| las wrote:|
|Hi, has anyone noticed a pattern that seems to occur in nearly every photo I have seen of a dense field of stars? the stars are all neatly arranged in a string of pearls between three and six in number. Is this a known optical effect? Could this be some sort of grvitational lensing? |
This is an observational bias effect. Our brains are wired for pattern-matching, but they are not especially good at preventing us from finding patterns where there are none. A considerable amount of work has been done on astrometric software that recognizes star patterns. A concept called "neighborhooding" is used to detect gross patterns in star fields, and it is based on the very idea you suggest. It is one of the least effective of the astrometric analysis algorithms, but it is good for a quick analysis that orients two starfields relative to one another where they overlap. I spent a considerable amount of time in photo analysis of the Palomar Sky Survey plates using acetate patterns which embodied this same concept. It does not work very well.
Also - concerning the nature of light- say I observe a star (star X) traveling thru space at a distance of say 10,000 light years and the light I observe indicates it's relative motion to me as traveling away from me at a standard rate that agrees with our present understanding of the universe's expansion. Now switch to a different vantage point 100 million miles from the present position of star X which of course is 10,000 light years ahead of my home planet observation. The two observation points put X in radically different locations, the second of course being much the more valid. In short, of course the light I see now from planet earth has no real correlation to the actual position of the star 10,000 light years away. Here is my question- imagine that I were able to travel instantaneously to the actual position of X and it has been gobbled up in a black hole- when in 10,000 years I begin to finally observe the last flicker of light from X what will I really see? I mean if light is something like a long train traveling from X to me and the caboose has already left X with the time and position stamped on it's side and then our nasty black hole systematically gobbles up the caboose and many more cars, how does this affect my earthly observation? Can the train be completely pulled off its tracks say if the relative motion of the b.h. is 90 degrees from X and 10 million m.p.h. - m.p.s.? Is it possible that observing the star X from earth I might suddenly be left with just the trunkated version of the train of light suddenly gone having been sucked back by the black hole like a spighetti noodle? Maybe I'm way overestimating the gravitational strength and reach of the singularity. Anyway, it is interesting to think of this and there are any number of other variables you can play with in this scenario.
I may misunderstand you here, sorry. But if I do understand, the final situation is that X has moved during 10,000 years some distance at a right angle to the original line of sight with Earth and has been sucked into a black hole that is moving rapidly away from the star's initial position (position X 10,000 years ago). And what you want to know is the effect on the light that you see near the end of the 10,000-year period.
If that is correct, then here's the deal:
- Black holes are not cosmic vacuum cleaners that suck up stars at vast distances from the singularity: the doomed star must be very near the black hole to begin with.
- Otherwise, the black hole must "accidentally" encounter the star during its headlong flight through the universe.
In case 1, the observer on Earth sees no change in the star since it is not pulled toward the (too-distant) black hole at all. The star simply continues its original proper motion (whatever that was), and has its initial red-shift (corrected for the time of expansion since first measurement). However, if the black hole is sufficiently massive, and if it is at a distance of 100 million miles from X at the beginning of the 10,000-year light-travel time, then the star will simply wink out very soon thereafter after a brief interval of brightening (mostly in X-rays) because the black hole will ingest it rather quickly.
In case 2, there are two scenarios: (A) the flight path of the black hole toward the star is from farther away from the Earth toward the Earth, or vice-versa; or, (B) the flight path of the black hole toward the star is from the right of the line of sight between Earth and the star, or from the left.
In scenario A, during the last few hundred years of the "incoming light train's" trip, the photons would appear to be accelerated toward, or away from, the Earth (depending on the approach direction of the black hole) and the red-shift would be altered accordingly. Then sometime in the last few years the X-ray emissions from the star would appear to increase both in strength and in apparent visual diameter as the star is ripped asunder and spread around the accretion disc of the black hole. Finally, the star would simply wink out in visible light, but continue to glow in X-rays as long as sufficient material remained in orbit in the accretion disc to produce the radiation.
In scenario B, as the black hole approached to a point where the star is attracted to it, the star's proper motion would change (toward the black hole) and its red-shift would diminish (it acceleration relative to the Earth would no longer be directly away from the Earth). At some later time the star's proper motion in the direction of black hole would increase, and the star's red-shift would change accordingly. And at some still later time (when the star begins to come apart under the influence of the black hole's gravity), an effect similar to the end-game in scenario A would occur and the star would brighten in X-rays before winking out.