Are the 'stars' that don't twinkle in the night sky actually planets?

not necessarily. if the air is very steady, nothing will twinkle. if the air is very unsteady, everything twinkles.

where in the sky is your object? what time of night? at the moment the most prominent planets are venus (west at dusk) and jupiter (south at dusk).

later: sounds like jupiter. have a look with binoculars or a telescope and see for yourself. even in binoculars you'll see the four large moons, and will see that jupiter is not a point like the stars are.

Your are correct, that point of light that isn't twinkling is a planet, not a star. Planets may look just like points of light to the naked eye but they are actually close enough to the Earth that with even a pair of binoculars you can see that they appear as disks. Stars, on the other hand, are so distant that even with the greatest magnification they appear only as pin-pricks of light. That's the difference that makes stars twinkle and planets appear as steady lights. When the pin-pricks of light get distorted they are small enough that it appears that the light flickers on and off. The light from the planet still gets distorted as it passes through the atmosphere but since the planet appears bigger you see the image of the planet gets distorted a little but there's always some light getting through to you so it doesn't flicker on and off.

If you keep watching it for several nights (or weeks) it won't always appear in the same position compared with the other stars in the sky. Planets wander across the sky. In fact that's where the name planet came from. It's Greek for "wanderer". The ancients could tell that the planets were different from stars because they didn't twinkle and they moved around.

The bright planet you're seeing is Jupiter, which will be in the night sky a couple more months, although it will be progressively lower in the west during that time.

Stars don't necessarily twinkle if the air is very still, although brighter ones still don;t quite glow like planets. And planets can twinkle slightly if the atmosphere is disturbed enough. A few nights ago, I even saw Venus twinkling while still fairly far from the horizon, because it was a windy evening.

That last answer puts it very well.

honestly stars, honestly dont' twinkle. The twinkle is led to from the atmospehere, temperatures, and density. Stars are to this point away that a twin of a robust gentle of a action picture star is marvelous to work out. simply by fact the ambience is changing the celebs image strikes alongside for this reason seeing a twinkle.

Right, planets don't twinkle.

Aint that the northern star?