The NASA Swift observatory is expected to re-enter Earth’s atmosphere on Wednesday, marking the end of a two-decade mission dedicated to studying the most powerful explosions in the cosmos. The satellite, which was designed to operate for just two years, is no longer able to steer or observe, and its re-entry is uncontrolled.
The US Space Force predicts the 3,200-pound spacecraft will hit the atmosphere at approximately 3:30 a.m. EST on November 4. NASA states that most of the spacecraft is set to burn up during the process, but some components are expected to survive the descent.
Uncontrolled Descent and Safety Risks
Re-entry locations for any surviving components can vary depending on the hemisphere and the exact timing of the atmospheric entry. The agency noted in a blog post that surviving fragments are limited to a band between 20.6 degrees south latitude and 20.6 degrees north latitude. This restriction exists because the satellite’s orbit is inclined, meaning it only passes over regions within this latitudinal range.
NASA has assessed the risk of harm to people on Earth as unlikely, estimating it at approximately one in 2,100. The agency and the Space Force will continue to monitor the re-entry and update predictions as the event approaches. The last attempt to push the Swift observatory into a higher orbit using a private space contractor failed last year when the contractor could not rendezvous with the satellite. Swift was estimated to be orbiting 171 miles above Earth last month before operations were ended to prepare for re-entry.
Two Decades of Cosmic Discovery
Launched in 2004 as part of NASA’s Medium Explorer program, the Swift observatory was built to explore cosmic gamma-ray bursts. These events are considered the most powerful explosions in the universe since the Big Bang. Over its operational life, the observatory detected and tracked more than 2,000 gamma-ray bursts. These bursts of energy occur approximately once per day and are brief, intense flashes of gamma radiation that can last from a few milliseconds to a few hundred seconds.
Scientists still do not know exactly what causes these bursts, theorizing that they may be the birth of a black hole in a massive stellar explosion or produced by the collision of two neutron stars. Swift provided critical data on these events, quickly returning observations of their location and strength to Earth.
In July, the observatory observed a wandering mega black hole shredding a star. This event, known as a tidal disruption event, occurs when a star passes fatally close to a supermassive black hole. The black hole, described as an orphan because it was located on the outskirts of a galaxy, lit up as it devoured the star. A paper describing the results in The Astrophysical Journal Letters stated that the event outshone its entire host galaxy in ultraviolet wavelengths, temporarily radiating with the light of about 10 billion suns.
Robert Stein, a research fellow at the University of Maryland and NASA’s Goddard Space Flight Center, explained that the team was looking for these star-shredding events to find otherwise invisible supermassive black holes wandering away from galactic cores. The key question remains how common these wandering black holes are and how they came to drift so far from their centers.
NASA stated that the Swift observatory has broadened our understanding of a wide variety of cosmic objects and events. These include active galaxies powered by supermassive black holes, stars undergoing X-ray flares, supernova explosions, and comets and asteroids in our own solar system. The mission’s legacy will remain in the data collected over its 20 years of operation.
Source: The Guardian
