A full moon can be quite a sight to behold, but it can also be something of a nuisance! In August, the latter is more likely to be true as a full moon — indeed a ‘supermoon’ — will drown out all but the brightest meteors in the annual Perseid meteor shower. Meteors occur when dust-sized particles from space burn up in the earth’s atmosphere, producing a fast-moving trail of light that lasts usually for no more than a second or two. The Perseids are the result of debris ejected from a fairly large comet called Swift-Tuttle.
The earth crashes into this debris every August on its orbit around the sun. Swift-Tuttle takes 133 years to orbit the sun and right now it’s about 42 times farther away from the earth than the sun is. That means it’s also very cold and pretty much impossible to spot from the earth as the amount of sunlight falling on it is tiny and without sunlight, it’s effectively invisible.
People watch the moon rise from the observation tower in Syke, Germany, Wednesday, July 13, 2022. At the same time, the moon is close to the earth, which is why it is called a supermoon. (Thomas Lindemann/dpa via AP)The peak of the Perseids occurs around August 11, 12 and 13, but this year the best time to watch is August 1, 2 and 3. This is because the moon is “new” in early August, meaning it doesn’t rise until late and even then it’s only a thin crescent, so it doesn’t overwhelm the brightness of the Perseids. You might be able to see some 10-20 meteors per hour, but this estimate carries a significant degree of uncertainty with it. You could be lucky and see a burst of bright meteors but you won’t know unless you go out and look. Meteors are best observed with the unaided eye, and give yourself about 10-20 minutes for your eyes to dark adapt for optimum sensitivity. It’s great fun, has zero cost, and everyone can take part.
It’s worth keeping an eye out for satellites as you scan the skies for meteors. Satellites appear as points, not trails, moving slowly enough such that they take a couple of minutes to cross the sky. Sometimes they vary in brightness — this can be because they are tumbling in orbit — and sometimes they gradually fade and disappear — this is usually because their orbit takes them into the earth’s shadow and just as comet Swift-Tuttle is dark without sunlight to illuminate it, so too are satellites.
Meteors and star trails during the Perseid meteor shower seen from near Hawes in the Yorkshire Dales National Park. Picture: Danny Lawson/PA WireWhat would the Perseids look like if you were an astronaut on the moon? Given the moon has no atmosphere, there is no mechanism to stop the dust from Swift-Tuttle from reaching the lunar surface. Without an atmosphere, there is also no mechanism to vaporise the dust, so it would be a pointless exercise to lie comfortably on the lunar surface and look up in the vain hope of seeing the characteristic “shooting star” that we’re familiar with on earth.
That doesn’t mean that an astronaut would be blissfully unaware of the Perseid meteor shower. Indeed they might be rather concerned. Without an atmospheric blanket to protect them, they would be vulnerable to being hit directly by Perseid dust travelling at around 209,000 km/hr. That’s enough to puncture any space suit!
It’s not only lunar astronauts who might worry about meteors. The James Webb Space Telescope has already been hit seven times by high-speed dust particles — that’s roughly one hit per month. One was big enough to permanently damage a section of the main mirror, although not seriously enough to affect the overall image quality. Nevertheless, engineers anxiously wait for new collisions, somewhat resigned to the knowledge there’s precious little they can do to protect a telescope that’s over 1.5 million km away.
