Cool, flimsy, and tiny, red dwarfs have more than any other stars in the universe, yet they aren’t accessible to the naked eye, and not even the star closest to the Sun proxima red dwarf Centauri. “They’re secret stealth stars,” claims Todd Henry of Georgia State University in Atlanta. “They account for three out of every four stars.”

The observed luminosity gap has revealed the secrets of red dwarf star interiors, where stars make their energy and then transport it to their surface. The artist’s rendition depicts the view from a spacecraft that orbits around a red dwarf known as TRAPPIST-1. It’s only 40 light-years away from Earth. Image Credit: European Southern Observatory.

OPEN IN VIEWER Despite their number; they’re not huge “common folk” Stars that have been easy to overlook since they do not have much to offer apart from emitting flares. They do not explode or transform into black holes. The red dwarfs consume their fuel so slowly and consistently that some last for more than a trillion years. That’s more than the entire duration of our universe. Five years ago, however, these dull stars produced a shock by revealing a difference in their luminosity distribution — a chart of the numbers of stars against the amount of light they release into space–marked the long-anticipated change between two kinds of red dwarfs. “It’s the first concrete evidence that this transition does in fact occur,” claims Gregory Feiden at the University of North Georgia in Dahlonega.

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MANAGE ALERTS Although, at first, it’s a bit confusing. The observed luminosity gap is uncovering the secrets of what’s happening in the dark interiors of stars, where they create their energy before transferring it to their surface. This provides insights into the precise nuclear reactions these populous stars employ to generate power for their own. Additionally, some astronomers believe that red dwarfs are among the most likely to be the stars with life-sustaining planets. In theory, the gap observed refines models of leads that may play an essential role in life in the universe.

Find the Gap

On the evening of the 27th of April, 2018 Wei-Chun Jao, an astronomer at Georgia State University who, as a graduate student collaborated with Henry He was studying research results that other researchers had published two days prior. “There’s something weird there!” Jao recalls thinking. The latest data comes from the Gaia spacecraft that measures precise distances and levels of brightness for a myriad of stars to discover their properties and determine their locations within the galaxy. He found that red dwarfs emitting around 0.3 percent as much bright visible light asas the Sun are rarer than stars slightly brighter or smaller ( 1).

“This is an absolutely amazing step towards advancing our knowledge and understanding of .”–Pavel Kroupa

It was the first time anyone had noticed this gap in the red dwarf population before this, Jao says because it’s so tiny. The hole was discovered by analyzing thousands of red dwarfs and precise luminosities. The gap’s origin: “I had no clue,” the scientist admits. However, his team noticed that the hole appeared in an unorthodox location. Red dwarfs are about 8 percent to 60% larger thanthan the Sun,, and the hole was observed in stars with around a third of the Sun’s mass. Since the late 1950s, scientists have believed that stars higher and lower this mass would have distinct inner structure ( 2, 3 ). The distinction is in how the Sun’s energy is transported from its center of hotness to its cooler outer. The Sun’s central area is scorching, and its gas is almost charged. In the absence of atoms, electrons tend to be less able to absorb or scatter light and, consequently, permit them to move through relatively quickly. This means that the energy transfer process is carried out through radiation. The Sun’s outer envelope,, however, is more excellent; more atoms have electrons that absorb or scatter passing photons. Thus, the Sun appears like a hot pot of water: The hot gas rises, releases its heat, then sinks back down,, a process referred to as convection. Like the Sun, the red dwarf larger than a third of the solar mass must have a radiative center and an envelope of convective. Contrarily, a smaller red dwarf has a temperature so high it is expected to be fully convective from its center to its surface. That means newly formed elements produced through nuclear reactions within the stellar core are blown across the entire star instead of accumulating in the center.

The Generation Gap

In 2012, six years before the Jao discovery, an unrepeated scientific paper predicted that red dwarfs close to the line between full and partial convection would slowly begin to pulsate ( 4). Two nuclei of helium-3 collide to form helium-4. There are two neutrons and two protons. There are also two protons in free form. It requires temperatures that exceed 8 million Kelvin. The Sun’s core is double that temperature, and red dwarfs greater than 35 percent of the Sun’s are also hot enough. However, in smaller stars below about 35% solar mass, the helium-3-destroying reaction runs so slow that nuclei of helium-3 continue to accumulate and create a selective set of red dwarfs that could be a candidate for an unexpected nuclear event.