{"id":55286,"date":"2024-02-25T08:33:00","date_gmt":"2024-02-25T08:33:00","guid":{"rendered":"http:\/\/48ebcc04-70d1-4656-883a-434bd1194366"},"modified":"2024-02-26T09:33:47","modified_gmt":"2024-02-26T09:33:47","slug":"dips-in-starlight-how-the-transit-method-is-used-to-detect-and-measure-the-mass-of-exoplanets","status":"publish","type":"rss_feed","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/rss_feed\/dips-in-starlight-how-the-transit-method-is-used-to-detect-and-measure-the-mass-of-exoplanets\/","title":{"rendered":"Dips in starlight: how the transit method is used to detect and measure the mass of exoplanets"},"content":{"rendered":"
How dips in starlight can indicate the presence or an exoplanet in orbit around a star. <\/p>
By Ezzy Pearson\n <\/p>
Published: Sunday, 25 February 2024 at 08:33 AM<\/p>
\n\n
There are several ways of detecting exoplanets, but the vast majority are found using the transit method.<\/p>
Exoplanets are planets orbiting stars beyond our Solar System, and as such they can be hard to spot against the bright light of their host star.<\/p>
But the transit method is one particularly successful way astronomers can detect exoplanets.<\/p>
Astronomers carefully monitor a star, looking for a brief, tell-tale dip in the star\u2019s brightness as a planet passes across \u2013 or transits \u2013 briefly blocking out the starlight.<\/p>
The time between dips reveals how long the planet takes to orbit the star, and so how far out it is.<\/p>
The dip\u2019s depth is determined by how much light the planet blocks, showing its physical size or radius.<\/p>Astronomers can also search for atmospheric biosignatures – signs of life – in transiting exoplanets. Credit: NASA<\/figcaption><\/figure>
Measuring mass in transiting exoplanets<\/strong><\/h2>
Once at least three dips have been found, it is considered a planetary candidate, but it still needs its mass measured to be a confirmed world.<\/p>
To do this, astronomers measure the effect the planet\u2019s gravitational pull has on other objects in the system.<\/p>
If there are multiple planets, then their orbital times will be slightly irregular as they pull on each other.<\/p>
For most cases, though, astronomers have to undertake follow-up observations of the host star, looking for signs of a slight wobble as the planet pulls it to and fro. \u00a0<\/p>
Planets can only be detected by the transit method if they block out enough light to be noticeable against the bright glare of the star.<\/p>An artist\u2019s impression of the CHEOPS spacecraft observing a transiting exoplanet. Credit: ESA\/ATG medialab<\/figcaption><\/figure>
The closer a planet is, the bigger the dip, meaning most transiting exoplanets have orbit times of just a few days or weeks.<\/p>
While larger planets are easier to spot, it is possible to detect smaller worlds, provided they are in orbit around dimmer stars, such as red dwarfs.<\/p>
What’s more, astronomers can analyse the starlight that passes through the exoplanet’s atmosphere to search learn more about its chemical composition.<\/p>
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