The orbiting X-ray telescope XMM-Newton of the European Space Agency has captured the rebirth of the planetary nebula A78.
The orbiting X-ray telescope XMM-Newton (sensitive to the range of 0.1-15 keV), created by the European Space Agency (ESA), was launched into orbit on December 10, 1999.
Photo: ESA / D. Ducros
One of the most complex in structure nebula - "Cat's Eye" (NGC 6543). Image taken jointly by Chandra X-ray telescope and Hubble optical telescope
Photo: NASA / CXC / SAO, NASA / STScI
Behind the beautiful image of the nebula in the shape of an eye, lies the difficult story of the life, death and short-lived revival of a single star. The nebula, which is called planetary due to its spherical shape, forms at a late stage in the evolution of stars. A typical star, like our Sun, shines for billions of years due to the thermonuclear reaction of converting hydrogen into helium. When a star runs out of fuel, its core begins to shrink and heat up, while the outer layers greatly increase in size - the star turns into a red giant.
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The multiply increased core temperature triggers new thermonuclear reactions, in which the fuel is no longer hydrogen, but helium - it turns into heavier elements such as carbon or oxygen. This reaction is very unstable, as a result of which the star can throw off its outer shell, sending it into the surrounding space at a speed of several tens of kilometers per second. The flows of matter are gradually moving away from the center, and the energy that the remaining star still emits illuminates this cloud. However, this is a very short, by cosmic standards, period of life - having lost some of its mass, the star can no longer maintain a high temperature, thermonuclear reactions quickly fade away, and it turns into a white dwarf.
Usually at this point in the life of a planetary nebula, you can put an end. But, although very rarely, there are exceptions - an extinct star can light up again. The high density of the compressed core can re-start the "combustion" of helium. The renewed thermonuclear reaction generates a strong stellar wind, which blows off even more matter from the star at a tremendous speed. This new, fast flow meets the remnants of matter from the old flow, forming intricate complex structures that can be seen in the photograph. Where the new and old stellar winds meet, the gas temperature can reach a million degrees, causing it to emit in the X-ray range. These streams of incandescent gas from the revived star were captured by the XMM-Newton X-ray telescope.
Speaking of the further fate of the planetary nebula. A new flash brought this star back to life for a very short time. Having lost even more of its mass and having exhausted the remnants of helium, it will gradually cool down and after a few billion years will completely go out, turning into a so-called "black dwarf". If the star had a mass slightly more solar (Chandrasekhar limit), then it would turn into a neutron star, and if it was even heavier, then into a black hole.
Does our Sun expect a similar fate? Very likely. However, more than one billion years will pass until this moment, since the Sun is now approximately in the middle of its life cycle.