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Uncommon galaxy 22 EP

IC 4557

RA 233.6539° · Dec 39.7289° · openngc

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Score breakdown

· 3 badges
22 pts · Uncommon
Uncommon 34 pts → Rare
  • Galaxy +14
  • Spiral galaxy +5
  • Faint fuzzy (mag > 13) +3
Total score 22

12 more points to reach Rare.

Badges

  • Galaxy · +14
  • Spiral galaxy · +5
  • Faint fuzzy (mag > 13) · +3

Trivia

What it actually is

  • What it actually is. A galaxy: a gravitationally bound city of stars, gas and dark matter, turning so slowly that a single rotation takes hundreds of millions of years.
  • Spiral. A spiral galaxy. Those arms are not solid structures but traffic jams — density waves that stars drift into and out of as they orbit.

Sense of scale

  • Scale. Home to hundreds of billions of stars — a universe unto itself, and every one of those points of light could have planets.

Find it in the sky

  • How to spot it. At magnitude 15.7 it is far too faint for the eye: this one belongs to cameras and long exposures, over in Boötes.
  • Northern sky. It rides the northern half of the sky — an easier target the further north you are.
  • Best time of year. It stands highest in the middle of the night around May — that's when to go looking.

Its true colour

  • Its true colour. Its colour is a census: blue where gas is still collapsing into hot young stars, yellow-red in the old, settled core.

How we came to know it

  • The Index Catalogue. The IC was the 1895 and 1908 supplement to the NGC — the first catalogue in history to be filled largely with objects found on photographic plates rather than by eye.

Properties

constellation
Boo
dso type
G
hubble
Sbc
mag
15.71
name
IC 4557
size arcmin
0.52
surface brightness
22.82

Nearby objects

About IC 4557

IC 4557 is an uncommon galaxy. It sits in the constellation Boo and shines at apparent magnitude 15.71.

A galaxy: a gravitationally bound city of stars, gas and dark matter, turning so slowly that a single rotation takes hundreds of millions of years.

How to see it

Look for IC 4557 in the constellation Boo. At apparent magnitude 15.71, it takes a larger telescope or a long-exposure image to capture.

Like any astronomical target, IC 4557 is best seen from a dark site away from city lights, and when it is above the horizon depends on your latitude and the time of year. The visibility panel above works out tonight's viewing window for your saved location.

Why IC 4557 is an uncommon galaxy

IC 4557 scores 22 points on Spacedle's rarity scale, which places it in the uncommon tier. Another 12 points would lift it into a rarer tier.

That score comes from 3 science badges — Galaxy, Spiral galaxy and Faint fuzzy (mag > 13) — each earned for a real, measurable property of the object. Rarity on Spacedle is never random: the more remarkable an object's astrophysics, the more badges it collects, the higher it scores, and the rarer it ranks.