What are some of the unsolved mystery of space?

Here are some unsolved mysteries:

(1) The great attractor

There is something really attractive 220 million light years away which is pulling us and all the galaxies near us closer to it. Our galaxy is movig toward it at 1.4 million miles per hour. We can’t see it because our own galaxy is blocking the view of that attractor. Scientists don’t know what it is.

(2) Black knight satellite

Black knight satellite is a mysterious spacecraft alleged to be of alien provenance and covered up by nasa for more than 60 years. It was caught changing direction by ISS . Scientists are not sure that whether it was alien spaceship or just space debris.

(3) Mysterious knocking heard in a chinese spacecraft.

During 21 hour mission of chinese spacecraft, astronaut Yang Liwei said that he heard a strange knocking noise like someone was hitting the body of the spaceship. He tried to figure out what it could be but found nothing. No one could explain what was actually happended.

(4) wow! Signal

It is a strong radio signal received in August 1977 by astronomer Jerry Ehman. It was received from constellation sagittarius where the centre of our galaxy located. It lasted for 72 second. But it has not been detected again after several subsequent attempts by Ehman and others. Many hypothesis have been made about the origin of signal but none of them satisfy. So it remains mystery.

Thank you!!