Stars like the sun are highly energetic bodies capable of blasting away the atmospheres of planets in their orbits before life could have a chance to take hold, and a new study of a cluster of especially 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 might affect planet formation in their accretion disks, the mass surrounding young stars that supplies the material they need to develop planetary bodies.
To investigate this idea, researchers 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 to earlier Chandra studies of stars as young as 500,000 years old. These stars are a particularly strong source of X-rays that are produced by intense magnetic fields generated by the nascent stars' internal dynamos.
Because X-rays are tied to more magnetically active stars, researchers can measure the level of X-rays the stars produce at different ages to identify a constant X-ray-brightness for the first several million years of a star's life, which is followed by a sharp decline in magnetic activity between 7 million and 25 million years. The heavier the star, the quicker the decline, the researchers found.
In cases like the open cluster NGC 3293, seen in this NASA photo released in December 2022, the stars are old enough that the internal convection zones that power the dynamo that produces the magnetic field shrink or, in the case of large stars, fade away entirely, taking the dynamo along 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 especially young stars are likely to have completely cleared away the gas and dust in their accretion disks in very short order, thereby stunting the growth of planets around them. What's more, those planets that do form are likely to have their hydrogen-rich atmospheres stripped away in a few million years unless they can produce a strong magnetic field of their own to beat back the barrage, as is the case with our planet.