The microlensing method reveals a distant planet
Direct link to this page: https://www.hayadan.org.il/exoplanet0404.html
The microlensing method reveals a distant planet
Hazel Moir, New Scientist (translation: Dikla Oren)
A new planet was discovered in the Sagittarius constellation using a method called microlensing. Astronomers say the discovery is a victory for the controversial method, which can discover invisible planets orbiting distant stars.
Ian Bond, an astronomer at the Royal Observatory in Edinburgh, Scotland, announced the discovery at a NASA press conference on Thursday. "This proves that we can collect information about the number of planets in the galaxy and even beyond it," he says. "Basically, we can discover planets as small as Earth."
Astronomers have discovered more than a hundred planets outside the solar system. The great majority of them were discovered thanks to their gravitational influence on the star they orbit, since the star "dances" a little when the planet orbits it. However, this "dance" can only be detected in stars, whose distance from us does not exceed 170 light years.
To try to find more distant planets, astronomers use another method - microlensing. Microlensing occurs when, from Earth's perspective, a star passes directly in front of another star.
The gravity of the front star in between can bend the path of the light from the back star and sharpen it, causing its brightness to increase for a short period of time. If the front lens star has a planet around it, the planet can create perturbations in brightness that give away the fact of its existence.
Two of the leading teams looking for microlensing events are called MOA and OGLE. MOA is a collaboration between scientists from Japan and New Zealand. They are using a 0.6 meter telescope at Mount John Observatory in New Zealand. OGLE is a collaboration between Polish and American scientists, who use the 1.3 meter telescope at Las Campanes Observatory in Chile.
In 2002 the MOA team announced that they may have detected a planet roughly the size of Earth through the microlensing process. However, the signal was weak, and few were convinced of its truth. "The signal was not received enthusiastically, mainly because it was right at the limit of detection," says Bond, a member of the MOA team.
Now both teams have seen a planet in the process of microlensing, which looks very promising. OGLE detected a microlensing event in the constellation Sagittarius in June 2003, and in July 2003 Bond saw the planet's characteristic brightness perturbations in the MOA data.
The analysis of the observations from the two telescopes convinced the astronomers that it was a planet. The results suggest that the planet is 1.5 times heavier than Jupiter. Although the star the planet orbits is not bright enough to be seen, evidence suggests it is a red dwarf about 17,000 light-years away.
Critics have always regarded microlensing with disdain, as it is difficult to verify detection. A microlensing event occurs once, so the observations cannot be repeated several times using several instruments.
"The microlensing method does not enjoy the spotlight as other methods for discovering planets," admits Bond.
Experts say that this discovery may change the situation. Hugh Jones, a planet hunter at Liverpool John Moores University in England, refers to the new discovery as "interesting material".
Despite his warning that it will be difficult to gather detailed information from very distant planets, he thinks that this may be the beginning of a new era, in which astronomers will discover planets at the far ends of the Milky Way and even in other galaxies.
Astronomers discovered a planet using a new method
Avi Blizovsky
Astronomers said that for the first time they were able to discover a distant planet by detecting its gravitational influence on the parent star.
They said the technique could be used to expand the search for new planets and enable the discovery of smaller worlds, those with a mass similar to that of Earth, in solar systems more similar to our own.
The new planet, whose size is estimated to be one and a half times the mass of Jupiter, is about 17 light-years away, and orbits a star in the Sagittarius system.
The finding is the first to be made by measuring the effect of the combined mass of the planet and its parent star on the light of an even more distant star. More extensive details will appear in the May 10 issue of the Astrophysical Journal Letters. The lead scientist on this paper is astronomer Ian Bond of the Institute of Astronomy in Edinburgh, Scotland.
The possibility of finding the gravitational tag of a pair against the light of a star that is another 7,000 light-years away is the result of an effect predicted by Albert Einstein. Astronomers' observations of the brightness of a distant star indicate that two separate objects are influencing the light. The international team concluded that the second body must be a planet with a mass of only 0.4 percent of the mass of the parent star.
Other techniques used to detect exoplanets work only on massive worlds, which are typically found very close to the star. This arrangement is different from that of our solar system, and is almost certainly not friendly to life. The new planet orbits the Sun at a distance 3 times the distance between the Earth and the Sun, and this raises the possibility that the same star is also accompanied by smaller planets that are in closer orbits.
So far, 125 extrasolar planets have been found.
For the second news - the Yahoo version
The article in New Scientist
Know planets outside the solar system
https://www.hayadan.org.il/BuildaGate4/general2/data_card.php?Cat=~~~820638306~~~54&SiteName=hayadan
