Podcaster: Richard Drumm
Title: Space Scoop: The Legend of Terzan 5
Organization:365 Days Of Astronomy
Link : astrosphere.org ; http://unawe.org/kids/unawe1619/
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:
The Legend of Terzan 5
Scientists don’t always get things right first time, particularly when working with fossils. For example, paleontologists, y’know, dinosaur scientists, have made a whole host of hilarious blunders.
They couldn’t imagine a giant lizard like the Stegosaurus could have such a tiny bird-sized brain. So they decided a second brain must be hidden in it’s bum! Just an FYI: This turned out to be very, totally untrue. Very. Totally.
In a way, astronomers also deal with fossils, and these are much, much older than dinosaur skeletons, and equally challenging to study.
In 1968, the cluster of stars in the image in today’s album artwork, called Terzan 5, was discovered. It’s one of 11 globular clusters, what we astronomers call GCs or globs for short, that were discovered by Agop Terzan, a French/Armenian astronomer.
This classic-looking GC was found in the constellation Sagittarius, in the direction of the center of the Milky Way, and it’s 19,000 light years away. The supermassive black hole at our galaxy’s center is 26,000 light years away, so Terzan 5 is closer to us than it is.
A little background.
There are two known types of star cluster: open clusters and globular clusters. Astronomers decided that this was a glob, a GC, which contains tens of thousands of ancient stars that all formed around the same time, from the same material.
It looked like a glob, so that’s what it was called. They’re all in a big globe-shaped ball, hence the “globular” name.
However, it turns out that this is a cluster like no other! Because all the stars in both open and globular clusters form at the same time, they are all the same age. But this cluster contains two groups of stars that are unmistakably different – with an age-gap of roughly 7 billion years!
For a second group of stars to form, Terzan 5 must have started life as an enormous cloud of star-making material – as much mass as at least few 100 million Suns!
This quantity of star forming material would be required for the cluster hang onto its gas and have a second round of star formation, which is the only thing that would explain the two ages of stars in the cluster.
One population of Terzan’s stars is about 12 billion years old, and the other is about 4.5 billion years, a mere baby in comparison. It’s like finding a day care center in an old folks home! There are only a few other GCs that have multiple age populations. M54, also in Sagittarius, and Omega Centauri, in nearby Centaurus, are among them.
While the properties of Terzan 5 are uncommon for a globular cluster, they’re very similar to the stellar population which can be found in the galactic bulge, the tightly packed central region of the Milky Way.
To visualize this, you can make a model of our galaxy by cutting a ping-pong ball in half and gluing the halves to the center of a CD. The ratio of the thickness to the diameter of the CD is approximately correct for the disc of the galaxy and the ping-pong ball is the galactic bulge.
This gives you an idea of the shape & scale of the bulge.
But the chemistry of this cluster is very, very different from GCs. So it appears it isn’t really a GC after all.
There are 2 main sub-populations of stars here:
– The Sub-solar, or less metallic than the Sun, the 12 billion year old stars,
– The Super-solar, or more metallic than the Sun, the 4.5 billion year old stars.
Its unusual properties make Terzan 5 a living fossil from the early days of the Milky Way. Most scientists believe that galaxies form when enormous clumps of gas merge together. And this fossil of the early Milky Way seems to suggest this theory is right!
Imagine a giant Milky Way made out of Legos. Terzan 5 is a left-over block from the building of the bulge of that Lego galaxy.
A single left-over Lego.
Hey, Here’s a Cool Fact:
There IS another possibility, though, for Terzan 5. It’s possible that it’s the remains of a very massive, metal-enriched satellite galaxy of ours from the period of early galaxy formation. This early satellite would have been much, much more massive than the satellite galaxies the Milky Way has nowadays.
Thank you for listening to the 365 Days of Astronomy Podcast!
End of podcast:
365 Days of Astronomy
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