This is the Milky Way from Concordia Camp, in Pakistan’s Karakoram Range. It’s commonly reported that many of the stars we see in the sky have already burned out and we just don’t know it yet, but that may be more of a myth than reflective of our astronomical reality. (ANNE DIRKSE / HTTP://WWW.ANNEDIRKSE.COM)

Are Any Stars Visible In The Night Sky Already Dead?

Have any of the stars we can see burned themselves out completely?

When we look out across the Universe, we’re also peering back in time.

In the early 21st-century, we’ve successfully mapped out practically all the stars in our neighborhood in three-dimensional space. The closest stars to us don’t always align with the stars we can see, as what’s visible is determined by a combination of distance and intrinsic brightness. (RICHARD POWELL / ATLAS OF THE UNIVERSE)

Light only travels at a finite speed across the vastness of space.

Through the vacuum of space, all light, regardless of wavelength or energy, travels at the same speed: the speed of light in a vacuum. When we observe light from a distant star, we are observing light that has already completed that journey from the source to the observer. (LUCASVB / WIKIMEDIA COMMONS)

The light arriving now already completed a multi-light-year journey.

When we send a light signal from Earth, it only travels at the speed of light. A star that’s located 100 light-years away will need to wait 100 years before receiving that signal. Similarly, when we look at a star 100 light-years away, we are seeing it as it was 100 years ago: when the light we’re receiving now was first emitted. (ESO/F. KAMPHUES)

Meanwhile, every star only lives for a finite amount of time.

The open star cluster NGC 290, imaged by Hubble. When new stars form, they form with a variety of masses, colors, luminosities, and other properties. The heaviest stars will be the most luminous, but will live the shortest; the lightest stars will be the least luminous, but can persist for many trillions of years. (ESA & NASA, ACKNOWLEDGEMENT: DAVIDE DE MARTIN (ESA/HUBBLE) AND EDWARD W. OLSZEWSKI (UNIVERSITY OF ARIZONA, USA))

The shortest-lived stars may live just 1 or 2 million years total, while others survive for billions to trillions of years.