Human curiosity about space runs deep across cultures. In astronomy, researchers push the boundaries of what we know as they chase answers to the Universe’s oldest questions. To do that, powerful telescopes are essential, capable of catching faint light from distant corners of the cosmos. In North America, scientists from Canada and the United States collaborate on these explorations, pooling data and expertise to build a clearer map of the sky.
Using a space-based observatory called WISE, paired with a network of ground-based telescopes, researchers have identified two of the oldest brown dwarfs known. These ancient objects likely formed when the Milky Way was still young, more than ten billion years ago, drifting through the early Milky Way as faint, chilly sources that only infrared eyes can see.
Brown dwarfs are sometimes described as failed stars. In size they lie between giant planets like Jupiter and small stars. Yet unlike stars such as the Sun, they never reach the extreme internal temperatures needed to ignite nuclear fusion, the process that fuels true stars. Without fusion, these objects simply cool and fade as the billions of years pass.
After their birth, brown dwarfs cool steadily. The two newly found dwarfs exhibit temperatures ranging from about 250 to 600 degrees Celsius, far lower than the Sun’s surface. The Sun shines at roughly 5,600 degrees Celsius, making these brown dwarfs some of the coolest substellar objects detectable with infrared measurements. Their subdued glow underscores how much the universe still hides from visible-light surveys, waiting for infrared eyes to reveal their secrets.
Finding these two brown dwarfs is akin to uncovering rare treasure. What makes them especially intriguing is their rapid motion through space, clocking speeds around 100 to 200 kilometers per second. That pace is much faster than the majority of stars and brown dwarfs, suggesting these objects belong to older stellar populations that have wandered through the Galaxy for eons. Their swift journeys offer a window into the dynamics of our galaxy long before the Sun formed.
Cool Fact
In the current year, astronomers flagged a nearby star system that ranks among the closest to the Sun. Located about 6.5 light-years away, this system includes at least two brown dwarfs, illustrating how the neighborhood around the Sun still contains surprises for infrared surveys and future observations.