NASA has created what is essentially a time-lapse movie of the skywhich reveals changes spanning a decade, using images taken by its NEOWISE space observatory.
Every six months, the Near-Earth Object Wide Field Infrared Survey Explorer spacecraft, complete a trip to the middle of the Sun, taking pictures in all directions. Together, those images form a map from “all heaven” showing the location and brightness of hundreds of millions of objects. Using 18 all-sky maps produced by the spacecraft (the 19th and 20th will be released in March 2023), the film has been created, available on Youtube:
Each map is a great resource for astronomers, but when viewed in sequence as a time lapse, they serve as an even stronger resource for trying to better understand the universe. Comparing the maps can reveal distant objects that have changed position or brightness over time, known as time-domain astronomy.
“If you go out and look at the night sky, it may seem like nothing ever changes, but that’s not the case.”Amy Mainzer, principal investigator for NEOWISE at the University of Arizona in Tucson, said in a statement. “The stars are shining and exploding. Asteroids zoom by. Black holes are destroying stars. The universe is a very busy and active place.”
NEOWISE was originally a data processing project to retrieve asteroid detections and features from WISE, an observatory launched in 2009 tasked with scanning the entire sky to find and study objects outside our solar system. The spacecraft used cryogenically cooled detectors that made them sensitive to infrared light.
Not visible to the human eye, infrared light is radiated by a plethora of cosmic objects, including nearby cool stars and some of the most luminous galaxies in the universe. The WISE mission ended in 2011 after the onboard coolant needed for some infrared observations ran out, but the spacecraft and some of its infrared detectors were still functional. So in 2013, NASA repurposed it to track asteroids and other near-Earth objects, or NEOs. Both the mission and the spacecraft received a new name: NEOWISE.
Despite the change, the infrared telescope has continued to scan the sky every six months, and astronomers have continued to use the data to study objects outside our solar system.
For example, in 2020, scientists released the second version of a project called CatWISE: an object catalog of 12 NEOWISE all-sky maps. Researchers use the catalog to study brown dwarfs, a galaxy-wide population of objects that lurk in the dark near our Sun. Although they form like stars, brown dwarfs don’t accumulate enough mass to initiate fusion. , the process that makes stars shine.
Due to their proximity to Earth, nearby brown dwarfs appear to move faster across the sky compared to more distant stars moving at the same speed. So one way to identify brown dwarfs among the billions of objects in the catalog is to look for moving objects. A companion project to CatWISE called Backyard Worlds: Planet 9 invites citizen scientists to sift through NEOWISE data for moving objects that computer searches might have missed.
Using the original two WISE all-sky maps, scientists found about 200 brown dwarfs just 65 light-years from our Sun. Additional maps revealed another 60 and doubled the number of known Y dwarfs, the coolest brown dwarfs. Compared to warmer brown dwarfs, Y dwarfs may have a stranger story to tell in terms of how and when they formed. These discoveries help illuminate the collection of objects in our solar neighborhood. And a more complete count of near-Sun brown dwarfs tells scientists how efficient star formation is in our galaxy and when it began.
Watching the sky change for more than a decade has also contributed to studies of how stars form. NEOWISE can peer into the dusty blankets that envelop protostars, or balls of hot gas that are on their way to becoming stars. Over the years, protostars flicker and light up as they gather more mass from the surrounding dust clouds. Scientists are conducting long-term follow-up of nearly 1,000 protostars with NEOWISE to gain insight into the earliest stages of star formation.
NEOWISE data have also improved our understanding of black holes. The original WISE study discovered millions of supermassive black holes at the centers of distant galaxies. In a recent study, scientists used data from NEOWISE and a technique called echo mapping to measure the size of disks of hot, glowing gas surrounding distant black holes, which are too small and too distant for any telescope to resolve. .
“We never anticipated that the spacecraft would be operating this long, and I don’t think we could have anticipated the science that we would be able to do with this amount of data,” said Peter Eisenhardt, an astronomer at NASA’s Jet Propulsion Laboratory (JPL) and WISE project scientist.