When you wish upon a star
Makes no difference who you are
Anything your heart desires
Will come to you
("When You Wish Upon a Star" by Leigh Harline and Ned Washington for the movie "Pinocchio")
Well, just make sure what you’re wishing upon is really a star. That’s the warning from a new study published in The Astrophysical Journal Letters which details the discovery of a binary pair of space objects that don’t fit the usual definition of stars (which, it turns out, isn’t so usual) nor planets. These wanderers don’t seem to be happy either – they’ve taken social distancing to a new level by traveling together while staying around 19 billion miles apart – five times the distance between Pluto and the Sun.
“We are really witnessing an incredibly rare output of stellar formation processes.”
Clémence Fontanive from the Center for Space and Habitability (CSH) at the University of Bern, Switzerland, and the National Centre of Competence in Research (NCCR) PlanetS discovered Oph 98 A and Oph 98 B in the constellation Ophiuchus 450 light years away. Initially named binary system CFHTWIR-Oph 98, Fontanive soon found that they were an unusually large distance apart for brown dwarf stars … if that’s really what they are.
The more they were analyzed, the more it appeared that Oph 98 A has a mass only 15 times that of Jupiter, which, according to the press release, is almost exactly on the boundary separating brown dwarfs from planets. Oph 98 B is only 8 times heavier than Jupiter, putting in firmly in the planetary category, but not one orbiting Oph 98 A. If they are planets, they have no star and In fact, if it instead is the smallest brown dwarf ever, that would make Oph 98 a binary system with the weakest binding energy of any known to date. Upon analyzing more data taken over time, Fontanive confirmed the latter.
"We observed the system again this summer from another Hawaiian observatory, the United Kingdom Infra-Red Telescope. Using these data, we were able to confirm that Oph 98 A and B are moving together across the sky over time, relative to other stars located behind them, which is evidence that they are bound to each other in a binary pair."
While the binary-or-not question is settled, what they are is not. Oph 98 A and Oph 98 B are lower in mass than brown dwarfs, warmer than planets, colder than brown dwarfs, and only about 3 million years old – far too young to be fading old stars. Will Best, an astronomer at the University of Texas at Austin who studies brown dwarfs and reviewed the report for Inside Science, thinks they may be something else.
“We have a sun and we have planets, and nothing in between, but the universe makes everything in between. Maybe we should find some other way to define planets -- by how they form, or whether they orbit a star.”
In other words, more research is needed. In the meantime, here’s a new song for when you happen to spot Oph 98 A and Oph 98 B together in the sky.
When you wish upon a binary
Be aware results may vary
Stick with something more ordinary
Like a fortune cookie