Astro Pop: Catch Mercury at Dawn – Duluth News Tribune

Over the next two weeks, Mercury will blow its plumage at dawn, making it the best morning appearance since February for northern hemisphere watchers. Of course, the planet has no feathers. But it moves very fast around the sun, and we might imagine it as the peregrine falcon of the solar system

Mercury rises roughly eastward and is between 5° and 8° before sunrise an hour or so. One of the many things I love about October is the late sunrise – after 7 am from most locations. This makes it easy to squeeze in watching the sky at dawn without taking a serious blow to your sleep.

Mercury in October

Mercury shines low in the east below Leo. You probably won’t see the full lion outline in twilight, but you can glimpse its brightest star, Regulus.

Contribute / Stellarium

Given the low altitude of the planet, find a place with an unobstructed view to the east to ensure the search is successful. Binoculars can also help especially if there is fog around. You can use the map or check exactly where you are looking on the interactive stellarium web page at Click the time readings in the lower right side of the page and change the time to an hour before sunrise. Then zoom in and drag the map with the mouse to face east. I’m planning to head to Lake Superior to have a look. If you are lucky and a windless morning turns the lake into glass, two Mercurys will shine.

And as long as you’ll have trouble seeing the planet, consider detour around the sunrise. It’s easy to see and yet, among the most satisfying of astronomical sights, I would never live long enough to fill it.

Mercury moves around the sun every 88 days. The last time we saw speed was in late August in the west after sunset. Six weeks later, it swings to the other side of our star and shines in the morning sky. Mercury’s appearances are short because it rotates quickly and spends a lot of time in roughly the same line of sight as the Sun, and it’s hard to catch in the glare. That is why it is worth looking for when it is at or near its maximum elongation, when it stands as far east or west of the sun as possible.

phases of mercury

Since Mercury revolves around the Sun, we see it best at the time of greatest elongation, when it swings away from the Sun in the sky. We also see that the planet goes through phases like the moon during its 88-day orbit. At the moment, the Sun illuminates about half of Mercury from our perspective. Through the telescope it looks like a “half moon”.

Contribute / ESO

The planet begins the week with a magnitude of 0.5 on the Richter scale, and is almost as bright as Orion’s red Betelgeuse. But it soon lights up. On Thursday, October 6, Mercury will shine at −0.3, much brighter than Arcturus. Before it disappears in the solar glare around October 20, it will rival Sirius, the brightest star of the night. This does not mean that they will look as bright as those shining stars. We have to take into account its low altitude and aurorae glow, both of which dim its light.

The changing phase of the planet is the reason for the steady increase in its brilliance. When Mercury first appears in the morning sky, it is located almost directly between the Earth and the sun and in the crescent phase. Then it swings to the east (right in the diagram) and halves. Just like our moon, Mercury gets brighter as its phase toward fullness increases, the reason why it will continue to be brighter in the coming weeks.

mercury comparison

Mercury (far left) is the smallest of the terrestrial planets, shown here for comparison.

Contribute / ESA

Unlike the Moon, its apparent size varies greatly over the course of its orbit. Mercury appears larger when it is a crescent because it is closest to Earth, and then shrinks to a small point when it is on the other side of the sun and farthest from us.

Mercury rotates quickly because it is very close to the sun. It is also the smallest planet with a diameter of only 3,031 miles or 1.4 times the size of the Moon and home to some of the most extreme temperatures in the Solar System. Daytime peaks on its surface rise to about 800 degrees Fahrenheit and nighttime lows fall to −290 degrees. Mercury lacks an atmosphere, so all the heat it absorbs during the day quickly dissipates at night.

mercury close up

Mercury’s surface is saturated with craters and appears superficially like the moon.

Contribute / NASA, Messenger

Although the planet rotates on its axis every 59 days, the day continues Many long. Mercury’s rapid revolution delays the sun’s daily movement across the sky, increasing the day’s length from 29.5 Earth days (half 59) to 176! No wonder it’s getting so hot And the so cold.

When you set the alarm to meet Mercury face to face, try to imagine a place infernal and barren compared to Earth, where you can still have a cup of coffee almost anywhere and at any time.

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