Which type of stars have the shortest lifetimes and why?

The cosmic truth about stellar existence boils down to one primary factor: mass. The types of stars destined for the shortest lives are unequivocally the most massive ones that exist on the main sequence. While it might seem intuitive that having more fuel means living longer, the opposite is true in the stellar realm. Stars that are about ten times the mass of our Sun, or even significantly more, exhaust their nuclear fuel reserves in a spectacular, yet brief, burst of energy.

# Mass Dominates Life

The duration a star spends fusing hydrogen in its core—its main sequence life—is determined almost entirely by how quickly it consumes that fuel. Massive stars are inherently hotter and brighter, often appearing blue or blue-white in color, which signifies an extreme internal furnace operating under immense pressure.

To sustain the crushing force of gravity exerted by such large amounts of mass, the star's core must maintain extraordinarily high temperatures and pressures. These conditions dramatically accelerate the rate of nuclear fusion. Even though these giants begin with a reservoir of hydrogen fuel vastly larger than a Sun-like star, the sheer rate of consumption overwhelms the initial supply, leading to a lifespan measured in mere millions of years.

Consider the scale of this effect. Our own Sun, a star of intermediate mass, is expected to reside on the main sequence for a total lifespan nearing 10 billion years. In contrast, the most massive stars—those reaching perhaps a hundred solar masses—could be extinguished in only a few million years. This creates a stark, inverse relationship: the bigger the star, the shorter its existence.

# Fuel Consumption Rate

The underlying principle driving this brevity is related to the Mass-Luminosity Relation, which dictates that a star’s luminosity (its energy output) increases steeply with its mass. For a star roughly ten times the Sun's mass, the energy output is hundreds of thousands of times greater than the Sun’s.

To illustrate the consequence of this imbalance, imagine two runners with equally sized fuel tanks: Runner A (our Sun) runs at a steady jog, while Runner B (a massive star) runs a marathon sprint. Even if Runner B starts with five or ten times the fuel, their sprint pace guarantees they will reach empty far sooner than Runner A’s gentle pace. A star that is only a few times the mass of the Sun will burn through its hydrogen fuel in a fraction of the time the Sun takes to burn through the same percentage of its total mass. This intense consumption is necessary to keep the star in hydrostatic equilibrium, balancing the inward crush of gravity with the outward push of thermal pressure.

If we map the stellar population, the shortest-lived stars fall into the high end of the spectral classification, likely corresponding to O-type and B-type main sequence stars. These are the behemoths that dominate the early light of a galaxy but quickly fade from view.

Which type of stars have the shortest lifespan?

# Massive Star Ends

The short life of a massive star is not just brief; it is also incredibly dramatic. When a star nears the end of its hydrogen-fusing phase, the subsequent steps of core fusion are completed much more rapidly than in a solar-mass star.

For stars in the upper mass range, the process accelerates as they burn successively heavier elements in their core—from helium to carbon, neon, oxygen, silicon, and finally, iron. Each new element provides energy for a shorter period than the last, with silicon fusion lasting only days. Since fusing iron consumes energy rather than releasing it, the outward pressure fails instantly. The core collapses, rebounds, and triggers a supernova explosion.

What remains is equally dramatic. Stars that were massive enough—generally those exceeding about eight to ten solar masses—do not leave behind a gentle white dwarf. Instead, their core collapse results in an extremely dense neutron star or, if the original mass was great enough, a black hole. The core of a massive star, unable to be supported by electron degeneracy pressure, succumbs to gravity, forming these compact objects after the explosive end of their short lives.

# Stellar Spectrum Contrast

To fully appreciate how quickly these massive stars perish, it helps to place them against their counterparts in the stellar population. The stars we observe span a vast range in mass and time.

This table starkly illustrates the trade-off: the very low-mass Red Dwarfs consume their fuel so efficiently, aided by convection that continuously stirs fresh hydrogen into the core, that some scientists believe their lifespans will exceed the current age of the universe. Conversely, the massive stars live fast and die young, but their swift, violent end is essential for seeding the galaxy with the heavy elements necessary for the next cycle of star and planet formation, including the creation of elements heavier than iron. Their brief existence is thus a necessary contribution to cosmic chemistry.

What type of galaxies have mostly younger stars?

# Stellar Aftermaths

The end products of stellar evolution offer a final contrast in longevity. The most massive stars end their lives in a supernova, leaving behind something so dense that even the atomic structure is crushed—a neutron star or black hole.

For stars of lower or intermediate mass, typically up to about $8$ to $10$ times the mass of the Sun, the end is much quieter: a white dwarf. These remnants, composed mostly of electron-degenerate matter, cease fusion entirely. A white dwarf's "life" after this point is not driven by fusion but by cooling down, radiating away residual heat. This cooling process is incredibly slow, taking timescales estimated to be on the order of $10^{19}$ to $10^{20}$ years, potentially much longer, depending on proton decay models. This post-main sequence cooling period vastly outstrips the main sequence life of any star, highlighting just how temporary the main sequence phase is for the shortest-lived stars.

Ultimately, the stars that live the shortest lives are those at the top of the stellar mass ladder. They are massive, incredibly luminous, and burn through their nuclear supplies in a fiery rush, ensuring their spectacular demise occurs before their less massive neighbors have even reached middle age.