No, the moon and Mars will not be the same size in the sky, tonight -- or ever

‘Darn hoax keeps coming back’ about Mars opposition, astronomers say

A full strawberry moon is expected on June 5th. (Matt Cardy, Matt Cardy/Getty Images)

About every two years when Mars and Earth are on the same side of the solar system, the astronomical event stirs up a bit of fake news and woe for astronomers everywhere.

Every 26 months Mars and Earth are on the same side of the Sun, which is known as Mars opposition, making the Red Planet closer to our home planet. It’s a good opportunity to look at Mars with the naked eye or through a telescope and it’s also when NASA and other space agencies choose to launch spacecraft to the Red Planet because of the shortened travel time.

What doesn’t happen during opposition, even if your Facebook friends say it does, is make Mars appear just as big as the moon in the night sky to the naked eye. Astronomers have been trying to bust this fake news for years but it keeps coming back around.

According to American Astronomical Society Press Officer Rick Fienberg, the trouble started more than 17 years ago.

In 2003, Mars was roughly 35 million miles away, the closest it had been to Earth in nearly 60,000 years. For context, the moon is about 240,000 miles from Earth. That opposition year Mars appeared bigger and brighter in the night sky but still not the same size as the moon, that’s just not possible.

“Somehow, things got mixed up a bit to claim that Mars would look as big as the moon,” Fienberg said.

An illustration of the relative 'tilt' in the orbits of Earth and Mars during opposition. (Image: NASA) (WKMG 2020)

However, if you look through a telescope using a little magnification-- 75 or 80 power-- Mars will appear to your eye about half a degree wide, similar to the moon viewed by the unaided eye.

“In other words, if you look into a telescope eyepiece at Mars in August of 2003, when Mars was closest at 75 power, Mars looked to your eye in angular size, about the same as the moon looks to your eye in angular size when you just look at it up in the sky with your naked eye,” Fienberg explained.

Somehow, between Photoshopped images and bogus articles, the views got conflated.

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“All of those images that you see of, you know, Mars next to the moon, are, you know, they’re fake ...or they’re a real image of Mars through a telescope and a real image of the moon,” Fienberg said about images circulating online.

It’s gotten to the point that Fienberg waits for questions and calls about this fake astronomy event.

“It was debunked back then by astronomers,” Fienberg said of the 2003 opposition. “We all said, ’Hey, wait a minute. You’re missing something. You’re overlooking something. This is crazy, right?’ But every time Mars comes back to opposition, which happens roughly once every 26 months ... The darn hoax keeps coming back.”

There are several ways to avoid getting fooled by this hoax or others.

“I recommend taking anything that you see on social media that’s science-related with a grain of salt, first of all, and then I suggest seeking out information from reliable sources,” Fienberg said.

NASA will publicize any major astronomy event and NASA’s Jet Propulsion Laboratory releases a monthly stargazing preview.

Sky and Telescope Magazine has been around for 80 years and is sometimes known as “the Bible of amateur astronomy,” according to Fienberg. It also happens to be published by the AAS, the largest astronomy group in the U.S. and is written by and for astronomers.

He warns if Sky and Telescope or NASA isn’t covering the astronomical event, it’s likely not a big deal or even worse, it’s fake news.

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