Stargazing Wasp-76b is a planet where it rains iron

[DennisN]

Summary:: A planet where it rains iron!

https://www.bbc.co.uk/news/science-environment-51828871
"Wasp-76b, as it's known, orbits so close into its host star, its dayside temperatures exceed 2,400C - hot enough to vaporise metals.

Can we really be sure this is the case? In other words, is the result ironclad?

Because,

Using the Espresso spectrometer, the scientists detected a strong iron vapour signature at the evening frontier, or terminator, where the day on Wasp-76b transitions to night.

My critique:

Using a spectrometer designed to measure the components of caffeine does seem suspect.
There could have been caffeine residual in the spectrometer.
And espresso is strong, so the person doing the measurements could have had shaky hands.

 

[Borek]

Wow, it is not a typo: https://en.wikipedia.org/wiki/ESPRESSO

 

[trurle]

Weird! If it rained iron on the cold side, one might expect sooner or later all the iron would be there if the planet is tidally locked, so maybe despite its closeness, it isn't. Alternatively, deep down, there must be some means of transporting it back to the hot side. As an aside, deep down, the pressure is immense and iron might be expected to be solid. I suspect there is a lot we don't know about this world.

The same neutral iron signatures were detected in WASP-121b too, therefore occurrence must be pretty common. Interesting, both WASP-76b and WASP-121b are orbiting F-class stars. It may be coincidence or consequence of neutral iron circulation requiring abundant ultraviolet irradiation.
Regarding transport of iron, i suspect both WASP-121b and WASP-76b could have rapidly super-rotating atmospheres with complex clouds, similar to Venus. In this case, ultraviolet-rich sunlight will result in strong temperature inversion at subsolar point (tropopause at pretty high pressure). And strong wind at high enough pressure may prevent a layer of "iron clouds" from settling. If my hypothesis is correct, these planets will not have iron rain - only iron haze/fog will be present.

 

[Auston Louis]

Gosh! A planet that rains nuts, bolts, washers and nails!

 

[Nick-stg]

maybe it's raining aluminum on one side and aluminium on the other

Aluminium is sufficiently active that it would only exist as the oxide. Iron oxide would be reduced to iron by the hot hydrogen, but aluminium should remain as an oxide

If there would be oxidized aluminium falling from the sky. Would it not be more accurate to describe it as snowing? Oxidized aluminium is alumina a fine white powder.

 

[sysprog]

If there would be oxidized aluminium falling from the sky. Would it not be more accurate to describe it as snowing? Oxidized aluminium is alumina a fine white powder.

I imagine that you know that what we in the US call aluminum oxide (as distinguished from what the Brits call 'aluminium' oxide -- same stuff; different spelling), is used as a pigment in some white paints, so maybe yes, 'snowing' might be more apropos than 'raining'. I was joking about a small difference between US English and Brit English regarding the orthography of the term for the element.

I think that it's not entirely Humphrey Davy's fault, although apparently he vacillated on the spelling of the name for the element that he had identified; it was the people pushing the agenda of 'ium' ending for names of elements instead of acceding to the wishes of the person who had isolated and characterized the element -- their fault too -- from https://www.thoughtco.com/aluminum-or-aluminium-3980635:

​

In 1808, Sir Humphry Davy identified the existence of the metal in alum, which he at first named "alumium" and later "aluminum." Davy proposed the name aluminum when referring to the element in his 1812 book Elements of Chemical Philosophy, despite his previous use of "alumium." The official name "aluminium" was adopted to conform with the -ium names of most other elements. The 1828 Webster's Dictionary used the "aluminum" spelling, which it maintained in later editions. In 1925, the American Chemical Society (ACS) decided to go from aluminium back to the original aluminum, putting the United States in the "aluminum" group. In recent years, the IUPAC had identified "aluminium" as the proper spelling, but it didn't catch on in North America, since the ACS used aluminum. The IUPAC periodic table presently lists both spellings and says both words are perfectly acceptable.​

I suppose that if $\rm {Al_2O_3}$ is descending from the sky, whether to call it rain or snow should depend at least in part on the temperature.

 

[Nick-stg]

I suppose that if Al2O3Al2O3\rm {Al_2O_3} is descending from the sky, whether to cal it rain or snow should depend at least in part on the temperature.

its dayside temperatures exceed 2,400C

According to wikipedia alumina has a melting temp 2072C. Darn! I missed by 300C.

I knew the melting point was high. I guess the strategy of post first, check facts later has failed me again.

 

[sysprog]

I guess the strategy of post first, check facts later has failed me again.

No way man 'ready; fire; aim' always works for me . . .

 

[swampwiz]

This will be Earth's fate about 6 billion years hence.

 

[trurle]

Warning! The "iron rain" on WASP-76 b is now refuted. Seems the confusion happened due light pollution from nearby star.
https://arxiv.org/pdf/2005.02374.pdf

 

[PAllen]

I think that @russ_watters, if he's not too busy stargazing , might be able to answer that question better than I am able to answer it.

Isn't that Russ_dihydrogen_monoxide (with t added to make it a better drink) ?

 

[Dragrath]

Warning! The "iron rain" on WASP-76 b is now refuted. Seems the confusion happened due light pollution from nearby star.
https://arxiv.org/pdf/2005.02374.pdf

Reading this through it hasn't been refuted per say since refuted is a strong word. Here there still seems to be a signal but it is just below the threshold for detection using the given spectrometer and telescope without the contamination of the systems K type companion star. There also is still strong signals of TiO and water but the Vanadium oxide signature has disappeared. I feel we need to be careful not to over-sensationalize or make preemptive claims. This is the sort of things that leads to confusion among the general public and results in their errosion of confidence in science as it "contradicts itself" I feel the uncertainty of observations need to be better conveyed so that things in that grey area are described as such.