Detection of Earth-like planets around nearby stars using a petal-shaped occulter

[sheeny]

The following first paragraph is from aletter published in physics@nature today:

Letter

Nature 442, 51-53 (6 July 2006) | doi:10.1038/nature04930; Received 16 January 2006; Accepted 19 May 2006
Detection of Earth-like planets around nearby stars using a petal-shaped occulter

Webster Cash1 (http://www.nature.com/nature/journal/v442/n7098/abs/nature04930.html#a1)

Direct observation of Earth-like planets is extremely challenging, because their parent stars are about 1010 times brighter but lie just a fraction of an arcsecond away1. In space, the twinkle of the atmosphere that would smear out the light is gone, but the problems of light scatter and diffraction in telescopes remain. The two proposed solutions—a coronagraph internal to a telescope and nulling interferometry from formation-flying telescopes—both require exceedingly clean wavefront control in the optics2. An attractive variation to the coronagraph is to place an occulting shield outside the telescope, blocking the starlight before it even enters the optical path3. Diffraction and scatter around or through the occulter, however, have limited effective suppression in practically sized missions4, 5, 6. Here I report an occulter design that would achieve the required suppression and can be built with existing technology. The compact mission architecture of a coronagraph is traded for the inconvenience of two spacecraft, but the daunting optics challenges are replaced with a simple deployable sheet 30 to 50 m in diameter. When such an occulter is flown in formation with a telescope of at least one metre aperture, terrestrial planets could be seen and studied around stars to a distance of ten parsecs.


Hmmm... the occulter seems huge!?:shrug:

Al.

PS. Just edited to add a PDF file with Supplementary information FYI.

[sheeny]

Here's another article which seems to be what the letter above is in response to:

Editor's Summary

6 July 2006
The search for a sister earth

It is difficult to observe Earth-like extrasolar planets as they lie only a fraction of an arcsecond away from their parent stars, and are 10 billion times less bright. That does not stop researchers designing ways to search for and observe them. The 'New Worlds Observer', described in this issue, uses two space-craft: a large conventional space telescope and a flower-shaped star-shade parked between the telescope and the target star. The cover simulation shows a sister solar system as it might appear to the NWO. Most prominent feature is a dust ring trapped in orbital resonances with a planet like Uranus. Within the ring are Jupiter and Saturn-like planets. Closer to the hidden central star, planets like Earth and Mars are visible, as is zodiacal light scattered by interplanetary dust. Inset is a familiar Solar System view for comparison. The mission could be flown for a reasonable budget using current technologies.

[casstony]

It certianly is an exciting time of discovery right now. I'm just sad that I won't be alive when someone figures out how to travel to those planets. As impossible as it seems now, I don't see how we can predict what will be possible in the future.

Tony

[josh]

Har far we have come...
But how very,very far we have yet to go
I cant wait to see a clear photo of a world in another system.
Maybe when im an old fella

[xelasnave]

The pace is picking up, to think I have worked for a man who was a teenager before man first flew and now I live in an era when man is taking the first steps to leave the planet, maybe our first steps of moving to other worlds. Wild ideas but only as wild as, to a teenager hearing that a man had flown under power, only a relatively short time ago.
I always thought Timothy Leary and his "induced visions" of humans leaving the system in a hollowed out asteriod not beyond what may come to pass.
Such a method may already be common place if there are species more advanced than us..and there must be one would think.
That is very interesting progress thanks for bringing it to the table
alex

[Jupiter]

That will be the next big question, we know the Earth like planets are there, how do we get their attention, or more to the point how do we get there?

[Doug]

Whoa what did I miss? What Earthlike planets have been discovered?
And if Discovered how was it done without these proposed occulting telescopes?

What qualifies as an earth like planet?
A rocky body orbiting a G2V star within a distance of 0.7 to 1.8 AU?
Hello Venus, Hello Mars.
A planet of similar mass with extensive deposits of water, oxygen atmosphere, a polar inclination of around 20-30 degrees?
Seriously, what is considered 'Earthlike'?
I'm thinking that when 'Earth like' is mentioned, a planet capable of approximating conditions here would be in mind. That means not only similar mass and dist from parent star, but seasonal changes, polar caps tidal influences on its oceans by at least one influential satelite, or are Mars and Venus also Earth like planets?

seriously wondering what peoples expectations are here,
Doug

[xelasnave]

Doug this is an opinion only but I think "earth like" is to cover planets in the "Goldielocks zone" ..that far away enough from the Sun not to be "too hot" and not that far that it is "too cold" but as our little hero would say "just right" (for life to be possible).
alex

[mattweather]

You saying is those planets are very different to us?

[xelasnave]

No not trying to comment on similarities only that it is beieved there is a "just right zone" for life. One can only speculate from that point but I think it goes this way. We will find a certain number of planets that look better than others by virtue of being in the zone and that maybe those could the be targetted to see if any tell tale signs of life are reflected in their atmospheres (as their being in the right zone suggests that there well could be atmosphere).
I cant offer authority on any of that it is a view formed by what has come my way when reading about the searches that may take place in the future. If the spectrum of a planet could ever be taken it may show the presence of methane, carbon di oxide, oxygen (and that stuff they preserve dead annimals with which I cant recall) and other signs that would point to the possibility of life. I imagine why the approach the subject of this post will take us a step closer to determining their presence and suitable candidates for further investigation.
It is rather mind bending to contemplate we are this close. I came from a time where it was believed we were to only planet..in fact that there was only one gallaxy ..ours..and that the other faint smudges were "island universes". How they could not contemplate the possibiliy of planets is strange but thank goodness someone did and got funding to find them.
alex

[Doug]

Alex, I think there is sufficient diversity in our own (do we own it?) solar system to advise caution in claiming 'Earth like' planet discoveries. Consider a planet orbiting in the comfort zone of a distant G2V star. It has a mass and orbital period similar to Earth. It has an atmosphere that might be coaxed into supporting living organisms, and spectroscopic studies suggest plentifull water deposits. What I suspect we are a very long way short of is determining that it has a day equal to its year or not, and that its polar axis is within 1 or 2 degrees of pepandicular to the plane of its orbit or not.
I am assuming that it would be feasable for a planetary body of Earth like mass, in the comfort zone to only rotate once a year, and or also have no polar inclination and or have no influential moon.
Such a planet would not be 'Earth like' IMHO and might not be host to any living things.
I guess discovery of a planetary body of Earth like mass in the comfort zone of a G2V star should stop short of being claimed an Earth like planet, but rather be described as a small inner planet that might turn out to be similar to the Earth.
Cheers,
Doug

[xelasnave]

I have no problems with anything you say I was simply trying to second guess the author who first mentioned Earth like,. as for my money the is no place like home er Earth. I effectively was making it up as I went along it has not been a primary interest for me but I recalled that sort of thing.
Still as a personal opinion now that I consider the possibilities it would not surprise me if there were not many "Earth like" planets in the closest of comparision, I see no reason why we should be the only place like this or very similar. I mean look at Star Trek they think so:D What i do doubt is that we will ever be able to observe a planet that is truely Earth like a twin. Solar systems may follow a pattern the same as ours, formation may dictate a similar distribution of planets and sizes similar to our system..in fact one would think it more probable that the one pattern will repeat over and over as with other things we see. Its the first time I have given it any thought and all this is off the top of my head not a recollection from something I have read.
All planets if the system is moving will be inclined to the axis of their Sun, that comes about from the speed of gravity really, planets will orbit an "imaginary" Sun that has moved down the road by the time the gravity message is recieved, so a tilt in axis must result. The Suns speed thru space I would think to be similar to others Suns in another galaxy within a similar distance from the gallactic centre that our Sun enjoys. I think solar systems (and spiral gallaxies) must travel as does a "pie in the face" through space and as such this produces an incline and hence the seasons. I dont know really again off the top of my head..thinking aloud to share my idea.
Dam it I have developed an interest now and will look at what they are really doing.
alex

[Greg Bryant]

The tally of extrasolar planets has risen to 199 with the announcement of five new discoveries. Some diverse ones, in terms of mass and orbital distance.

I've briefly summarised the finds in the below article.

http://www.astmag.com.au/news20060716_extrasolar_planets.htm

[ballaratdragons]

I am not 100% a believer in lifeforms elsewhere, but I could be wrong (wouldn't be the first time) BUT...
Why does a planet have to be Earth-like to harbour life.

Lifeforms have been found on Earth that do not need an Earth-like planet to survive. The simplest form of life 'Bacteria' is found in Boiling Sulphur Springs and a whole range of fish and other critters live in permanent pitch dark, freezing, extreme gravity/pressure conditions, and some plants live in Dark methane filled caves.
So what actually constitutes the ether for life to live in? We still tend to think in the 'Earth is flat' and 'The Universe revolves around us' ideology, and that is very self-centred. We tend to only envisage that life must have what we have to survive. Other lifeforms here on Earth prove that to be a phallicy.

Lifeforms DO exist here on Earth in hotter than boiling point and at freezing point, no oxygen, no light etc etc. There's plenty of planets that fit those categories.

If you are talking about 'Intelleigent' life. . . ahhh, I'm sure those fish down in the dark under tons of pressure think they are pretty intelligent.

Just something to consider. :lol:

[Doug]

Ken, there is a lot of sense in what you say about the extreme environments here that support life. But those extremes do not characterize the Earth, so a planet that did major in those extremes could not be called 'Earthlike', do you think?

cheers,
Doug

[ballaratdragons]

Those extremes are a part of our Earth. So therefore, all environments on this planet characterise 'Earth'.



No, it wouldn't. That's my point.



What I am saying is that it is possible for a dark, boiling, freezing, methane, sulphur infested planet to contain life. It can be a Giant, or miniscule, rotating fast or slow, or anything out of 'our' ordinary. But extreme and hostile environments have proven beyond doubt that life 'could' exist almost anywhere. We can't wrap it all up neatly and say "because it's not Earthlike, it can't harbour life".

Now stop making me sound all serious :lol:

[Doug]

Sorry:)

[xelasnave]

The fact that only a decade ago ? we knew of no planets and now we know of approx 200 tells me that we may be in for many surprises contrary to what we believed only years ago:shrug: .
The numbers of Suns (300 billion approx per gallaxy) in the number of gallaxies (how many billions of gallaxies in the observable Universe let alone the non observable Universe...to me means the numbers are such that indeed intelligent life will be not unusual. It would be unusual to find there was none other than ours. How we find that for a fact I have no idea, however to see ourselves as the only intelligent life is a little self centred and takes little account of the numbers of places there are in the Universe.. if we are the only ones what does that mean.. are we charged with seeing that intelligent life continues..and it is then all up to us..what a responsibility..when we go, (become extinct and we will) is that the end..I hope not and I doubt if intelligence dies when we become extinct...and yes we will become extinct..its like thinking of dieing it happens to everyone and it happens to us... somehow we often forget the finallity of it all. But think of the numbers and the chances of in all there is we are the only ones..if we are we are indeed the most special species in the Universe:eyepop: .. Now I can believe that of myself but the whole human population I dont know:D ;) :lol: .
alex
alex

[xelasnave]

I found this news at Newscientist..

"A giant telescope with a mirror up to 60 metres wide is being planned by the European Southern Observatory. The telescope would be able to detect Earth-like planets around other stars and spot the universe's first galaxies.

The ESO has created a new office to design the European Extremely Large Telescope (E-ELT). "ESO aims to put the E-ELT on a fast track," says Roberto Gilmozzi, the principal investigator for the project.

Project managers have not yet chosen the size of the mirror but say it could range from 30 to 60 metres wide. Their goal is to build it for €750 million ($950 million) and have it ready to observe by 2015."

I guess next week they will be telling us how they are going to radar map their surface.. gee that is a big mirror even at 30 mt
alex

[Richard F]

Even @30Mtrs,it may be able to take spectra of atmosphere,around Earthmass planets,in goldilocks zones,out to around 100light years or so!
Imagine if they found a Nitrogen/Oxygen atmosphere,on one of these nearby planets!?Let alone possibly multi-pixel images(of 4-16 pixels),out to about 100 light years,of any jupiters,also.
A scope with these capabilities will change (&enlighten)mankinds view of
his universe,& i can hardly wait to see first light shots,from a monster like that!BRING it!...stay on target...almost there...(A New Hope 77):eyepop: :thumbsup: