Deep Sky · 5 of 5

The Plane of the Galaxy

Where is the centre of our galaxy in your sky?

The Milky Way is our galaxy seen edge-on from inside. Find its midline, its centre in Sagittarius, and the empty window above it.

You’ll be able to trace the Milky Way’s midline and point to the galaxy’s centre in Sagittarius.

9 steps · about 7 min

Before this: The Ecliptic (8 min)

Where and which night

Working out when this is best placed from where you are…

Where

Which night

Date

Time

Kept for this guide only, until you change it here — your map settings, and every other guide, stay as they are.

Print, play outside or present

Present on a big screen

Scan with a phone's camera, or open

Sources

ESA, The Hipparcos and Tycho Catalogues (SP-1200, 1997), vol. 1 §1.5.3 — the galactic frame in J2000: north galactic pole at RA 192.85948°, Dec +27.12825°; every galactic position, crossing and angle here is computed from it
GRAVITY Collaboration, A&A 625, L10 (2019) — distance to the Galactic centre, 8.178 ± 0.026 kpc (26,700 light-years)
HYG stellar database v4.2 — star positions and every separation quoted here
d3-celestial deep-sky catalogue, as this map ships it (public/data/dsos.10.json) — the 126 galaxies counted by galactic latitude
Binggeli, Sandage & Tammann, "Studies of the Virgo Cluster. II. A catalog of 2096 galaxies in the Virgo Cluster area", AJ 90, 1681 (1985) — about 1,300 of them members
Bortle, "The Bortle Dark-Sky Scale", Sky & Telescope, February 2001

← GUIDES

More below ↓

With a keyboard, focus the sky, aim it with the up and down arrow keys, and press Enter to drop the pin at the centre of the view; or press Show me.

You are here

Settings

Screen

Night mode Turns every page red, to keep your eyes adjusted to the dark.

High contrast Bolder constellation lines, larger and brighter names on the sky, and stronger text and edges everywhere. Starts on if your device asks for more contrast.

Reduce motion The camera cuts to where it is going instead of flying there, and panels and sheets appear without sliding. Starts on if your device asks for less motion.

Battery saver Draws the sky thirty times a second at most: smoothness traded for battery.

Night brightness Dims the screen below your phone’s lowest setting, down to a fifth, while night mode is on.

Clock and voice

Clock How every time is written. Until you choose, your language’s own clock decides.

D describes What D says about the view on the sky: one sentence, or in full with the field, the constellation and five names.

Sounds Quiet tones as you use the map: a tick as you drag the clock past a mark or dusk, a chime for the star you pick — higher for hotter stars — and a low swell while a figure is out of the dome. Made in your browser, and off until you turn them on.

All settings and your progress

Run two hours. The band over Capella is the Milky Way, our galaxy's disc edge-on; the dashed line is the galactic equator.

From outside, the galaxy is a thin disc 100,000 light-years across, the Sun 26,700 light-years from its centre. This lesson is one night, three directions: away from the centre in the evening, up out of the disc at midnight, in towards it at dawn.

Away first. Places on the line are given as galactic longitude, l, counted from the centre. The point marked beside Elnath is l = 180°, the anticentre. This way you look out through the thin outer disc, and the band is faint.

Run two hours: Coma Berenices, between Arcturus and Denebola, climbs. In it is the north galactic pole, straight out of the disc.

Of the 126 galaxies this map draws, 35 lie inside this ring, a fifteenth of the sky. Partly that is the clear view out of the disc, and partly the Virgo cluster, a real crowd near the pole: is one of well over a thousand galaxies in it.

The fair test: every galaxy this map draws, in bands by distance from the Milky Way's midline. Only eight lie within 10° of it, a strip that covers 17% of the sky. The dust in our own disc hides what lies behind it.

Last, in. Before dawn Sagittarius rises, and the ecliptic crosses the band here, at the December solstice point; it crosses back opposite, at the June one. So each December the Sun stands in front of the heart of the Milky Way.

At dawn it is low in twilight, so take the ground and air away and follow the band in, to l = 0°: the galactic centre. Looking in through the whole inner disc, the band is broadest and brightest, split down its length by dust.

Three directions, one night.

Away, the faint disc
Up, the galaxies; in, the heart