The outer galaxy

The sun is located inside one of the spiral arms of the Milky Way galaxy, roughly two-thirds of the way from the galactic center to the outer regions. Because we are inside the galaxy, obscuration by dust and the confusion ...

Mapping dark matter

About eighty-five percent of the matter in the universe is in the form of dark matter, whose nature remains a mystery. The rest of the matter in the universe is of the kind found in atoms. Astronomers studying the evolution ...

Using the universe as a 'cosmological collider' (Update)

Physicists are capitalizing on a direct connection between the largest cosmic structures and the smallest known objects to use the universe as a "cosmological collider" and investigate new physics.

More to life than the habitable zone

Two separate teams of scientists have identified major challenges for the development of life in what has recently become one of the most famous exoplanet systems, TRAPPIST-1.

Y-type stars

Brown dwarf stars are failed stars. Their masses are so small, less than about eighty Jupiter-masses, that they lack the ability to heat up their interiors to the roughly ten million kelvin temperatures required for normal ...

The shapes of galaxies

Since Edwin Hubble proposed his galaxy classification scheme in 1926, numerous studies have investigated the physical mechanisms responsible for the shapes of spiral and elliptical galaxies. Because the processes are complex, ...

The anatomy of Orion

The Orion molecular cloud is a large complex of hot young stars, nebulae, and dark clouds of gas and dust located in the constellation of Orion. Two particularly famous sights in the night sky, the Orion Nebula and the Horsehead ...

Extended hard X-ray emission from a galactic nucleus

Supermassive black holes containing millions or even billions of solar masses of material are found at the nuclei of almost all galaxies. The Milky Way, for example, has a nuclear black hole with about 4 million solar masses ...

Understanding star-forming galaxies

The more stars a typical spiral galaxy contains, the faster it makes new ones. Astronomers call this relatively tight correlation the "galaxy main sequence." The main sequence might be due simply to the fact that galaxies ...

Star-forming filaments

Interstellar molecular clouds are often seen to be elongated and "filamentary" in shape, and come in a wide range of sizes. In molecular clouds, where stars form, the filamentary structure is thought to play an important ...

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