{"id":28018,"date":"2022-01-20T00:00:00","date_gmt":"2022-01-20T00:00:00","guid":{"rendered":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/?post_type=purple_issue&p=28018"},"modified":"2022-02-14T08:52:35","modified_gmt":"2022-02-14T08:52:35","slug":"exoplanets-30-years-of-discovery","status":"publish","type":"post","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/2022\/01\/20\/exoplanets-30-years-of-discovery\/","title":{"rendered":"Exoplanets \u2013 30 years of discovery"},"content":{"rendered":"\n

The fundamentals of astronomy for beginners<\/p>\n\n

EXPLAINER<\/span><\/h2>\n\n
\n\n

Exoplanets \u2013 30 years of discovery <\/h4>\n\n

Penny Wozniakiewicz looks at advances in the field since the first worlds were announced<\/p>\n\n

\"\"
As our observing technology advances, so does the potential for finding Earth\u2019s twin among the huge variety of exoplanets<\/figcaption><\/figure><\/div>\n\n

On 9 January 1992, astronomers Aleksander Wolszczan and Dale Frail introduced the world to the first two planets to be found outside the Solar System, alien worlds observed orbiting the pulsar PSR B1257+12, around 2,300 lightyears away. The hunt for \u2018exoplanets\u2019 \u2013 as they are also known \u2013 was then, as now, heavily driven by our quest to find out just how unique (or not) our Solar System is, and whether there is life beyond it.<\/p>\n\n

Given the latter aim, finding exoplanets orbiting a pulsar \u2013 effectively a dead (no longer burning) star \u2013 is far from ideal. Rather fittingly, a competition run by the International Astronomical Union (IAU) resulted in the pulsar and its planets being named after various macabre characters from mythology and popular culture: Lich for the star, and Draugr, Poltergeist and Phobetor for its worlds (the third was discovered two years later). Nevertheless, the discovery spurred interest in strange alien worlds among the public and the scientific community, and now, after three decades of searching, some 4,500 confirmed exoplanets have been identified.<\/p>\n\n

So many planets to choose from<\/strong><\/h5>\n\n

And strange worlds they are indeed \u2013 the sheer variety observed among these exoplanets is vast. To date, they range from rocky terrestrial planets similar in size to Earth, to gas giants much larger than Jupiter; from extremely hot to exceedingly cold, with orbits taking them insanely close or excessively far from their stars. They have also been found around all sorts of stars \u2013 small, large, young, old and dead.<\/p>\n\n

\"\"
Making history: in 2004 the exoplanet 2M1207b (in red)
became the first to be directly imaged near its host star,
the brown dwarf 2M1207 (centre)<\/figcaption><\/figure><\/div>\n\n

Some even orbit multiple star systems, while so-called \u2018rogue planets\u2019 do not even orbit a star.<\/p>\n\n

Both ground and space-based telescopes have been instrumental in exoplanet discoveries, perhaps most notably the Kepler Space Telescope, which is credited with more than 2,600 confirmed finds. Although it is possible to directly image some exoplanets (particularly those that are bright, massive and orbit at large distances from their star), the vast majority of exoplanets have been identified through indirect methods \u2013 the planets are found by <\/span>studying the effect they have on their stars.<\/p>\n\n

For example, the \u2018radial velocity\u2019 and \u2018astrometric methods\u2019 both search for evidence of wobbles in the motions of stars caused by orbiting planets, while the \u2018transit method\u2019 studies the dip in the brightness of stars caused as planets <\/span>pass in front of them.<\/p>\n\n

Combined, these studies allow us to work out details of each planet\u2019s orbit and size, and then determine whether it is a rocky terrestrial planet or a gas or ice giant, and whether it orbits within the star\u2019s habitable zone. This is the region around a star where temperatures may permit the existence of liquid water on a planet\u2019s surface \u2013 and from what we know about life, liquid water is an essential ingredient.<\/span><\/p>\n\n

But finding a planet like Earth in the habitable zone of its star does not mean liquid water is present or that it will be habitable \u2013 key to the ability to host liquid water is the presence of an atmosphere to maintain sufficient surface pressure. Atmospheres also provide a means to explore the conditions present on these planets, as their compositions may reveal details of surface processes and even potentially the presence of life.<\/p>\n\n

\"\"
A common way to detect exoplanets is by using the \u2018transit method\u2019; where a dip in the brightness of a star can indicate a passing planet<\/figcaption><\/figure>\n\n
\"\"
As it unravels the mysteries of early planetary systems, the James Webb Space Telescope (JWST) will be on the look out for new worlds<\/figcaption><\/figure>\n\n
On the trail of exoplanets<\/strong><\/h5>\n\n

Studies of exoplanet atmospheres are performed using spectroscopy. For a transiting exoplanet this involves measuring the intensity of the star\u2019s light at different wavelengths as the planet passes in front. Gaps in the spectrum result from absorption by elements or molecules present in its atmosphere.<\/p>\n\n

Several different atmospheric constituents have been identified in exoplanet atmospheres, including water vapour, carbon dioxide and methane, and scientists have even interpreted details such as the presence of clouds, rain and extremely high-speed winds on some.<\/p>\n\n

Current studies estimate that trillions of planets could exist in our Galaxy, so it\u2019s safe to say that we have barely touched the surface when it comes to finding and learning about exoplanets. As new telescopes come online from now and in forthcoming years, such as the long-awaited James Webb Space Telescope (JWST), the Nancy Grace Roman Space Telescope (2027) and the Atmospheric Remotesensing Infrared Exoplanet Large-survey (2028), they will surely identify more exoplanets and investigate their atmospheres \u2013 perhaps one day finding that exoplanet which is truly similar to Earth.<\/p>\n\n

<\/div>
\n

Exoplanets, great and small<\/h4>\n\n\n\n

The search for exoplanets has revealed a previously unimaginable variety. We reveal some notable examples:<\/strong><\/p>\n\n\n\n

\"This
WASP-12b, a jet black planet being pulled apart by its host star, absorbs 94 per cent of the light on its surface<\/figcaption><\/figure>\n\n\n\n

WASP-12b <\/strong><\/em>is one of the largest gas giants observed, twice Jupiter\u2019s size. Discovered in 2008, it orbits so close to its star that it\u2019s being torn apart!<\/p>\n\n\n\n

Mysterium Cosmographicum TOI-849b <\/strong><\/em>is an extremely dense rocky planet lacking atmosphere, which was discovered in 2015. It is thought to be the core of a gas giant.<\/p>\n\n\n\n

Proxima Centauri b <\/strong><\/em>is our nearest neighbour at 4.22 lightyears away. Spotted in 2016, it\u2019s a bit bigger than Earth and orbits a small dwarf star.<\/p>\n\n\n\n

Kepler 452b <\/strong><\/em>is a contender for the title of \u2018most Earth-like planet\u2019, Kepler 452b (discovered in 2015) orbits a similar star to our Sun at approximately the same distance in about the same amount of time.<\/p>\n\n\n\n

The Kepler-90 system <\/strong><\/em>is the largest system of planets outside our own Solar System, thanks to the discovery of an eighth planet around this star in 2017.<\/p>\n<\/div><\/section>\n\n

\n
\n
\"\"<\/figure>\n<\/div>\n\n\n\n
\n

Dr Penny Wozniakiewicz <\/strong>is a planetary scientist and space dust expert based at the University of Kent<\/p>\n<\/div>\n<\/div>\n\n

Photos: OORKA\/ISTOCK\/GETTY IMAGES, ESO, NASA\/GSFC\/CIL\/ADRIANA MANRIQUE GUTIERREZ, DZIKA_MROWKA\/ISTOCK\/GETTY IMAGES, NASA\/ESA AND G. BACON (STSCI)<\/p>\n","protected":false},"excerpt":{"rendered":"

Penny Wozniakiewicz looks at advances in the field since the first worlds were announced<\/p>\n","protected":false},"author":24,"featured_media":28013,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"ub_ctt_via":"","purple_page_number":"72","purple_custom_meta_purple_page_number":"72","purple_seq_number":"1","purple_custom_meta_purple_seq_number":"1","purple_source_article":"article_72-1.xml","purple_custom_meta_purple_source_article":"article_72-1.xml","purple_source_issue":"February-2022","purple_custom_meta_purple_source_issue":"February-2022","purple_external_id":"February-2022-72-1","purple_custom_meta_purple_external_id":"February-2022-72-1","purple_issue_code":"|0000086549||","purple_custom_meta_purple_issue_code":"|0000086549||","purple_android_product":"com.im.skyatnight.201","purple_custom_meta_purple_android_product":"com.im.skyatnight.201","purple_ios_product":"com.im.skyatnight.201","purple_custom_meta_purple_ios_product":"com.im.skyatnight.201","purple_web_product":"","purple_custom_meta_purple_web_product":"","purple_publication_id":"075fab74-0a21-4201-866a-899d6c41c40c","purple_migrated":"","kt_blocks_editor_width":""},"categories":[21],"tags":[88,14],"featured_image_src":"https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/01\/83dd4f6b-64ae-4321-9487-e4bc95dbbd64.jpg","author_info":{"display_name":"importmanagerhub@sprylab.com","author_link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/author\/importmanagerhubsprylab-com\/"},"acf":{"readingTimeMinutes":"6","apple_news_title":""},"uagb_featured_image_src":{"full":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/01\/83dd4f6b-64ae-4321-9487-e4bc95dbbd64.jpg",1176,1176,false],"thumbnail":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/01\/83dd4f6b-64ae-4321-9487-e4bc95dbbd64-150x150.jpg",150,150,true],"medium":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/01\/83dd4f6b-64ae-4321-9487-e4bc95dbbd64-300x300.jpg",300,300,true],"medium_large":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/01\/83dd4f6b-64ae-4321-9487-e4bc95dbbd64-768x768.jpg",768,768,true],"large":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/01\/83dd4f6b-64ae-4321-9487-e4bc95dbbd64-1024x1024.jpg",800,800,true],"1536x1536":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/01\/83dd4f6b-64ae-4321-9487-e4bc95dbbd64.jpg",1176,1176,false],"2048x2048":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/01\/83dd4f6b-64ae-4321-9487-e4bc95dbbd64.jpg",1176,1176,false]},"uagb_author_info":{"display_name":"importmanagerhub@sprylab.com","author_link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/author\/importmanagerhubsprylab-com\/"},"uagb_comment_info":0,"uagb_excerpt":"Penny Wozniakiewicz looks at advances in the field since the first worlds were announced","_links":{"self":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/posts\/28018"}],"collection":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/users\/24"}],"replies":[{"embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/comments?post=28018"}],"version-history":[{"count":26,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/posts\/28018\/revisions"}],"predecessor-version":[{"id":29615,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/posts\/28018\/revisions\/29615"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/media\/28013"}],"wp:attachment":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/media?parent=28018"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/categories?post=28018"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/tags?post=28018"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}