Revelation 9 - What is meant by the "last days?" What is wormwood?

Rev 9:1
And the fifth angel sounded, and I saw a star from heaven which had fallen to the earth; and the key of the bottomless pit was given to him.

Who is this star that has fallen from heaven? There is no reason to believe that this is any different than the same star and burning mountain that is described in chapter 8.

Rev 8:8-11 And the second angel sounded, and something like a great mountain burning with fire was thrown into the sea; and a third of the sea became blood; 9and a third of the creatures, which were in the sea and had life, died; and a third of the ships were destroyed. 10And the third angel sounded, and a great star fell from heaven, burning like a torch, and it fell on a third of the rivers and on the springs of waters; 11and the name of the star is called Wormwood; and a third of the waters became wormwood; and many men died from the waters, because they were made bitter.

This star was given the key to the "bottomless pit" or "the abyss." What is the "pit" being spoken of here? We are told in Scripture that a "pit" is related to a trap that nations have ignorantly set for themselves.

Psalm 9:15 The nations have sunk down in the pit which they have made; In the net which they hid, their own foot has been caught.

A pit is also described as the lips of an adulteress or whore.

Prov. 22:14 The mouth of an adulteress is a deep pit; He who is cursed of the LORD will fall into it.

Isaiah says the nations will be kept there for a long time in the last days.

Isa 24:21-22 So it will happen in that day, That the LORD will punish the host of heaven, on high, And the kings of the earth, on earth. 22And they will be gathered together Like prisoners in the dungeon, And will be confined in prison; And after many days they will be punished.

We are told that the key to the pit was given to the star. If this is consistent with the previous chapter, we are now told that the nations of the Roman Empire are given the key to leave the realm where they are kept.