Caoimhín's Content

Today, I’m going to try and take a look at misconceptions about space. In the attached video, I talk through a couple of the common misconceptions. However, to continue my tendency toward being a bit clearer and more explicit in these articles, I’m really trying to take a look at the reasons these things are labeled misconceptions.

The first example misconception is the colour of the Sun. People usually think of the Sun as yellow. When people draw the Sun it’s usually yellow. To be fair, that is the colour of the Sun in the sky. We don’t normally get to see the Sun without our atmosphere around us, a bunch of oxygen and nitrogen gets in the way. As the light of the Sun comes through our atmosphere, it gets broken up by the atmosphere. The atmosphere does bend light, changing the direction of the light or refracting it in the same way water does, but this isn’t the main reason for the change in colour. Instead, photons hit atoms in the atmosphere, causing the light to get scattered. Thanks to the high frequency waves of blue light, they tend to bounce around more and get scattered further. This spreads the blue colour across the sky, leaving the rest of the colours behind, giving us a yellow Sun. The exact physics behind this does is a little complicated and the phenomenon is known as Rayleigh scattering. Essentially, our yellow Sun is what we’re seeing distorted by our own atmosphere. As always, I must repeat that you should never look directly at the Sun, but the Sun does seem to have a yellowish tint to it from here on Earth. In reality the Sun is essentially white, emitting all wavelengths, or colours, of visible light pretty equally. The Sun we see in the sky is yellow to us, but the star we call the Sun is white. What you mean when you say the Sun, and the context it’s used in, can mean different things. This gives you a different answer to the same question.

There’s not really anything wrong with the way we talk about the colours of stars. We call the Sun a yellow dwarf mostly because it’s small and it is cooler than a lot of stars. The Sun and similar stars range from pale yellow to white, and are still bigger and brighter than the real dwarf stars, like red and white dwarfs. White dwarfs aren’t even real stars, but they are often hotter than the Sun, and blue stars and especially giant white and blue stars, are quite hot. The Sun is kind of a middling star, it’s not the hottest, but it’s also not as cool as a truly yellow star, certainly not the red and orange stars. However, the heat of stars seemed like a good segue into the misconception about where this heat comes from. An oft quoted misconception is that our Sun is a burning ball of gas, or a giant fire of some sort. Of course, the Sun isn’t a ball of fire, nor are any of the other stars. This is one misconception that I find a little disingenuous. I think that burning gas is a simple way to conceptualize what a star truly is without getting into the nitty gritty technical truth. I also think that many people who conceptualize the Sun as a burning ball of gas understand that the Sun is like a burning ball of gas, and can see that if the Sun is a fire of some sort, it is different from what we normally see on Earth. I can’t speak for everyone of course. The truth of course is that the Sun and all stars are huge balls of plasma, with a process of nuclear fusion going on in their core. Nuclear fusion isn’t really burning. If you burn something with fire, an oxidation reaction occurs. Oxygen pulls on molecules and snaps their bonds, forming new molecules. This is easier to do when things are hot. Nuclear fusion generates energy when light atoms are fused together into heavier forms. Atomic nuclei crash into each other, and fuse together, creating bigger and heavier nuclei, while energy is released. Atoms are composed of atomic nuclei and electrons, with the nuclei being composed of protons and neutrons, or just a proton for most hydrogen atoms. We don’t really have to worry about the electrons in this case, because plasma is a soup of protons and neutrons, atomic nuclei, surrounded by electrons. These electrons are usually free from the atomic nuclei that they would be attached to in cooler substances. Electricity can break electrons away from atoms, creating ions, but in a plasma it is heat that separates them out. A general trend when it comes to the phases of matter is decreasing bonds with increasing temperature. Starting with a solid, most if not all of the electrons will be stuck around their atomic nuclei, and each whole atom will be bonded very closely to their neighbours. In solids, the individual atoms are locked together, usually through ionic or covalent forces, holding the atoms together by their electron orbitals and charge. When you start heating things up, solids melt into liquids, where the molecules, are still bound loosely together but they can flow around each other. Even in liquids and solids that are only made of one element, atoms will still usually bind together into molecules or form weak bonds with each other. At high enough temperatures you get a gas, where either the molecules or the individual atoms will be flowing around without really any bond to their neighbours. Most gases are still at least two atoms bound together, even if they are of the same element, though monoatomic gasses do exist. Even as a gas, the atom’s electrons are still bonded to them. However, getting even hotter, when you get up to the state of plasma you get electrons flowing around a little bit more freely, where all the atoms are ionized to bare atomic nuclei. Under the pressure at the core of a star, these bare atomic nuclei are squeezed so tight and whizzing around so much that they can crash together. This can cause nuclei to collide and create a new nucleus and, sometimes with parts flying off into space and creating energy. usually, this is hydrogen nuclei, so just a proton. The details behind two protons colliding, and how one becomes a neutron generating a positron in the process, is a reasonably complicated bit of particle physics, but that’s one of the key steps in how the Sun generates heat. This isn’t burning only because burning means oxidation, and if we were to broaden the category of burning that might not be the case. Usually when people say nuclear fire, they mean a normal oxidation fire started by a nuclear explosion, but sometimes it’s the actual nuclear activity. Here on Earth that is normally fission rather than fusion, which is a whole other process. The Sun isn’t burning if by burning you only mean fire, for example if I spill acid on my hand it’s going to burn, or it will feel like it’s burning. This certainly isn’t fire, and it isn’t the same oxidation reaction we get when things burn, but people still call it burning. Corroding would be more accurate, and the same term is also used to describe rusting. Rusting however is an oxidation reaction, very similar to burning despite the lower temperature and slower speed. The Sun isn’t a burning ball of gas, it’s a ball of plasma undergoing nuclear fusion. However it is “burning” hot, and metaphorically burning through it’s reserves of hydrogen. The Sun is certainly plasma, the next stage of matter after gas, but it is certainly hot, and its ability to generate heat while sitting in space with no oxygen for an oxidation reaction is important, but not a necessary distinction for most people, most of the time.

Moving away from the Sun and daytime, we will take a look towards other stars that we see at night time. One misconception that I do think many people believe, a misconception that I believe to be genuine and not just a case of differing meanings in different contexts is about the stars we see. People say that the stars are so far away, that by the time their light reaches you they are already dead. Whether you say dead, or that the stars are burned out, or simply gone, the idea is that the stars are so far away that their lives have ended and we are just still seeing their light. That may be true for some stars, but not most of the ones we see with our eyes. Firstly, we’ll take Vega, the brightest star in Lyra, one of the corners of the summer triangle. Vega is just about 25 light years away from us. Vega almost certainly hasn’t died within the past 25 years. If it did, if that star had died within the past 25 years, its light would still be reaching us, and we wouldn’t know until the 25 years had elapsed and we saw its final moments after the delay caused by distance. However, by looking at stars like Vega, and many other stars, we can get a pretty good idea of their age and how long they’re going to last. The shortest lived stars a generally big, bright and blue, they will still last millions of years, about 3 or four at a minimum. Vega will probably last a little less than a billion years, compared to our Sun’s 10 billion. Vega right now is only about 400 million years old, so it has about that long left yet, way more than 25 years. Vega is a big blue star, but not quite a blue giant. The furthest away stars that we see in our sky are only thousands of light years away from us, for the vast majority of more distant stars, where we are actually seeing them after they’ve blown up, you would need a telescope for them. they’re way way more distant. Deneb is an example of a more distant star, over 2600 light years away, give or take about 200 light years. It is an older hot star, a blue supergiant, old enough to have swelled in size. However, it hasn’t cooled off to red yet, nor has it’s behaviour hasn’t changed to indicate it becoming one of the stranger blue stars that can go supernova while still hot, such as a Wolf-Rayet star. It may be older and off the main sequence, where stars spend most of their lives, but it has thousands if not hundreds of thousands of stellar evolution left, certainly more than it’s distance from us.

For some stars it gets a little bit more difficult to tell how old they are exactly. Betelgeuse is one example of a particularly famous and certainly quite old star. Betelgeuse is about 500 light years, give or take 50-odd light years away from us. Being an older star, it’s brightness varies a little, up and down, over time. It has also shed a lot of material into space, meaning it’s apparent mass now isn’t the same as what it once had. It most likely became a red giant about 400,000 years ago, having bean a main sequence star about a million years before that. These are estimates, but it seems likely that Betelgeuse has hundreds of thousands of years yet before it blows up. However, if some of the established measurement are wrong, or if Betelgeuse is simply a type of red giant that hasn’t been seen age before, then it may have blown up within the past 500 years and we don’t know about it yet. It isn’t very likely, and for many other stars, we know their ages and distance with a higher degree of certainty. Pollux is a rather short lived kind of star, having been a blue star like Sirius, it has now cooled and swelled to a warm yellow giant. With a lifespan of hundreds of millions of years, even though it is in the older stages, it is only 33 light years away. Castor just next to it is only 51 light years away, and is really a group of six stars. Some are red dwarfs, invisible to the naked eye and incredibly long lived. The bright ones we see are bigger, hotter and shorter lived than our Sun, and they haven’t cooled and swelled like Pollux just yet. These two stars (or stellar systems) are very different ages, neither is very long lived, but both were certainly still alive 33 or 51 years ago, and both will still be burning for at least hundreds of thousands of years to come.

The Pleiades are a particularly young group of stars, around 100 million years old, and the brightest of them is about 440 light-years away, Alycone. All of the Pleiades are bright blue stars meaning they will have comparatively short lifespans, but they’re quite new, having only recently burst out of their envelope of gas, the star-forming region that served as their stellar nursery. Being an open cluster, they are reasonably close together, with the whole group being about 20 light years across. This puts them all close to 400 hundred light years away. Stars as hot as the Pleiades usually last for just a few hundred million years, and so some of the Pleiades may have just a few millions of years left, before they at least move off the main sequence. Luckily, that’s a lot more than 400 years, so they will be alive when we see them for a long time yet.

A less straight forward misconception is that stars don’t twinkle. This is similar to the issue of the Sun’s colour, as it comes down to our atmosphere. When you look at the stars in the sky they appear to twinkle, but it is the atmosphere distorting the star light that causes this effect. Without the atmosphere, this would not occur, so in space the stars themselves aren’t really twinkling. If somebody asks you “Do stars twinkle?”, well, from our perspective, yes they do. When you look at the star in the sky the atmosphere distorts it, and that’s what causes twinkling. However, you could say that stars do not twinkle, they’re big balls of plasma going through nuclear fusion, that are sending out light pretty evenly. Except of course for when they’re not. Variable stars exist, who’s brightness does change over time. Algol, the Eye of the Demon, is one of the brighter stars in Perseus and it is an eclipsing binary star. This means that there are two stars orbiting around each other, and they can appear brighter or fainter depending on their arrangement, depending on whether or not they’re aligned with each other. Algol is a star that still suppose winks or blinks, is supposed to be the Eye of the Gorgon, and this occurs independently of the atmosphere.

Even without the extra complication of variable stars, this is one of those tricky questions. Do stars twinkle? From our perspective yes they do. Do stars twinkle in space? No. In a way, these questions can be a little deceptive, what is the right or acceptable answer can vary. Unless you’re specifying exactly what you’re talking about, or how accurate, or pedantic, you want your answer to be, some answers can be a little fuzzy. The Sun isn’t yellow, it’s white, unless you’re looking at it through our atmosphere and the stars don’t twinkle, unless you’re looking at them through our atmosphere. The Sun isn’t a burning ball of gas, it’s a “burning” ball of plasma, as long as you include the heat generated by nuclear fusion as a form of burning. Most people don’t necessarily mean to specify an oxidation reaction when they say burning. Physicists might do, of course, and it can be necessary to specify in certain contexts. More often than not, down here on Earth, if you see a fire, that’s oxidation, but of course we normally just say fire. That is meaningfully different from nuclear fusion in many contexts, but when it comes to the Sun, it’s far enough away that we can just enjoy it’s heat.

A final misconception is that out in space nobody, can hear you scream, famously the tagline of the Alien sci-fi movie franchise. This is broadly true, unless you are on the International Space Station, which has it’s own packet of gas. In fact, any time two people are sharing a common envelope of gas, even if they are otherwise in space, they should be able to hear each other, shouting will certainly work onboard a space ship. Even if this isn’t the exact case, there are other possible exceptions. Going to the Moon, if there were two astronauts standing next to each other on the Moon, shouting at each other, without any atmosphere or radio they wouldn’t hear each other. However if there was an explosion near them, they’d still feel the vibration, there’s solid matter on the Moon that vibrations can travel through. If you produced a loud enough noise, or if you smacked a the ground hard enough, other people could feel that vibration, as long as the space suit was thin enough not to block it out. No one can hear you scream if you’re actually floating in the vacuum of space, without being surround by a packet of gas the way most people we send into space are. Even then, it seems like large explosions could still be felt at least, as long as there is some matter for them to be transported through. Pressure waves may propagate through the near vacuum of space, because space is really only a near vacuum. The vacuum of space is less of a misconception, it is a near vacuum, a place where the concentration of atoms is so low that particles or energy just pops into existence. Vacuum energy and the Casimir effect are another area of physics where things can get a bit complicated and that of course complicates the answers.

Even with the answers to these questions being a little weird, complicated or dependent on your perspective, I still hope that you enjoyed this little write up. If you’d like to see more from me then I do hope you subscribe to my website or my YouTube channel, and I hope that I see you back here next time.