As Luke Skywalker gazed longingly across the plains surrounding his aunt and uncle's desert dwelling as the binary stars of Tatoo set over the horizon, imagine how much better that classic "Star Wars" scene would have looked if there were three suns!
Whether or not a stellar addition would have impacted this iconic space opera scene is debatable, but astronomers have just announced the discovery of just that: an exoplanet in a stable orbit around a star that occupies a triple star system.
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But don't go having fantasies of standing on that planet's surface admiring some complex stellar dynamics at dusk, this particular world doesn't have a solid surface. And it would be a really bad place to hang out if you didn't want to be burned to a crisp.
Introducing KELT-4Ab: a gas giant world that orbits its parent star once every 3 days, but occupies a very rare multi-star system nearly 700 light-years from Earth.
The exoplanet was discovered by the wonderfully-named Kilodegree Extremely Little Telescope (KELT), a system of two small telescopes located in Arizona (KELT-North) and South Africa (KELT-South). Although the KELT-4 system has been known of for some time, it's only recently that their triple-star nature has been realized. The system consists of a main bright star called KELT-4A and a binary pair of stars - called KELT-4B and KELT-4C, collectively known as KELT-4BC. KELT 4BC orbit one another every 30 years at a distance of only 10 AU (the approximate distance Saturn orbits the sun).
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This binary pair then orbits KELT-4A once every 4,000 years or so at a distance of approximately 330 AU (over 8 times the distance Pluto orbits the sun). It is around KELT-4A that a transiting exoplanet, designated KELT-4Ab, a world around 50 percent bigger than Jupiter, has been discovered.
As if this triple star system wasn't bizarre enough, KELT-4Ab speeds around its host star in only 3 days, making this a "hot-Jupiter". Its close proximity to KELT-4A has caused the exoplanet's atmosphere to dramatically inflate. According to the planet's discoverers in a study published in The Astrophysical Journal, its host star is the brightest host of any inflated hot-Jupiter discovered to date, so it could prove to be an invaluable astronomical target for further studies into the nature of these extreme worlds.
KELT-4Ab is only the fourth such exoplanet to be found in a stable orbit within a multi-star system, so this will be a great scientific opportunity to understand how exoplanets can form in multiple star systems when logic suggests they shouldn't be gravitationally stable. But what would the sky of a planet in a 3-star system look like? Well, young Skywalker would be in for a shock.
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If you were able to float in the upper layers of KELT-4Ab's bloated atmosphere, you'd see the blindingly-bright main star, KELT-4A, take up a huge portion of the sky, 40 times wider than our sun appears to us on a clear day. The more distant KELT-4BC binary would appear much, much smaller as they are orbiting much further away, appearing no brighter than a full moon. They would, however, appear to be constantly hugging one another in their eternal orbital dance.
Source: The Astrophysical Journal via Physorg.com