Orientation

[BeerMe]

I've often wondered whether the stars and constellations were always orientated a certain way i.e if 2 stars in the sky are directly above each other, will they remain in that position as they traverse across my line of sight.

I came across an image someone else posted on the forum about how to locate Andromeda and since it's something at the top of my list of things to see when I finally get a chance, I decided to see if I could locate the stars in the image that person posted in the Stellarium software.  The results are below, the Stellarium image coming second...

The orientation of the stars has changed by around 45 degrees....is this normal and if so, isn't it confusing when it comes to trying to "star hop"? 

Sorry if this seems somewhat stupid.  I feel I should know this already..

[brantuk]

The stars always stay in the same orientation and position in space. What changes is the position you view from as the Earth spins and traverses it's orbit round the sun (and to some extent as the galaxy rotates). So if one star is above another today - later on (eg a couple of months) you may see them side by side or diagonally opposed. The key is to track the constellations and remember their shape.

Have a look at Pegasus as it rises - then in the morning twilight have a look at how it appears as it sets - and all should become clear. Night to night you can check the Ecliptic and over time you'll see it rises in different positions on the Eastern horizon and sets in different positions in the West - look at the position of the constellations relative to that. Hth

[BeerMe]

The stars always stay in the same orientation and position in space. What changes is the position you view from as the Earth spins and traverses it's orbit round the sun (and to some extent as the galaxy rotates). So if one star is above another today - later on (eg a couple of months) you may see them side by side or diagonally opposed. The key is to track the constellations and remember their shape.

Have a look at Pegasus as it rises - then in the morning twilight have a look at how it appears as it sets - and all should become clear. Night to night you can check the Ecliptic and over time you'll see it rises in different positions on the Eastern horizon and sets in different positions in the West - look at the position of the constellations relative to that. Hth

So if you are able, cloud-permitting, to see the constellations on a daily basis you would only see a gradual shift in its axis?  But over a period of months this shift becomes more pronounced?

Do the different constellations rotate differently through the seasons, or do they all follow the same path?

Thanks for the reply by the way

[Dave In Vermont]

As you have Stellarium on your desktop, you can set it to show you the sky in a month from today - at the same time of night. Say 12:00am. Then in another month at Midnight. And so forth. You will see the constellations are all moving in unison as the Earth travels around the Sun in it's orbit.

In 100 years - set Stellarium for this - you will note the position of the constellations in regards to one another remains the same. In 1,000 years, things may change a little. And so forth. This as the stars are all moving closer, or further, away from our reference point.

Hope this makes a little sense,

Dave

[brantuk]

They always follow the same path round the pole star - but the relative position of the Earth shifts with time through each night. Seasonally the orbit of Earth around the sun changes the angle of view (due also to the tilt of the Earth). It's initially hard to perceive but our galaxy is within a fixed dome of the universe where all star positions are fixed. That's why RA and Dec never change. But Earths position does.

[baggywrinkle]

Rather than rely on Stellerium get a planisphere, old tech maybe, but simple to use and to quickly see the rotational effects on the constellations. Great to aid star hopping too.

[rockystar]

A good way to see the effect is in stellarium select Polaris and then increase the speed of time a little bit, you will see the constellations rotate around this point.

[Gazabone]

The Stars advance just under 4 minutes a day; that is to say that if you see a star in a particular place at 9pm tonight, it will be in the same place at 8:56 tomorrow night and 8:52 the night after that. Over the course of a year it will eventually come back to the same place again.

The planets are slightly different, but they don't change very much from night to night.

Happy viewing

[acey]

Just watch the stars (the real ones) and in the space of a single clear night you'll see that they look like points stuck on the inside of a sphere rotating around the Earth. The axis of the sphere is marked by the Pole Star (nothing special about that star except its chance location). The reason is that Earth is rotating amid a sea of stars which, because they are so distant, are effectively stationary at infinite range. Once you've seen the effect for yourself all your questions will be answered - and you'll have had a lovely night

[brantuk]

One other thing to bear in mind is "where" on Earth you view from. I was quite surprised when I went to S.Africa to find that the Orion constellation appears upside down. All quite logical but I just hadn't thought about it before lol.

[BeerMe]

Thanks everyone.  You all have a nice way of explaining things in laymans terms which really helps a novice like myself