NGC1999/L1641N

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Powerful jets of outflowing gas are often the first visible manifestations of the birth of young stars. These jets punch holes through the opaque clouds in which the star is formed, holes through which the light of the new-born stars can escape to produce what are known as reflection nebulae. Several such nebulae are seen in this image.

The bright object below and to the left of center is the reflection nebula NGC1999, which contains the young star V380 Orionis. A small, triangle shaped patch of dusty material is seen in silhouette against the reflection nebula. NGC1999 lies at the center of a network of nebulous filaments which billow out and away like the spokes of a bicycle wheel. These features may trace a wide-angle wind emerging from NGC1999.

Near the upper half of the image, bright young stars in a forming cluster named L1641N light up another reflection nebula which contains several dense clumps of opaque material. Infrared images have identified over 50 forming stars in this region. More than six jets and outflows are erupting from this region.

Outflowing jets from young stars also power luminous shock waves known as Herbig-Haro (HH) objects, which move through the surrounding gas at speeds of up to hundreds of kilometers per second (over 100,000 miles an hour). As these shock waves ram their surroundings, they heat up bow-shaped nebulae of glowing plasma. This image shows dozens of such objects.

The region below the NGC1999 reflection nebula contains a cluster of deeply embedded young stars which power oppositely directed bow shocks. These objects were first recognized by Guillermo Haro and George Herbig around 1950 and today they are known as HH 1 and HH 2.

Recent observations indicate that the cone shape located near the right edge of the image (known as HH 401) may be a giant bow shock powered by the source of the HH 1 & 2 outflow. If so, this outflow is more than 10 light-years long!

The arc of light which looks like a waterfall (located above and to the left of HH 401) is the enigmatic object HH 222. Unlike most other HH objects, it is a source of polarized, non-thermal radio waves. The nature of this feature remains largely unknown.

Between HH 401 and HH 222 runs a long chain of Herbig-Haro objects associated with the object HH 34. HH 34 itself is the bright and compact bow shock located near the bottom of HH 222. Just above HH 34, a compact jet can be seen to emerge from the source star, which is not visible in this image. This jet and its first bow shock (HH 34) mark the inner portion of a chain of shocks which trace a graceful S-shaped curve from the upper right hand corner of the image down towards HH 1 & 2. The north end of the flow is just below the top of the image (objects HH 33 & 40); the south end of the flow terminates in a group of small bow shocks known as HH 86 & 87, which reside in the dark region between HH 401 and NGC 1999.

Many other smaller nebulous patches in this image mark small reflection nebulae, Herbig-Haro objects, and stellar jets. The rich detail in this image reveals one of the most fascinating areas of the night sky.

Minimum credit line: T.A.Rector, B.Wolpa and G.Jacoby (NOAO/AURA/NSF) and Hubble Heritage Team (STScI/AURA/NASA) (for details see Conditions of Use)