APOD: A Galaxy of Horrors (2020 Oct 31)

[APOD Robot]

A Galaxy of Horrors

Explanation: Explore extreme and terrifying realms of the Universe tonight. If you dare to look, mysterious dark matter, a graveyard galaxy, zombie worlds, and gamma-ray bursts of doom are not all that awaits. Just follow the link and remember, it's all based on real science, even the scary parts. Have a safe and happy halloween!

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[Ann]

Well, I was a little bit disappointed in the galaxy of horrors in this APOD, so I thought I'd post my own:

Bear Paw galaxy, NGC 2537. Two prints appear to be visible. Horror! Photo: nytecam.

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Bear Paw galaxy, NGC 2547. Horror! It's aglow! Photo: SDSS.

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Warning, there's a bear in the sky!

Ann

[heehaw]

Unbearable horror!

[sillyworm 2]

Fun! A little frustrating....the closest one is 1411 light years away.Let's hurry things up a little with the the space warp drive please.It's all such a big tease.

[johnnydeep]

A Galaxy of Horrors

Explanation: Explore extreme and terrifying realms of the Universe tonight. If you dare to look, mysterious dark matter, a graveyard galaxy, zombie worlds, and gamma-ray bursts of doom are not all that awaits. Just follow the link and remember, it's all based on real science, even the scary parts. Have a safe and happy halloween!

This was fun and I was looking forward to not thinking too much, but... clicking the link shows one "horror" being

Eternal Darkness
Are you afraid of the dark? Welcome to TrEs-2b, the planet of eternal night. The darkest planet ever discovered orbiting a star, this alien world is less reflective than coal with a burning atmosphere – the air is as hot as lava.

So, if the atmosphere of this planet is as hot as lava, wouldn't it radiate to space with the light that lava would, and therefor not be that dark after all? That is, lava on earth at least, can be red hot. Could something be as hot as lava and radiate only in the infrared?

[johnnydeep]

Well, I was a little bit disappointed in the galaxy of horrors in this APOD, so I thought I'd post my own:

Bear Paw galaxy, NGC 2537. Two prints appear to be visible. Horror! Photo: nytecam.

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Bear Paw galaxy, NGC 2547. Horror! It's aglow! Photo: SDSS.

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[/floa




Warning, there's a bear in the sky!

Ann

Nice. I don't suppose the Bear Paw galaxy is anywhere near Ursa Major or Ursa Minor is it?

[Ann]

Nice. I don't suppose the Bear Paw galaxy is anywhere near Ursa Major or Ursa Minor is it?

A lynx. Photo: Bernard Landgraf

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Wouldn't that have been suitable?

Actually, though, the Bear Paw galaxy is stalking its prey in the constellation of the Lynx.

Ann

[neufer]

Eternal Darkness

Welcome to TrEs-2b, the planet of eternal night. The darkest planet ever discovered orbiting a star, this alien world is less reflective than coal with a burning atmosphere – the air is as hot as lava.

So, if the atmosphere of this planet is as hot as lava, wouldn't it radiate to space with the light that lava would, and therefor not be that dark after all? That is, lava on earth at least, can be red hot. Could something be as hot as lava and radiate only in the infrared?

<<GSC 03549-02811 (sometimes referred to as TrES-2 A or TrES-2a parent star in reference to its exoplanet TrES-2b), also known as Kepler-1) is a yellow main-sequence star similar to our Sun. This star is located approximately 700 light-years away in the constellation of Draco. Though TrES-2b is currently the darkest known exoplanet, reflecting less than 1 percent of local sunlight, it shows a faint red glow. This is because its surface is 1,100 °C, it is so hot that it glows red. It is assumed to be tidally locked to its parent star.>>

[Ann]

Eternal Darkness
Are you afraid of the dark? Welcome to TrEs-2b, the planet of eternal night. The darkest planet ever discovered orbiting a star, this alien world is less reflective than coal with a burning atmosphere – the air is as hot as lava.

So, if the atmosphere of this planet is as hot as lava, wouldn't it radiate to space with the light that lava would, and therefor not be that dark after all? That is, lava on earth at least, can be red hot. Could something be as hot as lava and radiate only in the infrared?

Chris Peterson once said that there are many people who will be able to see near infrared light as a faint red glow.

Anyway, it is only the red-sensitive cones in our retinas that react to the reddest, longest wavelengths of the visible spectrum. I guess some red-sensitive cones also respond faintly to near-infrared light.

Check out this page and go as red as you can. Or rather, start at 645 nm. This corresponds to red light that is easily visible to normal human eyes. The RGB values of 645 nm are R=255, G=0 and B=0. The RGB values stay exactly the same as you scroll right all the way to 700 nm. Beyond 700 nm our red-sensitive cones give less and less of a response to the ever-longer wavelengths. At 751 nm, the RGB values are down to R=159, G=0 and B=0. At 780 nm, the RGB values are R=97, G=0 and B=0.

I'm pretty sure that 780 nm counts as near infrared light.

Ann

[johnnydeep]

Eternal Darkness
Are you afraid of the dark? Welcome to TrEs-2b, the planet of eternal night. The darkest planet ever discovered orbiting a star, this alien world is less reflective than coal with a burning atmosphere – the air is as hot as lava.

So, if the atmosphere of this planet is as hot as lava, wouldn't it radiate to space with the light that lava would, and therefor not be that dark after all? That is, lava on earth at least, can be red hot. Could something be as hot as lava and radiate only in the infrared?

Chris Peterson once said that there are many people who will be able to see near infrared light as a faint red glow.

Anyway, it is only the red-sensitive cones in our retinas that react to the reddest, longest wavelengths of the visible spectrum. I guess some red-sensitive cones also respond faintly to near-infrared light.

Check out this page and go as red as you can. Or rather, start at 645 nm. This corresponds to red light that is easily visible to normal human eyes. The RGB values of 645 nm are R=255, G=0 and B=0. The RGB values stay exactly the same as you scroll right all the way to 700 nm. Beyond 700 nm our red-sensitive cones give less and less of a response to the ever-longer wavelengths. At 751 nm, the RGB values are down to R=159, G=0 and B=0. At 780 nm, the RGB values are R=97, G=0 and B=0.

I'm pretty sure that 780 nm counts as near infrared light.

Ann

Thanks. So, per neufer’s post, the planet is only “dark” in that it reflects just 1% of the light it receives from it’s star. But it still glows red due to its high temperature. Though now I have to wonder how they can differentiate the light it reflects from the light it emits from its own heat.

And, at least on my iPad, using that color slider, I see 780nm as a very dark purple. Does that make me extraordinary?

[Fred the Cat]

Creepy Halloween full moon

This year has been scary enough

and tonight's moon proves it!

[Chris Peterson]

So, if the atmosphere of this planet is as hot as lava, wouldn't it radiate to space with the light that lava would, and therefor not be that dark after all? That is, lava on earth at least, can be red hot. Could something be as hot as lava and radiate only in the infrared?

Rock is a decent blackbody. Optically thin gases are not. Many solid materials (like rock), when heated, produce a continuum spectrum that is quite close to that of a theoretical blackbody. Gases, when heated, produce narrow emission lines. The atmosphere of this planet will produce very little light in comparison with what the surface emits. It will essentially be transparent in the visual and near IR spectra.

[Ann]

Thanks. So, per neufer’s post, the planet is only “dark” in that it reflects just 1% of the light it receives from it’s star. But it still glows red due to its high temperature. Though now I have to wonder how they can differentiate the light it reflects from the light it emits from its own heat.

And, at least on my iPad, using that color slider, I see 780nm as a very dark purple. Does that make me extraordinary?

Well, TrES-2 is a G-type star, which means it is reasonably similar to the Sun, and it produces a lot of visual light. The only way a planet orbiting such a star can be so dark, the way my math-allergic brain understands it, is if the planet absorbs almost all the visual light that reaches it and only lets some deep dark red and infrared light escape.

Incoming solar energy and outgoing infrared heat. The average amount of the sun's radiation that penetrates the atmosphere and reaches the earth is 51% of the total incoming energy as illustrated above. Of the 49% that does not reach the earth, 30% is reflected back into space and 19% is absorbed by the atmosphere and clouds. The total solar energy absorbed by Earth's atmosphere, oceans and land masses is approximately 3,850,000 exajoules (EJ) per year. The earth's energy use by mankind is approximately 500 exajoules per year. This is about 0.01% of the total yearly energy coming from the sun. Putting this in another way, the earth absorbs more energy in one hour than the world uses in one year according to physicist Steven Chu, US Energy Secretary and former Director of Lawrence Berkeley National Laboratory. In total, the sun emits about 2.2 billion times the amount of radiation that is received by the earth. See the Energy Profiles Page for more general energy information. Source: http://solarcellcentral.com/solar_page.html.

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In the big fat book that I own by Roger Penrose, Penrose said that the Sun-Earth system works in such a way that daytime Earth absorbs a certain number of visual-light photons from the Sun, and then night-time Earth re-emits the extra energy that it just received from the Sun as a much larger number of longer-wave photons. Say, two shortwave visible-light photons absorbed during the daytime generate (perhaps) six longer-wave infrared-light photons emitted by the Earth at night. According to Penrose, this process lowers the entropy on the Earth and helps make life possible on the Earth.

So, the way I understand it, TrES-2 b absorbs basically all the visible light that hits it and emits (some or most of it) as near-infrared light. In other words, the planet reflects little (or almost nothing) of the (visible or infrared) light that reaches it from its sun.

Let's talk about the color slider! 780 nm looks (sort of) deep purple because our eyes are quite insensitive to this wavelength. Its looks like a mixture of red and black, sort of like this.

Let's check the other end of the color slider, the one that "goes dark" because the wavelengths are too short for our eyes, near ultraviolet light. The shortest wavelength on the color slider is 380 nm, which, fascinatingly, stimulates the red-sensitive and the blue-sensitive cones in our eyes equally: Its RGB values are, R=97, G=0, B=97. This deep purple color looks like this.

Fascinatingly, while there is a relatively long part of the spectrum that stimulates only the receptors of red light in our eyes, the color slider doesn't show a single wavelength that only stimulates the blue color receptors in our eyes. But 439 nm has the following RGB values: R=10, G=0, B=255. 441 nm has these RGB values: R=0, G=11, B=255. Perhaps 440 nm is "all blue", that is, R=0, G=0 and B=255.

What about green? The greenest wavelength on the slider appears to be 511 nm, whose RGB values are R=9, G=255 and B=0. At 509 nm, the RGB values are, R=0, G=255 and B=23. Maybe 510 nm is the greenest of the green?

Ann

[Ann]

Creepy Halloween full moon
IMG_0675 (2).JPG
This year has been scary enough
IMG_0667 (2).JPG
and tonight's moon proves it!

Great horror moon, Fred!

Ann

[johnnydeep]

Thanks Chris and Ann! More stuff for me to chew on.

[Ann]

It seems I posted a picture that only I can see, so here it is again:

Earth's energy budget. Source: https://marine.rutgers.edu/cool/education/class/yuri/srb.gif.

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[MarkBour]

It seems I posted a picture that only I can see . . .

Ah, you must have posted it in infrared.

[Chris Peterson]

It seems I posted a picture that only I can see . . .

Ah, you must have posted it in infrared. :-)

Don't be ridiculous! She would never post it in infrared. Only ultraviolet for Ann.

[Ann]

It seems I posted a picture that only I can see . . .

Ah, you must have posted it in infrared.

Don't be ridiculous! She would never post it in infrared. Only ultraviolet for Ann.

Ann

[MarkBour]

It seems I posted a picture that only I can see . . .

Ah, you must have posted it in infrared.

Don't be ridiculous! She would never post it in infrared. Only ultraviolet for Ann.

or ultrablue.