A Major Test for Relativity

A Major Test for Relativity

It isn’t often that a scientist correctly predicts something that will occur within less than two years in a galaxy 3.5 billion light-years away. Yet that’s what Finnish physicist Mauri Valtonen did last year as reported in the January 2008 the American Astronomical Society Meeting held in Austin, Texas, and published in both the January 18, 2008 issue of Science (requires subscription) and the February 2008 issue of Sky and Telescope.

The distant galaxy OJ 287 has garnered the attention of astronomers in recent years because its brightness was observed to increase 100,000 times for a short period every 12 years. Since this brightening was periodic, it was natural to attribute the occurrence to one object orbiting another. It has also been noted that the peak of brightness was, itself, split into two peaks separated by roughly a year.

In a paper published in the April 20, 2007 issue of the Astrophysical Journal, Valtonen proposed a model for this phenomenon. His proposal consists of a large black hole of a mass 100 million times the mass of our Sun orbiting an even larger black hole of a mass 18 billion times the mass of our Sun at the center of the galaxy. Valtonen’s model envisioned the largest black hole being surrounded by a disk of accreting material, with the smaller black hole in a highly eccentric orbit around it but in a plane tilted relative to the disk. In this way, the smaller object plunging through the disk twice in each orbit around the central black hole caused the double brightening.

In the model, the two-disk incursions were separated by a time difference that depended on some geometric and data-fitting details, but also, more importantly, on two predictions of Einstein’s theory of general relativity. In the extremely strong gravitational fields that distort space-time near a super-massive object like this black hole, general relativity predicts a rapidly changing orientation of the companion’s orbit as well as shrinkage of this orbit due to the emission of gravitational radiation.

At the time the paper was published in April 2007, the first of the most recent 12-year brightening had already occurred in November 2005. The model predicted the next crossover would occur in the range of September 9-16, 2007. However, if Einstein’s theory was wrong regarding the space-time curvature, then the peak would occur about ten days earlier, if wrong regarding gravitational radiation, the peak would occur about three weeks later.

Valtonen and a team of some 30 professional and amateur astronomers prepared to observe this next encounter using a variety of instruments. They were encouraged when the flare showed up as predicted by the model that included both predictions of relativity. This was a triumph for Einstein’s theory in a circumstance of intense gravity not previously tested. Additionally, the 18 billion solar-mass black hole is the largest ever detected (by a factor of 6 over the previous record holder). Its size is staggering at almost 10 percent of the mass of the Milky Way Galaxy.

Einstein has once again been proven correct. The research also provides key evidence in support of the big bang model for the universe and, because it incorporates the big bang, of RTB’s creation model.