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Fraser
2004-Jul-01, 05:27 PM
SUMMARY: New observations of Procyon from MOST, Canada's space telescope, have called long-held assumptions about the star into doubt. Launched a year ago, MOST watched Procyon 8-times a minute, making a total of 250,000 observations over the course of 32 days. It found that the star is completely stable, and doesn't pulsate or vibrate in any way. This challenges 20 years of speculation that Procyon does vibrate, and could reveal insights about its interior - astronomers will need to find a new candidate.

What do you think about this story? Post your comments below.

Planetwatcher
2004-Jul-01, 06:43 PM
So would this now make Procyon a more viable candidate to have exo planet(s)? :unsure:

We can hope, we can hope, we can hope. B)

VanderL
2004-Jul-01, 07:46 PM
This challenges 20 years of speculation that Procyon does vibrate, and could reveal insights about its interior - astronomers will need to find a new candidate.

They also need to look at the stellar models. Why is the Sun pulsing and vibrating and Procyon not. The question behind this is what else is wrong with our solar model.

Cheers.

madman
2004-Jul-02, 03:13 AM
"These results contradict theories and observational evidence that had mounted over the last 20 years."

"The MOST team was surprised to find that Procyon was not vibrating, and soon showed that a more careful treatment of stellar models indicated that it should indeed be stable."

20 years of supposedly "sloppy work" and "mistaken observations"?

how was it possible that vibrations had been detected if none ever existed?

Jaymie Matthews
2004-Jul-03, 12:58 AM
I just wanted to reply to a few of the comments and questions posted in the forum on the recent results from MOST about the star Procyon.

> Our findings don't really tell us anything about the odds of Procyon having (or not having) planets, other than the fact that we see no clear evidence for transit of planets in the Procyon system, nor any reflected light signal from a "hot Jupiter" in a tight orbit. Procyon is approaching the end of its stable hydrogen-burning phase, so any planets that are in orbit around it won't be able to support life for much longer, if they are habitable at present.

> It's certainly possible that our incomplete understanding of solar oscillations and hence the Sun could be the explanation for our surprising non-detection of pulsations in Procyon. The exciting thing is that this finding is forcing us to reexamine a number of ideas and observations about stars and their oscillations.

> The previous ground-based observations of Procyon were not flawed or sloppy in any way. They are in fact superb measurements of the radial velocity variations of the star. However, the variations detected may not be due to the oscillations that theory predicted, or if they are, to be consistent with the MOST result, they need to be reinterpreted. As for any deficiencies in theories, well, if all our theories were perfect, astronomers like me could just pack it in right now. It's part of the scientific process to continually test theories, refining (or sometimes rejecting) them as the data demand.

Cheers from Vancouver,

Jaymie

Dr. Jaymie Matthews
MOST Mission Scientist

madman
2004-Jul-03, 01:29 AM
i qualified the statement with the term "supposedly"...because that seemed to be the gist of the story.

thanks for the clarification that it was "radial velocity measurements" taken from the ground.

but what did these results tell you before?...that there seemed to be a few orbiting bodies?

what was the "more careful treatment of stellar models" that showed that procyon should in fact be stable?..and what does that mean?....it has no orbitals?
how does that jibe with the previous results of "radial velocity measurements".

are you talking about the problem of large sunspots appearing like extremely close orbitals?

***************************
ps: thanks for contributing to this thread.

Greg
2004-Jul-05, 07:22 PM
My understanding of the theory of why the sun pulsates is that it is caused by the effects of Jupiter's and Saturn's gravatational tug on it. In fact the gravatational effects of the gas giants has been deductively theorized to be behind the cycles of variable solar output and sunspots.
My understanding of this intriguing MOST result is that despite reliable radial velocity measurements from the ground indicating orbitals around Procyon, no transits were seen by MOST and furthermore no pulsations were seen. In my mind both of these results argue that there are no SIZEABLE orbitals around Procyon to cause it to pulsate like the sun. I do not think that the observational time was long enough to conclusively rule out more distant orbitals, whose transits simply needed more observational time to detect. Conisdering that Procyon is more massive, perhaps it take a larger orbital to generate pulsations. Perhaps the radial velocity measurements picked up orbitals too small to cause pulsations and were not detected making transits due to a relatively short observational time. At least this is my feeble attempt to reconcile the findings with prior theory.
Of course my thoughts are limited by the relatively scant data I have just read on this subject. I think the MOST mission is a nice coup for the CSA and will add alot of valuable and timely input on the extra-solar planet venue of research. I am delighted to see feedback from one of the mission members as well.

om@umr.edu
2004-Jul-06, 09:09 PM
The origin of solar pulsations has fascinated researchers for decades.

Peter Toth of the Tihany Geophysical Observatory published a paper on this subject 27 years ago in Nature 270 (1977) 159-160.

The title of the paper is intriguing.

"IS THE SUN A PULSAR?"

With kind regards,

Oliver
http://www.umr.edu/~om

Dr. Jaymie Matthews
2004-Jul-08, 11:30 PM
I may not be able to check this thread again for a few weeks, but I thought
I'd try to give a little background on the solar oscillations and what we expect
(and see) in some other Sun-like stars.

Think of stars as giant gaseous bells held together by gravity. If you "kick"
one, you could make it ring. However, stars are not struck by objects often
or large enough to trigger vibrations. Even if they were once in a while, the
vibrations would die out very quickly, unlikely to be observed by astronomers,

However, stars like the Sun "kick" themselves in a manner of speaking.
In the outer 30% of the radius of the Sun, energy is carried to the surface by
convection - gas physically rising and carrying heat energy with it, releasing
some of that energy in the form of light at the surface and then sinking back
down to continue the cycle. Like a solar bucket brigade. This convection is a
very turbulent process, and creates noise - literally sound energy in the gas.
These sound waves can't travel outward to the vacuum of space, but they can
travel inside the gas of the Sun (or a star). Some of these waves set up
resonances, making the Sun vibrate. The process is somewhat random so any
one vibration pattern comes and goes but there are tens of millions of such
patterns excited in the Sun, so we always get to observe the oscillations, albeit
at a very low level.

The tidal influences of planets in our Solar System, even Jupiter, are too weak
to trigger vibrations in the Sun, and if they did, they would have much much
longer timescales than what is observed. It's believed that in some close
binary systems, the gravitation interactions may excite certain types of
oscillations in stars. In other cases, it might suppress them. In the case of
the close-in giant exoplanets around some Sun-like stars, it will be exciting to
explore whether they influence the vibrational behaviour of their parent stars.
We hope to start checking that out with MOST.

The solar oscillations were discovered by accident during spectroscopic studies of
solar convection in 1960 by John Leibacher and colleagues. (John is now one of
the leaders of the GONG global solar monitoring network.) The oscillations, with
periods near 5 minutes, were totally unexpected and not really understood for
at least a decade later. The paper that one person included in the forum was
one of the last vestiges of that search for an explanation, but that particular one
has been long rejected.

Procyon also has convection at its surface, as was expected to vibrate with
amplitudes even larger than the Sun. The MOST light measurements strongly
indicate it doesn't. The earlier spectroscopic measurements may have been
seeing the variations due to convective turbulence I described above, but not
well enough sampled to recognise it for what it was. Or they saw oscillations,
and the light amplitude is low for some other physical reason, or the lifetimes
of the individual oscillations are much shorter than in the Sun, or ???? No matter
what the real explanation(s), it's a surprising result.

We're definitely having fun with these unique data, and you'll be hearing more
from us as we look at other exciting targets, including stars known to have
exoplanets.

Cheers from Vancouver,

Jaymie

Dr. Jaymie Matthews
MOST Mission Scientist

om@umr.edu
2004-Jul-10, 04:37 AM
Originally posted by Dr. Jaymie Matthews@Jul 8 2004, 11:30 PM
The solar oscillations were discovered by accident during spectroscopic studies of solar convection in 1960 by John Leibacher and colleagues. (John is now one of the leaders of the GONG global solar monitoring network.) The oscillations, with periods near 5 minutes, were totally unexpected and not really understood for at least a decade later.

The paper that one person included in the forum was one of the last vestiges of that search for an explanation, but that particular one has been long rejected.

Cheers from Vancouver,

Jaymie

Dr. Jaymie Matthews
MOST Mission Scientist
Thanks, Jamie, for the explanation.

In an earlier posting you said:

"It's certainly possible that our incomplete understanding of solar oscillations and hence the Sun could be the explanation for our surprising non-detection of pulsations in Procyon.

The exciting thing is that this finding is forcing us to reexamine a number of ideas and observations about stars and their oscillations."

Does that include reexamination of the ideas in Peter Toth's paper in Nature 270 (1977) 159-160?

With kind regards,

Oliver
http://www.umr.edu/~om

StarLab
2004-Jul-17, 05:33 PM
Maybe the observable pulsations in the incoming photons die out after a while as the photon travels even farther away....or Procyon is at a particular stage in its life cycle in which the star does not vibrate. Or Procyon is not a main sequence star in the way we are used to thinking of it.

Guest
2004-Oct-15, 03:08 PM
good report B)