A typical lunch outing with friends lasts about an hour and a half. If it’s bottomless brunch, maybe tack on a few more hours. But supermassive black holes don’t care for our human constructions of time — it turns out they will eat for a decade if they choose.
Illustration: CXC/M. Weiss; X-ray: NASA/CXC/UNH/D. Lin et al, Optical: CFHT. (Image: NASA)
New research, published on February 6 in Nature Astronomy, details the longest black hole brunch ever studied, in which a supermassive giant ripped apart a neighbouring star and feasted on it for almost 10 years. The team first observed the black hole — called XJ1500+0154 — using the ESA’s XMM-Newton on 23 July 2005. Since then, the group used other instruments including NASA’s Chandra X-ray Observatory to keep an eye on the black hole, located in a small galaxy roughly 1.8 billion lightyears from Earth. XJ1500+0154 became increasingly bright up until its luminosity peaked in 2008 — by that time, it was 100 times brighter than when it was first observed.
“For most of the time we’ve been looking at this object, it has been growing rapidly,” co-author James Guillochon of the Harvard-Smithsonian Center for Astrophysics said in a press release. “This tells us something unusual — like a star twice as heavy as our Sun — is being fed into the black hole.”
After multiple rounds of observation, the team is confident that what they have observed is a tidal disruption event (TDE), in which a star wanders too close to a black hole and is consequently ripped apart by its gravity. While TDEs have been observed before, this one is the longest ever studied. Interestingly, the material surrounding the black hole consistently exceeded the Eddington limit, which describes the maximum luminosity a body — in this case, a star — can reach, given the outward force of radiation and the inward pull of gravity from the black hole.
“It represents a new, very energetic class of TDEs,” Dacheng Lin, a co-author on the study, told Gizmodo. “[The research also shows] black holes can eat mass at a large rate and grow very fast.”
Lin hopes the team’s findings will help unlock some of the secrets of these hungry black holes, including how they reached masses up to a billion times higher than that of our sun in the early days of the universe.
“Events like this will aid future research on the so-called super-Eddington accretion of supermassive black holes, when the black hole is fed too much mass in a short time,” he said.