How old is the Sun currently?

About 13.8 billion years old — the same age as the universe About 4.6 billion years old About 1 billion years old About 10,000 years old

What will happen in the Sun's core in about 5 billion years when it exhausts its hydrogen fuel?

The Sun will suddenly explode in a supernova The core will contract and heat up, while the outer layers expand dramatically, transforming the Sun into a red giant The Sun will cool rapidly and become a brown dwarf The Sun will collapse into a black hole

Approximately how large will the Sun become when it turns into a red giant?

About 2 times its current radius — slightly larger About 200 times its current radius — large enough to possibly swallow Earth's orbit About 2 million times its current radius About 10 times its current radius — expanding to Mars's orbit

Even before the red giant phase, when will conditions on Earth become too harsh for life as we know it?

In about 5 billion years — only when the red giant phase begins In about 100 million years — the Sun is brightening very rapidly In about 1 billion years — as the Sun gradually brightens, Earth's oceans will evaporate and surface temperatures will become too high for life Earth will remain habitable forever — life will always adapt

What is a planetary nebula?

A disk of gas and dust around a young star from which planets will form The atmosphere of a giant planet like Jupiter A shell of glowing gas expelled by a star like the Sun at the end of its red giant phase — it has nothing to do with planets A cloud of gas between stars from which new planetary systems can form

Why will the Sun not explode as a supernova when it dies?

The Sun will explode as a supernova — it is just a matter of timing Supernovae only happen to cold, old stars — the Sun is too warm The Sun is not massive enough — only stars more than about 8 times the Sun's mass have the gravity to trigger a supernova explosion The Sun will explode but only as a small nova, not a supernova

What is a white dwarf — the object the Sun will become after the planetary nebula phase?

A very bright star in the final stages of hydrogen burning The exposed, extremely dense core of a dead star — roughly Earth-sized but containing over half the Sun's mass, no longer fusing fuel, slowly cooling over billions of years A neutron star formed when a massive star's core collapses A star in the process of becoming a red giant

The Helix Nebula is often called the Eye of God nebula. What is it an example of?

A spiral galaxy shaped like an eye A massive black hole surrounded by a glowing accretion disk A planetary nebula — the glowing expelled outer shell of a dying star, similar to what our Sun will produce A star forming region where new planets are being born

During the red giant phase, which planets in our solar system might be swallowed by the expanding Sun?

Only Mercury — all other planets are safely far away All planets from Mercury to Saturn — the Sun will be enormous Mercury and Venus will definitely be swallowed; Earth may be swallowed depending on how much mass the Sun loses No planets — the Sun will expand but not enough to reach any planet

After the Sun becomes a white dwarf, what will eventually happen to it over the very long term?

It will collapse into a neutron star after cooling It will re-ignite as a new main sequence star when it cools enough It will slowly radiate away its heat over trillions of years and become a cold, dark black dwarf It will explode as a nova, scattering its material back into space