I’ve got to say, you are one of the luckiest people I’ve ever met.
For starters, you are the descendant of an incomprehensible number of lifeforms who were successful, and survived long enough to find a partner, procreate, and have an offspring. Billions of years, and you are the result of an unbroken chain of success, surviving through global catastrophe after catastrophe. Nice going.
Not only that, but your lineage happened to be born on a planet, which was in just the right location around just the right kind of star. Not too hot, not too cold, just the right temperature where liquid water, and whatever else was necessary for life to get going. Again, I like your lucky streak.
Yup, you are pretty lucky to call this place home. Credit: NASA
In fact, you happened to be born into a Universe that has the right physical constants, like the force of gravity or the binding force of atoms, so that stars, planets and even the chemistry of life could happen at all.
But there’s another lottery you won, and you probably didn’t even know about it. You happened to be born on an unassuming, mostly harmless planet orbiting a G-type main sequence star in the habitable zone of the Milky Way.
Wait a second, even galaxies have habitable zones? Yep, and you’re in it right now.
The Milky Way is a big place, measuring up to 180,000 light years across. It contains 100 to 400 billion stars spread across this enormous volume.
We’re located about 27,000 light years away from the center of the Milky Way, and tens of thousands of light-years away from the outer rim.
Credit: ESA
The Milky Way has some really uninhabitable zones. Down near the center of the galaxy, the density of stars is much greater. And these stars are blasting out a combined radiation that would make it much more unlikely for life to evolve.
Radiation is bad for life. But it gets worse. There’s a huge cloud of comets around the Sun known as the Oort Cloud. Some of the greatest catastrophes in history happened when these comets were kicked into a collision course with the Earth by a passing star. Closer to the galactic core, these disruptions would happen much more often.
There’s another dangerous place you don’t want to be: the galaxy’s spiral arms. These are regions of increased density in the galaxy, where star formation is much more common. And newly forming stars blast out dangerous radiation.
Fortunately, we’re far away from the spiral arms, and we orbit the center of the Milky Way in a nice circular orbit, which means we don’t cross these spiral arms very often.
We stay nice and far away from the dangerous parts of the Milky Way, however, we’re still close enough to the action that our Solar System gathered the elements we needed for life.
The first stars in the Universe only had hydrogen, helium and a few other trace elements left over from the Big Bang. But when the largest stars detonated as supernovae, they seeded the surrounding regions with heavier elements like oxygen, carbon, even iron and gold.
Early stars were made almost entirely of hydrogen and helium. Credit: NASA/WMAP Science Team
Our solar nebula was seeded with the heavy elements from many generations of stars, giving us all the raw materials to help set evolution in motion.
If the Solar System was further out, we probably wouldn’t have gotten enough of those heavier elements. So, thanks multiple generations of dead stars.
According to astrobiologists the galactic habitable zone probably starts just outside the galactic bulge – about 13,000 light-years from the center, and ends about halfway out in the disk, 33,000 light-years from the center.
Remember, we’re 27,000 light-years from the center, so just inside that outer edge. Phew.
The Milky Way’s habitable zone. Credit: NASA/Caltech
Of course, not all astronomers believe in this Rare Earth hypothesis. In fact, just as we’re finding life on Earth wherever we find water, they believe that life is more robust and resilient. It could still survive and even thrive with more radiation, and less heavier elements.
Furthermore, we’re learning that solar systems might be able to migrate a significant distance from where they formed. Stars that started closer in where there were plenty of heavier elements might have drifted outward to the safer, calmer galactic suburbs, giving life a better chance at getting a foothold.
As always, we’ll need more data, more research to get an answer to this question.
Just when you thought you were already lucky, it turns out you were super duper extra lucky. Right Universe, right lineage, right solar system, right location in the Milky Way. You already won the greatest lottery in existence.
Special Guests:
This week’s guests will be the Universe Sandbox Developers Dan Dixon (Project Lead & Creator) and Jenn Seiler (Astrophysicist & Developer).
We’ve had an abundance of news stories for the past few months, and not enough time to get to them all. So we are now using a tool called Trello to submit and vote on stories we would like to see covered each week, and then Fraser will be selecting the stories from there. Here is the link to the Trello WSH page (http://bit.ly/WSHVote), which you can see without logging in. If you’d like to vote, just create a login and help us decide what to cover!
We record the Weekly Space Hangout every Friday at 12:00 pm Pacific / 3:00 pm Eastern. You can watch us live on Universe Today, or the Universe Today YouTube page.
We usually record Astronomy Cast as a live Google+ Hangout on Air every Friday at 1:30 pm Pacific / 4:30 pm Eastern. You can watch here on Universe Today or from the Astronomy Cast Google+ page.
Fraser, Morgan and Sondy were all at the Kennedy Space Center in Florida to watch the launch of the OSIRIS-REx Mission. Sondy and Morgan talked about the mission, answered questions about space and astronomy, Cassini.
Just a sneak preview before the Weekly Space Hangout starts up later this week!
We’ve had an abundance of news stories for the past few months, and not enough time to get to them all. So we are now using a tool called Trello to submit and vote on stories we would like to see covered each week, and then Fraser will be selecting the stories from there. Here is the link to the Trello WSH page (http://bit.ly/WSHVote), which you can see without logging in. If you’d like to vote, just create a login and help us decide what to cover!
We record the Weekly Space Hangout every Friday at 12:00 pm Pacific / 3:00 pm Eastern. You can watch us live on Google+, Universe Today, or the Universe Today YouTube page.
You can also join in the discussion between episodes over at our
The interior structure of the Sun. Credit: Wikipedia Commons/kelvinsong
From here on Earth, the Sun like a smooth ball of light. And prior to Galileo’s discovery of sunposts, astronomers even thought it was a perfect orb with no imperfections. However, thanks to improved instruments and many centuries of study, we know that the Sun is much like the planets of our Solar System.
In addition to imperfections on its surface, the Sun is also made up of several layers, each of which serves its own purpose. It’s this structure of the Sun that powers this massive engine that provides the planets with all the light and heat they receive. And here on Earth, it is what provides all life forms with the energy they need to thrive and survive.
Composition:
If you could take the Sun apart, and stack up its various elements, you would find that the Sun is made of hydrogen (74%) and helium (about 24%). Astronomers consider anything heavier than helium to be a metal. The remaining amount of the Sun is made of iron, nickel, oxygen, silicon, sulfur, magnesium, carbon, neon, calcium and chromium. In fact, the Sun is 1% oxygen; and everything else comes out of that last 1%.
Where did these elements come from? The hydrogen and helium came from the Big Bang. In the early moments of the Universe, the first element, hydrogen, formed from the soup of elementary particles. The pressure and temperatures were still so intense that the entire Universe had the same conditions as the core of a star.
Hydrogen was fused into helium until the Universe cooled down enough that this reaction couldn’t happen any more. The ratios of hydrogen and helium that we see in the Universe today were created in those first few moments after the Big Bang. The other elements were created in other stars. Stars are constantly fusing hydrogen into helium in their cores.
Once the hydrogen in the core runs out, they switch to fusing heavier and heavier elements, like helium, lithium, oxygen. Most of the heavier metals we see in the Sun were formed in other stars at the end of their lives. The heaviest elements, like gold and uranium, were formed when stars many times more massive that our Sun detonated in supernova explosions.
In a fraction of a second, as a black hole was forming, elements were crushed together in the intense heat and pressure to form the heaviest elements. The explosion scattered these elements across the region, where they could contribute to the formation of new stars.
Our Sun is made up of elements left over from the Big Bang, elements formed from dying stars, and elements created in supernovae. That’s pretty amazing.
Structure:
Although the Sun is mostly just a ball of hydrogen and helium, it’s actually broken up into distinct layers. The layers of the Sun are created because the temperatures and pressures increase as you move towards the center of the Sun. The hydrogen and helium behave differently under the changing conditions.
The Core: Let’s start at the innermost layer of the Sun, the core of the Sun. This is the very center of the Sun, where temperatures and pressures are so high that fusion can happen. The Sun is combining hydrogen into helium atoms, and this reaction gives off the light and heat that we see here on Earth. The density of the core is 150 times the density of water, and the temperatures are thought to be 13,600,000 degrees Kelvin.
Astronomers believe that the core of the Sun extends from the center out to about 0.2 solar radius. And within this region, temperatures and pressures are so high that hydrogen atoms are torn apart to form separate protons, neutrons and electrons. With all of these free floating particles, the Sun is able to reform them into atoms of helium.
This reaction is exothermic. That means that the reaction gives off a tremendous amount of heat – 3.89 x 1033 ergs of energy every second. The light pressure of all this energy streaming from the core of the Sun is what stops it from collapsing inward on itself.
Radiative Zone: The radiative zone of the Sun starts at the edge of the core of the Sun (0.2 solar radii), and extends up to about 0.7 radii. Within the radiative zone, the solar material is hot and dense enough that thermal radiation transfers the heat of the core outward through the Sun.
The core of the Sun is where nuclear fusion reactions are happening – protons are merged together to create atoms of helium. This reaction produces a tremendous amount of gamma radiation. These photons of energy are emitted, absorbed, and then emitted again by various particles in the radiative zone.
The path that photons take is called the “random walk”. Instead of going in a straight beam of light, they travel in a zigzag direction, eventually reaching the surface of the Sun. In fact, it can take a single photon upwards of 200,000 years to make the journey through the radiative zone of the Sun.
As they transfer from particle to particle, the photons lose energy. That’s a good thing, since we wouldn’t want only gamma radiation streaming from the Sun. Once these photons reach space, they take a mere 8 minutes to get to Earth.
Most stars will have radiative zones, but their size depends on the star’s size. Small stars will have much smaller radiative zones, and the convective zone will take up a larger portion of the star’s interior. The smallest stars might not have a radiative zone at all, with the convective zone reaching all the way down to the core. The largest stars would have the opposite situation, where the radiative zone reaches all the way up to the surface.
Convective Zone: Outside the radiative zone is another layer, called the convective zone, where heat from inside the Sun is carried up by columns of hot gas. Most stars have a convective zone. In the case of the Sun, it starts at around 70% of the Sun’s radius and goes to the outer surface (the photosphere).
Gas deeper inside the star is heated up so that it rises, like globs of wax in a lava lamp. As it gets to the surface, the gas loses some of its heat, cools down, and sinks back towards the center to pick up more heat. Another example would be a pot of boiling water on the stove.
The surface of the Sun looks granulated. These granules are the columns of hot gas that carry heat to the surface. They can be more than 1,000 km across, and typically last about 8 to 20 minutes before dissipating. Astronomers think that low mass stars, like red dwarfs, have a convective zone that goes all the way down to the core. Unlike the Sun, they don’t have a radiative zone at all.
Photosphere: The layer of the Sun that we can see from Earth is called the photosphere. Below the photosphere, the Sun becomes opaque to visible light, and astronomers have to use other methods to probe its interior. The temperature of the photosphere is about 6,000 Kelvin, and gives off the yellow-white light that we see.
Above the photosphere is the atmosphere of the Sun. Perhaps the most dramatic of these is the corona, which is visible during a total solar eclipse.
Graphic showing a model of the layers of the Sun, with approximate mileage ranges for each layer. Credit: NASA
Diagram:
Below is a diagram of the Sun, originally developed by NASA for educational purposes.
Visible, IR and UV radiation – The light that we see coming from the Sun is visible, but if you close your eyes and just feel the warmth, that’s IR, or infrared radiation. And the light that gives you a sunburn is ultraviolet (UV) radiation. The Sun produces all of these wavelengths at the same time.
Photosphere 6000 K – The photosphere is the surface of the Sun. This is the region where light from the interior finally reaches space. The temperature is 6000 K, which is the same as 5,700 degrees C.
Photosphere 6000 K – The photosphere is the surface of the Sun. This is the region where light from the interior finally reaches space. The temperature is 6000 K, which is the same as 5,700 degrees C.
Radio emissions – In addition to visible, IR and UV, the Sun also gives off radio emissions, which can be detected by a radio telescope. These emissions rise and fall depending on the number of sunspots on the surface of the Sun.
Coronal Hole – These are regions on the Sun where the corona is cooler, darker and has less dense plasma.
2100000 – This is the temperature of the Sun’s radiative zone.
Convective zone/Turbulent convection – This is the region of the Sun where heat from the core is transferred through convection. Warm columns of plasma rise to the surface in columns, release their heat and then fall back down to heat up again.
Coronal loops – These are loops of plasma in the Sun’s atmosphere that follows magnetic flux lines. They look like big arches, stretching up from the surface of the Sun for hundreds of thousands of kilometers.
Core – The is the heart of the Sun, where the temperatures and pressures are so high that nuclear fusion reactions can happen. All of the energy coming from the Sun originates from the core.
14500000 K – The temperature of the core of the Sun.
Radiative Zone – The region of the Sun where energy can only be transferred through radiation. It can take a single photon 200,000 years to get from the core, through the radiative zone, out to the surface and into space.
Neutrinos – Neutrinos are nearly mass-less particles blasted out from the Sun as part of the fusion reactions. There are millions of neutrinos passing through your body every second, but they don’t interact, so you can’t feel them.
Chromospheric Flare – The Sun’s magnetic field can get twisted up and then snap into a different configuration. When this happens, there can be powerful X-ray flares emanating from the surface of the Sun.
Magnetic Field Loop – The Sun’s magnetic field extends out above its surface, and can be seen because hot plasma in the atmosphere follows the field lines.
Spot – A sunspot. These are areas on the Sun’s surface where the magnetic field lines pierce the surface of the Sun, and they’re relatively cooler than the surrounding areas.
Prominence – A bright feature that extends above the surface of the Sun, often in the shape of a loop.
Energetic particles – There can be energetic particles blasting off the surface of the Sun to create the solar wind. In solar storms, energetic protons can be accelerated to nearly the speed of light.
X-rays – In addition to the wavelengths we can see, there are invisible X-rays coming from the Sun, especially during flares. The Earth’s atmosphere protects us from this radiation.
Bright spots and short-lived magnetic regions – The surface of the Sun has many brighter and dimmer spots caused by changing temperature. The temperature changes from the constantly shifting magnetic field.
Yes, the Sun is like an onion. Peel back one layer and you’ll find many more. But in this case, each layers is responsible for a different function. And what they add to is a giant furnace and light source that keeps us living beings here on Earth warm and illuminated!
And be sure to enjoy this video from the NASA Goddard Center, titled “Snapshots from the Edge of the Sun”:
It turns out I’ve got a few things in common with Elon Musk, the founder of SpaceX and Tesla. We’ve both got Canadian passports, we’re absolutely fascinated by space exploration and believe that humanity’s future is in the stars.
Oh, and we’re kind of obsessed at the possibility that we might be living in a computer simulation.
In the recent 2016 Code Conference, Elon Musk casually mentioned his fascination with the concept first put forth by the scientist Nick Bostrom. Apparently, Musk has brought up the argument so many times, he’s banned from discussing it in hot tubs.
I haven’t received any bans yet, but I’m sure that’s coming.
The argument goes like this:
Advanced civilizations (such as our own) will develop faster and faster computers, capable of producing better and better simulations. You know, how the Sims 2 was a little better than the Sims 1? The Sims 3 was sort of crappy and really felt like a money grab, but the Sims 4 was a huge improvement. Well… imagine the Sims, version 20, or 400, or 4 million.
Computer model of the Milky Way and its smaller neighbor, the Sagittarius dwarf galaxy. Image by Tollerud, Purcell and Bullock/UC Irvine
Not only will the simulations get more sophisticated, but the total number of simulations will go up. As computers get faster, they’ll run more and more simulations simultaneously. You’ll get one mediocre simulation, and then a really great simulation, and then thousands of great simulations, and then an almost infinite number of near perfect simulations.
Nick Bostrom calls these ancestor simulations.
Which means that for all the beings living in all the realities, the vast majority of them will be living in a simulation.
According to this argument, and according to Elon Musk, the chance that you or I happen to be living in the actual reality is infinitesimally low.
Is it true then, are we living in a simulation? And if we are, is there any way to tell?
Nick Bostrom’s ancestor simulation argument is actually a little more complex. Either humans will go extinct before they reach the post-human stage. In other words, we’ll wipe ourselves out before we design computers fast enough to run ancestor-simulations.
I’m really hoping this one isn’t true. I’m looking forward to humanity’s long lived future.
Or, posthuman civilizations won’t bother getting around to running ancestor simulations. Like, the artificial superintelligent machines will have more interesting things to do, and won’t consider sparing a few computer cycles to simulate what it might have been like to watch YouTube videos back in 2016.
Again, this doesn’t sound likely to me. I’m sure those computers will be a tiny bit curious about what it was like to watch Jacksepticeye and Markiplier in their glory, before the terrible Five Nights at Freddy’s Theme Park disaster of 2023.
Those were dark days. Animatronics… blue hair… the horror.
At this point, you’re going to fall into one of two camps. Either you’ve thought through the argument and you find it airtight, like me and Elon Musk, or you’re skeptical.
That’s fine, let’s get skeptical.
For starters, you might say, computers can never simulate actual reality. From our current perspective, that true. Our current simulations suck. But, take a look at the simulations from 10 years ago, and you’ll have to agree that today’s simulations suck less than they did in the past. And in the future, they’re going to suck even less; maybe even be downright acceptable.
A simulation of the impact a cosmic ray has on entering the atmosphere (credit: AIRES package/Chicago University)
Scientific simulations are getting much much better. Cosmologists have developed simulations that accurately model the early Universe, starting from about 300,000 years after the Big Bang and then tracking forward for 13.8 billion years until now.
They’ve been able to model the interaction of dark matter, dark energy, the formation of the first stars and the interactions of galaxies at the largest scale. They have been able to tweak the simulation and get roughly the same Universe as we see today.
They provide all the starting material, and then simulate the gravity and hydrodynamics, the chemical properties of all that gas, radiation and magnetic fields.
These simulations only recreate the Universe at the largest scales, but I’m sure you can imagine a time when they get better and better, capable of simulating planetary formation, and maybe even the beginnings and evolution of life.
If an advanced civilization ran hundreds, thousands or even billions of these simulations, making them more and more advanced, who knows what they might come up with?
Could we know if we’re actually living in a simulation? The answer is maybe. And you might be amazed to know that scientists have worked out a few tests to try and get an answer.
The first thing to consider is that a simulation can never match the processing power of the reality that it’s trying to simulate. For example, if you made your computer simulate another computer, it wouldn’t be quite as fast as the computer is natively.
Things might seem a bit slow. Credit: CSIRO (CC BY 3.0)
A simulation would need to take shortcuts, use compression and other tricks to make it seem like it’s reality. Sort of how a television show uses a facade of a building, or a cosy living room. There’s nothing behind the door but a sound stage.
In theory, it could be possible to detect those tricks from within the simulation. A team of researchers from the University of Washington have proposed that there might be an underlying grid to the Universe, visible in our observations. They’ve proposed that the observed energy limitations of ultra high-energy cosmic rays might reveal the resolution of the simulation.
Of course, if the simulators are super intelligent enough, they’d have thought of that, and fixed the simulation to account for it. Or went back to a previous save file, once the simulatees figured out reality.
They should have insisted on Ironman Mode.
The reality is that there’s no way we can ever know if we’re actually living in a simulation, or we’re the real reality. We just need to live our lives as if we’re real, until better evidence comes along, or our simulations get so good, their inhabitants start questioning their own existence.
As long as you’re not actually in a hot tub with Elon Musk, feel free to argue about whether or not we’re living in a simulation. What strong reasons do you have to believe we are? Why do you think we aren’t? I’d love to hear your insights.
Today we’re going to have the most surreal conversation. I’m going to struggle to explain it, and you’re going to struggle to understand it. And only Stephen Hawking is going to really, truly, understand what’s actually going on.
But that’s fine, I’m sure he appreciates our feeble attempts to wrap our brains around this mind bending concept.
All right? Let’s get to it. Black holes again. But this time, we’re going to figure out their temperature.
The very idea that a black hole could have a temperature strains the imagination. I mean, how can something that absorbs all the matter and energy that falls into it have a temperature? When you feel the warmth of a toasty fireplace, you’re really feeling the infrared photons radiating from the fire and surrounding metal or stone.
And black holes absorb all the energy falling into them. There is absolutely no infrared radiation coming from a black hole. No gamma radiation, no radio waves. Nothing gets out.
As with most galaxies, a supermassive black hole lies at the heart of NGC 5548. Credit: ESA/Hubble and NASA. Acknowledgement: Davide de Martin
Now, supermassive black holes can shine with the energy of billions of stars, when they become quasars. When they’re actively feeding on stars and clouds of gas and dust. This material piles up into an accretion disk around the black hole with such density that it acts like the core of a star, undergoing nuclear fusion.
But that’s not the kind of temperature we’re talking about. We’re talking about the temperature of the black hole’s event horizon, when it’s not absorbing any material at all.
The temperature of black holes is connected to this whole concept of Hawking Radiation. The idea that over vast periods of time, black holes will generate virtual particles right at the edge of their event horizons. The most common kind of particles are photons, aka light, aka heat.
Normally these virtual particles are able to recombine and disappear in a puff of annihilation as quickly as they appear. But when a pair of these virtual particles appear right at the event horizon, one half of the pair drops into the black hole, while the other is free to escape into the Universe.
From your perspective as an outside observer, you see these particles escaping from the black hole. You see photons, and therefore, you can measure the temperature of the black hole.
Artist’s concept of the black hole at the center of the Pinwheel Galaxy. Credit: NASA/JPL-Caltech
The temperature of the black hole is inversely proportional to the mass of the black hole and the size of the event horizon. Think of it this way. Imagine the curved surface of a black hole’s event horizon. There are many paths that a photon could try to take to get away from the event horizon, and the vast majority of those are paths that take it back down into the black hole’s gravity well.
But for a few rare paths, when the photon is traveling perfectly perpendicular to the event horizon, then the photon has a chance to escape. The larger the event horizon, the less paths there are that a photon could take.
Since energy is being released into the Universe at the black hole’s event horizon, but energy can neither be created or destroyed, the black hole itself provides the mass that supplies the energy to release these photons.
The black hole evaporates.
The most massive black holes in the Universe, the supermassive black holes with millions of times the math of the Sun will have a temperature of 1.4 x 10^-14 Kelvin. That’s low. Almost absolute zero, but not quite.
Artist’s impression of a feeding stellar-mass black hole. Credit: NASA, ESA, Martin Kornmesser (ESA/Hubble)
A solar mass black hole might have a temperature of only .0.00000006 Kelvin. We’re getting warmer.
Since these temperatures are much lower than the background temperature of the Universe – about 2.7 Kelvin, all the existing black holes will have an overall gain of mass. They’re absorbing energy from the Cosmic Background Radiation faster than they’re evaporating, and will for an incomprehensible amount of time into the future.
Until the background temperature of the Universe goes below the temperature of these black holes, they won’t even start evaporating.
A black hole with the mass of the Earth is still too cold.
Only a black hole with about the mass of the Moon is warm enough to be evaporating faster than it’s absorbing energy from the Universe.
As they get less massive, they get even hotter. A black hole with the mass of the asteroid Ceres would be 122 Kelvin. Still freezing, but getting warmer.
A black hole with half the mass of Vesta would blaze at more than 1,200 Kelvin. Now we’re cooking!
Less massive, higher temperatures.
When black holes have lost most of their mass, they release the final material in a tremendous blast of energy, which should be visible to our telescopes.
Artist’s conception of the event horizon of a black hole. Credit: Victor de Schwanberg/Science Photo Library
Some astronomers are actively searching the night sky for blasts from black holes which were formed shortly after the Big Bang, when the Universe was hot and dense enough that black holes could just form.
It took them billions of years of evaporation to get to the point that they’re starting to explode now.
This is just conjecture, though, no explosions have ever been linked to primordial black holes so far.
It’s pretty crazy to think that an object that absorbs all energy that falls into it can also emit energy. Well, that’s the Universe for you. Thanks for helping us figure it out Dr. Hawking.
Composite satellite image of Antarctica, the location of the largest desert on Earth. Credit: NASA/Dave Pape
When you hear the word desert, what comes to mind? Chances are, you’d think of sun, sand, and very little in the way of rain. Perhaps cacti, vultures, mesas, and scorpions come to mind as well, or possibly camels and oases? But in truth, deserts come in all shapes and sizes, and vary considerably from one part of the world to the next.
Like all of Earth’s climates, it all comes down to some basic characteristics that they share – which in this case, involves being barren, dry, and hostile to life. For this reason, you might be surprised to learn that the largest desert in the world is actually in Antarctica. How’s that for a curveball?
Definition:
To break it down, a desert is a region that is simply very dry because its receives little to no water. To be considered a desert, an area must receive than 250 millimeters of annual precipitation. But precipitation can take the form of rain, snow, mist or fog – literally any form of water being transferred from the atmosphere to the earth.
The Lut Desert of Iran, as observed by NASA’s Earth Observatory. It was here that the hottest temperature ever was recorded between 2003-9. Credit: NASA
Deserts can also be described as areas where more water is lost by evaporation than falls as precipitation. This certainly applies in regions that are subject to “desertification”, where increasing temperatures (i.e. climate change) result in river beds drying up, precipitation patterns changing, and vegetation dying off.
Deserts are often some of the hottest and most inhospitable places on Earth, as exemplified by the Sahara Desert in Africa, the Gobi desert in northern China and Mongolia, and Death Valley in California. But they can also be cold, windswept landscapes where little to no snow ever falls – like in the Antarctic and Arctic.
So in the end, being hot has little to do with it. In fact, it would be more accurate to say that deserts are characterized by little to no moisture and extremes in temperature. All told, deserts make up one-third of the surface of the Earth. But most of that is found in the polar regions.
Antarctica:
In terms of sheer size, the Antarctic Desert is the largest desert on Earth, measuring a total of 13.8 million square kilometers. Antarctica is the coldest, windiest, and most isolated continent on Earth, and is considered a desert because its annual precipitation can be less than 51 mm in the interior.
A Sun halo seen among the the landscape and ice flows of Antarctica. Credit and copyright: Alex Cornell
It’s covered by a permanent ice sheet that contains 90% of the Earth’s fresh water. Only 2% of the continent isn’t covered by ice, and this land is strictly along the coasts, where all the life that is associated with the land mass (i.e. penguins, seals and various species of birds) reside. The other 98% of Antarctica is covered by ice which averages 1.6 km in thickness.
There are no permanent human residents, but anywhere from 1,000 to 5,000 researchers inhabit the research stations scattered across the continent – the largest being McMurdo Station, located on the tip of Ross Island. Beyond a limited range of mammals, only certain cold-adapted species of mites, algaes, and tundra vegetation can survive there.
Despite having very little precipitation, Antarctica still experiences massive windstorms. Much like sandstorms in the desert, the high winds pick up snow and turn into blizzards. These storms can reach speeds of up to 320 km an hour (200 mph) and are one of the reasons the continent is so cold.
In fact, the coldest temperature ever recorded was taken at the Soviet Vostok Station on the Antarctic Plateau. Using ground-based measurements, the temperature reached a historic low of -89.2°C (-129°F) on July 21st, 1983. Analysis of satellite data indicated a probable temperature of around -93.2 °C (-135.8 °F; 180.0 K), also in Antarctica, on August 10th, 2010. However, this reading was not confirmed.
Antarctica’s McMurdo Station at night. Credit: m.earthtripper.com
Other Deserts:
Interestingly, the second-largest desert in the world is also notoriously cold – The Arctic Desert. Located above 75 degrees north latitude, the Arctic Desert covers a total area of about 13.7 million square km (5.29 million square mi). Here, the total amount of precipitation is below 250mm (10 inches), which is predominantly in the form of snow.
The average temperature in the Arctic Desert is -20 °C, reaching as low as -50 °C in the winter. But perhaps the most interesting aspect of the Arctic Desert is its sunshine patterns. During the summer months, the sun doesn’t set for a period of 60 days. These are then followed in the winter by a period of prolonged darkness.
The third largest desert in the world is the more familiar Sahara, with a total size of 9.4 million square km. The average annual rainfall ranges from very low (in the northern and southern fringes of the desert) to nearly non-existent over the central and the eastern part. All told, most of the Saraha receives less than 20 mm (0.79 in).
However, in northern fringe of the desert, low pressure systems from the Mediterranean Sea result in an annual rainfall of between 100 to 250 mm (3.93 – 9.84 in). The southern fringe of the desert – which extends from coastal Mauritania to the Sudan and Eritrea – receives the same amount of rainfall from the south. The central core of the desert, which is extremely arid, experiences an annual rainfall of less than 1 mm (0.04 in).
Temperatures are also quite intense in the Sahara, and can rise to more than 50 °C. Interestingly, this is not the hottest desert on the planet though. The hottest temperature ever recorded on Earth was 70.7 °C (159 °F), which was taken in the Lut Desert of Iran. These measurements were part of a global temperature survey conducted by scientists at NASA’s Earth Observatory during the summers of 2003 to 2009.
In short, deserts are not just sand dunes and places where you might come across Bedouins and Berbers, or a place you have to drive through to get to Napa Valley. They are common to every continent of the world, and can take the form of sandy deserts or icy deserts. In the end, the defining characteristic is their pronounced lack of moisture.
In that respect, the polar regions are the largest deserts in the world, with Antarctica narrowly beating out the Arctic for first place. And going by this definition – i.e. cold, arid, and with little to no precipitation – we’re sure to find some particularly big deserts elsewhere in Solar System. After all, what is Mars if not one big, cold, arid, and extremely dry climate?
Wow, my first acceptable image of the Milky Way. Credit: Me/Cory & Tanja Schmitz
Wow, my first acceptable image of the Milky Way. Credit: Me/Cory & Tanja Schmitz
I’m really fortunate to live in a region of the world with pretty dark skies. And, I’ve got pretty nice camera gear that we use to make all our YouTube videos. But for some reason, I’ve never been able to take an acceptable photo of the Milky Way, and I wasn’t exactly sure where I was going wrong. Turns out… I was going wrong everywhere; wrong exposure, aperture, ISO, JPG vs RAW.
I finally reached out to two of the best astrophotographers I know, Cory and Tanja Schmitz from PhotographingSpace.com. Both are world-class astrophotographers, with amazing shots of the Milky Way, galaxies, star clusters, nebulae and other deep space objects. And you should see their timelapses. They generously agreed to give me direct advice using the gear I have available, and then helped turn the raw photos into something usable through Photoshop (which is another area of dark wizardry).
I ended up using my Canon 5D MkII camera, which we shoot all our Guide to Space videos on. I tried taking pictures with its regular lens, and then got better results with a Rokinon 14mm lens that I actually don’t really use very often. It’s the wide angle lens we use in the car driving up to Comox Lake.
I captured the image at f/2.8, 30 second exposure, ISO 3200. Our shooting location had pretty dark skies, but it was earlier in the evening, and there was some light pollution off to the southern skies.
Here’s the final collaboration video, where Tanja and Cory give me their advice on which gear to use, how to set up and take the picture, and then how to clean it all up in Photoshop afterwards.
This is just the beginning of a whole new rabbit hole hobby for me, so hopefully you’ll see me improve over time as I learn to get more out of my gear, and find darker and darker skies.
Of course, you should check out Cory and Tanja’s PhotographingSpace.com, follow them on Instagram, and begin your own journey of learning how to shoot the night sky.
