An compact, extragalactic object which is highly luminous and looks like a star. Their redshifts can be large and their brightness varies. Quasars have an intrinsic luminosity which can reach some 100
times that of bright galaxies. They are thought to be active galactic nuclei with a size a little larger than the solar system. The first quasar to be identified as such, in 1963, was the radio source 3C 273 at a redshift of 0.158. With its 13th magnitude, it is the optically brightest quasar as observed from Earth. Some quasars are strong radio sources.
An compact, extragalactic object which is highly luminous and looks like a star. Their redshifts can be large and their brightness varies. Quasars have an intrinsic luminosity which can reach some 100
times that of bright galaxies. They are thought to be active galactic nuclei with a size a little larger than the solar system. The first quasar to be identified as such, in 1963, was the radio source 3C 273 at a redshift of 0.158. With its 13th magnitude, it is the optically brightest quasar as observed from Earth. Some quasars are strong radio sources.
An compact, extragalactic object which is highly luminous and looks like a star. Their redshifts can be large and their brightness varies. Quasars have an intrinsic luminosity which can reach some 100
times that of bright galaxies. They are thought to be active galactic nuclei with a size a little larger than the solar system. The first quasar to be identified as such, in 1963, was the radio source 3C 273 at a redshift of 0.158. With its 13th magnitude, it is the optically brightest quasar as observed from Earth. Some quasars are strong radio sources.
An compact, extragalactic object which is highly luminous and looks like a star. Their redshifts can be large and their brightness varies. Quasars have an intrinsic luminosity which can reach some 100
times that of bright galaxies. They are thought to be active galactic nuclei with a size a little larger than the solar system. The first quasar to be identified as such, in 1963, was the radio source 3C 273 at a redshift of 0.158. With its 13th magnitude, it is the optically brightest quasar as observed from Earth. Some quasars are strong radio sources.
An compact, extragalactic object which is highly luminous and looks like a star. Their redshifts can be large and their brightness varies. Quasars have an intrinsic luminosity which can reach some 100
times that of bright galaxies. They are thought to be active galactic nuclei with a size a little larger than the solar system. The first quasar to be identified as such, in 1963, was the radio source 3C 273 at a redshift of 0.158. With its 13th magnitude, it is the optically brightest quasar as observed from Earth. Some quasars are strong radio sources.
A system or flow that evolves slowly in time compared to the rotation period of the earth, has a length scale of the deformation radius or larger, and undergoes only limited vertical excursions.
The climate of the last 2 500 000 years, including the alternating glacial-interglacial climate of the Pleistocene and the comparatively warm climate of the Holocene or postglacial (the last 10 000 ye
ars).
The last two million years of geologic time, comprising the Pleistocene and Holocene glacial epochs. Estimates of the date of the beginning of the Quaternary vary between 2.5 and 1.6 million years ago
.