Broadly speaking, our Universe is in the clutches of two competing processes. One is the Hubble’s expansion due to Big Bang and the other is the gravitational contraction. While as the measured value of the Hubble’s constant yields the kinetic energy of expansion; the matter density determines the gravitational attraction.
The most obvious technique for discriminating between an open (expanding) and a closed (contracting) universe is to measure the average density of matter. If the present density is below the critical value at which the expansion and contraction balance, then gravity cannot halt the expansion and the universe must be open. In this context, rogue planets may come to play a key role in determining the fate of the universe.
A rogue planet also termed as an interstellar planet, nomad planet, free-floating planet, unbound planet, orphan planet, wandering planet, starless planet, or sunless planet is a planetary-mass object that orbits a galactic center directly. Such objects have been ejected from the planetary system in which they were formed and have never been gravitationally bound to any star. These planets got literally tossed out into space, wandering in the galaxies forever. The Milky Way alone may have billions of rogue planets.
These wandering planets are so dark and distant that it iscurrently essentially impossible to detect them using the regular techniques,and we do not know if there are any in our galactic neighborhood. The only wayto get a grip on how close one might be is to look at it in a statisticalsense: on average in the galaxy, how many of these planets are there per cubiclight year of space? Then we can fiddle with the number a bit to see how faraway one of these planets could be. Considering the mind-numbing volume ofspace, even if a planet gets as close as a light year away, the effect on usessentially seems to be nothing.
But given the fact that universe is expanding and notshrinking, we may be in a danger from a close encounter with one of thesegalactic nomads. To predict what canhappen is less likely than winning the Power Ball Lottery by a lot. Dependingon the planet, it could have little or catastrophic effect in the short or longterm.
One possibility is that the planet could go into an orbit ofthe outer planets and can throw off their orbits so there is a re-balance ofthe orbits of the outer planets (most of which are gas giants). This can becatastrophic for Earth as a change in the orbit of Jupiter and Saturn canaffect the orbit of Earth over the long term.
There is also a probability that the planet could have anear miss with one of the other planets and throw one or both of them out oforbit so that we lose a planet from the solar system.
The planet can also be captured in a highly elliptical orbitlike a comet and pass through the Solar System then not seen for hundreds, orthousands of years before it makes its way back into the orbits of the currentplanets in the Solar System.
If, however, the planet comes close to the Sun, it willaccelerate to over 1 km per second and heat up thousands of degrees Celsius. Ifthat happens, we are screwed. There will be no survivors.
Believers in the doomsday event usually refer to a supposeddisastrous encounter between the Earth and a large planetary object (either acollision or a near-miss) as also thrown a direct hint at in the glorious Quranin the chapter 99, surah zilzaal.
When the earth is violently shaken
And the earth brings forth her burdens,
And man says, what has befallen her?
On that day she shall tell her news
There’s nothing stopping a rogue planet from entering oursolar system. If there is one incoming, our puny technology is far from beingcapable of deflecting such an intruder.
Dr. Qudsia Gani is Assistant Professor, Department ofPhysics, Cluster University Srinagar