Releases from NASA, HubbleSite, Spitzer, ESO, ESA, NASA’s Chandra X-ray Observatory, Royal Astronomical Society, Harvard-Smithsonian Center For Astrophysics, Max Planck Institute, Gemini Observatory, Subaru Telescope, W. M. Keck Observatory, JPL-Caltech, ICRAR, Webb Space Telescope, etc
This diagram shows the 100-million-year-long trajectory of the Smith
Cloud as it arcs out of the plane of our Milky Way galaxy and then
returns like a boomerang. Hubble Space Telescope measurements show that
the cloud, because of its chemical composition, came out of a region
near the edge of the galaxy's disk of stars 70 million years ago. The
cloud is now stretched into the shape of a comet by gravity and gas
pressure. Following a ballistic path, the cloud will fall back into the
disk and trigger new star formation 30 million years from now.Illustration Credit:NASA,ESA, and A. Feild (STScI) - Science Credit:NASA,ESA, and A. Fox (STScI)
Size of Smith Cloud on the Sky
This composite image shows the size and location of the Smith Cloud on
the sky. The cloud appears in false-color, radio wavelengths as observed
by the Robert C. Byrd Green Bank Telescope in West Virginia. The
visible-light image of the background star field shows the cloud's
location in the direction of the summer constellation Aquila. The cloud
is 15 degrees across in angular size — the width of an outstretched
hand at arm's length. The apparent size of the full moon is added for
comparison.
Hubble Characterizes the High-Velocity Smith Cloud
The infalling Smith Cloud does not emit light at wavelengths that the
Hubble Space Telescope is sensitive to. However, Hubble's Cosmic Origins
Spectrograph can measure how the light from distant background objects
is affected as it passes through the cloud. These measurements yield
clues to the chemical composition of the cloud. By using these
intergalactic forensics, Hubble astronomers trace the cloud's origin to
the disk of our Milky Way. Combined ultraviolet and radio observations
correlate to the cloud's infall velocities, providing solid evidence
that the spectral features link to the cloud's dynamics.Illustration Credit:NASA,ESA, and A. Feild (STScI) - Science Credit:NASA,ESA, and A. Fox (STScI)
Hubble Space Telescope astronomers are finding that the old adage
"what goes up must come down" even applies to an immense cloud of
hydrogen gas outside our Milky Way galaxy. The invisible cloud is
plummeting toward our galaxy at nearly 700,000 miles per hour.
Though hundreds of enormous, high-velocity gas clouds whiz around the
outskirts of our galaxy, this so-called "Smith Cloud" is unique
because its trajectory is well known. New Hubble observations suggest
it was launched from the outer regions of the galactic disk, around 70
million years ago. The cloud was discovered in the early 1960s by
doctoral astronomy student Gail Smith, who detected the radio waves
emitted by its hydrogen.
The cloud is on a return collision course and is expected to plow
into the Milky Way's disk in about 30 million years. When it does,
astronomers believe it will ignite a spectacular burst of star
formation, perhaps providing enough gas to make 2 million suns.
"The cloud is an example of how the galaxy is changing with time,"
explained team leader Andrew Fox of the Space Telescope Science
Institute in Baltimore, Maryland. "It's telling us that the Milky Way
is a bubbling, very active place where gas can be thrown out of one
part of the disk and then return back down into another."
"Our galaxy is recycling its gas through clouds, the Smith Cloud
being one example, and will form stars in different places than before.
Hubble's measurements of the Smith Cloud are helping us to visualize
how active the disks of galaxies are," Fox said.
Astronomers have measured this comet-shaped region of gas to be
11,000 light-years long and 2,500 light-years across. If the cloud
could be seen in visible light, it would span the sky with an apparent
diameter 30 times greater than the size of the full moon.
Astronomers long thought that the Smith Cloud might be a failed,
starless galaxy, or gas falling into the Milky Way from intergalactic
space. If either of these scenarios proved true, the cloud would
contain mainly hydrogen and helium, not the heavier elements made by
stars. But if it came from within the galaxy, it would contain more of
the elements found within our sun.
The team used Hubble to measure the Smith Cloud's chemical
composition for the first time, to determine where it came from. They
observed the ultraviolet light from the bright cores of three active
galaxies that reside billions of light-years beyond the cloud. Using
Hubble's Cosmic Origins Spectrograph, they measured how this light
filters through the cloud.
In particular, they looked for sulfur in the cloud which can absorb
ultraviolet light. "By measuring sulfur, you can learn how enriched in
sulfur atoms the cloud is compared to the sun," Fox explained. Sulfur
is a good gauge of how many heavier elements reside in the cloud.
The astronomers found that the Smith Cloud is as rich in sulfur as
the Milky Way's outer disk, a region about 40,000 light-years from the
galaxy's center (about 15,000 light-years farther out than our sun and
solar system). This means that the Smith Cloud was enriched by material
from stars. This would not happen if it were pristine hydrogen from
outside the galaxy, or if it were the remnant of a failed galaxy devoid
of stars. Instead, the cloud appears to have been ejected from within
the Milky Way and is now boomeranging back.
Though this settles the mystery of the Smith Cloud's origin, it
raises new questions: How did the cloud get to where it is now? What
calamitous event could have catapulted it from the Milky Way's disk,
and how did it remain intact? Could it be a region of dark matter — an
invisible form of matter — that passed through the disk and captured
Milky Way gas? The answers may be found in future research.
The team's research appears in the January 1, 2016, issue of The Astrophysical Journal Letters.
Contact:
Ann Jenkins / Ray Villard Space Telescope Science Institute, Baltimore, Maryland 410-338-4488 / 410-338-4514 jenkins@stsci.edu/villard@stsci.edu
Andrew Fox Space Telescope Science Institute, Baltimore, Maryland 410-338-5083 afox@stsci.edu
Credit: ESA/Hubble & NASA Acknowledgement: Judy Schmidt
Despite its unassuming appearance, the edge-on spiral galaxy captured
in the left half of this NASA/ESA Hubble Space Telescope image is
actually quite remarkable.
Located about one billion light-years away in the constellation of Eridanus, this striking galaxy — known as LO95 0313-192
— has a spiral shape similar to that of the Milky Way. It has a large
central bulge, and arms speckled with brightly glowing gas mottled by
thick lanes of dark dust. Its companion, sitting pretty in the right of
the frame, is known rather unpoetically as [LOY2001] J031549.8-190623.
Jets,
outbursts of superheated gas moving at close to the speed of light,
have long been associated with the cores of giant elliptical galaxies,
and galaxies in the process of merging. However, in an unexpected
discovery, astronomers found LO95 0313-192 to have intense radio jets
spewing out from its centre! The galaxy appears to have two more regions
that are also strongly emitting in the radio part of the spectrum,
making it even rarer still.
The discovery of these giant jets in 2003 — not visible in this image, but indicated in this earlier Hubble composite
— has been followed by the unearthing of a further three spiral
galaxies containing radio-emitting jets in recent years. This growing
class of unusual spirals continues to raise significant questions about
how jets are produced within galaxies, and how they are thrown out into
the cosmos.
A Hubble image of the star Gliese 229 together with its brown dwarf companion, Gliese 229B. A new systematic radial velocity search for brown dwarf and stellar-mass companions to stars has discovered one new giant exoplanet and four new companion stars.
NASA/Hubble
The
search for exoplanets via the radial velocity technique has been
underway for nearly 30 years. The method searches for wobbles in a
star's motion caused by the presence of orbiting bodies. It has been has
been very successful, detecting hundreds of exoplanets, but has been
overtaken (at least in numbers of detections) by the transit method,
which looks for dips in the star's light. The velocity technique also
naturally spots orbiting bodies that are larger than planets, which can
be either stellar-mass companions or smaller companions that are not
quite large enough to become stars, called brown-dwarfs. These larger
companions have been largely ignored by surveys dedicated to finding
exoplanets, but they are valuable discoveries for astronomers trying to
study the smallest classes of stars which are very dim and otherwise
difficult to detect.
The indications so far are that there are fewer
brown dwarf stars than expected in the mass range from about 13 to 80
Jupiter-masses, a phenomenon known as the "brown dwarf desert" that is
unexplained. There is another important puzzle: About half of all nearby
stars are binary systems yet there are very few known exoplanets around
them - only about five percent of all known exoplanets. The dynamics
of forming a planetary system around (or within) a multiple-star system
are complex and important but poorly understood.
CfA astronomer John Johnson and six colleagues decided to study brown
dwarf stars directly with a dedicated, five-year survey that emphasized
large companions (stars or brown dwarfs) to mid-sized stars.
The
scientists selected forty-eight candidate stars for detailed
observations from an initial sample of 167 likely candidates based on
preliminary observations. They discovered one new giant exoplanet in
this set and four stellar-mass companions, one of which may in fact be a
brown dwarf. All the objects orbit their stars at distances less than a
few astronomical units (one AU is the average distance of the Earth
from the Sun). The new results include the orbital parameters of the
objects, and the paper considers the possibility of imaging directly
these multiple systems with a new generation of optical instruments. The
work also marks one of the first efforts to address the nature of the
"brown-dwarf desert" by searching for them systematically in order to
improve the statistics.
Reference (s): "The Pan-Pacific Planet Search III: five Companions orbiting giant
stars," R. A. Wittenmyer, R. P. Butler, L. Wang, C. Bergmann, G. S.
Salter, C. G. Tinney and J. A. Johnson,MNRAS 445, 1398, 2016.
Many galaxies are chock-full of dust,
while others have occasional dark streaks of opaque cosmic soot swirling
in amongst their gas and stars. However, the subject of this new image,
snapped with the OmegaCAM camera on ESO’s VLT Survey Telescope in
Chile, is unusual — the small galaxy, named IC 1613, is a veritable
clean freak! IC 1613 contains very little cosmic dust, allowing
astronomers to explore its contents with great clarity. This is not just
a matter of appearances; the galaxy’s cleanliness is vital to our
understanding of the Universe around us.
IC 1613 is a dwarf galaxy in the constellation of Cetus (The Sea Monster). This VST image [1] shows the galaxy’s unconventional beauty, all scattered stars and bright pink gas, in great detail.
German astronomer Max Wolf discovered IC 1613’s faint glow in 1906. In 1928, his compatriot Walter Baade used the more powerful 2.5-metre telescope at the Mount Wilson Observatory
in California to successfully make out its individual stars. From these
observations, astronomers figured out that the galaxy must be quite
close to the Milky Way, as it is only possible to resolve single
pinprick-like stars in the very nearest galaxies to us.
Astronomers have since confirmed that IC 1613 is indeed a member of the Local Group,
a collection of more than 50 galaxies that includes our home galaxy,
the Milky Way. IC 1613 itself lies just over 2.3 million light-years
away from us. It is relatively well-studied due to its proximity;
astronomers have found it to be an irregular dwarf that lacks many of
the features, such as a starry disc, found in some other diminutive
galaxies.
However, what IC 1613 lacks in form, it makes up for in tidiness. We
know IC 1613’s distance to a remarkably high precision, partly due to
the unusually low levels of dust lying both within the galaxy and along
the line of sight from the Milky Way — something that enables much
clearer observations [2].
The second reason we know the distance to IC 1613 so precisely is that the galaxy hosts a number of notable stars of two types: Cepheid variables and RR Lyrae variables[3]. Both types of star rhythmically pulsate, growing characteristically bigger and brighter at fixed intervals (eso1311).
As we know from our daily lives on Earth, shining objects such as
light bulbs or candle flames appear dimmer the further they are away
from us. Astronomers can use this simple piece of logic to figure out
exactly how far away things are in the Universe— so long as they know
how bright they really are, referred to as their intrinsic brightness.
Cepheid and RR Lyrae variables have the special property that their
period of brightening and dimming is linked directly to their intrinsic
brightness. So, by measuring how quickly they fluctuate astronomers can
work out their intrinsic brightness. They can then compare these values
to their apparent measured brightness and work out how far away they
must be to appear as dim as they do.
Stars of known intrinsic brightness can act like standard candles,
as astronomers say, much like how a candle with a specific brightness
would act as a good gauge of distance intervals based on the observed
brightness of its flame’s flicker.
Using standard candles — such as the variable stars within IC 1613 and the less-common Type Iasupernova explosions, which can seen across far greater cosmic distances — astronomers have pieced together a cosmic distance ladder, reaching deeper and deeper into space.
Decades ago, IC 1613 helped astronomers work out how to utilise
variable stars to chart the Universe’s grand expanse. Not bad for a
little, shapeless galaxy.
Notes
[1] OmegaCAM is a 32-CCD, 256-million-pixel camera mounted on the
2.6-metre VLT Survey Telescope at Paranal Observatory in Chile.Click hereto view more images taken by OmegaCAM.
[2] Cosmic dust is made of various
heavier elements, such as carbon and iron, as well as larger, grainier
molecules. Not only does dust block out light, making dust-shrouded
objects harder to see, it also preferentially scatters bluer light. As a
result, cosmic dust makes objects appear redder when seen through our
telescopes than they are in reality. Astronomers can factor out thisreddeningwhen studying objects. Still, the less reddening, the more precise an observation is likely to be.
[3] Other than the twoMagellanic Clouds, IC 1613 is the only irregular dwarf galaxy in the Local Group in which RR Lyrae type variable stars have been identified.
More Information
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”.
The space mission RadioAstron (Russian Space Agency) has observed, along with fifteen other radio telescopes spread across the globe, the environment of the black hole at the core of the active galaxy BL Lacertae
Since 1974, observations with very long baseline interferometry (VLBI)
have combined the signals from a cosmic object received at different
radio telescopes spread around the globe to synthetize an antenna with
the equivalent size of the largest separation between them. This has
provided unprecedented sharpness of the images, with over 1000 times
better resolution than the Hubble Space Telescope can achieve in visible
light. Now, an international collaboration has broken all records by
combining fifteen radio telescopes on Earth and the radio dish of the
RadioAstron mission (Russian Space Agency), in orbit around Earth. The
work, lead by the Instituto de Astrofísica de Andalucía (IAA-CSIC),
provides new insights into the nature of active galaxies, where an
extremely massive black hole swallows surrounding matter while
simultaneously shooting out a pair of jets of high-energy particles and
magnetic fields at nearly light speed.
Observations of microwave light are essential for exploring these jets,
since high-energy electrons moving in magnetic fields are very
proficient at producing microwaves. But most active galaxies with bright
jets are billions of light years away from Earth, so their jets are
tiny on the sky. High resolution is essential for viewing the jets in
action to reveal phenomena like shock waves and turbulence that control
how much light is produced at any given time. “Combining for the first
time ground-based radio telescopes with the space radio telescope of the
RadioAstron mission, operating at its maximum resolution, has allowed
our team to imitate an antenna with a size of eight times the Earth’s
diameter, corresponding to about twenty microarcseconds”, said José L.
Gómez, the team leader at the Instituto de Astrofísica de Andalucía
(IAA-CSIC).
Seen from Earth, twenty microarcseconds corresponds to the size of a
two euro coin on the Moon; this high resolution probes with
unprecedented detail the central regions of BL Lacertae, an active
galactic nucleus located nine hundred million light-years from Earth,
powered by a supermassive black hole two hundred million times more
massive than our Sun.
Artist concept showing how long base interferometry works.
Credit: MPIfR/A. Lobanov.
Extreme Sources
Active galactic nuclei (AGN) are the most energetic objects in the Universe, harboring a giant black hole at the center. Accretion of material toward the black hole leads to the formation of an accretion disk that tightly orbits the black hole, plus a pair of jets of particles shooting out of the nucleus in opposite directions at speeds nearly equal to that of light. “It is thought that jets originate from material drawn toward the black hole, but how the jets are collimated and accelerated is still largely unknown,” said Gómez. “We know, however, that the magnetic field should play an important role”.
Current models suggest that, due to the rotation of the black hole and accretion disk, the magnetic field lines are “twisted” into a spiral structure. Such a coiled field confines the jet to a narrow beam and accelerates its motion. This model is confirmed by the BL Lacertae observations, which reveal the existence of a large-scale spiral magnetic field in one of the jets.
Artist concept of an active galactic nuclei
Credit: Wolfgang Steffen, UNAM.
The exceptional resolution obtained with RadioAstron also reveals an
unusually intensity of light at the upstream end of BL Lacertae’s jet
not observed before in other AGN. This is making astronomers wonder
whether their established ideas on how the jets produce microwave light
is correct.
“Our current understanding of how the emission is generated in AGN
establishes a clear limit on the intensity of microwaves that their
cores can produce over long time spans. The extreme intensity observed
in BL Lacertae exceeds that limit, requiring either velocities in the
jet even closer to the speed of light than thought before or a revision
of our theoretical models”, concludes Jose L. Gómez (IAA-CSIC).
Reference:
J. L. Gómez et al. "Probing the innermost regions of AGN jets and their magnetic fields with Radioastron. I. Imaging BL Lacertae at 21 microarcsecond resolution". The Astrophysical Journal, 817, 96 (2016). DOI: 10.3847/0004-637X/817/2/96
The connection between internal structure of galaxy clusters and distribution of galaxy clusters
Credit: Sloan Digital Sky Survey, Kavli IPMU
An international team of researchers has found for the first time
that the connection between a galaxy cluster and surrounding dark matter
is not characterized solely by the mass of clusters, but also by their
formation history.
Galaxy clusters are the biggest celestial objects in the sky
consisting of thousands of galaxies. They form from nonuniformity in the
matter distribution established by cosmic inflation in the beginning of
the Universe. Their growth is a constant fight between the gathering of
dark matter by gravity and the accelerated expansion of the universe
due to dark energy. By studying galaxy clusters, researchers can learn
more about these biggest and most mysterious building blocks of the
Universe.
Led by Hironao Miyatake, (formerly JSPS fellow, currently at NASA’s
Jet Propulsion Laboratory), Surhud More and Masahiro Takada of the Kavli
Institute for the Physics and Mathematics (Kavli IPMU), the research
team challenged the conventional idea that the connection between galaxy
clusters and the surrounding dark matter environment is solely
characterized by their mass. Based on the nature of the non-uniform
matter distribution established by cosmic inflation, it was
theoretically predicted that other factors should affect the connection.
However, no one had succeeded in seeing it in the real Universe until
now.
The team divided almost 9000 galaxy clusters from the Sloan Digital
Sky Survey DR8 galaxy catalog into two samples based on the spatial
distribution of galaxies inside each cluster. By using gravitational
lensing they confirmed the two samples have similar masses, but they
found that the distribution of clusters was different. Galaxy clusters
in which member galaxies bunched up towards the center were less clumpy
than clusters in which member galaxies were more spread out. The
difference in distribution is a result of the different dark matter
environment in which they form.
Researchers say their findings show that the connection between a
galaxy cluster and surrounding dark matter is not characterized solely
by the mass of clusters, but also by their formation history.
The results from this study would need to be taken into account in
future large scale studies of the universe, and research looking into
the nature of dark matter or dark energy, neutrinos, and the early
universe.
The study will be published on January 25 in Physical Review Letters, and has been selected as an Editor’s Suggestion.
(from left) Authors Hironao Miyatake, Surhud More and Masahiro Takada Credit: Kavli IPMU
Comment from Surhud More
“The signal we measure is puzzlingly large compared to naive
theoretical estimates. The sheer number of tests for systematics that we
had to perform to convince ourselves that the signal is real, was the
most difficult part of this research.”
Comment from Masahiro Takada
“This is truly exciting finding! We can use the upcoming Subaru Hyper
Suprime-Cam (HSC) data to further check and advance our understanding
of the assembly history of galaxy clusters.”
Comment from Hironao Miyatake
“I am thrilled that we have finally found clear evidence of the
connection between the internal structure of clusters and surrounding
dark matter environment. We checked lots of things to make sure this
result, and finally concluded this is real! I am also excited that our
findings will give insights on many aspects of the universe, such as
large scale structure, dark matter and dark energy, and inflation
physics. It is just starting. We hope we can get more exciting results
from the upcoming HSC data.”
Comment from David Spergel
“Cosmologist have long held a very simple theory: " the properties of
a cluster is determined solely by its mass”. These results show that
the situation is much more complex: the clusters environment also plays
an important role. Astronomers have been trying to detect evidence for
this more complex picture for many years: this is the first definitive
detection.”
Paper Details
Journal: Physical Review Letters, vol 116 (2016)
Title: Evidence of halo assembly bias in massive clusters
Authors: Hironao Miyatake (1, 2, 3), Surhud More (2), Masahiro Takada
(2), David N. Spergel (1, 2), Rachel Mandelbaum (4), Eli S. Rykoff (5,
6), Eduardo Rozo (7)
Author affiliations:
1 Department of Astrophysical Sciences, Princeton University, Peyton Hall, Princeton, NJ 08544, USA
2 Kavli Institute for the Physics and Mathematics of the Universe (WPI), UTIAS, The University of Tokyo, Chiba, 277-8583, Japan
3 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
4 McWilliams Center for Cosmology, Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA
5 Kavli Institute for Particle Astrophysics & Cosmology, P. O. Box 2450, Stanford University, Stanford, CA 94305, USA
6 SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA
7 Department of Physics, University of Arizona, 1118 E 4th St, Tucson, AZ 85721, USA
DOI: 10.1103/PhysRevLett.116.041301
Paper Abstract (Physical Review Letters) - link to be added once available
Motoko Kakubayashi Press Officer Kavli Institute for the Physics and Mathematics of the Universe, The University of Tokyo Institutes for Advanced Study, The University of Tokyo TEL: +81-04-7136-5980 E-mail:press@ipmu.jp
Research contacts：
Surhud More Project Assistant Professor The Kavli Institute for the Physics and Mathematics of the Universe TEL (office): +81-04-7136-6566 E-mail:surhud.moreAipmu.jp
Invisible structures shaped like noodles, lasagne sheets or hazelnuts could be floating around in our Galaxy radically challenging our understanding of gas conditions in the Milky Way.
CSIRO astronomer and first author of a paper released in Science Dr Keith Bannister said the structures appear to be ‘lumps’ in the thin gas that lies between the stars in our Galaxy.
“They could radically change ideas about this interstellar gas, which
is the Galaxy’s star recycling depot, housing material from old stars
that will be refashioned into new ones,” Dr Bannister said.
Dr Bannister and his colleagues described breakthrough observations
of one of these ‘lumps’ that have allowed them to make the first
estimate of its shape.
The observations were made possible by an innovative new technique the scientists employed using CSIRO’s Compact Array telescope in eastern Australia.
Astronomers got the first hints of the mysterious objects 30 years
ago when they saw radio waves from a bright, distant galaxy called a
quasar varying wildly in strength.
They figured out this behaviour was the work of our Galaxy’s
invisible ‘atmosphere’, a thin gas of electrically charged particles
which fills the space between the stars.
“Lumps in this gas work like lenses, focusing and defocusing the
radio waves, making them appear to strengthen and weaken over a period
of days, weeks or months,” Dr Bannister said.
These episodes were so hard to find that researchers had given up looking for them.
But Dr Bannister and his colleagues realised they could do it with CSIRO’s Compact Array.
Pointing the telescope at a quasar called PKS 1939–315 in the
constellation of Sagittarius, they saw a lensing event that went on for a
year.
Astronomers think the lenses are about the size of the Earth’s orbit
around the Sun and lie approximately 3000 light-years away – 1000 times
further than the nearest star, Proxima Centauri.
Until now they knew nothing about their shape, however, the team has
shown this lens could not be a solid lump or shaped like a bent sheet.
“We could be looking at a flat sheet, edge on,” CSIRO team member Dr Cormac Reynolds said.
“Or we might be looking down the barrel of a hollow cylinder like a noodle, or at a spherical shell like a hazelnut.”
Getting more observations will “definitely sort out the geometry,” he said.
While the lensing event went on, Dr Bannister’s team observed it with other radio and optical telescopes.
The optical light from the quasar didn’t vary while the radio lensing
was taking place. This is important, Dr Bannister said, because it
means earlier optical surveys that looked for dark lumps in space
couldn’t have found the one his team has detected.
So what can these lenses be? One suggestion is cold clouds of gas
that stay pulled together by the force of their own gravity. That model,
worked through in detail, implies the clouds must make up a substantial
fraction of the mass of our Galaxy.
Nobody knows how the invisible lenses could form. “But these
structures are real, and our observations are a big step forward in
determining their size and shape,” Dr Bannister said.
Credit: ESA/Hubble & NASA Acknowledgement: Judy Schmidt (Geckzilla)
Most galaxies possess a majestic spiral or elliptical structure.
About a quarter of galaxies, though, defy such conventional, rounded
aesthetics, instead sporting a messy, indefinable shape. Known as
irregular galaxies, this group includes NGC 5408, the galaxy that has
been snapped here by the NASA/ESA Hubble Space Telescope.
English polymath John Herschel recorded the existence of NGC 5408 in June 1834. Astronomers had long mistaken NGC 5408 for a planetary nebula,
an expelled cloud of material from an aging star. Instead, bucking
labels, NGC 5408 turned out to be an entire galaxy, located about 16
million light-years from Earth in the constellation of Centaurus (The Centaur).
In
yet another sign of NGC 5408 breaking convention, the galaxy is
associated with an object known as an ultraluminous X-ray source, dubbed
NGC 5408 X-1, one of the best studied of its class. These rare objects
beam out prodigious amounts of energetic X-rays. Astrophysicists believe
these sources to be strong candidates for intermediate-mass black holes. This hypothetical type of black hole has significantly less mass than the supermassive black holes found in galactic centres, which can have billions of times the mass of the Sun, but have a good deal more mass than the black holes formed when giant stars collapse.
A version of this image was entered into the Hubble's Hidden Treasures image processing competition by contestant Judy Schmidt.
Resembling an opulent diamond tapestry, this image
from NASA’s Hubble Space Telescope shows a glittering star cluster that
contains a collection of some of the brightest stars seen in our Milky
Way galaxy. Credits: NASA, ESA, and J. Maíz Apellániz
(Institute of Astrophysics of Andalusia, Spain), Acknowledgment: N.
Smith (University of Arizona)
Resembling an opulent diamond tapestry, this image from NASA’s Hubble
Space Telescope shows a glittering star cluster that contains a
collection of some of the brightest stars seen in our Milky Way galaxy.
Called Trumpler 14, it is located 8,000 light-years away in the Carina
Nebula, a huge star-formation region. Because the cluster is only
500,000 years old, it has one of the highest concentrations of massive,
luminous stars in the entire Milky Way. The small, dark knot left of
center is a nodule of gas laced with dust, and seen in silhouette.
These blue-white stars are burning their hydrogen fuel so ferociously
they will explode as supernovae in just a few million years. The
combination of outflowing stellar “winds” and, ultimately, supernova
blast waves will carve out cavities in nearby clouds of gas and dust.
These fireworks will kick-start the beginning of a new generation of
stars in an ongoing cycle of star birth and death.
This composite image of Trumpler 14 was made with data taken in
2005-2006 with Hubble's Advanced Camera for Surveys. Blue, visible and
infrared broadband filters combine with filters that isolate hydrogen
and nitrogen emission from the glowing gas surrounding the open cluster.
For images and more information about Hubble, visit:
A new theory developed by the Brookhaven National Laboratory suggests that, after the Big Bang, there was a secondary inflation, able to explain the quantity of dark matter present in the Universe
A dense, boiling hot primordial nucleus, extremely rapid expansion and a progressive and increasingly slow cooling period. These are the main stages that, according to standard cosmological theory, mark our Universe's very first “action” after the Big Bang: inflation.
The inflation theory is in fact the theory stating that the Universe inflated exponentially a few moments after its birth (to be precise, over an interval of time equal to 10 to the power of minus 35 seconds) and is still expanding today. Most scientists agree with this theory, because it can explain a great many known physical phenomena. Nevertheless, it does not explain all of them: for example, it does not explain one of the greatest mysteries of modern cosmology - that of the quantity of dark matter present in the Universe.
For this reason, a group of physicists from the American Brookhaven National Laboratory has speculated that there could be a passage missing from standard cosmological theory. An intermediate stage, something that happened after the first, great expansion of the Universe: a smaller and shorter expansion that researchers have called “secondary inflation”.
This theory, which will be published on 18 January in the Physical Review Letters magazine, could offer a more precise explanation of what Hooman Davoudiasl, the first author of the study, calls “dilution of dark matter”.
In fact, this phenomenon cannot be explained by the many theories branching from the standard cosmological model, which envisage more dark matter than can be demonstrated by empirical observations.
This is where the idea of “adding” another cosmic inflation came from - an inflation that took place between the great expansion and the beginning of the Universe's cooling period. It is believed that this second inflation took place when temperatures were still very high: this is a fundamental feature, because it is precisely the heat that would have made it possible for the particles of dark matter to collide with each other and annihilate one another, thus creating particles like electrons and quarks. Above all, this makes sense with regard to the quantity of dark matter calculated today.
The secondary inflation suggested by the Brookhaven National Laboratory was much gentler than the primary one, but crucial in taking the primordial particles to conditions of temperature, volume and density consistent with what we can observe almost 14 billion years later.
Therefore, this is a potentially simple and coherent theory. Nevertheless, we are still a long way from moving from theory to practice, as Hooman Davoudiasl, the father of the inflation theory himself, asserts: the next step will be to try to identify particle interactions according to the new theory through experiments within the scope of the LHC. Thus, empirical proof of this double inflation at the origin of our Universe can be found.
“The best explanations in physics are the simple ones – explains the president of the Italian Space Agency (ASI), Roberto Battiston - but in the Universe's case the simplest one may not be the best! In order to make sense of the quantity of dark matter observed in our universe, which is approximately 6 times more abundant than normal matter, according to this new theory, the hyper-fast phase of expansion that accompanied the big-bang (called inflation, editor’s note) had a sort of hiccup and repeated itself a second time, in quick succession to the first. There was much less intensity in this phase, but it was sufficient to dilute the dark matter produced in the first phase and reach a figure compatible with that measured.”
Battiston points out that “This is a theory and, as such, requires verification. For this reason - he concludes - a new generation of instruments will be needed, able to observe the effect of what happened during the initial moments, such as, for example, the impression made in the radiation of the Big Bang, due to the effect of the gravitational waves produced during the initial phases of the great explosion”.
This
artistic rendering shows the distant view from Planet Nine back towards
the sun. The planet is thought to be gaseous, similar to Uranus and
Neptune. Hypothetical lightning lights up the night side. Credit: Caltech/R. Hurt (IPAC)
The
six most distant known objects in the solar system with orbits
exclusively beyond Neptune (magenta) all mysteriously line up in a
single direction. Also, when viewed in three dimensions, they tilt
nearly identically away from the plane of the solar system. Batygin and
Brown show that a planet with 10 times the mass of the earth in a
distant eccentric orbit anti-aligned with the other six objects (orange)
is required to maintain this configuration.Credit: Caltech/R. Hurt (IPAC); [Diagram created using WorldWide Telescope.]
Caltech's
Konstantin Batygin, an assistant professor of planetary science, and
Mike Brown, the Richard and Barbara Rosenberg Professor of Planetary
Astronomy, discuss new research that provides evidence of a giant planet
tracing a bizarre, highly elongated orbit in the outer solar system.Credit: Caltech AMT
A predicted
consequence of Planet Nine is that a second set of confined objects
should also exist. These objects are forced into positions at right
angles to Planet Nine and into orbits that are perpendicular to the
plane of the solar system. Five known objects (blue) fit this prediction
precisely. Credit: Caltech/R. Hurt (IPAC) [Diagram was created using WorldWide Telescope.]
Caltech
professor Mike Brown and assistant professor Konstanin Batygin have
been working together to investigate distant objects in our solar system
for more than a year and a half. The two bring very different
perspectives to the work: Brown is an observer, used to looking at the
sky to try and anchor everything in the reality of what can be seen;
Batygin is a theorist who considers how things might work from a physics
standpoint. Credit: Credit: Lance Hayashida/Caltech
Caltech researchers have found evidence of a giant planet tracing a
bizarre, highly elongated orbit in the outer solar system. The object,
which the researchers have nicknamed Planet Nine, has a mass about 10
times that of Earth and orbits about 20 times farther from the sun on
average than does Neptune (which orbits the sun at an average distance
of 2.8 billion miles). In fact, it would take this new planet between
10,000 and 20,000 years to make just one full orbit around the sun.
The researchers, Konstantin Batygin and Mike Brown,
discovered the planet's existence through mathematical modeling and
computer simulations but have not yet observed the object directly.
"This
would be a real ninth planet," says Brown, the Richard and Barbara
Rosenberg Professor of Planetary Astronomy. "There have only been two
true planets discovered since ancient times, and this would be a third.
It's a pretty substantial chunk of our solar system that's still out
there to be found, which is pretty exciting."
Brown notes that the
putative ninth planet—at 5,000 times the mass of Pluto—is sufficiently
large that there should be no debate about whether it is a true planet.
Unlike the class of smaller objects now known as dwarf planets, Planet
Nine gravitationally dominates its neighborhood of the solar system. In
fact, it dominates a region larger than any of the other known planets—a
fact that Brown says makes it "the most planet-y of the planets in the
whole solar system."
Batygin and Brown describe their work in the current issue of the Astronomical Journal
and show how Planet Nine helps explain a number of mysterious features
of the field of icy objects and debris beyond Neptune known as the
Kuiper Belt.
"Although we were initially quite skeptical that this
planet could exist, as we continued to investigate its orbit and what
it would mean for the outer solar system, we become increasingly
convinced that it is out there," says Batygin, an assistant professor of
planetary science. "For the first time in over 150 years, there is
solid evidence that the solar system's planetary census is incomplete."
The
road to the theoretical discovery was not straightforward. In 2014, a
former postdoc of Brown's, Chad Trujillo, and his colleague Scott
Shepherd published a paper noting that 13 of the most distant objects in
the Kuiper Belt are similar with respect to an obscure orbital feature.
To explain that similarity, they suggested the possible presence of a
small planet. Brown thought the planet solution was unlikely, but his
interest was piqued.
He took the problem down the hall to Batygin,
and the two started what became a year-and-a-half-long collaboration to
investigate the distant objects. As an observer and a theorist,
respectively, the researchers approached the work from very different
perspectives—Brown as someone who looks at the sky and tries to anchor
everything in the context of what can be seen, and Batygin as someone
who puts himself within the context of dynamics, considering how things
might work from a physics standpoint. Those differences allowed the
researchers to challenge each other's ideas and to consider new
possibilities. "I would bring in some of these observational aspects; he
would come back with arguments from theory, and we would push each
other. I don't think the discovery would have happened without that back
and forth," says Brown. " It was perhaps the most fun year of working
on a problem in the solar system that I've ever had."
Fairly
quickly Batygin and Brown realized that the six most distant objects
from Trujillo and Shepherd's original collection all follow elliptical
orbits that point in the same direction in physical space. That is
particularly surprising because the outermost points of their orbits
move around the solar system, and they travel at different rates.
"It's
almost like having six hands on a clock all moving at different rates,
and when you happen to look up, they're all in exactly the same place,"
says Brown. The odds of having that happen are something like 1 in 100,
he says. But on top of that, the orbits of the six objects are also all
tilted in the same way—pointing about 30 degrees downward in the same
direction relative to the plane of the eight known planets. The
probability of that happening is about 0.007 percent. "Basically it
shouldn't happen randomly," Brown says.
"So we thought something else
must be shaping these orbits."
The first possibility they
investigated was that perhaps there are enough distant Kuiper Belt
objects—some of which have not yet been discovered—to exert the gravity
needed to keep that subpopulation clustered together. The researchers
quickly ruled this out when it turned out that such a scenario would
require the Kuiper Belt to have about 100 times the mass it has today.
That
left them with the idea of a planet. Their first instinct was to run
simulations involving a planet in a distant orbit that encircled the
orbits of the six Kuiper Belt objects, acting like a giant lasso to
wrangle them into their alignment. Batygin says that almost works but
does not provide the observed eccentricities precisely. "Close, but no
cigar," he says.
Then, effectively by accident, Batygin and Brown
noticed that if they ran their simulations with a massive planet in an
anti-aligned orbit—an orbit in which the planet's closest approach to
the sun, or perihelion, is 180 degrees across from the perihelion of all
the other objects and known planets—the distant Kuiper Belt objects in
the simulation assumed the alignment that is actually observed.
"Your
natural response is 'This orbital geometry can't be right. This can't
be stable over the long term because, after all, this would cause the
planet and these objects to meet and eventually collide,'" says Batygin.
But through a mechanism known as mean-motion resonance, the
anti-aligned orbit of the ninth planet actually prevents the Kuiper Belt
objects from colliding with it and keeps them aligned. As orbiting
objects approach each other they exchange energy. So, for example, for
every four orbits Planet Nine makes, a distant Kuiper Belt object might
complete nine orbits. They never collide. Instead, like a parent
maintaining the arc of a child on a swing with periodic pushes, Planet
Nine nudges the orbits of distant Kuiper Belt objects such that their
configuration with relation to the planet is preserved.
"Still, I was very skeptical," says Batygin. "I had never seen anything like this in celestial mechanics."
But
little by little, as the researchers investigated additional features
and consequences of the model, they became persuaded. "A good theory
should not only explain things that you set out to explain. It should
hopefully explain things that you didn't set out to explain and make
predictions that are testable," says Batygin.
And indeed Planet
Nine's existence helps explain more than just the alignment of the
distant Kuiper Belt objects. It also provides an explanation for the
mysterious orbits that two of them trace. The first of those objects,
dubbed Sedna, was discovered by Brown in 2003. Unlike standard-variety
Kuiper Belt objects, which get gravitationally "kicked out" by Neptune
and then return back to it, Sedna never gets very close to Neptune. A
second object like Sedna, known as 2012 VP113, was announced by Trujillo
and Shepherd in 2014. Batygin and Brown found that the presence of
Planet Nine in its proposed orbit naturally produces Sedna-like objects
by taking a standard Kuiper Belt object and slowly pulling it away into
an orbit less connected to Neptune.
But
the real kicker for the researchers was the fact that their simulations
also predicted that there would be objects in the Kuiper Belt on orbits
inclined perpendicularly to the plane of the planets. Batygin kept
finding evidence for these in his simulations and took them to Brown.
"Suddenly I realized there are objects like that," recalls Brown. In the
last three years, observers have identified four objects tracing orbits
roughly along one perpendicular line from Neptune and one object along
another. "We plotted up the positions of those objects and their orbits,
and they matched the simulations exactly," says Brown. "When we found
that, my jaw sort of hit the floor."
"When the simulation aligned
the distant Kuiper Belt objects and created objects like Sedna, we
thought this is kind of awesome—you kill two birds with one stone," says
Batygin. "But with the existence of the planet also explaining these
perpendicular orbits, not only do you kill two birds, you also take down
a bird that you didn't realize was sitting in a nearby tree."
Where
did Planet Nine come from and how did it end up in the outer solar
system? Scientists have long believed that the early solar system began
with four planetary cores that went on to grab all of the gas around
them, forming the four gas planets—Jupiter, Saturn, Uranus, and Neptune.
Over time, collisions and ejections shaped them and moved them out to
their present locations. "But there is no reason that there could not
have been five cores, rather than four," says Brown. Planet Nine could
represent that fifth core, and if it got too close to Jupiter or Saturn,
it could have been ejected into its distant, eccentric orbit.
Batygin
and Brown continue to refine their simulations and learn more about the
planet's orbit and its influence on the distant solar system.
Meanwhile, Brown and other colleagues have begun searching the skies for
Planet Nine. Only the planet's rough orbit is known, not the precise
location of the planet on that elliptical path. If the planet happens to
be close to its perihelion, Brown says, astronomers should be able to
spot it in images captured by previous surveys. If it is in the most
distant part of its orbit, the world's largest telescopes—such as the
twin 10-meter telescopes at the W. M. Keck Observatory and the Subaru
Telescope, all on Mauna Kea in Hawaii—will be needed to see it. If,
however, Planet Nine is now located anywhere in between, many telescopes
have a shot at finding it.
"I would love to find it," says Brown.
"But I'd also be perfectly happy if someone else found it. That is why
we're publishing this paper. We hope that other people are going to get
inspired and start searching."
In terms of understanding more
about the solar system's context in the rest of the universe, Batygin
says that in a couple of ways, this ninth planet that seems like such an
oddball to us would actually make our solar system more similar to the
other planetary systems that astronomers are finding around other stars.
First, most of the planets around other sunlike stars have no single
orbital range—that is, some orbit extremely close to their host stars
while others follow exceptionally distant orbits. Second, the most
common planets around other stars range between 1 and 10 Earth-masses.
"One
of the most startling discoveries about other planetary systems has
been that the most common type of planet out there has a mass between
that of Earth and that of Neptune," says Batygin. "Until now, we've
thought that the solar system was lacking in this most common type of
planet. Maybe we're more normal after all."
Brown, well known for
the significant role he played in the demotion of Pluto from a planet to
a dwarf planet adds, "All those people who are mad that Pluto is no
longer a planet can be thrilled to know that there is a real planet out
there still to be found," he says. "Now we can go and find this planet
and make the solar system have nine planets once again."
The paper is titled "Evidence for a Distant Giant Planet in the Solar System."
Artists
impression of the power of background galaxies to measure the size of
gas clouds as compared to the conventional method of using quasars. The
plane to the far right shows the background galaxy and overlaid in the
center of the galaxy is a bright white light representing a quasar. The
DLA gas cloud is shown at the center of the plane in between the galaxy
and Earth. The blue/white narrow beam indicates the small area of the
DLA gas cloud probed by quasars, the wider red cone of light indicates
the large area of the DLA probed by galaxies, which is a 100
million-fold increase in area.
Credit: Adrian Malec (Swinburne University) and Marie Martig (Max Planck Institute for Astronomy, Heidelberg)
MAUNAKEA, Hawaii – Using the world’s largest
telescopes, researchers discovered ancient cold gas clouds larger than
galaxies in the early Universe. The discovery was announced today at a
press conference at the 227th meeting of the American Astronomical
Society in Orlando, Florida.
The discovery, led by Associate
Professor Jeff Cooke, Swinburne University of Technology, and Associate
Professor John O’Meara, St. Michael’s College, has helped solve a
decades-old puzzle on the nature of gas clouds, known as damped Lyman
alpha systems, or DLAs.
Cooke and O’Meara realized that finding
DLA gas clouds in the line of sight to background galaxies would enable
measurements of their size by determining how much of the galaxy they
cover.
“Our new method first identifies galaxies that are more
likely to have intervening DLA gas clouds and then searches for them
using long, deep exposures on the powerful Keck Observatory 10m
telescopes on Maunakea and deep data from the VLT 8m telescopes in
Chile,” Cooke said. “The technique is timely as the next generation of
giant 30m telescopes will be online in several years and are ideal to
take advantage of this method to routinely gather large numbers of DLAs
for study.”
DLA clouds contain most of the cool gas in the
Universe and are predicted to contain enough gas to form most of the
stars we see in galaxies around us today, like the Milky Way. However,
this prediction has yet to be confirmed.
DLAs currently have
little ongoing star formation, making them too dim to observe directly
from their emitted light alone. Instead, they are detected when they
happen to fall in the line of sight to a more distant bright object and
leave an unmistakeable absorption signature in the background object’s
light.
Previously, researchers used quasars as the background
objects to search for DLAs. Although quasars can be very bright, they
are rare and are comparatively small, only a fraction of a light year
across, whereas galaxies are quite common and provide a 100 million-fold
increase in area to probe DLAs.
“Using the galaxy technique,
DLAs can be studied in large numbers to provide a 3-D tomographic
picture of distribution of gas clouds in the early Universe and help
complete our understanding of how galaxies formed and evolved over
cosmic time,” O’Meara said.
The W. M. Keck Observatory operates
the largest, most scientifically productive telescopes on Earth. The
two, 10-meter optical/infrared telescopes near 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 spectrographs and world-leading laser guide star adaptive
optics systems.
Keck Observatory is a private 501(c) 3 non-profit
organization and a scientific partnership of the California Institute
of Technology, the University of California and NASA.
