An astronomer examining a compact object could conclude that it was a black hole if it _____.
a. emits regular pulses of radiation
b. has a defined event horizon that emits X-rays
c. has an accretion disk
d. has a mass greater than 1.4 solar masses
e. has a mass greater than 3 solar masses
Question 2
Which statement best describes a theory?
a. A group of ideas about how something should be done, made, or thought about
b. A specific statement about nature that needs further testing
c. An idea considered so obviously true that the idea does not need to be questioned
d. A fundamental principle in which scientists have great confidence
e. A general description of some aspect of nature that has been thoroughly tested and widely accepted
The black-capped chickadee is a permanent resident in biomes with harsh winter conditions.
Black flies are blood-sucking insects who vector disease, like River Blindness, while feeding on hum
Chest X-ray. A physician is examining chest X-rays with the aid of a plastic model of the bronchial
Evaporation of a Black Hole
Attributed to José de Alcíbar, From Spaniard and Black, Mulatto (De Español y Negra, Mulato).
Black-tailed Prairie Dog (Cynomys ludovicianus).