A quark star is a hypothetical type of compact, exotic star, where extremely high core temperature and pressure has forced nuclear particles to form quark matter, a continuous state of matter consisting of free quarks. Born in a supernova's blast, 3C58 seems too cool to be made of normal matter. Astronomers may have discovered two of the strangest objects in the universe two stars that appear to be composed of a dense soup of subatomic particles called quarks. The matter of a neutron star is a close-packed medium of such neutrons, each in its own bag, with the Pauli Exclusion Principle keeping them some distance apart. The matter of a quark star, on the other hand, has no bags of quarks. Its X-ray emissions indicate that it has a surface temperature of about 1 million degrees Celsius pretty hot, but only half the temperature expected for a neutron star so young.

A zombie star is a hypothetical result of a Type Iax supernova which leaves behind a remnant star, rather than completely dispersing the stellar mass. Type Iax supernovae are similar to Type Ia, but have a lower ejection velocity and lower luminosity. Pa 30 and Parker's Star have previously been proposed as the result of a merger of two white dwarf stars in a binary system, which is known as a “Type Iax supernova: a.k.a. a “zombie star.” The first zombie Star was discovered in 2005, hyper-velocity stars move through space at such a high speed that they will escape from our galaxy at some point. Despite an intense search no more than two dozen HVS have been discovered up to now. The zombie star can become a Vampire Star by consuming fuel and energy from a nearby star to revive itself. It gets its name from the supernatural creation where the monster has died but comes back alive to feast on the living.

In loop quantum gravity theory, a Planck star is a hypothetical astronomical object, theorized as a compact, exotic star, that exists within a black hole's event horizon, created when the energy density of a collapsing star reaches the Planck energy density. Recent work demonstrates that Planck stars may exist inside black holes as part of a cycle between black and white holes. It's approximately equal to 1.6 x 10^-35 m, in other words, it's about 10^-20 times the size of a proton (or about a trillion times smaller than a proton - one of the smallest particles in existence). So, it's very, very tiny.

A black star or dark star is a gravitational object composed of matter. It is a theoretical alternative to the black hole concept from general relativity. The theoretical construct was created through the use of semiclassical gravity theory. Dark stars only exist at high redshifts, making them an observing challenge. The infrared Ultra Deep Field images taken by Hubble were used to look for dark stars, but none were found. This doesn't necessarily mean they don't exist, as there could be less luminous dark stars lurking beyond Hubble's vision. As it turns out, any star greater than 3 solar masses must eventually form such a "dark star" after thermonuclear reactions have ceased, since no known source of pressure can support it. These objects are called "black holes" and this term was first coined by the physicist John Wheeler. Scientists think that out of this rich environment, a new breed of star was born: dark stars. Dark stars are somewhat of a misnomer they're not actually dark. In fact, they're likely some of the biggest and brightest stars in our universe. Yet no one has ever seen one.

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