In the lead-up to the end of mission, Spitzer also took another look at the Tarantula nebula (pictured) in the Large Magellanic Cloud. The Tarantula nebula was one of Spitzer’s first targets, and it has been a regular repeat visit. The left panel shows the most recent view of the nebula, with Spitzer in ‘warm mission’ mode, that is, with only the IRAC 3.6 μm and 4.5 μm bands operational. The 3.6 μm emission, shown in blue, comes predominantly from polycyclic aromatic hydrocarbon (PAH) molecules, and the 4.5 μm emission, shown here in red, is from hot dust, which picks out the heart of the nebula where tens of massive stars reside. The right panel shows the nebula with the addition of 8.0 μm emission, IRAC’s longest available wavelength band during the early, cryogenic part of the Spitzer emission. Note that in the right panel the colours assigned to the different bands have changed: 3.6 μm is in blue, 4.5 μm is in green and the additional 8.0 μm band is now in red. The 8.0 μm band is also sensitive to PAH emission, making the regions bright in PAHs appear purple and white. The Tarantula nebula is a vigorous star-forming region, where young and hot stars illuminate their surrounding dust structures with ultraviolet light, which is reradiated in the infrared by PAHs.
Another Spitzer favourite can just be made out in the images too. In the upper region a small point of light marks the remnant of supernova 1987A. Spitzer was seminal in tracking the dust content of the supernova remnant, in particular constraining the balance between newly created dust and that destroyed by the shockwave in the supernova explosion.
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