1.
If you describe an amount, especially the cost of something as ~, you are emphasizing that it is very large indeed.
Houses in the village are selling for ~ prices...
ADJ emphasis
~ly
He was ~ly wealthy...
House prices had risen ~ly.
ADV: ADV adj, ADV after v
2.
Astronomical means relating to astronomy.
...the British Astronomical Association.
ADJ: usu ADJ n