Starship Asterisk*

by **bystander** » Sat Feb 11, 2012 1:30 am

nealmcb wrote:Another reference to the magnificent jets of Centaurus A is in today's paper:
Kate Becker: Supermassive black holes may not be such bullies after all - Boulder Daily Camera

http://asterisk.apod.com/viewtopic.php?f=31&t=27151

by **nealmcb** » Sat Feb 11, 2012 12:39 am

Another reference to the magnificent jets of Centaurus A is in today's paper:
Kate Becker: Supermassive black holes may not be such bullies after all - Boulder Daily Camera

It reminds me that what I'd like to see is this image overlaid on the real star / constellation background. But the best I've found is this old image: Centaurus_A - a long overdue synthesis imaging survey which suggests coordinates, but shows no stars.

Has anyone seen such an overlay, or a FITS image that could be accurately fit onto other charts? I want to be able to point this out for the mind's eye in the night sky, and it is big enough that it would be "visible" on the horizon in much of the northern hemisphere.

by **BMAONE23** » Thu Apr 14, 2011 5:03 pm

astrotrigg wrote:Anyone notice that the background sky in the image is a fake? There are multiple repetitions throughout.... ???? Was it a simulated night sky?

As per the last line in the write up on the image

The light dots in the image depict not stars, but typically other radio bright galaxies in the even more distant universe.

by **alphachap** » Thu Apr 14, 2011 10:52 am

astrotrigg wrote:Anyone notice that the background sky in the image is a fake? There are multiple repetitions throughout.... ???? Was it a simulated night sky?

Yo, you're right!

by **biddie67** » Thu Apr 14, 2011 4:03 am

My first thought upon seeing today's APOD was the amount of light surrounding each of those huge telescopes and wondering if the staff was concerned about light polution interferring with their work. But then I realized that light probably doesn't interfere with radio waves .....

by **astrotrigg** » Thu Apr 14, 2011 3:44 am

Anyone notice that the background sky in the image is a fake? There are multiple repetitions throughout.... ???? Was it a simulated night sky?

by **nstahl** » Wed Apr 13, 2011 8:49 pm

larnyx wrote:Where can I find more infos about angular area of space objects in the sky?

Here are two Wikipedia articles on the units you might see: square degrees and steradians. The one on degrees is quite short but I think you're more likely to see degrees used in APOD. The one on steradians is longer and a bit more mathematical. It includes a useful table to help you visualize these angular areas. But the one on degrees leads to this list of constellations by area.

by **larynx** » Wed Apr 13, 2011 5:37 pm

HI all I've found the image very interesting. Where can I find more infos about angular area of space objects in the sky? I'd really like to see more images like that one, for example I once read the Andromeda is six times bigger than the moon in the sky! any help appreciated.
L

by **kaigun** » Wed Apr 13, 2011 4:13 pm

VictorB wrote:I really enjoy pictures like this of CenA that shows its size relative to things we are familiar with. More pictures like this please: M30, Orion, etc.

Me too. There was a long exposure picture a while back that showed the real sizes of of the Orion area nebulae and a bunch of other objects above a house. I thought it was the coolest thing I ever seen.

by **VictorB** » Wed Apr 13, 2011 4:03 pm

I really enjoy pictures like this of CenA that shows its size relative to things we are familiar with. More pictures like this please: M30, Orion, etc.

Victor B

by **orin stepanek** » Wed Apr 13, 2011 2:07 pm

Slow process to develope

: Click to view full size image

by **bystander** » Wed Apr 13, 2011 1:57 pm

neufer wrote:
Grenesir wrote:
I believe to know we have a black hole in our galaxy too.
Does such an image exist for our black hole as well?
How would it look like "from the inside"?
Something akin perhaps: http://apod.nasa.gov/apod/ap101110.html

http://asterisk.apod.com/viewtopic.php? ... 66#p136345

by **JuanAustin** » Wed Apr 13, 2011 11:53 am

Does anybody think elliptical galaxies are the results of two spiral galaxies colliding in the first place?
Also, will a collision between an elliptical and a sprial always result in an elliptical galaxy eventually being the only long term result?

by **neufer** » Wed Apr 13, 2011 11:47 am

alphachap wrote:
Are we not inside a black hole? Nothing can escape our universe, not even light.
The more massive a black hole, the less dense it is.
Our universe's density corresponds to a universe's black hole.

It would probably be more appropriate to suggest that we are inside of a white hole:

http://en.wikipedia.org/wiki/White_hole wrote:
<<A white hole, in general relativity, is a hypothetical region of spacetime which cannot be entered from the outside, but from which matter and light may escape. In this sense it is the reverse of a black hole, which can be entered from the outside, but from which nothing, including light, may escape.

A more recently proposed view of black holes might be interpreted as shedding some light on the nature of classical white holes. Some researchers proposed that when a black hole forms, a big bang occurs at the core, which creates a new universe that expands outside of the parent universe. The initial feeding of matter from the parent universe's black hole and the expansion that follows in the new universe might be thought of as a cosmological type of white hole. Unlike traditional white holes, this type of white hole would not be localized in space in the new universe, and its horizon would have to be identified with the cosmological horizon.>>

by **alphachap** » Wed Apr 13, 2011 10:38 am

Grenesir wrote:Good morning!
I believe to know we have a black hole in our galaxy too. Does such an image exist for our black hole as well? How would it look like "from the inside"?

Are we not inside a black hole? Nothing can escape our universe, not even light.
The more massive a black hole, the less dense it is.
Our universe's density corresponds to a universe's black hole.

by **neufer** » Wed Apr 13, 2011 10:19 am

Grenesir wrote:
I believe to know we have a black hole in our galaxy too.
Does such an image exist for our black hole as well?
How would it look like "from the inside"?

Something akin perhaps: http://apod.nasa.gov/apod/ap101110.html

by **nstahl** » Wed Apr 13, 2011 7:02 am

Chris Peterson wrote:From here it [the black hole at the center of our galaxy] would be too small to resolve... smaller than a single pixel in the image.

And the black hole at the center of our galaxy could be even stranger than surely most of us realized.

The Physics arXive Blog: "Planets Could Orbit Singularities Inside Black Holes"

This is a calculated possible stable orbit of an object Inside a black hole.

The discovery of stable orbits inside certain kinds of black hole implies that planets and perhaps even life could survive inside these weird objects, says one cosmologist

by **alter-ego** » Wed Apr 13, 2011 6:49 am

neufer wrote:It would be even more impressive if they hadn't overexposed the moon so that
it occupies an angular area over 5 times greater than the full Moon in Earth's sky.

Hello Art,
I can't speak for the radio telescope scaling, but a close look shows the moon size scaling wrt Cen A jets appears quite accurate. I scaled a semi-transparent, stand-alone image of the jets on the APOD (matching the overlap of perimeter stars),and transferring the 50kpc scale bar over to the moon shows the moon is at most 1/2 deg. I assumed a close estimate for Cen A distance = 3Mpc.

: Scaling Cen A radio jets to moon
(click to enlarge)

by **Chris Peterson** » Wed Apr 13, 2011 5:28 am

Grenesir wrote:Good morning!
I believe to know we have a black hole in our galaxy too. Does such an image exist for our black hole as well? How would it look like "from the inside"?

From here it would be too small to resolve... smaller than a single pixel in the image.

by **Grenesir** » Wed Apr 13, 2011 5:11 am

Good morning!
I believe to know we have a black hole in our galaxy too. Does such an image exist for our black hole as well? How would it look like "from the inside"?

by **neufer** » Wed Apr 13, 2011 4:43 am

It would be even more impressive if they hadn't overexposed the moon so that
it occupies an angular area over 5 times greater than the full Moon in Earth's sky.

by **APOD Robot** » Wed Apr 13, 2011 4:06 am

Centaurus Radio Jets Rising

Explanation: What if you could see the huge radio jets of Centaurus A rising? The Cen A radio jets are not only over a million light years long, they occupy an angular area over 200 times greater than the full Moon in Earth's sky. The jets are expelled by a violent black hole millions of times the mass of our Sun embedded deep in the center of nearby Cen A. Somehow, the black hole creates the fast moving jets as other matter falls in. In this picture, radio telescopes from the Australian Telescope Compact Array (ATCA) near Narrabri, NSW, Australia, were captured in front of a full Moon, with a radio image of Cen A superposed at its real angular size in the background. The above picture includes the most detailed map yet of any galaxy-class radio jets in the universe, taking several years and over 1,000 hours exposure time to complete. Details in the photo may yield clues as to how radio jets interact with stars and intergalactic dust. The light dots in the image depict not stars, but typically other radio bright galaxies in the even more distant universe.

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Starship Asterisk*

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