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[[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"/>
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 thousand years, while previous episode started about 6000 years ago and lasted for 3000–4000 years.<ref name=Reipurth1990/>


===Molecular outflow===
===Molecular outflow===
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<ref name=Alma2013>{{cite web|url=http://www.almaobservatory.org/en/press-room/press-releases/632-alma-takes-close-look-at-drama-of-starbirth|title=ALMA Takes Close Look at Drama of Starbirth|last=Foncea|first=Valeria|author2=Arce|author3=Héctor|date=20 August 2013|work=Atacama Large Millimeter/Submillimeter Array|accessdate=11 October 2013|deadurl=yes|archiveurl=https://web.archive.org/web/20130927154903/http://www.almaobservatory.org/en/press-room/press-releases/632-alma-takes-close-look-at-drama-of-starbirth|archivedate=27 September 2013|df=}}</ref>
<ref name=Alma2013>{{cite web|url=http://www.almaobservatory.org/en/press-room/press-releases/632-alma-takes-close-look-at-drama-of-starbirth|title=ALMA Takes Close Look at Drama of Starbirth|last=Foncea|first=Valeria|author2=Arce|author3=Héctor|date=20 August 2013|work=Atacama Large Millimeter/Submillimeter Array|accessdate=11 October 2013|deadurl=yes|archiveurl=https://web.archive.org/web/20130927154903/http://www.almaobservatory.org/en/press-room/press-releases/632-alma-takes-close-look-at-drama-of-starbirth|archivedate=27 September 2013|df=}}</ref>


<ref name="Reipurth1997">{{cite conference |date=1997 |title=50 Years of Herbig–Haro Research. From discovery to HST |booktitle=Herbig–Haro Flows and the Birth of Stars |conference=IAU Symposium No. 182 |editor1=Reipurth, B. |editor2=Bertout, C. |publisher=[[Kluwer Academic Publishers]] |pages=3–18 |bibcode=1997IAUS..182....3R}}</ref>
<ref name="Reipurth1997">{{cite conference |date=1997 |author=Reipurth, B. |title=50 Years of Herbig–Haro Research. From discovery to HST |booktitle=Herbig–Haro Flows and the Birth of Stars |conference=IAU Symposium No. 182 |editor1=Reipurth, B. |editor2=Bertout, C. |publisher=[[Kluwer Academic Publishers]] |pages=3–18 |bibcode=1997IAUS..182....3R}}</ref>

<ref name=Reipurth1990>{{cite book |author=Reipurth, B. |date=1991 |title=Herbig–Haro objects |booktitle=The Physics of Star Formation and Early Stellar Evolution |editor1=Lada, C. J. |editor2=Kylafis, N. D. |publisher=Springer |location=Dordrecht, Netherlands|pages=497–530 |isbn=978-94-011-3642-6|doi=10.1007/978-94-011-3642-6_15}}</ref>


<ref name=Stanke1999>{{cite journal |author=Stanke, T. |author2=McCaughrean, M. J. |author3=Zinnecker, H. |date=October 1999 |title=HH46/47: Also a parsec scale flow |journal=Astronomy and Astrophysics |volume=350 |pages=L43–L46 |arxiv=astro-ph/9909357|bibcode=1999A&A...350L..43S}}</ref>
<ref name=Stanke1999>{{cite journal |author=Stanke, T. |author2=McCaughrean, M. J. |author3=Zinnecker, H. |date=October 1999 |title=HH46/47: Also a parsec scale flow |journal=Astronomy and Astrophysics |volume=350 |pages=L43–L46 |arxiv=astro-ph/9909357|bibcode=1999A&A...350L..43S}}</ref>

Revision as of 20:00, 2 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 1470 light-years) away in a Bok globule near Gum nebula.[2] 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.[3] It also contains a mostly unipolar molecular outflow.[4]

History

This object was discovered in 1977 by American astronomer R. D. Schwartz.[5] The jet was soon identified in the object. 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.[4] With the discovery of jet in HH 46/47, the jet driven nature of HH objects was understood for the first time.[6]

Formation

During early stages of formation, stars launch bipolar outflows 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 jets.[7] The source of HH 46/47 is a binary 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[a] into a bipolar jet which emerges out of the cloud. Upon impact the jet drives shocks in the surrounding medium, which lead to emission in the visible spectrum.[9] Variations in eruptions lead to different velocities of ejected material. This leads to shocks within the jet, making it visible.[8]

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.[7] 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. From HH 46 emerges HH 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.[4] 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.[2] The complex stretches across 0.57 parsecs from HH 47C to HH 47D on the sky plane.[4] 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.[7][10] Whole structure is inclined at approximately 30° with respect to sky plane; this makes actual length around 3 parsecs.[10]

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.

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.[8] Eruptions from the star are episodic. Current episode has been ongoing for about thousand years, while previous episode started about 6000 years ago and lasted for 3000–4000 years.[11]

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.[7] 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.[4] 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.[12][13]

See also

Notes

  1. ^ This is with respect to star. Space velocity is 300 km/s.[8]

References

  1. ^ a b Reipurth, B. (1999). "A general catalogue of Herbig-Haro objects" (2 ed.).
  2. ^ a b 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.
  3. ^ 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.
  4. ^ a b c d e 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)
  5. ^ 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.
  6. ^ 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.
  7. ^ 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.
  8. ^ 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.
  9. ^ 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)
  10. ^ 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.
  11. ^ 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)
  12. ^ 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.
  13. ^ "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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