Date: January 27, 2010
Title: Earth Clones
Podcaster: Chris Impey
Links: http://planetquest.jpl.nasa.gov/
http://exoplanet.eu/
http://kepler.nasa.gov/
http://www.chrisimpey.com/
Description: There are over 400 planets know orbiting other star, but most are gas giants like Jupiter and likely to be uninhabitable? How long before we find a clone of the Earth? This podcast talks about the issues involved in detecting terrestrial planets and the likelihood that they will be discovered in the next few years.
Bio: Chris Impey is a University Distinguished Professor and Deputy Head of the Department, in charge of all academic programs. His research interests are observational cosmology, gravitational lensing, and the evolution and structure of galaxies. As a professor, he has won eleven teaching awards, and he has been heavily involved in curriculum and instructional technology development. Impey is a past Vice President of the American Astronomical Society. He has also been an NSF Distinguished Teaching Scholar, a Phi Beta Kappa Visiting Scholar, and the Carnegie Council on Teaching’s Arizona Professor of the Year. Impey has written over thirty popular articles on cosmology and astrobiology and co-authored two introductory textbooks. His first popular book “The Living Cosmos,” was published in 2007 by Random House; his second popular book called “How It Ends,” will be published in 2010 by Norton. He recently was a co-chair of the Education and Public Outreach Study Group for the Astronomy Decadal Survey of the National Academy of Sciences. Impey is a 2009 Fellow of the American Association for the Advancement of Science.
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Transcript:
365 Days of Astronomy Podcast
January 27, 2010
Chris Impey, Professor, University of Arizona
Welcome. This is a podcast for 365 Days of Astronomy for the year 2010. My name is Chris Impey I’m a professor of astronomy at the University of Arizona. My research is on cosmology but I take a keen interest in Astrobiology, the search for life in the universe. And my topic today is Earth clones – what will it take to find twins of Earth out there in deep space.
As I’m sure you know – the success of exoplanet hunting is phenomenal. In 1995 we knew of no planets beyond the solar system. Now we have over 400. However almost all of those planets are gas giants, Jupiter mass ranging down to Neptune and Uranus mass. Almost certainly they’re uninhabitable, we don’t think there is life in Jupiter or Saturn’s atmosphere. So what’s really interesting is pushing down the mass limit towards terrestrial planets so we can find planets that might harbor biology. What will it take to do this?
Simulations and theory give us the expectation that terrestrial planets exist out in space even though we haven’t found them yet. The current record holder for a low mass planet beyond the solar system is a planet 1.9 times the mass of Earth. However it’s not in the habitable zone of its star. Simulations however suggest that for every gas giant planet that forms at the periphery of a solar nebula there will be a handful of terrestrial planets on orbits much like those of Earth, Venus, and Mars.
If we scale up these numbers to the Milky Way we conclude a phenomenal billion habitable worlds in the Milky Way, including moons of giant planets as well. And possibly a tenth of those or about a hundred million will be planets like the Earth, Earth-clones more or less. That’s an amazing amount of habitable real estate in just one galaxy in the universe.
So how do we find such planets, with four hundred in the bag but none of them Earth-like? Well the most direct method, making an image, is the most difficult. The Earth reflects less than a billionth of the light of the Sun, and as seen from afar would be like trying to detect a firefly in the glare of nearby stadium floodlights. Essentially impossible with current technology. So we can’t image these planets. Also, the Doppler Effect, which has been most successful in finding almost all of the 400 known exoplanets, runs out of steam when it goes to the low mass planets. By the time we get down to a terrestrial planet, the Doppler shift, the wobble on the star caused by the orbiting planet, is a small enough velocity that it can be confused by turbulent motions in the star atmosphere. Essentially noise from the star itself prohibits us detecting earths with the doppler method.
The method that may work, and we hope it will work, is the eclipse method. Every now and then, seen from the right orientation, a terrestrial planet will pass in front of its parent star dimming it very slightly in proportion to the ratio of the area of the planet to the area of the star.
For an Earth-like planet orbiting a Sun-like star, this dimming is tiny, about one hundreth of a percent. That can’t be detected from the Earth. But from space, with the stability of that environment it is possible.
Last year the Kepler spacecraft was launched with the deliberate purpose and agenda of detecting terrestrial planets and Earth clones. Kepler has gone through its early paces and has shown that it has the stability and the sensitivity to detect eclipses by Earth-like planets. It’s staring at a region of sky containing over 100,000 stars and it’ll stare at it for several years trying to detect the momentary dimming of the star. Remember, it’s one hundreth of a percent. Imagine trying to stare at a 100W lightbulb to see if it’d dim by hundreth of a watt. It’s a difficult task but Kepler has shown it’s up for the job.
We’ll have to be patient however. An Earth-like planet in orbit around a Sun-like star will of course transit only once every year. And Kepler will need to see the eclipse recurr maybe twice or three times to be sure it’s detected a real planet. That means, we’ll have to wait a couple of years before Kepler starts announcing Earths. But they are expected.
Nobody really knows how many Earth-like planets Kepler will find. It could be dozens, or it could be as many as hundreds. Meanwhile, we have to look after Earth 1.0. We’re not going anywhere else soon. Even if we find an Earth clone, a place that might be hospitable to life, or a place where we might go and colonize, it’s going to be very far away. Most of the stars that Kepler is looking at are dozens, if not hundreds, of light years away. With current technology, that would take hundreds or thousands of years to get to. Even with a space probe, and we have no way of sending humans that far.
Alpha Centauri, it turns out, is the nearest place we might look for a terrestrial planet, only about 4 light years away. Careful work on that double star system may well find Earth-like planets within the next few years. This whole work of finding Earth clones will put into sharper focus the next stage in the search for life in the universe. Because once we start finding places with all the ingredients for life: energy from a star, organic material and liquid water on the surface, it should only be a matter of time before we can detect the signs of life on one of those planets.
This has been 365 Days of Astronomy, and this is Chris Impey signing out. Goodbye.
End of podcast:
365 Days of Astronomy
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This podcast is great! Saludos desde Mexico
Hi Chris,
Are there earth clones? I think most certainly. In 1971 I questioned the idea that planetals formed in collapsing nebula. I imagined the environment they were supposed to survive in and to me it was a big no. Rough, to say the least.
Also, there seemed to be a processional aging from Mercury to Mars, plus the probability that the planets and their families were spiralling away from the sun. The sun was known to be shrinking, therefore it was losing gravity. From what info I had it seemed to me that each planet was about 2.5 billion years older than its inner neighbor.
I also felt that there would be an iron rich dust belt between the sun and Mercury, growing from eruption of iron compounds from the sun as a constant solar activity. That was late in 1972 and in 1983 it was discovered.
Just before the turn of the century it was suggested that Mars was like earth 3 billion years ago and shortly after came the announcement that Venus presents us with a baby earth. – All I needed now was the discovery of planets freely moving through space in a galaxy. Sure enough they have been sighted and Science is puzzled by their presence.
To me, at around 2 to 3 billion year intervals, not only are new planetal cores formed but that the oldest planets lose their gravitational hold from their star and drift away gathering more atmosphere and finally make the transition to become a nebular. Clearly they could drift away in any tangential direction, ‘slingshot’ [Or is it Expansion]?
However, I think your question finds its answer here, and I suppose very few dare to say outright that ‘we came from Mars’. Yet, out of all the stuff we are supposed to believe about ‘origins’ would someone give me a 9 out of 10?
On top of this the next step – Venus the virgin. How on earth did she get that qualification? Yet, if what I say is correct, and if Science would accept it, just think of how we would view our course, from Mars and onto Venus, would answer so many questions: like, how come there are and have been so many species on earth? Did they all just drop out of the sky? Was there a god or gods who incubated all these species, many of them related to one another. We have plant species here in New Zealand that can be found elsewhere on the planet, all slightly different from each other. Mahogany and rosacea, and that’s just 2. Skinks, lizards, flightless birds closely related to ostrich and emu. And the tuatara, probably the last of the dinosaurs. Did they all spread themselves around via the oceans?
Bodes Law, has been a pain to Science, and although the progressional pattern exists very very closely, it’s left on the back burner, or been thrown out with the stove. To me, Bode’s law says it all, and comes from a constant supply of iron from the sun to an orbit 2 solar widths from it; held in that orbit by solar wind, preventing it from falling back by gravity. As the sun shrinks so that belt too moves away having rolled up into a planetal core.
So Chris that’s my evolutionary picture of a solar system, and the making of galaxies. Each system has the capability of producing many more stars and even new galaxies – although in a boundless universe a true balance continuum exists, that always was and always will be. Boring, isn’t it?
I’ve had my website on the www for 14 or 15 years; I get hits every day, and I have only had two people knock it. One of those said didn’t I know that the universe was formed in 4004 BC and the other said that a collapsing nebula was in orbit and there was no pressure or friction to destroy the planetals. I asked the question; Why did everything else finish up in the star with the planetals left behind?
Best wishes
David
Further to my comments above; It will be seen that people here on earth have a responsibility to demand the truth about global warming and anything that spells the end to our organic phase. Unless we can capture our burned fossil fuel, thereby keeping it out of the atmosphere, we run a terrible risk of shortening earths period of organic hospitality.
I want to know; if we add the fossil carbon compounds into the atmosphere can this be a normal thing to do? Fossil fuels are derived from carbon deposits that have lain safely underground for hundreds of thousands of years. They are a plus to the normal organic addition. Does the heavier carbon gas push up the hydrogen and lighter gases to be skimmed off by solar wind?
Best wishes
David
I think you should shut up, David.