Question

What evidence do we have that the energy source that powers quasars is small in size?

Answer 1

The evidence supporting the small size of the energy source that powers quasars lies in their extreme luminosity and rapid variability, indicating a compact region. Observations show that the emitted light varies on timescales as short as hours, suggesting a confined space significantly smaller than a galaxy.

Step-by-step explanation:

Quasars, or quasi-stellar radio sources, exhibit extraordinary luminosity, outshining entire galaxies. This intense brightness implies a highly concentrated source of energy, as such brilliance over a vast volume is unlikely. The rapid variability in quasar brightness further supports a compact energy source. Light fluctuations occurring on timescales of hours indicate a confined region, much smaller than the scale of a galaxy. This dynamic behavior aligns with the characteristics expected from a compact, centrally located powerhouse.

The size of the energy source can be estimated through the light travel time argument. Considering the rapid variability observed, the size (R) of the emitting region can be determined by the equation R = ct, where c is the speed of light (approximately 3 x 10^8 m/s) and t is the characteristic timescale of variability. For instance, if the variability occurs over 1 hour (3.6 x 10^3 seconds), the size of the energy source would be on the order of 1.08 x 10^12 meters, or around 720 astronomical units (AU), considerably smaller than a typical galaxy. This calculation reinforces the notion that the energy source powering quasars is indeed compact, providing empirical support for their small size.

Answer 2

The evidence indicating that the energy source powering quasars is small in size lies in their rapid variability and the immense luminosity observed. This variability occurs on timescales as short as hours or days, suggesting a compact region emitting the energy. Additionally, the high luminosity emanating from a relatively confined area supports the notion of a compact energy source within quasars.

Step-by-step explanation:

The rapid variability of quasars' luminosity provides crucial evidence for a compact energy source. Observations have recorded fluctuations in brightness occurring within incredibly short periods, sometimes mere hours apart. This rapid variability suggests that the source emitting this immense energy is physically small. To quantify this, consider the distance light can travel in the observed timescale compared to the physical size of the emitting region. Calculations show that the observed changes in luminosity can only originate from a source considerably smaller than our solar system.

Moreover, the luminosity emitted by quasars is astoundingly high, equivalent to the energy output of billions of stars. However, this enormous energy output emerges from a relatively confined area. By estimating the size of the emitting region using the luminosity and the maximum speed achievable in that space, calculations reveal a compact energy source. The dimensions derived from these calculations align with the incredibly short timescales of variability observed, further supporting the theory of a small-sized energy source within quasars.

In essence, the evidence supporting a small-sized energy source in quasars stems from their rapid luminosity fluctuations and the immense energy emitted from a relatively confined space. Both observations and calculations strongly suggest that the powerful energy driving quasars originates from a compact region, significantly smaller than conventional astronomical scales.