We deploy telescopes in space to avoid interference from the atmosphere and other radiation sources, but it isn’t always enough. The NuSTAR X-Ray telescope has had to deal with radiation pouring in from nearby objects, making it more difficult to find a signal in the noise. Astronomers have recently published the first study based on an object analyzed in this fashion, which uses this “nuisance light” to provide NuSTAR a larger effective field of view than predicted. SMC X-1 is a system that contains a neutron star that is brilliant in the X-ray region of the spectrum and is somewhat more massive than the Sun. However, the brightness of the stars changes drastically, and scientists want to know how and why. One team uses nuisance light that sneaked into NuSTAR to give some answers in The Astrophysical Journal.
The name SMC X-1 stems from the fact that it is located in the Small Magellanic Cloud, one of the nearest galaxies to our own. It’s a binary pulsar with a lot of flaring activity, which has perplexed scientists for a long time. The volatility of SMC X-1 is explained in part by its orbit around another, 15 times more massive, star, which obscures it from our view at times, but scientists believe something more is at work. The article doesn’t entirely answer the problem, but it does reveal how much mass SMC X-1 is absorbing from its larger and less dense neighbor, which causes it to spin faster.
Because the environment does such a fantastic job of shielding X-Rays, they are a particularly difficult section of the electromagnetic spectrum to study. X-Ray astronomy first began when rockets delivered the first equipment to vast altitudes, and it only became a significant field after X-Ray telescopes could be placed in orbit. Because there are so few telescopes in space, time spent on them is even more limited than time spent on other significant devices, therefore we don’t get to examine SMC X-1 as often as anybody in the field would want.
However, things change if you can gather data on numerous items at the same time. Caltech’s Dr. Brian Grefenstette characterized it thus way in a statement: “Imagine yourself sitting in a calm movie theater, watching a drama while hearing the explosions from the action movie next door. In the past, stray light served as a distraction from what we were attempting to concentrate on. Now that we have the skills to transform that additional noise into meaningful data, NuSTAR can be used to investigate the cosmos in whole new ways.”
Grefenstette is the leader of the StrayCats team, which collects data on 80 X-Ray sources that are bright enough and close enough in the sky to for NuSTAR to pick up large levels of nuisance radiation from them. Even though we don’t have the kind of focussed pictures obtained by staring directly at an X-ray source, this signals a significant increase in the time period over which we can watch their brightness for some of them. Because there are so many other X-ray sources in the Magellanic Clouds, NuSTAR spends a lot of time studying at objects near to it, SMC X-1 being a particularly notable example. It is dazzling enough at its peaks that much of its light spills into neighboring fields of vision. Nonetheless, many additional things are likely to become the focus of articles based on the principles initially described here.