One of the "hottest" fields in astronomy in recent years is the search for planets outside our solar system. In the recent past, the astronomers looking for these planets were considered delusional and dreamers, but with the advancement of technology, more and more planets are being discovered that orbit other suns and are many light years away from us
Tal Inbar, "Galileo" magazine
The challenge facing the searchers of planets outside the solar system is enormous - an Earth-like planet reflects light 10 billion times weaker than the light of the Sun it orbits. To visualize the challenge for yourself, imagine that you are trying to watch the light of a firefly moving around a strong spotlight, two kilometers away from us. Scientists currently engaged in the search for planets outside the solar system have several methods for locating them, and the two leading methods are indirect (in this regard, see also: Michal Saaf, "Runners into Space", "Galileo" 106):
* Transits of the planets (Planetary Transits). With this method, one watches the star and tries to detect tiny periodic changes in its brightness, which indicate the existence of a planet moving around it. When the planet is between the observed star and the Earth, the intensity of the light coming from the star decreases slightly. This method is of course only suitable for situations where the plane of the planet's orbit around the star places it between us and the observed star.
* Oscillations of the star. Since the planet orbiting the star also exerts a gravitational force on the star, there are tiny wobbles of the star around the center of mass shared by it and the planet. The problem is that it is not always possible to notice these fluctuations, but if possible, the fluctuations of the star are translated into changes in the wavelength of the light emitted from it, due to the Doppler effect. Thus, when the star moves away from us, its light is shifted to longer wavelengths, and when it approaches us, its light is shifted to shorter wavelengths. A translation of these changes in the wavelength can indicate the mass of the body moving around the star, and even its distance from it.
The disadvantages of these two indirect methods are clear - at this stage we can only identify massive planets, which are many times larger than the Earth, and we also do not have the ability to observe the planets directly, but to touch on their properties indirectly and imprecisely. In order to observe them directly, we must look for new and creative ways.
To hear first-hand how NASA is dealing with this challenge - direct observation of small, Earth-like planets - I had the opportunity at Tekhnode in Givat Olga (see box) to hear the lecture of Dr. Amir Givon, a research fellow at NASA's Jet Propulsion Laboratory (JPL), located in Pasadena, California.
Dr. Givon, an Israeli living and working in the United States, received his doctorate from Princeton University. Today he is a partner in the team developing the next generation space telescope, designed for the discovery of Earth-like planets in other solar systems. Givon's work is part of NASA's TPF (Terrestrial Planets Finder) project - the development of an array of telescopes in space that will locate Earth-like planets within a radius of 30 light years from Earth. In this range it is known (following observations) that there are two hundred stars with planetary systems.
Why look specifically for small Earth-like planets?
Life as we know it, and presumably other life as well, can only develop on planets or the moons of planets. Our solar system has one star (the Sun) and nine planets (eight, if we take into account Pluto's "demotion" to dwarf planet status).
The planets are divided into two types: the terrestrial planets, similar in composition and size to the Earth, and the giant gaseous planets - Jupiter, Saturn, Uranus and Neptune. As far as we know, life similar to life on Earth cannot exist on giant planets. The temperature and composition of the atmosphere in them (due to their high gravity) are not suitable for life as we know it.
The composition of the materials of the terrestrial planets - Hama, Venus and Mars - is much more suitable, and it must be assumed that life could have formed in all of them, if conditions similar to those that existed then on Earth existed there, in the distant past. But the temperatures on the surface of a hot planet and Venus are higher than the boiling temperature of water (on a hot planet due to its proximity to the sun, and on Venus mainly due to the strong greenhouse effect) and there is no chance of life existing there.
On the surface of Mars the situation is different. Because of its great distance from the Sun and the composition of its atmosphere, the water on the surface of Mars is in a state of ice, and life cannot exist on its surface. In our solar system only one planet is "life-supporting" - our planet.
A life-supporting planet is a planet whose surface conditions are suitable for the creation of life. Since life as we know it is based on water, the temperature on the surface of the planet, at the time of the formation of life, must be such that the water in it is in a liquid state of aggregation.
The temperature depends on the planet's distance from the sun and the composition of its atmosphere. The density of the atmosphere and its composition have a great influence on the temperature of the planet's surface, due to processes such as the greenhouse effect and the spread of glaciers. If the conditions are right, and the necessary materials are present on the surface of the planet, life may form on it.
When astronomers realized that in our galaxy there are about a hundred billion stars, suns, near many of which life and even intelligent life can exist, it was clear that it was worth looking for these planets. This cannot be done in one of the two indirect ways mentioned. In order to measure and examine the atmospheres of Earth-like planets, it is necessary to directly observe the light coming from them, analyze it and look for characteristics of life - for example, the presence of free oxygen in the atmosphere.
The challenge of discovering a terrestrial planet by direct observation is enormous. Dr. Givon: "If the intensity of the light reaching us from the star is equal to the height of Mount Everest, then the light coming from the planet (actually, it is reflected light originating from the sun which it surrounds) is equal to a bump on Everest, at a height of a hundredth of a human hair." The intensity of the light reflected from a planet is 10 billion times smaller than the intensity of the light of the Sun that it surrounds. The TPF telescope will operate in the visible light range of the electromagnetic spectrum, since in this range signs of life can be seen better than in the infrared or other areas.
The work of Givon and his colleagues at JPL exploits the properties of light as a wave phenomenon, specifically the interference property of light. The researchers' intention is to create a situation in which a destructive conflict will take place, in which a significant part of the star's light will be eliminated, and a glimpse of the planet's light will be possible. The principle of utilizing interference for the purposes of observations of celestial bodies with low light intensity is called interferometry (and see: Yoram Ored, "Seeing the Faces of the Suns", "Galileo" 107). This method is also used by large ground telescopes, such as the Keck Observatory in Hawaii. Givon is involved in the development of another method, called coronagraphy, in which the interference is created by one telescope.
However, while interferometry in ground telescopes uses shape-changing mirrors (in a technique called adaptive optics), the work being carried out at NASA makes use of a sophisticated geometry of the telescope's key (known as the "pupil"), in order to create interferences with a highly sophisticated structure, which will leave dark parts Relatively, where it will be possible to locate the faint light of the planets that we are interested in finding. This method is called coronagraphy.
"It is impossible to get a good enough observation from the ground," says Dr. Givon, "since the atmosphere moves at too great a speed for the adaptive optics to be able to adapt to it. My research deals with on-demand warping mirrors that will be installed in the future space telescope to search for planets. This research, along with the research into advanced geometrical configurations of the telescope's pupils (the shape of its key, T.E.), will lead to the ability to directly observe light reflected from Earth-like planets outside our solar system, and possibly to detect signs of life on them."
The future of the telescope is unknown
When Dr. Givon is asked "why is it good", why invest in a project of this kind, he lists several reasons, which also put the opinion of cynics in the listening audience to rest. "The first reason is scientific - to improve our understanding of the Earth and the processes that enable life on it. A second reason is specifically utilitarian - the development of control systems for sophisticated optical systems, promoting the subject of adaptive optics and solving problems we encounter in other fields.
Third reason - peripheral benefit: the scientific and technological efforts during the research will be able to bear fruit in diverse fields, such as precise cutting, the production of precise mirrors and even the discovery of new fields in optics. The fourth reason: the discovery of Earth-like planets... At some point we will have to leave the Earth," he adds with a smile, "so we should have an initial idea in which direction to turn."
At this point, the future of the TPF telescope is unclear, as parts of the project are slated for cuts and cancellation, due to NASA's budget cuts. In any case, the telescope is not expected to be launched into space in the coming years, and hence the groups of researchers still have time to deal with the great technological challenges that require a solution before this telescope can take off from the researchers' computers into the depths of space.
Tal Inbar is the head of the Center for Space Research, the Fisher Institute for Strategic Air and Space Research, and the chairman of the Israel Space Association.
Published in "Galileo" magazine
14 תגובות
Can someone write a bit about planets?
thank you =)
Greetings,
I am the researcher mentioned in the article and I will be happy to answer any relevant question.
Amir
Colonies in space is good
my peace -
one after one. First the moon, then Mars, and from there to the asteroid belt... and hopefully someday we can also reach Earth-like stars.
Technologies are constantly evolving, and hopefully we will reach this point as well. It is better to try than to give up in advance.
Do you know Frank Drake's formula from the sixties or seventies before you jump in and start slandering the scientists here? Frank Drake was a physicist who calculated the proper conditions for life to exist. By the way, he claimed that there are many Earth-like stars in space. And it is true by the way that the difference is the distance and of course one more difference - the technology of the culture we will encounter. Has this culture passed a certain technological threshold? The physicist also included this variable in his formula... and by the way, in view of the painful condition of the earth, it is not a waste of money. Note that our planet is heating up and polluting and we need to find an alternative. Therefore, appropriate technologies need to be developed, otherwise the human race and other species will not survive here. What's more, either way, in about five billion years, our sun will run out of fuel, and even so, we'll have to move from here... because it will turn into a red giant that will reach the size of Mars. It's true in the short term it's not burning, but in the long term you have to think about it too.
What's more, colonies in space are good anyway, especially when it comes to a large population, you don't want to closely monitor the population like it was in China at the time.... Killing babies with formalin and other gruesome methods... So space exploration is not a fantasy of mad scientists.
Let's continue your line of thought:
We finally found an Earth-like planet. Y-Shhhhhh!!!
And it is only 30 light days away. You probably know how much it is in km: 777,600,000,000(!). Now we need to develop airplanes that will fly at the appropriate speed.
Tell me: is it practical? realistic?
In my opinion, and I'm ignorant and with the country, it's a pleasant fantasy, and that's all
Mr. Peretz -
There are many reasons for leaving Earth. One of them is the death of the sun within hundreds of millions of years. You are right in saying that it is too far to think about it, but there are also other, more urgent reasons.
1. 'Local' disasters that can endanger the existence of the human race (earthquake on a huge scale, sharp climate changes such as another ice age, etc.). If man had already established colonies on Earth-like stars, then such an event would not wipe out the entire human race.
2. Disasters as a result of the impact of an extremely large asteroid, comet, etc.
3. Deadly epidemics that could lead to the elimination of most or all of the population on Earth.
4. Disasters of human origin - for example nuclear war, or environmental pollution that will lead to the undermining of the entire ecosystem.
In short, we are not so far from the days when the whole world was panicked and believed that humans were about to annihilate themselves in a nuclear war. If you want to preserve the species, one way of 'self-insurance' is to find and colonize other stars - and for this it is necessary to find Earth-like stars.
Once again wasting money in vain?... Life cannot be created randomly. There is nothing to be done... Why? A simple answer - even if a cell is created with its many organs and parts, there is no one to breathe life into it. A molecule by itself is inert and without consciousness.
"At some point we will have to leave the Earth" ... "So we should have an initial idea where to turn" !!
Like quite a few scientists, these people live in delusions .. for those who didn't understand, he means when the sun will cease to exist or actually a few thousand years before .. which means in a billion or two years !!
Some scientists take themselves seriously in this matter! I mean they are really worried about what will happen in a billion years!! It's so idiotic and ridiculous when global warming and other evils could end everything in a span of years!
So I want to say to Mr. Givon.. I have no urgent need to leave the earth in the next million years!! After that he will come back to me and we will examine the situation again!
Let's think probabilistically...
The amount of stars is huge, you can even use the word "limited time", so why can't there be at least one planet that has life on it, the more stars there are, the greater the chances that there is life on one of them.
So if we said that the amount is "infinite" then surely there is another planet that has life on it.
Where is Sabdarmish?
When TPF is launched and starts its work again everyone will be shocked to find in a radius of only 30 light years
Dozens of Earth-like stars teeming with primitive life
Stop being shocked, use your imagination
And I thought that God created the sky where there are only stars and our only earth.
🙁