Energy is generated in the cores of stars by fusing ___

• hydrogen into helium
• helium into hydrogen
• hydrogen into lithium
• helium into lithium

The expansion created by the heat of fusion is usually balanced by a star's gravity, creating ___

• an imbalance
• a conversion
• an inversion
• an equilibrium

In gas giants, like Jupiter, the force of gravity is balanced by ___

• the heat of fusion
• simple gas pressure
• tidal forces
• centripetal forces

The minimum mass for fusing hydrogen, and becoming a star, is roughly ___

• twice the mass of Jupiter
• 7 times the mass of Jupiter
• 75 times the mass of Jupiter
• half the mass of the Sun

Stars form from collapsing gas clouds,  just like the Sun did ___ years ago

• 4.6 million
• 14.6 million
• 4.6 billion
• 14.6 billion

Objects with a mass range between the heaviest planets and the lightest stars became known as ___

• red gnomes
• brown gnomes
• red dwarfs
• brown dwarfs

Astronomers classify stars, using letters, based on their ___

• temperature
• size
• luminosity
• composition

A new cooler class of star, discovered in 1988, was given the letter ___

• 'O'
• 'L'
• 'F'
• 'M'

Which element is found in low-mass brown-dwarfs, but not in regular stars?

• sodium
• magnesium
• lithium
• beryllium

The very first true brown dwarf was found in 1995 among a cluster of stars called ___

• the Pleiades
• the nine sisters
• Hyades
• the Beehive Cluster