bow shocks seen at for example Earth. These observations were all made near perihelion when the bow shocks already were fully developed. The Rosetta spacecraft followed comet 67P/Churyumov–Gerasimenko from far out in the solar system, at a heliocentric distance of 3.6 AU, in toward perihelion at 1.24 AU, and back out again. This allowed Rosetta to observe the bow shock as it formed when the outgassing increased during the comet's journey toward the Sun. In this early state of development the shock was called the "infant bow shock". The infant bow shock is asymmetric and, relative to the distance to the nucleus, wider than fully developed bow shocks. Around the Sun For several decades, the solar wind has been thought to form a bow shock at the edge of the heliosphere, where it collides with the surrounding interstellar medium. Moving away from the Sun, the point where the solar wind flow becomes subsonic is the termination shock, the point where the interstellar medium and solar wind pressures balance is the heliopause, and the point where the flow of the interstellar medium becomes subsonic would be the bow shock. This solar bow shock was thought to lie at a distance around 230 AU from the Sun – more than twice the distance of the termination shock as encountered by the Voyager spacecraft. However, data obtained in 2012 from NASA's Interstellar Boundary Explorer (IBEX) indicates the lack of any solar bow shock. Along with corroborating results from the Voyager spacecraft, these findings have motivated some theoretical refinements; current thinking is that formation of a bow shock is prevented, at least in the galactic region through which the Sun is passing, by a combination of the strength of the local interstellar magnetic-field and of the relative velocity of the heliosphere. Around other stars In 2006, a far infrared bow shock was detected near the AGB star R Hydrae. Bow shocks are also a common feature in Herbig Haro objects, in which a much stronger collimated outflow of gas and dust from the star interacts with the interstellar medium, producing bright bow shocks that are visible at optical wavelengths. The Hubble Space Telescope captured these images of bow shocks made of dense gasses and plasma in the Orion Nebula. Around massive stars If a massive star is a runaway star, it can form an infrared bow-shock that is detectable in 24 μm and sometimes