The team used Hubble's Wide Field Camera 3 to look at the planets' spectral fingerprints, which measure chemical composition. "The effect that clouds have on the spectral signature of water allows us to measure the amount of clouds in the atmosphere," Bruno said. "More clouds mean that the water feature is reduced." The teams found that for WASP-67 b there are more clouds at the altitudes probed by these measurements.

"This tells us that there had to be something in their past that is changing the way these planets look," said Bruno.

Perhaps one planet formed differently than the other, under a different set of circumstances. "You can say it's nature versus nurture," explains co-investigator Kevin Stevenson. "Right now, they appear to have the same physical properties. So, if their measured composition is defined by their current state, then it should be the same for both planets. But that's not the case. Instead, it looks like their formation histories could be playing an important role."

Then, the team used Hubble data to see if the sources revealed two peaks near their center in the optical image. “These two peaks might show that a pair of supermassive black holes is present or that a recoiling black hole has moved away from the cluster of stars in the center of the galaxy.”

Following up with SDSS, further light spectra data shows telltale signatures of the supermassive black hole presence. “The latter source shows the properties of a growing supermassive black hole and its position matches that of a bright X-ray source detected with Chandra (right image in inset). Using data from the SDSS and the Keck telescope in Hawaii, the team determined that the growing black hole located near, but visibly offset from, the center of the galaxy has a velocity that is different from the galaxy. These properties suggest that this source may be a recoiling supermassive black hole.”

Gabriel Brammer of the Space Telescope Science Institute and second author of the study, explains “Our spectroscopic observations reveal the galaxy to be even further away than we had originally thought, right at the distance limit of what Hubble can observe.”

"They were actually looking at another exploding star and one happened to go right off in the exact patch of sky in the exact moment they were looking at it. It was the definition of luck. It's that singular moment when we can see the periodic table happening, when we can see the process of creating these new elements, and also see a switch from fission to fusion all at the same time because of this residual shockwave going through this star."

Mr Williams added: We didn’t know what was there, and that was the whole purpose of the observation, basically — to get a core sample of the universe.

You do the same thing if you're trying to understand the geology of the Earth: Pick some typical spot to drill down to try to understand exactly what the various layers of the Earth are and what they mean in terms of its geologic history.