Al Stahler: The Shape of the Solar System


Looking at the North Pole, our solar system – the sun and the planets – rotates counterclockwise. The planets revolve around the sun, the sun itself revolves counterclockwise.

This rotation dates back to the birth of the solar system.

Four and a half billion years ago there were no planets circling the sun – there was no sun. All we could claim as a home, at the time, was a huge ball of gas and dust, drifting across the galaxy.



Spinning around the galaxy, this enormous ball of gas and dust would pass through one star… after another… after another.

With perfect timing, our cloud passed close to a large star, just as the star was burning the last fuel to make it glow. The dying star collapsed on itself… collapsed so violently… gripped its core so tight… it bounced – it bounced – and exploded: the star became a supernova.



The supernova explosion hit our ball of gas and dust, and squeezed it – triggered our cloud to collapse, shrink it. Like a figure skater drawing in her arms, the shrinking ball spun faster and faster.

When a pizza maker spins a round ball of dough over his head, the ball flattens out. Just so the spinning ball of gas and dust flattened out

The dust and gas in the collapsing cloud were compressed and stuck together. The resulting tufts were compressed further, becoming larger and larger tufts.

In the center of the collapsing cloud, enough material has agglomerated to form a star: our sun is born. Other clusters have joined together to form planets, encircling the sun. The solar system was born.

Flattened by its rotation, our solar system is shaped like a pizza.

As of this writing, at the start of the week, the skies should clear up this weekend. As soon as the sky darkens, Venus shines brightly in the west; the moon near the first quarter (exactly Friday’s first quarter) is shining high in the south. And shining brightly, west of the moon, the planet Jupiter.

Draw a line from Venus to Jupiter (the moon to Jupiter, if you cannot see Venus), and continue this line – in the form of an arc – around the world. The circle you draw traces the flat disk of our solar system.

Our eye can only perceive the light that passes through its pupil – the dark “opening” in the front. Most of the universe is too dark to be seen with the naked eye. The primary job of a telescope is to collect light.

Large telescopes collect light with a mirror. The Hubble Space Telescope’s mirror measures just under eight feet in diameter. The soon-to-launch James Webb Space Telescope’s mirror measures just over twenty-one feet.

The James Webb Space Telescope will launch on the 22nd of this month – more information on our next-generation Space Telescope next week.

Every now and then the orbit of the International Space Station carries it over the foothills, and I issue a warning. Its huge expanse of glass-covered solar panels reflects a lot of sunlight, making the ISS easy to spot.

Now another space station – Tiangong – is under construction, to allow Chinese astronauts to live in space. Its solar panel workforce is much smaller than that of the ISS, but still large enough to make it easy to spot. Tiangong will pass over the foothills tomorrow (Friday) evening, rising in the west at 6:17 p.m., flying over a few minutes later.

Al Stahler enjoys sharing science and nature with his friends and neighbors on The Union and on KVMR-FM. He teaches for children and adults and can be contacted at [email protected]

Seen from Earth (here, from the Hubble Space Telescope), Venus shows phases.
Photo courtesy of L. Esposito (UColo / Boulder), NASA, ESA


Arline J. Mercier