Fool me once, shame on you; fool me twice, shame on me; fool me three times … you must be an astronomer.
Gamma ray bursts are celebrities in the astronomy world for a number of reasons – they’re the brightest electromagnetic events known in the universe; many are so far away that they’re thought to be the afterglow of massive supernova blasts from just after the Big Bang. It’s the second reason that gets the most attention, which is why a recent burst from the galaxy farthest away from us gets a lot of attention – a flash from galaxy GN-z11 looks like it occurred 13.2 billion years ago, just 400 million years after the Big Bang. It’s also why it gets a lot of scrutiny, and two new studies suggest it’s not 13.2 billion light years from Earth … it may actually be so close we can almost touch it. Don’t astronomers know it’s Halloween season, not April Fools Day?
“This is a typical problem in astronomy – it's difficult to measure distances."
OK, that’s true for DIY carpenters … but we expect better from astronomers. Astronomer Michał Michałowski of the Adam Mickiewicz University in Poland led one study of the GN-z11-flash, published in Nature Astronomy. He commented in Science Alert on the assessment made in 2020 by Kavli Institute for Astronomy and Astrophysics and Peking University researcher Linhua Jiang and his team that the gamma-ray burst picked up by the MOSFIRE instrument on the Keck I telescope in Hawaii in 2017 appeared to have occurred 13.2 billion years ago. Another study, also published in Nature Astronomy and led by astrophysicist Charles Steinhardt of the University of Copenhagen's Niels Bohr Institute in Denmark, agreed with Michalowski – those measurements looked astronomically fishy – and not in a Pisces constellation way. They both agreed the Hubble picked up something with the brightness of a gamma ray burst but not from GN-z11.
"An object with a given recorded brightness may be a faint nearby object or a luminous distant object. In both cases they would appear equally bright for us. The object in question turned out to be a very nearby piece of space junk, but its brightness was equally compatible with a huge stellar explosion at the edge of the observable Universe."
Space junk! Specifically, a discarded Breeze-M upper stage of a Russian Proton rocket launched in 2015 that records confirmed was at a distance of 13,758 kilometers from Earth, and would have appeared in the MOSFIRE field of view during the time the flash was taking place. The ‘flash’ was actually a refection of the Sun off of the rocket. At the time of its discovery in 2017, Jiang and his team considered the space junk possibility but ruled it out. With the new information, did Jiang and his team admit they were wrong?
"We cannot completely rule out the possibility of unknown satellites (or debris). Despite this fact, our new calculations have suggested that our original conclusion remains valid."
Of course not! In their response in Nature Astronomy (the go-to place for astronomy spats), they defended their original assessment that the GN-z11-flash was a gamma ray burst from 13.2 billion years ago, but the seed of doubt has been planted in the astronomy community and they will need to build a stronger case.
To paraphrase the rule of thumb for carpenters into the astronomy world: “Measure twice, publish once.”