Spitzer's legacy

Spitzer discovered Saturn’s outermost ring in 2009. Named after the moon Phoebe that orbits just beyond it, the dusty ring extends roughly from 3.7 million miles (6 million km) to 7.4 million miles (12 million km) from the planet. This artist’s concept shows the ring to scale with Saturn as a dot. (The inset shows an infrared view of the planet through the 10-meter Keck Telescope.)

Spitzer discovered water vapor in the atmospheres of several “hot Jupiters,” gas giant exoplanets that orbit close to their host stars. This illustration depicts an infrared view of such a world as it begins to transit its parent star.

Spitzer discovered four of the seven known planets around TRAPPIST-1, a dwarf star located 40 light-years away in the constellation Aquarius. The system stands out because all of the planets appear to be roughly Earth-sized, and at least three lie in the star’s habitable zone where liquid water could exist. This artist’s view shows the scene from one of those potentially watery worlds.

Brown dwarfs are failed stars that don’t possess enough mass to trigger hydrogen fusion in their cores. As such, they remain cool and emit most of their light at infrared wavelengths. Spitzer found the two young brown dwarfs seen at the center of this image with the help of ground-based telescopes at Calar Alto Observatory in Spain and the Caltech Submillimeter Observatory in Hawaii.

The Carina Nebula (NGC 3372) hosts one of the most massive and luminous stars in our galaxy, Eta Carinae, which gleams at the center of this Spitzer image. Infrared light from this behemoth destroys dust particles and sculpts cavities into the surrounding nebula. The dust glows red in this image and hydrogen gas appears green.

The Eagle Nebula (M16) in Serpens gained fame in the 1990s, when the Hubble Space Telescope photographed three “Pillars of Creation.” In this Spitzer infrared view, the pillars appear as greenish columns protruding in front of some reddish nebulosity to the right of center. The green denotes cool dust, while red signifies warmer material that might have been energized by a supernova explosion 1,000 to 2,000 years ago.

The universe has a different look at infrared wavelengths. In visible light, dark dust blocks the glow of more distant gas to create the outline of the North America Nebula (NGC 7000) in Cygnus. But the continent disappeared to Spitzer’s eye because it peered through this dust to reveal the cocoons of embryonic stars within the nebula. Many of the stars seen here are only about a million years old.

The Serpens South star cluster harbors some 50 young stars. Of these, 35 are protostars — objects that have not yet started fusing hydrogen and are still collecting matter from the surrounding molecular cloud. The cluster members appear as a tightly packed group of green, yellow, and orange stars at the center of this Spitzer infrared image.

Delicate tendrils of dust glow brightly in the infrared as the massive star Zeta Ophiuchi approaches. As Zeta — the luminous blue star at center — plows forward (to the left) at about 53,000 mph (86,000 km/h), its powerful stellar winds create a bow shock in the surrounding dust, similar to the ripples that form in front of a moving ship’s bow. The red hues arise from the warmest, most compressed dust.

The tangled spiral arms of M101 glow with a pinkish hue in this Spitzer portrait. Located 22 million light-years away in Ursa Major, M101 shows patchy spiral arms that are not as well defined as in typical grand design spirals.

Part of what made Spitzer special was its ability to observe some of the same objects targeted by NASA’s other Great Observatories. This view of the Orion Nebula (M42) combines Spitzer infrared data (in yellow, orange, and red) with Hubble visible-light observations (in green and blue). Spitzer revealed many infant suns embedded so deeply in their dusty cocoons that even Hubble could not show them.

The Eagle Nebula (M16) in Serpens gained fame in the 1990s, when the Hubble Space Telescope photographed three “Pillars of Creation.” In this Spitzer infrared view, the pillars appear as greenish columns protruding in front of some reddish nebulosity to the right of center. The green denotes cool dust, while red signifies warmer material that might have been energized by a supernova explosion 1,000 to 2,000 years ago.

Once the Sun exhausts its nuclear fuel in another 5 billion years or so, it will puff off its outer layers and create a planetary nebula, perhaps similar to the Helix Nebula (NGC 7293) in Aquarius. When viewed in the infrared, the Helix’s expanding outer layers shine brightest at shorter wavelengths (shown as blue and green), while a central disk of dust and the final layers ejected by the dying star glow at longer wavelengths (red).

When a massive star dies, it explodes as a supernova and seeds the galaxy with heavy elements that one day may find their way into future generations of stars and planets. This image of the supernova remnant Cassiopeia A blends observations from three of NASA’s Great Observatories: Spitzer infrared data (in red) highlight warm dust in the outer shell; Hubble visible-light observations (yellow) reveal delicate filaments of hot gas; and Chandra X-ray data (green and blue) expose the hottest gases.

Spitzer’s infrared vision captured different components of the Large Magellanic Cloud, the Milky Way’s largest satellite galaxy. Blue depicts light from older stars, red reveals dust heated by stars, and green shows cooler interstellar gas and dust grains. Spitzer’s sharp eye captured nearly a million objects that hadn’t been seen before.

Infrared radiation often comes from dust that absorbs visible and ultraviolet starlight and then reradiates it at longer wavelengths. That’s why Spitzer proved so adept at tracing the dust-laden spiral arms of nearby galaxies. In this image, the telescope revealed the winding arms of M81 in Ursa Major from 12 million light-years away.

. Although Spitzer revealed the Milky Way to be a barred spiral galaxy, our home’s structure was harder to discern than that of more distant examples such as NGC 1097 in Fornax. Spitzer scientists color-coded this image so the galaxy’s dusty bar and spiral arms appear pink. The space observatory also revealed a ring of stars around the supermassive black hole that lurks at the galaxy’s center.