Previous: Why Is the Night Sky Dark?
Next: 3 Galaxies That Shouldn't Exist



View count:116,848
Last sync:2020-11-20 08:15
The universe gets a little weirder, and more dangerous, every time we study it. Understanding space weather, which can mess with our communications systems, will take strategic planning to monitor.

Hosted by: Hank Green
Support SciShow by becoming a patron on Patreon:
Dooblydoo thanks go to the following Patreon supporters—we couldn't make SciShow without them! Shout out to Bella Nash, Kevin Bealer, Mark Terrio-Cameron, Patrick Merrithew, Charles Southerland, Fatima Iqbal, Benny, Kyle Anderson, Tim Curwick, Will and Sonja Marple, Philippe von Bergen, Bryce Daifuku, Chris Peters, Patrick D. Ashmore, Charles George, Bader AlGhamdi
Like SciShow? Want to help support us, and also get things to put on your walls, cover your torso and hold your liquids? Check out our awesome products over at DFTBA Records:
Looking for SciShow elsewhere on the internet?

Artist’s impression of ram pressure stripping (Credit: ICRAR/NASA/ESA/Hubble Heritage Team) -
Galaxy cluster (Credit: NASA/ESA/Hubble Heritage Team, public domain) -

CME (Credit: NASA Goddard Space Flight Center) -
For reference: Earth-Sun Lagrange points -
Hank: Our space weather forecasts are about to get a lot better, because the ESA recently got funding for a satellite to predict solar weather, which they’re planning to launch by around 2023.

Solar weather satellites monitor the radiation streaming out from the Sun, which can sometimes become extra dangerous. Solar flares can send lots of extra radiation toward Earth, which can mess with our communications systems. Then there are Solar flares, or CMEs, where a wave of highly magnetic plasma is sometimes blown away from the sun. They’re actually kind of scary.

A severe CME hasn’t hit Earth since the 1800s, but if one does, it has the potential to cause a lot of problems – including knocking out communications satellites and power grids. With the space weather satellites we have now, we could detect one of these CMEs about 16 hours before it gets to Earth, which would give us much less than the 2-3 days we’d need to prepare for the hit.

But this new satellite would give us about 5 days of warning, because the ESA will probably put it in a spot called L5, one of Earth’s Lagrange points. Lagrange points are like the parking spots of the solar system, where the gravitational force of two objects – in this case, the Earth and the Sun – balance out. Placing a satellite in a Lagrange point means it will stay in the same position relative to the Earth and the sun, so it’s perfect for observation.

The L5 spot is 60 degrees behind Earth in its orbit around the Sun, and right now, we don’t have any space weather satellites there. But it’s a great place to monitor the Sun’s activity, because the satellite will be able to see developing sunspots, which can release CMEs, before they face Earth directly. Other satellites can’t detect CMEs until they’re hurtling toward us, which is why they can only give us less than a day’s warning. But an L5 satellite could see sunspots coming 4-5 days before other satellites, so astronomers could at least raise the alarm that there’s a higher risk for solar weather.

The first design phase of the satellite recently received funding, and they’re hoping to get the rest of the money they need during the next major ESA funding meeting in 2019. So hopefully soon we’ll be keeping a closer eye on that strange, unpredictable Sun of ours.

Speaking of plasma messing with things: in a study published last week in Monthly Notices of the Royal Astronomical Society, a group of astronomers announced that they’ve figured out why some galaxies die early.

Galaxies are considered dead when they stop producing new stars. This usually means all the thick gas in the galaxy, which can condense into stars, is either lost or used up. Normally, by determining the amount of gas in a galaxy, astronomers can calculate approximately how long it will take for a galaxy to die off. But in galaxy clusters -- groups of hundreds of galaxies -- we’ve seen some galaxies die much earlier than we’d expect.

We already know why that happens: these galaxies are basically murdered by intergalactic plasma, an electrically charged gas that’s spread throughout galaxy clusters. It’s all part of a process called ram-pressure stripping. If like "murdered by intergalactic plasma" wasn't a cool enough phrase, now we have "ram-pressure stripping."

Galaxy clusters seem to have a lot of dark matter inside of them, and that causes the galaxies to drift around as the dark matter draws them in. While they’re wandering through their neighborhood, these galaxies might pass through clouds of intergalactic plasma, which creates drag on the thick gas in the galaxy -- kind of like how the Earth’s atmosphere slows down a rocket going to space.

If it’s strong enough, the drag can be enough to overcome the galaxy’s gravitational force, and the gas can be swept away. Less gas means less star creation, so bye bye, galaxy!

But until now, we’ve only seen this happen in those big galaxy clusters. In the new study, the researchers found that ram-pressure stripping happens in galaxies outside of big clusters, too. Most galaxies don’t live in clusters — instead, they float around in groups of two to a hundred galaxies, where there’s much less dark matter to push them around.

The researchers analyzed more than 10,000 galaxies outside of clusters, and found that their gas was being stripped away too. And based on their analysis, they think ram-pressure stripping might be the biggest galaxy killer in the universe. From galaxy-killing plasma to solar storms, the universe gets a little weirder -- and more dangerous -- every time we study it. Hope that you don't get murdered by intergalactic plasma...

Thanks for watching this episode of SciShow Space, and thanks especially to our patrons on Patreon, who give us money so that we can keep making this show. If you want to help us keep bringing you the lateset space news to you, go to And don’t forget to go to and subscribe!