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A stellar halo is the component of a galaxy's galactic halo that contains stars. The stellar halo extends far outside a galaxy's ... halo in the Milky Way has been ...
The discovery of the star in the Milky Way Galaxy suggests that the galaxy may be at least 3 billion years older than previously thought. [265] [266] [267] Several individual stars have been found in the Milky Way's halo with measured ages very close to the 13.80-billion-year age of the Universe.
In our stellar halo, stars tend to be old (most are greater than 12 billion years old) and metal-poor, but there are also halo star clusters with observed metal content similar to disk stars. The halo stars of the Milky Way have an observed radial velocity dispersion of about 200 kilometres per second and a low average velocity of rotation of ...
The nature of the Milky Way's bar, which extends across the Galactic Center, is also actively debated, with estimates for its half-length and orientation spanning between 1–5 kpc (short or a long bar) and 10–50°. [23] [25] [27] Certain authors advocate that the Milky Way features two distinct bars, one nestled within the other. [28]
In the Milky Way, stars usually have velocities on the order of 100 km/s, whereas hypervelocity stars typically have velocities on the order of 1000 km/s. Most of these fast-moving stars are thought to be produced near the center of the Milky Way, where there is a larger population of these objects than further out.
The bars take shape when stars within spiral galaxies rotate in an orderly fashion, as they do in the Milky Way. Until now, astronomers didn’t believe early galaxies had enough stability for ...
Astronomers using the Gaia space telescope have located two ancient streams of stars that helped the Milky Way galaxy grow and evolve more than 12 billion years ago.
In the Milky Way galaxy, globular clusters are distributed roughly spherically in the galactic halo, around the Galactic Center, orbiting the center in highly elliptical orbits. In 1917, the astronomer Harlow Shapley made the first respectable estimate of the Sun's distance from the Galactic Center, based on the distribution of globular clusters.