APOD: M22 and the Wanderers (2018 Apr 12)

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APOD: M22 and the Wanderers (2018 Apr 12)

Post by APOD Robot » Thu Apr 12, 2018 4:06 am

Image M22 and the Wanderers

Explanation: Wandering through the constellation Sagittarius, bright planets Mars and Saturn appeared together in early morning skies over the last weeks. They are captured in this 3 degree wide field-of-view from March 31 in a close celestial triangle with large globular star cluster Messier 22. Of course M22 (bottom left) is about 10,000 light-years distant, a massive ball of over 100,000 stars much older than our Sun. Pale yellow and shining by reflected sunlight, Saturn (on top) is about 82 light-minutes away. Look carefully and you can spot large moon Titan as a pinpoint of light at about the 5 o'clock position in the glare of Saturn's overexposed disk. Slightly brighter and redder Mars is 9 light-minutes distant. While both planets are moving on toward upcoming oppositions, by July Mars will become much brighter still, with good telescopic views near its 2018 opposition a mere 3.2 light-minutes from planet Earth.

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De58te
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Re: APOD: M22 and the Wanderers (2018 Apr 12)

Post by De58te » Thu Apr 12, 2018 10:44 am

Cool pic. Unfortunately I am too tired at this time to get up in the morning to look for myself. When will Mars and Saturn and M22 make a similar appearance in the evening skies?
Another question about M22. What is it's actual size in light years? It looks quite compact. Are the stars closer to each other than 4 light years? Say if the average distance is 1 light year, then the constellations in the night sky of a planet there would look completely different than here on Earth. It reminds me of Issac Asimov's story Nightfall, where the inhabitants never seen a black sky at night their entire lives. Then again if all the stars were old yellow stars than likely there weren't too many supernovas creating rocks and iron for rocky planets. Although I presume there would be a huge number of gaseous Jupiter type planets there. Wonder if an intelligent space faring civilization could evolve on a gaseous planet given enough time? If so then star travel for them would be a lot shorter.

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Re: APOD: M22 and the Wanderers (2018 Apr 12)

Post by neufer » Thu Apr 12, 2018 1:06 pm

De58te wrote:
Thu Apr 12, 2018 10:44 am

Another question about M22. What is it's actual size in light years? It looks quite compact. Are the stars closer to each other than 4 light years? Say if the average distance is 1 light year, then the constellations in the night sky of a planet there would look completely different than here on Earth. It reminds me of Issac Asimov's story Nightfall, where the inhabitants never seen a black sky at night their entire lives. Then again if all the stars were old yellow stars than likely there weren't too many supernovas creating rocks and iron for rocky planets. Although I presume there would be a huge number of gaseous Jupiter type planets there. Wonder if an intelligent space faring civilization could evolve on a gaseous planet given enough time? If so then star travel for them would be a lot shorter.
  • An average distance of 1 light year sounds about right
    ...although their night skies are probably no darker than our own during a full moon.
https://en.wikipedia.org/wiki/Messier_22
<<M22 is one of the nearer globular clusters to Earth at a distance of about 10,600 light-years away. It spans 32' on the sky which translates to a spatial diameter of 99 light-years. 32 variable stars have been recorded in M22. It is projected in front of the galactic bulge and is therefore useful for its microlensing effect on the background stars in the bulge.

Despite its relative proximity to us, this metal-poor cluster's light is limited by dust extinction, giving it an apparent magnitude of 5.5 making it the brightest globular cluster visible from mid-northern latitudes. However, due to its southerly declination, M22 never rises high in the sky and so appears less impressive to northern hemisphere observers than other summer sky globulars such as M13 and M5.

M22 is very unusual in that it is one of only four globulars (the others being M15, NGC 6441 and Palomar 6) that are known to contain a planetary nebula. It was discovered using the IRAS satellite by Fred Gillett et al.,in 1986 as a pointlike source (IRAS 18333-2357) and subsequently identified as a planetary nebula in 1989 by Gillett et al. The planetary nebula's central star is a blue star. The planetary nebula (designated GJJC1) is estimated to be a mere ~6,000 years old.

Two black holes of between 10 and 20 solar masses each have been discovered, initially with the Very Large Array radio telescope in New Mexico, and corroborated by the Chandra X-ray telescope, in 2012. Their detection implies that gravitational ejection of black holes from clusters is not as efficient as was previously thought, and leads to estimates of a total 5 to 100 black holes within M22. Interactions between stars and black holes could explain the unusually large core of the cluster.>>
Art Neuendorffer

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Re: APOD: M22 and the Wanderers (2018 Apr 12)

Post by MarkBour » Thu Apr 12, 2018 3:28 pm

neufer wrote:
Thu Apr 12, 2018 1:06 pm
  • An average distance of 1 light year sounds about right
    ...although their night skies are probably no darker than our own during a full moon.
I assume you meant "no brighter than ..."
https://en.wikipedia.org/wiki/Messier_22<< ... estimates of a total 5 to 100 black holes within M22 ...>>
Wow! That's surprising to me.

Thanks for posting the fine image of M22, neufer. In that image, I think I am now understanding that most of the dots one sees (the many smaller ones) are actually not part of the cluster, but are part of our galaxy's central bulge which is behind M22. The first couple of times I saw this view (I only see this on the computer, never through a scope), I was not aware of that, so I thought the cluster had many more stars in it than it actually does?

Well, but then Wikipedia has this: https://en.wikipedia.org/wiki/Messier_22
It was one of the first globular clusters to be carefully studied first by Harlow Shapley in 1930. He discovered roughly 70,000 stars and found it had a dense core
And the caption says about 100,000 stars. So, I'm not very good at estimating on that scale, but it seems like every dot in the image you posted might barely make it to 70,000.

I'm somewhat confused, for sure.
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neufer
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Re: APOD: M22 and the Wanderers (2018 Apr 12)

Post by neufer » Thu Apr 12, 2018 5:06 pm

MarkBour wrote:
Thu Apr 12, 2018 3:28 pm
neufer wrote:
Thu Apr 12, 2018 1:06 pm
  • An average distance of 1 light year sounds about right
    ...although their night skies are probably no darker than our own during a full moon.
I assume you meant "no brighter than ..."
https://en.wikipedia.org/wiki/Cleaner_(crime) wrote:
<<A cleaner, or fixer, is a person who "cleans up" after crimes to physically erase their trace, or uses pressure or bribes to limit fallout from a criminal act. A fixer plays a similar but often less hands-on role, often minimizing bad publicity for public officials or media figures by quelling stories of their misadventures, but also capable of more heavy handed tactics, as necessary.

A cleaner may destroy or remove incriminating evidence at the scene of a crime. A popular figure in crime fiction, a cleaner may also be a contract killer who commits murder to "clean up" a situation. Cleaner is also a slang term for someone, usually a member of a crime organization or a covert government agency, who disposes of a corpse after a hit.

In contrast, legal crime scene cleanup is a legitimate industry, eliminating blood and other biohazardous materials such as dangerous chemicals used in an illegal drug lab as permitted by responsible authorities.

A fictional example of a cleaner is Shoulders from the comic strip Dick Tracy. More contemporary are the roles played by Jean Reno as Victor in the film La Femme Nikita (1990), Harvey Keitel as Victor in Point of No Return (1993), and a year later as Mr. Wolf in Quentin Tarantino's Pulp Fiction (1994) (parodied on Seinfeld`s episode 155, "The Muffin Tops" (1997), where Newman makes the problem of leftover muffin stumps go away by eating them).>>
------------------------------------------------
  • "The Muffin Tops" (1997)
At the muffin shop.

Mr. Lippman: What is this guy again?

Elaine: They call him a Cleaner. He makes problems go away.

Newman enters.

Newman: Hello Elaine. Where are they?

Elaine: In the back.

Newman: All right, I'm going to need a clean 8 ounce glass.

Mr. Lippman: What is going on here?

Newman: If I'm curt, then I appologize. But as I understand it, we have a situation here and time is of the essence.

Newman goes to the back room with the muffin stumps and sets down a cooler and an empty glass. From the cooler he takes out 4 bottles of milk and sets them down. He bites into a stump, then takes a drink of milk from the glass. He swishes the muffin and the milk together and swallows. He takes another stump.
Art Neuendorffer

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Re: APOD: M22 and the Wanderers (2018 Apr 12)

Post by Uncle Jeff » Thu Apr 12, 2018 5:09 pm

Where are Saturn's rings? (lost in over-exposure, edge on...)

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Re: APOD: M22 and the Wanderers (2018 Apr 12)

Post by Ann » Thu Apr 12, 2018 5:35 pm

De58te wrote:
Thu Apr 12, 2018 10:44 am

Another question about M22. What is it's actual size in light years? It looks quite compact. Are the stars closer to each other than 4 light years? Say if the average distance is 1 light year, then the constellations in the night sky of a planet there would look completely different than here on Earth. It reminds me of Issac Asimov's story Nightfall, where the inhabitants never seen a black sky at night their entire lives. Then again if all the stars were old yellow stars than likely there weren't too many supernovas creating rocks and iron for rocky planets. Although I presume there would be a huge number of gaseous Jupiter type planets there. Wonder if an intelligent space faring civilization could evolve on a gaseous planet given enough time? If so then star travel for them would be a lot shorter.

NGC 602 in the Small Magellanic Cloud.
Photo: Hubble/Chandra/Spitzer Space Telescopes.
We can be sure that any cluster as rich in stars as a globular cluster must have been born with many massive blue stars in them.

Take a look at NGC 602 in the Small Magellanic Cloud. At upper right in this picture, you can see a rich cluster of young stars. From the looks of it, there are about ten really massive blue stars in it (there are certainly more, since several of the hot blue stars are undoubtedly multiple), but there are also hundreds of faint stars swarming around the dominant bright ones.

Any globular cluster that still exists after billions of years was born richer than the cluster of NGC 602 in the Small Magellanic Cloud. That is why globulars like M22 still contain tens of thousands of small stars. We can be sure that any process of star formation that leads to the formation of tens of thousands of small stars also gives rise to the formation of many very massive stars. So how many really massive stars were globular clusters like M22 born with? Well, in my amateur opinion, when M22 was newborn, there were probably several hundred stars in there that were massive enough to explode as supernovas.

A couple of hundred supernovas in M22 would go a long way towards explaining the presence of 5-100 black holes in this globular.

Ann
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Re: APOD: M22 and the Wanderers (2018 Apr 12)

Post by MarkBour » Fri Apr 13, 2018 12:41 am

Hey Ann, today your post count is exactly 4000 more than your wavelength.
I'll be eating a muffin stump in celebration.
Mark Goldfain

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Ann
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Re: APOD: M22 and the Wanderers (2018 Apr 12)

Post by Ann » Fri Apr 13, 2018 6:30 am

MarkBour wrote:
Fri Apr 13, 2018 12:41 am
Hey Ann, today your post count is exactly 4000 more than your wavelength.
I'll be eating a muffin stump in celebration.
Thanks! I finished off the last piece of my version of the ultimate chocolate cake yesterday - it looked messy, but it tasted good!

Ann
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MarkBour
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Re: APOD: M22 and the Wanderers (2018 Apr 12)

Post by MarkBour » Fri Apr 13, 2018 3:56 pm

That chocolate cake looks outrageously delicious.
Mark Goldfain

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neufer
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Re: APOD: M22 and the Wanderers (2018 Apr 12)

Post by neufer » Fri Apr 13, 2018 4:05 pm

Click to play embedded YouTube video.
MarkBour wrote:
Fri Apr 13, 2018 3:56 pm
Ann wrote:
Fri Apr 13, 2018 6:30 am
MarkBour wrote:
Fri Apr 13, 2018 12:41 am

Hey Ann, today your post count is exactly 4000 more than your wavelength. I'll be eating a muffin stump in celebration.
Thanks! I finished off the last piece of my version of the ultimate chocolate cake yesterday - it looked messy, but it tasted good!
That chocolate cake looks outrageously delicious.
Art Neuendorffer