{"id":10735,"date":"2023-12-14T22:00:00","date_gmt":"2023-12-14T22:00:00","guid":{"rendered":"https:\/\/modernsciences.org\/staging\/4414\/?p=10735"},"modified":"2023-12-01T06:44:28","modified_gmt":"2023-12-01T06:44:28","slug":"massive-planet-too-big-for-its-own-sun-pushes-astronomers-to-rethink-exoplanet-formation","status":"publish","type":"post","link":"https:\/\/modernsciences.org\/staging\/4414\/massive-planet-too-big-for-its-own-sun-pushes-astronomers-to-rethink-exoplanet-formation\/","title":{"rendered":"Massive planet too big for its own sun pushes astronomers to rethink exoplanet\u00a0formation"},"content":{"rendered":"\n
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\n LHS 3154b, a newly discovered massive planet that should be too big to exist.\n The Pennsylvania State University<\/span><\/span>\n <\/figcaption>\n <\/figure>\n\nSuvrath Mahadevan<\/a>, Penn State<\/a><\/em>; Gu\u00f0mundur K\u00e1ri Stef\u00e1nsson<\/a>, Princeton University<\/a><\/em>, and Megan Delamer<\/a>, Penn State<\/a><\/em><\/span>\n\n

Imagine you\u2019re a farmer searching for eggs in the chicken coop \u2013 but instead of a chicken egg, you find an ostrich egg, much larger than anything a chicken could lay.<\/p>\n\n

That\u2019s a little how our team<\/a> of astronomers<\/a> felt when we<\/a> discovered a massive planet<\/a>, more than 13 times heavier than Earth, around a cool, dim red star, nine times less massive than Earth\u2019s Sun, earlier this year. <\/p>\n\n

The smaller star, called an M star, is not only smaller than the Sun in Earth\u2019s solar system, but it\u2019s 100 times less luminous. Such a star should not have the necessary amount of material in its planet-forming disk to birth such a massive planet.<\/p>\n\n

The Habitable Zone Planet Finder<\/h2>\n\n

Over the past decade, our team designed and built a new instrument at Penn State capable of detecting the light from these dim, cool stars at wavelengths beyond the sensitivity of the human eye \u2013 in the near-infrared \u2013 where such cool stars emit most of their light<\/a>. <\/p>\n\n

Attached to the 10-meter Hobby-Eberly Telescope in West Texas, our instrument, dubbed the Habitable Zone Planet Finder<\/a>, can measure the subtle change in a star\u2019s velocity as a planet gravitationally tugs on it. This technique, called the Doppler radial velocity technique, is great for detecting exoplanets<\/a>. <\/p>\n\n

\u201cExoplanet<\/a>\u201d is a combination of the words extrasolar and planet, so the term applies to any planet-sized body in orbit around a star that isn\u2019t Earth\u2019s Sun.<\/p>\n\n

Thirty years ago, Doppler radial velocity observations enabled the discovery of 51 Pegasi b<\/a>, the first known exoplanet orbiting a Sunlike star. In the ensuing decades, astronomers like us have improved this technique. These increasingly more precise<\/a> measurements have an important goal: to enable the discovery of rocky planets in habitable zones<\/a>, the regions around stars where liquid water can be sustained on the planetary surface. <\/p>\n\n

The Doppler technique doesn\u2019t yet have the capabilities to discover habitable zone planets the mass of the Earth around stars the size of the Sun. But the cool and dim M stars show a larger Doppler signature for the same Earth-size planet. The lower mass of the star leads to it getting tugged more by the orbiting planet. And the lower luminosity leads to a closer-in habitable zone<\/a> and a shorter orbit, which also makes the planet easier to detect. <\/p>\n\n

Planets around these smaller stars were the planets our team designed the Habitable Zone Planet Finder to discover. Our new discovery, published in the journal Science<\/a>, of a massive planet orbiting closely around the cool dim M star LHS 3154 \u2013 the ostrich egg in the chicken coop \u2013 came as a real surprise.<\/p>\n\n

LHS 3154b: The planet that should not exist<\/h2>\n\n

Planets form in disks<\/a> composed of gas and dust. These disks pull together dust grains that grow into pebbles and eventually combine to form a solid planetary core. Once the core is formed, the planet can gravitationally pull in the solid dust, as well as surrounding gas such as hydrogen and helium. But it needs a lot of mass and materials to do this successfully. This way to form planets is called core accretion<\/a>.<\/p>\n\n

A star as low mass as LHS 3154, nine times less massive than the Sun, should have a correspondingly low-mass planet forming disk. <\/p>\n\n

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