APOD: M57: The Ring Nebula (2018 Apr 17)

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APOD: M57: The Ring Nebula (2018 Apr 17)

Post by APOD Robot » Tue Apr 17, 2018 4:05 am

Image M57: The Ring Nebula

Explanation: Except for the rings of Saturn, the Ring Nebula (M57) is probably the most famous celestial band. Its classic appearance is understood to be due to our own perspective, though. The recent mapping of the expanding nebula's 3-D structure, based in part on this clear Hubble image,indicates that the nebula is a relatively dense, donut-like ring wrapped around the middle of a (American) football-shaped cloud of glowing gas. The view from planet Earth looks down the long axis of the football, face-on to the ring. Of course, in this well-studied example of a planetary nebula, the glowing material does not come from planets. Instead, the gaseous shroud represents outer layers expelled from the dying, once sun-like star, now a tiny pinprick of light seen at the nebula's center. Intense ultraviolet light from the hot central star ionizes atoms in the gas. The Ring Nebula is about one light-year across and 2,000 light-years away.

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Re: APOD: M57: The Ring Nebula (2018 Apr 17)

Post by Case » Tue Apr 17, 2018 7:08 am

If you get a change to have a look for yourself, the best opportunity around this time of year is in the early hours (around 4 a.m., before dawn) in the East. You’ll find it in between Beta and Gamma Lyrae.

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Re: APOD: M57: The Ring Nebula (2018 Apr 17)

Post by De58te » Tue Apr 17, 2018 11:44 am

This arouses my curiosity. Why is it that most planetary nebulae are donut shaped. Some perfectly two dimensional with the escaping gas in a donut shape heading to the left and the right, and top and bottom. Yet we always see the hole in the center with the remnant star. Why is it none of the escaping energized red gas was blown away from us in the background? Or blown directly towards us? For example what if the solar system was the same 2,000 light years away, but on the right side of this two dimensional frame. We'd see the red energized gas but not the hole behind it. This assuming because we don't see a hint of the red gas in the center of our viewpoint.

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Re: APOD: M57: The Ring Nebula (2018 Apr 17)

Post by Sa Ji Tario » Tue Apr 17, 2018 12:03 pm

When I located it for the first time it was with a binocular that "swept" the constellation, then I went to the 150 mm telescope and there it looked like a very small milky crown without details. In some APOD images it is seen that it emits symmetric lobes of different sizes.-
To locate it, take an imaginary line between Beta and Gamma Lyr into the ring and closer to Beta

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Re: APOD: M57: The Ring Nebula (2018 Apr 17)

Post by Fred the Cat » Tue Apr 17, 2018 1:14 pm

Feynman's Felicity "Only ascertain as a cat box survivor"

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Re: APOD: M57: The Ring Nebula (2018 Apr 17)

Post by Chris Peterson » Tue Apr 17, 2018 1:24 pm

De58te wrote:
Tue Apr 17, 2018 11:44 am
This arouses my curiosity. Why is it that most planetary nebulae are donut shaped. Some perfectly two dimensional with the escaping gas in a donut shape heading to the left and the right, and top and bottom. Yet we always see the hole in the center with the remnant star. Why is it none of the escaping energized red gas was blown away from us in the background? Or blown directly towards us? For example what if the solar system was the same 2,000 light years away, but on the right side of this two dimensional frame. We'd see the red energized gas but not the hole behind it. This assuming because we don't see a hint of the red gas in the center of our viewpoint.
I think many (perhaps most) planetary nebulas are roughly spherical in shape, not donut shaped. A sphere of expanding gas looks like a bubble or ring, dense at the edge and thin at the center.

Asymmetric planetary nebulas occur because stars themselves are not symmetrical systems, having both spin axes and magnetic axes. That can result in material being blown off in some kind of jet-like structures (or rings). We see these at different orientations, giving rise to all the peculiar shaped planetary nebulas we see.
Chris

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Re: APOD: M57: The Ring Nebula (2018 Apr 17)

Post by mjsakers » Tue Apr 17, 2018 1:31 pm

How do we know that the central star (white dwarf) seen in the image is in fact the central star of the nebula and not just a background star that happens to line up with the center. There's no way to be certain of this it seems. I hope it is not just an assumption.

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Re: APOD: M57: The Ring Nebula (2018 Apr 17)

Post by Chris Peterson » Tue Apr 17, 2018 1:37 pm

mjsakers wrote:
Tue Apr 17, 2018 1:31 pm
How do we know that the central star (white dwarf) seen in the image is in fact the central star of the nebula and not just a background star that happens to line up with the center. There's no way to be certain of this it seems. I hope it is not just an assumption.
Well, it's a pretty safe assumption. A planetary nebula has to have a central star, and that's the only candidate in the right place.
Chris

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Re: APOD: M57: The Ring Nebula (2018 Apr 17)

Post by neufer » Tue Apr 17, 2018 2:28 pm

Chris Peterson wrote:
Tue Apr 17, 2018 1:37 pm
mjsakers wrote:
Tue Apr 17, 2018 1:31 pm

How do we know that the central star (white dwarf) seen in the image is in fact the central star of the nebula and not just a background star that happens to line up with the center. There's no way to be certain of this it seems. I hope it is not just an assumption.
Well, it's a pretty safe assumption. A planetary nebula has to have a central star, and that's the only candidate in the right place.
  • It should shine brightly in both the ultraviolet & infrared...like the Helix Nebula (NGC 7293):
https://apod.nasa.gov/apod/ap091231.html wrote: APOD Explanation: <<Dust makes this cosmic eye look red. The eerie Spitzer Space Telescope image shows infrared radiation from the well-studied Helix Nebula (NGC 7293) a mere 700 light-years away in the constellation Aquarius. The two light-year diameter shroud of dust and gas around a central white dwarf has long been considered an excellent example of a planetary nebula, representing the final stages in the evolution of a sun-like star. But the Spitzer data show the nebula's central star itself is immersed in a surprisingly bright infrared glow. Models suggest the glow is produced by a dust debris disk. Even though the nebular material was ejected from the star many thousands of years ago, the close-in dust could be generated by collisions in a reservoir of objects analogous to our own solar system's Kuiper Belt or cometary Oort cloud. Formed in the distant planetary system, the comet-like bodies would have otherwise survived even the dramatic late stages of the star's evolution.>>
https://www.nasa.gov/mission_pages/spitzer/multimedia/pia15817.html wrote: Helix Nebula - Unraveling at the Seams

<<A dying star is throwing a cosmic tantrum in this combined image from NASA's Spitzer Space Telescope and the Galaxy Evolution Explorer (GALEX), which NASA has lent to the California Institute of Technology in Pasadena. In death, the star's dusty outer layers are unraveling into space, glowing from the intense ultraviolet radiation being pumped out by the hot stellar core.

Planetary nebulae are actually the remains of stars that once looked a lot like our sun. When the hydrogen fuel for the fusion reaction runs out, the star turns to helium for a fuel source, burning it into an even heavier mix of carbon, nitrogen and oxygen. Eventually, the helium will also be exhausted, and the star dies, puffing off its outer gaseous layers and leaving behind the tiny, hot, dense core, called a white dwarf. The white dwarf is about the size of Earth, but has a mass very close to that of the original star; in fact, a teaspoon of a white dwarf would weigh as much as a few elephants!

The glow from planetary nebulae is particularly intriguing as it appears surprisingly similar across a broad swath of the spectrum, from ultraviolet to infrared. The Helix remains recognizable at any of these wavelengths, but the combination shown here highlights some subtle differences.

The intense ultraviolet radiation from the white dwarf heats up the expelled layers of gas, which shine brightly in the infrared. GALEX has picked out the ultraviolet light pouring out of this system, shown throughout the nebula in blue, while Spitzer has snagged the detailed infrared signature of the dust and gas in yellow A portion of the extended field beyond the nebula, which was not observed by Spitzer, is from NASA's all-sky Wide-field Infrared Survey Explorer (WISE). The white dwarf star itself is a tiny white pinprick right at the center of the nebula.

The brighter purple circle in the very center is the combined ultraviolet and infrared glow of a dusty disk circling the white dwarf (the disk itself is too small to be resolved). This dust was most likely kicked up by comets that survived the death of their star. Before the star died, its comets, and possibly planets, would have orbited the star in an orderly fashion. When the star ran out of hydrogen to burn, and blew off its outer layers, the icy bodies and outer planets would have been tossed about and into each other, kicking up an ongoing cosmic dust storm. Any inner planets in the system would have burned up or been swallowed as their dying star expanded.>>
Art Neuendorffer

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Re: APOD: M57: The Ring Nebula (2018 Apr 17)

Post by GoshOGeeOGolly » Tue Apr 17, 2018 4:25 pm

Some people say, 'Old Blue Eyes got to heaven after all!' And he did it his way. Well, maybe yes, maybe no.

heehaw

Re: APOD: M57: The Ring Nebula (2018 Apr 17)

Post by heehaw » Tue Apr 17, 2018 10:06 pm

Lyra is just the nicest darn little constellation! And Epsilon is cute as can be!

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Re: APOD: M57: The Ring Nebula (2018 Apr 17)

Post by MarkBour » Tue Apr 17, 2018 11:01 pm

APOD Robot wrote:
Tue Apr 17, 2018 4:05 am
Except for the rings of Saturn, the Ring Nebula (M57) is probably the most famous celestial band.
Okay, I guess we're excepting Disaster Area as well. :-)
Its classic appearance is understood to be due to our own perspective, though. The recent mapping of the expanding nebula's 3-D structure, based in part on this clear Hubble image,indicates that the nebula is a relatively dense, donut-like ring wrapped around the middle of a (American) football-shaped cloud of glowing gas. The view from planet Earth looks down the long axis of the football, face-on to the ring.
Notwithstanding the caption speaks about the discovery and mapping of material in the football-shaped region, I believe that the vast majority of the mass ejecta is in the ring (a doughnut shaped region). A natural axis can be drawn through the center of the doughnut shape (as the APOD and its sources indicated, this axis points almost straight toward us).

I wonder if this axis is the same axis as was the star's axis of rotation in "life", and indeed, I wonder if it is the same axis along which it would have produced jets during its birth. (Okay, the star moved a lot through its life, and may have reoriented some due to billions of years of influences, but hopefully it is clear what I mean by "the same axis".)
Mark Goldfain