The central star is an old star. Themax-diametrical temperature of the central star is estimated to be 6000 K (by Wegner and Glass[16] 1978 or earlier)[13] or 7000 K (Bujarrabal & Bachiller before July 1990).[16]
The Boomerang Nebula is believed to be astar system evolving toward theplanetary nebula phase. It continues to form and develop due to the outflow of gas from its core where a star in its late stage life sheds mass and emits starlight, illuminating dust in the nebula.Millimeter scale dust grains obscure portions of the nebula's center, so most escaping visiblelight is in two opposing lobes forming a distinctive hourglass shape as viewed byspace telescope data on Earth. The outflowing gas at about 164 km/s expands rapidly into space; this gas expansion results in the nebula's unusual K.
Using observations from 1994 and 1995 with the 15-metreSwedish-ESO Submillimetre Telescope inChile, the astronomers Sahai & Nyman concludedcarbon monoxide (CO) molecules produced after stellar co-absorption in abinary system of the nebula which outflow as agas wind were less kinetically excited than the localouter space (cmbr).[a]Radiation transfer of cmbr into the CO parts[b] of the nebula wind indicated those parts only[c] must have a kelvin temperature state which is uniquely the least of any observed location in nature.[15][18]
The kinetic energy (KE) of the CO outflow is theorized[d] as the product ofcommon-envelope evolution,[21] which was a change in the outer environment (an envelope) of the dual orbital system of the binary system.[19] The KE within the outflow is theorized as an environment forced out from the area of the orbital system of the larger star by the absorption of the lesser sized star into thecore of the larger by terminal gravitational attraction.[21] Cooling to sub cmbr temperature is byadiabatic expansion.[22]
A succession of periodic observations from November 2011 (Atacama Large Millimeter Array) ending June 2012 (Australia Telescope Compact Array) with archived observations fromHubble (HST) (1998 & 2005)[22] revealed other features.[23] The nebula's visible double lobe was observed to be surrounded by a larger spherical region of cold gas seen only in sub-millimeter radio wavelengths. The nebula's outer fringes appear to be gradually warming.
As of mid-2017, it is believed that the star at the center of the nebula is a dyingred giant.[24][25]
^In the 1997 paper the researchers provide alternate quantities for the microwave background temperature of 3 K or 2.8 K.[15] A more specific quantity of kelvin stated elsewhere of the microwave background is 2.72548 ± 0.00057 K.[17]
^"We have discovered absorption of the 3 K microwave background radiation by ultracold CO gas in the Boomerang Nebula-losing mass through a fast (164 km s 1) molecular wind-This wind contains ultracold gas at temperatures below the microwave background temperature"
^The theory uses a concept after Paczynski (1976)[19] who usedV471 Tauri[20]
^Wakely, S. P.; Horan, D. (2008). "TeVCat: An online catalog for Very High Energy Gamma-Ray Astronomy".Proceedings of the 30th International Cosmic Ray Conference. July 3–11, 2007, Mérida, Yucatán, Mexico.3: 1341.Bibcode:2008ICRC....3.1341W.
^ab"182".www.tevcat.org. SAO/NASA Astrophysics Data System. Retrieved3 April 2025.
^"88 Constellations".noirlab.edu. NSF NOIRLab (U.S. National Science Foundation National Optical-Infrared Astronomy Research Laboratory). Retrieved3 April 2025.
^abcSahai, Raghvendra; Nyman, Lars-Åke (1997)."The Boomerang Nebula: The Coolest Region of the Universe?".The Astrophysical Journal.487 (2):L155–L159.Bibcode:1997ApJ...487L.155S.doi:10.1086/310897.hdl:2014/22450.L156: We have measured a 9 mK upper limit (3 σ) on continuum emission at 89.2 and 145.6 GHz toward the Boomerang Nebula, which is much smaller than the negative temperatures seen in the CO and13COJ 1–0 spectra, so these must result from absorption of the microwave background, requiring the excitation temperature (Tex) to be less than 2.8K (Tbb).3. A TWO–SHELL MODEL In shell 2 (R1,o <r <R2),Tkin < 2.8 K." "1994-1995 :2. OBSERVATIONS AND RESULTS
^abIvanova, N.; Justham, S.; Chen, X.; De Marco, O.; Fryer, C. L.; Gaburov, E.; Ge, H.; Glebbeek, E.; Han, Z.; Li, X.-D.; Lu, G.; Marsh, T.; Podsiadlowski, P.; Potter, A.; Soker, N.; Taam, R.; Tauris, T. M.; van den Heuvel, E. P. J.; Webbink, R. F. (2013). "Common envelope evolution: where we stand and how we can move forward".The Astronomy and Astrophysics Review.21 (59) 59.arXiv:1209.4302.Bibcode:2013A&ARv..21...59I.doi:10.1007/s00159-013-0059-2.
^Paczynski, B. (1976). "Common Envelope Binaries".Symposium - International Astronomical Union.73:75–80.doi:10.1017/S0074180900011864.
^abSahai, R.; Vlemmings, W. H. T.; Huggins, P.J.; Nyman, L.-Å.; Gonidakis, I. (10 November 2013). "Alma Observations of the Coldest Place in the Universe: The Boomerang Nebula".The Astrophysical Journal.777 (92): 92.arXiv:1308.4360.Bibcode:2013ApJ...777...92S.doi:10.1088/0004-637X/777/2/92.adiabatic expansion: 4. DISCUSSION." "2011-2012 & HST: 2. OBSERVATIONS
