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'''HH 46/47''' is a complex of [[Herbig-Haro object]]s, located around 450 [[parsec]]s (about 1470 [[light-years]]) away in a [[Bok globule]] near [[Gum nebula]]. [[Astrophysical jet|Jets]] of partially ionized gas emerging from a [[Protostar|young star]] produce visible shocks upon impact with [[Interstellar medium|ambient medium]]. Discovered in 1977, it is one of the most studied HH objects and the first ever jet to be associated with young stars was found in HH 46/47. Four emission nebula HH 46, HH 47A, HH 47C and HH 47D and a jet, HH 47B, have been identified in the complex. It also contains a mostly unipolar molecular outflow, and two large [[Bow shock (aerodynamics)|bow shock]]s on opposite sides of the source star. Overall size of the complex is about 3 parsecs (10 light years).
'''HH 46/47''' is a complex of [[Herbig-Haro object]]s, located around 450 [[parsec]]s (about 1,470 [[light-years]]) away in a [[Bok globule]] near the [[Gum nebula]]. [[Astrophysical jet|Jets]] of partially ionized gas emerging from a [[Protostar|young star]] produce visible shocks upon impact with the [[Interstellar medium|ambient medium]]. Discovered in 1977, it is one of the most studied HH objects and the first jet to be associated with young stars was found in HH 46/47. Four emission nebula, HH 46, HH 47A, HH 47C and HH 47D and a jet, HH 47B, have been identified in the complex. It also contains a mostly unipolar molecular outflow, and two large [[Bow shock (aerodynamics)|bow shock]]s on opposite sides of the source star. The overall size of the complex is about 3 parsecs (10 light years).


==History==
==History==
This object was discovered in 1977 by American astronomer [[R. D. Schwartz]].<ref name=Schwartz1977/> Per naming convention of HH objects, he named two nebulae he found HH 46 and HH 47 i.e, they were the 46th and 47th HH objects to be discovered.<ref name=HerbigCat/> The jet and other nebulae were soon identified in the complex.<ref name=Dopita1982/><ref name=RBHS1991/> This was first jet to be discovered near a protostar. Prior to this, it was unclear how Herbig–Haro objects are formed. One model at that time suggested that they reflect light from embedded stars and hence are [[reflection nebula]]e. Based on spectral similarities between [[Supernova remnant]]s and HH objects, Schwartz theorized in 1975 that HH objects are produced by radiative shocks. In this model [[Stellar wind|winds]] from [[T Tauri stars]] would collide with surrounding medium and generate shocks leading to emission.<ref name="Reipurth1997"/> With the discovery of jet in HH 46/47, it became clear that HH objects were not reflection nebulae, but shock driven emission nebulae which were powered by jets ejected from protostars.<ref name=Raga2018/> Due to its impact on the field, brightness and collimated jet, it is one of the most studied HH objects.<ref name=RBHS1991/><ref name=Reipurth1990/>
This object was discovered in 1977 by American astronomer, [[R. D. Schwartz]].<ref name=Schwartz1977/> In accordance with the naming convention for HH objects, he named two nebulae he found HH 46 and HH 47, as they were the 46th and 47th HH objects to be discovered.<ref name=HerbigCat/> The jet and other nebulae were soon identified in the complex.<ref name=Dopita1982/><ref name=RBHS1991/> This was first jet to be discovered near a protostar. Prior to this, it was unclear how Herbig–Haro objects are formed. One model at that time suggested that they reflect light from embedded stars and hence are [[reflection nebula]]e. Based on spectral similarities between [[supernova remnant]]s and HH objects, Schwartz theorized in 1975 that HH objects are produced by radiative shocks. In this model [[Stellar wind|winds]] from [[T Tauri stars]] would collide with surrounding medium and generate shocks leading to emission.<ref name="Reipurth1997"/> With the discovery of jet in HH 46/47, it became clear that HH objects were not reflection nebulae, but shock driven emission nebulae which were powered by jets ejected from protostars.<ref name=Raga2018/> Due to its impact on the field, brightness and collimated jet, it is one of the most studied HH objects.<ref name=RBHS1991/><ref name=Reipurth1990/>
[[File:HH 47 Jet HST video.ogv|thumb|[[Hubble space telescope]] video shows material is moving away from the source. Changes in brightness over the period of 14 years can be noted. ]]
[[File:HH 47 Jet HST video.ogv|thumb|[[Hubble space telescope]] video shows material is moving away from the source. Changes in brightness over the period of 14 years can be noted. ]]


==Formation==
==Formation==
During early stages of formation, stars launch [[bipolar outflow]]s of partially ionized material along the rotation axis. It is generally believed that interaction of [[accretion disk]] magnetic fields with [[stellar magnetic field]] propels some of the accreting material in the form of outflows. In some cases, outflow is collimated into [[Astrophysical jet|jet]]s.<ref name=JBally2016/> The source of HH 46/47 is a [[Binary star|binary]] [[Protostar#Observed_classes_of_young_stars|class I protostar]] located inside the dark cloud of gas and dust, invisible at visual wavelengths. It is ejecting material at about 150 km/s{{efn|1=This is with respect to star. Space velocity is 300 km/s.<ref name="Hartigan1994"/>}} into a bipolar jet which emerges out of the cloud.{{efn|1=Receding jet is a bit slower at 125 km/s with respect to star.<ref name=RBHS1991/>}} Upon impact the jet drives shocks in the surrounding medium, which lead to emission in the visible spectrum.<ref name=Alma2013/> Variations in eruptions lead to different velocities of ejected material. This leads to shocks within the jet, making it visible.<ref name="Hartigan1994"/>
During early stages of formation, stars launch [[bipolar outflow]]s of partially ionized material along the rotation axis. It is generally believed that the interaction of [[accretion disk]] magnetic fields with [[stellar magnetic field]]s propels some of the accreting material in the form of outflows. In some cases, outflow is collimated into [[Astrophysical jet|jet]]s.<ref name=JBally2016/> The source of HH 46/47 is a [[Binary star|binary]] [[Protostar#Observed_classes_of_young_stars|class I protostar]] located inside a dark cloud of gas and dust, invisible at visual wavelengths. It is ejecting material at about 150 km/s{{efn|1=This is with respect to star. Space velocity is 300 km/s.<ref name="Hartigan1994"/>}} into a bipolar jet which emerges out of the cloud.{{efn|1=Receding jet is a bit slower at 125 km/s with respect to star.<ref name=RBHS1991/>}} Upon impact the jet drives shocks in the surrounding medium, which lead to emission in the visible spectrum.<ref name=Alma2013/> Variations in eruptions lead to different velocities of ejected material. This leads to shocks within the jet, making it visible.<ref name="Hartigan1994"/>


==Properties==
==Properties==
[[File:Baby Star HH 46 47.jpg|thumb|left|upright=1.3|Star (center), approaching lobe (top left) and receding lobe (lower right) are clearly visible in this infrared image by [[Spitzer Space Telescope|Spitzer]]. Absence of molecular outflow in approaching lobe is evident. This structure is 0.57 parsec across.]]
[[File:Baby Star HH 46 47.jpg|thumb|left|upright=1.3|Star (center), approaching lobe (top left) and receding lobe (lower right) are clearly visible in this infrared image by [[Spitzer Space Telescope|Spitzer]]. Absence of molecular outflow in approaching lobe is evident. This structure is 0.57 parsec across.]]
Although the outflow is bipolar, only one jet is visible. The counterjet is [[redshift]]ed (moving away from Earth) and is invisible at visual wavelengths due to dark cloud. At infrared wavelengths, however, it is clearly visible. It terminates in HH 47C, a bright bow shock, as it interacts with the surrounding gas.<ref name=JBally2016/> HH 46 is located near the source and is an emission/reflection nebula; it reflects light from the source in addition to emission caused by the jet. Its brightness changes radically in the course of years, which is directly related to variability of the parent star. From HH 46 emerges HH 47B, a long and twisted jet which is [[blueshift]]ed. The bent and twisted appearance of the outflow is caused by variations in the ejection direction, i.e., precession of the source star.<ref name="Reipurth1997"/> The jet ends in HH 47, also called HH 47A, the brightest nebula in the entire complex. A little farther is somewhat fainter and diffuse HH 47D.<ref name="Schwartz1983"/> The complex stretches across 0.57 parsecs from HH 47C to HH 47D on the sky plane.<ref name="Reipurth1997"/> Two relatively large bow shocks appear at even larger distances, with HH 47SW lying on the far side of the receding lobe and HH 47NE lying on the near side of the approaching blueshifted lobe. Each of them is about the 1.3 parsecs from the source star, making whole complex 2.6 parsecs long.<ref name=JBally2016/><ref name=Stanke1999/> Whole structure is projected at approximately 30° with respect to sky plane; this makes actual length around 3 parsecs.<ref name=Stanke1999/>
Although the outflow is bipolar, only one jet is visible. The counterjet is [[redshift]]ed (moving away from Earth) and is invisible at visual wavelengths due to dark cloud. At infrared wavelengths, however, it is clearly visible. It terminates in HH 47C, a bright bow shock, as it interacts with the surrounding gas.<ref name=JBally2016/> HH 46 is located near the source and is an emission/reflection nebula; it reflects light from the source and from the emission caused by the jet. Its brightness changes radically in the course of years, which is directly related to the variability of the parent star. From HH 46HH emerges 47B, a long and twisted jet which is [[blueshift]]ed. The bent and twisted appearance of the outflow is caused by variations in the ejection direction, i.e., precession of the source star.<ref name="Reipurth1997"/> The jet ends in HH 47, also called HH 47A, the brightest nebula in the complex. A little farther is the somewhat fainter and more diffuse HH 47D.<ref name="Schwartz1983"/> The complex stretches across 0.57 parsecs from HH 47C to HH 47D on the sky plane.<ref name="Reipurth1997"/> Two relatively large bow shocks appear at even larger distances, with HH 47SW lying on the far side of the receding lobe and HH 47NE lying on the near side of the approaching blueshifted lobe. Each of them is about the 1.3 parsecs from the source star, making whole complex appear 2.6 parsecs long in the sky plane.<ref name=JBally2016/><ref name=Stanke1999/> The whole structure is projected at approximately 30° with respect to the sky plane; this makes its actual length around 3 parsecs.<ref name=Stanke1999/>
[[File:Ssc2003-06g.jpg|thumb|upright=1.3|[[Infrared spectroscopy|Infrared spectrum]] of the gaseous envelope of [[HH-47|HH 46/47]], obtained by [[NASA]] [[Spitzer Space Telescope]]. The medium in immediate vicinity of the star is silicate-rich.|alt=Plot of light intensity vs wavelength has several dips in it, caused by absorption of light emitted from the star by the molecules in surrounding medium]]
[[File:Ssc2003-06g.jpg|thumb|upright=1.3|[[Infrared spectroscopy|Infrared spectrum]] of the gaseous envelope of [[HH-47|HH 46/47]], obtained by [[NASA]] [[Spitzer Space Telescope]]. The medium in immediate vicinity of the star is silicate-rich.|alt=Plot of light intensity vs wavelength has several dips in it, caused by absorption of light emitted from the star by the molecules in surrounding medium]]


Combined luminosity of the source star and disk is about 24 [[Solar luminosity|{{Solar luminosity}}]]. It is accreting mass at the rate of {{val|6e-6}} [[Solar mass|{{Solar mass}}]] per year. Mass loss rate in the approaching jet has been determined to be about {{val|4e-7}} {{Solar mass}} per year, which is approximately 7% of the total mass accreted in a year. Around 3.6% of total material in the jet is ionized and average jet density is roughly 1400 cm<sup>-3</sup>. [[Moving shock|Shock velocity]] in the jet is about 34 km/s.<ref name="Hartigan1994"/>
The combined luminosity of the source star and disk is about 24 [[Solar luminosity|{{Solar luminosity}}]]. It is accreting mass at the rate of {{val|6e-6}} [[Solar mass|{{Solar mass}}]] per year. Mass loss rate in the approaching jet has been determined to be about {{val|4e-7}} {{Solar mass}} per year, which is approximately 7% of the total mass accreted in a year. Around 3.6% of total material in the jet is ionized and average jet density is roughly 1400 cm<sup>-3</sup>. [[Moving shock|Shock velocity]] in the jet is about 34 km/s.<ref name="Hartigan1994"/>


Eruptions from the star are episodic. Current episode has been ongoing for about a thousand years, while previous episode started about 6000 years ago and lasted for 3,000 to 4,000 years.<ref name=Reipurth1990/> Large eruptions in current episode occur every 400 years. Based on the extent of the complex, age of the source star has been estimated to be 10<sup>4</sup> to 10<sup>5</sup> years.<ref name=Hartigan2005/>
Eruptions from the star are episodic. The current episode has been ongoing for about a thousand years, while the previous episode started about 6,000 years ago and lasted for 3,000 to 4,000 years.<ref name=Reipurth1990/> Large eruptions in the current episode occur every 400 years. Based on the extent of the complex, the age of the source star has been estimated to be 10<sup>4</sup> to 10<sup>5</sup> years.<ref name=Hartigan2005/>


===Molecular outflow===
===Molecular outflow===
Jet emanating from the star is transferring momentum into molecular gas surrounding it, which lifts up the gas. This results in a 0.3 parsec long molecular outflow around the jet.<ref name=JBally2016/> This outflow, however, is largely unipolar and aligned with the receding jet. Approaching molecular outflow is extremely weak, which is probably because jet breaks out of the cloud and there is little material outside to be lifted up in form of molecular outflow.<ref name="Reipurth1997"/> Speeds in molecular flows are much less than in jets. Several organic and inorganic compounds have been detected in the molecular outflow including [[methane]], [[methanol]], [[water]] ([[ice]]), [[carbon monoxide]], [[carbon dioxide]] ([[dry ice]]) and various [[silicates]]. Presence of ices implies that dusty shroud of the star is cool as opposed to jet and shock regions where temperatures reach thousands of degrees.<ref name=Noriega2004/><ref name=Spitzeroutflow/>
The jet emanating from the star is transferring momentum into the molecular gas surrounding it, which lifts up the gas. This results in a 0.3 parsec long molecular outflow around the jet.<ref name=JBally2016/> This outflow, however, is largely unipolar and aligned with the receding jet. Approaching molecular outflow is extremely weak, which is probably because the jet breaks out of the cloud and there is little material outside to be lifted up in the form of molecular outflow.<ref name="Reipurth1997"/> Speeds in molecular flows are much less than in jets. Several organic and inorganic compounds have been detected in the molecular outflow including [[methane]], [[methanol]], [[water]] [[ice]], [[carbon monoxide]], [[carbon dioxide]] ([[dry ice]]) and various [[silicates]]. The presence of ices implies that the dusty shroud of the star is cool as opposed to the jet and shock regions where temperatures reach thousands of degrees.<ref name=Noriega2004/><ref name=Spitzeroutflow/>


==See also==
==See also==

Revision as of 20:03, 13 June 2018

For the helicopter, see Boeing CH-47 Chinook § HH-47.
HH 46/47
Emission nebula
Herbig–Haro object
HH object 46/47. HH 46 is the nebula on lower left, while HH 47 is in the upper right. HH 47B connects the two.
Observation data: J2000 epoch
Right ascension08h 25m 43.6s[1]
Declination−51° 00′ 36″[1]
Distance1470 ly   (450 pc)
ConstellationVela
DesignationsHH 46/47, HH 46, HH 47.
See also: Lists of nebulae

HH 46/47 is a complex of Herbig-Haro objects, located around 450 parsecs (about 1,470 light-years) away in a Bok globule near the Gum nebula. Jets of partially ionized gas emerging from a young star produce visible shocks upon impact with the ambient medium. Discovered in 1977, it is one of the most studied HH objects and the first jet to be associated with young stars was found in HH 46/47. Four emission nebula, HH 46, HH 47A, HH 47C and HH 47D and a jet, HH 47B, have been identified in the complex. It also contains a mostly unipolar molecular outflow, and two large bow shocks on opposite sides of the source star. The overall size of the complex is about 3 parsecs (10 light years).

History

This object was discovered in 1977 by American astronomer, R. D. Schwartz.[2] In accordance with the naming convention for HH objects, he named two nebulae he found HH 46 and HH 47, as they were the 46th and 47th HH objects to be discovered.[3] The jet and other nebulae were soon identified in the complex.[4][5] This was first jet to be discovered near a protostar. Prior to this, it was unclear how Herbig–Haro objects are formed. One model at that time suggested that they reflect light from embedded stars and hence are reflection nebulae. Based on spectral similarities between supernova remnants and HH objects, Schwartz theorized in 1975 that HH objects are produced by radiative shocks. In this model winds from T Tauri stars would collide with surrounding medium and generate shocks leading to emission.[6] With the discovery of jet in HH 46/47, it became clear that HH objects were not reflection nebulae, but shock driven emission nebulae which were powered by jets ejected from protostars.[7] Due to its impact on the field, brightness and collimated jet, it is one of the most studied HH objects.[5][8]

Hubble space telescope video shows material is moving away from the source. Changes in brightness over the period of 14 years can be noted.

Formation

During early stages of formation, stars launch bipolar outflows of partially ionized material along the rotation axis. It is generally believed that the interaction of accretion disk magnetic fields with stellar magnetic fields propels some of the accreting material in the form of outflows. In some cases, outflow is collimated into jets.[9] The source of HH 46/47 is a binary class I protostar located inside a dark cloud of gas and dust, invisible at visual wavelengths. It is ejecting material at about 150 km/s[a] into a bipolar jet which emerges out of the cloud.[b] Upon impact the jet drives shocks in the surrounding medium, which lead to emission in the visible spectrum.[11] Variations in eruptions lead to different velocities of ejected material. This leads to shocks within the jet, making it visible.[10]

Properties

Star (center), approaching lobe (top left) and receding lobe (lower right) are clearly visible in this infrared image by Spitzer. Absence of molecular outflow in approaching lobe is evident. This structure is 0.57 parsec across.

Although the outflow is bipolar, only one jet is visible. The counterjet is redshifted (moving away from Earth) and is invisible at visual wavelengths due to dark cloud. At infrared wavelengths, however, it is clearly visible. It terminates in HH 47C, a bright bow shock, as it interacts with the surrounding gas.[9] HH 46 is located near the source and is an emission/reflection nebula; it reflects light from the source and from the emission caused by the jet. Its brightness changes radically in the course of years, which is directly related to the variability of the parent star. From HH 46HH emerges 47B, a long and twisted jet which is blueshifted. The bent and twisted appearance of the outflow is caused by variations in the ejection direction, i.e., precession of the source star.[6] The jet ends in HH 47, also called HH 47A, the brightest nebula in the complex. A little farther is the somewhat fainter and more diffuse HH 47D.[12] The complex stretches across 0.57 parsecs from HH 47C to HH 47D on the sky plane.[6] Two relatively large bow shocks appear at even larger distances, with HH 47SW lying on the far side of the receding lobe and HH 47NE lying on the near side of the approaching blueshifted lobe. Each of them is about the 1.3 parsecs from the source star, making whole complex appear 2.6 parsecs long in the sky plane.[9][13] The whole structure is projected at approximately 30° with respect to the sky plane; this makes its actual length around 3 parsecs.[13]

Plot of light intensity vs wavelength has several dips in it, caused by absorption of light emitted from the star by the molecules in surrounding medium
Infrared spectrum of the gaseous envelope of HH 46/47, obtained by NASA Spitzer Space Telescope. The medium in immediate vicinity of the star is silicate-rich.

The combined luminosity of the source star and disk is about 24 L☉. It is accreting mass at the rate of 6×10−6 M☉ per year. Mass loss rate in the approaching jet has been determined to be about 4×10−7 M☉ per year, which is approximately 7% of the total mass accreted in a year. Around 3.6% of total material in the jet is ionized and average jet density is roughly 1400 cm-3. Shock velocity in the jet is about 34 km/s.[10]

Eruptions from the star are episodic. The current episode has been ongoing for about a thousand years, while the previous episode started about 6,000 years ago and lasted for 3,000 to 4,000 years.[8] Large eruptions in the current episode occur every 400 years. Based on the extent of the complex, the age of the source star has been estimated to be 104 to 105 years.[14]

Molecular outflow

The jet emanating from the star is transferring momentum into the molecular gas surrounding it, which lifts up the gas. This results in a 0.3 parsec long molecular outflow around the jet.[9] This outflow, however, is largely unipolar and aligned with the receding jet. Approaching molecular outflow is extremely weak, which is probably because the jet breaks out of the cloud and there is little material outside to be lifted up in the form of molecular outflow.[6] Speeds in molecular flows are much less than in jets. Several organic and inorganic compounds have been detected in the molecular outflow including methane, methanol, water ice, carbon monoxide, carbon dioxide (dry ice) and various silicates. The presence of ices implies that the dusty shroud of the star is cool as opposed to the jet and shock regions where temperatures reach thousands of degrees.[15][16]

See also

Notes

  1. ^ This is with respect to star. Space velocity is 300 km/s.[10]
  2. ^ Receding jet is a bit slower at 125 km/s with respect to star.[5]

References

  1. ^ a b Reipurth, B. (1999). "A general catalogue of Herbig-Haro objects" (2 ed.).
  2. ^ Schwartz, R. D. (February 1977). "Evidence of star formation triggered by expansion of the Gum Nebula". Astrophysical Journal Letters. 212: L25–L26. Bibcode:1977ApJ...212L..25S. doi:10.1086/182367.
  3. ^ Herbig, G. H. (1974). "Draft Catalog of Herbig-Haro Objects". Lick Observatory Bulletin (658): 1–11. Bibcode:1974LicOB.658....1H.
  4. ^ Dopita, M. A.; Schwartz, R. D.; Evans, I. (December 1982). "Herbig-Haro Objects 46 and 47 - Evidence for bipolar ejection from a young star". Astrophysical Journal Letters. 263: L73–L77. Bibcode:1982ApJ...263L..73D. doi:10.1086/183927.
  5. ^ a b c Reipurth, B.; Heathcote, S. (June 1991). "The jet and energy source of HH 46/47". Astronomy and Astrophysics. 246 (2): 511–534. Bibcode:1991A&A...246..511R.
  6. ^ a b c d Reipurth, B. (1997). "50 Years of Herbig–Haro Research. From discovery to HST". In Reipurth, B.; Bertout, C. (eds.). Herbig–Haro Flows and the Birth of Stars. IAU Symposium No. 182. Kluwer Academic Publishers. pp. 3–18. Bibcode:1997IAUS..182....3R. {{cite conference}}: Unknown parameter |booktitle= ignored (|book-title= suggested) (help)
  7. ^ Raga, A. C.; Velázquez, P. F.; Noriega-Crespo, A. (April 2018). "Is HH 47 Slowing Down?". Revista Mexicana de Astronomía y Astrofísica. 54: 261–270. Bibcode:2018RMxAA..54..261R.
  8. ^ a b Reipurth, B. (1991). Lada, C. J.; Kylafis, N. D. (eds.). Herbig–Haro objects. Dordrecht, Netherlands: Springer. pp. 497–530. doi:10.1007/978-94-011-3642-6_15. ISBN 978-94-011-3642-6. {{cite book}}: Unknown parameter |booktitle= ignored (help)
  9. ^ a b c d Bally, J. (September 2016). "Protostellar Outflows". Annual Review of Astronomy and Astrophysics. 54: 491–528. Bibcode:2016ARA&A..54..491B. doi:10.1146/annurev-astro-081915-023341.
  10. ^ a b c Hartigan, P.; Morse, J. A.; Raymond, J. (November 1994). "Mass-loss rates, ionization fractions, shock velocities, and magnetic fields of stellar jets". Astrophysical Journal. 436 (1): 125–143. Bibcode:1994ApJ...436..125H. doi:10.1086/174887.
  11. ^ Foncea, Valeria; Arce; Héctor (20 August 2013). "ALMA Takes Close Look at Drama of Starbirth". Atacama Large Millimeter/Submillimeter Array. Archived from the original on 27 September 2013. Retrieved 11 October 2013. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  12. ^ Schwartz, R. D. (1983). "Herbig–Haro Objects". Annual Review of Astronomy and Astrophysics. 21: 209–237. Bibcode:1983ARA&A..21..209S. doi:10.1146/annurev.aa.21.090183.001233.
  13. ^ a b Stanke, T.; McCaughrean, M. J.; Zinnecker, H. (October 1999). "HH46/47: Also a parsec scale flow". Astronomy and Astrophysics. 350: L43–L46. arXiv:astro-ph/9909357. Bibcode:1999A&A...350L..43S.
  14. ^ Hartigan, P.; Heathcote, S.; Morse, J. A.; et al. (November 2005). "Proper Motions of the HH 47 Jet Observed with the Hubble Space Telescope". Astronomical Journal. 130 (5): 2197–2205. arXiv:astro-ph/0507526. Bibcode:2005AJ....130.2197H. doi:10.1086/491673.
  15. ^ Noriega-Crespo, A.; Morris, P.; Marleau, F. R.; et al. (September 2009). "A New Look at Stellar Outflows: Spitzer Observations of the HH 46/47 System". Astrophysical Journal Supplement Series. 154 (1): 352–358. Bibcode:2004ApJS..154..352N. doi:10.1086/422819.
  16. ^ "Embedded Outflow in HH 46/47". NASA Spitzer Space Telescope. Jet Propulsion Laboratory, California Institute of Technology. December 18, 2003. Retrieved May 31, 2018.
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