HH 1/2

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
Declination	−06° 46′ 03″
Distance	1500 ly
Constellation	Orion
Designations	HH 1-2, HH 1/2, HH 1, HH 2
	See also: Lists of nebulae

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]

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.

References

^ ^a ^b "HH 1-2". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-02-15.
^ ^a ^b ^c ^d Bally, John; Heathcote, Steve; Reipurth, Bo; Morse, Jon; Hartigan, Patrick; Schwartz, Richard (May 2002). "Hubble Space Telescope Observations of Proper Motions in Herbig-Haro Objects 1 and 2". The Astronomical Journal. 123 (5): 2627–2657. Bibcode:2002AJ....123.2627B. doi:10.1086/339837. ISSN 0004-6256. S2CID 118242041.
^ ^a ^b Herbig, George H. (May 1951). "The Spectra of Two Nebulous Objects Near NGC 1999". The Astrophysical Journal. 113: 697–699. Bibcode:1951ApJ...113..697H. doi:10.1086/145440. ISSN 0004-637X.
^ Haro, Guillermo (May 1952). "Herbig's Nebulous Objects Near NGC 1999". The Astrophysical Journal. 115: 572. Bibcode:1952ApJ...115..572H. doi:10.1086/145576. ISSN 0004-637X.
^ Raga, A. C.; Reipurth, Bo; Castellanos-Ramírez, A.; Chiang, Hsin-Fang; Bally, J. (October 2015). "High Angular Resolution Multi-line Study of HH 1 and 2". The Astronomical Journal. 150 (4): 105. Bibcode:2015AJ....150..105R. doi:10.1088/0004-6256/150/4/105. ISSN 0004-6256. S2CID 125612968.
^ Herbig, G. H.; Jones, B. F. (August 1981). "Large proper motions of the Herbig-Haro objects HH 1 and HH 2". The Astronomical Journal. 86: 1232–1244. Bibcode:1981AJ.....86.1232H. doi:10.1086/113003. ISSN 0004-6256.
^ Pravdo, Steven H.; Feigelson, Eric D.; Garmire, Gordon; Maeda, Yoshitomo; Tsuboi, Yohko; Bally, John (October 2001). "Discovery of X-rays from the protostellar outflow object HH2". Nature. 413 (6857): 708–711. Bibcode:2001Natur.413..708P. doi:10.1038/35099508. ISSN 0028-0836. PMID 11607024. S2CID 13878953.
^ Bohigas, J.; Torrelles, J. M.; Echevarria, J.; Canto, J.; Enriquez, R.; Firmani, C.; Gutierrez, L.; Ruiz, E.; Salas, L. (December 1985). "Optical images of the region around HH1 and HH2 taken with the MEPSICRON system". Revista Mexicana de Astronomía y Astrofísica. 11: 149–157. Bibcode:1985RMxAA..11..149B. ISSN 0185-1101.
^ Rodríguez, Luis F.; Delgado-Arellano, Víctor G.; Gómez, Yolanda; Reipurth, Bo; Torrelles, José M.; Noriega-Crespo, Alberto; Raga, Alejandro C.; Cantó, Jorge (February 2000). "New VLA Observations of the HH 1-2 Region: Evidence for Density Enhancements Moving along the Axis of the VLA 1 Radio Jet". The Astronomical Journal. 119 (2): 882–889. Bibcode:2000AJ....119..882R. doi:10.1086/301231. ISSN 0004-6256. S2CID 59520064.
^ "HH 1-2 VLA 1". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-02-15.
^ Reipurth, Bo; Heathcote, Steve; Roth, M.; Noriega-Crespo, A.; Raga, A. C. (May 1993). "A New Herbig-Haro Flow in the HH 1--2 Complex". The Astrophysical Journal. 408: L49. Bibcode:1993ApJ...408L..49R. doi:10.1086/186828. ISSN 0004-637X.
^ Hester, J. Jeff; Stapelfeldt, Karl R.; Scowen, Paul A. (July 1998). "Hubble Space Telescope Wide Field Planetary Camera 2 Observations of HH 1-2". The Astronomical Journal. 116 (1): 372–395. Bibcode:1998AJ....116..372H. doi:10.1086/300396. ISSN 0004-6256.
^ Noriega-Crespo, A.; Raga, A. C. (May 2012). "Spitzer Observations of the HH 1/2 System: The Discovery of the Counterjet". The Astrophysical Journal. 750 (2): 101. arXiv:1203.1032. Bibcode:2012ApJ...750..101N. doi:10.1088/0004-637X/750/2/101. ISSN 0004-637X. S2CID 1793062.