About 7Rho Cas
7Rho Cas is a rare variable star. It sits in the constellation Cas, shines at apparent magnitude 4.51 and has spectral type F8Iavar.
Its spectrum reads F8Iavar — an F-type star — a little hotter, whiter and shorter-lived than the Sun.
Rare variable star 45 EP
7Rho Cas
RA 358.5960° · Dec 57.4994° · star
Score breakdown
· 7 badgesRare 50 pts → Epic
- Supergiant +18
- Naked-eye visible +8
- Variable star +5
- Never sets (northern circumpolar) +4
- Gently variable +4
- Yellow-white F-type star +3
- A named variable star +3
Total score 45
5 more points to reach Epic.
Badges
- Variable star · +5
- Naked-eye visible · +8
- Never sets (northern circumpolar) · +4
- Yellow-white F-type star · +3
- Supergiant · +18
- Gently variable · +4
- A named variable star · +3
Trivia
What it actually is
- Spectral class. Its spectrum reads F8Iavar — an F-type star — a little hotter, whiter and shorter-lived than the Sun.
- Where it is in life. It is a luminous supergiant — among the largest and rarest stars in the galaxy.
- 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 4.5 you can see it with your own eyes from a dark site, over in Cassiopeia.
- 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 September — that's when to go looking.
Its true colour
- Its true colour. Measured through blue and visual filters it comes out orange (B−V 1.2) — cooler than the Sun, and the kind of star that burns steadily for tens of billions of years.
By the numbers
- Surface temperature. Its colour puts the surface at roughly 4330 K, against the Sun's 5778 K.
Properties
- absmag
- -15.49
- bv
- 1.19
- constellation
- Cas
- luminosity
- 136772882.5596
- mag
- 4.51
- name
- 7Rho Cas
- spect
- F8Iavar
- var amplitude
- 0.18
- var designation
- Rho
- var max
- 4.412
- var min
- 4.592
How to see it
Look for 7Rho Cas in the constellation Cas. At apparent magnitude 4.51, it can be glimpsed with the unaided eye under dark skies.
Like any astronomical target, 7Rho Cas 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 7Rho Cas is a rare variable star
7Rho Cas scores 45 points on Spacedle's rarity scale, which places it in the rare tier. Another 5 points would lift it into a rarer tier.
That score comes from 7 science badges — Variable star, Naked-eye visible, Never sets (northern circumpolar), Yellow-white F-type star, Supergiant, 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.