{"id":33427,"date":"2025-08-22T06:00:13","date_gmt":"2025-08-22T10:00:13","guid":{"rendered":"https:\/\/www.monsffa.ca\/?p=33427"},"modified":"2025-08-21T08:50:16","modified_gmt":"2025-08-21T12:50:16","slug":"the-backward-tail-of-comet-3i-atlas","status":"publish","type":"post","link":"https:\/\/www.monsffa.ca\/?p=33427","title":{"rendered":"THE BACKWARD TAIL OF COMET 3I\/ATLAS:"},"content":{"rendered":"<p align=\"left\"><strong><span style=\"color: #ff0000;\">THE BACKWARD TAIL OF COMET 3I\/ATLAS: <\/span><\/strong>Last month, when astronomers used the Hubble Space Telescope to photograph 3I\/ATLAS, they had a &#8220;Eureka!&#8221; moment. The mysterious interstellar visitor had a fuzzy atmosphere and a growing tail. Clearly, it was a comet.<\/p>\n<p>However, something was not quite right. Take a look, and see if you can spot the problem:<\/p>\n<p align=\"center\"><a href=\"https:\/\/spaceweather.com\/images2025\/19aug25\/hubbleimage.webp\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/spaceweather.com\/images2025\/19aug25\/hubbleimage_strip.jpg\" alt=\"\" width=\"520\" height=\"386\" \/><\/a><\/p>\n<p>The tail of 3I\/ATLAS points <a href=\"https:\/\/spaceweather.com\/images2025\/19aug25\/hubbleimage_theproblem.jpg\">almost straight toward the sun<\/a>. Normally, comet dust tails are pushed away from the sun by radiation pressure. 3I\/ATLAS is doing the opposite\u2014it&#8217;s backwards.<\/p>\n<p>Why? Researchers led by David Jewitt of UCLA believe they have an explanation: &#8220;It is due to the preferential sublimation of ice on the hot day side of the nucleus and the near absence of sublimation on the night side,&#8221; they wrote in <a href=\"https:\/\/arxiv.org\/pdf\/2508.02934\">a paper<\/a> reporting the observations.<\/p>\n<p>In other words, 3I\/ATLAS *is* a comet, but only the sun-heated side is producing lots of dust. The emerging dust particles are too big for radiation pressure to bend them back into an ordinary tail.<\/p>\n<p><a href=\"https:\/\/spaceweather.com\/images2025\/20aug25\/comettails2.png\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/spaceweather.com\/images2025\/20aug25\/comettails2_med.png\" alt=\"\" width=\"270\" height=\"197\" align=\"right\" \/><\/a>This is unusual, but not unheard of. Solar system comets have been known to produce <span data-start=\"1297\" data-end=\"1321\">sunward fans or jets<\/span>, typically from localized &#8220;hot spots&#8221; on their rotating nuclei. What makes 3I\/ATLAS different is the dominance of its sunward plume, dwarfing a barely visible anti-solar tail behind it.<\/p>\n<p><a href=\"https:\/\/spaceweather.com\/\"><strong>READ MORE<\/strong><\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>THE BACKWARD TAIL OF COMET 3I\/ATLAS: Last month, when astronomers used the Hubble Space Telescope to photograph 3I\/ATLAS, they had a &#8220;Eureka!&#8221; moment. The mysterious interstellar visitor had a fuzzy atmosphere and a growing tail. Clearly, it was a comet. However, something was not quite right. Take a look, and see if you can spot &hellip; <a href=\"https:\/\/www.monsffa.ca\/?p=33427\" class=\"more-link\">Continue reading <span class=\"screen-reader-text\">THE BACKWARD TAIL OF COMET 3I\/ATLAS:<\/span> <span class=\"meta-nav\">&rarr;<\/span><\/a><\/p>\n","protected":false},"author":645,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[133],"tags":[136],"class_list":["post-33427","post","type-post","status-publish","format-standard","hentry","category-astronomy-news","tag-comet"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/www.monsffa.ca\/index.php?rest_route=\/wp\/v2\/posts\/33427","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.monsffa.ca\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.monsffa.ca\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.monsffa.ca\/index.php?rest_route=\/wp\/v2\/users\/645"}],"replies":[{"embeddable":true,"href":"https:\/\/www.monsffa.ca\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=33427"}],"version-history":[{"count":1,"href":"https:\/\/www.monsffa.ca\/index.php?rest_route=\/wp\/v2\/posts\/33427\/revisions"}],"predecessor-version":[{"id":33428,"href":"https:\/\/www.monsffa.ca\/index.php?rest_route=\/wp\/v2\/posts\/33427\/revisions\/33428"}],"wp:attachment":[{"href":"https:\/\/www.monsffa.ca\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=33427"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.monsffa.ca\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=33427"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.monsffa.ca\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=33427"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}