Matt Williams, Author at Universe Today

May 23, 2018 by Matt Williams

The Ant Nebula Actually has Intense Laser Emissions Coming From its Core

From ground-based telescopes, the so-called "ant nebula" (Menzel 3, or Mz 3) resembles the head and thorax of a garden-variety ant. This dramatic NASA/ESA Hubble Space Telescope image, showing 10 times more detail, reveals the "ant's" body as a pair of fiery lobes protruding from a dying, Sun-like star. Credit: NASA/ESA/Hubble Heritage Team (STScI/AURA)

When low- to middleweight stars like our Sun approach the end of their life cycles they eventually cast off their outer layers, leaving behind a dense, white dwarf star. These outer layers became a massive cloud of dust and gas, which is characterized by bright colors and intricate patterns, known as a planetary nebula. Someday, our Sun will turn into such a nebula, one which could be viewed from light-years away.

This process, where a dying star gives rise to a massive cloud of dust, was already known to be incredibly beautiful and inspiring thanks to many images taken by Hubble. However, after viewing the famous Ant Nebula with the European Space Agency’s (ESA) Herschel Space Observatory, a team of astronomers discovered an unusual laser emission that suggests that there is a double star system at the center of the nebula.

The study, titled “Herschel Planetary Nebula Survey (HerPlaNS): hydrogen recombination laser lines in Mz 3“, recently appeared in the Monthly Notices of the Royal Astronomical Society. The study was led by Isabel Aleman of the University of São Paulo and the Leiden Observatory, and included members from the Herschel Science Center, the Smithsonian Astrophysical Observatory, the Institute of Astronomy and Astrophysics, the Royal Observatory of Belgium and multiple universities.

*The life cycle of a Sun-like star, from its birth on the left side of the frame to its evolution into a red giant on the right after billions of years. Credit: ESO/M. Kornmesser*

The Ant Nebula (aka. Mz 3) is a young bipolar planetary nebula located in the constellation Norma, and takes its name from the twin lobes of gas and dust that resemble the head and body of an ant. In the past, this nebula’s beautiful and intricate nature was imaged by the NASA/ESA Hubble Space Telescope. The new data obtained by Herschel also indicates that the Ant Nebula beams intense laser emissions from its core.

In space, infrared laser emissions are detected at very different wavelengths and only under certain conditions, and only a few of these space lasers are known. Interestingly enough, it was astronomer Donald Menzel – who first observed and classified the Ant Nebula in 1920 (hence why it is officially known as Menzel 3 after him) – who was one of the first to suggest that lasers could occur in nebula.

According to Menzel, under certain conditions natural “light amplification by the stimulated emissions of radiation” (aka. where we get the term laser from) would occur in space. This was long before the discovery of lasers in laboratories, an occasion that is celebrated annually on May 16th, known as UNESCO’s International Day of Light. As such, it was highly appropriate that this paper was also published on May 16th, celebrating the development of the laser and its discoverer, Theodore Maiman.

As Isabel Aleman, the lead author of a paper, described the results:

“When we observe Menzel 3, we see an amazingly intricate structure made up of ionized gas, but we cannot see the object in its center producing this pattern. Thanks to the sensitivity and wide wavelength range of the Herschel observatory, we detected a very rare type of emission called hydrogen recombination line laser emission, which provided a way to reveal the nebula’s structure and physical conditions.”

Artist's impression of the Herschel Space Telescope. Credit: ESA/AOES Medialab/NASA/ESA/STScI — *Artist’s impression of the Herschel Space Telescope. Credit: ESA/AOES Medialab/NASA/ESA/STScI*

“Such emission has only been identified in a handful of objects before and it is a happy coincidence that we detected the kind of emission that Menzel suggested, in one of the planetary nebulae that he discovered,” she added.

The kind of laser emission they observed needs very dense gas close to the star. By comparing observations from the Herschel observatory to models of planetary nebula, the team found that the density of the gas emitting the lasers was about ten thousand times denser than the gas seen in typical planetary nebulae, and in the lobes of the Ant Nebula itself.

Normally, the region close to the dead star – in this case, roughly the distance between Saturn and the Sun – is quite empty because its material was ejected outwards after the star went supernova. Any lingering gas would soon fall back onto it. But as Professor Albert Zijlstra, from the Jodrell Bank Center for Astrophysics and a co-author on the study, put it:

“The only way to keep such dense gas close to the star is if it is orbiting around it in a disc. In this nebula, we have actually observed a dense disc in the very center that is seen approximately edge-on. This orientation helps to amplify the laser signal. The disc suggests there is a binary companion, because it is hard to get the ejected gas to go into orbit unless a companion star deflects it in the right direction. The laser gives us a unique way to probe the disc around the dying star, deep inside the planetary nebula.”

*The planetary nebula Abell 39. According to a new study, our Sun will similarly become a luminous planetary nebula by the end of its life cycle. Credit: WIYN/NOAO/NSF*

While astronomers have not yet seen the expected second star, they are hopeful that future surveys will be able to locate it, thus revealing the origin of the Ant Nebula’s mysterious lasers. In so doing, they will be able to connect two discoveries (i.e. planetary nebula and laser) made by the same astronomer over a century ago. As Göran Pilbratt, ESA’s Herschel project scientist, added:

“This study suggests that the distinctive Ant Nebula as we see it today was created by the complex nature of a binary star system, which influences the shape, chemical properties, and evolution in these final stages of a star’s life. Herschel offered the perfect observing capabilities to detect this extraordinary laser in the Ant Nebula. The findings will help constrain the conditions under which this phenomenon occurs, and help us to refine our models of stellar evolution. It is also a happy conclusion that the Herschel mission was able to connect together Menzel’s two discoveries from almost a century ago.”

Next-generation space telescopes that could tell us more about planetary nebula and the life-cycles of stars include the James Webb Space Telescope (JWST). Once this telescope takes to space in 2020, it will use its advanced infrared capabilities to see objects that are otherwise obscured by gas and dust. These studies could reveal much about the interior structures of nebulae, and perhaps shed light on why they periodically shoot out “space lasers”.

Further Reading: University of Manchester, ESA, MNRAS

May 20, 2018 by Matt Williams

The Pressure Inside Every Proton is 10x That Inside Neutron Stars

The first measurement of a subatomic particle’s mechanical property reveals the distribution of pressure inside the proton. Credit: DOE's Jefferson Lab

Neutron stars are famous for combining a very high-density with a very small radius. As the remnants of massive stars that have undergone gravitational collapse, the interior of a neutron star is compressed to the point where they have similar pressure conditions to atomic nuclei. Basically, they become so dense that they experience the same amount of internal pressure as the equivalent of 2.6 to 4.1 quadrillion Suns!

In spite of that, neutron stars have nothing on protons, according to a recent study by scientists at the Department of Energy’s Thomas Jefferson National Accelerator Facility. After conducting the first measurement of the mechanical properties of subatomic particles, the scientific team determined that near the center of a proton, the pressure is about 10 times greater than the pressure in the heart of a neutron star.

The study which describes the team’s findings, titled “The pressure distribution inside the proton“, recently appeared in the scientific journal Nature. The study was led by Volker Burkert, a nuclear physicist at the Thomas Jefferson National Accelerator Facility (TJNAF), and co-authored by Latifa Elouadrhiri and Francois-Xavier Girod – also from the TJNAF.

*Cross-section of a neutron star. Credit: Wikipedia Commons/Robert Schulze*

Basically , they found that the pressure conditions at the center of a proton were 100 decillion pascals – about 10 times the pressure at the heart of a neutron star. However, they also found that pressure inside the particle is not uniform, and drops off as the distance from the center increases. As Volker Burkert, the Jefferson Lab Hall B Leader, explained:

“We found an extremely high outward-directed pressure from the center of the proton, and a much lower and more extended inward-directed pressure near the proton’s periphery… Our results also shed light on the distribution of the strong force inside the proton. We are providing a way of visualizing the magnitude and distribution of the strong force inside the proton. This opens up an entirely new direction in nuclear and particle physics that can be explored in the future.”

Protons are composed of three quarks that are bound together by the strong nuclear force, one of the four fundamental forces that government the Universe – the other being electromagnetism, gravity and weak nuclear forces. Whereas electromagnetism and gravity produce the effects that govern matter on the larger scales, weak and strong nuclear forces govern matter at the subatomic level.

Previously, scientists thought that it was impossible to obtain detailed information about subatomic particles. However, the researchers were able to obtain results by pairing two theoretical frameworks with existing data, which consisted of modelling systems that rely on electromagnetism and gravity. The first model concerns generalized parton distributions (GDP) while the second involve gravitational form factors.

*Quarks inside a proton experience a force an order of magnitude greater than matter inside a neutron star. Credit: DOE’s Jefferson Lab*

Patron modelling refers to modeling subatomic entities (like quarks) inside protons and neutrons, which allows scientist to create 3D images of a proton’s or neutron’s structure (as probed by the electromagnetic force). The second model describes the scattering of subatomic particles by classical gravitational fields, which describes the mechanical structure of protons when probed via the gravitational force.

As noted, scientists previously thought that this was impossible due to the extreme weakness of the gravitational interaction. However, recent theoretical work has indicated that it could be possible to determine the mechanical structure of a proton using electromagnetic probes as a substitute for gravitational probes. According to Latifa Elouadrhiri – a Jefferson Lab staff scientist and co-author on the paper – that is what their team set out to prove.

“This is the beauty of it. You have this map that you think you will never get,” she said. “But here we are, filling it in with this electromagnetic probe.”

For the sake of their study, the team used the DOE’s Continuous Electron Beam Accelerator Facility at the TJNAF to create a beam of electrons. These were then directed into the nuclei of atoms where they interacted electromagnetically with the quarks inside protons via a process called deeply virtual Compton scattering (DVCS). In this process, an electron exchanges a virtual photon with a quark, transferring energy to the quark and proton.

*The bare masses of all 6 flavors of quarks, proton and electron, shown in proportional volume. Credit: Wikipedia/Incnis Mrsi*

Shortly thereafter, the proton releases this energy by emitting another photon while remaining intact. Through this process, the team was able to produced detailed information of the mechanics going on in inside the protons they probed. As Francois-Xavier Girod, a Jefferson Lab staff scientist and co-author on the paper, explained the process:

“There’s a photon coming in and a photon coming out. And the pair of photons both are spin-1. That gives us the same information as exchanging one graviton particle with spin-2. So now, one can basically do the same thing that we have done in electromagnetic processes — but relative to the gravitational form factors, which represent the mechanical structure of the proton.”

The next step, according to the research team, will be to apply the technique to even more precise data that will soon be released. This will reduce uncertainties in the current analysis and allow the team to reveal other mechanical properties inside protons – like the internal shear forces and the proton’s mechanical radius. These results, and those the team hope to reveal in the future, are sure to be of interest to other physicists.

“We are providing a way of visualizing the magnitude and distribution of the strong force inside the proton,” said Burkert. “This opens up an entirely new direction in nuclear and particle physics that can be explored in the future.”

Perhaps, just perhaps, it will bring us closer to understanding how the four fundamental forces of the Universe interact. While scientists understand how electromagnetism and weak and strong nuclear forces interact with each other (as described by Quantum Mechanics), they are still unsure how these interact with gravity (as described by General Relativity).

If and when the four forces can be unified in a Theory of Everything (ToE), one of the last and greatest hurdles to a complete understanding of the Universe will finally be removed.

Further Reading: Jefferson Lab, Cosmos Magazine, Nature

May 18, 2018 by Matt Williams

NASA Cubesat Takes a Picture of the Earth and Moon

The first image captured by one of NASA's Mars Cube One (MarCO) CubeSats. The image, which shows both the CubeSat's unfolded high-gain antenna at right and the Earth and its moon in the center, was acquired by MarCO-B on May 9. Credit: NASA/JPL-Caltech

In 1990, the Voyager 1 spaceprobe took a picture of Earth when it was about 6.4 billion km (4 billion mi) away. In this image, known as the “pale blue dot“, Earth and the Moon appeared as mere points of light because of the sheer distance involved. Nevertheless, it remains an iconic photo that not only showed our world from space, but also set long-distance record.

As it turns out, NASA set another long-distance record for CubeSats last week (on May. 8th, 2018) when a pair of small satellites called Mars Cube One (MarCO) reached a distance of 1 million km (621,371 mi) from Earth. On the following day, one of the CubeSats (MarCO-B, aka. “Wall-E”) used its fisheye camera to take its own “pale blue dot” photo of the Earth-Moon system.

The two CubeSats were launched on May 5th along with the Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) lander, which is currently on its way to Mars to explore the planet’s interior structure. As the first CubeSats to fly to deep pace, the purpose of the MarCO mission is to demonstrate if CubeSats are capable of acting as a relay with long-distance spacecraft.

*An artist’s rendering of the twin Mars Cube One (MarCO) spacecraft as they fly through deep space. Credit: NASA/JPL-Caltech*

To this end, the probes will be responsible for monitoring InSight as it makes its landing on Mars in late November, 2018. The photo of Earth and the Moon was taken as part of the process used by the engineering team to confirm that the spacecraft’s high-gain antenna unfolded properly. As Andy Klesh, MarCO’s chief engineer at NASA’s Jet Propulsion Laboratory, indicated in a recent NASA press release:

“Consider it our homage to Voyager. CubeSats have never gone this far into space before, so it’s a big milestone. Both our CubeSats are healthy and functioning properly. We’re looking forward to seeing them travel even farther.”

This technology demonstration, and the long-distance record recently set by MarCO satellites, provides a good indication of just how far CubeSats have come in the past few years. Originally, CubeSats were developed to teach university students about satellites, but have since become a major commercial technology. In addition to providing vast amounts of data, they have proven to be a cost-effective alternative to larger, multi-million dollar satellites.

The MarCO CubeSats will be there when the InSight lander accomplishes the most difficult part of its mission, which is entering Mars’ extremely thin atmosphere (which makes landings extremely challenging). As the lander travels to Mars, MarCO-A and B will travel along behind it and (should they make it all the way to Mars) radio back data about InSight as it enters the atmosphere and descends to the planet’s surface.

*Artist’s interpretation of the InSight mission on the ground on Mars. Credit: NASA*

The job of acting as a data relay will fall to NASA’s Mars Reconnaissance Orbiter (MRO), which has been in orbit of Mars since 2006. However, the MarCOs will also be monitoring InSight to see if future missions will be capable of bringing their own relay to Mars, rather than having to rely on an orbiter that is already there. They may also demonstrate a number of experimental technologies, which includes their radio and propulsion systems.

The main attraction though, are the high-gain antennas which will be providing information on InSights’ progress. At the moment, the team has received early confirmation that the antennas have successfully deployed, but they will continue to test them in the weeks ahead. If all goes according to plan, the MarCOs could demonstrate the ability of CubeSats to act not only as relays, but also their ability to gather information on other planets.

In other words, if the MarCOs are able to make it to Mars and track InSight’s progress, NASA and other agencies may contemplate mounting full-scale missions using CubeSats – sending them to the Moon, Mars, or even beyond. Later this month, the MarCOs will attempt their first trajectory correction maneuvers, which will be the first such maneuver are performed by CubeSats.

In the meantime, be sure to check out this video of the MarCO mission, courtesy of NASA 360:

Further Reading: NASA

May 17, 2018August 7, 2018 by Matt Williams

Are Mysterious Fast Radio Bursts Coming From the Collapse of Strange Star Crusts?

According to a new study, the strongest material in the Universe is the "nuclear pasta" found inside neutron stars. Credit: NASA/Goddard Space Flight Center

Fast Radio Bursts (FRBs) have fascinated astronomers ever since the first one was detected in 2007. This event was named the “Lorimer Burst” after it discoverer, Duncan Lorimer from West Virginia University. In radio astronomy, this phenomenon refers to transient radio pulses coming from distant cosmological sources, which typically last a few milliseconds on average.

Over two dozen events have been discovered since 2007 and scientists are still not sure what causes them – though theories range from exploding stars and black holes to pulsars and magnetars. However, according to a new study by a team of Chinese astronomers, FRBs may be linked to crusts forming around “strange stars”. According to a model they created, it is the collapse of these crusts that lead to high-energy bursts that can be seen light-years away.

The study, titled “Fast Radio Bursts from the collapse of Strange Star Crusts“, recently appeared in The Astrophysical Journal. The team was led by Yue Zhang of the School of Astronomy and Space Science (SASC) at Nanjing University and included Jin-Jun Geng and Yong-Feng Huang – a postdoc and professor from the SASC and the Key Laboratory of Modern Astronomy and Astrophysics (also at Nanjing University), respectively.

As they state in their study, all previous attempts to explain FRBs have been unable to resolve where these strange phenomena come from. What’s more, no counterparts in other wavebands have been detected for non-repeating FRBs so far and research into their origins has been confounded by the study of repeating FRBs. This is due to the fact that the former are often attributed to catastrophic events, which are incapable of repeating.

In the case of the FRBs, these catastrophic events include “magnetar giant flares, the collapses of magnetized supramassive rotating neutron stars, binary neutron star mergers, binary white dwarf mergers, collisions between neutron stars and asteroids/comets, collisions between neutron stars and white dwarfs, and evaporation of primordial black holes.”

Alternately, in the case of the repeating FRBs, various models suggest that these could be caused by “highly magnetized pulsars traveling through asteroid belts, neutron star-white dwarf binary mass transfer, and star quakes of pulsars.” For the sake of their study, the team proposed a new model whereby the build up and collapse of matter on certain types of neutron stars (aka. “strange stars”) could explain the behavior of FRBs. As they explain:

“It has been conjectured that strange quark matter (SQM), a kind of dense material composed of approximately equal numbers of up, down, and strange quarks, may have a lower energy per baryon than ordinary nuclear matter (such as 56 Fe) so that it may be the true ground state of hadronic matter. If this hypothesis is correct, then neutron stars (NSs) may actually be ‘strange stars'”.

*This artist’s impression of the cosmic web, the filamentary structure that fills the entire Universe, showing radio sources associated with FRBs. Credit: M. Weiss/CfA*

According to this model, strange stars build up a layer of hadronic (aka. “normal”) matter on their surface over time. As these SQM stars accrete matter from their environment, their crusts becomes heavier and heavier. Eventually, this leads the crust to collapse, leaving a hot and bare strange star that becomes a powerful source of electrons and positron pairs.

These pairs would then be released along with large amounts of magnetic energy over a very short timescale. The team further hypothesized that during a collapse, a fraction of magnetic energy would be transferred to the polar cap region of the SQM stars, where the magnetic field energy is released. This would cause the electrons and positrons to be accelerated to ultra-relativistic speeds, which would then expand along magnetic field lines to form a shell.

Beyond a certain distance from the star, coherent emission in radio bands will be produced, giving birth to an FRB event. They also theorize that this same phenomenon could give to rise to repeating FRBs. One possibility is that the crust of an SQM star could be reconstructed over time, thus allowing for repeated events. A second is that only small sections of crust collapse at any given time, thus resulting in repeated events.

As they conclude, further studies will be needed before this can be said either way:

Owing to this long reconstruction timescale, multiple FRB events from the same source seem not likely to happen in our scenario. Our model thus is more suitable for explaining the non- repeating FRBs… However, we should also note that during the collapse process, if only a small portion (in the polar cap region) of the crust falls onto the SQM core while the other portion of the crust remains stable, then the rebuilt timescale for the crust can be markedly reduced and repeating FRBs would still be possible.

*The CHIME telescope, a massive radio telescope located in Penticton, British Columbia. Credit: CHIME/DRAO*

Another thing that they claim will require further investigation is whether or not the collapse of a strange star’s crust could result in electromagnetic radiation other than radio waves. At present, any emissions in the X-ray and Gamma-ray bands would be too faint for current detectors to observe. For these reasons, further investigations of FRB sources with more sensitive instruments are needed.

These include the Canadian Hydrogen Intensity Mapping Experiment (CHIME) telescope – located in Penticton, British Columbia – and the Square Kilometer Array (SQA) currently under construction in South Africa and Australia. These facilities, which are optimized for radio astronomy, are expected to reveal a great deal more about FRBs and other mysterious cosmic phenomena.

Further Reading: arXiv

May 17, 2018 by Matt Williams

There was Evidence for Europa’s Geysers Hiding in Plain Sight in Old Spacecraft Data From 1997

Artist’s illustration of Jupiter and Europa (in the foreground) with the Galileo spacecraft after its pass through a plume erupting from Europa’s surface. Credits: NASA/JPL-Caltech/Univ. of Michigan

Jupiter’s moon Europa continues to fascinate and amaze! In 1979, the Voyager missions provided the first indications that an interior ocean might exist beneath it’s icy surface. Between 1995 and 2003, the Galileo spaceprobe provided the most detailed information to date on Jupiter’s moons to date. This information bolstered theories about how life could exist in a warm water ocean located at the core-mantle boundary.

Even though the Galileo mission ended when the probe crashed into Jupiter’s atmosphere, the spaceprobe is still providing vital information on Europa. After analyzing old data from the mission, NASA scientists have found independent evidence that Europa’s interior ocean is venting plumes of water vapor from its surface. This is good news for future mission to Europa, which will attempt to search these plumes for signs of life.

The study which describes their findings, titled “Evidence of a plume on Europa from Galileo magnetic and plasma wave signatures“, recently appeared in the journal Nature Astronomy. The study was led by Xianzhe Jia, a space physicist from the Department of Climate and Space Sciences and Engineering at the University of Michigan, and included members from UCLA and the University of Iowa.

*Artist’s concept of the Galileo space probe passing through the Jupiter system. Credit: NASA*

The data was collected in 1997 by Galileo during a flyby of Europa that brought it to within 200 km (124 mi) of the moon’s surface. At the time, its Magnetometer (MAG) sensor detected a brief, localized bend in Jupiter’s magnetic field, which remained unexplained until now. After running the data through new and advanced computer models, the team was able to create a simulation that showed that this was caused by interaction between the magnetic field and one of the Europa’s plumes.

This analysis confirmed ultraviolet observations made by NASA’s Hubble Space Telescope in 2012, which suggested the presence of water plumes on the moon’s surface. However, this new analysis used data collected much closer to the source, which indicated how Europa’s plumes interact with the ambient flow of plasma contained within Jupiter’s powerful magnetic field.

In addition to being the lead author on this study, Jia is also the co-investigator for two instruments that will travel aboard the Europa Clipper mission – which may launch as soon as 2022 to explore the moon’s potential habitability. Jia’s and his colleagues were inspired to reexamine data from the Galileo mission thanks to Melissa McGrath, a member of the SETI Institute and also a member of the Europa Clipper science team.

During a presentation to her fellow team scientists, McGrath highlighted other Hubble observations of Europa. As Jiang explained in a recent NASA press release:

“The data were there, but we needed sophisticated modeling to make sense of the observation. One of the locations she mentioned rang a bell. Galileo actually did a flyby of that location, and it was the closest one we ever had. We realized we had to go back. We needed to see whether there was anything in the data that could tell us whether or not there was a plume.”

*Artist’s impression of a water vapor plume on Europa. Credit: NASA/ESA/K. Retherford/SWRI*

When they first examined the information 21 years ago, the high-resolution data obtained by the MAG instrument showed something strange. But it was thanks to the lessons provided by the Cassini mission, which explored the plumes on Saturn’s moon Enceladus, that the team knew what to look for. This included material from the plumes which became ionized by the gas giant’s magnetosphere, leaving a characteristic blip in the magnetic field.

After reexamining the data, they found that the same characteristic bend (localized and brief) in the magnetic field was present around Europa. Jia’s team also consulted data from Galileo’s Plasma Wave Spectrometer (PWS) instrument to measure plasma waves caused by charged particles in gases around Europa’s atmosphere, which also appeared to back the theory of a plume.

This magnetometry data and plasma wave signatures were then layered into new 3D modeling developed by the team at the University of Michigan (which simulated the interactions of plasma with Solar system bodies). Last, they added the data obtained from Hubble in 2012 that suggested the dimensions of the potential plumes. The end result was a simulated plume that matched the magnetic field and plasma signatures they saw in the Galileo data.

As Robert Pappalardo, a Europa Clipper project scientist at NASA’s Jet Propulsion Laboratory (JPL), indicated:

“There now seem to be too many lines of evidence to dismiss plumes at Europa. This result makes the plumes seem to be much more real and, for me, is a tipping point. These are no longer uncertain blips on a faraway image.”

*Artist’s concept of a Europa Clipper mission, which will study Europa in 2022-2025 to search for signs of life. Credit: NASA/JPL*

The findings are certainly good news for the Europa Clipper mission, which is expected to make the journey to Jupiter between 2022 and 2025. When this probe arrives in the Jovian system, it will establish an orbit around Jupiter and conduct rapid, low-altitude flybys of Europa. Assuming that plume activity does take place on the surface of the moon, the Europa Clipper will sample the frozen liquid and dust particles for signs of life.

“If plumes exist, and we can directly sample what’s coming from the interior of Europa, then we can more easily get at whether Europa has the ingredients for life,” Pappalardo said. “That’s what the mission is after. That’s the big picture.”

At present, the mission team is busy looking at potential orbital paths for the Europa Clipper mission. With this new research in hand, the team will choose a path that will take the spaceprobe above the plume locations so that it is in an ideal position to search them for signs of life. If all goes as planned, the Europa Clipper could be the first of several probes that finally proves that there is life beyond Earth.

And be sure to check out this video of the Europa Clipper mission, courtesy of NASA:

Further Reading: NASA, Nature

May 16, 2018 by Matt Williams

Gaia Turns Up 13,928 White Dwarfs Nearby the Sun, Including Several Formed Through Mergers

Using information from Gaia's second data release, a team of scientists have made refined estimates of the Milky Way's mass. Credit: ESA/Gaia/DPAC

In 2013, the European Space Agency (ESA) deployed the Gaia mission, a space observatory designed to measure the positions of movements of celestial bodies. For the past four years, Gaia has been studying distant stars, planets, comets, asteroids, quasars and other astronomical objects, and the data it has acquired will be used to construct the largest and most precise 3D space catalog ever made, totaling 1 billion objects.

The second release of Gaia data, which took place on April 25th, 2018, has already resulted in a number of impressive discoveries. The latest was made by an international team of scientists who identified 13,928 white dwarfs within 100 parsecs (326 light-years) of the Sun, many of which were formed through mergers. This is the first time that white dwarf stars have been directly detected within the Solar neighborhood.

The study which describes their findings, “Gaia Reveals Evidence for Merged White Dwarfs“, recently appeared online and is being considered for publication in the Monthly Notices of the Royal Astronomical Society. The study was led by Dr. Mukremin Kilic, an associate professor at the University of Oklahoma, and included members from the Institute for Astronomy at the University of Edinburgh and the University of Montreal.

*Artist impression of colliding white dwarfs. Credit: CfA*

Basically, white dwarfs are what become of the majority of stars (with masses less than 8 Solar masses) once they exit the main sequence phase of their lives. This consists of a star exhausting its hydrogen fuel and expanding to several times its size (entering its Red Giant Branch Phase). These stars then blow off their external layers (a supernova) and leaving behind a white dwarf remnant.

By studying them, astronomers can learn far more about the life cycle of stars and how they evolve. As Dr. Kilic explained to Universe Today via email:

“[W]e’re basically doing Galactic archaeology when we study nearby white dwarfs. They tell us about the ages and star formation histories of the Galactic disk and halo. More importantly, white dwarfs explode as a Type Ia supernova when they reach 1.4 times the mass of the Sun. We use these supernovae to study the shape of the Universe and conclude that the expansion of the universe is accelerating. However, we have not yet found the progenitor systems of these supernovae. One of the channels to form Type Ia supernovae is through mergers of white dwarfs. Hence, the direct detection of merged white dwarfs is important for understanding the frequency of these white dwarf mergers.”

However, until recently only a few hundred white stars have been found within the local galactic neighborhood (500 within a 40 parsec radius). In addition, astronomers were only able to obtain accurate parallax (distance) measurements for about half of these. But thanks to the Gaia data, the number of white dwarfs systems that astronomers are able to study has increased exponentially.

*Artist’s impression of a white dwarf star in orbit around Sirius (a white supergiant). Credit: NASA, ESA and G. Bacon (STScI)*

“Gaia provided distance measurements,” said Kilic. “We can now create complete samples of white dwarfs within a given volume. For example, prior to Gaia, we only knew about 100 white dwarfs within 20 parsecs of the Sun. With Gaia Data Release 2, we identified more than 13,000 white dwarfs within 100 parsecs of the Sun. The difference in numbers is amazing!”

The Gaia data was also helpful in determining the nature of these white dwarf systems and how they formed. As they indicate in their study, previous research has shown that the majority of white dwarf stars in our local galaxy (roughly 56%) are the product of single-star evolution, whereas 7 to 23% were the product of mergers between binaries. The remainder were white dwarf binaries, or binaries with one white dwarf and a main sequence star.

Using the Gaia data – which included the color and distribution data of thousands of white dwarf stars within ~326 light-years of the Sun – the team was able to determine how massive these stars are. This, in turn, provided vital clues as to how they formed, which indicated that mergers were far more common than previous studies suggested. As Kilic explained:

“Massive white dwarfs tend to be smaller, which means that they are also fainter (since they have a smaller surface area). Since Gaia gave us a complete sample of white dwarfs within 100 parsecs of the Sun, for the first time, we were able to derive the magnitude distribution (hence the mass distribution) of thousands of white dwarfs and find a large fraction of massive white dwarfs. We see that the number of massive white dwarfs is significantly higher than expected from single star evolution. Therefore, we concluded that many of these massive white dwarfs actually formed through mergers in previously binary systems.”

*Artist’s impression of white dwarf binary pair CSS 41177. Credit: Andrew Taylor.*

From this, the team was able to assemble the first reliable Hertzsprung-Russell Diagram for nearby field white dwarf stars, as well as estimates on how often white dwarf binaries merge. As Kilic indicated, this could have significant implications for other areas of astronomical study.

“Based on the frequency of these single white dwarfs that formed through mergers, we can estimate how many white dwarf mergers occur on average and with what mass distribution,” he said. “We can then infer the rate of Type Ia supernovae from these mergers and see if it’s enough to explain part or all of the Ia supernova explosions. This is an ongoing area of research and I’m sure we will some results on these very soon.”

These findings are yet another gem to come from the second Gaia data release, which has proven to be a treasure trove for astronomers. The third release of Gaia data is scheduled to take place in late 2020, with the final catalog being published in the 2020s. Meanwhile, an extension has already been approved for the Gaia mission, which will now remain in operation until the end of 2020 (to be confirmed at the end of this year).

Further Reading: arXiv

May 15, 2018February 8, 2023 by Matt Williams

If There is a Multiverse, Can There be Life There Too?

*Could our Universe be part of a wider Multiverse? And could these other Universes support life? Credit: Jaime Salcido/EAGLE Collaboration*

The Multiverse Theory, which states that there may be multiple or even an infinite number of Universes, is a time-honored concept in cosmology and theoretical physics. While the term goes back to the late 19th century, the scientific basis of this theory arose from quantum physics and the study of cosmological forces like black holes, singularities, and problems arising out of the Big Bang Theory.

One of the most burning questions when it comes to this theory is whether or not life could exist in multiple Universes. If indeed the laws of physics change from one Universe to the next, what could this mean for life itself? According to a new series of studies by a team of international researchers, it is possible that life could be common throughout the Multiverse (if it actually exists).

Continue reading “If There is a Multiverse, Can There be Life There Too?”

May 14, 2018December 13, 2018 by Matt Williams

Pros and Cons of Various Methods of Interstellar Travel

A new study considers what life could be like for civilizations 1 trillion years from now, when every star in the Universe will expand beyond the cosmic horizon. Credit: ESO/S. Brunier

It’s a staple of science fiction, and something many people have fantasized about at one time or another: the idea of sending out spaceships with colonists and transplanting the seed of humanity among the stars. Between discovering new worlds, becoming an interstellar species, and maybe even finding extra-terrestrial civilizations, the dream of spreading beyond the Solar System is one that can’t become reality soon enough!

For decades, scientists have contemplated how humanity might one-day reach achieve this lofty goal. And the range of concepts they have come up with present a whole lot of pros and cons. These pros and cons were raised in a recent study by Martin Braddock, a member of the Mansfield and Sutton Astronomical Society, a Fellow of the Royal Society of Biology, and a Fellow of the Royal Astronomical Society. Continue reading “Pros and Cons of Various Methods of Interstellar Travel”

May 13, 2018May 13, 2018 by Matt Williams

NASA is Sending a Helicopter to Mars as Part of the 2020 Rover

NASA's Mars Helicopter, a small, autonomous rotorcraft, will travel with the agency's Mars 2020 rover, currently scheduled to launch in July 2020, to demonstrate the viability and potential of heavier-than-air vehicles on the Red Planet. Credits: NASA/JPL-Caltech

At present, there are over a dozen robotic missions exploring the atmosphere and surface of Mars. These include, among others, the Curiosity rover, the Opportunity rover, the Mars Orbiter Mission (MOM), the Mars Reconnaissance Orbiter (MRO), the Mars Atmosphere and Volatile EvolutioN (MAVEN) orbiter, and the soon-to-arrive InSight Lander. In the coming decade, many more missions are planned.

For instance, NASA plans to expand on what Curiosity has accomplished by sending the Mars 2020 rover to conduct a sample-return mission. According to a recent announcement issued by NASA, this mission will also include the Mars Helicopter – a small, autonomous rotorcraft that will demonstrate the viability and potential of heavier-than-air vehicles on the Red Planet.

As NASA Administrator Jim Bridenstine declared in a recent NASA press release, this rotocraft is in keeping with NASA’s long-standing traditions of innovation. “NASA has a proud history of firsts,” she said. “The idea of a helicopter flying the skies of another planet is thrilling. The Mars Helicopter holds much promise for our future science, discovery, and exploration missions to Mars.”

*This artist’s concept depicts NASA’s Mars 2020 rover exploring Mars. Credit: NASA*

U.S. Rep. John Culberson of Texas echoed Bridenstine statement. “It’s fitting that the United States of America is the first nation in history to fly the first heavier-than-air craft on another world,” he said. “This exciting and visionary achievement will inspire young people all over the United States to become scientists and engineers, paving the way for even greater discoveries in the future.”

The Mars Helicopter began as technology development project at NASA’s Jet Propulsion Laboratory (JPL), where it spent the past four years being designed, developed, tested and retested. The result of this is a football-sized rotorcraft that weights just under 1.8 kg (four pounds) and relies on two counter-rotating blades to spin at a rate of almost 3,000 rpm (10 times the rate of a helicopter here on Earth).

As Mimi Aung, the Mars Helicopter project manager at JPL, indicated:

“The altitude record for a helicopter flying here on Earth is about 40,000 feet. The atmosphere of Mars is only one percent that of Earth, so when our helicopter is on the Martian surface, it’s already at the Earth equivalent of 100,000 feet up. To make it fly at that low atmospheric density, we had to scrutinize everything, make it as light as possible while being as strong and as powerful as it can possibly be.”

*Artist’s impression of the Mars 2020 with its sky crane landing system deployed. Credit: NASA/JPL*

This concept is ideal for navigating through Mars’ thin atmosphere, where the mean surface pressure is about 0.6% that of Earth’s at sea level (0.60 kPa compared to 101.3 kPa). This low-flying helicopter would not only be able to increase the range of a rover, it will be able to explore areas that the rover would find inaccessible. As Thomas Zurbuchen, the Associate Administrator for NASA’s Science Mission Directorate, explained:

“Exploring the Red Planet with NASA’s Mars Helicopter exemplifies a successful marriage of science and technology innovation and is a unique opportunity to advance Mars exploration for the future. After the Wright Brothers proved 117 years ago that powered, sustained, and controlled flight was possible here on Earth, another group of American pioneers may prove the same can be done on another world.”

Other capabilities that make it optimized for Mars exploration include lithium-ion batteries, solar cells to keep them charged, and heating mechanisms that will keep it warm during Martian nights – where average temperatures can get as low as 210 K (-63 °C; -82 °F) around the mid-latitudes. In addition, the helicopter is programmed to fly autonomously, since it cannot be flown in real-time (given the distances involved).

Commands will be issued from controllers on Earth, using the rover as a relay, who will instruct the helicopter to commence flight once it is ready to deploy. This will begin shortly after the rover arrives on the planet (which is expected to happen by February 2021) with the helicopter attached to its belly pan. The rover will then select a location to deploy the helicopter onto the ground.

*Artist’s concept of the dragonfly being deployed to Titan and commencing its exploration mission. Credit: APL/Michael Carroll*

After it is finished charging its batteries and a series of pre-flight tests are performed, controllers on Earth will relay commands to the Mars Helicopter to commence its first 30-day flight test campaign. This will include up to five flights that will take it to increasingly greater distances from the rover (up to a few hundred meters) for longer periods of time (up to 90 seconds).

On its first flight, the helicopter will make a short vertical climb to 3 meters (10 feet) where it will hover for about 30 seconds. Once these tests are complete, the Mars Helicopter will assist the rover as it conducts geological assessments and determines the habitability of its landing sight. The purpose of this will be to search for signs of ancient life on Mars and assesses the natural resources and hazards for future missions involving human explorers.

The rover will also conduct the first-ever sample-return mission from Mars, obtaining samples of rock and soil, encasing them in sealed tubes, and leaving them on the planet for future retrieval by astronauts. If all goes well, the helicopter will demonstrate that low-flying scouts and aerial vehicles can be a valuable part of any future missions. These will likely include robotic missions to Saturn’s largest moon, Titan, where researchers are hoping to explore the surface and atmosphere using helicopter (such as the Dragonfly concept).

The Mars 2020 mission is expected to reveal some very impressive things about the Red Planet. If the helicopter proves to be a viable part of the mission, we can expect that additional information and images will be provided from locations that a conventional rover cannot go. And in the meantime, be sure to enjoy this animation of the Mars Helicopter in action, courtesy of NASA-JPL:

Further Reading: NASA

May 12, 2018 by Matt Williams

Evidence for Thousands of Black Holes Buzzing Around the Center of the Milky Way

On September 14th, 2013, astronomers caught the largest X-ray flare ever detected from the supermassive black hole at the center of the Milky Way, known as Sagittarius A* (Sgr A*). Credit: NASA/CXC/Stanford/I. Zhuravleva et al.

Since the 1970s, astronomers have understood that a Supermassive Black Hole (SMBH) resides at the center of the Milky Way Galaxy. Located about 26,000 light-years from Earth between the Sagittarius and Scorpius constellations, this black hole has come to be known as Sagittarius A* (Sgr A*). Measuring 44 million km across, this object is roughly 4 million times as massive as our Sun and exerts a tremendous gravitational pull.

Since that time, astronomers have discovered that most massive galaxies have SMBHs at their core, which is what separates those that have an Active Galactic Nuclei (AGN) from those that don’t. But thanks to a recent survey conducted using NASA’s Chandra X-ray Observatory, astronomers have discovered evidence for hundreds or even thousands of black holes located near the center of the Milky Way Galaxy.

The study which described their findings was recently published in the journal Nature under the title “A density cusp of quiescent X-ray binaries in the central parsec of the Galaxy“. The study was led by Chuck Hailey, the Pupin Professor of Physics and the Co-Director of the Columbia Astrophysics Laboratory (CAL) at Columbia University, and including members from the Instituto de Astrofísica at the Pontificia Universidad Católica de Chile and the Harvard-Smithsonian Center for Astrophysics.

The center of the Milky Way Galaxy, with X-ray binaries circled in red, other X-ray sources circled in yellow, and Sagittarius A* circled in blue at the center. Credit: NASA/CXC/Columbia University/C. Hailey et al.

Using Chandra data, the team searched for X-ray binaries containing black holes that were in the vicinity of Sgr A*. To recap, black holes are not detectable in visible light. However, black holes (or neutron stars) that are locked in close orbits with a star will pull material from their companions, which will then be accreted onto the black holes’ disks and heated up to millions of degrees.

This will result in the release of X-rays which can then be detected, hence why these systems are called “X-ray binaries”. Using Chandra data, the team sought out X-ray of sources that were located within roughly 12 light years of Sgr A*. They then selected sources with X-ray spectra similar to those of known X-ray binaries, which emit relatively large amounts of low-energy X-rays.

Using this method, they detected fourteen X-ray binaries within about three light years of Sgr A*, all of which contained stellar-mass black holes (between 5 and 30 times the mass of our Sun). Two of these sources had been identified by previous studies and were eliminated from the analysis, while the remaining twelve (circled in red in the image above) were newly-discovered.

Other sources which relatively large amounts of high energy X-rays (labeled in yellow) were believed to be binaries containing white dwarfs. Hailey and his colleagues concluded that the majority of the dozen X-ray binaries were likely to contain black holes, based on their variability and the fact that their X-ray emissions over the course of several years was different from what is expected from binaries containing neutron stars.

*Artist”s impression of a black hole binary, consisting of a black hole siphoning material from its companion. Credit: ESO/L. Calçada*

Given that only the brightest X-ray binaries containing black holes are likely to be detectable around Sgr A* (given its distance from Earth), Hailey and his colleagues concluded that this detection implies the existence of a much larger population. By their estimates, there could be at least 300 and as many as one thousand stellar-mass black holes present around Sgr A*.

These findings confirmed what theoretical studies on the dynamics of stars in galaxies have indicated in the past. According to these studies, a large population of stellar mass black holes (as many as 20,000) could drift inward over the course of millions of years and collect around an SMBH. However, the recent analysis conducted by Hailey and his colleagues was the first observational evidence of black holes congregating near Sgr A*.

Naturally, the authors acknowledge that there are other explanations for the X-ray emissions they detected. This includes the possibility that half of the dozen sources they observed are millisecond pulsars – very rapidly rotating neutron stars with strong magnetic fields. However, based on their observations, Hailey and his team strongly favor the black hole explanation.

In addition, a follow-up study conducted by Aleksey Generozov (et al.) of Columbia University – titled “An Overabundance of Black Hole X-Ray Binaries in the Galactic Center from Tidal Captures” – indicated that there could be as many as 10,000 to 40,000 black holes binaries at the center of our galaxy. According to this study, these binaries would be the result of companions being captured by black holes.

In February 2016, LIGO detected gravity waves for the first time. As this artist's illustration depicts, the gravitational waves were created by merging black holes. The third detection just announced was also created when two black holes merged. Credit: LIGO/A. Simonnet. — *Artist’s impression of merging binary black holes. Credit: LIGO/A. Simonnet.*

In addition to revealing much about the dynamics of stars in our galaxy, this study has implications for the emerging field of gravitational wave (GW) research. Essentially, by knowing how many black holes reside at the center of galaxies (which will periodically merge with one another), astronomers will be able to better predict how many gravitational wave events are associated with them.

From this, astronomers could create predictive models about when and how GW events are likely to happen, and well as discerning what role they may play in galactic evolution. And with next-generation instruments – like the James Webb Space Telescope (JWST) and the ESA’s Advanced Telescope for High Energy Astrophysics (ATHENA) – astronomers will be able to determine exactly how many black holes reside near the center of our galaxy.

Further Reading: NASA