A Spitzer retrospective

The Spitzer Space Telescope recently ceased operations, powering down its remaining detector after more than a decade and a half of revealing the infrared Universe. Its legacy will be continued by far more expensive missions that will have big boots to fill.

Michael Werner, project scientist of the Spitzer Space Telescope and emeritus chief scientist for astronomy and physics at the Jet Propulsion Laboratory, discusses the legacy of one of NASA’s Great Observatories.

The Spitzer Space Telescope may be modest in size compared to its optical counterparts, but the low temperatures of its optics gave its infrared instruments excellent sensitivity, explains Facility Scientist Thomas Roellig.

In 2010, the Spitzer Space Telescope detected evidence of a complex form of carbon that had never been seen in extraterrestrial environments. Jan Cami recounts the discovery of buckminsterfullerene in space.

The Spitzer Space Telescope returned infrared images and spectra with unprecedented sensitivity and resolution, enabling the characterization of the dust-enshrouded star formation of and within galaxies. This has yielded indicators of total star formation, used as unbiased tracers of the stellar production across cosmic times.

In the Spitzer Space Telescope’s 16 years of operation, it observed many Solar System objects and environments. In this first Review Article of a pair, Spitzer’s insights into comets, centaurs and Kuiper belt objects—all remnants of the Solar System’s formation—are summarized.

In the Spitzer Space Telescope’s 16 years of operation, it observed many Solar System objects and environments. In this second Review Article of a pair, Spitzer’s insight into asteroids, dust clouds and rings and the ice giant planets are summarized.

Spitzer revealed the power of astrophysical polycyclic aromatic hydrocarbon molecules to probe the local physical and chemical conditions and processes, for example, establishing the relation between their abundance and galaxy metallicity for the first time.

The Spitzer Space Telescope made huge advances in the study of debris disks around main-sequence stars and white dwarfs, increasing their number by an order of magnitude, and leading the way for the next generation of space-based infrared missions.

Spitzer revolutionized studies of active galactic nuclei through its high sensitivity and mapping speed at mid-infrared wavelengths. This Review summarizes key Spitzer insights on active galactic nuclei, including the properties of their dust and shocked gas.

The Spitzer Space Telescope launched when the study of exoplanets was in its infancy, and yet it was remarkably successful in characterizing both exoplanet and brown dwarf systems through their mid-infrared emissions. This Review collates the highlights of Spitzer-based research in these fields.

Spitzer revealed the properties of luminous and ultraluminous infrared galaxies, the role of starbursts and actively accreting supermassive black holes in powering these sources and found evidence for energetic feedback on their interstellar gas and dust.

The Spitzer Space Telescope accurately measured stellar masses, ages and star formation rates for a large sample of typical galaxies at high redshifts, allowing an initial exploration of some of the key science drivers of the James Webb Space Telescope.

Orbital parameters for the seventh Earth-sized transiting planet around star TRAPPIST-1 are reported, along with an investigation into the complex three-body resonances linking every member of this planetary system.

Global circulation theory predicts strong equatorial jets at the equators of hot gas giant exoplanets that blow hot gas to the east, resulting in an eastward hotspot. Here, Dang et al. present a detection of a hotspot significantly offset to the west.

A comprehensive set of Hubble and Spitzer observations reveal a hydrogen-rich, low-metallicity atmosphere on the sub-Neptune exoplanet GJ 3470 b. Water vapour is detected, but the planet is surprisingly depleted in methane, possibly because of photochemical or thermal processes. Sub-millimetre-sized Mie-scattering cloud particles partially attenuate the molecular signatures at short wavelength, but are largely transparent beyond 3 µm.

The authors find that a nearby planetary system has two terrestrial planets that transit in front of their star (from our perspective). Transiting terrestrial planets are sought after, as they can be characterized in detail, including their atmospheres. Having two in the same system is very rare.

Phase curves from a sample of 12 hot Jupiters show that this type of planet keeps the same nightside temperature (~1,100 K) regardless of the irradiation they receive from their star. This effect is due to an optically thick layer of the same species of clouds on the nightside hemisphere.

The relatively unexplored southwestern region of the Large Magellanic Cloud is host to a massive, embedded star-forming complex that rivals the star-forming efficiency of 30 Doradus. Its most luminous object could be a super star cluster in formation.