Free Astronomy Magazine March-April 2025

43 MARCH-APRIL 2025 ASTRO PUBLISHING This mass loss could offset the en- ergy removed by gravitational waves, halting the companion’s in- ward motion.” So what could this companion be? A small black hole would plunge straight in, and a normal star would quickly be torn apart by the tidal forces near the monster black hole. But the team found that a low-mass white dwarf — a stellar remnant about as large as Earth — could re- main intact close to the black hole’s event horizon while shedding some of its matter. A paper led by Master- son summarizing these results ap- pears in the Feb. 13 edition of the journal Nature . This model makes a key prediction, Masterson notes. If the black hole does have a white dwarf compan- ion, the gravitational waves it pro- duces will be detectable by LISA (Laser Interferometer Space An- tenna), an ESA (European Space Agency) mission in partnership with NASA, which is expected to launch in the next decade. bital cycle,” said Master- son. If the fluctuations were caused by an orbiting mass, then the period would shorten as the object fell ever closer to the black hole’s event horizon, the point of no return. Orbiting masses gen- erate ripples in space-time called gravitational waves. These waves drain away or- bital energy, bringing the ob- ject closer to the black hole, increasing its speed, and shortening its orbital period. Over two years, the fluctua- tion period dropped from 18 minutes to just 7 — the first- ever measurement of its kind around a supermassive black hole. If this represented an or- biting object, it was now mov- ing at half the speed of light. Then something unexpected happened — the fluctuation period stabilized. “We were shocked by this at first,” Masterson explained. “But we realized that as the object moved closer to the black hole, its strong gravita- tional pull could begin to strip matter from the companion. D iagram depicting the spectacular accretion-disk, corona and jet evolution in the enigmatic changing-look AGN 1ES 1927+654. From left to right gives us the temporal evolution of the system which includes soft X-ray rise, QPO detection, jet formation and jet evolution. [S. Laha et al. 2025] R adio images of 1ES 1927+654 reveal emerging structures that appear to be jets of plasma erupting from both sides of the galaxy’s central black hole following a strong radio flare. The first image, taken in June 2023, shows no sign of the jet, likely because hot gas screened it from view. Then, starting in February 2024, the features emerge and expand away form the galaxy’s center, cover- ing a total distance of about half a light-year as measured from the center of each struc- ture. [NSF/AUI/NSF NRAO/Meyer at al. 2025] “One way to produce these oscilla- tions is with an object orbiting within the black hole’s accretion disk. In this scenario, each rise and fall of the X-rays represents one or- !