The light extending from where the sun passed below the horizon is what scientists call the zodiacal light, which is created when sunlight bounces off the dust in the Solar System. Although this might be a common sight on Earth, not all planets have this and those who do are rarely detected.
But in a recent study of astronomers and high school students from China, they describe seeing zodiacal light on at least three potentially habitable exoplanets. Study lead author and astronomer Jian Ge from Shanghai Astronomical Observatory said that detecting zodiacal light from a distant planet system could mean it has asteroids and comets similar to the Solar System.
Stars and the Milky Way are seen in the night sky over Lebanon late on August 12, 2018 in the mountain area of Tannourine, north of Beirut.
Zodiacal Light Detected in "Super-Earths"
Space.com reported that astronomers and a team of high school students in China evaluated 47 potentially habitable exoplanets studied by NASA's Kepler space telescope. They found that zodiacal light is also present in three of these planets considered "super-Earths" - Kepler-69c, Kepler-1229b, and Kepler-395c.
Ge noted that what the skies of these planets would look like varies from one another. For instance, Kepler 1229b's zodiacal light could look very red because it orbits around a red dwarf star.
Meanwhile, Kepler-69c could have an atmosphere that resembles Venus so it could also have a view of the zodiacal light similar to Venus. On the other hand, the thick atmosphere would likely make it more difficult to see.
Ge said that they may have only detected zodiacal light on three out of the 47 exoplanets they have examined, but it could change when astronomers use a more powerful observation tool than NASA's WISE mission.
"When the sensitivity improves, we may see more systems that have weaker dust emissions," the news outlet quoted Ge.
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When is a Zodiacal Light Most Visible?
According to Skybrary, the zodiacal light is also called false dawn when seen before sunrise. It is a faint, diffused, and somehow triangular light that can be seen in the night sky that appears to extend from where the Sun is on the horizon and along the zodiac. This phenomenon is caused by interplanetary dust in the Solar System that forms a thick cloud called "zodiacal cloud."
Asteroids and comets leave remnants that form a stream of dust larger than 300 to 10,000 micrometers in diameter and fall into smaller zodiacal dust grains, which caused the zodiacal light seen on Earth. In 2015, the secondary ion dust spectrometer COSIMA onboard ESA's Rosetta orbiter confirmed that the parent bodies of interplanetary dust came from the comets near Jupiter.
The zodiacal light is most visible during equinoxes in which light follows the ecliptic pathway of the Sun, Moon, and planets in the Solar System, according to EarthSky. The ecliptic shape makes extreme angles in the horizon around the equinoxes, making its steepest angle during spring evenings and autumn mornings.
More so, it is most visible in tropical latitudes for the same reason as the ecliptic pathway of the Sun and Moon that hits the steep horizon all year long.
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