First 'image' of a dark matter web that connects galaxies
Researchers at the University of Waterloo have been able to capture the first composite image of a dark matter bridge that connects galaxies together. The scientists publish their work in a new paper in Monthly Notices of the Royal Astronomical Society.
The composite image, which combines a number of individual images, confirms predictions that galaxies across the universe are tied together through a cosmic web connected by dark matter that has until now remained unobservable.
A cosmic snapshot from May 19, this colorful telescopic field of view spans about 1 degree or 2 full moons on the sky. Spiky in appearance, foreground Milky Way stars are scattered toward the royal constellation Cepheus while stars of open cluster NGC 6939 gather about 5 thousand light-years in the distance near the top of the frame. Face-on spiral galaxy NGC 6946 is toward the lower left nearly 22 million light-years away. The helpful red lines identify recently discovered supernova SN 2017eaw, the death explosion of a massive star nestled in the galaxy’s bluish spiral arms. In fact in the last 100 years, 10 supernovae have been discovered in NGC 6946. By comparison, the average rate of supernovae in our Milky Way is about 1 every 100 years or so. Of course, NGC 6946 is also known as The Fireworks Galaxy.
Pictures of celestial phenomena like the eclipse can electrify the imagination, generate wonder, and spark that most human desire: to go out and see for yourself. For our era, the spectacular images from the Hubble Space Telescope, the wondrous details of Saturn from Cassini, or the realistic images from the Mars rover make us want to go further into the cosmos. For Americans in the post-Civil War years, the most iconic images of the cosmos were largely the work of one man: Étienne Leopold Trouvelot (1827-1895), an artist and amateur astronomer who produced incredible images of the heavens.
The Easterbunny Comes to NGC 4725 : At first called Easterbunny by its discovery team, officially named Makemake is the second brightest dwarf planet of the Kuiper belt. The icy world appears twice in this astronomical image, based on data taken on June 29 and 30 of the bright spiral galaxy NGC 4725. Makemake is marked by short red lines, its position shifting across a homemade telescopes field-of-view over two nights along a distant orbit. On those dates nearly coincident with the line-of-sight to the spiral galaxy in the constellation Coma Berenices, Makemake was about 52.5 astronomical units or 7.3 light-hours away. NGC 4725 is over 100,000 light-years across and 41 million light-years distant. Makemake is now known to have at least one moon. NGC 4725 is a famous one-armed spiral galaxy. via NASA
Resembling festive lights on a holiday wreath, this NASA/ESA Hubble Space Telescope image of the nearby spiral galaxy M74 is an iconic reminder of the impending season. Bright knots of glowing gas light up the spiral arms, indicating a rich environment of star formation.
Messier 74, also called NGC 628, is a stunning example of a “grand-design” spiral galaxy that is viewed by Earth observers nearly face-on. Its perfectly symmetrical spiral arms emanate from the central nucleus and are dotted with clusters of young blue stars and glowing pink regions of ionized hydrogen (hydrogen atoms that have lost their electrons). These regions of star formation show an excess of light at ultraviolet wavelengths. Tracing along the spiral arms are winding dust lanes that also begin very near the galaxy’s nucleus and follow along the length of the spiral arms.
M74 is located roughly 32 million light-years away in the direction of the constellation Pisces, the Fish. It is the dominant member of a small group of about half a dozen galaxies, the M74 galaxy group. In its entirety, it is estimated that M74 is home to about 100 billion stars, making it slightly smaller than our Milky Way.
The spiral galaxy was first discovered by the French astronomer Pierre Méchain in 1780. Weeks later it was added to Charles Messier’s famous catalog of deep-sky objects.
This Hubble image of M74 is a composite of Advanced Camera for Surveys data taken in 2003 and 2005. The filters used to create the color image isolate light from blue, visible, and infrared portions of the spectrum, as well as emission from ionized hydrogen (known as HII regions).
A small segment of this image used data from the Canada-France-Hawaii Telescope and the Gemini Observatory to fill in a region that Hubble did not image.
For additional information, contact:
Space Telescope Science Institute, Baltimore, Md.
Space Telescope Science Institute, Baltimore, Md.
Lars Lindberg Christensen
ESA/Hubble, Garching, Germany
Object Names: M74, NGC 628
Image Type: Astronomical
Credit: NASA, ESA, and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration
Acknowledgment: R. Chandar (University of Toledo) and J. Miller (University of Michigan)
NGC 6670 is a gorgeous pair of overlapping edge-on galaxies resembling a leaping dolphin. Scientists believe that NGC 6670 has already experienced at least one close encounter and is now in the early stages of a second. The nuclei of the two galaxies are approximately 50,000 light-years apart. NGC 6670 glows in the infrared with more than a hundred billion times the luminosity of our Sun and is thought to be entering a starburst phase. The pair is located some 400 million light-years away from Earth.
This image is part of a large collection of 59 images of merging galaxies taken by the Hubble Space Telescope and released on the occasion of its 18th anniversary on 24th April 2008.
Object Names: NGC 6670, NGC 6670A/B, VII Zw 812
Image Type: Astronomical
Credit: NASA, ESA, the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration, and A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University)
HEART OF AN EXPLODED STAR OBSERVED IN 3-D:
SUPERNOVA FORGES BILLOWING, TANGLED KNOTS OF NEW MOLECULES
** Summary: Deep inside the remains of an exploded star lies a twisted knot of newly minted molecules and dust. Using ALMA, astronomers mapped the location of these new molecules to create a high-resolution 3-D image of this “dust factory,” providing new insights into the relationship between a young supernova remnant and its galaxy. **
Supernovas – the violent endings of the brief yet brilliant lives of massive stars – are among the most cataclysmic events in the cosmos. Though supernovas mark the death of stars, they also trigger the birth of new elements and the formation of new molecules.
In February of 1987, astronomers witnessed one of these events unfold inside the Large Magellanic Cloud, a tiny dwarf galaxy located approximately 160,000 light-years from Earth.
Over the next 30 years, observations of the remnant of that explosion revealed never-before-seen details about the death of stars and how atoms created in those stars – like carbon, oxygen, and nitrogen – spill out into space and combine to form new molecules and dust. These microscopic particles may eventually find their way into future generations of stars and planets.
Recently, astronomers used the Atacama Large Millimeter/submillimeter Array (ALMA) to probe the heart of this supernova, named SN 1987A. ALMA’s ability to see remarkably fine details allowed the researchers to produce an intricate 3-D rendering of newly formed molecules inside the supernova remnant. These results are published in the Astrophysical Journal Letters.
The researchers also discovered a variety of previously undetected molecules in the remnant. These results appear in the Monthly Notices of the Royal Astronomical Society.
“When this supernova exploded, now more than 30 years ago, astronomers knew much less about the way these events reshape interstellar space and how the hot, glowing debris from an exploded star eventually cools and produces new molecules,” said Rémy Indebetouw, an astronomer at the University of Virginia and the National Radio Astronomy Observatory (NRAO) in Charlottesville. “Thanks to ALMA, we can finally see cold ‘star dust’ as it forms, revealing important insights into the original star itself and the way supernovas create the basic building blocks of planets.”
Supernovas – Star Death to Dust Birth
Prior to ongoing investigations of SN 1987A, there was only so much astronomers could say about the impact of supernovas on their interstellar neighborhoods.
It was well understood that massive stars, those approximately 10 times the mass of our Sun or more, ended their lives in spectacular fashion.
When these stars run out of fuel, there is no longer enough heat and energy to fight back against the force of gravity. The outer reaches of the star, once held up by the power of fusion, then come crashing down on the core with tremendous force. The rebound of this collapse triggers a powerful explosion that blasts material into space.
As the endpoint of massive stars, scientists have learned that supernovas have far-reaching effects on their home galaxies. “The reason some galaxies have the appearance that they do today is in large part because of the supernovas that have occurred in them,” Indebetouw said. “Though less than ten percent of stars become supernovas, they nonetheless are key to the evolution of galaxies.”
Throughout the observable universe, supernovas are quite common, but since they appear – on average – about once every 50 years in a galaxy the size of the Milky Way, astronomers have precious few opportunities to study one from its first detonation to the point where it cools enough to form new molecules. Though SN 1987A is not in our home galaxy, it is still close enough for ALMA and other telescopes to study in fine detail.
Capturing 3-D Image of SN1987A with ALMA
For decades, radio, optical, and even X-ray observatories have studied SN 1987A, but obscuring dust in the remnant made it difficult to analyze the supernova’s innermost core. ALMA’s ability to observe at millimeter wavelengths – a region of the electromagnetic spectrum between infrared and radio light – make it possible to see through the intervening dust. The researchers were then able to study the abundance and location of newly formed molecules – especially silicon monoxide (SiO) and carbon monoxide (CO), which shine brightly at the short submillimeter wavelengths that ALMA can perceive.
The new ALMA image and animation show vast new stores of SiO and CO in discrete, tangled clumps within the core of SN 1987A. Scientists previously modeled how and where these molecules would appear. With ALMA, the researchers finally were able to capture images with high enough resolution to confirm the structure inside the remnant and test those models.
Aside from obtaining this 3-D image of SN 1987A, the ALMA data also reveal compelling details about how its physical conditions have changed and continue to change over time. These observations also provide insights into the physical instabilities inside a supernova.
New Insights from SN 1987A
Earlier observations with ALMA verified that SN 1987A produced a massive amount of dust. The new observations provide even more details on how the supernova made the dust as well as the type of molecules found in the remnant.
“One of our goals was to observe SN 1987A in a blind search for other molecules,” said Indebetouw. “We expected to find carbon monoxide and silicon monoxide, since we had previously detected these molecules.” The astronomers, however, were excited to find the previously undetected molecules formyl cation (HCO+) and sulfur monoxide (SO).
“These molecules had never been detected in a young supernova remnant before,” noted Indebetouw. “HCO+ is especially interesting because its formation requires particularly vigorous mixing during the explosion.” Stars forge elements in discrete onion-like layers. As a star goes supernova, these once well-defined bands undergo violent mixing, helping to create the environment necessary for molecule and dust formation.
The astronomers estimate that about 1 in 1,000 silicon atoms from the exploded star is now found in free-floating SiO molecules. The overwhelming majority of the silicon has already been incorporated into dust grains. Even the small amount of SiO that is present is 100 times greater than predicted by dust-formation models. These new observations will aid astronomers in refining their models.
These observations also find that ten percent or more of the carbon inside the remnant is currently in CO molecules. Only a few out of every million carbon atoms are in HCO+ molecules.
New Questions and Future Research
Even though the new ALMA observations shed important light on SN 1987A, there are still several questions that remain. Exactly how abundant are the molecules of HCO+ and SO? Are there other molecules that have yet to be detected? How will the 3-D structure of SN 1987A continue to change over time?
Future ALMA observations at different wavelengths may also help determine what sort of compact object – a pulsar or neutron star – resides at the center of the remnant. The supernova likely created one of these dense stellar objects, but as yet none has been detected.
TOP IMAGE….Supernova 1987A in the Large Magellanic Cloud
UPPER IMAGE….close up of Supernova 1987A
CENTRE IMAGE….Astronomers combined observations from three different observatories to produce this colorful, multiwavelength image of the intricate remains of Supernova 1987A.The red color shows newly formed dust in the center of the supernova remnant, taken at submillimeter wavelengths by the Atacama Large Millimeter/submillimeter Array (ALMA) telescope in Chile.The green and blue hues reveal where the expanding shock wave from the exploded star is colliding with a ring of material around the supernova. The green represents the glow of visible light, captured by NASA’s Hubble Space Telescope. The blue color reveals the hottest gas and is based on data from NASA’s Chandra X-ray Observatory.The ring was initially made to glow by the flash of light from the original explosion. Over subsequent years the ring material has brightened considerably as the explosion’s shock wave slams into it. Supernova 1987A resides 163,000 light-years away in the Large Magellanic Cloud, where a firestorm of star birth is taking place.
Credit: NASA/ESA, ALMA (ESO/NAOJ/NRAO)
LOWER IMAGE….This artist’s illustration of Supernova 1987A reveals the cold, inner regions of the exploded star’s remnants (red) where tremendous amounts of dust were detected and imaged by ALMA. This inner region is contrasted with the outer shell (blue), where the energy from the supernova is colliding (green) with the envelope of gas ejected from the star prior to its powerful detonation.
Credit: A. Angelich; NRAO/AUI/NSF
BOTTOM IMAGE….Remnant of Supernova 1987A as seen by ALMA. Purple area indicates emission from SiO molecules. Yellow area is emission from CO molecules. The blue ring is Hubble data that has been artificially expanded into 3-D.
Credit: ALMA (ESO/NAOJ/NRAO); R. Indebetouw; NASA/ESA Hubble
New images from NASA’s Hubble Space Telescope are helping researchers view in unprecedented detail the spiral arms and dust clouds of a nearby galaxy, which are the birth sites of massive and luminous stars.
The Whirlpool galaxy, M51, has been one of the most photogenic galaxies in amateur and professional astronomy. Easily photographed and viewed by smaller telescopes, this celestial beauty is studied extensively in a range of wavelengths by large ground- and space-based observatories. This Hubble composite image shows visible starlight as well as light from the emission of glowing hydrogen, which is associated with the most luminous young stars in the spiral arms.
M51, also known as NGC 5194, is having a close encounter with a nearby companion galaxy, NGC 5195, just off the upper edge of this image. The companion’s gravitational pull is triggering star formation in the main galaxy, as seen in brilliant detail by numerous, luminous clusters of young and energetic stars. The bright clusters are highlighted in red by their associated emission from glowing hydrogen gas.
This Wide Field Planetary Camera 2 image enables a research group, led by Nick Scoville (Caltech), to clearly define the structure of both the cold dust clouds and the hot hydrogen and link individual clusters to their parent dust clouds. Team members include M. Polletta (U. Geneva); S. Ewald and S. Stolovy (Caltech); R. Thompson and M. Rieke (U. of Arizona).
Intricate structure is also seen for the first time in the dust clouds. Along the spiral arms, dust “spurs” are seen branching out almost perpendicular to the main spiral arms. The regularity and large number of these features suggests to astronomers that previous models of “two-arm” spiral galaxies may need to be revisited. The new images also reveal a dust disk in the nucleus, which may provide fuel for a nuclear black hole.
The team is also studying this galaxy at near-infrared wavelengths with the NICMOS instrument onboard Hubble. At these wavelengths, the dusty clouds are more transparent and the true distribution of stars is more easily seen. In addition, regions of star formation that are obscured in the optical images are newly revealed in the near-infrared images.
This image was composed by the Hubble Heritage Team from Hubble archival data of M51 and is superimposed onto ground-based data taken by Travis Rector (NOAO) at the 0.9-meter telescope at the National Science Foundation’s Kitt Peak National Observatory (NOAO/AURA) in Tucson, AZ.
Object Names: The Whirlpool Galaxy, M51
Image Type: Astronomical
Image Credit: NASA and The Hubble Heritage Team (STScI/AURA)
Acknowledgment: N. Scoville (Caltech) and T. Rector (NOAO)
Can you see them? This famous Messier object M89, a seemingly simple elliptical galaxy, is surrounded by faint shells and plumes. The cause of the shells is currently unknown, but possibly tidal tails related to debris left over from absorbing numerous small galaxies in the past billion years. Alternatively the shells may be like ripples in a pond, where a recent collision with another large galaxy created density waves that ripple through this galactic giant. Regardless of the actual cause, the featured image highlights the increasing consensus that at least some elliptical galaxies have formed in the recent past, and that the outer halos of most large galaxies are not really smooth but have complexities induced by frequent interactions with – and accretions of – smaller nearby galaxies. The halo of our own Milky Way Galaxy is one example of such unexpected complexity. M89 is a member of the nearby Virgo cluster of galaxies which lies about 50 million light years distant.
ASTRONOMERS LET GASEOUS DISCS TILT AND SHRINK IN VIRTUAL WIND TUNNEL
A team of Dutch astronomers, led by Thomas Wijnen (Radboud University), has managed to tilt and shrink gaseous discs, in which planets form, in a virtual wind tunnel. The research helps for example in finding an explanation for the tilted planetary orbits in our own solar system. Wijnen and his colleagues publish their findings in two articles in the journal Astronomy & Astrophysics.
A newborn star is surrounded by a disc of gas and dust out of which planets form. In addition, there is a lot of remaining gas in star forming areas, which was not used to form stars (and their discs). Dutch astronomers presume that the gaseous disc from which our own planet system originated was tilted under the influence of its movement through gas.
To investigate the hypothesis of the tilting gaseous discs, Dutch astronomers placed a star with a gaseous disc in a virtual wind tunnel and tested several different conditions. A real wind tunnel was not an option because that wind tunnel should be larger than a complete solar system and because the processes last for hundreds of thousands of years.
Thomas Wijnen (at the time of the research employed at Radboud University, now working at Leiden University), is the first author of two scientific articles on the tilting and shrinking discs. He explains: “In a video of our simulation you see the disc tilting. You can also see how the outer layers of the dust disc are stripped by the flow. The disc also shrinks because it continuously sweeps up gas from the flow, but that is harder to see in the video.”
The researchers are able to describe the shrinking of the discs theoretically and applied their theory by simulating discs in, among others, the Trapezium Cluster, a star-forming region in the Orion Nebula in the constellation of Orion at ‘only’ 1,300 light-years from Earth.
The Dutch simulations appear to resemble the reality well. Wijnen: “We have discovered that near collisions between two discs are less important than previously thought. Our simulations show that sweeping up gas from the environment is more important. Until now, no one had investigated the influence of the swept up gas and no one had thought that it can play such a big role.”
In the future, the researchers would like to investigate the influence of a shrinking disc on the formation of planets. They suggest that due to the shrinking, planets that originate on the outside of the system can move to their star. Research on planet formation is “hot” because in early 2017 the TRAPPIST-1 system was discovered which has seven big planets orbiting close to its star. Since that discovery, scientists, for example Amsterdam astronomers, try to explain how such a system could have formed.
IMAGES….Dutch astronomers let planet-forming gaseous disks tilt and shrink in a virtual wind tunnel. The leftmost movie still shows the startingpoint. The second picture shows the situation after 250 years, then after 500 years and eventually after 1000 years.
While ground-based observers experienced the awe-inspiring view of a total solar eclipse yesterday, astronauts aboard the International Space Station, and our Sun-watching satellites, enjoyed unique perspectives of this spectacular sight from space.
Thanks to a quirk of our cosmos, the Moon’s average distance from Earth is just right for it to appear as the same size in the sky as the significantly larger Sun: the Sun’s diameter is 400 times wider than the Moon’s, but it is also 400 times farther away.
When the two align such that the Moon slides directly between Earth and the Sun, it appears to cover our star completely, temporarily blocking out its light and creating a total solar eclipse for those along the narrow path cast by the Moon’s shadow.
Yesterday, 21 August, observers situated along a 115 km-wide swath stretching from Oregon to South Carolina in the US were under this path of totality. The eclipse shadow took about 1.5 hours to cross the continent, with the peak totality lasting for about 2 minutes 40 seconds.
A team of astronomers from ESA imaged the eclipse from the US and captured phenomena such as beads of light shining through gaps in the lunar terrain, and the glittering ‘diamond ring’ effect as the last and first slither of sunlight glints through immediately before and after totality.
They also imaged the Sun’s extended atmosphere, the corona, which is visible to the naked eye only during totality when the rest of the Sun’s light is blocked out.
Astronomers at ESA’s Spaceport in Kourou, French Guiana, enjoyed a partial eclipse after totality had finished in North America. On the north-eastern coast of South America, it was one of the last places to observe the eclipse before it ended worldwide.
Lucky observers in the westernmost parts of Europe also captured a few moments of the partial eclipse at sunset, including astronomers observing from ESA’s European Space Astronomy Centre near Madrid, in Spain.
Meanwhile, from their unique vantage point about 400 km above Earth, astronauts aboard the International Space Station, including ESA’s Paolo Nespoli, viewed partial eclipses and the Moon’s fuzzy shadow on the surface of the planet. The space station traversed across the path of totality three times on its 90 minute-long orbits around the Earth.
Also orbiting Earth 14.5 times a day in its 800 km altitude polar orbit is ESA’s Proba-2 satellite, which was predicted to see the Moon pass four times through its field-of-view, with three partial eclipses.
Further away, some 1.5 million kilometres from Earth towards the Sun, the ESA/NASA Solar and Heliospheric Observatory, SOHO, captured views of the Sun’s activity and extended coma.
For SOHO, eclipses are business as usual: it permanently blocks out the light from the Sun’s disc in order to see fine details in the corona and features in the Sun’s extended atmosphere.
These space-based images provide useful context for the ground-based astronomers, offering wide views of the corona and the Sun’s activity at the time of the eclipse, and at a range of wavelengths. This helps to link the features seen at a range of scales, giving an insight into the Sun’s dynamic activity.
TOP IMAGE….The total solar eclipse seen from Casper, Wyoming (US), by a team of ESA astronomers. The image shows the moment of totality, when the Moon passed directly in front of the Sun, blocking its light and revealing the details of the Sun’s atmosphere, its corona. Copyright ESA/M.P. Ayucar, CC BY-SA 3.0 IGO
UPPER IMAGE….Astronomers observing from ESA’s Spaceport in Kourou enjoyed views of the partial eclipse yesterday. The image here was taken during the maximum extent of the partial eclipse. Sunspots are also visible on the solar disc. Copyright Cédric Laffay (2017)
CENTRE INMAGE….ESA astronaut Paolo Nespoli took this picture during the total solar eclipse of the Sun over the US on 21 August 2017.
From their unique vantage point 400 km above Earth’s surface, astronauts aboard the International Space Station saw the Moon’s fuzzy shadow on the surface of our planet during the eclipse. The space station crossed the path of the eclipse three times on its 90 minute-long orbits around the Earth. Copyright ESA/NASA
LOWER IMAGE….As the US enjoyed a total solar eclipse on 21 August 2017, ESA’s Sun-watching Proba-2 satellite captured partial eclipses from its viewpoint, 800 km above Earth. Proba-2 orbits Earth about 14.5 times per day, and thanks to the constant change in viewing angle, it can dip in and out of the Moon’s shadow several times during a solar eclipse. This still image shows one of the first images available from today’s eclipse, taken at 17:08 GMT. The image was taken by the SWAP imager, and shows the solar disc in extreme-ultraviolet light to capture its turbulent surface and swirling corona corresponding to temperatures of about a million degrees. Copyright ESA/Royal Observatory Belgium
BOTTOM IMAGE….This composite image of the Sun and its corona was taken by the ESA/NASA SOHO satellite and ESA’s Proba-2 satellite yesterday, during the time of Earth’s total solar eclipse. The central image shows an extreme-ultraviolet image of the solar disc taken by Proba-2 at 18:55 GMT, while the corona and extended atmospheric features are seen by SOHO in the red image from 2–6 solar radii, and beyond in blue (SOHO can see up to about 32 solar radii) at 18:48 and 19:06 GMT, respectively. The black circular region corresponds to an occulting mask to cut out direct sunlight that would otherwise obscure the details close to the Sun – similar to the effect of the Moon in a total solar eclipse. As such, these images provide important context for images captured during the eclipse by ground-based astronomers.
The image was composed using JHelioviewer. Copyright SOHO (ESA & NASA); Proba-2: ESA/Royal Observatory of Belgium
What created this unusual hole in Mars? Actually, there are numerous holes pictured in this Swiss cheese-like landscape, with all-but-one of them showing a dusty, dark, Martian terrain beneath evaporating, light, carbon-dioxide ice. The most unusual hole is on the upper right, spans about 100-meters, and seems to punch through to a lower level. Why this hole exists and why it is surrounded by a circular crater remains a topic of speculation, although a leading hypothesis is that it was created by a meteor impact. Holes such as this are of particular interest because they might be portals to lower levels that extend into expansive underground caves. If so, these naturally-occurring tunnels are relatively protected from the harsh surface of Mars, making them relatively good candidates to contain Martian life. These pits are therefore prime targets for possible future spacecraft, robots, and even human interplanetary explorers.