[Europan Ocean (OP)]

I think it was the 11th century and people witnessed a supernova in the sky. The light reached the Earth and following this will come the mass ejection. It must have been larger star than the sun. After such a time and distance the blast must have thinned in dispersion, like an expanding bubble, and grown cold. My question is, what measure of matter, be it Oxygen, iron or gold... will actually hit the Earth? A million tonnes? And over how many hours? What effect will it have?


News reports mention our nearest star. I read it is a red dwarf with small rock planets in the habitable zone that contain water. After the red giant phase, I wonder how any water remained, or did it come from the shrinking back of the red giant? Perhaps a mass ejection could leave behind residue.

[Europan Ocean (OP)]

The remnant of the star is called the crab nebula, it is 6,500 light years away and was recorded as a supernova in 1054 by Chinese astronomers.

[Kryptid]

Proxima Centauri was never a red giant.

[evan_au]

Can mass ejection from a remote supernova reach the Earth?

In one sense, the heavy elements making up the Earth were created in a series of supernova events. So yes, the mass ejected from remote supernova has reached the Earth, about 5 billion years ago.

However, there is evidence from the presence of Fe⁶⁰ on Earth that there was a supernova near the Earth sometime in the past few million years. The half-life of Fe⁶⁰ is about 2.6 million years.
See: https://en.wikipedia.org/wiki/Isotopes_of_iron#Iron-60

The remnant of the star is called the crab nebula, it is 6,500 light years away and was recorded as a supernova in 1054 by Chinese astronomers.

For remnants of the crab nebula to have reached Earth by 2017, the debris would have had to travel at 85% of the speed of light.
I find this unlikely, since many old stars puff off their outer layers, forming shells of gas around the dying star. These clouds of gas then slow down the debris emitted by the supernova. Wikipedia suggests that the debris of a supernova only travels at around 10% of the speed of light.
See: https://en.wikipedia.org/wiki/Supernova_remnant

...our nearest star. I read it is a red dwarf with small rock planets in the habitable zone that contain water. After the red giant phase...

Proxima Centauri is a red dwarf because it has a very low mass - about 1/8 the mass of the Sun. This means Proxima is burning its hydrogen fuel very slowly, and it will still be glowing long after the Sun has passed the red giant phase and turned into a dark cinder.

Proxima is quite dim compared to the Sun, and so the "Goldilocks" planet is much closer to the star than Mercury is to the Sun.

The red giant phase occurs when a star finishes burning hydrogen, and starts burning helium in its core. However, the mass of Proxima Centauri is too low to initiate helium fusion, so it will not enter the red giant phase.
See: https://en.wikipedia.org/wiki/Proxima_Centauri

[Europan Ocean (OP)]

So the mass ejection will reach Earth in about 60,000 years from now?

[evan_au]

So the mass ejection will reach Earth in about 60,000 years from now?

According to our current understanding, neutrinos from the supernova would have reached the earth almost simultaneously with the visible flash. Neutrinos have a tiny mass, and pass through the interstellar medium (and planets and stars) without hindrance.

Plasma from the supernova starts with a velocity around 10% of c, but it soon hits the clouds of gas and dust that were ejected by the star in its red-giant phase. This would slow it down considerably. After it cleared this barrier, the rapidly attenuating shock wave would have to contend with the interstellar medium which would slow it down more.

The galactic magnetic field would bend the path of the charged particles which make up this plasma, so it probably won't take a straight-line path.

So some particles might make it to Earth in 60,000 years, but it will be a fairly small number, and most that do make will take considerably longer than this.