Our Sun is a main-sequence star. This means that sometime in the far distant future, about five billion years down the road, our star will puff up into a red giant. Even further down the road, it may blow off enough material to become a white dwarf. In the process, expanding shells of gas and dust might be ejected and form a planetary nebula, which would be gorgeous to see, if any of us were still around in our robot bodies to do so.

In the meantime, we have other planetary nebulae we can observe that can help us understand the chemical evolution of stars and even galaxies. A new paper on arxiv.org examines one such planetary nebula – IC 4997 – using the Five-hundred-meter Aperture Spherical radio Telescope (FAST) in China. This particular planetary nebula is about 8,000 light-years away in the constellation of Sagitta and has a relatively high surface brightness and bright central star. Additionally, IC 4997 is rapidly evolving, which makes it a great observational target.

Analyzing the radio data, scientists detected neutral atomic hydrogen absorption in IC 4997, which is a fancy way of saying there is cold hydrogen gas. And the atomic shell of the planetary nebula contains about 17 septendecillion hydrogen atoms (that’s 17 followed by 54 zeros), a number I never thought I would write let alone say. The evidence further suggests that this particular shell was ejected at least 1,000 years ago, but – and this is pretty common when it comes to planetary nebula – the nebular mass is still less than expected.

All of that is a long-winded way to say that the data collected is interesting but doesn’t solve the ongoing missing mass problem that seems to be common with planetary nebulae. However, FAST seems to be up to the challenge, and the team plans to look at more planetary nebulae in the near future.

More Information

Research sheds more light on the properties of young planetary nebula IC 4997 (Phys.org)

“FAST search for circumstellar atomic hydrogen–I: the young planetary nebula IC 4997,” Xu-Jia Ouyang et al., to be published in The Astrophysical Journal (preprint on arxiv.org)