Our Solar System

Sonia Said:

What is the plane of our solar systemrelative to the plane of our galaxy?

We Answered:

The inclination is 60.2 degrees. I gave a long explanation of this a week ago. You can find it here:

The period of the sun around the center of the galaxy is a tricky issue. The Observer’s Handbook lists a value of 200 million years, while other sources indicate 225 to 250 million years. On the other hand, in his 2006 book “The Infinite Cosmos”, cosmologist Joe Silk states that the period is 100 million years.

This period depends on the mass distribution within the galaxy. The length of the ‘galactic year’ is quite uncertain because of uncertainties in the mass distribution.

The solar system is so tiny compared to the galaxy that our view of the cosmos is essentially the same from anywhere in the solar system. (The closest stars will shift position relative to the background very slightly as we travel through the solar system.)

Finally, it’s interesting to note that since the sun appeared 4.5 billion years ago, we’ve made only about 20 to 50 orbits around the center of the galaxy.

Don Said:

How close to our solar system would a supernova have to be to affect us?

We Answered:

An ordinary core collapse supernova would have to occur with 30 light years to seriously damage the biosphere, but even one considerably farther away would likely bombard us with a lot of extra gamma, x-ray and ultraviolet radiation. That will have numerous effects upon the environment and life, probably among other things accelerating mutations and evolution as well as causing extinctions. Within 30 light years a supernova would probably so damage the ozone layer wholesale die offs will occur, and human survival would be severely challenged to say the least. The same would be true of a white dwarf destabilizing and runaway nuclear fusion blowing it completely apart as a Type 1A supernova. These are at least 10 times more numerous that the Type 1b, 1c and 2 supernovae that destroy massive stars.

However, if a very massive star explodes as a hyper nova, a black hole is formed. As it forms, twin jets of highly focused plasma will burst out of the star and fire off deadly gamma rays in tightly collimated beams. This happens even before the shock waves can rip through the outer envelope and hurl it into space. If one should hit Earth even from 6,000 light years away, it would wipe out most species of life on Earth. If the Earth should be struck from a hyper nova and the accompanying gamma ray burst from 30 light years away, the Earth would not only be sterilized, the surface of the planet would be melted and fused like everything would be near ground zero of a nuclear explosion.

Stars capable of exploding as a hyper nova are very rare now, and there are no stars within 150 light years that can go off as a supernova. The nearest one is IK Pegasi, which is a white dwarf very near the maximum mass it can have and still be supported by mutual repulsion between electrons. When it goes over the tipping point feeding off of another star in orbit around it, it will blow itself completely apart, turn itself into a rapidly expanding cloud of elements like iron, nickel, sulfur and titanium, and light up the sky so brightly it will outshine the full moon for weeks, if not months. It won’t do any serious damage to us, but it’s radiation will leave traces of radioactivity that will be recorded in the ice sheets, sea floor and other places. Evidence for supernova going off near us in the past has in fact been found in this manner.

Philip Said:

What would happen to our solar system if the sun exploded?

We Answered:

Funny thing. Even if the sun did explode,you couldn’t hear it!

Melinda Said:

If a stray planet entered our solar system, is there anything we could do to get rid of it?

We Answered:

Our technology doesn’t have anything even remotely close to being able to change the path of an object with that kind of mass. We would be in for the most spectacular (and lethal) fireworks show in the history of our planet.

Something like a white dwarf would affect the planetary orbit of anything within its gravitational field (which would be big, but not a guaranteed thing). Even the slightest change in our orbit would throw the ecological cycle on Earth out of whack. Probably to the point that it could not sustain life. (Our ecosystem is a resilient, yet fragile thing.)

A direct collision of white dwarf vs. yellow star would be cool. I couldn’t even guess what would happen.

Arnold Said:

What would happen to our solar system if our galaxy collided with the Andromeda galaxy?

We Answered:

Total destruction. No need for heavy physics. Even if the sun did not collide with another star, the tidal effects from near by stars would alter orbits and make the solar system unrecognizable.

Christy Said:

How many planets are in our solar system and what are they called?

We Answered:

The IAU considers the following as planets (or “Classical Planets”);

In addition the IAU considers the following as “dwarf planets”;

NASA has little say in what to classify a planet, that’s the IAU’s job.