What was the biggest explosion in the Universe?

The Universe, everywhere we look, is full of cataclysmic events and transient outbursts.

A combination of X-ray, optical, and infrared data reveal the central pulsar at the core of the Crab Nebula, including the winds and outflows that the pulsars carry in the surrounding matter. The central bright purplish-white spot is, indeed, the Crab pulsar, which itself spins at about 30 times per second. The material shown here spans about 5 light-years in extent, originating from a star that went supernova about 1,000 years ago, teaching us that the typical speed of the ejecta is around 1,500 km/s. The neutron star originally reached a temperature of ~1 trillion K, but even now, it’s already cooled to “only” about 600,000 K.

They come in all sorts of varieties, from supernovae to black holes to merger events and more.

Zw II 96 in the constellation of Delphinus, the Dolphin, is an example of a galaxy merger located some 500 million light-years away. Star formation is triggered by these classes of events, and can use up large amounts of gas within each of the progenitor galaxies, rather than a steady stream of low-level star formation found in isolated galaxies. Note the streams of stars between the interacting galaxies, which can either become part of a population of stars in the post-merger galaxy’s stellar halo, or could get expelled from the post-merger galaxy entirely, roaming the intergalactic medium. The end result will be larger numbers of stars bound together in a smaller number of total galaxies.

Whether in light, particles, or gravitational waves, energy output can always be quantified.

In this artistic rendering, a blazar is accelerating protons that produce pions, which produce neutrinos and gamma rays. Photons of all energies are also produced. Extreme events in energy are generated by processes occurring around the largest supermassive black holes known in the Universe when they’re actively feeding, as well as around highly magnetic neutron stars and actively feeding stellar mass black holes.

Supernovae release up to 10⁴⁴ joules (J) of energy: totaling the Sun’s entire lifetime output.

For the real black holes that exist or get created in our Universe, we can observe the radiation emitted by their surrounding matter, and the gravitational waves produced by the inspiral, merger, and ringdown. The electromagnetic radiation that we see solely originates from outside the event horizon itself; the Hawking radiation that black holes are predicted to emit is thus far unobservable in practice.

LIGO’s black hole mergers were even more energetic: up to ~10⁴⁷ J.

The second-largest black hole as seen from Earth, the one at the center of the galaxy M87, is shown in three views here. At the top is optical from Hubble, at the lower-left is radio from NRAO, and at the lower-right is X-ray from Chandra. These differing views have different resolutions dependent on the optical sensitivity, wavelength of light used, and size of the telescope mirrors used to observe them. These are all examples of radiation emitted from the regions around black holes, demonstrating that black holes aren’t so black, after all.

But the most extreme, energetic outbursts arise from jets emitted by supermassive black holes.

The galaxy Centaurus A is the closest example of an active galaxy to Earth, with its high-energy jets caused by electromagnetic acceleration around the central black hole. The extent of its jets are far smaller than the jets that Chandra has observed around Pictor A, which themselves are much smaller than the jets of Alcyoneus, which are still smaller than jets found in the newly discovered Porphyrion. This picture, alone, illustrates temperatures ranging from ~10 K to as high as several millions of K, and relativistic jets that are even physically larger than the stellar extent of the galaxy itself.

Accreted matter gets accelerated by these behemoths, ejecting particles all the way into intergalactic space.

The active galaxy IRAS F11119+3257 shows, when viewed up close, outflows that may be consistent with a major merger. Supermassive black holes may only be visible when they’re ‘turned on’ by an active feeding mechanism, explaining why we can see these ultra-distant black holes at all.

Smashing into the surrounding gas and plasma, they can carve cavities that span millions of light-years.

This image, which shows radio data overlaid atop WISE (infrared) data, displays the full physical extent of the giant radio galaxy Alcyoneus, now identified, at a scale of 16 million light-years (5 Megaparsecs), as presently the largest known galaxy in the Universe. If this were to occur inside a galaxy cluster, the energy would have been injected into the intracluster gas instead, carving out a large cavity.

The most extreme one ever was recently discovered in the Ophiuchus galaxy cluster, 390 million light-years away.

The radio data of the Ophiuchus galaxy cluster reveals the presence of supermassive black holes (in white), but also an extraordinarily large population of gas and ultra-hot plasma, at temperatures in excess of tens of millions of K.

NASA’s Chandra X-ray telescope found an enormous source of X-rays there, 15 times our galaxy’s diameter.

The X-ray data, shown here in pink and overlaid atop the infrared data, transforms this nondescript cluster of galaxies into an enormously bright and large source in the sky. The X-ray data, even at a distance of 390 million light-years, takes up about a quarter of a degree on the sky: half the size of the full Moon.

Combined with infrared and radio observations, an enormous cavity emerges.

A combination of data from X-ray, radio, and infrared observatories revealed an enormous cavity spanning ~1.5 million light-years across, corresponding to the largest single-event release of energy ever discovered.

It was carved by an ancient, explosive, supermassive black hole outburst, requiring 5 × 10⁵⁴ J of energy.

In concert with JWST, next-generation X-ray observatories like Lynx or Athena could serve as the ultimate complement for understanding the Universe. Without either of them, the X-ray community will remain underserved, still reliant on Chandra’s now-ancient capabilities.

A more distant, energetic event likely awaits discovery via ESA’s Athena or NASA’s Lynx.

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. This system is a binary supermassive system, where one component is approximately 18 billion solar masses and the other is 150 million solar masses. When they merge, they may emit as much energy, albeit in the form of gravitational waves, as was found in the most energetically-injected galaxy cluster.

Only supermassive black hole mergers, hitherto unseen, may surpass them.

Mostly Mute Monday tells an astronomical story in images, visuals, and no more than 200 words. Talk less; smile more.