APOD: Zeta Oph: Runaway Star (2012 Dec 29)

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APOD: Zeta Oph: Runaway Star (2012 Dec 29)

Post by APOD Robot » Sat Dec 29, 2012 5:06 am

Image Zeta Oph: Runaway Star

Explanation: Like a ship plowing through cosmic seas, runaway star Zeta Ophiuchi produces the arcing interstellar bow wave or bow shock seen in this stunning infrared portrait. In the false-color view, bluish Zeta Oph, a star about 20 times more massive than the Sun, lies near the center of the frame, moving toward the left at 24 kilometers per second. Its strong stellar wind precedes it, compressing and heating the dusty interstellar material and shaping the curved shock front. Around it are clouds of relatively undisturbed material. What set this star in motion? Zeta Oph was likely once a member of a binary star system, its companion star was more massive and hence shorter lived. When the companion exploded as a supernova catastrophically losing mass, Zeta Oph was flung out of the system. About 460 light-years away, Zeta Oph is 65,000 times more luminous than the Sun and would be one of the brighter stars in the sky if it weren't surrounded by obscuring dust. The image spans about 1.5 degrees or 12 light-years at the estimated distance of Zeta Ophiuchi.

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Re: APOD: Zeta Oph: Runaway Star (2012 Dec 29)

Post by Beyond » Sat Dec 29, 2012 5:22 am

Zeta Oph seems to have a lot of oomph. Yeah, lame... but it's late on friday. :mrgreen:
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Re: APOD: Zeta Oph: Runaway Star (2012 Dec 29)

Post by bystander » Sat Dec 29, 2012 5:32 am

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Re: APOD: Zeta Oph: Runaway Star (2012 Dec 29)

Post by rghoeing@buffalo.edu » Sat Dec 29, 2012 10:31 am

Absolutely beautiful image --- thanks again for keeping APOD shining for so many years! It's my first visit every morning...

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Re: APOD: Zeta Oph: Runaway Star (2012 Dec 29)

Post by Boomer12k » Sat Dec 29, 2012 1:05 pm

I don't see a supernova remnant anywhere nearby. But maybe it is too faint now. I am thinking that if a larger companion exploded, then THIS would become the more massive, and the companion would now be dragged along with Zeta Oph. It would not have been "Flung" out of the system. It would just become the dominant mass of the system. The other could now be a small dwarf star, or even a black hole and traveling along too close to see maybe, or it just got blown away, and then Zeta Oph would just have "continued on its way". But I don't see an S.R. anywhere nearby, and I suppose it could be obscured by denser dust in another part of the nebulosity.

I like the "Curly Q" at the front of the star, and the tendrils streaming down from it.

There is also a vast nebulosity surrounding Zeta Oph.

http://www.ne.jp/asahi/stellar/scenes/o ... ta_oph.htm

And wider view...
http://www.cloudynights.com/ubbarchive/ ... sb/5/o/all

And another from a sky survey. Showing the whole complex. Picture is a the very bottom of the page.

http://www.astro.wisc.edu/~baker/

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Re: APOD: Zeta Oph: Runaway Star (2012 Dec 29)

Post by BDanielMayfield » Sat Dec 29, 2012 1:30 pm

Beyond wrote:Zeta Oph seems to have a lot of oomph. Yeah, lame... but it's late on friday. :mrgreen:
Yes indeed Beyond, that would be a lot of oomph. An object of about 20 times the Sun’s mass would be about 4E31 kg, which is much easier to write and to comprehend than 40,000,000,000,000,000,000,000,000,000,000 is. And if by “oomph” you mean momentum then you’d have to multiply Zeta Oph’s mass by its velocity of 24 km/second, which in kg x meters/second would be 9.6E35 kg m/s.

But one could also define “oomph” to mean energy content too I suppose. In this case you’d have to use E=mc^2 and multiply Zeta Oph’s mass by the speed of light squared: 4E31kg x 3E8s^2 = 3.6E47 joules. Since joules isn’t exactly a household word I looked up this fact; About 63 terajoules were released by the atomic bomb that exploded over Hiroshima. A terajoule is 1E12 joules, so if supernovas were 100% efficient at coverting mater into energy (which very happily they aren’t) when Zeta Oph pops off in about four million years the bast would equal 3.6E47/6.3E13 or about 5.7E33 times as powerful as the Hiroshima blast. Again for those unfamilar with exponential notation what I am saying is that Zeta Oph’s mass in terms of engery content is approximately
5,700,000,000,000,000,000,000,000,000,000,000 times as powerful as the Hiroshima blast.

My math could be off in the above, if so please advise.

This leads to 2 questions: (1) How big will the blast be when Zeta Oph pops off? Or equivallently, what percentage of it’s mass will be converted into energy? (2) How far away from the Earth will this star be in 4 milion years?

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Post by neufer » Sat Dec 29, 2012 2:17 pm

bystander wrote:Data From NASA's Voyager 1 Point to Interstellar Future
NASA JPL-Caltech | Voyager | 2012 June 14
Data from NASA's Voyager 1 spacecraft indicate that the venerable deep-space explorer has encountered a region in space where the intensity of charged particles from beyond our solar system has markedly increased. Voyager scientists looking at this rapid rise draw closer to an inevitable but historic conclusion - that humanity's first emissary to interstellar space is on the edge of our solar system.

"The laws of physics say that someday Voyager will become the first human-made object to enter interstellar space, but we still do not know exactly when that someday will be," said Ed Stone, Voyager project scientist at the California Institute of Technology in Pasadena. "The latest data indicate that we are clearly in a new region where things are changing more quickly. It is very exciting. We are approaching the solar system's frontier."

The data making the 16-hour-38 minute, 11.1-billion-mile (17.8-billion-kilometer), journey from Voyager 1 to antennas of NASA's Deep Space Network on Earth detail the number of charged particles measured by the two High Energy telescopes aboard the 34-year-old spacecraft. These energetic particles were generated when stars in our cosmic neighborhood went supernova.

"From January 2009 to January 2012, there had been a gradual increase of about 25 percent in the amount of galactic cosmic rays Voyager was encountering," said Stone. "More recently, we have seen very rapid escalation in that part of the energy spectrum. Beginning on May 7, the cosmic ray hits have increased five percent in a week and nine percent in a month."

This marked increase is one of a triad of data sets which need to make significant swings of the needle to indicate a new era in space exploration. The second important measure from the spacecraft's two telescopes is the intensity of energetic particles generated inside the heliosphere, the bubble of charged particles the sun blows around itself. While there has been a slow decline in the measurements of these energetic particles, they have not dropped off precipitously, which could be expected when Voyager breaks through the solar boundary.

The final data set that Voyager scientists believe will reveal a major change is the measurement in the direction of the magnetic field lines surrounding the spacecraft. While Voyager is still within the heliosphere, these field lines run east-west. When it passes into interstellar space, the team expects Voyager will find that the magnetic field lines orient in a more north-south direction. Such analysis will take weeks, and the Voyager team is currently crunching the numbers of its latest data set.
ritwik wrote:Voyager 1 Encounters New Region in Deep Space
NASA JPL-Caltech | 2012 Dec 03
PASADENA, Calif. -- NASA's Voyager 1 spacecraft has entered a new region at the far reaches of our solar system that scientists feel is the final area the spacecraft has to cross before reaching interstellar space.

Scientists refer to this new region as a magnetic highway for charged particles because our sun's magnetic field lines are connected to interstellar magnetic field lines. This connection allows lower-energy charged particles that originate from inside our heliosphere -- or the bubble of charged particles the sun blows around itself -- to zoom out and allows higher-energy particles from outside to stream in. Before entering this region, the charged particles bounced around in all directions, as if trapped on local roads inside the heliosphere.

The Voyager team infers this region is still inside our solar bubble because the direction of the magnetic field lines has not changed. The direction of these magnetic field lines is predicted to change when Voyager breaks through to interstellar space. The new results were described at the American Geophysical Union meeting in San Francisco on Monday.

"Although Voyager 1 still is inside the sun's environment, we now can taste what it's like on the outside because the particles are zipping in and out on this magnetic highway," said Edward Stone, Voyager project scientist based at the California Institute of Technology, Pasadena. "We believe this is the last leg of our journey to interstellar space. Our best guess is it's likely just a few months to a couple years away. The new region isn't what we expected, but we've come to expect the unexpected from Voyager."

Since December 2004, when Voyager 1 crossed a point in space called the termination shock, the spacecraft has been exploring the heliosphere's outer layer, called the heliosheath. In this region, the stream of charged particles from the sun, known as the solar wind, abruptly slowed down from supersonic speeds and became turbulent. Voyager 1's environment was consistent for about five and a half years. The spacecraft then detected that the outward speed of the solar wind slowed to zero.

The intensity of the magnetic field also began to increase at that time.

Voyager data from two onboard instruments that measure charged particles showed the spacecraft first entered this magnetic highway region on July 28, 2012. The region ebbed away and flowed toward Voyager 1 several times. The spacecraft entered the region again Aug. 25 and the environment has been stable since.

"If we were judging by the charged particle data alone, I would have thought we were outside the heliosphere," said Stamatios Krimigis, principal investigator of the low-energy charged particle instrument, based at the Johns Hopkins Applied Physics Laboratory, Laurel, Md. "But we need to look at what all the instruments are telling us and only time will tell whether our interpretations about this frontier are correct."

Spacecraft data revealed the magnetic field became stronger each time Voyager entered the highway region; however, the direction of the magnetic field lines did not change.

"We are in a magnetic region unlike any we've been in before -- about 10 times more intense than before the termination shock -- but the magnetic field data show no indication we're in interstellar space," said Leonard Burlaga, a Voyager magnetometer team member based at NASA's Goddard Space Flight Center in Greenbelt, Md. "The magnetic field data turned out to be the key to pinpointing when we crossed the termination shock. And we expect these data will tell us when we first reach interstellar space."
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Re: APOD: Zeta Oph: Runaway Star (2012 Dec 29)

Post by Shamanomaha » Sat Dec 29, 2012 2:31 pm

I notice a bright red dot in the star field just to the left of the shock wave. Any ideas what that could be?

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Re: APOD: Zeta Oph: Runaway Star (2012 Dec 29)

Post by Lordcat Darkstar » Sat Dec 29, 2012 2:49 pm

Shamanomaha wrote:I notice a bright red dot in the star field just to the left of the shock wave. Any ideas what that could be?
If you zoom in you can see it has a halo around it. Kind of looks like planetary nebula to me.

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Re: APOD: Zeta Oph: Runaway Star (2012 Dec 29)

Post by neufer » Sat Dec 29, 2012 3:10 pm

Lordcat Darkstar wrote:
Shamanomaha wrote:
I notice a bright red dot in the star field just to the left of the shock wave. Any ideas what that could be?
If you zoom in you can see it has a halo around it. Kind of looks like planetary nebula to me.
I'm skeptical about it being a planetary nebula.

Nothing shows up at that spot in WISE: http://apod.nasa.gov/apod/ap110204.html
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Re: APOD: Zeta Oph: Runaway Star (2012 Dec 29)

Post by Psnarf » Sat Dec 29, 2012 3:11 pm

You can find two of them on the full-sized image. They appear to be triangular in shape. Pretty hot to show up so bright in the infrared. Probably the same space monkeys that the ufo enthusiasts saw floating over south Phoenix/Tempe, AZ. a couple of years ago.
https://en.wikipedia.org/wiki/Black_triangle_%28UFO%29

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Re: APOD: Zeta Oph: Runaway Star (2012 Dec 29)

Post by Case » Sat Dec 29, 2012 3:31 pm

Image
A summer view on Zeta Ophiuchi from Tenerife latitude.

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Re: APOD: Zeta Oph: Runaway Star (2012 Dec 29)

Post by neufer » Sat Dec 29, 2012 4:42 pm

Psnarf wrote:
You can find two of them on the full-sized image. They appear to be triangular in shape. Pretty hot to show up so bright in the infrared. Probably the same space monkeys that the ufo enthusiasts saw floating over south Phoenix/Tempe, AZ. a couple of years ago.

https://en.wikipedia.org/wiki/Black_triangle_%28UFO%29
  • Or possibly, it's Upsilon OPH :arrow:
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Re: APOD: Zeta Oph: Runaway Star (2012 Dec 29)

Post by CMatisse » Sat Dec 29, 2012 5:19 pm

Since it is moving so fast, does this mean it is in a different position every night?

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Re: APOD: Zeta Oph: Runaway Star (2012 Dec 29)

Post by rr_carroll » Sat Dec 29, 2012 6:14 pm

Boomer12k wrote:I don't see a supernova remnant anywhere nearby. But maybe it is too faint now. I am thinking that if a larger companion exploded, then THIS would become the more massive, and the companion would now be dragged along with Zeta Oph. It would not have been "Flung" out of the system. It would just become the dominant mass of the system. The other could now be a small dwarf star, or even a black hole and traveling along too close to see maybe, or it just got blown away, and then Zeta Oph would just have "continued on its way". But I don't see an S.R. anywhere nearby, and I suppose it could be obscured by denser dust in another part of the nebulosity...
I was thinking along the same lines as Boomer12k - follow Zeta Oph's track backward and see if it passes near a supernova remnant. When I followed the links in the story, this seems to have been done for some runaway stars. But links to supernova info say that the supernova explosion can be assymetrical, so the SNR could recoil from the blast. I suppose it could gain a new velocity of unknown speed and direction. Still, it might be possible to find an SNR that's consistent with Zeta Oph's speed, distance and timing. I assume the companion SNR would have been mentioned if it were known.

Let's see, the last link in the story implies that Zeta Oph is about 4 million years old. At 24 km./sec. X 31 million sec/yr. X 4,000,000 yr. = about 3 X 10 to the 15th power kilometers moved since the explosion. So Zeta Oph has moved (3 X 10 to 15th km.) X (9.5 trillion km./light-year) = 316 light-years since the explosion. Since it's 460 l.y. away, it's moved about arctan(316/460) = 34 degrees across the sky, unless my math is wrong. Assuming the remnant's speed is the same or less, you'd have a circle of sky to search that's 68 degrees across. At least, it's within a thousand l.y. from us, which is pretty close.

Boomer12k, unless you have a very large telescope, I presume you did not "see" a consistent supernova remnant in a list of them. I'm curious to know what that list is.
Last edited by rr_carroll on Sat Dec 29, 2012 6:20 pm, edited 1 time in total.

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Re: APOD: Zeta Oph: Runaway Star (2012 Dec 29)

Post by BDanielMayfield » Sat Dec 29, 2012 6:15 pm

CMatisse wrote:Since it is moving so fast, does this mean it is in a different position every night?
No CMatisse. Since it’s so far away it, like almost all other stars takes an extremely long time (in human terms) to change apparent position relative to other stars. Wikipedia lists it’s proper motions as +15.26 and +24.79 mas/yr in RA and Dec respectively, with mas meaning milliarcseconds. A milliarcsecond is only 1/3600th of 1 degree, and 1 degree is only 1/180th of the distance across the entire sky.

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Re: APOD: Zeta Oph: Runaway Star (2012 Dec 29)

Post by astronomy » Sat Dec 29, 2012 6:44 pm

rr_carroll wrote:
Boomer12k wrote:I don't see a supernova remnant anywhere nearby. But maybe it is too faint now. I am thinking that if a larger companion exploded, then THIS would become the more massive, and the companion would now be dragged along with Zeta Oph. It would not have been "Flung" out of the system. It would just become the dominant mass of the system. The other could now be a small dwarf star, or even a black hole and traveling along too close to see maybe, or it just got blown away, and then Zeta Oph would just have "continued on its way". But I don't see an S.R. anywhere nearby, and I suppose it could be obscured by denser dust in another part of the nebulosity...
I was thinking along the same lines as Boomer12k - follow Zeta Oph's track backward and see if it passes near a supernova remnant. When I followed the links in the story, this seems to have been done for some runaway stars. But links to supernova info say that the supernova explosion can be assymetrical, so the SNR could recoil from the blast. I suppose it could gain a new velocity of unknown speed and direction. Still, it might be possible to find an SNR that's consistent with Zeta Oph's speed, distance and timing. I assume the companion SNR would have been mentioned if it were known.

Let's see, the last link in the story implies that Zeta Oph is about 4 million years old. At 24 km./sec. X 31 million sec/yr. X 4,000,000 yr. = about 3 X 10 to the 15th power kilometers moved since the explosion. So Zeta Oph has moved (3 X 10 to 15th km.) X (9.5 trillion km./light-year) = 316 light-years since the explosion. Since it's 460 l.y. away, it's moved about arctan(316/460) = 34 degrees across the sky, unless my math is wrong. Assuming the remnant's speed is the same or less, you'd have a circle of sky to search that's 68 degrees across. At least, it's within a thousand l.y. from us, which is pretty close.

Boomer12k, unless you have a very large telescope, I presume you did not "see" a consistent supernova remnant in a list of them. I'm curious to know what that list is.

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Re: APOD: Zeta Oph: Runaway Star (2012 Dec 29)

Post by neufer » Sat Dec 29, 2012 6:51 pm

BDanielMayfield wrote:
CMatisse wrote:
Since it is moving so fast, does this mean it is in a different position every night?
No CMatisse. Since it’s so far away it, like almost all other stars takes an extremely long time (in human terms) to change apparent position relative to other stars. Wikipedia lists it’s proper motions as +15.26 and +24.79 mas/yr in RA and Dec respectively, with mas meaning minute arc seconds. A minute arc second is only 1/3600th of 1 degree, and 1 degree is only 1/180th of the distance across the entire sky.
Correct... except that that should read milliarcsecond rather than minute arc second
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Re: APOD: Zeta Oph: Runaway Star (2012 Dec 29)

Post by Ann » Sat Dec 29, 2012 7:09 pm

BDanielMayfield wrote:
This leads to 2 questions: (1) How big will the blast be when Zeta Oph pops off? Or equivallently, what percentage of it’s mass will be converted into energy? (2) How far away from the Earth will this star be in 4 milion years?
Good questions. I have no idea how far away it will be from the Earth in 4 million years. As to how intrinsically bright the supernova explosion will be, there are a few things to keep in mind. First of all, it will be a supernova type II explosion, a core-collapse supernova. In all probability, the supernova explosion will not give rise to a black hole, which means that the core of the star will become a neutron star, with a probable mass of a bit more than 1.4 solar masses.

So how much of Zeta Ophiuchi's mass will be converted into energy? Today the star probably contains about 20 solar masses. Perhaps 1.5 solar masses will go into making a neutron star. Does that mean that the other 18.5 solar masses will be converted into energy?

No, that will not happen. It is almost certain that Zeta Ophiuchi will lose a lot of mass through a strong stellar wind before it goes supernova. There is some evidence, or at least some suggestion, that very massive stars often don't make extremely bright supernovae, because they lose so much mass through their own stellar wind before they pop. An example of a star which has really "lost weight" is the Wolf-Rayet component of Gamma Velorum. Jim Kaler wrote about this star:
The windy WR star probably started with somewhere around 40 solar masses and has now stripped itself down by an unknown amount, perhaps to under 10.
Zeta Ophiuchi will almost certainly not lose three quarters of its own mass before it explodes, but it will certainly lose mass. How much mass it loses and how much it retains will determine how bright it will become when it explodes.

An interesting example of a mass-loss star that went supernova is the progenitor of Supernova 1987A. Before this supernova exploded in the Large Magellanic Cloud, it was a truism among astronomers that only red supergiant stars exploded as supernovae. But because the LMC is so nearby, the progenitor of the supernova had been photographed and classified before it popped and could be identified as a blue supergiant of spectral class B3. However, it was soon understood that the star, Sanduleak -69° 202, had previously been a red supergiant and had turned blue by shedding a lot of mass and shrinking. This meant that even though the core of Sanduleak -69° 202 was ripe for an explosion, the star as a whole was underweight. Therefore the explosion was unusually faint.
http://en.wikipedia.org/wiki/SN_1987A wrote:
It is of note that the supernova of the blue giant Sanduleak -69° 202 was about one-tenth as luminous as the average observed type II supernova, which is associated with the denser makeup of the star
So it is anybody's guess, actually, how bright the Zeta Ophiuchi supernova will be when it explodes.

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Last edited by Ann on Sat Dec 29, 2012 7:17 pm, edited 5 times in total.
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Re: APOD: Zeta Oph: Runaway Star (2012 Dec 29)

Post by rr_carroll » Sat Dec 29, 2012 7:11 pm

CMatisse, Zeta Oph is moving about 24 km./sec X 31,000,000 sec./yr. = 744 million km./yr. It's distance is about 460 light-years X 9.5 trillion km./l.y. = 4.37 quadrillion km. So it moves about arctan(744 million km./4.37 quadrillion km.) = 0.000000170 degrees across the sky in a year, which is 0.000000170 degree X 3600 sec. of arc/degree = 0.0006.1 sec. of arc/yr. So it takes about 1,600 years to see a change of 1 sec. of arc.

Edit: Oops! According to the Hipparchos values cited by BDanielMayfield, the proper motion I calc'ed (0.6 milliarcsec/yr.) is about 50 times to small! So it should "only" take about 32 years to see 1 arcsec of movement.
Last edited by rr_carroll on Sat Dec 29, 2012 7:31 pm, edited 2 times in total.

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Re: APOD: Zeta Oph: Runaway Star (2012 Dec 29)

Post by BDanielMayfield » Sat Dec 29, 2012 7:12 pm

Thanks neufer. Now corrected.
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Re: APOD: Zeta Oph: Runaway Star (2012 Dec 29)

Post by BDanielMayfield » Sat Dec 29, 2012 7:17 pm

rr_carroll wrote:
Boomer12k wrote:I don't see a supernova remnant anywhere nearby. But maybe it is too faint now. I am thinking that if a larger companion exploded, then THIS would become the more massive, and the companion would now be dragged along with Zeta Oph. It would not have been "Flung" out of the system. It would just become the dominant mass of the system. The other could now be a small dwarf star, or even a black hole and traveling along too close to see maybe, or it just got blown away, and then Zeta Oph would just have "continued on its way". But I don't see an S.R. anywhere nearby, and I suppose it could be obscured by denser dust in another part of the nebulosity...
I was thinking along the same lines as Boomer12k - follow Zeta Oph's track backward and see if it passes near a supernova remnant. When I followed the links in the story, this seems to have been done for some runaway stars. But links to supernova info say that the supernova explosion can be assymetrical, so the SNR could recoil from the blast. I suppose it could gain a new velocity of unknown speed and direction. Still, it might be possible to find an SNR that's consistent with Zeta Oph's speed, distance and timing. I assume the companion SNR would have been mentioned if it were known.

Let's see, the last link in the story implies that Zeta Oph is about 4 million years old. At 24 km./sec. X 31 million sec/yr. X 4,000,000 yr. = about 3 X 10 to the 15th power kilometers moved since the explosion. So Zeta Oph has moved (3 X 10 to 15th km.) X (9.5 trillion km./light-year) = 316 light-years since the explosion. Since it's 460 l.y. away, it's moved about arctan(316/460) = 34 degrees across the sky, unless my math is wrong. Assuming the remnant's speed is the same or less, you'd have a circle of sky to search that's 68 degrees across. At least, it's within a thousand l.y. from us, which is pretty close.

Boomer12k, unless you have a very large telescope, I presume you did not "see" a consistent supernova remnant in a list of them. I'm curious to know what that list is.
This is a very interesting discussion. I found these statements in the Wikipedia article on Zeta Ophiuchi which may be of help, (or, add to the confusion):

“This is a young star with an age of only three million years.”

If that’s true then it wasn’t even around 4 million years ago.

"ζ Ophiuchi is moving through space with a peculiar velocity of 30 km s–1. Based upon the age and direction of motion of this star, it is a member of the Upper Scorpius sub-group of the Scorpius-Centaurus Association of stars that share a common origin and space velocity.[5] Such runaway stars may be ejected by dynamic interactions between three or four stars. However, in this case the star may be a former component of a binary star system in which the more massive primary was destroyed in a Type II supernova explosion. The pulsar PSR B1929+10 may be the leftover remnant of this supernova, as it too was ejected from the association with a velocity vector that fits the scenario (within a margin of error).[3]"

So, if you want to find the supernova remains Boomer12k, locate pulsar PSR B1929+10 and then backtrack it and Zeta Oph’s paths back to see where (and when) they converge.

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Re: APOD: Zeta Oph: Runaway Star (2012 Dec 29)

Post by neufer » Sat Dec 29, 2012 7:31 pm

Boomer12k wrote:
I don't see a supernova remnant anywhere nearby... The other could now be a small dwarf star, or even a black hole and traveling along too close to see maybe, or it just got blown away, and then Zeta Oph would just have "continued on its way". But I don't see an S.R. anywhere nearby, and I suppose it could be obscured by denser dust in another part of the nebulosity.
After ~40,000 years there is not much left of a supernova remnant to observe and we would likely be inside of any remnant this close. One must look rather for pulsars. :arrow:
http://en.wikipedia.org/wiki/Zeta_Ophiuchi wrote:
<<ζ Ophiuchi is moving through space with a peculiar velocity of 30 km/s. Based upon the age and direction of motion of this star, it is a member of the Upper Scorpius sub-group of the Scorpius-Centaurus Association of stars that share a common origin and space velocity. Such runaway stars may be ejected by dynamic interactions between three or four stars. However, in this case the star may be a former component of a binary star system in which the more massive primary was destroyed in a Type II supernova explosion. The pulsar PSR B1929+10 may be the leftover remnant of this supernova, as it too was ejected from the association with a velocity vector that fits the scenario.>>
http://en.wikipedia.org/wiki/Scorpius-Centaurus_Association wrote:

<<The Scorpius-Centaurus Association (sometimes called Sco-Cen or Sco OB2) is the nearest OB Association to the Sun. This stellar association is composed of three subgroups (Upper Scorpius, Upper Centaurus-Lupus, and Lower Centaurus-Crux), whose mean distances range from 380 to 470 light years.

Many of the bright stars in the constellations Scorpius, Lupus, Centaurus, and Crux are members of the Sco-Cen association, including Antares (the most massive member of Upper Scorpius), and most of the stars in the Southern Cross. The Sco-Cen OB association appears to be the most pronounced part of a large complex of recent (<20 million years) and ongoing star-formation. The complex contains several star-forming molecular clouds in Sco-Cen's immediate vicinity—the Rho Oph, Pipe Nebula, Barnard 68, Chamaeleon, Lupus, Corona Australis, and Coalsack cloud complexes (all at distances of ~120-200 parsecs), and several less populous, young stellar groups on the periphery of Sco-Cen, including the ~3-5 million-year-old epsilon Cha group, ~7 million-year-old eta Chamaeleontis cluster (also called Mamajek 1), ~8 million-year-old TW Hydrae association, ~12 million-year-old Beta Pictoris moving group, and possibly the ~30-50 million-year-old IC 2602 open cluster.

The stellar members of the Sco-Cen association have convergent proper motions of approximately 0.02-0.04 arcseconds per year, indicative that the stars have nearly parallel velocity vectors, moving at about 20 km/s with respect to the Sun. The dispersion of the velocities within the subgroups are only of order 1–2 km/s, and the group is most likely gravitationally unbound. Several supernovae have exploded in Sco-Cen over the past 15 million years, leaving a network of expanding gas superbubbles around the group, including the Loop I Bubble. To explain the presence of radioactive 60Fe in deep ocean ferromanganese crusts, it has been hypothesized that a nearby supernova, possibly a member of Sco-Cen, exploded in the Sun's vicinity roughly 3 million years ago.>>
Art Neuendorffer

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Re: APOD: Zeta Oph: Runaway Star (2012 Dec 29)

Post by rr_carroll » Sat Dec 29, 2012 7:38 pm

Thanks, all. This is showing the approximate nature of many astronomical values, which I should have been aware of already. :)

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Chris Peterson
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Re: APOD: Zeta Oph: Runaway Star (2012 Dec 29)

Post by Chris Peterson » Sat Dec 29, 2012 8:35 pm

Boomer12k wrote:I don't see a supernova remnant anywhere nearby. But maybe it is too faint now.
It is almost certain that no detectable supernova remnant remains. Remnants dissipate very rapidly- a few tens of thousands of years is as long as they exist. It's likely that the companion supernova that isolated this star occurred more than a million years ago. The most we could hope to detect would be some sort of cool, compact body, and it's doubtful we could do so for technical reasons.
I am thinking that if a larger companion exploded, then THIS would become the more massive, and the companion would now be dragged along with Zeta Oph.
No, that is dynamically impossible. The center of mass of the entire system must be close to where it always was. Supernovas release anywhere from ~1% to ~15% of their rest mass as energy. So even the most energetic core-collapse supernova will still retain at least 85% of its mass after the explosion. Much will be dissipated fairly symmetrically in the remnant nebula. The core body will remain in substantially the same place (perhaps with a small velocity imparted by an asymmetrical explosion). The companion was ejected because of the nature of orbital dynamics. In a suitable orbit, a rapid change in the mass and position of the body it was orbiting could substantially shift the angular momentum of the system between different bodies, and allow the companion to achieve escape velocity.
Chris

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