Planet or Star? How to Tell the Difference Just by Looking Up at the Night Sky Tonight

Stars twinkle. Planets, almost always, do not.
This is not folklore. It is atmospheric physics. A star is so far away that even through the most powerful ground telescope, it appears as a perfect point of light, no width, no disc, just a geometric dot. When that dot passes through the churning layers of Earth's atmosphere, pockets of air at different temperatures bend the light in slightly different directions from one millisecond to the next. The result is the shimmer astronomers call scintillation. To your eye, the star appears to flicker.
A planet is different. Even to the naked eye, a planet subtends a small but real disc in the sky. Jupiter, at its closest approach, spans about 50 arcseconds across. That disc is wide enough that the atmospheric turbulence affects different parts of it simultaneously and averages itself out. The light reaching your eye stays steady.
The test is simple. Find a bright object in the night sky. Stare at it for five seconds. If it flickers and changes color slightly at the edges, white to blue to orange, it is a star. If it holds its brightness without wavering, it is almost certainly a planet. The method works on any clear night, without any equipment at all.Once you have run the twinkling test, color and brightness confirm the identification.

Venus is the brightest object in the night sky after the Moon. It reaches a magnitude of -4.6 at its brightest, bright enough to cast a faint shadow on a dark night, bright enough that it has been mistaken for an aircraft, a drone, or a UFO thousands of times. It appears pure white, almost blue-white, and it is only ever visible near the horizon, either in the west just after sunset or in the east just before sunrise. If you see something impossibly bright low on the horizon and wonder whether it is a plane, it is Venus.
Jupiter is the second-brightest planet, reaching magnitude -2.9 at opposition. It glows steady and cream-white, high in the sky. Saturn sits nearby in color but is noticeably dimmer and has a slight golden tinge. Mars is the easiest to name by color alone: it is distinctly reddish-orange, the iron oxide on its surface coloring the light it reflects. When Mars is near opposition, its closest point to Earth, it is bright enough to rival Jupiter. When it is far away, it dims considerably and the red hue becomes the main identifier.

Mercury is the trickiest. It never strays far from the Sun, so it only appears in deep twilight, very low on the horizon. Many dedicated sky-watchers have never spotted it cleanly.The word planet comes from the ancient Greek planetes, meaning wanderer. The Greeks named them that because they watched these objects move against the fixed background of stars over nights and weeks.
Stars hold their positions relative to each other. The constellation Orion looks the same tonight as it did a thousand years ago, save for the imperceptible drift of proper motion across geological time. Planets do not hold still. Watch a bright object over several nights and mark its position against the stars around it. If it has shifted, even slightly, it is a planet. If it has not moved at all relative to its neighbors, it is a star.

This method takes patience, but it is the oldest astronomical technique humans ever used. Babylonian astronomers were tracking planetary motion against star charts by 1200 BCE. The same observation is available to anyone standing on a terrace in Jaipur or a rooftop in Mysuru with nothing but clear skies and two consecutive nights.India's geography gives sky-watchers a real advantage. The Thar Desert in Rajasthan, the high-altitude plateaus of Ladakh, and the coastal plains of Tamil Nadu all offer stretches of sky with low light pollution. Even from cities, the brightest planets cut through the haze.
Venus is visible for months at a time as either the morning or evening star, depending on where it sits in its orbit relative to Earth. When it is the evening star, look west within an hour of sunset. When it is the morning star, look east about an hour before sunrise. It is unmistakable.
Jupiter is visible for roughly ten months of every year and spends long periods rising in the east after dark. Through even a basic pair of 10x50 binoculars, you can see its four Galilean moons, Io, Europa, Ganymede, and Callisto, as tiny pinpoints of light on either side of the planet's disc. Galileo first observed them in 1610. You can repeat the observation tonight.
Mars follows a two-year cycle of visibility. Near opposition it is a vivid red-orange beacon. Between oppositions it retreats and dims. Saturn, when visible, is worth finding specifically because binoculars will show its rings as a slight elongation of the disc, the planet appears not quite round, which is enough to confirm what you are looking at.
ISRO's Chandrayaan-3 mission, which landed near the Moon's south pole in 2023, and the Aditya-L1 solar observatory, positioned at the Sun-Earth Lagrange point L1, are both products of the same sky that Indian observers have been reading for millennia. The Jantar Mantar observatories built by Maharaja Jai Singh II in the early 18th century in Jaipur, Delhi, Varanasi, Ujjain, and Mathura were precision instruments for tracking exactly these objects, planets against stars, wanderers against the fixed sky.
The twinkling test, the color check, and the night-to-night movement test each answer a different question about the same object. Together they give you a complete identification. The planet holds steady, glows in a color specific to its surface and distance, and refuses to stay in one place. The star flickers, holds its position, and has been exactly where it is for longer than the solar system has existed.