Unexplainable – “Mysterious objects near the beginning of time”

Podcast: Unexplainable (Vox)
Date: February 4, 2026
Host: Sally Helm
Guest: Dr. Caitlin Casey, Astrophysicist

Episode Overview

This episode delves into astronomical discoveries made possible by the James Webb Space Telescope (JWST), focusing on bizarre and mysterious “little red dots” found in the earliest images of the universe. These objects, seen shortly after the Big Bang, could revolutionize our understanding of supermassive black holes, galaxy formation, and the fundamental structure of the cosmos. Host Sally Helm and returning guest Caitlin Casey discuss the evolving theories, puzzling data, and the thrill of chasing the unknown at the edge of cosmic history.

Key Discussion Points and Insights

1. The JWST and Its Cosmic “Time Machine” Power

• JWST Launch: Launched Christmas Day 2021, JWST allows astronomers to "peer back in time" and see further than ever before.
• Ongoing Impact: "It's given us so much of a new picture, new lens on how the universe came to be. I just can't get enough of it." — Caitlin Casey [02:30]

2. From “Weird Red Smudges” to “Little Red Dots”

• Initial Mystery: Early JWST images revealed strange, red objects—far bigger or stranger than expected. Theories included:
  • Overly massive early galaxies (challenging the cosmological model)
  • Supermassive black holes forming extremely early [03:19–03:40]
• Quote from 2022: “Some folks want to throw out our cosmological model completely. And… that would change everything…” — Caitlin Casey [03:19]

3. Update on the Mystery: Supermassive Black Holes—Without Galaxies?

• New Data: Now termed “little red dots,” these remain leading topics in scientific conferences.
• Consensus Shift: The preponderance of little red dots points more to the supermassive black hole theory, though not all mysteries are solved.
  • "There are just oodles and oodles of black holes in the early universe, and we don't know what to do with them." — Caitlin Casey [05:03]

4. The “Missing Galaxy” Problem

• Normal Model: Every galaxy is expected to have a supermassive black hole at its center (~1/1000th of total mass).
  • Milky Way analogy: “If the Milky Way disk is about the size of the continental United States, the supermassive black hole… would be about the tip of a pencil.” — Caitlin Casey [08:16]
• What’s Weird?: These little red dots seem to be massive black holes without any obvious surrounding galaxy.
  • “Little red dots are so puzzling because they seem to be isolated black holes. We don’t know why the galaxy… seems to be missing.” — Caitlin Casey [09:11]

5. Is the Black Hole Forming First?

• Possible Scenarios:
  • The galaxy is there but too faint or primitive to detect
  • Galaxies form after the black hole—like a heart developing before the rest of the body
• Galactic Evolution Analogy:
  • “It would be like… only the heart grows first, and then the heart is born alone, and then the rest of the human grows around the heart.” — Caitlin Casey [10:56]

6. The Origins and Growth Limits of Black Holes

• Stellar-Mass vs. Supermassive:
  • “Stellar mass black holes” come from dead, massive stars—a different regime than the million-solar-mass supermassive black holes seen in JWST data. [15:28–15:54]
• The Eddington Limit:
  • There’s a theoretical “speed limit” to how fast black holes can grow (Eddington-limited accretion).
    • “The more [a black hole] gobbles up, that’s called accretion… if you crank up the speed… it’s going to shine too brightly that it’ll actually cause the disk to effectively blow up.” — Caitlin Casey [16:57–17:28]
• Theories for Growth Beyond the Limit:
  • Super-Eddington accretion is plausible but unobserved
  • Or maybe these black holes didn’t start from stars, but from collapsing gas clouds (“direct collapse black holes”)
    • “Some theories suggest that you can instantly collapse [a gas cloud] into something much more massive than any star...” — Caitlin Casey [18:17]

7. Why Are They Red? (And Why Is That Weird?)

• Redness Explained:
  • Many faraway objects look red due to distance (“redshift”), but little red dots are intrinsically red.
  • Dust is the usual explanation for space objects looking red, but teams aren’t finding dust here.
    • “So little red dots don’t seem to be red because of dust… [they're] fundamentally different black holes…” — Caitlin Casey [20:14]
• A New Cosmic Object? "Black Hole Stars":
  • Hypothesis: these are black holes wrapped in the primordial atmosphere of a star—a combination never observed before.
    • “This combination, a supermassive black hole wrapped in the atmosphere of a star. We have never seen this before.” — Sally Helm [21:07]

8. The Cutting Edge—and How Much Remains Mysterious

• JWST Is Just Getting Started:
  • Future JWST studies aim to find even earlier little red dots, possibly unlocking the story of all supermassive black holes.
• Limits of Knowledge:
  • Assumptions about black hole masses are based on data from the nearby universe, which may not apply to the early universe:
    • “…fundamental relations that we take for granted…just don’t hold… so we actually might not know the masses as well as we think...” — Caitlin Casey [22:30]
• On Astronomy’s Surprises:
  • “We turned on JWST… and it felt like we went from a black and white world to a colored world.” — Caitlin Casey [23:17]
  • “I don’t have answers today for you… maybe, maybe in another two years we’ll have answers.” — Caitlin Casey [24:07]

9. Looking Ahead

• Sally’s Closing Question: “If you do come back on Unexplainable for appearance number 015 in 10 years… what would you hope to be able to tell me?” [24:20]
• Caitlin’s Reply: “The most exciting thing are the things that I can’t even imagine.” [24:29]

Notable Quotes & Memorable Moments

• On Ongoing Wonder:
  “The novelty is there every single day. I’m still just as excited to look at JWST data as I was in July of 2022…” — Caitlin Casey [02:25]

• On the Puzzling Little Red Dots:
  “There are just oodles and oodles of black holes in the early universe, and we don’t know what to do with them.” — Caitlin Casey [05:03]

• On the Missing Galaxies:
  “Little red dots are so puzzling because they seem to be isolated black holes. We don’t know why the galaxy that should be surrounding them seems to be missing.” — Caitlin Casey [09:11]

• On Scientific Surprises:
  “You know what I love about this field is it always has a surprise for you.” — Caitlin Casey [23:13]

Important Timestamps

• [02:25] – Dr. Casey’s ongoing excitement over JWST discoveries
• [03:19–03:40] – Early debate: massive galaxies vs. black holes as the explanation for the red smudges
• [05:03] – Shift toward the supermassive black hole hypothesis
• [08:16] – Milky Way/black hole size analogy
• [09:11] – The missing galaxies puzzle
• [10:56] – Black hole before galaxy analogy (the ‘heart before body’)
• [16:57–17:28] – Eddington Limit and why black holes can’t just eat endlessly
• [18:17] – Explanation of “direct collapse” black hole theory
• [20:14] – Why the little red dots' redness is mysterious
• [23:13–24:07] – Astronomy as a field of constant surprises and unresolved mysteries
• [24:29] – “The most exciting thing are the things that I can’t even imagine.”

Summary Takeaway

Thanks to JWST, astronomers are wrestling with totally unexpected cosmic phenomena—dozens or hundreds of “little red dots,” likely supermassive black holes, possibly predating the galaxies we expect to surround them. Their unique redness, lack of dust, and absence of visible galaxies challenge all previous models, hint at new classes of cosmic objects, and push our understanding of the early universe to the brink. As Dr. Casey puts it, the big answers may still be beyond our reach, but the most thrilling surprises in astronomy are yet to come.