Answer to Question 1
Neutrinos travel directly out of the Sun to the Earth in about 8 minutes. Neutrino detectors can detect these, confirming the nuclear reactions happening in the Sun's core.
Answer to Question 2
An interstellar cloud, disturbed in some way, begins to gravitationally collapse. It heats up as it collapses, and spins faster. (If the spinning is too great it may defeat the entire process, as the protostar tears itself apart.) Eventually the core of the cloud is hot enough that it develops a definite glowing edge (photosphere), and begins to resemble a star. When the core temperature reaches 10 million K and nuclear fusion of hydrogen into helium begins, it is officially a star. When the outward pressure equalizes with gravity, the star enters the main sequence. Collisions between galaxies can set up a shock wave to initiate collapse, as can the shock waves from supernovae and the density wave moving through the spiral arms of the galaxy.
The ornate red lionfish as seen from a head-on view
The female reproductive system. (a) Sagittal section through the pelvis. (b) Top view of pelvic orga
Skull Right Lateral View Labeled
Aerial view of old hutong area, Beijing.
The Kidney with an Expanded View of the Nephron
Birds-eye view of land