Detecting Planets

Detecting Planets

Other methods of detecting planets around the stars are under development, including one where the obscuring light from the star is artificially oculted – with a disk in front of a space telescope, or using the dark edge of the Moon as such a disk – and the reflected light from the planet, no longer hidden by the brightness of the nearby star, emerges.

In the next few decades we should have definite answers to which of the hundred nearest stars have large planetary companions. In recent years, infrared observations have revealed a number of likely preplanetary disk-shaped clouds of gas and dust around some of the nearby stars. Meanwhile, some provocative theoretical studies have suggested that planetary systems are a galactic commonplace. A set of computer investigations has examined the evolution of a flat, condensing disk of gas and dust of the sort that is thought to lead to stars and planets. Small lumps of matter – the first condensations in the disk – are injected at random times into the cloud. The lumps accrete dust particles as they move. When they become sizable, they also gravitationaly attract gas, mainly hydrogen, in the cloud. When two moving lumps collide, the computer program makes them stick. The process continues until all the gas and dust has been in this way used up. The results depend on the initial conditions, particularly on the distribution of gas and dust density with distance from the center of the cloud.

There may be a hundred billion planetary systems in the Galaxy awaiting exploration. Image: © Elena

But for a range of plausible initial conditions, planetary systems – about ten planets, terrestrials close to the star, Jovians on the exterior – recognizable like ours are generated. Under other circumstances, there are no planets – just a smattering of asteroids; or there may be Jovian planets near the star; or a Jovian planet may accrete so much gas and dust as to become a star, the origin of binary star system. It is still too early to be sure, but it seems that a splendid variety of planetary systems is to be found throughout the Galaxy, and with high frequency – all stars must come, we think, from such clouds of gas and dust.

Landscape on one of the detected planets. Photo by Elena