APOD: Haunting the Cepheus Flare (2021 Oct 29)

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APOD: Haunting the Cepheus Flare (2021 Oct 29)

Post by APOD Robot » Fri Oct 29, 2021 4:06 am

Image Haunting the Cepheus Flare

Explanation: Spooky shapes seem to haunt this dusty expanse, drifting through the night in the royal constellation Cepheus. Of course, the shapes are cosmic dust clouds visible in dimly reflected starlight. Far from your own neighborhood, they lurk above the plane of the Milky Way at the edge of the Cepheus Flare molecular cloud complex some 1,200 light-years away. Over 2 light-years across and brighter than most of the other ghostly apparitions, vdB 141 or Sh2-136 is also known as the Ghost Nebula, seen at the right of the starry field of view. Inside the nebula are the telltale signs of dense cores collapsing in the early stages of star formation. With the eerie hue of dust reflecting bluish light from hot young stars of NGC 7023, the Iris Nebula stands out against the dark just left of center. In the broad telescopic frame, these fertile interstellar dust fields stretch almost seven full moons across the sky.

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Re: APOD: Haunting the Cepheus Flare (2021 Oct 29)

Post by orin stepanek » Fri Oct 29, 2021 11:34 am

IrisGhost_LeoShatz_RevB1024.jpg
Doggie Ghost watching over the Iris Nebula! Halloween is coming! :mrgreen:
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Re: APOD: Haunting the Cepheus Flare (2021 Oct 29)

Post by neufer » Fri Oct 29, 2021 4:32 pm

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Re: APOD: Haunting the Cepheus Flare (2021 Oct 29)

Post by Zuben L. Genubi » Fri Oct 29, 2021 5:06 pm

How dense ARE molcular clouds? At great distance, they are capable of completely blocking out starlight. If I were in the middle of one, would I be able to see my hand in front of my face? Or would it be more like a fog through which I might be able to vaguely discern things a few lightyears away? Would they block all forms of radiation -- kind of like a cosmic saferoom?

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Re: APOD: Haunting the Cepheus Flare (2021 Oct 29)

Post by Chris Peterson » Fri Oct 29, 2021 5:35 pm

Zuben L. Genubi wrote: Fri Oct 29, 2021 5:06 pm How dense ARE molcular clouds? At great distance, they are capable of completely blocking out starlight. If I were in the middle of one, would I be able to see my hand in front of my face? Or would it be more like a fog through which I might be able to vaguely discern things a few lightyears away? Would they block all forms of radiation -- kind of like a cosmic saferoom?
The densest such clouds are still harder vacuums than we can achieve in most labs. If you were in the middle of one, you wouldn't reliably know it without instrumentation. It would be more apparent if you were near one edge and could then notice an asymmetry in the number of stars you could see in different directions. In a dense cloud, of course, you'd not see many stars. But if you evolved there, you'd consider that normal. Molecular clouds block visible light. They are more transparent to IR, and don't block radio at all. They also radiate in some IR bands, which would be very apparent to anybody inside with suitable instrumentation.
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Re: APOD: Haunting the Cepheus Flare (2021 Oct 29)

Post by neufer » Fri Oct 29, 2021 5:59 pm

Chris Peterson wrote: Fri Oct 29, 2021 5:35 pm
Zuben L. Genubi wrote: Fri Oct 29, 2021 5:06 pm
How dense ARE molcular clouds? At great distance, they are capable of completely blocking out starlight. If I were in the middle of one, would I be able to see my hand in front of my face? Or would it be more like a fog through which I might be able to vaguely discern things a few lightyears away? Would they block all forms of radiation -- kind of like a cosmic saferoom?
The densest such clouds are still harder vacuums than we can achieve in most labs. If you were in the middle of one, you wouldn't reliably know it without instrumentation. It would be more apparent if you were near one edge and could then notice an asymmetry in the number of stars you could see in different directions. In a dense cloud, of course, you'd not see many stars. But if you evolved there, you'd consider that normal. Molecular clouds block visible light. They are more transparent to IR, and don't block radio at all. They also radiate in some IR bands, which would be very apparent to anybody inside with suitable instrumentation.
https://en.wikipedia.org/wiki/Great_Smog_of_London wrote: <<The Great Smog of London, or Great Smog of 1952, was a severe air pollution event that affected London, England, in December 1952. A period of unusually cold weather, combined with an anticyclone and windless conditions, collected airborne pollutants—mostly arising from the use of coal—to form a thick layer of smog over the city. It lasted from Friday 5 December to Tuesday 9 December 1952, then dispersed quickly when the weather changed. The smog caused major disruption by reducing visibility and even penetrating indoor areas, far more severely than previous smog events, called "pea-soupers". The Great Smog is the central event of season 1, episode 4 of Netflix's show The Crown.

Although London was accustomed to heavy fogs, this one was denser and longer-lasting than any previous fog. In the inner London suburbs and away from town centres, there was no disturbance by moving traffic to thin out the dense fog in the back streets. As a result, visibility could be down to a metre or so in the daytime. Walking out of doors became a matter of shuffling one's feet to feel for potential obstacles such as road kerbs. This was made even worse at night since each back street lamp at the time was fitted with an incandescent light bulb, which gave no penetrating light onto the pavement for pedestrians to see their feet or even a lamp post. Fog-penetrating fluorescent lamps did not become widely available until later in the 1950s. "Smog masks" were worn by those who were able to purchase them from chemists.>>
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Re: APOD: Haunting the Cepheus Flare (2021 Oct 29)

Post by Ann » Fri Oct 29, 2021 7:27 pm

orin stepanek wrote: Fri Oct 29, 2021 11:34 am Doggie Ghost watching over the Iris Nebula! Halloween is coming! :mrgreen:
Are you sure that's a dog, Orin? :puppy: It looks more like a cat to me! :kitty:

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Re: APOD: Haunting the Cepheus Flare (2021 Oct 29)

Post by neufer » Fri Oct 29, 2021 10:07 pm

Ann wrote: Fri Oct 29, 2021 7:27 pm
Are you sure that's a dog, Orin? :puppy:
It looks more like a cat to me! :kitty:
https://en.wikipedia.org/wiki/National_Cat_Day wrote:


<<In the US, National Cat Day is an awareness day to raise public awareness of cat adoption, taking place on October 29. The day was founded in 2005 by Colleen Paige, a pet and family lifestyle expert, who was supported by the ASPCA, which is a nonprofit pet adoption organization.>>
https://en.wikipedia.org/wiki/S5_0014%2B81 wrote: <<S5 0014+81 is a distant, compact, hyperluminous, broad-absorption-line quasar, or blazar, located near the high declination region of the constellation Cepheus. In 2009, a team of astronomers using the Swift spacecraft used the luminosity of S5 0014+81 to measure the mass of its black hole. They found it to be about 10,000 times more massive than the black hole at the center of our galaxy, or equivalent to 40 billion solar masses. This makes it more than six times the value of the black hole of Messier 87, which was thought to be the largest black hole for almost 60 years, and was coined to be an "ultramassive" black hole. The Schwarzschild radius of this black hole is 800 AU, or about 20 times the radius of Pluto's orbit. The fact that such a large black hole existed so early in the universe, at only 1.6 billion years after the Big Bang, suggests that supermassive black holes formed very quickly.

S5 0014+81 is one of the most luminous quasars known with a total luminosity of over 1041 watts, equal to an absolute bolometric magnitude of −31.5. If the quasar were at a distance of 280 light-years from Earth, it would give out as much energy per square meter as the Sun does at Earth, despite being 18 million times more distant. The quasar's luminosity is therefore about 300 trillion times the Sun, or over 25,000 times as luminous as all the 100 to 400 billion stars of the Milky Way combined, making it one of the most powerful objects in the observable universe. However, because of its huge distance of 12.1 billion light-years it can only be studied by spectroscopy. The central black hole of the quasar devours an extremely huge amount of matter, equivalent to 4,000 solar masses of material every year. The quasar is also a very strong source of radiation, from gamma rays and X-rays down to radio waves.>>
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Re: APOD: Haunting the Cepheus Flare (2021 Oct 29)

Post by orin stepanek » Fri Oct 29, 2021 11:00 pm

Ann wrote: Fri Oct 29, 2021 7:27 pm
orin stepanek wrote: Fri Oct 29, 2021 11:34 am Doggie Ghost watching over the Iris Nebula! Halloween is coming!
Are you sure that's a dog, Orin? :puppy: It looks more like a cat to me! :kitty:

Ann
Probably my terrible way of outlining! look at it before I outlined it! :oops:
Orin

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