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From binary systems to solar systems, things in space tend to exist together, like little families. Stars will form out of the same parent cloud, many asteroids can come from a single parent body, and even Earth has siblings in Mars and Venus.

And this week, we're on the brink of learning a lot more about one of our own planet's siblings, and a new photo of a companion star is solving a mystery. But let’s start closer to home: at the time we’re filming this, the InSight lander is set to launch this Saturday from the. Vandenberg Air Force Base in California, weather permitting.

InSight stands for Interior Exploration using Seismic Investigations, Geodesy and Heat Transport, and the mission’s main goal is to learn more about the geology of Mars. We’ve been visiting the planet for almost fifty years, and we still know next to nothing about what’s happening inside it. We don’t even know how thick Mars’ crust is, for example.

Or the size of its core. Or how much of its core is liquid. So this mission is going to help us figure some of that out, which should give us more clues about the planet’s formation and history.

InSight is a lander, not a rover, so it’s going to be staying in one place. But it’ll be able to do all kinds of science from that one place, using three main instruments:. HP3, RISE, and SEIS.

To figure out Mars’ rate of cooling, HP3, the Heat Flow and Physical Properties Probe, is going to drill 5 meters into the crust, leaving behind heat sensors every so often along the way. RISE, or the Rotation and Interior Structure Experiment, is going to get really precise measurements of Mars’s rotation and wobble. Those tiny fluctuations in the planet’s movements are affected by the stuff inside it, like if there’s liquid sloshing around.

So these measurements should tell us how big and solid Mars’s core is. Meanwhile, SEIS, the Seismic Experiment for Interior Structure, is going to monitor Mars’s seismic vibrations, telling us how active it is right now. We know that Mars used to be geologically active, because it has all kinds of leftovers from that time: volcanoes, remnants of hot springs, and lava flows all over the place.

And while Earth’s geological activity is driven by our internal heat and plate tectonics, for Mars, it’s a different story. Mars is still cooling down from its formation. But it’s a lot smaller than Earth, so it’s been able to cool down faster, and these days its tectonic activity is much more subtle.

A few times a year, the planet experiences “marsquakes,” which are caused by things like cracks in its crust or meteorite impacts. This will be the first time we’re able to directly measure these quakes, and we should be able to use the data to model Mars’s interior, just like we use earthquakes to model Earth’s interior. We’re about to learn so much about our space sibling, and why it’s cold and dead!

So stay tuned for lots of exciting Mars updates once InSight lands in November. But for now, let’s move farther away, and talk about dead stars! Last week, the Hubble Space Telescope’s website released a picture of the star that’s solving one of the major mysteries of supernovas.

When stars are about to die, they often become red giants: they puff out their outermost layers, creating a fluffy, red envelope full of hydrogen and helium. Then, if they’re big enough, they go supernova. But there’s a certain kind of supernova called a stripped-envelope supernova, where a lot of that fluffy blanket seems to be missing.

And when we look at the leftover cloud of dead star stuff, there’s way less hydrogen than there should be. For about half of these supernovas, we think wind from the star blew away that material because the star was so big and unstable. But for the rest, the stars aren’t quite massive enough to generate those kinds of winds, so there must be some other explanation.

One possibility is that each of those stars was in a binary system. The gravitational pull from the companion star could have spun off a lot of that main star’s outer envelope, taking all of that hydrogen and helium for itself. And in the process, it could have destabilized that main star, triggering its explosion.

If this is really what happens, then for a lot of these stripped-envelope supernovas, we should see a companion star after the main star bites it. We’ve taken some measurements of the light coming from stripped-envelope supernovas that seemed to indicate a companion, but those kinds of indirect detections aren’t always the clearest evidence. For example, there could be something between you and your target interfering with the observations.

But in a paper published in the Astrophysical Journal in March, astronomers announced that they’d made a direct detection! They were able to take an actual picture of a supernova’s companion star, and the photo released on the Hubble site last week. Supernova 2001ig used to live in galaxy NGC 7424, about 36 million light years away.

Then it exploded spectacularly in, you guessed it, 2001. And in 2016, the researchers used Hubble to look at the remnants, and they found another star there. The companion star is pretty bright and massive, especially since it stole a whole bunch of matter off of its main star.

It probably survived the supernova because all the matter around it kind of cushioned the impact of the explosion. Before this, the idea that stripped-envelope supernovas might have had thieving companions was a good hypothesis. But now that we’ve directly detected a companion, we know for sure that these kind of star systems do exist!

That helps explain the abundance of supernovas, and especially the abundance of this type of supernova. So this stellar sibling helped us solve a big mystery. Although it also probably contributed to the supernova itself, so it’s both causing problems and solving them.

Which seems about on track for a sibling. Thanks for watching this episode of SciShow Space News. To stay up to date on all the latest discoveries happening in space exploration and research, just go to youtube.com/scishowspace and subscribe! [♪ OUTRO].