Starship Asterisk*

by **Chris Peterson** » Tue Jun 04, 2024 4:26 pm

beryllium732 wrote: ↑Tue Jun 04, 2024 4:05 pm
Chris Peterson wrote: ↑Tue Jun 04, 2024 12:48 pm
beryllium732 wrote: ↑Tue Jun 04, 2024 11:49 am What would happen with the solar system if we were within 20 lightyears from a wolf rayet star and the bubble was expanding into it?
Nothing. The bubble is a hard vacuum.
Ok I see that's cool to know! What if we replaced the Alpha Centauri system with a Wolf Rayet star would we be impacted?

I don't think the outgassing and ejected material is likely to ever be an issue. At some point it's problematic from a radiation standpoint to be too close to this sort of object, though.

by **beryllium732** » Tue Jun 04, 2024 4:05 pm

Chris Peterson wrote: ↑Tue Jun 04, 2024 12:48 pm
beryllium732 wrote: ↑Tue Jun 04, 2024 11:49 am What would happen with the solar system if we were within 20 lightyears from a wolf rayet star and the bubble was expanding into it?
Nothing. The bubble is a hard vacuum.

Ok I see that's cool to know! What if we replaced the Alpha Centauri system with a Wolf Rayet star would we be impacted?

by **Chris Peterson** » Tue Jun 04, 2024 12:48 pm

beryllium732 wrote: ↑Tue Jun 04, 2024 11:49 am What would happen with the solar system if we were within 20 lightyears from a wolf rayet star and the bubble was expanding into it?

Nothing. The bubble is a hard vacuum.

by **beryllium732** » Tue Jun 04, 2024 11:49 am

What would happen with the solar system if we were within 20 lightyears from a wolf rayet star and the bubble was expanding into it?

by **Ann** » Sun Jun 02, 2024 5:45 am

Chris Peterson wrote: ↑Sat Jun 01, 2024 4:15 pm
Rauf wrote: ↑Sat Jun 01, 2024 7:49 am
Ann wrote: ↑Sat Jun 01, 2024 4:43 am
Massive stars form from particularly large disks. It seems likely, at least to me, that large disks are more prone than smaller ones to fragmenting, thus creating massive stars that are born as binaries.
Thanks Ann. But what causes this fragmentations? Gravity from a nearby star, or a black hole? Or maybe radiation and wind from the original star?
The protostellar disk is a fluid. That means there are turbulence and friction and viscosity effects. I don't think "fragmentation" is quite the right way to look at it. Stir some cream into your coffee and you'll see secondary vortexes appear.

I like this video of primary and secondary vortexes:

Click to play embedded YouTube video.

I found this video of what happens when you pour cream into coffee:

Click to play embedded YouTube video.

Someone has said that when you pour cream into coffee, you can see the evolution of the Universe. What we find when we first start pouring cream is turbulence, but almost immediately structure appears. We can see the structure evolving, then dissolving, until the coffee and the cream are completely mixed together.

This is what is going to happen to our Universe. We live in the sprightly youth of the Universe, since, after all, we believe that the Universe is only three times older than the Earth itself. But already the Universe is "winding down", and star formation has turned into a trickle of what it was in the cosmic dawn. When the Universe is twice its current age, perhaps no brilliant massive stars like the beacons of Orion will be born any more. More Sunlike stars will die than be born, until, perhaps a trillion years from now, only the little red dwarfs and the black holes will remain. After another trillion years, most of the red dwarfs will have died too, and eventually only the black holes remain, until they, too, evaporate and die.

And then the entire Universe will be a soup of a homogeneous density and temperature, from which no more energy can be extracted and nothing more can happen.

This is the end of everything. Drink up now.

Ann

by **Ann** » Sat Jun 01, 2024 6:41 pm

Christian G. wrote: ↑Sat Jun 01, 2024 4:56 pm Just in case this question was missed earlier (and if it wasn't but just inspired no comments, that's fine!) - are Wolf-Rayet stars the brightest of stars intrinsincally? Supposedly THE brightest star currently known is a Wolf-Rayet (R136a 1), but is it also the case with any Wolf-Rayet compared to stars of similar mass, even luminous blue variables?

Very good question. Wikipedia has a long list of stars with a luminosity of more than a million solar luminosities.

https://en.wikipedia.org/wiki/List_of_m ... stars#Data

If you look at this list, you can see that the most luminous star known to humanity, according to Wikipedia, is BAT99-98. This is indeed a Wolf-Rayet star of spectral class WN6. The second and fourth most luminous stars are also Wolf-Rayet stars (the fourth being R136a1).

But stars #3, #5, #6, #7, 8# and #9 are other spectral types, five of them O-type stars of luminosity class Ia, one Luminous Blue Variable (eta Carina) and one star of spectral class B0Iae.

By the way, the background colors behind the star names used to designate spectral classes are a mess! Purple supposedly means a Wolf-Rayet star, and O-type stars should have a blue background. But the stars in in 3rd and 6th place, stars in in the Triangulum Galaxy, supposedly belong to spectral classes O4Ia (so that the star names should be written on a blue background), but instead they are written on a purple background, as if the stars were Wolf-Rayet stars.

By the way: The star in 3rd place, [BMS2003] 867, supposedly belongs to spectral class O4Iab. That's impossible! The "b" in luminosity class "Iab" means a bright supergiant, but not the very brightest type of supergiant. But this particular star is supposedly the third most luminous star known to humanity? Get rid of that "b", because in this context it is impossible!

But in any case, this is a fun list to look at, and you will find many Wolf-Rayet stars among the most luminous stars known to humanity.

Ann

by **Christian G.** » Sat Jun 01, 2024 4:56 pm

Just in case this question was missed earlier (and if it wasn't but just inspired no comments, that's fine!) - are Wolf-Rayet stars the brightest of stars intrinsincally? Supposedly THE brightest star currently known is a Wolf-Rayet (R136a 1), but is it also the case with any Wolf-Rayet compared to stars of similar mass, even luminous blue variables?

by **Chris Peterson** » Sat Jun 01, 2024 4:15 pm

Rauf wrote: ↑Sat Jun 01, 2024 7:49 am
Ann wrote: ↑Sat Jun 01, 2024 4:43 am
Massive stars form from particularly large disks. It seems likely, at least to me, that large disks are more prone than smaller ones to fragmenting, thus creating massive stars that are born as binaries.
Thanks Ann. But what causes this fragmentations? Gravity from a nearby star, or a black hole? Or maybe radiation and wind from the original star?

The protostellar disk is a fluid. That means there are turbulence and friction and viscosity effects. I don't think "fragmentation" is quite the right way to look at it. Stir some cream into your coffee and you'll see secondary vortexes appear.

by **johnnydeep** » Sat Jun 01, 2024 4:00 pm

Chris Peterson wrote: ↑Fri May 31, 2024 11:21 pm
johnnydeep wrote: ↑Fri May 31, 2024 6:36 pm
Chris Peterson wrote: ↑Fri May 31, 2024 6:25 pm

It's complicated. W-R stars blow off a lot of material which often generates a local nebula, similar in some ways to a planetary nebula. But they can certainly exist within existing nebulas. I think we're seeing both of those here.
The "fingery" blue ring is clearly from the W-R star, but are you saying that the blue gas arc is likely at least partly gas from the W-R or, that only the ring material is and the arc is just nearby gas? (Though there may be nothing definitive here to prove it one way of the other.)
Since it's not really concentric with the star I'm inclined to guess it's a shock front created when material from the stellar wind hits the surrounding medium. But that really is just a hunch.

by **Christian G.** » Sat Jun 01, 2024 12:12 pm

Rauf wrote: ↑Sat Jun 01, 2024 7:49 am
Ann wrote: ↑Sat Jun 01, 2024 4:43 am
Rauf wrote: ↑Fri May 31, 2024 2:10 pm

OK, so I ask: Why 85% of high mass stars are part of binary systems?
One answer probably has to do with the formation process of high-mass stars.

A binary star is in the process of forming as the disk around 'the first star' has fragmented. Credit: NRAO.

Spaceref.com wrote:

Thanks Ann. I have hard time understanding what are the possible causes for a stellar disk to fragment. Gravity a nearby star, or blackhole maybe? Or maybe the original star's radiation and wind?
Astronomers know that about half of all Sun-like stars are members of double or multiple-star systems, but have debated over how such systems are formed.

“The only way to resolve the debate is to observe very young stellar systems and catch them in the act of formation,” said John Tobin, of the National Radio Astronomy Observatory (NRAO). “That’s what we’ve done with the stars we observed, and we got valuable new clues from them,” he added.

Their new clues support the idea that double-star systems form when a disk of gas and dust whirling around one young star fragments, forming another new star in orbit with the first. Young stars that still are gathering matter from their surroundings form such disks, along with jet-like outflows rapidly propelling material in narrow beams perpendicular to the disk.

Massive stars form from particularly large disks. It seems likely, at least to me, that large disks are more prone than smaller ones to fragmenting, thus creating massive stars that are born as binaries.

Ann
Thanks Ann. But what causes this fragmentations? Gravity from a nearby star, or a black hole? Or maybe radiation and wind from the original star?

One thing I've read is that as the dust and gas cloud increasingly falls onto the protostar, it speeds up the latter's rotation to the point where it could tear itself apart. This rotational acceleration can be slowed down either by jets as in HH objects, or it can be slowed down if the cloud, which is itself rotating to begin with, fragments into two star-forming clouds, in which case part of the rotational energy is converted to orbital energy. (provided I got that correctly!)

by **Rauf** » Sat Jun 01, 2024 7:49 am

Ann wrote: ↑Sat Jun 01, 2024 4:43 am
Rauf wrote: ↑Fri May 31, 2024 2:10 pm
Chris Peterson wrote: ↑Fri May 31, 2024 2:07 pm

Given that something like 85% of high mass stars are part of binary systems, maybe the question to ask is why only 50% of WR stars are binaries?
OK, so I ask: Why 85% of high mass stars are part of binary systems?
One answer probably has to do with the formation process of high-mass stars.

A binary star is in the process of forming as the disk around 'the first star' has fragmented. Credit: NRAO.

Spaceref.com wrote:

Thanks Ann. I have hard time understanding what are the possible causes for a stellar disk to fragment. Gravity a nearby star, or blackhole maybe? Or maybe the original star's radiation and wind?
Astronomers know that about half of all Sun-like stars are members of double or multiple-star systems, but have debated over how such systems are formed.

“The only way to resolve the debate is to observe very young stellar systems and catch them in the act of formation,” said John Tobin, of the National Radio Astronomy Observatory (NRAO). “That’s what we’ve done with the stars we observed, and we got valuable new clues from them,” he added.

Their new clues support the idea that double-star systems form when a disk of gas and dust whirling around one young star fragments, forming another new star in orbit with the first. Young stars that still are gathering matter from their surroundings form such disks, along with jet-like outflows rapidly propelling material in narrow beams perpendicular to the disk.

Massive stars form from particularly large disks. It seems likely, at least to me, that large disks are more prone than smaller ones to fragmenting, thus creating massive stars that are born as binaries.

Ann

Thanks Ann. But what causes this fragmentations? Gravity from a nearby star, or a black hole? Or maybe radiation and wind from the original star?

by **Ann** » Sat Jun 01, 2024 6:01 am

Can't help myself, I've got to show you planetary nebula Abell 78:

: Abell 78. Note the underlying faint and symmetrical nebula and the irregular new shell and the bright 'spikes' all pointing at the central star. ESA/Hubble & NASA, M. Guerrero. Acknowledgement: Judy Schmidt

ESA/Hubble wrote:

After exhausting the nuclear fuel in their cores, stars with a mass of around 0.8 to 8 times the mass of our Sun collapse to form dense and hot white dwarf stars. As this process occurs, the dying star will throw off its outer layers of material, forming an elaborate cloud of gas and dust known as a planetary nebula. This phenomenon is not uncommon, and planetary nebulae are a popular focus for astrophotographers because of their often beautiful and complex shapes. However, a few like Abell 78 are the result of a so-called “born again” star.

Although the core of the star has stopped burning hydrogen and helium, a thermonuclear runaway at its surface ejects material at high speeds. This ejecta shocks and sweeps up the material of the old nebula, producing the filaments and irregular shell around the central star seen in this Picture of the Week, which features data from Hubble’s Wide Field Camera 3 and PANSTARSS.

Ann

by **Ann** » Sat Jun 01, 2024 5:28 am

I have to show you this new JWST picture of the Ring Nebula:

: A NIRCam (near infrared) image of the Ring Nebula. Note the tremendous numbers of 'fingers', or cometary knots, along both the inner and the outer rim of the nebula. Credit: NASA/ESA/JWST

Central stars of planetary nebulas are in some ways similar to Wolf-Rayet stars. A crucial difference is that white dwarf of a planetary nebula formed from a much smaller star, so that it is a lot less powerful. The white dwarf of the Ring nebula has a mass of 0.61–0.62 M_☉ and a luminosity of 200 L_☉ according to Wikipedia, versus 18 M_☉ and some 400,000 L_☉ for WR 134.

Yes, but the central star of the Ring Nebula is twice as hot as WR 134, 125,000±5,000 K, versus some 63,000 K for WR 134. My own guess is that the wind of the central star of the Ring Nebula also blows much faster, perhaps twice as fast, as the wind of WR 134.

Ann

by **Ann** » Sat Jun 01, 2024 4:43 am

Rauf wrote: ↑Fri May 31, 2024 2:10 pm
Chris Peterson wrote: ↑Fri May 31, 2024 2:07 pm
Rauf wrote: ↑Fri May 31, 2024 1:59 pm

But why they occur in binary systems? And why their companion is most likely a compact object?
Given that something like 85% of high mass stars are part of binary systems, maybe the question to ask is why only 50% of WR stars are binaries?
OK, so I ask: Why 85% of high mass stars are part of binary systems?

One answer probably has to do with the formation process of high-mass stars.

: A binary star is in the process of forming as the disk around 'the first star' has fragmented. Credit: NRAO.

Spaceref.com wrote:

Astronomers know that about half of all Sun-like stars are members of double or multiple-star systems, but have debated over how such systems are formed.

“The only way to resolve the debate is to observe very young stellar systems and catch them in the act of formation,” said John Tobin, of the National Radio Astronomy Observatory (NRAO). “That’s what we’ve done with the stars we observed, and we got valuable new clues from them,” he added.

Their new clues support the idea that double-star systems form when a disk of gas and dust whirling around one young star fragments, forming another new star in orbit with the first. Young stars that still are gathering matter from their surroundings form such disks, along with jet-like outflows rapidly propelling material in narrow beams perpendicular to the disk.

Massive stars form from particularly large disks. It seems likely, at least to me, that large disks are more prone than smaller ones to fragmenting, thus creating massive stars that are born as binaries.

Ann

by **Chris Peterson** » Fri May 31, 2024 11:21 pm

johnnydeep wrote: ↑Fri May 31, 2024 6:36 pm
Chris Peterson wrote: ↑Fri May 31, 2024 6:25 pm
johnnydeep wrote: ↑Fri May 31, 2024 6:14 pm Is the source of the gas in prominent blue arc at the upper left the W-R star? Or is that just gas that happened to be in the vicinity?
It's complicated. W-R stars blow off a lot of material which often generates a local nebula, similar in some ways to a planetary nebula. But they can certainly exist within existing nebulas. I think we're seeing both of those here.
The "fingery" blue ring is clearly from the W-R star, but are you saying that the blue gas arc is likely at least partly gas from the W-R or, that only the ring material is and the arc is just nearby gas? (Though there may be nothing definitive here to prove it one way of the other.)

Since it's not really concentric with the star I'm inclined to guess it's a shock front created when material from the stellar wind hits the surrounding medium. But that really is just a hunch.

by **johnnydeep** » Fri May 31, 2024 6:36 pm

Chris Peterson wrote: ↑Fri May 31, 2024 6:25 pm
johnnydeep wrote: ↑Fri May 31, 2024 6:14 pm Is the source of the gas in prominent blue arc at the upper left the W-R star? Or is that just gas that happened to be in the vicinity?
It's complicated. W-R stars blow off a lot of material which often generates a local nebula, similar in some ways to a planetary nebula. But they can certainly exist within existing nebulas. I think we're seeing both of those here.

The "fingery" blue ring is clearly from the W-R star, but are you saying that the blue gas arc is likely at least partly gas from the W-R or, that only the ring material is and the arc is just nearby gas? (Though there may be nothing definitive here to prove it one way of the other.)

by **Chris Peterson** » Fri May 31, 2024 6:25 pm

johnnydeep wrote: ↑Fri May 31, 2024 6:14 pm Is the source of the gas in prominent blue arc at the upper left the WR star? Or is that just gas that happened to be in the vicinity?

It's complicated. W-R stars blow off a lot of material which often generates a local nebula, similar in some ways to a planetary nebula. But they can certainly exist within existing nebulas. I think we're seeing both of those here.

by **johnnydeep** » Fri May 31, 2024 6:14 pm

Is the source of the gas in prominent blue arc at the upper left the W-R star? Or is that just gas that happened to be in the vicinity?

by **Cousin Ricky** » Fri May 31, 2024 4:41 pm

It looks like the mouth of a sandworm (Villeneuve version).

by **Chris Peterson** » Fri May 31, 2024 2:21 pm

Ann wrote: ↑Fri May 31, 2024 2:16 pm
Rauf wrote: ↑Fri May 31, 2024 2:10 pm
Chris Peterson wrote: ↑Fri May 31, 2024 2:07 pm

Given that something like 85% of high mass stars are part of binary systems, maybe the question to ask is why only 50% of WR stars are binaries?
OK, so I ask: Why 85% of high mass stars are part of binary systems?
Probably because high-mass stars typically form in clusters, and the very high-mass stars bend spacetime so strongly that other stars of that cluster will fall down into the "gravity well" of the largest star. Sometimes this probably leads to stellar mergers, but much more often the smaller star will simply start orbiting the larger star.

Ann

Keep in mind, however, that one star cannot capture another into a closed orbit. That requires at least three bodies to interact (which may well happen in a cluster).

by **Ann** » Fri May 31, 2024 2:16 pm

Rauf wrote: ↑Fri May 31, 2024 2:10 pm
Chris Peterson wrote: ↑Fri May 31, 2024 2:07 pm
Rauf wrote: ↑Fri May 31, 2024 1:59 pm

But why they occur in binary systems? And why their companion is most likely a compact object?
Given that something like 85% of high mass stars are part of binary systems, maybe the question to ask is why only 50% of WR stars are binaries?
OK, so I ask: Why 85% of high mass stars are part of binary systems?

Probably because high-mass stars typically form in clusters, and the very high-mass stars bend spacetime so strongly that other stars of that cluster will fall down into the "gravity well" of the largest star. Sometimes this probably leads to stellar mergers, but much more often the smaller star will simply start orbiting the larger star.

Ann

by **Chris Peterson** » Fri May 31, 2024 2:14 pm

Rauf wrote: ↑Fri May 31, 2024 2:10 pm
Chris Peterson wrote: ↑Fri May 31, 2024 2:07 pm
Rauf wrote: ↑Fri May 31, 2024 1:59 pm

But why they occur in binary systems? And why their companion is most likely a compact object?
Given that something like 85% of high mass stars are part of binary systems, maybe the question to ask is why only 50% of WR stars are binaries?
OK, so I ask: Why 85% of high mass stars are part of binary systems?

I think it's just the nature of how stars form from collapsing nebulas. The product of fluid dynamics- viscosity and turbulence.

by **Rauf** » Fri May 31, 2024 2:10 pm

Chris Peterson wrote: ↑Fri May 31, 2024 2:07 pm
Rauf wrote: ↑Fri May 31, 2024 1:59 pm
https://astronomy.swin.edu.au/cosmos/W/Wolf-Rayet+Star wrote:It is estimated that about 50% of Wolf-Rayet stars occur in binary systems. Proposed companions are another Wolf-Rayet star, or a compact companion such as a black hole or neutron star. There is some evidence for both of these scenarios, but conclusive observations have yet to be obtained. The only confirmed companions to Wolf-Rayet stars have so far been other massive stars.

But why they occur in binary systems? And why their companion is most likely a compact object?
Given that something like 85% of high mass stars are part of binary systems, maybe the question to ask is why only 50% of WR stars are binaries?

OK, so I ask: Why 85% of high mass stars are part of binary systems?

by **Chris Peterson** » Fri May 31, 2024 2:07 pm

Rauf wrote: ↑Fri May 31, 2024 1:59 pm
https://astronomy.swin.edu.au/cosmos/W/Wolf-Rayet+Star wrote:It is estimated that about 50% of Wolf-Rayet stars occur in binary systems. Proposed companions are another Wolf-Rayet star, or a compact companion such as a black hole or neutron star. There is some evidence for both of these scenarios, but conclusive observations have yet to be obtained. The only confirmed companions to Wolf-Rayet stars have so far been other massive stars.

But why they occur in binary systems? And why their companion is most likely a compact object?

Given that something like 85% of high mass stars are part of binary systems, maybe the question to ask is why only 50% of WR stars are binaries?

by **Ann** » Fri May 31, 2024 2:06 pm

JimB wrote: ↑Fri May 31, 2024 9:03 am
Ann wrote: ↑Fri May 31, 2024 6:34 am a Wolf-Rayet nebula is primarily shaped by the tremendous heat and wind of its own central star
Ann
I have trouble getting my head wrapped round the way that things work on these scales.

If the nebula has something like a 40 light year radius, does that mean that the glow from the nebula has actually been created by radiation that left the star 40 years previously? Or does the nebula glow because it is composed of hot plasma from the star?

The Wolf-Rayet phase of a very massive star's life begins when it starts blowing an incredibly strong wind that blows off its outer layers. I don't know how long this stage lasts, but I am sure, nevertheless, that it lasts more than 40 years. So yes, WR 134 is eminently capable of ionizing the gas that it has blown off of itself.

Ann

Starship Asterisk*

APOD: The Nebulous Realm of WR 134 (2024 May 31)

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