Rogue Planets : Elusive worlds hidden in perpetual dakness

Our vast universe is home to billions of galaxies which contain billions of stars and many more planets. Among countless planets, Some planets revolve around stars as in our own solar system. But not every planet is lucky enough to orbit a star. Some planets actually wander the galaxy alone, without any star. These lonely planets exist in perpetual darkness without the warmth of a day. We know these wandering cold worlds as rogue planets.

Planetary systems form in chaos. Debris and cosmic fog around stars begins to take the shape of planets under the influence of gravity. Things are chaotic here and collisions between planetary embryos, or proto-planets, are common. Stars are formed in clusters of hundreds or thousands of stars at once, and encounters between their infant planetary systems cause further havoc, strong gravitational interactions between those stars either result in capture of each other’s planet or entirely casting it out into deep space.

These mysterious worlds are hard to find in the dark and vast space. Among many exoplanets that the scientists have discovered , only about a dozen are sunless and wandering on their own, in the milky way galaxy. Like any other planet, rogue planets are formed around a star but, owing to gravitational perturbations of other bodies, these worlds get thrown out of their star system and like a lone traveler they circle the center of the galaxy in solitude.

Some solitary planets might form another way, without the help of a parent star. These worlds emerge from collapsed clouds of gas and dust, as stars do, but they don’t have enough mass to spark the nuclear reactions that make stars shine. These objects, known as “failed stars” resemble planets from afar.

Rogue planets are extremely difficult to detect, astronomers can’t search for them like common exoplanets, which reveal their presence by their gravitational effect on parent stars or briefly blocking out their light as they go around. But nearly invisible rogue planets just like blackholes evade detection.So astronomers rely on gravitational lensing to detect such elusive space objects. Imagine a line of sight from Earth’s telescopes to a distant star. When an object crosses that line, its gravitation can bend and magnify the star’s light, making the star appear more luminous than usual to us. The duration of the brightening indicates the nature of the object responsible; a brightening that lasts several days indicates a star, a day means a Jupiter mass object, and hours suggest something equaling the mass of Earth. The rogue planet recently discovered signaled its existence for just a few hours. The process of figuring out whether rogue planets are, in fact, rogue is extremely lengthy which spans decades. 

There’s no doubt about one thing: Without a star to warm themselves by, rogue planets must be frozen if not to their core, certainly at their outermost layer. They might not be so alone, either; planets could take their moons with them when they’re hurled out of their cosmic homes.

About 5 billion years from now, our glowing, life giving sun will start to die. The star will lose mass until it can no longer hold onto its outermost planets. Neptune, Uranus and Pluto will probably become rogue planets. They will drift away, taking their icy atmospheres with them. Unbothered by the cold of interstellar space, the planets will remain mostly unchanged, relics of a solar system that once huddled close around a warm sun. Earth will meet a different fate. Dying stars lose mass because they eject gas and dust in all directions, leaving exposed their spent cores. Our planet is expected to become enveloped in this hot mist and vaporized.