Could vampires be explained by a blood disorder?
Porphyrias, a group of eight known blood disorders, affect the body's molecular machinery for making haem, which is a component of the oxygen-transporting protein, haemoglobin.
When haem binds with iron, it gives blood its hallmark red colour.
The different genetic variations that affect haem production give rise to different clinical presentations of porphyria - including one form that may be responsible for vampire folklore.
Erythropoietic protoporphyria (EPP), the most common kind of porphyria to occur in childhood, causes people's skin to become very sensitive to light.
Prolonged exposure to sunshine can cause painful, disfiguring blisters.
"People with EPP are chronically anaemic, which makes them feel very tired and look very pale with increased photosensitivity because they can't come out in the daylight," said Dr Barry Paw, a biologist at the Dana-Farber/Boston Children's Cancer and Blood Disorders Centre.
"Even on a cloudy day, there's enough ultraviolet light to cause blistering and disfigurement of the exposed body parts, ears and nose."
Staying indoors during the day and receiving blood transfusions containing sufficient haem levels can help alleviate some of the disorder's symptoms.
In ancient times, drinking animal blood and emerging only at night may have achieved a similar effect - adding further fuel to the legend of vampires.
In a new study, Paw and his team of international investigators report a newly discovered genetic mutation that triggers EPP.
Their discovery illuminates a novel biological mechanism potentially responsible for stories of vampires, and identifies a potential therapeutic target for treating EPP.
"Although vampires aren't real, there is a real need for innovative therapies to improve the lives of people with porphyrias."
What lit up our universe?
Soon after the Big Bang, the universe went completely dark.
The intense, seminal event that created the cosmos churned up so much hot, thick gas that light was completely trapped.
Much later - perhaps as many as one billion years after the Big Bang - the universe expanded, became more transparent, and eventually filled up with galaxies, planets, stars, and other objects that give off visible light.
That's the universe we know today.
But how it emerged from the cosmic dark ages to a clearer, light-filled state remains a mystery.
In a new study, researchers at the University of Iowa offer a theory of how that happened.
They think black holes that dwell in the centre of galaxies fling out matter so violently that the ejected material pierces its cloudy surroundings, allowing light to escape.
The researchers arrived at their theory after observing a nearby galaxy from which ultraviolet light is escaping.
"The observations show the presence of very bright x-ray sources that are likely accreting black holes," lead author Professor Philip Kaaret said.
"It's possible the black hole is creating winds that help the ionizing radiation from the stars escape.
"Thus, black holes may have helped make the universe transparent."
Kaaret and his team focused on a galaxy called Tol 1247-232, located some 600 million light years from Earth, one of only three nearby galaxies from which ultraviolet light has been found to escape.
Using an Earth-orbiting telescope called Chandra, the researchers saw a single x-ray source whose brightness waxed and waned and was located within a vigorous star-forming region of Tol 1247-232.
The team determined it was something other than a star.
"Stars don't have changes in brightness," Kaaret said.
"Our sun is a good example of that. To change in brightness, you have to be a small object, and that really narrows it down to a black hole."
But how would a black hole, whose intense gravitational pull sucks in everything around it, also eject matter?
The quick answer was no one knew for sure.
Black holes, after all, were hard to study, in part because their immense gravitational pull allowed no light to escape and because they were embedded deep within galaxies.
Recently, however, astronomers have offered an explanation: the jets of escaping matter were tapping into the accelerated rotational energy of the black hole itself.
Imagine a figure skater twirling with outstretched arms.
As the skater folds her arms closer to her body, she spins faster.
Black holes operated much the same way: as gravity pulls matter inward toward a black hole, the black hole likewise spins faster.
As the black hole's gravitational pull increases, the speed also creates energy.
"As matter falls into a black hole, it starts to spin and the rapid rotation pushes some fraction of the matter out," Kaaret said.
"They're producing these strong winds that could be opening an escape route for ultraviolet light.
"That could be what happened with the early galaxies."
Kaaret plans to study Tol 1247-232 more closely and find other nearby galaxies that are leaking ultraviolet light, which would help corroborate his theory.