Starship Asterisk*

The Elusive Jellyfish Nebula

Explanation: Normally faint and elusive, the Jellyfish Nebula is caught in this alluring telescopic view. Drifting near bright star Eta Geminorum, at the foot of a celestial twin, the Jellyfish Nebula is seen dangling tentacles from the bright arcing ridge of emission left of center. In fact, the cosmic jellyfish is part of bubble-shaped supernova remnant IC 443, the expanding debris cloud from a massive star that exploded. Light from the explosion first reached planet Earth over 30,000 years ago. Like its cousin in astrophysical waters the Crab Nebula supernova remnant, IC 443 is known to harbor a neutron star, the remnant of the collapsed stellar core. The Jellyfish Nebula is about 5,000 light-years away. At that distance, this image would be about 100 light-years across.

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APOD Robot wrote:
Drifting near bright star Eta Geminorum, at the foot of a celestial twin, the Jellyfish Nebula
is seen dangling tentacles from the bright arcing ridge of emission left of center.

• Use your private parts as Jellyfish Nebula bait
  http://asterisk.apod.com/viewtopic.php? ... 50#p190601

Oh man, that's a beautiful photo! Not only is there Ha emission, but there's that nice glaze of reflection from Eta. There's also a faint glint of reflection nebula from an out of frame star on the upper left, giving a real 3D feel to the nebula.

In addition to Ha, some OIII emission is also seen due to this image containing exposures taken through an OIII filter!!

Looks to me to be more of a brain shape. Not jellyfish and tentacles.

The very bottom of what you call tentacles is like the brain stem. The rest of the 'tentacles', merely become the back half of the brain.

Hi,

Who gives this award? This is one of the worst IC443 I've ever seen!!!!
Just google for it and you will see lots of them much nicer!

Cheers ,
paulo

Looks like a brain to me also. But I don't get to name them. Huuuuuuummmm.

:---[===] *

Boomer12k wrote:

Selador wrote:
Looks to me to be more of a brain shape. Not jellyfish and tentacles.

The very bottom of what you call tentacles is like the brain stem. The rest of the 'tentacles', merely become the back half of the brain.

Looks like a brain to me also. But I don't get to name them. Huuuuuuummmm.

• Gee Whiz It's both:

They call it Jelly Belly (with apologies to Donovan)!

Ann

the 1953 movie was a better movie

"First light from supernova in IC443 reached us 30,000 years ago." "IC443 is about 5,000 light years distant now." So, it's covered 25,000 light years in 25,000 years. That gives a relative velocity of over .8 c. Seems unlikely. What am I missing?

Oops, sorry I meant 25,000 light years in 30,000 years. That's the over 80% of the speed of light I was talking about.

you just have to love this stuff. It is all relative. It is possible something is 5000 light years away and blew up 30000 years ago. Just means the first light took 5000 years to get here, at the speed of light. I need an ice cold one ...

Selador wrote:Looks to me to be more of a brain shape. Not jellyfish and tentacles.

The very bottom of what you call tentacles is like the brain stem. The rest of the 'tentacles', merely become the back half of the brain.

In this wider-angle picture, the nebula looks more like a jellyfish.

It's interesting to me how constellations, nebulas, etc. look like different things to different people. I wonder if any enterprising psychologist has designed a projective test using astronomical images?

it is very possible our ancient astronomers were looking up from the desert floor, after smoking some local horticulture and ............

ta152h0 wrote:
it is very possible our ancient astronomers were looking up from the desert floor, after smoking some local horticulture and ............

" Light from the explosion first reached planet Earth over 30,000 years ago."
Distance from Earth to IC 443 Supernova remnant, 5,000 light years.
Then the explosion of this Supernova was 35,000 years ago.

saturno2 wrote:
" Light from the explosion first reached planet Earth over 30,000 years ago."
Distance from Earth to IC 443 Supernova remnant, 5,000 light years.
Then the explosion of this Supernova was 35,000 years ago.

• Maybe:

http://en.wikipedia.org/wiki/IC_443 wrote:
<<IC 443 (also known as the Jellyfish Nebula and Sharpless 248 (Sh2-248)) is a Galactic supernova remnant (SNR) in the constellation Gemini. IC 443 is an extended source, having an angular diameter of 50 arcmin (by comparison, the full moon is 30 arcmin across). At the estimated distance of 5,000 ly from Earth, it corresponds to a physical size of roughly 70 light years. The remnant's age is still uncertain. There is some agreement that the progenitor supernova happened between 3,000 and 30,000 years ago.>>

<<The remnant's age is still uncertain. There is some agreement that the progenitor supernova happened between 3,000 and 30,000 years ago.>>

Well, that really narrows it down. It doesn't sound like there is agreement on this at all, or is this considered a narrow window for age guessing?

Diana wrote:<<The remnant's age is still uncertain. There is some agreement that the progenitor supernova happened between 3,000 and 30,000 years ago.>>

Well, that really narrows it down. It doesn't sound like there is agreement on this at all, or is this considered a narrow window for age guessing?

It's sobering to realize how much uncertainty and disagreement there is regarding the basic physical parameters of many astronomical phenomena. Many values that look like hard numbers are really inferences based on assumptions -- if you change the initial assumptions you will calculate different numbers. In this case, we seem to know pretty well how big the supernova remnant is at present, so if you infer that the remnant has been expanding more quickly into the surrounding gas and dust you will get a younger age, and if you infer that it has been expanding more slowly you will get an older age.

On the bright side, all this uncertainty and disagreement provides fertile ground for dissertations and post-doctoral fellowships, and improves the employment prospects for aspiring professional astronomers.

I think professional astronomers teach classes to overcome uncertaities

Anthony Barreiro wrote:

Diana wrote:<<The remnant's age is still uncertain. There is some agreement that the progenitor supernova happened between 3,000 and 30,000 years ago.>>

Well, that really narrows it down. It doesn't sound like there is agreement on this at all, or is this considered a narrow window for age guessing?

It's sobering to realize how much uncertainty and disagreement there is regarding the basic physical parameters of many astronomical phenomena. Many values that look like hard numbers are really inferences based on assumptions -- if you change the initial assumptions you will calculate different numbers. In this case, we seem to know pretty well how big the supernova remnant is at present, so if you infer that the remnant has been expanding more quickly into the surrounding gas and dust you will get a younger age, and if you infer that it has been expanding more slowly you will get an older age.

On the bright side, all this uncertainty and disagreement provides fertile ground for dissertations and post-doctoral fellowships, and improves the employment prospects for aspiring professional astronomers.

Very good points, Anthony.

There are so many things we don't know about space, but personally I'm amazed at the number of things that we actually do know with some certainty. Considering how small our bodies are, and how briefly they last, and how young our technological civilization is, I think it's quite amazing that we know what we actually know.

Where was humanity 3,000 to 30,000 years ago? I don't know if Chinese astronomers were recording "guest stars" (supernovae) in the sky 3,000 years ago. Maybe they were. They certainly weren't 30,000 years ago. Anyway, if our ancestors saw a new brilliant "star*" in the sky, how were they to know what that star was, or where it was? And why would they leave cuneiform records about it? To my knowledge, there is absolutely no known ancient records of the supernova that left the Jellyfish Nebula behind.

And no supernova has been recorded in the Milky Way since the telescope was invented in the seventeenth century. How are we to know how what kind of supernova remnants are possible, exactly how old they are and how they evolve in 30,000 years? Remember that although supernovae type Ia are remarkably uniform, this is not the case for core-collapse supernovae, like the one that left IC 443 behind. We don't know how massive core-collapse supernovae typically are when they explode, and how much of their outer atmospheres they typically hold on to when they pop.

Modern astronomy has developed spectral analysis of starlight, parallax measurements of the positions of stars, mathematical analyses of how and why stars shine and what makes them go supernova, and many, many other things. But even though we can use parallax measurements to determine the distance to objects a few hundred light-years away, our current instruments aren't good enough to determine the exact distance to IC 443.

Figuring out that the star that left the Jellyfish Nebula behind exploded 3,000 to 30,000 years ago is not so bad.

If ants knew as much about the Earth as we know about space, they might be studying human architecture by now and be busy changing the design of their anthills.

Ann

Ann wrote:...

There are so many things we don't know about space, but personally I'm amazed at the number of things that we actually do know with some certainty. Considering how small our bodies are, and how briefly they last, and how young our technological civilization is, I think it's quite amazing that we know what we actually know.

....

Ann

You're right of course, and it is inspiring to reflect on everything we've been able to figure out. But there is a consistent human bias toward overconfidence in what we "know". Ignoring or glossing over the unknown, unreliable, and uncertain, we cling to certainty at the expense of truth.

Anthony Barreiro wrote:You're right of course, and it is inspiring to reflect on everything we've been able to figure out. But there is a consistent human bias toward overconfidence in what we "know". Ignoring or glossing over the unknown, unreliable, and uncertain, we cling to certainty at the expense of truth.

This reminds me of Loren Eiseley's essay "The Hidden Teacher" (meditations on a golden orb spider and her web encountered along a Western arroyo), which you may find in either The Star Thrower or The Unexpected Universe (it was published in both collections).

... Man, too, lies at the heart of a web, a web extending through the starry reaches of sidereal space, as well as backward into the realm of prehistory. His great eye upon Mount Palomar looks into a distance of millions of light-years, his radio ear hears the whisper of even more remote galaxies, he peers through the electron microscope upon the minute particles of his own being. It is a web no creature of earth has ever spun before. Like the orb spider, man lies at the heart of it, listening. ... Yet still my spider lingers in memory against the sunset sky. Spider thoughts in a spider universe - sensitive to raindrop and moth flutter, nothing beyond, nothing allowed for the unexpected, the inserted pencil from the world outside. ... What is it we are a part of that we do not see...?

Charles Fort's The Book of the Damned ruminated to much the same effect.