Podcaster: Richard Drumm
Title: Space Scoop: A Puzzling Geometry Conundrum
Organization: 365 Days Of Astronomy
Link : http://365daysofastronomy.org/ ; http://www.spacescoop.org/en/scoops/2013/a-puzzling-geometry-conundrum/
Description: Space scoop, news for children.
Imagine standing on the planet Tatooine from Star Wars and seeing two suns in the sky. Planets and stars also have their own geometry, but sometimes the answer doesn’t add up.
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.
Today’s story is…
A Puzzling Geometry Conundrum
3 April 2020
Imagine standing on the planet Tatooine from Star Wars and seeing two suns in the sky…
Whoa!
When we study geometry in school, we’re learning about the shapes and dimensions of different objects. Sines, cosines & tangents, that sort of stuff. Great stuff! I LOVE geometry!
Planets and stars also have their own geometry, but sometimes the answer doesn’t add up.
By studying the geometry of the birthplaces of planets, astronomers hope to discover how planets form in different environments.
In the earliest part of its life, a star is called a ‘protostar’. The star is simply a ball of cold gas and dust that’s collapsing under the force of its own gravity. It doesn’t even have nuclear fusion in its core, so it really isn’t even a star yet.
But just wait!
With time, the cloud collapses and it begins to spin – forming a flattened disc around the protostar.
This is SO cool! It’s called the conservation of angular momentum! Think of an ice skater pulling in her arms and spinning faster & faster.
At the start there is some small, insignificant rotation to the cloud. This rotation is amplified as the outer parts move inward.
Material from this disc feeds the star and makes it grow. As it continues to collapse, the protostar squashes into an ever tighter, hotter ball.
Our proverbial ice skater spins faster & faster!
Eventually, the left-over material in this disc forms rings. In these rings of dust and gas, called protoplanetary discs, is where planets are born.
But these rings are not found just around single stars.
When two stars are born together and orbit around each other, they are what we call a binary star system. Most stars are part of binary systems. We also believe that around half of all planets are in binary systems!
It’s like a special cosmic geometry problem that forces us to look at all of the different pieces of the puzzle.
Astronomers using ALMA, the Atacama Large Millimeter/Submillimeter Array radio telescope in Chile, are studying these protoplanetary discs around protostars in binary systems.
To their surprise, the geometry is not very clean & simple. The binary stars and their discs of material do not always line up like you might expect them to.
They found that if the two protostars in a binary system take a longer time to orbit each other, and are in a large, slow orbit where the two stars are relatively far apart, then it appears more likely that their protoplanetary discs will not be aligned to the parent stars.
The shorter the orbital period of the binary star, the more likely it is to have a disk in line with its orbit.
How short?
Well, where the central stars have orbital periods less than 40 days, the orbital planes are quite closely aligned, within 3 degrees.
When the binaries have periods longer than 40 days they typically have misaligned disks. In one case the disk was fully perpendicular, with a polar orbit. This appeared to be a stable system in the computer models.
So you might well ask: “Well, why does this happen?”
Short orbital period binary stars, with their closeness to each other, exert tidal friction on each other and gradually change their orbits from ellipses to circles.
Then, over millions of years, this gravitationally tugs the protoplanetary disk into alignment with the orbit of the two stars.
And the binary stars that have longer orbits, those over 40 days? They have disks that are arranged in all possible inclinations from co-planar to polar.
Based on this finding, the astronomers believe that so-called “misaligned” planets around binary stars should also be out there for us to find!
Now, it’s not likely that there’s a huge number of them, but they’ll be out there! And you can be sure that astronomers are looking for them!
Tatooine here we come!
Hey Here’s A Cool Fact:
As a protostar grows and evolves into a star, it experiences a huge increase in temperature. Eventually the heat & pressure is enough to start nuclear fusion and voila! A star is born!
This can take it from a freezing -250°Celsius to anywhere up to 40,000°C on its surface when it becomes a fully fledged star!
If our spinning ice skater does this she’ll melt right through the ice!
Thank you for listening to the 365 Days of Astronomy Podcast!
Oh, and wash your hands everybody! Please.
End of podcast:
365 Days of Astronomy
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