The farthest thing most backyard telescopes will ever show you is a quasar
Point a modest 6-inch telescope at Virgo between March and July and you can catch 3C 273, light that left a feeding black hole about 2.4 billion years ago. It was the first quasar ever identified, and it outshines its whole host galaxy more than sixteen times over.
The name is a catalogue number: object 273 in the Third Cambridge Catalog of Radio Sources, published in 1959 and ordered by right ascension. Cyril Hazard pinned down its position at the Parkes Radio Telescope by timing when the Moon passed in front of it, and astronomers matched the radio signal to what looked like an ordinary faint star. In 1963 Maarten Schmidt and Bev Oke showed in two Nature papers that its light was redshifted by 0.158, which put it billions of light-years away. Other radio sources such as 3C 48 had been tied to starlike points before, and objects like BL Lac had been mistaken for variable stars, but nobody knew what they were until this one was cracked.
Its power is hard to picture. With an absolute magnitude of minus 26.7, it would look almost as bright as the Sun if it sat at the distance of Pollux, roughly 10 parsecs. In visible light it emits over 4 trillion times what our star does. The engine is a supermassive black hole of about 886 million solar masses, measured by reverberation mapping of its broad emission lines; nothing else known could supply that much energy.
A narrow jet stretches roughly 200,000 light-years from the core. Hubble images in 1995 showed it broken into bright knots separated by fainter stretches, and in 2003 it swung abruptly by 2 degrees, more than its own 1.1-degree opening angle. Radio, infrared and optical light from the jet share the same polarisation, the signature of synchrotron emission from particles moving near light speed. Brightness flickers across the spectrum, from radio to gamma rays, over days to decades.
The quasar also does quiet practical work. Its catalogued position helps standardise 23 extragalactic radio sources that define the International Celestial Reference System, the framework astronomers use to say exactly where anything in the sky is. It was among the first extragalactic X-ray sources found, in 1970, though the cause of those X-rays was still argued over in 2006.
Source: 3C 273
