Podcaster: Richard Drumm

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Title: UNAWE Space Scoop – A Stellar Ballet

Organization: 365 Days Of Astronomy

Link : http://365daysofastronomy.org/ ; https://spacescoop.org/en/scoops/2121/a-stellar-ballet/

Description: Space scoop, news for children. 

By studying white dwarf stars, and finding some of them, well, in a way polluted, astronomers have found that most rocky exoplanets are made of rocks we can’t find anywhere in our Solar System.

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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…

These exo-rocks are stranger than fiction

We know there are thousands of planets orbiting distant stars in our galaxy. We call them exoplanets. 

However, knowing what these exoplanets are made of has always been kinda tricky.

Until now. 

By studying white dwarf stars, and finding some of them, well, in a way polluted, astronomers have found that most rocky exoplanets are made of rocks we can’t find anywhere in our Solar System.

White dwarfs are what stars like our Sun become at the end of their lives. 

As they die, they expel the gas around them until all that remains is the dense, collapsed, hot core of the star.

The so-called ‘polluted’ stars contain material from planets or asteroids that used to orbit the former star that eventually fell into the white dwarf, polluting its atmosphere. 

An atmosphere that had been mostly made of hydrogen and helium, now had other elements mixed in.

Astronomer Siyi Xu of NOIRLab and geologist Keith Putirka of Cal State University, Fresno, studied 23 of the polluted white dwarfs that are within 650 light-years from our Sun. Comparatively close by.

They used the time-tested technology of spectroscopy to look for elements that were not hydrogen or helium, you know, just to see what they would find. 

By measuring how abundant these other elements are, it’s possible to reconstruct the minerals and rocks that formed the rocky planets that once orbited around these distant, dead stars. 

And guess what? 

The researchers found much more than your everyday calcium, magnesium or iron. 

You see, some combinations of minerals do not even exist in our Solar System and the team had to come up with some quite interesting names to classify these new types of rocks.

For example, on our Earth we can find:

– Periclase, a magnesium mineral from rocks that have changed over millennia as a result of high heat and pressure. 

– Pyroxene, a silicate mineral found in volcanic rocks, and 

– Quartz, a crystalline form of glass.

But you probably won’t hear about geologists finding “quartz pyroxenites” or “periclase dunites” anywhere on our planet. 

That’s because they don’t exist on our planet. 

They had to invent the terms to describe what they found.

These rocky exoplanets were chock-a-block with the stuff. 

Some of these rocks could even dissolve more water and some might melt at much lower temperatures than the rocks we have on Earth. 

These minerals could affect the formation of oceans and plate tectonics in those worlds.

There will be some very interesting next steps for scientists to figure out what’s going on. 

So if you think all rocky planets look like our Earth, think again!

Hey, here’s a cool fact!

Stars have atmospheres of a sort, gasses that aren’t part of the core, or the other inner zones of the star, but are near the surface of the star.

An outer part of our Sun’s atmosphere is called the photosphere and light from there powers life on Earth.

The atmospheres of these polluted white dwarfs are rich in magnesium and poor in silicon.

Our Earth has a metal core and silicon dioxide rich rocks closer to the surface. 

So the lack of silicon in the white dwarf atmospheres suggests that the pollution in the star that the team was looking at, came from the interior of the doomed rocky planets and not their surface.

Poor planets. Swallowed whole by their stars.

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 Planetary Science Institute. 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. 

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