{"id":30284,"date":"2022-03-24T00:00:00","date_gmt":"2022-03-24T00:00:00","guid":{"rendered":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/?post_type=purple_issue&p=30284"},"modified":"2022-04-20T13:26:58","modified_gmt":"2022-04-20T13:26:58","slug":"qa-with-a-planet-hunter","status":"publish","type":"post","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/2022\/03\/24\/qa-with-a-planet-hunter\/","title":{"rendered":"Q&A with a planet hunter"},"content":{"rendered":"\n
Melissa Brobby interviews Dr Rosanne Di Stefano<\/h5>\n\n

The first evidence of a planet outside our Galaxy is leading the way to a very exciting new era of planet hunting<\/p>\n\n

\"\"
The first signs of a planet beyond the Milky Way were found after scientists looked for a dip in X-ray emissions from the galaxy M51<\/figcaption><\/figure><\/div>\n\n

You\u2019ve found hints of what could be the first extragalactic planet to be found, in M51, the Whirlpool Galaxy. How was this discovery made and when?<\/strong><\/p>\n\n

There was data that had been taken over a 20-year period by the Chandra X-ray Observatory, and the XMM-Newton Observatory, which is a European project. And these observatories both look regularly at galaxies outside the Milky Way. There are some galaxies, like M51, that have been observed many times over the years. We were looking for a dip in the X-ray emission, and what we realised is that the passage of a planet in front of an X-ray source would give a dip that would tell us that the planet was there. This is a pretty big signal.<\/p>\n\n

Why did you focus on M51? Were there other galaxies that were looked at in the research? <\/strong><\/p>\n\n

It really had to do with our collaborator, Ryan Urquhart, then a graduate student, now a postdoctoral fellow at Michigan State, who used M51 (also known as the Whirlpool Galaxy), M101, the Pinwheel Galaxy and M104, the Sombrero Galaxy. So that was the data that was ready for us. Each galaxy has several dozen bright sources, and each of these sources has been observed many times over this 20 year period. So when this was put together for M51, for example, there was about 10 days\u2019 worth of observation time for each of the dozens of sources in that galaxy. So this was a very wonderful resource for us to start with and that was our motivation. We would have started with other galaxies; and now, in fact, we have moved on to other galaxies.<\/p>\n\n

What can we tell about the planet you found? <\/strong>We can tell its size is likely to be similar to Saturn and we can also tell roughly how fast it is moving around this X-ray binary \u2013 about 17km\/s. That tells us that it\u2019s in a wide orbit. That\u2019s probably about all the information we\u2019re going to know for now as it will be a very long time before there\u2019s another transit.<\/span><\/p>\n\n

How difficult is it to find planets that are outside our Galaxy?<\/strong><\/p>\n\n

There are many methods that are used within the Milky Way to find planets. For example, you can use transits at optical wavelengths by taking a regular star that is emitting optical light and looking for what is generally a very tiny dip as a planet passes in front. Or you can study the velocity of a star and see it go back and forth. These methods wouldn\u2019t be able to succeed right now in other galaxies because, if a target galaxy is, say, 1,000 times farther away, then you would get a million times less light.<\/p>\n\n

When you look at other galaxies in the optical and infrared wavelengths, there are hundreds of billions of stars whose light is superposed. Even if you\u2019re looking at a very tiny portion of the galaxy, the light that you receive is a mixture of light from many different stars and that makes it difficult \u2013 or impossible at this point in time \u2013 to pull out the signal of a transit or another subtle signal.<\/p>\n\n

Our use of X-ray allowed this discovery, but it really depends entirely on how big the X-ray source is relative to the planet.<\/p>\n\n

What does the discovery of this planet mean for the future of planet hunting \u2013 does it mark a significant breakthrough?<\/strong><\/p>\n\n

This is a whole new way of planet hunting. We know of over 5,000 planets in our own Galaxy that have been found using other methods. A planet\u2019s significance really depends on whether that planet or the planetary system has something very unique about it. But here, we have taken a new method that has never been used before. We\u2019ve shown that it can find planet transits even in other galaxies, and we found a planet in a kind of system that has never been studied for planets before, so I would say because it\u2019s new, it\u2019s definitely significant.<\/p>\n\n

<\/p>\n\n

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

Dr Rosanne Di Stefano is a senior astrophysicist at the Smithsonian Astrophysical Observatory at the Harvard-Smithsonian Center for Astrophysics.<\/p>\n\n

<\/p>\n\n

<\/p>\n\n

Photo: KALTSEIS CHRISTOPH\/CCDGUIDE.COMP<\/p>\n","protected":false},"excerpt":{"rendered":"

The first evidence of a planet outside our Galaxy is leading the way to an exciting new era of planet hunting<\/p>\n","protected":false},"author":24,"featured_media":30282,"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":"April-2022","purple_custom_meta_purple_source_issue":"April-2022","purple_external_id":"April-2022-98-1","purple_custom_meta_purple_external_id":"April-2022-98-1","purple_issue_code":"|0000086551||","purple_custom_meta_purple_issue_code":"|0000086551||","purple_android_product":"com.im.skyatnight.203","purple_custom_meta_purple_android_product":"com.im.skyatnight.203","purple_ios_product":"com.im.skyatnight.203","purple_custom_meta_purple_ios_product":"com.im.skyatnight.203","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\/03\/3881dcba-6d6a-498c-8466-f727c014f30a.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\/03\/3881dcba-6d6a-498c-8466-f727c014f30a.jpg",1134,965,false],"thumbnail":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/03\/3881dcba-6d6a-498c-8466-f727c014f30a-150x150.jpg",150,150,true],"medium":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/03\/3881dcba-6d6a-498c-8466-f727c014f30a-300x255.jpg",300,255,true],"medium_large":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/03\/3881dcba-6d6a-498c-8466-f727c014f30a-768x654.jpg",768,654,true],"large":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/03\/3881dcba-6d6a-498c-8466-f727c014f30a-1024x871.jpg",800,680,true],"1536x1536":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/03\/3881dcba-6d6a-498c-8466-f727c014f30a.jpg",1134,965,false],"2048x2048":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/03\/3881dcba-6d6a-498c-8466-f727c014f30a.jpg",1134,965,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":"The first evidence of a planet outside our Galaxy is leading the way to an exciting new era of planet hunting","_links":{"self":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/posts\/30284"}],"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=30284"}],"version-history":[{"count":6,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/posts\/30284\/revisions"}],"predecessor-version":[{"id":30812,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/posts\/30284\/revisions\/30812"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/media\/30282"}],"wp:attachment":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/media?parent=30284"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/categories?post=30284"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/tags?post=30284"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}