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Uncommon variable star 28 EP

HD 181998

RA 291.0069° · Dec -33.5423° · star

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Score breakdown

· 7 badges
28 pts · Uncommon
Uncommon 34 pts → Rare
  • Toward the galactic centre +8
  • Variable star +5
  • Gently variable +4
  • On the zodiac +3
  • Yellow-white F-type star +3
  • A named variable star +3
  • Main-sequence star +2
Total score 28

6 more points to reach Rare.

Badges

  • Variable star · +5
  • Toward the galactic centre · +8
  • On the zodiac · +3
  • Yellow-white F-type star · +3
  • Main-sequence star · +2
  • Gently variable · +4
  • A named variable star · +3

Trivia

What it actually is

  • Spectral class. Its spectrum reads F0V — an F-type star — a little hotter, whiter and shorter-lived than the Sun.
  • Where it is in life. It is on the main sequence, quietly fusing hydrogen in its core exactly as the Sun does.
  • It changes. This star does not hold still: its brightness rises and falls on a rhythm of hours, days or years, either pulsing in size or being eclipsed by a companion.

Sense of scale

  • In perspective. Far away by human standards, yet still a local address inside the Milky Way's spiral arms.

Find it in the sky

  • How to spot it. At magnitude 7.7 it is just past naked-eye reach — ordinary binoculars will pull it in, over in Sagittarius.
  • Southern sky. It rides the southern half of the sky — an easier target the further south you are.
  • Best time of year. It stands highest in the middle of the night around July — that's when to go looking.

Could we get there?

  • Verdict. Hopelessly far for any craft humanity can build today.

Properties

absmag
2.657
bv
0.328
constellation
Sgr
dist ly
328.1247
luminosity
7.537
mag
7.67
name
HD 181998
spect
F0V
var amplitude
0.1
var designation
V5546
var max
7.607
var min
7.707

About HD 181998

HD 181998 is an uncommon variable star. It lies about 328.1 light-years from Earth, sits in the constellation Sgr, shines at apparent magnitude 7.67 and has spectral type F0V.

Its spectrum reads F0V — an F-type star — a little hotter, whiter and shorter-lived than the Sun.

How to see it

Look for HD 181998 in the constellation Sgr. At apparent magnitude 7.67, it is an easy target for binoculars.

Like any astronomical target, HD 181998 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 HD 181998 is an uncommon variable star

HD 181998 scores 28 points on Spacedle's rarity scale, which places it in the uncommon tier. Another 6 points would lift it into a rarer tier.

That score comes from 7 science badges — Variable star, Toward the galactic centre, On the zodiac, Yellow-white F-type star, Main-sequence star, Gently variable and A named variable star — 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.