Spitzer Water Vapor Image or Atmospheric Study (27 Feb 2007)

[TimeTravel123456789]

My immediate reaction was about Sptizer's detection ability with regard to Ganymede, Io,Europa, Enceladus, etc. I do not recall right now how many Solar System planets have water vapor detected.


I wrote on a similar topic to Science Magazine last Christmas. It was about how the Calcium around a star may not have anything to do with an asteroid but rather Calcium being found in the interstellar medium unrelated to asteroids. (I may be recalling the exact point incorrectly;it was not used.) Still the point is that chemicals are found in the ISM due to many causes not just one. Water vapor could be present and somehow not visible in a Spitzer image because of interference with other chemicals in the spectra.

Spectrum are complicated. Water vapor with 500 other chemicals might not be identifiable.

I thought the Russian rocket showed that our future missions really are threatened by space junk as we all know. I proposed a space junk scoop in 2001 and it did not go anywhere.

[ipaqgeek]

I'm curious about whether there is a deeper underlying motive for the search for extraterrestrial life - that is to make money. It is such an unbelievable long-shot to say with any certainty that there is life out there that if in 20 years all our sensors found a planet or found planets with all the right signatures, the chance that any of them would have life may still be exceedingly remote, and we would have no way of being certain without going there which likely won't happen for 100's of years, maybe 1000's (we're supposed to be using flying cars by now, remember?).

I'm not saying that is the #1 motivation for these efforts ... surely the motivation comes from a desire to connect with other life, to better understand our own life in every way (including metaphysics), and to find a treasure trove of knowledge that is astonishingly more abundant in living systems than in dead ones. Of course technologies resulting from living systems are likely to be far more exploitable (as are the systems themselves). But the most immediate benefit to finding such planets, and we don't even have to go ther to get this benefit, is to fan the flames of public support to futher the research because the dollars would soon follow.

Ask the general public what would excite them more: learning about the physics of the Universe, or finding extra-terrestrial life. I'm guessing 90% of the public would be far more interested in the latter effort. They don't care what a quark is.

[NoelC]

Is it just me, or does it seem HIGHLY unlikely that an extrasolar planet and its star would align well enough with us so that we could measure light from them during an eclipse?

I'm no statistician, but it seems to me the chances of viewing an eclipse of a pair of distant bodies is infinitessimal. How often do we see any of our planets eclipse another?

And even if we do happen to see a planetary system that eclipses, is it a given it will happen time and again? Don't our own planets wobble a bit on their orbits?

Yet I've seen time and again that measurements are being made by astronomers and conclusions implied by differences in light signatures before and during eclipses.

Perhaps I'm a skeptic, but is it possible that the assumption that an eclipse is taking place is not valid?

-Noel

[iamlucky13]

Some interesting comments. I have a few thoughts to offer.

Water vapor could be present and somehow not visible in a Spitzer image because of interference with other chemicals in the spectra.

To the best of my knowledge, this is true. It's also possible (I think probable) that there were trace amounts of water vapor to faint to detect by Spitzer. However, these planets are extremely close to their stars, and I don't think a strong water signal was expected in the spectra. Over time it would be ionized by heat and blown away by the solar wind or be sorted by mass toward the center of the gas giant.

Is it just me, or does it seem HIGHLY unlikely that an extrasolar planet and its star would align well enough with us so that we could measure light from them during an eclipse?

I'm no statistician, but it seems to me the chances of viewing an eclipse of a pair of distant bodies is infinitessimal. How often do we see any of our planets eclipse another?

It's not as rare as you might think. The key is that the system's eccliptic plane must be well-aligned with us, and the period has to be short enough that we can see it happen in the time we can devote to looking at it. Conveniently, these are the easiest planets to find because their stars show the greatest Doppler-shift for a given star/planet mass ratio, and they do so in short time frames. The bonus is planets that eclipse their stars can be found by the transit method, which was recently tested by the Hubble. This atmospheric investigation method will probably be utilized quite extensively after the launch of the Keplar mission, which will use the transit method to find planets. If a planet does eclipse, it will probably happen again, as the wobbles in an orbit are pretty small.

I don't know how often planets in our own solar system align with each other, but their orbits are relatively long. The planets in the APOD have orbits of days. Our neighbors also swing an entire 360 degrees around us (except Mercury and Venus, which occasionally transit the sun), as opposed to extrasolar planets, whose orbits represent only arc-seconds of sweep. The relative distance is to our advantage. If this isn't clear, I think I can come up with a drawing illustrating it.

I'm curious about whether there is a deeper underlying motive for the search for extraterrestrial life - that is to make money.

I don't doubt that the people most involved in SETI are genuinely interested in their work and honestly trying to find evidence. I don't think they're trying to cheat us, but the value and potential return is certainly debatable. When scientists went looking for quarks, they had really good theoretical evidence they should exist. The motivation for SETI is purely speculative.

[NoelC]

Big fat "hot Jupiter" planets in close orbits... Hmm...

Let's do some math...

Say we have a star the size of the sun: 865,000 miles.
Further let's say we have a hot Jupiter the size of, well, Jupiter: 89,000 miles.
Now put this hot Jupiter at the distance of Mercury's orbit from the star: 36,000,000 miles.

This image is to scale, and the lines show the angle within which at least a partial eclipse would be visible.



A bit of quick geometry tells us this angle is about 1-1/2 degrees, so the chance of alignment is, in fact 1-1/2 out of 180 degrees, or a bit less than 1%. That's WAY larger than the one in millions chance I had postulated earlier. I suppose I didn't take into account just how large a star is compared to the orbit size.

Of course, this assumes a big Jupiter-sized planet orbiting at the distance of Mercury. No one knows the likelihood of that.

-Noel

[BMAONE23]

Is there a way to tell the age of these stellar systems? Is there any guess as to the time that would be required to
"Boil Off" the atmospheric gas around just such a planet? Given that this process could take hundreds of millions
to billions of years, Is it possible that these solar systems are not unlike our own was 4 billion years ago? And that Mercury
could be the core of a descimated gas giant?

Food for thought...

[iamlucky13]

Nice diagram NoelC. Of course, at our distance, the lines of our view follow the black background of your image, so it shows the concept very well.

According to the wikipedia article linked in the APOD caption, the planets in the study are less than 10 million kilometers from their stars; much less than Mercury's orbit. I don't know all about the method for determining these distances, but I gather the confidence is pretty high. I do know that the periods (relates to distance) of transits match in these cases. Both planets are confirmed to be alternately eclipsed by their stars.


BMAONE23 - The solar systems are expected to be roughly the same age as ours, based on the stars' masses and spectra, but this really only places the age within one or two billion years, so we'd be presumptions not to chew on your "food for thought" for a little bit and figure out if it's possible.

I believe the current leading theory is that Mercury formed from heavier elements in roughly the position it is now. These two planets are thought because of their masses to be gas giants, but the models indicate that a gas giant can't form that close to its parent star, because all the light elements would be blown outward by the developing stellar wind. I've seen a few abstracts suggesting that they formed further out and over time lost orbital energy due to some undetermined process (the second planet in this case is also accompanied by a dwarf star in a much larger orbit...this may be a factor) and gradually fell to a closer orbit. Another study found similar hot Jupiters may be losing millions of tons of mass per day due to the stellar wind.

Feb. 27, 2007 APOD

[NoelC]

Hm, I did some more research... From what I understand very slight shifts in the spectra of the star indicate a certain amount of "wobbling motion" by the star as these massive planets orbit nearby, so not only are the astronomers measuring periodic dips in the light output from the star (i.e., when the planet transits) but also some motion toward and away from Earth because of the planet's pull on the star. So, in short, there's even more evidence for a huge planet in a close orbit.

What's becoming clear - and is in no small part amazing itself - is that the astronomers' instruments can detect these effects in starlight that cannot be resolved telescopically into anything more than a pinpoint of light. I'm now starting to appreciate the depth of TimeTravel123456789's post that started this thread.

-Noel