Astronomers from the European Southern Observatory (ESO), using the MUSE instrument on the Very Large Telescope (VLT) at the Paranal Observatory, have found unexpected halos around all the 19 quasars they were observing. The finding is surprising because based on estimates from data collected in previous studies, only 10 percent — about two out of 19 — of the quasars should have been surrounded by halos.
The halos around quasars — the brightest and the most active objects in the universe, they are galaxies formed less than 2 billion years after the Big Bang; they have supermassive black holes in their centers and consume stars, gas, interstellar dust and other material at a very fast rate — are made of gas known as the intergalactic medium and extend for up to 300,000 light-years from the centers of the quasars.
The team of ESO astronomers is not sure why it observed a higher-than-expected number of halos around quasars, but suspects it could be due to the vastly better observing power of MUSE, compared to previous similar instruments.
“It is still too early to say if this is due to our new observational technique or if there is something peculiar about the quasars in our sample. So there is still a lot to learn; we are just at the beginning of a new era of discoveries,” Elena Borisova from the Swiss Federal Institute of Technology in Zurich, who was also lead author of the research paper, said in a statement.
The observation of these quasars, selected from among the brightest observable by MUSE, threw up another surprising find. The intergalactic medium in the halos was at a relatively low temperature of only about 10,000 degrees Celsius (about 18,000 degrees Fahrenheit), which is widely divergent from the currently accepted models that put the temperature of gases in close proximity to galaxies at upward of 1 million degrees.