A chalazion is a small bump that appears on your eyelid because of a blocked oil gland.It can develop on the lower or upper eyelid, and it often disappears without treatment in about one month. chalazion is a small bump that appears on your eyelid because of a blocked oil gland.
Artist's conception of a white dwarf accreting hydrogen from a larger companion. A nova (plural novae or novas) is a cataclysmic nuclear explosion on a white dwarf, which causes a sudden brightening of the star.Novae are not to be confused with other brightening phenomena such as supernovae or luminous red novae.he recurrence interval for a nova is less dependent on the white dwarf's accretion rate than on its mass; with their powerful gravity, massive white dwarfs require less accretion to fuel an outburst than lower-mass ones.
A typical atom consists of three subatomic particles: protons, neutrons, and electrons (as seen in the helium atom below). Other particles exist as well, such as alpha and beta particles (which are discussed below). The Bohr model shows the three basic subatomic particles in a simple manner. Most of an atom's mass is in the nucleusâa small, dense area at the center of every atom, composed of nucleons. Nucleons include protons and neutrons. All the positive charge of an atom is contained in the nucleus, and originates from the protons. Neutrons are neutrally-charged.