Which is evidence for the existence of dark energy? *
1 point
galaxies that are rotating at a constant rate
Pulsars that seem to be moving closer at an accelerating rate
Black holes that are expanding at a constant rate
Supernovae that are moving away at an accelerating rate
Supernovae that are moving away at an accelerating rate is evidence for the existence of dark energy.
The evidence for the existence of dark energy comes from observing supernovae (option D) that are moving away at an accelerating rate.
To understand the evidence for dark energy, scientists have been studying the expansion of the universe. Initially, it was thought that the expansion of the universe was slowing down due to the gravitational pull of matter. However, in the late 1990s, astronomers made a surprising discovery. They found that Type Ia supernovae, which are incredibly bright and can be used as standard candles, were actually moving away from us at an accelerating rate.
To obtain this evidence, astronomers use telescopes to measure the brightness and redshift (a measure of how much the light from an object has been stretched) of distant supernovae. By comparing the observed brightness to the expected brightness, they can calculate the distance to the supernova. The redshift provides information about how fast the supernova is moving away from us.
When studying these Type Ia supernovae, scientists expected to see a decelerating universe due to the gravitational pull of matter. However, the observations showed that the supernovae were actually moving away at an increasing rate. This finding indicated the presence of a force that counteracts gravity and drives the acceleration, which was called dark energy.
It is important to note that the other options (A, B, and C) do not provide evidence for dark energy. Option A mentions galaxies rotating at a constant rate, which is not directly related to the expansion of the universe. Option C mentions black holes expanding at a constant rate, which is not supported by current scientific understanding. Option B mentions pulsars moving closer at an accelerating rate, which is not related to the expansion of the universe caused by dark energy.