Formation of the Solar System

Our sun, despite being a rather ordinary yellow dwarf star, holds great significance to us as it provides the essential conditions for life. However, there was a time when it potentially had a twin, perhaps even an evil one. The story begins in a giant molecular cloud, also known as a dark nebula, which contains numerous interstellar clumps filled with gas, dust, and stars. These clouds lacked clear boundaries and exhibit peculiar shapes. Some of them were even visible to the naked eye, appearing as dark spots amidst the bright Milky Way.

Approximately 4.5 billion years ago, our sun emerged from one of these molecular clouds. Through the accumulation and compression of material within the cloud's dense nuclei, a protostar, consisting of lukewarm hydrogen and helium, was formed. Over millions of years, as the temperature and pressure inside the protostar increased, it eventually transformed into a fully-fledged star—the Sun. However, not all the materials within the molecular cloud became part of the Sun. Some remnants began to orbit around the newborn star and gradually evolved into planets, including our Earth. This is how our solar system came into existence.

Nevertheless, it is plausible that there is more to this story. Recent statistical models exploring star formation indicate that many stars are not born in isolation but rather within clusters or with at least one companion. Further research has confirmed that most stars formed within molecular clouds have a companion. Sometimes, these companions remain in close proximity, with smaller stars orbiting larger ones. Multiple stars can even form double, triple, or other complex systems. However, in some cases, their paths diverge indefinitely. This could potentially be the fate of our sun as well. It might have had not just one sibling but an entire cluster of smaller siblings, along with a larger twin possessing similar mass and characteristics.

The hypothesis arises that this lost twin of the sun may not have had the best intentions. In the 1980s, scientists began noticing a peculiar pattern in Earth's history—large-scale extinctions occurring roughly every 27 million years. These catastrophic events reshaped the planet's biosphere, seemingly caused by a recurring celestial body. A dim dwarf star, hypothesized by astronomer Richard Mueller, is believed to exist at a distance of around 1.5 light-years from our location and orbits the Sun on a grand scale. It takes an astonishing 27 million years for this celestial troublemaker, nicknamed "Nemesis" after the ancient Greek deity of retribution, to complete its orbit. As Nemesis approaches closer to the Sun, it disrupts the trajectories of comets in the Oort cloud or Kuiper belt, causing them to hurtle towards Earth and leading to mass extinctions, reminiscent of the fate of the dinosaurs. Perhaps, Nemesis seeks retribution for the sun's role in depriving it of most of the molecular cloud's gas and dust, causing it to remain small and dark. Eventually, Nemesis is driven away and left to wander in the vastness of space—an outcome that would likely irritate anyone.

Various hypotheses have been proposed to explain the mysterious Nemesis. It could be a depleted brown or red dwarf star, or perhaps it is not a star at all but a massive rogue planet surpassing Jupiter in size. Despite the unsettling implications of its existence, our attempts to identify Nemesis have been unsuccessful thus far. There is still no concrete evidence supporting its presence. Recent studies have even cast doubt on the theory of regular mass extinctions, as the fossil records indicate more random occurrences rather than a fixed schedule. Additionally, scientists argue that any star moving in a similar orbit would be highly unstable, making its survival over such a long period highly improbable. Nevertheless, Nemesis has gained online fame and is often mentioned in articles and news stories, associated with various dramatic events like asteroid falls and tsunamis.

Even if Nemesis itself is not real, the probability remains high that the sun indeed had a twin. The initial premise still holds true—most stars are not born in isolation. Furthermore, there may be evidence of this lost twin within the Oort cloud, a vast region in the outer reaches of our solar system that contains comets and remnants from its formation. Scientists have observed anomalies within the Oort cloud, suggesting the presence of unknown celestial objects. When considering the possibility of a second sun, these anomalies align perfectly, providing a missing piece to the puzzle. The lost twin would account for the excess weight in the Oort cloud. Therefore, it is highly likely that the sun's twin exists, although its current location may be hundreds of light years away, making it extremely challenging to locate amidst the vastness of the Milky Way.

In conclusion, while the fate and whereabouts of the sun's lost twin remain unknown, it is probable that it exists. Finding it would require identifying stars similar to our sun throughout the Milky Way, which is a formidable task. Nonetheless, we should appreciate the sun's solitary presence as it has shaped our solar system and provided the conditions necessary for life to flourish on Earth. The absence of a twin has allowed our planet to thrive, even though the idea of twin sunsets, akin to those on Tatooine, may seem enticing.