A wispy ring of dust orbiting the sun along Venus’ orbit has just been revealed in the most detail so far, thanks to instruments carried by the Parker Solar Probe.
The pristine, white-light images, taken from Venus’ orbit, show the ring in almost its entirety. These are essential data to understand this ring and the dynamics of the solar system and its gravitational interactions.
“This is the first time that a circumsolar ring of matter in the inner Solar System can be revealed in its full glory in ‘white light’ images,” said US Naval Research Laboratory astronomer Guillermo Stenborg. “I think that’s quite special.”
(Stenborg et al.)
The solar system is a really dusty place. The whole is formed from dust (and gas); much of the dust was integrated into planets and asteroids and things like that (not to mention the sun); often it is shaken out again.
Asteroids and comets are like cosmic salt and pepper shakers, sprinkling their surrounding space everywhere. Recent research found that Mars could spray the stuff all over the place during the massive global storms that happen every year.
All that dust can just float around, but sometimes it can be snatched into orbital resonance with a planet; that is, it revolves along the same path, with an orbital time that is a ratio of one integer to that of the planet.
The Earth has a considerable resonance dust ring; Scientists have recently found evidence that Mercury has one too. And the dust ring of Venus has been known, and even partially observed, for some time by the joint German-American solar mission Helios and NASA’s solar mission STEREO.
Target the Parker Solar Probe, equipped with an instrument called the Wide-field Imager for Solar Probe (WISPR). WISPR consists of two heliospheric visible light imagers designed to image the interplanetary medium to study the solar wind – the constant stream of charged particles emerging from the sun.
Because interplanetary dust is so bright with reflected sunlight, it surpasses the solar wind, so special image processing is used to remove the background noise in solar wind observations. This also means that WISPR is uniquely able to observe Venus’s resonant dust ring.
During normal use, the dust ring would of course be automatically extracted from the data. Parker performed some rolling maneuvers in August and September 2019 to control momentum, which moved the WISPR cameras – and a bright streak appeared in the resulting footage.
Initially, the astronomers thought it was something else, like a glowing helmet streamer shooting from an active part of the sun, or even an image processing error. It was way too big to be a helmet streamer, and image processing oopsies were also ruled out. The next step was to look at what else is in that space, and then they found that the stripe was perfectly aligned with the orbit of Venus.
Since the glow is also consistent with the scattering of light from dust, the team concluded that the most likely explanation is the planet’s resonance dust ring.
The data can be extremely useful. Scientists think that interplanetary dust could be a transport mechanism for molecules within the solar system, a means by which material ejected from asteroids or comets find their way to other bodies.
However, we still don’t know how these dust rings formed, or where they came from, so the more information we have, the closer we can get to figuring it out.
“One idea is that the dust rings were naturally formed from the primeval cloud, but several researchers argue that the gravity of each planet has gradually trapped the particles, perhaps even asteroid or comet particles in its orbit,” explains astrophysicist Russell Howard of the US Naval Research. Laboratory explains. .
Another possibility is that the dust rings are constantly turned over; Collisions between grains can kick some of the old dust out of the track, while new dust comes from elsewhere.
There is also another mystery with the Venus ring. Analysis of the data from previous observations suggested that there was much more dust in Venus’s resonance ring than could be easily explained. A research team recently made some models and determined that the best explanation for the amount of dust is a group of invisible asteroids that share the orbit of Venus.
We still haven’t found those asteroids, so that hypothesis is far from being confirmed. Who knows, maybe Parker will see them; or perhaps the probe leads us to another explanation for the phenomenon. Either way, it will be exciting.
“We’re learning things about the dynamics, the exchanges, of dust particles in the heliosphere that we didn’t know before Parker Solar Probe,” said Stenborg.
The research is published in The Astrophysical Journal