Podcaster: Fraser Cain 

Title: Guide to Space: Are There Dark Matter Galaxies? ft. Sarah Pearson from Space with Sarah

Organization: Universe Today


Description: We know there’s dark matter, and there are galaxies, but are there galaxies entirely made up of dark matter? Astronomer Sarah Pearson joins Fraser to talk about what’s out there.

Bio: Fraser Cain is the publisher of Universe Today 

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Welcome back to the second part of our special, 2-part episode on finding and preventing asteroids from hitting Earth. In the first half, which you should totally watch first, we discussed the threat from asteroids, and what observatories and surveys are actively searching for dangerous space rocks.

But let’s say that we do find an asteroid, and we know with a high degree of certainty that it’s going to smash into the Earth in the future. What can we do about it? What missions, techniques and technologies do we have at our disposal?

Before we get into these ideas, though, it’s important to map out the problem, so you can understand why the solutions might not be as simple as you’re hoping.

First, anyone who’s played Kerbal Space Program understands that traveling in space is all about orbits. It’s not that a space rock is on a collision course with Earth, although there could be some on highly eccentric orbits. 

It’s that Earth shares a region with hundreds of thousands of rocks known as Near Earth Asteroids. Instead of a cosmic shooting gallery, imagine an asteroid race track, where various objects are going around and around the Sun in a cloud with the Earth. The Earth’s gravity, and their interactions with each other can cause their orbital trajectories to change.

A previously safe asteroid could be jostled into a new orbit that could bring it into a collision course with Earth after many many orbits into the future. Chaos reigns with these calculations, and beyond a number of orbits, it’s hard to predict the future trajectories again. Which is why we need to be constantly vigilant to the skies. 

The asteroids themselves aren’t the same either. Some are that classic chunk of rock, that you’ve seen the Millennium Falcon dodge, but many others are just a pile of rubble, held together by mutual gravity.

So, let’s imagine the various observatories and surveys we discussed in the previous episode do turn up an asteroid with a high likelihood of crashing into Earth, what can we do about it?

End of podcast:

365 Days of Astronomy
The 365 Days of Astronomy Podcast is produced by Planetary Science Institute. Audio post-production by Richard Drumm. Bandwidth donated by 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 or email us at This year we will celebrates the Year of Everyday Astronomers as we embrace Amateur Astronomer contributions and the importance of citizen science. Join us and share your story. Until tomorrow! Goodbye!

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