celestial equator Archives

Have you ever wondered if the Solar System and the Milky Way line up perfectly, like plates spinning within plates? This is something you can test out for yourself.

We love to answer your questions, this one is clearly a fan favorite in the category of the “Wouldn’t it be crazy if…”. Our Solar System is disk shaped, with all the planets orbiting around the Sun in roughly the same plane. AND the Milky Way is also disk shaped, with all the stars orbiting around and around the center of the galaxy. Wouldn’t it be crazy if the Milky Way and the Solar System lined up? Why would that happen?

Do all Solar Systems line up with the Milky Way, like plates spinning on plates spinning on plates? And those plates are on smaller plates. It’s spinning plates all the way down.

The answer is unfortunately “no”, because yes, it is cool when things line up. At this point, I know you’re immediately thinking I’m in the pocket of “Big Plate shape”, but I can assure you that’s not the truth. The Nibiruans, CIA and Big Dental pay much better than those cheap disc jerks have ever ponied up.

The good news is, you don’t have to take science’s word for this. In fact, you can check this out for yourself. If you’ve spent any time watching the sky, you’ll know that the Sun takes roughly the same path across the sky every day. It rises in the East, travels across the sky, and then sets in the West. For me here in Canada, the Sun rises over there in the Winter, it trundles sadly across the horizon to the South, and then sets in the West.

If you live on the equator, you might see the Sun pass right overhead during the day. And if you live in the Southern Hemisphere, you might see the Sun go across the North in the sky. As we spin, the Sun always goes along a predictable line. We can always point at it and say “There’s the center of our solar system”. The Moon takes the same path, and so do the rest of the planets. It’s the plane of the ecliptic, and we’re embedded right in the middle of it. If you get to dark enough skies, you can see the Milky Way. It’s that faint cloudy band that goes across the sky. If the Solar System and the Milky Way had their Frisbees lined up, we could see the Sun, Moon and planets always be in front of the Milky Way.

But they’re not, the Milky Way is actually inclined from the celestial equator at 63-degrees. They cross each other through the constellations of Monoceros and Aquila-Serpens-Ophiuchus. For me, the Milky Way starts over there and ends up over there. The plane of the ecliptic and the Milky Way make a big cross in the sky. The orientation between the Solar System and the Milky Way is coincidence. They just happen to be perpendicular-ish. But they could also just happen to line up, and that would be nothing more than a coincidence too.

The Milky Way and the Solar System aren’t lined up. They couldn’t be any more un-lined up if they tried. Here’s the Milky Way, here’s the Solar System. I’m a Power Ranger. So, I’m sorry, but just won’t be able to use that to justify your cosmic theories about the return of the Flying Spaghetti Monster. Or alternately… like any good conspiracy style thinking…

Good news! The Milky Way and Solar System are almost perpendicular and clearly that near-opposite alignment generates some kind of woogly ethereal gyroscopic metastatic force that clearly is causing your gluten sensitivity and heralds the coming of FSM. What magical effect is this perpendicular alignment causing for you? Tell us in the comments below.

A week ago I made a 45-minute time exposure of the southern sky featuring the planet Mars. As the Earth rotated on its axis, the stars trailed across the sky. But take a closer look at the photo and you’ll see something interesting going on.

The trails across the diagonal (upper right to lower left) are straight, those in the top third arc upward or north while those in the bottom third curve downward or south.

I've drawn part of the imaginary great circle in the sky called the celestial equator. Residents of cities on or near the Earth's equator see the celestial equator pass directly overhead. From mid-northern latitudes, it's about halfway up in the southern sky. From mid-southern latitudes, it's halfway up in the northern sky. Credit: Bob King — I’ve drawn part of the imaginary great circle in the sky called the celestial equator. Residents of cities on or near the Earth’s equator see the celestial equator pass directly overhead. From mid-northern latitudes, it’s about halfway up in the southern sky. From mid-southern latitudes, it’s halfway up in the northern sky. Credit: Bob King

I suspect you know what’s happening here. Mars happens to lie near the celestial equator, an extension of Earth’s equator into the sky. The celestial equator traces a great circle around the celestial sphere much as the equator completely encircles the Earth.

On Earth, cities north of the equator are located in the northern hemisphere, south of the equator in the southern hemisphere. The same is true of the stars. Depending on their location with respect to the celestial equator they belong either to the northern or southern halves of the sky.

Earth's axis points north to Polaris, the northern hemisphere's North Star, and south to dim Sigma Octantis. Illustration: Bob King — Earth’s axis points north to Polaris, the northern hemisphere’s North Star, and south to dim Sigma Octantis. Illustration: Bob King

Next, let’s take a look at Earth’s axis and where each end points. If you live in the northern hemisphere, you know that the axis points north to the North Star or Polaris. As the Earth spins, Polaris appears fixed in the north while all the stars in the northern half of the sky describe a circle around it every 24 hours (one Earth spin). The closer a star is to Polaris, the tighter the circle it describes.

Time exposure centered on Polaris, the North Star. Notice that the closer stars are to Polaris, the smaller the circles they describe. Stars at the edge of the frame make much larger circles. Credit: Bob King

Likewise, from the southern hemisphere, all the southern stars circle about the south pole star, an obscure star named Sigma in the constellation of Octans, a type of navigational instrument. Again, as with Polaris, the closer a star lies to Sigma Octantis, the smaller its circle.

Stars trail around the dim southern pole star Sigma Octantis as seen from the southern hemisphere. The two smudges are the Large and Small Magellanic Clouds, companion galaxies of the Milky Way. Credit: Ted Dobosz

But what about stars on or near the celestial equator? These gems are the maximum distance of 90 degrees from either pole star just as Earth’s equator is 90 degrees from the north and south poles. They “tread the line” between both hemispheres and make circles so wide they appear not as arcs – as the other stars do in the photo – but as straight lines. And that’s why stars appear to be heading in three separate directions in the photograph.

A view of the entire sky as seen from Quito, Ecuador on the equator this evening. The celestial equator crosses directly overhead while each pole star lies 90 degrees away on opposite horizons. Stellarium

In so many ways, we see aspects of our own planet in the stars above.

Tag: celestial equator

Does the Solar System Line Up with the Milky Way?

Star Trail Photo Hints at Hidden Polestars