Imagine what would happen if we had a second Sun. That is, there would be two luminaries in the sky. There is a high chance that the Earth’s orbit would be very unstable. If one of the Suns were larger and brighter and had a much stronger gravitational effect on us, then that Sun could pull the planet towards itself.

On the other hand, if the gravitational pull of none of the stars was strong enough, the Earth would fly away into space, becoming one of those rogue planets traveling the universe alone without a star system. Since the combined gravity of the two stars would be stronger, it would take the Earth 280 days instead of 365 to complete a full orbit. A year on Earth would be shorter, but not by much. The distance between the stars must be less than 15 million kilometers. Then, the orbits of all the planets in our system would be stable, including Mercury.

But let’s play it safe and imagine that the stars are about 5 million kilometers apart. In this case, the two stars would revolve around each other every ten days. Every five days, one star would pass in front of another. From Earth, it would look like a solar eclipse, but instead of our Moon blocking the Sun, it would be one star blocking the other. And instead of 7.5 minutes, this eclipse would last about 6 hours. Under these conditions, everything would be in a perfect alignment for the Earth to orbit the Two Suns. The only question is whether our planet would have formed in the first place in a binary star system…

You will learn about a type of stars called binary and their main features. After all, binary stars are considered fairly common objects in the observable universe. Nonetheless, they are of genuine interest to astronomers around the world. So what makes them so interesting?