How do we know it rains IRON on WASP-76b?

How do we know it rains IRON on WASP-76b?


I’m sure we’ve all heard of exoplanets
where some pretty bizarre stuff goes on, like evaporating exoplanets, whose orbits have
taken them too close to their parent star. Or a planet orbiting a pulsar, likely to be
composed of crystalline carbon, which would be similar, but denser than diamond. However, a newly discovered exoplanet called
WASP-76b, discovered using ESO’s VLT, has been found to have a very special characteristic:
on this planet, temperatures are so hot that instead of water rain, it rains molten iron. How can this be? And how can researchers know this from an
object 640 light years away? Exoplanets are pretty difficult to detect. Most exoplanets are only observed when the
planet’s orbit is aligned just right so that it transits in front of its parent star
from our perspective. Any whose orbits don’t align with our perspective
are exceptionally hard to discover, so chances are that there’s a lot more out there in
our relatively near vicinity that we don’t know about. Exoplanets that are very close to their stars,
with very small orbits, are the easiest to discover, because we can see a very clear
pattern on the star’s light curve over a short period of time. WASP-76b is one such planet. Plus, it is huge, way bigger than Jupiter,
and combine this with the fact that it only takes 1.8 Earth days to make one orbit, it
made it comparatively easy to detect. But detecting the presence of an exoplanet
is one thing, how do astronomers know anything about its physical characteristics? Interestingly, the first thing astronomers
do is find out the physical characteristics of the parent star, WASP-76. The distance to the star is first determined,
and then the star is classified based on its brightness and colour. Knowing the distance helps us determine how
bright it is, and we measure its colour simply by observing it, which helps us determine
how hot it is. If the star is on the main sequence, then
this chart also helps us know the radius and mass of the star, as they all tend to follow
a pattern. Once we have that information, we can determine
the characteristics of the orbiting planet itself. Knowing the mass and radius of the star means
we can measure the mass of the orbiting planet using some clever equations, based on the
Law of Universal Gravitation. As it happens, WASP-76b is a super-Jupiter,
way bigger than our Jupiter. That means that although it is massive, this
mass is spread out across a large volume, likely making it a gas giant. Orbiting this close to the star means the
planet is probably tidally locked, only one side faces the star at any given time. Also, due to the proximity of the planet,
it orbits within the star’s atmosphere, the physics of which we really don’t understand
yet. However, the star facing side will be extremely
hot, estimated to be around 2,400°c, easily hot enough to vaporise metals. Models go on to suggest the night side is
about 1500°c, still blisteringly hot, but much cooler. To really find out what WASP-76b is made of
though, we need to go back to the light curve of the transit. Scientists look for differences in the light
when the planet passes in front of the star, as light from the star will shine through
the planet’s atmosphere. Certain atoms block certain wavelengths of
light, so any reduced wavelengths help us know what is in the atmosphere. This is known as spectroscopy. For WASP-76b, the biggest surprise that scientists
detected was an abundance of iron in the atmosphere! Based on what we know about the planet so
far, it seems like iron exposed to the day side of the planet is vaporised, where it
is transported through strong wind processes to the terminator line between the day and
the night side of the planet. Here, the temperature is low enough for the
iron the cool and condense, producing iron raindrops which fall deeper into the atmosphere. By the time the wind has reached the “morning”
side of the planet, iron can no longer be detected. This remarkable measurement, taken by the
ESPRESSO instrument on ESO’s VLT, is the first time variations have been spotted like
this on an ultra-hot gas giant. Although it probably won’t be the last time! So, there we have it. How it can rain iron on WASP-76b. I have no doubt we’ll be hearing about more
astonishing exoplanet discoveries in the future, there are a lot of missions that have either
launched or will be launched in the not too distant future, helping us get a better understanding
of the universe around us. So, if you enjoyed this video and want to
learn about new discoveries as they come, subscribe so you don’t miss out! Also, a big thanks to my patrons and members
who help support the channel, if you would like the support too and also join the Astrum
Answer polls, check out the links in the description. All the best and see you next time!

95 thoughts on “How do we know it rains IRON on WASP-76b?”

  1. We can tell what the weather is like on a planet 640 light years away yet my local weather is never correct 🤣

  2. How do we know that it's raining iron, as opposed to the planet expelling iron from its orbit as it's very close to the Roche limit and the iron is already in the upper atmosphere? I remember hearing previously that it was leaking iron.

  3. My discord name has always been WASP… And I'm a pro Hearts of Iron IV player… Hearts of…" IRON " IV… This is my planet :D…..

  4. What would it even mean for a gas giant to be tidally locked. Would it be the atmosphere, the planet's core, or it's magnetic field that would always have the same side facing the star

  5. Sometimes I don't watch the videos but I just like listening to Astrum's voice and him talking about the beauties of space

  6. At Earth's atmospheric pressure iron boiling point is >2800°C. This wasn't mentioned, but I guess atmosphere of that giant should be thicker. Therefore I don't believe 2400°C there is enough for significant iron evaporation.

  7. complete non sense,,,,,,,,,,all of it,,,,,,yet we cant get one real photo of "space" or earth" and they're telling us what?

  8. Since the planet is tidally locked, there must be a constant flow of molten iron from the night side to the day side, where it evaporates again. Truly a sight to behold.

  9. If this hot Jupiter is raining iron that means its' core is so hot that it's no longer solid and convection currents are dredging up iron from its' core.

  10. These are the kind of planetary phenomena my 10 year old imagination so wanted to be true! I'm 58 now, and just as awe inspired….

  11. In a court room this would be considered circumstantial evidence and no one really knows. Its a great estimation for sure

  12. I don’t get why we look so far when we don’t know how Mars is like. Why waste time behind this which is light years away.

  13. It sounds like someone just told you something very funny and you are trying not to smirk or laugh while reading. I wanna know what the funny thing was :p

  14. I was watching a video about formation of our moon. When it was forming, it had what looked like oceans of lava. Of course that is too hot for us and we prefer it to be cooled to the point that it is solid rock. Then I thought of our oceans of water. How many life forms may think that is as hot to them as lava is to us. Life may be more adaptive and/or specific to its environment than we think.

  15. I've said it before and I'll say it again, Astrum's videos should make it on a streaming service like CuriosityStream or other documentary oriented services. They are simply THAT good.

  16. this claim is bogus…………..640 light years is one millon times as far as pluto.very hard to believe such detailed stats.

  17. I think we're going to be surprised when we get to all of these places only to find out it's nothing like we thought

  18. Seriously, every time I hear about something new in space, it reminds me how little of the universe exists on earth. Yet this is our whole world, and the only world we know of yet with life – or at least life that's definitely biologically compatable with us.

  19. "Iron Rain" would made a cool rock band name. Heck, we have had Iron Butterfly, Iron Maiden, Iron Angel, Iron Cross, et al. And let us not forget…METALLICA! Great video Alex…rock on!

  20. I see planets intersecting a star's corona but everything is fine 'cuz the 'cooler' planet condenses stellar matter (plasma and energetic particles) before the star boils the planet down to the interior. Maybe not for this planet in particular. The way I see it, this condensate combines with free atmosphere released from the crust to form a kind of 'doped' epidermis, a protective skin boundary usefull in later coronal interactions with the planet's orbit which is evening out its eccentric approach. The planet continues to be shielded by its very strong magnetosphere, and an ionosphere, its atmosphere and crust and all the structural spheres of its bodily matter. Being 'doped' to semiconduct the energy of solar radiation which traverses past the atmosphere down to the crust (spawning the arrival of photo-synthesizing multi-cellular plant-life perhaps).
    There is a fuzziness to the reality of nature, where all the variables required for a given, deterministically black-and-white logic, are also peripherally impacted by wider variables acting globally and locally.

  21. I love your channel, but non of this can be confirmed or denied and I have to take it on faith that it's true, because some so called expert somewhere declares it to be true.. How is this different from religion??

  22. In winter waspinators bundle up in asbestos to go skating on frozen iron lakes and have a nice cup of lava to warm up.

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