Saturday, May 14, 2016

Science Met Myth - Is Alien depleting the sun? Or is Comet Tsunami on i...





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WTF? 2016 crop circles planet X Nibiru aliens ufo ALL EXPLAINED





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Newest Crop Circles 2016





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Thursday, May 12, 2016

What is the Biggest Star in the Universe?

What is the Biggest Star in the Universe?:

This article was originally published in 2008, but has been updated several times now to keep track with our advancing knowledge of the cosmos!

My six-year old daughter is a question-asking machine. We were driving home from school a couple of days ago, and she was grilling me about the nature of the Universe. One of her zingers was, “What’s the Biggest Star in the Universe”? I had an easy answer. “The Universe is a big place,” I said, “and there’s no way we can possibly know what the biggest star is”. But that’s not a real answer.

So she refined the question. “What’s the biggest star that we know of?” Of course, I was stuck in the car, and without access to the Internet. But once I got back home, and was able to do some research, I learned the answer and thought I’d share it with the rest of you But to answer it fully, some basic background information needs to be covered first. Ready?



Solar Radius and Mass:

When talking about the size of stars, it’s important to first take a look at our own Sun for a sense of scale. Our familiar star is a mighty 1.4 million km across (870,000 miles). That’s such a huge number that it’s hard to get a sense of scale. Speaking of which, the Sun also accounts for 99.9% of all the matter in our Solar System. In fact, you could fit one million planet Earths inside the Sun.

Using these values, astronomers have created the terms “solar radius” and “solar mass”, which they use to compare stars of greater or smaller size and mass to our own. A solar radius is 690,000 km (432,000 miles) and 1 solar mass is 2 x 1030 kilograms (4.3 x 1030 pounds). That’s 2 nonillion kilograms, or 2,000,000,000,000,000,000,000,000,000,000 kg.

Artist's depiction of the Morgan-Keenan spectral diagram, showing the difference between main sequence stars. Credit: Wikipedia Commons
Artist’s depiction of the Morgan-Keenan spectral diagram, showing the difference between main sequence stars. Credit: Wikipedia Commons
Another thing worth considering is the fact that our Sun is pretty small, as stars go. As a G-type main-sequence star (specifically, a G2V star), which is commonly known as a yellow dwarf, its on the smaller end of the size chart (see above). While it is certainly larger than the most common type of star – M-type, or Red Dwarfs – it is itself dwarfed (no pun!) by the likes of blue giants and other spectral classes.

Classification:

To break it all down, stars are grouped based on their essential characteristics, which can be their spectral class (i.e. color), temperature, size, and brightness. The most common method of classification is known as the Morgan–Keenan (MK) system, which classifies stars based on temperature using the letters O, B, A, F, G, K, and M, – O being the hottest and M the coolest. Each letter class is then subdivided using a numeric digit with 0 being hottest and 9 being coolest (e.g. O1 to M9 are the hottest to coldest stars).

In the MK system, a luminosity class is added using Roman numerals. These are based on the width of certain absorption lines in the star’s spectrum (which vary with the density of the atmosphere), thus distinguishing giant stars from dwarfs. Luminosity classes 0 and I apply to hyper- or supergiants; classes II, III and IV apply to bright, regular giants, and subgiants, respectively; class V is for main-sequence stars; and class VI and VII apply to subdwarfs and dwarf stars.

The Hertzspirg-Russel diagram, showing the relation between star's color, AM. luminosity, and temperature. Credit: astronomy.starrynight.com
The Hertzspirg-Russel diagram, showing the relation between star’s color, AM. luminosity, and temperature. Credit: astronomy.starrynight.com
There is also the Hertzsprung-Russell diagram, which relates stellar classification to absolute magnitude (i.e. intrinsic brightness), luminosity, and surface temperature. The same classification for spectral types are used, ranging from blue and white at one end to red at the other, which is then combined with the stars Absolute Visual Magnitude (expressed as Mv) to place them on a 2-dimensional chart (see above).

On average, stars in the O-range are hotter than other classes, reaching effective temperatures of up to 30,000 K. At the same time, they are also larger and more massive, reaching sizes of over 6 and a half solar radii and up to 16 solar masses. At the lower end, K and M type stars (orange and red dwarfs) tend to be cooler (ranging from 2400 to 5700 K), measuring 0.7 to 0.96 times that of our Sun, and being anywhere from 0.08 to 0.8 as massive.

Based on the full of classification of our Sun (G2V), we can therefore say that it a main-sequence star with a temperature around 5,800K. Now consider another famous star system in our galaxy – Eta Carinae, a system containing at least two stars located around 7500 light-years away in the direction of the constellation Carina. The primary of this system is estimated to be 250 times the size of our Sun, a minimum of 120 solar masses, and a million times as bright – making it one of the biggest and brightest stars ever observed.

Eta Carinae, one of the most massive stars known. Image credit: NASA
Eta Carinae, one of the most massive stars known, located in the Carina constellation. Credit: NASA
There is some controversy over this world’s size though. Most stars blow with a solar wind, losing mass over time. But Eta Carinae is so large that it casts off 500 times the mass of the Earth every year. With so much mass lost, it’s very difficult for astronomers to accurately measure where the star ends, and its stellar wind begins. Also, it is believed that Eta Carinae will explode in the not-too-distant future, and it will be the most spectacular supernovae humans have ever seen.

In terms of sheer mass, the top spot goes to R136a1, a star located in the Large Magellanic Cloud, some 163,000 light-years away. It is believed that this star may contain as much as 315 times the mass of the Sun, which presents a conundrum to astronomers since it was believed that the largest stars could only contain 150 solar masses. The answer to this is that R136a1 was probably formed when several massive stars merged together. Needless to say, R136a1 is set to detonate as a hypernova, any day now.

In terms of large stars, Betelgeuse serves as a good (and popular) example. Located in the shoulder of Orion, this familiar red supergiant has a radius of 950-1200 times the size of the Sun, and would engulf the orbit of Jupiter if placed in our Solar System. In fact, whenever we want to put our Sun’s size into perspective, we often use Betelgeuse to do it (see below)!



Yet, even after we use this hulking Red Giant to put us in our place, we are still just scratching the surface in the game of “who’s the biggest star”. Consider WOH G64, a red supergiant star located in the Large Magellanic Cloud, approximately 168,000 light years from Earth. At 1.540 solar radii in diameter, this star is currently one of the largest in the known universe.

But there’s also RW Cephei, an orange hypergiant star in the constellation Cepheus, located 3,500 light years from Earth and measuring 1,535 solar radii in diameter. Westerlund 1-26 is also pretty huge, a red supergiant (or hypergiant) located within the Westerlund 1 super star cluster 11,500 light-years away that measures 1,530 solar radii in diameter. Meanwhile, V354 Cephei and VX Sagittarii are tied when it comes to size, with both measuring an estimated 1,520 solar radii in diameter.

The Largest Star:

As it stands, the title of the largest star in the Universe (that we know of) comes down to two contenders. For example, UY Scuti is currently at the top of the list. Located 9.500 light years away in the constellation Scutum, this bright red supergiant and pulsating variable star has an estimated average median radius of 1,708 solar radii – or 2.4 billion km (1.5 billion mi; 15.9 AU), thus giving it a volume 5 billion times that of the Sun.

However, this average estimate includes a margin of error of ± 192 solar radii, which means that it could be as large as 1900 solar radii or as small as 1516. This lower estimate places it beneath stars like as V354 Cephei VX Sagittarii. Meanwhile, the second star on the list of the largest possible stars is NML Cygni, a semiregular variable red hypergiant located in the Cygnus constellation some 5,300 light-years from Earth.

A zoomed-in picture of the red giant star UY Scuti. Credit: Rutherford Observatory/Haktarfone
A zoomed-in picture of the red giant star UY Scuti. Credit: Rutherford Observatory/Haktarfone
Due to the location of this star within a circumstellar nebula, it is heavily obscured by dust extinction. As a result, astronomers estimate that its size could be anywhere from 1,642 to 2,775 solar radii, which means it could either be the largest star in the known Universe (with a margin of 1000 solar radii) or indeed the second largest, ranking not far behind UY Scuti.

And up until a few years ago, the title of biggest star went to VY Canis Majoris; a red hypergiant star in the Canis Major constellation, located about 5,000 light-years from Earth. Back in 2006, professor Roberta Humphrey of the University of Minnesota calculated its upper size and estimated that it could be more than 1,540 times the size of the Sun. Its average estimated mass, however, is 1420, placing it in the no. 8 spot behind V354 Cephei and VX Sagittarii.

These are the biggest star that we know of, but the Milky way probably has dozens of stars that are even larger, obscured by gas and dust so we can’t see them. But even if we cannot find these stars, it is possible to theorize about their likely size and mass. So just how big can stars get? Once again, Professor Roberta Humphreys of the University of Minnesota provided the answer.

VY Canis Majoris. The biggest known star.
Size comparison between the Sun and VY Canis Majoris, which once held the title of the largest known star in the Universe. Credit: Wikipedia Commons/Oona Räisänen
As she explained when contacted, the largest stars in the Universe are the coolest. So even though Eta Carinae is the most luminous star we know of, it’s extremely hot – 25,000 Kelvin – and therefore only 250 solar radii big. The largest stars, in contrast, will be cool supergiants. Case in point, VY Canis Majoris is only 3,500 Kelvin, and a really big star would be even cooler.

At 3,000 Kelvin, Humphreys estimates that cool supergiant would be as big as 2,600 times the size of the Sun. This is below the upper estimates for NML Cygni, but above the average estimates for both it and UY Scutii. Hence, this is the upper limit of a star (at least theoretically and based on all the information we have to date).

But as we continue to peer into the Universe with all of our instruments, and explore it up close through robotic spacecraft and crewed missions, we are sure to find new and exciting things that will confound us further!

And be sure to check out this great animation that shows the size of various objects in space, starting with our Solar System’s tiny planets and finally getting to UY Scuti. Enjoy!



We have written many articles about stars for Universe Today. Here’s The Sun, What’s the Brightest Star in the Sky Past and Future?, and What Is The Smallest Star?

Want to learn more about the birth and death of stars? We did a two part podcast at Astronomy Cast. Here’s part 1, Where Stars Come From, and here’s part 2, How Stars Die.

The post What is the Biggest Star in the Universe? appeared first on Universe Today.

Posted by Nelio Inacio at 5:52 PM 0 comments

Development of High-Power Solar Electric Propulsion

Development of High-Power Solar Electric Propulsion: A prototype 13-kilowatt Hall thruster is tested at NASA's Glenn Research Center in Cleveland. This prototype demonstrated the technology readiness needed for industry to continue the development of high-power solar electric propulsion into a flight-qualified system.


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Light Echoes Used to Study Protoplanetary Disks

Light Echoes Used to Study Protoplanetary Disks: This illustration shows a star surrounded by a protoplanetary disk. A new study uses data from NASA's Spitzer Space Telescope and four ground-based telescopes to determine the distance from a star to the inner rim of its surrounding protoplanetary disk. Researchers used a method called "photo-reverberation," also known as "light echoes.


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Posted by Nelio Inacio at 5:49 PM 0 comments

Hubble Spies the Barred Spiral Galaxy NGC 4394

Hubble Spies the Barred Spiral Galaxy NGC 4394: Shown in this Hubble Space Telescope image, NGC 4394 is the archetypal barred spiral galaxy, with bright spiral arms emerging from the ends of a bar that cuts through the galaxy’s central bulge. These arms are peppered with young blue stars, dark filaments of cosmic dust, and bright, fuzzy regions of active star formation.


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Posted by Nelio Inacio at 5:47 PM 0 comments

Mercury Solar Transit

Mercury Solar Transit: The planet Mercury is seen in silhouette, lower third of image, as it transits across the face of the sun Monday, May 9, 2016, as viewed from Boyertown, Pennsylvania. Mercury passes between Earth and the sun only about 13 times a century, with the previous transit taking place in 2006.


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Will Earth Survive When the Sun Becomes a Red Giant?

Will Earth Survive When the Sun Becomes a Red Giant?:



Earth scorched by red giant Sun


Since the beginning of human history, people have understood that the Sun is a central part of life as we know it. It's importance to countless mythological and cosmological systems across the globe is a testament to this. But as our understand of it matured, we came to learn that the Sun was here long before us, and will be here long after we're gone. Having formed roughly 4.6 bullion years ago, our Sun began its life roughly 40 million years before our Earth had formed.



Since then, the Sun has been in what is known as its Main Sequence, where nuclear fusion in its core causes it to emit energy and light, keeping us here on Earth nourished. This will last for another 4.5 – 5.5 billion years, at which point it will deplete its supply of hydrogen and helium and go through some serious changes. Assuming humanity is still alive and calls Earth home at this time, we may want to consider getting out the way!



The Birth of Our Sun:

The predominant theory on how our Sun and Solar System formed is known as Nebular Theory, which states that the Sun and all the planets began billions of years ago as a giant cloud of molecular gas and dust. Then, approximately 4.57 billion years ago, this cloud experienced gravitational collapse at its center, where anything from a passing star to a shock wave caused by a supernova triggered the process that led to our Sun's birth.



Basically, this took place after pockets of dust and gas began to collect into denser regions. As these regions pulled in more and more matter, conservation of momentum caused them to begin rotating, while increasing pressure caused them to heat up. Most of the material ended up in a ball at the center while the rest of the matter was flattened out into a large disk that circled around it.







The ball at the center would eventually form the Sun, while the disk of material would form the planets. The Sun then spent the next 100,000 years as a collapsing protostar before temperature and pressures in the interior ignited fusion at its core. The Sun started as a T Tauri star – a wildly active star that blasted out an intense solar wind. And just a few million years later, it settled down into its current form.



Main Sequence:

For the past 4.57 billion years (give or take a day or two), the Sun has been in the Main Sequence of its life. This is characterized by the process where hydrogen fuel, under tremendous pressure and temperatures in its core, is converted into helium. In addition to changing the properties of its constituent matter, this process also produces a tremendous amount of energy. All told, every second, 600 million tons of matter are converted into neutrinos, solar radiation, and roughly 4 x 1027 Watts of energy.



Naturally, this process cannot last forever since it is dependent on the presence of matter which is being regularly consumed. As time goes on and more hydrogen is converted into helium, the core will continue to shrink, allowing the outer layers of the Sun to move closer to the center and experience a stronger gravitational force.



This will place more pressure on the core, which is resisted by a resulting increase in the rate at which fusion occurs. Basically, this means that as the Sun continues to expend hydrogen in its core, the fusion process speeds up and the output of the Sun increases. At present, this is leading to a 1% increase in luminosity every 100 million years, and a 30% increase over the course of the last 4.5 billion years.







Approximately 1.1 billion years from now, the Sun will be 10% brighter than it is today. This increase in luminosity will also mean an increase in heat energy, one which the Earth’s atmosphere will absorb. This will trigger a runaway greenhouse effect that is similar to what turned Venus into the terrible hothouse it is today.



In 3.5 billion years, the Sun will be 40% brighter than it is right now, which will cause the oceans to boil, the ice caps to permanently melt, and all water vapor in the atmosphere to be lost to space. Under these conditions, life as we know it will be unable to survive anywhere on the surface, and planet Earth will be fully transformed into another hot, dry world, just like Venus.



Red Giant Phase:

In 5.4 billion years from now, the Sun will enter what is known as the Red Giant phase of its evolution. This will begin once all hydrogen is exhausted in the core and the inert helium ash that has built up there becomes unstable and collapses under its own weight. This will cause the core to heat up and get denser, causing the Sun to grow in size.



It is calculated that the expanding Sun will grow large enough to encompass the orbit’s of Mercury, Venus, and maybe even Earth. Even if the Earth were to survive being consumed, its new proximity to the the intense heat of this red sun would scorch our planet and make it completely impossible for life to survive. However, astronomers have noted that as the Sun expands, the orbit of the planet's is likely to change as well.



https://youtu.be/nDm0hNWUQjU



When the Sun reaches this late stage in its stellar evolution, it will lose a tremendous amount of mass through powerful stellar winds. Basically, as it grows, it loses mass, causing the planets to spiral outwards. So the question is, will the expanding Sun overtake the planets spiraling outwards, or will Earth (and maybe even Venus) escape its grasp?



K.-P Schroder and Robert Cannon Smith are two researchers who have addressed this very question. In a research paper entitled "Distant Future of the Sun and Earth Revisted" which appeared in the Monthly Notices of the Royal Astronomical Society, they ran the calculations with the most current models of stellar evolution.



According to Schroder and Smith, when the Sun becomes a red giant star in 7.59 billion years, it will start to lose mass quickly. By the time it reaches its largest radius, 256 times its current size, it will be down to only 67% of its current mass. When the Sun does begin to expand, it will do so quickly, sweeping through the inner Solar System in just 5 million years.



It will then enter its relatively brief (130 million year) helium-burning phase, at which point, it will expand past the orbit of Mercury, and then Venus. By the time it approaches the Earth, it will be losing 4.9 x 1020 tonnes of mass every year (8% the mass of the Earth).



But Will Earth Survive?:

Now this is where things become a bit of a "good news/bad news" situation. The bad news, according to Schroder and Smith, is that the Earth will NOT survive the Sun's expansion. Even though the Earth could expand to an orbit 50% more distant than where it is today (1.5 AUs), it won't get the chance. The expanding Sun will engulf the Earth just before it reaches the tip of the red giant phase, and the Sun would still have another 0.25 AU and 500,000 years to grow.







Once inside the Sun's atmosphere, the Earth will collide with particles of gas. Its orbit will decay, and it will spiral inward. If the Earth were just a little further from the Sun right now, at 1.15 AU, it would be able to survive the expansion phase. If we could push our planet out to this distance, we'd also be in business. However, such talk is entirely speculative and in the realm of science fiction at the moment.



And now for the good news. Long before our Sun enters it's Red Giant phase, its habitable zone (as we know it) will be gone. Astronomers estimate that this zone will expand past the Earth's orbit in about a billion years. The heating Sun will evaporate the Earth's oceans away, and then solar radiation will blast away the hydrogen from the water. The Earth will never have oceans again, and it will eventually become molten.



Yeah, that's the good news... sort of. But the upside to this is that we can say with confidence that humanity will be compelled to leave the nest long before it is engulfed by the Sun. And given the fact that we are dealing with timelines that are far beyond anything we can truly deal with, we can't even be sure that some other cataclysmic event won't claim us sooner, or that we wont have moved far past our current evolutionary phase.



An interesting side benefit will be how the changing boundaries of our Sun's habitable zone will change the Solar System as well. While Earth, at a mere 1.5 AUs, will no longer be within the Sun's habitable zone, much of the outer Solar System will be. This new habitable zone will stretch from 49.4 AU to 71.4 AU - well into the Kuiper Belt - which means the formerly icy worlds will melt, and liquid water will be present beyond the orbit of Pluto.



https://youtu.be/hZJnMv5Ae8g



Perhaps Eris will be our new homeworld, the dwarf planet of Pluto will be the new Venus, and Haumeau, Makemake, and the rest will be the outer "Solar System". But what is perhaps most fascinating about all of this is how humans are even tempted to ask "will it still be here in the future" in the first place, especially when that future is billions of years from now.



Somehow, the subjects of what came before us, and what will be here when we're gone, continue to fascinate us. And when dealing with things like our Sun, the Earth, and the known Universe, it becomes downright necessary. Our existence thus far has been a flash in the pan compared to the cosmos, and how long we will endure remains an open question.



We have written many interesting articles on the Sun here at Universe Today. Here's What Color Is The Sun?, What Kind of Star is the Sun?, How Does The Sun Produce Energy?, and Could We Terraform the Sun?



Astronomy Cast also has some interesting episodes on the subject. Check them out- Episode 30: The Sun, Spots and All,  Episode 108: The Life of the Sun, Episode 238: Solar Activity.



For more information, check out NASA's Solar System Guide.

The post Will Earth Survive When the Sun Becomes a Red Giant? appeared first on Universe Today.

Posted by Nelio Inacio at 1:44 PM 0 comments

Can We Really Get to Alpha Centauri?

Can We Really Get to Alpha Centauri?:

In a previous episode, I said that traveling within the Solar System is hard enough, traveling to another star system in our lifetime is downright impossible. Many of you said it was the most depressing episode I’ve ever done .

The distance to Pluto is, on average, about 40 astronomical units. That’s 40 times the distance from the Sun to the Earth. And New Horizons, the fastest spacecraft traveling in the Solar System took about 10 years to make the journey.

The distance to Alpha Centauri is about 277,000 astronomical units away (or 4.4 light-years). That’s about 7,000 times further than Pluto. New Horizons could make the journey, if you were willing to wait about 70,000 years. That’s about twice as long as you’d be willing to wait for Half Life 3.

But my video clearly made an impact on a plucky team of rocket scientists, entrepreneurs and physicists, who have no room in their personal dictionary for the word “impossible”. Challenge accepted, they said to themselves.

In early April, 2016, just 8 months after I said it was probably never going to happen, the billionaire Yuri Milner and famed physicist Stephen Hawking announced a strategy to send a spacecraft to another star within our lifetime. In your face Fraser, they said… in your face.

Project Starshot, an initiative sponsored by the Breakthrough Foundation, is intended to be humanity's first interstellar voyage. Credit: breakthroughinitiatives.org
Project Starshot, an initiative sponsored by the Breakthrough Foundation, is intended to be humanity’s first interstellar voyage. Credit: breakthroughinitiatives.org
The project will be called Breakthrough Starshot, and it’s led by Pete Worden, the former director of NASA’s AMES Research Center – the people working on a warp drive.

The team announced that they’re spending $100 million to investigate the technology it’ll take to send a spacecraft to Alpha Centauri, making the trip in just 20 years. And by doing so, they might just revolutionize the way spacecraft travel around our own Solar System.

So, what’s the plan? According to their announcement, the team is planning to create teeny tiny lightsail spacecraft, and accelerate them to 20% the speed of light using lasers. Yes, everything’s made better with lasers .

We’ve talked about solar sails in the past, but the gist is that photons of light can impart momentum when they bounce off something. It’s not very much, but if you add a tremendous amount of photons, the impact can be significant. And because those photons are going the speed of light, the maximum speed for the spacecraft, in theory, is just shy of the speed of light (thanks relativity).

You can get those photons from the Sun, but you can also get them from a directed laser beam, designed to fill the sails with photons, without actually melting the spacecraft.

In the past, engineers have talked about solar sails that might be thousands of kilometers across, made of gossamer sheets of reflective fabric. Got that massive, complicated sail in your mind?

Now think smaller. The Starshot spacecraft will measure just a few meters across, with a thickness of just a few atoms. The sail would then pull a microscopic payload of instruments. A tiny chip, capable of gathering data and transmitting information – these are called Starchips. Not even enough room for water bear crew quarters.

A phased laser array, perhaps in the high desert of Chile, propels sails on their journey. Credit: Breakthrough Initiatives.
A phased laser array, perhaps in the high desert of Chile, propels sails on their journey. Credit: Breakthrough Initiatives.
With such a low mass, a powerful laser should be able to accelerate them to 20% the speed of light, almost instantly, making a trip to Alpha Centauri only take about 20 years.

Since each Starshot might only cost a few dollars to make, the company could manufacture thousands and thousands, place them into orbit, and then start bugzapping them off to different stars.

There are, of course, some massive engineering hurdles to overcome.

The first is the density of the interstellar medium. Although it’s almost completely empty in between the stars, there are the occasional dust particles. Normally harmless, the Starshots would be smashing into them at 20% the speed of light, which would be catastrophic.

The second problem is that this is a one-way trip. Once it’s going 20% the speed of light, there’s no way to slow the spacecraft down again (unless the Alpha Centaurans have a braking system in place). Just imagine the motion blur and targeting problems when you’re trying to take photos at relativistic speeds.

The third problem, and this is a big one, is that the miniaturization of the spacecraft means that you can’t have a big transmitter. Communicating across the light years takes a LOT of power. Maybe they’ll connect up into some kind of array and share the power requirement, or use lasers to communicate back. Maybe they’ll relay the data back like a Voltron daisy chain.

Even though the idea of traveling to another star might seem overly ambitious today, this technology actually makes a lot of sense for exploration in our own Solar System. We could bugzap little spacecraft to Venus, Mars, the outer planets and their moons – even deep into the Kuiper Belt and the totally unexplored Oort cloud. We could have this whole Solar System on exploration lockdown in just a few decades.

Even if a mission to Alpha Centauri is currently science fiction, this miniaturization is going to be the way we learn more about the Solar System we live in. Let’s get going!

The post Can We Really Get to Alpha Centauri? appeared first on Universe Today.

Posted by Nelio Inacio at 1:44 PM 0 comments

Watch Mercury Transit the Sun in Multiple Wavelengths

Watch Mercury Transit the Sun in Multiple Wavelengths:



A composite image of the May 9, 2016 transit of Mercury across the face of the Sun, as seen by the Solar Dynamics Observatory. Credit: NASA's Goddard Space Flight Center/SDO/Genna Duberstein


On May 9, 2016, Mercury passed directly between the Sun and Earth. No one had a better view of the event than the space-based Solar Dynamics Observatory, as it had a completely unobstructed view of the entire seven-and-a-half-hour event! This composite image, above, of Mercury’s journey across the Sun was created with visible-light images from the Helioseismic and Magnetic Imager on SDO, and below is a wonderful video of the transit, as it includes views in several different wavelenths (and also some great soaring music sure to stir your soul).











Mercury transits of the Sun happen about 13 times each century, however the next one will occur in only about three and a half years, on November 11, 2019. But then it's a long dry spell, as the following one won't occur until November 13, 2032.



Make sure you check out the great gallery of Mercury transit images from around the world compiled by our David Dickinson.

The post Watch Mercury Transit the Sun in Multiple Wavelengths appeared first on Universe Today.

Posted by Nelio Inacio at 1:43 PM 0 comments

What Are The Colors of the Planets?

What Are The Colors of the Planets?:



Planets and other objects in our Solar System. Credit: NASA.


When we look at beautiful images of the planets of our Solar System, it is important to note that we are looking at is not always accurate. Especially where their appearances are concerned, these representations can sometimes be altered or enhanced. This is a common practice, where filters or color enhancement is employed in order to make sure that the planets and their features are clear and discernible.



So what exactly do the planets of the Solar System look like when we take all the added tricks away? If we were to take pictures of them from space, minus the color enhancement, image touch-ups, and other methods designed to bring out their details, what would their true colors and appearances be? We already know that Earth resembles something of a blue marble, but what about the other ones?







To put it simply, the color of every planet in our Solar System is heavily dependent upon their composition. If it is a terrestrial planet - i.e. one composed of minerals and silicate rocks - then its appearance will likely be grey or take on the appearance of oxidized minerals. At the same time, the planet's atmospheres play a large role - i.e. how they reflect and absorb sunlight will determines which colors they present to an external observer.



The presence of an atmosphere can also determine whether or not there is vegetation, or warm, flowing water on the planet's surface. If, however, we are talking about gas or ice giants, then the planet's color will depend on what gases make it up, their absorption of light, and which ones are closer to the surface. All of this comes into play when observing the planets of our Solar System.







Mercury:

Mercury is difficult planet to get good images of, and for obvious reasons. Given its proximity to the Sun, it is virtually impossible to take clear  pictures using ground-based instruments here on the Earth. As a result, the only decent photographs we have of this planet have been taken by spacecraft, specifically missions like Mariner 10, and the more recent MESSENGER probe.



The surface of Mercury is very similar in appearance to our Moon, in that it is grey, pockmarked, and covered in craters that have been caused by impacting space rocks. As a terrestrial planet, Mercury is also composed of mostly iron, nickel and silicate rock, which is differentiated between a metallic core and a rocky mantle and crust.

Mercury also possesses an extremely thin atmosphere that is made up of hydrogen, helium, oxygen, sodium, calcium, potassium and other elements. This atmosphere is so tenuous that astronomers refer to it as an exosphere, one which neither absorbs nor reflects light. So when we look at Mercury, regardless of whether it is from the surface or space, we get a clear view of its surface. And what we have seen is a dark gray, rocky planet.







Venus:

The color of Venus, on the other hand, depends very much on the position of the observer. While Venus is also a terrestrial planet, it has an extremely dense atmosphere of carbon dioxide, nitrogen and sulfur dioxide. This means that from orbit, one sees little more than dense clouds of sulfuric acid and not its surface features. This lends the planet a yellowish appearance when seen from space, due to the cloud's absorption of blue light.



This image of Venus comes to us thanks to the many flyby missions that have taken place over the years. These include NASA's Vega 1 and 2 missions during the 1980s, followed by the Galileo (1990), Magellan (1994), and the NASA/ESA Cassini–Huygens mission in the 1990s. Since that time, the MESSENGER probe flew by Venus in 2006 on its way to Mercury, while the ESA's Venus Express entered orbit around Venus in April of 2006.

The view from the ground, however, is a different story. As a terrestrial planet with no vegetation or natural bodies of water, Venus' surface looks very rugged and rocky. The first images of the surface of Venus were provided by the Soviet-era Venera probes, but the true color was difficult to discern since Venus' atmosphere filters out blue light.



However, the surface composition (which is known to be rich in igneous basalt) would likely result in a greyish appearance. In this respect, Venus' surface looks much like Mercury's and Earth's Moon.







Earth:

The color of Earth is one we are intimately familiar with, thanks to decades of aerial, orbital, and space-based photography. As a terrestrial planet with a thick nitrogen-oxygen atmosphere, Earth's appearance comes down to the light-scattering effect of our planet's atmosphere and our oceans, which causes blue light to scatter more than other colors because of the shortness of its wavelength. The presence of water absorbs light from the red end of the spectrum, similarly presenting a blue appearance to space.



This leads to our planet having its "Blue Marble" appearance, along white clouds covering much of the skies. The surface features, depending on what one is looking at, can range from green (where sufficient vegetation and forests are to be found), to yellow and brown (in the case of deserts and mountainous regions, to white again (where clouds and large ice formations are concerned).

Mars:

Mars is known as the Red Planet for a reason. Thanks to its thin atmosphere and close proximity to Earth, human beings have been getting a clear view of it for over a century. And in the past few decades, thanks to the development of space travel and exploration, our knowledge of the planet has grown by leaps and bounds. From this, we have learned that Mars is similar to Earth in many ways, which includes similarities in composition and the existence of weather patterns.







Essentially, the majority of Mars is reddish-brown, owing to the presence of iron oxide on its surface. This color is also quite clear thanks to the rather thin nature of the atmosphere. Nevertheless, the occasional cloud can also be seen from orbit. The planet also has its share of white patches around the poles, due to the presence of polar ice caps.



Jupiter:

Jupiter is famous for its banded appearance, consisting of orange and brown intermixed with bands of white. This is due to its composition and the weather patterns that are common to the planet. As a gas giant, the outer layer of Jupiter is made up of swirling clouds of hydrogen, helium and other trace elements that move at speeds of up to 100 m/s (360 km/h).



At the same time, the color patterns of orange and white are due to the upwelling of compounds that change color when they are exposed to ultraviolet light from the Sun. These colorful compounds - known as chromophores, and which are likely made up of sulfur, phosphorus, or hydrocarbons - are formed when rising convection cells form crystallizing ammonia that masks out these lower clouds from view.







The most detailed image taken of Jupiter was constructed from images taken by the narrow angle camera on-board NASA's Cassini-Huygens spacecraft, which allowed for a "true-color" mosaic to be created. These images were taken on December 29th, 2000, during its closest approach to the giant planet at a distance of approximately 10 million kilometers (6.2 million miles).



Saturn:

Much like Jupiter, Saturn has a banded appearance that is due to the peculiar nature of its composition. However, due to Saturn's lower density, its bands are much fainter and are much wider near the equator. Like Jupiter, the planet is predominantly composed of hydrogen and helium gas with trace amounts of volatiles (such as ammonia) which surround a rocky core.



The presence of hydrogen gas results in clouds of deep red. However, these are obscured by clouds of ammonia, which are closer to the outer edge of the atmosphere and cover the entire planet. The exposure of this ammonia to the Sun's ultraviolet radiation causes it to appear white. Combined with its deeper red clouds, this results in the planet having a pale gold color.







Saturn's finer cloud patterns were not observed until the flybys of the Voyager 1 and 2 spacecraft during the 1980s. Since then, Earth-based telescopy has improved to the point where regular observations can be made. The greatest images to date were taken by the ESA's Cassini-Huygens spacecraft as it conducted multiple flybys of Saturn between 2004 and 2013.



Uranus:

As a gas/ice giant, Uranus is composed largely of molecular hydrogen and helium, along with ammonia, water, hydrogen sulfide and trace amounts of hydrocarbons. The presence of methane is what gives Uranus its aquamarine or cyan coloring, which is due to its prominent absorption bands in the visible and near-infrared spectrum.



To date, the only detailed photos we have of Uranus were provided by the Voyager 2 interplanetary probe, which conducted a flyby of the system in 1986. It's closest approach occurred on January 24th, 1986, when the probe came within 81,500 kilometers of the cloud tops, before continuing its journey to Neptune.







Neptune:

Neptune is similar in appearance to Uranus, which is due to its similar composition. Composed mainly of hydrogen and helium gas, this gas/ice giant also has traces of hydrocarbons, possibly nitrogen, and "ices" such as water, ammonia, and methane. However, Neptune's higher proportion of methane and ammonia, along with its greater distance from the Sun (which results in less illumination) is what leads to Neptune's darker blue color.



Compared to Uranus' relatively featureless appearance, Neptune's atmosphere has active and visible weather patterns. The most famous of these are the Great Dark Spot, an anticyclonic storm that is similar in appearance to Jupiter's Great Red Spot. Like the other dark spots on Neptune, this area is a darker shade of blue compared to its surroundings.



Like Uranus, Neptune has only been photographed up-close on one occasion. Again, this was by the Voyager 2 spacecraft, which made its closest approach to the planet on August 25th, 1989. Although the photographs it took were color-enhanced, they managed to capture Neptune's deeper blueish color.







As our exploration of the Solar System continues, our understanding of it continues to grow. In time, this knowledge will advance further as we begin to mounted crewed missions to planets like Mars, and additional robotic missions to the outer Solar System.



We have written many interesting articles about the Solar System's planets here at Universe Today. Here's our Solar System Guide, Order Of The Planets from the Sun, What Is The Atmosphere Like On Other Planets?, and Some Of The Best Pictures of the Planets In Our Solar System.



If you are interested in the colors of planets, you may also want to check out the color of plants on other worlds and the planets' true colors.



Astronomy Cast has episodes on all of the planets, starting with Episode 49: Mercury.

The post What Are The Colors of the Planets? appeared first on Universe Today.

Posted by Nelio Inacio at 1:42 PM 0 comments

Thanks, Comet Pluto. Solar System Nomenclature Needs A Major Rethink

Thanks, Comet Pluto. Solar System Nomenclature Needs A Major Rethink:



Four images from New Horizons’ Long Range Reconnaissance Imager (LORRI) were combined with color data from the Ralph instrument to create this global view of Pluto. Credits: NASA/JHUAPL/SwRI


Pluto can't seem to catch a break lately. After being reclassified in 2006 by the International Astronomical Union, it seemed that what had been the 9th planet of the Solar System was now relegated to the status of "dwarf planet" with the likes of Ceres, Eris, Haumea, and Makemake. Then came the recent announcements that the title of "Planet 9" may belong to an object ten times the mass of Earth located 700 AU from our Sun.



And now, new research has been produced that indicates that Pluto may need to be reclassified again. Using data provided by the New Horizons mission, researchers have shown that Pluto's interaction with the Sun's solar wind is unlike anything observed in the Solar System thus far. As a result, it would seem that the debate over how to classify Pluto, and indeed all astronomical bodies, is not yet over.







In a study that appeared in the Journal of Geophysical Research, a team of researchers from the Southwest Research Institute - with support from the Johns Hopkins University Applied Physics Laboratory, the Laboratory of Atmospheric and Space Physics at University of Colorado and other institutions - examined data obtained by the New Horizon mission's Solar Wind Around Pluto (SWAP) instrument.







Basically, solar wind effects every body in the Solar System. Consisting of electrons, hydrogen ions and alpha particles, this stream of plasma flows from our Sun to the edge of the Solar System at speeds of up to 160 million kilometers per hour. When it comes into contact with a comet, there is a discernible region behind the comet where the wind speed slows discernibly.



Meanwhile, where solar wind encounters a planet, the result is an abrupt diversion in its path. The region where this occurs around a planet is known as a "bow shock", owing to the distinctive shape it forms. The very reason the New Horizons mission was equipped with the SWAP instrument was so that it could gather solar wind data from the edge of the Solar System and allow astronomers to create more accurate models of the environment.



But when the Southwestern Research Institute team examined the SWAP data, which was obtained during the New Horizons' July 2015 flyby of Pluto, what they found was surprising. Previously, most researchers thought that Pluto was characterized more like a comet, which has a large region of gentle slowing of the solar wind, as opposed to the abrupt diversion solar wind encounters at a planet like Mars or Venus.



What they found instead was that the dwarf planet's interaction with solar wind was something the fell between that of a comet and a planet. As Dr. David J. McComas - the Assistant Vice President of the Space Science and Engineering Division at the Southwest Research Institute - said during a NASA news release about the study: “This is a type of interaction we’ve never seen before anywhere in our solar system. The results are astonishing.”







Examining both the lighter hydrogen ions that are thrown off by the Sun, and the heavier methane ions that are produced by Pluto, they found that the former showed a 20% rate of deceleration behind Pluto. This, and the bow shock Pluto produces, were both consistent with that of a comet. At the same time, they found that Pluto's gravity was strong enough that it is able to retain the heavier methane ions, which is consistent with a planet.

Between these two readings, it seems that Pluto is something of an anomaly, behaving as something of a hybrid. Yet another surprise from a celestial body that has been full of them lately. And under the circumstances, it may lead to another round of "classification debates", as astronomers attempt to find a new class for bodies that behave like both comets and planets.

As Alan Stern of the Southwestern Research Institute, and the principal investigator of the New Horizon's mission, explained, “These results speak to the power of exploration. Once again we’ve gone to a new kind of place and found ourselves discovering entirely new kinds of expressions in nature.”

Further Reading: Journal of Geophysical Research

The post Thanks, Comet Pluto. Solar System Nomenclature Needs A Major Rethink appeared first on Universe Today.

Posted by Nelio Inacio at 1:42 PM 0 comments

Watch Mercury Race Across the Sun, Courtesy of the Big Bear Solar Observatory

Watch Mercury Race Across the Sun, Courtesy of the Big Bear Solar Observatory:



Mercury transit


Just. Wow.



Just when we thought we'd seen every amazing image and video sequence from Monday's transit of Mercury, a new one surfaces that makes our jaw hit the floor.



The folks at the Big Bear Solar Observatory may have just won the internet this week with this amazing high-definition view of Mercury racing across the surface of the Sun:







Remember, Mercury is tiny a world, just 1.4 times the diameter of our Moon, at 4,880 kilometers across. At about 9" arc seconds across during the transit, it took Mercury seven and a half hours to race across the 30' (over 180 times the apparent size of Mercury as seen from the Earth) disk of the Sun.



The video has an ethereal three dimensional quality to it, as we seem to race along with the fleeting world. You can see the granulation in the dazzling solar photosphere whiz by in the background.



Big Bear Solar Observatory Telescope Engineer and Chief Observer Claude Plymate explains some of the technical aspects of the captured sequence:



"John Varsik assembled (the video) from our speckle reconstructed broadband filter images. The images were taken with a high speed PCO2000 CCD camera. Bursts of 100 frames were taken at a cadence of 15 seconds. After flat fielding and dark subtraction, speckle reconstruction is used on each burst to generate the final single frame. Exposure time was 1.0 ms through a broadband TiO (7057A, 10A FWHM) filter. 
Our actual primary science data was data taken with a fast scanning spectrometer that very quickly produces 2D Na D-line maps. The objective was to measure the Na distribution in Mercury's exosphere in absorption."
So there's some science there as well, as measurements taken from Big Bear will make a fine comparison and contrast with NASA's measurements of the tenuous exosphere of Mercury measured by the MESSENGER spacecraft.
Based on the shores of Big Bear Lake in the San Bernardino Mountains 120 kilometers east of downtown Los Angeles, the Big Bear Solar Observatory employed the 1.6-meter New Solar Telescope (NST) to follow the transit. The NST is the largest clear aperture solar telescope in the world currently in use. Capable of resolving features on the Sun just 50 kilometers across, the mirror blank for the NST was figured at the Mirror Lab at the University of Arizona in Tucson and served as a proof of concept for the seven mirror Giant Magellan Telescope currently under construction.
The Big Bear Solar Observatory is managed under the New Jersey Institute of Technology and is funded by NASA, the United States Air Force and the National Science Foundation.
The Big Bear Solar Observatory is also part of the GONG (Global Oscillation Network Group), a series of observatories worldwide dedicated to observing the Sun around the clock. It's strange to think, but in a sense, we live inside the outer atmosphere of our host star, and knowing just what it's doing is of paramount importance to our modern technology-dependent civilization.
An awesome capture, with some amazing science to boot. Big Bear will also get a sunrise view of the November 11th, 2019 transit of Mercury as well:
Stay tuned!
Also check out Universe Today's Flickr forum for more amazing images of the transit of Mercury, and Nancy Atkinson's roundup of the view from the Solar Dynamics Observatory.
Video used with permission of the BBSO.



The BBSO operation is supported by NJIT, US NSF AGS-1250818, and NASA

NNX13AG14G grants, and the NST operation is partly supported by the Korea

Astronomy and Space Science Institute and Seoul National University and by

the strategic priority research program of CAS with Grant No.

XDB09000000".



The post Watch Mercury Race Across the Sun, Courtesy of the Big Bear Solar Observatory appeared first on Universe Today.

Posted by Nelio Inacio at 1:41 PM 0 comments

Monday, May 9, 2016

Images of Today’s Transit of Mercury From Around the World

Images of Today’s Transit of Mercury From Around the World:



Mercury Transit


(Note: Awesome images are being added as they come in!)



It's not every day you get to see a planet pass in front of the Sun.



But today, skywatchers worldwide got to see just that, as diminutive Mercury passed in front of the disk of the Sun as seen from the Earth. This was the first transit of Mercury across the face of the Sun since November 8th, 2006, and the last one until November 11th, 2019.







Public events worldwide put the unique spectacle on display. Transits of innermost Mercury are much more frequent than Venus, the only other planet that can cross between the Sun and the Earth. Venus transited the Sun for the second and last time for this century on June 5th-6th, 2012, not to do so again until 2117.







Unlike a transit of Earth-sized Venus, you needed safely-filtered optical assistance to see tiny Mercury today against the Sun. At about 9" arc seconds in size, you could stack over 180 Mercury's across the 30' arc minute disk of the Sun.







Lots of live feeds came to the rescue of those of us with cloudy skies, including Slooh, NASA, and our good friends at the Virtual Telescope project.







As is customary, we thought we'd feature a running blog of all of the great images as they trickle in to us here at Universe Today, throughout the day. This is one of our favorite things to do, as we show off some of the unique images as they trickle in from the field. Watch this space, as we'll most likely be dropping in new images today throughout the day through to tomorrow.







Unlike solar eclipses, which are only usually picked up by solar observing satellites in low Earth orbit, spacecraft with different vantage points in space tend to see transits of Venus and Mercury as well, albeit at slightly different times. We're expecting to see images from the joint NASA/ESA SOHO mission located at the L1 sunward point, as well as NASA's Solar Dynamics Observatory, JAXA's Hinode, and ESA's Proba-2, all in orbit around the Earth.







It's amazing just how far the imaging tech has come, since the last transit of Mercury in 2006. Back then, Coronado hydrogen alpha 'scopes were the 'hot new thing' to observe the Sun with. Today, folks projected and shared the Sun safely with the world via social media online... and folks heeded our admonishment to stay cool and hydrate, and no reports of heat stroke from solar observers were noted.







Transits of Mercury occur on average about 13 times per century. The first was observed by Pierre Gassendi on November 7th, 1631. And although they have more of a purely aesthetic appeal than scientific value these days, transits of Mercury and Venus in past centuries were vital to pegging down the distance to the Sun via measuring the solar parallax, which in turn gave the scale of the solar system some hard numerical values in terms of the distance from the Earth to the Sun. Today, we know the solar parallax is tiny at a value of about 8.8", tinier than the disk of Mercury as seen against the Sun today.







Fun fact: a transit of Mercury as seen from space actually turns up in the 200- science fiction flick Sunshine... to our knowledge, a transit of Venus has yet to hit the big screen. We also made mention of Mercury transits and more unique astronomical events spanning space and time in our original scifi tale Exeligmos.







Ready for more transit weirdness? Journey to Mars in 2084, and you can witness a transit of the Earth, Moon AND the innermost Martian moon Phobos. Let's see, by then I'll be...







Looking further out, one can wonder just when Mercury and Venus will transit the Sun... at the same time. We came across an interesting paper this weekend on just this subject. Keep in mind, the paper notes that orbits of the planets become a bit uncertain the farther out in time you look.







Mark your calendars, as the next simultaneous transit of both Venus and Mercury occurs on September 17th, 13,425 AD. And hey, journey to Antarctica on July 5th, 6,757 AD and you can also witness a transit of Mercury during a partial solar eclipse;







Did anyone manage to catch a transit of the International Space Station during the Mercury transit? There were two good opportunities across North America today at 15:42 to 15:50 UT and 17:16 to 17:24 UT... a unique opportunity!







Well, it looks like the skies over southern Spain are clearing... time to set up our solar projection rig and observe the 2016 transit of Mercury for ourselves. Be sure to check this space for updates, and send those pics in to Universe Today's Flickr forum!

The post Images of Today’s Transit of Mercury From Around the World appeared first on Universe Today.

Posted by Nelio Inacio at 1:29 PM 0 comments
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