Podcaster: Richard Drumm
Title: Space Scoop: Ghost of the Southern Skies
Organization: 365 Days Of Astronomy
Link : astrosphere.org ; http://unawe.org/kids/unawe1535/
Description: Space scoop, news for children.
Bio: Richard Drumm is President of the Charlottesville Astronomical Society and President of 3D – Drumm Digital Design, a video production company with clients such as Kodak, Xerox and GlaxoSmithKline Pharmaceuticals. He was an observer with the UVa Parallax Program at McCormick Observatory in 1981 & 1982. He has found that his greatest passion in life is public outreach astronomy and he pursues it at every opportunity.
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Transcript:
This is 365 Days of Astronomy. Today we bring you a new episode in our Space Scoop series. This show is produced in collaboration with Universe Awareness, a program that strives to inspire every child with our wonderful cosmos.
Today’s story is…
Ghost of the Southern Skies
The beautiful bubble in the space photograph in today’s album artwork is the glowing ghost of a star that was caught haunting the darkness of space. Did you know stars turn into ghosts when they die?
Well, OK, not really. There’s no such thing as a ghost.
This object, though, is kinda like the ghost of a star that was once very similar to our own Sun. Similar but maybe 2 or 3 times the mass. It’s called a planetary nebula, and it’s formed from the lingering remains of a dead star. So in a way it’s like the mythical ghosts of legend.
The photograph was taken with the ESO’s VLT, the Very Large Telescope at the Paranal Observatory in northern Chile. This shimmering nebula is called ESO 378-1 and is also nicknamed the Southern Owl Nebula, because it looks a little like a barn owl when seen by smaller telescopes. The cloudy-looking interior of the bubble has a couple of darker spots that look a bit like the owl’s dark eyes.
Do a Google Images search for “barn owl” and you’ll see what I mean. It’s located in the southern end of the constellation Hydra, the Female Water Snake.
Why’d they have to call it the Female water snake? Got me. They did, though. Oh well. Whatchagonnado?
This constellation is located next to the small but pretty constellation Crater, the water cup, and Corvus the crow. The greek myth has it that Corvus the crow served the snake to Apollo in the water cup but Apollo wasn’t fooled and cast all 3 into the night sky.
Messin’ with the wrong guy there…
Hydra (in a different tale) is also the foul, many-headed monster which was the “Keeper of the gate” and guarded the entrance to the underworld at Lake Lerna in the Greek Peloponnese.
It was raised by Hera for the sole purpose of killing Heracles (in the Greek pronunciation) or Hercules (in the Latin.) The legend tells us that if one of the Hydra’s heads was cut off two more would grow back to replace it.
But Hercules burned or cauterized the neck stumps with a torch after cutting off the heads and thus kept the new heads from growing. This was the second of Hercules’ 12 labors. There really was a Lake Lerna, but unfortunately it was small and has silted up and vanished.
Back to the skies!
Planetary nebulae, called PNs for short by astronomers, form when dying stars run out of hydrogen fuel in their cores. The cores contract and heat up dramatically. They soon get hot and dense enough to fuse the abundant helium in the core and the star swells up into a red giant star.
As they do so, the outer parts of the star are forced by the terrific heat and radiation pressure of the core to basically leave the gravity well of the star. You can think of it being like the horn of a trumpet if you’d like. Up & out it goes! The intense stellar wind continues pushing the gas away, leaving behind the core of the star, which has by now run out of helium as well.
The core contracts yet again, heating even more, but not enough to start fusing the carbon & oxygen that was left over from the helium fusion. The remaining core starts off terrifically hot, around 40,000°F or more, and it cools slowly as no new heat is being generated within it. It’s pouring out ultraviolet light, which strikes the gasses that were pushed away, causing them to fluoresce or glow brightly.
Oxygen gets doubly ionized and glows a pretty green, for instance. Hydrogen, nitrogen and sulfur all glow in their characteristic colors which spectroscopes on our telescopes can detect. We can’t travel to PNs to take samples, but we don’t have to. The information we need, to know what they’re made of, has travelled here at the speed of light!
Although they are beautiful, planetary nebulae are short-lived cosmic marvels. They only last for a couple tens of thousands of years, whereas the stars that make them can shine for several billion years!
These space ghosts have an important role to play in the Universe, they create cosmic dust. Cosmic dust includes important elements such as carbon and oxygen.
Take a deep breath! Aaah! Without these elements there would be no life on Earth, and they are only created in the death (so to speak) of stars.
When a stars dies, these elements escape into space and can form into new stars or planets, or even living creatures like us! As Carl Sagan once said: “We are made of star stuff.”
Hey Here’s a Cool Fact:
The Southern Owl Nebula was made by a star similar to our Sun, but what you see in the picture has grown to almost four light years in diameter! If our Solar System was on one edge, the closest star to Earth, Alpha Centauri, would be close to the other side! And it’s still growing. Eventually it’ll get so thin it’ll be undetectable. But don’t worry, though. The galaxy will make more!
Thank you for listening to 365 Days of Astronomy!
End of podcast:
365 Days of Astronomy
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