The Journey of Light, From the Stars to Your Eyes

This week, millions of people will turn their eyes to the skies in anticipation of the 2015 Perseid meteor shower. But what happens on less eventful nights, when we find ourselves gazing upward simply to admire the deep, dark, star-spangled sky? Far away from the glow of civilization, we humans can survey thousands of tiny pinpricks of light. But how? Where does that light come from? How does it make its way to us? And how do our brains sort all that incoming energy into such a profoundly breathtaking sight?

Our story begins lightyears away, deep in the heart of a sun-like star, where gravity’s immense inward pressure keeps temperatures high and atoms disassembled. Free protons hurtle around the core, occasionally attaining the blistering energies necessary to overcome their electromagnetic repulsion, collide, and stick together in pairs of two.

2000px-FusionintheSun.svg
Proton-proton fusion in a sun-like star. Credit: Borb

So-called diprotons are unstable and tend to disband as quickly as they arise. And if it weren’t for the subatomic antics of the weak nuclear force, this would be the end of the line: no fusion, no starlight, no us. However, on very rare occasions, a process called beta decay transforms one proton in the pair into a neutron. This new partnership forms what is known as deuterium, or heavy hydrogen, and opens the door to further nuclear fusion reactions.

Indeed, once deuterium enters the mix, particle pileups happen far more frequently. A free proton slams into deuterium, creating helium-3. Additional impacts build upon one another to forge helium-4 and heavier elements like oxygen and carbon.

Such collisions do more than just build up more massive atoms; in fact, every impact listed above releases an enormous amount of energy in the form of gamma rays. These high-energy photons streak outward, providing thermonuclear pressure that counterbalances the star’s gravity. Tens or even hundreds of thousands of years later, battered, bruised, and energetically squelched from fighting their way through a sun-sized blizzard of other particles, they emerge from the star’s surface as visible, ultraviolet, and infrared light.

Ta-da!

But this is only half the story. The light then has to stream across vast reaches of space in order to reach the Earth – a process that, provided the star of origin is in our own galaxy, can take anywhere from 4.2 years to many thousands of years! At least… from your perspective. Since photons are massless, they don’t experience any time at all! And even after eluding what, for any other massive entity in the Universe, would be downright interminable flight times, conditions still must align so that you can see even one twinkle of the light from a faraway star.

That is, it must be dark, and you must be looking up.

Credit: Bruce Blaus
Credit: Bruce Blaus

The incoming stream of photons then makes its way through your cornea and lens and onto your retina, a highly vascular layer of tissue that lines the back of the eye. There, each tiny packet of light impinges upon one of two types of photoreceptor cell: a rod, or a cone.

Most photons detected under the low-light conditions of stargazing will activate rod cells. These cells are so light-sensitive that, in dark enough conditions, they can be excited by a single photon! Rods cannot detect color, but are far more abundant than cones and are found all across the retina, including around the periphery.

The less numerous, more color-hungry cone cells are densely concentrated at the center of the retina, in a region called the fovea (this explains why dim stars that are visible in your side vision suddenly seem to disappear when you attempt to look at them straight-on). Despite their relative insensitivity, cone cells can be activated by very bright starlight, enabling you to perceive stars like Vega as blue and Betelgeuse as red.

But whether bright light or dim, every photon has the same endpoint once it reaches one of your eyes’ photoreceptors: a molecule of vitamin A, which is bound together with a specialized protein called an opsin. Vitamin A absorbs the light and triggers a signal cascade: ion channels open and charged particles rush across a membrane, generating an electrical impulse that travels up the optic nerve and into the brain. By the time this signal reaches your brain’s visual cortex, various neural pathways are already hard at work translating this complex biochemistry into what you once thought was a simple, intuitive, and poetic understanding of the heavens above…

The stars, they shine.

So the next time you go outside in the darker hours, take a moment to appreciate the great lengths it takes for just a single twinkle of light to travel from a series of nuclear reactions in the bustling center of a distant star, across the vastness of space and time, through your body’s electrochemical pathways, and into your conscious mind.

It gives every last one of those corny love songs new meaning, doesn’t it?

Could We Terraform Jupiter?

So just what would it take to terraform Jupiter, the largest planet in our solar system?

Just a few videos ago, I blew minds with a “How to” on terraforming the Moon. Once we’ve developed a Solar System spanning civilization and have claimed mastery over the laws of physics, and have common-place technology which staggers and dwarf our current comprehension of what’s possible it should be easy enough.

In fact, it might even be easier than terraforming Mars or Venus, as long as you keep a steady flow of gas to the Moon replenishing the constantly escaping atmosphere.

And in the comments on that video, ABitOfTheUniverse threw down, he wants to know what it would take to terraform Jupiter. All right “ABitOfTheUniverse”, if that is your real name… I’m up for it.

On the surface, this is madness. We already explained how Jupiter is completely and totally inhospitable to life. An alien started a “Build a star kit” and stopped a ? of the way through, because he got bored and wandered away. Just like his Mom said he would.

Jupiter is a ball of hydrogen and helium, which compresses these gasses to almost starlike temperatures and pressures. Fine, Jupiter is the absolute worst. It makes traveling to Venus look like a spa visit.

Jupiter does have something we can work with. Astronomers think below the septillions tons of hydrogen and gas, there’s actually a rocky core. The mass of the core is still a mystery, but recent computer simulations put it at somewhere between 7 and 45 times the mass of the Earth, complete with plenty of water ices and other chemicals you might require on an Earthlike planet.

Furthermore, this core may contain similar constituents as the internal structure of Earth. This means a central core of iron and nickel, surrounded by liquid metal, surrounded by rock.

The problem is you need to strip away 95% of the planet’s mass. It’s all that hydrogen and helium, and that’s pretty much impossible. And almost completely impossible, is still very slightly completely possible.

Cutaway of Jupiter. Credit: Kevinsong
Cutaway of Jupiter. Credit: Kevinsong

Jupiter is made of fuel. It’s like looking at a pool of gasoline and wondering if there was some way to get rid of it all. What good Solar System-spanning civilization hasn’t worked out hydrogen fusion? It’s a technology that’s probably only 30 years away from us now.

You could fly a spacecraft down into Jupiter’s gravity well and scoop up hydrogen fuel from the clouds. Or you could create fusion-powered dirigibles filled with hot hydrogen, which float around the cloud tops of Jupiter, using their fusion reactors to spew hydrogen off into space.

Over untold lengths of time, you could get at that rocky juicy center, once you stripped it of its hydrogen. Then you’ll need to do all that other stuff I mentioned in previous videos, to turn it into a habitable world.

Sure, it’s a world with much higher gravity than Earth, but that’s not my problem. You said “Earthlike”. That’ll teach you to make wishes with a monkey’s paw!

What if you need to move Jupiter first, perhaps a little closer to the Sun. There’s an awesome idea cooked up by Larry Niven in his book, “A World Out of Time”. It’s a fusion candle, and it lets you shift gas giants around.

A Star Trek-inspired space station.
A Star Trek-inspired space station.

You take a long space station, and light up fusion thrusters on both ends. You dip one end down into the upper clouds, where it siphons hydrogen fuel. Both ends of the space station start blasting. One end keeps it from dropping down into the planet, and the other end pushes on the entire planet, pushing it around the Solar System.

Instead of trying to terraform Jupiter, we could just push the planet closer to the Sun, where its icy moons warm up and become habitable themselves.

Well, ABitOfTheUniverse, that sounds a little easier. What do you think? I’ll admit, trying to figure out how to terraform Jupiter was a good exercise in tomfoolery. Fortunately, my imagination is a limitless and renewable source of energy. We’ve done Mars, Venus, the Moon and now Jupiter. What should we terraform next? Tell us in the comments below.

Will the Universe Run Out Of Energy?

It seems like the good times will go on forever, so feel free to keep on wasting energy. But entropy is patient, and eventually, it’ll make sure there’s no usable energy left in the Universe.

Thanks to the donations of generations of dinosaurs and their plant buddies, we’ve got fossils to burn. If we ever get off our dependence on those kinds of fuels, we’ll take advantage of renewable resources, like solar, wind, tidal, smug and geothermal. And if the physicists really deliver the goods, we’ll harness the power of the Sun and generate a nigh unlimited amount of fusion energy using the abundant hydrogen in all the oceans of the world. Fire up that replicator, the raktajino is on the house. Also, everything is now made of diamonds.

We’ll never run out of H+. Heck that stuff is already cluttering up our daily experience. 75% of the baryonic mass of the Universe is our little one-protoned friend. Closely followed up by helium and lithium, which we’ll gladly burn in our futuristic fusion reactors. Make no mistake, it’s all goin’ in.

It looks like the good times will never end. If we’ve energy to burn, we’ll never be able to contain our urges. Escalating off into more bizarre uses. Kilimajaro-sized ocean cruise liners catering to our most indulgent fantasies, colossal megastructure orbital laser casinos where life is cheap in the arena of sport. We’ll build bigger boards and bigger nails.or something absolutely ridiculous and decadent like artificial ski-hills in Dubai. Sadly, it’s naive to think it’s forever. Someday, quietly, those good times will end. Not soon, but in the distant distant future, all energy in the Universe will have been spent, and there won’t a spare electron to power a single LED.

Astronomers have thought long and hard about the distant future of the Universe. Once the main sequence stars have used up their hydrogen and become cold white dwarfs and even the dimmest red dwarfs have burned off their hydrogen. When the galaxies themselves can no longer make stars. After all the matter in the Universe is absorbed by black holes, or has cooled to the background temperature of the Universe.

Combining observations done with ESO's Very Large Telescope and NASA's Chandra X-ray telescope, astronomers have uncovered the most powerful pair of jets ever seen from a stellar black hole. The black hole blows a huge bubble of hot gas, 1,000 light-years across or twice as large and tens of times more powerful than the other such microquasars. The stellar black hole belongs to a binary system as pictured in this artist's impression. Credit: ESO/L. Calçada
Artist’s impression of a Star feeding a black hole. Credit: ESO/L. Calçada

Black holes themselves will evaporate, disappearing slowly over the eons until they all become pure energy. Even the last proton of matter will decay into energy and dissipate. Well, maybe. Actually, physicists aren’t really sure about that yet. Free Nobel prize if you can prove it. Just saying.

And all this time, the Universe has been expanding, spreading matter and energy apart. The mysterious dark energy has been causing the expansion of the Universe to accelerate, pushing material apart until single photons will stretch across light years of distance. This is entropy, the tendency for energy to be evenly distributed. Once everything, and I do mean all things, are the same temperature you’ve hit maximum entropy, where no further work can be done.

This is known as the heat death of the Universe. The temperature of the entire Universe will be an infinitesimal fraction of a degree above Absolute Zero. Right above the place where no further energy can be extracted from an atom and no work can be done. Terrifyingly, our Universe will be out of usable energy.

The white dwarf G29-38 (NASA)
The white dwarf G29-38 (NASA)

Interestingly, there’ll still be the same amount it started with, but it’ll be evenly distributed across all places, everywhere. This won’t happen any time soon. It’ll take trillions of years before the last stars die, and an incomprehensible amount of time before black holes evaporate. We also don’t even know if protons will actually decay at all. But heat death is our inevitable future.

There’s a glimmer of good news. The entire Universe might drop down to a new energy state. If we wait long enough, the Universe might spontaneously generate a new version of itself through quantum fluctuations. So with an infinite amount of time, who knows what might happen?

Burn up those dirty dinosaurs while you can! Enjoy the light from the Sun, and the sweet whirring power from your counter-top Mr. Fusion reactor. Your distant descendants will be jealous of your wasteful use of energy, non-smothering climate and access to coffee and chocolate, as they huddle around the fading heat from the last black holes, hoping for a new universe to appear.

What’s the most extreme use of energy you can imagine? Tell us in the comments below.

Could the Death Star Destroy a Planet?

In the movie Star Wars, the Darth Vader’s Death Star destroyed a planet. Could this really happen?

You’ve watched Star Wars right? Is that still a thing? With the Starring and the Warring? Anyway, there’s this classic scene where the “Death Star” sidles up to Alderaan, and it is all like “Hey Planetoid, you lookin’ fine tonight” and then it fires up the superlaser and destroys the entire orb in a single blast. “BOOM”. Shortly followed by some collective group screaming on the interstellar forceway radio.

This is generally described as “science fiction”. And when you’re making up stories, anything you like can happen in them. George Lucas’ hunger for your childhood toy money wasn’t hampered by the pesky constraints of physics in any meaningful way.

Here at the Guide to Space, we get to take our own flights of fancy and pointlessly speculate for your amusement. That’s our job. Well, that and snark. Let’s consider what it would actually take to destroy a planet with a ‘pew pew’ style laser beam, and what kinds of energy would need to be harnessed in a fully armed and operational battle station.

Let’s go back and carefully review our “evidence”. The Death Star drifts in, charges up all its lasers into a superlaser blast focused on Alderaan. The planet then detonates and chunks fly off in every direction just like the pie eating contest in “Stand By Me”.

What we saw was every part of Alderaan given enough of a kick so that it was traveling at escape velocity from every other part of the planet. If the Death Star hadn’t delivered enough explosive energy, the planet might have fluffed up for a moment, but then the collective gravity would suck it all back in together, and then the slightly re-arranged, and likely now uninhabited planet would continue orbiting its star.

You can imagine doing this the slow way. Take each continent on Alderaan, load it up into a rocket and blast that rocket off into space as though it was on escape trajectory from the planet. Sure, you’d would need an incomprehensible number of rocket launches to get that material off the planet. But hey, midichlorians, blue finger lightning and ESP.

Fortunately, as you carted away more and more of the busted up rock, it would have less mutual gravity, and so the rocket launches would require less and less energy to get the job done. Eventually, you’d just be left with one last chunk of rock that you could just force ninja kick into the neighboring star.

Death Star beam. Credit: Lucasfilm
Death Star beam. Credit: Lucasfilm

So how much energy is that going to take? Well, there’s an “easy” calculation you can make. The energy you’d need is equal to 3 times the gravitational constant (6.673 x 10^-11) times the mass of the planet squared divided by 5 times the planet’s radius. Do this math for an Earth-sized/mass world, and let’s see that’s, two and one, carry the 5… and you get 2 x 10^36 joules. That’s a two followed by 36 zeros in joules. Is that a lot? That sounds like a lot.

Well, our own Sun puts out 3 x 10^26 joules per second. So, if you poured all the energy from the Sun into the task of tearing apart the Earth, it wouldn’t have enough energy to do it. In fact, you’d need to focus the light of the Sun for a full week to get that level of planet destruction done.

According to ancient Star Warsian dork scholars, the Death Star (SOLUS MORTIS) is powered by a hyperreactor with the output of multiple main sequence stars. So there you go, problem solved. It’s the size of a small moon, but it’s more powerful than many stars. Of course it can destroy a planet.

Exploding planet. Credit: ESO
Exploding planet. Credit: ESO

The Death Star clearly destroyed Alderaan. We watched it explode. I saw it, you saw it. We heard the screams of millions of souls cry out. It happened. But what if it wasn’t a beam thingy?

Our math is good, but clearly we’re not enlightened enough to comprehend the true wisdom hidden within the Lucasian scriptures. Perhaps the Death Star’s superlaser was just a targeting laser. Directing the placement of gigantic antimatter bomb. According to Ethan Siegel, from “Starts With a Bang,” you’d only need 1.24 trillion tonnes of antimatter.

Imagine you made a bomb out of that much antimatter iron – if that’s even a thing – you’d only need a sphere about 3 km across. If the Death Star is 150 km across or so, they could carry a bunch of these. Very carefully. Like super carefully. Okay, maybe it’d be a good idea if everyone took off their boots, and make sure they only talked with their inside voices.

Obviously, Star Wars is a story, so anything, ANYTHING can happen. The future is unknown, and we might discover all kinds of weirdo physics and harness them into all kinds of powerful weapons. I’m only suggesting, that a space station capable of deploying a week’s worth of solar energy in a single second might be a stretch. And maybe, George, if you just done a little back of the napkin math, we wouldn’t be talking about this right now. Also, maybe no Ewoks. I’m just saying.

Where do you stand on the feasibility of imaginary space station weaponry? How big a planet can your imagination destroy?

How Much Water Would Extinguish the Sun?

Have you ever wondered how much water it would take to put out the Sun? It turns out, the Sun isn’t on fire. So what would happen if you did try to hit the Sun with a tremendous amount of water?

How much water would it take to extinguish the Sun? I recently saw this great question on Reddit, and I couldn’t resist taking a crack at it: We know that the question doesn’t make a lot of sense.

A fire is a chemical reaction, where material releases heat as it oxidizes. If you take away oxygen from a fire, it goes out. But.. there’s no oxygen in space, it’s a vacuum. So, there’s not a whole lot of room for regular flavor water-extinguishable fire in space. You know this. How many times have we had to seal off the living quarters and open the bay doors to vent all the oxygen in the space because there was a fire in the cargo bay? We have to do that, like, all the time.

Our wonderful Sun is something quite different. It’s a nuclear fusion reaction, converting hydrogen atoms into helium under the immense temperatures and pressures at its core. It doesn’t need oxygen to keep producing energy. It’s already got its fuel baked in. All the Sun needs is our adoration, quiet, and yet ever present fear. Only if we constantly pray will it be happy and perhaps we’ll go another day where it doesn’t hurl a giant chunk of itself at our smug little faces because it’s tired of our shenanigans.

So, I’m still going to take a swing at this question… so let’s talk about what would happen if you did pour a tremendous amount of water on the Sun? Let’s say another Sun’s worth of H20. Conveniently, Hydrogen is what the Sun uses for fuel, so if you give the Sun more hydrogen, it should just get larger and hotter.

Oxygen is one of the byproducts of fusion. Right now, our Sun is turning hydrogen into helium using the proton-proton fusion reaction. But there’s another type of reaction that happens in there called the carbon-nitrogen-oxygen reaction. As of right now, only 0.8% of the Sun’s fusion reactions proceed along this path.

So if you fed the Sun more oxygen as part of the water, it would allow it to perform more of these fusion reactions too. For stars which are 1.3 times the mass of the Sun, this CNO reaction is the main way fusion is taking place. So, if we did dump a giant pile of water onto the Sun, we’d just be making Sun bigger and hotter.

Cutaway to the Interior of the Sun. Credit: NASA
Cutaway to the Interior of the Sun. Credit: NASA

Conveniently, larger hotter stars burn for a shorter amount of time before they die. The largest, most massive stars only last a few million years and then they explode as supernovae. So, if you’re out to destroy the Sun, and you’re playing a really, really long game, this might actually be a viable route.

I’m pretty sure that wasn’t the intent though. Let’s say we just want to snuff out the Sun. Vsauce provides a strategy for this. If you could somehow blast your water at the Sun at high enough velocity, you might be able to tear it apart. If you can reduce the Sun’s mass, you can decrease the temperature and pressure in its core so that it can no longer support fusion reactions.

I’m going to sum up. The Sun isn’t on fire. There’s no amount of water you could add that would quench it, you’d just make it explode, but if you used firehoses that could spray water at nearly the speed of light, you could probably shut the thing off and eventually freeze us all, which is what I think you were hoping for in the first place.

What do you think? What else could we do to snuff out the Sun?

Mr. Fusion? Compact Fusion Reactor Will be Available in 5 Years Says Lockheed-Martin

The Farnsworth Fusor; Pons and Fleishmann. It seems the trail to fusion energy has long gone cold — stone cold, that is, and not cold as in cold fusion. Despite the promise of fusion providing a sustainable and safe energy source, fusion reactors are not a dime a dozen and they won’t be replacing coal fired power plants any time soon. Or will they? Lockheed-Martin Skunk Works announced a prototype compact fusion reactor that could be ready within five years. This revelation has raised eyebrows and sparked moments of enthusiasm.

But, let’s considers this story and where it all fits in both the history and future.

For every Skunk Works project that has made the runway such as the Stealth Fighter or SR-71 Blackbird, there are untold others that never see the light of day. This adds to the surprise and mystery of Lockheed-Martin’s willingness to release images and a detailed narrative describing a compact fusion reactor project. The impact that such a device would have on humanity can be imagined … and at the same time one imagines how much is unimaginable.

Lockheed-Martin engineers in the Skunkworks prepare a vessel, one component of an apparatus that they announced will lead to nuclear fusion in a truck-sized reactor within 5 years. An international effort is underway in Europe to create the worlds first practical tokamak fusion reactor, a much larger and costlier design that has never achieved the long sought "breakeven" point. (Photo Credit: Lockheed-Martin)
Lockheed-Martin engineers in the Skunkworks prepare a vessel, one component of an apparatus that they announced will lead to nuclear fusion in a truck-sized reactor within 5 years. An international effort is underway in Europe to create the world’s first practical tokamak fusion reactor, a much larger and costlier design that has never achieved the long sought “breakeven” point. (Photo Credit: Lockheed-Martin)

The program manager of the Skunk Works’ compact fusion reactor experiment is Tom Maguire. Maguire and his team places emphasis on the turn-around time for modifying and testing the compact fusion device. With the confidence they are expressing in their design and the ability to quickly build, test and modify, they are claiming only five years will be needed to reach a prototype.

What exactly the prototype represents was left unexplained, however. Maguire continues by saying that in 10 years, the device will be seen in military applications and in 20 years it will be delivered to the world as a replacement for the dirty energy sources that are in use today. Military apps at 10 years means that the device will be too expensive initially for civilian operations but such military use would improve performance and lower costs which could lead to the 20 year milestone moment if all goes as planned.

Their system uses magnetic confinement, the same basic principle behind the tokamak toroidal plasma confinement system that has received the greatest attention and government funding for over 50 years.

The ITER Tokamak Fusion Reactor is expected to begin operational testing in 2020 and begin producing deuterium-tritium fusion reactions in 2027. (Credits: ITER, Illus. T.Reyes)
The ITER Tokamak Fusion Reactor is expected to begin operational testing in 2020 and begin producing deuterium-tritium fusion reactions in 2027. (Credits: ITER, Illus. T.Reyes)

The International Thermonuclear Experimental Reactor (ITER) is currently under construction in Europe under the assumption that it will be the first net energy producing fusion generator ever. It is funded by the European Union, India, Japan, People’s Republic of China, Russia, South Korea and the United States. But there are cost over-runs and its price has gone from $5 billion to $50 billion.

ITER is scheduled to begin initial testing in 2019 about the time Lockheed-Martin’s compact fusion reactor prototype is expected. If Lockheed-Martin succeeds in their quest, they will effectively have skunked ITER and laid to waste a $50 billion international effort at likely 1/1000th the cost.

There are a few reasons Lockheed-Martin has gone out on a limb. Consider the potential. One ton of Uranium used in Fission reactors has as much energy as 1,500 tons of coal. But fission reactors produce radioactive waste and are a finite resource without breeder reactors, themselves a nuclear proliferation risk. Fusion produces 3 to 4 times more energy per reaction than fission. Additionally, the fuel — isotopes of hydrogen — is available from sea water — which is nearly limitless — and the byproducts are far less radioactive than with fission. Fusion generators once developed could provide our energy needs for millions of years.

More pragmatically, corporations promote their R&D. They are in a constant state of competition. They present a profile that ranges from the practical to the cutting edge to instill confidence in their Washington coffers. Furthermore, their competitors have high profile individuals and projects. A fusion project demonstrates that Lockheed-Martin is doing more than creating better mouse-traps.

To date, no nuclear fusion reactor has achieved breakeven. This is when the fusion device outputs as much energy as is input to operate it. Magnetic confinement such as the various tokamak designs, Lawrence Livermore’s laser-based inertial confinement method, and even the simple Philo Farnsworth Fusor can all claim to be generating energy from fusion reactions. They are just all spending more energy than their devices output.

An example of a homemade Fusor. Originally invented in the 1960s by the inventor of the television, Philo Farnsworth. (Credit: Wikipedia, W.Jack)
An example of a homemade Fusor. Originally invented in the 1960s by the inventor of the television, Philo Farnsworth. (Credit: Wikipedia, W.Jack)

The fusor, invented in the 1960s by Farnsworth and Hirsh, is a electrostatic plasma confinement system. It uses electric fields to confine and accelerate ions through a central point at which some ions will collide with sufficient energy to fuse. Although the voltage needed is readily achieved by amateurs – about 4000 volts – not uncommon in household devices, no fusor has reached breakeven and theoretically never will. The challenge to reaching breakeven involves not just energy/temperature but also plasma densities. Replicating conditions that exist in the core of stars in a controllable way is not easy. Nevertheless, there is a robust community of “fusioneers” around the world and linked by the internet.

Mr Fusion, the compact fusion reactor that drove the 21st Century version of the DeLorian in Back to the Future. The movie trilogy grossed $1 billion at the box office. Mr Fusion could apparently function off of any water bearing material. (Credit: Universal Pictures)
Mr Fusion, the compact fusion reactor that drove the 21st Century version of the DeLorean in Back to the Future. The movie trilogy grossed $1 billion at the box office. Mr Fusion could apparently function off of any water bearing material. (Credit: Universal Pictures)

It remains to be seen who, what and when a viable fusion reactor will be demonstrated. With Lockheed-Martin’s latest announcement, once again, fusion energy is “just around the corner.” But many skeptics remain who will quickly state that commercial fusion energy remains 50 years in the future. So long as Maguire’s team meets milestones with expected performance improvements, their work will go on. The potential of fusion energy remains too great to dismiss categorically.

Source: Lockheed-Martin Products Page, Compact Fusion

Are All the Stars Really Dead?

Have you ever heard that meme, “When looking at stars, you’re actually looking into the past. Many of the stars we see at night have already died.” Is this true?

While you’re flipping through your Pinterest collection of cat-based inspirational posters, you might come across the saying, “When looking at stars, you’re actually looking into the past. Many of the stars we see at night have already died. Like your dreams.”

Aww, that’s mean and sad. But is it true, Squidward? Are all these beautiful stars in our night sky long gone? Like our dreams?

Light travels at about 300,000 km/s, which is incredibly fast. Stars are so far away, even light from the closest stars will take years to get to us travelling at that speed. Most of the stars we see with the naked eye are actually pretty close. The brightest in the night sky is Sirius in the constellation Canis Major. It’s only about 8.6 light years away.

Which means if you crashed a whole bunch of spaceships into it tomorrow, we here on Earth wouldn’t see it happen for almost a decade. Long after people had stopped wondering where you’d picked up all those spaceships, and why had you decided to crash them into a star instead of trading for gold pressed latinum, the spice Melange, or magical space cheese.

One of the most distant naked eye stars is Deneb in the constellation Cygnus, which is almost 3,000 light years away. The light we’re seeing from Deneb started its journey towards us when ancient Rome was just a few hamlets and not even on the map for real estate speculators.

Cygnus. Credit: Stellarium
Cygnus. Credit: Stellarium

This might seem like a really long time for those of us without immortal robot bodies, but a few thousand years is negligible to the age of a typical star, which is on the order of billions of years. So, Deneb, barring removal for an interstellar bypass, is probably still there.

There are a few stars that could possibly explode in the near future, such as the red giant star Betelgeuse in the constellation of Orion.

It’s about 650 light years away, if it had exploded a couple centuries ago, we still wouldn’t know. There are a few galaxies that can be seen with the naked eye, such as Andromeda, which is about 2.5 million light years away. Given that Andromeda has somewhere between 200 and 400 billion stars, it is almost certain that some of them have exploded in the last 2 and a half million years. But the vast majority of them have are still there, twinkling away.

So it is possible that you could look up in the night sky and see a “dead” star, but almost all of the stars you see are perfectly active main-sequence stars, and will be for quite some time. Telescopes allow us to see much further out into space, billions of light years away. Given that a star like our Sun has a lifetime of about 10 billion years, many stars in most of the distant galaxies we observe died long ago.

This cluster is 27,000 light-years away and lies farther than the center of our galaxy in the constellation Sagittarius. Credit: NASA/ESA/I. King, Univ. of Calif., Berkeley/Wikisky.org
This cluster is 27,000 light-years away and lies farther than the center of our galaxy in the constellation Sagittarius. Credit: NASA/ESA/I. King, Univ. of Calif., Berkeley/Wikisky.org

But don’t be sad, we’re not running out of stars. Because of this huge passage of time, it means many new stars have been born, and we just aren’t able to see them yet. There are some stars even in the most distant galaxies that are still around.

Smaller stars live longer than larger stars, and red dwarf stars can live for trillions of years. So when you look at the Hubble Ultra Deep Field, the most distant galaxies are around 13 billion years old, and the smaller stars in those galaxies are still shining. So don’t worry. Those stars are still there, and so are your dreams.

What do you think? If you go get a closeup look and see which stars were still around, where would you go look first? Tell us in the comments below.

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How Do You Jumpstart A Dead Star?

It’s a staple of science fiction, restarting our dying star with some kind of atomic superbomb. Why is our Sun running out of fuel, and what can we actually do to get it restarted?

Stars die. Occasionally threatening the Earth and its civilization in a variety plot devices in science fiction. Fortunately there’s often a Bruce Willis coming in to save the day, delivering a contraption, possibly riding a giant bomb shaped like a spaceship, to the outer proximity of our dying Sun that magically fixes the broken star and all humanity is saved.

Is there any truth in this idea? If our Sun dies, can we just crack out a giant solar defibrillator and shock it back into life? Not exactly.

First, let’s review at how stars die. Our Sun is halfway through its life. It’s been going for about 4.5 billion years, and in 5 billion years it’ll use up all the hydrogen in its core, bloat up as a red giant, puff off its outer layers and collapse down into a white dwarf.

Is there a point in there, anywhere, that we could get it back to acting like a sun? Technically? Yes. Did you know it will only use up a fraction of its fuel during its lifetime? Only in the core of the Sun are the temperatures and pressures high enough for fusion reactions to take place. This region extends out to roughly 25% of the radius, which only makes up about 2% of the volume.

Outside the core is the radiative zone, where fusion doesn’t take place. Here, the only way gamma radiation can escape is to be absorbed and radiated countless times, until it reaches the next layer of the Sun: the convective zone. Here temperatures have dropped to the point that the whole region acts like a giant lava lamp. Huge blobs of superheated stellar plasma rise up within the star and release their energy into space. This radiative zone acts like a wall, keeping the potential fuel in the convective zone away from the fusion furnace.

Cutaway to the Interior of the Sun. Credit: NASA
Cutaway to the Interior of the Sun. Credit: NASA

So, if you could connect the convective zone to the solar core, you’d be able to keep mixing up the material in the Sun. The core of the Sun would be able to efficiently fuse all the hydrogen in the star.

Sound crazy? Interestingly, this already happens in our Universe. For red dwarf stars with less than 35% the mass of the Sun, their convective zones connect directly to the core of the star. This is why these stars can last for hundreds of billions and even trillions of years. They will efficiently use up all the hydrogen in the entire star thanks to the mixing of the convective zone. If we could create a method to break through the radiative zone and get that fresh hydrogen into the core of the Sun, we could keep basking in its golden tanning rays for well past its current expiration date.

I never said it would be easy. It would take stellar engineering at a colossal scale to overcome the equilibrium of the star. A future civilization with an incomprehensible amount of energy and stellar engineering ability might be able to convert our one star into a collection of fully convective red dwarf stars. And these could sip away their hydrogen for trillions of years.

Tell us in the comments on how you think we should go about it. My money is on giant ‘magic bullet’ blender” or a perhaps a Dyson solar juicer.

Astronomy Cast Ep. 325: Cold Fusion

The Universe is filled with hot fusion, in the cores of stars. And scientists have even been able to replicate this stellar process in expensive experiments. But wouldn’t it be amazing if you could produce energy from fusion without all that equipment, and high temperatures and pressures? Pons and Fleischmann announced exactly that back in 1989, but things didn’t quite turn out as planned…

Continue reading “Astronomy Cast Ep. 325: Cold Fusion”

How Does a Star Form?

We owe our entire existence to the Sun. Well, it and the other stars that came before. As they died, they donated the heavier elements we need for life. But how did they form?

Stars begin as vast clouds of cold molecular hydrogen and helium left over from the Big Bang. These vast clouds can be hundreds of light years across and contain the raw material for thousands or even millions of times the mass of our Sun. In addition to the hydrogen, these clouds are seeded with heavier elements from the stars that lived and died long ago. They’re held in balance between their inward force of gravity and the outward pressure of the molecules. Eventually some kick overcomes this balance and causes the cloud to begin collapsing.

That kick could come from a nearby supernova explosion, collision with another gas cloud, or the pressure wave of a galaxy’s spiral arms passing through the region. As this cloud collapses, it breaks into smaller and smaller clumps, until there are knots with roughly the mass of a star. As these regions heat up, they prevent further material from falling inward.

At the center of these clumps, the material begins to increase in heat and density. When the outward pressure balances against the force of gravity pulling it in, a protostar is formed. What happens next depends on the amount of material.

Some objects don’t accumulate enough mass for stellar ignition and become brown dwarfs – substellar objects not unlike a really big Jupiter, which slowly cool down over billions of years.

If a star has enough material, it can generate enough pressure and temperature at its core to begin deuterium fusion – a heavier isotope of hydrogen. This slows the collapse and prepares the star to enter the true main sequence phase. This is the stage that our own Sun is in, and begins when hydrogen fusion begins.

If a protostar contains the mass of our Sun, or less, it undergoes a proton-proton chain reaction to convert hydrogen to helium. But if the star has about 1.3 times the mass of the Sun, it undergoes a carbon-nitrogen-oxygen cycle to convert hydrogen to helium. How long this newly formed star will last depends on its mass and how quickly it consumes hydrogen. Small red dwarf stars can last hundreds of billions of years, while large supergiants can consume their hydrogen within a few million years and detonate as supernovae. But how do stars explode and seed their elements around the Universe? That’s another episode.

We have written many articles about star formation on Universe Today. Here’s an article about star formation in the Large Magellanic Cloud, and here’s another about star formation in NGC 3576.

Want more information on stars? Here’s Hubblesite’s News Releases about Stars, and more information from NASA’s imagine the Universe.

We have recorded several episodes of Astronomy Cast about stars. Here are two that you might find helpful: Episode 12: Where Do Baby Stars Come From, and Episode 13: Where Do Stars Go When they Die?

Source: NASA