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Jet in M87?

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#26 Tarzanrock

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Posted 12 March 2010 - 06:18 PM

Hi Paul:
Thank you for your reply and your candor in your response. Have you seen it at Palomar Mountain?
I have looked at some scientific papers published on the internet where scientists have apparently measured the brightness of the jet through radio astronomy; x-ray astronomy; and, other spectroscopic means; and, as best as I can tell from these papers, it appears that the jet's magnitude is measured at: "R = 16.21 plus or minus 0.05;" and, "B = 15.0 plus or minus 0.1." Apparently, the jet is at its brightest peak about a mere 215 light years from the center of the nucleus of M87; and, thereafter it then fades and dims for the remainder of its measured 4,000 to 5,000 light year length. Of course, the diameter of M87 is stated to be approximately 130,000 Light Years.
Given the visual magnitude of M87 which is arguably listed at 8.6, I simply do not understand how it is possible for someone to visually observed the jet itself with a limited aperture telescope [considering associated related factors which obviously limit ground based observations, i.e. air masses, water vapor, atmospheric turbulence, mount vibrations, optics, collimation, mirror quality, light pollution, seeing and transparency, various human factors enginnering, etc.] when that magnitude 16 jet is directly adjacent to and part of a giant, brightly luminuous magnitude 8.6 object which itself radiates bright light out to a distance of 7-9 arc-minutes or longer (and some say its light extends out to 30 arc-minutes).
Simply put, it makes no sense to me. Perhaps, I am missing something in this analysis, but I would like to know the answer to this question.
Serious professional astronomers and scientists have been visually observing Messier class objects since at least 1780 using very large aperture high quality instruments (Clark and Brashears Refractors; giant reflectors; and, other very large aperture instruments) in eras before the electric light was even invented with little or no discernable light pollution and thereafter; and, no one has claimed to have visually seen the jet before 1917 or 1918 when Curtis noted it on photographic plate at the Lick.
Thereafter none of some of the most respected professional astronomers, men such as Hall; Barnard; Slipher; Hubble; Lowell; Minkowski; and, many, many others who worked with giant world class instruments such as 100 inch scopes (Hooker, Mt. Wilson); 60 inch (Mt. Wilson) 40 inch refractors (Clark, Yerkes); 30 inch refractors (Lick; USNO); 20 inch refractors all of which are mounted in world class observatories which sponsored by governments, science institutions and universities in countries all over the world ever recorded seeing it throughout the late 19th and 20th Centuries.
William

#27 Starman1

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Posted 12 March 2010 - 07:59 PM

Don't forget that the light of the jet would be ADDED to the light of the core, not diminished by it.
The light of a galaxy is ADDED to the light of the night sky, for instance, not diminished by it.
What you're referring to is contrast and visually the part of the nucleus the jet would be superimposed on has a lower surface brightness than the jet, so though the contrast would not be ideal (say, against a jet black background), there should still be enough contrast to see the jet if the scope has the resolution and magnification potential to do so. We're merely discussing how small a scope can see the jet, and it appears that there are a lot of observations in 18" and up and a few in smaller apertures.
So seeing it requires aperture, yes, and good seeing, and high power, but it always requires less aperture to see something you know is there than to discover it in the first place.
It's always been that way in astronomy.
It's how I found some globulars in M31 in my 8" SCT. I had a map of where they were, and I knew the slightly fuzzy star was actually a globular.
And if you have the privilege to view in a place where the night sky reaches magnitude 21.9-22.0 and you can see 30-40 Messier objects with the naked eye, the M87 jet may prove to not be the hardest of visual challenges, so long as you have enough aperture to get to the required magnification.

#28 palsing

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Posted 13 March 2010 - 12:25 AM

Given the visual magnitude of M87 which is arguably listed at 8.6, I simply do not understand how it is possible for someone to visually observed the jet itself with a limited aperture telescope... when that magnitude 16 jet is directly adjacent to and part of a giant, brightly luminuous magnitude 8.6 object which itself radiates bright light out to a distance of 7-9 arc-minutes or longer (and some say its light extends out to 30 arc-minutes)...


William, I think perhaps you need to fully understand the difference between magnitude and surface brightness, it has confused a lot of guys smarter than you or I many times in the past.

Understand that an object's magnitude represents its total integrated light, as though it were squeezed down to essentially a point source, like a star. M-87 is big, so its 8.6 total magnitude is spread out over a large area, and its average surface brightness is therefore only 13.1. On the other hand, its 15th (or whatever) mag jet is fairly small, and although I can find no source that tells me the surface brightness of the jet itself, I know there are many small galaxies that have a surface brightness that is actually brighter than the galaxy's stated overall magnitude. It is entirely possible that the brightness of the jet exceeds that of the galaxy, but this pure speculation on my part. In any case, the difference in surface brightness between them is nowhere near the difference in magnitude, in my view.

This may not be an acceptable explanation for you, but it is the best I can come up with on short notice ;>)

In my mind, it is clear that dozens and dozens of fellow amateurs have really seen this jet, so there must be a logical reason why, even if mine isn't it.

#29 tatarjj

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Posted 13 March 2010 - 02:39 AM

Ok, I see now that you have a real, legitimate doubt. I thought you were just trying to sow trouble before.

There are many images that show the jet, and give a good representation of how it looks through a scope. This is a good one:
http://virtualtelesc...ory.org/m87.jpg

That's very close to how the field appears through my 25". You can see the jet there, very near M87's core.

The guy used a C11 for the first shot, but here is another one by the same imager that was made with a C14. You can even see a decent amount of detail in the jet.

http://virtualtelesc...rg/m87b_c14.jpg

Your basic flaw in your thinking is that you are reading too much, and not looking for yourself. There are many images you can find for yourself using simple google searches, such as the ones I showed above, that show that your assertion that the jet is brightest just 215 light years or whatever from the core is clearly wrong, as is your assertion that it is a low surface brightness object. I'm not sure of the 5,000 light year length or not, it sounds a little too short, but maybe that is correct.

As you can clearly see, the surface brightness of the jet is very high, and it extends a considerable way out of the core. You need to keep in mind that the jet is a very high surface brightness object. Besides, if those numbers are correct at magnitude 15, which sounds a little too dim (alot of magnitude estimates seem to be wrong on many things) that is about two magnitudes brighter than the faintest galaxies visible in a 25" scope, and near the brightness of hte faintest galaxies possible in a 12.5" scope, the smallest scope that I know of that has successfully observed the jet.

Here is another image, this time a professional image, showing the jet. This one again illustrates the extreme high surface brightness of this feature, and that it is NOT brightest just 200 odd light years from the core.

http://www.ing.iac.e...nce/NGC4486.jpg

Another amatuer image, with enough dynamic range to show the jet (20" telescope):
http://www.kopernik....archive/m87.htm

A kinda cruddy image, amateur, where you can still see the jet (12" SCT):
http://www.astronomi.../bilder/m87.htm

Lots of M87 images are overexposed in the center, and the jet gets partially or entirely washed out. Here is an example:
http://quantumrelati.../Images/m87.jpg
Note that even with the overexposure, the jet is STILL visible, 11 o-clock.\

What better way to prove that the jet is NOT brightest just a meager 200 light years from the core than have the HST look at it?
http://yastro.narod....314/M87_jet.jpg

Another thing I don't understand is how you think you can ignore the many reported visual observations of this feature. Do you truely believe that observers who have clearly seen the jet, including a great many of the most respected deep sky observers, are delusional (or liars)?

None of the evidence seems to support your assertion that the jet is invisible visually. Even your original claimant you found that the jet is invisible, Roger Clark, reports to have seen it visually with just a 12.5" scope 14 years ago!

#30 Tom Polakis

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Posted 13 March 2010 - 09:36 AM

So seeing it requires aperture, yes, and good seeing, and high power, but it always requires less aperture to see something you know is there than to discover it in the first place.



Don's point here is very important. Many folks on this forum have gone beyond previously established "limits" by bringing charts and images out into the field. You can only infer so much from the literature, and then you have to go out and see for yourself. That's a big part of the fun of this hobby.

Regarding the subject of doubting others' observations, I have found that if one renegade claims to have gone a couple magnitudes beyond the consensus, doubting might be in order. But if a community of observers have seen something with consistent notes, then it really is visible. I have seen M87's jet using my 18-inch, but not in my 10-inch. As others have pointed out, the feature is very small, and high magnification is beneficial.

Tom

#31 jack45

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Posted 13 March 2010 - 02:29 PM

I have mag 6.3 skies and will try with a 16" discovery scope next clear sky. Using a TV 2x barlow and 13mm and 9mm Nagler maybe my best chance to see it. I think with this one you need both, excellent transparency and good seeing.

Clear Skies!

#32 skyward_eyes

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Posted 14 March 2010 - 01:33 PM

Well I gave it a shot this weekend with my 16" and got nothing. I will try again on my next dark sky outing, I did get a lot of other cool stuff so no complaints.

#33 Bret Ford

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Posted 14 March 2010 - 01:44 PM

Well I gave it a shot this weekend with my 16" and got nothing. I will try again on my next dark sky outing, I did get a lot of other cool stuff so no complaints.


I tried last night with a 20"--no see-um, either. The seeing wasn't the greatest... Good transparency--the cotton balls, almonds, sunflower seeds and toothpicks in Virgo and U. Major were bright--but mushy.

Bret

#34 Starman1

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Posted 14 March 2010 - 04:05 PM

Ditto.
Poor seeing and high winds kept me from getting above 100X.
Too bad, because the darkness reached mag. 21.78.

#35 Tarzanrock

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Posted 14 March 2010 - 05:58 PM

Hi Don:
You probably did not recognize my CN "Tarzanrock" moniker, but thanks for your efforts -- maybe "new moon" time next month will present an opportunity to view the jet in Joshua Tree.
Bill

#36 Mike Harvey

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Posted 14 March 2010 - 07:56 PM

No sighting last night with the 28" at Chiefland. But it was realy a matter of seing conditions - not aperture.
Good transparency...cancelled out by high turbulence.
Just couldn't use enough magnification.
Will try again tonight.

Mike

#37 Doug Brown

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Posted 15 March 2010 - 07:44 AM

Ditto Ditto Ditto
Will try again soon.

#38 Mateyhv

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Posted 15 March 2010 - 08:21 AM

Don't forget that the light of the jet would be ADDED to the light of the core, not diminished by it.
The light of a galaxy is ADDED to the light of the night sky, for instance, not diminished by it.


Hi Dan, the first example is not equal to the second. In the first you have some kind of matter that actually blocks part of the light from behind and its a source of light on its own so there could be several scenerios where light could be added in some degree, equaled or even subtracted but not necessarily just added. Think about eclipsing binaries for example where both are light sources but light blocked by the eclipsing body is subtracted from the total output of both sources.

The second example is true because night sky light is not produced by a compact body but by the reflection of million tiny particles in the atmosphere wich only block an extremely small portion of the light coming from behind so it could be said that both light intensity are added.

Matey

#39 Starman1

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Posted 15 March 2010 - 12:54 PM

:foreheadslap:
You're right! Doh!
The jet WOULD block the galaxy behind it. So it's visibility would be more dependent on the contrast between the jet and the portion of the galaxy immediately next to it.
I should remember: think first, write second.
Thanks, Matey.

#40 Tarzanrock

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Posted 15 March 2010 - 02:29 PM

Hi Guys:
I thought that such was Roger N. Clark's point when he wrote: "Moreover, the jet is superimposed on essentially the brightest part of the galaxy, so the contrast is very low."
I thought a great deal about this matter and about what Don had said last Saturday night when I was staring out of my 12th Floor window in Los Angeles while looking at a bright spotlight located about a block away; and, I couldn't help but wondering whether or not I would be able to visually discern a 15 watt to 40 watt light bulb if it were glowing either in front of or adjacent to the bright spotlight at that distance. I concluded that it would be very difficult to see that dim light adjacent to the bright light.
On Sunday, I had the opportunity to look at a few more published science articles where the jet is measured by optical surveys, radio wavelengths, X-ray wavelengths and gamma ray wavelengths. It appears that John Biretta is the American scientist who has been more or less the leading light on the study of the M87 jet. From what I can tell from the articles, it appears that that the first knot, HST-1, which is located closest to the core of the nucleus of M87, at about 0.7 or 0.8 arc-seconds from the core, is the brightest; and the next brightest knot is Knot "A" which is located at about, 12 arc-seconds from the core of the nucleus of M87.
The information about the length of the jet is generally referenced at about 20 arc seconds.
The only information that I could yet find on the width of the jet is only one measurement so far which in which the width is measured to be about 1/10 or a light year in width.
The measurements vary according to what "measuring rod" is used to measure the jet, i.e. X-ray emissions; Gamma ray emissions; radio astronomy wavelength; optical wavelengths; and, I suppose other such measurements.
Bill

#41 Tarzanrock

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Posted 15 March 2010 - 02:34 PM

Whoops -- that's 1/10 of a light year. Like Don, I should think first; write second; and, proofread third.

#42 kcolter

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Posted 15 March 2010 - 08:32 PM

The quest to see the M87 jet is one that I have a lot of interest in. I am quite certain that despite many attempts with a 40 inch f5 Dob at magnifications in the 350-600 range that I have not seen the brightest portion of the jet against the bright central core of the galaxy. I have seen some very dim but definite objects that may be the fluted ends of the jet that are seen so well in astrophotos of the jet. It is also possible that I am seeing a couple of very dim companion galaxies to M87 that I have seen show up in some of the phtographic images of the jet that lie just distal to the fluted end of the jet. I am not really sure why I haven't been able to see the jet in against the brightest central portion of the core of the galaxy. I have tried dozens of times. I suspect that high quality seeing is the most important factor. Obviously it needs to be dark enough to see M87 well, but one is looking for the jet against the background glow of the galaxy, not against dark sky. I suspect that like so many other elusive objects, once you have seen it well once, it becomes easier to see it a second time.

#43 Tarzanrock

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Posted 16 March 2010 - 04:55 PM

Hi Kim:
There is a very interesting article about the Jet which was published in The Astrophysical Journal, 564: 683-687, January 10, 2002 entitled: A HIGH-RESOLUTION X-RAY IMAGE OF THE JET IN M87 and authored by H. L. MARSHALL, B. P. MILLER, D. S. DAVIS, E. S. PERLMAN, M. WISE, C. R. CANIZARES, AND D. E. HARRIS. I think that you would enjoy it if you haven't already read it.
I would attach it here but I don't know how to do attachments; and, I suspect that the article might be copyrighted. I'm sure that you can find it with an internet search.
Bill

#44 kcolter

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Posted 16 March 2010 - 09:23 PM

Bill
Thanks for the detailed reference. I will try to track the article down.
Kim

#45 Starman1

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Posted 16 March 2010 - 09:31 PM

You can probably find it here:
http://arxiv.org/archive/astro-ph

#46 Olivier Biot

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Posted 17 March 2010 - 02:44 PM

Hi Kim:
There is a very interesting article about the Jet which was published in The Astrophysical Journal, 564: 683-687, January 10, 2002 entitled: A HIGH-RESOLUTION X-RAY IMAGE OF THE JET IN M87 and authored by H. L. MARSHALL, B. P. MILLER, D. S. DAVIS, E. S. PERLMAN, M. WISE, C. R. CANIZARES, AND D. E. HARRIS. I think that you would enjoy it if you haven't already read it.
I would attach it here but I don't know how to do attachments; and, I suspect that the article might be copyrighted. I'm sure that you can find it with an internet search.
Bill


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#47 tatarjj

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Posted 18 March 2010 - 05:12 PM

The quest to see the M87 jet is one that I have a lot of interest in. I am quite certain that despite many attempts with a 40 inch f5 Dob at magnifications in the 350-600 range that I have not seen the brightest portion of the jet against the bright central core of the galaxy. I have seen some very dim but definite objects that may be the fluted ends of the jet that are seen so well in astrophotos of the jet. It is also possible that I am seeing a couple of very dim companion galaxies to M87 that I have seen show up in some of the phtographic images of the jet that lie just distal to the fluted end of the jet. I am not really sure why I haven't been able to see the jet in against the brightest central portion of the core of the galaxy. I have tried dozens of times. I suspect that high quality seeing is the most important factor. Obviously it needs to be dark enough to see M87 well, but one is looking for the jet against the background glow of the galaxy, not against dark sky. I suspect that like so many other elusive objects, once you have seen it well once, it becomes easier to see it a second time.


kcolter,
I'd say the key to seeing the jet is using semi-adverted vision. Because it lies very close to the core of M87, you need to have good spatial resolution in your vision to separate it from the core. If you use adverted vision, it just blurs into the core due to the very poor resolution of adverted vision, and if you use direct vision, then it fades away. So your answer is to use a combination of both to see it- semi-adverted vision. Perhaps those without good spatial resolution in semi-adverted vision will always have trouble with this object- it varies from individual to individual, of course.

As far as seeing effects on the jet- I am somewhat skeptical that seeing plays a huge factor (unless the seeing is REALLY bad), though it does of course play some role. The jet is something like 20" or 30" long, by maybe 5" wide. This is quite a bit bigger than the amount than the angular size of the spreading that seeing causes. Of course if the seeing is really bad, then it will spread this feature out too much to be seen, or at least complicate efforts to see it, and if the seeing is good it will help make the edge of the jet more sharp and easy to pick out. It's just that seeing shouldn't be a HUGE factor with this object. Still, it is true that seeing is more of a factor for this object than for most DSOs.

The biggest factor with this object is probably aperture, with sky darkness a second. You need the inner regions of M87 represented in the eyepiece with enough size and at a bright enough level to pick out the jet. You also need decent enough contrast to pick it out- which sky darkness helps with. Now, with both the jet and the inner regions of M87 being very bright objects, seeing the jet will not be as sky darkness depedendent as say, seeing a faint nebula, but it will still matter, probably matter more than seeing on average.

I'm actually staying in a cabin at a dark site right now (in West Texas). Last night, I had the 25" scope on M87, and the jet wasn't very hard to pick out, using semi-adverted vision. There's another observer staying here right now, and he brought a 12.5" scope. Anyway, he went up to the eyepiece of the 25", and I told him to use semi-adverted vision, but I did NOT tell him the correct direction that the jet points away from the core. After about 10 seconds, he saw it, and said that it looked like a "little thing hanging off of M87's core" to the 4-o-clock direction- which was the correct direction, matching with both my observations and with images of M87 that are not overexposed and show the jet.

Next, we put his 12.5" scope on M87. I can't say that I saw it for sure, and neither could he, but both of us thought we could detect an asymmetry in M87's core. From this, I'd say that the likely minimum aperture is thus somewhere around 12.5", matching what others have found as well.

#48 kcolter

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Posted 19 March 2010 - 09:42 PM

John
I greatly appreciate your thoughts and advice. May I ask what magnification you were using in your 25" to see the jet last night? Have you found that it makes any difference to use eyepieces with fewer elements when looking for the jet? Is the jet as likely to be revealed in a Nagler or Ethos design as in an orthoscopic? Thanks again for your thoughts and the coaching regarding semi-averted vision.

#49 tatarjj

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Posted 19 March 2010 - 11:12 PM

John
I greatly appreciate your thoughts and advice. May I ask what magnification you were using in your 25" to see the jet last night? Have you found that it makes any difference to use eyepieces with fewer elements when looking for the jet? Is the jet as likely to be revealed in a Nagler or Ethos design as in an orthoscopic? Thanks again for your thoughts and the coaching regarding semi-averted vision.


Well, I'd imagine you might have a better shot in a high contrast eyepiece, like an Ortho. Alot of people really like those TMB planetary eyepieces alot- they have a reputation of being very nice, high-contrast eyepieces (but with an incredibly narrow FOV). However, really, I'd suspect that the difference between using something like that and a Nagler would be pretty slight, but I can't speak from first hand experience. The observations the other night with the 25" were made with a 7mm T6 Nagler, giving me about 380X.

#50 Olivier Biot

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Posted 20 March 2010 - 04:43 AM

Well, I'd imagine you might have a better shot in a high contrast eyepiece, like an Ortho. Alot of people really like those TMB planetary eyepieces alot- they have a reputation of being very nice, high-contrast eyepieces (but with an incredibly narrow FOV).


Do you mean the BO/TMB Planetary eyepieces or the TMB Supermonocentric eyepieces? The former have an apparent field of view of 60° while the latter only have 30°.

I tried observing DSOs with both EP lines. The former allow averted vision, while the latter don't because you're constantly distracted by the field stop when using averted vision.


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