The star V1298 Tau is only 20 million years old, a baby in cosmic terms. Orbiting it are four giant planets, each ranging from the size of Neptune to Jupiter. What\u2019s unique is not their size, but their puffiness. Despite their large radii, they are surprisingly light. \u201cWhat\u2019s so exciting is that we\u2019re seeing a preview of what will become a very normal planetary system,\u201d says John Livingston, the study\u2019s lead author from the Astrobiology Center in Tokyo, Japan. <\/p>\n \u201cThe four planets we studied will likely contract into \u2018super-Earths\u2019 and \u2018sub-Neptunes\u2019\u2014the most common types of planets in our galaxy, but we\u2019ve never had such a clear picture of them in their formative years.\u201d<\/p>\n This finding, published in Nature <\/a>on January 7, 2026, shifts our understanding of how planetary systems form. The V1298 Tau system shows that the compact exoplanets dominating our galaxy may begin their lives as oversized, low-density worlds before shrinking over billions of years.<\/p>\n Weighing Worlds With Gravity, Not Light<\/p>\n Traditional methods of determining a planet\u2019s mass often rely on the Doppler technique, which observes the subtle wobble of a star as its planets tug on it. But that method struggles when stars are very young and active, just like V1298 Tau. Its surface is chaotic, filled with sunspots and magnetic activity, making precise measurements nearly impossible.<\/p>\n This challenge led scientists to use a different tool: Transit Timing Variations (TTVs). This method tracks the minute delays in a planet\u2019s transit across the face of its star, caused by the gravitational pull of neighboring planets. Over ten years, researchers monitored the four planets\u2019 movements with ground- and space-based telescopes.<\/p>\n \u201cFor astronomers, our go-to \u2018Doppler\u2019 method for weighing planets involves making careful measurements of the star\u2019s velocity as it\u2019s tugged by its retinue of planets,\u201d said Erik Petigura, a co-author from UCLA. \u201cBut young stars are so extremely spotty, active, and temperamental, that the Doppler method is a non-starter.\u201d He adds, \u201cBy using TTVs, we essentially used the planets\u2019 own gravity against each other. Precisely timing how they tug on their neighbors allowed us to calculate their masses, and sidestep the issues with this young star.\u201d<\/p>\n This approach confirmed what researchers had suspected but never confirmed: these young planets are inflated giants with extremely low density, so light and fluffy that they resemble cosmic marshmallows.<\/p>\n Proof That Puffy Planets Exist<\/p>\n The physical properties of these planets make them unlike anything found in our solar system. Their radii are 5 to 10 times that of Earth, yet their masses are only 5 to 15 times Earth\u2019s mass. That mismatch suggests they are composed mostly of gas with very little core, giving them a cotton candy-like structure.<\/p>\n \u201cThe unusually large radii of young planets led to the hypothesis that they have very low densities, but this had never been measured,\u201d said Trevor David, a co-author from the Flatiron Institute who led the system\u2019s original discovery in 2019. \u201cBy weighing these planets for the first time, we have provided the first observational proof. They are indeed exceptionally \u2018puffy,\u2019 which gives us a crucial, long-awaited benchmark for theories of planet evolution.\u201d<\/p>\n This measurement is more than a scientific curiosity. It gives planetary scientists the first hard data on what happens to planets in the early stages of their development, supporting the idea that atmospheric loss plays a major role in shaping planetary systems.<\/p>\n The Fast Evolution Of Cosmic Giants<\/p>\n The study also provides evidence that these planets are already evolving. Their original gas-rich atmospheres are likely evaporating due to intense radiation from their young star. As this gas escapes, the planets cool and contract. This rapid transformation challenges long-standing models of planet formation, which assumed a slower, more gradual evolution.<\/p>\n \u201cThese planets have already undergone a dramatic transformation, rapidly losing much of their original atmospheres and cooling faster than what we\u2019d expect from standard models,\u201d explains James Owen, a co-author from Imperial College London. \u201cBut they\u2019re still evolving. Over the next few billion years, they will continue to lose their atmosphere and shrink significantly, transforming into the compact worlds we see throughout the galaxy.\u201d<\/p>\n This dynamic evolution is a major clue in solving the mystery of how the galaxy ended up with so many super-Earths and sub-Neptunes. It also helps explain why our own solar system lacks such planets, they may have formed differently, or lost their atmospheres in other ways.<\/p>\n","protected":false},"excerpt":{"rendered":"A new study published in Nature has revealed a rare glimpse into the early life of four young…\n","protected":false},"author":2,"featured_media":234217,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[23],"tags":[111,139,69,147,392],"class_list":["post-234216","post","type-post","status-publish","format-standard","has-post-thumbnail","category-space","tag-new-zealand","tag-newzealand","tag-nz","tag-science","tag-space"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts\/234216","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/comments?post=234216"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts\/234216\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/media\/234217"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/media?parent=234216"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/categories?post=234216"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/tags?post=234216"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}![\"41586](\"https:\/\/www.newsbeep.com\/nz\/wp-content\/uploads\/2026\/01\/41586_2025_9840_Fig1_HTML.webp.webp\")
Top left, points show the transit times of planet c measured against a reference linear ephemeris;\u00a0error bars represent 1\u03c3\u00a0uncertainties. Grey curves show credible transit times drawn from the\u00a0N-body models described in the text. Bottom left, same as above but for planet d. The interactions between c and d are nearly sinusoidal and anticorrelated. Top and bottom right, the same but for planets b and e. The TTVs of b and e are also sinusoidal and anticorrelated. (Nature)
<\/p>\n![\"41586](\"https:\/\/www.newsbeep.com\/nz\/wp-content\/uploads\/2026\/01\/41586_2025_9840_Fig2_HTML.webp.webp\")
a,b, Planetary radius versus orbital period (a) and planetary radius versus planetary mass (b) for the V1298 Tau system (red filled circles); error bars represent 1\u03c3\u00a0uncertainties. The low-density planets of the Kepler-51 system are shown for comparison (purple squares), along with kernel density estimates of the distributions of well-characterized exoplanets (shaded contours), drawn from the NASA Exoplanet Archive (n\u2009=\u2009624 planets with mass and radius uncertainties less than 20%,\u00a0P\u2009<\u2009150\u2009days and host\u00a0Teff\u2009=\u20094,500\u20136,500\u2009K to exclude M dwarfs). (Nature)
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