What makes quasars quasi stellar

But, as we saw, quasars also emit energy at X-ray and ultraviolet wavelengths, and some are radio sources as well. When all their radiation is added together, some QSOs have total luminosities as large as a hundred trillion Suns 10 14 L Sun , which is 10 to times the brightness of luminous elliptical galaxies.

Finding a mechanism to produce the large amount of energy emitted by a quasar would be difficult under any circumstances. But there is an additional problem. When astronomers began monitoring quasars carefully, they found that some vary in luminosity on time scales of months, weeks, or even, in some cases, days. This variation is irregular and can change the brightness of a quasar by a few tens of percent in both its visible light and radio output.

Think about what such a change in luminosity means. A quasar at its dimmest is still more brilliant than any normal galaxy. Whatever mechanism is responsible must be able to release new energy at rates that stagger our imaginations. The most dramatic changes in quasar brightness are equivalent to the energy released by , billion Suns. To produce this much energy we would have to convert the total mass of about ten Earths into energy every minute.

Moreover, because the fluctuations occur in such short times, the part of a quasar that is varying must be smaller than the distance light travels in the time it takes the variation to occur—typically a few months. Suppose every star in this cluster somehow brightens simultaneously and remains bright. When the light from this event arrives at Earth, we would first see the brighter light from stars on the near side; 5 years later we would see increased light from stars at the center.

Ten years would pass before we detected more light from stars on the far side. Figure 5. How the Size of a Source Affects the Timescale of Its Variability: This diagram shows why light variations from a large region in space appear to last for an extended period of time as viewed from Earth. Suppose all the stars in this cluster, which is 10 light-years across, brighten simultaneously and instantaneously. From Earth, star A will appear to brighten 5 years before star B, which in turn will appear to brighten 5 years earlier than star C.

It will take 10 years for an Earth observer to get the full effect of the brightening. Even though all stars in the cluster brightened at the same time, the fact that the cluster is 10 light-years wide means that 10 years must elapse before the increased light from every part of the cluster reaches us. From Earth we would see the cluster get brighter and brighter, as light from more and more stars began to reach us. Not until 10 years after the brightening began would we see the cluster reach maximum brightness.

In other words, if an extended object suddenly flares up, it will seem to brighten over a period of time equal to the time it takes light to travel across the object from its far side. We can apply this idea to brightness changes in quasars to estimate their diameters. Because quasars typically vary get brighter and dimmer over periods of a few months, the region where the energy is generated can be no larger than a few light-months across.

If it were larger, it would take longer than a few months for the light from the far side to reach us. How large is a region of a few light-months? Pluto, usually the outermost dwarf planet in our solar system, is about 5. Clearly a region a few light months across is tiny relative to the size of the entire Galaxy. And some quasars vary even more rapidly, which means their energy is generated in an even smaller region. Whatever mechanism powers the quasars must be able to generate more energy than that produced by an entire galaxy in a volume of space that, in some cases, is not much larger than our solar system.

Even before the discovery of quasars, there had been hints that something very strange was going on in the centers of at least some galaxies. Back in , American astronomer Heber Curtis used the large Lick Observatory telescope to photograph the galaxy Messier 87 in the constellation Virgo.

On that photograph, he saw what we now call a jet coming from the center, or nucleus, of the galaxy Figure 6. This jet literally and figuratively pointed to some strange activity going on in that galaxy nucleus. But he had no idea what it was. No one else knew what to do with this space oddity either. The random factoid that such a central jet existed lay around for a quarter century, until Carl Seyfert, a young astronomer at Mount Wilson Observatory, also in California, found half a dozen galaxies with extremely bright nuclei that were almost stellar, rather than fuzzy in appearance like most galaxy nuclei.

Using spectroscopy, he found that these nuclei contain gas moving at up to two percent the speed of light. That may not sound like much, but it is 6 million miles per hour, and more than 10 times faster than the typical motions of stars in galaxies.

Figure 6. It was launched in and is one of the great observatories of NASA. Description: Hubble was created with a need to capture high-resolution images of universe.

It is capable of taking high-resolution images with negligible background light. History: Though the HST launched in , the idea of maki. Heliopause is the outer edge of the heliosphere which acts as the surface of the bubble that surrounds our solar system. The Heliopause is that part of the solar system which is exposed to particles and ions of deep space. Description: Heliopause is the boundary of the heliosphere which is the spherical region around the Sun.

It is filled with solar magnetic fields and solar wind that consists. Solar panels are those devices which are used to absorb the sun's rays and convert them into electricity or heat. Description: A solar panel is actually a collection of solar or photovoltaic cells, which can be used to generate electricity through photovoltaic effect. These cells are arranged in a grid-like pattern on the surface of solar panels. Thus, it may also be described as a set of. An aurora is a natural phenomenon which is characterised by a display of a natural-coloured green, red, yellow or white light in the sky.

It is predomi. ISRO was formed in with a vision to develop and harness space technology in national development, while pursuing planetary exploration and space science research. A Lagrangian point is a position or location in space where the combined gravitational forces of two large bodies is equal to the centrifugal force that is felt by a third body which is relatively smaller. The two large bodies here may be the Earth and Sun or the Earth and Moon.

Description: A lagrangian point is also known as a Lagrange point, Liberation point, or L-point. These points are loc. Choose your reason below and click on the Report button. This will alert our moderators to take action. Nifty 18, Zomato Ltd. Market Watch. ET NOW. Brand Solutions. Video series featuring innovators. ET Financial Inclusion Summit. Malaria Mukt Bharat. Wealth Wise Series How they can help in wealth creation. Honouring Exemplary Boards. It took years of study to realize that these distant specks, which seemed to indicate stars, are created by particles accelerated at velocities approaching the speed of light.

Scientists now suspect that the tiny, point-like glimmers are actually signals from galactic nuclei outshining their host galaxies. Quasars live only in galaxies with supermassive black holes — black holes that contain billions of times the mass of the sun. Although light cannot escape from the black hole itself, some signals can break free around its edges.

While some dust and gas fall into the black hole , other particles are accelerated away from it at near the speed of light. The particles stream away from the black hole in jets above and below it, transported by one of the most powerful particle accelerators in the universe. Most quasars have been found billions of light-years away. Because it takes light time to travel, studying objects in space functions much like a time machine; we see the object as it was when light left it, billions of years ago.

Thus, the farther away scientists look, the farther back in time they can see. Most of the more than 2, known quasars existed in the early life of the galaxy. Galaxies like the Milky Way may once have hosted a quasar that has long been silent. In December , the most distant quasar was found sitting more than 13 billion light-years from Earth. Quasars this young can reveal information about how galaxies evolved over time.

Quasars emit energies of millions, billions, or even trillions of electron volts.