The phenomenology of jet in astrophysics was studied. Analytical methods were used to obtain an equation for describing jet motion. From the analysis, we understood that βT > 1, where βT is the apparent jet velocity along the observers line of sight. The observed motions of the components show curvatures and changes in velocity. Curved trajectories are due to observed perpendicular acceleration, while variations in velocity are due to changes in apparent parallel acceleration.
Astrophysical jets are observed in the Universe in a large variety of environments and under a wide range of sizes and powers. They are generated in active galactic nuclei (AGNs) and YSOs, can travel up to a few thousands of Megaparsecs, and reach the largest powers observed in the Universe (up to ∼1047−48 erg s−1), (Zanni et al., 2003; Godfrey and Shabala, 2013). Astrophysical jets can be found in giant molecular clouds, emanating in the vicinities of young stellar objects (YSOs), and reaching distances of some parsecs (Reipurth and Bally, 2001). They are also located near neutron stars in galactic X-ray binary star systems, such as GRS 1915 + 105 that behave as microquasars generating relativistic jets (Fender, 2004). Astrophysical jets can be found in the asymptotic giant branch (post-AGB) stars as well in pre-planetary and planetary nebulae. Opposite, precessing jets are observed in the SS433 binary source, leading to a peculiar phenomenology (Frank, 2011). A jet-like structure is observed, at X-ray energies, inside the Crab Nebula departing from the embedded pulsar (Hester, 2008). Finally, jets can be at the base of the phenomenology of gamma-ray bursts, observed at the highest radiation energies that are still elusive phenomena because of their extreme distances (Granot, 2007).