The chances are it’s Jupiter or Venus (or just occasionally Mars). Planets will appear to move across the sky as the Earth turns, keeping their position with respect to the surrounding stars. Unlike stars, they generally don’t twinkle as they have an apparent diameter large enough that the effect of turbulence in the Earth’s atmosphere averages out.
Jupiter and Venus can both be strikingly bright. At maximum brightness Jupiter is four times and Venus 19 times as brilliant as Sirius, the next brightest star after the Sun. Once every 17 years Mars can be as bright as Jupiter (the last time was in 2003).
If the object you saw twinkled (possibly appearing to change colour as it does so) then it was probably a star. For example, in winter in Britain Sirius is visible fairly low in the south and shows exactly this behaviour.
Aeroplanes and satellites
Closer to home, if an aeroplane is flying directly towards you, it can appear to be stationary for a while (although the flashing landing lights may be visible) and can also be confused with a star or planet. However at some point the aircraft will appear to veer sideways or upwards as it passes by.
Many artificial satellites are also visible to the unaided eye and can be brighter than many stars. Satellites typically take about two minutes to cross the sky from one horizon to another. They are silent and do not have flashing lights. They fade out if they enter the Earth’s shadow.
- Night sky guide (National Schools Observatory) – details of what's currently visible from the UK, updated monthly.
Find out more
- Jupiter (fact file)
- Venus (fact file)
- Mars (fact file)
- The 25 brightest stars (fact file)
- See also: I think I saw a satellite / How can I see a satellite?