The total number of stars in our galaxy, the Milky Way, is estimated to be 100 billion. (There are at least 100 billion galaxies.) These estimates may actually be on the low side. But look up at the stars on a clear night. How many do you see? If you have pretty good eyesight, approximately 5000 are visible from the Northern Hemisphere, or about 10,000 from all points on the earth. The stars you see are generally as large as the sun or larger. Yet the most common stars are completely invisible to the naked eye, even those that are relatively close. They can only be seen through powerful telescopes because they are considerably smaller, and therefore less bright than our sun. These small stars do not shine ‘yellow’ but rather have a reddish glow.
In the world of stars, the biggest and brightest burn out the fastest. They flame out and explode in millions of years. However, a star the size of our sun can expect to be around for 7-9 billion years. The small red stars have lifespans double that. When it comes to stars and their lifespans, it helps if you’re small. A crude comparison can be made with campfires. Throw a lot of wood on a hot fire and it will burn quickly in minutes while a small fire may smolder for hours.
Modern telescopes have also revealed that most of what appear to be single stars to the naked eye are actually two or more stars revolving around each other. Single stars, like our sun, appear to be in the minority. So with binary and multiple star systems so common, astronomers have long wondered if our sun, too, has a companion star. If it does, where is it and how come we don’t see it in the sky?
The sun could have a companion but it would have to be distant and a small red star. To the naked eye, it would be invisible. Through a telescope, it would appear as just another point of light amongst the billions of background stars. To find it, astronomers would have to monitor vast regions of the night sky over long periods of time in order to spot one star that moved against the background stars. This method is commonly used to find near earth asteroids, so the technology exists.
There is another object that may be discovered from this search. It is another large planet well beyond Neptune, the most distant planet known. Speculation for the existence of this large undiscovered member of the solar system has resulted in various names including Nemesis and Planet X. Some have speculated that this planet’s orbit periodically brings it close enough to disrupt the orbits of comets creating periods of chaos in the inner solar system and earth.
These theories are grounded in modern science but are speculative. Yet the idea of Planet X is not a modern hypothesis. In ancient times, this distant object was called Nibiru, The Destroyer. It was said to come close enough to earth every 3,600 years to cause major planetary disruptions. While this is the stuff of legions and unsupported by contemporary science, it is nonetheless interesting that the existence of Planet X was taken for granted by a non-technical culture thousands of years ago.
Astronomers hypothesize Planet X would have a ‘year’ (one revolution around the sun) equivalent to 10,000 earth years. By comparison, one Neptune ‘year’ is equivalent to 165 earth years. Finding a planet that distant, even a large one, would be much more difficult than spotting a small star, since it gives off no light of its own. Yet it would not be impossible, and astronomers are gearing up for the search.