The massive galaxy M87, the central object of the Virgo cluster, has drawn our attention for a long time. It was in 1918 that Heber Curtis discovered a jet pushing at least 5000 light years away from the center of the galaxy. In 1949, the radio source Virgo A was identified with M87, and by the 1960s it was believed that the jet was actually two sided, its one-sided appearance due to relativistic Doppler beaming, which increased the luminosity of the jet in the direction of the observer.
That latter point was confirmed by recent observations using the Very Long Baseline Array (VLBA), with a resulting image showing detail down to a resolution of one milli-arcsecond. Some fifty times better than what Hubble can manage at optical wavelengths, the radio image (seen below in false color) shows the faint counter-jet structure that had been posited by the Russian astrophysicist Iosif Shklovsky. The latter noted that the jet liberated as much energy as the explosion of ten million supernovae.
Image: The Inner Jet of the Radio Galaxy M87 located in the Virgo cluster. The angular resolution of this false-color radio image observed by the VLBA at 2 cm wavelength is approximately one milli-arcsecond, fifty times better than that of the Hubble Space Telescope at optical wavelengths. The image shows a limb brightened jet and a faint counter-jet. The central gap is consistent with the presence of a fast inner jet which is beamed away from the observer surrounded by a slower moving outer plasma seen by the VLBA. Credit: Y.Y. Kovalev, MPIfR Bonn.
The apparent mechanism in all this is a supermassive black hole in the center of the galaxy. The rapidly rotating accretion disk surrounding it feeds the hole, while matter is ejected from the nucleus in the observed jets. Of course, a playful look for macro-engineering might suggest alternative explanations. M87 fascinated Arthur C. Clarke, who wrote about it in a book called The Scientist Speculates: An Anthology of Partly-Baked Ideas (New York: Capricorn Books, 1962), likening it to a scenario he had painted in his 1954 novel The City and the Stars:
Man was about to leave his Universe, as long ago he had left his world. And not only Man, but the thousand other races that had worked with him to make the Empire. They were gathered together, here at the edge of the Galaxy, with its whole thickness between them and the goal they would not reach for ages.
They had assembled a fleet before which imagination quailed. Its flagships were suns, its smallest vessels planets. An entire globular cluster, with all its solar systems and all their teeming worlds, was about to be launched across infinity.
The long line of fire smashed through the heart of the Universe, leaping from star to star. In a moment of time a thousand suns had died, feeding their energies to the monstrous shape that had torn along the axis of the Galaxy and was now receding into the abyss . . .
It’s that last line that seizes the attention, a galactic jet’s inconceivable energies created by artificial means. Clarke later noted in a postscript to the reprint of this essay in Cosmic Search magazine that he had written it before the realization that explosive events tied to such active galactic nuclei (AGN) seem to be common in the universe. He also gave a nod both to Freeman Dyson and to Stanley Schmidt’s chilling line in The Sins of the Fathers (1976) that “Seyfert galaxies are industrial accidents.”
Now we have a better look at the central region of M87 than ever before, one corresponding to a linear resolution of three light months. Adding the Effelsberg 100m radio telescope to provide a trans-Atlantic baseline should provide an even more detailed image of the galaxy’s jet. An industrial accident it’s doubtless not, nor is it evidence of extraterrestrial engineering, but what a magnificent natural phenomenon grows out of the tortured interactions at this galaxy’s heart.