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Does Europa Have Plate Tectonics

December 11, 2017 by  
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The case for plate tectonics on Jupiter’s ocean-harboring moon Europa keeps getting stronger.

Scientists had already spotted geological signs that plates within the moon’s ice shell may be diving beneath one another toward the moon’s buried ocean. Now, a new study suggests that such “subduction” is indeed possible on Europa and shows how the phenomenon might be happening. 

The new results should intrigue astrobiologists and anyone else who hopes that Earth isn’t the only inhabited world in the solar system.

“If, indeed, there’s life in that ocean, subduction offers a way to supply the nutrients it would need,” study lead author Brandon Johnson, an assistant professor in the Department of Earth, Environmental and Planetary Sciences at Brown University in Rhode Island, said in a statement.  

Such nutrients include oxidants, electron-stripping substances that are common on Europa’s surface and that could help provide an energy source for life, the researchers said. 

Here on Earth, subduction is driven primarily by temperature differences between relatively cool (and, therefore, dense) rocky plates and the superhot surrounding mantle. Thermal gradients can’t be the prime mover on Europa, however: Ice plates would warm up as they dove, quickly equilibrating to the temperature of the ice below, study team members said.

But that doesn’t mean subduction can’t be happening on the Jovian moon, Johnson and his colleagues found. Their computer models suggest that Europan ice plates can indeed dive — if they’re saltier than their surroundings.

“Adding salt to an ice slab would be like adding little weights to it, because salt is denser than ice,” Johnson said in the same statement. “So, rather than temperature, we show that differences in the salt content of the ice could enable subduction to happen on Europa.”

Such differences may indeed exist within the moon’s ice shell, the researchers said. Upwelling from the underground ocean could deposit salt patchily on the surface, as could eruptions of cryovolcanoes, the scientists said.

The presence of plate tectonics on Europa could help us learn more about our own planet as well as the icy moon, Brown said.

“It’s fascinating to think that we might have plate tectonics somewhere other than Earth,” he said. “Thinking from the standpoint of comparative planetology, if we can now study plate tectonics in this very different place, it might be able to help us understand how plate tectonics got started on the Earth.”

The new study has been accepted for publication in the Journal of Geophysical Research: Planets.

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Astronomers Try To Size-Up The Density Of Neutron Stars

December 8, 2017 by  
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Astronomers are getting a better handle on the densest objects in the universe.

These bizarre bodies, known as neutron stars, are the corpses of stars that were once far heftier than the sun. Neutron stars generally pack between 1.1 and 3 solar masses into a space about the size of a big city, crushing pretty much all of their electrons and protons together to form neutrons (hence the name).

But much about neutron stars remains unknown, including their exact size. The veil may be lifting, however, thanks to recent observations of a dramatic neutron-star merger.

On Aug. 17, detectors run by the Laser Interferometer Gravitational-wave Observatory (LIGO) and Virgo projects picked up gravitational waves — the ripples in space-time first predicted by Albert Einstein a century ago — emanating from the galaxy NGC 4993, which lies about 130 million light-years from Earth.

In October, researchers announced that these waves were generated by a collision involving two neutron stars, which together harbored 2.74 times more mass than the sun. This marked an astronomical first; LIGO had picked up gravitational waves from black-hole mergers before, but never from a collision of neutron stars.

Scientists using other instruments also spotted flashes of light coming from the merger, opening up a new era of “multimessenger astrophysics.”

Now, a team of scientists has performed computer simulations of the merger, modeling a bunch of different ways that it could have gone down in a new study that was published last week in The Astrophysical Journal Letters.

Calculations based on these simulations help constrain the size of neutron stars. The results suggest that a neutron star harboring 1.6 solar masses must be at least 13.3 miles (21.4 kilometers) wide, study team members said.

This number is not set in stone, the researchers stress; it will likely be refined as the LIGO and Virgo teams gather more and more data.

“We expect that more neutron-star mergers will soon be observed, and that the observational data from these events will reveal more about the internal structure of matter,” study lead author Andreas Bauswein, from the Heidelberg Institute for Theoretical Studies in Germany, said in a statement.

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Does Pluto Have Buried Oceans

December 7, 2017 by  
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Our solar system may harbor many more potentially habitable worlds than scientists had thought.

Subsurface oceans could still slosh beneath the icy crusts of frigid, faraway worlds such as the dwarf planets Pluto and Eris, kept liquid by the heat-generating tug of orbiting moons, according to a new study. 

“These objects need to be considered as potential reservoirs of water and life,” lead author Prabal Saxena, of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, said in a statement. “If our study is correct, we now may have more places in our solar system that possess some of the critical elements for extraterrestrial life.”  

Underground oceans are known, or strongly suspected, to exist on a number of icy worlds, including the Saturn satellites Titan and Enceladus and the Jovian moons Europa, Callisto and Ganymede. These oceans are kept liquid to this day by “tidal heating”: The powerful gravitational pull of these worlds’ giant parent planets stretches and flexes their interiors, generating heat via friction.

The new study suggests something similar may be going on with Pluto, Eris and other trans-Neptunian objects (TNOs).

Many of the moons around TNOs are thought to have coalesced from material blasted into space when objects slammed into their parent bodies long ago. That’s the perceived origin story for the one known satellite of Eris (called Dysnomia) and for Pluto’s five moons (as well as for Earth’s moon). 

Such impact-generated moons generally begin their lives in relatively chaotic orbits, team members of the new study said. But over time, these moons migrate to more-stable orbits, and as this happens, the satellites and the TNOs tug on each other gravitationally, producing tidal heat.

Saxena and his colleagues modeled the extent to which this heating could warm up the interiors of TNOs — and the researchers got some intriguing results.

“We found that tidal heating can be a tipping point that may have preserved oceans of liquid water beneath the surface of large TNOs like Pluto and Eris to the present day,” study co-author Wade Henning, of NASA Goddard and the University of Maryland, said in the same statement.

As the term “tipping point” implies, there’s another factor in play here as well. It’s been widely recognized that TNOs could harbor buried oceans thanks to the heat produced by the decay of the objects’ radioactive elements. But just how long such oceans could persist has been unclear. This type of heating peters out eventually, as more and more radioactive material decays into stable elements. And the smaller the object, the faster it cools down.

Tidal heating may do more than just lengthen subsurface oceans’ lives, researchers said.Next Up

“Crucially, our study also suggests that tidal heating could make deeply buried oceans more accessible to future observations by moving them closer to the surface,” said study co-author Joe Renaud, of George Mason University in Virginia. “If you have a liquid-water layer, the additional heat from tidal heating would cause the next adjacent layer of ice to melt.” 

The new study was published online last week in the journal Icarus

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A Planets Equator May Inhibit Astronomers From Finding Life

December 5, 2017 by  
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Spotting signs of life in an alien planet’s atmosphere may be tougher than scientists had thought.

One prominent such “biosignature” target, ozone, may get trapped near the equators of Proxima b, TRAPPIST-1d and other potentially habitable worlds that orbit close to their host stars, making the gas hard to detect from afar, a new study suggests.

“Absence of traces of ozone in future observations does not have to mean there is no oxygen at all,” study lead author Ludmila Carone, of the Max Planck Institute for Astronomy in Heidelberg, Germany, said in a statement. “It might be found in different places than on Earth, or it might be very well hidden.”

Ozone is an unstable molecule that consists of three oxygen atoms. Here on Earth, the stuff is generally produced in the atmosphere after ultraviolet (UV) radiation from the sun splits “normal” diatomic oxygen (O2). 

The vast majority of Earth’s O2 is generated by living organisms — plants and photosynthetic microbes — so ozone serves as a sort of secondary biomarker, at least for Earth-like life.

Earth’s atmospheric flows distribute most ozone relatively evenly into our planet’s famous ozone layer, which helps shield life from harmful UV radiation. So hypothetical aliens studying Earth from afar with powerful telescopes would have a good chance of detecting the gas.

But the situation is likely different on Proxima b, TRAPPIST-1d and other tidally locked worlds — those that always show the same face to their parent stars, and therefore have a “dayside” and a “nightside” — according to Carone and her colleagues. (Tidal locking is a consequence of a very tight orbit; TRAPPIST-1d and Proxima b complete one lap around their stars every four Earth days and 11 Earth days, respectively.)

Modeling work performed by the researchers indicates that, on planets with orbital periods of 25 Earth days or less, airflows tend to concentrate ozone (and other photochemically produced molecules) in an equatorial band.

“We all knew from the beginning that the hunt for alien life will be a challenge,” Carone said. “As it turns out, we are only just scratching the surface of how difficult it really will be.”

The new results also suggest that worlds like Proxima b don’t have a global ozone layer. That may or may not have a significant negative effect on their habitability, Carone said.

“Proxima b and TRAPPIST-1d orbit red dwarfs, reddish stars that emit very little harmful UV light to begin with,” she said in the statement. (Tidally locked planets pretty much have to orbit dim dwarf stars to be habitable; worlds that orbit so close to sunlike stars are far too hot to host life as we know it.) 

“On the other hand, these stars can be very temperamental, and prone to violent outbursts of harmful radiation, including UV,” she added. “There is still a lot that we don’t know about these red dwarf stars. But I’m confident we will know much more in five years.”

In five years, astronomers will have a lot more data — from telescopes such as NASA’s $8.8 billion James Webb Space Telescope, which is scheduled to launch in early 2019 — to inform their inferences about the habitability of red-dwarf planets. And advances in modeling techniques over this time span should help as well, study team members said.

The new study will appear in the Feb. 1, 2018, issue of the journal Monthly Notices of the Royal Astronomical Society.

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Astronomers Find 72 Potential New Galaxies

December 4, 2017 by  
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Astronomers have found 72 potential galaxies hiding in plain sight inside a vast patch of the sky previously observed by the Hubble Space Telescope. The discovery not only gives astronomers new targets to study, but also will aid studies of star motion and formation and other properties of old galaxies, the researchers said.

The new study was performed by the MUSE instrument on the European Southern Observatory’s Very Large Telescope in Chile. Astronomers discovered the newfound galaxies while measuring the distances and properties of 1,600 galaxies captured by the Hubble Space Telescope during its Ultra Deep Field survey.

The 72 newfound galaxies shine in Lyman-alpha light, which is a particular wavelength of ultraviolet light. Because the galaxies are receding from us, their wavelength was stretched from ultraviolet to visible, or near-infrared.

The discoveries were made in the Hubble Ultra Deep Field, which is a tiny region of the sky in the southern constellation Fornax (the Furnace). The Hubble data were originally obtained in 2004, two years after NASA space shuttle astronauts visited the space telescope to install the Advanced Camera for Surveys (ACS) and perform other needed maintenance.

Using ACS, Hubble peered at a small region of the sky and found galaxies that had formed less than 1 billion years after the Big Bang, which kick-started the universe. (The Big Bang took place about 13.8 billion years ago, making those galaxies more than 12.8 billion years old.)

“MUSE can do something that Hubble can’t — it splits up the light from every point in the image into its component colors to create a spectrum. This allows us to measure the distance, colors and other properties of all the galaxies we can see — including some that are invisible to Hubble itself,” stated Roland Bacon, who led the survey team and is also an astrophysicist at the Center for Astrophysics Research of Lyon at the University of Lyon in France.

MUSE is a spectroscopic instrument, meaning it measures light emitted, absorbed or scattered in space. Using spectroscopy, astronomers can learn about stars, galaxies and other objects, including properties such as how fast the objects are moving and what elements they are made of. MUSE recently underwent an adaptive-optics upgrade, which could help with future studies of old galaxies, Bacon added.

The new work resulted in 10 science papers that will be published in a special issue of the journal Astronomy & Astrophysics.

“MUSE has the unique ability to extract information about some of the earliest galaxies in the universe — even in a part of the sky that is already very well-studied,” stated Jarle Brinchmann, lead author of one of the papers.

“We learn things about these galaxies that [it] is only possible [to learn] with spectroscopy, such as chemical content and internal motions — not galaxy by galaxy, but all at once for all the galaxies,” added Brinchmann, who is an astronomer at Leiden University in the Netherlands and the Institute of Astrophysics and Space Sciences at CAUP (Center for Astrophysics of the University of Porto) in Portugal. 

Astronomers also found hydrogen halos in old galaxies, which could provide more information about how material leaves and enters galaxies formed early in the universe’s history. Future research directions could include looking at star formation, galactic winds, galaxy mergers or even a phenomenon known as cosmic reionization. 

That phenomenon explains how light returned to a dark universe hundreds of millions of years ago. “First light” in the universe was roughly 380,000 years after the Big Bang, when the cosmos cooled down and fundamental particles were able to combine into atoms. However, once these combinations ceased, the universe entered a dark age, because there was no other light available — the first stars weren’t shining yet. Reionization occurred between 150 million years and 650 million years after the Big Bang, when the first stars and galaxies were formed from collapsing groups of gas, producing light in the universe again.

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Astronomers Find Intense Illumination In Early Universe

December 1, 2017 by  
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Imagine what the iconic pillars of the Eagle Nebula would look like if a powerful force caused the stellar nursery to create stars at a thousand times its current rate.

New observations confirm that a bright point of light in the constellation Dorado is in fact an intense, extraordinarily bright region of star birth. It was formed by the repetitive collision of two spiral galaxies so far away that their light comes from the early universe. 

Dominik Riechers, an astronomer at Cornell University in Ithaca, New York, and lead author on the new study, observed the colliding starburst galaxies with his team using the Atacama Large Millimeter/submillimeter Array (ALMA) in northern Chile. The galaxies are similar in structure to Earth’s home, the Milky Way galaxy, which also hosts the star-forming Eagle Nebula..

The new findings suggest that the brightness of the two starburst galaxies isn’t merely a result of their collision. The two spiral structures located 12.7 billion light-years away from Earth, known collectively as the ADFS-27 system, also have more star-making material to work with than Earth’s home galaxy does. In fact, ADFS-27 has “50 times the amount of star-forming gas as the Milky Way,” researchers said in a statement from ALMA.

Starburst galaxies are relatively rare, and the research team said they were astounded to find two of the massive galaxies near each other. These observations are also a dramatic look into the past: Because the starburst galaxies are so far away, astronomers are actually observing them as they appeared when the universe was only 1 billion years old. At that time, the universe was just becoming transparent, as the process of reionization finished.

“Considering their extreme distance from Earth and the frenetic star-forming activity inside each, it’s possible we may be witnessing the most intense galaxy merger known to date,” Riechers said in the statement. Their predicted course is to ultimately merge into one large elliptical galaxy. And because distance creates a long lag time between when events in those galaxies occur and when we can observe them here, that massive merger may have already occurred.

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Does Space Dust Transport Life Around The Galaxy

November 29, 2017 by  
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It may not take an asteroid strike to transport life from one planet to another.

Fast-moving dust could theoretically knock microbes floating high up in a world’s atmosphere out into space, potentially sending the bugs on a trip to another planet — perhaps even one orbiting a different star, according to a new study.

“The proposition that space-dust collisions could propel organisms over enormous distances between planets raises some exciting prospects of how life and the atmospheres of planets originated,” study author Arjun Berera, a professor in the School of Physics and Astronomy at the University of Edinburgh in Scotland, said in a statement.  

“The streaming of fast space dust is found throughout planetary systems and could be a common factor in proliferating life,” Berera added.

Berera isn’t the first person to propose that organisms could hop from world to world throughout the cosmos. That basic idea, known as panspermia, has been around for thousands of years. It has received renewed interest recently, however, as scientists have demonstrated that some organisms — such as certain bacteria, and micro-animals known as tardigrades — can survive for extended periods in space.

But researchers have generally regarded comet or asteroid impacts as the only viable way to get simple life-forms off a planet and into space, whence they could perhaps blunder their way to a different habitable world. (We won’t consider here the “directed panspermia” idea, which posits that intelligent aliens have seeded the galaxy with life or its building blocks.)

Comet or asteroid impacts do indeed blast rocks from planet to planet. Scientists have found numerous meteorites here on Earth that were once part of Mars — including one known as ALH84001, which some scientists think may preserve signs of ancient Red Planet life.

In the new study, Berera examined what likely happens when bits of interplanetary dust hit molecules and particles in Earth’s atmosphere. This space stuff rains down on us every day, hitting the planet at speeds of between 22,400 mph and 157,000 mph (36,000 to 253,000 km/h).

He calculated that small particles floating at least 93 miles (150 kilometers) above Earth’s surface could theoretically get knocked into space by this wandering dust. It’s unclear if microbes could survive such violent collisions; that’s an area ripe for future research, Berera wrote in the new paper, which has been accepted for publication in the journal Astrobiology. (You can read the study for free at the online preprint site arXiv.org.)

And even if these micro-impacts are invariably fatal, they could still help life get a foothold on other worlds by sending its building blocks — the complex molecules that make up a microbe corpse, for example — out into space, he added.

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Astronomers Get New Telescope To Find Exploding Stars

November 22, 2017 by  
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A powerful new camera that will help scientists search for exploding stars and fast-moving objects in Earth’s solar system has captured its first image of the night sky.

The Zwicky Transient Facility (ZTF) is officially up and running at the California Institute of Technology’s Palomar Observatoryin the mountains northeast of San Diego. Its primary piece of hardware is a wide-field camera, attached to a 48-inch (122 centimeters) telescope, that can image the entire visible plane of the Milky Way galaxy twice per night and the entire night sky every three nights, according to a statement from Caltech.

The first image from ZTF shows a region of the sky in the constellation Orion that includes the Horsehead Nebula, a star-forming region imaged in glorious detailby the Hubble Space Telescope. But the ZTF camera has a considerably larger field of view compared with Hubble’s — each image captures an area on the sky measuring 47 square degrees, or about 247 times the area of the full moon, according to the statement.  

Photographing huge areas of the sky extremely quickly is ZTF’s primary function. By comparing images of the same region of the sky taken within a few hours or a few days of one another, scientists can look for cosmic objects that are moving or changing in brightness over those short timescales.

Of course, most stars, galaxies, nebulas and other large cosmic objects remain more or less stagnant — in brightness and position — over a few hours or days. But the universe is also full of so-called variable objects (those that change in brightness) and transient objects (that appear to move relatively quickly). These include things like dying stars that explode as supernovasand, in a matter of hours, become exponentially brighter than they were the day before; asteroids that zip through the solar system; black holes that devour entire stars, causing the material from the star to rapidly change in brightness; and pairs of neutron stars, the densest objects in the universe, that mergeand release great bursts of radiation.

“The universe is an extremely dynamic place,” Mansi Kasliwal, an assistant professor of astronomy at Caltech and a member of the ZTF team, said in a video from Caltech. Referring specifically to supernovas and other brief eruptions of light, Kasliwal said, “These short-lived explosions — they could last for seconds, for minutes, for months, but [eventually], they disappear on us. And catching these flashes of light, catching these cosmic fireworks, that’s what ZTF can uniquely do.”

The ZTF science survey, scheduled to run from early 2018 until the end of 2020, will turn up objects that are of interest to a wide range of astronomy subfields. Supernovas are obviously interesting to astronomers who study the life cycles of stars, but they are also used by cosmologists to measure cosmic distances. ZTF’s ability to find comets and asteroids will be of interest to astronomers who look for space rocks that could come dangerously close to Earth. But mostly, ZTF will increase the volume of transient and variable objects that astronomers have to study.

“There’s a lot of activity happening in our night skies,” Shrinivas Kulkarni, the principal investigator for ZTF and a professor of astronomy and planetary science at Caltech, said in the statement. “In fact, every second, somewhere in the universe, there’s a supernova that’s exploding. Of course, we can’t see them all, but with ZTF, we will see up to tens of thousands of explosive transients every year over the three-year lifetime of the project.”

Identifying objects in the night sky that flicker, flash, move or change in other ways is a game of comparison. Scientists take an image of the sky, then wait a few hours or a full day, and image the same area again. With ZTF, researchers can use computer software to literally subtract one image from the other, eliminating objects that haven’t changed in the time between when the two images were taken.

“The universe is so dynamic that if you subtract two identical [images] of the sky, separated by an hour or a night, [you can] see new flashes of light that weren’t there in the image from an hour before or a night before,” Kasliwal said in the video. “Those new flashes of light in the subtracted images are what we are after.”

Before astronomers could take digital images of the sky and utilize software to look for these variable objects, this comparison of identical regions of the sky was done manually. Astronomers would take two images of the same patch of the sky (separated by some period of time) using glass photographic plates. Then, the scientists would set these plates next to one another and look for differences. An instrument called a blink comparator, introduced in the early 20th century, would rapidly flip between the images to make it easier to spot transient objects. Astronomer Clyde Tombaugh used a blink comparator to discover Pluto.

ZTF is named after Caltech astrophysicist Fritz Zwicky, who arrived at the university in 1925 and did a great deal of work to systematically search the sky for variable objects; he discovered 120 supernovas in his lifetime, according to the statement

ZTF is a successor to the Palomar Transient Factory (PTF), which ran from 2009 until earlier this year, and also had a camera installed on the 48-inch telescope at Palomar. Astronomers then used the other two telescopes at the observatory, as well as the telescopes at the Keck Observatory in Hawaii (which is co-managed by Caltech), to conduct follow-up observations of particularly interesting objects.

“Going from one telescope to the next allowed us to perform a sort of triage and pick out the most interesting objects for further study; it was a vertically integrated observatory,” Kulkarni said in the statement. “The reason we called it the Palomar Transient Factory is because it did astronomy on an industrial scale.”

ZTF will utilize those same resources to conduct follow-up studies of variable objects that it identifies. But its wide-field camera also gives it some significant improvements over its predecessor program. For example, ZTF can image an area of the sky seven times larger than PTF could, and it can resolve objects out to greater distances, according to the ZTF scientists. Plus, its “upgraded electronics and telescope-drive systems” enable the ZTF camera to take 2.5 times as many exposures each night, according to the statement.

Combined, that means ZTF can scan the sky on the order of 10 times faster than PTF could, the project scientists said in the statement. But there is yet another all-sky survey on the horizon, and it will be about 10 times faster than ZTF. It’s called the Large Synoptic Survey Telescope, and it’s set to come online in 2023. 

“ZTF is a step toward the future,” Kulkarni said

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Astronomers Find New Alien Planet Suitable For Life

November 21, 2017 by  
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A newfound exoplanet may be one of the best bets to host alien life ever discovered — and it’s right in Earth’s backyard, cosmically speaking.

Astronomers have spotted a roughly Earth-mass world circling the small, dim star Ross 128, which lies just 11 light-years from the sun. The planet, known as Ross 128b, may have surface temperatures amenable to life as we know it, the researchers announced in a new study that will appear in the journal Astronomy & Astrophysics.

Ross 128b is 2.6 times more distant from Earth than Proxima b, the potentially habitable planet found in the nearest solar system to the sun. But Proxima b’s parent star, Proxima Centauri, blasts out a lot of powerful flares, potentially bathing that planet in enough radiation to stunt the emergence and evolution of life, scientists have said. [10 Exoplanets That Could Host Alien Life]

Radiation is likely much less of an issue for Ross 128b, because its parent star is not an active flarer, said discovery team leader Xavier Bonfils, of the Institute of Planetology and Astrophysics of Grenoble and the University of Grenoble Alpes in France.

“This is the closest Earth-mass planet potentially in the habitable zone that orbits a quiet star,” Bonfils told Space.com

Bonfils and his colleagues found Ross 128b using the High Accuracy Radial velocity Planet Searcher (HARPS), an instrument at the European Southern Observatory’s La Silla Observatory in Chile.

As its name suggests, HARPS employs the “radial velocity” method, noticing the wobbles in a star’s movement induced by the gravitational tugs of orbiting planets. (NASA’s prolific Kepler space telescope, by contrast, uses the “transit” technique, spotting tiny brightness dips caused when a planet crosses its host star’s face from the spacecraft’s perspective.)

The HARPS observations allowed Bonfils and his team to determine that Ross 128b has a minimum mass 1.35 times that of Earth, and that the planet orbits its host star once every 9.9 Earth days.

Such a tight orbit would render Ross 128b uninhabitable in our own solar system. But Ross 128 is much cooler than the sun, so the newfound world is likely temperate, the researchers said. Determining whether  the planet is actually capable of supporting life as we know it, however, would require a better understanding of its atmosphere, Bonfils said.

“Ross 128b receives 1.38 times [more] irradiation than Earth from our sun,” he said. “Some models made by theorists say that a wet Earth-size planet with such irradiation would form high-altitude clouds. Those clouds would reflect back to space a large fraction of the incident light, hence preventing too much greenhouse heating. With those clouds, the surface would remain cool enough to allow liquid water at the surface. Not all models agree, though, and others predict this new planet is rather like Venus.

Though both Ross 128 and Proxima Centauri are red dwarfs — the most common type of star in the Milky Way galaxy — they are very different objects.

“Proxima Centauri is particularly active, with frequent, powerful flares that may sterilize (if not strip out) its atmosphere,” Bonfils said. “Ross 128 is one of the quietest stars of our sample and, although it is a little further away from us (2.6x), it makes for an excellent alternative target.”

And the star may indeed be targeted in the not-too-distant-future — by giant ground-based instruments such as the European Extremely Large Telescope, the Giant Magellan Telescope and the Thirty Meter Telescope, all of which are scheduled to be up and running by the mid-2020s.

Such megascopes should be able to resolve Ross 128b and even search its atmosphere for oxygen, methane and other possible signs of life, Bonfils said. (NASA’s $8.9 billion James Webb Space Telescope, which is scheduled to launch in early 2019, probably won’t be able to perform such a biosignature search, the researchers said in their discovery paper. If Ross 128b transited its host star from Webb’s perspective, it would likely be a different story, they added.)

Earlier this year, by the way, radio astronomers detected a strange signal that seemed to be emanating from Ross 128. But further investigation revealed that the signal most likely came from an Earth-orbiting satellite, not an alien civilization.

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Did Researchers Find The Missing Link To Life

November 20, 2017 by  
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Four billion years ago, Earth was covered in a watery sludge swarming with primordial molecules, gases, and minerals — nothing that biologists would recognize as alive. Then somehow, out of that prebiotic stew emerged the first critical building blocks — proteins, sugars, amino acids, cell walls — that would combine over the next billion years to form the first specks of life on the planet.

A subset of chemists have devoted their careers to puzzling out the early chemical and environmental conditions that gave rise to the origins of life. With scant clues from the geological record, they synthesize simple molecules that may have existed billions of years ago and test if these ancient enzymes had the skills to turn prebiotic raw material into the stuff of life.

A team of such chemists from the Scripps Research Institute reported Nov. 6 in the journal Nature Chemistry that they identified a single, primitive enzyme that could have reacted with early Earth catalysts to produce some of the key precursors to life: the short chains of amino acids that power cells, the lipids that form cell walls, and the strands of nucleotides that store genetic information.

Ramanarayanan Krishnamurthy is an associate professor of chemistry at Scripps and lead author of the origins of life paper. For a number of years, his lab has been experimenting with a synthetic enzyme called diamidophosphate (DAP) that’s been shown to drive a critical chemical process called phosphorylation. Without phosphorylation — which is simply the process of adding a phosphate molecule to another molecule — life wouldn’t exist.

“If you look at life today, and how it probably was at least three billion years ago, it was based on a lot of phosphorylation chemistry,” Krishnamurthy told Seeker. “Your RNA, DNA, and a lot of your biomolecules are phosphorylated. So are sugars, amino acids, and proteins.”

The enzymes that trigger phosphorylation are called kinases. They use phosphorylation to send signals instructing cells to divide, to make more of one protein than another, to tell DNA strands to separate, or RNA to form. DAP may have been one of the first primordial kinases to get the phosphorylation ball rolling, Krishnamurthy believed.

To test his theory, Krishnamurthy and his colleagues simulated early Earth conditions in the lab, using both a water base and a muddy paste set to varying pH levels. They combined DAP with different concentrations of magnesium, zinc, and a compound called imidazole that acted as a catalyst to speed the reactions, which still took weeks or sometimes months to complete.

For DAP to pass the test, it had to successfully trigger phosphorylation events that resulted in simple nucleotides, peptides, and cell wall structures under similar conditions. Past candidates for origin-of-life enzymes could only phosphorylate certain structures under wildly different chemical and environmental conditions. DAP, Krishnamurthy found, could do it all, phosphorylating the four nucleoside building blocks of RNA, then short RNA-like strands, then fatty acids, lipids, and peptide chains.

Does that mean that DAP is the pixie dust that transformed random matter into life? Not quite, said Krishnamurthy.

“The best we can do is try to demonstrate that simple chemicals under the right conditions could give rise to further chemistry which may lead to life-like behavior. We can’t make a claim that this is the way that life formed on the early Earth.”

For one thing, Krishnamurthy has no proof that DAP even existed four billion years ago. He synthesized the molecule in his lab as a way to solve one of the fundamental challenges to phosphorylating in wet, early Earth conditions. For most phosphorylation reactions to work, they need to remove a molecule of water in the process.

“How do you remove water from a molecule when you are surrounded by a pool of water?” asked Krishnamurthy. “That’s thermodynamically an uphill task.”

DAP gets around that problem by removing a molecule of ammonia instead of water.

Krishnamurthy is working with geochemists to identify potential sources of DAP in the distant geological past. Phosphate-rich lava flows may have reacted with ammonia in the air to create DAP, or it could have been leached out of phosphate-containing minerals. Or maybe it even arrived on the back of a meteorite forged by a far-off star.

One thing is clear, without DAP or something like it, Earth might still be a lifeless mud puddle.

Courtesy-Space

Are Researchers Close To Finding The Evasive Tetraquark

November 17, 2017 by  
Filed under Around The Net

Flit, zip, jitter, boom. Quarks, the tiny particles that make up everything tangible in the universe, remain deeply mysterious to physicists even 53 years after scientists first began to suspect these particles exist. They bop around at the edge of scientific instruments’ sensitivities, are squirreled away inside larger particles, and decay from their higher forms into their simplest in half the time it takes a beam of light to cross a grain of salt. The little buggers don’t give up their secrets easily.

That’s why it took more than five decades for physicists to confirm the existence of an exotic particle they’ve been hunting since the beginning of quark science: the massive (at least in subatomic particle terms), elusive tetraquark.

Physicists Marek Karliner of Tel Aviv University and Jonathan Rosner of the University of Chicago have confirmed that the strange, massive tetraquark can exist in its purest, truest form: four particles, all interacting with one another inside a single, larger particle, with no barriers keeping them apart. It’s stable, they found, and can likely be generated at the Large Hadron Collider, a particle smasher at the CERN particle physics laboratory in Switzerland, they report in a paper to be published in a forthcoming issue of the journal Physical Review Letters.

If you know a little about particle physics, you probably know that everything with mass is made up of atoms. Diving a little deeper into particle physics would reveal that those atoms are made up of subatomic particles — protons, neutrons and electrons. An even deeper look would reveal quarks.

Neutrons and protons are the most common examples of a class of particles known as hadrons. If you could peer into a hadron, you’d find it’s made up of even more basic particles, clinging tightly together. Those are quarks.

Like atoms, which adopt different properties depending on the combinations of protons and neutrons in their nuclei, hadrons derive their properties from combinations of their resident quarks. A proton? That’s two “up” quarks and one “down” quark. Neutrons? Those are made up of two “down” quarks and one “up” quark. [Wacky Physics: The Coolest Little Particles in Nature]

(Electrons aren’t made up of quarks because they aren’t hadrons — they’re leptons, part of a class of distant cousins of quarks.)

“Up” and “down” are the most common flavors of quark, but they’re just two out of six. The other four — “charm,” “top,” “strange” and “bottom” quarks — existed in the moments after the Big Bang, and they appear in extreme situations, such as during high-velocity collisions in particle colliders. But they’re much heavier than up and down quarks, and they tend to decay into their lighter siblings within moments of their creation.

But those heavier quarks can last long enough to bind together into strange hadrons with unusual properties that are stable for the very short lifetimes of the quarks zipping around inside them. Some good examples: the “doubly charmed baryon,” or a hadron made up of two charm quarks and a lighter quark; and its cousin, formed when a hadron made up of two bulky bottom quarks and one lighter quark fuse together in a flash more powerful than the individual fusion reactions inside hydrogen bombs. (Of note, the bottom quark fusion is militarily useless thanks to heavy quarks’ short lifetimes.)

Playing with colors

“The suspicion had been for many years that [the tetraquark] is impossible,” Karliner told Live Science.

That’s because physical laws suggested four quarks couldn’t actually bind together into a stable hadron. Here’s why: Just like in atoms, where the attraction between positively charged protons and negatively charged electrons is what holds them together, hadrons are held together by forces as well. In atoms, positive and negative particles constantly try to neutralize their charges to zero, so protons and electrons stick together, canceling each other out. [7 Strange Facts About Quarks]

Quarks have positive and negative electrodynamic charges, but they also interact with one another via the much more powerful “strong” force. And the strong force also has charges, called color charges: red, green and blue.

Any quark can have any color charge. And when they bind together to form hadrons, all those charges have to cancel out. So a red quark, for example, has to hook up with either a green quark and a blue quark, or its antimatter twin — an “antiquark” with a color charge of “antired.” (This is your brain on quantum mechanics.) Any combination of a color and its anticolor, or all three colors, sticking together has a neutral color charge. Physicists call these particles “white.”

The tetraquark: It’s like a relationship (in that it doesn’t always work)

So, Karliner said, it’s not hard to imagine a four-quark hadron: Just stick two quarks to two matching antiquarks. But just because you stick four matching quarks together, he said, doesn’t mean they’ll be stable enough to form an actual hadron — they could fly apart.

“Just because you move two men and two women into an apartment,” Karliner said, “doesn’t mean they’ll settle down and form a nuclear family.”

Quarks have mass, which physicists measure in units of energy: megaelectron volts, or MeV. When they bind together, some of that mass converts into the binding energy holding them together, also measured in MeV. (Remember Einstein’s E=mc^2? That’s energy equals mass-times-the-speed-of-light-squared, the equation governing that conversion.)

If the mass is too high compared with the binding force, the energy of the quarks careening around inside the hadron will tear the particle apart. If it’s low enough, the particle will live long enough for the quarks to settle down and develop group properties before they decay. A big, happy quark-foursome family needs to have a mass lower than two mesons (or quark-antiquark pairs) stuck together, according to Karliner.

Unfortunately, the mass of a quark family after some of its bulk is converted into binding force is incredibly difficult to calculate, which makes it hard to figure out whether a given theoretical particle is stable.

Scientists have known for about a decade that mesons can bind to other mesons to form ad-hoc tetraquarks, which is why you might have seen reports touting the existence of tetraquarks before. But in those tetraquarks, each quark interacts primarily with its pair. In a true tetraquark, all four would mix with one another equally.

“It’s charming and interesting, but not the same,” Karliner said. “It’s very different to have two couples in different rooms sharing an apartment, and two men and two women all together with everyone … interacting with everyone else.”

But those double-meson tetraquarks provide the mass threshold that true tetraquarks must cross to be stable, he said.

In theory, Karliner said, it would be possible to predict the existence of a stable tetraquark from pure calculation. But the quantum mechanics involved were just too difficult to make work with any reasonable degree of confidence.

Karliner and Rosner’s key insight was that you could start to figure out the mass and binding energy of rare hadrons by analogy to more common hadrons that had already been measured.

Remember that doubly charmed baryon from earlier? And its explosive cousin with the two bottom quarks? In 2013, Karliner and Rosner began to suspect they could calculate its mass, after thinking carefully about the binding energy inside mesons made up of charm quarks and anticharm quarks.

Quantum mechanics suggests that two different-colored charm quarks — say, a red charm and a green charm — should bind together with exactly half the energy of a charm quark and its antimatter twin — say, a red charm quark and an antired charm antiquark. And scientists have already measured the energy of that bond, so the energy of acharm-charm bond should be half of that.

So Karliner and Rosner worked with those numbers, and they found that the doubly charmed baryon and double-bottom baryon should have a mass of 3627 MeV, plus or minus 12 MeV. They published their papers and pushed the experimentalists at CERN (European Organization for Nuclear Research) to start hunting, Karliner said.

But Karliner and Rosner offered CERN a road map, and eventually, the CERN scientists acceded. In July 2017, the first definite doubly charmed baryons turned up in the Large Hadron Collider (LHC). [Photos: The World’s Largest Atom Smasher (LHC)]”The experimentalists were quite skeptical at first” that it would be possible to find the doubly charmed baryons in the real world, Karliner said. “It’s like looking for a needle not in a haystack, but in a haystack of haystacks.”

“We predicted in 2014 that the mass of this doubly charmed baryon was going to be 3,627 MeV, give or take 12 MeV,” Karliner said. “The LHC measured 3,621 MeV, give or take 1 MeV.”

In other words, they nailed it.

And because their calculation turned out to be correct, Karliner and Rosner had a road map to the true stable tetraquark.

In quantum mechanics, Karliner explained, there’s a general rule that heavier quarks tend to bind much more tightly to each other than lighter quarks do. So if you’re going to find a stable tetraquark, it’s probably going to involve some quarks from the heavier end of the flavor spectrum.

Karliner and Rosner got to work as soon as the doubly charmed baryon measurement was announced. First, they calculated the mass of a tetraquark made up of two charm quarks and two lighter antiquarks; charm quarks, after all, are pretty chunky, at about 1.5 times the mass of a proton. The result? A doubly-charmed tetraquark turns out to be right on the edge of stable and unstable, with room for error on both sides — in other words, too uncertain to call a discovery.

But charm quarks aren’t the heaviest quarks around. Enter the bottom quark, a true monster of an elementary particle at about 3.5 times the mass of its charmed sibling, with an accompanying leap in binding energy.

Fuse two of those together, Karliner and Rosner calculated, along with an up antiquark and a down antiquark, and you’ll end up with a stable foursome — converting so much of their bulk into binding energy that they end up 215 MeV under the maximum mass threshold, with a margin of error of just 12 MeV.

“The upshot of all this is that we now have a robust prediction for the mass of this object which had been the holy grail of this branch of theoretical physics,” Karliner said.

This kind of tetraquark won’t live very long once it’s created; it winks out after just one-tenth of a  picosecond, or the length of time it takes a beam of light to cross a single microscopic skin cell. It then will decay into simpler combinations of up and down quarks. But that 0.1 picoseconds (one ten-trillionth of a second) is plenty long enough on the quantum mechanical scale to be considered a stable particle.

“It’s like if you compared a human lifetime to [the movement of continents],” Karliner said. “If you have some creatures living on the scale of fractions of seconds, a human lifetime would seem almost infinite.”

Onward to Switzerland

The next step, once a particle has been predicted by theorists, is for the experimentalists at CERN to try to create it in the miles-long tubes of their particle smasher, the LHC.

That can be a grueling process, especially because of the specific properties of bottom quarks.

The LHC works by slamming protons together at large fractions of the speed of light, releasing enough energy into the collider that some of it turns back into mass. And some tiny fraction of that mass will condense into rare forms of matter — like that doubly charmed baryon.

But the heavier a particle is, the lower the odds it will pop into being in the LHC. And bottom quarks are exceptionally unlikely creations.

In order to build a tetraquark, Karliner said, the LHC has to generate two bottom quarks in close enough proximity to each other that they bind, and then “decorate” them with two light antiquarks. And then it has to do it again, and again — until it’s happened enough times that the researchers can be sure of their results.

But that’s not as unlikely as it may sound.

“It turns out that, if you consider how you would make such things in a lab,” Karliner said, “the probability of making them is only slightly less likely than finding that baryon with two bottom quarks and one light quark.”

And that hunt is already underway.

Once the two-bottom-quark baryon is discovered, Karliner said — a result he expects within the next few years — “the clock starts ticking” on the appearance of the tetraquark.

Somewhere out there in the ether is a hadron that physicists have been hunting for 53 years. But now they’ve caught its scent.

Courtesy-Space

Supernova Baffles Astronomers

November 15, 2017 by  
Filed under Computing

The appearance of a years-long supernova explosion challenges scientist’s current understanding of star formation and death, and work is underway to explain the bizarre phenomenon.

Stars more than eight times the mass of the sun end their lives in fantastic explosions called supernovas. These are among the most energetic phenomena in the universe. The brightness of a single dying star can briefly rival that of an entire galaxy. Supernovas that form from supermassive stars typically rise quickly to a peak brightness and then fade over the course of around 100 days as the shock wave loses energy.

In contrast, the newly analyzed supernova iPTF14hls grew dimmer and brighter over the span of more than two years, according to a statement by Las Cumbres Observatory in Goleta, California, which tracked the object. Details of the discovery appeared on Nov. 8 in the journal Nature.

 Supernova iPTF14hls was unremarkable when first detected by a partner telescope in San Diego on Sept. 22, 2014. The light spectrum was a textbook example of a Type II-P supernova, the most common type astronomers see, lead author Iair Arcavi, an astronomer at the University of California, Santa Barbara, told Space.com. And the supernova looked like it was already fading, he said.

The observatory was in the middle of a 7.5-year collaborative survey, so Arcavi focused on more-promising objects. But in February, 2015, Zheng Chuen Wong, a student working for Arcavi that winter, noticed the object had become brighter over the past five months.

“He showed me the data,” Arcavi said, “and he [asked], ‘Is this normal?’ and I said, ‘Absolutely not. That is very strange. Supernovae don’t do that,'” Arcavi said.

At first, Arcavi thought it might be a local star in our galaxy, which would appear brighter because it was closer, he said. Many stars are also known to have variable brightness. But the light signature revealed that the object was indeed located in a small, irregular galaxy about 500 million light-years from Earth.

And the object only got weirder. After 100 days, the supernova looked just 30 days old. Two years later, the supernova’s spectrum still looked the way it would if the explosion were only 60 days old. The supernova recently emerged from behind Earth’s sun, and Arcavi said it’s still bright, after roughly three years. But at one one-hundredth of its peak brightness, the object appears to finally be fading out.

“Just to be clear, though, there is no existing model or theory that explains all of the observations we have,” said Arcavi. The supernova may fade out; it may grow brighter, or it may suddenly disappear.

One reason for Arcavi’s uncertainty is that a supernova was seen in the same location in 1954. This means that the event Acavi has been observing, whatever it is, may actually be 60 years running. There’s a 1 to 5 percent chance the two events are unrelated, but that would be even more surprising, said Arcavi. Astronomers have never observed unrelated supernova in the same place decades apart. “We are beyond the cutting-edge of models,” Arcavi said.

“I’m not sure, and I don’t think anyone else is sure, just what the hell is happening,” astrophysicist Stanford Woosley, at University of California, Santa Cruz, told Space.com. “And yet it happened, and so it begs explanation.”

Woosley is not affiliated with the study, but he is among the theoreticians working to understand the event. Two hypotheses show promise in explaining it, he said.

The first involves the famous equation E = mc2. With this formula , Albert Einstein demonstrated that matter and energy are fundamentally interchangeable. Stars burn by converting matter into energy, fusing lighter elements like hydrogen and helium into heavier elements, which build up in the star’s core and also release energy. When a star more than 80 times the mass of the sun reaches a temperature of 1 billion degrees Celsius (1.8 billion degrees Fahrenheit), this energy-matter equivalence produces pairs of electrons and their antiparticle counterparts, positrons, Woosley said. The process robs the star of energy, and so the object shrinks.

But as this happens, the temperature rises in the star’s core. At 3 billion C (5.4 billion F), oxygen fuses explosively, blowing off massive amounts of material and resetting the cycle. This process repeats until the star reaches a stable mass, explained Woosley. When the front of an ejected shell of material hits the trailing edge of a previous shell, it releases energy as light.

The star continues to fuse oxygen and the elements of greater masses, up until iron, at which point the reaction fails to release enough energy to keep the star from collapsing in on itself.Eventually, a star like the one that gave rise to iPTF14hls will collapse into a black hole without another explosion, said Woosley.

This phenomenon, called a pulsation pair instability (PPI) supernova, could account for iPTF14hls’ sustained luminosity as well as the object’s varying brightness. This explanation would require the star to have been 105 times the mass of the sun, said Woosley. However, the PPI model cannot account for the tremendous amount of energy iPTF14hls has released. The first explosion of 2014 had more energy than the model predicts for all the explosions combined, said Arcavi.

What’s more, this phenomenon has yet to be verified observationally. “Stars between 80 and 140 solar masses, which do this kind of thing, have to exist,” said Woosley, “and they have to die, and so, somewhere, this has to be going on.” But no one has seen it yet, he said.

A magnetic superstorm

An alternative explanation involves a star 20 to 30 times the mass of Earth’s sun. After a more conventional supernova, such a star could have condensed into a rapidly spinning neutron star, called a magnetar.

A neutron star packs the mass of 1.5 suns into an object with a diameter about the size of New York City. A neutron star rotating at 1,000 times per second would have more energy than a supernova, according to Woosley. It would also generate a magnetic field 100 trillion to 1 quadrillion times the strength of Earth’s field. As the star spun down over the course of several months, its incredible magnetic field could transfer the star’s rotational energy into the remnants of the supernova that it formed from, releasing light, Woosley explained.

“It’s like there’s a lighthouse down in the middle of the supernova,” said Woolsey.

But the magnetar explanation is not perfect, either. It has trouble explaining the dips and peaks in iPTF14hls’ brightness, and the physics behind how such a phenomenon might work is still uncertain, said Woosley.

As iPTF14hls sheds energy, Arcavi said he hopes to be able to see deeper into the object’s structure. If it is a magnetar, then he expects to see X-rays, previously obscured by the supernova itself, beginning to break through, he said. “Maybe by combining pulsation pair instability with [a magnetar], you can start to explain the supernova,” Arcavi said. 

Keeping busy while keeping watch

The existence of iPTF14hls has far-reaching implications, the researchers said. At 500 million light-years away, the supernova is still relatively close to Earth, and the universe is practically the same today — in terms of composition and organization —as it was when this event occurred,  according to Arcavi. If the event was a PPI supernova, it tells astronomers that stars more than 100 times the mass of the sun — thought to be more prevalent in the early universe — are still forming today.

The event also had far more hydrogen than researchers expected to see. The explosion in 1954 should have expelled nearly all of the star’s hydrogen, said Arcavi. Astrophysicists will have to revisit their models of supernovas to understand how this can occur, he said.

The finding has ramifications for the study of galaxies as well. “The energy of the gravity that’s keeping that galaxy together is about the same order of magnitude as the energy that was released in the supernova,” Arcavi said. “So, a few of these in a galaxy could actually unbind the entire galaxy.”

Arcavi and his team plan to continue monitoring iPTF14hls for at least one to two years. And a suite of international telescopes and observatories will join the effort. Swedish colleagues at the Nordic Optical Telescope, in the Canary Islands, will track the object as it continues to dim beyond what Arcavi’s telescope array can detect. NASA’s Swift spacecraft will look for X-ray emissions, while the Hubble Space Telescope is scheduled to image the location beginning in December, and others will follow, Arcavi said.

For now, the event remains a mystery.

“It’s just a puzzle in the sky,” said Woosley. “That’s what we live for, what astronomers love.”

Courtesy-Space

Can An Ancient Spiral Galaxy Reveal The Secrets Of The Milky Way

November 13, 2017 by  
Filed under Around The Net

Astronomers have uncovered an ancient cosmic artifact 11 billion light-years from Earth: the oldest spiral galaxy ever seen.

The newly discovered galaxy, known as A1689B11, is an ancestor of modern spiral galaxies like our own Milky Way, which are defined by long tentacles of gas, dust and stars that wrap around the galaxy’s central bulge.

“Spiral galaxies are exceptionally rare in the early universe, and this discovery opens the door to investigating how galaxies transition from highly chaotic, turbulent discs to tranquil, thin discs like those of our own Milky Way galaxy,” Renyue Cen, a co-author of the new paper describing the findings and a senior research astronomer at Princeton University, said in a statement.

Galaxies come in many different shapes and sizes, and researchers think many spiral galaxies form mainly through mergers of smaller elliptical galaxies, although many factors can affect how a galaxy changes its shape over time, according to NASA. Elliptical galaxies are disks that can be mostly circular or very elongated but lack the arm-like features of spiral galaxies.

Astronomer Edwin Hubble was one of the first people to theorize that elliptical galaxies evolved to form spiral galaxies, although he did not fully appreciate the complexity of galaxy evolution, according to the European Space Agency’s Hubble Space Telescope website. Nonetheless, researchers still refer to the time in cosmic history when spiral galaxies began to form from elliptical galaxies as “the Hubble sequence.”

“Studying ancient spirals like A1689B11 is a key to unlocking the mystery of how and when the Hubble sequence emerges,” Cen said in the statement from Swinburne University in Australia (where some of the other co-authors are based). Previously, researchers reported finding spiral galaxies that date back 10.7 billion years.

The newly discovered galaxy is too far away to be observed directly with modern instruments. So the researchers took advantage of a natural phenomenon known as gravitational lensing, in which the gravity of a massive object (like a galaxy or a cluster of galaxies) bends and amplifies the light from an object that lies beyond it (as seen by an observer). In this way, the authors of the new research paper were able to detect light from the very distant spiral galaxy A1689B11 by looking for the effects of gravitational lensing around the edge of a galaxy cluster that is nearer to Earth.

The observations were conducted using an instrument called the Near-infrared Integral Field Spectrograph on the Gemini North telescope, located on Mauna Kea in Hawaii. The researchers were able to “look 11 billion years back in time and directly witness the formation of the first, primitive spiral arms of a galaxy,” Cen said in the statement.

Because light travels at a finite speed, the light from A1689B11 left that galaxy 11 billion years ago, when the universe was less than 3 billion years old. In this way, astronomers can look back in time and learn about the history of the universe through direct observations

Courtesy-Space

Does Proxima b Have Neighbors

November 10, 2017 by  
Filed under Around The Net

The nearest alien planet to Earth may not be an only child.

Astronomers have spotted a dusty ring around the nearby star Proxima Centauri, hinting at the existence of other planets in addition to the famous Proxima b, a new study reports.

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“This result suggests that Proxima Centauri may have a multiple-planet system with a rich history of interactions that resulted in the formation of a dust belt,” study lead author Guillem Anglada, an astronomer at the Instituto de Astrofisica de Andalucia in Spain, said in a statement. “Further study may also provide information that might point to the locations of as-yet unidentified additional planets.” [Proxima b: Closest Earth-Like Planet Discovery in Pictures]

Proxima Centauri is a red dwarf that lies about 4.2 light-years from Earth, in the southern constellation of Centaurus (The Centaur). In 2016, researchers spotted Proxima b, an apparently Earth-size world orbiting the star in what seems to be the habitable zone, the region where liquid water could exist on the surface. The star itself is about the same age as the sun. (Coincidentally, the team that discovered Proxima b was led by Guillem Anglada-Escudé of Queen Mary University of London, a part of Anglada’s team but no relation to the author of the new research.)

Anglada and his colleagues studied Proxima Centauri using the Atacama Large millimeter/submillimeter Array (ALMA), a network of telescopes in Chile. The researchers discovered a belt of dusty material containing about 1 percent the mass of Earth. The belt — which lies a few hundred million kilometers from the star, far beyond Proxima b’s orbit — has a temperature of about minus 328 degrees Fahrenheit (minus 230 degrees Celsius), roughly the same temperature of the solar system’s Kuiper Belt, researchers said.

The dusty material might range in size from grains of only a few millimeters to asteroid-like bodies several kilometers across, study team members said. Dust belts like this are thought to be the remains of material that didn’t manage to clump together to form planets, they added.

ALMA also spotted signs of a possible second dust ring, about 10 times farther from the star than the other one, though this feature awaits confirmation. If the outer ring does indeed exist, its material would be very cold, lying so far from a star that is much smaller and dimmer than the sun.

The faint outer belt could prove useful to astronomers: Studying its shape could yield a better understanding of Proxima b’s mass, which is not known very well at the moment, the researchers said.  

And then there’s the exploration angle. The $100 million Breakthrough Starshot project aims to send sail-equipped, laser-driven microprobes zooming past Proxima b in the not-too-distant-future, and mapping out the system’s dust environment could be key to the success of such a mission, study team members said.

“These first results show that ALMA can detect dust structures orbiting around Proxima. Further observations will give us a more detailed description of Proxima’s planetary system,” study co-author Pedro Amado, also from the Instituto de Astrofiscia de Andaluicia, said in the same statement. “What we are seeing now is just the appetizer compared to what is coming!”

The new study has been accepted for publication in Astrophysical Journal Letters.

Courtesy-Space

Did Jupiter Start Off As A Steam World

November 8, 2017 by  
Filed under Around The Net

Jupiter may not always have been a big ball of hydrogen and helium. 

A new study suggests that, in their youth, Jupiter and other gas-giant planets may have been “steam worlds” — warm ocean planets a bit bigger than Earth, with water-vapor atmospheres. 

John Chambers, a researcher at the Carnegie Institution for Science in Washington, D.C., proposes that some protoplanets may grow into steam worlds from their modest beginnings as accretions of rock and ice pebbles.

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As the accreting bodies come together and the protoplanet grows, increasing pressure liquefies the ices, and oceans form. Without any air present, water and any other liquids sublimate, creating an atmosphere dominated by water vapor, the idea goes. Even a relatively small protoplanet of between 0.08 and 0.16 Earth masses can be quite warm — from 32 to 704 degrees Fahrenheit (0 to 347 degrees Celsius), Chambers said. 

 

“I calculated the structure of atmospheres in this case, and worked out when conditions are right for rapid inflow of gas to form a giant planet,” Chambers told Space.com. “The answer is, this happens when a planet is a few Earth masses, which is somewhat lower than the conventional value of 10 Earth masses.” 

In his model, Chambers started with a planet that orbits a sun-like star about three times farther away than Earth circles the sun. The makeup of the initial protoplanet is half ice and half rock. The pebbles accrete into a small protoplanet, whose atmosphere is very thin and made up of sublimating ices. Once the protoplanet hits 0.084 Earth masses, there’s enough atmospheric pressure for ice to melt, and the object becomes a small ocean world. As more ice and rock accrete, the protoplanet gets bigger and starts to accumulate hydrogen and helium. 

Since there’s a lot of water in the atmosphere, the planet gets warmer. (Water is a powerful greenhouse gas.) As the protoplanet gains mass, the atmospheric pressure also keeps rising, allowing the atmosphere to absorb more water vapor. Eventually the pressure gets so high that the water is no longer an ocean of liquid but a “supercritical fluid” mixed with hydrogen and helium, with no clear boundary between the atmosphere and the surface. 

Once about two to five Earth masses of rock and ice come together, a runaway process starts, and the protoplanet picks up more gas from the disk around its host star quickly. That’s what allows a gas giant to grow, according to the new study.

Most models of planet formation assume that planetesimals — the bits that accrete to form planets — are roughly kilometer-size bodies. Pebble accretion, on the other hand, assumes that the accreting objects are, as the name implies, the size of pebbles. 

Michiel Lambrechts, a researcher at Lund University in Sweden who was not involved in Chambers’ study, said the scheme is a logical one. 

“It’s all about some physics that is very plausible,” Lambrechts said. 

Whether this scenario applies to Jupiter is not known, though there is some data from NASA’s Jupiter-orbiting Juno mission that seems to show a core that’s more diffuse than scientists initially thought. One implication is that, if Chambers and others are correct about the pebble-accretion model, one would expect to find that Jupiter’s core harbors only a few Earth masses, Lambrechts said.

Planetary scientists generally think that gas giants must pick up most of their mass in just a few million years, because the solar wind from a newborn star blows away most of the gas in its protoplanetary disk quickly. 

That fast timeline can cause problems for some planet-formation models. But it suits the pebble-accretion idea just fine, Chambers said.

“At a certain point, it’s about how you avoid accreting quickly,” he said. 

Chambers said the next step is to look at more exoplanet data. 

“I’m still working through the implications of this, but the next step is to feed this result into more general models for planet formation,” he said. “The idea is to compare the outcome of these models with the observed population of extrasolar planets to pin down other unknown factors in planet formation.” 

The study has been accepted for publication in The Astrophysical Journal. You can read a copy of it for free at on the online preprint server arXiv.org. 

Editor’s note: This story was updated Nov. 5 to correct the name of the Carnegie Institution for Science.

Courtesy-Space

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