Chapter 9 - Queen The Red Giant - From Blue Giant to Blue Marble

Figure 21 Red giant vs. Sun size comparison
(http://en.wikipedia.org/wiki/File:Sun_red_giant.svg)

A Red Giant is a luminous giant star of low or  intermediate mass (roughly 0.5–10 solar masses) that is in a late phase of stellar evolution.The outer  atmosphere is inflated and tenuous, making the radius immense and the surface temperature low, somewhere from 5,000K and lower.–Wikipedia

All white dwarf stars are created from a red giant “parent” star. The fact that you see a white dwarf, means that it once was a red giant. Our own Sun (in about 4 billion years) will expand into a red giant which will eventually shed its outer layers and turn into a white dwarf.

An “average” red giant star is around 1 AU in diameter – meaning that its surface would come close to the orbit of the Earth (if placed in the center of the Solar System). This means that none of the inner planets existed when Queen was around. It also means that our own Sun did not exist at that time either (its age is only 4.7 Gya). NOTE: We are talking about the time period between 9 Gya to 5 Gya.

There is only one way a red giant can create a white dwarf – and that is to shed its outer shell of gas – exposing its core which becomes the white dwarf. This process creates a ring of gas called a planetary nebula, which continues to expand away from the white dwarf forever (the “average” planetary nebula expands to a light year in diameter!). But we need that nebular material! How else do you create planets? And how did our Sun get created 4.7 Gya?

We need some way to grab that material so it doesn’t disappear forever! The only way to do that is with gravity We would need a large gravitational source to slow down the expansion of the nebula. But where would this gravity come from?

Figure 22 M57 The Ring Nebula
(http://en.wikipedia.org/wiki/File:M57_The_Ring_Nebula.JPG)

A black hole could provide enough gravity – but the Solar System (probably) wouldn’t survive an encounter with it. A huge gas giant planet like Jupiter wouldn’t have enough gravity – and the speeding nebula might just blow it away! A neutron star would make a good candidate since it can be up to 4 solar masses (see Tolman-Oppenheimer-Volkoff limit). Since we know that this planetary nebular material did stick around (we are here), let’s make the assumption that this “extra source of gravity” came from a neutron star (call it Spider) nearby. So where would Spider have been positioned when Queen shed its planetary nebula?

There are 3 possibilities as to where Spider was when this happened:

1. Spider was orbiting Queen.
2. Queen was orbiting Spider.
3. Both stars were orbiting a common barycenter.

My guess is #1, as that gives Spider the best chance to grab the most material. The planetary nebula would have intersected Spider’s orbit, and the neutron star’s enormous gravity would have slowed it down (so it wouldn’t expand out to a light year away).

Since Queen was 1AU in diameter, Spider must have been orbiting somewhere around Mars’ distance. If it was any closer, it would have intersected the outer surface of Queen and friction would have slowed it down and brought it closer and closer to the center of the solar system (where Queen’s core Rabbit was). But after the planetary nebula expansion and the “sweeping” up of material – Spider would have encountered this friction and “spiraled” toward the center.

Note: Neutron stars like Spider are created from a progenitor star through a supernova. The progenitor of Spider was a blue giant star (call him King). Oh great another star . . .