The categorization of the statements about black holes based on current scientific understanding:
True:
- A black hole can have the mass of a star in a space less than a few kilometers across
- Two orbiting black holes can merge and emit gravitational waves
- Material from a binary companion can form an X-ray-emitting accretion disk around a black hole
- A black hole can form during a supernova explosion
Not true:
- A black hole is an object smaller than its own Schwarzschild radius
- A 3-solar-mass black hole may be hidden between Jupiter and Saturn
- You would be squashed by gravity at the event horizon of any black hole
- Black holes emit X-ray light from within their event horizons
Unknown:
- Black holes make up 1% of the mass of the Milky Way Galaxy
- The singularity of a black hole has infinite density
What are the not trues and unknowns?
A black hole is an object smaller than its own Schwarzschild radius
This statement contradicts the definition of the Schwarzschild radius, which is the radius of an object at which its escape velocity equals the speed of light. By definition, no object can be smaller than its own Schwarzschild radius.
A 3-solar-mass black hole may be hidden between Jupiter and Saturn
While it's possible that a small black hole could exist between Jupiter and Saturn, there is no current evidence to support this claim.
You would be squashed by gravity at the event horizon of any black hole
While the gravity near the event horizon of a black hole is extremely strong, it's not strong enough to instantly crush an object. Instead, the object would be stretched and torn apart as it falls into the black hole.
Black holes emit X-ray light from within their event horizons
Black holes themselves do not emit light. However, material that falls into a black hole can heat up to millions of degrees and emit X-rays. This X-ray emission is observed from accretion disks around black holes.
Unknown:
Black holes make up 1% of the mass of the Milky Way Galaxy
The exact amount of mass that black holes contribute to the Milky Way Galaxy is still unknown. Current estimates suggest that it could be anywhere from 0.1% to 10%.
The singularity of a black hole has infinite density
The nature of the singularity at the center of a black hole is one of the biggest mysteries in physics. It is believed to be a point of infinite density and curvature, where the laws of physics as we know them break down. However, we do not have a definitive understanding of what happens at the singularity.
Complete question:
Each statement below makes a claim about black holes. Based on current scientific understanding of black holes, sort the statements into the correct bin according to whether the statement is:
True (based on current science), meaning that scientists are confident in this statement based on current understanding of gravity (general relativity) and stellar evolution
Not true, either because it contradicts current scientific theory or is contradicted by observations
Unknown, meaning the statement makes a claim that may or may not be true, and for which we would need new science or new observations to decide which it is.
a black hole can have the mass of a star in a space less than a few kilometers across
a black hole is an object smaller than its own Schwarzschild radius
two orbiting black holes can merge and emit gravitational waves
material from a binary companion can form an X-ray-emitting accretion disk around a black hole
a black hole can form during a supernova explosion
a 3-solar-mass black hole may be hidden between Jupiter and Saturn
a black hole will suck in any binary companion star
you would be squashed by gravity at the event horizon of any black hole
black holes emit x-ray light from within their event horizons
black holes make up 1% of the mass of the Milky Way Galaxy
the singularity of a black hole has infinite density