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Comment by phyller | Hacker News Reader

I call BS. I'm not saying the planet doesn't have iron or titanium, just that I don't think their data shows it.

The researchers supposed that this planet might have iron and titanium in the atmosphere, they have an image of the star with a slight dimming from the passing of the planet across it, and they find the spectral signature of iron and titanium.

The percentage of the light collected that was emitted by iron and titanium, if it existed in the atmosphere, would be so mind-boggling minuscule compared to the light of the star itself, I would think that the iron and titanium signatures would come from elements trapped in or around the star.

I think if they looked hard enough they could find whatever elements they want.

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So quick to call BS without knowing what you're talking about. Transit spectroscopy is a well established scientific method. To put it simply... obviously they accounted for that.

I should apologize, I am probably, hopefully wrong. I'm still skeptical but clearly more work has been put into this than I realized and I shouldn't have been so quick to condemn it.

Life is short. It's fun to have opinions if you are willing to be wrong :)

I'm glad this had a happy ending! :D

Sometimes I feel bad piling on a downvote train -- especially considering the psychology research showing that people usually just dig in further in such situations...

Honestly I feel like we shouldn't be down voting opposing opinions. Those should be the ones rising to the top, because that's the best way to cross reference, and get a different perspective.

I think the only things that should sink to the bottom are distasteful or rude comments.

To be honest, it would have been better to explain how they do the spectroscopy than to just say "you don't understand" and downvote. I should have raised a question instead of making a statement, the response should have been an explanation, instead of basically "you're an idiot" (which still no one has done as of this time). They are making the same error I did. The article posted didn't explain, the paper costs $9 to read. I wouldn't call this a productive discussion at this point.

Edit: someone just attempted to explain the technology behind it, thanks amluto

Respect for recognizing that you started things off on the wrong foot. Not everyone is willing to take ownership like that.

You are totally right, the best response is a clear, calm explanation. Unfortunately, the time, energy, and expertise to do so is not always available. It's in moments like those where I hesitate between ignoring the comment entirely and downvoting.

As for transit spectroscopy, I'm going off memory/rederivation/speculation here (not sure how much of each), but I believe it works by first taking the spectrum of the parent star by itself, then observing the spectrum of the starlight travelling through the transiting planet's atmosphere, and then diffing the two results to isolate the spectrum of the planet's atmosphere.

It works basically like that. The spectrum of the star will be an absorption spectrum. The star produces a continuous spectrum and then the atoms in its atmosphere absorb specific wavelengths. The light then travels through the planet's atmosphere where other atoms and molecules absorb other wavelengths; the signatures of which are known, telling scientists the makeup of the atmosphere.

Ah yeah, that makes sense. Thanks for clarifying!

Email the authors. There's a 50-50 chance they'll just give you the paper.

Though I wouldn't lead with calling BS ...

Totally agree with you anecdotally. When I am heavily downvoted on any site, I instantly believe my own dogma more, whether it is right or wrong, because now it is "mine" and it's under attack like a poor little defenseless puppy.

The fact that this was doable doesn’t surprise me. A spectrometer essentially outputs an intensity as a function of wavelength. The output is a combination of the signal plus a background from the star plus mostly additive noise. The researchers knew what signal they wanted to find, and standard statistical techniques are very good at this.

The data used in this paper came from an instrument called HARPS North. This is an amazing spectrometer. Forget finding a signature from iron — HARPS North can detect a Doppler shift of a bright spectral line or less than 1 cm/s. This lets it detect planets by measuring the degree to which they wiggle their star.

(For an old classic example, there’s a device called a lock-in amplifier that looks for a specific sine wave modulation of a noisy signal. They are extremely sensitive.)

Compulsory link to save google a search:

https://en.wikipedia.org/wiki/Lock-in_amplifier

Did you read the paper?

https://www.nature.com/articles/s41586-018-0401-y

Tone judgments aside, I think it's okay to be skeptical because spectroscopy is far from an exact science. Reminds me of the sensational "diamond planet"[0] a few years ago that was based on a dubious interpretation of the host star's spectrum.[1]

[0] https://www.forbes.com/sites/petercohan/2012/10/12/diamond-p...

[1] https://uanews.arizona.edu/story/diamond-super-earth-may-not...

The research is fine, but the clickbait title of this article is BS. The Iron and Titanium are not in a metalic state, so - no metalic sky

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