Cosmic discovery: the solar system is not spherical, but spiral!

The solar system is not this flat plate that you imagine when you think of the sun and its procession of eight planets, as learned at school and observes it on many illustrations. In science, everything is always more complicated!

In this case, the solar system, like probably all stellar systems in the universe, is a plan in the first approach. But as you move away from the sun and its gravitational influence, this flat disc turns into a large bazaar organized more or less in sphere.
This big bazaar is called Oort cloud and is made up of 99 % excessively distant comets.

To represent the distances at stake, know that the outer part of the Oort cloud is 100,000 times further than the earth of the sun! Its radius probably reaches around 40,000,000,000 km, the equivalent of approximately one light year.

Here's how we used to see the Oort Oort cloud schematized This published study By a group of American, Argentinian and Czech astronomers, which upsets our past design of the solar system:

The “internal” oort cloud distorted by galactic tides

But it was without taking into account gravitational interactions with the center of the Milky Way. Admittedly, for objects, planets and asteroids close to our star, it is the influence of the latter which predominates, and the centrifugal effect gives a plane aspect to about Neptune, The last known planet of our system.

For much more distant objects, beyond 1000 astronomical units (1 UA = 150 million kilometers), the gravitational influence of the sun is then counterbalanced by that of all the very numerous objects of the center of the galaxy. This is how a galactic tide phenomenon comes into play.

Our space region is not in the Milky Way plan, but 60 ° from it, as represented in legend of the image at the top of this article. It is this particular position which, combined with the attraction of the center of the galaxy, induces this strange spiral form for part of the oort cloud. The computer simulations (Galaxy) of a NASA supermarket, used by the authors of the recent study, have perfectly reproduced this “S” form of the Oort cloud.

Is this spiral shape of the oort cloud observable?

Very difficult according to the authors. On the one hand, these objects are small, dark and excessively distant. On the other hand, the distances that separate them are colossal. However, astronomers have determined how easily they would seem easier to detect this spiral structure, around 300-400 μm. They nevertheless specify: “Unfortunately, we do not have enough statistics in the Galaxy simulation to precision predict the expected signature of this population.”