ray Spectrometer (SXS) on Hitomi,
photographed Nov. 27, 2015, at Tsukuba Space Center in Japan. The SXS
permitted scientists to observe the detailed motions and chemical
composition of gas permeating the Perseus galaxy cluster. Credits: JAXA.Hi-res image
Before its brief mission ended unexpectedly in March 2016, Japan's Hitomi X-ray observatory captured exceptional information about the motions of hot gas in the Perseus galaxy cluster.
Now, thanks to unprecedented detail provided by an instrument developed
jointly by NASA and the Japan Aerospace Exploration Agency (JAXA),
scientists have been able to analyze more deeply the chemical make-up of
this gas, providing new insights into the stellar explosions that
formed most of these elements and cast them into space.
The Perseus cluster, located 240 million light-years away in its
namesake constellation, is the brightest galaxy cluster in X-rays and
among the most massive near Earth. It contains thousands of galaxies
orbiting within a thin hot gas, all bound together by gravity. The gas
averages 90 million degrees Fahrenheit (50 million degrees Celsius) and
is the source of the cluster's X-ray emission.
Using Hitomi's high-resolution Soft X-ray Spectrometer (SXS)
instrument, researchers observed the cluster between Feb. 25 and March
6, 2016, acquiring a total exposure of nearly 3.4 days. The SXS observed
an unprecedented spectrum, revealing a landscape of X-ray peaks emitted
from various chemical elements with a resolution some 30 times better
than previously seen.
"There was no reason to expect that initially," said coauthor Michael
Loewenstein, a University of Maryland research scientist at NASA's
Goddard Space Flight Center in Greenbelt, Maryland. "The Perseus cluster
is a different environment with a different history from our Sun's.
After all, clusters represent an average chemical distribution from many
types of stars in many types of galaxies that formed long before the
One group of elements is closely tied to a particular class of stellar
explosion, called Type Ia supernovas. These blasts are thought to be
responsible for producing most of the universe's chromium, manganese,
iron and nickel — metals collectively known as "iron-peak" elements.
Type Ia supernovas entail the total destruction of a white dwarf, a
compact remnant produced by stars like the Sun. Although stable on its
own, a white dwarf can undergo a runaway thermonuclear explosion if it's
paired with another object as part of a binary system. This occurs
either by merging with a companion white dwarf or, when paired with a
nearby normal star, by stealing some of partner's gas. The transferred
matter can accumulate on the white dwarf, gradually increasing its mass
until it becomes unstable and explodes.
An important open question has been whether the exploding white dwarf
is close to this stability limit — about 1.4 solar masses — regardless
of its origins. Different masses produce different amounts of iron-peak
metals, so a detailed tally of these elements over a large region of
space, like the Perseus galaxy cluster, could indicate which kinds of
white dwarfs blew up more often.
"It turns out you need a combination of Type Ia supernovas with
different masses at the moment of the explosion to produce the chemical
abundances we see in the gas at the middle of the Perseus cluster," said
Hiroya Yamaguchi, the paper's lead author and a UMD research scientist
at Goddard. "We confirm that at least about half of Type Ia supernovas
must have reached nearly 1.4 solar masses."
Taken together, the findings suggest that the same combination of
Type Ia supernovas producing iron-peak elements in our solar system also
produced these metals in the cluster's gas. This means both the solar
system and the Perseus cluster experienced broadly similar chemical
evolution, suggesting that the processes forming stars — and the systems
that became Type Ia supernovas — were comparable in both locations.
"Although this is just one example, there’s no reason to doubt that
this similarity could extend beyond our Sun and the Perseus cluster to
other galaxies with different properties," said coauthor Kyoko
Matsushita, a professor of physics at the Tokyo University of Science.
Although short-lived, the Hitomi mission and its revolutionary SXS
instrument —developed and built by Goddard scientists working closely
with colleagues from several institutions in the United States, Japan
and the Netherlands — have demonstrated the promise of high-resolution
"Hitomi has permitted us to delve deeper into the history of one of
the largest structures in the universe, the Perseus galaxy cluster, and
explore how particles and materials behave in the extreme conditions
there," said Goddard's Richard Kelley, the U.S. principal investigator
for the Hitomi collaboration. "Our most recent calculations have
provided a glimpse into how and why certain chemical elements are
distributed throughout galaxies beyond our own."
JAXA and NASA scientists are now working to regain the science capabilities lost in the Hitomi mishap by collaborating on the X-ray Astronomy Recovery Mission (XARM), expected to launch in 2021. One of its instruments will have capabilities similar to the SXS flown on Hitomi.
Hitomi launched on Feb. 17, 2016, and suffered a mission-ending
spacecraft anomaly 38 days later. Hitomi, which translates to "pupil of
the eye," was known before launch as ASTRO-H. The mission was developed
by the Institute of Space and Astronautical Science,
a division of JAXA. It was built jointly by an international
collaboration led by JAXA, with contributions from Goddard and other
institutions in the United States, Japan, Canada and Europe.
Credit:ESO/T. Contini (IRAP, Toulouse), B. Epinat (LAM, Marseille)
Measuring more than 300 000 light-years across, three times the diameter of the Milky Way, this colourful bubble of ionised
gas is the biggest to ever have been discovered. The enormous bubble
contains 10 individual galaxies and is situated in a particularly dense
region of a galaxy group called COSMOS-Gr30, 6.5 billion light-years
away from Earth. Targeted due to its high density of galaxies, this
group is extremely varied — some galaxies are actively forming stars
while others are passive; some are bright while others are dim; some are
massive and others are tiny.
This record-breaking bubble was discovered and studied in detail thanks to the incredible sensitivity of the MUSE instrument, mounted on ESO’s Very Large Telescope.
Operating in visible wavelengths, MUSE combines the capabilities of an
imaging device with the measuring capacity of a spectrograph, creating a
unique and powerful tool that can shed light on cosmological objects
that would otherwise remain in the dark.
MUSE’s powerful eye on
the sky has allowed astronomers to understand that this large pocket of
gas is not pristine, but was expelled from galaxies either during
violent interactions or by superwinds driven by active black holes and
supernovae. They also studied how this magnificent bubble became
ionised. It is believed that the gas in the upper area (shown in blue)
was ionised by intense electromagnetic radiation from newborn stars and
shock waves stemming from galactic activity.
Astronomers suspect that
the violent red active galactic nucleus towards the lower left of the image could have ripped the electrons from their atoms.
Composite image of ADFS-27 galaxy pair. The background
image is from ESA's Herschel Space Observatory. The object was then
detected by ESO's Atacama Pathfinder EXperiment (APEX) telescope (middle
image). ALMA (right) was able to identify two galaxies: ADFS-27N (for
North) and ADFS-27S (for South). The starbursting galaxies are about
12.8 billion light-years from Earth and destined to merge into a single,
massive galaxy. Credit: NRAO/AUI/NSF, B. Saxton; ESA Herschel; ESO APEX; ALMA (ESO/NAOJ/NRAO); D. Riechers
Artist impression of two starbursting galaxies beginning to merge in the early universe.
Animation zoom-in of the composite image of ADFS-27 galaxy
pair. The initial image is from ESA's Herschel Space Observatory. The
object was then detected by ESO's Atacama Pathfinder EXperiment (APEX)
telescope. ALMA (final zoom) was able to identify two galaxies: ADFS-27N
(for North) and ADFS-27S (for South). The starbursting galaxies are
about 12.8 billion light-years from Earth and destined to merge into a
single, massive galaxy. Credit: ESA/Herschel; ESO/APEX; ALMA (ESO/NAOJ/NRAO); D. Riechers et al. 2017
Pair of Exceptionally Rare Hyper-luminous Galaxies Discovered with ALMA
New observations with the Atacama Large Millimeter/submillimeter Array (ALMA)
have uncovered the never-before-seen close encounter between two
astoundingly bright and spectacularly massive galaxies in the early
universe. These so-called hyper-luminous starburst galaxies are
exceedingly rare at this epoch of cosmic history — near the time when
galaxies first formed — and may represent one of the most-extreme
examples of violent star formation ever observed.
Astronomers captured these two interacting galaxies, collectively
known as ADFS-27, as they began the gradual process of merging into a
single, massive elliptical galaxy. An earlier sideswiping encounter
between the two helped to trigger their astounding bursts of star
formation. Astronomers speculate that this merger may eventually form
the core of an entire galaxy cluster. Galaxy clusters are among the most
massive structures in the universe.
“Finding just one hyper-luminous starburst galaxy is remarkable in
itself. Finding two of these rare galaxies in such close proximity is
truly astounding,” said Dominik Riechers, an astronomer at Cornell
University in Ithaca, New York, and lead author on a paper appearing in
the Astrophysical Journal. “Considering their extreme distance
from Earth and the frenetic star-forming activity inside each, it’s
possible we may be witnessing the most intense galaxy merger known to
The ADFS-27 galaxy pair is located approximately 12.7 billion
light-years from Earth in the direction of the Dorado constellation. At
this distance, astronomers are viewing this system as it appeared when
the universe was only about one billion years old.
Astronomers first detected this system with the European Space
Agency’s Herschel Space Observatory. It appeared as a single red dot in
the telescope’s survey of the southern sky. These initial observations
suggested that the apparently faint object was in fact both extremely
bright and extremely distant. Follow-up observations with the Atacama
Pathfinder EXperiment (APEX) telescope confirmed these initial
interpretations and paved the way for the more detailed ALMA
With its higher resolution and greater sensitivity, ALMA precisely
measured the distance to this object and revealed that it was in fact
two distinct galaxies. The pairing of otherwise phenomenally rare
galaxies suggests that they reside within a particularly dense region of
the universe at that period in its history, the astronomers said.
The new ALMA observations also indicate that the ADFS-27 system has
approximately 50 times the amount of star-forming gas as the Milky Way.
“Much of this gas will be converted into new stars very quickly,” said
Riechers. “Our current observations indicate that these two galaxies are
indeed producing stars at a breakneck pace, about one thousand times
faster than our home galaxy.”
The galaxies — which would appear as flat, rotating disks — are
brimming with extremely bright and massive blue stars. Most of this
intense starlight, however, never makes it out of the galaxies
themselves; there is simply too much obscuring interstellar dust in
This dust absorbs the brilliant starlight, heating up until it glows
brightly in infrared light. As this light travels the vast cosmic
distances to Earth, the ongoing expansion of the universe shifts the
once infrared light into longer millimeter and submillimeter
wavelengths, all thanks to the Doppler efecct.
ALMA was specially designed to detect and study light of this nature,
which enabled the astronomers to resolve the source of the light into
two distinct objects. The observations also show the basic structures of
the galaxies, revealing tail-like features that were spun-off during
their initial encounter.
The new observations also indicate that the two galaxies are about
30,000 light-years apart, moving at roughly several hundred kilometers
per second relative to each other. As they continue to interact
gravitationally, each galaxy will eventually slow and fall toward the
other, likely leading to several more close encounters before merging
into one massive, elliptical galaxy. The astronomers expect this process
to take a few hundred million years.
“Due to their great distance and dustiness, these galaxies remain
completely undetected at visible wavelengths,” noted Riechers.
“Eventually, we hope to combine the exquisite ALMA data with future
infrared observations with NASA’s James Webb Space Telescope. These two
telescopes will form an astronomer’s ‘dream team’ to better understand
the nature of this and other such exceptionally rare, extreme systems.”
The National Radio Astronomy Observatory is a facility of the
National Science Foundation, operated under cooperative agreement by
Associated Universities, Inc.
The Atacama Large Millimeter/submillimeter Array (ALMA), an
international astronomy facility, is a partnership of ESO, the U.S.
National Science Foundation (NSF) and the National Institutes of Natural
Sciences (NINS) of Japan in cooperation with the Republic of Chile.
ALMA is funded by ESO on behalf of its Member States, by NSF in
cooperation with the National Research Council of Canada (NRC) and the
National Science Council of Taiwan (NSC) and by NINS in cooperation with
the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space
Science Institute (KASI).
ALMA construction and operations are led by ESO on behalf of its
Member States; by the National Radio Astronomy Observatory (NRAO),
managed by Associated Universities, Inc. (AUI), on behalf of North
America; and by the National Astronomical Observatory of Japan (NAOJ) on
behalf of East Asia. The Joint ALMA Observatory (JAO) provides the
unified leadership and management of the construction, commissioning and
operation of ALMA.
This NASA/ESA Hubble Space Telescope image seems to sink into the screen, plunging the viewer into the dark depths of the early Universe. Massive galaxy clusters
— such as the subject of this image, Abell 1300 — help us to better
understand the cosmos. They are essentially giant natural telescopes,
magnifying the light from any galaxies sitting behind them and helping
us peer further back in time.
This bizarre kind of time travel is possible due to a phenomenon called gravitational lensing,
whereby the gravitational influence of a massive object such as Abell
1300 acts like a lens, bending the very fabric of space around it and
thus causing more distant light to move in a curved path. To the
observer, the source of the light — a background object such as a
primordial galaxy, for example — appears both distorted and magnified.
The lensing power of massive clusters has helped us to discover some of
the most distant known galaxies in the Universe. Hubble has observed
this phenomenon many times; see a selection of images here.
Voices reverberating off mountains and the sound of footsteps
bouncing off walls are examples of an echo. Echoes happen when sound
waves ricochet off surfaces and return to the listener.
Space has its own version of an echo. It’s not made with sound but with light, and occurs when light bounces off dust clouds.
The Hubble telescope has just captured one of these cosmic echoes,
called a “light echo,” in the nearby starburst galaxy M82, located 11.4
million light-years away. A movie assembled from more than two years’
worth of Hubble images reveals an expanding shell of light from a
supernova explosion sweeping through interstellar space three years
after the stellar blast was discovered. The “echoing” light looks like a
ripple expanding on a pond. The supernova, called SN 2014J, was
discovered on Jan. 21, 2014.
A light echo occurs because light from the stellar blast travels
different distances to arrive at Earth. Some light comes to Earth
directly from the supernova blast. Other light is delayed because it
travels indirectly. In this case, the light is bouncing off a huge dust
cloud that extends 300 to 1,600 light-years around the supernova and is
being reflected toward Earth.
So far, astronomers have spotted only 15 light echoes around
supernovae outside our Milky Way galaxy. Light echo detections from
supernovae are rarely seen because they must be nearby for a telescope
to resolve them.
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Composite image of Abell 2744 region, with radio, X-Ray, and optical (visible light) data combined.
Credit: Pearce et al.; Bill Saxton, NRAO/AUI/NSF; Chandra, Subaru; ESO.Hi-res image
Radio-only image of Abell 2744 region, showing radio-emitting features caused by subatomic particles accelerated to high speeds by the collisions of giant clusters of galaxies. Credit: Pearce et al., NRAO/AUI/NS.Hi-res image
Animated GIF cycles through the individual images (radio, X-ray, optical) of Abell 2744.
Credit: Pearce et al.; Bill Saxton, NRAO/AUI/NSF; Chandra; Subaru; ESO.Hi-res image
A giant collision of several galaxy clusters, each containing
hundreds of galaxies, has produced this spectacular panorama of shocks
and energy. The collisions generated shock waves that set off a
celestial fireworks display of bright radio emission, seen as red and
orange. In the center of the image, the purple indicates X-rays caused
by extreme heating.
The region is collectively known as Abell 2744, some 4 billion
light-years from Earth. The radio portion of the image comes from new
observations made with the National Science Foundation’s Karl G. Jansky
Very Large Array (VLA), and is combined with earlier data from NASA’s
Chandra X-ray observatory. Both are overlaid on an image at
visible-light wavelengths made with data from the Subaru telescope and
the Very Large Telescope (VLT). The new VLA observations revealed
previously undetected regions where shocks accelerated subatomic
particles, causing radio emission.
Astronomers are studying the combined image in an attempt to decipher
the sequence of galaxy-cluster collisions. Currently, they said,
evidence indicates a North-South (top-bottom in the image) collision of
subclusters and an East-West (left-right in the image) collision. There
is a possible third collision, and the astronomers continue to analyze
their data to uncover more details about the region’s complex history of
collisions and their aftermath.
The scientists reported their findings in a paper in the Astrophysical Journal
by Connor Pearce, of the Harvard-Smithsonian Center for Astrophysics
and the University of Southampton in the UK, and an international team
The National Radio Astronomy Obser vatory is a facility of the
National Science Foundation, operated under cooperative agreement by
Associated Universities, Inc.
Jupiter's intense northern and southern lights, or auroras, behave independently of each other according to a new study using NASA's Chandra X-ray and ESA's XMM-Newton observatories.
Using XMM-Newton and Chandra X-ray observations from March 2007 and
May and June 2016, a team of researchers produced maps of Jupiter's
X-ray emissions and identified an X-ray hot spot at each pole. Each hot spot can cover an area equal to about half the surface of the Earth.
The team found that the hot spots had very different characteristics. The X-ray emission at Jupiter's south pole consistently pulsed every 11 minutes, but the X-rays seen from the north pole were erratic, increasing and decreasing in brightness — seemingly independent of the emission from the south pole.
This makes Jupiter particularly puzzling. X-ray auroras have never been detected from our Solar System's other gas giants, including Saturn.
Jupiter is also unlike Earth, where the auroras on our planet's north
and south poles generally mirror each other because the magnetic fields
To understand how Jupiter produces its X-ray auroras, the team of
researchers plans to combine new and upcoming X-ray data from Chandra
and XMM-Newton with information from NASA's Juno mission, which is
currently in orbit around the planet. If scientists can connect the
X-ray activity with physical changes observed simultaneously with Juno,
they may be able to determine the process that generates the Jovian
auroras and by association X-ray auroras at other planets.
Illustration of Jupiter
One theory that the X-ray and Juno observations may help to prove or
disprove is that Jupiter's X-ray auroras are caused by interactions at
the boundary between Jupiter's magnetic field, which is generated by
electrical currents in the planet's interior, and the solar wind, a
high-speed flow of particles streaming from the Sun. The interactions
between the solar wind
and Jupiter's magnetic field can cause the latter to vibrate and
produce magnetic waves. Charged particles can surf these waves and gain
energy. Collisions of these particles with Jupiter's atmosphere produce
the bright flashes of X-rays observed by Chandra and XMM. Within this
theory the 11-minute interval would represent the time for a wave to
travel along one of Jupiter's magnetic field lines.
The difference in behavior between the Jovian north and south poles
may be caused by the difference in visibility of the two poles. Because
the magnetic field of Jupiter is tilted, we are able to see much more of
the northern aurora than the southern aurora. Therefore for the north
pole we may be able to observe regions where the magnetic field connects
to more than one location, with several different travel times, while
for the south pole we can only observe regions where the magnetic field
connects to one location. This would cause the behavior of the north
pole to appear erratic compared to the south pole.
A larger question is how does Jupiter give the particles in its magnetosphere
(the realm controlled by Jupiter's magnetic field) the huge energies
needed to make X-rays? Some of the X-ray emission observed with Chandra
can only be produced if Jupiter accelerates oxygen ions to such high
energies that when they violently collide with the atmosphere all eight
of their electrons are torn off. Scientists hope to determine what
impact these particles, which crash into the planet's poles at thousands
of kilometers per second, have on the planet itself. Do these
high-energy particles affect the Jovian weather and the chemical
composition of its atmosphere? Can they explain the anomalously high
temperatures found in certain places in Jupiter's atmosphere? These are
the questions that Chandra, XMM-Newton, and Juno may be able to help
answer in the future.
A paper describing these results
appeared in the October 30th issue of Nature Astronomy, led by William
Dunn of the University College London. NASA's Marshall Space Flight
Center in Huntsville, Alabama, manages the Chandra program for NASA's
Science Mission Directorate in Washington. The Smithsonian Astrophysical
Observatory in Cambridge, Massachusetts, controls Chandra's science and
Fast Facts for Jupiter: Scale: This image is about 37 arcsec across (139,822 km = Jupiter's diameter) as viewed from Earth Category:Solar System Observation Date: May 24 & Jun 01, 2016 Observation Time: 22 hours Obs. ID: 18608 & 18609 Instrument: HRC References: Dunn, W.R. et al, 2017,Nature Astronomy, 1, 758 Color Code: X-ray (purple), optical (pseudocolor) Distance Estimate: About 793 million km (on date of Chandra observations)
MACS J1149.5+2233 (MACS J1149 for short) is a system of merging galaxy clusters located about 5 billion light years from Earth. This galaxy cluster was one of six that have been studied as part of the "Frontier Fields" project. This research effort included long observations of galaxy clusters with powerful telescopes that detected different types of light, including NASA's Chandra X-ray Observatory.
Astronomers are using the Frontier Fields data to learn more about how galaxy clusters grow via collisions. Galaxy clusters are enormous collections of hundreds or even thousands of galaxies and vast reservoirs of hot gas embedded in massive clouds of dark matter, invisible material that does not emit or absorb light but can be detected through its gravitational effects.
This new image of MACS J1149 combines X-rays from Chandra (diffuse blue), optical data from Hubble (red, green, blue), and radio emission from the Very Large Array (pink). The image is about four million light years across at the distance of MACS J1149.
The Chandra data reveal gas in the merging clusters with temperatures of millions of degrees. The optical data show galaxies in the clusters and other, more distant, galaxies lying behind the clusters. Some of these background galaxies are highly distorted because of gravitational lensing, the bending of light by massive objects. This effect can also magnify the light from these objects, enabling astronomers to study background galaxies that would otherwise be too faint to detect. Finally, the structures in the radio data trace enormous shock waves and turbulence. The shocks are similar to sonic booms, and are generated by the mergers of smaller clusters of galaxies.
NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra's science and flight operations.
Fast Facts for MACS J1149.5+2233: Scale: Image is 3.2 arcmin across (about 4.7 million light years) Category:Groups & Clusters of Galaxies Coordinates (J2000): RA 11h 49m 36.3s | Dec 22° 23´ 58.1" Constellation: Leo Observation Date: 8 pointings between Jun 2001 and Feb 2015 Observation Time: 101 hours 30 min (4 days 5 hours 30 min) Obs. ID: 1656, 3589, 16238, 16239, 16306, 16582, 17595, 17596 Instrument:ACIS Color Code: X-ray (Blue); Optical (Red, Green, Blue); Radio (Pink) Distance Estimate: About 5 billion light years
The massive galaxy cluster bends the light of the most ancient spiral galaxy behind it, producing two highly magnified images that allow astronomers to study the spiral structures in great details. Image credit: James Josephides.
Gemini Observatory, using the Near-Infrared Integral Field Spectrograph on the Gemini North telescope in Hawai‘i, has confirmed the spiral nature of what is now the most distant known spiral galaxy. The galaxy's light, revealing how the galaxy looked some 11 billion years ago, is gravitationally lensed by a massive foreground cluster of galaxies to help reveal the distant pinwheel nature of the galaxy.
The following is a press release from Swinburne University of Technology in Australia.
The most ancient spiral galaxy discovered to date is revealing its secrets to a team of astronomers at Swinburne University of Technology and the Australian National University (ANU), both part of the Australian Research Council Centre of Excellence in All Sky Astrophysics in 3D (ASTRO 3D).
The galaxy, known as A1689B11, existed 11 billion years in the past, just 2.6 billion years after the Big Bang, when the Universe was only one fifth of its present age. It is thus the most ancient spiral galaxy discovered so far.
The researchers used a powerful technique that combines gravitational lensing with the cutting-edge instrument, the Near-infrared Integral Field Spectrograph (NIFS) on the Gemini North telescope in Hawai‘i, to verify the vintage and spiral nature of this galaxy. NIFS is Australia’s first Gemini instrument that was designed and built by the late Peter McGregor at the ANU.
Gravitational lenses are Nature’s largest telescopes, created by massive clusters composed of thousands of galaxies and dark matter. The cluster bends and magnifies the light of galaxies behind it in a manner similar to an ordinary lens, but on a much larger scale.
“This technique allows us to study ancient galaxies in high resolution with unprecedented detail,” says Swinburne astronomer Dr Tiantian Yuan, who led the research team.
“We are able to look 11 billion years back in time and directly witness the formation of the first, primitive spiral arms of a galaxy.”
Co-author, Princeton University’s Dr Renyue Cen, says: “Studying ancient spirals like A1689B11 is a key to unlocking the mystery of how and when the Hubble sequence emerges.”
“Spiral galaxies are exceptionally rare in the early Universe, and this discovery opens the door to investigating how galaxies transition from highly chaotic, turbulent discs to tranquil, thin discs like those of our own Milky Way galaxy.”
Dr Yuan says the study shows some surprising features of A1689B11.
“This galaxy is forming stars 20 times faster than galaxies today – as fast as other young galaxies of similar masses in the early Universe. However, unlike other galaxies of the same epoch, A1689B11 has a very cool and thin disc, rotating calmly with surprisingly little turbulence. This type of spiral galaxy has never been seen before at this early epoch of the Universe!”
This research is an international collaboration including astrophysicists from the University of Lyon in France, Princeton University in the USA and Hebrew University in Israel. It has been accepted for publication in The Astrophysical Journal. A preprint version is available here.
Science Contacts: Tiantian Yuan Swinburne University of Technology Email:email@example.com Desk: +613 9214 5948 Cell: +61 404 029 550 Media Contacts: Lea Kivivali Swinburne University of Technology Email:firstname.lastname@example.org Desk: +613 9214 5428 Cell: +61 410 569 311 Peter Michaud Public Information and Outreach Manager Gemini Observatory Hilo, Hawai‘i Email:email@example.com Desk: 808 974-2510 Cell: 808 936-6643
Figure 1:The deep image of Messier 77 taken with the Hyper Suprime-Cam (HSC) mounted at the Subaru Telescope. The picture is created by adding the color information from the Sloan Digital Sky Survey (Note 1) to the monochromatic image acquired by the HSC. (Credit: NAOJ/SDSS/David Hogg/Michael Blanton. Image Processing: Ichi Tanaka)
The galaxy Messier 77 (M77) is famous for its super-active nucleus
that releases enormous energy across the electromagnetic spectrum,
ranging from x-ray to radio wavelengths. Yet, despite its highly active
core, the galaxy looks like any normal quiet spiral. There's no visual
sign of what is causing its central region to radiate so extensively. It
has long been a mystery why only the center of M77 is so active.
Astronomers suspect a long-ago event involving a sinking black hole,
which could have kicked the core into high gear.
To test their ideas about why the central region of M77 beams massive
amounts of radiation, a team of researchers at the National
Astronomical Observatory of Japan and the Open University of Japan used
the Subaru Telescope to study M77. The unprecedented deep image of the
galaxy reveals evidence of a hidden minor merger billions of years ago.
The discovery gives crucial evidence for the minor merger origin of
active galactic nuclei.
The Mystery of Seyfert Galaxies
The galaxy Messier 77 (NGC 1068) is famous for harboring an active
nucleus at its core that releases an enormous amount of energy. The
existence of such active galaxies in the nearby universe was first noted
by the American astronomer Carl Seyfert more than 70 years ago.
Nowadays they are called the Seyfert galaxies (Note 2).
Astronomers think that the source of such powerful activity is the
gravitational energy released from superheated matter falling onto a
supermassive black hole (SMBH) that resides in the center of the host
galaxy. The estimated mass of such a SMBH for M77 is about 10 million
times that of the Sun.
It takes a massive amount of gas dumped on the galaxy's central black
hole to create such strong energies. That may sound like an easy task,
but it's actually very difficult. The gas in the galactic disk will
circulate faster and faster as it spirals into the vicinity of the SMBH.
Then, at some point the "centrifugal force" balances with the
gravitational pull of the SMBH. That actually prevents the gas from
falling into the center. The situation is similar to water draining out
of a bathtub. Due to the centrifugal force, the rapidly rotating water
will not drain out rapidly. So, how can the angular momentum be removed
from the gas circling near an active galactic nucleus? Finding the
answer to that question is one of the big challenges for researchers
A Prediction Posed 18 Years Ago
In 1999, Professor Yoshiaki Taniguchi (currently at the Open
University of Japan), the team leader of the current Subaru study,
published a paper about the driving mechanism of the active nucleus of
Seyfert galaxies such as M 77. He pointed out that a past event – a
"minor merger" where the host galaxy ate up its "satellite" galaxy (a
small low-mass galaxy orbiting it) – would be the key to activating the
Seyfert nucleus (Note 3).
Usually, a minor merger event simply breaks up a low-mass satellite
galaxy. The resulting debris is absorbed into the disk of the more
massive host galaxy before it approaches the center. Therefore, it was
not considered as the main driver of the nuclear activity. "However, the
situation could be totally different if the satellite galaxy has a
(smaller) SMBH in its center (Note 4),"
Professor Taniguchi suggests, "because the black hole can never be
broken apart. If it exists, it should eventually sink into the center of
the host galaxy."
The sinking SMBH from the satellite galaxy would eventually create a
disturbance in the rotating gas disk around the main galaxy's SMBH.
Then, the disturbed gas would eventually rush into the central SMBH
while releasing enormous gravitational energy. "This must be the main
ignition mechanism of the active Seyfert nuclei," Taniguchi argued. "The
idea can naturally explain the mystery about the morphology of the
Seyfert galaxies," said Professor Taniguchi, pointing out the advantage
of the model of normal-looking galaxies also being very active at their
cores. (Note 5).
Probing the Theory Using the Subaru Telescope
Recent advances in observational technique allow the detection of the
extremely faint structure around galaxies, such as loops or debris that
are likely made by dynamical interactions with satellite galaxies.. The
outermost parts of galaxies are often considered as relatively "quiet"
with a longer dynamical timescale than anywhere inside. Simulations show
that the faint signature of a past minor merger can remain several
billion years after the event. "Such a signature can be a key test for
our minor merger hypothesis for Seyfert galaxies. Now it is time to
revisit M77," said Taniguchi.
The team's choice to look for 'the past case' was, of course, the
Subaru Telescope and its powerful imaging camera, Hyper Suprime-Cam. The
observing proposal was accepted and executed on Christmas night 2016.
"The data was just amazing," said Dr. Ichi Tanaka, the primary
investigator of the project. "Luckily, we could also retrieve the other
data that was taken in the past and just released from the Subaru
Telescope's data archive. Thus, the combined data we got finally is
Figure 2:(Left) The newly-discovered,
extremely diffuse structures around M77. The innermost color part of the
picture shows the bright part of the galaxy (from SDSS: see the center
of Figure 1).
The middle part in red-brown is the contrast-enhanced expression of the
faint one-arm structure (labeled as "Banana") to the right, as well as
the ripple structure (labeled as "Ripple") to the left. All the
fore/background objects unrelated to M77 are removed during the process.
The outermost monochrome part shows the faint ultra-diffuse structures
in yellow circles (labelled as "UDO-SE", "UDO-NE", "UDO-SW"). A deep
look at them indicates the latter two ("UDO-NE", "UDO-SW") constitute a
part of the large loop-like structure. (Credit: NAOJ)
(Right) Artist's impression of M77. The illustration in the right is
created and copyrighted by Mr. Akihiro Ikeshita. (Credit: Akihiro
Subaru's great photon-collecting power and the superb performance of
the Hyper Suprime-Cam were crucial in the discovery of the extremely
faint structures in M77. Their discovery reveals the normal-looking
galaxy's hidden violent past.. "Though people may sometimes make a lie,
galaxies never do. The important thing is to listen to their small
voices to understand the galaxies," said Professor Taniguchi.
The team will expand its study to more Seyfert galaxies using the
Subaru Telescope. Dr. Masafumi Yagi, who leads the next phase of the
project said, "We will discover more and more evidences of the satellite
merger around Seyfert host galaxies. We expect that the project can
provide a critical piece for the unified picture for the triggering
mechanism for active galactic nuclei."
Note 2: Seyfert galaxies are actually a subclass of the active
galactic nuclei. There are even more powerful active galactic nuclei
called quasar in the universe. Usually quasars are found much farther
away than M77.
Note 3: Satellite galaxies are common for large galaxies. For
example, there are two bright satellite galaxies called Large and Small
Magellanic Clouds associated with our Milky Way. The Andromeda galaxy,
our nearest neighbor, also has two bright satellites called Messier 32 and NGC 205.
Note 4: Astronomers believe that most galaxies have an SMBH in
their central regions, with its mass mysteriously scaled to the mass of
the host galaxy. It is also known that some satellite galaxies also
have smaller SMBH. For example, Messier 32 (satellite of the Andromeda
galaxy) is likely to have a SMBH much heavier than a million times the
mass of our Sun. It is however not easy to directly prove the existence
of the SMBH for satellite galaxies due to its light weight.
Note 5: Y. Taniguchi 1999, ApJ, 524, 65, for the reference.
The research team:
Ichi Tanaka: Subaru Telescope, National Astronomical Observatory of Japan
Masafumi Yagi: National Astronomical Observatory of Japan