Post by Andrei Tchentchik on Apr 5, 2019 13:05:57 GMT 2
(.#166).- Extraterrestrials: should we look for them in globular clusters?
Extraterrestrials: should we look for them in globular clusters ?
Xavier Demeersman
Journalist
The globular clusters, contrary to what one thinks, could overflow of habitable and inhabited planets. Indeed, according to researchers, the proximity of stars in these very dense spherical groups of the periphery of galaxies would facilitate the journey from one world to another for possible extraterrestrial civilizations.
Would globular clusters contain habitable planets and extraterrestrials? Here, the globular cluster 47 Tucanae photographed by Hubble. Concentrating hundreds of thousands of stars in a sphere of 120 light-years, it gravitates around the Milky Way about 17,000 light-years from Earth. Visible to the naked eye in the southern sky, it is the second most brilliant after Omega Centauri. © NASA, Esa, Hubble Heritage (STScI, Aura).
Life appeared on Earth probably more than 3.8 billion years ago - maybe even 4.1 billion years ago - while the younger Sun was less hot and brilliant than today hui. It's only been a few decades since our species explored the surroundings of its "cradle" with orbits and robots. At the scale of the galaxy, Homo sapiens made a leap of flies, in 1969, to go for the first time on the Moon ... Now, we plan to tread the soil of another planet, Mars, but it will probably not be until the 2030s. And after? Climb other solid bodies of the Solar System like asteroids or Europe and Enceladus, or even install colonies on our natural satellite ...
Many also fondle the dream that one day we can go for a ride in the triple neighbor Alpha Centauri system (Alpha Centauri C alias Proxima is only 4.22 light years) and beyond to see, for example, what looks like Wolf 1061c, the potentially liveable exoplanet closest to us known to date. At the speed of light, it would only take 14 years to get there; with a ship as fast as Voyager 1 (17 km / s), you can still be there in 250,000 years. Will we ever get there? We can be optimistic. The task would be easier, of course, if the distances with the neighboring stars were shorter. As is the case in a globular cluster ...
PSR B1620-26 b, nicknamed Methuselah for its great age (13 billion years), is a circumbinary exoplanet discovered in a globular cluster, in this case Messier at 12,400 light-years. © Nasa, G. Bacon.
What about rocky planets in globular clusters
We do not live around a star belonging to a globular cluster but, if it were there, there could be planets with complex life forms, as Rosanne DiStefano, researcher at the Harvard-Smithsonian Center for Astrophysics, argued. (CfA) and his colleague Alak Ray, of the Tata Institute for Basic Research, at a conference at the American Astronomical Society meetings this week in Florida. "A globular cluster could be the first place where an intelligent life form could be identified in our galaxy," said the astrophysicist.
This may be surprising, however, as these very compact star-shaped communities that live in the suburbs of galaxies (150 of which are known around the Milky Way) have no reputation for providing fertile ground for the emergence of planets. Most of the stars that appeared there, more than 10 billion years ago, do not have, indeed, the same metallicity as the more recent generations like that of the Sun, born there are 4.6 billion years. Moreover, only one exoplanet so far has been detected in one of these very dense stellar media. Faced with this argument, Rosanne DiStefano replies that the giant planets certainly seem to prefer a certain rate of heavy metals to develop but not the small rocky planets. After all, planets have been well dug around stars having only one tenth of the metallicity of our Sun.
To those who argue that the very close proximity of the stars - some clusters contain millions of stars in a sphere of 100 light years in diameter - can be a brake on the development of life on the planets (some can even be ejected ), the two researchers who refuse to be pessimistic argue that since a majority of the population is composed of red dwarfs (less massive, less hot and less brilliant than the Sun), their living area is therefore narrower. The rocky planets there would be less disturbed gravitationally by the neighbors. It should not be forgotten that these small, exceptionally long-lived stars are also capable of dreadful eruptions for the worlds around them (see "It's really hard to live next to a red dwarf").
In the center of Messier 13 (M13), here is the most brilliant globular cluster of the northern hemisphere. Observable in the constellation Hercules, it is located 25,000 light years from Earth. © Esa, Hubble, Garching bei München.
Nearby stars within clusters
In cases where the necessary conditions have been met, life may have had enough time to flourish and evolve, given the average age of the stars: 10 billion years. Also, the two researchers consider it probable that one (or more) technologically advanced civilization (s) was (were) able to conquer the neighboring stars. "We call this the opportunity for globular clusters," says Rosanne DiStefano in the CfA statement. To send a message to these stars would not take more time than a letter from the United States to Europe in the 18th century. "
If we lived in one of these globular clusters, the Voyager 1 spacecraft, which started in 1977 and is now at a little over 20 billion km, would have traveled a tenth of the distance between us and the star. close. In this context, it would be easier to visit other worlds. That would be the next door ...
Of course, everything would be different: the day and the night would be dotted with luminaries in the background of which one could guess the whirlwind of the Milky Way. Black night point or perspective on the confines of the universe ... except perhaps for those who live at the outer limits of these balls of stars. Moreover, it is these stars that we must look first to hope to detect a planet in transit. The task will not be easy, however, because the clusters are all thousands or tens of thousands of light-years away from Earth, moving around the Galaxy. A quicker way to flush out any extraterrestrial intelligence would be to pitch in their direction as part of the Seti program. This has already been done in 1974, but in the other direction - it was us who sent the message - to Messier 13 (M 13), one of the most beautiful globular cluster to observe. With Carl Sagan, the famous Frank Drake wrote a radio message consisting of 1,679 binary numbers that should arrive at their destination in 24,958 years. Then you have to wait for a possible answer.
F I N.
Extraterrestrials: should we look for them in globular clusters ?
Xavier Demeersman
Journalist
The globular clusters, contrary to what one thinks, could overflow of habitable and inhabited planets. Indeed, according to researchers, the proximity of stars in these very dense spherical groups of the periphery of galaxies would facilitate the journey from one world to another for possible extraterrestrial civilizations.
Would globular clusters contain habitable planets and extraterrestrials? Here, the globular cluster 47 Tucanae photographed by Hubble. Concentrating hundreds of thousands of stars in a sphere of 120 light-years, it gravitates around the Milky Way about 17,000 light-years from Earth. Visible to the naked eye in the southern sky, it is the second most brilliant after Omega Centauri. © NASA, Esa, Hubble Heritage (STScI, Aura).
Life appeared on Earth probably more than 3.8 billion years ago - maybe even 4.1 billion years ago - while the younger Sun was less hot and brilliant than today hui. It's only been a few decades since our species explored the surroundings of its "cradle" with orbits and robots. At the scale of the galaxy, Homo sapiens made a leap of flies, in 1969, to go for the first time on the Moon ... Now, we plan to tread the soil of another planet, Mars, but it will probably not be until the 2030s. And after? Climb other solid bodies of the Solar System like asteroids or Europe and Enceladus, or even install colonies on our natural satellite ...
Many also fondle the dream that one day we can go for a ride in the triple neighbor Alpha Centauri system (Alpha Centauri C alias Proxima is only 4.22 light years) and beyond to see, for example, what looks like Wolf 1061c, the potentially liveable exoplanet closest to us known to date. At the speed of light, it would only take 14 years to get there; with a ship as fast as Voyager 1 (17 km / s), you can still be there in 250,000 years. Will we ever get there? We can be optimistic. The task would be easier, of course, if the distances with the neighboring stars were shorter. As is the case in a globular cluster ...
PSR B1620-26 b, nicknamed Methuselah for its great age (13 billion years), is a circumbinary exoplanet discovered in a globular cluster, in this case Messier at 12,400 light-years. © Nasa, G. Bacon.
What about rocky planets in globular clusters
We do not live around a star belonging to a globular cluster but, if it were there, there could be planets with complex life forms, as Rosanne DiStefano, researcher at the Harvard-Smithsonian Center for Astrophysics, argued. (CfA) and his colleague Alak Ray, of the Tata Institute for Basic Research, at a conference at the American Astronomical Society meetings this week in Florida. "A globular cluster could be the first place where an intelligent life form could be identified in our galaxy," said the astrophysicist.
This may be surprising, however, as these very compact star-shaped communities that live in the suburbs of galaxies (150 of which are known around the Milky Way) have no reputation for providing fertile ground for the emergence of planets. Most of the stars that appeared there, more than 10 billion years ago, do not have, indeed, the same metallicity as the more recent generations like that of the Sun, born there are 4.6 billion years. Moreover, only one exoplanet so far has been detected in one of these very dense stellar media. Faced with this argument, Rosanne DiStefano replies that the giant planets certainly seem to prefer a certain rate of heavy metals to develop but not the small rocky planets. After all, planets have been well dug around stars having only one tenth of the metallicity of our Sun.
To those who argue that the very close proximity of the stars - some clusters contain millions of stars in a sphere of 100 light years in diameter - can be a brake on the development of life on the planets (some can even be ejected ), the two researchers who refuse to be pessimistic argue that since a majority of the population is composed of red dwarfs (less massive, less hot and less brilliant than the Sun), their living area is therefore narrower. The rocky planets there would be less disturbed gravitationally by the neighbors. It should not be forgotten that these small, exceptionally long-lived stars are also capable of dreadful eruptions for the worlds around them (see "It's really hard to live next to a red dwarf").
In the center of Messier 13 (M13), here is the most brilliant globular cluster of the northern hemisphere. Observable in the constellation Hercules, it is located 25,000 light years from Earth. © Esa, Hubble, Garching bei München.
Nearby stars within clusters
In cases where the necessary conditions have been met, life may have had enough time to flourish and evolve, given the average age of the stars: 10 billion years. Also, the two researchers consider it probable that one (or more) technologically advanced civilization (s) was (were) able to conquer the neighboring stars. "We call this the opportunity for globular clusters," says Rosanne DiStefano in the CfA statement. To send a message to these stars would not take more time than a letter from the United States to Europe in the 18th century. "
If we lived in one of these globular clusters, the Voyager 1 spacecraft, which started in 1977 and is now at a little over 20 billion km, would have traveled a tenth of the distance between us and the star. close. In this context, it would be easier to visit other worlds. That would be the next door ...
Of course, everything would be different: the day and the night would be dotted with luminaries in the background of which one could guess the whirlwind of the Milky Way. Black night point or perspective on the confines of the universe ... except perhaps for those who live at the outer limits of these balls of stars. Moreover, it is these stars that we must look first to hope to detect a planet in transit. The task will not be easy, however, because the clusters are all thousands or tens of thousands of light-years away from Earth, moving around the Galaxy. A quicker way to flush out any extraterrestrial intelligence would be to pitch in their direction as part of the Seti program. This has already been done in 1974, but in the other direction - it was us who sent the message - to Messier 13 (M 13), one of the most beautiful globular cluster to observe. With Carl Sagan, the famous Frank Drake wrote a radio message consisting of 1,679 binary numbers that should arrive at their destination in 24,958 years. Then you have to wait for a possible answer.
F I N.
