Exoplanet Guide

Scienceline’s Guide to the Exoplanets: The Flamewind Temple

HD 80606 b: Quite the 'eccentric' planet

March 16, 2020
A fake planet with "Scienceline's Guide to Exoplanets" labeled across its equator. Other planets zoom past behind it.
Your favorite planets, and you didn't even know they existed. [Credit: Curtis Segarra | CC BY-NC-ND 2.0]

HD 80606 b: The Flamewind Temple
Discovered by: Geneva Extrasolar Planet Survey
Discovered: 2001
Distance from Earth: ~217 light years
Size: ~1.0 Jupiter radii (~11.2 Earth radii)
Mass: ~4.1 Jupiter masses (~1300 Earth masses)
Surface climate: Balmy, with occasional hot spells and hypersonic gusts
Habitability for humans: No.

We’ll get to the exoplanet in a moment. For now, let’s talk about comets.

It’s hard to think of a comet more famous than Halley’s Comet. For most of its existence, this ball of dirt and ice wanders round the cold outskirts of the solar system. But, every 76 years or so, Halley plunges deep, close to the Sun, its ice boiling away into water vapor and — since objects orbit faster when they’re closer to the Sun — very fleetingly lighting up Earth’s sky. Halley’s last put in an appearance in the mid-1980s, and it will return to our sight again in the early 2060s.

If you look at Halley’s orbit from above, you’ll understand why Halley’s does this. Its orbit is very elongated, reaching out to a slow drift by Neptune’s orbit, then dropping and steadily accelerating back into the inner solar system and snapping round the Sun, before slowing back to a cold crawl.

Orbits like Halley’s have a very high eccentricity. In other words, they are stretched and elliptical — unlike, for instance, the planets of the solar system, whose orbits are very close to perfect circles, and therefore have low eccentricity.

Now, picture a Jupiter-sized world with an orbit as eccentric as Halley’s. That’s HD 80606 b, a planet orbiting one of a binary pair of Sun-like stars.

When it was first discovered, HD 80606 b had the most eccentric orbit of any exoplanet then known. It doesn’t quite go as far out as Halley’s — at its furthest, it only goes out to around 0.80 AU, four-fifths the distance from the Sun to the Earth. But it gets close to its star, very, very close: only 0.03 AU, less than a tenth of the distance from the Sun to Mercury.

So imagine if, in our solar system, Jupiter had a twin. Imagine if this twin started close to Earth, then slowly dropped further inwards and building speed. Imagine that Jupiter-duplicate then flashing past the Sun, baking in overwhelming heat and light, before swinging back round, slowing down and cooling as it slid back out to Earth’s environs.

Now imagine that this Jupiter-duplicate repeated this cycle, in an unending, tortuous clockwork, every 111 days.

And when HD 80606 b is at closest approach to its star, it heats up very, very quickly. Observations have suggested that the planet that’s already the temperature of Venus warms another 700 degrees Celsius or 1260 degrees Fahrenheit — in just eight hours. The results of air heating that fast are dramatic: winds rushing at as much as 15 times the speed of sound.

Sounds like a nice tropical breeze, doesn’t it?


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