Red Giant Stars – Aldebaran. Eventually, the majority of hydrogen in the core of the main sequence stars is consumed, and the core collapses due to gravity. Very low-mass stars form white dwarf stars, whereas most other stars collapse and heat up until helium fusion begins. This fusion causes the star to expand outward several times larger than before, forming a red giant star (making the star cooler...Aldebaran is an example). When this happens to our Sun (in about 4.5 billion to 5 billion years), what will happen to Earth? Choose one: Earth will be pushed by the expanding Sun to maintain its orbital distance from the Sun, allowing Earth to retain the same environmental conditions that it has now. Earth will experience increased temperatures but will retain its atmosphere and water. Earth will lose its atmosphere and water and may/may not be completely vaporized by the Sun as it expands close to Earth’s current orbit.