Astronomers have now gotten a very good measurement of how fast Venus is spinning, which means we know how long a day is on Earth’s fiery twin. It took 15 years of very accurate radio observations, but astronomers have now gotten a very good measurement of how fast Venus is rotating, which means we know how long a day is on Earth’s fiery twin. One Venusian day is equal to 243.0226 Earth days – about two-thirds of an Earth year – and it varies every 20 minutes or so. Nature Astronomy published the results.
Given the planet’s proximity, it can seem odd that we don’t know the exact duration of a day on Venus. If a planet has distinguishable features on its surface, calculating its rotation speed is easy. The gas giants are more difficult to map, but Jupiter has a massive red swirling storm to keep an eye on. Because of Venus’s dense atmosphere, identifying features is difficult, so astronomers had to be imaginative with their measurements.
Astronomers used the 70-meter-wide Goldstone antenna in California’s Mojave Desert to transmit radio waves to Venus between 2006 and 2020. These waves will pass through the atmosphere before being reflected back at the surface. They are picked up at the Goldstone observatory several minutes later, and then at the Green Bank observatory in West Virginia about 20 seconds later. The difference in speed between the two detections shows the team how fast the planet rotates.
In a tweet, lead author Jean-Luc Margot of UCLA said, “We use Venus as a giant disco ball.” “We light it up with a super-bright flashlight that’s 100,000 times brighter than your average flashlight. We can infer properties about the spin [state] by tracking the reflections from the disco ball.” The experiment appears to be a lot simpler than it is in fact. For the experiments to be accurate, Earth and Venus must be in the correct configuration, as well as the two radio observatories. Over the course of 15 years, twenty-one observations were made.
“We discovered that getting all to function perfectly in a 30-second cycle is actually very difficult,” Margot said. “The majority of the time, we get some details. But it’s rare that we get all of the information we’re looking for.” The motion of Venus’ dense atmosphere causes variations in the duration of the day. Since the pressure at the surface is around 93 times greater than on Earth, the planet’s rotation is affected by its sloshing around. Venus was also revealed as a result of the observations. The team calculated that the planet’s center measures about 3,500 kilometers (2,175 miles) in diameter. This is almost the same size as the Earth. However, we don’t know if it’s a liquid, a solid, or a gas based on our current knowledge.
The study also improves the calculation of the planet’s axial tilt in relation to its orbital plane. They discovered that Venus is tilted to one side at 2.64 degrees, which is a tenfold increase over previous estimates. Seasons do not exist on the earth due to its minute tilt. The tilt of the Earth is around 23 degrees, which is very different from the much smaller inclination of Venus. However, Venus is the only planet that spins in the opposite direction, resulting in some unusual results.
On Venus, keeping track of time is a little strange. The earth rotates every 243 days, but its year (revolution around the Sun) only lasts 225 days. However, due to the spinning in the opposite direction, a day will only last 117 days if we counted it from dawn to dawn. It’s no surprise that this strange world continues to be riddled with mysteries.
