Live like a massive star

Clouds of hydrogen gas to sentient carbon molecules

Comparison of star sizes

I’ve always loved astronomy and the cosmos since I was young, and so to be able to derive a quote (that someone has likely already made) is something that I think is cool.

Why massive stars?

Learn about stars

Hertzsprung-Russell Diagram

Stars come in tons of types, but their fates are ultimately determined by their initial mass. The diagram above is called the Hertzsprung-Russell diagram, which plots temperature on the x-axis versus absolute brightness on the y-axis. Temperature increases from right to left, so the leftmost stars are the hottest. Once you know the star’s initial mass, you can place it on this diagram and predict its entire life. For context, here’s a bullet point list of the events in a star’s life.

Life of stars

  1. Stars are giant balls of hydrogen and helium. In their cores, the extreme temperature and pressure fuses hydrogen to helium

  2. The energy released from fusion counterbalances the gravitational force crushing the star down. This phase is called the ‘main sequence’ of the star’s life and occupies the majority of the star’s lifespan

  3. As the star ages, helium accumulates in the core. Helium is denser than hydrogen and causes the core to contract. This raises the temperature and pressure, raising the fusion rate and power output of the star. As a result, stars gradually become more luminous as they age

  4. Once the core is exhausts hydrogen, fusion stops. The star leaves its main sequence. Gravity begins to crush the star down, but the temperature and pressure in the core rises to eventually fuse helium. At this point, the star has entered its giant/supergiant phase. Stars like our Sun will become giants, massive stars (≥ 8 Suns, 1 Sun = ~ 2×1030 kg) become supergiants. Very low mass stars (~ < 0.3 solar masses) never become giants

  5. At its largest, the Sun will engulf Earth’s orbital radius. For reference, the Sun’s radius is around 400 000 km and the Earth’s orbital radius is 150 000 000 km. Because of their incredible size, giant stars are the brightest and the most conspicuous. Supergiants are even bigger and brighter, they can extend past the orbit of Jupiter (~ 780 000 000 km radius)

  6. Giant stars die once their cores exhaust helium. With fusion gone, the star begins to collapse. The remnant is a white dwarf; the compacted, exposed core. This is the fate of the Sun

  7. Supergiants continue fusion until iron accumulates in their core. Fusing iron absorbs energy, and therefore the star can no longer resist gravity and implodes. It triggers a supernova, one of the most powerful explosions in the universe. During the supernova, very heavy elements such as gold, mercury, uranium, and lead are produced. The remnant is either a neutron star for lighter supergiants or a black hole for heavier ones

A massive star can be defined as one around 8 or more times massive than the Sun. All stars initially start in the main sequence, denoted by the pink line. During the main sequence, they don’t move much. Once they run out of core hydrogen, stars will move into the giant or supergiant branches. Giant stars will soon end up in the white dwarf area below, massive stars that evolve into supergiants are in the green box.

What’s so cool about massive stars?

  1. During the main sequence, a star’s luminosity is roughly proportional to mass4, so a star twice as massive as the Sun should be about 16 times more luminous

  2. Stars burn hotter and are bluer the more massive they are. The coolest stars are around 2500 °C at their surface and are redder, the hottest can reach over 35 000 °C and are extremely bright and bluer

  3. A star’s lifespan is inversely related to its mass. The smallest will live for over a trillion years, while the most massive only last for a few million. The Sun will live for around 10 billion years in the main sequence and has about 5 billion left

Massive stars are extreme

Picture a massive star of around 30 solar masses. It should be roughly 800 000 times more luminous than the Sun and produces more UV light than anything else. In just a few million years, the star becomes a supergiant that swallows the orbit of Jupiter. The star is so young that planets did not have enough time to form, and in just a few tens of thousands of years the star dies in a massive explosion. Supernovae are so bright that one within a few hundred light years can exceed the brightness of the full moon. Closer than this, and it can cause mass extinctions.

Drawing ties to us

Massive stars like to be extreme for everything. They’re the hottest, the brightest, become the biggest, die the youngest, and go out in the most fantastic way.

The Milky Way contains about 100 billion stars. Out of those, the Sun’s brightness is in the 85th percentile. This means that it outshines 85% of all the stars in the galaxy. When you look up into the night sky, very few of the stars you can see are part of that 85%. Most of them are nearby massive stars or giants. Massive stars are very rare, they make up less than 1% of stars in the galaxy, but they outshine everything else.

Massive stars can be thought of those at the top of the human pyramid. The rare ones that are the smartest, most clever, most impactful, the people that are found in history books. Most of us are the smaller stars, the ones that shine less brilliantly and aren’t known to most people.

Drawing physical ties

Perhaps the most magical part of massive stars is how they die. Nuclear fusion crushes hydrogen into helium, then some stars go on to make carbon and oxygen. But only a few can go beyond that. Look around and see how many heavy elements there are. Our Sun could never produce heavier metals; it can only produce oxygen, and that will only happen as it approaches its death. Therefore, all of these elements were produced by massive stars that existed before the Solar System.

The nitrogen in our DNA, the calcium in our teeth, the iron in our blood, the carbon in our apple pies were made in the interiors of collapsing stars. We are made of star stuff.

- Carl Sagan

At one point in their history, most of the atoms in you were all in the centers of these giant nuclear fusion engines. Cooked at temperatures of over 100M °C, scattered across the universe from a massive explosion, and finally settling into molecules that make up a sentient being, born from the ashes of stars that died billions of years ago. You’re literally made of the ash scraps of ancient stars.

Watching a massive star live and die is equivalent to seeing the first steps of life. The chemicals produced from the most short-lived stars in the universe were responsible for building life and everything around us. I find this connection of dying stars to life absolutely fascinating, it’s one of the reasons I love astronomy so much.

Maybe this is one more way in how massive stars are related to the best of humanity. The people that leave legacies and inspire sucessive generations to follow through, just like how the greatest stars left behind the ingredients for life.

Final words

There’s a quote about how astronomy is a humbling subject. You can find this everywhere; the insane scales of numbers from the age of the universe and distances, how puny the Earth looks even in just the Solar System, or how all life rose from the leftovers of long gone stars.

There are so many more fascinating facts from astronomy that teach us who we really are and where we belong. This is how I ended up thinking about ’living like a massive star’. Trying to be someone who burns bright and leaves behind a lasting legacy.