One of the most significant Russian space missions in the post-Soviet era was launched from Baikonur.
The Spektr-RG telescope is a joint venture with Germany that will map X-rays across the sky with unprecedented details.
The researchers say this information will help them trace the large-scale structure of the universe.
The hope is that Spektr-RG can provide new insights into the accelerating behavior of cosmic expansion.
It should also identify a staggering number of new X-ray sources, such as the colossal black holes found in the center of galaxies.
When the gas falls into these monsters, matter is heated and shredded and "screams" to X-rays. Radiation is essentially a revelation for the most violent phenomena of the universe.
Spektr-RG expects to detect perhaps three million super-massive black holes during its service life.
Superior courtesy image of RussianSpaceWeb.com
The telescope drove into orbit atop a Proton rocket that left the Baikonur cosmodrome in Kazakhstan at 17:31 local time (12:31 GMT).
However, it will be several weeks before the mission's work can begin in earnest.
The spacecraft must first travel to a popular observation location about 1.5 million km from Earth known as Lagrange Point 2.
It is here that Spektr-RG can enjoy a stable environment free from the oscillations and temperature oscillations that would otherwise prove if it were closer to our planet.
But once the test is complete, the observatory can go on with the sky scanning business.
Spektr-RG is built like a two-in-one telescope.
The eRosita system developed in Germany develops most of the room on the bus or on the spacecraft chassis. Next to it is the Russian-made scientific hardware known as ART-XC.
Both use a set of seven mirrored tubular modules to corrode X-ray light on sensitive camera detectors.
Working in tandem, eRosita and ART-XC will map radiation while invading the cosmos in the energy range from 0.2 to 30 kiloelectron volts (keV).
Over the course of six months, they should complete an open survey, which will then be repeated over and over again to improve the details.
Scientists expect the data to be a revelation. An all-sky radiographic map has never been produced before with the sought-after energies and with such a fine resolution.
A key goal of Spektr-RG will be to investigate the mysterious cosmic components referred to as "dark matter" and "dark energy".
This duo constitutes 96% of the energy density of the Universe, but almost nothing is known about them. The former seems to attract normal and visible matter gravitationally, while the latter seems to work to keep the cosmos at an ever-faster pace.
The Spektr-RG insights will come from mapping the distribution of hot X-ray gases.
This will illuminate the large clusters of galaxies that pass through the Universe. And in doing so, it will identify where the greatest concentrations of dark matter can be found.
"We aim to detect about 100,000 clusters and, in fact, above a certain mass limit, we expect to detect all the clusters in the universe," explained Professor Kirpal Nandra of the Max Planck Institute of extraterrestrial physics in Garching, Germany.
"We then measure their masses and see how the number of clusters of a given mass evolves in cosmic time, which gives us a potentially very accurate measure of the amount of dark matter and how it clusters," he told BBC News.
"Our sensitivity allows us to map all this over great distances, up to more than half of the time of the universe, which means that we see the structure on a large scale not just as it is today, but also at that time. we also see how it has evolved over time: this is what gives you the chance to test cosmological models and to see perhaps the influence of dark energy and if this has changed over time. "
Spektr-RG took decades to develop. Russian scientists have had to contend with inconsistent funding over the years and consequently the concept launched on Saturday is quite radically different from what was originally planned.
The mission has been described as the most important astrophysical enterprise in post-Soviet Russia. Prof. Nandra said that his Russian colleagues certainly saw it that way.
"It puts them at the forefront of X-ray astronomy, it's a great opportunity for them," he added.
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