How are stars born? Where does that happen? What does it look like? What would a map of the Milky Way galaxy look like? Are there many more galaxies in space?
These are a few of the questions that NASA’s Spitzer Space Telescope, which celebrated its 15th year in space this year, has been able to answer with visible imagery that is astonishing. Spitzer’s predicted lifespan was just 2½ years (in a best-case scenario, 5 years) because of the stressful environment of space, where temperatures range from well below freezing to planet surfaces as hot as stars, but it has lasted six times that forecast.
Spitzer is a can-do telescope, surpassing all predictions and then some. “It has been a bonanza and every day is a holiday,” said Michael Werner, project scientist for Spitzer Space Telescope, who has worked on the project for some 40 years. “Spitzer has exceeded all expectations for longevity and also discoveries.”
The raft of Spitzer’s otherworldly discoveries include: a stellar nursery, seven Earth-size planets, Saturn’s largest ring and the farthest and oldest galaxy ever known — all previously inconceivable, even to the astronomers and engineers who created and have maintained the telescope, which is managed by NASA’s Jet Propulsion Laboratory (JPL) at Caltech’s Spitzer Science Center. “Our ability to find and observe exoplanets [planets orbiting around a star other than the sun] has been really phenomenal,” added Werner. “We did a deep map to study galaxies almost as far back as the Big Bang. We mapped the Milky Way. We didn’t plan on it doing any of this.”
Spitzer was the fourth and final one of NASA’s so-called Great Observatories to reach space, joining Hubble Space Telescope, Chandra X-Ray Observatory and Compton Gamma-Ray Observatory. Spitzer has been described as the cornerstone of NASA’s Astronomical Search for Origins Program. Synthesizing data from various telescopes, which collect light in different wavelengths, helps scientists gain a clearer picture of the universe and wonders of the cosmos.
Spitzer was designed to observe the universe in infrared wavelengths of light, allowing a better view and retrieval of information about objects in space that are extremely far away or blocked by stellar dust. Infrared wavelengths of light are too long to be visible to the human eye and mostly emanate from heat radiation. The telescope’s infrared capabilities equip it to see through dust to detect and read stars and objects that are too faint or distant for optical telescopes, or that are obscured by turbulent clouds of space dust, said Sean Carey, manager of Spitzer Science Center. It is similar to what firefighters use to see through smoke, he added. “Spitzer told us how stars form,” said Carey. “We know they form in very dense infrared-dark clouds, [we] can see how many are forming, the spacing between stars and their sizes telling us how they form. Winds blow away the material they form out of so that you can see inside the stellar nurseries.” What creates the wind, said Carey, is light from massive hot stars, which pushes the material away from the stars after they form.
But Spitzer’s single most important discovery, scientists say, is the study of what is called the Trappist-1 system. Trappist-1 is an ultra-cool dwarf star 40 light years away. Trappist-1 has more Earth-size planets (called “exoplanets”) than any other known planetary system. These seven exoplanets are rocky but potentially habitable and are the most studied planetary system outside of our own solar system because of Spitzer. “Studying planets around other stars was in its infancy when Spitzer launched, but we now often spend more than half the time each year on these studies,” Lisa Storrie-Lombardi, project manager for Spitzer Telescope, said in an email. “The observatory wasn’t designed to do this, but it is really good at it.”
Spitzer accurately detects planets orbiting other stars by measuring the tiny dip in light from the star as the planet passes in front of it, known as “planetary transit.” This is now a commonly used technique to detect the depth and shape of the transit which provides information about the planets around other stars, added Storrie-Lombardi, who has worked on Spitzer for 19 years. Discoveries like these are beyond the scope of what Spitzer was originally designed to do in 2003 when it officially began its mission in space.
Spitzer’s infrared vision has also allowed scientists to study the most distant galaxies in the universe. Light from some of these distant galaxies traveled for 13.4 billion years to reach Earth, according to NASA’s website. Using data from the Spitzer and Hubble telescopes allowed “scientists to see these galaxies as they were less than 400 million years after the birth of the universe,” according to JPL’s website. Spitzer identified many distant galaxy clusters previously unknown. What surprised scientists was the discovery of so-called “big baby” galaxies that were much larger and more mature than early galaxies were believed to be. These big baby galaxies indicated that massive clusters of stars came together very early in the universe’s history, the website notes.
Spitzer has also mapped the entire disk of our home galaxy, the Milky Way. “We initially thought that the Milky Way galaxy disk would just be too bright for Spitzer,” said Storrie-Lombardi. “We figured out how to do it and this program provides one of the most spectacular science legacies of the mission.”
With data gleaned from Spitzer, scientists were able to create one of the most extensive maps of the Milky Way galaxy ever compiled, including the most accurate map of the large bar of stars in the galaxy’s center. There is now a map of the entire 360-degree expanse of the Milky Way available to astronomers and the public. A continually looping view of the entire galaxy moving past can be seen at spitzer.caltech.edu by searching for a video titled “Panning Through the Milky Way.”
Other Spitzer discoveries include the largest known ring around Saturn, a wispy, fine structure 300 times the planet’s diameter, and the first giant gas exoplanet (a hot Jupiter) weather map of temperature variations across its surface, showing the presence of fierce winds.
What the future holds for Spitzer is yet to be determined, but the revolutionary telescope’s space mission continues through November 2019. Thus far, Spitzer has logged 106,000 hours observing space, and thousands of scientists around the world have used Spitzer data in their studies. Spitzer data has been cited in more than 8,000 published papers. For the social media– and virtual reality–obsessed public, NASA has created a selfie app for IOS and Android phones that “dresses” you in a space suit (or you might follow Storrie-Lombardi’s example and use it to snap your pet — Maria the dog is on Facebook floating in the Milky Way; she posted that in August and just made it public). The backgrounds for the selfie app include the Galactic Center, the Cigar Galaxy or Cassiopeia A. There is also an Exoplanet Excursions Virtual Reality Experience for Vive or Oculus devices, found at spitzer.caltech.edu/vr. And to highlight Spitzer’s greatest discovery, Trappist-1, there is a 360-degree video on Youtube titled “NASA’s Exoplanet Excursions 360.”
From the dawn of human history people have been trying to understand what we see when we look up at the night sky, and how we fit into it. “Seeing the incredible response and excitement, worldwide, to the discovery of the Trappist-1 planetary system was one of the most rewarding moments of my professional life,” said Storrie-Lombardi. “There were over 5 billion web hits on stories about it. I think the biggest contribution space astronomy makes is connecting so many people with the wonders of our universe.”