Today I’m going to toss a little bit of math your way. If you’re an arithmophobe, never fear: It’s mostly just me throwing around some gee- whiz numbers, and I’ll help you swallow this medicine with the sweet, sweet eye candy above. That image is from Robert Gendler, Roberto Colombari, and Martin Pugh, and it shows the young star cluster called NGC 6. NGC 6. 18. 8. Both are very roughly 4,0. Ara. The image combines data from the huge 8. Very Large Telescope in Chile with some from a much smaller 3. The cluster is young, only a few million years old. The brightest stars in it are massive, hot, luminous, and blue. They flood out light, illuminating and ionizing the gas in the cloud, which responds by glowing red. I could go into details, but I already have in countless posts about emission nebulae, as well as in Crash Course: Nebulae. I’ll leave it up to you, Bad Readers, to determine how deeply you want to dive into those particulars by clicking those links.
But I want to point something out. Images like this are gorgeous, and always stop me in my tracks. The details, the colors, the structure of the gas . But in others, like NGC 6. In this case I mean that literally: The vast majority of energy pumped into the gas is being done by three stars. In the center of the nebula you can see two stars, their cores blurred into a single smear, but their distinct presence revealed by the pair of X- shaped diffraction spikes coming out from them. Please note Are you using a cell phone or tablet to reach AnnualCreditReport.com? Although this website is very secure, the wireless network that you are using to get. Breaking business news and financial news on U.S. Welcome to the official corporate site for the world's largest aerospace company and leading manufacturer of commercial jetliners and defense, space and security systems. This is no exaggeration. Hydrogen in deep space hums in the radio region of the electromagnetic spectrum, and that can be detected by radio telescopes. Moreover, one of those two is itself a binary star, two stars in close orbit, so close they appear as one. So you’re actually seeing three stars there! One is a brutal O3 star, probably 5. Sun, and the other two are O6, smaller but still beasts. All together they probably crank out 1. Sun does. If you replaced the Sun with any of those three stars, the Earth wouldn’t last long. It’d be fried to a crisp. But here’s the thing: The glowing part of that nebula, the gas energized by those stars, is roughly 2. That’s 2. 00 trillion kilometers! All that gas, probably several times the mass of the Sun, glowing due to the light of just three stars. That made me wonder: How many photons are those stars emitting? The math on that isn’t so bad. I won’t start from first physics principles, because that would take a lot of words. Instead, let me skip around a bit. First, how many photons does the Sun emit? Well, the energy of a photon is defined by its wavelength or frequency. The Sun emits most strongly in the green portion of the spectrum, and that’s a wavelength of about 0. The equation of the energy in a single photon is: Energy = h x c / wavelength. Where h is Planck’s constant (just a number that has units of energy times time), and c is the speed of light. You can look those numbers up, but in the end the answer is that a single green photon has an energy of about 4 x 1. Joules (a Joule is a unit of energy; the energy stored in a single calorie of food is equivalent to more than 4,0. Joules). The Sun emits about 4 x 1. Joules of energy every second. That’s spread out over many different colors, each with their own energy, but I’m being really rough here, so assume they’re all green for math purposes. Dividing that total energy by the energy per photon gives us the number of photons the Sun emits: 4 x 1. Holy. That’s a lot of photons. Written out it’s: 1,0. And that’s every second. The Sun has been doing this for 4. I’ll leave it to you to figure out how many photons total the Sun’s given off since it was born (but it’s roughly 1. Mind you, those stars lighting up NGC 6. Sun, so they emit 1. They also tend to emit higher energy light, like ultraviolet. That kind of light is preferentially absorbed by the hydrogen in the gas cloud. That ionizes the gas, blasting the electrons off the atoms. When the electron recombines, it re- emits that energy as light, usually that characteristic red you see in the image. That’s how (well, in part that’s how) just a few stars can light up gas for trillions of kilometers around. Funny, too: As bright as those stars are, distance is more important. At 4,0. 00 light- years away, they’re 2. Sun*. So even though they blast out 1. I’m not sure what’s more unnerving: The energies involved, or the vast distances. Both are mind- numbing. So in case you were wondering, when I see astronomical images, that’s the sort of stuff that goes through my mind. I’ve said it many times, but it bears repeating: There is great beauty in astronomy, but that’s dwarfed by what these cosmic artworks teach us about the Universe.*Correction (Oct. I originally wrote 2. Still, they're a long ways off.
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