Every Type of Star Explained in 21 Minutes

Brown dwarf. Brown dwarfs are the failed stars of the universe. They formed the same way a real star does, collapsing out of a cloud of gas and dust, but they never gathered enough mass to switch on hydrogen fusion in their cores. That makes them stuck in a weird middle zone, too heavy to be called a planet, but too light to be called a true star. Most brown dwarfs sit between 13 and 80 times the mass of Jupiter. They can fuse deuterium and sometimes lithium for a short while, but once that runs out, they just slowly cool and dim for the rest of time. Surface temperatures range from around 4,000 degrees Fahrenheit on the hot end all the way down to room temperature on the cool end. Matter of fact, some brown dwarfs are colder than a cup of coffee. They are extremely difficult to detect because they emit so little light, and astronomers think they might be nearly as common as ordinary stars. There could be billions of them drifting through our galaxy completely invisible to the naked eye. If you flew up to one in a spaceship, you would not see a glowing ball in the distance. You would see a dark featureless sphere only barely revealed by the faint infrared heat leaking off its surface. It would look less like a sun and more like a planet that forgot to find a star. Red dwarf. Red dwarfs are the most common type of star in the universe, making up roughly 75% of every star that exists. They are small, cool, and dim, with surface temperatures between 4,000 and 6,000 degrees Fahrenheit. Most of them are between 8% and 50% the mass of our sun. The interesting thing about red dwarfs is how slowly they burn through their fuel. They are so efficient that their lifespans can stretch past a trillion years. For comparison, the universe itself is only about 13.8 billion years old, which means no red dwarf that has ever formed has had enough time to die yet. Every single one ever born is still out there burning. However, life around a red dwarf would be brutal. These stars are infamous for their violent flares, sudden bursts of radiation that can strip the atmosphere off a nearby planet in a single event. If you were standing on a planet orbiting one, the sun in your sky would look small, dim, and angry red, and every few weeks the entire surface of your world could be bathed in a wave of deadly X-rays. Despite this, red dwarfs are still considered places worth searching for life, simply because they are so common and they live for so long. They give the cosmos more time to experiment than any other type of star. Orange dwarf. Orange dwarfs sit in the sweet spot between red dwarfs and stars like our sun. They are K-type main sequence stars with surface temperatures between roughly 6,000 and 8,500 degrees Fahrenheit, and they weigh in at about 60% to 80% the mass of the sun. What makes orange dwarfs interesting is how stable they are. They produce far fewer dangerous flares than red dwarfs, and they live for 15 to 30 billion years, which is two to three times longer than our sun will. That extra time matters because life on Earth took roughly 4 billion years to develop from microbes to anything you could have a conversation with. An orange dwarf would give a planet far more runway to do the same. If you were standing on a world orbiting one, the sky would look gentler than what we have. The sun would appear slightly smaller and would cast a warm amber light across the surface, almost like a permanent late afternoon. Many astronomers now believe orange dwarfs may be the single best type of star to look for habitable planets around. They are calm, patient, and they last long enough for biology to actually get going.