Swift: Our Sleuth for the Universe’s Gamma-ray Bursts
The
universe is full of mysteries, and we continue to search for answers. How can
we study matter and energy that we can’t see directly? What’s it like inside the crushed core
of a massive dead star? And how do some of the most
powerful explosions in the universe evolve and interact with their surrounding
environment?
Luckily
for us, NASA’s Neil Gehrels Swift Observatory is watching the skies and helping
astronomers answer that last question and more! As we celebrate its 15-year
anniversary, let’s get you up to speed about Swift.
What are gamma-ray bursts and why are they interesting?
Gamma-ray bursts are the most powerful explosions in the universe. When they occur, they are about a million trillion times as bright as the Sun. But these bursts don’t last long — from a few milliseconds (we call those short duration bursts) to a few minutes (long duration). In the 1960s, spacecraft were watching for gamma rays from Earth — a sign of nuclear testing. What scientists discovered, however, were bursts of gamma rays coming from space!
Gamma-ray bursts eventually became one of the biggest mysteries in science. Scientists wanted to know: What events sparked these fleeting but powerful occurrences?
So how do gamma-ray bursts and Swift connect?
When it roared into space on a rocket, Swift’s main goals included understanding the origin of gamma-ray bursts, discovering if there were additional classes of bursts (besides the short and long ones), and figuring out what these events could tell us about the early universe.
With
Swift as our eyes on the sky, we now know that gamma-ray bursts can be some of
the farthest objects we’ve ever detected and lie in faraway galaxies. In fact,
the closest known gamma-ray burst occurred more than 100 million light-years
from us. We also know that these explosions are associated with some of the
most dramatic events in our universe, like the collapse of a massive
star or the merger of two
neutron stars — the dense cores of collapsed stars.
Swift is still a powerful multiwavelength observatory and continues to help us solve mysteries about the universe. In 2018 it located a burst of light that was at least 10 times brighter than a typical supernova. Last year Swift, along with NASA’s Fermi Gamma-ray Space Telescope, announced the discovery of a pair of distant explosions which produced the highest-energy light yet seen from gamma-ray bursts.
Swift
can even study much, much closer objects like comets and asteroids!
Why is Swift unique?
How
do we study events that happen so fast? Swift is first on the scene because of
its ability to automatically and quickly turn to investigate sudden and
fascinating events in the cosmos. These qualities are particularly helpful in
pinpointing and studying short-lived events.
The
Burst Alert Telescope, which is one of Swift’s three instruments, leads the
hunt for these explosions. It can see one-sixth of the entire sky at one time.
Within 20 to 75 seconds of detecting a gamma-ray burst, Swift automatically
rotates so that its X-ray and ultraviolet telescopes can view the burst.
Because of the “swiftness” of the satellite, it can look at a lot in 24 hours — between 50 and 100 targets each day! Swift has new “targets-of-opportunity” to look at every day and can also look at objects for follow up observations. By doing so, it can see how events in our cosmos change over time.
How did Swift get its name?
You may have noticed that lots of spacecraft have long names that we shorten to acronyms. However, this isn’t the case for Swift. It’s named after the bird of the same name, and because of the satellite’s ability to move quickly and re-point its science instruments.
When
it launched, Swift was called NASA’s Swift Observatory. But in January 2018,
Swift was renamed the Neil Gehrels Swift Observatory in memory of the mission’s
original principal investigator, Neil Gehrels.
Follow along with Swift to see a typical day in the life of the satellite:
