A distant star has been acting like a porch light, dimming in bursts and then fading again. In new research, astronomers say the young F-type star, hotter than the Sun, may be getting eclipsed by dust from a smashup between planetesimals, the building blocks of planets.<\/p>\n\n\n\n
The object is called Gaia20ehk, also known as Gaia-GIC-1, about 11,000 light-years away. In a University of Washington news release<\/a>, Anastasios (Andy) Tzanidakis said the star\u2019s behavior \u201cwent completely bonkers,\u201d and senior author James R. A. Davenport added, \u201cHow rare is the event that created the Earth and moon? That question is fundamental to astrobiology.\u201d <\/p>\n\n\n\n The open-access study is available through IOPscience.<\/p>\n\n\n\n Gaia20ehk looked ordinary for years, with a light curve that was almost flat. Then, starting in 2016, it showed three dips, each lasting about seven months and cutting the star\u2019s visible light by about a third.<\/p>\n\n\n\n Astronomers call this kind of pattern a \u201cdipper,\u201d meaning something passes in front of the star and blocks part of its light. A \u201clight curve\u201d is simply a graph of brightness over time, and this one looked more like a storm system than a steady lamp.<\/p>\n\n\n\n The European Space Agency<\/a>\u2019s Gaia mission flagged the object through its alert system, and the public record shows how the dimming grew more dramatic over time. You can see that long track of measurements in the official Gaia Alerts listing for Gaia20ehk<\/a>.<\/p>\n\n\n\n Visible light tells you what the star is doing at the surface, but infrared light can reveal heat from surrounding material. Think of infrared like a heat camera.<\/p>\n\n\n\n The team compared Gaia\u2019s visible-light dimming with infrared measurements from NASA missions, including the sky-mapping telescope WISE<\/a>. As the star\u2019s visible brightness fell, the system got brighter in infrared, a common sign that dust is soaking up starlight and re-radiating it as heat.<\/p>\n\n\n\n That dust appears to be hot, around 900 kelvins, which is about 1,160 degrees Fahrenheit. The infrared level has stayed high for more than four years, and the mission SPHEREx<\/a> has confirmed the system is still glowing strongly at those wavelengths.<\/p>\n\n\n\n Before the infrared brightening took over, Gaia\u2019s data showed a repeating rhythm of about 381 days. That is just longer than an Earth year.<\/p>\n\n\n\n Using that period, the researchers inferred that a major dust clump was orbiting about 1.1 astronomical units from its star, or about 102 million miles. The infrared heat, though, matches dust much closer in, around 0.2 astronomical units, roughly 19 million miles.<\/p>\n\n\n\n By looking at how fast the starlight dropped, the team estimated the dust edge was moving across our line of sight at least about 6,700 miles per hour. That is slower than a clean circular orbit would suggest, which hints the debris might be stretched out or following a more oval path.<\/p>\n\n\n\n The study estimated a minimum blocking area for the dust cloud of 0.13 square astronomical units. If you imagine that area as a circle, it would work out to a disk roughly 38 million miles across, though the real shape could be longer and lopsided.<\/p>\n\n\n\n The mass in the warm dust that shows up in the infrared was estimated at at least 400 quintillion kilograms, which is about 880 quintillion pounds. The key word is \u201cdust,\u201d since infrared measurements are most sensitive to fine grains, not the boulder-size fragments that might be hiding in the same debris field.<\/p>\n\n\n\n That\u2019s why the team treats the mass as a floor, not a final tally. If only a fraction of the original bodies was ground down into infrared-bright powder, the colliding objects themselves could have been far larger than the dust alone suggests.<\/p>\n\n\n\n Whenever a star dims, astronomers have to ask a basic question first. Is the star changing, or is something in front of it doing the blocking?<\/p>\n\n\n\n The researchers examined other explanations, including the breakup of \u201cexocomets,\u201d meaning comets in another solar system, and more typical young-star variability driven by gas and accretion. Their follow-up spectra did not show the strong emission features many very young, actively feeding stars display, which makes a standard baby-star explanation less convincing.<\/p>\n\n\n\n They also point to other unusual systems that seem to show impact-generated dust clouds, including ASASSN-21qj and a \u201cstar-sized\u201d dust clump reported in the young system HD 166191. In those cases, as in Gaia20ehk, the story looks less like a calm disk of leftovers and more like ongoing wreckage.<\/p>\n\n\n\n Giant impacts are not just dramatic, they are a predicted stage of making rocky planets. A 2016 review in Space Science Reviews explains how debris disks, meaning rings of dust and rock around stars, can act like signposts for these collisions, letting astronomers study planet formation through the dust it produces in real time. <\/p>\n\n\n\n That overview is available as \u201cInsights into Planet Formation from Debris Disks\u201d on SpringerLink.<\/p>\n\n\n\n There is also a familiar echo here at home, since many scientists think the Moon formed after a massive impact early in Earth\u2019s history. A primer on Moon formation explains why that idea remains the leading framework, and Gaia20ehk\u2019s dust appears to be orbiting in a broadly similar star-planet zone.<\/p>\n\n\n\n Looking ahead, wide-field surveys should make these \u201ccaught in the act\u201d events less rare. The Vera C. Rubin Observatory\u2019s decade-long Legacy Survey of Space and Time<\/a> is built to spot changes across the sky night after night, and the Webb Space Telescope could track this debris as it cools using the Mid-Infrared Instrument.\u00a0<\/p>\n\n\n\n The main study has been published in The Astrophysical Journal Letters<\/a>.<\/em><\/p>\n","protected":false},"excerpt":{"rendered":" A distant star has been acting like a porch light, dimming in bursts and then fading again. In new research, … <\/p>\nA star that should not blink like that<\/h2>\n\n\n\n
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Heat in the infrared, shadows in visible light<\/h2>\n\n\n\n
A 381-day rhythm hints at where the debris orbits<\/h2>\n\n\n\n
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How much material was involved<\/h2>\n\n\n\n
Could it be something else<\/h2>\n\n\n\n
Why this matters and what comes next<\/h2>\n\n\n\n
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