APOD: Zeta Oph: Runaway Star (2015 Jul 05)

[APOD Robot]

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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[the old blind man]

The picture is sorely missing a star trek imperial cruiser getting in between the star and the nebula at full speed and disturbing the dust on the left in the process.

[Guest]

How accurately does one know the transverse motion of this star? I have seen this comment before. It is unfounded.

[geckzilla]

How accurately does one know the transverse motion of this star? I have seen this comment before. It is unfounded.

What is unfounded?

[Ann]

Click to view full size image

Copyright: Naoyuki Kurita

I searched for a good RGB image of Zeta Ophiuchi to compare with today's infrared image APOD, and I found the one on the left. The RGB image shows clearly that Zeta Ophiuchi is not in any way a red star, but it also doesn't look really bluish, but rather white. The non-red non-blue color of this star sitting in the middle of a large emission nebula shows that it is a hot star that is being reddened by dust.

More interesting is the RGB portrait of the large emission nebula surrounding Zeta Oph, Sharpless 2-27. Several "walls" of different kinds can be seen. The most obvious one is the bright (although somewhat "fluffy") red wall to the upper right of the star. The wall bifurcates at the left and the part nearest the star shows a bright knot, somewhat similar to IC 63 near hot bright star Gamma Cassiopeia.

The second most obvious wall (or maybe the most obvious one) is a sharply defined, wiggling, slightly curving dark dust lane to the left of the star. This wall may possibly be affected by a moderately bright star immediately to the left of it. It is also possible that this dark dust lane is part of a background latticework of dust structures that has nothing to do with Zeta Ophiuchi.

There is a fascinating wall, extremely thin and straight, much closer than the sharply defined dust lane to the left of the Zeta Oph. If this line isn't a photographic artifact, I'm guessing that it marks one side of the boundary of a "cavity" that the hot star has blown around itself.

There is also a an ill-defined, comet tail-like red "wall" apparently emerging from the star itself and stretching downwards and to the right.

I have to wonder which, if any, of these visible walls and structures correspond to the dusty arc in today's APOD. Perhaps none of them do. The visible nebula, Sharpless 2-27, is huge in angular size, but I have no idea how close to or far away from the star the infrared dust arc is located.

Ann

[Dad is watching]

In the description, it says that the star was 'flung out of the system' from a binary pair. Just so we understand it, has the correct terminology been used? Or would it be more accurate to say that the star escaped from the system because of preexisting momentum. If the star was actually flung (throw or hurl forcefully), would that imply some sort of 'gravity assist' as the smaller star fell in to the gravity well of the larger companion and was subsequently ejected?

[neufer]

How accurately does one know the transverse motion of this star?

• In it's 4 years of operation the Hipparcos satellite
  (with an operational accuracy of ~1 milliarcsecond) had no problem
  tracking the rapid 29 mas/yr transverse motion of ζ Ophiuchi.

[Craine]

The picture is sorely missing a star trek imperial cruiser getting in between the star and the nebula at full speed and disturbing the dust on the left in the process.

I am revoking your geek card.
It is either a Star Trek starship, possibly from the Federation's Starfleet, such as the USS Enterprise NCC-1701-D as shown in Star Trek - The Next Generation. Or it is a Star Wars Imperial I-Class Star Destroyer as shown in the original Star Wars movie.

Neither of which would leave any discernible trail in that much dust.

[Boomer12k]

Questions:
1: Toward which part of the sky is our Solar System headed? Can we see the direction the Solar System is going?
2: Are there any images of our Heliosphere? Not just depictions...
3: Is there a noticeable Bow Shock for our Solar System, and are there pictures of it? I guess is what I am really trying to get at....

Thanks.

:---[===] *

[Jim Leff]

"24 kilometers per SECOND."

Is "second" italicized because this is seen as remarkably fast? It's only about 1.5 times the velocity of Voyager 1.....

[Chris Peterson]

In the description, it says that the star was 'flung out of the system' from a binary pair. Just so we understand it, has the correct terminology been used? Or would it be more accurate to say that the star escaped from the system because of preexisting momentum. If the star was actually flung (throw or hurl forcefully), would that imply some sort of 'gravity assist' as the smaller star fell in to the gravity well of the larger companion and was subsequently ejected?

A purely binary system is stable. Gravity assist maneuvers can't result in bodies in closed orbits around each other suddenly being in open orbits.

In this case, I'd say the terminology is neither "correct" nor otherwise. "Flung" is not a word with a formal scientific definition. It's a word that, in a short caption, conveys a graphic sense of what's happening.

The star is escaping the system because the gravitational dynamics changed, shifting it from a closed orbit around a high mass to an open orbit around a low central mass and large distributed mass.

[starsurfer]

I'm amazed that there still hasn't been an optical image of the bowshock, which is actually brighter in OIII than Ha.

[Guest]

Is it going to keep moving indefinitely to the left? Besides neing affected by whatever gravitational force is exrted by "nearby" masses? Is there any way to detect how fat it's traveled from its otigin point within tbe theorized binary star system?

[neufer]

Is it going to keep moving indefinitely to the left?

Until it ends its life in a supernova explosion in a few million years
(i.e., a few hundred more light years to the left) leaving behind a left moving Neutron Star.

Is there any way to detect how far it's traveled from its origin point within the theorized binary star system?

One can make an educated guess:

<<ζ Ophiuchi is a young star with an age of only three million years. 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.>>

[geckzilla]

Is it going to keep moving indefinitely to the left?

Until it ends its life in a supernova explosion in a few million years
(i.e., a few hundred more light years to the left) leaving behind a left moving Neutron Star.

I imagine it'll arc in orbit around the galaxy, escaping from its previous orbit with another star, but not the galaxy itself. Does it have enough time to make an orbit or two before it explodes? Maybe, maybe not...

[DavidLeodis]

The picture of the cat brought up through the "relatively undisturbed" link made me . It may be thinking I'll have time for a cat nap as this internet connection is so slow! It may of course be wondering why the tab function is acting very oddly and why are all the onscreen letters in capitals? Perhaps it's a tabby cat .

[starsurfer]

The picture of the cat brought up through the "relatively undisturbed" link made me . It may be thinking I'll have time for a cat nap as this internet connection is so slow! It may of course be wondering why the tab function is acting very oddly and why are all the onscreen letters in capitals? Perhaps it's a tabby cat .

Tabby cats are lovely!

[Chris Peterson]

I imagine it'll arc in orbit around the galaxy, escaping from its previous orbit with another star, but not the galaxy itself. Does it have enough time to make an orbit or two before it explodes? Maybe, maybe not...

It isn't clear to me that this star is now in an open orbit with respect to its original companion, or the other stars in the grouping it originated in (all of which have a high peculiar motion themselves). I haven't tried to track down any formal studies, but I think it's possible this star is now in a highly eccentric, but still elliptical orbit around either its original companion or the Scorpius-Centaurus stellar association.

[Guest]

Just curious. The frame is mentioned as covering a diameter of 12 LY. Based on the image, this would put the most energetic part of the "bowshock" a light year from the star...how is there enough particle density, or radiation pressure...or combination of both, to produce this at this distance?

[neufer]

Just curious. The frame is mentioned as covering a diameter of 12 LY. Based on the image, this would put the most energetic part of the "bowshock" a light year from the star...how is there enough particle density, or radiation pressure...or combination of both, to produce this at this distance?

• Zeta Oph is 65,000 times more luminous than the Sun so it's radiation pressure
  (dropping off with the square of the distance) extends out ~ 250 times as far.
  
  However, really, it is caused by stellar-wind pressures ~ 65,000 times that of the sun:

<<Stellar-wind bubble is the astronomical term usually used to describe a cavity light years across filled with hot gas blown into the interstellar medium by the high-velocity (several thousand km/s) stellar wind from a single massive star of type O or B. Weaker stellar winds still blow bubble structures though, and these are also called astrospheres. The heliosphere blown by the solar wind, within which all the major planets of the Solar System are embedded, is a small example of a stellar-wind bubble.

Stellar-wind bubbles have a two-shock structure. The freely-expanding stellar wind hits an inner termination shock, where its kinetic energy is thermalized, producing 10⁶ K, X-ray emitting plasma. The hot, high-pressure, shocked wind expands, driving a shock into the surrounding interstellar gas. If the surrounding gas is dense enough (number densities or so), the swept up gas radiatively cools far faster than the hot interior, forming a thin, relatively dense shell around the hot, shocked wind.