APOD: Star Cluster R136 Breaks Out (2021 Jan 10)

[APOD Robot]

Star Cluster R136 Breaks Out

Explanation: In the center of nearby star-forming region lies a huge cluster containing some of the largest, hottest, and most massive stars known. These stars, known collectively as star cluster R136, part of the Tarantula Nebula, were captured in the featured image in visible light in 2009 through the Hubble Space Telescope. Gas and dust clouds in the Tarantula Nebula, have been sculpted into elongated shapes by powerful winds and ultraviolet radiation from these hot cluster stars. The Tarantula Nebula lies within a neighboring galaxy known as the Large Magellanic Cloud and is located a mere 170,000 light-years away.

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[Ann]

R136 is the central condensation of the magnificent star cluster NGC 2070. NASA, ESA, & F. Paresce (INAF-IASF), R. O'Connell (U. Virginia) et al.

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The central condensation of R136 resolved by Hubble in the image at left. The image on the right is a pseudo-image, created from the UV spectra collected with the Space Telescope Imaging Spectrograph (STIS). ESA/Hubble, NASA, K.A. Bostroem (STScI/UC Davis)

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Professor Paul Crowther, University of Sheffield, wrote about the data that had been collected about R136a by STIS:

The ultraviolet STIS spectral survey of all stars more massive than ~25 solar masses has revealed:

a) the bulk of the visual brightest members of R136 are O2-3 stars
b) comparison of wind velocities of early O stars with those elsewhere in the LMC and the Milky Way indicate somewhat lower velocities for R136 stars
c) physical parameter estimates reveal several dozen stars more massive than 50 solar masses, with 9 stars exceeding 100 solar masses (including R136c)
d) we obtain a cluster mass of approximately 1.5 Myr
e) we have considered the integrated UV spectrum of R136a - close to 100 per cent of the HeII 1640 flux and 32 per cent of the far-UV continuum arises from very massive stars. Prominent HeII emission in the integrated spectrum of young star clusters would favour a mass function that extends well above 100 solar masses

According to Wikipedia, the most massive star in R136, R136a1, has a mass of 215 M_☉ and a luminosity of 6.16 million L_☉.

Massive star forming region NGC 604 in the Triangulum Galaxy. ESA/Hubble and NASA, https://esahubble.org/images/potw1019a/

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R136 in the Large Magellanic Cloud is a truly magnificent cluster. Its only contender as a site of massive star formation in the Local Group of Galaxies (where the Milky Way is a member) is NGC 604 in M33, the Triangulum Galaxy.

Note in the image of NGC 604 how the fierce stellar winds have blown bubbles in the surrounding nebula. Note the "wall" separating two large cavities, one on the left and one on the right.

The cavity on the right is full of massive stars, whereas the cavity on the left seems almost empty by comparison. The cavity on the left is clearly older, and the most massive stars that were born there there have spent their youthful energy and exploded as supernovas or turned into white dwarfs. But the stars in the cavity on the right are still in the prime of their lives.

Ann

[De58te]

I think it is kind of interesting that in spite of all the 1,000 or so stars are all blue except for one single red loner, that the nebula they are breaking out of is all colors, red, yellow, orange, green, white and black ... except blue.

[Ann]

I think it is kind of interesting that in spite of all the 1,000 or so stars are all blue except for one single red loner, that the nebula they are breaking out of is all colors, red, yellow, orange, green, white and black ... except blue.

The colors have to do with the youthfulness of the stars (circa 1.5 million years) and their high mass and luminosity. Young massive stars emit most of their light in the invisible ultraviolet. In visual light, they emit more blue than green, yellow and red light.

The image is a composite of separate exposures made by the WFC3 instrument on the Hubble Space Telescope. Five filters were used to sample broad and narrow wavelength ranges for the UVIS image. Two filters were used to sample broad wavelength ranges from the IR image. The colors result from assigning different hues (colors) to each monochromatic image. In this case, the assigned colors are: Blue: F336W (U) + F438W (B) Green: F555W (V) Red: F814W (I) Orange/red: F656N (H-alpha). Photo: NASA, ESA, F. Paresce (INAF-IASF, Bologna, Italy), R. O'Connell (University of Virginia, Charlottesville), and the Wide Field Camera 3 Science Oversight Committee

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What about the filters used for the image that is today's APOD?

The filters for the image were 336W (U), 438W (B), 555W (V), 656N (H-alpha) and 814W (I).

Four of the filters were wideband filters, which is to say that they react to many wavelengths of a particular part of the electromagnetic spectrum. For example, 336W (U) means that this is a filter that reacts to invisible ultraviolet wavelengths both longer and shorter than 336 nm, but centered on 336 nm. (656N, by contrast, means a narrowband filter which will respond to just one wavelength.)

To understand the colors of the R136 as portrayed by Hubble, you must understand that the massive young stars of R136 emit absolutely huge amounts of invisible ultraviolet light. But in the Hubble picture, ultraviolet light is mapped as visible blue light. That will make the hot ultraviolet stars of R136 look very blue indeed.

In the picture at right, however, R136 is seen in infrared light, which corresponds to cool temperatures. Note how numerous small stars, which were almost invisible in the "blue" image of R136, suddenly pops out. These stars are small and cool and emit most of their light at infrared wavelengths, which is why they will be seen well in infrared images. Also some of the additional stars in the infrared image may be background objects whose infrared light penetrates the dark dust cloud to the "left" of R136.

The one red star in the "blue" picture of R136 looks very bright indeed in the infrared image. That is because all red or orange stars are bright at infrared wavelengths. It is clear that this one bright and orange star is different from the other stars of R136.

Ann

[orin stepanek]

I'm noticing what looks like a lot of double stars!
Very beautiful picture from 30 Doradus; Cluster R136!

[VictorBorun]

unusual to see spiked stars in another galaxy. They are bright and the LMC galaxy is near.

I wonder what large ghostly red tiles in the background of the top half of the left cavity can be.
They don't feel astronomic at all.

[Robolt]

Why do nearby stars, but not distant ones, show the spikes in the image?

[neufer]

Why do nearby stars, but not distant ones, show the spikes in the image?

Why do you think that all the stars with (diffraction) spikes are "nearby" stars?

[Chris Peterson]

Why do nearby stars, but not distant ones, show the spikes in the image?

Every star has diffraction spikes. Whether they rise above the noise floor and are visible is determined only by intensity. A star that is four times brighter and twice as far away will show identical spikes to one that is a quarter as bright and twice as close.

It looks like most or all of the bright stars in this image are at about the same distance, so the degree they show spikes is largely determined by their luminosity. There is no way from the image alone of accurately assessing which stars are closer and which are farther away.

[johnnydeep]

unusual to see spiked stars in another galaxy. They are bright and the LMC galaxy is near.

I wonder what large ghostly red tiles in the background of the top half of the left cavity can be.
They don't feel astronomic at all.

"Ghostly red tiles"? I don't see them. Can you point them out with a pic and arrows?

[Chris Peterson]

unusual to see spiked stars in another galaxy. They are bright and the LMC galaxy is near.

I wonder what large ghostly red tiles in the background of the top half of the left cavity can be.
They don't feel astronomic at all.

"Ghostly red tiles"? I don't see them. Can you point them out with a pic and arrows?

He's talking about the two red structures in the cavity, which look like a square and a triangle (or a square and square that is partly blocked from view along its diagonal). So yes, they do look a bit like tiles. But that's just pareidolia and our brain looking for patterns. It's a region of ionized hydrogen and it has some linear shock fronts around it (which are common enough). That they coincidentally lie at about 90° to each other makes our brains see structure that has no real physical meaning. Like the lines of stars that often jump out as us in rich star fields.

[johnnydeep]

Professor Paul Crowther, University of Sheffield, wrote about the data that had been collected about R136a by STIS:

The ultraviolet STIS spectral survey of all stars more massive than ~25 solar masses has revealed:

a) the bulk of the visual brightest members of R136 are O2-3 stars
b) comparison of wind velocities of early O stars with those elsewhere in the LMC and the Milky Way indicate somewhat lower velocities for R136 stars
c) physical parameter estimates reveal several dozen stars more massive than 50 solar masses, with 9 stars exceeding 100 solar masses (including R136c)
d) we obtain a cluster mass of approximately 1.5 Myr
e) we have considered the integrated UV spectrum of R136a - close to 100 per cent of the HeII 1640 flux and 32 per cent of the far-UV continuum arises from very massive stars. Prominent HeII emission in the integrated spectrum of young star clusters would favour a mass function that extends well above 100 solar masses

Minor correction to the Crowther article: a "mass" of 1.5 Myr? So, it's probably either an age of 1.5 Myr, or a mass of 1.5 M☉. Per the wikipedia article about R136, it's the age.

[VictorBorun]

"Ghostly red tiles"?

It's a region of ionized hydrogen and it has some linear shock fronts around it (which are common enough). That they coincidentally lie at about 90° to each other makes our brains see structure that has no real physical meaning.

linear shock front…
Like this?

Click to view full size image

[Chris Peterson]

"Ghostly red tiles"?

It's a region of ionized hydrogen and it has some linear shock fronts around it (which are common enough). That they coincidentally lie at about 90° to each other makes our brains see structure that has no real physical meaning.

linear shock front…
Like this?

Click to view full size image

If we view it that close, we tend to see other structure. But that one, viewed at lower resolution, would look pretty similar to a straight line.

[johnnydeep]

unusual to see spiked stars in another galaxy. They are bright and the LMC galaxy is near.

I wonder what large ghostly red tiles in the background of the top half of the left cavity can be.
They don't feel astronomic at all.

"Ghostly red tiles"? I don't see them. Can you point them out with a pic and arrows?

He's talking about the two red structures in the cavity, which look like a square and a triangle (or a square and square that is partly blocked from view along its diagonal). So yes, they do look a bit like tiles. But that's just pareidolia and our brain looking for patterns. It's a region of ionized hydrogen and it has some linear shock fronts around it (which are common enough). That they coincidentally lie at about 90° to each other makes our brains see structure that has no real physical meaning. Like the lines of stars that often jump out as us in rich star fields.

Ah. So these “tiles” then, I suppose:

Ghostly Red Tiles? Hardly!

Not very tile-like to me. Then again, I never see much of anything in Rorschach ink blot tests either.

[Chris Peterson]

"Ghostly red tiles"? I don't see them. Can you point them out with a pic and arrows?

He's talking about the two red structures in the cavity, which look like a square and a triangle (or a square and square that is partly blocked from view along its diagonal). So yes, they do look a bit like tiles. But that's just pareidolia and our brain looking for patterns. It's a region of ionized hydrogen and it has some linear shock fronts around it (which are common enough). That they coincidentally lie at about 90° to each other makes our brains see structure that has no real physical meaning. Like the lines of stars that often jump out as us in rich star fields.

Ah. So these “tiles” then, I suppose:

57F6A849-8904-4C32-A25A-5CADB156A504.jpeg

Not very tile-like me. Then again, I never see much of anything in Rorschach ink blot tests either. :ssmile:

But you were able to see them well enough once they were pointed out, given the precision of your outlines.

[MarkBour]

I've seen a couple of images of R136 before, but never realized that it was outside of the Milky Way.
To have this much resolution in an image of a star cluster that's 170,000 light years away seems quite amazing to me.

...
Note in the image of NGC 604 how the fierce stellar winds have blown bubbles in the surrounding nebula. Note the "wall" separating two large cavities, one on the left and one on the right.

The cavity on the right is full of massive stars, whereas the cavity on the left seems almost empty by comparison. The cavity on the left is clearly older, and the most massive stars that were born there there have spent their youthful energy and exploded as supernovas or turned into white dwarfs. But the stars in the cavity on the right are still in the prime of their lives.

Ann

I see what you're saying. The stars of the left cavity may have in some sense been the parents of the stars in the right cavity. (And, like good parents, they have faded, but can behold the glory of their children.)

[johnnydeep]

He's talking about the two red structures in the cavity, which look like a square and a triangle (or a square and square that is partly blocked from view along its diagonal). So yes, they do look a bit like tiles. But that's just pareidolia and our brain looking for patterns. It's a region of ionized hydrogen and it has some linear shock fronts around it (which are common enough). That they coincidentally lie at about 90° to each other makes our brains see structure that has no real physical meaning. Like the lines of stars that often jump out as us in rich star fields.

Ah. So these “tiles” then, I suppose:

57F6A849-8904-4C32-A25A-5CADB156A504.jpeg

Not very tile-like to me. Then again, I never see much of anything in Rorschach ink blot tests either.

But you were able to see them well enough once they were pointed out, given the precision of your outlines.

Yes, but it was a struggle, and I still wasn’t positive I found the same shapes as you guys.

[VictorBorun]

Click to view full size image

And are they background tiles? They may be foreground cast-iron fence, two adjoining squares of different size:

[VictorBorun]

Nice sight: if a garland of super giant stars is partially eclipsed by a super dense Bok globule, the light may just barely come through.

In near infrared 110W+160W that Bok globule is not nearly so dense and the stars shine right through.
It proves that in visible light they were trying to get through the ink-black globule and just showed it.

[orin stepanek]

OMG! Has anyone seen the man smiling to the right looking at the
stars?

[VictorBorun]

OMG! Has anyone seen the man smiling to the right looking at the
stars?

He has just drawn a puzzle for us: what black is background black and what black is foreground black.

on the left the black is cosmologic background and on the right the black is foreground Bok globules.

[Ann]

OMG! Has anyone seen the man smiling to the right looking at the
stars?

He has just drawn a puzzle for us: what black is background black and what black is foreground black.

on the left the black is cosmologic background and on the right the black is foreground Bok globules.

Galaxy 2MASXJ00482185-2507365 with a small foreground galaxy in front of it. Note the dusty arms of the foreground galaxy in silhouette against the bright bulge of the larger galaxy. Photo: NASA.

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Got a better one for you.

Dark is dark, and sometimes the dark stuff is foreground dust and sometimes it's just space.

Which begs the question as to why space is dark. Well, the best of the short answers, I guess, is that space is young and it has expanded fast, so that its expansion has outrun the speed of light, so that the light from many distant stars has not yet reached us and perhaps never will.

And maybe there is so much space out there that there simply aren't enough stars to cram space full of starlight anyway.

Ann

[VictorBorun]

" a small foreground galaxy " has a bar, doesn't it?

By the way, ink-black gobule is easy to tell from deep space black when you have an infrared picture to compare.
Ink-black is quite see-through in infrared.

[Ann]

" a small foreground galaxy " has a bar, doesn't it?

Barred irregular galaxy NGC 6822. Photo: Bruce Waddington.

Victor, I wish I knew, but I don't! I joined Galaxy Zoo for a while, where you were supposed to classify galaxies, but I gave up quickly because they asked me if the little blobs they showed me had a bar. How the heck would I know?

As for that little foreground thing seen in front of the large galaxy with the impossibly long name, it looks like an irregular galaxy to me. Not that that means it can't be barred!

By the way, ink-black gobule is easy to tell from deep space black when you have an infrared picture to compare.
Ink-black is quite see-through in infrared.

Right you are, Victor. Dusty areas usually look transparent in infrared photography, whereas the emptiness of space looks black.

Ann