First up, further proof for the existence of dark energy in the form of a new measurement of the Hubble constant.
The Hubble constant is pretty much the most important number in cosmology, a number that indicates the current rate the universe is expanding at (i.e. the rate at which galaxies are receding from one another).
Using the Hubble Space Telescope’s new infrared camera, scientists have derived a refined Hubble constant of 73.8 kilometers per second per megaparsec (for every million parsecs separating two galaxies, they move apart 73.8 kilometers per second faster). This new value has an uncertainty of only 3.3 percent, about 30 times better than previous estimates.
But what does this have to do with dark energy?
The new value of the Hubble constant rules out an alternative explanation for accelerated cosmic expansion, which basically states that Earth and its environs sit at the center of a vast void (a few billion light-years across), the configuration of which would produce an optical illusion making it appear that the universe’s expansion is accelerating. This scenario requires a much lower Hubble constant that the one recently measured, however.
Interestingly enough, dark energy is not the only thing impacted by the more precise constant. The new value indicates that the universe is about 75 million years older than we originally thought (putting her at the ripe old age of, what, roughly 13.83 billion?).
But now, dear galleons, we turn our attention to the folks at NASA and their attempts at forensic sleuthing.
Turns out, the rings around planets might share similarities to those found within the trunks of trees:
Using data from NASA’s Cassini, Galileo and New Horizons missions, scientists have found that some of the imperfections (ripples) in the rings of Jupiter and Saturn can be traced back to cometary fragments and debris clouds hurtling through the ring systems.
“What’s cool is we’re finding evidence that a planet’s rings can be affected by specific, traceable events that happened in the last 30 years, rather than a hundred million years ago,” said Matthew Hedman, a Cassini imaging team associate and research associate at Cornell University. “The solar system is a much more dynamic place than we gave it credit for.”
This all began when scientists first noticed corrugations in Saturn’s innermost ring (the D ring), and that these grooves appeared to wind together more tightly over time. They determined this was caused when something tilted the D ring off its axis by about 100 meters in late 1983. Combined with the effect of Saturn’s gravity, this caused the tight spiral in the ripples:
Later studies found these ripples spread into the neighboring C ring, meaning the mystery “something” had tilted a region more than 19,000 kilometers wide. Unfortunately, because no spacecraft were visiting Saturn and it was situated on the far side of the sun (effectively hidden from the gaze of telescopes), astronomers don’t know what happened in ’83 to cause the imperfections in the rings.
It was time to go CSI on some planetary ass, and our intrepid scientists had a target in mind: Jupiter.
Hidden within Jupiter’s own ring system was a long-forgotten pattern that might help shed some light on how Saturn’s rings gained their striations. After confirming that Jupiter’s ring ripples showed a similar winding pattern, scientists applied the same math they used in Saturn’s case, and “unwound” the spiral to the point where the ring was tilted off its axis- between June and September 1994.
This time, however, we knew what had occurred during that time period: Comet Shoemaker-Levy 9 plunged into the Jovian atmosphere during late July 1994. The timing, coupled with the fact that the size of the comet’s nucleus was consistent with the amount of material needed to disturb Jupiter’s ring, gave us our answer. Comets and cometary debris passing through ring systems could shift them off their axes, causing spiraling ring ripples.
Further study found more of these patterns in Jupiter’s rings, proving these ring collisions are rather common.
“Finding these fingerprints still in the rings is amazing and helps us better understand impact processes in our solar system,” said Linda Spilker, Cassini project scientist. “Cassini’s long sojourn around Saturn has helped us tease out subtle clues that tell us about the history of our origins.”
Just like the rings in an old tree can give us clues about the environment of past years, so too can these planetary ring patterns help us understand the history of our solar system.
As Mark Showalter, a Cassini co-investigator based at the SETI Institute, said, “Now scientists know that the rings record these impacts like grooves in a vinyl record, and we can play back their history later.”
Musica universalis, indeed.