Aug 31st: Which Will Slow First: a Star or a Fidget Spinner?


Podcaster: Richard Drumm
Space Scoop: Which Will Slow First: a Star or a Fidget Spinner?

Organization:365 Days Of Astronomy

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Description: Space scoop, news for children.

Jets of gas spinning with the stars

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.

Today’s sponsor: This episode of “365 Days of Astronomy” is sponsored by — no one. We still need sponsors for many days in 2016, so please consider sponsoring a day or two. Just click on the “Donate” button on the lower left side of this webpage, or contact us at

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.

Which Will Slow First: a Star or a Fidget Spinner?

Fidget spinners are the new yoyo or Rubik’s cube. They’re toys designed to keep fidgety hands busy and help concentration.

To give you something to concentrate on, the Internet is filling up with new videos and articles about “the physics of fidget spinners”.

The physics of spinning is an important topic in Astronomy because lots of cosmic objects spin. For example, Earth spins around its axis, the Sun spins around the centre of our galaxy, and cosmic gas clouds spin when contracting and new stars are forming.

Studying these spinning cosmic objects can tell a really interesting and unexpected story. It’s the story of the conservation of angular momentum.

Stars form from clouds of cosmic gas floating in space. The clouds collapse, growing smaller, denser and hotter. When the core reaches a scorching 10 million degrees, the clump flares into life as a bright new star.

As the cloud shrinks, it also begins to rotate, spinning faster as it grows smaller. If you’ve played with a fidget spinner, you’ll know that no matter how fast they go, they eventually slow down and stop. This is due to friction.

Out in the vacuum of space, there’s much less friction and newborn stars should be seen spinning rapidly. But, the massive young stars in our Universe rotate much slower than expected. So, what’s slowing them down?

Astronomers might have discovered the answer: jets of gas.

New images from the ALMA radio telescope array in the Atacama high desert of Chile have shown gas pouring out of a massive star.

The gas is spinning along with the star, causing it to lose energy and slow down.

To understand why, consider an ice skater who is spinning. First her hands & arms are out away from her body. Then she pulls them in close to her chest and spins much more rapidly.

Then if she extends her arms again she slows down again. In this demonstration her arms are the gas jets, slowing down the rotation of the star in the very same way.

Hey, Here’s A Cool Fact:

Well, not so much a cool fact as a bit of homework.

Go to Google and type in “conservation of angular momentum”. Click on the links there, especially the Wikipedia page and the Bozeman Science YouTube link and take a deep dive into the physics there.

But to answer the question in the title of today’s episode, both the spinner and the star will slow down, but the fidget spinner will stop first. It has mechanical friction that’s slowing it down, and it doesn’t have as much mass contributing to the angular momentum.

Thank you for listening to the 365 Days of Astronomy Podcast!
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365 Days of Astronomy
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