The nature of the Galaxy's bar is actively debated

The Sun is 26,000–28,000 ly (8.0–8.6 kpc) from the Galactic Center. This value is estimated based upon geometric-based methods or using selected astronomical objects that serve as standard candles, with different techniques yielding different values within this approximate range.[8][50][51][52][53] In the inner few kpc (˜10,000 light-years) is a dense concentration of mostly old stars in a roughly spheroidal shape called the bulge.[54] It has been proposed that our galaxy lacks a bulge formed due to a collision and merger between previous galaxies and that instead has a pseudobulge formed by its central bar.[55]
The Galactic Center is marked by an intense radio source named Sagittarius A*. The motion of material around the center indicates that Sagittarius A* harbors a massive, compact object.[56] This concentration of mass is best explained as a supermassive black hole[nb 4][8][50] with an estimated mass of 4.1–4.5 million times the mass of the Sun.[50] Observations indicate that there are supermassive black holes located near the center of most normal galaxies.[57][58]
The nature of the Galaxy's bar is actively debated, with estimates for its half-length and orientation spanning from 1–5 kpc (3,300–16,000 ly) and 10–50 degrees relative to the line of sight from Earth to the Galactic Center.[52][53][59] Certain authors advocate that the Galaxy features two distinct bars, one nestled within the other.[60] In most galaxies, Wang et al. report, the rate of accretion of the supermassive black hole is slow, but the Milky Way seems to be an important exception. The central bar, delineated by red clump stars, shows that x-ray emissions show elongation in alignment with surrounding massive stars.[61] However, RR Lyr variables do not trace a prominent Galactic bar.[53][62][63] The bar may be surrounded by a ring called the "5-kpc ring" that contains a large fraction of the molecular hydrogen present in the Galaxy, as well as most of the Milky Way's star formation activity. Viewed from the Andromeda Galaxy, it would be the brightest feature of our own Galaxy.[64]
In 2010, two gigantic spherical bubbles of high energy emission were detected to the north and the south of the Milky Way core, using data of the Fermi Gamma-ray Space Telescope. The diameter of each of the bubbles is about 25,000 light-years (7.7 kpc); they stretch up to Grus and to Virgo on the night-sky of the southern hemisphere.[65][66] Subsequently, observations with the Parkes Telescope at radio frequencies identified polarized emission which is associated with the Fermi bubbles. These observations are best interpreted as a magnetized outflow driven by star formation in the central 640 ly (200 pc) of the Galaxy