Harvard Physicist Creates Metallic Hydrogen Using Diamond Vise

Harvard Physicist Creates Metallic Hydrogen Using Diamond Vise

For some time, scientists have been fascinated by the concept of metallic hydrogen. Such an element is believed to exist naturally when hydrogen is placed under extreme pressures (like in the interior of gas giants like Jupiter). But as a synthetic material, it would have endless applications, since it is believed to have superconducting properties at room temperature and the ability to retain its solidity once it has been brought back to normal pressure.

For this reason, condensed matter physicists have been attempting to create metallic hydrogen for decades. And according to a recent study published in Science Magazine, a pair of physicists from the Lyman Laboratory of Physics at Harvard University claim to have done this very thing. If true, this accomplishment could usher in a new age of super materials and high-pressure physics.

The existence of metallic hydrogen was first predicted in 1935 Princeton physicists Eugene Wigner and Hillard Bell Huntington. For years, Isaac Silvera (the Thomas D. Cabot Professor at Harvard University) and Ranga Dias, a postdoctorate fellow, have sought to create it. They claim to have succeeded, using a process which they described in their recently-published study, “Observation of the Wigner-Huntington transition to metallic hydrogen“.

This cut-away illustrates a model of the interior of Jupiter, with a rocky core overlaid by a deep layer of liquid metallic hydrogen. Credit: Kelvinsong/Wikimedia Commons

Such a feat, which is tantamount to creating the heart of Jupiter between two diamonds, is unparalleled in the history of science. As Silvera described the accomplishment in a recent Harvard press release:

“This is the Holy Grail of high-pressure physics. It’s the first-ever sample of metallic hydrogen on Earth, so when you’re looking at it, you’re looking at something that’s never existed before.”

In the past, scientists have succeeded in creating liquid hydrogen at high temperature conditions by ramping up the pressures it was exposed to (as opposed to cryogenically cooling it). But metallic hydrogen has continued to elude experimental scientists, despite repeated (and unproven) claims in the past to have achieved synthesis. The reason for this is because such experiments are extremely temperamental.

For instance, the diamond anvil method (which Silvera and Dias used a variation of) consists of holding a sample of hydrogen in place with a thin metal gasket, then compressing it between two diamond-tipped vices. This puts the sample under extreme pressure, and a laser sensor is used to monitor for any changes. In the past, this has proved problematic since the pressure can cause the hydrogen to fill imperfections in the diamonds and crack them.

While protective coatings can ensure the diamonds don’t crack, the additional materials makes it harder to get accurate readings from laser measurements. What’s more, scientists attempting to experiment with hydrogen have found that pressures of ~400 gigapascals (GPa) or more need to be involved – which turns the hydrogen samples black, thus preventing the laser light from being able to penetrate it.

Microscopic images of the stages in the creation of metallic hydrogen: Transparent molecular hydrogen (left) at about 200 GPa, which is converted into black molecular hydrogen, and finally reflective atomic metallic hydrogen at 495 GPa. Credit: Isaac Silvera

For the sake of their experiment, Professors Ranga Dias and Isaac Silvera took a different approach. For starters, they used two small pieces of polished synthetic diamond rather than natural ones. They then used a reactive ion etching process to shave their surfaces, then coated them with a thin layer of alumina to prevent hydrogen from diffusing into the crystal structure.

They also simplified the experiment by removing the need for high-intensity laser monitoring, relying on Raman spectroscopy instead. When they reached a pressure of 495 GPa (greater than that at the center of the Earth), their sample reportedly became metallic and changed from black to shiny red. This was revealed by measuring the spectrum of the sample, which showed that it had become highly reflective (which is expected for a sample of metal).

As Silvera explained, these experimental results (if verified) could lead to all kinds of possibilities:

“One prediction that’s very important is metallic hydrogen is predicted to be meta-stable. That means if you take the pressure off, it will stay metallic, similar to the way diamonds form from graphite under intense heat and pressure, but remain diamonds when that pressure and heat are removed. As much as 15 percent of energy is lost to dissipation during transmission, so if you could make wires from this material and use them in the electrical grid, it could change that story.”

Superconducting links developed to carry currents of up to 20,000 amperes are being tested at CERN. Credit: CERN

In short, metallic hydrogen could speed the revolution in electronics already underway, thanks to the discovery of materials like graphene. Since metallic hydrogen is also believed to be a superconductor at room temperature, its synthetic production would have immense implications for high-energy research and physics – such as that being conducted by CERN.

Beyond that, it would also enable research into the interior’s of gas giants. For some time, scientists have suspected that a layer of metallic hydrogen may surround the cores of gas giants like Jupiter and Saturn. Naturally, the temperature and pressure conditions in the interiors of these planets make direct study impossible. But by being able to produce metallic hydrogen synthetically, scientists could conduct experiment to see how it behaves.

Naturally, the news of this experiment and its results is being met with skepticism. For instance, critics wonder if the pressure reading of 495 GPa was in fact accurate, since Silvera and Dias only obtained that as a final measurement and were forced to rely on estimates prior to that. Second, there are those who question if the reddish speck that resulted is in fact hydrogen, and some material that came from the gasket or diamond coating during the process.

However, Silvera and Dias are confident in their results and believe they can be replicated (which would go far to silence doubts about their results). For one, they emphasize that a comparative measurement of the reflective properties of the hydrogen dot and the surrounding gasket suggest that the hydrogen is pure. They also claim their pressure measurements were properly calibrated and verified.

In the future, they intend to obtain additional spectrographic readings from the sample to confirm that it is in fact metallic. Once that is done, they plan to test the sample to see if it is truly metastable, which will consist of them opening the vise and seeing if it remains in a solid state. Given the implications of success, there are many who would like to see their experiment borne out!

Be sure to check out this video produced by Harvard University that talks about the experiment:

Further Reading: Science Magazine, Harvard Gazette

The post Harvard Physicist Creates Metallic Hydrogen Using Diamond Vise appeared first on Universe Today.

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Four Planet System Directly Imaged In Motion

Four Planet System Directly Imaged In Motion

Located about 129 light years from Earth in the direction of the Pegasus constellation is the relatively young star system of HR 8799. Beginning in 2008, four orbiting exoplanets were discovered in this system which – alongside the exoplanet Formalhaut b – were the very first to be confirmed using the direct imaging technique. And over time, astronomer have come to believe that these four planets are in resonance with each other.

In this case, the four planets orbit their star with a 1:2:4:8 resonance, meaning that each planet’s orbital period is in a nearly precise ratio with the others in the system. This is a relatively unique phenomena, one which inspired a Jason Wang – a graduate student from the Berkeley arm of the NASA-sponsored Nexus for Exoplanet System Science (NExSS) – to produce a video that illustrates their orbital dance.

Using images obtained by the W.M. Keck Observatory over a seven year period, Wang’s video provides a glimpse of these four exoplanets in motion. As you can see below, the central star is blacked out so that the light reflecting off of its planets can be seen. And while it does not show the planets completing a full orbital period (which would take decades and even centuries) it beautifully illustrates the resonance that exists between the star’s four planets.

As Jason Wang told Universe Today via email:

“The data was obtained over 7 years from one of the 10 meter Keck telescopes by a team of astronomers (Christian Marois, Quinn Konopacky, Bruce Macintosh, Travis Barman, and Ben Zuckerman). Christian reduced each of the 7 epochs of data, to make 7 frames of data. I then made a movie by using a motion interpolation to interpolate those 7 frames into 100 frames to get a smooth video so that it’s not choppy (as if we could observe them every month from Earth).”

The images of the four exoplanets were originally captured by Dr. Christian Marois of the National Research Council of Canada’s Herzberg Institute of Astrophysics. It was in 2008 that Marois and his colleagues discovered the first three of HR 8799’s planets – HR 8799 b, c and d – using direct imaging technique. At around the same time, a team from UC Berkeley announced the discovery of Fomalhaut b, also using direct imaging.

These planets were all determined to be gas giants of similar size and mass, with between 1.2 and 1.3 times the size of Jupiter, and 7 to 10 times its mass. At the time of their discovery, HR 8799 d was believed to be the closest planet to its star, at a distance of about 27 Astronomical Units (AUs) – while the other two orbit at distances of about 42 and 68 AUs, respectively.

Image of HR 8799 (left) taken by the HST in 1998, image processed to remove scattered starlight (center), and illustration of the planetary system (right). Credit: NASA/ESA/STScI/R. Soummer

It was only afterwards that the team realized the planets had already been observed in 1998. Back then, the Hubble Space Telescope’s Near Infrared Camera and Multi-Object Spectrometer (NICMOS) had obtained light from the system that indicated the presence of planets. However, this was not made clear until after a newly-developed image-processing technique had been installed. Hence, the “pre-discovery” went unnoticed.

Further observations in 2009 and 2010 revealed the existence of fourth planet – HR 8799 e – which had an orbit placing it inside the other three. Even so, this planet is fifteen times farther from its star than the Earth is from the Sun, which results in an orbital period of about 18,000 days (49 years). The others take around 112, 225, and 450 years (respectively) to complete an orbit of HR 8799.

Ultimately, Wang decided to produce the video (which was not his first), to illustrate how exciting the search for exoplanets can be. As he put it:

“I had written this motion interpolation algorithm for another exoplanet system, Beta Pictoris b, where we see one planet on an edge-on orbit looking like it’s diving into its star (it’s actually just circling in front of it). We wanted to do the same thing for HR 8799 to bring this system to life and share our excitement in directly imaging exoplanets. I think it’s quite amazing that we have the technology to watch other worlds orbit other stars.”

In addition, the video draws attention to a star system that presents some unique opportunities for exoplanet research. Since HR 8799 was the first multi-planetary system to be directly-imaged means that astronomers can directly observe the orbits of the four planets, observe their dynamical interactions, and determine how they came to their present-day configuration.

Astronomers will also be able to take spectra of these planet’s atmospheres to study their composition, and compare this to our own Solar System’s gas giants. And since the system is really quite young (just 40 million years old), it can tell us much about the planet-formation process. Last, but not least, their wide orbits (a necessity given their size) could mean the system is less than stable.

In the future, according to Wang, astronomers will be watching to see if any planets get ejected from the system. I don’t know about you, but I would consider a video that illustrates one of HR 8799’s gas giants getting booted out of its system would be pretty inspiring too!

Further Reading: NASA

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JPL Needs Citizen Scientists To Hunt Martian Polygonal Ridges

JPL Needs Citizen Scientists To Hunt Martian Polygonal Ridges

Mars has some impressive geological features across its cold, desiccated surface, many of which are similar to featured found here on Earth. By studying them, scientists are able to learn more about the natural history of the Red Planet, what kinds of meteorological phenomena are responsible for shaping it, and how similar our two planets are. A perfect of example of this are the polygon-ridge networks that have been observed on its surface.

One such network was recently discovered by the Mars Reconnaissance Orbiter (MRO) in the Medusae Fossae region, which straddles the planet’s equator. Measuring some 16 story’s high, this ridge network is similar to others that have been spotted on Mars. But according to a survey produced by researchers from NASA’s Jet Propulsion Laboratory, these ridges likely have different origins.

This survey, which was recently published in the journal Icarus, examined both the network found in the Medusae Fossae region and similar-looking networks in other regions of the Red Planet. These ridges (sometimes called boxwork rides), are essentially blade-like walls that look like multiple adjoining polygons (i.e. rectangles, pentagons, triangles, and similar shapes).

 Shiprock, a ridge-feature in northwestern New Mexico that is 10 meters (30 feet) tall, whic formed from lava filling an underground fracture that resisted erosion better than the material around it did. Credit: NASA

While similar-looking ridges can be found in many places on Mars, they do not appear to be formed by any single process. As Laura Kerber, of NASA’s Jet Propulsion Laboratory and the lead author of the survey report, explained in a NASA press release:

“Finding these ridges in the Medusae Fossae region set me on a quest to find all the types of polygonal ridges on Mars… Polygonal ridges can be formed in several different ways, and some of them are really key to understanding the history of early Mars. Many of these ridges are mineral veins, and mineral veins tell us that water was circulating underground.”

Such ridges have also been found on Earth, and appear to be the result of various processes as well. One of the most common involves lava flowing into preexisting fractures in the ground, which then survived when erosion stripped the surrounding material away. A good example of his is the Shiprock (shown above), a monadrock located in San Juan County, New Mexico.

Examples of polygon ridges on Mars include the feature known as “Garden City“, which was discovered by the Curiosity rover mission. Measuring just a few centimeters in height, these ridges appeared to be the result of mineral-laden groundwater moving through underground fissures, which led to standing mineral veins once the surrounding soil eroded away.

Mineral veins at the “Garden City” site, examined by NASA’s Curiosity Mars rover. Credit: NASA/JPL

At the other end of the scale, ridges that measure around 2 kilometers (over a mile) high have also been found. A good example of this is “Inca City“, a feature observed by the Mars Global Surveyor near Mars’ south pole. In this case, the feature is believed to be the result of underground faults (which were formed from impacts) filling with lava over time. Here too, erosion gradually stripped away the surrounding rock, exposing the standing lava rock.

In short, these features are evidence of underground water and volcanic activity on Mars. And by finding more examples of these polygon-ridges, scientists will be able to study the geological record of Mars more closely. Hence why Kerber is seeking help from the public through a citizen-science project called Planet Four: Ridges.

Established earlier this month on Zooniverse – a volunteer-powered research platform – this project has made images obtained by the MRO’s Context Camera (CTX) available to the public. Currently, this and other projects using data from CTX and HiRISE have drawn the participation of more than 150,000 volunteers from around the world.

By getting volunteers to sort through the CTX images for ridge formations, Kerber and her team hopes that previously-unidentified ones will identified and that their relationship with other Martian features will be better understood.

Further Reading: NASA

The post JPL Needs Citizen Scientists To Hunt Martian Polygonal Ridges appeared first on Universe Today.

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Boeing Unveils Blue Spacesuits for Starliner Crew Capsule

Boeing Unveils Blue Spacesuits for Starliner Crew Capsule

Chris Ferguson, Boeing director of Starliner Crew and Mission Systems and a former NASA astronaut and Space Shuttle commander wears the brand new spacesuit from Boeing and David Clark that crews will wear on Starliner missions to the ISS. Credit: Boeing

Boeing has unveiled the advanced new lightweight spacesuits that astronauts will sport as passengers aboard the company’s CST-100 Starliner space taxi during commercial taxi journey’s to and from and the International Space Station (ISS) and other low Earth orbit destinations.

The signature ‘Boeing Blue’ spacesuits will be much lighter, as well as more flexible and comfortable compared to earlier generations of spacesuits wore by America’s astronauts over more than five decades of human spaceflight, starting with the Mercury capsule to the latest gear worn by Space Shuttle astronauts.

“The suit capitalizes on historical designs, meets NASA requirements for safety and functionality, and introduces cutting-edge innovations,” say NASA officials.

The suits protect the astronauts during both launch and reentry into the Earth’s atmosphere during the return home.

Indeed Chris Ferguson, a former NASA Space Shuttle Commander who now works for Boeing as a Starliner program director, helped reveal the ‘Boeing Blue’ spacesuits during a Facebook live event, where he modeled the new suit.

“We slogged through some of the real engineering challenges and now we are getting to the point where those challenges are largely behind us and it’s time to get on to the rubber meeting the road,” Ferguson said.

The suits offer superior functionality, comfort and protection for astronauts who will don them when crewed Starliner flights to the space station begin as soon as next year.

Astronaut Eric Boe evaluates Boeing Starliner spacesuit in mockup of spacecraft cockpit. Credits: Boeing

At roughly half the weight (about 10 pounds vs. 20 pounds) compared to the launch-and-entry suits worn by space shuttle astronauts, crews look forward to wearing the ‘Boeing Blue’ suits.

“Spacesuits have come in different sizes and shapes and designs, and I think this fits the Boeing model, fits the Boeing vehicle,” said Chris Ferguson, Boeing director of Starliner Crew and Mission Systems and a former NASA astronaut.

Among the advances cited are:

• Lighter and more flexible through use of advanced materials and new joint patterns
• Helmet and visor incorporated into the suit instead of detachable. The suit’s hood-like soft helmet sports a wide polycarbonate visor to give Starliner passengers better peripheral vision throughout their ride to and from space.
• A communications headset within the helmet also helps connect astronauts to ground and space crews
• Touchscreen-sensitive gloves that allow astronauts to interact with the capsule’s tablets screens overhead
• Vents that allow astronauts to be cooler, but can still pressurize the suit immediately
• Breathable, slip resistant boots
• Zippers in the torso area will make it easier for astronauts to comfortably transition from sitting to standing
• Innovative layers will keep astronauts cooler

“The most important part is that the suit will keep you alive,” astronaut Eric Boe said, in a statement. “It is a lot lighter, more form-fitting and it’s simpler, which is always a good thing. Complicated systems have more ways they can break, so simple is better on something like this.”

The astronauts help the designers to perfect the suits very practically by wearing them inside Starliner mock-ups, moving around to accomplish tasks, reaching for the tablets screens, and climbing in and out of the capsule repeatedly, says Boe “so they can establish the best ways for astronauts to work inside the spacecraft’s confines.”

Astronaut Sunni Williams puts on the communications carrier of Boeing’s new Starliner spacesuit. Credits: Boeing

“The spacesuit acts as the emergency backup to the spacecraft’s redundant life support systems,” said Richard Watson, subsystem manager for spacesuits for NASA’s Commercial Crew Program.

“If everything goes perfectly on a mission, then you don’t need a spacesuit. It’s like having a fire extinguisher close by in the cockpit. You need it to be effective if it is needed.”

Boeing graphic of Starliner spacesuit features. Credit: NASA/Boeing

Boe is one of four NASA astronauts that form the core cadre of astronauts training for the initial flight tests aboard either the Boeing Starliner or SpaceX Crew Dragon now under development as part of NASA’s Commercial Crew program.

The inaugural flight tests are slated to begin in 2018 under contract to NASA.

The procedure on launch day will be similar to earlier manned launches. But for Starliner, the capsule will launch atop a United Launch Alliance Atlas V rocket – currently being man-rated.

Fiery blastoff of a United Launch Alliance (ULA) Atlas V rocket carrying the EchoStar XIX satellite from Space Launch Complex-41 on Cape Canaveral Air Force Station, Fl., at 2:13 p.m. EST on Dec. 18, 2016. Note recently installed crew access tower and arm to be used for launches of Boeing Starliner crew spacecraft. Credit: Ken Kremer/kenkremer.com

Astronauts will don the new ‘Boeing Blue’ suit in the historic Crew Quarters. The will ride out to the rocket inside an astrovan. After reaching Space Launch Complex 41, they will take the elevator up, stride across the recently installed Crew Access Arm and board Starliner as it stands atop a United Launch Alliance Atlas V rocket.

The first test flight will carry a crew of two. Soon thereafter the crew size will grow to four when regular crew rotation flights to the ISS start as soon as 2019.

“To me, it’s a very tangible sign that we are really moving forward and we are a lot closer than we’ve been,” Ferguson said. “The next time we pull all this together, it might be when astronauts are climbing into the actual spacecraft.”

Boeing is currently the Starliner spacecraft at the company’s Commercial Crew and Cargo Processing Facility at NASA’s Kennedy Space Center in Florida.

Hull of the Boeing CST-100 Starliner Structural Test Article (STA)- the first Starliner to be built in the company’s modernized Commercial Crew and Cargo Processing Facility high bay at NASA’s Kennedy Space Center in Florida. Credit: Ken Kremer/kenkremer.com

Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news.

Ken Kremer

A crane lifts the Crew Access Arm and White Room for Boeing’s CST-100 Starliner spacecraft for mating to the Crew Access Tower at Cape Canaveral Air Force Station’s Space Launch Complex 41 on Aug. 15, 2016. Astronauts will walk through the arm to board the Starliner spacecraft stacked atop a United Launch Alliance Atlas V rocket. Credit: Ken Kremer/kenkremer.com

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What’s That Bright Star in the Sky?

What’s That Bright Star in the Sky?

Every few months a bright star appears in the sky. Sometimes it’s off to the East, bright in the morning before the Sun rises. Other times, you can see it in the West right after the Sun sets.

Experienced stargazers know this isn’t a star at all, of course, it’s Venus. That horrible twin planet, surrounded by a toxic choking atmosphere of superheated carbon dioxide. For a while it becomes the fourth brightest object in the sky: after the Sun, Moon and the International Space Station, if you can believe it.

In dark skies, Venus gets so bright you can even read a book to it.

Inexperienced stargazers, however, suddenly notice this super bright star in the sky. How come they never noticed it before? Was it always right next to the Moon like that? And that’s when the UFO calls to 911 start up.

Credit: nosha (CC BY-SA 2.0)

I know none of them are going to be watching this video. But for everyone else, even mildly interested in the science here, let’s dig into the orbit of Venus, how we finally figured out what that thing is, how you can observe the planet, and some cool tricks Venus can do.

We’ve written several articles on what planet Venus actually is, and why it sucks so much. You know, a runaway greenhouse effect giving the planet 90 times the Earth’s atmospheric pressure at the surface. It’s a 462-degree furnace, anywhere you go, with a rain of sulfuric acid.

A radar view of Venus taken by the Magellan spacecraft, with some gaps filled in by the Pioneer Venus orbiter. Credit: NASA/JPL

Nope, we’re not going to talk about visiting that place. Instead, we’re just going to talk about looking at it from afar, and how it changed our whole understanding about our place in the Solar System.

Venus is, of course, the second planet from the Sun. But for the vast majority of human history, nobody really understood what it was. It’s easy to see in the sky, even if you live in one of the most light polluted cities on Earth.

Ancient civilizations tried to grapple with what they were looking at, and of course, they assumed there was something supernatural going on. Probably dark and vengeful gods wandering through the heavens, staring down at us with their beady eyes. Judging, always judging. Some civilizations figured out that it’s a single object, while others believed they were looking at two separate entities.

The Ancient Greeks, for example, called the morning edition of Venus Phosphoros, the “Bringer of Light”, and they called the evening star Hesperos, the, uh, “Star of the Evening”. Then they realized it was a single object, and upgraded it to Aphrodite, the goddess of love. The Romans turned that into Venus, and the name stuck.

Heliocentric Model

Andreas Cellarius’s illustration of the Copernican system, from the Harmonia Macrocosmica (1708). Credit: Public Domain

The ancient astronomers assumed the Earth was the center of the Universe, and all the planets and even the Sun and stars revolved around us. but Nicholas Copernicus worked out the true nature of the Solar System in the early 16th century. The Sun was at the center of the Solar System, and all planets, including Earth, orbited around it.

It was a cool story, and nicely fit the motions of the planets, however, the best evidence came almost a century later when Galileo turned his first crude telescope to Venus and realized that the planet goes through phases, just like the Moon. In fact, with a small telescope, you can confirm this all for yourself.

Each of the planets orbit the Sun. Mercury and Venus orbit closer to the Sun, then Earth, then the rest of the planets. When we observe Venus, we look inwards, down towards the Sun. When we see the rest of the planets, we’re looking outward, away from the Sun.

The best analogy is a car race. If you’re in the stands watching those cars go around and around, you’re turning your head back and forth as the cars pointlessly circle in front of you. But to see cars in the ring road around the racetrack, you’ll need to look all the way round you. Make sense?

 

The orbits of Earth and Venus around the Sun. Credit: Universe Sandbox ²

Here’s a simplified version of the Solar System, with just the Earth, Venus, and the Sun. Earth, as you probably know, takes just over 365 days to go around the Sun, while Venus only takes 225 days to complete an orbit.

Which means that Venus completes more than 3 orbits every time Earth completes 2. Which means that we’re always seeing Venus from different angles compared to the Sun.

Sometimes it’s on the same side of the Sun as us. Other times it’s on the opposite. And sometimes Venus is on one side of the Sun, or the other. For about 9 and a half months, Venus is the evening star, brightening to its maximum, and then it spends another 9 and a half months as the morning star.

When all three are lined up, astronomers call that a conjunction. It’s a superior conjunction if Venus is on the opposite side of the Sun, and an inferior conjunction if it’s between us and the Sun.

When Venus is on either side, we measure its elongation, eastern or western. Because Venus orbits close to the Sun, the absolute maximum it can get is 47-degrees elongation. Make a triangle, where you point one line at the Sun, and another line at Venus, the angle of this triangle can’t get any bigger than 47-degrees.

And this is why we always see Venus relatively close to the Sun in the sky. There are 360 total degrees you can look, but Venus never leaves 90 of them.

The phases of Venus. Credit: Statis Kalyvas – VT-2004 programme

Now, onto the phases. Just like the Moon, when Venus is in between us and the Sun, then all the light is falling on the far side of Venus. The side facing towards the Sun, but facing away from us. Of course, Venus is also hidden by the glare of the Sun, which means we really can’t even see it. The opposite happens when it’s on the other side of the Sun. It would be fully illuminated from our perspective. Too bad we can’t see it in all that glare.

But when Venus is on either side, this is when we can finally see it. As our perspective changes, we’re seeing more and more of the planet illuminated, and less in shadow. We see phases. We can see a crescent Venus, or a quarter Venus, or a gibbous Venus.

When Venus is almost fully illuminated, it’s actually at its dimmest because it’s so far away. Then as it moves higher and higher in the sky, we see less of it illuminated, but more overall surface area, so it gets brighter. The point of maximum brightness, when it’s blazing brighter than almost any other object in the sky is when the greatest amount of surface area of Venus is visible to us. Astronomers call this the greatest illuminated extent.

Venus is beautiful in the evening right now as I’m recording this video. We won’t see it this bright in the evening sky until August 2017, and then March, 2020. So, get out and enjoy it while you can.

When Venus passes directly in front of the Sun, that’s a planetary transit. The last time it happened was back in 2012, and before that, 2004. Unfortunately, the next transit of Venus won’t happen until 2117. I’m sure I’ll be still around, living it up in my robot body.

You’d might wonder why they don’t line up every time Venus passes between the Earth and the Sun. That’s because both Earth and Venus are slightly tilted in their orbits. Sometimes we see Venus above the Sun when it’s directly across from us, other times it’s below the Sun. It’s only after more than 100 years they directly line up again.

 

A planetary transit of Venus. Credit: NASA/Goddard Space Flight Center/SDO

It turns out that transits of Venus gave us some of the most valuable discoveries in human history.

Today we know that the Sun is approximately 150 million kilometers away. But for the longest time we had no idea how far away the planets are. We know how far away everything is in proportion to everything else, but not in absolute terms.

In 1663, the Scottish mathematician James Gregory calculated that by making very precise measurements of the transits of Venus or Mercury, you could use trigonometry to figure out the actual distance from the Earth to the Sun. The famed astronomer Edumund Halley did even more detailed calculations and suggesedt places on the Earth to make measurements from.

It wasn’t until the 1700s that astronomers got organized enough to make worldwide measurements during a transit of Venus.

Astronomers tried to observe the Venus transit of 1761, but the weather conditions were pretty bad. In the 1769 transit, however, astronomers were sent to various corners of the globe. In Canada, Norway and the South Pacific. Nations fighting each other allowed astronomers safe passage through on ships through the warzone.

All of the observers made 4 observations: when Venus was touching the edge of the Sun, when it was fully inside, when it had touched the other side, and when it was fully out.

By combining all these measurements across the Earth, astronomers calculated that the distance from the Earth to the Sun was 93,726,900 English miles. The most accurate number we have today is 92,955,000 miles, or about 150 million kilometers. They were only off by about 1%. Not bad.

Once we knew the distance from the Earth to the Sun, we could calculate the distance to the other planets, even to other stars.  All thanks to Venus.

Venus is one of the most dependable companions we have in the night sky. Sure, it’s a hellish death world, but from our perspective here on Earth, it’s really cool to look at. Don’t miss the next opportunity to see Venus with your own eyeballs. And if you can, get your hands on a telescope and see the planet going through its phases. You won’t regret it.

Did you get a chance to see the last transit of Venus, back in 2012? Give me the details of your experience in the comments.

The post What’s That Bright Star in the Sky? appeared first on Universe Today.

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Weekly Space Hangout – January 27, 2017: Kimberly Cartier

Weekly Space Hangout – January 27, 2017: Kimberly Cartier

Host: Fraser Cain (@fcain)

Special Guest: Kimberly Cartier ( KimberlyCartier.org / @AstroKimCartier )

Kimberly Cartier is a PhD candidate in the Department of Astronomy & Astrophysics at the Pennsylvania State University where her primary research interest is extra-solar planets. Kimberly focuses on communication, public speaking, teaching, and public outreach, and is a regular contributor to the Weekly Space Hangout.

Kimberly is the lead author on a recent paper in which the atmospheric characteristics of exoplanet WASP 103b are analysed. (https://arxiv.org/pdf/1611.09272v1.pdf) Please join us today as Kimberly discusses their findings.

Guests:
Morgan Rehnberg (MorganRehnberg.com / @MorganRehnberg)
Paul M. Sutter (pmsutter.com / @PaulMattSutter)

Their stories this week:
Using AI to study supernovae

We finally made metallic hydrogen!

Quality conrol problems with Russian rockets

A new test for life on other planets

We use a tool called Trello to submit and vote on stories we would like to see covered each week, and then Fraser will be selecting the stories from there. Here is the link to the Trello WSH page (http://bit.ly/WSHVote), which you can see without logging in. If you’d like to vote, just create a login and help us decide what to cover!

If you would like to join the Weekly Space Hangout Crew, visit their site here and sign up. They’re a great team who can help you join our online discussions!

If you would like to sign up for the AstronomyCast Solar Eclipse Escape, where you can meet Fraser and Pamela, plus WSH Crew and other fans, visit our site linked above and sign up!

We record the Weekly Space Hangout every Friday at 12:00 pm Pacific / 3:00 pm Eastern. You can watch us live on Universe Today, or the Universe Today YouTube page

The post Weekly Space Hangout – January 27, 2017: Kimberly Cartier appeared first on Universe Today.

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Space Jellyfish Show Types Of Pulsar Wind Nebulas

Space Jellyfish Show Types Of Pulsar Wind Nebulas

Since they were first discovered in the late 1960s, pulsars have continued to fascinate astronomers. Even though thousands of these pulsing, spinning stars have been observed in the past five decades, there is much about them that continues to elude us. For instance, while some emit both radio and gamma ray pulses, others are restricted to either radio or gamma ray radiation.

However, thanks to a pair of studies from two international teams of astronomers, we may be getting closer to understanding why this is. Relying on data collected by the Chandra X-ray Observatory of two pulsars (Geminga and B0355+54), the teams was able to show how their emissions and the underlying structure of their nebulae (which resemble jellyfish) could be related.

The former of these studies – “Deep Chandra Observations of the Pulsar Wind Nebula Created by PSR B0355+54” – appeared in the November issue of The Astrophysical Journal while the latter- “Geminga’s Puzzling Pulsar Wind Nebula” – has been accepted for publication. For both studies, the teams relied on x-ray data from the Chandra Observatory to examine the Geminga and B0355+54 pulsars and their associated pulsar wind nebulae (PWN).

An artist’s impression of an accreting X-ray millisecond pulsar. Credit: NASA/Goddard Space Flight Center/Dana Berry

Located 800 and 3400 light years from Earth (respectively), the Geminga and B0355+54 pulsars are quite similar. In addition to having similar rotational periods (5 times per second), they are also about the same age (~500 million years). However, Geminga emits only gamma-ray pulses while B0355+54 is one of the brightest known radio pulsars, but emits no observable gamma rays.

What’s more, their PWNs are structured quite differently. Based on composite images created using Chandra X-ray data and Spitzer infrared data, one resembles a jellyfish whose tendrils are relaxed while the other looks like a jellyfish that is closed and flexed. And whereas the Geminga PWN has three distinct elongated structures (two long, lateral tails and a segmented axial tail), B0355+54’s PWN has a narrow double trail extending almost five light years.

In all likelihood, Geminga’s and B0355+54 tails are narrow jets emanating from the pulsar’s spin poles. These jets lie perpendicular to the donut-shaped disk (aka. a torus) that surrounds the pulsars equatorial regions. As Noel Klingler, a graduate student at the George Washington University and the author of the B0355+54 paper, told Universe Today via email:

“The interstellar medium (ISM) isn’t a perfect vacuum, so as both of these pulsars plow through space at hundreds of kilometers per second, the trace amount of gas in the ISM exerts pressure, thus pushing back/bending the pulsar wind nebulae behind the pulsars, as is shown in the images obtained by the Chandra X-ray Observatory.”

Their apparent structures appear to be due to their disposition relative to Earth. In Geminga’s case, the view of the torus is edge-on while the jets point out to the sides. In B0355+54’s case, the torus is seen face-on while the jets points both towards and away from Earth. From our vantage point, these jets look like they are on top of each other, which is what makes it look like it has a double tail. As Klingler put it:

“The Chandra X-ray images show that, despite their different appearances, both pulsar wind nebulae are made of the same structures: two jets of particles launched out from the pulsar poles, and an outflow of particles emanating out from the equator – both of which, in these cases, are then bent back behind the pulsars (the particle jets are initially aligned with the radio beams, but particles get bent back by the pressure, while radio beams do not). Their contrasting appearances are due to our different viewing angles (lines of sight).”

This orientation could also help explain why the two pulsars appear to emit different types of electromagnetic radiation. Basically, the magnetic poles – which are close to their spin poles – are where a pulsar’s radio emissions are believed to come from. Meanwhile, gamma rays are believed to be emitted along a pulsar’s spin equator, where the torus is located.

“The images reveal that we see Geminga from edge-on (i.e., looking at its equator) because we see X-rays from particles launched into the two jets (which are initially aligned with the radio beams), which are pointed into the sky, and not at Earth,” said Klingler. “This explains why we only see Gamma-ray pulses from Geminga.  The images also indicate that we are looking at B0355+54 from a top-down perspective (i.e., above one of the poles, looking into the jets).  So as the pulsar rotates, the center of the radio beam sweeps across Earth, and we detect the pulses;  but the  gamma-rays are launched straight out from the pulsar’s equator, so we don’t see them from B0355.”

An all-sky view from the Fermi Gamma-ray Space Telescope, showing the position of Geminga in the Milky Way. Credit : NASA/DOE/International LAT Team.

“So basically, by studying the X-ray images of the nebulae and its features, we were able to determine our orientations (viewing angles) with respect to the pulsars. This explains why we see only radio emission in B0355, and only gamma-ray emission in Geminga.”

These observations were part of a larger campaign to study six pulsars that have been seen to emit gamma-rays. This campaign is being led by Roger Romani of Stanford University, with the collaboration of astronomers and researchers from GWU (Oleg Kargaltsev), Penn State University (George Pavlov) – and Harvard University (Patrick Slane).

Not only are these studies shedding new light on the properties of pulsar wind nebulae, they also provide observational evidence to help astronomers create better theoretical models of pulsars. In addition, studies like these – which examine the geometry of pulsar magnetospheres – could allow astronomers to better estimate the total number of exploded stars in our galaxy.

By knowing the range of angles at which pulsars are detectable, they should be able to better estimate the amount that are not visible from Earth. Yet another way in which astronomers are working to find the celestial objects that could be lurking in humanity’s blind spots!

Further Reading: Chandra X-Ray Observatory

The post Space Jellyfish Show Types Of Pulsar Wind Nebulas appeared first on Universe Today.

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Carl Sagan’s Theory Of Early Mars Warming Gets New Attention

Carl Sagan’s Theory Of Early Mars Warming Gets New Attention

Ah, the good old days. ESA’s Mars Express imaged Reull Vallis, a river-like structure believed to have formed when running water flowed in the distant Martian past, cuts a steep-sided channel on its way towards the floor of the Hellas basin. A thicker atmosphere that included methane and hydrogen in addition to carbon dioxide may have allowed liquid water to flow on Mars at different times in the past according to a new study. Credit and copyright: ESA/DLR/FU Berlin (G. Neukum)

Water. It’s always about the water when it comes to sizing up a planet’s potential to support life. Mars may possess some liquid water in the form of occasional salty flows down crater walls,  but most appears to be locked up in polar ice or hidden deep underground. Set a cup of the stuff out on a sunny Martian day today and depending on conditions, it could quickly freeze or simply bubble away to vapor in the planet’s ultra-thin atmosphere.

These rounded pebbles got their shapes after polished in a long-ago river in Gale Crater. They were discovered by Curiosity rover at the Hottah site. Credit: NASA/JPL-Caltech

Evidence of abundant liquid water in former flooded plains and sinuous river beds can be found nearly everywhere on Mars. NASA’s Curiosity rover has found mineral deposits that only form in liquid water and pebbles rounded by an ancient stream that once burbled across the floor of Gale Crater. And therein lies the paradox.  Water appears to have gushed willy-nilly across the Red Planet 3 to 4 billion years ago, so what’s up today?

Blame Mars’ wimpy atmosphere. Thicker, juicier air and the increase in atmospheric pressure that comes with it would keep the water in that cup stable. A thicker atmosphere would also seal in the heat, helping to keep the planet warm enough for liquid water to pool and flow.

Different ideas have been proposed to explain the putative thinning of the air including the loss of the planet’s magnetic field, which serves as a defense against the solar wind.

This figure shows a cross-section of the planet Mars revealing an inner, high density core buried deep within the interior. Magnetic field lines are drawn in blue, showing the global scale magnetic field associated with a dynamic core. Mars must have had such a field long ago, but today it’s not evident. Perhaps the energy source that powered the early dynamo shut down. Credit: NASA/JPL/GSFC

Convection currents within its molten nickel-iron core likely generated Mars’ original magnetic defenses. But sometime early in the planet’s history the currents stopped either because the core cooled or was disrupted by asteroid impacts. Without a churning core, the magnetic field withered, allowing the solar wind to strip away the atmosphere, molecule by molecule.

Solar wind eats away the Martian atmosphere

Measurements from NASA’s current MAVEN mission indicate that the solar wind strips away gas at a rate of about 100 grams (equivalent to roughly 1/4 pound) every second. “Like the theft of a few coins from a cash register every day, the loss becomes significant over time,” said Bruce Jakosky, MAVEN principal investigator.

This graph shows the percent amount of the five most abundant gases in the atmosphere of Mars, as measured by the  Sample Analysis at Mars (SAM) instrument suite on the Curiosity rover in October 2012. The season was early spring in Mars’ southern hemisphere. Credit: NASA/JPL-Caltech, SAM/GSFC

Researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) suggest a different, less cut-and-dried scenario. Based on their studies, early Mars may have been warmed now and again by a powerful greenhouse effect. In a paper published in Geophysical Research Letters, researchers found that interactions between methane, carbon dioxide and hydrogen in the early Martian atmosphere may have created warm periods when the planet could support liquid water on its surface.

The team first considered the effects of CO2, an obvious choice since it comprises 95% of Mars’ present day atmosphere and famously traps heat. But when you take into account that the Sun shone 30% fainter 4 billion years ago compared to today, CO2  alone couldn’t cut it.

“You can do climate calculations where you add CO2 and build up to hundreds of times the present day atmospheric pressure on Mars, and you still never get to temperatures that are even close to the melting point,” said Robin Wordsworth, assistant professor of environmental science and engineering at SEAS, and first author of the paper.

NASA’s Cassini spacecraft looks toward the night side of Saturn’s largest moon and sees sunlight scattering through the periphery of Titan’s atmosphere and forming a ring of color. The breakdown of methane at Titan into hydrogen and oxygen may also have occurred on Mars. The addition of hydrogen in the company of methane and carbon dioxide would have created a powerful greenhouse gas mixture, significantly warming the planet. Credit: NASA/JPL-Caltech/Space Science Institute

Carbon dioxide isn’t the only gas capable of preventing heat from escaping into space. Methane or CH4 will do the job, too. Billions of years ago, when the planet was more geologically active, volcanoes could have tapped into deep sources of methane and released bursts of the gas into the Martian atmosphere. Similar to what happens on Saturn’s moon Titan, solar ultraviolet light would snap the molecule in two, liberating hydrogen gas in the process.

When Wordsworth and his team looked at what happens when methane, hydrogen and carbon dioxide collide and then interact with sunlight, they discovered that the combination strongly absorbed heat.

Carl Sagan, American astronomer and astronomy popularizer, first speculated that hydrogen warming could have been important on early Mars back in 1977, but this is the first time scientists have been able to calculate its greenhouse effect accurately. It is also the first time that methane has been shown to be an effective greenhouse gas on early Mars.

This awesome image of the Tharsis region of Mars taken by Mars Express shows several prominent shield volcanoes including the massive Olympus Mons (at left). Volcanoes, when they were active, could have released significant amounts of methane into Mars’ atmosphere. Click for a larger version. Credit: ESA

When you take methane into consideration, Mars may have had episodes of warmth based on geological activity associated with earthquakes and volcanoes. There have been at least three volcanic epochs during the planet’s history — 3.5 billion years ago (evidenced by lunar mare-like plains), 3 billion years ago (smaller shield volcanoes) and 1 to 2 billion years ago, when giant shield volcanoes such as Olympus Mons were active. So we have at least three potential opportunities for water to exist as a liquid under a denser, warmer atmosphere.

The sheer size of Olympus Mons practically shouts massive eruptions over a long period of time. During the in-between times, hydrogen, a lightweight gas, would have continued to escape into space until replenished by geological upheaval.

“This research shows that the warming effects of both methane and hydrogen have been underestimated by a significant amount,” said Wordsworth. “We discovered that methane and hydrogen, and their interaction with carbon dioxide, were much better at warming early Mars than had previously been believed.”

I’m tickled that Carl Sagan walked this road 40 years ago. He always held out hope for life on Mars. Several months before he died in 1996, he recorded this:

” … maybe we’re on Mars because of the magnificent science that can be done there — the gates of the wonder world are opening in our time. Maybe we’re on Mars because we have to be, because there’s a deep nomadic impulse built into us by the evolutionary process, we come after all, from hunter gatherers, and for 99.9% of our tenure on Earth we’ve been wanderers. And, the next place to wander to, is Mars. But whatever the reason you’re on Mars is, I’m glad you’re there. And I wish I was with you.”

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A Farewell to Plutoshine

A Farewell to Plutoshine

Looking back at an overexposed Charon and Plutoshine. Credit: NASA/JPL/New Horizons

Sometimes, its not the eye candy aspect of the image, but what it represents. A recent image of Pluto’s large moon Charon courtesy of New Horizons depicting what could only be termed ‘Plutoshine’ caught our eye. Looking like something from the grainy era of the early Space Age, we see a crescent Charon, hanging against a starry background…

So what, you say? Sure, the historic July 14th , 2015 flyby of New Horizons past Pluto and friends delivered images with much more pop and aesthetic appeal. But look closely, and you’ll see something both alien and familiar, something that no human eye has ever witnessed, yet you can see next week.

We’re talking about the reflected ‘Plutoshine‘ on the dark limb of Charon. This over-exposed image was snapped from over 160,000 kilometers distant by New Horizons’ Ralph/Multispectral imager looking back at Charon, post flyby. For context, that’s just shy of half the distance between the Earth and the Moon. “Bigger than Texas” (Cue Armageddon), Charon is about 1200 kilometers in diameter and 1/8th the mass of Pluto. Together, both form the only true binary (dwarf) planetary pair in the solar system, with the 1/80th Earth-Moon pair coming in at a very distant second.

Earthshine on the Moon. Credit: Dave Dickinson

We see reflected sunlight coming off of a gibbous Pluto which is just out of frame, light that left the Sun 4 hours ago and took less than a second to make the final Pluto-Charon-New Horizons bounce. You can see a similar phenomenon next week, as Earthshine or Ashen Light illuminates the otherwise dark nighttime side of the Earth’s Moon, fresh off of passing New phase this weekend. Snow and cloud cover turned Moonward can have an effect on how bright Earthshine appears. One ongoing study based out of the Big Bear Solar observatory in California named Project Earthshine seeks to characterize long-term climate variations looking at this very phenomenon.

The view on the evening of January 28th looking west at dusk. Credit: Stellarium.

Standing on Pluto, you’d see a 3.5 degree wide Charon, 7 times larger than our own Full Moon. Of course, you’d need to be standing in the right hemisphere, as Pluto and Charon are tidally locked, and keep the same face turned towards each other. It would be a dim view, as the Sun shines at -20 magnitude at 30 AU distant, much brighter than a Full Moon, but still over 600 times fainter than sunny Earth. Dim Plutoshine on the nightside of Charon would, however, be easily visible to the naked eye.

A small 6 cm instrument, Ralph images in the visual to near-infrared range. Ralph compliments New Horizons larger LORRI instrument, which has a diameter and very similar optical configuration to an amateur 8-inch Schmidt-Cassegrain telescope.

Charon as seen from Pluto. Credit: Starry Night.

Don’t look for Pluto now; it just passed solar conjunction on the far side of the Sun on January 7th, 2017. Pluto reaches opposition and favorable viewing for 2017 on July 10th, one of the 101 Astronomical Events for 2017 that you’ll find in our free e-book, out from Universe Today.

And for an encore, New Horizons will visit the 45 kilometer in diameter Kuiper Belt Object 2014 MU69 on New Year’s Day 2019. From there, New Horizons will most likely chronicle the environs of the the distant solar system, as it joins Pioneer 10 and 11 and Voyagers 1 and 2 as human built artifacts cast adrift along the galactic plane.

A pretty pair: Pluto and Charon. Credit: NASA/JPL/New Horizons

And to think, it has taken New Horizons about 18 months for all of its flyby data to trickle back to the Earth. Enjoy, as it’ll be a long time before we visit Pluto and friends again.

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Rogue NASA, EPA, NPS Twitter Accounts Launched to Protest Trump Directives

Rogue NASA, EPA, NPS Twitter Accounts Launched to Protest Trump Directives

Twitter page of Rogue NASA. Credit: Twitter

Three federal agencies — the National Park Service, the EPA and now NASA — have allegedly launched unofficial “protest” accounts on Twitter in defiance of the Trump team’s directives to not blog, tweet or talk to the news media about climate changes issues. While it’s not unusual for a new administration to want to control the message, many bristle at what they see as an administration that wants to redefine and control scientific fact.

That brings us to these accounts. Are they really created by NASA and other government employees or are they the work of ticked off science advocates not connected to the agencies? In at least one case earlier this week in Badlands National Park, a former employee posted this unauthorized tweet:

“Today, the amount of carbon dioxide in the atmosphere is higher than at any time in the last 650,000 years.” The tweet was later removed.

The @RogueNASA Twitter account uses NASA’s logo — a no-no unless you have specific permission. The site describes itself as “the unofficial “Resistance” team of NASA. Not an official NASA account. Follow for science and climate news and facts. REAL NEWS, REAL FACTS.”

NASA’s very strict about how it’s logo is used. Under Media Usage Guidelines, here’s what the agency has to say:

“The NASA insignia logo (the blue “meatball” insignia), the retired NASA logotype (the red “worm” logo) and the NASA seal may not be used for any purpose without explicit permission. These images may not be used by persons who are not NASA employees or on products, publications or web pages that are not NASA-sponsored. These images may not be used to imply endorsement or support of any external organization, program, effort, or persons.”

AltEPA Twitter page. Credit: Twitter

Moreover, NASA reported that it had not given permission for another group or person to use its logo on the new account. While the sites may be legit and you and I sympathetic to the cause, exercise skepticism when poking around these accounts. Be cautious of opening up or downloading files the same way you’re careful with e-mail attachments. Take a look, participate, but be wary.

For your perusal, the current “alt science” sites I’m aware of are listed below. My hunch after looking at them is that it’s possible they may have been created by the same group of people. Whatever their origin, they’re quickly becoming very popular. As of Wednesday evening (Jan. 25), Rogue NASA has 209,000 followers; AltEPA 41,600 and 883,000 at AltUSNatParkService.

* AltUSNatParkService
* AltEPA
* Rogue NASA
* AltNASA

For more on the new administration and NASA, check out Nancy Atkinson’s story “Could NASA Be Muzzled Under Trump Administration?”

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