An artist’s depiction illustrates a red dwarf (on the left) and a white dwarf (in the center) closely orbiting each other. Astronomers theorize that their tight orbit causes their magnetic fields to interact, resulting in the emission of radio pulses every two hours. – Artwork by Daniëlle Futselaar from artsource.nl
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In recent years, scientists have observed an intriguing phenomenon within our Milky Way galaxy: radio pulses pulsating like a cosmic heartbeat every two hours. These extended radio bursts, lasting from 30 to 90 seconds, were initially detected from the Ursa Major constellation, home to the Big Dipper.
Now, researchers have pinpointed the source of these unique radio pulses: a white dwarf, a type of dead star, closely orbiting a small, cool red dwarf star. Red dwarfs are the most abundant type of star in the universe.
These two stars, collectively known as ILTJ1101, are in such close proximity that their magnetic fields interact, producing what is termed a long period radio transient (LPT). Previously, such long radio bursts were only associated with neutron stars, remnants of massive stellar explosions.
However, a new study published in Nature Astronomy reveals that the movements of stars within a binary pair can also generate rare LPTs. Lead researcher Dr. Iris de Ruiter, a postdoctoral scholar at the University of Sydney, highlights that this discovery sheds light on the enigmatic class of long period radio transients.
These groundbreaking observations of bright, extended radio bursts from this binary star system represent just the beginning. This finding may enhance our comprehension of the stars capable of emitting radio pulses across space, offering insights into the intertwined history and dynamics of these celestial partners.
To unravel the Milky Way mystery, de Ruiter developed a method to detect radio pulses lasting seconds to minutes within the data collected by the Low-Frequency Array telescope (LOFAR), a network of radio telescopes across Europe operating at the lowest frequencies detectable from Earth.
Based on observations dating back to 2015, de Ruiter identified a single pulse followed by six more pulses from the same region of the sky, originating from a faint red dwarf star. However, she deduced that this star alone could not produce radio waves, suggesting an external influence.
While similar to fast radio bursts (FRBs), which are brief and intense flashes of radio waves, these radio pulses differ in duration and energy. FRBs are typically extragalactic events and exhibit higher luminosity compared to the pulses observed here.
Research coauthor Charles Kilpatrick, from Northwestern University, notes that the radio pulses share similarities with FRBs but have distinct characteristics, including lower energy levels and longer durations.
“The radio pulses are very similar to FRBs, but they each have different lengths,” remarked Kilpatrick.
“There is still a significant question about whether a continuum of objects exists between long-period radio transients and FRBs, or if they represent distinct populations.” De Ruiter and her team conducted follow-up observations of the red dwarf star using the 21-foot (6.5-meter) Multiple Mirror Telescope at the MMT Observatory on Mount Hopkins in Arizona, as well as the LRS2 instrument on the Hobby-Eberly Telescope at the McDonald Observatory in the Davis Mountains in Texas. The observations revealed that the red dwarf was moving rapidly back and forth, with its motion aligning with the two-hour period between radio pulses, as noted by Kilpatrick. This motion was caused by the gravitational influence of another star on the red dwarf. By measuring the motions, the researchers determined the mass of the companion star, identifying it as a white dwarf. The team observed that the two stars, situated 1,600 light-years away from Earth, were pulsing synchronously as they orbited a common center of gravity, completing one orbit every 125.5 minutes.
Regarding the mysterious pulses, the research team proposed two potential causes. Either the white dwarf emits the pulses periodically due to a strong magnetic field, or the magnetic fields of the red dwarf and the white dwarf interact during their orbital motion. The team plans to further study ILTJ1101 and observe any ultraviolet light emissions from the system to gain insights into the historical interactions between the two stars. De Ruiter also aims to observe the system in radio and X-rays during a pulse event, which could provide additional information on the interplay of magnetic fields.
While the radio pulses have currently ceased, de Ruiter mentioned that they may reappear in the future. The team is also analyzing LOFAR data to locate other long pulses. Dr. Kaustubh Rajwade, a study coauthor and radio astronomer from the University of Oxford, noted that discovering these long radio pulse-emitting systems has been significant, as their origins within the Milky Way are unlike anything previously known. These long pulses, unlike the short bursts from pulsars, can extend from seconds to nearly an hour, explained Natasha Hurley-Walker, a radio astronomer at the Curtin University node of the International Centre for Radio Astronomy Research in Australia, who was not involved in the study.
Hurley-Walker reflected on how transient radio sources have led to groundbreaking discoveries in astrophysics, such as pulsars, FRBs, and now, LPTs. She emphasized that these sources are starting to be uncovered in historical data spanning decades, indicating that they were previously overlooked. The study of these sources holds immense potential for revealing new insights into the universe.
She highlighted the remarkable discoveries, stating, “One of the most significant findings would probably be the detection of technosignatures through SETI.” Hurley-Walker referred to signals that may indicate the presence of intelligent life, a goal pursued by the SETI Institute for many years. To access additional CNN news and newsletters, you can sign up for an account on CNN.com.
