- 5/26/2025
Are we alone in the universe? The dream of answering that question might finally be coming true. For most of this century, astronomers have tried and failed to find evidence of other planets beyond the Solar System. Suddenly, with improved telescopes and faster computers, we now have the tools to find, for the first time, worlds beyond our own. NOVA follows a new breed of planet hunters as they race to find proof that other planets do exist.
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00:00Tonight on NOVA.
00:02Here we go. Starting.
00:04Science on the verge of a breakthrough.
00:06We're going to find a universe filled with different kinds of planets than we ever dreamed.
00:11Are we ready for what's out there?
00:13All of the science fiction novels that we all read might in fact have some bearing on reality.
00:20New discoveries from the farthest reaches of the universe.
00:24Hunt for alien worlds.
00:30NOVA is funded by Prudential.
00:46Prudential. Insurance, health care, real estate and financial services.
00:54For more than a century, bringing strength and stability to America's families.
01:02And by Merck.
01:06Merck. Pharmaceutical research.
01:09Dedicated to preventing disease and improving health.
01:15Merck. Committed to bringing out the best in medicine.
01:20The Corporation for Public Broadcasting and viewers like you.
01:45Since I've been a little child I thought to myself, wouldn't it be wonderful
01:49if we could learn whether or not there are other planets out there like our own.
01:55And I thought, if so, all of the science fiction novels that we all read
01:59might in fact have some bearing on reality.
02:02There may in fact be other beings out there who are indeed thinking about us and wondering if we're here.
02:11I just relate my own experiences and experiences of people who I've talked to around the world
02:17who look up at the night sky and wonder, are we alone?
02:22We may never know the answer to that question, but we're at such an exciting time.
02:27We are on the cutting edge of having the technology to begin to understand this.
02:38Throughout the century, astronomers have been searching for evidence of other planets beyond the solar system.
02:47Finally, their telescopes have become so powerful, with the ability to capture images light years away,
02:55the worlds they have dreamed of finding are now within reach.
03:09The only planets that we can directly observe are those within our own solar system.
03:14Some can be seen with the naked eye.
03:17Those in the farthest-reaching orbits took centuries to discover.
03:22With the aid of telescopes, Uranus was found in 1781, Neptune in 1843,
03:31and not until 1930 was Pluto finally found,
03:36captured in this telescopic photograph, a speck of light moving against a stationary background of stars.
03:45So distant was this small, frozen world, it would take another 50 years to discover its moon,
03:54only clearly visible in this 1990 Hubble Space Telescope photograph.
04:03Faced with the task of looking beyond our solar system for evidence of other worlds,
04:07astronomers in this century hit a technological brick wall.
04:13But now, that wall is tumbling down.
04:23A new breed of planet hunter has come upon the scene,
04:26with better telescopes, faster computers, and new ideas of what to look for.
04:36The first problem to overcome in detecting distant planets is that you can't see them.
04:43So astronomers have come up with techniques to get around this.
04:52At Allegheny Observatory in Pittsburgh, George Gatewood.
04:57Well, you can't just simply image a planet.
04:59An ideal thing would be to just simply take the telescope and look at the star and see the planets moving around it.
05:05The difficulty is that planets do not give out much light.
05:08It's entirely reflected light.
05:10A good analogy of the difficulty is to consider the problem of trying to spot a firefly sitting on the edge of a huge searchlight.
05:21You can see the searchlight.
05:22If the searchlight wasn't there, you might be able to see the firefly.
05:25But in the presence of the searchlight, the glare just overpowers you.
05:28And this is why we can't just simply look directly.
05:32Because they cannot see what they are searching for,
05:35planet hunters must look instead for the very subtle effect a planet's gravity has on the star it orbits.
05:42Here, the hammer thrower represents a star, like our sun, being pulled at by the gravity of a planet.
05:50Every time the planet circles, the star wobbles from side to side.
05:57In space, we cannot see the planet, but we can, in theory, detect the influence it has on its parent star.
06:10In this scaled-down version of a solar system, we watch as the planet orbits the star.
06:19Each time it circles, the star is pulled.
06:25Much exaggerated in this demonstration, astronomers must strain to see these subtle shifts.
06:35Detecting wobbling stars is the main technique astronomers have for finding planets.
06:42It was established earlier this century.
06:46But as optics and data collection have improved, so have its chances for success.
06:52The technique we use here is called astrometry.
06:55Basically, what we're doing is collecting single frames in a movie.
07:00We look at a section of the sky, and we, on a particular night, find where each of the stars in that section of the sky are,
07:07and we measure their relative positions.
07:09Then on a later night, we do the same thing again.
07:12We take another measurement of the relative positions of all the stars in this area of the sky.
07:19To search for the planet, we then compare all of these frames as if they were put together in a single movie
07:25to see if the star's motion is linear or if it has that very small, wavy pattern that we're seeking.
07:36The wobbles these observers are trying to find are minute.
07:42Even a giant planet like Jupiter, a thousand times the size of Earth, would have a barely discernible effect on a star.
07:51It's like trying to see a man waving on the moon.
07:59The problem is made even worse by the swirling atmosphere of the Earth.
08:04It causes starlight to twinkle, and even those tiny variations are enough to obscure the wobbles caused by orbiting planets.
08:13Observing stars from space helps eliminate the problem.
08:17Well, we're using a space-based device to find guidance sensors on Hubble Space Telescope
08:22to do roughly the same kind of work, looking for the wobbles.
08:25If you get up above the Earth's atmosphere, the hope is that the signal that the Earth's atmosphere impresses
08:31on any astronomical research that's done from the ground won't be there,
08:35and so we'll get perhaps slightly better results.
08:39Yeah, we're down to a third of a Jupiter for a 600-day period.
08:43Fritz Benedikt started using the Hubble Space Telescope three years ago.
08:48It's the most expensive telescope ever built, and orbiting high above the atmosphere,
08:53it should give him the edge in planet detection.
08:56Ultimately, what we want to do is treat the...
08:59The problem is you don't get a lot of time with the Hubble Space Telescope.
09:02I can't go to a telescope time allocation committee and say I want to look for little green men,
09:06but I sure can go to a telescope time allocation committee and ask to look for planets.
09:10And even though the planets that I may find aren't habitable, they would be examples of solar systems,
09:17and if they're solar systems like ours, they'll have planets like the Earth.
09:20The chemistry on the surface of that planet will be the same chemistry as on the surface of our planet.
09:25It's a start. It really is a start.
09:29But Fritz Benedikt's efforts are frustrated.
09:32The Hubble is much in demand, and planet hunting is not its main priority.
09:37To date, the Hubble has studied only two stars for signs of wobbles.
09:44Because of these time constraints,
09:46Fritz Benedikt has seen no more success than his counterparts on the ground,
09:50despite his unencumbered view.
09:53We say that going above the Earth's atmosphere is the best thing in the world,
09:56and perhaps the best thing in the world is to be smart enough to figure out how to make these observations
10:00from the surface of this planet, because that's the cheapest way to do it.
10:07Working from the Lick Observatory near San Francisco,
10:10astronomers are perfecting another technique less vulnerable to atmospheric distortions.
10:16LICK
10:22Instead of photographing a star to look for changes in its position,
10:26the Lick astronomers measure variations in the color of a star.
10:31Changes in color would indicate that the star is in motion,
10:35wobbling from the gravitational pull of an orbiting planet.
10:40When you look up at the stars at night,
10:42those white dots actually contain an enormous amount of information, each one of them.
10:50The white light can be spread into all of its composite colors,
10:54blue through red, much like the sun's light is spread into all of its colors in a rainbow.
11:00In the star's light, however, we have additional information
11:03due to the fact that the star's light must pass through the star's atmosphere
11:08on its journey toward us at the Earth.
11:11Atoms and molecules in a star's atmosphere absorb part of its light before it passes into space.
11:18Each time Jeff Marcy observes a star, he splits the star's light into a spectrum.
11:26The wavelengths absorbed by the star's atmosphere show up as lines, called absorption lines.
11:39By recording the absorption lines, Jeff Marcy can create a kind of fingerprint of the light
11:45that can be precisely fixed to one location.
11:49And if the star is being pulled by an unseen planet,
11:52Jeff Marcy will see this image shift from side to side.
11:57This technique is called spectroscopy.
12:01We're getting 20 counts a second. That's excellent. Here we go. Starting.
12:06Precision is essential, for if the star is wobbling,
12:10he must be able to detect a shift plus or minus a handful of atoms.
12:15Photons. Signal and noise.
12:18Should be pretty good. Should be adequate. What did we say? 30,000.
12:21Yeah, 25-ish. I think it's going to be about 150 to 1.
12:24There's a glorious effect in physics called the Doppler effect.
12:28When the star is coming at you, the spectral lines,
12:32these absorption features due to atoms and molecules, shift one direction.
12:37And when the star is moving away from you, the spectral lines shift in the other direction.
12:42We actually measure the radial velocity of the star,
12:45the speed with which it's coming at you and away from you.
12:48And we measure this radial velocity by watching the amount of Doppler shift.
12:53Now, the interesting thing is that the larger the Doppler shift back and forth,
12:58the more mass of the planet.
13:00A low-mass planet can hardly shove the star around at all,
13:03and so we hardly see any Doppler shift at all.
13:06On the other hand, if the mass of the planet is large,
13:09we see a great, large, easily detectable Doppler shift.
13:14Given that giant planets like Jupiter would be, in theory, easier to detect,
13:19the odds were great that the first planet found would also be immense,
13:24and, like Jupiter, lifeless.
13:27That did not deter Jeff Marcy,
13:30for Jupiter-sized planets may be the key to finding inhabited worlds like our own.
13:36Jupiter acts as a sort of cosmic vacuum system.
13:40Jupiter acts as a sort of cosmic vacuum cleaner.
13:43As Jupiter orbits around, it would sweep up the early planetesimals
13:48out of which the planets were forming.
13:50The comets, the asteroids would all get gravitationally scattered out
13:53or sucked into Jupiter,
13:55cleansing the solar system of all of this debris.
13:59And the debris, of course, is death for the evolution of organic material,
14:04which requires a very quiescent sort of atmosphere and environment.
14:08So it may be that Jupiter itself is a requirement for the development of life.
14:15Despite improvements in technology,
14:17planet hunters remain constrained in their search.
14:21In order to find a planet, they must look for a wobbling star.
14:25And in order to find a planet like our own, they must look for one much larger.
14:33Jeff Marcy had been hunting planets for over ten years.
14:38George Gatewood had been running his astrometry project in Pittsburgh for even longer.
14:45And Fritz Benedict was using the world's most expensive telescope.
14:51All together, they studied more than 30 stars.
14:57So precisely how many of these giant planets have they uncovered?
15:03I haven't found any planets yet.
15:05We've not found any.
15:06We were shocked at this.
15:07This is really quite surprising to us, because when we began,
15:10we assumed that every star, every single star, probably had a planetary system,
15:14and they must all have Jupiters.
15:16Indeed, Jupiter was probably just an average, run-of-the-mill-sized large planet.
15:20But they don't have them.
15:22It sent chills up my spine, frankly.
15:25And the reason was that I thought to myself,
15:28hey, we haven't found planets of a little more mass than Jupiter.
15:32Who's to say that when we begin detecting planets
15:35or have the ability to detect planets slightly less massive than Jupiter,
15:38who's to say that suddenly we're going to find them?
15:41Perhaps our own Jupiter is itself a rarity,
15:44which then may imply that our own solar system has some very rare characteristics,
15:49which bodes ill for life in other planetary systems.
15:55But planet hunters still believe that out of the billions of stars that surround us,
15:59ours cannot be the only sun with planets orbiting around it.
16:05Although astronomers have not found these planets,
16:08they do have evidence of new planetary systems being born.
16:14And I'm Roberta Piaz at Vandenberg Air Force Base,
16:17where the launch of an infrared satellite telescope
16:19may give scientists a new view of the heavens.
16:23In 1983, a specially designed space telescope called IRAS
16:27was sent into orbit above the Earth's atmosphere.
16:31Rather than photographing visible light,
16:34IRAS took pictures in the infrared,
16:39capturing images of the heat generated by distant stars.
16:44One startling discovery was a star surrounded by a strange band
16:48of solid particles captured in the star's gravity.
16:54It is believed that planets in our solar system
16:56were formed from the same kind of stardust,
16:59which is why they are called star dust.
17:04The discovery of star dust was the first in the history of astronomy,
17:08it is believed that planets in our solar system
17:11were formed from the same kind of stardust.
17:16More evidence of young planetary systems followed
17:19once IRAS showed us where to look.
17:22This is Beta Pictoris, also surrounded by a ring of dust.
17:28But it was the Hubble Space Telescope
17:30that later gave us the most vivid images
17:32of yet-to-be-born planetary systems.
17:36We know that there are stars being formed.
17:38We've seen this in ground-based telescopes for many years.
17:41We've had it confirmed in a spectacular way
17:43recently with the Hubble Telescope.
17:45We know that stars are formed in what we call giant molecular clouds.
17:48These are immense regions.
17:50The average cloud is a thousand to a million times the mass of the Sun.
17:55But what happens is that some of this material gets together
17:58by a process that we frankly don't fully understand,
18:01becomes unstable to its own gravity
18:04and begins to collapse.
18:06When it collapses, it has a little bit of rotation, not much.
18:10These clouds would typically take about 200 million years
18:15to go through one revolution.
18:18As the collapse proceeds with these clouds,
18:20they spin faster and faster.
18:22And as they spin, they flatten out into,
18:24just like when you make a pizza, it tends to flatten out.
18:27So we think that that process leads to a disk-like structure.
18:33The center ends up making the star, the Sun in our case,
18:37and you have a disk out of which the planets could form.
18:40So this was a natural view then that suggested that planetary systems
18:45should occur almost every time that a star forms.
18:50These images, taken by the Hubble Space Telescope,
18:53look deep into stellar nurseries.
18:56The telescope showed evidence of dust disks around young stars.
19:01In fact, these telltale smudges were found
19:04around more than half the stars observed.
19:09If stars shrouded in dust are that common,
19:11so, the thinking goes, must be the planets they produce.
19:18This new evidence confirmed old beliefs.
19:21Astronomers have always imagined a universe full of planets,
19:24even though they were never able to find one.
19:29Some astronomers, in fact, were so sure that other worlds existed,
19:33they skipped the planet search entirely and chose instead
19:37to listen for signs of intelligent life.
19:42Almost 40 years ago, SETI was born.
19:46The Search for Extraterrestrial Intelligence.
19:49The reasoning behind it was simple.
19:52If E.T. did exist, he might be giving us a call.
20:00The project started out in 1960.
20:03With a single radio telescope,
20:05astronomer Frank Drake made the first radio search,
20:10scanning the interstellar airwaves for messages from other civilizations.
20:14Over the years, the project grew.
20:18Steven Spielberg even joined the effort,
20:20providing funds to help construct a radio telescope
20:23dedicated to finding extraterrestrial life.
20:29Eventually, scientists devised ways of listening
20:33to thousands of radio frequencies simultaneously.
20:37But these advances have yielded only a handful of results,
20:43none of which were ever confirmed.
20:49No matter how much money or equipment is put into it,
20:52SETI has always suffered a major flaw.
20:57Part of the argument with SETI is that
20:59it's not just a matter of how much money or equipment is put into it,
21:04Part of the argument with SETI is that
21:06the absence of evidence is not evidence of absence.
21:10We may be out to lunch when the signal comes,
21:12we may have picked the wrong channel for the observing.
21:16There are a whole host of things in the chain of assumptions
21:19that goes through SETI,
21:21where a null result doesn't necessarily constrain your understanding.
21:26The beauty of the planetary detection problem
21:28is that a null result does constrain your understanding.
21:31If we don't find the signals
21:33down to the level of capability of the telescopes,
21:36the planets aren't there.
21:37The massive planets, or however low the mass would be
21:40based on the technique, just don't exist.
21:42And that's the significance.
21:44A null result from this technique is truly a null result.
21:48We don't even know if in this vast cosmos of ours
21:52there is an Earth-like planet.
21:54We're in 1996 and we still don't know.
21:57So before we even think about people sitting on planets
22:00transmitting radio waves,
22:02shouldn't we see if there are planets?
22:06Ironically, it was not a planet hunter at all
22:09who was the first astronomer this decade
22:11to find evidence of a planet beyond our solar system.
22:15Andrew Lyon was listening to the heavens,
22:17but not for signs of intelligent life.
22:20Lyon's interest was in exotic stars known as pulsars.
22:26Here we hear the pulses cross as a beam
22:32from the rotating pulsar
22:34crosses the line of sight of the Earth.
22:36In this case, it's about once every 0.714519 seconds.
22:42Very precise rotation.
22:50This pulsar is a younger one.
22:52This is a pulsar in the Vela supernovae.
22:55We can still see the remnants of the explosion.
22:58Andrew Lyon has found more pulsars than anyone else in the world.
23:04These strange astronomical objects are thought to be dead stars.
23:10Stars that have exploded in a supernova.
23:14All that's left behind is a core of material
23:17the size of a city spinning up to 600 times a second.
23:23As it spins, the pulsar emits a beam of radio waves
23:27that can be detected on Earth as regular pulses.
23:32It's because of this regularity
23:34that pulsars are considered the most accurate clocks in the cosmos,
23:38predictable down to the last microsecond.
23:42At one such object,
23:44the pulses were arriving earlier and later
23:49by a few milliseconds.
23:52The natural interpretation here was that
23:55this body was moving by a couple of thousand kilometers
23:59or something like that.
24:01And it was doing it periodically.
24:03About every six months, it moved away towards us and back again.
24:08Incredibly, Lyon seemed to have stumbled across evidence
24:11of a wobbling pulsar being pulled at by a planet.
24:15He published his findings in the journal Nature.
24:18The announcement, however, was just too fantastic for some to believe.
24:22Not only people's, but our own reaction was one of great surprise.
24:27On the whole, we would not expect planetary bodies
24:31to be around pulsars, certainly normal pulsars,
24:35because of the violence of their formation.
24:40In preparation for an upcoming meeting of the American Astronomical Society,
24:44Andrew Lyon went back to examine his data
24:47to make sure his calculations were correct.
24:51I was doing some more work trying to find ways
24:54in which we might be able to confirm or otherwise
24:57the hypothesis that it was a planetary body we were looking at.
25:02And for some reason,
25:07I had a flash of insight as to what might cause this.
25:19Unfortunately, my insight was correct,
25:23and I found that when appropriate correction was made,
25:28the six-month period disappeared.
25:31And, of course, so did the planet.
25:37Lyon had indeed found a wobble,
25:40but it was the wobble of the Earth as it orbits the Sun.
25:44A computer error had failed to take this into account.
25:47When Lyon made the correction, the wobble in the pulsar disappeared.
25:59I was just completely numb for half an hour, an hour.
26:04I just sat there going through everything that I'd said
26:07over the last six months to all sorts of people,
26:11realising that it was mostly complete rubbish
26:19and that I'd really made a really fundamental error.
26:29I had to let them, let everyone know as soon as possible
26:34so that they would not dwell on an object which did not exist
26:38and would not tax their ingenuity for understanding it.
26:44Andrew Lyon went to the Astronomical Society meeting.
26:48Hundreds of astronomers gathered to hear about the new planet
26:52from the man that had beaten them to it.
26:55I was in this room with 500 astronomers, very excited.
26:59Here was a guy who was going to announce the discovery of a planet around a pulsar.
27:04And we expected to hear the technical details of that
27:08and share in his triumph because we're all in this game together.
27:12And he stood up there and he listed three things that this signal could be
27:18and the last of them was a mistake.
27:20And he said, unfortunately, it's the last of those reasons.
27:26And I went, ah, and 500 people in the audience went, ah.
27:31This poor scientist had to get up there and tell the world
27:35that he had been wrong and publicly wrong.
27:38And I felt very proud, frankly, to be a member of a group
27:41in which, in the end, honesty was the most important thing.
27:45Honesty was the most important thing.
27:47Andrew Lyon's example was a terrific object lesson
27:52that you've got to be absolutely sure.
27:56You can make a living at a certain level saying maybe for a long time,
28:00but if you're going to say absolutely yes, you'd better be absolutely sure.
28:05Lyon was received with a standing ovation.
28:09Many in the room knew what it was like to have years of work suddenly fall apart.
28:16But there was another pulsar watcher prepared to speak that day.
28:20But unlike Andrew Lyon, he had indisputable proof
28:24of not just one planet orbiting a pulsar.
28:27He had evidence of a whole planetary system.
28:31I found it much more challenging and less relaxing than it would be
28:36simply because a certain atmosphere was set,
28:39after what Andrew had said,
28:43a certain climate around the whole story,
28:46and I had to break through this.
28:48There was an important difference between the two claims.
28:51Rather than finding a simple wobble,
28:54Volchan's looked far more complicated and could be explained
28:57by the combined effect of three different planets orbiting the pulsar.
29:03In the end, it was the relationship among the orbits of these planets
29:08that provided the final proof of their existence.
29:11Very, very fortunately, the planets sort of meet together once every 200 days.
29:16They get very close to each other
29:18and interact gravitationally stronger than in any other situation.
29:22Each time they met up, the two larger planets pulled on each other
29:26producing minute changes in their orbits.
29:30Volchan knew he was right about the planets
29:33when he was able to predict their gravitational influence on the pulsar.
29:38The very nice thing about this is that it's just celestial mechanics.
29:42It's Newtonian mechanics.
29:44So you can build the model of perturbations and it has to work exactly.
29:47There's really no way out of it.
29:49It either does work and it's planets or it doesn't and it must be something else.
29:53For the first time in history,
29:56a planetary system had been detected elsewhere in the universe.
30:02But not everyone was enthusiastic.
30:05Pulsar planets really don't move me emotionally.
30:08The reason, of course, is that ultimately the big payoff in this game
30:14is to find a harbor for life.
30:18And we all know that life can't form around those so-called pulsar planets.
30:23The environment is far too harsh
30:26with x-rays and radio waves beaming onto the planet.
30:29And so for those reasons, it's almost certainly the case
30:32that such a planet doesn't yield the possibility of the real excitement,
30:36namely intelligent life.
30:38If we want to be optimistic about it,
30:41and I think we have every reason to be optimistic,
30:46then the message simply is
30:49there are many more planets to find around all kinds of stars.
30:53If you can make planets in such a strange and maybe even hostile environment
30:57as the environment of a rotating neutron star,
31:00the product of a supernova explosion, a dead star,
31:03if you want to use really big and dramatic words,
31:06then what's wrong with making planets around such nice and quiet stars like our Sun?
31:13For those in search of planets with conditions conducive to life,
31:17the trick is finding the right kind of wobbling star.
31:24It's a natural tendency to assume that life elsewhere
31:27has the same requirements as life on Earth.
31:30A Sun like our own, and a planet the same distance from it.
31:36We select stars that are more or less like the Sun,
31:39We select stars that are more or less like the Sun,
31:42bright enough, close enough to be examined carefully with an optical telescope.
31:46And the problem is that there are literally thousands of stars that are more or less like the Sun.
31:51Fortunately, they're all catalogued in this world-renowned source of information
31:55called the Bright Star Catalogue.
31:57And so we actually look through all of the thousands of stars in this catalogue
32:02that I've been using now for years,
32:04and we selected out those stars which are solar-like.
32:08I think since it's clear, we should do the faint stars.
32:11All planet hunters have their own list of favorite stars,
32:15one that can focus their observations for years to come.
32:20Choosing the right stars to examine can mean the difference between failure and success
32:25in the race to find the first habitable world.
32:29Jeff Marcy was not the only one measuring color shifts in starlight to look for planets.
32:34Over in France, two Swiss astronomers were starting up a search of their own
32:38using a similar technique.
32:42Their observing list had 140 stars on it,
32:45an ambitious number given the potential time commitments required for each observation.
32:50But the Swiss team had luck on their side.
32:53One of the first stars they chose to observe was in the constellation Pegasus.
32:58Called 51 Peg, this star began showing promise just a few months into their search.
33:04Their data suggested the star was wobbling,
33:07but so frequently, astronomer Didier Caylo was surprised.
33:13In fact, the first reaction that you have at that time is,
33:16oh, something is wrong with the experiment.
33:18You never think about the planets.
33:21And you observe it again, the day after, and the day after,
33:24and then it was more and more awful because it was moving every day.
33:30And you say, all right, there is really a big problem with this star.
33:34And then you observe it again, the day after, and the day after,
33:37and then it was more and more awful because it was moving every day.
33:41And you say, all right, there is really a big problem with the experiment.
33:46Month after month, Mayer and Caylo made the drive from Geneva to the observatory.
33:55Each time they looked at the star, they plotted its speed on a graph.
34:00And each time they looked, the speed had changed.
34:05Every visit to the observatory gave them more data,
34:08and eventually, a pattern emerged.
34:11When they looked at the graph as a whole, it showed not just one wobble,
34:15there were dozens of them.
34:17The planet around 51 Pegs seemed to be racing around the star every four days.
34:23Difficult to believe, but the evidence was there.
34:30It didn't take long before Caylo and Mayer were ready to not just observe,
34:34but predict 51 Pegs every move.
34:44On the first night, the reading for 51 Pegs was exactly what they had expected.
34:49The second night, it was the same.
34:52By the end of the week, they had all the proof they needed.
34:56They decided to break the news at a conference in Florence.
35:00The response was overwhelming.
35:03Mayer and Caylo became the first astronomers to discover a planet orbiting a living star,
35:09a sun like our own.
35:11They had won the race, and the press had a field day.
35:15It was a completely crazy time, with calls from papers, from television, from radio,
35:23from all over the world, and emails, a hundred emails per day or something like this.
35:30It was absolutely, completely a time where we had no possibility to work at all.
35:36Astronomers, however, had trouble fathoming the news.
35:42For the planet around 51 Pegs was much too large to be in such a close orbit.
35:49It defied all expectations about the location of Jupiter-sized worlds.
35:55It was in the wrong place, and I was frankly irritated by this result.
36:00Many people have worked for many years to come up with a theory that explains planetary systems,
36:06and we're kind of stuck because we've only got one to explain, and that's ours.
36:10And here is a discovery that throws it all into a cocked hat, basically.
36:1451 Pegs is a counterexample to everything I, I don't know if I should use the word belief,
36:21but everything I had accepted up to that point.
36:24So it's, it shakes things up. If it is a planet, it shakes things up.
36:33One explanation for its close proximity is that the planet around 51 Peg evolved further out
36:39and then got dragged in as it mopped up dust surrounding the developing star.
36:45When no more dust remained to draw it in, the planet stayed in its close orbit.
36:52Well, when I first heard about 51 Peg, I thought of at least five or six different ways
36:56that the detection of this planet might have been totally wrong.
36:59It could be a mistake.
37:01First, maybe the data is bogus.
37:03Yes, maybe.
37:05If the data points are bad, the whole thing disappears.
37:10In fact, the most strongest argument against this possibility
37:14is the fact that two other groups in the state have observed exactly the same phenomena.
37:19You can have pulsation also of the star.
37:21As a star pulsates, when it gets large, it gets much brighter,
37:25and when it gets small, it's much fainter.
37:27We don't see any variation from the light.
37:29The star could have alternatively had spots on the surface that rotate around.
37:34Sunspots.
37:35That could have mimicked a planet.
37:37If we have a star with some huge spot, and you have a rotation,
37:41we can have some change of the velocity, apparent change of the velocity of the star.
37:46Well, the explanation for these velocity variations around 51 Peg can't be due to star spots,
37:51because the star rotates around once every 30 days,
37:55and yet the velocities come back and forth every four days,
37:58so those two periods are not the same.
38:01We can say that there is a real consensus
38:03that saying this is a real low-mass object orbiting around these stars.
38:08That's the main point of it.
38:10Everybody agrees that this is a real object.
38:13This is not pulsation or rotation.
38:17The broad consensus now is that we're left with a planet,
38:20probably between a half of a Jupiter mass to two Jupiter masses,
38:24orbiting 1 20th of the Earth-Sun distance from the star.
38:28And there's almost no question that this thing is best described as a planet.
38:34Jeff Marcy had been confident that he could find planets as immense as the one orbiting 51 Peg.
38:40So why had the Swiss team gotten there first?
38:45Both teams had used the same technique and had chosen stars from the same directory.
38:50But Jeff Marcy had removed 51 Peg from his own observation list.
38:55And we rejected it from our sample, because in this particular 1982 edition,
39:0051 Peg is classified as a G2 sub-giant star, meaning it's an old, evolved star.
39:06Old stars begin to puff out, and their atmospheres become frothy and gurgly,
39:11much like a pot of boiling water.
39:13And when an atmosphere is gurgling like that, there are Doppler shifts.
39:17The light is suffering Doppler shifts,
39:19and the stars begin to puff out,
39:21And when an atmosphere is gurgling like that, there are Doppler shifts.
39:24The light is suffering Doppler shifts due to these motions,
39:27and it obscures the signal from the planet.
39:30And therefore we rejected it. We threw it out of the sample.
39:34As it turns out, 51 Peg had been misclassified.
39:38Later catalogues correctly entered the star as an identical twin of the Sun.
39:4351 Peg had been a perfect candidate for a planetary search.
39:49The Swiss astronomers' search differed in another vital way.
39:53They could get their information faster.
39:56The most important difference between Jeff and our own technique
40:01is mostly the reduction processes,
40:04the way to extract the information of the huge quantity of data
40:09we are measuring with the spectral graph.
40:11We have a black box, and with this black box,
40:15we compute right after the observation the speed of the star.
40:19It's 10 minutes after.
40:21And that's very original compared to Jeff Marcy.
40:26And that's a key point,
40:28because as you have your result right after the observation,
40:34you can interact very rapidly with your data.
40:37Yeah, I think it's 20 to 30 arc seconds away.
40:42Jeff Marcy had not worried about interacting quickly with his data
40:46because he had been looking for planets like Jupiter
40:49that took years, not days, to orbit a star.
40:5251 Peg turned his preconceptions upside down.
40:57We have to get 1262. We don't understand that star at all.
41:00Well, I think the planet around 51 Peg is a great step forward.
41:04Certainly it will go down in history
41:06as the first planet ever found around a normal star.
41:10But it doesn't quite hit home for me
41:12because it's not like any of the planets in our own solar system.
41:16And so the question still remains after all of this,
41:19do we find among other solar-type stars
41:23planets that are like the Earth, like our own Jupiter?
41:26And that question has not yet been answered.
41:30Despite his dissatisfaction,
41:32the discovery prompted Jeff Marcy to change his own procedures.
41:38He went back and took a fresh look at some of his past observations.
41:44At the next gathering of the American Astronomical Society,
41:48two weeks after the discovery of the planet around 51 Peg,
41:52Jeff Marcy was ready to make an announcement of his own.
41:55You look on a guy's star, you correct for the atmosphere,
41:57and then you integrate for a very long time.
41:59And she said, oh, he used 48. So I did.
42:02You know, she's the expert.
42:04In the world of astronomy, if there's anything to be said,
42:07this meeting is the place to say it.
42:10And soon rumors spread among the delegates
42:12that something big was indeed about to break.
42:18Okay, Dr. Jeffrey Marcy from San Francisco State University.
42:23Today I would like to announce here for the first time
42:27the definitive discovery of two new planets around two other stars.
42:34The first is the star 47 Ursa Majoris.
42:38After almost ten years of planet hunting,
42:41Jeff Marcy found evidence of not one,
42:44but two new planets orbiting suns like our own.
42:47And finally, one of those planets showed some promise of life.
42:52Another planet that we feel even more strongly about.
42:56What's fantastic about this planet is that it is in close enough,
43:01but not so close at this Mercury-Venus distance,
43:04that the planet's surface will be warmed up
43:07to a temperature that is, well, almost comfortable for all of us.
43:12And, in fact, here are...
43:14Yeah, well, the really exciting planet, I think,
43:16is the one that's around the star 70 Virginis.
43:18The planet is about 80 degrees centigrade,
43:21which is about the temperature of warm tea.
43:24And it means that water would not be in steam form or ice form,
43:29but instead water would be in liquid form.
43:33But Jeff Marcy's real hopes were pinned not on the planet around 70 Virginis,
43:38but on the moons he believed would be circling it.
43:42Moons perhaps as large as Mars or even the Earth.
43:49Warmed by their parent star,
43:51Marcy believed these moons could have enough mass and atmospheric pressure
43:55to contain small bodies of water
43:58before the slow crawl of biological evolution could be taking place.
44:05This hypothesis was strengthened with recent pictures from the Galileo spacecraft,
44:11which hint at the possibility of liquid water on two of Jupiter's moons.
44:16The frozen surfaces of Ganymede and Europa
44:19may conceal deep global oceans and perhaps some form of primitive life.
44:29Well, yeah, I think if you look at the temperature in these giant planets,
44:34certainly in some regions they may be cool enough where you might have liquid water.
44:40But we need to be very careful about suggesting
44:45that that's a place then where you might find signs of life.
44:48Certainly if you look in our own planetary system
44:50where we only know of life with certainty in one place,
44:55and that's here on the Earth,
44:57our prejudice suggests that water is very critical
45:00to the existence, the formation of life in fact.
45:03And not just water in any state, but water in the liquid state.
45:06So that arguably bounds it between the freezing point and the boiling points of water.
45:15That though is not enough to guarantee that you might have life.
45:20But the question of life will remain unresolved
45:23until we can observe the planets directly.
45:26A breakthrough in technology that NASA is now firmly behind.
45:31Much of the increase, I think, in the interest in the activities
45:35associated with searching for other planetary systems
45:37has come about in no small part
45:39because the NASA administrator has expressed a strong interest.
45:41I remember one day I had a conversation with him in his office
45:45and he actually pointed to a picture behind his desk,
45:49that famous picture from Apollo, Earthrise.
45:52And what struck Dan was that if we can find images like that
45:56of other Earths around other stars,
45:58just as that striking image has in a way signaled
46:02the fragility of the Earth on which we live,
46:04finding images, getting images of similar planets around other stars
46:09might convey a sense of hope.
46:11Could you imagine if in 25, 30 or 40 years
46:15we could take a picture of a planet
46:17that's perhaps 50 light years from Earth
46:21and if the resolution was high enough to measure,
46:25to take a picture of oceans and clouds and continents and mountain ranges?
46:30Breathtaking! Breathtaking!
46:35This grand vision for a portrait of an alien world
46:38may be possible in the future.
46:41The more immediate goal is to capture the light of distant planets,
46:45a kind of family snapshot of another solar system.
46:52If you think of the challenge of actually being able to detect
46:55and image a planet around a distant star,
46:59you're led by the laws of physics
47:01to consider something that's large in scale.
47:03We're here talking about something that's 50 to 100 metres in scale
47:07and you immediately think, well, I have one large telescope.
47:10Well, that would be a very tough job.
47:13Most people think that doing this with one large telescope
47:16would be very hard.
47:18So you're led then into the notion not of a large telescope
47:22but several small telescopes
47:24which we can put together in what we call an interferometer.
47:27An interferometer is made of small telescopes
47:29with the various apertures spaced apart
47:31so that by looking through this telescope
47:34and comparing the image you see through that telescope
47:36you can put together what the image would have been
47:38in a large instrument at the same time.
47:40That's the glory of an interferometer
47:42is that it behaves as if the whole telescope
47:45were the size of the distance between the two telescopes.
47:49With that possibility we might be able to directly image another planet.
47:55Testing for such a device has begun in California
47:58at the foot of the Palomar Observatory.
48:01From these modest beginnings
48:03astronomers hope to develop an interferometer
48:06100 times more powerful than any ground-based telescope now in use.
48:12One less susceptible to atmospheric distortions.
48:21NASA also plans to send an interferometer into space.
48:27There is hope that this telescope will be strong enough
48:30to capture the dim light of distant planets.
48:34And once we can directly image a planet
48:36we can study it for signs of life.
48:41Well there is just a glorious prospect
48:43if we can actually detect a planet itself
48:46because then we can take the planet's light
48:48shove it through one of our spectrometers
48:51and analyze that light for the presence of chemicals
48:54the chemicals of life such as oxygen, methane
48:57and most importantly actually water.
49:00The neat thing about detecting methane and oxygen
49:04in a planet's atmosphere
49:06is that we know that those two chemicals react
49:09with each other almost instantly.
49:11So if you find both oxygen and methane
49:14in a planet's atmosphere
49:15you know that those two chemicals
49:17must be in the process of being produced
49:20literally every minute, every month
49:23and obviously one strong possibility
49:26for the production of those chemicals is life itself.
49:30Looks like it's going pretty good.
49:32Ok, that's great news, Shannon, thanks.
49:34Finding chemical signs of life from outer space
49:37is not merely wishful thinking.
49:39In fact, it's already been done.
49:42The spacecraft is stable.
49:44Galileo is on its way to another world.
49:47Fly safe.
49:48In case there was ever any doubt
49:51the Galileo space probe proved
49:53there is life on Earth.
49:57The notion that we can actually look at planets
49:59and say something about the existence of life
50:01is of course a theoretical one for the most part.
50:04But we had a great opportunity
50:05with the Galileo spacecraft.
50:07On its way as it went out to Jupiter
50:10it was able to swing by the Earth
50:12and we had the idea of actually doing an experiment
50:14using the Galileo sensors
50:15to look back at the Earth
50:17and to try and see whether these signposts
50:19these signals that we think would
50:21clearly indicate the presence of life
50:23could in fact be detected
50:24and were clear indicators.
50:26And the Galileo experiment
50:27was very successful in that regard.
50:29You couldn't see highways,
50:30you couldn't see the structures
50:32that would be the things that
50:33most people might associate with life.
50:35But the signatures, these molecular signatures
50:38in the atmosphere of the planet
50:39were very clear and very readily detected.
50:41Now those instruments themselves
50:43wouldn't be the ones that would allow us to detect
50:45that sort of signature on planets around other stars.
50:49But it was a proof of concept
50:51that I think was quite dramatic.
50:54Science has finally broken the barrier
50:56between our world and the worlds beyond our sun.
51:00Now we have proof that other planets do exist
51:04and we have hope that soon we'll discover
51:06what life, if any, inhabits them.
51:10What's happening in effect
51:11is that a number of technological advances
51:14are taking place around the world.
51:16We're in the middle of the process
51:18of discovering what life, if any, inhabits.
51:21A number of technological advances
51:23are sweeping by us at amazing speed.
51:26Computers are much faster.
51:28We need fast computers.
51:30Light optics, spectrometers,
51:33diffraction gratings are much better
51:35than they were before.
51:36Lenses are much better.
51:38And finally, our software is slowly but surely progressing
51:41so that we can analyze the data that we collect
51:44to find lower and lower mass planets.
51:46So I hope someday they really will be
51:48coming out of our ears,
51:49euphemistically speaking,
51:50but we have a ways to go.
51:55Since Jeff Marcy's announcement in early 1996,
51:58new planets have been found almost every month.
52:11And with more powerful telescopes
52:13we may someday gaze upon these worlds.
52:19Images we can now only imagine
52:21in these artist renderings.
52:27Alien landscapes that could hold
52:30the promise of life.
52:34There's more to life than survival.
52:37We all search for our God.
52:39We all search for meaning to life.
52:43And if, if we would even have a discovery
52:47that there is a habitable planet,
52:50let alone life on it,
52:52I think it would uplift the human spirit.
53:01If we end up finding enough evidence
53:04that we are not alone,
53:06or if we find a convincing proof that we are,
53:09the consequences of that find will be revolutionary.
53:12There's no question about it.
53:14It's a little like the excitement of a hunt.
53:16You're looking for something,
53:18you haven't found it yet,
53:19but you always feel that just over the next horizon
53:22it's going to be there.
53:23It's not frustration, it's excitement.
53:28The diversity of planets is much greater
53:32than we ever imagined from theory
53:34or even from our imaginations.
53:36We're going to find a universe
53:37filled with different kinds of planets
53:39than we ever dreamed.
53:47We are on the threshold of a new age,
53:51and I think in 25 or 30 years
53:56when my grandson has children,
53:59and those children are in kindergarten,
54:03there's a high probability
54:04there'll be a picture on the wall
54:06of a planet with oceans and continents
54:10and mountains and clouds,
54:14and those children will look at that picture
54:16and then they'll look up at the sky.
54:18I think we could do it.
54:20We're not afraid.
54:29The evidence is out there.
54:31Scientists now know there are other solar systems,
54:34and NOVA can show you how to find them in the night sky.
54:38Point to NOVA's website at pbs.org.
54:44NASA Jet Propulsion Laboratory
54:46California Institute of Technology
55:01Educators can order this show for $19.95
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55:05by calling 1-800-255-9424
55:10And to learn more about how science
55:13can solve the mysteries of our world,
55:15ask about our many other NOVA videos.
55:21Next time on NOVA,
55:23when the best T-Rex ever is found,
55:26it's a showdown in the Badlands.
55:28Curse of T-Rex.
55:41NOVA is a production of WGBH Boston.
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