Thursday, May 5, 2016

A Mercury Transit Sequence

A Mercury Transit Sequence:

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2016 May 4



See Explanation. Clicking on the picture will download the highest resolution version available.


A Mercury Transit Sequence

Image Credit & Copyright: Dominique Dierick


Explanation: This coming Monday, Mercury will cross the face of the Sun, as seen from Earth. Called a transit, the last time this happened was in 2006. Because the plane of Mercury's orbit is not exactly coincident with the plane of Earth's orbit, Mercury usually appears to pass over or under the Sun. The above time-lapse sequence, superimposed on a single frame, was taken from a balcony in Belgium shows the entire transit of 2003 May 7. The solar crossing lasted over five hours, so that the above 23 images were taken roughly 15 minutes apart. The north pole of the Sun, the Earth's orbit, and Mercury's orbit, although all different, all occur in directions slightly above the left of the image. Near the center and on the far right, sunspots are visible. After Monday, the next transit of Mercury will occur in 2019.

NASA Coverage: 2016 May 9 Mercury Transit of the Sun

Tomorrow's picture: open space


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Wednesday, May 4, 2016

Is A New Particle About To Be Announced?

Is A New Particle About To Be Announced?:



Data from two experiments at the LHC have independently hinted at the existence of a new type of particle. Image: CMS/LHC/CERN


Particle physicists are an inquisitive bunch. Their goal is a working, complete model of the particles and forces that make up the Universe, and they pursue that goal with a vigour matched by few other professions.



The Standard Model of Physics is the result of their efforts, and for 25 years or so, it has guided our thinking and understanding of particle physics. The best tool we have for studying physics further is the Large Hadron Collider (LHC), near Geneva, Switzerland. And some recent, intriguing results from the LHC points to the existence of a newly discovered particle.







The LHC has four separate detectors. Two of them are "general purpose" detectors, called ATLAS and CMS. Last year, separate experiments in both the ATLAS and CMS detectors produced what is best called a "bump" in their data. Initially, the two teams conducting the experiments were puzzled by the data. But when they compared them, they found that the bumps in their data were the same in both experiments, and they hinted at what could be a new type of particle, never before detected.



The two experiments involved smashing protons into each other at near-relativistic speeds. The collisions produced more high-energy photons than theory predicts. Not a lot more, but physics is a detailed endeavour, so even a slight increase in the amount of photons produced is a big deal. In physics, everything happens for a reason.



To be more specific, ATLAS and CMS recorded increased activity at an energy level around 750 giga electron-volts (GeV). What that means, for all you non-particle physicists, is that the new particle decays into two photons at the point of the proton-proton collision. If the new particle exists, that is.



A new particle would be a huge discovery. The Standard Model has describe all the particles present in nature pretty well. It even predicted the existence of one type of particle, the Higgs Boson, long before the LHC actually verified its existence. The discovery of a new type of particle would be very exciting news indeed, and could break the Standard Model.



Since this data from the experiments at the LHC was released last year, the physics world has been buzzing. Over 100 papers have been written to try to explain what the results might mean. But some caution is required.



The first thing scientists do when faced with results like this is to try to quantify the likelihood that it could be chance. If only one experiment had this bump in its data, then the likelihood that it was just a chance occurrence is pretty high. There are many reasons why an experiment can have a result like this, which is why repeatability is such a big deal in science. But when two independent, separate, experiments have the same result, people's ears perk up.



A few months have passed since the experiments were run, and in that time, the experimenters have tried to determine exactly what the likelihood is of these result occurring by chance. After working with the data, a funny thing has happened. The significance of the extra photons detected by CMS has risen, while the significance of the extra photons detected by ATLAS has fallen. This has definitely left physicists scratching their heads.



Also in that time, about four main explanations for the experimental results have percolated to the surface. One states that the new particle, if it exists, is made up of smaller particles, similar to how a proton is made up of quarks. These smaller particles could be held together by an unknown force. Some theoretical physicists think this is the best fit with the data.



Another possibility is that the new particle is a heavier version of the Higgs Boson. About 12 times heavier. Or it could be that the Higgs Boson itself is made up of smaller particles, and that's what the experiment detected.







Or, it could be the much-hypothesized graviton, the theoretical particle that carries the gravitational force. The four fundamental forces in the Universe are electromagnetism, the strong nuclear force, the weak nuclear force, and gravity. So far, we have discovered the particles that transmit all of those forces, except for gravity. If their was a new particle detected, and if it proved to be the graviton, that would be enormous, earth-shattering news. At least for those who are passionate about understanding nature.



That's a lot of "ifs" though.



There are a lot of holes in our knowledge of the Universe, and physicists are eager to fill those gaps. The discovery of a new particle might very well answer some basic questions about dark matter, dark energy, or even gravity itself. But there's a lot more experimentation to be done before the existence of a new particle can be announced.





The post Is A New Particle About To Be Announced? appeared first on Universe Today.

Posted by Nelio Inacio at 4:36 PM 0 comments

Aurora over Sweden

Aurora over Sweden:

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2016 May 3



See Explanation. Moving the cursor over the image will bring up an annotated version. Clicking on the image will bring up the highest resolution version available.
Explanation: It was bright and green and stretched across the sky. This striking aurora display was captured last month just outside of Östersund, Sweden. Six photographic fields were merged to create the featured panorama spanning almost 180 degrees. Particularly striking aspects of this aurora include its sweeping arc-like shape and its stark definition. Lake Storsjön is seen in the foreground, while several familiar constellations and the star Polaris are visible through the aurora, far in the background. Coincidently, the aurora appears to avoid the Moon visible on the lower left. The aurora appeared a day after a large hole opened in the Sun's corona allowing particularly energetic particles to flow out into the Solar System. The green color of the aurora is caused by oxygen atoms recombining with ambient electrons high in the Earth's atmosphere.

Posted by Nelio Inacio at 4:34 PM 0 comments

Monday, May 2, 2016

A Super-Fast Star System Shrugs Its Shoulders At Physics

A Super-Fast Star System Shrugs Its Shoulders At Physics:



This annotated artist's conception illustrates our current understanding of the structure of the Milky Way galaxy. Image Credit: NASA


Astronomers have found a pair of stellar oddballs out in the edges of our galaxy. The stars in question are a binary pair, and the two companions are moving much faster than anything should be in that part of the galaxy. The discovery was reported in a paper on April 11, 2016, in the Astrophysical Journal Letters.The binary system is called PB3877, and at 18,000 light years away from us, it's not exactly in our neighborhood. It's out past the Scutum-Centaurus Arm, past the Perseus Arm, and even the Outer Arm, in an area called the galactic halo. This binary star also has the high metallicity of younger stars, rather than the low metallicity of the older stars that populate the outer reaches. So PB3877 is a puzzle, that's for sure.PB3877 is what's called a Hyper-Velocity Star (HVS), or rogue star, and though astronomers have found other HVS's, more than 20 of them in fact, this is the first binary one found. The pair consists of a hot sub-dwarf primary star that's over five times hotter than the Sun, and a cooler companion star that's about 1,000 degrees cooler than the Sun.Hyper-Velocity stars are fast, and can reach speeds of up to 1,198 km. per second, (2.7 million miles per hour,) maybe faster. At that speed, they could cross the distance from the Earth to the Moon in about 5 minutes. But what's puzzling about this binary star is not just its speed, and its binary nature, but its location.Hyper-Velocity stars themselves are rare, but PB3877 is even more rare for its location. Typically, hyper velocity stars need to be near enough to the massive black hole at the center of a galaxy to reach their incredible speeds. A star can be drawn toward the black hole, accelerated by the unrelenting pull of the hole, then sling-shotted on its way out of the galaxy. This is the same action that spacecraft can use when they gain a gravity assist by travelling close to a planet.This video shows how stars can accelerate when their orbit takes them close to the super-massive black holes at the center of the Milky Way.[embed]https://www.youtube.com/watch?v=duoHtJpo4GY[/embed]But the trajectory of PB3877 shows astronomers that it could not have originated near the center of the galaxy. And if it had been ejected by a close encounter with the black hole, how could it have survived with its binary nature intact? Surely the massive pull of the black hole would have destroyed the binary relationship between the two stars in PB3877. Something else has accelerated it to such a high speed, and astronomers want to know what, exactly, did that, and how it kept its binary nature.Barring a close encounter with the super-massive black hole at the center of the Milky Way, there are a couple other ways that PB3877 could have been accelerated to such a high velocity.One such way is a stellar interaction or collision. If two stars were travelling at the right vectors, a collision between them could impart energy to one of them and propel it to hyper-velocity. Think of two pool balls on a pool table.Another possibility is a supernova explosion. It's possible for one of the stars in a binary pair to go supernova, and eject it's companion at hyper-velocity speeds. But in these cases, either stellar collision or supernova, things would have to work out just right. And neither possibility explains how a wide-binary system like this could stay intact.Fraser Cain sheds more light on Hyper-Velocity Stars, or Rogue Stars, in this video.[embed]https://www.youtube.com/watch?v=JCj_EsoM6eM[/embed]There is another possibility, and it involves Dark Matter. Dark Matter seems to lurk on the edge of any discussion around something unexplained, and this is a case in point. The researchers think that there could be a massive cocoon or halo of Dark Matter around the binary pair, which is keeping their binary relationship intact.As for where the binary star PB3788 came from, as they say in the conclusion of their paper, "We conclude that the binary either formed in the halo or was accreted from the tidal debris of a dwarf galaxy by the Milky Way." And though the source of this star's formation is an intriguing question, and researchers plan follow up study to verify the supernova ejection possibility, its possible relationship with Dark Matter is also intriguing.

The post A Super-Fast Star System Shrugs Its Shoulders At Physics appeared first on Universe Today.

Posted by Nelio Inacio at 3:54 PM 0 comments

Icy Hot: Europa’s Frozen Crust Could Be Warmer Than We Thought

Icy Hot: Europa’s Frozen Crust Could Be Warmer Than We Thought:



Europa's cracked, icy surface imaged by NASA's Galileo spacecraft in 1998. Credit: NASA/JPL-Caltech/SETI Institute.


All the worlds may be ours except Europa but that only makes the ice-covered moon of Jupiter all the more intriguing. Beneath Europa's thin crust of ice lies a tantalizing global ocean of liquid water somewhere in the neighborhood of 100 kilometers deep—which adds up to more liquid water than is on the entire surface of the Earth. Liquid water plus a heat source(s) to keep it liquid plus the organic compounds necessary for life and...well, you know where the thought process naturally goes from there.And now it turns out Europa may have even more of a heat source than we thought. Yes, a big component of Europa's water-liquefying warmth comes from tidal stresses enacted by the massive gravity of Jupiter as well as from the other large Galilean moons. But exactly how much heat is created within the moon's icy crust as it flexes has so far only been loosely estimated. Now, researchers from Brown University in Providence, RI and Columbia University in New York City have modeled how friction creates heat within ice under stress, and the results were surprising.Although 3,100-km-wide Europa is coated in ice and technically has the smoothest surface in the Solar System, it's far from featureless. Its frozen crust features enormous regions of broken "chaos terrain"  and is covered in long, crisscrossing fractures filled with reddish-brown material (which may be a form of sea salt), as well as crumpled, mountain-like ridges that appear curiously fresh.These ridges are thought to be a result of a form of tectonics, except not with plates of rock like on Earth but rather shifting slabs of frozen water. But where the energy needed to drive that process is coming from—and what happens to all the frictional heat created during it—isn't well known."People have been using simple mechanical models to describe the ice," said geophysicist Christine McCarthy, Lamont Assistant Research Professor at Columbia University who led the research while a graduate student at Brown University. "They weren't getting the kinds of heat fluxes that would create these tectonics. So we ran some experiments to try to understand this process better."By mechanically subjecting ice samples to various forms of pressure and stress, similar to the conditions that would be found on Europa as it orbits Jupiter, the researchers found that most of the heat is generated within deformities in the ice, rather than between the individual grains as was previously thought. This difference means there's likely a lot more heat moving through Europa's ice layers, which would affect both its behavior and its thickness."Those physics are first order in understanding the thickness of Europa's shell," said Reid Cooper, Earth science professor and McCarthy's research partner at Brown. "In turn, the thickness of the shell relative to the bulk chemistry of the moon is important in understanding the chemistry of that ocean. And if you're looking for life, then the chemistry of the ocean is a big deal."When it comes to Europa's icy crust there have traditionally been two camps of thought: the thin-icers and the thick-icers. Thin-icers estimate the moon's crust to be at most only a few kilometers thick—possibly coming very close to the surface in places, if not breaking through entirely—while those in the thick-ice camp think it could be tens of times thicker. While there are data to support both hypotheses, it remains to be seen which these new findings will best support.Luckily we won't have to wait terribly long to find out how thick the moon's icy crust really is. A recently-approved NASA mission will launch to Europa in the 2020s to explore its surface, interior composition, and potential habitability. The mission may (i.e., should) also include a lander, although of what fashion has yet to be determined. But when the data from that mission do finally come in, many of our long-standing questions about this mystifying icy world will finally be answered.The team's research is published in the June 1 issue of Earth and Planetary Science Letters.Source: PhysOrg.com 

The post Icy Hot: Europa’s Frozen Crust Could Be Warmer Than We Thought appeared first on Universe Today.

Posted by Nelio Inacio at 3:53 PM 0 comments

Is Alpha Centauri The Best Place To Look For Aliens?

Is Alpha Centauri The Best Place To Look For Aliens?:



Project Starshot, an initiative sponsored by the Breakthrough Foundation, is intended to be humanity's first interstellar voyage. Credit: breakthroughinitiatives.org


For generations, human beings have fantasized about the possibility of finding extra-terrestrial life. And with our ongoing research efforts to discover new and exciting extrasolar planets (aka. exoplanets) in distant star systems, the possibility of actually visiting one of these worlds has received a real shot in the arm. Unfortunately, given the astronomical distances involved, not to mention the cost of mounting an expedition, doing so presents numerous significant challenges.However, Russian billionaire Yuri Milner and the Breakthrough Foundation - an international organization committed to exploration and scientific research -  is determined to mount an interstellar mission to Alpha Centauri, our closest stellar neighbor, in the coming years. With the backing of such big name sponsors as Mark Zuckerberg and Stephen Hawking, his latest initiative (named "Project Starshot") aims to send a tiny spacecraft to the Alpha Centauri system to search for planets and signs of life.Consisting of an ultra-light nanocraft and a lightsail, the concept calls for a ground-based laser array to push the lightsail up to speeds of hundreds of kilometers a second, towing the nanocraft into deep space. Such a system would allow the tiny spacecraft to conduct a flyby mission to Alpha Centauri in about 20 years after it is launched, which could then beam home images of possible planets, as well as other scientific data such as analysis of magnetic fields.In essence, Starshot seeks to leverage recent technological developments to mount an interstellar mission that will reach another star within a single generation. As we explained in another article ("How Long Would It Take To Travel To The Nearest Star?"), using existing technology, it would take between 19,000 to 81,000 years for a spacecraft to make the trip to even the nearest star, depending on whether chemical rockets or ion engines were used.Hence, the Foundation's advisory board explored all potential methods for creating a craft that could travel at relativistic speeds - up to 20% the speed of light - so it could traverse the 4.37 light year distance in just 20 years. They determined that a tiny craft, roughly the size of a refrigerator magnet and weighing in the vicinity of a few grams, would be the best model for a spacecraft. They further determined that the best propulsion method would be laser-driven lightsail, which is not hampered by the limits of conventional methods.With a massive ground-based laser directing the sail, the plan is to accelerate the nanocraft to its terminal velocity before it reaches a distance of about one million km from Earth (which is the limit to which the laser beam can be focused on the meter-scale sail). All told, the nanocraft will experience an acceleration of about 60,000 g (sixty-thousands times the force of Earth's gravity, which works out to just under 600,000 m/s²).As Professor Avi Loeb, the Frank B. Baird, Jr. Professor of Science at Harvard University and chairman of the Foundation's Advisory Board, explained to Universe Today via email:

"{O]nly one offers a path forward: using beamed (laser) light to push a sail attached to a lightweight (gram-scale) smart payload (with a camera, transmitter and thrusters). This approach benefits from two major technological advances that were realized recently: miniaturization of electronics (developed by the cell phone industry) and the construction arrays of lasers that combine to make a very powerful and focused beam of light (developed by the defense industry). Interstellar travel is challenging, but based on these technological advances, we believe that there is a path forward without obvious show stoppers. The project is ambitious but doable."
In addition to accomplishing the dream of countless generations (i.e. traveling to another star system), Breakthrough Starshot hopes to generate important supplementary benefits to astronomy in the meantime. Much like the Apollo Program of the 1960s, the Breakthrough Starshot program hopes to stimulate the development of technologies that will be beneficial here on Earth.These include demonstrating proof-of-concept technology that will enable the exploration the solar system, the detection and study of Near Earth Objects (NEOs), and the benefits to material science that solar sail development will bring. The development of laser arrays will also have major implications for the science of optical systems, and the laser communication devices used on Starshot will likely lead to better communication with airplanes and satellites around Earth.As Pete Worden, the Executive Director Project Breakthrough StarShot, told Universe Today via email:

"The project goals are to develop and demonstrate the technologies, particularly with respect to high power laser beaming technology and gram-class lightsail-craft that could enable humanity to send these craft to the nearest star system, Alpha Centauri within a generation.  We hope to mobilize the world’s expertise to make this possible.  The program will be an open international program.  Yuri Milner has provided our initial funding.  Renowned physicist Stephen Hawking and Facebook founder Mark Zuckerberg have joined Yuri Milner as the governing board of the project."
Based on the Foundation's best estimates, this project could achieve its goal of dispatching their interstellar traveler within a few decades time. And with a 20 some-odd year transit time, we could be gaining vital information about the nearest star system (including whether or not it has life-supporting exoplanets) by the 2050s or 2060s.Naturally, there are still several engineering hurdles that would need to be overcome before Starshot can become a reality. For example, propelling a gram-scale spacecraft to 20% the speed of light will require a laser beam of that could generate about 100 Gigawatts of power over the course of a few minutes. The Project intends to build this laser array on the ground, simply because that would be much cheaper than building one in space.This, in turn, creates the challenge of optical-blurring due to atmospheric turbulence. Using adaptive optics (measuring atmospheric effects and correcting for them) is believed to be able to compensate for that. Such a method has been tested on the scale of the largest telescopes (10 meters in diameter), but would need to be tested on a scale of 1 km before it can be considered feasible.What's more, there are plenty of doubts as to the missions intended target, not to mention the likelihood that the mission will succeed. For instance, while Alpha Centauri may be the nearest star, thus making it the natural choice for interstellar exploration, there is little reason to suspect we will find any exoplanets there.Years back, astronomers announced the detection of a possible planet circling Alpha Centauri B with an orbital period of 3.24 days - which was named Alpha Cen Bb. However, subsequent examinations revealed that the detection of this exoplanet was the result of the window function (time sampling) of the original data. If we hope to find exoplanets, then we might need to look further afield - like Epsilon Eridani, a mere 10.5 light years away (which would result in a travel time of 55 years for the proposed nanocraft).And, as Paul Gilster of Centauri Dreams points out, the concept presents numerous challenges that will require technical advances not currently in existence. For example, beyond the issue of laser power and adaptive optics, there are issues with the sail concept itself that are likely to prove difficult. Essentially, this comes down to the need for a balance to be struck between powerful lasers and a sail that is capable of withstanding them:

"Moreover, we have to design a sail that will ‘ride’ the beam rather than be blown off it, and one that will be so highly reflective that it will absorb less than 1/100,000th of the energy applied to it. These are problems that Robert Forward faced with his Starwisp design, a kilometer-wide ‘spider web’ of a sail driven by microwaves, with sensors scattered throughout the sail itself. It was Geoffrey Landis who would go on to show that as described, Starwisp would likely vaporize under the powerful beam meant to drive it to Alpha Centauri, causing a flurry of re-thinking of sail materials and design. But leaving the fuel at home is a powerful technique, and advances in technology may get us to the kind of materials that can withstand the photon torrent."
Addressing the design called for by Breakthrough Starshot - a thin, round disc that is about the size of a picnic table in diameter, and which would have its entire electronics suite in the center - Gilster sees additional problems. "We’ve also got a problem in that concept,"  he says, "because Jim Benford has pointed out that a flat sail is not a good ‘beam-rider’ - we’ll likely have to look at the kind of curved sail designs both Jim and brother Gregory Benford have studied in lab work at the Jet Propulsion Laboratory."In the end, the only reason to send a probe to Alpha Centauri is because of its proximity. And mounting the mission will require that the Breakthrough Foundation and its supporters come up with new and innovative solutions to the hurdles they face. But given that the opportunities for research and exploration will still be abundant, the reasonable timelines involved, and the likelihood of success, the mission certainly appears to be doable.Previous efforts by the Breakthrough Foundation's include Breakthrough Listen, the largest scientist research program aimed at detecting transmissions from distant stars. These include monitoring for radio transmissions and optical laser transmissions using advanced instruments that are significantly more sensitive than anything currently in use, combined with advanced software and data analysis. The program will span 10 years and cost an estimated $100 million, surveying the 1,000,000 closest stars to Earth and the 100 closest galaxies to the Milky Way.There's also Breakthrough Message, a $1 million competition aimed at encouraging a global debate about the ethics and possible methods of communicating with possible intelligent beings beyond Earth. The competition is open, and the prize will be awarded to anyone who is able to design a message (in digital format) that best represents Earth and humanity to other civilizations.And be sure to enjoy this video from the Breakthrough Foundation that illustrates the mission concept:https://youtu.be/RoCm6vZDDiQFurther Reading: Breakthrough Initiatives

The post Is Alpha Centauri The Best Place To Look For Aliens? appeared first on Universe Today.

Posted by Nelio Inacio at 3:39 PM 0 comments

Dwarf Dark Matter Galaxy Hides In Einstein Ring

Dwarf Dark Matter Galaxy Hides In Einstein Ring:



The large blue light is a lensing galaxy in the foreground, called SDP81, and the red arcs are the distorted image of a more distant galaxy. By analyzing small distortions in the red, distant galaxy, astronomers have determined that a dwarf dark galaxy, represented by the white dot in the lower left, is companion to SDP81. The image is a composite from ALMA and the Hubble. Image: Y. Hezaveh, Stanford Univ./ALMA (NRAO/ESO/NAOJ)/NASA/ESA Hubble Space Telescope


Everybody knows that galaxies are enormous collections of stars. A single galaxy can contain hundreds of billions of them. But there is a type of galaxy that has no stars. That's right: zero stars.These galaxies are called Dark Galaxies, or Dark Matter Galaxies. And rather than consisting of stars, they consist mostly of Dark Matter. Theory predicts that there should be many of these Dwarf Dark Galaxies in the halo around 'regular' galaxies, but finding them has been difficult.Now, in a new paper to be published in the Astrophysical Journal, Yashar Hezaveh at Stanford University in California, and his team of colleagues, announce the discovery of one such object. The team used enhanced capabilities of the Atacamas Large Millimeter Array to examine an Einstein ring, so named because Einstein's Theory of General Relativity predicted the phenomenon long before one was observed.An Einstein Ring is when the massive gravity of a close object distorts the light from a much more distant object. They operate much like the lens in a telescope, or even a pair of eye-glasses. The mass of the glass in the lens directs incoming light in such a way that distant objects are enlarged.Einstein Rings and gravitational lensing allow astronomers to study extremely distant objects, by looking at them through a lens of gravity. But they also allow astronomers to learn more about the galaxy that is acting as the lens, which is what happened in this case.If a glass lens had tiny water spots on it, those spots would add a tiny amount of distortion to the image. That's what happened in this case, except rather than microscopic water drops on a lens, the distortions were caused by tiny Dwarf Galaxies consisting of Dark Matter. “We can find these invisible objects in the same way that you can see rain droplets on a window. You know they are there because they distort the image of the background objects,” explained Hezaveh. The difference is that water distorts light by refraction, whereas matter distorts light by gravity.As the ALMA facility increased its resolution, astronomers studied different astronomical objects to test its capabilities. One of these objects was SDP81, the gravitational lens in the above image. As they examined the more distant galaxy being lensed by SDP81, they discovered smaller distortions in the ring of the distant galaxy. Hezaveh and his team conclude that these distortions signal the presence of a Dwarf Dark Galaxy.[embed]https://vimeo.com/158971342[/embed]But why does this all matter? Because there is a problem in the Universe, or at least in our understanding of it; a problem of missing mass.Our understanding of the formation of the structure of the Universe is pretty solid, at least in the larger scale. Predictions based on this model agree with observations of the Cosmic Microwave Background (CMB) and galaxy clustering. But our understanding breaks down somewhat when it comes to the smaller scale structure of the Universe.One example of our lack of understanding in this area is what's known as the Missing Satellite Problem. Theory predicts that there should be a large population of what are called sub-halo objects in the halo of dark matter surrounding galaxies. These objects can range from things as large as the Magellanic Clouds down to much smaller objects. In observations of the Local Group, there is a pronounced deficit of these objects, to the tune of a factor of 10, when compared to theoretical predictions.Because we haven't found them, one of two things needs to happen: either we get better at finding them, or we modify our theory. But it seems a little too soon to modify our theories of the structure of the Universe because we haven't found something that, by its very nature, is hard to find. That's why this announcement is so important.The observation and identification of one of these Dwarf Dark Galaxies should open the door to more. Once more are found, we can start to build a model of their population and distribution. So if in the future more of these Dwarf Dark Galaxies are found, it will gradually confirm our over-arching understanding of the formation and structure of the Universe. And it'll mean we're on the right track when it comes to understanding Dark Matter's role in the Universe. If we can't find them, and the one bound to the halo of SDP81 turns out to be an anomaly, then it's back to the drawing board, theoretically.It took a lot of horsepower to detect the Dwarf Dark Galaxy bound to SDP81. Einstein Rings like SDP81 have to have enormous mass in order to exert a gravitational lensing effect, while Dwarf Dark Galaxies are tiny in comparison. It's a classic 'needle in a haystack' problem, and Hezaveh and his team needed massive computing power to analyze the data from ALMA.ALMA, and the methodology developed by Hezaveh and team will hopefully shed more light on Dwarf Dark Galaxies in the future. The team thinks that ALMA has great potential to discover more of these halo objects, which should in turn improve our understanding of the structure of the Universe. As they say in the conclusion of their paper, "... ALMA observations have the potential to significantly advance our understanding of the abundance of dark matter substructure."

The post Dwarf Dark Matter Galaxy Hides In Einstein Ring appeared first on Universe Today.

Posted by Nelio Inacio at 3:38 PM 0 comments

Antarctica Provides Plenty Of Mars Samples Right Now

Antarctica Provides Plenty Of Mars Samples Right Now:



Mars! Martian meteorites make their way to Earth after being ejected from Mars by a meteor impact on the Red Planet. Image: NASA/National Space Science Data Center.


Sometimes, the best way to study Mars is to stay home. There's no substitute for actual missions to Mars, but pieces of Mars have made the journey to Earth, and saved us the trip. Case in point: the treasure trove of Martian meteorites that NASA is gathering from Antarctica.NASA scientists aren't the first ones to find meteorites in the Earth's polar regions. As early as the 9th century, people in the northern polar regions made use of iron from meteorites for tools and hunting weapons. The meteorite iron was traded from group to group over long distances. But for NASA, the hunt for meteorites is focused on Antarctica.In Antarctica, the frigid temperatures preserve meteorites for a long time, which makes them valuable artifacts in the quest to understand Mars. Meteorites tend to accumulate in places where creeping glacial ice moves them to. When the ice meets a rock obstacle, the meteorites are deposited there, making them easier to find. Recently arrived meteorites are also easily spotted on the surface of the Antarctica ice.[embed]https://www.youtube.com/watch?v=60w3WbVwhh8[/embed]The US began collecting meteorites in Antarctica in 1976, and to date more than 21,000 meteorites and meteorite fragments have been found. In fact, more of them are found in Antarctica than in the rest of the world combined. These meteorites are then shared with scientists around the world.Collecting meteorites in Antarctica is not a walk in the park. It's physically gruelling and hazardous work. Antarctica is not an easy environment to live and work in, and just surviving there takes planning and teamwork. But the scientific payoff is huge, which keeps NASA going back.Meteorites from the Moon and other bodies also arrive on Earth, and are collected in Antarctica. They can tell scientists important things about the evolution and formation of the Solar System, the origin of organic chemical compounds necessary for life, and the origin of the planets themselves.

How Do Martian Meteorites Get To Earth?

A few things have to go right for a Martian meteorite to make it to Earth. First, a meteorite has to collide with Mars. That meteorite has to be big enough, and hit the surface of Mars with enough force, that rock from Mars is propelled off the surface with enough speed to escape Mars' gravity.[embed]https://www.youtube.com/watch?v=oZNSszq9O-g[/embed]After that, the meteor has to travel through space and avoid a thousand other fates, like being drawn to one of the other planets, or the Sun, by the gravitational pull of those bodies. Or being flung off into the far reaches of empty space, lost forever. Then, if it manages to make it to Earth, and be pulled in by Earthly gravity, it must be large enough to survive entry into Earth's atmosphere.

The Science

Part of the scientific value in meteorites lies not in their source, but in the time that they were formed. Some meteorites have travelled through space for so long, they're like time travellers. These ancient meteorites can tell scientists a lot about conditions in the early Solar System.Meteorites from Mars tell scientists a few things. Since they've survived re-entry into Earth's atmosphere, they can tell engineers about the dynamics of such a journey, and help inform spacecraft design. Since they contain chemical signatures and elements unique to Mars, they can also tell mission specialists things about surviving on Mars.They can also provide clues to one of the greatest mysteries in space exploration: Did life exist on Mars? A Martian meteorite found in the Sahara desert in 2011 contained ten times the amount of water as other Martian meteorites, and added evidence to the idea that Mars was once a wet world, suitable for life.NASA's program to hunt for meteorites in Antarctica has been going strong for many years, and there's really no reason to stop doing it, since this is the only way to get Martian samples into a laboratory. Each one they find is like a puzzle piece, and like a jigsaw puzzle, you never know which one will complete the big picture.

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April Lunacy: Getting Ready for the Full ‘Mini-Moon’

April Lunacy: Getting Ready for the Full ‘Mini-Moon’:



2015 Mini-Moon


Do you welcome the extra evening light of the Full Moon, or curse the additional light pollution? Either way, this week's Full Moon on Friday April 22nd is special. It's the smallest Full Moon of 2016, something we here at Universe Today have christened the Mini-Moon.Mini-Moon 2016: This year's Mini-Moon falls on April 22nd at 5:25 Universal Time (UT), just 13 hours and 19 minutes after lunar apogee the evening prior at 16:06 UT on April 21st. Though apogee on the 21st is 406,350 km distant – a bit on the far end, but the third most distant for the year by 300 km — this week's Full Moon is the closest to apogee for 2016 time-wise. The 2015 Mini-Moon was even closer, in the 10 hour range, but you'll have to wait until December 10th, 2030 to find a closer occurance.What is the Mini-Moon, you might ask? As with the often poorly defined Supermoon, we like to eschew the ambiguous '90% of its orbit' definition, and simply refer to it as a Full Moon occurring within 24 hours of lunar apogee, or its farthest point from the Earth in its orbit.Fun fact: the 29.55 day period from perigee to perigee (or lunar apogee-to-apogee) is known as an anomalistic month.Thank our Moon's wacky orbit for all this lunacy. Inclined 5.14 degrees relative to the ecliptic plane, the Moon returns to the same phase (say, Full back to Full) every 29.53 days, known as a synodic month. The Moon can appear 33.5' across during perigee, and shrink to 29.4' across near apogee.And don't fear the 'Green Moon,' and rumors going 'round ye' ole internet that promise a jaded Moon will occur in April or May; this is 100% non-reality based, seeking to join the legends of Super, Blood, and Full Moons, Black and Blue.The April Full Moon is also known as the Full Pink Moon to the Algonquin Indians. The April Full Moon, can, on occasion be the Full Moon ushering in Easter (known as the Paschal Moon) as per the rule established by the 325 AD council of Nicaea, stating Easter falls on the first Sunday after the first Full Moon after the fixed date of the Vernal Equinox of March 21st. Easter can therefore fall as late as April 25th, as next occurs on 2038. The future calculation of Easter by the Church gets the Latin supervillain-sounding name of Computus.Of course, the astronomical vernal equinox doesn't always fall on March 21st, and to complicate matters even further, the Eastern Orthodox Church uses the older Julian Calendar and therefore, Easter doesn't always align with the modern western Gregorian calendar used by the Roman Catholic Church.The Moon can create further complications in modern timekeeping as well.Here's one wonderful example we recently learned of in our current travels. The Islamic calendar is exclusively based on the synodic cycle of the Moon, and loses 11 days a year in relation to the Gregorian solar calendar. Now, Morocco officially adopted Daylight Saving (or Summer) Time in 2007, opting to make the spring forward during the last weekend of March, as does the European Union to the north. However, the country reverts back to standard time during the month of Ramadan... otherwise, the break in the daily fast during summer months would fall towards local midnight.You can see a curious future situation developing. In 2016, Ramadan runs from sundown June 5th, to July 4th. Each cycle begins with the sighting of the thin waxing crescent Moon. However, as Ramadan falls earlier, you'll get a bizarre scenario such as 2022, when Morocco springs forward on March 27th, only to fall back to standard time six days later on April 2nd on the start of Ramadan, only to jump forward again one lunation later on April 30th!Morocco is the only country we've come across in our travels that follows such a convoluted convention of timekeeping.Fun fact #2: the next 'Mini-Moon' featuring a lunar eclipse occurs on July 27th 2018.And the Spring Mini-Moon sets us up for Supermoon season six months later this coming October-November-December. Though lunar perigees less than 24 hours from Full usually occur as a trio, an apogee less than 24 hours from Full is nearly always a solitary affair, owing to the slightly slower motion of the Moon at a farther distance.Don't miss the shrunken Mini-Moon rising on the evenings of Thursday April 21st and Friday 22nd, coming to a sky near you.

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Posted by Nelio Inacio at 3:32 PM 0 comments

Gravity Waves On Pluto?

Gravity Waves On Pluto?:



The varying brightness in Pluto's atmosphere is caused by atmospheric gravity waves, or buoyancy waves. Image: NASA/New Horizons/Johns Hopkins APL/SWRI


New Horizons' historic journey to Pluto and beyond continues to provide surprises. As data from the spacecraft's close encounter with Pluto and its moons arrives at Earth, scientists are piecing together an increasingly intriguing picture of the dwarf planet. The latest discovery is centred around Pluto's atmosphere, and what are called 'atmospheric gravity waves.'Atmospheric gravity waves are a different phenomenon than the gravity waves that were detected for the first time in February, 2016. Those gravity waves are ripples in the fabric of space time, first predicted by Albert Einstein back in 1916. After years of searching, the LIGO instrument detected gravity waves that resulted from two black holes colliding. The discovery of what you might call 'Einsteinian Gravity Waves' may end up revolutionizing astronomy.New Horizons has revealed surprise after surprise in its study of Pluto. Its atmosphere has turned out to be much more complex than anybody expected. It's composed of 90% nitrogen, with extensive haze layers. Scientists have discovered that Pluto's atmosphere can vary in brightness depending on viewpoint and illumination, while the vertical structure of the layered haze remains unchanged.Scientists studying the New Horizons' data think that atmospheric gravity waves, also called buoyancy waves, are responsible. Atmospheric gravity waves are known to exist on only two other planets; Earth and Mars. They are typically caused by wind flowing over obstructions like mountain ranges.[embed]https://www.youtube.com/watch?v=yXnkzeCU3bE[/embed]The layers in Pluto's atmosphere, and their varying brightness, are most easily seen when they are backlit by the Sun. This was the viewpoint New Horizons had when it captured these images on its departure from Pluto on July 14, 2015. The spacecraft's Long Range Reconnaissance Imager (LORRI) captured them, using time intervals of 2 to 5 hours. What they show is the brightness of the layers changing by 30% without any change in their height above the surface of the planet.LORRI, as its name suggests, is a long range image capture instrument. It also captures high resolution geologic data, and was used to map Pluto's far side. The principal investigator for LORRI is Andy Cheng, from the Applied Physics Laboratory at Johns Hopkins University, in Maryland. “Pluto is simply amazing,” said Andy Cheng. “When I first saw these images and the haze structures that they reveal, I knew we had a new clue to the nature of Pluto’s hazes. The fact that we don’t see the haze layers moving up or down will be important to future modelling efforts.”Overall, Pluto and its system of moons has turned out to be a much more dynamic place than previously thought. A geologically active landscape, possible ice volcanoes, eroding cliffs made of methane ice, and more, have woken us up to Pluto's complexity. But its atmosphere has turned out to be just as complex and puzzling.[embed]https://www.youtube.com/watch?v=C3fniYbhTCk&list=PLiuUQ9asub3RUlLBXMFGq8aFEPS5yONT2&index=12[/embed] New Horizons has departed the Pluto system now, and is headed for the Kuiper Belt. The Kuiper Belt is considered a relic of the early Solar System. New Horizons will visit another icy world there, and hopefully continue on to the edge of the heliosphere, the same way the Voyage probes have. New Horizons has enough energy to last until approximately the mid-2030's, if all goes well.[embed]https://www.youtube.com/watch?v=hjSZ8054faU&list=PLiuUQ9asub3RUlLBXMFGq8aFEPS5yONT2&index=4[/embed]

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Posted by Nelio Inacio at 3:32 PM 0 comments

What’s Outside the Universe?

What’s Outside the Universe?:

A few hundred episodes ago, I answered the question, “What is the Universe Expanding Into?” The gist of the answer is that the Universe as we understand it, isn’t really expanding into anything.

If you go in any one direction long enough, you just return to your starting point. As the Universe expands, that journey takes longer, but there’s still nothing that it’s going into.

Okay, so, I need to put an asterisk on that answer, and then when you read the fine print it’d say something like, “unless we live in a multiverse”.

One of the super interesting and definitely way out there ideas is that our cosmos to actually just one universe in a vast multiverse. Each universe is sort of like a soap bubble embedded in the cosmic void of the multiverse, expanding from its own Big Bang.

Our universe could actually be part of a larger multiverse. Credit: Jim Misti (Misti Mountain Observatory)
Our universe could actually be part of a larger multiverse. Credit: Jim Misti (Misti Mountain Observatory)
And in each one of these universes, the laws of physics are completely different. There are actually a bunch of physical constants in the Universe, like the force of gravity or the binding strength of atoms. For each one of those basic constants, it’s as if the laws of physics randomly rolled the dice, and came up with our Universe – a place that’s almost, but not completely hostile to life.

So imagine all these different bubble universes popping up in this vast cosmic foam of the multiverse, and the laws of physics are different. Maybe in another universe, the force of gravity is repulsive, or green, or spawns unicorns.

In the vast majority of those universes, no life could ever form, but roll the dice an infinite number of times and you’ll eventually get the conditions for life.

Any lifeform capable of perceiving the Universe had to evolve into a universe capable of life.

Of course, this sounds like pseudo scientific mumbo jumbo, and next you’ll expect me to talk about chakras, astrology and channeling the spirit of Big Foot.

However, hang on a second, this might actually be science. If these bubble universes got close enough, there might be a way they could rub together, to interact in ways that were detectable from within the Universe.

In other words, we could look out into space and see a cosmic bruise, and know that’s where our universe is colliding with another one.

Well, have astronomers looked out into space, in search of some sign that our Universe is interacting with other universes? Indeed they have, and they’ve found something really strange.

The cosmic microwave background radiation, enhanced to show the anomalies. Credit: ESA and the Planck Collaboration
The cosmic microwave background radiation, enhanced to show the anomalies. Credit: ESA and the Planck Collaboration
When examining the Cosmic Microwave Background Radiation, the afterglow leftover from the Big Bang, astronomers have found a temperature fluctuations. These different temperatures, or anisotropies are regions where different densities of matter in the early Universe were scaled up to enormous scales by the ongoing expansion.

While most of these differences in temperature are explained by the current cosmological theories for the Universe, there’s one region that defies the theories. It’s so strange, the researchers who discovered it hilariously named it the “Axis of Evil” after something some president said.

Anyway, there are lots of ideas for what the Axis of Evil might be. Seriously, every single one of them is more reasonable and more likely than what I’m about to say.

But one really fascinating idea is that we’re seeing a region where our Universe is bumping into another universe, violating each other’s laws of physics.

So if this is the case, and astronomers are witnessing a universal interaction, what does this mean for the poor aliens who might be getting overlapped by the next universe over?

We have no idea, but imagine what might happen as the laws of physics from two completely different universes overlap. What is the average of 7 and green? Or 26 and unicorn dreams? Whatever it is, it can’t be good for the aliens and their continued healthy existence.

But don’t worry, that region is billions of light years away, and it’s probably not another universe anyway, we just need better observations.

We covered this topic in great detail in episode 408 of Astronomy Cast, so if you want hear more from Dr. Pamela Gay, click here and watch the show. You’ll especially enjoy watching me pick up the shattered pieces of my brain as I try to wrap my head around this mind bending concept.

The post What’s Outside the Universe? appeared first on Universe Today.

Posted by Nelio Inacio at 3:31 PM 0 comments

What Is The Surface of Neptune Like?

What Is The Surface of Neptune Like?:



Neptune Hurricanes


As a gas giant (or ice giant), Neptune has no solid surface. In fact, the blue-green disc we have all seen in photographs over the years is actually a bit of an illusion. What we see is actually the tops of some very deep gas clouds, which in turn give way to water and other melted ices that lie over an approximately Earth-size core made of silicate rock and a nickel-iron mix. If a person were to attempt to stand on Neptune, they would sink through the gaseous layers.As they descended, they would experience increased temperatures and pressures until they finally touched down on the solid core itself. That being said, Neptune does have a surface of sorts, (as with the other gas and ice giants) which is defined by astronomers as being the point in the atmosphere where the pressure reaches one bar. Because of this, Neptune's surface is one of the most active and dynamic places in entire the Solar System.

Composition and Structure:

With a mean radius of 24,622 ± 19 km, Neptune is the fourth largest planet in the Solar System. But with a mass of 1.0243 × 1026 kg - which is roughly 17 times that of Earth - it is the third most massive, outranking Uranus. Due to its smaller size and higher concentrations of volatiles relative to Jupiter and Saturn, Neptune (much like Uranus) is often referred to as an “ice giant” - a subclass of a giant planet.As with Uranus, the absorption of red light by the atmospheric methane is part of what gives Neptune its blue hue, although Neptune’s is darker and more vivid. Because Neptune’s atmospheric methane content is similar to that of Uranus, some unknown atmospheric constituent is thought to contribute to Neptune’s more intense coloring.Also like Uranus, Neptune’s internal structure is differentiated between a rocky core consisting of silicates and metals; a mantle consisting of water, ammonia and methane ices; and an atmosphere consisting of hydrogen, helium and methane gas. It's atmosphere is also divided into four layers, consisting of (from innermost to outermost) the lower troposphere, the stratosphere, the thermosphere and the exosphere.The two main regions of Neptune's atmosphere are the two innermost ones: the lower troposhere, where temperatures decrease with altitude; and the stratosphere, where temperature increases with altitude. Within the troposphere, pressure levels range from one to five bars (100 and 500 kPa), hence the surface of Neptune is defined as being within this region.

Atmosphere:

Neptune's "surface" can therefore be said to be composed of about 80% hydrogen and 19% helium, with a trace amount of methane. The surface layer is also permeated by roving bands of clouds with varying compositions, depending on altitude and pressure. At the upper-level, temperatures are suitable for methane to condense, and the pressure conditions are such that clouds consisting of ammonia, ammonium sulfide, hydrogen sulfide and water can exist.At lower levels, clouds of ammonia and hydrogen sulfide are thought to form. Deeper clouds of water ice should be also found in the lower regions of the troposphere, where pressures of about 50 bars (5.0 MPa) and temperature of 273 K (0 °C) are common.For reasons that remain obscure, the planet’s thermosphere experiences unusually high temperatures of about 750 K (476.85 °C/890 °F). The planet is too far from the Sun for this heat to be generated by ultraviolet radiation, which means another heating mechanism is involved – which could be the atmosphere’s interaction with ion’s in the planet’s magnetic field, or gravity waves from the planet’s interior that dissipate in the atmosphere.Because Neptune is not a solid body, its atmosphere undergoes differential rotation. The wide equatorial zone rotates with a period of about 18 hours, which is slower than the 16.1-hour rotation of the planet’s magnetic field. By contrast, the reverse is true for the polar regions where the rotation period is 12 hours.This differential rotation is the most pronounced of any planet in the Solar System, and results in strong latitudinal wind shear and violent storms. The three most impressive were all spotted in 1989 by the Voyager 2 space probe, and then named based on their appearances.The first to be spotted was a massive anticyclonic storm measuring 13,000 x 6,600 km and resembling the Great Red Spot of Jupiter. Known as the Great Dark Spot, this storm was not spotted five later (Nov. 2nd, 1994) when the Hubble Space Telescope looked for it. Instead, a new storm that was very similar in appearance was found in the planet’s northern hemisphere, suggesting that these storms have a shorter life span than Jupiter’sThe Scooter is another storm, a white cloud group located farther south than the Great Dark Spot. This nickname first arose during the months leading up to the Voyager 2 encounter in 1989, when the cloud group was observed moving at speeds faster than the Great Dark Spot. The Small Dark Spot, a southern cyclonic storm, was the second-most-intense storm observed during the 1989 encounter. It was initially completely dark; but as Voyager 2 approached the planet, a bright core developed and could be seen in most of the highest-resolution images.

Internal Heat:

For reasons that astronomers are still not clear on, the interior of Neptune is unusually hot. Even though Neptune is much further from the Sun than Uranus and receives 40% less sunlight, its surface temperature is about the same. In fact, Neptune gives off 2.6 times more energy than it takes in from the Sun. Even without the Sun, Neptune glows.This high amount of interior heat matched with the coldness of space creates a huge temperature difference. And this sets the winds blasting around Neptune. Maximum wind speeds on Jupiter can be more than 500 km/hour. That's twice the speed of the strongest hurricanes on Earth. But that's nothing compared to Neptune. Astronomers have calculated winds blasting across the surface of Neptune at 2,100 km/hour.Deep down inside Neptune, the planet might have an actual solid surface. At the very core of the gas/ice giant is thought to be a region of rock with roughly the mass of the Earth. But temperatures at this region would be thousands of degrees; hot enough to melt rock. And the pressure from the weight of all the atmosphere would be crushing.In short, there is simply no way one could stand on the "surface of Neptune", let alone walk around on it.https://youtu.be/COI5LBpvDyUWe have many interesting articles about Neptune here at Universe Today. Here is one about the Rings of Neptune, the Moons of Neptune, Who Discovered Neptune?, Are There Oceans on Neptune?If you’d like more information on Neptune, take a look at Hubblesite’s News Releases about Neptune, and here’s a link to NASA’s Solar System Exploration Guide to Neptune.Astronomy Cast has some interesting episodes about Neptune. You can listen here, Episode 63: Neptune and Episode 199: The Voyager Program.

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Posted by Nelio Inacio at 3:30 PM 0 comments

Our Sun May Have Eaten A Super Earth For Breakfast

Our Sun May Have Eaten A Super Earth For Breakfast:



A new paper says that a Super-Earth may have formed in our Solar System and been swallowed by the Sun. Image Credit: ESA/Hubble, M. Kornmesser


Our Solar System sure seems like an orderly place. The orbits of the planets are predictable enough that we can send spacecraft on multi-year journeys to them and they will reliably reach their destinations. But we've only been looking at the Solar System for the blink of an eye, cosmically speaking.The young Solar System was a much different place. Things were much more chaotic before the planets settled into the orbital stability that they now enjoy. There were crashings and smashings aplenty in the early days, as in the case of Theia, the planet that crashed into Earth, creating the Moon.Now, a new paper from Rebecca G. Martin and Mario Livio at the University of Nevada, Las Vegas, says that our Solar System may have once had an additional planet that perished when it plunged into the Sun. Strangely enough, the evidence for the formation and existence of this planet may be the lack of evidence itself. The planet, which may have been what's called a Super-Earth, would have formed quite close to the Sun, and then been destroyed when it was drawn into the Sun by gravity.In the early days of our Solar System, the Sun would have formed in the centre of a mass of gas and dust. Eventually, when it gained enough mass, it came to life in a burst of atomic fusion. Surrounding the Sun was a protoplanetary disk of gas and dust, out of which the planets formed.[embed]https://www.youtube.com/watch?v=UNPj7e6XJCQ[/embed]What's missing in our Solar System is any bodies, or even rocky debris in the zone between Mercury and the Sun. This may seem normal, but the Kepler mission tells us it's not. In over half of the other solar systems it's looked at, Kepler has found planets in the same zone where our Solar System has none.A key part of this idea is that planets don't always form in situ. That is, they don't always form at the place where they eventually reach orbital stability. Depending on a number of factors, planets can migrate inward towards their star or outwards away from their star.Martin and Livio, the authors of the study, think that our Solar System did form a Super-Earth, and rather than it migrating outward, it fell into the Sun. According to them, the Super-Earth most probably formed in the inner regions of our Solar System, on the inside of Mercury's orbit. The fact that there are no objects there, and no debris of any kind, suggests that the Super-Earth formed close to the Sun, and that its formation cleared that area of any debris. Then, once formed, it fell into the Sun, removing all evidence of its existence.The authors also note another possible cause for the Super-Earth to have fallen into the Sun. They propose that Jupiter may have migrated inward to about 1.5 AUs from the Sun. At that point, it got locked into resonance with Saturn. Then, both gas giants migrated outward to their current orbits. This process would have shepherded a Super-Earth into the Sun, destroying it.Some of the thinking behind this whole theory involves the size of the inner terrestrial planets in our Solar System. They're very small in comparison to other systems studied by the Kepler Mission. If a Super-Earth had formed in the inner part of our System, it would have dominated the accretion of available material, leaving Mercury, Venus, Earth and Mars starved for matter.A key idea behind this study is what's known as a dead zone. In terms of a solar system and a protoplanetary disk, a dead zone is a zone of low turbulence which favors the formation of planets. A system with a dead zone would have enough material to allow Super-Earths to form in-situ, and they would not have to migrate inward from further out in the system. However, since large planets like Super-Earths take a long time to fully form, this dead zone would have to be long-lived.If a protoplanetary disk lacks a dead zone, it is likely too turbulent for the formation of a Super-Earth close to the star. A turbulent protoplanetary disk favors the formation of Super-Earths further out, which would then migrate inwards towards the star. Also, a turbulent disk allows for quicker migration of planets, while a pronounced dead zone inhibits migration.As the authors say in the conclusion of their study, "The lack of Super–Earths in our solar system is somewhat puzzling given that more than half of observed exoplanetary systems contain one. However, the fact that there is nothing inside of Mercury’s orbit may not be a coincidence." They go on to conclude that in our Solar System, the likely scenario is the in situ formation of a Super-Earth which subsequently fell into the Sun.There are a lot of variables that have to be fine-tuned for this scenario to happen. The young solar system would need a dead zone, the depth of the turbulence in the protoplanetary disk would have to be just right, and the disk would have to be the right temperature. The fact that these things have to be within a certain range may explain why we don't have a Super-Earth in our system, while over half of the systems studied by Kepler do have one.

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Posted by Nelio Inacio at 3:29 PM 0 comments
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