{"id":32972,"date":"2022-06-16T00:00:00","date_gmt":"2022-06-16T00:00:00","guid":{"rendered":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/?post_type=purple_issue&p=32972"},"modified":"2022-07-12T15:00:14","modified_gmt":"2022-07-12T15:00:14","slug":"qa-with-a-planet-hunter-2","status":"publish","type":"post","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/2022\/06\/16\/qa-with-a-planet-hunter-2\/","title":{"rendered":"Q&A with a planet hunter"},"content":{"rendered":"\n

Melissa Brobby interviews Dr Iain McDonald <\/h4>\n\n

The Kepler space telescope was retired in 2018 but its data is still revealing planetary candidates, including free\u2013floating worlds <\/p>\n\n

\"\"
Kepler (inset) found hundreds of planets during its primary missions; now its data has also revealed free-floating worlds <\/figcaption><\/figure><\/div>\n\n

What is microlensing and how many planetary candidates have been found in data from the Kepler space telescope using the method? <\/strong><\/p>\n\n

We found five planetary candidates via microlensing, which works by waiting until the planets pass in front of a background star. Einstein\u2019s theory of relativity states that light from the background star should be bent around the planet, which acts as a lens, making the background star brighter for a short time. This length of time depends on the mass of the lens and how fast it is moving, and for planets this is only a few hours. Sadly, microlensing events are one-time-only, meaning we might struggle to take more data of these planetary candidates. <\/p>\n\n

At this stage, can the composition and masses of these planetary candidates be determined? <\/strong><\/p>\n\n

We don\u2019t know much about these planetary candidates, but we\u2019re collecting together old data from Earth-bound observatories that was taken at the same time. Differences in the time and strength of the brightening on Earth can help us separate the mass of the lens from its speed, and also prove these aren\u2019t just normal stars that are getting brighter of their own accord. Based on the short timescales of their brightening, though, we expect these planets to be about the same mass as Jupiter or smaller. Unfortunately, we can\u2019t say anything about their compositions. <\/p>\n\n

As Kepler was not designed to find planets using microlensing, how difficult was it to find these signals using data from the space telescope? <\/strong><\/p>\n\n

Kepler was very useful because it was able to stare at a fairly large part of the sky continuously. It was pointed at the most star-rich parts of the Galaxy, where there can be dozens of stars in every pixel. <\/p>\n\n

However, many of these stars are variable and undergo brightening events of their own accord, and passing asteroids keep getting in the way. The fact that the spacecraft kept drifting off course, because one of its stabilising wheels was broken, didn\u2019t help either! That meant it took four years for us to weed out the planetary candidates we wanted from the data, and be convinced that the stars weren\u2019t getting brighter for some other reason.<\/span><\/p>\n\n

Do we know if these planetary candidates have host stars? <\/strong><\/p>\n\n

Stars should produce their own, much stronger and longer microlensing signals, which should be visible in the light-curves too. One of our planetary candidates appears to be a Jupiter-like planet going around a star. The other four candidates we found don\u2019t show a star-like signal to go with the planetary signal. That could be because they are orbiting very far from their host stars, but is more likely to be because they are floating freely in space. <\/p>\n\n

Is there a theory to explain how some of these planetary candidates came to be free-floating? <\/strong><\/p>\n\n

We think free-floating planets form when planetary systems are disrupted. If one planet comes too close to another, one can be thrown towards its star (maybe making a \u2018hot Jupiter\u2019) and the other one gets thrown out of the system, becoming freefloating. By studying these free-floating planets, we can look at how stable planetary systems are. <\/p>\n\n

What impact could the use of microlensing have on exoplanet-hunting? <\/strong><\/p>\n\n

Most exoplanet-hunting techniques either find planets really close into their star (like the transit and radial-velocity methods), or very big, young planets far away from their star (the direct-imaging method). <\/p>\n\n

Microlensing is really helpful for catching the planets in the middle \u2013 planets that are similar to our own Jupiter \u2013 and smaller planets much further out, including free-floating ones. It\u2019s even quite effective at detecting Earth-like planets. Other methods require many years to detect such planets. Instead, microlensing relies on the blind luck of the planet passing in front of a star. <\/p>\n\n

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

Dr Iain McDonald is a Research Fellow in Astrophysics at the University of Manchester, whose field of research is in the discovery and characterisation of exoplanets<\/p>\n\n

Photos: NASA\u2019S GODDARD SPACE FLIGHT CENTER CONCEPTUAL IMAGE LAB, NASA AMES\/JPL-CALTECH\/T PYLE<\/p>\n","protected":false},"excerpt":{"rendered":"

An interview with Dr Iain McDonald<\/p>\n","protected":false},"author":24,"featured_media":33197,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"ub_ctt_via":"","purple_page_number":"98","purple_custom_meta_purple_page_number":"98","purple_seq_number":"1","purple_custom_meta_purple_seq_number":"1","purple_source_article":"article_98-1.xml","purple_custom_meta_purple_source_article":"article_98-1.xml","purple_source_issue":"July-2022","purple_custom_meta_purple_source_issue":"July-2022","purple_external_id":"July-2022-98-1","purple_custom_meta_purple_external_id":"July-2022-98-1","purple_issue_code":"|0000086554||","purple_custom_meta_purple_issue_code":"|0000086554||","purple_android_product":"com.im.skyatnight.206","purple_custom_meta_purple_android_product":"2022skyatnightJuly","purple_ios_product":"com.im.skyatnight.206","purple_custom_meta_purple_ios_product":"2022skyatnightJuly","purple_web_product":"","purple_custom_meta_purple_web_product":"","purple_publication_id":"075fab74-0a21-4201-866a-899d6c41c40c","purple_migrated":"","kt_blocks_editor_width":""},"categories":[36],"tags":[14],"featured_image_src":"https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/06\/60KYZE1IYIMX8H3E5EP5618O72XY.jpg","author_info":{"display_name":"importmanagerhub@sprylab.com","author_link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/author\/importmanagerhubsprylab-com\/"},"acf":{"readingTimeMinutes":"4","apple_news_title":""},"uagb_featured_image_src":{"full":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/06\/60KYZE1IYIMX8H3E5EP5618O72XY.jpg",1162,946,false],"thumbnail":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/06\/60KYZE1IYIMX8H3E5EP5618O72XY-150x150.jpg",150,150,true],"medium":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/06\/60KYZE1IYIMX8H3E5EP5618O72XY-300x244.jpg",300,244,true],"medium_large":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/06\/60KYZE1IYIMX8H3E5EP5618O72XY-768x625.jpg",768,625,true],"large":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/06\/60KYZE1IYIMX8H3E5EP5618O72XY-1024x834.jpg",800,652,true],"1536x1536":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/06\/60KYZE1IYIMX8H3E5EP5618O72XY.jpg",1162,946,false],"2048x2048":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/06\/60KYZE1IYIMX8H3E5EP5618O72XY.jpg",1162,946,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":"An interview with Dr Iain McDonald","_links":{"self":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/posts\/32972"}],"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=32972"}],"version-history":[{"count":4,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/posts\/32972\/revisions"}],"predecessor-version":[{"id":33356,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/posts\/32972\/revisions\/33356"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/media\/33197"}],"wp:attachment":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/media?parent=32972"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/categories?post=32972"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/tags?post=32972"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}