AFGL 5173 in Orion

AFGL 5173 Nebula - Astrophotography Martin Rusterholz

​Lying at a dis­tance of 6500 light years, AFGL 5173 (also known as RAFGL 5173 and G192.16–3.82) is a com­pact HII region with the reflec­tion neb­ula Parsami­an 4. It’s most strik­ing fea­ture are a pair of Herb­ig Haro objects HH 396 and HH 397 that rep­res­ent a giant Herb­ig Haro out­flow with a length of 18 arcminutes or 32 light years! This is one of the largest and bright­est known Herb­ig Haro com­plexes and is powered by a mod­er­ately massive protostar.

The HH 396–7 out­flow is com­prised of mul­tiple Herb­ig Haro objects with HH 396 to the right and HH 397 to the left. They are the res­ult of jets from a pro­tostar and the optic­ally vis­ible nebu­los­ity is pro­duced either when fast mov­ing ejecta over­take slow mov­ing ejecta or when the ejec­ted mater­i­al impacts ambi­ent gas in the sur­round­ing area. This pro­duces shocks and the energy gen­er­ated ion­izes the ejec­ted gas and makes it glow in both optic­al and infrared wavelengths. The struc­ture of the bipolar out­flow indic­ates mul­tiple epis­odes of ejecta events.

The pro­tostar respons­ible for driv­ing the HH 396–7 out­flow isn’t vis­ible optic­ally and is shrouded behind a veil of dust. Stud­ies by pro­fes­sion­al astro­nomers with radio tele­scopes have detec­ted a rotat­ing cir­cum­s­tel­lar disk around this pro­tostar. Usu­ally out­flows and Herb­ig Haro objects are a con­sequence of excess mater­i­al fall­ing from the disk onto the star. The age of the out­flow has been estim­ated to be between 10,000 and 100,000 years. In the south­ern half of this deep image, extremely faint emis­sion nebu­los­ity is also vis­ible, which is likely to be uncata­logued and pre­vi­ously unknown.

[descrip­tion from Sakib Rasool]


RCOS 14.5″ f/​8
Apo­gee U16M
Astro­don Gen2
HaLRGB 1200:440:180:180:180 min.
ROSA Remote Obser­vat­or­ies South­ern Alps
© Mar­tin Ruster­holz, Astrophotographer

Find­er Chart AFGL 5173 in Orion

AFGL 5173 Nebula Sky Chart - Astrophotography Martin Rusterholz

Image cre­ated by Skychart