The discovery of another planet moving at a great distance from its star substantiates the hypothesis that systems similar to the solar system exist this time, the researchers claim, the evidence is "etched in rock" (or at least in the dust cloud)
Photo: AL University An image of the star Pumalot and its planet. The researchers deduced the existence of the planet from analyzing the distortion in the dust cloud surrounding the star
A British-American team of researchers has discovered a distant solar system that is similar in many of its characteristics to our own solar system. The discovery is another step in the search for planets outside the solar system. In the coming years, several space missions are planned, which should provide the first fragments of images of these distant worlds.
The team of researchers, which includes researchers from UCLA University in California and the Center for Astronomical Technologies in Edinburgh, made use of observations from the Maxwell Observatory in Hawaii. In this observatory, an advanced sensor is installed that allows viewing in the frequency range between radio waves and infrared light. The head of the American group, Prof. Benjamin Zuckerman, reports that "we now have 'set in stone' evidence for large planets in wide orbits around stars."
The search for planets outside the solar system is one of the main fields in astronomy today. The stars we see in the sky are, as we know, suns like our sun, which are very far from the earth. Until the nineties, astronomers assumed that some of those distant suns revolved around planets, like in our system, but there was no evidence for this. Although it was unlikely to assume that out of the millions upon millions of stars in the universe only around our sun, planets were formed, but for the scientists the question remained open until observational evidence was obtained.
The last decade brought with it many developments in the technology of telescopes and other astronomical instruments. These provided evidence for the existence of planets outside our solar system for the first time. During the nineties, about a hundred planets were discovered around different stars and more planets are being discovered at an increasing rate.
The search for planets outside the solar system has two important scientific goals. The first: finding them would strengthen the possibility that there is life elsewhere in the universe. In order for extraterrestrial life to exist, life similar in nature to the life we know, it must develop on the surface of a planet. The fact that there are planets around many stars, and that the appearance of planets is a common phenomenon, strengthens the possibility of the existence of extraterrestrial life.
The second scientific goal is to understand the formation of our solar system. Observations of solar systems in different places and at different stages of development provide us with essential information about the way our solar system developed and the development of the Earth. The system reported by the British-American team is about two hundred million years old and is an early image of our solar system, which is about five billion years old.
Despite the great development in observational technologies in the last decade, planet hunting is still considered extremely difficult: the stars are very bright and the holiday planets around them only reflect the starlight and are very faint, so they are difficult to see. It can be compared to trying to find the light of a candle placed next to a powerful lighthouse lantern. Even if we have binoculars with sufficient separation to distinguish the candle, the strong spotlight will make it difficult for us to see it. The telescopes and modern observation instruments are extremely powerful, but even with them it is still not possible to see planets directly. On the other hand, these devices allow indirect observation using different techniques.
The identification method that led to the discovery of most of the planets is the measurement of the vibration (wobble) in the movement of the star. The planets cause small periodic changes in the observed motion of the star around which they orbit, due to the pull they exert on it. The planet does not revolve around the star exactly - in fact the star and the planet both revolve around a point in space called the "center of mass of the system". This can be clarified if we think about throwing a hammer: the observer from the side sees that the movement of the athlete is affected by the weight of the ball at the end of the rope, and it seems that both are in a kind of dance around some intermediate point. Even if the ball could not be seen at all, it was clear to any observer that the athlete was swinging some heavy object. Similarly, it can be concluded from observations, without direct sight of the planet, that it is indeed there and "attracts" its star. Small changes observed in the movement of the star betray the planets that slightly change its movement.
The limitation of this detection method is that it is possible to detect mainly very large planets (about the size of Jupiter, the largest of the planets of our Sun), which are in orbit very close to their star. These planets were called "Hot Jupiters".
Another method for discovering planets outside the solar system is measuring the change in the observed light intensity of the star as a result of the planet's passage between it and the observer. Sometimes there is a kind of small eclipse of the star by the planet that passes in front of it and hides a small part of it. Since the planet is significantly smaller than the star, the decrease in light intensity is very small - up to only about XNUMX percent. From repeated observations of the star it is possible to notice the same minimal but cyclical change in the intensity of the light and deduce the presence of the planet. This method has two notable limitations. First: the change in light intensity is so small that it is difficult to decide whether it was caused by a planet or as a result of some disturbance. Second: using this method it is possible to locate only planets whose orbits pass between the star and the observer.
Members of the British-American team used another method, which focuses on detecting planets by analyzing the distortions in the dust clouds observed around their star. In young solar systems one can observe a huge cloud of gas and dust surrounding the entire system. In their movement around the star, the planets drag behind them a trail of dust and create a distortion in the cloud that can be seen in the observations. The British-American group of researchers studied this type of dust cloud and identified a planet similar in size to the planet Saturn in a wide orbit around the star Fomalhaut (Fomalhaut) which is about 25 light years from Earth.
In order to move to the next stage in the research, the detection devices must be moved outside the Earth's atmosphere, thus bypassing the severe interference caused by it. The American Space Agency and the European Space Agency are going to launch several spacecraft in the coming years that are supposed to break new ground in this field of research. The upcoming projects are the "Kepler" spacecraft of the American Space Agency and the "Corot" and "Eddington" spacecraft of the European Space Agency, which should be launched around the year 2005. These three projects are supposed to place powerful telescopes in space that will be able to locate planets using the eclipse method.
More distant and complex projects are the American "Planet Finder" and the European "Darwin" planned for launch around 2015. These are huge interferometer-type observation devices that include about six separate bodies that will travel through space in a wide structure and collect data through well-timed cooperation between them. The state-of-the-art technology of these devices (which is still under development) should give them the ability to "cancel" the strong light coming from the star itself in order to allow, for the first time, direct observation of the planets.
Prof. Zvi Maza, chairman of the Institute of Astronomy at Tel Aviv University, is one of the senior researchers in the field of discovering stars outside the solar system and was involved in many discoveries in this field, including the discovery of the first candidate for a planet outside our solar system. Referring to the publication of the article by the British-American team, Prof. Mazza commented that "the identification of planets from observations of dust clouds around stars has already been done in previous years, but the very research that is gradually developing of these clouds can lead to important discoveries." Prof. Maza noted that an Israeli project to locate planets outside the solar system, in collaboration with research groups from the USA and Hungary, will soon begin at the Wise Observatory in Mitzpe Ramon. The project will include a wide-field telescope that will continuously photograph tens of thousands of stars, and a computer that will compare the light intensity of different stars in order to try and locate defects that indicate the presence of planets in orbit around them.
