Did you know that Venus has a ring? Well, sort of. Not a ring of icy or dusty “moonlets” or grains like those surrounding the gas and ice giants in our solar system, Jupiter, Saturn, Uranus and Neptune. Instead, it’s a circumsolar ring of dust, that is, a ring of dust moving around the sun along Venus’ orbit. Now, NASA’s Parker Solar Probe has sent back the first complete view of this ring, the space agency reported on April 16, 2021.
Previous spacecraft had provided partial views of the ring, but this is the first time it has been imaged for nearly the full 360 degrees around the sun.
Researchers published the peer-reviewed results in The Astrophysical Journal on April 7, 2021.
Lead author Guillermo Stenborg from the U.S. Naval Research Laboratory said that:
This is the first time that a circumsolar dust ring in the inner solar system could be revealed in its full glory in ‘white light’ images. I find that pretty special.
Venus is embedded within the ring, which circles the sun much as the asteroid belt does. But this ring is only composed of very fine, microscopic dust particles. The ring isn’t that easy to see, so how did Parker Solar Probe image it?
The probe used its Wide-field Imager for Solar Probe (WISPR) instrument, which is primarily for observing the solar wind, a stream of charged particles from the sun. The solar wind is fainter than the dust in interplanetary space. The dust is easier to see in images since it reflects about 100 times more light than the particles in the solar wind. That same kind of dust creates the zodiacal light, which can be seen on Earth as a faint column of light projecting upwards from the horizon.
To observe the solar wind, the mission team processed the images to remove the space dust. What they didn’t realize at first was that the Venus dust ring was also removed from the images during this process. It was seen later, however, after Parker Solar Probe changed the orientation of its cameras during rolling maneuvers (to prepare for its next flyby of the sun). Parker Solar Probe Project Scientist Nour Raouafi said:
It’s funny that spacecraft operations can sometimes lead to the discovery of new things. It’s kind of amazing.
Analysis of the images suggests that the dust in the ring is about 10 times more dense than dust in the surrounding interplanetary space.
Two earlier missions that observed the Venus dust ring are the German-American Helios spacecraft and NASA’s STEREO mission. Scientists have been able to develop new models of the dust ring based on those measurements. But the new data from Parker Solar Probe provide unprecedented new details.
Scientists are still trying to figure out exactly where the dust in Venus’ orbit comes from. It’s been long thought that most of it comes from asteroids and comets, but as reported previously in EarthSky, a new study suggest much of it may come from dust storms on Mars, where some of the dust escapes into space.
The new views of the dust ring are exciting for scientists, but the researchers are also interested in an absence of dust. Each orbit of Parker Solar Probe brings it closer to the sun, and it has been long thought that there is a dust-free zone close to the sun. This would result from the dust being heated and vaporized in this region. Parker Solar Probe could confirm the existence of this dust-free zone, and indeed has already observed regions of thinning dust as it gets closer to the sun.
Parker Solar Probe is one of NASA’s latest missions to study the closest star, our sun, in more detail than ever before. It is already providing researchers with valuable new information about how the sun behaves, particularly with respect to its outer corona (the part we see during a total eclipse of the sun, when the sun’s body is blocked by the moon) and the solar wind.
Space dust might sound lowly, in contrast to mighty stars and planets. But this dust can tell scientists a lot about the origins of the planets and other bodies in our solar system. The building blocks of both planets and stars might be formed from this kind of dust As Stenborg said:
We’re learning things about the dynamics, the exchanges, of dust particles throughout the heliosphere [the sphere of our sun’s influence] that before Parker Solar Probe we didn’t know.
NASA’s Solar Orbiter spacecraft craft is also expected to be able to provide new views of the dust ring, since its orbit around the sun takes it beyond Venus’ path and high above the ecliptic plane.
Bottom line: NASA’s Parker Solar Probe, currently studying the sun, has observed the entire dust ring that encircles the sun along Venus’ orbit. It is the first complete view of this dust band from any spacecraft.
Source: Pristine PSP/WISPR Observations of the Circumsolar Dust Ring near Venus’s Orbit
Via John Hopkins Applied Physics Laboratory