Active galaxies give off bright radiation from their cores, where gas heats up as it is compressed into a swirling accretion disk encircling the black hole.

活动星系从它们的核部发出明亮的光芒，在那里，气体被加热并压缩成一个漩涡状的圆盘，漩涡的中心便是黑洞。

youdao

Earlier studies looked only at galaxies with the brightest active nuclei, which could have biased their results, Jahnke said.

先前的研究只关注存在有明显活动星核的星系，这很可能导致结果产生偏差，Jahnke说。

youdao

This scenario may explain why only 10% of active galaxies have radio jets, and how active galaxies evolve over time.

这种假设或许可以解释为什么活跃星系中只有10%存在喷流，以及它们如何持续演变。

youdao

Blazars are a special case of "active galaxies" - those whose supermassive black holes spray out great quantities of light across the whole electromagnetic spectrum as they feed on surrounding matter.

BBC: Blazar Markarian 421's flare-up is cosmic coincidence

Active galaxies emit jets of light - up to trillions of times more energetic than the light we see - and a blazar is one with a jet pointing toward the Earth.

BBC: Blazar Markarian 421's flare-up is cosmic coincidence