New Neptune-sized exoplanet found with an enormous ambiance ripe for research – SciTechDaily

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The artist’s impression shows an exoplanet orbiting the sun-like star. Photo credit: ESO / M. Grain knife

An international group of employees, including scientists from NASA‘s Jet Propulsion Laboratory and the University of New Mexico have created a new, moderate sub-Neptune large Exoplanet with a 24-day orbital period orbiting a nearby M dwarf star. The recent discovery offers exciting research opportunities thanks to the planet’s sizeable atmosphere, small star, and the speed at which the system is moving away from Earth.

The research paper, entitled TOI-1231 b: A Temperate, Neptune-Sized Planet Transiting the Near M3 Dwarf NLTT 24399, will be published in a future issue of the Astronomical Journal. The exoplanet TOI-1231 b was measured with photometric data from the Transiting Exoplanet Survey Satellite (TESS) and followed observations with the Planet Finder Spectrograph (PFS) at the Magellan Clay Telescope at the Las Campanas Observatory in Chile. The PFS is a sophisticated instrument that recognizes exoplanets through the influence of gravity on their host stars. As the planets orbit their hosts, the measured stellar velocities vary periodically and provide information about the planet’s presence and information about its mass and orbit.

NASA’s TESS observation strategy, which divides each hemisphere into 13 sectors surveyed for approximately 28 days, enables the most comprehensive sky-high search for planets in transit. This approach has already demonstrated its ability to detect both large and small planets around stars, ranging from sun-like to low-mass M dwarf stars. M dwarf stars, also known as red dwarfs, are the most common type of star in the world Milky Way They make up about 70 percent of all stars in the galaxy.

M dwarfs are smaller and have a fraction of the solar mass and have a low luminosity. Because an M dwarf is smaller, the amount of light blocked by the planet will be greater when a planet of a certain size passes the star, making the transit easier to see. Imagine an Earth-like planet passing in front of a star the size of the Sun, it will block a tiny bit of light; but when it passes in front of a much smaller star, the amount of light that is blocked out increases. In a way, this creates a larger shadow on the surface of the star, making planets around M-dwarfs easier to see and easier to study.

Although it enables the discovery of exoplanets in the sky, TESS’s surveying strategy also creates significant observation errors based on orbital duration. Exoplanets must traverse their host stars at least twice within the observation span of TESS in order to be detected with the correct period by the Science Processing Operations Center (SPOC) pipeline and the Quick Look Pipeline (QLP), which cover the 2-minute and 30-minute intervals. Minute Cadence TESS Data, or Since 74 percent of the total sky coverage is observed by TESS for only 28 days, most TESS exoplanets discovered have periods of less than 14 days. The TOI-1231b’s 24-day period therefore makes its discovery even more valuable.

NASA JPL Scientist Jennifer Burt, the lead author of the paper, along with her staff including Diana Dragomir, an assistant professor in the UNM’s Department of Physics and Astronomy, measured both the radius and mass of the planet.

“Working with a group of excellent astronomers around the world, we were able to compile the necessary data to characterize the host star and measure both the radius and mass of the planet,” said Burt. “These values, in turn, enabled us to calculate the planet’s bulk density and hypothesize what the planet is made of. TOI-1231b is quite similar in size and density to Neptune, so we think it has a similarly sized gaseous atmosphere. “

“Another advantage of exoplanets orbiting M dwarf hosts is that we can measure their masses more easily, as the ratio of planetary mass to stellar mass is also greater. If the star is smaller and less massive, the detection methods work better because the planet suddenly plays a bigger role because it is easier to stand out from the star, ”explains Dragomir. “Like the shadow that casts on the star. The smaller the star, the less massive the star, the more the effect of the planet can be demonstrated.

“Although TOI 1231b is eight times closer to its star than Earth is to the Sun, its temperature is similar to Earth thanks to its cooler and less bright host star,” says Dragomir. “However, the planet itself is actually larger than Earth and a bit smaller than Neptune – we could call it a sub-Neptune.”

Burt and Dragomir, who actually initiated this research when they were fellows at. were WITH‘s Kavli Institute, worked with scientists who specialize in observing and characterizing the atmospheres of small planets to find out what current and future space-based missions might look into the outer layers of TOI-1231b for the researchers inform what types of gases there are swirling around the planet. At a temperature of 330 Kelvin or 140 degrees Fahrenheit, TOI-1231b is one of the coolest small exoplanets available for atmospheric studies to date.

Previous research suggests that such cool planets might have clouds high in their atmosphere, making it difficult to determine what types of gases surround them. But new observations of another small, cool planet called K2-18b broke that trend and showed evidence of water in its atmosphere, which surprised many astronomers.

“TOI-1231b is one of the few other planets we know of a similar size and temperature range, so through future observations of this new planet we will be able to determine how often (or rarely) water clouds form around it.” Temperate worlds “Said Burt.

In addition, with the high brightness of its host star in the near infrared (NIR), it is an exciting target for future missions with the Hubble Space Telescope (HST) and the James Webb Space Telescope (JWST). The first set of these observations, led by one of the co-authors of the paper, was due to take place with the Hubble Space Telescope later this month.

“The low density of TOI 1231b suggests that it is surrounded by a sizeable atmosphere and is not a rocky planet. But the composition and extent of this atmosphere are unknown! ”Said Dragomir. “TOI1231b could have a large hydrogen or hydrogen-helium atmosphere, or a denser water vapor atmosphere. Each of them would point to a different origin, which enables astronomers to understand whether and how planets around M-dwarfs, for example, form differently than the planets around our sun. Our upcoming HST observations will answer these questions, and the JWST promises to provide an even deeper insight into the planet’s atmosphere. “

Another way to study the planet’s atmosphere is to see if gas is being blown away by looking for evidence of atoms such as hydrogen and helium surrounding the planet as it travels across the surface of its host star. In general, hydrogen atoms are almost impossible to detect as their presence is masked by interstellar gas. But this planet-star system offers a unique opportunity to use this method because it is moving away from Earth so quickly.

“One of the most fascinating results of the last two decades of exoplanet research is that none of the new planetary systems we have discovered looks like our own solar system,” said Burt. “They are full of planets between the size of Earth and Neptune in orbits much shorter than Mercury’s, so we have no local examples to compare them to. This new planet we discovered is still weird – but it’s one step closer to being like our neighboring planets. Compared to most of the transit planets discovered so far, which often have scorching temperatures of many hundreds or thousands of degrees, TOI-1231 b is downright cold. “

In conclusion, Dragomir says that “This planet is just one of two or three other nearby small exoplanets that will be studied at every opportunity and with a wide range of telescopes in the years to come, so keep your eyes peeled for the new one.” TOI1231b “Developments!”

Reference: “TOI-1231 b: A Temperate, Neptun-Sized Planet Transiting the Near M3 Dwarf NLTT 24399” by Jennifer A. Burt, Diana Dragomir, Paul Mollière, Allison Youngblood, Antonio García Muñoz, John McCann, Laura Kreidberg, Chelsea X. Huang, Karen A. Collins, Jason D. Eastman, Lyu Abe, Jose M. Almenara, Ian JM Crossfield, Carl Ziegler, Joseph E. Rodriguez, Eric E. Mamajek, Keivan G. Stassun, Samuel P. Halverson, Steven Jr Villanueva , R. Paul Butler, Sharon Xuesong Wang, Richard P. Schwarz, George R. Ricker, Roland Vanderspek, David W. Latham, S. Seager, Joshua N. Winn, Jon M. Jenkins, Abdelkrim Agabi, Xavier Bonfils, David Ciardi , Marion Cointepas, Jeffrey D. Crane, Nicolas Crouzet, Georgina Dransfield, Fabo Feng, Elise Furlan, Tristan Guillot, Arvind F. Gupta, Steve B. Howell, Eric LN Jensen, Nicholas Law, Andrew W. Mann, Wenceslas Marie -Sainte , Rachel A. Matson, Elisabeth C. Matthews, Djamel Mékarnia, Joshua Pepper, Nic Scott, Stephen A. Shectman, Joshua E. Schlieder, François-Xavi er Schmider, Daniel J. Stevens, Johanna K. Teske, Amaury HMJ Triaud, David Charbonneau, Zachory K. Berta-Thompson, Christopher J. Burke, Tansu Daylan, Thomas Barclay, Bill Wohler and CE Brasseurs, Accepted, The Astronomical Journal.
arXiv: 2105.08077

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