One of the most prolific observatories - the Hubble Space Telescope (HST), has reached 33 years of service. NASA and the Space Telescope Science Institute are celebrating this moment revealing another great image taken by HST. NGC 1333, a nebula in the Perseus Molecular Cloud, is the centerpiece of this event.
The anniversary image, located approximately 960 light-years away, showcases HST’s unique capability to observe ultraviolet (UV) light; which is critical for studying regions of star formation like NGC 1333. In the anniversary image, we see a reflection nebula bright and majestic among dark clouds, as well as jets of material most likely produced by stars still in formation and obscured by the dark dust and cold molecular gas also apparent in most of the image.
At the top of this image, we see BD +30°54, a young helium-weak silicon bright star[3] type K7 D, surrounded by what is known as a reflection nebula. HST’s unique capability to detect UV light allows us to see, in great detail, this blue scattered light.
This is light emitted by the star that gets redirected towards us by the dust and molecules that still surround it, light that otherwise would have never reached us because it was not initially traveling in our direction. The blue light, in this case, is more efficiently scattered than the red light and makes the reflection nebula look bluer than the emission of the star at its center. Because dust and molecules still surround BD +30°549, this object has not yet reached the status of "star" and it is still called a pre-main sequence star.
At the center of the image, below the reflection nebula, we see a dark cloud with a bright core made of stars. These are still embedded within the molecular material but slowly carving their way out. There are more dark regions under this cloud that cannot be penetrated by Hubble. These are extensions filled with cold molecular gas and obscuring dust. In these clouds, many more stars are being formed in numbers that, among other things, depending on the density of the molecular gas.
The bright red region at the bottom of the image is a region with strong H and twice ionized Nitrogen emission. Because some of the gas in this region appears to form jets with bright emission regions in the form of shock waves, these have been associated with objects called Herbig-Haro (HH), which are common to many star-forming regions. One of these objects is at the top of this nebulosity, at the end of a line formed by the hands of an imaginary clock indicating 9:15[3]. This object, cataloged as HH 12, is a bright bow shock at the right end of the jet[4]. Astronomers believe that this jet is a high-velocity outflow coming from a protostar cataloged as IRAS 6, still embedded in the dark cloud further to the left. This nebulosity, however, is quite complex and shows other outflows. Thus, it may be a superposition of shocks powered by at least two and possibly three sources, some of which are not captured in this image[4].
Years before, in 2018, HST took another quite interesting image of another region in the Perseus Molecular Cloud.
RCOS 24-inch telescope; University of Arizona Mount Lemmon SkyCenter.
This object also shows multiple HH objects cataloged as HH 7–11. In the image, HH 7 is the brightest object at the top of the reflection nebula, which is about 20,000 times the distance between the Earth and the Sun. The young star, the source of the HH objects, is called SVS 13. All five HH objects are moving away from SVS 13 toward the upper left at a speed of up to about 150,000 miles per hour. These objects, and HH 12, will disappear within a few tens of thousands of years.
HST was launched on August 24 1990 on board the NSA Space Shuttle Discovery. It was deployed into space on April 25, 1990 by the STS-31 crew.
References:
[1] https://www.nasa.gov/image-feature/goddard/2023/hubble-celebrates-33rd-anniversary-with-a-peek-into-nearby-star-forming-region
[2] Potravnov I., Mashonkina L. & Ryabchikova T. 2023, MONRAS, 520, 1296
[3] Tomoharu O. ,1 Mitsuhiro I., Hiroyuki M., Masafumi I., Tetsuya I., Kazuhisa K., Takeshi S. & Satoshi Y. 2004, 602, 803
[4] J. Bally & D. Devine 1996, ApJ, 473, L49
[5] LRGB color composite CCD image taken with an SBIG STL-11000M CCD and a RCOS 24-inch telescope. The image was taken at the University of Arizona Mount Lemmon SkyCenter.
[6] ESA/Hubble & NASA, K. Stapelfeldt
See also: https://www.youtube.com/watch?v=nLxF3g4yWVI