In 2004, scientists, using Hubble, discovered a mysterious planet. But later on, Hubble’s observations showed the planet had disappeared.
To date, more than 4,000 exoplanets have been discovered and scientists consider them “confirmed. However, there are thousands of other “candidate” exoplanet detections that require further observations to decide whether or they are real or not.
In 2004 Paul Kalas, an astronomer at the University of California made a surprising find.
Together with his colleagues, using Hubble data, they detected direct evidence of an exoplanet moving around the star Fomalhaut, only about 25 light-years away from us in the southern constellation Piscis Austrinus.
Scientists once considered Fomalhaut b to be one of the few planets around another star that a telescope had directly imaged.
As of April 2020, scientists had discovered only 50 exoplanets with direct imaging. They found most of them indirectly, as they passed in front of their stars. Scientists call this technique a transit method.
However, back to Fomalhaut b. When astronomers first spotted this exoplanet, it appeared to be a massive world, potentially as massive as three Jupiters, zipping along the inner edge of a giant ring of debris.
But, later images from 2014 showed that the exoplanet had virtually disappeared, as compared to how it appeared in the earlier images. NASA, ESA, and A. Gáspár and G. Rieke (University of Arizona)
And this is not a science fiction movie. It’s reality.
Unlike other directly imaged exoplanets, Fomalhaut b was really strange since the beginning. The object was unusually bright in visible light but did not have any detectable infrared heat signature when NASA’s Spitzer Space Telescope observed it.
Scientists thought that the brightness came from a huge ring of dust surrounding the planet that may have been collision-related. The exoplanet’s orbit also appeared unusual, possibly very eccentric.
But new Hubble observations suggest that perhaps, Fomalhaut b disappeared before Hubble’s eyes because Fomalhaut b was never a planet in the first place. One interpretation is that the exoplanet was actually a colossal and expanding dust cloud that formed after two large icy bodies collided. In the ensuing decade, the debris drifted apart.
Fomalhaut b seems to be slowly expanding from the smashup that blasted a dissipating dust cloud into space. Those ever-drifting pieces of leftover ice and dust must each measure smaller than the width of a human hair, far below Hubble’s detection threshold.
The suggested collision, which possibly took place in an icy ring of debris similar to our solar system’s Kuiper Belt, must have occurred very shortly before the Hubble first caught sight of the alleged exoplanet when the expanding cloud of post-collision dust particles was still densely concentrated and apparent in visible light.
Scientists estimate the dust cloud has expanded by now to a size larger than the orbit of Earth around our Sun. The distance from Earth to the Sun — called an astronomical unit— is 92,955,807 miles (149,597,870 kilometers).
The discovery, however, is not to be disappointed. Astronomer András Gáspár of the University of Arizona and lead author of the study said these collisions are exceedingly rare. And so this is a big deal that we actually get to see one. He believes they were at the right place at the right time to have witnessed such an unlikely event with NASA’s Hubble telescope.
Since the exoplanet is so far away from us, it still looks like just a bright dot in the images. But Hubble’s additional analysis, not previously possible, revealed Fomalhaut b for what it really is.
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For the new study, the team of scientists reviewed nearly two decades of archival Hubble observations. These analyses revealed Fomalhaut b slowly growing dimmer and dimmer before completely vanishing in 2014.
Using computer models, the researchers calculated that a collision between two icy bodies roughly 125 miles (200 kilometers) in diameter could have created a dust cloud that matched the Hubble observations.
The host star, Fomalhaut, is only twice the size of the Sun but 16 times brighter. That made Fomalhaut b, a billion times fainter than its star, remarkably difficult to spot. This may be one of the most difficult detections in the history of exoplanet science.
While the discovery still needs confirmation, is there still hope for the planet hypothesis?
And that’s because unlike science-fiction, planets in real life don’t just vanish. And scientists doubt we will ever see this object again now that it has disappeared.
Our understanding of the universe is constantly evolving. Discoveries are scrutinized and, with new evidence, hypotheses change.
However, future observations from Hubble and the long-delayed James Webb Space Telescope will confirm the new finding.
We are all impatiently waiting for the Webb telescope to go out there and start bringing data back home.
NASA and Northrop Grumman confirmed the Hubble’s successor remains on track for launch on 31 October 2021 atop an Ariane 5 rocket from Kourou, French Guiana.
Scientists published their study back on April 20, 2020, in the journal Proceedings of the National Academy of Sciences (PNAS).