A scientific fact/tidbit you recently learned that you thought was interesting

[Emily's Cat]

Proximity to a star is not essential for liquid water. There are oceans of water under the surface of several of the moons of Jupiter and Saturn, where life might well exist.

But being too close to the star prevents the formation of liquid water, as well as increases the damage from stellar ejections, radiation, etc.

There's a generally accepted "habitable zone" for planets where it's possible for liquid water to form, and thus for life (as we know it) to evolve. Planets need to be close enough to receive enough energy to prompt the formation of complex organic molecules, but far enough away that the formation of liquid water isn't impossible. For red dwarfs, in order to have enough energy to develop complex organic molecules, the planet also has to be so close that it can't form water. There is no habitable zone.

 

[Emily's Cat]

And which could also be happening on moons in the planetary systems of red dwarfs, so such systems could support life. If we rule them out because there would be no planets in the Goldilocks zone, as was suggested, we might be significantly underestimating the number of possible abodes of life in the universe.

Hypothetically, perhaps. But then we're talking about trying to locate the teapot that might or might not be circling Mercury... rather than trying to locate one of several possible teapots at the local antique store.

It's playing the odds. We have limited resources and a really, really, really big universe. Why would we spend effort looking for cases around red dwarfs where outlier conditions capable of producing life might or might not exist... when there are still a whole lot of other stars that we know for sure produce a habitable zone?

 

[lomiller]

Actually, no, not really. Earth receives 44 quadrillion (4.4 x 10¹⁶ W) watts of energy (well, ok, POWER) from the Sun. Earth's core is estimated to produce about 44 terawatts (4.4. x 10¹³ W). That's 0.1% of the energy that comes from the Sun, or about the same percentage of the total energy.

Google seems to agree with you but I think this number is wrong.

Radius of the Earth ~ 6.4*10^6m
This means the earth carves out a spear of 3.14 * 6.4 * 6.4 * 10^12 m^2
or: 129*10^12 m^2
TSI at the top of the atmosphere is ~1370W/m^2

so total power = 1.37*129*10^15 = 1.76*10^17W


The Google answer seems to come from this NASA pdf which says
https://www.nasa.gov/pdf/135642main_balance_trifold21.pdf

The Sun is the major source of energy for Earth’s
oceans, atmosphere, land, and biosphere. Averaged
over an entire year, approximately 342 watts of solar
energy fall upon every square meter of Earth. This is
a tremendous amount of energy—44 quadrillion (4.4
x 1016) watts of power to be exact.

But...
The total surface area of the earth is 5.1*10^14 m^2
342*5.1*10^14 = 1.74*10^17W (same as above)

TSI ~1370 W/m^2 for the part of the earth facing the sun, to find the average over the entire earth you can divide by 4 (area of a Sphere/area of a circle with the same radius) which is where the 342 number comes from. I suspect someone (probably me lol) is applying this conversion incorrectly.

 

[bigred]

Why the latter?

Red dwarf stars last much longer than stars like our sun, so the window of opportunity for life to begin and evolve in such systems would be immense. Earth was already about two thirds of the way through its window when complex life evolved here.

- Highly prone to flares that would wipe out life
- Extremely high emission of x-rays that could sterilize the planet
- One or two other things I forget

 

[bigred]

Well, what I learned recently: Hi, my name is Hans and I'm stupid. A stupid audiophile, to be exact. Turns out that getting a sound card that does 32 bits sampling at 384 kHz makes no difference whatsoever:

Yeah basically anything beyond 24 bit depth and 96kHz sample rate is overkill and in fact higher sample rates are if anything worse. More isn't always better. In fact, odds are you could never tell a diff beyond 24/44.1 for that matter (which is what CDs are made at).

 

[bigred]

Looking up something on stars from this and found that apparently we are finding really....really...cool stars: https://skyandtelescope.org/astronomy-news/the-coolest-stars-ever-found/

And it brought up an interesting point we are reaching of when is it a star and when is it just a really big gas planet? This leads me to think that maybe we should say we have 6 planets, not 8, and two really cool stars in the middle. I mean what's a star? A big ball of gas!

 

[lomiller]

Looking up something on stars from this and found that apparently we are finding really....really...cool stars: https://skyandtelescope.org/astronomy-news/the-coolest-stars-ever-found/

And it brought up an interesting point we are reaching of when is it a star and when is it just a really big gas planet? This leads me to think that maybe we should say we have 6 planets, not 8, and two really cool stars in the middle. I mean what's a star? A big ball of gas!

A star needs to have enough gravity and pressure to fuse hydrogen into helium in their core and Jupiter is too small for that. It would need to be at least 85 times more massive for that.

A science tidbit I learned while checking the minimum mass for a star is that brown dwarfs ~15 - 85 times larger than Jupiter are massive enough to fuse Deuterium and in some cases Lithium but not Hydrogen.

 

[Ziggurat]

Looking up something on stars from this and found that apparently we are finding really....really...cool stars: https://skyandtelescope.org/astronomy-news/the-coolest-stars-ever-found/

And it brought up an interesting point we are reaching of when is it a star and when is it just a really big gas planet? This leads me to think that maybe we should say we have 6 planets, not 8, and two really cool stars in the middle. I mean what's a star? A big ball of gas!

A star should have self-sustaining fusion reactions. I don't think Jupiter and Saturn qualify.

 

[bigred]

I was kidding...but it was interesting to me how the differences aren't as stark as I'd always felt they were. I do still think it's weird to call a big ball of gas a "planet," but I guess the options are limited...it looks like one after all.

 

[Ziggurat]

I was kidding...but it was interesting to me how the differences aren't as stark as I'd always felt they were. I do still think it's weird to call a big ball of gas a "planet," but I guess the options are limited...it looks like one after all.

Trivia for you: the sun and the moon were originally categorized as planets, and Earth was not.

 

[Jack by the hedge]

... In fact, odds are you could never tell a diff beyond 24/44.1 for that matter (which is what CDs are made at).

I suspect you meant 16/44.1 as the CD standard is 16 bit. But your point stands; 16 bits are enough, if the recording is properly mastered to use the full range.

 

[Emily's Cat]

Google seems to agree with you but I think this number is wrong.

That's a lot of numbers and my brain is tired. That said... Off the top, I think you need to adjust for the fact that only half the earth is facing the sun at a time, not the entire thing.

Maybe I'm being overly simplistic?

Radius of the Earth ~ 6.4*10^6m
This means the earth carves out a spear of 3.14 * 6.4 * 6.4 * 10^12 m^2
or: 129*10^12 m^2
TSI at the top of the atmosphere is ~1370W/m^2

so total power = 1.37*129*10^15 = 1.76*10^17W


The Google answer seems to come from this NASA pdf which says
https://www.nasa.gov/pdf/135642main_balance_trifold21.pdf



But...
The total surface area of the earth is 5.1*10^14 m^2
342*5.1*10^14 = 1.74*10^17W (same as above)

TSI ~1370 W/m^2 for the part of the earth facing the sun, to find the average over the entire earth you can divide by 4 (area of a Sphere/area of a circle with the same radius) which is where the 342 number comes from. I suspect someone (probably me lol) is applying this conversion incorrectly.

 

[bigred]

I suspect you meant 16/44.1 as the CD standard is 16 bit. But your point stands; 16 bits are enough, if the recording is properly mastered to use the full range.

Yes, my bad. Of course you will get those arguing the superiority of 24 bit or even 32 24 does give you a better noise floor, but about oh 99.9% of the time even that is overkill and unnecessary.

That said, I record at 24/48. lol

 

[HansMustermann]

That particular tidbit is new to me.

Would moons like the ones in our solar system that might potentially have life, i.e. that circle gas giants a long way out from the star, be as badly affected?

It's fairly new-ish to everyone, scientists included.

Of course, if you're far away enough from the star, you're not going to a be affected as much by a mega-flare. The inverse square law still applies. But we're probably back to the same situation as those moons. They might have liquid water under the ice, and possibly support bacterial life, but probably wouldn't be top candidates for colonization.

 

[HansMustermann]

@lomiller
I suspect that the difference is in the albedo. As they say later in the paper, not all energy from the sun is making it all the way to the surface. Most of it is reflected right back by the clouds, ice, hell, even plants don't absorb green which is why they're green, but also is the spectral peak. Which is also why I didn't just use that cross section.

Of course, since they don't actually show their maths in the paper, it's hard to be sure.

 

[lomiller]

@lomiller
I suspect that the difference is in the albedo. As they say later in the paper, not all energy from the sun is making it all the way to the surface. Most of it is reflected right back by the clouds, ice, hell, even plants don't absorb green which is why they're green, but also is the spectral peak. Which is also why I didn't just use that cross section.

Of course, since they don't actually show their maths in the paper, it's hard to be sure.

~30% of the sunlight that reached is the earth is reflected, but the discrepancy between the two numbers is almost exactly 4X which is exactly the difference between TSI and average insolation across the entire earths surface after accounting for the fact only one side of the earth faces the sun.

 

[Skeptic Ginger]

Looking up something on stars from this and found that apparently we are finding really....really...cool stars: https://skyandtelescope.org/astronomy-news/the-coolest-stars-ever-found/

And it brought up an interesting point we are reaching of when is it a star and when is it just a really big gas planet? This leads me to think that maybe we should say we have 6 planets, not 8, and two really cool stars in the middle. I mean what's a star? A big ball of gas!

I have an image in my head of an astronaut with a Bic lighter about to ignite Jupiter.

 

[pzkpfw]

I have an image in my head of an astronaut with a Bic lighter about to ignite Jupiter.

2010 was 13 years ago.

(https://en.wikipedia.org/wiki/2010:_Odyssey_Two)

 

[Oystein]

That's a lot of numbers and my brain is tired. That said... Off the top, I think you need to adjust for the fact that only half the earth is facing the sun at a time, not the entire thing.

Maybe I'm being overly simplistic?

What counts is the projection of the planet - i.e. the circle that has the same radius.
Remember: The bit of planet surface that is directly facing the sun, i.e. where the sun is in the very zenith, receives 100% of the power, whereas a point where the sun is curretly hugging the horizon (subrise or sundown) is barely getting any wattage at all.
The amount of energy from the sun available to be absorbed by the planet is the amount of radiation within a circle with the circumference of the equator.

 

[arthwollipot]

According to some people, it's possible that the Icelandic Vikings independently invented gunpowder and used it in weapons.

Personally, I'm still a bit skeptical, but here it is:

Viking Atgeirr: Reevaluating the Origins of European Firearms (Forgotten Weapons, 19:24)