HH 1/2

The Herbig-Haro objects HH 1/2 are the first such objects to be recognized as Herbig-Haro objects and were discovered by George Herbig and Guillermo Haro.^[3][4][2][5] They are located at a distance of about 1343 light-years (412 parsec) in the constellation Orion near NGC 1999.^[3] HH 1/2 are among the brightest Herbig-Haro objects in the sky and consist of a pair of oppositely oriented bow shocks, separated by 2.5 arcminutes (a projected separation of about 1.1 light year). The HH 1/2 pair were the first Herbig-Haro objects with detected proper motion^[6] and HH 2 was the first Herbig-Haro object to be detected in x-rays.^[7] Some of the structures in the Herbig-Haro Objects move with a speed of 400 km/s.^[2]

HH 1/2

Emission nebula
Herbig–Haro object
Hubble Space Telescope WFC3 image of HH 1/2 and the jet pointing to HH 1 (right)
Observation data: J2000.0 epoch
Right ascension	05h 36m 22.8s[1]
Declination	−06° 46′ 03″[1]
Distance	1500[2] ly
Constellation	Orion[2]
Designations	HH 1-2, HH 1/2, HH 1, HH 2
See also: Lists of nebulae

The central region

The central region contains an opaque cloud core with an astrophysical jet^[8] and a highly embedded multiple-star system that remains invisible below 3 Microns. These sources were first detected with the Very Large Array and are therefore named VLA 1 and 2.^[9] The source HH 1-2 VLA 1^[10] drives the HH 1/2 pair and the source VLA 2 drives the Herbig-Haro objects HH 144/145.^[11] There might be even a third outflow in the central region of HH 1/2, indicating a third member.^[12]

The jet towards HH 1 is visible in optical images, but the counterjet towards HH 2 was detected in the infrared with the Spitzer Space Telescope.^[13]

Gallery

• 
  An older version of the region mapped by the WFPC2 of the Hubble Space Telescope. The image also shows the jet in the lower right part in more detail
• 
  Multiple Herbig-Haro Objects mapped by the Hubble Space Telescope, including HH 2 at the lower right. HH 47 is at the top part and part of HH 34 is at the lower left.
• 
  The reflection nebula NGC 1999 (blue cloud in the center) and the Herbig-Haro Objects HH 1/2 below NGC 1999 as small pink clouds.