Bacterial Cell Structure
They are as unrelated to human beings as living things can be, but bacteria are essential to human life and life on planet Earth. Although they are notorious for their role in causing human diseases, from tooth decay to the Black Plague, there are beneficial species that are essential to good health.
The bacterium, despite its simplicity, contains a well-developed cell structure which is responsible for some of its unique biological structures and pathogenicity. Many structural features are unique to bacteria and are not found among archaea or eukaryotes. Because of the simplicity of bacteria relative to larger organisms and the ease with which they can be manipulated experimentally, the cell structure of bacteria has been well studied, revealing many biochemical principles that have been subsequently applied to other organisms.
Low-Mass X-ray Binary
X-ray binaries are a class of binary stars consisting in a normal star and a degenerate compact object, a neutron star or black hole. Material is continuously transferred from the normal star (the donor which usually fills its Roche lobe) to the compact object (the accretor). X-ray binaries are called low-mass X-ray binaries (LMXBs) if the donor is less massive than the accretor and high-mass X-ray binaries (HMXBs) if the opposite is true. X-ray binaries are bright sources of X-rays produced by matter falling from the donor to the accretor, and realising gravitational potential energy. The artist impression shows a LMXB composed by an evolved low-mass star, a red giant (the donor), and a neutron star (the accretor). The infalling material form an accretion disk around the neutron star and jets originates from its poles and are collimated by the magnetic field.
Credits: INAF - Osservatorio Astronomico di Palermo.