How do we know that the cores of quasars are very small?

How do we know that the cores of quasars are very small?

The small sizes were confirmed by interferometry and by observing the speed with which the quasar as a whole varied in output, and by their inability to be seen in even the most powerful visible-light telescopes as anything more than faint starlike points of light.

Why do astronomers think that there are fewer quasars today?

Since then, astronomers have realized that quasars mark a phase in the life of galaxies, when their central black holes are lit up by accreting matter. This trait was more com- mon in the past, so there are fewer quasars today. Now starved of fuel, black holes linger in galaxies, including our Milky Way.

What makes astronomers the energy source in quasars is only a few light months across that is the distance light travels in a few months?

Fluctuations in the energy output of a quasar can change over relatively short time periods (a few months to a few years at most). This means that the region from which the changing energy is coming cannot be larger than the distance that light can travel over a few month or a few years.

Why do astronomers conclude that quasars are very far away?

A: The simple answer: because luminous quasars are still visible from large distances, while fainter active galactic nuclei (AGNs) are not. Quasars are the highest luminosity (more than 100 billion times that of the Sun) and most massive (more than 100 million solar masses) subset of AGNs.

What evidence do we have that quasars are small?

What evidence do we have that quasars are small? They have rapid fluctuations in brightness.

Why must the sources of quasars be tiny?

Why must the source of Quasars be tiny? They change brightness in days or weeks. A phenomena of infinite density captured in the size of “zero” that explains the beginning of the universe. -A tiny change caused an explosion which expanded the point of singularity and thus created the universe into an intense fireball.

What are quasars and why are they difficult to see?

Quasars are farther away from Earth than any other known object in the universe. Because they are so far away from us, it takes billions of years for the light they give off to reach Earth. The light stays the same, it just has to travel a long time to get to us.

How do we know that quasars are very distant objects?

What evidence do we have that quasars are very far away? -Their spectral lines have large redshifts. -Some are gravitationally lensed by distant galaxies. -Some light from quasars contains less redshifted absorption lines of distant galaxies.

Why is it difficult to get information on quasars?

This is because the feeding black hole stirs up gas and dust, cloaking the quasar and making it difficult to detect in visible light surveys.

How do we know that the energy emitting regions of many active galaxies must be very small?

How do we know that the energy-emitting regions of many active galaxies must be very small? If an object’s luminosity fluctuates rapidly, then it must be compact; an object cannot ‘flicker’ in less time than radiation takes to cross it.

How can we explain the existence of bright quasars?

Bottom line: Quasars are extremely bright and extremely distant objects. Their huge energy output is thought to be due to activity around the central supermassive black hole in young galaxies, near the edge of the observable universe.

Why is it thought that quasars probably spend only a fairly short time in their highly luminous phase?

Why is it thought that quasars probably spend only a fairly short time in their highly luminous phase? when there was still sufficient mass to fuel the supermassive black holes at their center.

Why do we think that quasars are extremely distant quizlet?

Why do we think that quasars are extremely distant? Their spectra show immense redshifts. Why do we think that active galaxies have small core regions? Their light varies rapidly, implying small radius.

Why do astronomers think that quasars are extremely luminous?

Quasars are extremely luminous and were first identified as being high redshift sources of electromagnetic energy, including radio waves and visible light, that appeared to be similar to stars, rather than extended sources similar to galaxies.

Why do quasars emit so much energy?

At the center of a quasar, the black hole is surrounded by a large, rotating cloud of gas. As the gas falls into the black hole, it is heated up to millions of degrees. The gas emits thermal radiation due to its enormous heat.

How do we know the size of quasars?

Space and time are inextricably linked, and how space is bent can be used in part to measure how big a quasar is through a concept called “microlensing.” Quasar sizes can also be measured by tracking how the quasar’s energy released changes with time.

How do we know that quasars are very distant objects?

What evidence do we have that quasars are very far away? -Their spectral lines have large redshifts. -Some are gravitationally lensed by distant galaxies. -Some light from quasars contains less redshifted absorption lines of distant galaxies.

What is the smallest quasar?

A microquasar, the smaller version of a quasar, is a compact region surrounding a stellar black hole with a mass several times that of its companion star.

Are quasars big or small?

The size of a quasar accretion disk, which scales with the mass of its black hole, is typically a few light-days across. That dwarfs in comparison to its host galaxy; the Milky Way for comparison is roughly 100,000 light-years across. Yet quasars often outshine their hosts.