New technique can multiply insights provided by NASA's NuSTAR telescope

Stray light is often a nuisance that needs to be filtered out. It can interfere with observations much like external noise can drown out a phone call. However, a new approach has made it possible to use this stray X-ray light to learn about more cosmic objects in the universe.

Astronomers have designed a technique to use the unwanted stray light trickling into NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) X-ray space observatory to study even more cosmic objects than before whilst performing normal targeted observations.

The development has the potential to multiply the insights that NuSTAR provides, NASA says.

What an illuminating discovery.Astronomers with @NASA’s NuSTAR X-ray space observatory are using previously unwanted light to study even more cosmic objects than before – and it's all thanks to a design quirk! https://t.co/DMd8Z6zLtE pic.twitter.com/QkKmfLSGa1

— NASA JPL (@NASAJPL) March 1, 2022

Stray light is often a nuisance that needs to be filtered out. It can interfere with observations much like external noise can drown out a phone call. However, a new approach has made it possible to use this stray X-ray light to learn about more cosmic objects in the universe.

The paper describing the first use of NuSTAR's stray light observations is published in the Astrophysical Journal. Researchers are using the telescope's stray light observations to learn about a neutron star in a system called SMC X-1. Neutron stars are some of the densest objects in the universe, second only to black holes.

The neutron star in SMC X-1 orbits a living star in one of two small galaxies orbiting our Milky Way galaxy. Decades of direct observations by telescopes including NuSTAR have revealed a pattern to the brightness fluctuations in the neutron star, with researchers pinpointing several reasons why SMC X-1 changes in brightness when studied by X-ray telescopes.

"A group of NuSTAR team members has spent the last few years separating the stray light from various NuSTAR observations. After identifying bright, known X-ray sources in the periphery of each observation, they used computer models to predict how much stray light should appear based on which bright object was nearby. They also looked at almost every NuSTAR observation to confirm the telltale sign of stray light," according to a post on NASA's website.

The team created a catalog of NuSTAR's stray light observations of X-Ray sources, named "StrayCats".

"In the past, that's what the stray light was like – a distraction from what we were trying to focus on. Now we have the tools to turn that extra noise into useful data, opening an entirely new way of using NuSTAR to study the universe," says Brian Grefenstette, a senior research scientist at Caltech and the NuSTAR team member leading the StrayCats work.

Researchers believe that observing the frequency and intensity of a neutron star's changes in brightness can help them decipher what’s happening to those objects.

More information can be found here.