Many stars in our galaxy are in pairs, but our Sun is not on that list. However, scientists now seek evidence that it may have had a companion.
The question is, where did it go?
Our Sun is like a lone wanderer. It takes us on a journey around the galaxy about every 23 million years as it orbits.
Proxima Centauri is the closest star to the Sun, four and a half light years away. It is so far away that even the fastest spacecraft ever built would take more than 7,000 years to reach. Wherever we look in our galaxy, the Sun at the center of our solar system seems like a strange object. Binary stars, that is, stars that orbit the galaxy tightly together in pairs, are visible from the outside.
Recently, astronomers discovered one such pair orbiting unusually close to a black hole, at the heart of our galaxy (the Milky Way).
A place where astronomers think stars will either tear apart or collide with each other through intense gravity.
The discovery of binary star systems has become so common that some scientists believe that all stars may have once been in binary relationships.
Or, rather, were born as pairs.
Everyone had a companion. This leads us to an interesting question: Was our sun once a binary star, meaning that it had another star with it and that it and its companion separated long ago?
Astronomer Gunji Lee, who is affiliated with the Georgia Institute of Technology in the US, says it is certainly possible and interesting.
Fortunately for us, our sun does not have a companion today.
If it were, the gravitational pull of the sun and its planets would affect the orbits of our Earth and the planets orbiting it.
This would cause extreme heat and extreme cold in our homes, making life difficult for us.
The closest binary stars to Earth are Alpha Centauri A and B. They orbit each other at a distance of 24 times the distance between the Earth and the Sun or three and a half billion miles.
This suggests that a very faint companion to our Sun is still orbiting our Solar System today.
That is, a hypothetical star, often called Nemesis, that was out of favor when it was hypothesized in 1984. Subsequent surveys and studies have not found any such star.
But when our Sun formed 4.6 billion years ago, the situation may have been different.
When huge clouds of gas and dust spread over decades and cool together, stars are born. These gases and dust, called nebulae, collapse under their gravity and form large clusters.
Throughout this process and decades, the clusters heat up and become hotter. Eventually, they generate enough heat to start nuclear fusion, forming a new star, or protostar.
The remaining material around this protostar spins in a rotating disk, and over time, this material turns into planets.
In 2017, astronomer Sarah Sadavoy of Queen’s University in Canada used data from a radio survey of the Perseus Molecular Cloud (a molecular cloud that is like a nursery full of new binary star systems). They found that stars often form in pairs. Based on their findings, their team suggested that most stars probably form in pairs or groups of more than one star.
“Processes are going on within these clouds of gas and dust that can form larger clumps that can collide and become stars,” Sadavai explains. “We call this process ‘fragmentation.’”
“If these stars are far apart, they might never interact with each other… but if they are close together, gravity can hold them together.”
Sadavai’s research suggests that all stars start their lives in pairs. Some stay together forever, while others drift apart over a million years.
“Stars live for billions of years,” she says. In this sense, a million years is just a moment, but a lot can happen in that short time.
This raises the question: Could the same thing have happened to our sun?
Sadavai says there is no reason not to believe it. But if the sun was also born with a companion, we have lost it over time.
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