The earth’s magnetic field is an underrated wonder of nature. It protects our atmosphere, offers some of the most breathtaking scenery when it creates northern lights, and allows people to navigate from one end of the world to the other. Unfortunately, however, it will not save us from the death of the sun. At least that’s the result of some new research by Dr. Dimitri Veras from the University of Warwick and Dr. Aline Vidotto from Trinity College Dublin.
The expected life cycle of the sun is pretty well described by scientists. After its current main sequence phase is over, it will run out of the hydrogen fuel source that powers the nuclear fusion in its core. Without the thrust of fusion, the sun contracts itself and then heats up. This extra heat will push their outer atmosphere many times their current size, and possibly even engulf the earth, but will definitely consume Venus and Mercury.
UT video about the final state of the sun.
During its red giant phase, the sun also generates a strong, fluctuating solar wind. Normally, our magnetic field is able to prevent the particles of the solar wind from removing the earth’s atmosphere. However, due to the increased amount of particles that the red giant is constantly bombing, the magnetic field has little chance of protecting its atmosphere. When removed, the likelihood of life on the planet will slowly decrease, although Earth is likely to move further away from the Sun due to the decreasing gravity associated with the star’s lower mass.
The habitable zone around the red giants is much farther away than the main sequence yellow stars – they protrude beyond Neptune’s orbit. The slow orbital path that Earth will take will not get us there in time before all life is boiled on the planet’s surface. So we can be sure that a dying sun could likely kill us in more ways than one.
UT video on how to ward off the destructive phase of the red giant in the sun’s life cycle.
After its red giant phase, however, a white dwarf appears, which is much more stable and does not emit any solar wind at all. But for life to survive to this point, its planet’s magnetic sphere must be about 100 times as strong as that of Jupiter, and it must be able to move quickly between the habitable zones of three different types of stars.
These are at least the necessary properties of a planet based on the models of Drs. Veras and Vidotto. They performed simulations for the winds of 11 different stars with different masses. Any planet that resembles Earth’s place in the solar system and with its current magnetic field is a lost cause.
UT video discussing how we can possibly survive when the sun dies – with astronaut Mike Massimino.
Fortunately, all of this will happen in billions of years, giving humanity plenty of time to devise a technological defense strategy. However, for now, this model has an impact on the number of exoplanets other astronomers are preoccupied with.
Some have already been found near white dwarfs, including a few Jupiter-sized ones in the habitable zone of these ultra-stable stars. While the agony required to create a white dwarf would likely have eliminated any previously evolved life, white dwarfs are stable for billions of years themselves, giving life plenty of time to evolve again in a much friendlier environment.
Artistic performance of a spectacular solar flare.
Credit – Casey Reed / NASA
Right now, our own solar system is also a relatively friendly environment, despite the occasional outburst that could paralyze humanity’s entire electrical grid. Until that happens, our magnetic field will give us enough time to study other white dwarfs and watch their exoplanets for tell-tale signs of their sun after life.
RAS – Planetary Shields will buckle under the star winds of their dying stars
RAS Monthly Notices – Planetary magnetospheric evolution around post-main sequence stars
LiveScience – No life will survive the death of the sun – but new life could be born after that, new research suggests
California News Times – No life will survive the death of the sun – but new life could be born after that, new research suggests
Artistic illustration of ejecta from the sun being blocked by the earth’s magnetosphere.
Credit – MSFC / NASA