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3C273, the nearest bright quasar

Visible image of 3C273
Visible image of 3C273 Deeper optical image of 3C273

Visible spectrum of 3C273
Visible spectrum of 3C273, showing the redshifted H lines

3C273's one-sided jet
Overexposed optical image of 3C273 showing jet
Radio
3C273 radio 		Visible
3C273 optical 		X-ray
3C273 x-ray

3C273's jet at various wavelengths
3C273's jet at various wavelengths

3C273's jet is superluminal (appears to travel faster than light)
3C273 jet 1994-1998

The Lyman alpha forest

The Lyman alpha line is the strongest spectral line of hydrogen. In the laboratory it is an ultraviolet line; in quasars the Lyman alpha line is redshifted into the visible or even infrared.

Quasars typically emit strong Lyman alpha. Blueward of the emission line is a forest of Lyman alpha absorption lines, produced by the cosmic web of hydrogen gas along the line of sight between us and the quasar.

Spectrum of a quasar at redshift 2.536

High redshift quasars

Spectrum of a quasar at redshift 5.0 Spectrum of a quasar at redshift 5.80
A quasar at redshift 6.2 Spectrum of the quasar at redshift 6.2
A quasar at redshift 6.2 Spectrum of the quasar at redshift 6.8

Quasars were more common when the Universe was younger

Number density of quasars as a function of age
The quasar PKS 2349
A montage of six quasars
Quasar animation
 Black Hole silhouetted against the Milky Way Spring 2019 ASTR 2030 Homepage

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Updated 2019 Jan 10