Galaxies are classified into the few general shapes of the ‘Hubble sequence’, named after the astronomer Edwin Hubble. To see a diagram of this sequence, check my earlier post on the subject.
Now it appears that galaxies can change their form over time.
A team of astronomers compared 116 local galaxies with 148 distant ones. Because of the amount of time it takes for light to reach us from those distant galaxies, they were affectively comparing modern galaxies with ancient one.
They found that 6 billion years ago there was a much greater percentage of ‘peculiar’ galaxies that did not fit the standard galactic taxonomy. This indicates that the oddly shaped galaxies must have become normal spirals over time. The astronomers speculate that collisions and mergers with other galaxies were responsible for this reshaping.
| Credits: NASA, ESA, Sloan Digital Sky Survey, R. Delgado-Serrano and F. Hammer (Observatoire de Paris) |
Prior to this study, it was understood that collisions and mergers between galaxies happened, but that those events had mostly ended by 8 billions years ago. This new data suggests that the clashes continued until at least 4 billion years ago.
Very interesting. No matter how many times I hear it (or even explain it to kids), I still manage to find a bit of surprise in the notion that looking up and out is looking into the past.
ReplyDeleteLast night on the TV show NUMB3RS, a character mused that he had always looked on one particular star as a bit of a touchstone, something he looked for every night in the sky. One night he looked, and it was gone. It wasn't just the realization that "his" star had died (so to speak), but that for his entire life, and much longer, it had been dead--and he just didn't know it.
The science is a bit shaky (is the star really dead or now just below the threshold of naked-eye visibility?), but the philosophy behind his realization is valid.
It's like that letter "Dear Astrology" (http://sciencedigestive.blogspot.com/2010/01/dear-astrology-from-science-no-3.html), IF the alignment of stars were to affect humans, wouldn't the actual alignment be the influence, not our perception (which represents a mish-mash of information that is recent, outdated, and very, very outdated)?
Of course, the alignment of stars has no influence, which is very lucky, since it would be really hard to compute actual star charts.