nasa apod NASA APOD 11th July 2017 - Omega Centauri ( NGC 5139 ) - by Mike O'Day

[MikeODay]

12 hours ago, Rodd said:

Intense.  I have often wondered what the density of the core of a great globular is. 

Rodd

This came up as well in the Asterisk.APOD.com discussions and I did a little digging ... 

( http://asterisk.apod.com/viewtopic.php?f=9&t=37373#p272861 )

As a first approximation perhaps one could assume a sphere with radius 75 light years and total of 10 million stars evenly spread through the sphere giving an average cubic volume per star of a little under 0.6cu light years ( if there is such a unit ) or say an average separation of 0.6 light years. 

Wikipedia states 

"Globular clusters can contain a high density of stars; on average about 0.4 stars per cubic parsec, increasing to 100 or 1000 stars per cubic parsec in the core of the cluster.[28] The typical distance between stars in a globular cluster is about 1 light year,[29] but at its core, the separation is comparable to the size of the Solar System (100 to 1000 times closer than stars near the Solar System)"

[Rodd]

20 minutes ago, mike005 said:

This came up as well in the Asterisk.APOD.com discussions and I did a little digging ... 

( http://asterisk.apod.com/viewtopic.php?f=9&t=37373#p272861 )

As a first approximation perhaps one could assume a sphere with radius 75 light years and total of 10 million stars evenly spread through the sphere giving an average cubic volume per star of a little under 0.6cu light years ( if there is such a unit ) or say an average separation of 0.6 light years. 

Wikipedia states 

"Globular clusters can contain a high density of stars; on average about 0.4 stars per cubic parsec, increasing to 100 or 1000 stars per cubic parsec in the core of the cluster.[28] The typical distance between stars in a globular cluster is about 1 light year,[29] but at its core, the separation is comparable to the size of the Solar System (100 to 1000 times closer than stars near the Solar System)"

Yes--its the core that fascinates me.  Imagine living on a planet that has 20 suns as bright as Sol, and dozens as bright as the Full Moon.  That is where we must go to obtain a top notch LP filter!

Rodd

[MikeODay]

3 hours ago, Rodd said:

Yes--its the core that fascinates me.  Imagine living on a planet that has 20 suns as bright as Sol, and dozens as bright as the Full Moon.  That is where we must go to obtain a top notch LP filter!

Rodd

I wonder how much you would be able see out beyond the cluster?  Top notch LP filter indeed

From an article by NASA ( https://www.nasa.gov/pdf/519382main_Core_of_Omega_Centauri.pdf "

"All of the stars in the image are cozy neighbors.  Thee average distance between any two stars in the cluster’s crowded core is roughly 13 times closer than our Sun’s nearest stellar neighbor, Alpha Centauri. Although the stars are close together, WFC3 can resolve each of them as individual stars. If anyone lived in this globular cluster, they would behold a star-saturated sky that is roughly 100 times brighter than Earth’s sky."

 

[wimvb]

4 hours ago, mike005 said:

This came up as well in the Asterisk.APOD.com discussions and I did a little digging ... 

( http://asterisk.apod.com/viewtopic.php?f=9&t=37373#p272861 )

As a first approximation perhaps one could assume a sphere with radius 75 light years and total of 10 million stars evenly spread through the sphere giving an average cubic volume per star of a little under 0.6cu light years ( if there is such a unit ) or say an average separation of 0.6 light years. 

Actually, an average distance of abt 0.84 ly

(0.84 ly)^3 = 0.6 (cu ly),

but who's counting?

Very neat image, and splendid use of hdr composition.

[MikeODay]

39 minutes ago, wimvb said:

Actually, an average distance of abt 0.84 ly

(0.84 ly)^3 = 0.6 (cu ly),

but who's counting?

Very neat image, and splendid use of hdr composition.

Thanks Wim

I made a correction to the separation on the other site ( should be 0.6 ) and then for some reason while I was editing I changed the volume as well to 0.6 - it should be 0.18.  I put it down to creeping old age

[MikeODay]

I went back to the linear set of integrated images and re-processed them using my new process for removing light pollution.  It allowed me to go deeper without producing an ugly colour balance in the darkest parts of the image ...

Omega Centauri ( NGC 5139 )

( please click / tap on image to see larger and sharper )

 

[pietervdv]

Awesome!

Imagine how the nightsky must look on a planet orbiting one of the stars in this cluster.

 

Pieter

[wimvb]

29 minutes ago, pietervdv said:

Awesome!

Imagine how the nightsky must look on a planet orbiting one of the stars in this cluster.

 

Pieter

Bright, very likely.

[MikeODay]

On 16/07/2017 at 18:49, pietervdv said:

Awesome!

Imagine how the nightsky must look on a planet orbiting one of the stars in this cluster.

 

Pieter

A belated thanks Pieter - sorry I did not see your post at the time.

[MikeODay]

Re-processed using Pixinsight PhotometricColorCalibration tool applied to the linear HDR image prior to stretching.

Omega Centauri ( NGC 5139 ) - an HDR image  ( Brightness range of individual stars visible in image: mag 7.6 to 20+ )

( please click / tap on image to see larger and shaper )