NASA is talking about a new space telescope that will launch in the mid-2020s. The new telescope is the Nancy Grace Roman Space Telescope, or simply the Roman Space Telescope. It’s an infrared telescope that will help NASA peer into the infrared universe in an unprecedented fashion. One of the most important things that the Roman Space Telescope will allow NASA to do is detect solitary small black holes for the first time.
Solitary and small black holes are formed when a star with more than 20 solar masses consumes all of its nuclear fuel and collapses under its own weight. This type of black hole is known as stellar-mass black holes. Like other black holes, the stellar-mass black holes have enough gravity that nothing escapes, not even light, meaning they are invisible.
Because the black holes are invisible, they can only be discovered indirectly by searching for how they impact their surroundings. When looking for supermassive black holes, astronomers look for how the blackhole disrupts the orbits of nearby stars and occasionally tears them apart. Astronomers believe most stellar-mass black holes, which are much less massive, have nothing around them to signal their presence. Roman will be able to find planets around the galaxy by observing how gravity distorts distant starlight.
It will use the same technique to discover stellar-mass black holes because they produce the same effect on starlight. Astronomers have identified about 20 stellar-mass black holes in the Milky Way so far, but most have a companion that we can see. Scientists believe Roman may finally make it possible to find black holes that don’t have companions.
Roman will use a primary technique called gravitational microlensing to discover planets and possibly black holes beyond our solar system. From our viewpoint, when a massive object like a star crosses in front of a more distant star, light from the more distant star will bend as it travels through the curved space-time around the closer star. The result acts like a natural lens, magnifying light from the background star.