The Forgotten Stars Trivia Quiz

Answer: All of these

All of these are techniques used to find brown dwarfs.The majority of stars have companions and stars that appear single may have faint brown dwarf partners. Gliese 229B was found this way, it was a companion to the red dwarf star GI 229A. Brown dwarfs emit mainly in the infrared and scanning for faint red sources would help find field brown dwarfs like Kelu-1. PPI 15 was found in the young star cluster, the Pleiades. Brown dwarfs are brightest and easiest to find when they are young.

Answer: Lithium

With very faint sources, it is difficult to distinguish a low-mass star from a brown dwarf. The presence of lithium reveals the object to be a brown dwarf. Brown dwarfs never attain the mass or pressure needed to initiate thermonuclear hydrogen burning in their cores like normal stars. During hydrogen burning, stars destroy the lithium in their cores and convert it into two helium atoms. Brown dwarfs never reach this stage and therefore retain their lithium forever.

Answer: It was part of a binary system with another brown dwarf

They were able to determine that PPI 15 had a brown dwarf companion. The two brown dwarfs have an orbital period of six days. Using this information, the masses of the two brown dwarfs can be calculated.

Answer: Methane

Methane is the gas that gives Neptune and Uranus their unique color. Normal stars are too hot to allow methane to form and therefore faint objects with methane in their spectra cannot be stars.

Answer: Brown dwarfs are degenerate

Brown dwarfs are supported in a unique manner by what is called degeneracy. As young brown dwarfs contract, they start deuterium fusion which releases energy. This stops the contraction and brightens the object. The deuterium runs out in a few million years and the brown dwarf begins to contract again due to the loss of the radiation combating the gravitational force. During contraction, the temperature in the core rises and the heat separates the electrons from their nuclei.

The electrons begin to fill in quantum energy states. Only one electron can occupy an energy state; as the core becomes denser, the lower energy states are filled and the electrons must go to higher ones.

This releases energy that is not dependent upon temperature. Heavier brown dwarfs are therefore denser than lighter ones, they do not have more mass. Degeneracy also supports white dwarfs and neutron stars.

Answer: Above this mass deuterium fusion occurs

A major distinction made between brown dwarfs and gas planets is that brown dwarfs have undergone some form of fusion while planets have not. Brown dwarfs undergo deuterium fusion and if they are large enough lithium fusion. Anything above 13 Jupiter masses will be massive enough to initiate deuterium fusion and cannot be a planet.

Answer: True

Like all stars, brown dwarfs tend to fade as they age and the fuel needed to emit radiation runs out. One way of determining the age of a brown dwarf is to study its brightness.

Answer: They were older

The presence of methane indicates a surface temperature below 1,300 kelvins. In order for a brown dwarf to have cooled to such a low temperature it must be one to two billion years old. Younger brown dwarfs are hotter and brighter and have not formed methane in their atmospheres yet.

Answer: Magenta

Astronomers think that brown dwarfs are actually more magenta due to the presence of sodium and potassium in their spectral lines. Brown dwarfs are composed of molecules of hydrides and alkali metals. The dust grains from these molecules form into clouds and astronomers can observe "weather" on brown dwarfs.

Answer: All of these

Brown dwarfs are essentially failed stars and therefore they do have some similarities with them. Both form from the gravitational collapse of a rapidly spinning cloud of gas and dust. Both undergo deuterium fusion when young (stars continue on to hydrogen fusion). Both are fully convective which means that their contents are continually mixed throughout their lives.