GoKawiilMany astronomers concluded that big black holes dotted the universe, washing out the light of the stars in their host galaxies. As black holes, the little red dots would appear red because dust — grainy stuff much more complicated than gas — was blocking their blue light.
Yet they still seemed weird. Most supermassive black holes flicker as they gulp down chunky streams of gas around them. They also beam powerful X-rays across the universe. Most little red dots seemed to be doing neither of these things.
But that didn’t trouble astronomers much; they expected to see some strangeness during the pandemonium of the early universe. And at least the black holes weren’t breaking any cosmological theories.
Then, in the spring of 2025, de Graaff and Naidu’s teams unveiled the two strangest dots yet.
A New Interpretation
What made these two little red dots exceptional was how red they were. Webb picked up almost no light in the bluer hues of their spectra. And at a particular shade of red, the colors abruptly got much, much brighter. This feature, known as a Balmer break, is something you see when looking at a hot ball of hydrogen gas — typically, certain types of stars or galaxies (which are made of many stars). Deep in a star’s core, nuclear fusion pumps out heat and light, which slowly filters up to the star’s surface. There, hydrogen atoms can become energized in a way that blocks bluer light and lets through only redder light. These red colors have a hump-shaped spectrum that reveals the overall temperature of the star’s surface.
But the new little red dots couldn’t literally be stars — they were way too bright. And they didn’t look much like black holes either. Black holes have an assortment of ringlike structures of different temperatures. They don’t typically produce a Balmer break, or the red, hump-shaped curve indicative of a stellar surface burning at a uniform 5,000 or so degrees Kelvin.
Rohan Naidu, an astronomer at the University of Hawai‘i, co-led a survey team that discovered the reddest little red dot yet. He suggests it’s a member of a whole new class of astrophysical object. Dr. Michelle Peters
Naidu and de Graaff concluded that they were looking at the first examples of something combining the vigor of a black hole with the outward appearance of a star: a black hole star.
From the outside, a black hole star would appear as a huge agglomeration of hydrogen gas. If our sun were replaced with a black hole star, it would extend a dozen times farther than the orbit of Pluto. Out toward the edge, the star would boil unstably, sloughing off outer layers and explosively ejecting mass. “It’s going to be a very messy system where stuff is being blown out and falling back in,” de Graaff said. “I wouldn’t want to come too close.”
... continue reading