Big Questions
It's something mysterious that seems to interact only via gravity.
What is dark matter?
We can't tell because no light can escape it.
What is inside a black hole?
We used to believe this was definitely going to happen, but now we estimate that there is a 50% chance.
Will we collide with Andromeda?
Evidence includes observations of atmospheric molecules like phopshine on Venus.
Is there other life in the Universe?
It makes up most of the energy density of the Universe.
What is dark energy?
We mostly see them at stellar masses or at millions to billions of solar masses.
Are there intermediate-mass black holes?
We think they are "waves" of increased density of gas, dust, and stars.
How do galaxy spiral arms form?
We are trying to find out by looking at things like temperature and atmospheric composition.
How many habitable exoplanets are there?
We measure a rate of 67-73 km/s/Mpc.
How fast is the Universe expanding?
We aren't sure if they come from very massive "seeds" or grow quickly through super-Eddington accretion.
How do supermassive black holes form?
Our biggest recent merger was with the Gaia "Sausage."
What is the formation history of the Milky Way?
We can't see anything earlier than the Cosmic Microwave Background, so we have to infer.
What happened in the very early Universe?
The leading theory is that it will continue expanding and cooling forever.
What is the fate of the Universe?
They form disks of hot, accreted gas and impart energy back into the interstellar medium, suppressing star formation.
What effect do black holes have on their host galaxies?
We keep observing them with JWST and we can't explain them.
Why do we see "mature" galaxies so early in the history of the Universe?
We don't know the exact physical description, but we know that it is full of incredibly densely packed subatomic particles.
What does the inside of a neutron star look like?
We believe it to be both isotropic and homogeneous.
Is the Universe the same everywhere?
We don't know how they are launched, but they contain electrons traveling close to the speed of light.
What are black hole jets?
The dense, energetic environments of galaxy clusters drive evolution through mergers, quenching of star formation, etc.
How do galaxies' environments shape their evolution?
We know that the Universe was neutral a couple hundred million years after the Big Bang and fully ionized by the time is was 1 Gyr old.
When did reionization happen?