<p>imo, all the 5 stars are already present and with a little separation in the left image.<br>
Their distance to Earth should have been investigated on the image of the right. The ones nearer could travel, proper motion, much faster than the ones on the background.<br>
In short: they could be at large distances one from the others and it is a coincidence the fact that in the left image they are aligned. With zillions of stars out there the probability is not null.<br>
There are very fast stars (VFS) for ex. <a href="https://en.wikipedia.org/wiki/US_708" rel="nofollow noreferrer">US 708</a> (1200 km/s on WP e 708 km/s heliocentric radial velocity - Hirsch et al. 2005) not known at Feynman time.<br>
The time of discovery of VFS was 2005 and 10 years later, Warren R, Brown et al, reported on the PROPER MOTIONS AND TRAJECTORIES FOR 16 EXTREME RUNAWAY AND HYPERVELOCITY STARS (2015).  </p>

<p>EDIT ADD:<br>
One thing that can be done is to use software enabled with <a href="https://en.wikipedia.org/wiki/Point_spread_function" rel="nofollow noreferrer">Point Spread Function (PSF)</a> to discriminate the number of sources and decide how many stars are in each of the images.<br>
I will not do it because it takes time that I do not have.  </p>

<p>There are several packages available, fi, DS9 (<a href="https://www.youtube.com/watch?v=63umWDsHcEY" rel="nofollow noreferrer">video: find a moving star</a>), MAXIM DL, <a href="http://www.astromatic.net/software/sextractor" rel="nofollow noreferrer">SExtractor</a>. The images have to be scaned, eventually formated as FITS (<a href="http://docs.astropy.org/en/stable/generated/examples/io/split-jpeg-to-fits.html" rel="nofollow noreferrer">python code</a>) and if using SExtractor look at the procedure used by <a href="https://ui.adsabs.harvard.edu//#abs/1997A&amp;A...317...43B/abstract" rel="nofollow noreferrer">E. Bertin and M. Dennefeld (1997)</a>.<br>
Search on youtube <a href="https://www.youtube.com/results?search_query=Detecting%20asteroids" rel="nofollow noreferrer">'Detecting asteroids'</a></p>

CC BY-SA 4.0
2018-08-18T16:33:52.577Z
Thank you for your answer! I can't give the bounty for an opinion though, even though I agree with it.
uhoh
CC BY-SA 4.0
2018-08-18T18:23:31.277Z
In the absence of measures only opinions can be made. Even Feynman formulated his opinion. To the possibility of a photo artifact I do  not gave too much credit - there is a vertical dimmed stripe on the middle of the substrate of the right image.
Helder Velez
CC BY-SA 4.0
2018-08-25T14:48:18.303Z
I've  EDIT ADD to include rferences to software to count the sources in an image
Helder Velez
CC BY-SA 4.0
2018-08-25T19:58:45.847Z
I think this is possibly the answer.
ProfRob
CC BY-SA 4.0
2018-08-18T03:37:01.457Z
2018-08-25T14:47:05.253Z
2018-08-25T14:47:05.253Z
Helder Velez
<p>It could be caused by 2 rotating binary star systems. If the rotation rates are less than say 30 years then 7 years would show a significant movement of the bodies. I don't know how rare 2 rotating systems are so seeing both of these may be too rare to be practical.</p>

CC BY-SA 4.0
2018-08-17T22:46:25.100Z
Unlikely. Kepler 3 says an orbital period of 30 years means separation of about 10 au (and only increases as mass to the one  third) The nearest star forming region is >100 pc away, so the stars would have an angular separation of <0.1 arcsec. No 1954 optical telescope is resolving this
ProfRob
CC BY-SA 4.0
2018-08-18T00:22:51.773Z
my mistake. thanks for pointing this out.
Natsfan
CC BY-SA 4.0
2018-08-18T00:25:06.043Z
But more likely this answer than star formation.  lol
Natsfan
CC BY-SA 4.0
2018-08-18T16:34:34.750Z
Thank you for your answer! I can't give the bounty for speculation though, even though I probably agree with it.
uhoh
CC BY-SA 4.0
2018-08-18T17:00:10.720Z
sure. Whatever you think is best, I understand.
Natsfan
CC BY-SA 4.0
2018-08-17T22:10:19.807Z
2018-08-17T22:10:19.807Z
Natsfan
<p>I've stumbled upon this curious passage addressing the formation of stars in Feynman's lectures on physics:</p>

<blockquote>
  <p>Whether we have ever seen a star form or not is still debatable.
  Figure 7–12 shows the one piece of evidence which suggests that we
  have. At the left is a picture of a region of gas with some stars in
  it taken in 1947, and at the right is another picture, taken only 7
  years later, which shows two new bright spots.</p>
</blockquote>

<p>While I fully agree with Feynman's later note† that it's extremely unlikely that this picture shows stars forming, <em>what does it actually show</em>?</p>

<p>There is no reference to it, and no mention of filter used, the physical scale or even of the celestial object shown, and I've gotten rather curious as to what the seven-year change represents. Variable stars? Or is the displacement due to proper motions? Film artifact? Something else entirely?</p>

<p>Figure in question (<a href="http://www.feynmanlectures.caltech.edu/I_07.html#Ch7-F12" rel="noreferrer">Source</a>):</p>

<p><a href="https://i.sstatic.net/rlyMd.png" rel="noreferrer"><img src="https://i.sstatic.net/rlyMd.png" alt="enter image description here"></a></p>

<p>† Feynman concludes the paragraph with "[has the star formation somehow occurred?] <em>Perhaps, and perhaps not. It is unreasonable that in only seven years we should be so lucky as to see a star change itself into visible form; it is much less probable that we should see two!"</em> - indeed, the star formation rate of the whole Galaxy would be of this order!</p>

CC BY-SA 4.0
2018-08-12T23:34:06.517Z
The formation of a (visible) star takes about a million years.
ProfRob
CC BY-SA 4.0
2018-08-15T06:49:15.930Z
Could this be gravitational lensing of a transient body?
J. Chomel
<star><star-formation>
The formation of new stars as depicted in Feynman's lectures
Vlas Sokolov
# The formation of new stars as depicted in Feynman's lectures

(Asked by: username_0 on 2018-08-09)

I've stumbled upon this curious passage addressing the formation of stars in Feynman's lectures on physics:

> Whether we have ever seen a star form or not is still debatable.
> Figure 7–12 shows the one piece of evidence which suggests that we
> have. At the left is a picture of a region of gas with some stars in
> it taken in 1947, and at the right is another picture, taken only 7
> years later, which shows two new bright spots.

While I fully agree with Feynman's later note† that it's extremely unlikely that this picture shows stars forming, *what does it actually show*?

There is no reference to it, and no mention of filter used, the physical scale or even of the celestial object shown, and I've gotten rather curious as to what the seven-year change represents. Variable stars? Or is the displacement due to proper motions? Film artifact? Something else entirely?

Figure in question ([Source](http://www.feynmanlectures.caltech.edu/I_07.html#Ch7-F12)):

[![enter image description here](https://i.sstatic.net/rlyMd.png)](https://i.sstatic.net/rlyMd.png)

† Feynman concludes the paragraph with "[has the star formation somehow occurred?] *Perhaps, and perhaps not. It is unreasonable that in only seven years we should be so lucky as to see a star change itself into visible form; it is much less probable that we should see two!"* - indeed, the star formation rate of the whole Galaxy would be of this order!

**Tags:** star, star-formation

> **Comments:**
> **username_1**: The formation of a (visible) star takes about a million years.  
> **username_2**: Could this be gravitational lensing of a transient body?  

---

## 2 answers

### Answer by username_3 on 2018-08-18. Score: 3

imo, all the 5 stars are already present and with a little separation in the left image.  
Their distance to Earth should have been investigated on the image of the right. The ones nearer could travel, proper motion, much faster than the ones on the background.  
In short: they could be at large distances one from the others and it is a coincidence the fact that in the left image they are aligned. With zillions of stars out there the probability is not null.  
There are very fast stars (VFS) for ex. [US 708](https://en.wikipedia.org/wiki/US_708) (1200 km/s on WP e 708 km/s heliocentric radial velocity - Hirsch et al. 2005) not known at Feynman time.  
The time of discovery of VFS was 2005 and 10 years later, Warren R, Brown et al, reported on the PROPER MOTIONS AND TRAJECTORIES FOR 16 EXTREME RUNAWAY AND HYPERVELOCITY STARS (2015).

EDIT ADD:  
One thing that can be done is to use software enabled with [Point Spread Function (PSF)](https://en.wikipedia.org/wiki/Point_spread_function) to discriminate the number of sources and decide how many stars are in each of the images.  
I will not do it because it takes time that I do not have.

There are several packages available, fi, DS9 ([video: find a moving star](https://www.youtube.com/watch?v=63umWDsHcEY)), MAXIM DL, [SExtractor](http://www.astromatic.net/software/sextractor). The images have to be scaned, eventually formated as FITS ([python code](http://docs.astropy.org/en/stable/generated/examples/io/split-jpeg-to-fits.html)) and if using SExtractor look at the procedure used by [E. Bertin and M. Dennefeld (1997)](https://ui.adsabs.harvard.edu//#abs/1997A&A...317...43B/abstract).  
Search on youtube ['Detecting asteroids'](https://www.youtube.com/results?search_query=Detecting%20asteroids)

> **Comments:**
> **username_4**: Thank you for your answer! I can't give the bounty for an opinion though, even though I agree with it.  
> **username_3**: In the absence of measures only opinions can be made. Even Feynman formulated his opinion. To the possibility of a photo artifact I do  not gave too much credit - there is a vertical dimmed stripe on the middle of the substrate of the right image.  
> **username_3**: I've  EDIT ADD to include rferences to software to count the sources in an image  
> **username_1**: I think this is possibly the answer.  

---

### Answer by username_5 on 2018-08-17. Score: 1

It could be caused by 2 rotating binary star systems. If the rotation rates are less than say 30 years then 7 years would show a significant movement of the bodies. I don't know how rare 2 rotating systems are so seeing both of these may be too rare to be practical.

> **Comments:**
> **username_1**: Unlikely. Kepler 3 says an orbital period of 30 years means separation of about 10 au (and only increases as mass to the one  third) The nearest star forming region is >100 pc away, so the stars would have an angular separation of <0.1 arcsec. No 1954 optical telescope is resolving this  
> **username_5**: my mistake. thanks for pointing this out.  
> **username_5**: But more likely this answer than star formation.  lol  
> **username_4**: Thank you for your answer! I can't give the bounty for speculation though, even though I probably agree with it.  
> **username_5**: sure. Whatever you think is best, I understand.  

---

