Monster Black Holes Are Everywhere

Before Hubble, astronomers theorized the existence of supermassive black holes, but they had no conclusive evidence. Quasars, extremely bright quasi-stellar objects in remote active galaxies, indirectly hinted at their existence, but direct evidence of supermassive black holes didn’t come until 1994 when Hubble’s Faint Object Camera observed the heart of the giant elliptical galaxy M87. Hubble’s observations found a whirlpool of hot, ionized gas orbiting the heart of the galaxy at a speed of about 1.2 million miles per hour (550 kilometers per second). Only a supermassive black hole would have the gravitational power to create a vortex of hot gas at such velocities.

Bright, golden light in the upper-left corner. It diffuses out from the point gradually giving way to a darker background in the lower-right corner. Emanating from the bright point is a clumpy stream of white gas that stretches toward the lower-right corner.

Observations with Hubble not only helped confirm that the center of the elliptical galaxy M87 harbors a black hole 2.6 billion times more massive than our Sun but showed unprecedented detail in the jet of subatomic particles streaming away from the central black hole.

NASA and the Hubble Heritage Team (STScI/AURA)

Supermassive black holes are millions to tens of billions times the mass of the Sun. A Hubble galaxy census showed that a black hole’s mass is dependent on the mass of its host galaxy’s central bulge of stars: the larger the galaxy, the larger the black hole. This close relationship may be evidence that black holes grew along with their galaxies, devouring a fraction of the galaxy’s mass and intrinsically linking the black hole to the galaxy’s evolution.

Black holes aren’t just associated with galaxies. Astronomers estimate that 100 million black holes roam the stars of our Milky Way galaxy alone. In 2022, two teams using Hubble data measured how a suspected isolated black hole’s gravity acted like a lens, warping and deflecting the light from a background star. Their measurements indicate the lensing object’s size is either a black hole or a compact neutron star.

Four quadrants. The upper two hold images of the galaxies NGC 3377 (left) and NGC 3379 (right). The bottom left quadrant holds and image of the galaxy NGC 4486B. The lower-right quadrant shows an expanded view of NGC 4486B's center. Each image holds a bright-yellow core surrounded by more diffuse a yellow, then orange, and later red glow.

Combining images with data from Hubble’s spectrographs, researchers have peered into the center of many galaxies and established the existence of large black holes. These massive black holes surround themselves with luminous stars and gas, which are visible as bright knots. In a census performed by Hubble in the late 1990s, galaxies NGC 3379 and NGC 3377 were found to have black holes that “weighed in” at 50 million and over 100 million solar masses, respectively, and NGC 4486B was revealed to have a double nucleus at its core.

NASA, Karl Gebhardt (University of Michigan), and Tod Lauer (NOAO)

Two images. Left: A yellow-orange, and reddish disk (looking like a doughnut) surrounded by broader white and rust colored disk. Right: A nearly edge-on rusty-colored disk the far side appearing more white.

These Hubble images show disks of dust that fuel black holes at the centers of the galaxies NGC 4261 (left) and NGC 7052 (right).

Left: NASA, H. Ford, L. Ferrarese (Johns Hopkins University); Right: NASA, Roeland P. van der Marel (STScI), Frank C. van den Bosch (Univ. of Washington)

Left: A diffuse, white cloud that is vertically bisected by two dark dust lanes. A turquoise, vertical rectangle denotes the area that the spectrograph sampled. Right: A vertical zig-zag of colors that are green through the middle (top to bottom) and blue on the left and red on the right.

(Left) This Hubble image shows the bright core at the center of galaxy M84, surrounded by a vertical dark band of gas and dust. (Right) This plot was generated by passing light from near the galaxy’s core through a spectrograph. The thin, vertical rectangle in the center of the left panel shows the size and shape of the spectrograph’s sampling slit. A spectrum was taken at each point along the slit, recording the rotational motion of stars and gas at each position. Blueshifted light indicates the material is moving toward Earth, while redshifted light indicates the material is moving away. The farther the light is plotted to the left or right, the greater the source’s rotational velocity. At 880,000 miles per hour, stars and glowing gases nearest to M84’s core are moving the fastest. They are circling a black hole at the center of the galaxy, with material plotted on the left moving rapidly toward Earth and material on the right rapidly receding.

NASA, Gary Bower, Richard Green (NOAO), and the STIS Instrument Definition Team

Dr. Jennifer Wiseman, Hubble's Senior Project Scientists, explains how black holes moved from a theory to a reality.
NASA; Director, Producer & Editor: James Leigh

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