Scientists suggest that the transformation of the stars in the red giant stage does not mean a death sentence for the organisms living on the subjects she planets. The thing is that the resulting after the white dwarf is more stable star, for example, than our Sun. And it can create better conditions for the re-emergence of life.

The search for exoplanets is the most intriguing subject in cosmology from the twentieth century to present day! Of course, an important driving time is the desire to find the planetary worlds like our Solar system, finding a planet with potential biological activity - life developed in conditions similar to our earth...

The last candidates for such searches were white dwarfs close to the Sun type stars, a little more weight. Their stellar activity is very intensive: the cyclic variations of the magnetic field, spots and flare star activity, strong and AC electromagnetic radiation - UV and x-ray... Can their exoplanet to be suitable for life and what phase of stellar cycle of light is this possible?

White dwarfs, apparently, are slightly more stable than the Sun-like star (yellow dwarfs). After all, it's anticipated by scientists prospects, only a billion years will make it impossible for the existence of life on the planet Earth! Our star will become brighter, increasing its luminosity and increasing in size.

In the end, after a billion years of solar radiation will increase by about 20 percent. The Earth's climate will change, but our life, let me remind you, very sensitive to small variations in temperature, humidity, atmospheric composition. But the stars of the type of white dwarfs perform such a transformation luminosity much more slowly, which implies the ability to adapt.

White dwarfs are born as the kernel running up inside planetary nebula after the red giant phase. Then stable light inside a young planetary nebula begins a new phase of its stellar life. It should be noted that in General our Sun expects the same way - a few billion years, it will be transformed into a dwarf star and will be thrown into the outer space ring-shaped planetary nebula, pre ispaniu and transforming their neighbors, and partly distant planet...

However, there are some differences - nuclear energy sources in white dwarfs no, and they are very slowly cool down due to the radiation of its energy, gradually lose it. This process is very long and stable. And because of the great density of the bodies of white dwarfs it takes a very very long time.

Scientists have made calculations and found that the planet at a distance of 0.01 astronomical units (astronomical unit is 150 million kilometers) from such stars can develop life for eight billion years. The emergence of life on Earth has happened over a far shorter period of time, at least for the time in about 4.5 billion years. So, as you can see, white dwarfs be reliable candidates to create the conditions for the origin of life on their exoplanets.

However, opponents have expressed objections to the proponents of this hypothesis. In their opinion, powerful ultraviolet burns all at a distance of 0.01 astronomical unit, and this circumstance is a categorical ban on the origin of life on such planets and development of biological forms. But supporters of the new hypothesis in response to criticism held numerical simulation of conditions on the exoplanet, supplying it with the atmosphere type earthly gas envelope, and received favorable for the life of the solution.

In their view, ultraviolet light should not be fatal for the development of biota, although it will be several more of terrestrial radiation of the Sun - about 1.65 times more current radiation received by the Earth from the Sun. This is moderate dose will cause the ozone layer shielding exoplanet from the above damaging radiation.

A very interesting question about spectral composition of visible radiation on ekzoplaneta around white dwarfs. Here differences with Earth almost not received: the flora of the planets around white dwarfs is green (or slight variations of color, since plants with leaves reddish, brown and white are on the Ground, but not so much as mostly green).

It is established that white dwarfs are not Champions in penoobrazovatel and circular forms. This means that flare their activity should not be extremely high. This greatly contributes to the conception and development of forms of biological life.

Therefore, such stars is acceptable candidates for the presence "cradles of life" on their planetary orbits. It only remains to analyze the most important moment - will there be a planet at distances of the order of 0.01 astronomical units from the Central body, a white dwarf? If the analogy with the Sun, it turns out that it is, before becoming dwarf star, will swell a red giant before Mars orbit, will swallow mercury, then Venus and the Earth... flies into space mantle of red giant, undressed dim Central star, and the empty space will surround him very, very long time...

However, for a long time - it doesn't mean forever. Already in the hands of scientists has studied theoretical solution (I'm talking about the theory of migration, rather popular among the planetary community). Presumably scientists indicate that at least half of the planets in our Solar system, how would occupy "no place" - they migrate, seeking its stable orbit.

It is possible that the dynamic reset shell of the red giant will produce a new cycle of migration of planets are lined up in a new planetary hierarchy in stable orbits around the white dwarf. However, it is not clear which of the surviving planets can become a place of origin of life? This will be a gas giant that have lost their outer gaseous layer, gone with the flow of the stellar wind of the red giant? Or surviving in the transformation of planet earth-like?

While such systems are not found, because to detect planets will be very difficult. Low luminosity of white dwarfs, the lack of nearby gas giants that are easiest found by existing methods, suggest that to establish the truth will be very difficult in the near future.

However, all these worries - it wasn't about the nearest future, because rationale significant and encouraging. Improvement of the observatories in space promises many discoveries, apparently, among them will be and the search ekzoplanety systems in the tranquil surroundings of the longest space - type stars of white dwarfs.