Hubble Delivers First Hints of Possible Water Content of TRAPPIST-1 Planets

Hubble Delivers First Hints of Possible Water Content of TRAPPIST-1 Planets:

An international team of astronomers used the NASA/ESA Hubble Space Telescope to estimate whether there might be water on the seven earth-sized planets orbiting the nearby dwarf star TRAPPIST-1. The results suggest that the outer planets of the system might still harbor substantial amounts of water. This includes the three planets within the habitable zone of the star, lending further weight to the possibility that they may indeed be habitable.

On 22 February 2017 astronomers announced the discovery of seven Earth-sized planets orbiting the ultracool dwarf star TRAPPIST-1, 40 light-years away. This makes TRAPPIST-1 the planetary system with the largest number of Earth-sized planets discovered so far.

Following up on the discovery, an international team of scientists led by the Swiss astronomer Vincent Bourrier from the Observatoire de l’Université de Genève, used the Space Telescope Imaging Spectrograph (STIS) on the NASA/ESA Hubble Space Telescope to study the amount of ultraviolet radiation received by the individual planets of the system. “Ultraviolet radiation is an important factor in the atmospheric evolution of planets,” explains Bourrier. “As in our own atmosphere, where ultraviolet sunlight breaks molecules apart, ultraviolet starlight can break water vapor in the atmospheres of exoplanets into hydrogen and oxygen.”

While lower-energy ultraviolet radiation breaks up water molecules — a process called photodissociation — ultraviolet rays with more energy (XUV radiation) and X-rays heat the upper atmosphere of a planet, which allows the products of photodissociation, hydrogen and oxygen, to escape.

As it is very light, hydrogen gas can escape the exoplanets’ atmospheres and be detected around the exoplanets with Hubble, acting as a possible indicator of atmospheric water vapor. The observed amount of ultraviolet radiation emitted by TRAPPIST-1 indeed suggests that the planets could have lost gigantic amounts of water over the course of their history.

This is especially true for the innermost two planets of the system, TRAPPIST-1b and TRAPPIST-1c, which receive the largest amount of ultraviolet energy. “Our results indicate that atmospheric escape may play an important role in the evolution of these planets,” summarizes Julien de Wit, from MIT, USA, co-author of the study.

The inner planets could have lost more than 20 Earth-oceans-worth of water during the last eight billion years. However, the outer planets of the system — including the planets e, f and g which are in the habitable zone — should have lost much less water, suggesting that they could have retained some on their surfaces. The calculated water loss rates as well as geophysical water release rates also favor the idea that the outermost, more massive planets retain their water. However, with the currently available data and telescopes no final conclusion can be drawn on the water content of the planets orbiting TRAPPIST-1.

“While our results suggest that the outer planets are the best candidates to search for water with the upcoming James Webb Space Telescope, they also highlight the need for theoretical studies and complementary observations at all wavelengths to determine the nature of the TRAPPIST-1 planets and their potential habitability,” concludes Bourrier.

Credit: spacetelescope.org

FINESSE Mission to Investigate Atmospheres of Hundreds of Alien Worlds

FINESSE Mission to Investigate Atmospheres of Hundreds of Alien Worlds:

One of NASA’s proposed missions, known as the Fast INfrared Exoplanet Spectroscopy Survey Explorer (FINESSE) could greatly improve our understanding of extrasolar worlds. If selected for development, the spacecraft will investigate at least 500 exoplanet atmospheres, providing detailed information about climate processes on distant alien planets.

FINESSE has been recently chosen by NASA for concept studies and evaluations. It is one of the agency’s six astrophysics Explorers Program proposals that could be selected by 2019 to proceed with construction and launch.

The mission’s main objective is to study the processes that govern planet formation and global climate. It will investigate the mechanisms that establish atmospheric chemical composition and shape atmospheric evolution.

“FINESSE will spectroscopically observe the atmospheres of many hundreds of transiting exoplanets to measure their molecular abundances and thermal profiles,” Robert Zellem, FINESSE science team member at NASA’s Jet Propulsion Laboratory (JPL), told Astrowatch.net.

In order to conduct the planned studies, FINESSE will use the transit method. It will measure how a planet’s atmosphere absorbs light from its host star as a function of wavelength. This will allow to infer the molecules in the planet’s atmosphere.

“By doing this for hundreds of planets, FINESSE will determine how planets form and the crucial factors that establish planetary climate,” Zellem said.

These observations will require a proper imaging system. That is why the FINESSE spacecraft will be equipped in a telescope with a 75-centimeter (29.5-inch) primary mirror and a spectrometer that will observe planets in the visible and infrared wavelengths (from 0.5 to 5 microns).

According to Zellem, wide spectral coverage will enable FINESSE to measure the abundances of molecules such as water, methane, carbon dioxide, and carbon monoxide as well as look for the presence of clouds and hazes.

Data collected by the spacecraft are expected to provide important information that could improve our knowledge about various exoplanets, from rocky terrestrial planets to gas giants like Jupiter. FINESSE could help us discover what these alien worlds are like, determining what makes them they way they are, and allowing this knowledge to be applied in the broader planetary context, including the search for life outside of our Solar System.

If selected for the development, FINESSE is targeted for the launch around 2023. Zellem hopes that during its operational lifetime of two years it will carry out important observations of even more than 1,000 extrasolar worlds.

“FINESSE has the capability in its two year mission to observe the atmospheres of over 1000 transiting exoplanets,” he concluded.

Small Asteroid 2017 QB35 Flies by Earth

Small Asteroid 2017 QB35 Flies by Earth:

A newly spotted asteroid, designated 2017 QB35, flew by Earth on Sunday, September 3, missing our planet at a distance of 0.93 lunar distances (LD), or 345,600 kilometers. The space rock flew by Earth at 8:40 UTC with a relative velocity of 4.1 km/s.

2017 QB35 was discovered on August 31, 2017 by the Mount Lemmon Survey (MLS), which uses a 1.52 m cassegrain reflector telescope at Mount Lemmon Observatory in Arizona. MLS is one of the most prolific surveys when it comes to discovering new NEOs. It has detected more than 50,000 minor planets to date.

2017 QB35 is an Aten-type asteroid with and an absolute magnitude of 29.3 and an estimated diameter between 2 and 8 meters. The object has a semimajor axis of 0.93 AU and an orbital period of 326 days.

Next close approach of 2017 QB35 will occur on June 4, 2025, when it will pass by our planet at a much larger distance of about 100 LD.

Currently, there are 1,803 Potentially Hazardous Asteroids (PHAs) detected, however none of them is on a collision course with our planet. PHAs are asteroids larger than 100 meters that can come closer to Earth than 19.5 LD.

Stellar Corpse Sheds Light on Origin of Cosmic Rays

Stellar Corpse Sheds Light on Origin of Cosmic Rays:

The origin of cosmic rays, high-energy particles from outer space unceasingly impinging on Earth, is among the most challenging open questions in astrophysics. Discovered more than 100 years ago and considered a potential health risk to airplane crews and astronauts, cosmic rays are believed to be produced by shock waves — for example, those resulting from supernovae explosions. The most energetic cosmic rays streaking across the universe carry 10 to 100 million times the energy generated by particle colliders such as the Large Hadron Collider at CERN. New research published in the Monthly Notices of the Royal Astronomical Society sheds new light on the origin of those energetic particles.

"The new result represents a significant advance in our understanding of particle acceleration at shock waves, traditionally regarded as the main sources of energetic particles in the universe," said the study's lead author, Federico Fraschetti, a staff scientist at the University of Arizona's Departments of Planetary Sciences and Astronomy.

The Crab Nebula, remnant of a supernova explosion that was observed almost 1,000 years ago, is one of the best studied objects in the history of astronomy and a known source of cosmic rays. It emits radiation across the entire electromagnetic spectrum, from gamma rays, ultraviolet and visible light, to infrared and radio waves. 

"Most of what we observe comes from very energetic particles such as electrons that did not yet leave the source," said Fraschetti. "Since we can only observe the electromagnetic radiation that they emit from the source itself, we rely on models to reproduce the radiation spectrum we see from the nebula."

The new study, co-authored by Martin Pohl at the University of Potsdam, Germany, revealed that the entire zoo of electromagnetic radiation streaming from the Crab Nebula can arise from a single population of electrons, previously deemed impossible, and that they originate in a different way than scientists have traditionally thought. 

According to the generally accepted model, once the particles reach the shock, they bounce back and forth many times due to the magnetic turbulence. During this process they gain energy — in a similar way to a tennis ball being bounced between two rackets that are steadily moving nearer to each other — and are pushed closer and closer to the speed of light. Such a model follows an idea introduced by Italian physicist Enrico Fermi in 1949.

"The current models do not include what happens when the particles reach their highest energy," said Federico Fraschetti. "Only if we include a different process of acceleration can we explain the entire electromagnetic spectrum we see, and that tells us that while the shock wave still is the source of the acceleration of the particles, the mechanisms must be different."

At the heart of the Crab Nebula lies a pulsar, a rapidly rotating neutron star originating from the explosion of a star a few times more massive than the sun. When it exploded, the star shredded its outer layers, creating the stunning colorscape that makes the Crab Nebula so popular with professional and amateur astronomers. The pulsar emits a wind of electrons and positrons traveling at what astrophysicists call relativistic speed — close to the speed of light. 

"Those particles are the fastest things in the universe," Fraschetti said. "Anything we experience in our everyday lives is very far from relativistic effects. But these highly energetic particles still need to be accelerated even more to produce the electromagnetic radiation that we see coming from the Crab Nebula."

That acceleration, scientists believe, happens at a boundary called the termination shock, where the particle wind slams into the cloud of gas and dust that the star blew off into space when it went supernova. 

Except that just when the particles become energetic enough to leave the system and become cosmic radiation, they go beyond the limits of the models traditionally used to account for the origin of cosmic radiation, Fraschetti and Pohl found. The authors conclude that a better understanding is needed of how particles are accelerated in cosmic sources, and how the acceleration works when the energy of the particles become very large.

Several NASA missions, including ACE, STEREO and WIND, are dedicated to studying the effects of shocks caused by plasma explosions on the surface of the sun as they travel to Earth. Scientists hope that results from those experiments may shed light on the mechanisms of acceleration in objects such as the Crab Nebula.

Credit: arizona.edu

Jupiter’s Aurora Presents a Powerful Mystery

Jupiter’s Aurora Presents a Powerful Mystery:

Scientists on NASA’s Juno mission have observed massive amounts of energy swirling over Jupiter’s polar regions that contribute to the giant planet’s powerful aurora – only not in ways the researchers expected.

Examining data collected by the ultraviolet spectrograph and energetic-particle detector instruments aboard the Jupiter-orbiting Juno spacecraft, a team led by Barry Mauk of the Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, observed signatures of powerful electric potentials, aligned with Jupiter’s magnetic field, that accelerate electrons toward the Jovian atmosphere at energies up to 400,000 electron volts. This is 10 to 30 times higher than the largest auroral potentials observed at Earth, where only several thousands of volts are typically needed to generate the most intense aurora -- known as discrete aurora -- the dazzling, twisting, snake-like northern and southern lights seen in places like Alaska and Canada, northern Europe, and many other northern and southern polar regions.

Jupiter has the most powerful aurora in the solar system, so the team was not surprised that electric potentials play a role in their generation. What’s puzzling the researchers, Mauk said, is that despite the magnitudes of these potentials at Jupiter, they are observed only sometimes and are not the source of the most intense auroras, as they are at Earth.

“At Jupiter, the brightest auroras are caused by some kind of turbulent acceleration process that we do not understand very well,” said Mauk, who leads the investigation team for the APL-built Jupiter Energetic Particle Detector Instrument (JEDI). “There are hints in our latest data indicating that as the power density of the auroral generation becomes stronger and stronger, the process becomes unstable and a new acceleration process takes over. But we’ll have to keep looking at the data.”

Scientists consider Jupiter to be a physics lab of sorts for worlds beyond our solar system, saying the ability of Jupiter to accelerate charged particles to immense energies has implications for how more distant astrophysical systems accelerate particles. But what they learn about the forces driving Jupiter’s aurora and shaping its space weather environment also has practical implications in our own planetary backyard.

“The highest energies that we are observing within Jupiter’s auroral regions are formidable. These energetic particles that create the aurora are part of the story in understanding Jupiter’s radiation belts, which pose such a challenge to Juno and to upcoming spacecraft missions to Jupiter under development,” said Mauk. “Engineering around the debilitating effects of radiation has always been a challenge to spacecraft engineers for missions at Earth and elsewhere in the solar system. What we learn here, and from spacecraft like NASA’s Van Allen Probes and Magnetospheric Multiscale mission (MMS) that are exploring Earth’s magnetosphere, will teach us a lot about space weather and protecting spacecraft and astronauts in harsh space environments. Comparing the processes at Jupiter and Earth is incredibly valuable in testing our ideas of how planetary physics works.” 

Mauk and colleagues present their findings in the Sept. 7 issue of the journal Nature.

NASA’s Jet Propulsion Laboratory, Pasadena, California, manages the Juno mission for the principal investigator, Scott Bolton, of the Southwest Research Institute in San Antonio. Juno is part of NASA’s New Frontiers Program, which is managed at NASA’s Marshall Space Flight Center in Huntsville, Alabama, for NASA’s Science Mission Directorate. Lockheed Martin Space Systems, Denver, built the spacecraft.

Credit: NASA

X-rays Reveal Temperament of Possible Planet-hosting Stars

X-rays Reveal Temperament of Possible Planet-hosting Stars:

A new X-ray study has revealed that stars like the Sun and their less massive cousins calm down surprisingly quickly after a turbulent youth. This result has positive implications for the long-term habitability of planets orbiting such stars.

A team of researchers used data from NASA’s Chandra X-ray Observatory and ESA’s XMM-Newton to see how the X-ray brightness of stars similar to the Sun behaves over time. The X-ray emission from a star comes from a thin, hot, outer layer, called the corona. From studies of solar X-ray emission, astronomers have determined that the corona is heated by processes related to the interplay of turbulent motions and magnetic fields in the outer layers of a star.

High levels of magnetic activity can produce bright X-rays and ultraviolet light from stellar flares. Strong magnetic activity can also generate powerful eruptions of material from the star’s surface. Such energetic radiation and eruptions can impact planets and could damage or destroy their atmospheres, as pointed out in previous studies, including Chandra work reported in 2011 and 2013.

Since stellar X-rays mirror magnetic activity, X-ray observations can tell astronomers about the high-energy environment around the star. The new study uses X-ray data from Chandra and XMM-Newton to show that stars like the Sun and their less massive cousins decrease in X-ray brightness surprisingly quickly.

Specifically, the researchers examined 24 stars that have masses similar to the Sun or less, and ages of a billion years or older. (For context, the Sun is 4.5 billion years old.) The rapid observed decline in X-ray brightness implies a rapid decline in energetic activity, which may provide a hospitable environment for the formation and evolution of life on any orbiting planets.

“This is good news for the future habitability of planets orbiting Sun-like stars, because the amount of harmful X-rays and ultraviolet radiation striking these worlds from stellar flares would be less than we used to think,” said Rachel Booth, a graduate student at Queen’s University in Belfast, UK, who led the study.

This result is different from other recent work on Sun-like and lower mass stars with ages less than a billion years. The new work shows that older stars drop in activity far more quickly than their younger counterparts.

“We’ve heard a lot about the volatility of stars less massive than the Sun, like TRAPPIST-1 and Proxima Centauri, and how that’s bad for life-supporting atmospheres on their planets,” said Katja Poppenhaeger, a co-author from Queen’s University and the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass. “It’s refreshing to have some good news to share about potential habitability.”

To understand how quickly stellar magnetic activity level changes over time, astronomers need accurate ages for many different stars. This is a difficult task, but new precise age estimates have recently become available from studies of the way that a star pulsates using NASA’s Kepler and ESA’s CoRoT missions. These new age estimates were used for most of the 24 stars studied here.

Astronomers have observed that most stars are very magnetically active when they are young, since the stars are rapidly rotating. As the rotating star loses energy over time, the star spins more slowly and the magnetic activity level, along with the associated X-ray emission, drops.

“We’re not exactly sure why older stars settle down relatively quickly,” said co-author Chris Watson of Queen’s University. “However, we know it’s led to the successful formation of life in at least one case – around our own Sun.”

One possibility is that the decrease in rate of spin of the older stars occurs more quickly than it does for the younger stars. Another possibility is that the X-ray brightness declines more quickly with time for older, more slowly rotating stars than it does for younger stars.

A paper describing these results has been accepted for publication in the Monthly Notices of the Royal Astronomical Society, and is available online. The other co-authors are Victor Silva Aguirre from Aarhus University in Denmark and Scott Wolk from CfA.

NASA’s Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA’s Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra’s science and flight operations.

Credit: NASA

Earth as Hybrid Planet: New Classification Scheme Places Anthropocene Era in Astrobiological Context

Earth as Hybrid Planet: New Classification Scheme Places Anthropocene Era in Astrobiological Context:

For decades, as astronomers have imagined advanced extraterrestrial civilizations, they categorized such worlds by the amount of energy their inhabitants might conceivably be able to harness and use. They sorted the hypothetical worlds into three types according to a scheme named in 1964 for Soviet astronomer Nikolai Kardashev. A Type 1 civilization could manipulate all the energy resources of its home planet (a distant goal yet for Earth) and Type 2 all the energy in its star/planetary system. A super-advanced Type 3 civilization would command the energy of its whole home galaxy. The Kardashev Scale has since become a sort of gold standard for dreaming about possible civilizations beyond Earth.

Now, a team of researchers including Marina Alberti of the University of Washington has devised a new classification scheme for the evolutionary stages of worlds based on “non-equilibrium thermodynamics” — a planet’s energy flow being out of synch, as the presence of life could cause. The categories range from imagined planets with no atmosphere whatsoever to those with an “agency-dominated biosphere” or even a “technosphere,” reflecting the achievements of a vastly advanced, “energy-intensive technological species.”

Their paper, “Earth as a Hybrid Planet: The Anthropocene in an Evolutionary Astrobiological Context,” was published Sept. 6 in the journal Anthropocene. Lead author is Adam Frank, professor of physics and astronomy at the University of Rochester. Alberti is a professor of urban design and planning in the UW College of Built Environments, and director of the college’s Urban Ecology Research Lab.

The new classification system, the researchers say, is a way of thinking about sustainability on a planetary scale in what is being recognized as the Anthropocene epoch — the geological period of humanity’s significant impact on Earth and its ecosystems. Alberti contends in her research that humans and the urban areas we create are having a strong, planetwide effect on evolution.

“Our premise is that Earth’s entry into the Anthropocene represents what might, from an astrobiological perspective, be a predictable planetary transition,” they write. “We explore this problem from the perspective of our own solar system and exoplanet studies.

“In our perspective, the beginning of the Anthropocene can be seen as the onset of the hybridization of the planet — a transitional stage from one class of planetary systems to another.”

That would be, in their scheme, Earth’s possible transition from Class IV — marked by a thick biosphere and life having some effect on the planet — to the final Class V, where a planet is profoundly affected by the activity of an advanced, energy-intensive species.

The classification scheme, the researchers write, is based on “the magnitude by which different planetary processes — abiotic, biotic and technologic — generate free energy, i.e. energy that can perform work within the system.”

• Class I represents worlds with no atmosphere at all, such as the planet Mercury and the Earth’s moon.
• Class II planets have a thin atmosphere containing greenhouse gases, but no current life, such as the current states of planets Mars and Venus.
• Class III planets have perhaps a thin biosphere and some biotic activity, but much too little to “affect planetary drivers and alter the evolutionary state of the planet as a whole.” No current examples exist in the solar system, but early Earth may have represented such a world — and possibly early Mars, if life ever flickered there in the distant past.
• Class IV planets have a thick biosphere sustained by photosynthetic activity and life has begun strongly affecting the planetary energy flow.

Alberti said, “The discovery of seven new exoplanets orbiting the relatively close star TRAPPIST-1 forces us to rethink life on Earth. It opens the possibility to broaden our understanding of coupled system dynamics and lay the foundations to explore a path to long-term sustainability by entering into a cooperative ecological-evolutionary dynamic with the coupled planetary systems.”

The researchers write, “Our thesis is that the development of long-term sustainable, versions of an energy-intensive civilization must be seen on a continuum of interactions between life and its host planet.”

The classifications lay the groundwork, they say, for future research on the “co-evolution” of planets along that continuum.

“Any world hosting a long-lived energy-intensive civilization must share at least some similarities in terms of the thermodynamic properties of the planetary system,” they write. “Understanding these properties, even in the broadest outlines, can help us understand which direction we must aim our efforts in developing a sustainable human civilization.”

In other words, they added, “If one does not know where one is going, it’s hard to get there.”

Co-author on the paper is Axel Kleidon of the Max Planck Institute for Biogeochemistry in Jena, Germany.

Credit: washington.edu

Accretion-Powered Pulsar Reveals Unique Timing Glitch

Accretion-Powered Pulsar Reveals Unique Timing Glitch:

The discovery of the largest timing irregularity yet observed in a pulsar is the first confirmation that pulsars in binary systems exhibit the strange phenomenon known as a ‘glitch’. The study is published in the journal Monthly Notices of the Royal Astronomical Society.

Pulsars are one possible result of the final stages of evolution of massive stars. Such stars end their lives in huge supernova explosions, ejecting their stellar materials outwards into space and leaving behind an extremely dense and compact object; this could either be a white dwarf, a neutron star or a black hole.

If a neutron star is left, it may have a very strong magnetic field and rotate extremely quickly, emitting a beam of light that can be observed when the beam points towards Earth, in much the same way as a lighthouse beam sweeping past an observer. To the observer on Earth, it looks as though the star is emitting pulses of light, hence the name ‘pulsar’.

Now a group of scientists from the Middle East Technical University and Başkent University in Turkey have discovered a sudden change in the rotation speed of the peculiar pulsar SXP 1062. These jumps in frequency, known as ‘glitches’, are commonly seen in isolated pulsars, but have so far never been observed in binary pulsars (pulsars orbiting with a companion white dwarf or neutron star) such as SXP 1062.

SXP 1062 is located in the Small Magellanic Cloud, a satellite galaxy of our own Milky Way galaxy, and one of our nearest intergalactic neighbors at 200,000 light years away. Lead author of the study, Mr M. Miraç Serim, a senior PhD student working under the supervision of Prof Altan Baykal, said, “This pulsar is particularly interesting, since as well as orbiting its partner star as part of a binary pair, it is also still surrounded by the remnants of the supernova explosion which created it.”

The pulsar is thought to pull in the leftover material from the supernova explosion, feeding on it in a process known as accretion. The team believe that the size of the glitch is due to the gravitational influence of its companion star and this accretion of the surrounding remnant material, which together exert large forces on the crust of the neutron star. When these forces are no longer sustainable, a rapid change in internal structure transfers momentum to the crust, changing the rotation of the pulsar very suddenly and producing a glitch.

“The fractional frequency jump observed during this glitch is the largest, and is unique to this particular pulsar”, commented Dr Şeyda Şahiner, a co-author of the study. “The size of the glitch indicates that the interiors of neutron stars in binary systems may be quite different to the interiors of isolated neutron stars.”

This work was initially presented in 2017 at the European Week of Astronomy and Space Science, which will be held next year in Liverpool jointly with the UK National Astronomy Meeting. The work will be followed up with NASA’s Neutron Star Interior Composition Explorer (NICER) mission, launched in June this year – the team hope that the finding may lead to a better understanding of the interior of the neutron stars, putting new constraints on the neutron star equation of state.

Credit: ras.org.uk

Exchanges of Identity in Deep Space

Exchanges of Identity in Deep Space:

Like in a nail-biting thriller full of escapes and subterfuge, photons from far-off light sources, such as blazars, could go up against a continuous exchange of identity in their journey through the Universe. This is an operation that would allow these very tiny particles of light to escape an enemy which, if encountered, would annihilate them.

This is the phenomenon studied by a group of researchers from the University of Salento, Bari, the National Institute for Nuclear Physics (INFN), the National Institute for Astrophysics (INAF) and SISSA thanks to brand new simulation models that reproduce the complexity of the cosmos as never before. Normally, very high energy photons (gamma rays) should "collide" with the background light emitted by galaxies transformed into pairs of matter and antimatter particles, as envisaged by the Theory of Relativity. For this reason, the sources of very high energy gamma rays should appear significantly less bright than what is observed in many cases.

A possible explanation for this surprising anomaly is that light photons are transformed into hypothetical weakly-interacting particles, "axions" which, in turn, would change into photons, all due to the interaction with magnetic fields. With these metamorphoses, a part of the photons would escape interaction with the intergalactic background light that would make them disappear. The importance of this process is emphasized by the study published on Physical Review Letters, which re-created an extremely refined model of the Cosmic Web, a network of filaments composed of gas and dark matter present throughout the Universe and of its magnetic fields. The aforementioned effects are now awaiting comparison with those obtained experimentally through Cherenkov Telescope Array new generation telescopes.

In this research, through complex and unprecedented computer simulations made at the CSCS Supercomputing Centre in Lugano, scholars have reproduced the so-called Cosmic Web and the magnetic fields associated with this to investigate the possibility, advanced from previous theories, that photons from a light source are transformed into axions, hypothetical elementary particles, on interacting with an extragalactic magnetic field. Axions could then be retransformed into photons by interacting with other magnetic fields. 

Researchers Daniele Montanino, Franco Vazza, Alessandro Mirizzi and Matteo Viel explain: "Photons from luminous bodies disappear when they encounter extragalactic background light (EBL). But if on their journey they head into these transformations as envisaged by these theories, it would explain why, in addition to giving very important information on processes that occur in the universe, distant celestial bodies are brighter than expected from an observation on Earth. These changes would, in fact, enable a greater number of photons to reach the Earth".

In the simulations made by scientists, thanks to the wealth of magnetic fields present in the Cosmic Web's filaments recreated with the simulations, the conversion phenomenon would seem much more relevant than predicted by previous models: "Our simulations reproduce a very realistic picture of the cosmos' structure. From what we have observed, the distribution of the Cosmic Web envisaged by us would markedly increase the probability of these transformations".

The next step in the research? To compare simulation results with the experimental data obtained through the use of the Cherenkov Telescope Array Observatories detectors, the new-generation astronomical observatories, one of which is positioned in the Canary Islands and the other in Chile, that will study the Universe through very high energy gamma rays.

Credit: sissa.it

Ultraviolet Light from Superluminous Supernova Key to Revealing Explosion Mechanism

Ultraviolet Light from Superluminous Supernova Key to Revealing Explosion Mechanism:

An international team of researchers has discovered a way to use observations at ultraviolet (UV) wavelengths to uncover characteristics about superluminous supernovae previously impossible to determine, reports a new study published in Astrophysical Journal Letters on August 3, 2017.

The team, led by Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) Project Researcher Alexey Tolstov, studies stellar explosions called Superluminous Supernovae (SLSNe), an extra bright type of supernova discovered in the last decade that is 10 to 100 times brighter than ordinary supernovae. Recently, the team came upon Gaia16apd in a faint dwarf galaxy 1.6 billion light years away.

This SLSNe had an extraordinary UV-bright emission for a supernova of its kind, but no one could explain what explosion mechanism could produce that feature. Theorists have debated that Gaia16apd could fit one of three SLSNe scenarios. These are the pair-instability supernova, having a large mass of radioactive Nickel-56, or a magnetar-powered supernova where there would be a rapidly spinning and highly magnetized neutron star as an additional energy source, or a shock-interacting supernova where the supernova ejecta would interact with the surrounding dense circumstellar matter.

Researchers from Kavli IPMU therefore decided to simulate each model using multicolor radiation hydrodynamics to study light in different colors and ranges of wavelengths and see whether any of the simulations matched with the observed supernova. These simulations produced ultraviolet, visible-light and infrared light curves, photospheric radius and velocity, making it possible to investigate the appearance of the explosion at any wavelength.

Not only did they discover that Gaia16apd was most likely a shock-interacting supernova, Tolstov and his team found a way to model three different scenarios at UV wavelengths using the same numerical technique. In the future, their technique could help researchers in identifying the explosion mechanism of supernova they observe.

“The current study makes one more step to the understanding of the physics of superluminous supernova and helps to identify the scenario of the explosion. The observations and more detailed modeling of the peculiar objects similar to Gaia16apd are highly in demand to find out the nature of the phenomenon of superluminous supernovae,” said Tolstov.

The next step in their research will be to apply simulations on other SLSNe, and make more realistic models by considering the asymmetry of the explosion and physics of the magnetar-powered supernova.

Credit: ipmu.jp

Scientists Produce Unique Simulation of Magnetic Reconnection

Scientists Produce Unique Simulation of Magnetic Reconnection:

Jonathan Ng, a Princeton University graduate student at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL), has for the first time applied a fluid simulation to the space plasma process behind solar flares northern lights and space storms. The model could lead to improved forecasts of space weather that can shut down cell phone service and damage power grids, as well as to better understanding of the hot, charged plasma gas that fuels fusion reactions.

The new simulation captures the physics of magnetic reconnection, the breaking apart and snapping together of the magnetic field lines in plasma that occurs throughout the universe. The simulations approximate kinetic effects in a fluid code, which treats plasma as a flowing liquid, to create a more detailed picture of the reconnection process. 

Previous simulations used fluid codes to produce simplified descriptions of reconnection that takes place in the vastness of space, where widely separated plasma particles rarely collide. However, this collisionless environment gives rise to kinetic effects on plasma behavior that fluid models cannot normally capture.

The new simulation estimates kinetic behavior. “This is the first application of this particular fluid model in studying reconnection physics in space plasmas,” said Ng, lead author of the findings reported in August in the journal Physics of Plasmas.

Ng and coauthors approximated kinetic effects with a series of fluid equations based on plasma density, momentum and pressure. They concluded the process through a mathematical technique called “closure” that enabled them to describe the kinetic mixing of particles from non-local, or large-scale, regions. The type of closure involved was originally developed by PPPL physicist Greg Hammett and the late Rip Perkins in the context of fusion plasmas, making its application to the space plasma environment an example of fruitful cross-fertilization.

The completed results agreed better with kinetic models as compared with simulations produced by traditional fluid codes. The new simulations could extend understanding of reconnection to whole regions of space such as the magnetosphere, the magnetic field that surrounds the Earth, and provide a more comprehensive view of the universal process.

Coauthoring the paper were physicists Ammar Hakim of PPPL and Amitava Bhattacharjee, head of the Theory Department at PPPL and a professor of astrophysical sciences at Princeton University, together with physicists Adam Stanier and William Daughton of Los Alamos National Laboratory. Support for this work comes from the DOE Office of Science, the National Science Foundation and NASA. Computation was performed at the National Energy Research Scientific Computer Center, a DOE Office of Science User Facility, and the University of New Hampshire.

Credit: pppl.gov

Are We Being Watched? Tens of Other Worlds Could Spot the Earth

Are We Being Watched? Tens of Other Worlds Could Spot the Earth:

A group of scientists from Queen’s University Belfast and the Max Planck Institute for Solar System Research in Germany have looked at how an alien observer might be able to detect Earth using our own methods. They find that at least nine exoplanets are ideally placed to observe transits of Earth, in a new work published in the journal Monthly Notices of the Royal Astronomical Society.

Thanks to facilities and missions such as SuperWASP and Kepler, we have now discovered thousands of planets orbiting stars other than our Sun, worlds known as ‘exoplanets’. The vast majority of these are found when the planets cross in front of their host stars in what are known as ‘transits’, which allow astronomers to see light from the host star dim slightly at regular intervals every time the planet passes between us and the distant star.

In the new study, the authors reverse this concept and ask, “How would an alien observer see the Solar System?” They identified parts of the distant sky from where various planets in our Solar System could be seen to pass in front of the Sun – so-called ‘transit zones’ -- concluding that the terrestrial planets (Mercury, Venus, Earth, and Mars) are actually much more likely to be spotted than the more distant ‘Jovian’ planets (Jupiter, Saturn, Uranus, and Neptune), despite their much larger size.

”Larger planets would naturally block out more light as they pass in front of their star”, commented lead author Robert Wells, a PhD student at Queen’s University Belfast. ”However the more important factor is actually how close the planet is to its parent star – since the terrestrial planets are much closer to the Sun than the gas giants, they’ll be more likely to be seen in transit.”

To look for worlds where civilizations would have the best chance of spotting our Solar System, the astronomers looked for parts of the sky from which more than one planet could be seen crossing the face of the Sun. They found that three planets at most could be observed from anywhere outside of the Solar System, and that not all combinations of three planets are possible.

Katja Poppenhaeger, a co-author of the study, added: “We estimate that a randomly positioned observer would have roughly a 1 in 40 chance of observing at least one planet. The probability of detecting at least two planets would be about ten times lower, and to detect three would be a further ten times smaller than this.”

Of the thousands of known exoplanets, the team identified sixty-eight worlds where observers would see one or more of the planets in our Solar System transit the Sun. Nine of these planets are ideally placed to observe transits of Earth, although none of the worlds are deemed to be habitable.

In addition, the team estimate that there should be approximately ten (currently undiscovered) worlds which are favorably located to detect the Earth and are capable of sustaining life as we know it. To date however, no habitable planets have been discovered from which a civilization could detect the Earth with our current level of technology.

The ongoing K2 mission of NASA’s Kepler spacecraft is to continue to hunt for exoplanets in different regions of the sky for a few months at a time. These regions are centered close to the plane of Earth’s orbit, which means that there are many target stars located in the transit zones of the Solar System planets. The team’s plans for future work include targeting these transit zones to search for exoplanets, hopefully finding some which could be habitable.

Credit: qub.ac.uk

Large Asteroid to Fly by Earth Today

Large Asteroid to Fly by Earth Today:

Large near-Earth object (NEO), designated 2017 OP68, will fly by our planet today, missing the Earth at a distance of about 19.9 lunar distances (LD), or 7.6 million kilometers. The close approach is expected to occur at 18:25 UTC, when the space rock will whiz by our planet with a velocity of 11.7 km/s.

2017 OP68 is an Amor-type asteroid first spotted on July 25, 2017 by NASA’s Wide-field Infrared Survey Explorer (WISE). WISE is infrared-wavelength astronomical space telescope that has discovered thousands of minor planets.

Astronomers reveal that 2017 OP68 has an absolute magnitude of 20.6 and a diameter between 150 and 470 meters. The asteroid has an orbital period of nearly four years and a semimajor axis of about 2.5 AU.

Next close approach of 2017 OP68 to Earth is expected to take place on July 17, 2021, when it will pass by our planet at a much larger distance of 131 LD (50.3 million kilometers).

On September 10, 2017, there were 1,803 potentially hazardous asteroids (PHAs) discovered to date. PHAs are space rocks larger than approximately 100 meters that can come closer to Earth than 19.5 LD. However, none of the known PHAs is on a collision course with our planet.

Explosive Birth of Stars Swells Galactic Cores

Explosive Birth of Stars Swells Galactic Cores:

Astronomers found that active star formation upswells galaxies, like yeast helps bread rise. Using three powerful telescopes on the ground and in orbit, they observed galaxies from 11 billion years ago and found explosive formation of stars in the cores of galaxies. This suggests that galaxies can change their own shape without interaction with other galaxies.

"Massive elliptical galaxies are believed to be formed from collisions of disk galaxies," said Ken-ichi Tadaki, the lead author of two research papers and a postdoctoral researcher at the National Astronomical Observatory of Japan (NAOJ). "But, it is uncertain whether all the elliptical galaxies have experienced galaxy collision. There may be an alternative path."

Aiming to understand galactic metamorphosis, the international team explored distant galaxies 11 billion light-years away. Because it takes time for the light from distant objects to reach us, by observing galaxies 11 billion light-years away, the team can see what the Universe looked like 11 billion years ago, 3 billion years after the Big Bang. This corresponds the peak epoch of galaxy formation; the foundations of most galaxies were formed in this epoch.

Receiving faint light which has traveled 11 billion years is tough work. The team harnessed the power of three telescopes to anatomize the ancient galaxies. First, they used NAOJ's 8.2-m Subaru Telescope in Hawai`i and picked out 25 galaxies in this epoch. Then they targeted the galaxies for observations with NASA/ESA's Hubble Space Telescope (HST) and the Atacama Large Millimeter/submillimeter Array (ALMA). The astronomers used HST to capture the light from stars which tells us the "current" (as of when the light was emitted, 11 billion years ago) shape of the galaxies, while ALMA observed submillimeter waves from cold clouds of gas and dust, where new stars are being formed. By combining the two, we know the shapes of the galaxies 11 billion years ago and how they are evolving.

Thanks to their high resolution, HST and ALMA could illustrate the metamorphosis of the galaxies. With HST images the team found that a disk component dominates the galaxies. Meanwhile, the ALMA images show that there is a massive reservoir of gas and dust, the material of stars, so that stars are forming very actively. The star formation activity is so high that huge numbers of stars will be formed at the centers of the galaxies. This leads the astronomers to think that ultimately the galaxies will be dominated by the stellar bulge and become elliptical or lenticular galaxies.

"Here, we obtained firm evidence that dense galactic cores can be formed without galaxy collisions. They can also be formed by intense star formation in the heart of the galaxy." said Tadaki. The team used the European Southern Observatory's Very Large Telescope to observe the target galaxies and confirmed that there are no indications of massive galaxy collisions.

Almost 100 years ago, American astronomer Edwin Hubble invented the morphological classification scheme for galaxies. Since then, many astronomers have devoted considerable effort to understanding the origin of the variety in galaxy shapes. Utilizing the most advanced telescopes, modern astronomers have come one step closer to solving the mysteries of galaxies.

Credit: alma-telescope.jp

Galaxies Swell due to Explosive Action of New Stars

Galaxies Swell due to Explosive Action of New Stars:

In 1926, famed astronomer Edwin Hubble developed his morphological classification scheme for galaxies. This method divided galaxies into three basic groups – Elliptical, Spiral and Lenticular – based on their shapes. Since then, astronomers have devoted considerable time and effort in an attempt to determine how galaxies have evolved over the course of billions of years to become these shapes.

One of th most widely-accepted theories is that galaxies changed by merging, where smaller clouds of stars – bound by mutual gravity – came together, altering the size and shape of a galaxy over time. However, a new study by an international team of researchers has revealed that galaxies could actually assumed their modern shapes through the formation of new stars within their centers.

The study, titled “Rotating Starburst Cores in Massive Galaxies at z = 2.5“, was recently published in the Astrophysical Journal Letters. Led by Ken-ichi Tadaki – a postdoctoral researcher with the Max Planck Institute for Extraterrestrial Physics and the National Astronomical Observatory of Japan (NAOJ) – the team conducted observations of distant galaxies in order to get a better understanding of galactic metamorphosis.

Evolution diagram of a galaxy. First the galaxy is dominated by the disk component (left) but active star formation occurs in the huge dust and gas cloud at the center of the galaxy (center). Then the galaxy is dominated by the stellar bulge and becomes an elliptical (or lenticular) galaxy. Credit: NAOJ

This involved using ground-based telescopes to study 25 galaxies that were at a distance of about 11 billion light-years from Earth. At this distance, the team was seeing what these galaxies looked like 11 billion years ago, or roughly 3 billion years after the Big Bang. This early epoch coincides with a period of peak galaxy formation in the Universe, when the foundations of most galaxies were being formed. As Dr. Tadaki indicated in a NAOJ press release:

“Massive elliptical galaxies are believed to be formed from collisions of disk galaxies. But, it is uncertain whether all the elliptical galaxies have experienced galaxy collision. There may be an alternative path.”

Capturing the faint light of these distant galaxies was no easy task and the team needed three ground-based telescopes to resolve them properly. They began by using the NAOJ’s 8.2-m Subaru Telescope in Hawaii to pick out the 25 galaxies in this epoch. Then they targeted them for observations with the NASA/ESA Hubble Space Telescope (HST) and the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile.

Whereas the HST captured light from stars to discern the shape of the galaxies (as they existed 11 billion years ago), the ALMA array observed submillimeter waves  emitted by the cold clouds of dust and gas – where new stars are being formed. By combining the two, they were able to complete a detailed picture of how these galaxies looked 11 billion years ago when their shapes were still evolving.

Observation images of a galaxy 11 billion light-years away. Credit: ALMA (ESO/NAOJ/NRAO), NASA/ESA Hubble Space Telescope, Tadaki et al.

What they found was rather telling. The HST images indicated that early galaxies were dominated by a disk component, as opposed to the central bulge feature we’ve come to associate with spiral and lenticular galaxies. Meanwhile, the ALMA images showed that there were massive reservoirs of gas and dust near the centers of these galaxies, which coincided with a very high rate of star formation.

To rule out alternate possibility that this intense star formation was being caused by mergers, the team also used data from the European Southern Observatory’s Very Large Telescope (VLT) – located at the Paranal Observatory in Chile – to confirm that there were no indications of massive galaxy collisions taking place at the time. As Dr. Tadaki explained:

“Here, we obtained firm evidence that dense galactic cores can be formed without galaxy collisions. They can also be formed by intense star formation in the heart of the galaxy.”

These findings could lead astronomers to rethink their current theories about galactic evolution and howthey came to adopt features like a central bulge and spiral arms. It could also lead to a rethink of our models regarding cosmic evolution, not to mention the history of own galaxy. Who knows? It might even cause astronomers to rethink what might happen in a few billion years, when the Milky Way is set to collide with the Andromeda Galaxy.

As always, the further we probe into the Universe, the more it reveals. With every revelation that does not fit our expectations, our hypotheses are forced to undergo revision.

Further Reading: ALMA, Astrophysical Journal Letters

The post Galaxies Swell due to Explosive Action of New Stars appeared first on Universe Today.

Astronomers create best ever image of star outside our Solar System

Astronomers create best ever image of star outside our Solar System:

Using ESO’s Very Large Telescope Interferometer astronomers have constructed this image of the red supergiant star Antares. This is the most detailed image ever of this object, or any other star apart from the Sun. Image & Caption Credit: K. Ohnaka / ESO

A map of activity on the surface and in the atmosphere of the star Antares by a team of astronomers is considered to be the most detailed ever created for a star other than the Sun. The red supergiant is located some 550 light-years distant in the constellation Scorpius and is in its final stages of its existence. It will eventually die in a supernova explosion.

While Antares likely started its life with about 15 times the mass of our Sun, it is now shedding mass and is estimated to have lost about three solar masses. Its current diameter is approximately 700 times that of the Sun.

Researchers led by Keiichi Ohnaka of the Universidad Catolico del Norte in Chile used the European Southern Observatory’s (ESO) Very Large Telescope Interferometer (VLTI) at Paranal Observatory to map the surface of the luminous, low-density star and measure the speed at which surface material is moving.

The VLTI is an instrument composed of several telescopes that create the equivalent of a single large telescope with a mirror boasting a diameter up to 656 feet (200 meters). It combines the light from as many as four telescopes, including either the 26.9-foot (8.2-meter) Unit Telescopes or the 5.9-foot (1.8-meter) Auxiliary Telescopes, enabling scientists to view the star in incredible detail.

This artist’s impression shows the red supergiant star Antares in the constellation of Scorpius. Image & Caption Credit: M. Kornmesser / ESO

Using three Auxiliary Telescopes along with the near-infrared AMBER instrument, astronomers imaged several locales on Antares’ surface in various infrared wavelengths to measure the speed at which gases are moving in these different regions and across the entire star. The technique yielded the most detailed map of surface activity by atmospheric gases on any star besides our Sun.

Ohnaka said a central goal of the study is to determine how stars like Antares lose so much mass at the end of their lives.

“The VLTI is the only facility that can directly measure the gas motions in the extended atmosphere of Antares – a crucial step towards clarifying this problem. The next challenge is to identify what’s driving the turbulent motions,” Ohnaka said.

This is the first such velocity map of any star other than the Sun. In red regions, the material is moving away from Earth, and in the blue areas, the material is approaching. The empty region around the star is not a real feature but shows where velocity measurements were not possible. Image & Caption Credit: K. Ohnaka / ESO

Low-density gas was discovered extending much further from the star than the researchers expected, leading them to conclude it was brought there by a process other than convection, which involves the transfer of energy from a star’s core to its outer atmosphere. Just what that process is remains unknown.

Other stars of various types will need to be studied using the technique astronomers used to map Antares in the same degree of detail for scientists to determine what that process is, Ohnaka said.

“Our work brings stellar astrophysics to a new dimension and opens an entirely new window to observe stars,” Ohnaka said.

Ohnaka is the lead author of a paper on the study published in the journal Nature.

This chart shows the constellation of Scorpius. At the heart of this grouping of stars lies the bright red supergiant star Antares. Image & Caption Credit: ESO / IAU / Sky & Telescope

This article was updated at 16:55 EDT on Aug. 27, 2017, with distance to Antares.



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