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

About Me

Hello, my name is Martin Rusterholz. I’m a Swiss amateur astrophotographer living near Zurich, the biggest town in Switzerland. My interest in astronomy started when I was 16. At that time, I built my first Newtonian telescope and mount. I studied physics at the Swiss Federal Institute of Technology (ETH) which was the only study including at least some aspects of astronomy and astrophysics. “Looking at the nights sky is an experience touching everybody deeply inside, something common to all human beings independent to the language spoken by the individuals”. Deep-sky astrophotography is my passion.