L183 (=L134N), Spitzer/IRAC bands 1 and 4 showing the L183 dense filament in absorption at 8 μm and its glow at 3.6 μm
The Coreshine phenomenum (the term is due to A. Bacmann) is a well-known physical process, namely the scattering of light by dust grains but which was not expected to be observable in the 3-5 μm range. It is seen in the visible and in the near infrared (cloudshine) but the standard grains (typically 0.1 μm radius) which could explain most or all of the scattering below 2 μm are too small to be efficient above 3 μm. Though grains are expected to grow in dark clouds, it was not expected that this growth could be by a factor 10 in size (1000 in mass!) and that this could encompass a large fraction of the dark clouds until my discovery of the phenomenon in L183 (see image above). This growth and this scattering have multiple interests concerning dust composition and star formation, which we have not yet explored. . . Stay tuned!
Lefèvre, C., Pagani, L. Min, M., Poteet, C., Whittet, D., 2016, A&A, 585, L4,On the importance of scattering at 8 μm: Brighter than you think
Lefèvre, C., Pagani, L., Juvela, M., Paladini, R., et al., 2014, A&A, 572, A20,Dust properties inside molecular clouds from coreshine modeling and observations
Pagani, L., Lefèvre, C., Bacmann, A., Steinacker, J., 2012, A&A, 541, A154, Absence of coreshine in the Gum/Vela region
Pagani, L., Steinacker, J., Bacmann, A., Stutz, A., & Henning, T., 2010, Science, 329, 1622, The ubiquity of micrometer-size grains in the interstellar medium
Steinacker, J., Pagani, L., Bacmann, A., Guieu, S., 2010, A&A 511, A9, Direct evidence for dust growth in L183 from MIR light scattering