M45
M 45 · Pleiades — seven sisters in dust that is not theirs
No star cluster has kept humanity company longer: the Pleiades appear on the Nebra sky disk, they mark the sowing season in Hesiod's farming calendar, and in almost every culture they carry a name of their own — Seven Sisters, Subaru, Matariki. With the naked eye you count six to nine stars depending on the sky; in this image they become hundreds, spun into blue veils.
Physically the Pleiades are the textbook case of an [open star cluster](#/wissen/sternhaufen) in mid-life: around 100 million years old, long since parted from its birth gas, with well over a thousand members — dominated by a few dozen hot, blue-white B stars. In another 250 million years or so the tides of the Milky Way will have dissolved the cluster; we catch it at its best age.
The distance was a decades-long dispute. The astrometry satellite Hipparcos measured about 390 light-years in the 1990s, in open contradiction to every other method. Only radio interferometry and Gaia settled the matter: roughly 445 light-years — the classical methods were right and the satellite carried a systematic error. A healthy reminder that precision measurements need checking too.
The famous blue nebulosity does not belong to the cluster. A 100-million-year-old cluster lost its birth gas long ago — what glows here is a foreign dust cloud that the Pleiades happen to be passing through right now. The dust reflects the light of the B stars, and because blue is scattered most efficiently, the veils are that deep blue. The fine parallel strands — catalogued as striae — probably follow the magnetic field lines of the cloud: the starlight makes visible a structure that would otherwise stay hidden. This more deeply worked version shows how far the dust really reaches — right into the corners of the field.
The names tell of a family — and here it is complete. All seven sisters of the Greek legend stand in the field — Alcyone, Maia, Electra, Merope, Taygeta, Celaeno and the double pair Sterope — and since this version was extended eastward as a mosaic, so do the parents Atlas and Pleione once again. The overlay assigns the names to the stars. The "lost Pleiad" of the legends, incidentally, fits Pleione remarkably well: a variable Be star that really does change its brightness noticeably.
Where in the sky
The rectangle is this image's real field of view, with its measured rotation — not a symbol. Constellation figures and star positions come from SIMBAD.
Crops
Electra
Electra — a sister in the veil
13.5′ × 21.4′·03h 45m 19.48s +24° 05′ 33.1″
Electra, one of the bright sisters, with her own soft halo in the dust drifting past. Clearly visible: the halo is not a pure instrumental effect but genuine reflection — it is structured, slightly asymmetric, and follows the density distribution of the cloud rather than the optics.
The fine bright filaments running across the field are offshoots of the striae — the same magnetic-field strands that show their densest pattern at the Merope nebula.
Merope & nebula
Merope and NGC 1435 — the great veil
27.8′ × 31.2′·03h 46m 48.08s +23° 50′ 16.8″
The most extended nebula region of the image: the Merope nebula NGC 1435, a soft curtain spreading out from Merope across half a degree — with a hint of warmer tones where the dust grows denser and filters out the blue more strongly.
Surfaces exactly like these are the reason the Pleiades are photographically never finished: the veil runs on without a sharp boundary until first the exposure time and then the sky background swallow it.
Alcyone
Alcyone — the brightest at the center
19.8′ × 27.3′·03h 47m 30.28s +24° 06′ 09.9″
Alcyone is the brightest of the sisters: a hot B giant with the luminosity of well over a thousand suns, accompanied by a pretty little chain of stars right next to her. Her broad halo is partly optics — but partly genuine dust throwing her light back.
Like all the bright Pleiades she rotates extremely fast; such Be stars fling gas into a disk around their equator again and again. The quiet center of the cluster is physically anything but quiet.
Southern edge
The southern edge — cluster members against the Milky Way field
32.3′ × 19.4′·03h 47m 33.16s +23° 41′ 40.0″
At the southern edge of the field the last blue-white cluster members mingle with the Milky Way field: the cooler, yellow-orange stars behind them have nothing to do with the Pleiades — they merely happen to lie on the same line of sight, most of them far more distant.
At the top of the crop faint dust streaks still run through — the outermost reaches of the cloud, barely illuminated any more. The color contrast between cluster and background is an age map in a single image: in front the 100-million-year-young generation of B stars, behind it the old population of the Galaxy.
Maia & Asterope
Maia, her nebula and the double pair Sterope
24.6′ × 21.7′·03h 46m 10.82s +24° 24′ 33.3″
The star in the densest reflection cloud is Maia; her veil carries its own catalog number as NGC 1432 and glows like a lantern lit from within the nebula. The blue is physics, not processing: the dust grains scatter short wavelengths far more efficiently than long ones — the same mechanism that makes the daytime sky blue.
Beside her stands the close pair Sterope I and II (21 and 22 Tauri) — one sister in the legends, two stars in the sky sharing a single name.
Celaeno
Celaeno — the inconspicuous one among the sisters
11.1′ × 19.2′·03h 44m 46.61s +24° 17′ 53.3″
Celaeno is the faintest of the seven sisters — at magnitude 5.4 just barely visible to the naked eye, and a long-standing candidate for the “lost Pleiad” of the legends. Physically she is entirely the equal of the others: a hot, fast-rotating B star.
Her soft halo is reflection off the dust drifting past, which in this deep version fills the whole surroundings — even between the sisters there is no truly empty spot left.
Taygeta
Taygeta — at the edge of cloud and cluster
16.0′ × 19.7′·03h 45m 17.72s +24° 31′ 08.9″
Taygeta stands at the northwestern edge of the dense veil: her surroundings are noticeably darker than those of the sisters in the middle of the cloud, even if the deep mosaic version shows that the dust never quite stops even here.
Her conspicuous halo with the violet rim, on the other hand, is largely a gift of the optics: diffraction and scattering in the telescope. Telling genuine reflection from instrumental effect is one of the constant small exercises of astrophotography — the cloud is structured, the halo is round.
Northern edge
The northern edge — where the cluster thins out
24.4′ × 23.2′·03h 47m 40.05s +24° 30′ 02.3″
North of the bright sisters the cluster visibly thins out: a few brighter members, and between them increasingly the ordinary star field of the Milky Way — easy to tell from the blue-white cluster members by the warmer colors of the background stars.
The dark blue shred of dust in the field still belongs to the cloud drifting past: its extensions reach farther than the bright veil suggests — after all, only what lies close enough to a B star gets illuminated.
18 Tauri
18 Tauri — the cluster member at the northwestern edge
11.0′ × 19.2′·03h 45m 14.28s +24° 48′ 33.9″
18 Tauri belongs to the cluster but stands apart from the famous central quartet, at the northwestern edge — a hot B star of magnitude 5.6, wrapped in a delicate reflection glow of its own.
The crop shows that the Pleiades are more than their seven namesakes: the cluster counts well over a thousand members, and its bright B stars are spread across a field several full-moon diameters wide.
The heart of the cluster
The whole family — sisters, parents, veils and striae
0.80° × 1.20°·03h 47m 01.17s +24° 10′ 11.7″
The entire cluster in one field: all seven sisters from Alcyone to the Sterope pair, plus, at the lower edge, the parents Atlas and Pleione — every one of them with a halo of their own in the dust drifting past. Between them stretch the fine parallel striae — strands that probably follow the magnetic field lines of the cloud.
The color change of the dust is clearly visible too: radiant blue near the B stars, gray and tired in the gaps between. It is the same material everywhere — only the lighting differs.
Atlas & Pleione
Atlas and Pleione — the parents are back in the frame
46.3′ × 18.8′·03h 49m 12.59s +24° 03′ 36.0″
The bright pair for which this mosaic was extended: Atlas, the mythological father of the sisters, and close beside him the fainter Pleione. She is a fast-rotating Be star that sheds rings of gas in cycles of decades and visibly changes brightness in the process — the best physical candidate for the “lost Pleiad” that turns up in the legends of many cultures.
At the eastern edge of the cluster the drifting dust grows thin; only a breath of veil still lies over the field. Anyone counting the Pleiades with the naked eye usually counts as far as this pair.
Acquisition and processing
This image comes from the Newtonian era of this gallery, around 2016: a GSO 8″ f/4 Newtonian at 800 mm and an astro-modified Canon EOS 70D (documented in the file name as well). The original exposure sequences and logs have not been handed down; frame counts and total exposure are therefore not reconstructed.
What has survived is a 32-bit version reworked in 2026 — in this third elaboration extended eastward as a mosaic, so that Atlas and Pleione are back in the frame as well: 5,024 × 4,584 pixels at native resolution, stretched more deeply and with distinctly more dust detail right out to the edges. The blue reflection veils are broadband color information from the DSLR — for a reflection nebula, broadband is the physically correct route; narrowband filters would wipe it out.
The published file was solved astrometrically on its own: 659 Gaia reference stars, residual error 0.40″, scale 1.0472″/pixel, field 1.46 × 1.33°, image rotation -88° — north lies to the left, west at the top. Crop coordinates, size figures and all object markers are computed from this solution and not laid onto the preview by eye.