“Things fall apart; the centre cannot hold;”
from W. B. Yeats’ poem “The Second Coming.”
Imagine a planet without a star to orbit, drifting alone through vast space. Such lone wanderers, known as rogue planets, are planets not bound to any star. Astronomers think a collision with another proto-planet knocked them out of their star systems early in their formation. This may have happened many times in many star systems in the tumult of the early universe. Or they may have formed independently of stars altogether from space debris of shattered stars that collided or condensed from gas and dust. Some astronomers speculate rogue planets formed in the center of the galaxy and then ejected by gravitational turbulence. However, they form rogue planets are difficult to detect, but scientists have estimated that there may be trillions of them in our galaxy.
In recent years, astronomers have made significant progress in detecting and studying rogue planets. Dr. David Bennett, an astronomer at NASA’s Goddard Space Flight Center, along with his team, analyzed nine years’ of data collected from an observatory in New Zealand. They exoplanets by observing how their gravitational pull altered and amplified the light coming from distant stars behind them. Through their analysis, they concluded that our Milky Way houses approximately 20 times more unbound planets than stars, with planets of Earth’s size being 180 times more prevalent than rogue Jupiters.
Rogue planets interest scientists because they could provide clues about the formation and evolution of planetary systems. Some speculate rogue planets could also be potential habitats for life. However, they are likely very cold and dark, and they may not have the necessary materials to support life as we know it.
Here are some of the open questions that scientists are trying to answer about rogue planets:
- How are rogue planets formed?
- How common are rogue planets?
- What are the conditions on rogue planets like?
- Could rogue planets support life?
Scientists hope that future research will shed more light on the mysteries of rogue planets. For example, the Nancy Grace Roman Space Telescope, which is scheduled to launch in 2027, will have the capability to directly image rogue planets. For the present, they are great subjects for science fiction—and poetry.