Magnetospheric eternally collapsing object
Magnetospheric eternally collapsing objects or MECOs were proposed in 2003 as alternative models for 
A proposed observable difference between MECOs and black holes is that the MECO can produce its own intrinsic magnetic field. An uncharged black hole cannot produce its own magnetic field, though its accretion disc can.
Theoretical model 1
- Eternal collapse 1.1
- Magnetic field 1.2
- Observational evidence 2
- Reception of the MECO model 3
- See also 4
- References 5
In the theoretical model a MECO begins to form in much the same way as a 
As the matter becomes denser and hotter, it glows more brightly. Eventually its interior approaches the 
In fact, the further the collapse the slower the continuing collapse, so that collapse to a singularity would take an infinite time and, unlike a black hole, the MECO never fully collapses. Rather, according to the model it slows down and enters an eternal collapse.
A MECO can carry electric and magnetic properties.
A MECO has a finite size, can carry angular momentum and rotate.
The rotation of an electromagnetically active MECO creates a magnetic field.
Astronomer Rudolph Schild of the Harvard–Smithsonian Center for Astrophysics claimed in 2006 to have found evidence consistent with an intrinsic magnetic field from the black hole candidate in the quasar Q0957+561. Chris Reynolds of the University of Maryland has criticised the MECO interpretation, suggesting instead that the apparent hole in the disc could be filled with very hot, tenuous gas, which would not radiate much and would be hard to see, however Leiter in turn questions the viability of Reynolds' interpretation.
It is expected that future observations by instruments such as the Event Horizon Telescope will either prove that Black Holes exist or provide evidence the MECO model is more realistic.
Reception of the MECO model
There are now incontrovertible evidences that many X-ray binaries and quasars contain massive or super-massive ultra-compact objects. Popularly such ultra-compacts objects are referred to as "Black Holes". Thus any claim such as "quasars do not contain black holes" is met with suspicion. Accordingly, the description of black hole candidates as ECOs or MECOs has not been widely adopted.
Mitra's proof that black holes cannot form is based in part on the argument that in order for a black hole to form, the collapsing matter must travel faster than the speed of light with respect to a fixed observer. In 2002; Paulo Crawford and Ismael Tereno cited this as an example of a "wrong and widespread view," and explain that in order for a frame of reference to be valid, the observer must be moving along a timelike worldline. At or inside the event horizon of a black hole, it is not possible for such an observer to remain fixed; all observers are drawn toward the black hole. Mitra argues that he has proven that the world-line of an in-falling test particle would tend to be lightlike at the event horizon, independent of the definition of 'velocity'.
- A. Mitra, J. Math. Phys. 50, 042502 (2009) (American Institute of Physics)
- A. Mitra, Phys. Rev. D 74, 024010 (2006) (American Physical Soc., USA)
- A. Mitra, MNRAS, 367, L66-L68 (2006) (Royal Astronomical Soc., London)
- A. Mitra, MNRAS, 369, 492–496 (2006) (Royal Astronomical Soc. London)
- A. Mitra, New Astronomy, Volume 12, 146–160 (2006) (Elsevier, Netherlands)
- A. Mitra & N.K. Glendenning, MNRAS 404, L50-L54 (2010) (Royal Astronomical Soc., London)
- Shiga, D.; "Mysterious quasar casts doubt on black holes", New Scientist: Space, 2006. (retrieved 2 December 2014)
- A. Mitra and K. K. Singh, Int. J. Mod. Phys. D 22, 1350054 (2013) (World Scientific)