Travel the universe with Dr. Ethan Siegel as he answers the biggest questions of all
We’re one step closer to solving the mystery of how they get so big so fast.
A great cosmic mystery for science is explaining how supermassive black holes form.
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. Many quasars even outshine the most luminous galaxies of all. (X-RAY: NASA/CXC/UNIV OF MICHIGAN/R.C.REIS ET AL; OPTICAL: NASA/STSCI)
The first stars should lead to modest black holes: hundreds or thousands of solar masses.
As viewed with our most powerful telescopes, such as Hubble, advances in camera technology and imaging techniques have enabled us to better probe and understand the physics and properties of distant quasars, including their central black hole properties. (NASA AND J. BAHCALL (IAS) (L); NASA, A. MARTEL (JHU), H. FORD (JHU), M. CLAMPIN (STSCI), G. HARTIG (STSCI), G. ILLINGWORTH (UCO/LICK OBSERVATORY), THE ACS SCIENCE TEAM AND ESA (R))
But when we see the Universe’s first black holes, they’re already ~1 billion solar masses.
This image of ULAS J1120+0641, a very distant quasar powered by a black hole with a mass two billion times that of the Sun, was created from images taken from surveys made by both the Sloan Digital Sky Survey and the UKIRT Infrared Deep Sky Survey. The quasar appears as a faint red dot close to the centre. This quasar was the most distant one known from 2011 until 2017, and is seen as it was just 770 million years after the Big Bang. Its black hole is so massive it poses a challenge to modern cosmological theories of black hole growth and formation. (ESO/UKIDSS/SDSS)
The leading idea is black holes form and merge, and then rapidly accrete matter at maximal rates.
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. (NASA’S GODDARD SPACE FLIGHT CENTER/SDSS/S. VEILLEUX)
But those rapidly growing black holes should be invisible, obscured by the dense gas clouds they feed upon.
This artist’s rendering shows a galaxy being cleared of interstellar gas, the building blocks of new stars. Winds driven by a central black hole are responsible for this phenomenon. However, there should be an intermediate time, while the central black hole is shrouded in the dense gas that enables it to grow, where X-rays and radio/sub-mm light may be visible, but no optical signatures will be present, as the gas itself is capable of obscuring the light from the quasar almost entirely. (ESA/ATG MEDIALAB)
Realistically, in order to grow from its initial seeds to the supermassive, billion-solar-mass behemoths we see less than a billion years after the Big Bang, black holes will have to go through a period where they’re feeding on matter at an extraordinary rate. The amount of gas that must be present is so great that the black hole is expected to be obscured, or cloaked, for hundreds of millions of years. For the first time, a black hole this obscured while simultaneously being so young, massive and distant has been discovered. (C. CARREAU / ESA)
Although 180 ultra-distant (z > 6) quasars have been discovered, all were found with optical telescopes.
In the center of the image, just above and to the right of the brightest central light source, is the X-ray and infrared/sub-mm source detected, for the first time, with no optical counterpart. You’re not seeing anything in this Pan-STARRS image because there’s nothing to see, but going to different wavelengths changes that story dramatically. (PAN-STARRS COLLABORATION)
In the optical, as Pan-STARRS shows, there’s little to see.
Although Hubble is most famous for its visible light observations, it is capable of viewing sources in the infrared. At 1.4 microns, it detects light associated with PSO167–13 that corresponds to ultraviolet light in this object’s rest frame, but is shifted into the infrared by the expansion of the Universe. (F. VITO ET AL., A&A 628, L6 (2019))
But Hubble, in the near-infrared, uncovered a blurred, distant source of light.
ALMA, the millimeter/sub-millimeter observatory, was able to image the region around PSO167–13 in a variety of wavelengths, where it uncovered emission lines corresponding, at this high redshift (z = 6.515), to singly-ionized carbon. Two independent sources can be seen, with a 99.96% probability of association with the newly detected Chandra X-ray signal. (F. VITO ET AL., A&A 628, L6 (2019))
ALMA, in sub-millimeter wavelengths, resolved two independent sources by measuring ionized carbon emission lines.
This is indeed a quasar: PSO167–13, but it would take X-ray data to confirm it.
Chandra X-ray data revealed what may be the most distant shrouded black hole. Found at a time only about 850 million years after the Big Bang, this black hole could help astronomers better understand an important epoch in the Universe. Optical light searches, represented by the large PanSTARRS image, generally only uncover unobscured quasars. The X-rays from PSO167–13 show this black hole is veiled by thick clouds of gas and dust. The Chandra (X-ray) and ALMA (sub-mm) images show the same fields of view around PSO167–13. (X-RAY: NASA/CXO/PONTICIFCA CATHOLIC UNIV. OF CHILE/F. VITO; RADIO: ALMA (ESO/NAOJ/NRAO); OPTICAL: PANSTARRS)
With soft (low-energy) X-ray data, at left, this object is invisible. But on the right, in hard (high-energy) X-rays, there is clearly an object there. Hard X-rays are typically emitted by quasars that are accelerating matter to tremendous energies, with the position of PSO167–13 shown with the cyan cross. The X-ray source is better aligned with the location of the companion galaxy, visible in the ALMA image shown earlier. (F. VITO ET AL., A&A 628, L6 (2019))
Its light is 12.95 billion years old: the most distant gas-shrouded, growing black hole ever seen.
Mostly Mute Monday tells an astronomical story in images, visuals, and no more than 200 words. Talk less; smile more.
