{"id":2320,"date":"2026-09-27T01:14:00","date_gmt":"2026-09-26T16:14:00","guid":{"rendered":"https:\/\/onepress.co.kr\/index.php\/briefing\/2026-09-27-gj3090b-retrograde-en\/"},"modified":"2026-09-27T01:14:00","modified_gmt":"2026-09-26T16:14:00","slug":"2026-09-27-gj3090b-retrograde-en","status":"publish","type":"briefing","link":"https:\/\/onepress.co.kr\/index.php\/briefing\/2026-09-27-gj3090b-retrograde-en\/","title":{"rendered":"A small Neptune-like planet was confirmed orbiting red dwarf GJ 3090 backwards"},"content":{"rendered":"

2026-09-27 01:14 KST<\/strong><\/p>\n

The planet is about 2.2 Earth radii and 4.5 Earth masses and circles every 2.85 days. NIRPS transit spectroscopy and stellar rotation information yielded the three-dimensional angle.<\/p>\n

Stars and planets normally inherit a shared disk direction. An angle beyond 90\u00b0 places the planet\u2019s orbital angular momentum in the opposite hemisphere from the stellar spin.<\/p>\n

The expected perturber is missing<\/h2>\n

Extreme tilts often involve a massive outer planet or companion star. Imaging and velocity data found none capable of easily producing this configuration within current detection limits.<\/p>\n

Formation remains a hypothesis<\/h2>\n

The star may have acquired a second, misaligned gas disk in youth. The present orbit and absent massive companion are observations; the second disk is an unobserved historical explanation.<\/p>\n

\"A
This AI-generated image explains the topic; it is not a photograph of an actual event, observation or field site.<\/figcaption><\/figure>\n

What \u201csmallest\u201d means<\/h2>\n

The planet is a low-density sub-Neptune, not an Earth-like rocky world. It is the smallest M-dwarf planet with a measured 3D obliquity, not necessarily the smallest retrograde planet of every kind.<\/p>\n

Why more data matter<\/h2>\n

Longer velocity monitoring can reveal distant companions or tighten limits. Spin-orbit measurements in other red-dwarf systems can separate rare scattering from formation-environment pathways.<\/p>\n

Primary source and independent checks<\/h2>\n

Primary source: Astronomy & Astrophysics paper<\/a><\/p>\n

Institutional explanation: University of Geneva explanation<\/a><\/p>\n

Independent check: Queen Mary University independent check<\/a><\/p>\n

Read in other languages<\/h2>\n

\ud55c\uad6d\uc5b4<\/a> \u00b7 English<\/a> \u00b7 Espa\u00f1ol<\/a> \u00b7 \u65e5\u672c\u8a9e<\/a> \u00b7 Ti\u1ebfng Vi\u1ec7t<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

GJ 3090 b, about 22 parsecs away, has an orbital axis tilted roughly 136\u00b0 from its star\u2019s spin and is therefore retrograde. It is not the first retrograde exoplanet, but the first confirmed around an M-dwarf.<\/p>\n","protected":false},"featured_media":0,"template":"","meta":[],"class_list":["post-2320","briefing","type-briefing","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/onepress.co.kr\/index.php\/wp-json\/wp\/v2\/briefing\/2320","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/onepress.co.kr\/index.php\/wp-json\/wp\/v2\/briefing"}],"about":[{"href":"https:\/\/onepress.co.kr\/index.php\/wp-json\/wp\/v2\/types\/briefing"}],"wp:attachment":[{"href":"https:\/\/onepress.co.kr\/index.php\/wp-json\/wp\/v2\/media?parent=2320"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}