Young planets are born and embedded inside ‘Circumstellar Disks.’
By Sreekanth A Nair
(Courtesy: NASA)
Huge spiral patterns seen around some newborn stars, merely a few million years old (about one percent our sun’s age), may be evidence for the presence of giant, unseen planets, says NASA.
Astronomers have listed thousands of planets orbiting other stars. But the earliest stages of planet formation are difficult to understand because young planets are born and embedded inside vast, pancake-shaped disks of dust and gas encircling newborn stars, known as ‘Circumstellar Disks.’
NASA Hubble Fellows, Ruobing Dong of Lawrence Berkeley National Laboratory, and Zhaohuan Zhu of Princeton University did a detailed computer modeling of how gas-and-dust disks evolve around newborn stars and arrived at the conclusion that newborn planets may show their presence by modifying circumstellar disks on large scales.
This idea not only opens the door to a new method of planet detection, but also could offer a look into the early formative years of planet birth, says NASA. This approach can help astronomers find currently forming planets, and address when, how, and where planets form.
“It’s difficult to see suspected planets inside a bright disk surrounding a young star. Based on this study, we are convinced that planets can gravitationally excite structures in the disk. So if you can identify features in a disk and convince yourself those features are created by an underlying planet that you cannot see, this would be a smoking gun of forming planets,” Dong said.
Ground-based telescopes have photographed two large-scale spiral arms around two young stars, SAO 206462 and MWC 758. A few other nearby stars also show smaller spiral-like features.
The first planet orbiting a normal star was identified in 1995. With the help of ground-based telescopes and NASA’s Kepler mission, a few thousand planets outside solar system have been cataloged to date. Since the planets are many millions or a few billion years old, it is very difficult to know how they were formed.
“There are many theories about how planets form, but very little work based on direct observational evidence confirming these theories,” Dong said. “If you see signs of a planet in a disk right now, it tells you when, where, and how planets form.”
Astronomers will use the upcoming NASA James Webb Space Telescope to probe circumstellar disks and look for features, as simulated by the modeling, and will then try to directly observe the predicted planet causing the density waves.