Quasars are dazzling objects in the sky with explosive backstories. They are formed amidst collisions between galaxies, the result of swirling matter and energy. Scientists have now gathered new images of these cosmic objects in their 'teenage years' — looking a bit awkward and gangly — which have helped unveil some of their previously hidden origins.
Alongside being a spectacular sight, these observations are helping scientists figure out how the energetic objects are 'switched on'. The switch from a merging galaxy to a glowing quasar is still not fully understood.
“The new images capture the transitional phase in the merger-driven black hole scenario,” said Eilat Glikman of Middlebury College, Vermont.
“The Hubble observations are definitely telling us that the peak of quasar activity in the early universe is driven by galaxies colliding and then merging together,” said Glikman. “We are seeing the quasars in their teenage years, when they are growing quickly and all messed up."
Hubble astronomers looked at dusty quasars where their glow was suppressed by dust, allowing a view of the quasar's surroundings. NASA.
At the center of the majority of galaxies' cores is a black hole: the most massive object in the universe with amazingly strong gravitational attraction. So when galaxies collide, it's safe to assume that their central black holes will too. And because there's so much energy packed into these objects, a black hole collision is a powerful thing. The energy emitted from a black hole collision is so vast that some scientists hope that these events will emit gravitational waves — ripples in the spacetime field. Gravitational waves are predicted by Einstein's theory of general relativity, but they are so small we have never been able to observe them.
"These mergers are also the sites of future black hole mergers, which we hope will one day be visible with gravitational wave telescopes," Megan Urry, the Israel Munson professor of Astronomy and Astrophysics at Yale University said.
Quasars are elusive stellar objects because they are so bright that we can't always get a good idea of their surroundings; they outshine any surrounding matter. So the team had to pull out all their tricks in order to figure out what was going on around these quasars. The astronomers used the NASA Hubble Space Telescope's infrared vision to peer through the chaos: The dust surrounding the quasar dimmed its light enough that the surrounding galaxies could be seen in infrared.
“We’ve been trying to understand why galaxies start feeding their central black holes, and galaxy collisions are one leading hypotheses. These observations show that the brightest quasars in the universe really do live in merging galaxies,” said co-investigator Kevin Schawinski of the Swiss Federal Institute of Technology Zurich.
