Pictures of the sky can reveal the wonders of the cosmos, but movies can make them come to life. Videos taken by NASA’s NEOWISE satellite telescope show movement and change in the sky.
The Near-Earth Object Wide Field Infrared Survey Explorer, or NEOWISE, spacecraft from NASA makes one trip halfway around the Sun every six months while collecting photos from all angles. An “all-sky” map made out of those photos can be stitched together to display the location and brightness of hundreds of millions of objects. Scientists have constructed what is essentially a time-lapse movie of the sky using 18 of the all-sky maps that the spacecraft has produced (the 19th and 20th will be revealed in March 2023). This movie shows changes that have occurred over the course of a decade.
Each map is a priceless tool for astronomers, but when seen in a time-lapse sequence, they become much more valuable for attempting to grasp the nature of the cosmos. In time-domain astronomy, comparing the maps can reveal distant objects that have altered position or brightness over time.
The night sky could make it appear as though nothing ever changes, but that is untrue, according to Amy Mainzer, the NEOWISE principle investigator at the University of Arizona in Tucson. “Stars are bursting into flames. Asteroids are flying past quickly. Stars are being torn apart by black holes. The universe is a very lively, busy place.
NEOWISE began as a data processing initiative to obtain asteroid detections and features from WISE, an observatory that was launched in 2009 and charged with searching the whole sky for and studying extrasolar objects. The infrared light-sensitive detectors used by the spacecraft were cryogenically cooled.
Many cosmic objects, including cold, close stars and some of the most luminous galaxies in the cosmos, emit infrared light, which is invisible to the human eye. The onboard coolant, which was required for some infrared studies, ran out during the WISE mission in 2011, yet the spacecraft and several of its infrared detectors were still operational. In order to track asteroids and other near-Earth objects, or NEOs, NASA repurposed it in 2013. The spacecraft’s name was changed to NEOWISE, as well as the mission’s.
The infrared telescope has kept on scanning the sky every six months despite the change, and astronomers have kept using the data to investigate things outside of our solar system.
For instance, in 2020 researchers published the updated version of the CatWISE project, which is a catalogue of objects compiled from 12 NEOWISE all-sky maps. The catalogue is used by researchers to investigate brown dwarfs, a class of objects that are widespread throughout the galaxy and hide in the shadows near our Sun. Despite having a similar formation to stars, brown dwarfs are unable to build up enough mass to initiate fusion, the process that gives stars their light.
Nearby brown dwarfs appear to travel across the sky more quickly than more distant stars moving at the same speed because of their proximity to Earth. In order to find brown dwarfs among the trillions of things in the catalogue, one strategy is to search for moving objects. Backyard Worlds: Planet 9, an initiative that complements CatWISE, asks citizen scientists to examine through NEOWISE data for moving objects that computer searches might have missed.
Using the first two WISE all-sky maps, researchers discovered 200 brown dwarfs just 65 light-years from the Sun. The extra maps revealed an additional 60, doubling the number of Y-dwarfs, the coldest brown dwarfs, that are known. Y-dwarfs may have a different origin and formation history as compared to warmer brown dwarfs. These discoveries shed light on the assortment of objects that make up our solar neighbourhood. The efficiency of star formation in our galaxy and the time when it first started are both revealed by a more thorough survey of brown dwarfs near to the Sun.
Studies on the formation of stars have also benefited from observing how the sky has changed over the past ten years. NEOWISE can look inside the dusty cloaks that are encasing protostars, or hot gaseous balls that are almost ready to become stars. Protostars flare and flicker as they gain mass from the surrounding dust clouds over the period of years. To learn more about the beginnings of star formation, researchers are using NEOWISE to observe nearly 1,000 protostars over an extended period of time.
The information from NEOWISE has also increased our knowledge of black holes. Millions of supermassive black holes were found in the nuclei of far-off galaxies during the initial WISE study. Researchers have measured the size of discs of hot, blazing gas encircling far-off black holes, which are too small and too far away for any telescope to resolve. They did this using NEOWISE data and a method called echo mapping.
Peter Eisenhardt, an astronomer at NASA’s Jet Propulsion Laboratory and the WISE project scientist, said, “We never thought that the spacecraft would be running for this long, and I don’t think we could have envisioned the research we’d be able to accomplish with this much data.”
Details of the Mission
The Planetary Defense Coordination Office of NASA, part of the Science Mission Directorate in Washington, delegated management and operation of the NEOWISE mission to NASA’s Jet Propulsion Laboratory in Pasadena, California. Amy Mainzer, the lead researcher, works at the University of Arizona. The scientific apparatus was made by the Logan, Utah-based Space Dynamics Laboratory. The spacecraft was made by Boulder, Colorado-based Ball Aerospace & Technologies Corp. IPAC at Caltech in Pasadena processes scientific data. JPL is overseen by Caltech for NASA.
WISE was overseen and run by JPL on behalf of NASA’s Science Mission Directorate. Investigator Edward Wright from UCLA served as the lead. The Goddard Space Flight Center in Greenbelt, Maryland, which oversees NASA’s Explorers Program, conducted a competitive selection process for the mission.