Stars like the Sun are highly energetic bodies capable of blasting away the atmospheres of planets in their orbits before life has a chance to take hold, and a new study of a cluster of particularly young stars has given us an even better understanding of how this process occurs.
The Chandra X-ray Observatory undertook the most thorough study of magnetically active stars ever conducted to see how the activity of these young stars can affect planet formation in their accretion disks, the mass around young stars that supplies the material they need to develop planetary bodies.
To investigate this idea, scientists used the telescope to look at nearly a dozen “open clusters” containing a total of more than 6,000 young stars that formed around the same time, with ages ranging from 7 million to 25 million years old, and compared the data with previous Chandra studies of stars as young as 500,000 years old. These stars are a particularly strong source of X-rays produced by intense magnetic fields generated by the nascent stars’ internal dynamos.
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Because X-rays are associated with more magnetically active stars, scientists can measure the level of X-rays the stars produce at different ages to identify a constant X-ray luminosity during the first million years of a star’s life, which is followed. by a sharp decrease in magnetic activity between 7 million and 25 million years. The heavier the star, the faster the fall, the researchers found.
In cases such as the open cluster NGC 3293, seen in this NASA image released in December 2022the stars are old enough that the inner convection zones that drive the dynamo that produces magnetic field shrink or, in the case of large stars, wither away altogether, taking the dynamo with it.
The study, which was published in The Astrophysical Journal in August 2022, found that the high X-ray and ultraviolet radiation from these particularly young stars likely completely removed the gas and dust in their accretion disks in a very short time, thereby stunting the growth of planets around them. Also, those planets that do form are likely to have their hydrogen-rich atmospheres stripped away within a few million years unless they can produce a strong magnetic field to reverse the blockage, as is the case with our planet.
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