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NGC 2170 is an emission/reflection/dark nebula located in the constellation Monoceros, approximately 2,400 light-years from Earth. Discovered bt William Herschel in the 18th century, this nebula is a complex region where new stars are forming. The area including NGC 2170 contains emission nebulae, which glow mainly red due to ionized Hydrogen gas, reflection nebulae that shine primarily in blue by reflecting light from nearby young stars embedded within the surrounding dust clouds -which also scatter a significant proportion of this light. There is also a third kind of nebulae, the dark nebulae, that are neither hot enough to ionize its atoms/molecules and emit light, nor close enough to reflect the received light from nearby stars.
NGC 2170 is part of a larger star-forming region, making it an important subject in research of stellar nurseries. It lies near the Monoceros R2 (Mon R2) molecular cloud complex, a well-known site of active star formation that spans about 20 degrees in the sky. Observations in infrared, such as those from the Spitzer Space Telescope and WISE, reveal numerous protostars and young stellar objects (YSOs) embedded within the dusty environment. Most of these stars are well within the dust clouds and therefore faint enough in their visible wavelengths, that they are not visible in this image. These stars emit strong infrared radiation, heating the surrounding dust and gas and making the region particularly luminous at non-visible wavelengths.
The blue hue of NGC 2170 in optical images, is due to the scattering of shorter-wavelength starlight by fine dust particles—a process similar to why Earth’s sky appears blue. Additionally, nearby red and yellow regions are indicative of emission nebulae and dark absorption lanes.
The presence of both reflection and emission features points to a range of stellar evolutionary stages within NGC 2170’s vicinity. Protostars in this area are believed to be forming through the gravitational collapse of cold, dense regions in the molecular cloud. As they evolve, their stellar winds and radiation begin to carve cavities and illuminate the surrounding dust, shaping the nebula’s intricate appearance. NGC 2170’s nature offers a natural scenario to study early stellar development and the influence of young stars on their environments.
This image was mainly taken with a 20″ telescope located in Australia, but enhanced with several hours of extra images taken, later on, with a 24″ telescope located in New Mexico, US.
Additional Information
Object
Name(s): NGC 2170. The Angel Nebula
Type: Emission/Reflection Nebula
RA: 06h 07m 48s
Dec: -06º 23’ 10”
Constellation: Monoceros
Size (arcmin): 19×14 arcmin
Magnitude: ND
Distance: 2,400 ly
Image
Date: 2019-Jan + 2019-Nov-Dec @SSO and 2020-Jan @NMSkies, New Mexico US.
Location: iTelescope.net, SSO near Coonabarabran, NSW Australia
Size (arcmin): 35×35 arcmin
Telescope: 20inch f/6.8 reflector scope
Camera: SBIG STX16803 (4096x4096pix)
Guiding: Astrodon MonsterMOAG off-axis guider
Total exposure: 49.75 hours (L: 15h 30m; Ha: 25h 30m; RGB: 8h 45m)
Processing: CCDStack, PixInsight (one process) and Photoshop CC 2024