Is there such a thing as “North” in outerspace?

Question

On Earth, North is determined by the magnetic poles of our planet. Is there such a thing as "North" in outerspace? To put it another way, is there any other way for astronauts to navigate besides starcharts? For instance, if an astronauts spaceship were to be placed somewhere (outside of our solar system) in the milkyway galaxy, would there be a way for them to orient themselves?

Answer 1

North is determined by the geographic poles of our planet, i.e., by the axis on which the planet rotates. There is such a thing as "magnetic north", determined by the poles of the Earth's magnetic field, but "north" by itself almost always refers to geographic north. (For one thing, both sets of poles move over time, but the geographic poles are much more stable.)

We do use magnetic compasses for navigation, but typically only when (a) the few degrees difference between magnetic north and "true" north doesn't matter or (b) when we know what the offset ("magnetic declination") is.

There are other possible meanings of "north", determined by whatever rotation axis happens to be relevant:

• The plane of the ecliptic, determined by the Earth's orbit around the Sun, defines a kind of "north", about 23.5° away from geographic north.
• If you're on or near another planet, "north" is typically determined by the rotational axis of that planet. Most of the planets in the Solar System have axes that are close to parallel to Earth's axis; Uranus is a notable exception, and Venus rotates in the opposite direction.
• The Galaxy itself rotates on an axis; if you're in deep interstellar space, you might use that as a frame of reference.

So far no astronauts have gone far enough out for most of this to be relevant. Unmanned spacecraft such as Voyager have gone to other planets, and their navigation is quite precise, but it doesn't necessarily depend on defining what "north" means; you just need a way of determining where you are and a consistent way of describing it.

Within our Galaxy, it should be possible to navigate by observing the positions of known stars.

It's not likely we'll be using magnetic fields as a primary source of navigation information in deep space. As long as you can see the stars, there are better sources of information.

Answer 2

You could orient yourself using the CMB fluctuations as your compass--- given a detailed WMAP picture of the CMB flutuations, you could tell which way is which anywhere in the local galactic region, and how fast you are going relative to the CMB.

Answer 3

On Earth the north and the south are defined by the south and north magnetic poles respectively of the Earth's Magnetic field. In space there is a thing called the Galactic Magnetic field which permeates galaxies, including the Milky Way (http://arxiv.org/abs/astro-ph/0207240). However, the strength of the Galactic magnetic field is much much lower than the Earth's magnetic field. Our compasses wont be able to detect this and be much more influenced by magnetic fields of nearby planets or stars, rather than the Galactic field. The Galactic magnetic field acts on much larger scales. In 1997 one scientist discovered that the supernova remnants (left overs of an exploded star) align them selves to Milky Way's magnetic field. Intergalactic magnetic fields have also been recently discovered but I believe little is known about their structure.

So in short, I think, theoretically there can be a "north" in space because there is a magnetic field present. Whether or not we can make use of it (due to its weak strength) is a different story. There are other coordinate systems that are used e.g the Galactic Coordinate system and Right ascension/declination.