APOD: Halloween and the Ghost Head Nebula (2016 Oct 30)

Comments and questions about the APOD on the main view screen.
User avatar
APOD Robot
Otto Posterman
Posts: 3921
Joined: Fri Dec 04, 2009 3:27 am

APOD: Halloween and the Ghost Head Nebula (2016 Oct 30)

Post by APOD Robot » Sun Oct 30, 2016 4:10 am

Image Halloween and the Ghost Head Nebula

Explanation: Halloween's origin is ancient and astronomical. Since the fifth century BC, Halloween has been celebrated as a cross-quarter day, a day halfway between an equinox (equal day / equal night) and a solstice (minimum day / maximum night in the northern hemisphere). With a modern calendar however, even though Halloween occurs tomorrow, the real cross-quarter day will occur next week. Another cross-quarter day is Groundhog Day. Halloween's modern celebration retains historic roots in dressing to scare away the spirits of the dead. Perhaps a fitting tribute to this ancient holiday is this view of the Ghost Head Nebula taken with the Hubble Space Telescope. Similar to the icon of a fictional ghost, NGC 2080 is actually a star forming region in the Large Magellanic Cloud, a satellite galaxy of our own Milky Way Galaxy. The Ghost Head Nebula spans about 50 light-years and is shown in representative colors.

<< Previous APOD This Day in APOD Next APOD >>
[/b]

Boomer12k
:---[===] *
Posts: 2663
Joined: Sun Apr 22, 2007 12:07 am

Re: APOD: Halloween and the Ghost Head Nebula (2016 Oct 30)

Post by Boomer12k » Sun Oct 30, 2016 4:43 am

Reminds me of the Asian Continent with India at the bottom....

:---[===] *

ta152h0
Schooled
Posts: 1368
Joined: Mon Aug 29, 2005 12:46 am
Location: Auburn, Washington, USA

Re: APOD: Halloween and the Ghost Head Nebula (2016 Oct 30)

Post by ta152h0 » Sun Oct 30, 2016 9:37 am

Has anyone taken an image with a pinhole camera of the heavens ?
Wolf Kotenberg

User avatar
neufer
Vacationer at Tralfamadore
Posts: 17039
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Halloween and the Ghost Head Nebula (2016 Oct 30)

Post by neufer » Sun Oct 30, 2016 11:20 am

ta152h0 wrote:
Has anyone taken an image with a pinhole camera of the heavens ?
Every pinhole camera image of the heavens is simply
a pinhole camera image of the Sun, clouds and daytime panorama.

Nothing else shows up.
Art Neuendorffer

heehaw

Re: APOD: Halloween and the Ghost Head Nebula (2016 Oct 30)

Post by heehaw » Sun Oct 30, 2016 12:07 pm

Makes me want to dive right in!

alcor
Ensign
Posts: 32
Joined: Fri Nov 06, 2015 10:12 pm

Re: APOD: Halloween and the Ghost Head Nebula (2016 Oct 30)

Post by alcor » Sun Oct 30, 2016 2:48 pm

The star-forming region and the surrounding dust-ring (nearly closed) reminds me of looking down the Olympian torch, with the handle lower left. Image
Arne

R Venable

Re: APOD: Halloween and the Ghost Head Nebula (2016 Oct 30)

Post by R Venable » Sun Oct 30, 2016 3:42 pm

It looks more like the face of a ghost if you turn it upside down. Then, the brightest spots are eyes and there are dusky nose and mouth-like features. I suppose that it's upside down because professional astronomers still think that north is up in space.

User avatar
Chris Peterson
Abominable Snowman
Posts: 14996
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA

Re: APOD: Halloween and the Ghost Head Nebula (2016 Oct 30)

Post by Chris Peterson » Sun Oct 30, 2016 4:29 pm

R Venable wrote:I suppose that it's upside down because professional astronomers still think that north is up in space.
But this isn't "in space". It's a 2D projection on the sky, which has a conventional coordinate system associated with it.
Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Boomer12k
:---[===] *
Posts: 2663
Joined: Sun Apr 22, 2007 12:07 am

Re: APOD: Halloween and the Ghost Head Nebula (2016 Oct 30)

Post by Boomer12k » Sun Oct 30, 2016 7:30 pm

It is the "Kooky Space Ghost"... from Scooby-Doo.... helmet and all...

:---[===] *

Boomer12k
:---[===] *
Posts: 2663
Joined: Sun Apr 22, 2007 12:07 am

Re: APOD: Halloween and the Ghost Head Nebula (2016 Oct 30)

Post by Boomer12k » Sun Oct 30, 2016 7:32 pm

R Venable wrote:It looks more like the face of a ghost if you turn it upside down. Then, the brightest spots are eyes and there are dusky nose and mouth-like features. I suppose that it's upside down because professional astronomers still think that north is up in space.
Then it looked like a "Ghost CAT" to me...

:---[===] *

heehaw

Re: APOD: Halloween and the Ghost Head Nebula (2016 Oct 30)

Post by heehaw » Sun Oct 30, 2016 9:20 pm

Chris Peterson wrote:..., which has a conventional coordinate system associated with it.
We astronomers, and our "conventional" coordinate systems! With Right Ascension increasing to the left. And temperature, in the Hertzsprung-Russell diagram, increasing to the left. Hmmm....

User avatar
Chris Peterson
Abominable Snowman
Posts: 14996
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA

Re: APOD: Halloween and the Ghost Head Nebula (2016 Oct 30)

Post by Chris Peterson » Sun Oct 30, 2016 9:57 pm

heehaw wrote:
Chris Peterson wrote:..., which has a conventional coordinate system associated with it.
We astronomers, and our "conventional" coordinate systems! With Right Ascension increasing to the left. And temperature, in the Hertzsprung-Russell diagram, increasing to the left. Hmmm....
Yeah. But there is logic behind those choices... they're not arbitrary.
Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

saturno2
Commander
Posts: 667
Joined: Wed Jun 29, 2011 10:05 pm

Re: APOD: Halloween and the Ghost Head Nebula (2016 Oct 30)

Post by saturno2 » Sun Oct 30, 2016 10:38 pm

Interesting

ta152h0
Schooled
Posts: 1368
Joined: Mon Aug 29, 2005 12:46 am
Location: Auburn, Washington, USA

Re: APOD: Halloween and the Ghost Head Nebula (2016 Oct 30)

Post by ta152h0 » Sun Oct 30, 2016 11:38 pm

now i have to make a pinhole camera and prove Mr Neufer right ! Can you still get glass plate negative film ???
Wolf Kotenberg

User avatar
neufer
Vacationer at Tralfamadore
Posts: 17039
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Halloween and the Ghost Head Nebula (2016 Oct 30)

Post by neufer » Mon Oct 31, 2016 1:01 am

ta152h0 wrote:
now i have to make a pinhole camera and prove Mr Neufer right !

Can you still get glass plate negative film ???
Why would you need glass plate negative film ???

https://kikkerland.com/products/pinhole ... graphy-kit
Art Neuendorffer

Evenstar
Ensign
Posts: 35
Joined: Sun Mar 28, 2010 6:28 am

Re: APOD: Halloween and the Ghost Head Nebula (2016 Oct 30)

Post by Evenstar » Mon Oct 31, 2016 2:50 am

I've been viewing a couple Great Courses on the universe that, although both are over 10 years old now, describe a 'spatially flat' universe one minute but acknowledge too that one (Hubble Telescope) can see off in every direction some 13+ billion light years and still find galaxies (~14 billion light years still being the 'big bang'). I am clearly missing on how tens of billions of galaxies in every direction in a 3-dimensional universe can be described as 'spatially flat'?! Thanks.

Drastically edited summary... What does a 'spatially flat' universe mean? Please define 'spatially flat' in a three dimensional universe?
Last edited by Evenstar on Mon Oct 31, 2016 3:23 pm, edited 3 times in total.
<Evenstar>

User avatar
Ann
4725 Å
Posts: 10397
Joined: Sat May 29, 2010 5:33 am

Re: APOD: Halloween and the Ghost Head Nebula (2016 Oct 30)

Post by Ann » Mon Oct 31, 2016 3:48 am

Evenstar wrote:My big problem isn't Halloween... I've been viewing a couple Great Courses on the universe that, although both are over 10 years old now, describe a 'spatially flat' universe one minute but acknowledge too that one (Hubble Telescope) can see off in every direction some 13+ billion light years and still find galaxies (~14 billion light years still being the 'big bang'). I am clearly missing on how tens of billions of galaxies in every direction in a 3-dimensional universe can be described as 'spatially flat'?!

I have never tried putting all this into words before and doing so should actually help but it hasn't yet. One thing also involved that I cannot grasp is how in this spatially flat 3-dimensional universe spacetime curves. I would love to KISS.

Okay...go for it. Somewhere I figure that if I read enough different descriptions of my topic all will click into place... Please--no math. And if the curvature of spacetime can be left out of spatially flat that would be terrific. Also...pointing me favorite links to resolve this rather than writing it all out here is logical. Perhaps I'll try googling this one more time too but dare to post anyway. Thanks.
If you don't like math, then I should be the perfect person to explain it to you, because I am math-allergic, too. (And at least I hope that I will be able to explain it to you.)
Image
The Earth in curved spacetime. Source:
http://physics.stackexchange.com/questi ... of-gravity
The way I understand curved spacetime, it means that spacetime can be thought of as an "elastic sheet", and any massive object which is "resting on this sheet" will make bumps in it. The illustration at left shows the Earth in curved spacetime.

Another thing to remember about curved spacetime is that more massive objects will make bigger bumps. This illustration suggests that the Earth is not inside the Sun's "bump", or gravity well, but that is certainly not true. Anything that orbits the Sun is inside the Sun's gravity well, otherwise it wouldn't orbit it.

In black holes, a lot of mass is concentrated in a small or perhaps zero volume. Therefore a black hole is thought to punch a hole right through spacetime. Einstein's theory of relativity can't explain how deep that hole would be.

So there are bumps and gravity wells in spacetime, and likely even holes. But that doesn't necessarily mean that spacetime considered as an entirety is curved.
I believe you can think of "curved but flat space" as a road with potholes in it. The potholes represent the numerous gravity wells in spacetime. Yet the road itself may well be "flat". The road doesn't necessarily go "uphill" or downhill". For all its potholes, it may well be sort of "flat".

That's how I think of it.

Ann
Color Commentator

User avatar
geckzilla
Ocular Digitator
Posts: 9071
Joined: Wed Sep 12, 2007 12:42 pm
Location: Modesto, CA

Re: APOD: Halloween and the Ghost Head Nebula (2016 Oct 30)

Post by geckzilla » Mon Oct 31, 2016 9:10 am

I find relatively complicated topics such as "flat space" are best explained with online courses. It can take several lectures and days of study building up to a concept to understand what is really meant by it. If you've only ever read news articles here and there or maybe a wikipedia article, then your status is going to remain confused. You'd want to study cosmology. RJN has a lecture on it here at this very forum, if you wish. You'll notice it's fairly late in the series. There's some build up to it. It's not exactly simple stuff... well, perhaps it is simple compared to some stuff, but for most of us, it's complicated.
http://asterisk.apod.com/viewtopic.php?f=24&t=18003
Just call me "geck" because "zilla" is like a last name.

User avatar
neufer
Vacationer at Tralfamadore
Posts: 17039
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Halloween and the Ghost Head Nebula (2016 Oct 30)

Post by neufer » Mon Oct 31, 2016 2:02 pm

Boomer12k wrote:
it looked like a "Ghost CAT" to me...
https://en.wikipedia.org/wiki/Aye-aye wrote: <<The aye-aye is the world's largest nocturnal primate, and is characterized by its unusual method of finding food; it taps on trees to find grubs, then gnaws holes in the wood using its forward slanting incisors to create a small hole in which it inserts its narrow middle finger to pull the grubs out. The aye-aye was thought to be extinct in 1933, but was rediscovered in 1957. Nine individuals were transported to Nosy Mangabe, an island near Maroantsetra off eastern Madagascar, in 1966. Researchers in Madagascar report remarkable fearlessness in the aye-aye; some accounts tell of individual animals strolling nonchalantly in village streets or even walking right up to naturalists in the rainforest and sniffing their shoes. However, the aye-aye is often viewed as a harbinger of evil and killed on sight. Others believe, if one points its narrowest finger at someone, they are marked for death. Some say the appearance of an aye-aye in a village predicts the death of a villager, and the only way to prevent this is to kill it. The Sakalava people go so far as to claim aye-ayes sneak into houses through the thatched roofs and murder the sleeping occupants by using their middle finger to puncture the victim's aorta.>>
Art Neuendorffer

Evenstar
Ensign
Posts: 35
Joined: Sun Mar 28, 2010 6:28 am

Re: APOD: Halloween and the Ghost Head Nebula (2016 Oct 30)

Post by Evenstar » Mon Oct 31, 2016 3:52 pm

Ann wrote:If you don't like math, then I should be the perfect person to explain it to you, because I am math-allergic, too. (And at least I hope that I will be able to explain it to you.)

So there are bumps and gravity wells in spacetime, and likely even holes. But that doesn't necessarily mean that spacetime considered as an entirety is curved. I believe you can think of "curved but flat space" as a road with potholes in it. The potholes represent the numerous gravity wells in spacetime. Yet the road itself may well be "flat". The road doesn't necessarily go "uphill" or downhill". For all its potholes, it may well be sort of "flat".

That's how I think of it.

Ann
Rats... I have edited original topic. Wasn't after gravity or spacetime but the observable universe. However I think now that one cannot describe the observable universe as spatially flat--that 'spatially flat' is not observable. ...unless one thinks of our 'roads with gravitational potholes/bumps' as radiating off in infinite observable directions making up a finite out to ~13.7 billion light year old observable (spherical) universe that is still impossibly definable since or if the big bang cannot be defined from starting at one point? STOP... Nuff said here and now if 'spatially flat' cannot be described in a more/less 3-dimensional observable universe or enough has been said. Thank you.
<Evenstar>

ta152h0
Schooled
Posts: 1368
Joined: Mon Aug 29, 2005 12:46 am
Location: Auburn, Washington, USA

Re: APOD: Halloween and the Ghost Head Nebula (2016 Oct 30)

Post by ta152h0 » Mon Oct 31, 2016 9:10 pm

I nowhave to buy a solar pinhole camera. Got a couple kids that talk to me about astronomy. I also need a 1968 Plymouth Roadrunner HEMI
Wolf Kotenberg

User avatar
geckzilla
Ocular Digitator
Posts: 9071
Joined: Wed Sep 12, 2007 12:42 pm
Location: Modesto, CA

Re: APOD: Halloween and the Ghost Head Nebula (2016 Oct 30)

Post by geckzilla » Mon Oct 31, 2016 9:50 pm

That aye aye illustration is such a stark contrast to the really bad photography of the animal. They're all blinding the poor things making them look all crazy with tiny pupils and wide irises.
Just call me "geck" because "zilla" is like a last name.

cleofus

Re: APOD: Halloween and the Ghost Head Nebula (2016 Oct 30)

Post by cleofus » Tue Nov 01, 2016 2:17 am

Regarding Cross-Quarter day, it is true that Halloween has traditionally been a cross-quarter day which it isn't BUT also Groundhog day is called cross-Quarter day but it isn't either. Figure it yourself: Dec 21 - Mar 21 is 10 days in Dec, 31 in January, plus 28 in February and 20 in March for a total of:
10 + 31 + 28 + 20 + 1 = 90 (ignoring the about ½ day on either end, but adding in 1 to account for both 1/2's)

½ of 90 is 45 which occurs on Feb 4th or 5th

= 10 + 31 + 4 (+1) = 45/46

P.S. SOL is NOT the Latin name for the Sun - Solis is.

User avatar
geckzilla
Ocular Digitator
Posts: 9071
Joined: Wed Sep 12, 2007 12:42 pm
Location: Modesto, CA

Re: APOD: Halloween and the Ghost Head Nebula (2016 Oct 30)

Post by geckzilla » Tue Nov 01, 2016 2:52 am

cleofus wrote:P.S. SOL is NOT the Latin name for the Sun - Solis is.
Solis would be Sun's.
Just call me "geck" because "zilla" is like a last name.

User avatar
Chris Peterson
Abominable Snowman
Posts: 14996
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA

Re: APOD: Halloween and the Ghost Head Nebula (2016 Oct 30)

Post by Chris Peterson » Tue Nov 01, 2016 3:21 am

geckzilla wrote:
cleofus wrote:P.S. SOL is NOT the Latin name for the Sun - Solis is.
Solis would be Sun's.
Or a bit more formally, sol is the Latin nominative, solis is the Latin genitive.
Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com