APOD: Millions of Stars in Omega Centauri (2023 Mar 16)

Comments and questions about the APOD on the main view screen.
User avatar
APOD Robot
Otto Posterman
Posts: 5308
Joined: Fri Dec 04, 2009 3:27 am

APOD: Millions of Stars in Omega Centauri (2023 Mar 16)

Post by APOD Robot » Thu Mar 16, 2023 4:05 am

Image Millions of Stars in Omega Centauri

Explanation: Globular star cluster Omega Centauri, also known as NGC 5139, is 15,000 light-years away. The cluster is packed with about 10 million stars much older than the Sun within a volume about 150 light-years in diameter. It's the largest and brightest of 200 or so known globular clusters that roam the halo of our Milky Way galaxy. Though most star clusters consist of stars with the same age and composition, the enigmatic Omega Cen exhibits the presence of different stellar populations with a spread of ages and chemical abundances. In fact, Omega Cen may be the remnant core of a small galaxy merging with the Milky Way. Omega Centauri's red giant stars (with a yellowish hue) are easy to pick out in this sharp, color telescopic view.

<< Previous APOD This Day in APOD Next APOD >>

User avatar
VictorBorun
Captain
Posts: 1025
Joined: Fri Oct 16, 2020 10:25 pm

Re: APOD: Millions of Stars in Omega Centauri (2023 Mar 16)

Post by VictorBorun » Thu Mar 16, 2023 4:23 am

I thought you can't very well see both red giants and old under-Suns in the same exposure at the same distance?
And how come there are thousands of red giants — they mostly should long since had gone white dwarfs… or are they being created in the thick of the cluster from star to star mergers?

User avatar
Chris Peterson
Abominable Snowman
Posts: 18035
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA

Re: APOD: Millions of Stars in Omega Centauri (2023 Mar 16)

Post by Chris Peterson » Thu Mar 16, 2023 5:20 am

VictorBorun wrote: Thu Mar 16, 2023 4:23 am I thought you can't very well see both red giants and old under-Suns in the same exposure at the same distance?
And how come there are thousands of red giants — they mostly should long since had gone white dwarfs… or are they being created in the thick of the cluster from star to star mergers?
There are no star mergers. They're forming the usual way... stars run out of hydrogen to fuse and move off the main sequence.
Chris

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

User avatar
Ann
4725 Å
Posts: 13297
Joined: Sat May 29, 2010 5:33 am

Re: APOD: Millions of Stars in Omega Centauri (2023 Mar 16)

Post by Ann » Thu Mar 16, 2023 7:28 am

VictorBorun wrote: Thu Mar 16, 2023 4:23 am I thought you can't very well see both red giants and old under-Suns in the same exposure at the same distance?
And how come there are thousands of red giants — they mostly should long since had gone white dwarfs… or are they being created in the thick of the cluster from star to star mergers?
The red giants in Omega Centauri are low-mass stars. Apart from the likely presence of blue straggler stars (or post-blue stragglers, which have evolved away from the blue stage and become red giants themselves), all stars in Omega Centauri are probably less massive than the Sun. That is because all the stars in Omega Centauri that started out more massive than the Sun have already turned into white dwarfs, or, just possibly, into neutron stars.
Wikipedia wrote:
Omega Centauri is very different from most other galactic globular clusters to the extent that it is thought to have originated as the core remnant of a disrupted dwarf galaxy.
Bright central part of M33 Hubble annotated.png
Bright central part of M33, perhaps slightly similar to Omega Centauri.

M33 doesn't qualify as a dwarf galaxy, because it is too big. Still it is considerably smaller than the Milky Way. You can see that its central part is brighter than the rest of the galaxy and yellowish in color. This means that the stellar density is higher here than in other parts of M33, and also the stars residing here are typically old and yellow.

The galaxy whose core became Omega Centauri may have been slightly similar to M33, but smaller and a lot more metal-poor.

Because the stars of Omega Centauri are indeed very metal-poor, which is to say they contain extremely few elements other than hydrogen and helium. This also means that for a given mass, energy generated in the core of the star will pass a bit more unhindered through the thick surrounding gaseous layers of the star and emerge at the photosphere (the visible "surface" of the star) a bit bluer in metal-poor stars than in metal-rich ones (like the Sun). That is because the photon will lose a bit less energy during its passage through the star if the star is metal-poor (i.e., if it contains extremely few elements other than hydrogen and helium).

The energetic photon's journey from the core to the photosphere of a star is called a "random walk".


In a metal-poor globular cluster, the overall color of the cluster is "shifted toward the blue". We may be fooled to think that individual blue stars that we see in a globular cluster are massive, because we associate blue stars with high mass. But in a globular cluster, the reasonably bright blue stars are almost always "horizontal branch stars", which is an evolutionary stage where evolved (giant) stars become blue if they are metal-poor and yellow if they are metal-rich. In globular clusters, these blue stars are less massive than the Sun.


These are the different populations of stars inside a globular cluster:

M55 blue stragglers and turnoff point.png

Main sequence stars are fusing hydrogen to helium in their cores, like the Sun. Well, all main sequence stars in old globular clusters like Omega Centauri are less massive than the Sun! They may be the same color as the Sun, so that we are deceived to think that they are the same mass as the Sun, but they are not. If they had been metal-rich stars like the Sun, then all the stars that are still on the main sequence in old globular clusters would have looked more orange than the Sun, because they are all less massive than the Sun!

Consider RR Lyrae stars, which belong to the horizontal branch of globular clusters. These stars are only about half the mass of the Sun, yet they are 40-50 times brighter than the Sun! :shock:
Wikipedia wrote about RR Lyrae variables:

They are pulsating horizontal branch stars of spectral class A or F, with a mass of around half the Sun's. They are thought to have shed mass during the red-giant branch phase, and were once stars at around 0.8 solar masses.
Wikipedia wrote about RR Lyrae variables:

RR Lyraes are old, relatively low mass, Population II stars, in common with W Virginis and BL Herculis variables, the type II Cepheids. (...) The average absolute magnitude of an RR Lyrae star is about +0.75, only 40 or 50 times brighter than the Sun.

So the RR Lyrae stars that we see in globular clusters started out with a mass of about 0.8 solar masses! They would have started out as rather faint K-type main sequence stars just a little more massive than the components of binary star 61 Cygni if they had been metal-rich! And yet they are now 40-50 times brighter than the Sun!


This is my point. All stars in globular clusters (with perhaps an extremely few rare exceptions) are less massive than the Sun. After billions and billions of years, these low-mass stars slowly start evolving into gianthood. That is why we see red giants in globular clusters. These red giants are reasonably bright, perhaps, oh, 300 times brighter than the Sun? 500 times brighter? But they are all less massive than the Sun, perhaps only half as massive as the Sun!

So the red giants of globular clusters started out as low-mass main sequence stars no more massive than the Sun (and probably less massive), and after more than 10 billion years, they have used up the hydrogen in their cores and evolved into red giants.

Does that mean that there were never any really massive stars in globular clusters? 😲

Of course there were! Duh!!! But they used up their core hydrogen very quickly and ran through all their evolutionary stages and exploded as supernovas! And the stars that were not massive enough to go supernova, but still more massive than the Sun, have all turned into white dwarfs.

Except that Omega Centauri may have been different. Omega Centauri is the core of a disrupted dwarf galaxy, and I'm not absolutely convinced that cores of dwarf galaxies ever contained a lot of massive stars. But who knows?

This is my point. Omega Centauri is still going strong.


But he is an old man!!!

Ann
You do not have the required permissions to view the files attached to this post.
Color Commentator

User avatar
Ann
4725 Å
Posts: 13297
Joined: Sat May 29, 2010 5:33 am

Re: APOD: Millions of Stars in Omega Centauri (2023 Mar 16)

Post by Ann » Thu Mar 16, 2023 9:37 am

VictorBorun wrote: Thu Mar 16, 2023 4:23 am I thought you can't very well see both red giants and old under-Suns in the same exposure at the same distance?
And how come there are thousands of red giants — they mostly should long since had gone white dwarfs… or are they being created in the thick of the cluster from star to star mergers?
The red giants in Omega Centauri are low-mass stars. Apart from the likely presence of some blue straggler stars, which are merger products and therefore more massive, all stars in Omega Centauri are probably less massive than the Sun. That is because all the stars in Omega Centauri that started out more massive than the Sun have already turned into white dwarfs, or in a few cases even into neutron stars.

That's because these stars are so old! And all those massive stars that were once there have already gone poof!

Click to play embedded YouTube video.
The evolution of a star cluster. Note the stars that go poof.


Slowly time eats away at the massive stars. Fewer and fewer of them remain. But even the lesser stars eventually run out of hydrogen in their cores. Even they turn into red giants eventually, even those that are less massive than the Sun.

The red giants of Omega Centauri are in most cases either about half as massive as the Sun, or, at best, the same mass as the Sun.

Consider the red giants of Omega Centauri as a preview of what will eventually happen to the Sun!

Ann
Color Commentator

User avatar
AVAO
Science Officer
Posts: 486
Joined: Tue May 28, 2019 12:24 pm
AKA: multiwavelength traveller
Location: Zurich, Switzerland

Re: APOD: Millions of Stars in Omega Centauri (2023 Mar 16)

Post by AVAO » Thu Mar 16, 2023 4:12 pm

Ann wrote: Thu Mar 16, 2023 7:28 am ... Except that Omega Centauri may have been different. Omega Centauri is the core of a disrupted dwarf galaxy, and I'm not absolutely convinced that cores of dwarf galaxies ever contained a lot of massive stars. But who knows? ...

Ann
ThanX 4 you great explanations, Ann! Maybe NGC 1705 is a good example.

"The dwarf galaxy NGC 1705 lies in the southern constellation Pictor, and is approximately 17 million light-years from Earth. NGC 1705 is a cosmic oddball — it is small, irregularly shaped, and has recently undergone a spate of star formation known as a starburst ... NGC 1705 is an ideal laboratory to conduct investigations on the history of star formation. Young, blue, hot stars are strongly concentrated toward the galaxy's centre."

Image
Image credit:ESA/Hubble & NASA, R. Chandar
zoooom:https://esahubble.org/images/potw2205a/zoomable/
Image
Image credit: NASA, ESA and the Hubble Heritage Team (STScI/AURA)

More details: https://www.researchgate.net/figure/HST ... _231045485

User avatar
johnnydeep
Commodore
Posts: 2698
Joined: Sun Feb 20, 2011 8:57 pm

Re: APOD: Millions of Stars in Omega Centauri (2023 Mar 16)

Post by johnnydeep » Thu Mar 16, 2023 7:43 pm

I'll note that one of the links describes Omega Centauri as "highly flattened" (compared to the typical GC). It doesn't look all that flattened to me, but I suppose there is some flattening along a line through the 7 and 1 o'clock positions? But are we even looking at it from within the plane of it's primary flattening (i.e., more edge-on thar face-on")?
--
"To B̬̻̋̚o̞̮̚̚l̘̲̀᷾d̫͓᷅ͩḷ̯᷁ͮȳ͙᷊͠ Go......Beyond The F͇̤i̙̖e̤̟l̡͓d͈̹s̙͚ We Know."{ʲₒʰₙNYᵈₑᵉₚ}

HughV
Asternaut
Posts: 2
Joined: Thu Mar 16, 2023 10:09 pm

Re: APOD: Millions of Stars in Omega Centauri (2023 Mar 16)

Post by HughV » Thu Mar 16, 2023 10:24 pm

Sitting around, I am calculating that the mean instellar distance in this cluster is around 0.262 light years. 150 ly dia, 1.8E6 ly^3, 55.55 stars/ly^3, 55.55^0.3333≈3.82, 1/3.82≈0.262ly. Just checking. Interesting that they don't end up in one big accretion! Perpetually in orbit around each other?
Thanks,
Hugh

User avatar
Fred the Cat
Theoretic Apothekitty
Posts: 955
Joined: Mon Feb 22, 2016 4:09 pm
AKA: Ron
Location: Eagle, Idaho

Re: APOD: Millions of Stars in Omega Centauri (2023 Mar 16)

Post by Fred the Cat » Thu Mar 16, 2023 11:13 pm

What Ann said condensed in a video? Bees buzzing around not inclued. :wink:
Freddy's Felicity "Only ascertain as a cat box survivor"

User avatar
Chris Peterson
Abominable Snowman
Posts: 18035
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA

Re: APOD: Millions of Stars in Omega Centauri (2023 Mar 16)

Post by Chris Peterson » Fri Mar 17, 2023 12:48 am

HughV wrote: Thu Mar 16, 2023 10:24 pm Sitting around, I am calculating that the mean instellar distance in this cluster is around 0.262 light years. 150 ly dia, 1.8E6 ly^3, 55.55 stars/ly^3, 55.55^0.3333≈3.82, 1/3.82≈0.262ly. Just checking. Interesting that they don't end up in one big accretion! Perpetually in orbit around each other?
Thanks,
Hugh
There's no mechanism for them to accrete. That would require collisions, and while the distance between the stars may seem small, those distances are huge compared with the size of the stars. And the volume of the star in a cubic light year is but the tiniest fraction of a cubic light year. So while they're close enough together to influence each other's orbits as they pass, that's all they do.

Another way of looking at it is that this globular cluster is mostly empty space. Images fool us, because stars appear massively larger than they actually are. If everything were to scale, every star in the image would be a tiny, tiny fraction of the size of a single pixel. I wrote a simulation of a million star globular years ago and projected lines through it (kind of like sticking long pins in a fluffy ball). It takes thousands of such random lines before one actually contacts a star.
Chris

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

HughV
Asternaut
Posts: 2
Joined: Thu Mar 16, 2023 10:09 pm

Re: APOD: Millions of Stars in Omega Centauri (2023 Mar 16)

Post by HughV » Fri Mar 17, 2023 12:57 pm

Hello Chris,

Point taken, thank you.

In thinking about an individual star inside a very large homogeneously-distributed 3D array of similar stars, it stands to reason that the net gravitational force in any direction, on said star, is nearly zero. For the stars at the edge of such a cluster I imagine that this quickly moves into consideration of dark/interstellar matter's gravitational contributions to the forces pulling on these stellar objects....

I am now running away screaming and waving my hands from these calculations on the blackboard!

Thanks again for the reality check on how far 1/4 ly actually is, compared to the size of any given star.

-Hugh

User avatar
johnnydeep
Commodore
Posts: 2698
Joined: Sun Feb 20, 2011 8:57 pm

Re: APOD: Millions of Stars in Omega Centauri (2023 Mar 16)

Post by johnnydeep » Fri Mar 17, 2023 1:55 pm

HughV wrote: Thu Mar 16, 2023 10:24 pm Sitting around, I am calculating that the mean instellar distance in this cluster is around 0.262 light years. 150 ly dia, 1.8E6 ly^3, 55.55 stars/ly^3, 55.55^0.3333≈3.82, 1/3.82≈0.262ly. Just checking. Interesting that they don't end up in one big accretion! Perpetually in orbit around each other?
Thanks,
Hugh
I think it's only 5.6 stars / ly^3. That's 1e7 stars / 1.76e6 ly^3.
--
"To B̬̻̋̚o̞̮̚̚l̘̲̀᷾d̫͓᷅ͩḷ̯᷁ͮȳ͙᷊͠ Go......Beyond The F͇̤i̙̖e̤̟l̡͓d͈̹s̙͚ We Know."{ʲₒʰₙNYᵈₑᵉₚ}

User avatar
Ann
4725 Å
Posts: 13297
Joined: Sat May 29, 2010 5:33 am

Re: APOD: Millions of Stars in Omega Centauri (2023 Mar 16)

Post by Ann » Fri Mar 17, 2023 3:18 pm

Fred the Cat wrote: Thu Mar 16, 2023 11:13 pm What Ann said condensed in a video? Bees buzzing around not inclued. :wink:
Thanks, Fred! I love the Omega Centauri proper motion video! :D

Ann
Color Commentator

User avatar
Chris Peterson
Abominable Snowman
Posts: 18035
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA

Re: APOD: Millions of Stars in Omega Centauri (2023 Mar 16)

Post by Chris Peterson » Fri Mar 17, 2023 6:00 pm

Ann wrote: Fri Mar 17, 2023 3:18 pm
Fred the Cat wrote: Thu Mar 16, 2023 11:13 pm What Ann said condensed in a video? Bees buzzing around not inclued. :wink:
Thanks, Fred! I love the Omega Centauri proper motion video! :D

Ann
We often do compare globular clusters to bee swarms. How far can we take that? Stars at the very center of Omega Centauri average 0.16 light years apart. If we take an average star diameter to be 1 million km, then the stars are 1.5 million times their own diameter apart. So if we have a bee swarm, and bees are 1 cm long, that means each bee is 15 km from its nearest neighbor. Not a very scary "swarm"!

It also helps us visualize why stellar collisions in globulars are so rare. In a bee swarm where the bees are 15 km apart, how often will two of them fly into each other?
Chris

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

User avatar
johnnydeep
Commodore
Posts: 2698
Joined: Sun Feb 20, 2011 8:57 pm

Re: APOD: Millions of Stars in Omega Centauri (2023 Mar 16)

Post by johnnydeep » Fri Mar 17, 2023 6:52 pm

Chris Peterson wrote: Fri Mar 17, 2023 6:00 pm
Ann wrote: Fri Mar 17, 2023 3:18 pm
Fred the Cat wrote: Thu Mar 16, 2023 11:13 pm What Ann said condensed in a video? Bees buzzing around not inclued. :wink:
Thanks, Fred! I love the Omega Centauri proper motion video! :D

Ann
We often do compare globular clusters to bee swarms. How far can we take that? Stars at the very center of Omega Centauri average 0.16 light years apart. If we take an average star diameter to be 1 million km, then the stars are 1.5 million times their own diameter apart. So if we have a bee swarm, and bees are 1 cm long, that means each bee is 15 km from its nearest neighbor. Not a very scary "swarm"!

It also helps us visualize why stellar collisions in globulars are so rare. In a bee swarm where the bees are 15 km apart, how often will two of them fly into each other?
Yes, but you're overlooking the little known effect of "stellar pheromones" that enable stars to seek each other out. :ssmile:
--
"To B̬̻̋̚o̞̮̚̚l̘̲̀᷾d̫͓᷅ͩḷ̯᷁ͮȳ͙᷊͠ Go......Beyond The F͇̤i̙̖e̤̟l̡͓d͈̹s̙͚ We Know."{ʲₒʰₙNYᵈₑᵉₚ}

User avatar
Ann
4725 Å
Posts: 13297
Joined: Sat May 29, 2010 5:33 am

Re: APOD: Millions of Stars in Omega Centauri (2023 Mar 16)

Post by Ann » Fri Mar 17, 2023 7:06 pm

Chris Peterson wrote: Fri Mar 17, 2023 6:00 pm
Ann wrote: Fri Mar 17, 2023 3:18 pm
Fred the Cat wrote: Thu Mar 16, 2023 11:13 pm What Ann said condensed in a video? Bees buzzing around not inclued. :wink:
Thanks, Fred! I love the Omega Centauri proper motion video! :D

Ann
We often do compare globular clusters to bee swarms. How far can we take that? Stars at the very center of Omega Centauri average 0.16 light years apart. If we take an average star diameter to be 1 million km, then the stars are 1.5 million times their own diameter apart. So if we have a bee swarm, and bees are 1 cm long, that means each bee is 15 km from its nearest neighbor. Not a very scary "swarm"!

It also helps us visualize why stellar collisions in globulars are so rare. In a bee swarm where the bees are 15 km apart, how often will two of them fly into each other?
I get you, Chris.

My own greatest mathematical feat by far was creating a reasonable correct model of the inner Solar system, starting with a blue cotton ball 2 centimeters (a bit less than an inch) in diameter. From that, I created my own "Sun" (a table cloth, some two meters in diameter) and more cotton balls for Venus and Mars and yellow peas for Mercury and the Moon.

Well, after I had placed these things at reasonably correct distances from one another, I was gobsmacked! I couldn't believe how far they were from one another, and how impossibly "empty" the inner Solar system is! (Well, the Moon is very close to the Earth, of course - that became almost painfully obvious when I compared distances in my Solar system model, so it's no wonder that humans have visited the Moon.)

So it's really, really not surprising that the stars of globular clusters are nowhere near as closely packed together as we tend to think they are.

I love this picture of a part of globular cluster NGC 6752 and a small faint dwarf galaxy, Bedin 1, shining right through it:

bedin1[1].png

The caption of the picture reads like this:

This is a Hubble Space Telescope image of a concentration of stars within the globular cluster NGC 6752. Hidden among the stars is an image of a background galaxy that is much farther away. The diminutive galaxy, named by its discoverers as Bedin 1, measures only around 3,000 light-years at its greatest extent — a fraction of the size of the Milky Way. Not only is it tiny, but it is also incredibly faint. These properties led astronomers to classify it as a dwarf spheroidal galaxy that is as old as the universe.
Credits: NASA, ESA and L. Bedin (Astronomical Observatory of Padua, Italy)



So space is indeed incredibly empty, and stars almost never collide. But inside a globular cluster, stars do play pinball with each other.

Click to play embedded YouTube video.

Ann
You do not have the required permissions to view the files attached to this post.
Color Commentator

User avatar
johnnydeep
Commodore
Posts: 2698
Joined: Sun Feb 20, 2011 8:57 pm

Re: APOD: Millions of Stars in Omega Centauri (2023 Mar 16)

Post by johnnydeep » Fri Mar 17, 2023 7:53 pm

What I find even more amazing is that not only is inter-planetary, and interstellar space incredibly empty (though much less so inter-galactic space!), but intra-atomic space is also incredibly empty!
--
"To B̬̻̋̚o̞̮̚̚l̘̲̀᷾d̫͓᷅ͩḷ̯᷁ͮȳ͙᷊͠ Go......Beyond The F͇̤i̙̖e̤̟l̡͓d͈̹s̙͚ We Know."{ʲₒʰₙNYᵈₑᵉₚ}

User avatar
johnnydeep
Commodore
Posts: 2698
Joined: Sun Feb 20, 2011 8:57 pm

Re: APOD: Millions of Stars in Omega Centauri (2023 Mar 16)

Post by johnnydeep » Fri Mar 17, 2023 8:04 pm

Ann wrote "My own greatest mathematical feat by far was creating a reasonable correct model of the inner Solar system, starting with a blue cotton ball 2 centimeters (a bit less than an inch) in diameter. From that, I created my own "Sun" (a table cloth, some two meters in diameter) and more cotton balls for Venus and Mars and yellow peas for Mercury and the Moon."

Presumably you had to do this in a large field since your Earth would be about 214 meters away from your Sun, right? (107 Sun diameters).
--
"To B̬̻̋̚o̞̮̚̚l̘̲̀᷾d̫͓᷅ͩḷ̯᷁ͮȳ͙᷊͠ Go......Beyond The F͇̤i̙̖e̤̟l̡͓d͈̹s̙͚ We Know."{ʲₒʰₙNYᵈₑᵉₚ}

User avatar
Ann
4725 Å
Posts: 13297
Joined: Sat May 29, 2010 5:33 am

Re: APOD: Millions of Stars in Omega Centauri (2023 Mar 16)

Post by Ann » Fri Mar 17, 2023 8:21 pm

johnnydeep wrote: Fri Mar 17, 2023 8:04 pm Ann wrote "My own greatest mathematical feat by far was creating a reasonable correct model of the inner Solar system, starting with a blue cotton ball 2 centimeters (a bit less than an inch) in diameter. From that, I created my own "Sun" (a table cloth, some two meters in diameter) and more cotton balls for Venus and Mars and yellow peas for Mercury and the Moon."

Presumably you had to do this in a large field since your Earth would be about 214 meters away from your Sun, right? (107 Sun diameters).
I did have a long straight sidewalk and bicycle path in a park, where I set up my inner Solar system.

Ann
Color Commentator

User avatar
johnnydeep
Commodore
Posts: 2698
Joined: Sun Feb 20, 2011 8:57 pm

Re: APOD: Millions of Stars in Omega Centauri (2023 Mar 16)

Post by johnnydeep » Fri Mar 17, 2023 8:31 pm

Ann wrote: Fri Mar 17, 2023 8:21 pm
johnnydeep wrote: Fri Mar 17, 2023 8:04 pm Ann wrote "My own greatest mathematical feat by far was creating a reasonable correct model of the inner Solar system, starting with a blue cotton ball 2 centimeters (a bit less than an inch) in diameter. From that, I created my own "Sun" (a table cloth, some two meters in diameter) and more cotton balls for Venus and Mars and yellow peas for Mercury and the Moon."

Presumably you had to do this in a large field since your Earth would be about 214 meters away from your Sun, right? (107 Sun diameters).
I did have a long straight sidewalk and bicycle path in a park, where I set up my inner Solar system.

Ann
Nice. And using that same scale, Proxima Centauri would then be about 268000 * 214 meters (57000 km) away!
--
"To B̬̻̋̚o̞̮̚̚l̘̲̀᷾d̫͓᷅ͩḷ̯᷁ͮȳ͙᷊͠ Go......Beyond The F͇̤i̙̖e̤̟l̡͓d͈̹s̙͚ We Know."{ʲₒʰₙNYᵈₑᵉₚ}

User avatar
Ann
4725 Å
Posts: 13297
Joined: Sat May 29, 2010 5:33 am

Re: APOD: Millions of Stars in Omega Centauri (2023 Mar 16)

Post by Ann » Fri Mar 17, 2023 8:44 pm

johnnydeep wrote: Fri Mar 17, 2023 8:31 pm
Ann wrote: Fri Mar 17, 2023 8:21 pm
johnnydeep wrote: Fri Mar 17, 2023 8:04 pm Ann wrote "My own greatest mathematical feat by far was creating a reasonable correct model of the inner Solar system, starting with a blue cotton ball 2 centimeters (a bit less than an inch) in diameter. From that, I created my own "Sun" (a table cloth, some two meters in diameter) and more cotton balls for Venus and Mars and yellow peas for Mercury and the Moon."

Presumably you had to do this in a large field since your Earth would be about 214 meters away from your Sun, right? (107 Sun diameters).
I did have a long straight sidewalk and bicycle path in a park, where I set up my inner Solar system.

Ann
Nice. And using that same scale, Proxima Centauri would then be about 268000 * 214 meters (57000 km) away!
Yeah, well. I decided to give not only Proxima a miss, but to skip Jupiter, Saturn, Uranus, Neptune, Pluto and Charon, the Kuiper Belt and the Oort Cloud, too.

Ann
Color Commentator

User avatar
Chris Peterson
Abominable Snowman
Posts: 18035
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA

Re: APOD: Millions of Stars in Omega Centauri (2023 Mar 16)

Post by Chris Peterson » Fri Mar 17, 2023 9:12 pm

Ann wrote: Fri Mar 17, 2023 8:44 pm
johnnydeep wrote: Fri Mar 17, 2023 8:31 pm
Ann wrote: Fri Mar 17, 2023 8:21 pm

I did have a long straight sidewalk and bicycle path in a park, where I set up my inner Solar system.

Ann
Nice. And using that same scale, Proxima Centauri would then be about 268000 * 214 meters (57000 km) away!
Yeah, well. I decided to give not only Proxima a miss, but to skip Jupiter, Saturn, Uranus, Neptune, Pluto and Charon, the Kuiper Belt and the Oort Cloud, too.

Ann
I've done this with my science class, using a basketball for the Sun (and a peppercorn for the Earth). We can get to Pluto by walking from one end of town to the other, about a kilometer.
Chris

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

User avatar
Ann
4725 Å
Posts: 13297
Joined: Sat May 29, 2010 5:33 am

Re: APOD: Millions of Stars in Omega Centauri (2023 Mar 16)

Post by Ann » Sat Mar 18, 2023 8:02 am

johnnydeep wrote: Fri Mar 17, 2023 7:53 pm What I find even more amazing is that not only is inter-planetary, and interstellar space incredibly empty (though much less so inter-galactic space!), but intra-atomic space is also incredibly empty!

I've been wanting to reply to this since I read your post, Fred, but first I had to find out the English word for the yellow vertical things that you can see in this picture:


I've been googling for half an hour, and Google has helpfully suggested I should call them rods, bars, staffs or banisters. I'm tentatively going to call them poles!


So anyway, Johnny, this happened when I was 16, and I and three of my classmates were riding a bus together, and we couldn't get any seats, so we were standing up and holding on to a - pole, I guess. The bus was turning and braking, and we were all holding on to that same pole and giggling. And one of the boys, a really witty one, said, You know this pole doesn't exist? It's all emptiness inside! And we giggled even harder.


Indeed, the emptiness in the subatomic world is astounding. And yet that world isn't empty at all, but seething with particles, virtual and otherwise, and different kinds of forces. Here are a few attempts at visualizing the amazing proton:


Here is a video where we can see how artist James LaPlante came to create his visualization of the proton:

Click to play embedded YouTube video.


And I highly, highly recommend this article about the proton, where you can learn some pretty amazing facts and look at some totally cool animations!

Did you know, for example that the three long-lived quarks inside the proton - two "up" quarks and one "down" quark - together just comprise 1% of the proton's total mass? :shock: Amazing, isn't it?

Ann
Color Commentator

User avatar
johnnydeep
Commodore
Posts: 2698
Joined: Sun Feb 20, 2011 8:57 pm

Re: APOD: Millions of Stars in Omega Centauri (2023 Mar 16)

Post by johnnydeep » Sat Mar 18, 2023 2:55 pm

Ann wrote: Sat Mar 18, 2023 8:02 am
johnnydeep wrote: Fri Mar 17, 2023 7:53 pm What I find even more amazing is that not only is inter-planetary, and interstellar space incredibly empty (though much less so inter-galactic space!), but intra-atomic space is also incredibly empty!

I've been wanting to reply to this since I read your post, Fred, but first I had to find out the English word for the yellow vertical things that you can see in this picture:
...
Hey, what's Fred got to do with this? :ssmile:
Ann wrote:
Indeed, the emptiness in the subatomic world is astounding. And yet that world isn't empty at all, but seething with particles, virtual and otherwise, and different kinds of forces. Here are a few attempts at visualizing the amazing proton:
...

...

And I highly, highly recommend this article about the proton, where you can learn some pretty amazing facts and look at some totally cool animations!

Did you know, for example that the three long-lived quarks inside the proton - two "up" quarks and one "down" quark - together just comprise 1% of the proton's total mass? :shock: Amazing, isn't it?

Ann
No fair! It was I who posted that link to the Quanta Magazine article a while back about the amazing complexity of the proton! At the time Chris was in disagreement about whether it really was complex or not. I still happen to think it's pretty darn complex, the fact that all that complexity is due to extremely short lived "virtual" particles notwithstanding!

As for my remark on the empty space inside atoms, I was mainly referring to that between the electron cloud (which determines the size of an atom) and the much tinier nucleus. But consider this deep thought of the day: the fact that all matter can ultimately be compressed out of existence inside the singularity of a black hole makes me suspect that perhaps all matter is simply an epiphenomenological mirage, and it's really just "space all the way down"!
--
"To B̬̻̋̚o̞̮̚̚l̘̲̀᷾d̫͓᷅ͩḷ̯᷁ͮȳ͙᷊͠ Go......Beyond The F͇̤i̙̖e̤̟l̡͓d͈̹s̙͚ We Know."{ʲₒʰₙNYᵈₑᵉₚ}

User avatar
Ann
4725 Å
Posts: 13297
Joined: Sat May 29, 2010 5:33 am

Re: APOD: Millions of Stars in Omega Centauri (2023 Mar 16)

Post by Ann » Sat Mar 18, 2023 5:00 pm

johnnydeep wrote: Sat Mar 18, 2023 2:55 pm
Ann wrote: Sat Mar 18, 2023 8:02 am
johnnydeep wrote: Fri Mar 17, 2023 7:53 pm What I find even more amazing is that not only is inter-planetary, and interstellar space incredibly empty (though much less so inter-galactic space!), but intra-atomic space is also incredibly empty!

I've been wanting to reply to this since I read your post, Fred, but first I had to find out the English word for the yellow vertical things that you can see in this picture:
...
Hey, what's Fred got to do with this? :ssmile:
Sorry! 😳
Ann wrote:
Indeed, the emptiness in the subatomic world is astounding. And yet that world isn't empty at all, but seething with particles, virtual and otherwise, and different kinds of forces. Here are a few attempts at visualizing the amazing proton:
...

...

And I highly, highly recommend this article about the proton, where you can learn some pretty amazing facts and look at some totally cool animations!

Did you know, for example that the three long-lived quarks inside the proton - two "up" quarks and one "down" quark - together just comprise 1% of the proton's total mass? :shock: Amazing, isn't it?

Ann
No fair! It was I who posted that link to the Quanta Magazine article a while back about the amazing complexity of the proton! At the time Chris was in disagreement about whether it really was complex or not. I still happen to think it's pretty darn complex, the fact that all that complexity is due to extremely short lived "virtual" particles notwithstanding!
Sorry! You're right! Forgive me! 😳 :oops:
As for my remark on the empty space inside atoms, I was mainly referring to that between the electron cloud (which determines the size of an atom) and the much tinier nucleus. But consider this deep thought of the day: the fact that all matter can ultimately be compressed out of existence inside the singularity of a black hole makes me suspect that perhaps all matter is simply an epiphenomenological mirage, and it's really just "space all the way down"!
Yes... the proton is not the best example of the quantum world emptiness, is it?

And there is space all the way down. I agree.


In the picture at right, there are turtles all the way down. I wonder why the woman is naked and her lover is not. And what is that peeping old man up to? Disregarding that, it's a beautiful image.
Daniel Cook wrote:

Here is the painting I made for Valentine’s Day this year. If you haven’t planted a big juicy smacker on someone’s passionately pleasurable lips, you now have a mission. Precious moments of nibbling and kissing are ‘a wasting!

The painting title comes from a hilariously metaphysical physics joke. This is the sort of thing that kept all the science students chortling late into the night as we crunched vector fields and fudged probability envelopes.

A well-known scientist (some say it was Bertrand Russell) once gave a public lecture on astronomy. He described how the Earth orbits around the sun and how the sun, in turn, orbits around the centre of a vast collection of stars called our galaxy.

At the end of the lecture, a little old lady at the back of the room got up and said: “What you have told us is rubbish. The world is really a flat plate supported on the back of a giant tortoise.”

The scientist gave a superior smile before replying, “What is the tortoise standing on?”

“You’re very clever, young man, very clever,” said the old lady. “But it’s turtles all the way down!”
I'm with you, Johnny (not Fred). I think, like you, that there is "space all the way down".


Ann
Color Commentator