![](\"http:\/\/www.esa.int\/var\/esa\/storage\/images\/esa_multimedia\/images\/2014\/06\/herschel_s_population_of_trans-neptunian_objects\/14566827-1-eng-GB\/Herschel_s_population_of_trans-Neptunian_objects_small.jpg\"){kind=spacer}
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\nESA\u2019s Herschel space observatory has observed 132 of the known 1400 cold worlds that inhabit a region of the Solar System beyond the orbit of Neptune, some 4.5\u20137.5 billion km from the Sun.\n<\/p>\n
\nThese \u2018trans-Neptunian objects\u2019, or TNOs, include worlds such as Pluto, Eris, Haumea and Makemake, and make up a vast population of such objects thought to occupy these far-flung reaches of the Solar System.\n<\/p>\n
\nTNOs are particularly cold, at around \u2013230\u00baC, but these low temperatures lend themselves to observations by Herschel, which observes at far-infrared to sub-millimetre wavelengths. Indeed, the space observatory observed the thermal emission from 132 such objects during its nearly four-year lifetime.\n<\/p>\n
\nThese measurements provided their sizes and albedos (the fraction of visible light reflected from the surface), properties that are not otherwise easily accessible. The graphic presented here shows a sample of the population of TNOs observed with Herschel, arranged to showcase these properties.\n<\/p>\n
\nWhat is most striking is their diversity. They range from just below 50 km to almost 2400 km in diameter; Pluto and Eris are the largest. Two worlds have distinctly elongated shapes: Haumea (seen in white) and Varuna (brown). Some even host their own moons (not shown).\n<\/p>\n
\nThe albedo measurement implies a variety of surface compositions: low albedo (brown) is an indication of dark surface materials, such as organic material, while higher albedo (white) suggests pure ices.\n<\/p>\n
\nTNOs are thought to be some of the most primitive remnants of the planet-forming era. Thus the results of the Herschel \u201cTNOs are cool: A survey of the trans-Neptunian region\u201d open key time programme are being used to test different models of Solar System formation and evolution.<\/p>\n","protected":false},"excerpt":{"rendered":"
\t\t\t\t\t<\/p>\n
\nESA\u2019s Herschel space observatory has observed 132 of the known 1400 cold worlds that inhabit a region of the Solar System beyond the orbit of Neptune, some 4.5\u20137.5 billion km from the Sun.\n<\/p>\n
\nThese \u2018trans-Neptunian objects\u2019, or TNOs, include worlds such as Pluto, Eris, Haumea and Makemake, and make up a vast population of such objects thought to occupy these far-flung reaches of the Solar System.\n<\/p>\n
\nTNOs are particularly cold, at around \u2013230\u00baC, but these low temperatures lend themselves to observations by Herschel, which observes at far-infrared to sub-millimetre wavelengths. Indeed, the space observatory observed the thermal emission from 132 such objects during its nearly four-year lifetime.\n<\/p>\n
\nThese measurements provided their sizes and albedos (the fraction of visible light reflected from the surface), properties that are not otherwise easily accessible. The graphic presented here shows a sample of the population of TNOs observed with Herschel, arranged to showcase these properties.\n<\/p>\n
\nWhat is most striking is their diversity. They range from just below 50 km to almost 2400 km in diameter; Pluto and Eris are the largest. Two worlds have distinctly elongated shapes: Haumea (seen in white) and Varuna (brown). Some even host their own moons (not shown).\n<\/p>\n
\nThe albedo measurement implies a variety of surface compositions: low albedo (brown) is an indication of dark surface materials, such as organic material, while higher albedo (white) suggests pure ices.\n<\/p>\n
\nTNOs are thought to be some of the most primitive remnants of the planet-forming era. Thus the results of the Herschel \u201cTNOs are cool: A survey of the trans-Neptunian region\u201d open key time programme are being used to test different models of Solar System formation and evolution.<\/p>\n","protected":false},"author":5,"featured_media":615444,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[27],"tags":[],"class_list":["post-220255","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-multimedia"],"_links":{"self":[{"href":"https:\/\/spaceweekly.com\/index.php?rest_route=\/wp\/v2\/posts\/220255","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/spaceweekly.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/spaceweekly.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/spaceweekly.com\/index.php?rest_route=\/wp\/v2\/users\/5"}],"replies":[{"embeddable":true,"href":"https:\/\/spaceweekly.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=220255"}],"version-history":[{"count":0,"href":"https:\/\/spaceweekly.com\/index.php?rest_route=\/wp\/v2\/posts\/220255\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/spaceweekly.com\/index.php?rest_route=\/wp\/v2\/media\/615444"}],"wp:attachment":[{"href":"https:\/\/spaceweekly.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=220255"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/spaceweekly.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=220255"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/spaceweekly.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=220255"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}