Discovery of PLuto ...

took place on 18th of February 1930 - almost exactly 75 years ago.

However, the sattelite of PLuto Charon remained not discovered for ...
48 YEARS !
It was ACCIDENTLY discovered on pictures of PLuto in 1978.

The technology needed to discover Charon existed for all 48 years ( from
1930 to 1978 ).

Why it was not discovered ?

http://www.interlog.com/~wnowak/book

"wnowak" wrote in message
...
took place on 18th of February 1930 - almost exactly 75 years ago.

However, the sattelite of PLuto Charon remained not discovered for ...
48 YEARS !
It was ACCIDENTLY discovered on pictures of PLuto in 1978.

The technology needed to discover Charon existed for all 48 years ( from
1930 to 1978 ).

Why it was not discovered ?

http://www.interlog.com/~wnowak/book




It's sometimes hard to explain why something was not noticed for a long
time, but the usual answer is, no one looked hard enough, or possibly Charon
was occasionally seen, and dismissed as a flaw or background star.

Pluto was not regarded as a subject of great interest by most astronomers in
the '40s and '50s, except for the question of its size and mass. The best
way to look for evidence of mass was to measure deviations in the orbits of
Uranus and Neptune, so observational approaches were directed at accurate
observations of these other planets.

Back in the 1960s an effort to observe an occultation of a star by Pluto
produced upper limits for its size, and showed that Pluto was much smaller
than Earth, but Charon did not happen to occult the star for any observer.

You also have to remember that most photographic observations of Pluto were
done to determine or improve its orbit, so only relatively small telescopes
were used, such as astrographs, or long focus refractors adequate for the
task but often located in places with relatively poor seeing. Charon is
always within a second of arc or so of Pluto itself and would be extremely
hard to spot on such photographs.

It was only when Christy used a relatively large (1.5-m, ISTR) telescope to
get precise astrometry from a high-quality mountaintop site (for prediction
of possible occultations) that he noticed a small bump on one side of the
planet's image. He might have simply dismissed it as a background star or a
flaw, but because it was on several images in different positions he
realised it was a satellite.

This said, I recall that Gerard Kuiper observed Pluto visually with the
Palomar 5-m telescope in the late 40s or early 50s, on a night of excellent
seeing. He wanted to measure the diameter with a bifilar micrometer (or
similar), and it is slightly surprising that he did not spot Charon. Or
maybe he did, and dismissed it as a faint background star. Remember, this
was a single observation on one night.

--
Mike Dworetsky

(Remove "pants" spamblock to send e-mail)

In message , Mike Dworetsky
writes
"wnowak" wrote in message
...
took place on 18th of February 1930 - almost exactly 75 years ago.

However, the sattelite of PLuto Charon remained not discovered for ...
48 YEARS !
It was ACCIDENTLY discovered on pictures of PLuto in 1978.

The technology needed to discover Charon existed for all 48 years ( from
1930 to 1978 ).

Why it was not discovered ?

It was only when Christy used a relatively large (1.5-m, ISTR) telescope to
get precise astrometry from a high-quality mountaintop site (for prediction
of possible occultations) that he noticed a small bump on one side of the
planet's image. He might have simply dismissed it as a background star or a
flaw, but because it was on several images in different positions he
realised it was a satellite.

Interesting stuff snipped.

Can you imagine the feelings of astronomers if Charon hadn't been
discovered until 1990, and they realised they had missed a series of
eclipses which won't recur for over a century? :-)
--
Support the DEC Tsunami Appeal http://www.dec.org.uk/.
Remove spam and invalid from address to reply.

Jonathan Silverlight writes:

Can you imagine the feelings of astronomers if Charon hadn't been
discovered until 1990, and they realised they had missed a series of
eclipses which won't recur for over a century? :-)

Yes I can, because when the satellite was discovered in 1978, the
orbit was known to be nearly edge on, but it was not known whether
it was opening or closing, thus there was a 50 percent chance that
the eclipses had been missed.

I am curious. Do you remember the exact time of GK observations, or maybe you
can ask around ? I can calculate the exact angular distance between P and CH and
add this fact to my site

http://www.interlog.com/~wnowak/book

So far I thought that I knew everything about PLuto, but you proved me wrong
BTW, no observations of PLuto ( for sure no Charon with 2.5 meter Mt. Wilson
telescope in 1930s, 40s ?

Excellent seeing in California in 1930-50 would be 0.30 arcsec. right ?

WN.

Mike Dworetsky wrote:

"wnowak" wrote in message
...
took place on 18th of February 1930 - almost exactly 75 years ago.

However, the sattelite of PLuto Charon remained not discovered for ...
48 YEARS !
It was ACCIDENTLY discovered on pictures of PLuto in 1978.

The technology needed to discover Charon existed for all 48 years ( from
1930 to 1978 ).

Why it was not discovered ?

http://www.interlog.com/~wnowak/book




It's sometimes hard to explain why something was not noticed for a long
time, but the usual answer is, no one looked hard enough, or possibly Charon
was occasionally seen, and dismissed as a flaw or background star.

Pluto was not regarded as a subject of great interest by most astronomers in
the '40s and '50s, except for the question of its size and mass. The best
way to look for evidence of mass was to measure deviations in the orbits of
Uranus and Neptune, so observational approaches were directed at accurate
observations of these other planets.

Back in the 1960s an effort to observe an occultation of a star by Pluto
produced upper limits for its size, and showed that Pluto was much smaller
than Earth, but Charon did not happen to occult the star for any observer.

You also have to remember that most photographic observations of Pluto were
done to determine or improve its orbit, so only relatively small telescopes
were used, such as astrographs, or long focus refractors adequate for the
task but often located in places with relatively poor seeing. Charon is
always within a second of arc or so of Pluto itself and would be extremely
hard to spot on such photographs.

It was only when Christy used a relatively large (1.5-m, ISTR) telescope to
get precise astrometry from a high-quality mountaintop site (for prediction
of possible occultations) that he noticed a small bump on one side of the
planet's image. He might have simply dismissed it as a background star or a
flaw, but because it was on several images in different positions he
realised it was a satellite.

This said, I recall that Gerard Kuiper observed Pluto visually with the
Palomar 5-m telescope in the late 40s or early 50s, on a night of excellent
seeing. He wanted to measure the diameter with a bifilar micrometer (or
similar), and it is slightly surprising that he did not spot Charon. Or
maybe he did, and dismissed it as a faint background star. Remember, this
was a single observation on one night.

--
Mike Dworetsky

(Remove "pants" spamblock to send e-mail)

wrote:

Jonathan Silverlight writes:

Can you imagine the feelings of astronomers if Charon hadn't been
discovered until 1990, and they realised they had missed a series of
eclipses which won't recur for over a century? :-)

Yes I can, because when the satellite was discovered in 1978, the
orbit was known to be nearly edge on, but it was not known whether
it was opening or closing, thus there was a 50 percent chance that
the eclipses had been missed.

Hmm ... that is in contradiction with what Stern says in his book;

"... However, the fact that no observer had accidently stumbled onto one
in progress hinted it was more likely that the event were in future, than
in the recent past. " ( page #66 )

This suggests 50% ++, correct Mr. Tholen ?

To tell you the truth I do not quite understand what Stern is talking
about.
For sure you know, since your picture is in the same book a few pages down
the road. Please explain this to us.

wnowak writes:

Jonathan Silverlight writes:

Can you imagine the feelings of astronomers if Charon hadn't been
discovered until 1990, and they realised they had missed a series of
eclipses which won't recur for over a century? :-)

Yes I can, because when the satellite was discovered in 1978, the
orbit was known to be nearly edge on, but it was not known whether
it was opening or closing, thus there was a 50 percent chance that
the eclipses had been missed.

Hmm ... that is in contradiction with what Stern says in his book;

"... However, the fact that no observer had accidently stumbled onto one
in progress hinted it was more likely that the event were in future, than
in the recent past. " ( page #66 )

This suggests 50% ++, correct Mr. Tholen ?

I don't buy the argument. There wasn't a whole lot of accurate
photometry being done prior to the discovery of the satellite.
The events themselves lasted only about five hours, and that's
for a central event (less for the grazing events). With two
events per orbit and one orbit every 150 hours, you're talking
one part in 15. That is, if someone were making random observations,
there's a 94 percent chance that the observations would be at times
when no event was occurring. But as I said, there weren't a whole
lot of observations being made. I'd have to dig into the literature
to count the number of photometric points obtained in the 1970s,
but I'd guesstimate 30. If events were occurring, that's two
potential observations at the time of events. They could have been
easily dismissed as bad points. Furthermore, I don't know of
anybody who was taking high time resolution observations of Pluto
in the 1970s. You'd need several points during an event to see
the trend. A single low point could be easily dismissed as a
faulty observation.

Meanwhile, there is also a claim in the literature that events were
seen when we now know there could not have been events, which
demonstrates that faulty observations can be made.

To tell you the truth I do not quite understand what Stern is talking
about.
For sure you know, since your picture is in the same book a few pages down
the road. Please explain this to us.

I hope the above is sufficient.

I think that there was a substantial chance that Charon would have been
discovered exactly during the eclipse season. Considering the fact that PLuto was
getting closer to its perihelion point ( 1989 ), one would expect that big world
telescopes would place it inside its "focal point". This would be a real "jaw
dropper" , if Charon was discovered exactly during the eclipse season
Please note that the point of perihelion and the point of PLutonian equinox (
max. eclipses )
have nothing in common. It is simply a random coincidence that they happen now
almost
exactly at the same time.

If you are interested in other shocking coincidences surrounding PLuto+Charon,
please visit my site.


Jonathan Silverlight wrote:

In message , Mike Dworetsky
writes
"wnowak" wrote in message
...
took place on 18th of February 1930 - almost exactly 75 years ago.

However, the sattelite of PLuto Charon remained not discovered for ...
48 YEARS !
It was ACCIDENTLY discovered on pictures of PLuto in 1978.

The technology needed to discover Charon existed for all 48 years ( from
1930 to 1978 ).

Why it was not discovered ?

It was only when Christy used a relatively large (1.5-m, ISTR) telescope to
get precise astrometry from a high-quality mountaintop site (for prediction
of possible occultations) that he noticed a small bump on one side of the
planet's image. He might have simply dismissed it as a background star or a
flaw, but because it was on several images in different positions he
realised it was a satellite.

Interesting stuff snipped.

Can you imagine the feelings of astronomers if Charon hadn't been
discovered until 1990, and they realised they had missed a series of
eclipses which won't recur for over a century? :-)
--
Support the DEC Tsunami Appeal http://www.dec.org.uk/.
Remove spam and invalid from address to reply.

wrote:

wnowak writes:

Jonathan Silverlight writes:

Can you imagine the feelings of astronomers if Charon hadn't been
discovered until 1990, and they realised they had missed a series of
eclipses which won't recur for over a century? :-)

Yes I can, because when the satellite was discovered in 1978, the
orbit was known to be nearly edge on, but it was not known whether
it was opening or closing, thus there was a 50 percent chance that
the eclipses had been missed.

Hmm ... that is in contradiction with what Stern says in his book;

"... However, the fact that no observer had accidently stumbled onto one
in progress hinted it was more likely that the event were in future, than
in the recent past. " ( page #66 )

This suggests 50% ++, correct Mr. Tholen ?

I don't buy the argument. There wasn't a whole lot of accurate
photometry being done prior to the discovery of the satellite.
The events themselves lasted only about five hours, and that's
for a central event (less for the grazing events). With two
events per orbit and one orbit every 150 hours, you're talking
one part in 15. That is, if someone were making random observations,
there's a 94 percent chance that the observations would be at times
when no event was occurring. But as I said, there weren't a whole
lot of observations being made. I'd have to dig into the literature
to count the number of photometric points obtained in the 1970s,
but I'd guesstimate 30. If events were occurring, that's two
potential observations at the time of events. They could have been
easily dismissed as bad points. Furthermore, I don't know of
anybody who was taking high time resolution observations of Pluto
in the 1970s. You'd need several points during an event to see
the trend. A single low point could be easily dismissed as a
faulty observation.

Meanwhile, there is also a claim in the literature that events were
seen when we now know there could not have been events, which
demonstrates that faulty observations can be made.

To tell you the truth I do not quite understand what Stern is talking
about.
For sure you know, since your picture is in the same book a few pages down
the road. Please explain this to us.

I hope the above is sufficient.

Yes it is, and I agree 100% or to be more precise ( 50 + 50)% .

Talking about eclipses of PLuto and Charon, Stern says
"... Then exactly- half a Charon-orbit later - 3.194 days after Binzel's first
event, on February
20th, another young astronomer, the University of Hawaii's David Tholen, caught
Charon falling in PLuto's shadow, ...".
Binzel's and your discovery exactly 20 years ago. Happy anniversary

I understand that above you are referring also to observations made a month
earlier on 16th of January by Buratti and Tedesco, correct ?

So, we have a very precise date of the start, however the end is somehow not
clear. Some
sources say 1991, some other say 1990. Why is it like that ? The end was also
important since it would help us to calculate the precise date of the P+CH
equinox. Nobody rally cared to look for the end. People got tired ?

"wnowak" wrote in message
...
I am curious. Do you remember the exact time of GK observations, or maybe
you
can ask around ? I can calculate the exact angular distance between P and
CH and
add this fact to my site

http://www.interlog.com/~wnowak/book

If you do a search on the ADS you will find Kuiper's paper in the 1950 Publs
of the Astr Soc Pacific, v. 62, p133.

He states he was unable to get an accurate measurement on the Texas 82-inch
telescope owing to the faintness of Pluto. The equipment used was a disk
that simulated the angular diameters of stars or small objects (not a
micrometer). The measurement was therefore a direct comparison of visual
appearances.

He moved to the 200-inch telescope and observed on the night of 21 March
1950 as a guest of M. Humason. The angular diameter was found to be 0.23
arcsec (0.20 if some corrections were taken into account). This was so
small as to be a genuine surprise to some, because it meant that the mass
could not be as large as the 1 Earth-mass others were deriving from the
orbit of Neptune ( which of course turned out to be spurious).

He had Milton Humason check his observations at the telscope and they
independently observed the same value via the direct comparison disk device.

From the article, the impression I gain is that with an 82-in telescope the
observation was difficult owing to the faintness of Pluto (V mag 14.9 in the
early 1950s), but with a 200-inch telescope and an extra 1.5 mag gained
through increased aperture, and a smaller diffraction disk, it became much
easier. Charon is more than two magnitudes fainter than Pluto. Given the
difficulty of the visual measurement, and the fact that he was concentrating
on the size of the disk rather than looking for companions, it isn't really
surprising that Kuiper did not notice a second much fainter object next to
Pluto.

(It is possible that he saw Charon and dismissed it as a background star, as
it would have had an unresolved stellar angular diameter in the device used.
Remember, the observation was made on a single night so motion would not
have been detected.)

--
Mike Dworetsky

(Remove "pants" spamblock to send e-mail)


So far I thought that I knew everything about PLuto, but you proved me
wrong
BTW, no observations of PLuto ( for sure no Charon with 2.5 meter Mt.
Wilson
telescope in 1930s, 40s ?

Excellent seeing in California in 1930-50 would be 0.30 arcsec. right ?

WN.

Mike Dworetsky wrote:

"wnowak" wrote in message
...
took place on 18th of February 1930 - almost exactly 75 years ago.

However, the sattelite of PLuto Charon remained not discovered for ...
48 YEARS !
It was ACCIDENTLY discovered on pictures of PLuto in 1978.

The technology needed to discover Charon existed for all 48 years (
from
1930 to 1978 ).

Why it was not discovered ?

http://www.interlog.com/~wnowak/book




It's sometimes hard to explain why something was not noticed for a long
time, but the usual answer is, no one looked hard enough, or possibly
Charon
was occasionally seen, and dismissed as a flaw or background star.

Pluto was not regarded as a subject of great interest by most
astronomers in
the '40s and '50s, except for the question of its size and mass. The
best
way to look for evidence of mass was to measure deviations in the orbits
of
Uranus and Neptune, so observational approaches were directed at
accurate
observations of these other planets.

Back in the 1960s an effort to observe an occultation of a star by Pluto
produced upper limits for its size, and showed that Pluto was much
smaller
than Earth, but Charon did not happen to occult the star for any
observer.

You also have to remember that most photographic observations of Pluto
were
done to determine or improve its orbit, so only relatively small
telescopes
were used, such as astrographs, or long focus refractors adequate for
the
task but often located in places with relatively poor seeing. Charon is
always within a second of arc or so of Pluto itself and would be
extremely
hard to spot on such photographs.

It was only when Christy used a relatively large (1.5-m, ISTR) telescope
to
get precise astrometry from a high-quality mountaintop site (for
prediction
of possible occultations) that he noticed a small bump on one side of
the
planet's image. He might have simply dismissed it as a background star
or a
flaw, but because it was on several images in different positions he
realised it was a satellite.

This said, I recall that Gerard Kuiper observed Pluto visually with the
Palomar 5-m telescope in the late 40s or early 50s, on a night of
excellent
seeing. He wanted to measure the diameter with a bifilar micrometer (or
similar), and it is slightly surprising that he did not spot Charon. Or
maybe he did, and dismissed it as a faint background star. Remember,
this
was a single observation on one night.

--
Mike Dworetsky

(Remove "pants" spamblock to send e-mail)