Starship Asterisk*

Posted: **Thu Aug 27, 2015 4:11 am**

The Large Cloud of Magellan

Explanation: The 16th century Portuguese navigator Ferdinand Magellan and his crew had plenty of time to study the southern sky during the first circumnavigation of planet Earth. As a result, two fuzzy cloud-like objects easily visible to southern hemisphere skygazers are known as the Clouds of Magellan, now understood to be satellite galaxies of our much larger, spiral Milky Way galaxy. About 160,000 light-years distant in the constellation Dorado, the Large Magellanic Cloud (LMC) is seen here in a remarkably deep, colorful, image. Spanning about 15,000 light-years or so, it is the most massive of the Milky Way's satellite galaxies and is the home of the closest supernova in modern times, SN 1987A. The prominent patch below center is 30 Doradus, also known as the magnificent Tarantula Nebula, is a giant star-forming region about 1,000 light-years across.

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Posted: **Thu Aug 27, 2015 6:31 am**

That's a great picture. I love seeing the entire LMC, including the large complex seen at 10 o'clock in today's APOD, NGC 1760.

Ann

Posted: **Thu Aug 27, 2015 10:43 am**

Nice Shot!
This'll make a nice replacement for Ursa Major on my 2' display.

Posted: **Thu Aug 27, 2015 1:53 pm**

If you can see a man in the moon, you may see, in the upper left corner of this picture of the Large Cloud, a face, and either a skull in profile or a frontal view of a man in a space suit.

Posted: **Thu Aug 27, 2015 2:26 pm**

What would our Galaxy would look like from there...? I imagine it would nearly fill the nighttime sky if view from the outskirts of the LMC.

Posted: **Thu Aug 27, 2015 2:27 pm**

A cloud of loveliness bliss and peace seems absent from earth so much we miss your virtue bright but Megallanic you're hope in sight that yet, that yet, we'll be alright.

Posted: **Thu Aug 27, 2015 3:23 pm**

Asterhole wrote:What would our Galaxy would look like from there...? I imagine it would nearly fill the nighttime sky if view from the outskirts of the LMC.

The Milky Way is around 100,000 light-years in diameter and the Large Magellanic Cloud is 14,000 light-years across so I suspect our galaxy would look around 7 times the angular size of the LMC. I would imagine many astronomers would love to see that view. It might clear up some conjecture.

Posted: **Thu Aug 27, 2015 4:36 pm**

Please tell me how we know that there was a supernovae in "modern" times in the LMC. It is 160,000 light years away. Light must have taken that long to get here from there. Hence we could not know about anything going on there more recently that 160,000 years. Do you define this as" modern" times? I really want to know the answer.

Posted: **Thu Aug 27, 2015 5:02 pm**

apodviewer wrote:Please tell me how we know that there was a supernovae in "modern" times in the LMC. It is 160,000 light years away. Light must have taken that long to get here from there. Hence we could not know about anything going on there more recently that 160,000 years. Do you define this as" modern" times? I really want to know the answer.

The supernova was seen to be taking place in 1987 but since the light took 160 000 years to reach Earth, it happened 160 000 years prior to 1987. There have been many historical records of supernovae appearing in the sky, most notably in 1054, which is now the Crab Nebula.

Posted: **Thu Aug 27, 2015 5:05 pm**

Ann wrote:That's a great picture. I love seeing the entire LMC, including the large complex seen at 10 o'clock in today's APOD, NGC 1760.

Ann

I also love seeing the whole Large Magellanic Cloud as well as closeups of its many nebulae and clusters! I can't resist being pedantic, NGC 1760 refers to only a small part of that particular complex (which is the second largest in the LMC), one name for the whole complex is N11 (Henize 11). Also another point to mention, a few supernova remnants and Wolf Rayet nebulae in the LMC have been imaged by professionals but almost none by amateurs? I love that the LMC contains complexes that include a HII region, multiple clusters, a SNR and WR nebula all together, the best example is N206.

Posted: **Thu Aug 27, 2015 6:26 pm**

apodviewer wrote:Please tell me how we know that there was a supernovae in "modern" times in the LMC. It is 160,000 light years away. Light must have taken that long to get here from there. Hence we could not know about anything going on there more recently that 160,000 years. Do you define this as" modern" times? I really want to know the answer.

When we see it happen. You already know this. This question gets a lot less clever after you've seen it fifty times.

Posted: **Thu Aug 27, 2015 6:48 pm**

I thought it was quite the journey to drive to Alabama this summer. Good thing the early explorers had GPS – global positioning sextants along with a really a good set of "anchors"!!

"The Mag'ic Jewels will never do but to the crew it must be true" (OK – I'll stop posting and do my real job)

Posted: **Thu Aug 27, 2015 8:26 pm**

Ron-Astro Pharmacist wrote:
Asterhole wrote:What would our Galaxy would look like from there...? I imagine it would nearly fill the nighttime sky if view from the outskirts of the LMC.
The Milky Way is around 100,000 light-years in diameter and the Large Magellanic Cloud is 14,000 light-years across so I suspect our galaxy would look around 7 times the angular size of the LMC. I would imagine many astronomers would love to see that view. It might clear up some conjecture.

NIce thought! I'd love to have that view.
The poor people in the Southern Hemisphere have to put up with us arrogant Northern Hemisphere people ("Magellan indeed," no doubt they say): http://odtmaps.com/detail.asp?product_id=McA-23x35

Posted: **Thu Aug 27, 2015 8:36 pm**

any images takes at the turn of the last century of the LMC that can be compared to this image and detect changes ? Like how Mr Tombaugh found Pluto ?

Posted: **Thu Aug 27, 2015 9:38 pm**

ta152h0 wrote:
any images takes at the turn of the last century of the LMC that can be compared to this image and detect changes ?

The first photograph of the LMC was take in 1890 at the Sydney Observatory.

One can clearly detect an improvement in telescopic photographs since 1890.

Posted: **Thu Aug 27, 2015 10:36 pm**

ta152h0 wrote:any images takes at the turn of the last century of the LMC that can be compared to this image and detect changes ? Like how Mr Tombaugh found Pluto ?

100 years simply isn't long enough to detect any changes in objects of this size. With modern high resolution imaging we might just be able to detect the proper motion of a few stars over decadal measurement scales, but that's about it.

Posted: **Thu Aug 27, 2015 11:18 pm**

In this gorgeous image, I assume there are a lot of "foreground" stars from the Milky Way. Is there a good way to digitally "remove" them, so we can see what the LMC looks like from outside of our galaxy?

Posted: **Thu Aug 27, 2015 11:21 pm**

apodviewer wrote:Please tell me how we know that there was a supernovae in "modern" times in the LMC. It is 160,000 light years away. Light must have taken that long to get here from there. Hence we could not know about anything going on there more recently that 160,000 years. Do you define this as" modern" times? I really want to know the answer.

Nothing can travel faster than light. Nothing. And everything we can know about space we know because we detect signals that have travelled here at the speed of light.

What happened on the Moon a second ago? Could it have been hit by a large meteor, which caused a flash of light as it hit the ground? We can't know until the next second.

What is happening at the outer layers of the Sun "now"? Has there just been a tremendous solar eruption "now"? We can't know until after eight minutes. Well, can't we send a satellite and place it in a moderately tight orbit around the Sun? It could see a solar eruption before we can. And then it could send a message to us and tell us about it so that we would know about it sooner, right? Wrong. Because the message from the satellite still can't travel our way faster than the speed of light. We still wouldn't know about the solar eruption until its effects actually hit us.

What is happening at the Orion Nebula "now"? All we have is some information about the Orion Nebula's status some 1,500 years ago. What do we know about the Andromeda Galaxy? Any information we have about that galaxy is two million years old.

That's spacetime for you. You either accept it and take an interest in what we can know, because we detect signals that have been travelling our way at the speed of light. Or else you conclude that we don't know anything about any object in space outside the solar system "now", and then you may choose to stop taking an interest in astronomy altogether.

It's up to you, but don't complain when others still find outer space fascinating.

Ann

Posted: **Thu Aug 27, 2015 11:55 pm**

GaryJ wrote:In this gorgeous image, I assume there are a lot of "foreground" stars from the Milky Way. Is there a good way to digitally "remove" them, so we can see what the LMC looks like from outside of our galaxy?

Not really. The LMC is so close, and so similar in composition to our galaxy, that there's no good physical way to determine which stars belong to which. So short of manually removing the stars on the edges- most of which are local- there's not much that can be done.

Posted: **Fri Aug 28, 2015 3:19 am**

Chris Peterson wrote:
ta152h0 wrote:
any images takes at the turn of the last century of the LMC that can be compared to this image and detect changes ? Like how Mr Tombaugh found Pluto ?
100 years simply isn't long enough to detect any changes in objects of this size.

With modern high resolution imaging we might just be able to detect the proper motion of a few stars over decadal measurement scales, but that's about it.

https://en.wikipedia.org/wiki/Gaia_%28spacecraft%29 wrote:
<<[Gaia should be able to determine] the position, distance, and annual proper motion of 1 billion stars
with an accuracy of about 20 microarcseconds (µas) at 15 [apparent] mag, and 200 µas at 20 [apparent] mag.>>

Hence: Gaia should be able to determine the position, distance, and annual
proper motion of LMC stars [50,000 parsecs away] with an accuracy of about:
[1 AU] at -3.5 absolute magnitude, & [10 AU] at 1.5 absolute magnitude.

https://en.wikipedia.org/wiki/SN_1987A wrote:
[b][color=#0000FF]A time sequence of Hubble Space Telescope images, taken in the 15 years from 1994 to 2009, showing the collision of the expanding supernova remnant with a ring of dense material ejected by the progenitor star 20,000 years before the supernova.[/color][/b]
SN 1987A was a supernova in the outskirts of the Tarantula Nebula in the Large Magellanic Cloud (a nearby dwarf galaxy).

The three bright rings around SN 1987A are material from the stellar wind of the progenitor. These rings were ionized by the ultraviolet flash from the supernova explosion, and consequently began emitting in various emission lines. These rings did not "turn on" until several months after the supernova; the turn-on process can be very accurately studied through spectroscopy. The rings are large enough that their angular size can be measured accurately: the inner ring is 0.808 arcseconds in radius. Using the distance light must have traveled to light up the inner ring as the base of a right angle triangle and the angular size as seen from the Earth for the local angle, one can use basic trigonometry to calculate the distance to SN1987A, which is about 168,000 light-years. The material from the explosion is catching up with the material expelled during both its red and blue supergiant phases and heating it, so we observe ring structures about the star.

Around 2001, the expanding (>7000 km/s) supernova ejecta collided with the inner ring. This caused its heating and the generation of x-rays — the x-ray flux from the ring increased by a factor of three between 2001 and 2009. A part of the x-ray radiation, which is absorbed by the dense ejecta close to the center, is responsible for a comparable increase in the optical flux from the supernova remnant in 2001–2009. This increase of the brightness of the remnant reversed the trend observed before 2001, when the optical flux was decreasing due to the decaying of ⁴⁴Ti isotope.

A study reported in June 2015, using images from the Hubble Space Telescope and the Very Large Telescope taken between 1994 and 2014, shows that the emissions from the clumps of matter making up the rings are fading as the clumps are destroyed by the shock wave. It is predicted the ring will fade away between 2020 and 2030. As the shock wave passes the circumstellar ring it will trace the history of mass loss of the supernova's progenitor and provide useful information for discriminating among various models for the progenitor of SN 1987A.>>

Posted: **Fri Aug 28, 2015 4:07 am**

neufer wrote:
Chris Peterson wrote:
ta152h0 wrote:
any images takes at the turn of the last century of the LMC that can be compared to this image and detect changes ? Like how Mr Tombaugh found Pluto ?
100 years simply isn't long enough to detect any changes in objects of this size.

With modern high resolution imaging we might just be able to detect the proper motion of a few stars over decadal measurement scales, but that's about it.
https://en.wikipedia.org/wiki/Gaia_%28spacecraft%29 wrote:
<<[Gaia should be able to determine] the position, distance, and annual proper motion of 1 billion stars
with an accuracy of about 20 microarcseconds (µas) at 15 [apparent] mag, and 200 µas at 20 [apparent] mag.>>

Hence: Gaia should be able to determine the position, distance, and annual
proper motion of LMC stars [50,000 parsecs away] with an accuracy of about:
[1 AU] at -3.5 absolute magnitude, & [10 AU] at 1.5 absolute magnitude.

I'm not sure of your point. We still aren't detecting any change in the galaxy as a function of time. And the resolution of the Gaia telescopes is far too low to resolve stars in the LMC, and most are too dim. Gaia will be able to provide very little information about anything going on in the LMC.

Posted: **Fri Aug 28, 2015 5:11 am**

Actually Gaia can resolve some stars in the LMC. Gaia has just completed its' first year of normal operation and one of the things mentioned in the ESA's blog post is this:

"Gaia has delivered detailed light curves for dozens of RR Lyrae type variable stars in the LMC, and the fine details revealed in them testify to the very high quality of the data."

They also posted their first HR diagram of just 2 million stars. They are saying that they will have the first major data release after the second year of operation is completed next year. The link is http://sci.esa.int/gaia/56387-gaia-s-fi ... ervations/

Posted: **Fri Aug 28, 2015 12:09 pm**

Chris Peterson wrote:
neufer wrote:
https://en.wikipedia.org/wiki/Gaia_%28spacecraft%29 wrote:
<<[Gaia should be able to determine] the position, distance, and annual proper motion of 1 billion stars
with an accuracy of about 20 microarcseconds (µas) at 15 [apparent] mag, and 200 µas at 20 [apparent] mag.>>

Hence: Gaia should be able to determine the position, distance, and annual
proper motion of LMC stars [50,000 parsecs away] with an accuracy of about:
[1 AU] at -3.5 absolute magnitude, & [10 AU] at 1.5 absolute magnitude.
I'm not sure of your point. We still aren't detecting any change in the galaxy as a function of time. And the resolution of the Gaia telescopes is far too low to resolve stars in the LMC, and most are too dim. Gaia will be able to provide very little information about anything going on in the LMC.

Hubble has already measured the ~10 AU/yr relative proper motion of bright LMC stars to determine that the LMC has a rotation period of 250 million years (comparable to the rotation period of the Earth around the Milky Way). Gaia should be able to improve upon this as well as search for non rotational proper motion. (I'm assuming these are the sort of changes ta152h0 was asking about.)

Posted: **Fri Aug 28, 2015 1:54 pm**

neufer wrote:
Chris Peterson wrote:I'm not sure of your point. We still aren't detecting any change in the galaxy as a function of time. And the resolution of the Gaia telescopes is far too low to resolve stars in the LMC, and most are too dim. Gaia will be able to provide very little information about anything going on in the LMC.
Hubble has already measured the ~10 AU/yr relative proper motion of bright LMC stars to determine that the LMC has a rotation period of 250 million years (comparable to the rotation period of the Earth around the Milky Way). Gaia should be able to improve upon this as well as search for non rotational proper motion. (I'm assuming these are the sort of changes ta152h0 was asking about.)

Yeah, that's what I said. Modern high resolution imaging can resolve a few stars in the LMC well enough to make such measurements. That includes both Hubble and the much lower resolution and lower sensitivity Gaia.

I read the question to be about comparing images made at different epochs and looking for visible change. That's not happening.

Posted: **Fri Aug 28, 2015 1:57 pm**

BillT wrote:Actually Gaia can resolve some stars in the LMC.

Sure. Gaia is a great instrument that is going to immensely improve our understanding of the galaxy. But it's ill suited to examining other galaxies. So outside of a few special cases like you mention, we're not going to see much in that regard. As a survey tool, it simply lacks the resolution and sensitivity to closely examine most of the internals of other galaxies.

Starship Asterisk*

APOD: The Large Cloud of Magellan (2015 Aug 27)

APOD: The Large Cloud of Magellan (2015 Aug 27)

Re: APOD: The Large Cloud of Magellan (2015 Aug 27)

Re: APOD: The Large Cloud of Magellan (2015 Aug 27)

Re: APOD: The Large Cloud of Magellan (2015 Aug 27)

Re: APOD: The Large Cloud of Magellan (2015 Aug 27)

Re: APOD: The Large Cloud of Magellan (2015 Aug 27)

Re: APOD: The Large Cloud of Magellan (2015 Aug 27)

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Re: APOD: The Large Cloud of Magellan (2015 Aug 27)

Re: APOD: The Large Cloud of Magellan (2015 Aug 27)

Re: APOD: The Large Cloud of Magellan (2015 Aug 27)

Re: APOD: The Large Cloud of Magellan (2015 Aug 27)

Re: APOD: The Large Cloud of Magellan (2015 Aug 27)

Re: APOD: The Large Cloud of Magellan (2015 Aug 27)

Re: APOD: The Large Cloud of Magellan (2015 Aug 27)

Re: APOD: The Large Cloud of Magellan (2015 Aug 27)

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Re: APOD: The Large Cloud of Magellan (2015 Aug 27)

Re: APOD: The Large Cloud of Magellan (2015 Aug 27)