Nemesis: The Sun's 'twin' or 'death-bringer' to Earth?

Nemesis is a hypothetical red dwarf star. The existence of this star has been proposed to explain a cyclical pattern in the rate of biological extinctions over geologic time.

Surely everyone has heard the story of Hou Yi shooting the Sun, of course, myths and legends are fictional after all, there is no way there could be nine Suns in the sky!

However, the Sun may have a twin brother called Nemesis . The relationship between it and the Sun is not simple, every 26 million years, this star will rotate once and as a result, all living things on Earth will face the risk of extinction. It sounds unbelievable but this is actually an astronomical hypothesis to explain periodic extinction events on Earth and cometary activity in the Solar System.

Based on data from NASA's Chandra X-ray Observatory, it is estimated that more than 80% of the stars in the universe are in binary or multiple star systems.

The Nemesis Star hypothesis was first proposed by American astronomers Daniel Whitmire and Albert Jackson IV in 1984. They found that during the biological extinction events that spanned the past 500 million years, the Earth would experience a mass biological extinction approximately every 26 million years.

They believe that this periodic extinction event may be related to cometary activity in the Solar System . They speculate that the Sun may have a "twin" that humans have not yet discovered, a companion star.

The orbit of this companion star is very stable and it will return periodically about every 26 million years and each time it will bring devastating disaster to the creatures on Earth.

The Sun's "twin brother" is named Nemesis by astronomers - Nemesis is the goddess of revenge in Greek mythology, so Nemesis is also known as the revenge star and the dark companion star.

Nemesis is a red dwarf, or brown dwarf, located approximately 50,000 to 100,000 astronomical units from the Sun. According to Kepler's laws, astronomers calculate that if its orbital period is 26 million years, the semi-major axis of its orbit is approximately 1.4 light years. Accordingly, the relationship between the Sun and Nemesis is called a binary star system in physics .

The binary star model for our Solar System is an appealing prospect, because it could explain many of the "anomalies" in the single star hypothesis.

A binary star system is a celestial system consisting of two stars that appear to be very close to each other. Binary star systems can be divided into physical binaries and optical binaries.

If one star orbits another and has a gravitationally close relationship with each other, they are called a physical binary. If two stars appear close together but are actually very far apart, they are called an optical binary.

In the Milky Way galaxy where the Sun is located, more than 50% of the stars are binary star systems. It is generally believed that the structure of binary star systems is more stable than that of single star systems. In the field of physics, there have been different opinions about the cause of binary star systems, some people think that the formation of binary star systems is mainly influenced by gravity.

Many stars have companions, including the closest triple star system to Earth, Alpha Centauri.

In any case, Nemesis, as the companion star of the Sun, can have a profound effect on other stars in the Solar System. The star Nemesis approaches the Sun about once every 26 million years in its orbit around the Sun.

Every time it gets close, it gravitationally changes the orbits of asteroids and comets in the Oort Cloud. The Oort Cloud is a spherical cloud that is thought to surround the Solar System. It contains countless comets and a small number of asteroids. It is about 50,000 to 100,000 astronomical units from the Sun and has a maximum radius of about 1 light year.

It is estimated that the total mass of the Oort Cloud is about 3×10^25 kg, which is about 5 times the mass of the Earth. Under the enormous gravitational pull of the Nemesis star, some comets and asteroids in the Oort Cloud will be "pulled" into the inner orbit of the Solar System, and they will roam around the orbits of the 8 major planets. A small portion of them will be attracted by the Earth's gravity.

In the Milky Way galaxy where the Sun is located, more than 50% of the stars are binary star systems.

Once captured by Earth's gravity, smaller comets rub against the air and burn up as they enter the atmosphere, while larger comets and asteroids collide directly with Earth's surface, leaving large craters.

More seriously, the successive impacts would cause the Earth's internal environment to change dramatically, causing a sudden increase in temperature, causing a disaster for living organisms on Earth. This hypothesis can explain some famous impact events in Earth's history, such as the Chilean impact that wiped out the dinosaurs 65 million years ago and the Chesapeake Bay impact that killed off North American mammals 35 million years ago.

These impact events all coincide with Nemesis's approach to the Solar System.

In addition, this hypothesis can also explain the periodic changes in cometary activity in the Solar System. According to observations and statistical analysis of long-period and short-period comets by astronomers, it is found that these two types of comets have clear peaks and troughs of activity over the past few thousand years. These peaks and troughs correspond to the times when Nemesis moves closer to or farther away from the Solar System.

One astronomical unit is the average distance between the Sun and the Earth (150 million km).

The above analysis all comes from the hypothesis of astronomers, when assuming that the star Nemesis really exists. So, does Nemesis exist? In 1986, astronomers at the University of California, USA, used an infrared telescope to scan the space near the Sun, hoping to find traces of the star Nemesis, but the result was failure.

From 1997 to 2001, astronomers used a 2-micron sky survey to comprehensively classify and measure stars around the Solar System, but they did not find the existence of the Nemesis star.

These observations all suggest that the possibility of Nemesis' existence is very low , and can even be ruled out. However, this does not mean that Nemesis has absolutely no evidence of its existence.

In 2004, Caltech astronomer Michael Brown discovered a dwarf planet called Sedna outside the orbit of Pluto. The asteroid's orbital eccentricity is extremely high, with its perihelion at 76 astronomical units and its aphelion at an astonishing 975 astronomical units.

This extreme eccentricity strikes scientists as odd, as Sedna should not exist in such an orbit according to current theory. Scientists speculate that Sedna may have been formed by an unknown celestial disturbance.

This unknown object could be the Nemesis star. As the Nemesis star may exist and move closer to perihelion, Sedna could be affected by the gravitational pull of the Sun and the Nemesis star at the same time, thus greatly affecting its orbit and eccentricity.

Sedna is currently the only evidence that can prove the existence of Nemesis, but it is not conclusive evidence. Because Sedna's eccentricity could also be caused by other reasons, such as disturbances from other stars or planets, instability in the inner Solar System, or other unknown physical mechanisms.

Therefore, more observations and research are needed to prove the existence of Nemesis.