Travel the universe with Dr. Ethan Siegel as he answers the biggest questions of all
If you thought LIGO’s recent discoveries were profound and unusual, wait until you meet OJ 287.
Recently, LIGO has revolutionized our knowledge of the Universe by discovering merging black holes.
The gravitational wave signal from the first pair of detected, merging black holes from the LIGO collaboration. The raw data and the theoretical templates are incredible in how well they match up. (B. P. Abbott et al. (LIGO Scientific Collaboration and Virgo Collaboration))
Near the centers of galaxies, mergers, accretion, and collisions create supermassive black holes undetectable by LIGO.
The sensitivities of a variety of gravitational wave detectors, old, new, and proposed. Note, in particular, Advanced LIGO (in orange), LISA (in dark blue), and BBO (in light blue). LIGO can only detect low-mass and short-period events; longer-baseline observatories are needed for more massive black holes. (Minglei Tong, Class.Quant.Grav. 29 (2012) 155006)
Practically all galaxies contain them, including our Milky Way.
This artist’s impression shows the orbits of stars around the supermassive black hole at the centre of the Milky Way. In 2018 one of these stars, S0–2, will pass very close to the black hole, presenting the best opportunity to study the effects of very strong gravity on its light and orbit. The orbits have been so well studied that we have directly determined the black hole’s mass to be four million solar masses. (ESO / L. Calçada)
An ultra-distant quasar showing plenty of evidence for a supermassive black hole at its center. How that black hole got so massive so quickly is a topic of contentious scientific debate, but mergers of smaller black holes formed in early generations of stars might create the necessary seeds. (X-ray: NASA/CXC/Univ of Michigan/R.C.Reis et al; Optical: NASA/STScI)
Two bipolar jets are often emitted, creating a blazar when one points at us.
When black holes feed on matter, they create an accretion disk and a bipolar jet perpendicular to it. When a jet from a supermassive black hole points at us, we call it either a BL Lacertae object or a blazar. (NASA/JPL)
Over time, galaxies merge, causing their black holes to sink to the new galaxy’s core, where they coalesce.
Most black holes that exist are low in mass: 100 solar masses or less. But at the centers of galaxies, it isn’t always a single supermassive black hole that dominates, but sometimes there can be multiples. They will eventually coalesce and merge together. (NASA, ESA and G. Bacon (STScI))
The most massive pair of black holes in the known Universe is OJ 287, whose gravitational waves will be out of reach of LISA. A longer-baseline gravitational wave observatory could see it. (Ramon Naves of Observatorio Montcabrer)
Every 11–12 years since, it’s produced another burst, recently discovered to have two, narrowly-separated peaks.
When material gets accelerated and funneled into the enormous magnetic field surrounding a supermassive black hole, it can get ‘beamed’ in a particular direction. When those beams arrive at our eyes, we see a tremendous increase in flux. OJ 287 shows two distinct beaming enhancements every ~11–12 years. (KIPAC / SLAC / Stanford)
Its central, supermassive black hole is 18 billion solar masses, one of the largest known in the Universe.
An X-ray and radio composite of OJ 287 during one of its flaring phases. The ‘orbital trail’ that you see in both views is a hint of the secondary black hole’s motion. (False color: X-ray image from the Chandra X-ray Observatory; contours: 1.4 GHz radio image from the Very Large Array)
The most massive black hole binary signal ever seen: OJ 287. This tight binary black hole system takes on the order of 11–12 years to complete an orbit. Despite making an orbit 1/5th of a light year in size (hundreds of times the Sun-Pluto distance), it should merge in just thousands of years. (S. Zola & NASA/JPL)
Due to General Relativity, these orbits precess 27,000 times faster than Mercury’s around the Sun.
In Newton’s theory of gravity, orbits make perfect ellipses when they occur around single, large masses. However, in General Relativity, there is an additional precession effect due to the curvature of spacetime, and this causes the orbit to shift over time, in a fashion that is sometimes measurable. Mercury precesses at a rate of 43″ (where 1″ is 1/3600th of one degree) per century; the smaller black hole in OJ 287 precesses at a rate of 39 degrees per 12-year orbit.(NCSA, UCLA / Keck, A. Ghez group; Visualization: S. Levy and R. Patterson / UIUC)
The most distant X-ray jet in the Universe, from quasar GB 1428, is approximately the same distance and age, as viewed from Earth, as quasar S5 0014+81, which houses possibly the largest known black hole in the Universe. (X-ray: NASA/CXC/NRC/C.Cheung et al; Optical: NASA/STScI; Radio: NSF/NRAO/VLA)
A scaled-up version of LISA, with satellites at L4, L5, and around Earth, should detect it immediately.
Theproposed‘BigBangObserver’wouldtakethedesignofLISA,theLaserInterferometerSpaceAntenna,andcreatealargeequilateraltrianglearoundEarth’sorbittogetthelongest-baselinegravitationalwaveobservatoryever. (Gregory Harry, MIT, from the LIGO workshop of 2009, LIGO-G0900426)
Mostly Mute Monday tells the scientific story of an astronomical object, process, or phenomenon in images, visuals, and no more than 200 words. Talk less, smile more.
