Cosmic mysteries deepen

Astronomers have made a startling discovery about a new type of cosmic phenomenon.

The discovery of an object, a long-period transient (LPT), known as ASKAP J1832-0911, has been seen to emit pulses of radio waves and X-rays for two minutes every 44 minutes.

LPTs are a relatively new class of astrophysical objects that are known to emit radio waves in a periodic fashion – unusually slowly compared to most periodic radio objects. However, this is the first time such objects have been detected in X-rays.

Currently, there is no clear explanation for what causes the signals, or why they ‘switch on’ and ‘switch off’ at such long, regular and unusual intervals.

Astronomers from the International Centre for Radio Astronomy Research (ICRAR), in collaboration with international teams, made the discovery. They hope that this latest discovery may provide insights into the sources of similar mysterious signals observed across the sky.

The team discovered ASKAP J1832-0911 by using the ASKAP radio telescope on Wajarri Country in Australia, owned and operated by Australia’s national science agency, CSIRO. They correlated the radio signals with X-ray pulses detected by NASA’s Chandra X-ray Observatory, which was coincidentally observing the same part of the sky.

Dr Marcin Glowacki from the School’s Institute for Astronomy was involved in the collaboration. Using observations of ASKAP J1832-0911 and the surrounding Milky Way galaxy taken from South Africa’s MeerKAT radio telescope, he looked for hydrogen gas located between the LPT and Earth. When the LPT is ‘on’ it is so bright that observations found the Milky Way gas blocking out some of that radio light. By detecting this gas within the LPT signal, he was able to place a lower limit on how far away this unusual object is, which was important to rule out association with other objects in that part of the sky. 

Explanations for the LPT include the possibility of the object being a magnetar (the core of a dead star with powerful magnetic fields), or a pair of stars in a binary system where one of the two is a highly magnetised white dwarf (a low-mass star at the end of its evolution).

However, even those theories do not fully explain what is being observed. This discovery could indicate a new type of physics or new models of stellar evolution.