Twisted sisters
Two black holes collided while spinning in almost opposite directions. This suggests that they were both born in different locations and met later in life. James R. Riordon reported in “Discovered a new black hole merger type” (SN: 8/27/22, p. 13).
Reader Van SnyderI was curious if there is a reason why black holes spin in opposite directions. Perhaps a collision has flipped the parent star of one black hole.
It’s possible, though highly unlikely, that one of the black holes was flipped due to an earlier event, Riordon says. But even then, that event probably wouldn’t have been a collision.
The material it expels is what causes a dying star to explode in a supernova and form a black hole. The forces of those ejections could “kick” the dying star, causing it to tilt. Even if the star becomes a black hole, that tilt will remain. However, it is harder to kick the star that is larger. A star that is too big to be kicked. It is If you kicked enough to get a severe tilt, you probably would have been too far from your partner star to be able merge again as a dark hole. Riordon says.
Since the black holes in the study were spinning in such drastically different directions — one upside down relative to the other — it’s unlikely that the black holes began as a pair and were knocked out of sync by such a kick, Riordon says.
What’s more, the black holes are incredibly massive. “The lighter of the two was probably around three times the mass of the sun,” Riordon says. “Flipping it over wouldn’t be impossible, but it would be pretty tough to do while leaving the black holes close enough to merge when they did.”
Have an earful
Mammal ancestors experienced a rapid shrinkage in the inner ear canals around 233 million years back, which suggests that animals were warm-blooded at that time. This shift in the ear structure could have compensated for the thinner inner ear fluid that grew with rising body temperatures. Carolyn Gramling reported in “Triassic warm-bloodedness:” (SN: 8/27/22, p. 9).
Reader Van SnyderIt was a question about when warm-bloodedness or endothermy developed in theropods (the ancestors of modern birds). Could a look into birds’ ears also provide clues to that evolutionary timeline?
Researchers are still arguing about the date birds developed endothermy. Paleontologist says there is much to be said. Stephen BrusatteUniversity of Edinburgh
Some scientists argue that a fast metabolism, which is linked to warm-bloodedness, evolved early in birds’ history, Brusatte says. “Others argue that even many Mesozoic birds [from around 252 million to 66 million years ago] did not have modern avian-style metabolism,” he says, “and that full-on endothermy evolved late in bird history.”
Vertebrate paleontologist says that birds and their ancestors might have taken a different evolutionary path to develop small, tightly-curved inner ear canals. Ricardo AraújoThe University of Lisbon, Portugal.
Previous studies that looked at pigeons’ inner ear fluid, or endolymph, suggest that the endolymph of birds is a lot thicker than that of any other tetrapod, vertebrates that have four limbs or evolved from a four-limbed ancestor, Araújo says. “While maintaining a more or less primitive [inner ear] morphology, they changed the chemistry of the endolymph to compensate for the augmented body temperature,” he speculates.
