Are stars alive?  Staff writer Olivia Mitchell attended Columbia Astronomy Outreach’s October 18th lecture “Life in the Universe” to find out.

The night’s lecture was part of the Columbia Astronomy Outreach’s Stargazing and Lecture Series and was given by Dr. Joshua Tan, an assistant professor of Astronomy and Physics at LaGuardia Community College and a resident astrophysics research associate at the American Museum of Natural History. Dr. Tan began the lecture by explaining the seven traditional characteristics of life under which biologists have worked for ages: organization, metabolism, homeostasis, growth, reproduction, response, and evolution. For anything to be living, it must be organized, process energy in some way, exist in equilibrium, grow, reproduce and/or replicate life forms, respond to stimuli, and evolve by adapting to changes over time. But he explains, this list is problematic, for there are things that fit all of these characteristics but are also collectively seen as not being alive, such as, in this instance, stars. 

Dr. Tan again went through the list of these seven characters with the idea of stars in mind. Are stars organized? Yes! Stars have a variety of different parts, each with their own function that when put together, allows the star to function. Do stars metabolize? Yes! Stars don’t eat, but they do have an energy source: nuclear fusion in their cores. Do stars experience homeostasis? Sort of, yes! As homeostasis simply means that living systems stay in equilibrium, as stars do due to hydrostatic balance–keeping stars compact and composed due to the balance of outward pressure on the core and the inward pull of gravity–, then, technically, stars accomplish the same equilibrium that living beings do just in a different form. Do stars grow? Yes! But not over their entire lives; they start as gas clouds, get larger and larger, and then ignite. Do stars reproduce? Yes! Stars exist in an environment where the actions of the star can promote the creation of new stars; when they explode as supernovae, they send out a shock that creates a gas cloud and helps new stars to be created. If you poke a star, does it respond? Yes! If a shockwave goes past a star, its hydrostatic equilibrium causes it to respond to the stimulus, although how was not explained. Do stars evolve? Yes, through stellar evolution, which is the process by which stars change and grow over a period of time. Dr. Tan tells us that stars experience all seven of the characteristics of life to a degree. Yet, stars are not considered alive. Why?

The answer, as Dr. Tan explained, is relatively unknown; stars are just not considered to be alive in the traditional sense, as the requirements or “ingredients” of life on Earth are two chemicals: proteins and DNA. So, when looking for life out there in space, scientists stick to the strict definition of life by searching for the presence of DNA and proteins. Here, Dr. Tan began to delve into his specialty of Astrobiology: the study of life in space. He went on to explain the creation of life as a recipe. The “ingredients” are carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur, that we get “delivered” to our planet through meteors–as it’s too hot for these ingredients to be found naturally on earth–from the “grocery store” of interstellar medium, a.k.a, the material out of which the solar system was made. Before being brought to earth, these ingredients are produced one of six different ways–Big Bang Fusion, dying low-mass stars, exploding massive stars, cosmic ray fission, merging neutron stars, and exploding white dwarfs, all of which were only named, not explained, briefly during the lecture–and when finally on on a planet, in this case, Earth, the planet acts as a kitchen that “cooks” and creates life. And while life on Earth looks one way, that doesn’t guarantee that all life follows these same biological rules. However, it is fair to say that the astronomical processes of the universe are the reasons for human existence.

So, want to know how life is created? Just take a look at the stars.