Scientists inch closer than ever to signal from cosmic dawn

By: Thomas Schmitt Attorney on November 27, 2019 / comment : 0 Astronomy, Astrophysics, Universe

Around 12 billion years ago, the universe emerged from a great cosmic dark age as the first stars and galaxies lit up. With a new analysis of data collected by the Murchison Widefield Array (MWA) radio telescope, scientists are now closer than ever to detecting the ultra-faint signature of this turning point in cosmic history.

The Murchison Widefield Array radio telescope, a portion of which is pictured here, is searching  for a signal emitted during the formation of the first stars in the universe [Credit: Goldsmith/MWA Collaboration/Curtin University]

In a paper on the preprint site ArXiv and soon to be published in the Astrophysical Journal, researchers present the first analysis of data from a new configuration of the MWA designed specifically to look for the signal of neutral hydrogen, the gas that dominated the universe during the cosmic dark age. The analysis sets a new limit -- the lowest limit yet -- for the strength of the neutral hydrogen signal.

"We can say with confidence that if the neutral hydrogen signal was any stronger than the limit we set in the paper, then the telescope would have detected it," said Jonathan Pober, an assistant professor of physics at Brown University and corresponding author on the new paper. "These findings can help us to further constrain the timing of when the cosmic dark ages ended and the first stars emerged."

The research was led by Wenyang Li, who performed the work as a Ph.D. student at Brown. Li and Pober collaborated with an international group of researchers working with the MWA.

Despite its importance in cosmic history, little is known about the period when the first stars formed, which is known as the Epoch of Reionization (EoR). The first atoms that formed after the Big Bang were positively charged hydrogen ions -- atoms whose electrons were stripped away by the energy of the infant universe. As the universe cooled and expanded, hydrogen atoms reunited with their electrons to form neutral hydrogen. And that's just about all there was in the universe until about 12 billion years ago, when atoms started clumping together to form stars and galaxies. Light from those objects re-ionized the neutral hydrogen, causing it to largely disappear from interstellar space.

The goal of projects like the one happening at MWA is to locate the signal of neutral hydrogen from the dark ages and measure how it changed as the EoR unfolded. Doing so could reveal new and critical information about the first stars -- the building blocks of the universe we see today. But catching any glimpse of that 12-billion-year-old signal is a difficult task that requires instruments with exquisite sensitivity.

When it began operating in 2013, the MWA was an array of 2,048 radio antennas arranged across the remote countryside of Western Australia. The antennas are bundled together into 128 "tiles," whose signals are combined by a supercomputer called the Correlator. In 2016, the number of tiles was doubled to 256, and their configuration across the landscape was altered to improve their sensitivity to the neutral hydrogen signal. This new paper is the first analysis of data from the expanded array.

Neutral hydrogen emits radiation at a wavelength of 21 centimeters. As the universe has expanded over the past 12 billion years, the signal from the EoR is now stretched to about 2 meters, and that's what MWA astronomers are looking for. The problem is there are myriad other sources that emit at the same wavelength -- human-made sources like digital television as well as natural sources from within the Milky Way and from millions of other galaxies.

"All of these other sources are many orders of magnitude stronger than the signal we're trying to detect," Pober said. "Even an FM radio signal that's reflected off an airplane that happens to be passing above the telescope is enough to contaminate the data."

To home in on the signal, the researchers use a myriad of processing techniques to weed out those contaminants. At the same time, they account for the unique frequency responses of the telescope itself.

"If we look at different radio frequencies or wavelengths, the telescope behaves a little differently," Pober said. "Correcting for the telescope response is absolutely critical for then doing the separation of astrophysical contaminants and the signal of interest."

Those data analysis techniques combined with the expanded capacity of the telescope itself resulted in a new upper bound of the EoR signal strength. It's the second consecutive best-limit-to-date analysis to be released by MWA and raises hope that the experiment will one day detect the elusive EoR signal.

"This analysis demonstrates that the phase two upgrade had a lot of its desired effects and that the new analysis techniques will improve future analyses," Pober said. "The fact that MWA has now published back-to-back the two best limits on the signal gives momentum to the idea that this experiment and its approach has a lot of promise."

Source: Brown University [November 27, 2019]

Solving fossil mystery could aid quest for ancient life on Mars

By: Thomas Schmitt Attorney on November 26, 2019 / comment : 0 Astrobiology, Astronomy, Earth Science, Fossils, Universe

Research which suggests that structures previously thought to be fossils may, in fact, be mineral deposits could save future Mars missions valuable time and resources.

A life-like structure created in the lab by chemical gardening [Credit: Sean McMahon]

Microscopic tubes and filaments that resemble the remains of tiny creatures may have been formed by chemical reactions involving iron-rich minerals, the study shows. Previous research had suggested that such structures were among the oldest fossils on Earth.

The new findings could aid the search for extraterrestrial life during future missions to Mars by making it easier to distinguish between fossils and non-biological structures.

The discovery was made by a scientist from the University of Edinburgh who is developing techniques to seek evidence that life once existed on Mars.

Astrobiologist Sean McMahon created tiny formations in the lab that closely mimic the shape and chemical composition of iron-rich structures commonly found in Mars-like rocks on Earth, where some examples are thought to be around four billion years old.

Dr McMahon created the complex structures by mixing iron-rich particles with alkaline liquids containing the chemicals silicate or carbonate.

This process - known as chemical gardening - is thought to occur naturally where these chemicals abound. It can occur in hydrothermal vents on the seabed and when deep groundwater circulates through pores and fractures in rocks.

His findings suggest that structure alone is not sufficient to confirm whether or not microscopic life-like formations are fossils. More research will be needed to say exactly how they were formed.

The study, published in the journal Proceedings of the Royal Society B, was funded by the European Union's Horizon 2020 programme.

Dr Sean McMahon said: "Chemical reactions like these have been studied for hundreds of years but they had not previously been shown to mimic these tiny iron-rich structures inside rocks. These results call for a re-examination of many ancient real-world examples to see if they are more likely to be fossils or non-biological mineral deposits."

Source: University of Edinburgh [November 27, 2019]

Impact crater data analysis of Ryugu asteroid illuminates complicated geological history

By: Thomas Schmitt Attorney on November 26, 2019 / comment : 0 Astronomy, Universe

Analysis of the impact craters on Ryugu using the spacecraft Hayabusa 2's remote sensing image data has illuminated the geological history of the Near-Earth asteroid.

Individual images of each identified crater on Ryugu [Credit: Kobe University]

A research group led by Assistant Professor Naoyuki Hirata of the Department of Planetology at Kobe University's Graduate School of Science revealed 77 craters on Ryugu. Through analyzing the location patterns and characteristics of the craters, they determined that the asteroid's eastern and western hemispheres were formed at different periods of time.

It is hoped that the collected data can be used as a basis for future asteroid research and analysis. These results were first published in the scientific journal Icarus.

Introduction

The Japan Space Agency (JAXA)'s Hayabusa 2 has been used to carry out various missions to increase our understanding of the spinning top-shaped, Near-Earth asteroid Ryugu. Since arriving in June 2018, the unmanned spacecraft has taken samples and a great number of images of the asteroid. It is hoped that these can reveal more about Ryugu's formation and history.

This research group focused on using the image data to determine the number and location of impact craters on the asteroid. Impact craters are formed when a smaller asteroid or a comet hits the surface of the asteroid. Analyzing the spatial distribution and the number of impact craters can reveal the frequency of collisions and aid researchers in determining the age of different surface areas.

Research Methodology

First of all, the image data from Hayabusa 2 was analyzed. Hayabusa 2 has many different types of camera including Optical Navigation Cameras (ONC). The ONC team has been able to take around 5000 images of Ryugu, which have revealed many surface features- including impact craters. For this study, image data obtained from the 'ONC-T' camera between July 2018 and February 2019 was utilized.

Size and location of craters on Ryugu: The craters are numbered in order of size [Credit: Kobe University]

The research group had to determine which of these images showed craters. 340 images were used for crater counting, with stereopair images making it easier to identify the craters. A global image mosaic map was constructed from the ONC images and rendered onto the computer model of Ryugu's shape. Small Body Mapping Tool software was then used to measure the size, latitude and longitude of the craters. A LiDAR (Light Detection and Ranging pulsed laser) was also utilized to determine the overall size of Ryugu.

The depressions identified on Ryugu were divided into four categories- depending on how evident their circular appearance was. Category I to III depressions were classified as distinct craters. Category IV depressions only had quasi-circular features, therefore it was hard to determine whether they were craters or not. Many craters were filled with boulders or lacked a distinct shape. Depressions that were too vague to determine were left out of the results.

Research Results

The research team were able to identify all impact craters over 10 to 20m in diameter on Ryugu's entire surface- a total of 77 craters. Furthermore, a pattern was discovered in their distribution. The section of the eastern hemisphere near the meridian was found to have the most craters. This is the area near the large crater named Cendrillon - which is one of Ryugu's biggest. In contrast, there are hardly any craters in the western hemisphere- suggesting that this part of the asteroid was formed later. The analysis also revealed that there are more craters at lower latitudes than at higher latitudes on Ryugu. In other words, there are very few craters in Ryugu's polar regions.

The equatorial ridge in the eastern hemisphere was determined to be a fossil structure. When asteroids like Ryugu rotate at high speeds, this can alter their shape. It is thought that this ridge formed in the distant past during a period when it only took Ryugu 3 hours to rotate. As the eastern hemisphere and western hemisphere were formed at different periods of the asteroid's history- this suggests that there have been at least two instances where Ryugu's rotational speed has increased.

Further Research

The results of this study were compiled into a global impact crater catalogue for Ryugu. It is hoped that this database can be used as a basis for future research and that comparing these results with those of a similar asteroid will lead to greater understanding about these astronomical objects.

Hayabusa2 is scheduled to drop the capsule containing samples of Ryugu's surface into Earth's atmosphere in late 2020. Analysis of these samples should provide further insight into the asteroid and how it was formed.

Source: Kobe University [November 27, 2019]

Black hole nurtures baby stars a million light years away

By: Thomas Schmitt Attorney on November 25, 2019 / comment : 0 Astronomy, Astrophysics, Universe

Black holes are famous for ripping objects apart, including stars. But now, astronomers have uncovered a black hole that may have sparked the births of stars over a mind-boggling distance, and across multiple galaxies.

Credit: X-ray: NASA/CXC/INAF/R. Gilli et al.; Radio NRAO/VLA; Optical: NASA/STScI

If confirmed, this discovery, made with NASA's Chandra X-ray Observatory and other telescopes, would represent the widest reach ever seen for a black hole acting as a stellar kick-starter. The black hole seems to have enhanced star formation more than one million light-years away. (One light-year is equal to 6 trillion miles.)

"This is the first time we've seen a single black hole boost star birth in more than one galaxy at a time," said Roberto Gilli of the National Institute of Astrophysics (INAF) in Bologna, Italy, lead author of the study describing the discovery. "It's amazing to think one galaxy's black hole can have a say in what happens in other galaxies millions of trillions of miles away."

A black hole is an extremely dense object from which no light can escape. The black hole's immense gravity pulls in surrounding gas and dust, but particles from a small amount of that material can also get catapulted away instead at nearly the speed of light. These fast-moving particles form two narrow beams or "jets" near the poles of the black hole.

The supermassive black hole scientists observed in the new study is located in the center of a galaxy about 9.9 billion light-years from Earth. This galaxy has at least seven neighboring galaxies, according to observations with the European Southern Observatory's Very Large Telescope (VLT) and the Large Binocular Telescope (LBT).

Using the National Science Foundation's Karl Jansky Very Large Array, scientists had previously detected radio-wave emission from a jet of high-energy particles that is about a million light-years long. The jet can be traced back to the supermassive black hole, which Chandra detected as a powerful source of X-rays produced by hot gas swirling around the black hole. Gilli and colleagues also detected a diffuse cloud of X-ray emission surrounding one end of the radio jet. This X-ray emission is most likely from a gigantic bubble of hot gas heated by the interaction of the energetic particles in the radio jet with surrounding matter.


As the hot bubble expanded and swept through four neighboring galaxies, it could have created a shock wave that compressed cool gas in the galaxies, causing stars to form. All four galaxies are approximately the same distance, about 400,000 light-years, from the center of the bubble. The authors estimate that the star formation rate is between about two to five times higher than typical galaxies with similar masses and distance from Earth.

"The story of King Midas talks of his magic touch that can turn metal into gold," said co-author Marco Mignoli, also of INAF in Bologna, Italy. "Here we have a case of a black hole that helped turn gas into stars, and its reach is intergalactic."

Astronomers have seen many cases where a black hole affects its surroundings through "negative feedback"—in other words, curtailing the formation of new stars. This can occur when the black hole's jets inject so much energy into the hot gas of a galaxy, or galaxy cluster, that the gas can't cool down enough to make large numbers of stars.

In this newly discovered collection of galaxies, astronomers have found a less common example of "positive feedback," where the black hole's effects increase star formation. Moreover, when astronomers previously encountered positive feedback, it either involved increases in the star formation rate of 30% or less, or it occurred over scales of only about 20,000 to 50,000 light-years on a nearby companion galaxy. Whether the feedback is positive or negative depends on a delicate balance between the heating rate and cooling rate of a cloud. That is because clouds that are initially cooler when hit by a shock wave are more prone to experience positive feedback, and form more stars.

"Black holes have a well-earned reputation for being powerful and deadly, but not always," said co-author Alessandro Peca, formerly at INAF in Bologna and now a Ph.D. student at the University of Miami. "This is a prime example that they sometimes defy that stereotype and can be nurturing instead."

The researchers used a total of six days of Chandra observing time spread out over five months.

"It's only because of this very deep observation that we saw the hot gas bubble produced by the black hole," said co-author Colin Norman of the Johns Hopkins University in Baltimore, Maryland. "By targeting objects similar to this one, we may discover that positive feedback is very common in the formation of groups and clusters of galaxies."

A paper describing these results has been published in the most recent issue of the journal Astronomy and Astrophysics.

Source: Chandra X-ray Center [November 26, 2019]

Planets around a black hole?

By: Thomas Schmitt Attorney on November 24, 2019 / comment : 0 Astronomy, Astrophysics, Universe

Theoreticians in two different fields defied the common knowledge that planets orbit stars like the Sun. They proposed the possibility of thousands of planets around a supermassive black hole.

Artist's impression of planets orbiting a supermassive black hole [Credit: Kagoshima University]

"With the right conditions, planets could be formed even in harsh environments, such as around a black hole," says Keiichi Wada, a professor at Kagoshima University researching active galactic nuclei which are luminous objects energized by black holes.

According to the latest theories, planets are formed from fluffy dust aggregates in a protoplanetary disk around a young star. But young stars are not the only objects that possess dust disks. In a novel approach, the researchers focused on heavy disks around supermassive black holes in the nuclei of galaxies.

"Our calculations show that tens of thousands of planets with 10 times the mass of the Earth could be formed around 10 light-years from a black hole," says Eiichiro Kokubo, a professor at the National Astronomical Observatory of Japan who studies planet formation. "Around black holes there might exist planetary systems of astonishing scale."

Some supermassive black holes have large amounts of matter around them in the form of a heavy, dense disk. A disk can contain as much as a hundred thousand times the mass of the Sun worth of dust. This is a billion times the dust mass of a protoplanetary disk.

In a low temperature region of a protoplanetary disk, dust grains with ice mantles stick together and evolve into fluffy aggregates. A dust disk around a black hole is so dense that the intense radiation from the central region is blocked and low temperature regions are formed. The researchers applied the planet formation theory to circumnuclear disks and found that planets could be formed in several hundred million years.

Currently there are no techniques to detect these planets around black holes. However, the researchers expect this study to open a new field of astronomy.

The study is published in The Astrophysical Journal.

Author: Hitoshi Yamaoka | Source: National Astronomical Observatory of Japan [November 25, 2019]

Chemistry in the turbulent interstellar medium

By: Thomas Schmitt Attorney on November 21, 2019 / comment : 0 Astronomy, Chemistry, Universe

Over 200 molecules have been discovered in space, some (like Buckminsterfullerene) very complex with carbon atoms. Besides being intrinsically interesting, these molecules radiate away heat, helping giant clouds of interstellar material cool and contract to form new stars. Moreover, astronomers use the radiation from these molecules to study the local conditions, for example, as planets form in disks around young stars.

A multi-wavelength image of a portion of the Perseus molecular cloud, located about 850 light-years away, and its nebulae. Turbulence is pervasive in molecular clouds and plays an important role in producing small density and temperature fluctuations that in turn help determine the abundances of complex molecules in the cloud. A new set of chemical and hydrodynamical models is able to account for the effects of such turbulence and offers an improved explanation for observed chemical abundances [Credit: Agrupacio Astronomica d'Eivissa/Ibiza AAE, Alberto Prats Rodriguez]

The relative abundance of these molecular species is an important but longstanding puzzle, dependent on many factors from the abundances of the basic elements and the strength of the ultraviolet radiation field to a cloud's density, temperature, and age.

The abundances of the small molecules (those with two or three atoms) are particularly important since they form stepping stones to larger species, and among these the ones that carry a net charge are even more important since they undergo chemical reactions more readily.

Current models of the diffuse interstellar medium assume uniform layers of ultraviolet illuminated gas with either a constant density or a density that varies smoothly with depth into the cloud. The problem is that the models' predictions often disagree with observations.

Decades of observations have also shown, however, that the interstellar medium is not uniform but rather turbulent, with large variations in density and temperature over small distances. CfA astronomer Shmuel Bialy led a team of scientists investigating the abundances of four key molecules— H2, OH+, H2O+, and ArH+ —in a supersonic (with motions exceeding the speed of sound) and turbulent medium. These particular molecules are both useful astronomical probes and highly sensitive to the density fluctuations that naturally arise in turbulent media.

Building on their previous studies of the behavior of molecular hydrogen (H2) in turbulent media, the scientists performed detailed computer simulations that incorporate a wide range of chemical pathways together with models of supersonic turbulent motions under a variety of excitation scenarios driven by ultraviolet radiation and cosmic rays.

Their results, when compared to extensive observations of molecules, show good agreement. The range of turbulent conditions is wide and the predictions correspondingly wide, however, so that while the new models do a better job of explaining the observed ranges, they can be ambiguous and explain a particular situation with several different combinations of parameters. The authors make a case for additional observations and a next-generation of models to constrain the conclusions more tightly.

The study is published in The Astrophysical Journal.

Source: Harvard-Smithsonian Center for Astrophysics [November 22, 2019]

The simultaneous merging of giant galaxies

By: Thomas Schmitt Attorney on November 20, 2019 / comment : 0 Astronomy, Astrophysics, Universe

An international research team led by scientists from Gottingen and Potsdam proved for the first time that the galaxy NGC 6240 contains three supermassive black holes. The unique observations, published in the journal Astronomy & Astrophysics, show the black holes close to each other in the core of the galaxy. The study points to simultaneous merging processes during the formation of the largest galaxies in the universe.

The irregular galaxy NGC 6240. New observations show that it harbours not two but three supermassive black holes at its core. The northern black hole (N) is active and was known before. The zoomed-in new high-spatial resolution image shows that the southern component consists of two supermassive black holes (S1 and S2). The green colour indicates the distribution of gas ionized by radiation surrounding the black holes. The red lines show the contours of the starlight from the galaxy and the length of the white bar corresponds to 1000 light years [Credit: P Weilbacher (AIP), NASA, ESA, the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration,   and A Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University)]

Massive Galaxies like the Milky Way typically consist of hundreds of billions of stars and host a black hole with a mass of several million up to several 100 million solar masses at their centres. The galaxy known as NGC 6240 is known as an irregular galaxy due to its particular shape. Until now, astronomers have assumed that it was formed by the collision of two smaller galaxies and therefore contains two black holes in its core. These galactic ancestors moved towards each other at velocities of several 100 km/s and are still in the process of merging. The galaxy system which is around 300 million light years away from us - close by cosmic standards - has been studied in detail at all wavelengths, and has so far been regarded as a prototype for the interaction of galaxies.

"Through our observations with extremely high spatial resolution we were able to show that the interacting galaxy system NGC 6240 hosts not two - as previously assumed - but three supermassive black holes in its centre," reports Professor Wolfram Kollatschny from the University of Gottingen, the lead author of the study. Each of the three heavyweights has a mass of more than 90 million Suns. They are located in a region of space less than 3000 light-years across, i.e. in less than one hundredth of the total size of the galaxy. "Up until now, such a concentration of three supermassive black holes had never been discovered in the universe," adds Dr Peter Weilbacher of the Leibniz Institute for Astrophysics Potsdam (AIP). "The present case provides evidence of a simultaneous merging process of three galaxies along with their central black holes."

The discovery of this triple system is of fundamental importance for understanding the evolution of galaxies over time. Until now it has not been possible to explain how the largest and most massive galaxies, which we know from our cosmic environment in the "present time", were formed just by normal galaxy interaction and merging processes over the course of the previous 14 billion years approximately, ie the age of our universe. "If, however, simultaneous merging processes of several galaxies took place, then the largest galaxies with their central supermassive black holes were able to evolve much faster," Peter Weilbacher summarizes. "Our observations provide the first indication of this scenario."

For the unique high-precision observations of the galaxy NGC 6240 using the 8 metre VLT, a telescope operated by the European Southern Observatory in Chile, the 3D MUSE spectrograph was used in spatial high-resolution mode together with four artificially generated laser stars and an adaptive optics system. Thanks to the sophisticated technology, images are obtained with a sharpness similar to that of the Hubble Space Telescope but additionally contain a spectrum for each image pixel. These spectra were decisive in determining the motion and masses of the supermassive black holes in NGC 6240.

The scientists assume that the observed, imminent merging of the supermassive black holes in a few million years will also generate very strong gravitational waves. In the foreseeable future, signals of similar objects can be measured with the planned satellite-based gravitational wave detector LISA and further merging systems can be discovered.

Source: University of Gottingen [November 21, 2019]

Fractured ice sheets on Mars

By: Thomas Schmitt Attorney on November 20, 2019 / comment : 0 Astronomy, Space Exploration, Universe

Where the two hemispheres of Mars meet, the planet is covered in broken-up terrain: a sign that slow-but-steady flows of icy material once forged their way through the landscape, carving out a fractured web of valleys, cliffs and isolated mounds of rock.

This image shows a region of Mars named Deuteronilus Mensae. It comprises data gathered on 25 February 2018 during orbit 17913. The ground resolution is approximately 13 m/pixel and the images are centred at about 25.5°E/44°N. This image was created using data from the nadir and colour channels of the High Resolution Stereo Camera (HRSC). The nadir channel is aligned perpendicular to the surface of Mars, as if looking straight down at the surface. North is to the right [Credit: ESA/DLR/FU Berlin, CC BY-SA 3.0 IGO]

Mars is a planet of two halves. Its hemispheres are drastically different; the smooth northern lowlands sit up to three kilometres below the rugged southern highlands, and the surface in Mars' northern regions appears to be far younger than the ancient swaths of the south.

Where these regions meet, they sometimes form a transition area filled with a wide range of intriguing geological features, patterns and processes: a type of landscape unique to Mars known as fretted terrain. Fretted terrain is found in a couple of key areas on Mars, and an especially good example, named Deuteronilus Mensae, can be seen in these images from Mars Express' High Resolution Stereo Camera (HRSC).

This landscape shows clear and widespread signs of significant, lasting erosion. As is common with fretted terrain, it contains a mix of cliffs, canyons, scarps, steep-sided and flat-topped mounds (mesa), furrows, fractured ridges and more, a selection of which can be seen dotted across the frame.

This colour-coded topographic view shows a region of Mars named Deuteronilus Mensae. Lower parts of the surface are shown in blues and purples, while higher altitude regions show up in whites, yellows and reds, as indicated on the scale to the top right. This view is based on a digital terrain model of the region, from which the topography of the landscape  can be derived. It comprises data gathered on 25 February 2018 during orbit 17913. The ground resolution is approximately 13 m/pixel and the images are centred at about 25.5°E/44°N. North is to the right [Credit: ESA/DLR/FU Berlin, CC BY-SA 3.0 IGO]

These features were created as flowing material dissected the area, cutting through the existing landscape and carving out a web of winding channels. In the case of Deuteronilus Mensae, flowing ice is the most likely culprit. Scientists believe that this terrain has experienced extensive past glacial activity across numerous martian epochs.

It is thought that glaciers slowly but surely ate away at the plains and plateaus that once covered this region, leaving only a scattering of steep, flat, isolated mounds of rock in their wake.

Smooth deposits cover the floor itself, some marked with flow patterns from material slowly moving downhill—a mix of ice and accumulated debris that came together to form and feed viscous, moving flows of mass somewhat akin to a landslide or mudflow here on Earth.

This image from ESA’s Mars Express shows a region of Mars named Deuteronilus Mensae. This oblique perspective view was generated using a digital terrain model and Mars Express data gathered on 25 February 2018 during orbit 17913. The ground resolution is approximately 13 m/pixel and the images are centred at about 25.5°E/44°N. This image was created using data from the nadir and colour channels of the High Resolution Stereo Camera (HRSC). The nadir channel is aligned perpendicular to the surface of Mars, as if looking straight down at the surface [Credit: ESA/DLR/FU Berlin, CC BY-SA 3.0 IGO]

Studies of this region by NASA's Mars Reconnaissance Orbiter have shown that most of the features seen here do indeed contain high levels of water ice. Estimates place the ice content of some glacial features in the region at up to 90%.

This suggests that, rather than hosting individual or occasional icy pockets and glaciers, Deuteronilus Mensae may actually represent the remnants of an old regional ice sheet. This ice sheet may once have covered the entire area, lying atop the plateaus and plains. As the martian climate changed this ice began to shift around and disappear, slowly revealing the rock beneath.

Overall, the features seen in these Mars Express images are reminiscent of the rock- and debris-covered glaciers found in cold regions of Earth. Glaciers may actually be relatively common on both past and present-day Mars; recent studies suggest that the planet may have belts of glacial activity above and below its equator, containing huge amounts of ice covered in thick protective layers of dust, and many other areas show signs of having hosted glaciers in the past—just like Deuteronilus Mensae.

This image from ESA’s Mars Express shows a region of Mars named Deuteronilus Mensae. This oblique perspective view was generated using a digital terrain model and Mars Express data gathered on 25 February 2018 during orbit 17913. The ground resolution is approximately 13 m/pixel and the images are centred at about 25.5°E/44°N. This image was created using data from the nadir and colour channels of the High Resolution Stereo Camera (HRSC). The nadir  channel is aligned perpendicular to the surface of Mars, as if looking straight down at the surface [Credit: ESA/DLR/FU Berlin, CC BY-SA 3.0 IGO]

Mars Express has been orbiting the Red Planet since 2003. Using the HRSC, which obtained these new images, the mission has continually mapped the martian surface and characterised various key properties of and phenomena on the planet—from the presence of a planet-wide groundwater system to intricate old river systems, various intriguing surface deposits, giant regional dust storms, spikes of tell-tale gases in the planet's atmosphere, and much more.

The mission will continue to explore the Red Planet in collaboration with the ESA-Roscosmos ExoMars Trace Gas Orbiter, which arrived at Mars in 2016, and the ExoMars Rosalind Franklin rover and its accompanying surface science platform, which will arrive in 2021.

Source: European Space Agency [November 21, 2019]

Outback telescope captures Milky Way centre, discovers remnants of dead stars

By: Thomas Schmitt Attorney on November 20, 2019 / comment : 0 Astronomy, Universe

A radio telescope in the Western Australian outback has captured a spectacular new view of the centre of the galaxy in which we live, the Milky Way.

This image shows a new view of the Milky Way from the Murchison Widefield Array, with the lowest frequencies in red, middle frequencies in green, and the highest frequencies in blue. Huge golden filaments indicate enormous magnetic  fields, supernova remnants are visible as little spherical bubbles, and regions of massive star formation show up in blue. The supermassive black hole at the centre of our galaxy is hidden in the bright white region in the centre. [Credit: Dr Natasha Hurley-Walker (ICRAR/Curtin) and the GLEAM Team]

The image from the Murchison Widefield Array (MWA) telescope shows what our galaxy would look like if human eyes could see radio waves.

Astrophysicist Dr Natasha Hurley-Walker, from the Curtin University node of the International Centre for Radio Astronomy Research (ICRAR), created the images using the Pawsey Supercomputing Centre in Perth.

"This new view captures low-frequency radio emission from our galaxy, looking both in fine detail and at larger structures," she said.

"Our images are looking directly at the middle of the Milky Way, towards a region astronomers call the Galactic Centre."

These are the 27 newly-discovered supernova remnants—the remains of stars that ended their lives in huge stellar explosions thousands to hundreds of thousands of years ago. The radio images trace the edges of the explosions  as they continue their ongoing expansion into interstellar space. Some are huge, larger than the full moon, and others are small and hard to spot in the complexity of the Milky Way [Credit: Dr Natasha Hurley-Walker (ICRAR/Curtin) and the GLEAM Team]

The data for the research comes from the GaLactic and Extragalactic All-sky MWA survey, or 'GLEAM' for short.

The survey has a resolution of two arcminutes (about the same as the human eye) and maps the sky using radio waves at frequencies between 72 and 231 MHz (FM radio is near 100 MHz).

"It's the power of this wide frequency range that makes it possible for us to disentangle different overlapping objects as we look toward the complexity of the Galactic Centre," Dr Hurley-Walker said.

"Essentially, different objects have different 'radio colours', so we can use them to work out what kind of physics is at play."

This 28 image photomosaic captures the arch of the milky way over the Guilderton Lighthouse in Western Australia, and the Large and Small Magellanic Clouds. The location of a supernova that would have exploded 9,000 years ago and been visible in the night sky is shown in the image [Credit: Paean Ng/Astrordinary Imaging]

Using the images, Dr Hurley-Walker and her colleagues discovered the remnants of 27 massive stars that exploded in supernovae at the end of their lives.

These stars would have been eight or more times more massive than our Sun before their dramatic destruction thousands of years ago.

Younger and closer supernova remnants, or those in very dense environments, are easy to spot, and 295 are already known.

Unlike other instruments, the MWA can find those which are older, further away, or in very empty environments.

This is a 104 frame photomosaic capturing the Milky Way directly overhead taken at the Pinnacles Desert in Western Australia. A popular tourist location by day and incredible stargazing at night. The location of a supernova that would have exploded 9,000 years ago is shown in the image [Credit: Paean Ng/Astrordinary Imaging]

Dr Hurley-Walker said one of the newly-discovered supernova remnants lies in such an empty region of space, far out of the plane of our galaxy, and so despite being quite young, is also very faint.

"It's the remains of a star that died less than 9,000 years ago, meaning the explosion could have been visible to Indigenous people across Australia at that time," she said.

An expert in cultural astronomy, Associate Professor Duane Hamacher from the University of Melbourne, said some Aboriginal traditions do describe bright new stars appearing in the sky, but we don't know of any definitive traditions that describe this particular event.

"However, now that we know when and where this supernova appeared in the sky, we can collaborate with Indigenous elders to see if any of their traditions describe this cosmic event. If any exist, it would be extremely exciting," he said.


Dr Hurley-Walker said two of the supernova remnants discovered are quite unusual "orphans", found in a region of sky where there are no massive stars, which means future searches across other such regions might be more successful than astronomers expected. Other supernova remnants discovered in the research are very old, she said.

"This is really exciting for us, because it's hard to find supernova remnants in this phase of life--they allow us to look further back in time in the Milky Way."

The MWA telescope is a precursor to the world's largest radio telescope, the Square Kilometre Array, which is due to be built in Australia and South Africa from 2021.

"The MWA is perfect for finding these objects, but it is limited in its sensitivity and resolution," Dr Hurley-Walker said.

"The low-frequency part of the SKA, which will be built at the same site as the MWA, will be thousands of times more sensitive and have much better resolution, so should find the thousands of supernova remnants that formed in the last 100,000 years, even on the other side of the Milky Way."

A paper describing the GLEAM Survey is published in Publications of the Astronomical Society of Australia.

Source: International Centre for Radio Astronomy Research (ICRAR] [November 20, 2019]

NASA scientists confirm water vapour on Europa

By: Thomas Schmitt Attorney on November 19, 2019 / comment : 0 Astrobiology, Astronomy, Space Exploration, Universe

Forty years ago, a Voyager spacecraft snapped the first closeup images of Europa, one of Jupiter's 79 moons. These revealed brownish cracks slicing the moon's icy surface, which give Europa the look of a veiny eyeball. Missions to the outer solar system in the decades since have amassed enough additional information about Europa to make it a high-priority target of investigation in NASA's search for life.

On the left is a view of Europa taken from 2.9 million kilometers (1.8 million miles) away on March 2, 1979 by the Voyager 1 spacecraft. Next is a color image of Europa taken by the Voyager 2 spacecraft during its close encounter on July 9, 1979. On the right is a view of Europa made from images taken by the Galileo spacecraft in the late 1990s [Credit: NASA/JPL]

What makes this moon so alluring is the possibility that it may possess all of the ingredients necessary for life. Scientists have evidence that one of these ingredients, liquid water, is present under the icy surface and may sometimes erupt into space in huge geysers. But no one has been able to confirm the presence of water in these plumes by directly measuring the water molecule itself. Now, an international research team led out of NASA's Goddard Space Flight Center in Greenbelt, Maryland, has detected the water vapor for the first time above Europa's surface. The team measured the vapor by peering at Europa through W. M. Keck Observatory in Hawaii, one of the world's biggest telescopes.

Confirming that water vapor is present above Europa helps scientists better understand the inner workings of the moon. For example, it helps support an idea, of which scientists are confident, that there's a liquid water ocean, possibly twice as big as Earth's, sloshing beneath this moon's miles-thick ice shell. Another source of water for the plumes, some scientists suspect, could be shallow reservoirs of melted water ice not far below Europa's surface. It's also possible that Jupiter's strong radiation field is stripping water particles from Europa's ice shell, though the recent investigation argued against this mechanism as the source of the observed water.

"Essential chemical elements (carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur) and sources of energy, two of three requirements for life, are found all over the solar system. But the third—liquid water—is somewhat hard to find beyond Earth," said Lucas Paganini, a NASA planetary scientist who led the water detection investigation. "While scientists have not yet detected liquid water directly, we've found the next best thing: water in vapor form."

In a study published in the journal Nature Astronomy, Paganini and his team reported that they detected enough water releasing from Europa (5,202 pounds, or 2,360 kilograms, per second) to fill an Olympic-size swimming pool within minutes. Yet, the scientists also found that the water appears infrequently, at least in amounts large enough to detect from Earth, said Paganini: "For me, the interesting thing about this work is not only the first direct detection of water above Europa, but also the lack thereof within the limits of our detection method."


Indeed, Paganini's team detected the faint yet distinct signal of water vapor just once throughout 17 nights of observations between 2016 and 2017. Looking at the moon from Keck Observatory, the scientists saw water molecules at Europa's leading hemisphere, or the side of the moon that's always facing in the direction of the moon's orbit around Jupiter. (Europa, like Earth's moon, is gravitationally locked to its host planet, so the leading hemisphere always faces the direction of the orbit, while the trailing hemisphere always faces in the opposite direction.)

They used Keck Observatory's Near-Infrared Spectrograph (NIRSPEC), which measures the chemical composition of planetary atmospheres through the infrared light they emit or absorb. Molecules such as water emit specific frequencies of infrared light as they interact with solar radiation.

Mounting evidence for water

Before the recent water vapor detection, there have been many tantalizing findings on Europa. The first came from NASA's Galileo spacecraft, which measured perturbations in Jupiter's magnetic field near Europa while orbiting the gas giant planet between 1995 and 2003. The measurements suggested to scientists that electrically conductive fluid, likely a salty ocean beneath Europa's ice layer, was causing the magnetic disturbances. When researchers analyzed the magnetic disturbances more closely in 2018, they found evidence of possible plumes.

In the meantime, scientists announced in 2013 that they had used NASA's Hubble Space Telescope to detect the chemical elements hydrogen (H) and oxygen (O)—components of water (H2O)—in plume-like configurations in Europa's atmosphere. And a few years later, other scientists used Hubble to gather more evidence of possible plume eruptions when they snapped photos of finger-like projections that appeared in silhouette as the moon passed in front of Jupiter.

"This first direct identification of water vapor on Europa is a critical confirmation of our original detections of atomic species, and it highlights the apparent sparsity of large plumes on this icy world" said Lorenz Roth, an astronomer and physicist from KTH Royal Institute of Technology in Stockholm who led the 2013 Hubble study and was a co-author of this recent investigation.

Roth's research, along with other previous Europa findings, have only measured components of water above the surface. The trouble is that detecting water vapor at other worlds is challenging. Existing spacecraft have limited capabilities to detect it, and scientists using ground-based telescopes to look for water in deep space have to account for the distorting effect of water in Earth's atmosphere. To minimize this effect, Paganini's team used complex mathematical and computer modeling to simulate the conditions of Earth's atmosphere so they could differentiate Earth's atmospheric water from Europa's in data returned by the NIRSPEC.

"We performed diligent safety checks to remove possible contaminants in ground-based observations," said Avi Mandell, a Goddard planetary scientist on Paganini's team. "But, eventually, we'll have to get closer to Europa to see what's really going on."

Scientists will soon be able get close enough to Europa to settle their lingering questions about the inner and outer workings of this possibly habitable world. The forthcoming Europa Clipper mission, expected to launch in the mid-2020s, will round out half a century of scientific discovery that started with a modest photo of a mysterious, veiny eyeball.

When it arrives at Europa, the Clipper orbiter will conduct a detailed survey of Europa's surface, deep interior, thin atmosphere, subsurface ocean, and potentially even smaller active vents. Clipper will try to take images of any plumes and sample the molecules it finds in the atmosphere with its mass spectrometers. It will also seek out a fruitful site from which a future Europa lander could collect a sample. These efforts should further unlock the secrets of Europa and its potential for life.

Author: Lonnie Shekhtman | Source: W. M. Keck Observatory [November 20, 2019]

Exoplanet axis study boosts hopes of complex life, just not next door

By: Thomas Schmitt Attorney on November 19, 2019 / comment : 0 Astrobiology, Astronomy, Universe

"They're out there," goes a saying about extraterrestrials. It would seem more likely to be true in light of a new study on planetary axis tilts.

The Alpha Centauri group is the closest star - or solar - system outside of our own at a distance of 4.3 lightyears, and it can be found in the night sky in the constellation Centaurus. The stars Alpha Centauri A and Alpha Centauri B comprise a binary system, in which the two stars orbit one another, and close by is an additional faint red dwarf Alpha Centauri C, also called Proxima Centauri. Some astronomers have hoped to someday find an exoplanet capable of harboring advanced life in the system, but a new study lowers those expectations while raising  them for the rest of the universe [Credit: NASA/ESA Hubble Space Telescope]

Astrophysicists at the Georgia Institute of Technology modeled a theoretical twin of Earth into other star systems called binary systems because they have two stars. They concluded that 87% of exo-Earths one might find in binary systems should have axis tilts similarly steady to Earth's, an important ingredient for climate stability that favors the evolution of complex life.

"Multiple-star systems are common, and about 50% of stars have binary companion stars. So, this study can be applied to a large number of solar systems," said Gongjie Li, the study's co-investigator an assistant professor at Georgia Tech's School of Physics.

Single-star solar systems like our own with multiple planets appear to be rarer.

Alpha Centauri B? Wretched

The researchers started out contrasting how the Earth's axis tilt, also called obliquity, varies over time with the variation of Mars' axis tilt. Whereas our planet's mild obliquity variations have been great for a livable climate and for evolution, the wild variations of Mars' axis tilt may have helped wreck its atmosphere, as explained in the section below.

Then the researchers modeled Earth into habitable, or Goldilocks, zones in Alpha Centauri AB - our solar system's nearest neighbor, a binary system with one star called "A" and the other "B." After that, they expanded the model to a more universal scope.

"We simulated what it would be like around other binaries with multiple variations of the stars' masses, orbital qualities, and so on," said Billy Quarles, the study's principal investigator and a research scientist in Li's lab. "The overall message was positive but not for our nearest neighbor."

Alpha Centauri A actually didn't look bad, but the outlook for mild axis dynamics on an exo-Earth modeled around star B was wretched. This may douse some hopes because Alpha Centauri AB is four lightyears away, and a mission named Starshot with big-name backers plans to launch a space probe to look for signs of advanced life there.

No exoplanets have been confirmed around A or B; an exoplanet has been confirmed around the nearby red dwarf star Proxima Centauri, but it is very likely to be uninhabitable.

Earth? Just right

Even with its ice ages and hot phases, Earth's climatological framework has been calm for hundreds of millions of years - in part because of its mild orbital and axis-tilt dynamics - allowing evolution to take big strides. Wildly varying dynamics, and thus climate, like on Mars would stand to regularly kill off advanced life, stunting evolution.

Poor Earth: Modelled into an orbit in the habitable zone around Alpha Centauri B, in this artist's rendering by an author of a new study, our planet appears rather icy and inhospitable to advanced life [Credit: Georgia Tech/Billy Quarles]

Earth's orbit around the sun is on a slight incline that seesaws gently and very slowly through a slight precession, a kind of oscillation. As Earth revolves, it shifts position relative to the sun, circling it a little like a spirograph drawing. The orbit also precesses in shape between slightly more and slightly less oblong over 100,000-year periods.

Earth's axis tilt precesses between 22.1 and 24.5 degrees over the course of 41,000 years. Our large moon stabilizes our tilt through its gravitational relationship with Earth, otherwise, bouncy gravitational interconnections with Mercury, Venus, Mars, and Jupiter would jolt our tilt with resonances.

"If we didn't have the moon, Earth's tilt could vary by about 60 degrees," Quarles said. "We'd look maybe like Mars, and the precession of its axis appears to have helped deplete its atmosphere."

Mars' axis precesses between 10 degrees and 60 degrees every 2 million years. At the 10-degree tilt, the atmosphere condenses at the poles, creating caps that lock up a lot of the atmosphere in ice. At 60 degrees, Mars could grow an ice belt around its equator.

Universe? Hopeful

In Alpha Centauri AB, star B, about the size of our sun, and the larger star, A, orbit one another at about the distance between Uranus and our sun, which is a very close for two stars in a binary system. The study modeled variations of an exo-Earth orbiting either star but concentrated on a modeled Earth orbit in the habitable zone centered around B, with A being the orbiting star.

A's orbit is very elliptical, passing close by and then moving very far away from B and slinging powerful gravity, which, in the model, overpowered exo-Earth's own dynamics. Its tilt and orbit varied widely; adding our moon to the model didn't help.

"Around Alpha Centauri B, if you don't have a moon, you have a more stable axis than if you do have a moon. If you have a moon, it's pretty much bad news," Quarles said.

Even without a moon and with mild axis variability, complex, Earthlike evolution would seem to have a hard time on the modeled exo-Earth around B.

"The biggest effect you would see is differences in the climate cycles related to how elongated the orbit is. Instead of having ice ages every 100,000 years like on Earth, they may come every 1 million years, be worse, and last much longer," Quarles said.

But a sliver of hope for Earthlike conditions turned up in the model: "Planetary orbit and spin need to precess just right relative to the binary orbit. There is this tiny sweet spot," Quarles said.

When the researchers expanded the model to binary systems in the universe, the probability of gentle obliquity variations ballooned.

"In general, the separation between the stars is larger in binary systems, and then the second star has less of an effect on the model of Earth. The planet's own motion dynamics dominate other influences, and obliquity usually has a smaller variation," Li said. "So, this is quite optimistic."

The research is published in the Astrophysical Journal.

Source: Georgia Institute of Technology [November 20, 2019]

Blowtorch jets from a black hole drive starbirth

By: Thomas Schmitt Attorney on November 19, 2019 / comment : 0 Astronomy, Astrophysics, Universe

Supermassive black holes, weighing millions or even billions of times our Sun's mass, are still only a tiny fraction of the mass of the galaxies they inhabit. But in some cases, the central black hole is the tail wagging the dog. It seems that black holes can run hot or cold when it comes to either enhancing or squelching star birth inside a cluster of galaxies.

Phoenix Cluster [Credit: X-ray: NASA/CXC/MIT/M.McDonald et al;  Radio: NRAO/VLA; Optical: NASA/STScI]

Typically, giant black holes, pumping out energy via jets, keep interstellar gas too warm to condense and form stars. Now, astronomers have found a cluster of galaxies, called the Phoenix cluster, where stars are forming at a furious rate because of the black hole's influence. This stellar turboboost is apparently linked to less energetic jets from a central black hole that do not pump up the gas temperature. Instead, the gas loses energy as it glows in X-rays. The gas cools to where it can form large numbers of stars at a breathtaking rate. Where our Milky Way forms one star per year on average, newborn stars are popping out of this cool gas at a rate of about 500 solar masses per year in the Phoenix cluster.

Unraveling this mystery required the combined power of NASA's Hubble Space Telescope, NASA's Chandra X-ray Observatory, and the Very Large Array (VLA) radio observatory near Socorro, New Mexico.

The VLA radio data reveals jets blasting out from the vicinity of the central black hole. These jets inflated bubbles in the hot gas that are detected in X-rays by Chandra. Hubble resolves bright blue filaments of newborn stars in cavities between the hot jet and gas clouds. As the black hole has grown more massive and more powerful, its influence has been increasing.

Astronomers have confirmed the first example of a galaxy cluster where large numbers of stars are being born at its core. Using data from NASA space telescopes and a National Science Foundation radio observatory, researchers have gathered new details about how the most massive black holes in the universe affect their host galaxies.

Galaxy clusters are the largest structures in the cosmos that are held together by gravity, consisting of hundreds or thousands of galaxies embedded in hot gas, as well as invisible dark matter. The largest supermassive black holes known are in galaxies at the centers of these clusters.

For decades, astronomers have looked for galaxy clusters containing rich nurseries of stars in their central galaxies. Instead, they found powerful, giant black holes pumping out energy through jets of high-energy particles and keeping the gas too warm to form many stars.

Now, scientists have compelling evidence for a galaxy cluster where stars are forming at a furious rate, apparently linked to a less effective black hole in its center. In this unique cluster, the jets from the central black hole instead appear to be aiding in the formation of stars. Researchers used new data from NASA's Chandra X-ray Observatory and Hubble Space Telescope, and the NSF's Karl Jansky Very Large Array (VLA) to build on previous observations of this cluster.

"This is a phenomenon that astronomers had been trying to find for a long time," said Michael McDonald, astronomer at the Massachusetts Institute of Technology (MIT), who led the study. "This cluster demonstrates that, in some instances, the energetic output from a black hole can actually enhance cooling, leading to dramatic consequences."


The black hole is in the center of a galaxy cluster called the Phoenix Cluster, located about 5.8 billion light years from Earth in the Phoenix Constellation. The large galaxy hosting the black hole is surrounded by hot gas with temperatures of millions of degrees. The mass of this gas, equivalent to trillions of Suns, is several times greater than the combined mass of all the galaxies in the cluster.

This hot gas loses energy as it glows in X-rays, which should cause it to cool until it can form large numbers of stars. However, in all other observed galaxy clusters, bursts of energy driven by such a black hole keep most of the hot gas from cooling, preventing widespread star birth.

"Imagine running an air conditioner in your house on a hot day, but then starting a wood fire. Your living room can't properly cool down until you put out the fire," said co-author Brian McNamara of the University of Waterloo in Canada. "Similarly, when a black hole's heating ability is turned off in a galaxy cluster, the gas can then cool."

Evidence for rapid star formation in the Phoenix Cluster was previously reported in 2012 by a team led by McDonald. But deeper observations were required to learn details about the central black hole's role in the rebirth of stars in the central galaxy, and how that might change in the future.

By combining long observations in X-ray, optical, and radio light, the researchers gained a ten-fold improvement in the data quality compared to previous observations. The new Chandra data reveal that hot gas is cooling nearly at the rate expected in the absence of energy injected by a black hole. The new Hubble data show that about 10 billion solar masses of cool gas are located along filaments leading towards the black hole, and young stars are forming from this cool gas at a rate of about 500 solar masses per year. By comparison, stars are forming in the Milky Way galaxy at a rate of about one solar mass per year.

The VLA radio data reveal jets blasting out from the vicinity of the central black hole. These jets likely inflated bubbles in the hot gas that are detected in the Chandra data. Both the jets and bubbles are evidence of past rapid growth of the black hole. Early in this growth, the black hole may have been undersized, compared to the mass of its host galaxy, which would allow rapid cooling to go unchecked.

"In the past, outbursts from the undersized black hole may have simply been too weak to heat its surroundings, allowing hot gas to start cooling," said co-author Matthew Bayliss, who was a researcher at MIT during this study, but has recently joined the faculty at the University of Cincinnati. "But as the black hole has grown more massive and more powerful, its influence has been increasing."

The cooling can continue when the gas is carried away from the center of the cluster by the black hole's outbursts. At a greater distance from the heating influence of the black hole, the gas cools faster than it can fall back towards the center of the cluster. This scenario explains the observation that cool gas is located around the borders of the cavities, based on a comparison of the Chandra and Hubble data.

Eventually the outburst will generate enough turbulence, sound waves and shock waves (similar to the sonic booms produced by supersonic aircraft) to provide sources of heat and prevent further cooling. This will continue until the outburst ceases and the build-up of cool gas can recommence. The whole cycle may then repeat.

"These results show that the black hole has temporarily been assisting in the formation of stars, but when it strengthens its effects will start to mimic those of black holes in other clusters, stifling more star birth," said co-author Mark Voit of Michigan State University in East Lansing, Michigan.

The lack of similar objects shows that clusters and their enormous black holes pass through the rapid star formation phase relatively quickly.

A paper describing these results was published in a recent issue of The Astrophysical Journal, and a preprint is available online.

Source: ESA/Hubble Information Centre [November 19, 2019]

Scientists find evidence of missing neutron star

By: Thomas Schmitt Attorney on November 19, 2019 / comment : 0 Astronomy, Universe

The leftovers from a spectacular supernova that revolutionised our understanding of how stars end their lives have finally been spotted by astronomers at Cardiff University.

Artistic rendering of a neutron star enveloped by a shroud of dust and gas [Credit: Cardiff University]

The scientists claim to have found evidence of the location of a neutron star that was left behind when a massive star ended its life in a gigantic explosion, leading to a famous supernova dubbed Supernova 1987A.

For more than 30 years astronomers have been unable to locate the neutron star - the collapsed leftover core of the giant star - as it has been concealed by a thick cloud of cosmic dust.

Using extremely sharp and sensitive images taken with the Atacama Large Millimeter/submillimeter Array (ALMA) telescope in the Atacama Desert of northern Chile, the team have found a particular patch of the dust cloud that is brighter than its surroundings, and which matches the suspected location of the neutron star.

Lead author of the study Dr Phil Cigan, from Cardiff University's School of Physics and Astronomy, said: "For the very first time we can tell that there is a neutron star inside this cloud within the supernova remnant. Its light has been veiled by a very thick cloud of dust, blocking the direct light from the neutron star at many wavelengths like fog masking a spotlight."

Dr Mikako Matsuura, another leading member of the study, added: "Although the light from the neutron star is absorbed by the dust cloud that surrounds it, this in turn makes the cloud shine in sub-millimetre light, which we can now see with the extremely sensitive ALMA telescope."

Supernova 1987A was first spotted by astronomers on Feb 23, 1987, when it blazed in the night sky with the power of 100 million suns, and continuing to shine brightly for several months.

A close-up view of different components in the SN 1987A system: carbon monoxide molecular gas is shown in orange,  hot hydrogen gas is shown in purple, and the dust which surrounds the neutron star is shown in cyan [Credit: Cardiff University]

The supernova was discovered in a neighbouring galaxy, the Large Magellanic Cloud, only 160,000 light years away.

It was the nearest supernova explosion observed in over 400 years and, since its discovery, has continued to fascinate astronomers who have been presented with the perfect opportunity to study the phases before, during, and after the death of a star.

The supernova explosion that took place at the end of this star's life resulted in huge amounts of gas with a temperature of over a million degrees, but as the gas began to cool down quickly below zero degrees centigrade, some of the gas transformed into a solid, i.e. dust.

The presence of this thick cloud of dust has long been the main explanation as to why the missing neutron star has not been observed, but many astronomers were sceptical about this and began to question whether their understanding of a star's life was correct.

"Our new findings will now enable astronomers to better understand how massive stars end their lives, leaving behind these extremely dense neutron stars," continued Dr Matsuura.

"We are confident that this neutron star exists behind the cloud and that we know its precise location. Perhaps when the dust cloud begins to clear up in the future, astronomers will be able to directly see the neutron star for the very first time."

The findings have been published in The Astrophysical Journal.

Source: Cardiff University [November 19, 2019]