Telescopes are time machines.
With an amateur telescope you can look back in time to see things as they were long ago because space is so huge that light, even at a blistering speed 186,000 miles per second, it takes a long time to get from one place to another. When you use your backyard telescope to look at distant galaxy, you’re seeing it as it was when light from that galaxy began its millions of years-long journey to Earth. You’re seeing the galaxy as it was millions of years ago, not as it is now.
Even within our own galaxy a telescope is a time machine. A perfect example of this is the Ring Nebula, now perfectly positioned for observation in the eastern skies an hour after sunset this time of year.
The Ring Nebula was recently imaged by the Hubble Space Telescope, and as usual, Hubble created an absolutely eye-popping view. (Yes, you want to click on the image to get the full-sized glory of it.)
When you see the Ring Nebula you are looking back in time about 2,300 years, because that’s how far away the Ring Nebula is from us. Light from this nebula takes 2,300 years to reach us, making the Ring Nebula about 2,300 light-years distant.
BUT – this is also where your telescope can show you the future. The Ring Nebula offers us a view of what will become of our Sun in another five or so billion years when it has exhausted its core supply of hydrogen.
A few billion years from now, when our Sun has ceased fusing hydrogen into helium in its core, it will die and leave behind a beautiful, ghostly corpse looking very much the Ring Nebula.
You see that little white dot in the center of the nebula? That’s a “White Dwarf,” a type of stellar corpse that’s created when a star like our Sun dies.
A few billion years from now our dying Sun will go through a series of slow but powerful convulsions that end when the Sun gently expels its outer layers of gas, leaving behind a tiny and extremely dense ball of white-hot matter. How tiny? About the size of planet Earth. How dense? One teaspoon full of this stuff would weigh a ton.
This little white-hot ball of dead star is no longer generating energy through nuclear fusion. Instead, all the heat is has now is simply what’s left over after the star has died. A White Dwarf will spend the rest of forever slowly (and I mean very very slowly) cooling down and dimming until it becomes a “Black Dwarf,” a cold, dark end to a brilliant life.
White Dwarfs are ferociously hot and radiate fantastic amounts of ultraviolet energy into space, which cause the slowly expanding shell of their expelled gasses to emit their own colorful displays of light.
This is where YOUR telescope comes in. If you have a decent telescope of at least 4 inches (~120 mm) of aperture, and you know where to aim it, you can see the Ring Nebula for yourself.
Admittedly, it won’t look remotely like the Hubble image and it’ll appear without all those gorgeous colors, but when you find it for yourself with your own telescope and you see it “live” with your own eyes I guarantee that it will impress you greatly.
To find the Ring Nebula look to the eastern skies about an hour after sunset on a late spring or early summer evening. Start by finding the three very bright stars that make up an asterism called “The Summer Triangle.” Each of these three stars are themselves the brightest stars of their own constellations.
First above the eastern horizon as the evening progresses is the star Vega, brightest star of the constellation Lyra, the Lyre. Below Vega and a skosh to the north is Deneb, the star that marks the tail of Cygnus the Swan. Still a bit lower and a goodly distance to the south is Altair, the brightest star in Aquila, the Eagle.
Now look again at Vega. See that little parallelogram below it and slightly to the south? Find the two stars at mark the bottom of the parallelogram and aim your telescope right between the two of them.
If your optics are decent and your aim is good, you’ll see a little gray ring.
I call it “The Cosmic Cheerio.” That’s the Ring Nebula as it appears to the human eye through a small telescope. Kind of give you a new appreciation for Hubble, doesn’t it?
So here you are on a warm June evening, looking backwards in time thousands of years, and glimpsing a vision of our Sun’s ultimate fate.
See? Telescopes are Time Machines!