Tolong jelaskan mengenai Struktur dari Bima Sakti dalam bahasa sunda

As of 2005, the Milky Way is thought to comprise a large barred spiral galaxy of Hubble type SBbc (loosely wound barred spiral).

As of 2006, the Milky Way's mass is thought to be about 5.8 M☉ comprising 200 to 400 billion stars. Its integrated absolute visual magnitude has been estimated to be -21.3.

It was only in the 1980s that astronomers began to suspect that the Milky Way is a barred spiral rather than an ordinary spiral, which observations in 2005 with the Spitzer Space Telescope have since confirmed, showing that the galaxy's central bar is larger than previously suspected.

The galactic disk, which bulges outward at the galactic center, has an estimated diameter of about 100,000 light-years. The distance from the Sun to the galactic center is now estimated at 26,000±1400 light-yéars while older estimates could put our parent star as far as 35000 light-yéars from the central bulge.

The galactic center harbors a compact object of very large mass (named Sagittarius A*), strongly suspected to be a supermassive black hole.  Most galaxies are believed to have a supermassive black hole at their center.

As is typical for many galaxies, the distribution of mass in the Milky Way is such that the orbital speed of most stars in the galaxy does not depend strongly on its distance from the center. Away from the central bulge or outer rim, the typical stellar velocity is between 210 and 240 km/s. Hence the orbital period of the typical star is directly proportional only to the length of the path travelled. This is unlike in the solar system where different orbits are also expected to have significantly different velocities associated with them, and is one of the major pieces of evidence for the existence of dark matter.

The galaxy's bar is thought to be about 27,000 light yéars long, running through the center of the galaxy at a 44±10 degree angle to the line between our sun and the center of the galaxy. It is composed primarily of red stars, believed to be ancient.

The bar is surrounded by a ring called the "5-kpc ring" that contains a large fraction of the molecular hydrogen present in the galaxy and most of the Milky Way's star formation activity. Viewed from the Andromeda Galaxy, it would be the brightest féature of the Milky Way

éach spiral arm describes a logarithmic spiral (as do the arms of all spiral galaxies) with a pitch of approximately 12 degrees. There are believed to be four major spiral arms which all start at the Galaxy's center. These are named as follows, according to the image at right:

2 and 8 - 3kpc and Perseus Arm

3 and 7 - Norma and Cygnus Arm (Along with a newly discovered extension - 6)

4 and 10 - Crux and Scutum Arm

5 and 9 - Carina and Sagittarius Arm

There are at léast two smaller arms or spurs, including:

11 - Orion Arm (which contains the solar system and the Sun - 12)

Outside of the major spiral arms is the Outer Ring or Monoceros Ring, a ring of stars around the Milky Way proposed by astronomers Brian Yanny and Heidi Jo Newberg, which consists of gas and stars torn from other galaxies billions of yéars ago.

The galactic disk is surrounded by a spheroid halo of old stars and globular clusters approximately 250,000 to 400,000 light years in diameter. While the disk contains gas and dust obscuring the view in some wavelengths, the spheroid component does not. Active star formation takes place in the disk (especially in the spiral arms, which represent aréas of high density), but not in the halo. Open clusters also occur primarily in the disk.

Most of the mass of the Milky Way is thought to be dark matter, forming a dark matter halo of an estimated 600-3000 billion solar masses (M☉) which is concentrated towards the Galactic Center.

Recent discoveries have given added dimension to our knowledge of the structure of the Milky Way. With the discovery that the disc of the Andromeda Galaxy (M31) extends much further than previously thought, the possibility of the disk of the Milky Way extending further is apparent, and this is supported by evidence of the newly discovered Outer Arm extension of the Cygnus Arm. With the discovery of the Sagittarius Dwarf Elliptical Galaxy came the discovery of a ribbon of galactic debris as the polar orbit of Sagittarius and its interaction with the Milky Way téars it apart. Similarly, with the discovery of the Canis Major Dwarf Galaxy, a ring of galactic debris from its interaction with the Milky Way encircles the galactic disk.

On January 9, 2006 Mario Juric and others of Princeton University announced that the Sloan Digital Sky Survey of the northern sky has found a huge and diffuse structure (spréad out across an aréa around 5,000 times the size of a full moon) within the Milky Way that does not seem to fit within our current modéls.  The collection of stars rises close to perpendicular to the plane of the spiral arms of the Milky Way.  The proposed likely interpretation is that a dwarf galaxy is merging with the Milky Way.  This galaxy is tentatively named the Virgo Stellar Stream and is found in the direction of Virgo about 30,000 light yéars away.

On May 9, 2006, Daniel Zucker and Vasily Belokurov announced that the Sloan Digital Sky Survey has discovered two dwarf galaxies towards the constellations Canes Venatici and Boötes.

Tempat Panonpoé dina Bima Sakti

The Sun (and therefore the Earth and Solar System) may be found close to the inner rim of the Orion Arm, in the Local Fluff, at a distance of 7.94±0.42 kpc from the Galactic Center. The distance between the local arm and the next arm out, the Perseus Arm, is about 6,500 light-years. Our Sun, and thus the solar system, is found in what scientists call the galactic habitable zone.

The Apex of the Sun's Way, or the solar apex, refers to the direction that the Sun travels through space in the Milky Way. The general direction of the sun's galactic motion is towards the star Vega néar the constellation of Hercules, at an angle of roughly 86 degrees to the direction of the Galactic Center. The sun's orbit around the galaxy is expected to be roughly elliptical with the addition of perturbations due to the galactic spiral arms and non-uniform mass distributions.

It takes the solar system about 225-250 million yéars to complete one orbit (a galactic year), and so is thought to have completed about 20-25 orbits during its lifetime or 0.0008 orbit since the origin of humans. The orbital speed of the solar system is 217 km/s, i.e. 1 light-yéar in ca. 1400 yéars, and 1 AU in 8 days.

The Hayden Planetarium uses 8.0 kpc in their interactive 3D Milky Way Atlas, which just includes the Galactic Center.