A region of the Universe in which gravity is so strong that not even light can escape.
The shift in the spectrum of a source of electromagnetic radiation that’s approaching the observer. Equal to the shift in wavelength of a particular feature in the spectrum divided by the original (or rest) wavelength of the same feature. A blueshift corresponds to a shortening of the emitted wavelength.
Brown dwarfs are cool, faint objects, with a temperature too low for hydrogen burning to commence. They are inherently difficult to observe, but a number have been discovered.
A structural component of the Milky Way and other spiral galaxies, consisting of a thick, dense concentration of stars around the centre of the disc. Bulges are a common feature of spiral and lenticular galaxies. In the case of the Milky Way (and many other galaxies), the bulge is elongated to form a bar.