Scientists have discovered three giant planets in a binary star system composed of stellar ''twins'' that are also effectively siblings of our Sun. One star hosts two planets and the other hosts the third. The system represents the smallest-separation binary in which both stars host planets that has ever been observed. The findings, which may help explain the influence that giant planets like Jupiter have over a solar system's architecture.

New discoveries coming from the study of exoplanetary systems will show us where on the continuum of ordinary to unique our own Solar System's layout falls. So far, planet hunters have revealed populations of planets that are very different from what we see in our Solar System. The most-common exoplanets detected are so-called super-Earths, which are larger than our planet but smaller than Neptune or Uranus. Given current statistics, Jupiter-sized planets seem fairly rare--having been detected only around a small percentage of stars.

This is of interest because Jupiter's gravitational pull was likely a huge influence on our Solar System's architecture during its formative period. So the scarcity of Jupiter-like planets could explain why our home system is different from all the others found to date.

The new discovery from the Carnegie team is the first exoplanet detection made based solely on data from the Planet Finder Spectrograph--developed by Carnegie scientists and mounted on the Magellan Clay Telescopes at Carnegie's Las Campanas Observatory, shown at top of page. PFS is able to find large planets with long-duration orbits or orbits that are very elliptical rather than circular, including the new trio of planets discovered in this `"twin'" star study. This special capability comes from the long observing baseline of PFS; it has been taking observations for six years.

Led by Johanna Teske, the team included a number of Carnegie scientists from both the Department of Terrestrial Magnetism in Washington, DC, and the Carnegie Observatories in Pasadena, CA, as well as Steve Vogt of the University of California Santa Cruz.

"We are trying to figure out if giant planets like Jupiter often have long and, or eccentric orbits," Teske explained. "If this is the case, it would be an important clue to figuring out the process by which our Solar System formed, and might help us understand where habitable planets are likely to be found."

The twin stars studied by the group are called HD 133131A and HD 133131B. The former hosts two moderately eccentric planets, one of which is, at a minimum, about 1 and a half times Jupiter's mass and the other of which is, at a minimum, just over half Jupiter's mass. The latter hosts one moderately eccentric planet with a mass at least 2.5 times Jupiter's.

The two stars themselves are separated by only 360 astronomical units (AU). One AU is the distance between the Earth and the Sun. This is extremely close for twin stars with detected planets orbiting the individual stars. The next-closest binary system that hosts planets is comprised of two stars that are about 1,000 AU apart.

The system is even more unusual because both stars are "metal poor," meaning that most of their mass is hydrogen and helium, as opposed to other elements like iron or oxygen. Most stars that host giant planets are "metal rich." Only six other metal-poor binary star systems with exoplanets have ever been found, making this discovery especially intriguing.

Adding to the intrigue, Teske used very precise analysis to reveal that the stars are not actually identical "twins" as previously thought, but have slightly different chemical compositions, making them more like the stellar equivalent of fraternal twins.

This could indicate that one star swallowed some baby planets early in its life, changing its composition slightly. Alternatively, the gravitational forces of the detected giant planets that remained may have had a strong effect on fully-formed small planets, flinging them in towards the star or out into space.

"The probability of finding a system with all these components was extremely small, so these results will serve as an important benchmark for understanding planet formation, especially in binary systems," Teske explained.

The Daily Galaxy via Carnegie Institution for Science

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In a video uploaded to YouTube on August 3rd (below), engineers from the Russian space agency, Roscosmos, proposed an orbiter and lander mission to Ganymede. The video suggests a launch could come in the next decade. Although the commentary is in Russian, the video appears to suggest that Ganymede may be as good a candidate or better  for life than Europa.

In March of 2015, NASA's Hubble Space Telescope revealed the best evidence yet for an underground saltwater ocean on Ganymede, Jupiter's largest moon. The subterranean ocean is thought to have more water than all the water on Earth's surface. Identifying liquid water is crucial in the search for habitable worlds beyond Earth and for the search for life, as we know it.

"This discovery marks a significant milestone, highlighting what only Hubble can accomplish," said John Grunsfeld, recently retired assistant administrator of NASA's Science Mission Directorate at NASA Headquarters. "In its 25 years in orbit, Hubble has made many scientific discoveries in our own solar system. A deep ocean under the icy crust of Ganymede opens up further exciting possibilities for life beyond Earth."

Ganymede is the largest moon in our solar system and the only moon with its own magnetic field, shown above. The magnetic field causes aurorae, which are ribbons of glowing, hot electrified gas, in regions circling the north and south poles of the moon. Because Ganymede is close to Jupiter, it is also embedded in Jupiter's magnetic field. When Jupiter's magnetic field changes, the aurorae on Ganymede also change, "rocking" back and forth.

By watching the rocking motion of the two aurorae, scientists were able to determine that a large amount of saltwater exists beneath Ganymede's crust, affecting its magnetic field.

A team of scientists led by Joachim Saur of the University of Cologne in Germany came up with the idea of using Hubble to learn more about the inside of the moon. "I was always brainstorming how we could use a telescope in other ways," said Saur. "Is there a way you could use a telescope to look inside a planetary body? Then I thought, the aurorae! Because aurorae are controlled by the magnetic field, if you observe the aurorae in an appropriate way, you learn something about the magnetic field. If you know the magnetic field, then you know something about the moon's interior."

If a saltwater ocean were present, Jupiter's magnetic field would create a secondary magnetic field in the ocean that would counter Jupiter's field. This "magnetic friction" would suppress the rocking of the aurorae. This ocean fights Jupiter's magnetic field so strongly that it reduces the rocking of the aurorae to 2 degrees, instead of 6 degrees if the ocean were not present. Scientists estimate the ocean is 60 miles (100 kilometers) thick -- 10 times deeper than Earth's oceans -- and is buried under a 95-mile (150-kilometer) crust of mostly ice.

Scientists first suspected an ocean in Ganymede in the 1970s, based on models of the large moon. NASA's Galileo mission measured Ganymede's magnetic field in 2002, providing the first evidence supporting those suspicions. The Galileo spacecraft took brief "snapshot" measurements of the magnetic field in 20-minute intervals, but its observations were too brief to distinctly catch the cyclical rocking of the ocean's secondary magnetic field.

The new observations were done in ultraviolet light and could only be accomplished with a space telescope high above Earth's atmosphere, which blocks most ultraviolet light.

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The Daily Galaxy via Space Telescope Science Institute (STScI)

Image Credit: NASA/ESA and USGS Astrogeology Science Center/Wheaton/NASA/JPL-Caltech

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In a newly melted part of Greenland, Australian scientists found the leftover structure from a community of microbes that lived on an ancient seafloor, according to a study in Wednesday's journal Nature. The team have found what they think is the oldest fossil on Earth, a remnant of life from 3.7 billion years ago when Earth's skies were orange and its oceans green.

The discovery shows life may have formed quicker and easier than once thought, about half a billion years after Earth formed . And that may also give hope for life forming elsewhere, such as Mars, said study co-author Martin VanKranendonk of the University of New South Wales and director of the Australian Center for Astrobiology.

"It gives us an idea how our planet evolved and how life gained a foothold," VanKranendonk said.

"It would have been a very different world. It would have had black continents, a green ocean with orange skies," he said. The land was likely black because the cooling lava had no plants, while large amounts of iron made the oceans green. Because the atmosphere had very little oxygen and oxygen is what makes the sky blue, its predominant color would have been orange, he said.

Scientists had thought it would take at least half a billion years for life to form after the molten Earth started to cool a bit, but this shows it could have happened quicker, he said. That's because the newly found fossil is far too complex to have developed soon after the planet's first life forms, he said.

In an outcrop of rocks that used to be covered with ice and snow which melted after an exceptionally warm spring, the Australian team found stromatolites (shown at top of the page surviving in Antarctica), which are intricately layered microscopic layered structures that are often produced by a community of microbes. The stromatolites were about .4 to 1.6 inches high (1 to 4 centimeters).

It "is like the house left behind made by the microbes," VanKranendonk said.
Scientists used the layers of ash from volcanoes and tiny zircon with uranium and lead to date this back 3.7 billion years ago, using a standard dating method, VanKranendonk said.

In this photo provided by Allen Nutman, a rock with the stromatolites, tiny layered structures from 3.7 billion years ago that are remnants from a community of microbes that used to be live there.

The dating seems about right, said Abigail Allwood , a NASA astrobiologist who found the previous oldest fossil, from 3.48 billion years ago, in Australia. But Allwood said she is not completely convinced that what VanKranendonk's team found once was alive. She said the evidence wasn't conclusive enough that it was life and not a geologic quirk.

"It would be nice to have more evidence, but in these rocks that's a lot to ask," Allwood said in an email.

The Daily Galaxy via AP and Nature

Image credit: (Laure Gauthiez/The Australian National University via AP)

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"Ten billion years ago, galaxies like our Milky Way were much smaller, but they were forming stars 30 times faster than they are today," said Casey Papovich of Texas A&M University.

An international team of astronomers has charted the rise and fall of galaxies over 90 percent of cosmic history. Their work, which includes some of the most sensitive astronomical measurements made to date, is published by The Astrophysical Journal.

The FourStar Galaxy Evolution Survey (ZFOURGE) has built a multicolored photo album of galaxies as they grow from their faint beginnings into mature and majestic giants. They did so by measuring distances and brightnesses for more than 70,000 galaxies spanning more than 12 billion years of cosmic time, revealing the breadth of galactic diversity.

The team assembled the colorful photo album by using a new set of filters that are sensitive to infrared light and taking images with them with the FourStar camera at Carnegie's 6.5-meter Baade Telescope at our Las Campanas Observatory in Chile. They took the images over a period of 45 nights. The team made a 3-D map by collecting light from over 70,000 galaxies, peering all the way into the distant universe, and by using this light to measure how far these galaxies are from our own Milky Way.

The deep 3-D map also revealed young galaxies that existed as early as 12.5 billion years ago (at less than 10 percent of the current universe age), only a handful of which had previously been found. This should help astronomers better understand the universe's earliest days.

"Perhaps the most surprising result is that galaxies in the young universe appear as diverse as they are today," when the universe is older and much more evolved, said lead author Caroline Straatman, a recent graduate of Leiden University. "The fact that we see young galaxies in the distant universe that have already shut down star formation is remarkable."

But it's not just about distant galaxies; the information gathered by ZFOURGE is also giving the scientists the best-yet view of what our own galaxy was like in its youth.

"ZFOURGE is providing us with a highly complete and reliable census of the evolving galaxy population, and is already helping us to address questions like: How did galaxies grow with time? When did they form their stars and develop into the spectacular structures that we see in the present-day universe?" added Ryan Quadri, also of Texas A&M.

In the study's first images, the team found one of the earliest examples of a galaxy cluster, a so-called "galaxy city" made up of a dense concentration of galaxies, which formed when the universe was only three billion years old, as compared to the nearly 14 billion years it is today.

"The combination of FourStar, the special filters, Magellan, and the conditions at Las Campanas led to the detection of the cluster," said Persson, who built the FourStar instrument at the Carnegie Observatories in Pasadena. "It was in a very well-studied region of the sky--'hiding in plain sight.'"

The paper marks the completion of the ZFOURGE survey and the public release of the dataset, which can be found here: http://zfourge.tamu.edu/DR2016/data.html.

The Daily Galaxy via Carnegie Institution for Science

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"AlphaGo is not only a milestone in the quest of AI, but also an indication that IT now has entered a new era," said Fei-YueWang, at the Chinese Academy of Sciences and secretary general of the Chinese Association of Automation. The computer's win signaled a significant evolution of information technology (IT) and artificial intelligence (AI), according Wang, a professor at the Chinese Academy of Sciences. As the result, IT is no longer information or industrial technology, the New IT is Intelligent Technology. The world has entered  the fifth era of intelligent technology.

The world's oldest board game still has a few moves to play. Go, a game of strategy and instinct considered more difficult to master than chess, was created roughly in the same era as the written word. The game is uniquely human - or, it was. Last year, a computer program called AlphaGo defeated an internationally ranked professional player.

In a recent editorial published in the IEEE/CAA Journal of Automatica Sinica, Wang argues that core principles of automation and Al must be rethought as the world navigates an IT paradigm shift.

Wang sketches the progress of robotic and neural machine-human interaction in a timeline of five "control" eras. Automation evolved from the pure mechanics of ancient water clocks and steam engines to the eventual development of electric circuits and transfer functions that gave way to power grids. Digital computers and microprocessors signaled the third shift and paved the way for the fourth - the Internet and the World Wide Web.

In the first four controls, physical and mental realities were approximated as accurately as possible and adjusted through the use of dual control theory. A machine with a set of conditions and a goal could succeed or fail. As the machine acts, it also investigates to learn what action may result in a better future outcome.

Between the physical and mental spaces, another reality in need of double control exists. Augmented, or artificial, reality bridges the gap of actuality and imagination. Pokémon GO is a prime example, as people navigate the physical world to find fictional creatures with only experience as a guide. The parameters and goals shift with each new exposure.

"In Control 5.0...only association revealed by data or experience is available, and causality is a luxury that is no longer attainable with limited resources for uncertainty, diversity, and complexity," Wang said.

Recognition of all three worlds and the dual learning roles of each, according to Wang, will be essential in the fifth era of intelligent technology.

The Daily Galaxy via Chinese Association of Automation

Image credit: Google

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If humanity is to survive beyond the lifetime of our Sun, we must leave our Solar System and travel to the stars. If Proxima b is habitable, then it might be an ideal place to move. Perhaps we have just discovered a future home for humanity! But in order to know for sure, we must make many more observations, run many more computer simulations, and, hopefully, send probes to perform the first direct reconnaissance of an exoplanet. The challenges are huge, but Proxima offers a bounty of possibilities that fills me with wonder. Whether habitable or not, Proxima b offers a new glimpse into how planets and life fit into our universe.

The discovery of Proxima b is the biggest exoplanet discovery since the discovery of exoplanets. The planet is not much bigger than Earth and resides in the “habitable zone” of the Sun's nearest stellar neighbor. This planet may represent humanity's best chance to search for life among the stars. But is Proxima b habitable? Is it inhabited? These questions are impossible to answer at this time because we know so little about the planet. However, we can extrapolate from the worlds of our Solar System, as well as employ theoretical models of galactic, stellar, and planetary evolution, to piece together realistic scenarios for Proxima b's history.

The possibilities are varied and depend on phenomena usually studied by scientists in fields that are considered distinct, but an integrated perspective — an astrobiological perspective — can provide a realistic assessment of the possibility that life could have arisen and survived on the closest exoplanet.

As an astrobiologist and astronomer at the University of Washington, and a member of NASA's Virtual Planetary Lab, Roy Barnes has investigated the habitability of planets orbiting red dwarfs for years. His research involves building computer models that simulate how planetary interiors and atmospheres evolve, how stars change with time, and how planetary orbits vary. The discovery of Proxima b has me very excited, but being Earth-sized and in the habitable zone are just the first two requirements for a planet to support life, and the list of requirements is much longer for planets orbiting red dwarfs than for stars like our Sun.

If Proxima b is in fact habitable, meaning it possesses liquid water or even inhabited, meaning life is currently present, then it will have traversed a very different evolutionary path than Earth. This difference is frustrating, in that it will make our initial interpretations challenging, but also exciting, as it offers the chance to learn how Earth-sized planets evolve in our universe. Whether Proxima b is a sterile wasteland or teeming with life, we are now embarking on an unprecedented era of discovery, one that may finally provide an answer that age-old question “Are we alone?”.

What to make of Proxima b? It is at least as massive as Earth, and may be several times more massive. Its “year” is just over 11 days and its orbit may be circular or significantly elongated. Its host star is only 12% as massive as our Sun, 0.1% as bright, and it is known to flare. It may be joined to the stars Alpha Centauri A and B, 15,000 astronomical units (AU) away, by their mutual gravitational attraction.

All three stars contain substantially more heavy elements than our Sun, but we know very little of the composition of Proxima b, or how it formed. The new data point toward the presence of a second planet orbiting in the system with a period near 200 days, but its existence cannot be proven at this time. These are the facts we have and from them we must deduce whether Proxima b supports life.

Proxima b was detected via the radial velocity method, which does not provide a direct measurement of the planet's mass, only a minimum mass. So, the first question we'd like to answer is whether the planet's mass is low enough to be rocky like Earth. If the planet is much larger, it may be more like Neptune with a thick gaseous envelope. While we don't know where the dividing line between rocky and gaseous exoplanets is, models of planet formation and analyses of Kepler planets suggest the transition is between 5 and 10 times the mass of Earth. Only about 5% of allowed orbits place Proxima b's mass above 5 Earth masses, so it is very likely that this planet is in the rocky range.

The next question to ask is if the planet actually formed with water. Water consists of hydrogen and oxygen, the first and third most common elements in the galaxy, so we should expect it to be everywhere. Close to stars, however, where Proxima b resides, water is heated into its vapor phase while planets are forming, and hence it is difficult for planets to capture it. Planets that form at larger distances can gather more water, so if Proxima b formed farther out and moved to its current orbit later, it is more likely to be water-rich.

At this time, we don't know how the planet formed, but three scenarios seem most probable: 1) the planet formed where it is from mostly local material; 2) the planet formed farther out while the gas and dust disk that birthed the planetary system still existed, and forces from that disk drove the planet in to its present orbit; or 3) the planet formed elsewhere and some sort of system-wide instability rearranged the planets and b ultimately arrived in its current orbit.

The first method is how Earth and Venus formed, and so Proxima b may or may not possess significant water if it formed in this way. The second method produces planets that are very water-rich because water is more likely to be in its ice phase farther out in the disk and so the forming planet could easily gather it up. The third method is inconclusive as the planet could have come from an interior orbit and formed without water or farther out and be water-rich. We conclude that it is entirely possible that this planet has water, but we cannot be certain.

Next let's consider the clues from the stars themselves. Computer models of the evolution of our galaxy suggest that stars enriched in heavy elements like Proxima cannot form locally (25,000 light-years from the galactic center) as there just aren't enough heavy elements available. But closer to the galactic center, where star formation has been more vigorous and transpiring for longer, stars like Proxima are possible. Recent work has found that stars in our local solar neighborhood with compositions like Proxima must have formed at least 10,000 light-years closer to the galactic center. It would seem Proxima Centauri has wandered through our galaxy and this history may have played an important role in the evolution of Proxima b.

Computer models of the evolution of the Milky Way galaxy suggest Proxima Centauri has moved outward at least 10,000 light-years from where it formed, shown by the orange circle. The Sun and Earth probably formed near where they orbit today (blue circle), which is where we find Proxima Centauri, too.

The orbit of Proxima around Alpha Centauri A and B, assuming they are gravitationally connected, is large compared to other multiple star systems. In fact, it is so large that A and B's hold on Proxima is weak and the effects of the Milky Way galaxy have shaped Proxima's orbit significantly. The mass of the Milky Way as a whole causes Proxima's orbit to vary both in shape and orientation continuously.

Proxima is also susceptible to gravitational encounters from passing stars that can change its orbit. Recent simulations by Nate Kaib have found that these two effects can often lead to close passages between the stars in a multiple star system that disrupt their planetary systems. The disruption is often powerful enough to eject planets from the system and completely rearrange the orbits of the planets that remain.

New simulations by Russell Deitrick are revealing that this scenario is a real concern for Proxima, too; there is a significant probability that at some point in the past, Proxima swooped in close enough to Alpha Centauri A and B to cause its planetary system to break apart, hurling Proxima b's siblings into deep space. If such a disruption occurred, Proxima b may not have formed where we find it today because its orbit would have been affected by this disruption.

Even if Proxima is not currently bound to Alpha Cen A and B, it appears to be travelling with them, and it is very likely the stars formed from the same cloud of dust and gas. If they formed together, they should have similar compositions and nearly identical ages. Connecting their ages is important because it is very difficult to measure the ages of low mass stars like Proxima Centauri. Astronomers can estimate the age of Alpha Cen A via asteroseismology, the study of “starquakes.”

Stars bigger than the Sun vibrate with large enough amplitudes that brightness fluctuations can be observed, and careful monitoring of the pulsations can reveal a star's age. Recent work by Dr. Michaël Bazot has found that Alpha Cen A is between 3.5 and 6 billion years old. This range is larger than we would like, but Proxima is certainly old enough to support life, and Proxima b might even be about the same age as Earth!

Next we turn to clues from the Proxima Centauri planetary system. The vast majority of the energy used by life on Earth comes from our Sun, and small stars like Proxima can produce energy for trillions of years. The host star is almost as small as stars come, so for a planet to receive as much stellar energy as Earth, Proxima b must be about 25 times closer in than Earth is from the sun. This distance is where the habitable zone lies.

While Proxima is much dimmer than the Sun, it is still a thermonuclear explosion, and, everything else equal, life seems more likely at larger distances. And indeed the close-in orbit does produce numerous obstacles that life on Earth did not have to overcome. These include a long formation time for the star, short and energetic bursts of energy in UV and X-ray light, strong magnetic fields, larger starspots, larger coronal mass ejections, and gravitational tidal effects that cause rotational properties to change and frictional heating in oceans (if they exist) and the rocky interior.

The history of Proxima's brightness evolution has been slow and complicated. Stellar evolution models all predict that for the first one billion years Proxima slowly dimmed to its current brightness, which implies that for about the first quarter of a billion years, Proxima b's surface would have been too hot for Earth-like conditions. As Rodrigo Luger and Barnes recently showed, had our modern Earth been placed in such a situation, it would have become a Venus-like world, in a runaway greenhouse state that can destroy all of the planet's primordial water. This desiccation can occur because the molecular bonds between hydrogen and oxygen in water can be destroyed in the upper atmosphere by radiation from the star, and hydrogen, being the lightest of the elements, can escape the planet's gravity. Without hydrogen, there can be no water, and the planet is not habitable. Escaping or avoiding this early runaway greenhouse is the biggest hurdle for Proxima b's chances for supporting life.

Figure 2: Proxima Centauri's habitable zone has moved inward since it formed, which may mean that planet b lost its water shortly after it formed, when the system was 1—10 million years old. The habitable zone, shown in blue, doesn't arrive at the orbit of planet b until almost 200 million years after it formed. This early brightness may be the biggest obstacle for life to have gained a foothold on Proxima Centauri b.

As the star dims, the water destruction process halts, and so total desiccation is not inevitable. If some water remains, the atmosphere may also contain large quantities of oxygen leftover from the water vapor destruction. While having large amounts of water and oxygen may sound like a good recipe for life, it almost certainly is not. Oxygen is one of the most reactive elements, and its presence in the young atmosphere of Proxima b would likely prevent the development of pre-biotic molecules that require conditions with little oxygen to form. Life on Earth formed when no oxygen was present, and photosynthesis ultimately produced enough oxygen for it to become a major component of our atmosphere. Note that the destruction of only some water leads to the rather surprising possibility that the planet could possess oceans and an oxygen-rich atmosphere, but has been unable to support life!

Another intriguing possibility is that Proxima b started out more like Neptune and the early brightness and flaring eroded away a hydrogen-rich atmosphere to reveal a habitable Proxima below. Such a world was investigated by Rodrigo Luger, Barnes and others, and was found to be a viable pathway to avoid total desiccation. Essentially the hydrogen atmosphere protects the water. If Proxima b formed with about 0.1-1% of its mass in a hydrogen envelope, the planet would lose the hydrogen but not its water, potentially emerging as a habitable world after the star reached its current brightness.

This wide range of possible evolutionary pathways presents a daunting challenge as we imagine using space- and ground-based telescopes to search for life in the atmosphere of Proxima b. Nearly all the components of an atmosphere imprint their presence in a spectrum, so with our knowledge of the possible histories of this planet, we can begin to develop instruments and plan observations that pinpoint the critical differences.

For example, at high enough pressures, oxygen molecules can momentarily bind to each other and produce an observable feature in a spectrum. Crucially, the pressures required to be detectable are large enough to discriminate between a planet with too much oxygen, and one with just the right amount for life. As we learn more about the planet and the system, we can build a library of possible spectra from which to quantitatively determine how likely it is that life exists on Proxima b.

While the early brightness of the host star is the biggest impediment to life, other issues are also important. One of the original concerns for the habitability of planets orbiting red dwarfs was that they would become “tidally locked”, meaning that one hemisphere permanently faces the host star. This state is similar to the rotation of our Moon, in which the same tidal forces that raise waves in our ocean have caused the Moon to show only one face to Earth. Because it is so close to its star, Proxima b may be in this state, depending on the shape of its orbit.

For decades, astronomers were concerned that such a tidally locked planet would be uninhabitable because they believed the atmosphere would freeze and collapse to the surface on the permanently dark side. That possibility is now viewed as very unlikely because winds in the atmosphere will transport energy around the planet and maintain sufficient warmth on the backside to prevent this freeze out. Thus, as far as atmospheric stability is concerned, tidal locking is not a concern for this planet's potential habitability.

Although tidal locking is not very dangerous for life, it is possible for tides to provide large amounts of energy to the planet's atmosphere and interior. This energy is often called “tidal heating” and is a result of the deformation of the planet due to changes in the host star's gravitational force across the planet's diameter. For example, if the planet is on an elliptical orbit, when it is closer to the star, it feels stronger gravity than when it is farther away. This variation will cause the shape of the planet to change, and this deformation can cause friction between layers in the planet's interior, producing heat.

In extreme cases, tidal heating could trigger the onset of a runaway greenhouse like the one that desiccated Venus, independent of starlight. Proxima b is not likely to be in that state, but the tidal heating could still be very strong, causing continual volcanic eruptions as on Jupiter's moon Io, and/or raising enormous ocean waves. Based on the information we have now, we don't know the magnitude of tidal heating, but we must be aware of it and explore its implications.

The host star's short, high energy bursts, called flares, are also a well known concern for surface life on planets of red dwarfs. Flares are eruptions from small regions of the surfaces of stars that cause brief (hours to days) increases in brightness. Crucially, flares emit blasts of positively-charged protons, which have been shown by Antigona Segura and colleagues to deplete ozone layers that can protect life from harmful high-energy UV light.

Proxima flares far more often than our Sun and Proxima b is much closer to Proxima than Earth is to the Sun, so Proxima b is likely to have been subjected to repeated bombardments. If the atmosphere could develop a robust shield to these eruptions, such as a strong magnetic field that then flaring could be unimportant. Alternatively if it exists under just a few meters of water. Therefore, flares should not be considered fatal for life on Proxima b.

The concern over flaring naturally leads to the question of whether the planet actually does have a protective magnetic field like Earth's. For years, many scientists were concerned that such magnetic fields would be unlikely on planets like Proxima b because tidal locking would prevent their formation. The thinking went that magnetic fields are generated by electric currents moving in the planetary core, and the movement of charged particles needed to create these currents was caused by planetary rotation. A slowly rotating world might not transport the charged particles in the core rapidly enough to generate a strong enough magnetic field to repel the flares, and hence planets in the habitable zones of M dwarfs have no atmospheres.

However, more recent research has shown that planetary magnetic fields are actually supported by convection, a process by which hot material at the center of the core rises, cools, and then returns. Rotation helps, but Dr. Peter Driscoll and I recently calculated that convection is more than sufficient to maintain a strong magnetic field for billions of years on a tidally locked and tidally heated planet. Thus, it is entirely possible that Proxima b has a strong magnetic field and can deflect flares.

So is Proxima b habitable? The short answer is “It's complicated.” Our observations are few, and what we do know allow for a dizzying array of possibilities. Did Proxima b move halfway across the galaxy? Did it endure a planetary-system-wide instability that launched its sibling planets into deep space and changed its orbit? How did it cope with the early high luminosity of its host star? What is it made of? Did it start out as a Neptune-like planet and then become Earth-like? Has it been relentlessly bombarded with flares and coronal mass ejections? Is it tidally heated into an Io-like (or worse) state? These questions are central to unlocking Proxima's potential habitability and determining if our nearest galactic neighbor is an inhospitable wasteland, an inhabited planet, or a future home for humanity.

The last point is not as rhetorical as it might seem. Since all life requires an energy source, it stands to reason that, in the long term — by which I mean the loooong term — planets like Proxima b might be the ideal homes for life. Our Sun will burn out in a mere 4 billion years, but Proxima Centauri will burn for 4 trillion more. Moreover, if a “planet c” exists and slightly perturbs b's orbit, tidal heating could supply modest energy to b's interior indefinitely, providing the power to maintain a stable atmosphere.

The Daily Galaxy via PaleRedDot.org

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“This galaxy cluster isn't just remarkable for its distance, it's also going through an amazing growth spurt unlike any we've ever seen,” said Tao Wang of the French Alternative Energies and Atomic Energy Commission (CEA) who led the NASA study.

A new record for the most distant galaxy cluster has been set using NASA's Chandra X-ray Observatory and other telescopes. This galaxy cluster may have been caught right after birth, a brief, but important stage of evolution never seen before.

The galaxy cluster is called CL J1001+0220 (CL J1001 for short) and is located about 11.1 billion light years from Earth. The discovery of this object pushes back the formation time of galaxy clusters the largest structures in the Universe held together by gravity by about 700 million years.

The core of CL J1001 contains eleven massive galaxies nine of which are experiencing an impressive baby boom of stars. Specifically, stars are forming in the cluster's core at a rate that is equivalent to over 3,000 Suns forming per year, a remarkably high value for a galaxy cluster, including those that are almost as distant, and therefore as young, as CL J1001.

The diffuse X-ray emission detected by Chandra and ESA's XMM-Newton Observatory comes from a large amount of hot gas, one of the defining features of a true galaxy cluster.

“It appears that we have captured this galaxy cluster at a critical stage just as it has shifted from a loose collection of galaxies into a young, but fully formed galaxy cluster,” said co-author David Elbaz from CEA. Previously, only these loose collections of galaxies, known as protoclusters, had been seen at greater distances than CL J1001.

The results suggest that elliptical galaxies in galaxy clusters like CL J1001 may form their stars during shorter and more violent outbursts than elliptical galaxies that are outside clusters. Also, this discovery suggests that much of the star formation in these galaxies happens after the galaxies fall onto the cluster, not before.

In comparing their results to computer simulations of the formation of clusters performed by other scientists, the team of astronomers found that CL J1001 has an unexpectedly high amount of mass in stars compared to the cluster's total mass. This may show that the build-up of stars is more rapid in distant clusters than simulations imply, or it may show that clusters like CL J1001 are so rare that they are not found in today's largest cosmological simulations.

“We think we're going to learn a lot about the formation of clusters and the galaxies they contain by studying this object,” said co-author Alexis Finoguenov of the University of Helsinki in Finland, “and we're going to be searching hard for other examples.”

The result is based on data from a large group of observatories in space and on the ground including Chandra, NASA's Hubble Space Telescope and Spitzer Space Telescope, ESA's XMM-Newton and Herschel Space Observatory, the NSF's Karl G. Jansky Very Large Array, the Atacama Large Millimeter/submillimeter Array (ALMA) , the Institut de Radioastronomie Millimetrique Northern Extended Millimeter Array (IRAM NOEMA), and ESO's Very Large Telescope.
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The Daily Galaxy via NASA's Chandra X-ray Observatory.

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Don't miss this! Join Polygon's Charlie Hall as he mans an expedition to Alpha Centauri in Elite Dangerous, while space expert, Loren Grush, joins him to discuss last week's announcement that astronomers using European Southern Observatory (ESO) telescopes in Chile and other facilities have found clear evidence of a planet orbiting the closest star to Earth, Proxima Centauri may ultimately prove to be a habitable planet could that harbor an advanced technological civilization.

Red Dwarfs “may be one instance in which older is better,” said Seth Shostak, senior astronomer and director of California-based SETI. “Older solar systems have had more time to produce intelligent species.”

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