We have reported in the past how the Roman Space Telescope could potentially see hundreds of thousands of exoplanets using a technique known as “microlenses”. However, exoplanets aren’t the only things that can be found using this technique – they should also be able to find individual black holes.
Solitary black holes are unique in that most black holes that scientists “find” interact directly with another object. Those that are relatively small and could move around the galaxy on their own would be almost impossible to find as they absorb all electromagnetic wavelengths.
UT video describing the microlens
Typically, these tiny black holes weigh about ten times the weight of the sun. They are formed when a star dies and, depending on its weight, either goes into a supernova or falls directly into a black hole. Unless the black hole is surrounded by gas or dust to absorb, it becomes essentially invisible to almost all instruments.
So far, scientists have found 20 of these black holes with “stellar mass”, but only because they are next to another astronomical object, making their gravitational force visible in the way the accompanying object moves.
NASA video describing how to use gravitational lenses to detect black holes.
Photo credit: NASA
The beauty of the microlens technique that Roman uses to identify planets is that any large gravitational field causes the microlens effect. So if Roman sees a micro lens effect around something that doesn’t have an obvious mass source, it’s likely a black hole causing it.
To find the slight disturbances that the microlens would cause, Roman has to stare at hundreds of millions of stars for a long time. But that’s exactly what it’s designed for. With this additional data, scientists can answer questions such as why lone black holes appear to be massaging only about 10 times the mass of the Sun, or how many black holes with stellar mass are exactly in the galaxy. The current estimate is around 100 million.
UT video about the spread of black holes.
Regardless of the answers to these questions, Roman will provide more data to draw conclusions on these and many other questions when it starts around 2025.
Learn more:
NASA – How NASA’s Roman Space Telescope reveals lonely black holes
UT – What is the connection between stellar black holes and dark matter?
UT – How much of the universe are black holes?
Mission statement:
Graphic showing how microlenses would work around a black hole.
Photo credit: NASA’s Goddard Space Flight Center Conceptual Image Lab
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