is it a planet or a star ?

Question

in a night sky, naked eyed, using binoculars or an amateur telescope, how could i distinguish clearly between planets and stars?

i know that planet will move much faster through the night sky while stars are relatively stationary comparing to planets, but is there any other method to verify whether the observed object is a star or a planet?

Thanks !

Ssss · Accepted Answer

first of all, planet does not move fast in the night time sky, or the morning. if you want to know  if it's a planet or star, go buy a telescope and check it out

Anonymous · Answer

It is not possible to see the motion of a planet in the sky with the naked eye, the motion is only apparent after numerous observations on different nights. Any light you see moving visibly across the sky is not a planet, but rather an airplane or a satellite.

That said, you can often tell the difference between stars and planets because stars tend to twinkle whereas planets don't. This is because the star is so far away that it is very close to a single point of light in the sky, and individual molecules in the air can drift in front of the star and cause a disruption in the light. Planets, on the other hand, are much closer and form discs in the sky, so while they still appear like points to us, they are actually much larger (in terms of angular size) than stars and thus don't have the same effect.

Anonymous · Answer

You are confused about motion of a planet.  Only over many days, months, or years would you notice a planet moving among the stars.  In one night you wouldn't notice a planet move very much in the starfield.
A planet has larger apparent diameter than the much more distant stars.  So when the air moves to make all stars "twinkle", the planets don't.
Most of the time, planets like Venus, Jupiter, and Saturn are brighter than all but the brightest stars. 
Almost all the time, planets are close to a path called the ecliptic.  This is through the Zodiac, twelve constellations in a band around the sky.

Tom S · Answer

Learn the major constellations and brightest stars, if you see a bright star like object in or near the ecliptic, which you know doesn't "belong there" then it is most likely a planet.

Also, amateur telescopes will show a disk for most planets, Neptune might be tough as well as the "dwarfs".

Bullseye · Answer

And-- planets will always be found near the elliptic --- or the path of the sun across the sky.

grayure · Answer

Stars, with the exception of the sun, cannot be resolved into discs.  They are always points of light.

is it a planet or a star ?

6 Answers