This week in space: a wave on Venus and a mysterious object in Cygnus A
Elsewhere in the solar system, the latest data from Pluto shows us evidence of jagged, spiky, needle-like surface features called “penitentes.” If their presence is confirmed, this would be the first time these icy formations have been found anywhere other than Earth. On our home planet, we know these icy spikes can grow up to several feet tall. They form in higher-altitude environments, where the atmosphere is thinner and melting ice can sublimate directly away into water vapor, without ever becoming liquid. Sometimes you can also see them in melting snowbanks, with all their little points aimed at the sun.We are saddened by the loss of retired NASA astronaut Gene Cernan, the last man to walk on the moon. https://t.co/Q9OSdRewI5 pic.twitter.com/gPdFTnXF2C— NASA (@NASA) January 16, 2017
Lead author John Moores says these penitentes may well be found in other locations across the solar system. Europa is a prime suspect, because we have radar signatures from the Galileo spacecraft suggesting similar fields of ice pungees. But Moores says penitentes may even lurk in places more familiar and closest to home — like Mars.
Venus, in its turn, has shown us some notable surface features too, but instead of fields of ice spikes, now there’s a contender for the largest wave in the solar system hanging out on the Venusian surface. The researchers explain in their study: “The present study shows direct evidence of the existence of stationary gravity waves, and it further shows that such stationary gravity waves can have a very large scale – perhaps the greatest ever observed in the Solar System.”
Observed by the prodigal Japanese spacecraft Akatsuki, the giant wave is thought to be broadly similar to the way surface ripples form as water flows over rocks on a stream bed. In this case, the wave may form as the lower atmosphere flows over mountains on Venus’ surface. The mammoth waveform is called a gravity wave. Not gravitational waves; gravity waves. In short, gravity is pulling fluid whose surface has been disturbed, back to a position of lower gravitational potential.
Why don’t we see waves like this elsewhere? Why do we think this one is the biggest? Dr. Alvin Wilson, of the ESA’s Venus Express mission, explained to the BBC that because Venus rotates more slowly than Jupiter, its surface can support a standing fluid-dynamic feature like this, where Jupiter’s atmosphere is “broken up into belts” and would have destroyed the wavefront with turbulence on a planet-wide scale.
Last but not least, scientists are puzzling over something bright, shiny and new in the elliptical galaxy Cygnus A. We actually found it some years ago, but everyone thought it was just an artifact, perhaps of the enormous black hole at the center of the galaxy. Part of the problem was with the imaging tech; the bright spot is such a deep red that it barely shows up in the visible spectrum, so instead of relying only on Hubble’s snapshots of the region, astronomers compared data from Hubble and Keck with new observations from the NRAO’s Very Large Array. Sure enough, it’s not an artifact. But we don’t really know what it is. It’s twice as bright as any supernova we know of, which makes it puzzling.
Even more puzzling is that the object shows up in certain shots from Hubble, but not others. Usually, flares this bright only come from black holes eating something really big. Like another (much smaller) galaxy. So astronomers are pooling and circulating their data, trying to get everyone’s eyes on the readings from that region of the sky so that we can start making hypotheses. As with so many “we found a thing in space!” stories, the final word: more telescope time will tell for sure.