Another year is drawing to a close, and we’re looking back on all the discoveries that we’ve covered on AAS Nova this year. The top stories offer an astronomical smorgasbord and an in-depth look at some of the most recognizable objects in our galaxy. Without further ado, here are the top 10 most-read posts of 2024:
The first image of the Milky Way’s central supermassive black hole in polarized light. [EHT Collaboration; CC BY 4.0]
10. A New Way of Looking at the Milky Way’s Supermassive Black Hole
In 2022, the Event Horizon Telescope collaboration released the first image of the Milky Way’s supermassive black hole, Sagittarius A*. But the collaboration’s work didn’t stop there, and two years later they released an image of our hometown black hole in an entirely new light: polarized light, to be exact. The polarization of light — the orientation of the light waves as they travel through space — informs researchers as to the magnetic field conditions close to the black hole as well as in between the black hole and Earth. These results revealed a high degree of linear polarization as well as a lesser amount of circular polarization, suggesting a strong, orderly magnetic field.
An illustration of an exoplanet being engulfed by its home star. The planet 8 Ursae Minoris b has somehow escaped this fate. [International Gemini Observatory/NOIRLab/NSF/AURA/M. Garlick/M. Zamani; CC BY 4.0]
9. Astronomers Reopen the Mystery of a Planet That Shouldn’t Exist
Researchers thought they had solved the mystery of the exoplanet 8 Ursae Minoris b: unsure how the planet had survived its host star ballooning into a red giant, they proposed that the star had swallowed its one-time stellar companion, changing its evolution in a way that saved its planet from certain doom. But new data analyzed by Huiling Chen and collaborators upended this tale of a planet saved by a stellar merger: Ursae Minoris b is simply too young to have merged with a companion star. Luckily, the team’s research brought to light another possible resolution to the mystery.
The supernova SN 1994D illuminates the outskirts of its host galaxy, NGC 4526. [NASA, ESA, The Hubble Key Project Team, and The High-Z Supernova Search Team]
8. The Quest to Watch a Supernova in Real Time
The sooner researchers spot a supernova explosion, the more they can learn from it — but is there a way to know when a supernova is coming? The ejecta from a supernova explosion is so dense that light from the explosion is delayed on its way to our telescopes, but nearly massless particles called neutrinos can escape the blast and, in theory, announce the explosion before the light reaches us. Yuri Kashiwagi and collaborators examined how the upgraded Super-Kamiokande detector can be used to alert astronomers of an impending supernova, enhancing our ability to learn from these explosions.
7. How Common Are Solar Systems Like Our Own?
Illustration (orbits not to scale) of the planets in our solar system. [NASA/JPL]
An artist’s impression of light shining through the ocean of a “water world,” possibly like LHS 1140b. [NASA]
6. What Kind of World is LHS 1140b?
LHS 1140b is a bright, nearby star that is known to host two planets. The nature of the inner of the two planets, LHS 1140b, is unclear, despite the bevvy of telescopes that have observed this world. As Charles Cadieux and collaborators have shown, LHS 1140b might be the smallest known mini-Neptune exoplanet, or it might be a water world with a surface of ice and oceans.
Artist’s impression of the red supergiant star Betelgeuse. Though depicted solo, new research suggests that Betelgeuse might have a tiny companion. [Adapted from ESO/L. Calçada; CC BY 4.0]
5. Hiding in Plain Sight: Betelgeuse’s Binary Buddy
Betelgeuse is a highly recognizable red supergiant in the constellation Orion. Astrobites’s Alexandra Masegian reports on two AAS journal articles that independently arrived at the same conclusion: that Betelgeuse is not a single star, but rather a member of a binary system. While the two articles find slightly different masses and orbital separations for the proposed companion star, they both point to Betelgeuse’s long secondary pulsation period as evidence of the companion.
Cartoon showing a variety of exoplanet types. Figuring out whether a planet is rocky or gaseous can be a challenge, as is the case for K2-18b. [NASA/JPL-Caltech/Lizbeth B. De La Torre]
4. K2-18b May Not Be Habitable After All
The 8.6-Earth-mass exoplanet K2-18b made headlines when researchers reported that the planet might be a rocky world covered in oceans. Even more eyebrow raising was the potential detection of a faint signal from dimethyl sulfide, a compound that on Earth is only associated with the presence of life. Nicholas Wogan and coauthors used models to interpret JWST data of K2-18b, finding that the planet is instead most likely an uninhabitable gas-rich world — though they didn’t entirely rule out the inhabited ocean world scenario.
The Cassiopeia A supernova remnant as seen by JWST. [Rho et al. 2024]
3. Featured Image: A New Portrait of Cassiopeia A
The Cassiopeia A supernova remnant has sat for countless astronomical portraits, each of which reveals new details about this remnant of an exploded star. This portrait from JWST’s Mid-Infrared Instrument and Near-Infrared Camera highlighted electrons spiraling around magnetic field lines as well as light from argon and carbon monoxide, allowing a team led by Jeonghee Rho to study the connections between the formation of molecules like carbon monoxide and the creation of cosmic dust.
Red supergiant star Betelgeuse, pictured here in an infrared image from the Herschel Space Observatory, has ejected a considerable amount of material. [ESA/Herschel/PACS/L. Decin et al.]
2. Monthly Roundup: Betelgeuse, Betelgeuse, Betelgeuse
Everyone’s favorite red supergiant makes two appearances in this list! This article summoned three perspectives on Betelgeuse, which has made frequent news appearances over the past few years because of its pronounced, prolonged dimming episode in 2019–2021. Though the star has returned to its normal brightness, questions linger about the star’s future behavior and its uncertain past — including whether Betelgeuse is the product of a stellar merger.
1. The Odds of the Unthinkable
Radar images of the near-Earth object Apophis. [NASA/JPL-Caltech and NSF/AUI/GBO]
Thank you for joining us for another year of astronomy news — we hope to see you in 2025 for more discoveries. Happy New Year!