This is NGC 2736, the Pencil nebula.
The filamentary nature of the Pencil nebula strongly suggests an association with a supernova remnant. A 2001 study associates it with the supernova remnant RX J0852.0-4622
, also known as the Vela Junior supernova remnant. However, another 2001 study rejects this idea and argues that Vela Junior is located much further away. Even more recent papers suggest that this debate is still unresolved and the distance and age of Vela Junior are both still uncertain.
A rival theory in the scientific literature is that the Pencil nebula is associated with Knot D
at the edge of the main Vela supernova remnant
You can see a beautiful image of the Pencil nebula here
and an even more detailed Hubble image here
Associated with knot D in the main Vela SNR.[1
Is not associated with the Vela Jr. SNR.[2
Associated with the SNR RX J0852.0-4622[3
Argues that the Pencil nebula is a supernova remnant located within the shell of the main Vela supernova remnant and hence has the same distance of 250 pc. [4
1. ^ Sankrit, Ravi, Blair, William P., & Raymond, John C. (2003). "Optical and
Far-Ultraviolet Spectroscopy of Knot D in the Vela Supernova Remnant", The
Astrophysical Journal, Vol. 589, 242-252. [2003ApJ...589..242S]
2. ^ Slane, P., Hughes, J. P., Edgar, R. J., et al. (2001). "Nonthermal X-ray
emission from G266.2-1.2 (RX J0852.0-4622)", Young Supernova Remnants,
Vol. 565, 403-406. [2001AIPC..565..403S]
3. ^ Redman, M. P., Meaburn, J., O'Connor, J. A., et al. (2000). "An Optical
Nebula Associated with a Young X-Ray Supernova Remnant in Vela", The
Astrophysical Journal, Vol. 543, L153-L155. [2000ApJ...543L.153R]
4. ^ Redman, M. P., Meaburn, J., Bryce, M., et al. (2003). "The Connection
between the Vela Supernova Remnant, the Optical Nebula RCW 37, and the
Young X-Ray Supernova Remnant RX J0852.0-4622", Revista Mexicana de
Astronomia y Astrofisica Conference Series, Vol. 15, 270-272.