Answer:
<em>Ok</em><em> </em><em>we</em><em> </em><em>will</em><em> </em><em>help</em><em> </em><em>you</em><em> </em><em>if</em><em> </em><em>we</em><em> </em><em>know</em><em> </em><em>the</em><em> </em><em>answers</em><em> </em><em>of</em><em> </em><em>your</em><em> </em><em>questions</em><em> </em><em /><em />
Answer:
A. Danube river is the answer.
Answer: Massive star supernovae
2. Can only occur in a galaxy with ongoing star formation.
3. Black hole or neutron star left behind.
White dwarf supernovae
1. Star explodes completely, leaving no compact object behind.
4. Can only occur in a binary system.
5. Can occur in a very old star cluster.
6. Spectra always lack strong hydrogen lines.
7. Has a brighter peak luminosity.
Explanation: A supernova is a bright explosion of a star as it dies off. Supernova can occur due to the star losing the heat at its core which eventually makes it collapse. This is the type of supernova formed when massive stars die. They occur in a galaxy with ongoing star formation and a black hole or neutron star left behind.
Supernovae can also be occur when a star orbits another and crashes into another. This is what occurs in a white dwarf
. This is part of a binary system, can occur in a very old star cluster and leaves no compact object behind.
