![HR 8799 d: Photographed, Not Inferred](https://cdn.slatesource.com/f/8/8/f88aa9e1-ca34-4e8a-a795-fbb75309cbb7.webp) # HR 8799 d: Photographed, Not Inferred - [Made in Slatesource](https://slatesource.com/@steph/hr-8799-d-photographed-not-inferred) - By [Steph](https://slatesource.com/@steph) - Created on Sep 19, 2026 ## Gas giant around HR 8799 It is 1.16 times Jupiter's radius, closest in size to Jupiter, and 3000.0 times Earth's mass. A year there lasts 101.3 years, on an orbit 62.0 times Mercury's distance from the Sun. journey·4 Planets # HR 8799 from the inside out Orbit / Planet "gas giant, 1150 K. "gas giant, temperature unknown. "gas giant, temperature unknown. "gas giant, temperature unknown. Radius 13.00 Earth radii Mass 3000.0 Earth masses One year 101.3 years Orbit radius 24.0000 AU Distance 135 light-years 🔭🪐📅01.01.2008 – 01.01.2010 01.01.2008HR 8799 b, HR 8799 c, HR 8799 d 01.01.2008 01.01.2010HR 8799 e 01.01.2010 What the archive holds on this planet 0% A size. Yes. A weight, not just a width. Yes. A density, the one clue to composition. No. How far out it orbits. Yes. A temperature someone observed rather than calculated. No. An eccentricity, so the orbit shape is known. No. What a direct image buys you Where it is, how bright it is, and a spectrum taken from the planet directly. HR 8799 has 4 known planets. A crowded system is worth more than the sum of its planets: the timing of each transit constrains the others. This is one of the rare planets that has actually been photographed. Fewer than a hundred of the thousands known were found this way, and they are mostly young giants far from their stars. Found by W. M. Keck Observatory in 2008. # Fewer than a hundred planets have been photographed rather than inferred. Does \\ seeing one directly change how real it feels to you? No comments yet. Be the first. Log in to comment [NASA Exoplanet Archive: source data, including the values not used here](https://exoplanetarchive.ipac.caltech.edu/overview/HR%208799%20d?utm_source=slatesource)