About HD 179821
HD 179821 is an uncommon variable star. It sits in the constellation Aql, shines at apparent magnitude 7.9 and has spectral type G5.
Its spectrum reads G5 — a G-type star: the very same spectral class as our own Sun.
Uncommon variable star 28 EP
HD 179821
RA 288.4942° · Dec 0.1255° · star
Score breakdown
· 5 badgesUncommon 34 pts → Rare
- Sun-like G-type star +8
- Deep red star +8
- Variable star +5
- Gently variable +4
- A named variable star +3
Total score 28
6 more points to reach Rare.
Badges
- Variable star · +5
- Sun-like G-type star · +8
- Deep red star · +8
- Gently variable · +4
- A named variable star · +3
Trivia
What it actually is
- Spectral class. Its spectrum reads G5 — a G-type star: the very same spectral class as our own Sun.
- 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.
Find it in the sky
- How to spot it. At magnitude 7.9 it is just past naked-eye reach — ordinary binoculars will pull it in, over in Aquila.
- Seen from everywhere. It sits almost on the celestial equator, so it can be seen from essentially anywhere on Earth.
- Best time of year. It stands highest in the middle of the night around July — that's when to go looking.
Its true colour
- Its true colour. Measured through blue and visual filters it comes out deep orange-red (B−V 1.5) — one of the coolest surfaces a star can have while still fusing.
By the numbers
- Surface temperature. Its colour puts the surface at roughly 3840 K, against the Sun's 5778 K.
What's in a name
- Its catalogue. The HD number is from the Henry Draper Catalogue, in which Annie Jump Cannon personally classified the spectra of nearly 400,000 stars — still the largest such feat by one person.
Properties
- absmag
- -12.1
- bv
- 1.472
- constellation
- Aql
- luminosity
- 6025595.8607
- mag
- 7.9
- name
- HD 179821
- spect
- G5
- var amplitude
- 0.12
- var designation
- V1427
- var max
- 7.849
- var min
- 7.969
How to see it
Look for HD 179821 in the constellation Aql. At apparent magnitude 7.9, it is an easy target for binoculars.
Like any astronomical target, HD 179821 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 179821 is an uncommon variable star
HD 179821 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 5 science badges — Variable star, Sun-like G-type star, Deep red 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.