Quasars, the massive, enigmatic and energetic centers of distant galaxies, have long fascinated us with their bizarre behaviors. Why do they pump out so much energy? Why do they produce the radiation that they do? How did they affect the early universe? A recent publication, however, finds the a lack of bizarre activity of quasars that is, well, bizarre.
Mike Hawkins from the Royal Observatory in Edinburgh searched for, and did not find evidence for, so-called time dilation in distant quasars. Time dilation is a counter-intuitive, yet actual, feature of Einstein's special relativity in which time slows down for an object that is in motion relative to another.
Since the universe is expanding — and the distant quasars are racing away from us — a clock placed in one of these distant galaxies should be running more slowly than a clock we have on Earth. Therefore, the effects of time dilation for distant objects can be measured if we can observe the ticking clock in the distant galaxy.
Hawkins took advantage of the fact that quasars blink. This blinking, or variability, can be viewed as the "ticking clock." He used data from quasar monitoring programs stored on photographic plates to measure the timescale of of the blinking. Looking at the timescales for two groups of quasars, one distant and the other even farther away, there was no measurable difference. That meant no time dilation: meaning that for both groups of quasars, the clocks were the same.
This could mean several things. It could be a sign that the universe is not expanding. Or, it could indicate that quasars are not really what we think they are. However, for either of these scenarios to be true, you'd have to explain away or disprove mountains of evidence in favor of these models.
The possibility that a quasar's blinking isn't actually caused by the galaxy cores at all, but rather to mini-black holes that are distorting or interrupting in our view of it, is intriguing. But more evidence is needed to support that.
The most straightforward scenario, according to Hawkins, is that we just don't understand how quasars evolve. After all, as the supermassive black holes powering these beasts gobble up matter and grow, the blinking may change. Since this explanation has its problems as well, further study is certainly needed to determine why such a theoretically simple experiment gives a not-so-simple-to-explain result.
As cool as it would be to see a major scientific model overturned, I wouldn't rewrite the textbooks just yet. But I will stay tuned to see what other secrets we can unravel from distant quasars.
Thanks to @goddessgeek for tweeting about this story a few days ago!
Image: 3C273, my favorite quasar. From the Kitt Peak National Observatory.