ifteen years ago, I started my job at the Massachusetts Institute of Technology. As an astrophysicist and planetary scientist, my job is to search for alien life. Not little green humanoids like ET, but signs of life on planets orbiting other stars. Every star is a sun and if our sun has planets (Mercury, Venus, Earth, Mars, etc) it makes sense that other stars have planets also – and they do. We already know of thousands of stars that have planets. There are billions of stars in our galaxy making the possibilities “out there” huge and wondrous. Back then, I had the perfect life: a great career; my dream home, a pretty yellow Victorian house; two adorable toddlers; and a loving husband. But my husband Mike, a robust 45-year-old, suddenly had a series of nagging stomach aches that rapidly worsened. The doctors ignored his concerns, holding off on critical tests as the months passed. Mike ended up in the hospital emergency room with a complete intestinal blockage. Over the next several weeks and months we had bad news at every turn. Mike needed surgery. The blockage was cancer which had been found in his lymph nodes and was ready to spread. Two different chemotherapy regimens failed and Mike was now terminally ill. One day he came home and told me, “Sara, the doctor said I shouldn’t die at home because we have young children.” I remember getting white-hot angry. “What kind of lesson would that teach our children? That we dump sick people at the hospital to die? That’s ridiculous. The doctor should know better. Mike, we are going to teach our sons that we will love you and take care of you until the day you die.” Which we did. Afterwards, grief was a terrible thing. It felt like falling off a cliff. Isolated and broken at the bottom, there seemed to be no way out. Each day loomed like a giant canyon wall, impossible to climb. Thinking of the stars gave me a sense of perspective. Imagine an intelligent alien civilisation on a planet orbiting a nearby star, with the kind of sophisticated telescopes we are planning to build. To the aliens, Earth would be just a pinprick of light. A pale blue dot. Just another exoplanet among trillions of planets. It was somehow comforting to confront my tragedy against the vastness of the universe. To counter my catastrophic loss, I decided to pursue the most meaningful thing I could: the search for another Earth – a planet with oceans and continents and breathable air. One with signs of life – to show that we are not alone. Other Earths, however, are incredibly hard to find. Small and dim beside their massive, bright suns, they are the smallest lights in the universe. Back in reality, I had some really big problems on my hands. I was a widow at age 40 with children ages six and eight, a more than full-time career, and no family nearby, not even within hundreds of miles. My dream home was actually a very old and falling-apart house that I had no idea how to manage. I barely knew how to cook. My husband had worked part-time to support my career by taking care of things on the home front. Work was my only escape. My MIT research team, graduate students and postdoctoral fellows became my extended family. Our focus was on how to find signs of life on another planet orbiting a nearby star. We built on ideas that were many decades old, looking for gases in a planet atmosphere that “do not belong” and might be attributed to life. My team’s job was to use our complex computer models to come up with an exhaustive list of gases (other than oxygen) that might indicate life on another world – an incredibly ambitious and exciting project. Although I started to feel more hopeful, I could not shake an intense emotional fragility. One gorgeous blue-sky winter morning I took my sons to the local tobogganing hill. The snow cover was thin and my younger son got stuck midway down, blocking the path. One of two picture-perfect mothers standing nearby asked if I could help him and fix the situation. Instead of helping I broke into a giant meltdown, unleashing all my of anger about perfect happy families and my own unlucky situation. When I blurted out my husband died, one of the women, Melissa, brightened, and said, “Mine, too”. She had just started a widow’s group in our town – six women all about the same age, all with kids. We gathered on the important holidays. Valentine’s Day. Father’s Day. We began to meet every other Friday morning for coffee. The first topic was how to stay afloat financially. A close second was dating, a challenging topic for widows with kids and heavy emotional baggage. The widows were my lifeline for so many things. That spring, a large tree branch fell on my garage during a storm and one of them showed up, in her leather pants and ankle boots with heels, to lend me a chainsaw and give instructions. I learned so much over the following year or two and began to feel empowered, mentally tough and physically strong. “I survived, I can do anything,” I thought. I received the MacArthur “genius” award for my work and addressed the United States Congress with the first official statement about the search for other Earths. One evening, I was telling all of this to my kids, now eight and 10, while we were lounging on my bed. My younger son, trying out his new vocabulary said, “Mom, you are arrogant.” I burst out laughing for the first time in years. I started to bring my new best friend, Melissa, to MIT work events as my “plus one” and showed her the space satellites we were building. I took Melissa to Nasa’s Jet Propulsion Laboratory in California to see “Starshade,” the concept I was leading to find another Earth. Starshade is a giant screen that will block out the immense glare of starlight, so fainter planets can be detected. It’s a crazy engineering project – the screen has to be tens of metres in diameter, yet fold up like origami. Work was intense but with support at home from three young female babysitters who became extended family, I could travel again. Part of my job is educating peers as well as the public about new frontiers in the search for other planets. It was at one of these conferences, back in my home country, Canada, that my life changed again. Across the room I saw a tall man with a wide smile and I froze, thinking: “I have to meet him.” The next day, I headed to lunch in the university cafeteria, and it was mostly empty – except for the tall man. We found ourselves standing together at the salad bar and he introduced himself, and said: “Would you like to have lunch with me?” We told each other a little about ourselves and after the conference I emailed him, saying that it had been nice to meet. If I’m being honest, I didn’t think we’d cross paths again. He had his life, and I had mine. There were 549 miles between us. We might as well have been living in different worlds. Yet we kept in touch. There was no race to the next step in our relationship because there was no next step. Those probing weeks and months made me think about how we might approach aliens for the first time, should we find any. We were cautious when we first sent astronauts to the moon. When they came back to Earth, we put them in quarantine, on the deck of a ship in the middle of the ocean, in case something sinister had been hiding in the dust. After we find proof of another life in the universe, I imagine we will take our time to decide whether it’s a life that we want to know. That’s how it was with Charles and me. We knew we loved each other. Our connection was obvious. But we were careful in the finishing of our fit. Most important, I wanted to know that my sons were as happy as I was – because I was really happy. He was supportive about my work without being intrusive about it. He knew why I cared about the stars, and what that love of mine might mean. He knew the feeling that comes with looking through a telescope, the bigness and smallness, the knowledge and the mystery. That was seven years ago. Now we’re married and Charles has adopted my boys. In science, sometimes your hunt for one thing leads you to something better. At our best, scientists are explorers and what I’ve discovered is that life can change in the blink of an eye. We need to hold on to the glimmers of hope – however small – and to continue to search for what really matters. To buy a copy of The Smallest Lights in the Universe by Sara Seager (Harper Collins, £16.99) for £14.78, go to guardianbookshop.com