Podcaster: Richard Drumm
Title: Space Scoop: Only the Biggest Survive
Organization:365 Days Of Astronomy
Link : astrosphere.org ; http://unawe.org/kids/unawe1718/
Description: Space scoop, news for children.
Our Galaxy, the Milky Way, is surrounded by 152 groups of stars, which are called globular clusters. They appear to be the oldest things in the galaxy, the first thing to form, and hold valuable clues about how the first stars and galaxies formed.
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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 the 365 Days of Astronomy Podcast. 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.
Only the Biggest Survive
Our Galaxy, the Milky Way, is surrounded by 152 groups of stars, which are called globular clusters. There may be as many as 200 of them in total. They’re called globular because the cluster looks like a spherical globe of stars.
They appear to be the oldest things in the galaxy, the first thing to form, and hold valuable clues about how the first stars and galaxies formed.
Astronomers had thought that the total number of globular clusters increased during star-making frenzies called ‘starbursts’ when the galaxy, and the Universe too, was young.
However, using a computer simulation, a team of astronomers has found that starbursts actually may have destroyed more of these globular clusters than they helped to create.
Starbursts are often caused by the collision of two galaxies. It’s easy to think of the space between the stars in a galaxy as being empty, but it’s actually filled with a very thin gas. Very, very thin.
When 2 galaxies collide, the stars all miss each other, but the gas between the stars, called the Interstellar Medium or ISM, does hit the ISM from the other galaxy. This makes the gas denser and hotter, causing stars to form.
A very chaotic time, that!
This means that the pull of gravity, the tides, on the globular clusters from the gas around them is constantly changing. The stars are getting pulled this way and that!
In fact, the astronomers found that the tides were 10 times stronger than in galaxies that were isolated and weren’t colliding.
This is enough to rip apart most of the globular clusters. The astronomers call this ‘tidal shock heating’. Only the biggest ones have strong enough gravity of their own to survive.
The stars weren’t destroyed, they were flung out into the galaxy’s halo to orbit the galactic core by themselves.
The astronomers say that this explains why the number of stars contained within globular clusters is roughly the same across the entire Universe.
“In the early Universe, starbursts were commonplace – it therefore makes perfect sense that all globular clusters have approximately the same large number of stars.
Their smaller brothers and sisters that didn’t contain as many stars were doomed to be destroyed.” says astronomer Diederik Kruijssen of the Max-Plank Institute in Garching, Germany.
Hey, Here’s A Cool Fact:
The globular cluster survivors that surround the Milky Way contain up to a million stars each! We amateur astronomers call them “globs” for short.
Now that summer is here, it’s time to go out and look for globs! They are found in the Milky Way’s ‘halo’ and not in the disc, where most of the galaxy’s stars are located.
In the summer and early fall the center of the galaxy is visible from up here in the northern hemisphere. This is where the halo is centered and where you’ll see globs.
You can think of the galaxy’s structure this way. Imagine a ping-pong ball cut in half and glued to either side of the hole in the center of a CD disc. The ball is the halo and the CD is the galaxy’s disc.
You won’t see any globs in the wintertime unless you stay up till almost dawn! Use lots of magnification and you should see the individual stars if you have a good-sized 6″ or larger scope.
Don’t have a telescope? Then find an astronomy club near you and join up with them on an observing session. They can show you globs galore!
On a dark night, the view has been called “diamonds on black velvet.”
Thank you for listening to the 365 Days of Astronomy Podcast!
End of podcast:
365 Days of Astronomy
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The 365 Days of Astronomy Podcast is produced by Astrosphere New Media. Audio post-production by Richard Drumm. Bandwidth donated by libsyn.com and wizzard media. You may reproduce and distribute this audio for non-commercial purposes. Please consider supporting the podcast with a few dollars (or Euros!). Visit us on the web at 365DaysOfAstronomy.org or email us at info@365DaysOfAstronomy.org. This year we will celebrate more discoveries and stories from the universe. Join us and share your story. Until tomorrow! Goodbye!