"Here today, gone tomorrow."
It’s a common expression, one that dates back to John Calvin's 1549 “Life and Conversion of a Christian Man.” Unless you’re watching Star Trek or a Star Wars movie, it’s not something generally heard when discussing a planet … until now. Astronomers watching a Jupiter-sized exoplanet discovered in 2008 and tracked for years with the Hubble space telescope announced this week that it has disappeared. Did they look around for a Death Star?
“The NASA/ESA Hubble Space Telescope has taken the first visible light snapshot of a planet circling another star. Estimated to be no more than three times Jupiter's mass, the planet, called Fomalhaut b, orbits the bright southern star Fomalhaut, located 25 light-years away in the constellation Piscis Austrinus (the Southern Fish).”
In 2004, astronomers created the first-ever resolved visible light image of a large dust belt surrounding Fomalhaut. In 2005, Hubble astronomer Paul Kalas of the University of California, Berkeley proposed that the ring was being gravitationally modified by a planet lying between the star and the ring's inner edge, and in 2008 a point source of light was photographed which was named Fomalhaut b. Its unusual brightness suggested it either had a Saturn-like ring or multiple moons, and its orbit followed a strange, non-elliptical path. Still, astronomers were confident Fomalhaut b was a large exoplanet.
“To my surprise, it was not present on the latest images. So, I went through all the data and started to analyze it and noticed a pattern: it was fading.”
Astronomer András Gáspár of the University of Arizona told Vice.com that he was looking for something else when he noticed that Fomalhaut b had disappeared from Hubble images in 2014. Going back through older images, Gáspár also saw that the planet was visibly fading and its strange orbit was no longer an orbit but an “escape trajectory” sending whatever it was out of Fomalhaut’s star system. The new data was fed into models, which showed only one thing could have caused all of these anomalies to happen.
“We do have evidence of such collisions in other systems, but none of this magnitude has ever been observed. This is a blueprint for how planets destroy each other."
This was not a confrontation between a giant planet and a Death Star but a collision between two asteroid-sized bodies orbiting Fomalhaut – a collision that likely occurred just prior to the discovery of the dust cloud by Hubble astronomers in 2004. Neither of these space objects were planet-sized, but the resulting debris cloud was and it fooled them into thinking they had discovered exoplanet Fomalhaut b.
“Fool me once, shame on you; fool me twice, shame on me.”
That saying dates back to 1651 when it appeared in “The Court and Character of King James” by Anthony Weldon, and it applies to Fomalhaut b and its star. Fomalhaut can be described by yet another more recent adage: “Live fast, die young.” That one dates back to the 1947 book Knock on Any Door by Willard Motley (actually “Live fast, die young, and have a good-looking corpse"). Fomalhaut is a very hot star, which means it will have a short life in star terms. Its heat will keep its dust and debris ring agitated, so there could be more of these asteroid collisions, which means astronomers will be watching it carefully with the Hubble telescope and eventually the James Webb Space Telescope scheduled to launch in 2021.
Meanwhile, Fomalhaut b is fading fast into a massive cloud of dust, soon to be just a memory … and without a good-looking corpse. Perhaps Billy Joel wrote the best epitaph for this unusual space event.
“Only the good die young.”