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GJ 1214 b

From Wikipedia, the free encyclopedia

GJ 1214 b / Enaiposha
Size comparison of Enaiposha with Earth (left) and Neptune (right). The actual color of Enaiposha is not yet known.
Discovery[1]
Discovered byDavid Charbonneau, et al.
Discovery siteFred Lawrence Whipple Observatory
Discovery dateDecember 16, 2009
Transit (MEarth Project)
Designations
Enaiposha[2]
Orbital characteristics[3]
0.01490±0.00026 AU
Eccentricity<0.063
1.580404571(42) d[4]
Inclination88.7°±0.1°
Semi-amplitude14.36±0.53 m/s
StarOrkaria
Physical characteristics
Mean radius
2.742+0.050
−0.053 R🜨[3]
Mass8.17±0.43 M🜨[3]
Mean density
2.20+0.17
−0.16 g/cm3[3]
10.65+0.71
−0.67 m/s2[3] (1.09 g)
19.31+0.53
−0.54 km/s[3]
Albedo0.51±0.06 (Bond)[5]
Temperature553±9 K (280 °C; 536 °F, dayside)[5]
437±19 K (164 °C; 327 °F, nightside)[5]

GJ 1214 b (sometimes Gliese 1214 b,[6] formally named Enaiposha[2]) is an exoplanet that orbits the star GJ 1214, and was discovered in December 2009. Its parent star is 48 light-years from the Sun, in the constellation Ophiuchus. As of 2017, GJ 1214 b is the most likely known candidate for being an ocean planet.[1][7] For that reason, scientists often call the planet a "waterworld".[8]

It is a super-Earth, meaning it is larger than Earth but is significantly smaller (in mass and radius) than the gas giants of the Solar System. After CoRoT-7b, it was the second super-Earth to have both its mass and radius measured[1] and is the first of a new class of planets with small size and relatively low density.[9] GJ 1214 b is also significant because its parent star is relatively near the Sun and because it transits that parent star, which allows the planet's atmosphere to be studied using spectroscopic methods.[1]

In December 2013, NASA reported that clouds may have been detected in the atmosphere of GJ 1214 b.[10][11][12][13]

YouTube Encyclopedic

  • 1/5
    Views:
    15 669
    13 102
    8 472
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    12 607
  • Clouds on the Super-Earth Exoplanet GJ 1214b
  • Scientists confirm existence of new 'waterworld' planet GJ1214B
  • Atmosphere of SuperEarth GJ1214b - Eliza Kempton (SETI Talks)
  • GJ 1214b: un mondo d'acqua
  • New 'super-Earth' is a steamy 'waterworld'

Transcription

If you've ever wondered what scientists can learn about planets outside our solar system, this video is for you. My name is Laura Kreidberg, and I'm a grad student in the astrophysics department at the University of Chicago, and I spend most of my time studying the atmospheres of exoplanets, which are planets orbiting stars other than the sun. It turns out that the Milky Way is filled with exoplanets. We've barely searched even a tiny fraction of all the stars, and we've already found a thousand confirmed planets as of October 2013, and some of these planets are even close enough to us that we can start studying their atmospheres, to learn more about them - what they're made out of, what the conditions are on their surfaces, even whether they might be hospitable for life. That's what I've been working on. I've been studying one planet in particular called GJ 1214b. This planet is what's known as a super-Earth. That's a technical term for planets bigger than the Earth and smaller than Neptune. I have some really exciting results about it that I want to share. GJ 1214b is an awesome planet to study because its practically in our own backyard - it's about 40 light years away from us, which means that if you scale down the Milky Way to the size of the United States, the planet would only be about a mile from Earth. Realistically speaking, it's still too far away to actually go there, but it's close enough for us to be able to learn a lot about it. We already know that GJ 1214b is really different from the planets in the solar system. It's about 3 times the radius of Earth - so in between Earth and Neptune in size - and even though our solar system doesn't have any planets in that intermediate size range, super-Earths like GJ 1214b are one of the most common kinds of planets in the galaxy. Because these super-Earths are so abundant, astronomers would like to know whether these planets are truly scaled up versions of the Earth, or instead something more like a miniature Neptune. This difference would have big implications for whether life could exist on these planets. We're sure though that life as we know it couldn't survive on GJ 1214b. That's because it orbits its host star really close in - it only takes about a day and half - roughly 38 hours - for the planet to go all the way around the star. Because it's so close, the planet is really hot - could be hotter than 400 degrees Fahrenheit, which is a higher temperature than the most extreme life forms on Earth can tolerate. We can learn a lot more about the planet by studying its atmosphere. GJ 1214b is a transiting planet - it's lined up just right so that it passes between us and its host star every time it orbits. This is a fortunate situation for astronomers because we can use the star as a backlight to study the planet's atmosphere. When the planet is transiting, a small percentage of the starlight filters through the planetary atmosphere on its way to us, and information about the molecules that are present there is imprinted on the light that's passing through. Here's an example of what we would observe for an atmosphere made out of water vapor. Molecules can absorb light, and the amount of light that's absorbed depends on both what kind of molecule we're talking about, and the wavelength, or color, of light. By measuring very precisely for each wavelength how much starlight is being blocked by molecules in the planet's atmosphere, we can work backwards to learn what the atmosphere is made out of. A team of collaborators and I used the Hubble Space Telescope to observe GJ 1214b with this technique. We used a record amount of Hubble time for observing a single exoplanet, and this allowed us to make the first measurement ever that is precise enough to detect an Earth-like atmospheric composition on a planet outside the solar system. But what we found is very different from the Earth. We searched the spectrum for signs of water, carbon monoxide, carbon dioxide, methane, all the common molecules that we would expect to see in an atmosphere the temperature of GJ 1214b. But we didn't see any of those molecules. and what that means is that there must be clouds in the atmosphere blocking our view. These clouds are not going to be like the clouds on Earth - GJ 1214b is too hot for water to condense in the upper atmosphere. But its possible for other kinds of clouds to form - for example, in our own solar system, we see clouds made out of sulfuric acid on Venus and ammonia on Jupiter. We think the clouds on GJ 1214b could be made out something even more exotic, potentially potassium chloride or zinc sulfide. GJ1214b has yet to reveal all of its secrets, but there are some new telescopes being built that should help us get to the bottom of this. One is the successor to Hubble, called the James Webb Space Telescope, which is scheduled for launch by NASA within the next five years or so, and there are also some huge ground-based telescopes being built. Not only will these telescopes help us solve the mystery of GJ 1214b, but they'll also open the door to studying the atmospheres of smaller, cooler exoplanets more like our own Earth, and who knows what we'll find out there! So stay tuned.

Name

In August 2022, this planet and its host star were included among 20 systems to be named by the third NameExoWorlds project.[14] The approved names, proposed by a team from Kenya, were announced in June 2023. GJ 1214 b is named Enaiposha and its host star is named Orkaria, after the Maa words for a large body of water and for red ochre, alluding to the likely composition of the planet and color of the star.[2]

Physical characteristics

Mass, radius and temperature

Artist's impression of the planet with a hazy steam atmosphere[15]
Artist's impression of GJ 1214 b (foreground), illuminated by the red light of its parent star (center)
The newly discovered super-Earth orbiting the nearby star GJ 1214.
This artist's impression shows how GJ 1214 b may look as it transits its parent star. It is the second super-Earth for which astronomers have determined the mass and radius, giving vital clues about its structure.

The radius of GJ 1214 b can be inferred from the amount of dimming seen when the planet crosses in front of its parent star as viewed from Earth, yielding a radius of 2.742+0.050
−0.053 R🜨.[3] The mass of the planet can be inferred from sensitive observations of the parent star's radial velocity, measured through small shifts in stellar spectral lines due to the Doppler effect,[1] yielding a mass of 8.17±0.43 M🜨.[3] Given the planet's mass and radius, its density can be calculated. Through a comparison with theoretical models, the density in turn provides limited but highly useful information about the composition and structure of the planet.[1]

GJ 1214 b may be cooler than any other known transiting planet prior to the discovery of Kepler-16b in 2011 by the Kepler mission. Its equilibrium temperature is believed to be in the range of 393–555 K (120–282 °C; 248–539 °F), depending on how much of the star's radiation is reflected into space.[1][16]

Atmosphere

Due to the relatively small size of GJ 1214 b's parent star, it is feasible to perform spectroscopic observations during planetary transits. By comparing the observed spectrum before and during transits, the spectrum of the planetary atmosphere can be inferred. In December 2010, a study was published showing the spectrum to be largely featureless over the wavelength range of 750–1000 nm. Because a thick and cloud-free hydrogen-rich atmosphere would have produced detectable spectral features, such an atmosphere appears to be ruled out. Although no clear signs were observed of water vapor or any other molecule, the authors of the study believe the planet may have an atmosphere composed mainly of water vapor. Another possibility is that there may be a thick layer of high clouds, which absorbs the starlight.[17] Because of the estimated old age of the planetary system and the calculated hydrodynamic escape (loss of gasses that tends to deplete an atmosphere of higher molecular-weight constituents) rate of 900 tonnes per second, scientists conclude that there has been a significant atmospheric loss during the lifetime of the planet and any current atmosphere cannot be primordial.[1] The loss of primordial atmosphere was indirectly confirmed in 2020 as no helium was detected at GJ 1214 b.[18] Helium was detected in the atmosphere of GJ 1214 b by 2022 though.[19]

Possible compositions

While very little is known about GJ 1214 b, there has been speculation as to its specific nature and composition. On the basis of planetary models[20] it has been suggested that GJ 1214 b has a relatively thick gaseous envelope,[9] totaling about 5% of planetary mass.[3] It is possible to propose structures by assuming different compositions, guided by scenarios for the formation and evolution of the planet.[9] GJ 1214 b could be a rocky planet with an outgassed hydrogen-rich atmosphere, a mini-Neptune, or an ocean planet.[9] If it is a waterworld, it could possibly be thought of as a bigger and hotter version of Jupiter's Galilean moon Europa.[9] While no scientist has stated to believe GJ 1214 b is an ocean planet, if GJ 1214 b is assumed to be an ocean planet,[20] i.e. the interior is assumed to be composed primarily of a water core surrounded by more water, proportions of the total mass consistent with the mass and radius are about 25% rock and 75% water, covered by a thick envelope of gases such as hydrogen and helium (c. 0.05%).[1][16] Water planets could result from inward planetary migration and originate as protoplanets that formed from volatile ice-rich material beyond the snow-line but that never attained masses sufficient to accrete large amounts of H/He nebular gas.[9] Because of the varying pressure at depth, models of a water world include "steam, liquid, superfluid, high-pressure ices, and plasma phases" of water.[9] Some of the solid-phase water could be in the form of ice VII.[16]

Discovery

GJ 1214 b was first detected by the MEarth Project, which searches for the small drops in brightness that can occur when an orbiting planet briefly passes in front of its parent star. In early 2009, the astronomers running the project noticed that the star GJ 1214 appeared to show drops in brightness of that sort. They then observed the star more closely and confirmed that it dimmed by roughly 1.5% every 1.58 days. Follow-up radial-velocity measurements were then made with the HARPS spectrograph on the ESO's 3.6-meter telescope at La Silla, Chile; those measurements succeeded in providing independent evidence for the reality of the planet. A paper was then published in Nature announcing the planet and giving estimates of its mass, radius, and orbital parameters.[1]

See also

References

  1. ^ a b c d e f g h i j Charbonneau, David; et al. (2009). "A super-Earth transiting a nearby low-mass star" (PDF). Nature. 462 (7275): 891–894. arXiv:0912.3229. Bibcode:2009Natur.462..891C. doi:10.1038/nature08679. S2CID 4360404.
  2. ^ a b c "2022 Approved Names". nameexoworlds.iau.org. IAU. Retrieved 7 June 2023.
  3. ^ a b c d e f g h i Cloutier, Ryan; Charbonneau, David; Deming, Drake; Bonfils, Xavier; Astudillo-Defru, Nicola (2021). "A more precise mass for GJ 1214 b and the frequency of multiplanet systems around mid-M dwarfs". The Astronomical Journal. 162 (5): 174. arXiv:2107.14732. Bibcode:2021AJ....162..174C. doi:10.3847/1538-3881/ac1584. S2CID 236635146.
  4. ^ Kokori, A.; et al. (14 February 2023). "ExoClock Project. III. 450 New Exoplanet Ephemerides from Ground and Space Observations". The Astrophysical Journal Supplement Series. 265 (1) 4. arXiv:2209.09673. Bibcode:2023ApJS..265....4K. doi:10.3847/1538-4365/ac9da4. Vizier catalog entry 
  5. ^ a b c Kempton, Eliza M.-R.; Zhang, Michael; et al. (May 2023). "A reflective, metal-rich atmosphere for GJ 1214b from its JWST phase curve". Nature. 620 (7972): 67–71. arXiv:2305.06240. doi:10.1038/s41586-023-06159-5.
  6. ^ Rein, Hanno; et al. "Open Exoplanet Catalogue – Gliese 1214 b". Open Exoplanet Catalogue. Retrieved 2 January 2014.
  7. ^ Kuchner, Seager; Hier-Majumder, M.; Militzer, C.A. (2007). "Mass–radius relationships for solid exoplanets". The Astrophysical Journal. 669 (2): 1279–1297. arXiv:0707.2895. Bibcode:2007ApJ...669.1279S. doi:10.1086/521346. S2CID 8369390.
  8. ^ "10 real planets that are stranger than science fiction". iflscience.com. Retrieved 2015-06-13.
  9. ^ a b c d e f g Rogers, L.A.; Seager, S. (2010). "Three possible origins for the gas layer on GJ 1214 b". The Astrophysical Journal (abstract). 716 (2): 1208–1216. arXiv:0912.3243. Bibcode:2010ApJ...716.1208R. doi:10.1088/0004-637X/716/2/1208. S2CID 15288792.
  10. ^ Harrington, J.D.; Weaver, Donna; Villard, Ray (December 31, 2013). "Release 13-383 – NASA's Hubble Sees Cloudy Super-Worlds With Chance for More Clouds". NASA. Retrieved January 1, 2014.
  11. ^ Moses, Julianne (January 1, 2014). "Extrasolar planets: Cloudy with a chance of dustballs". Nature. 505 (7481): 31–32. Bibcode:2014Natur.505...31M. doi:10.1038/505031a. PMID 24380949. S2CID 4408861.
  12. ^ Knutson, Heather; et al. (January 1, 2014). "A featureless transmission spectrum for the Neptune-mass exoplanet GJ 436b". Nature. 505 (7481): 66–68. arXiv:1401.3350. Bibcode:2014Natur.505...66K. doi:10.1038/nature12887. PMID 24380953. S2CID 4454617.
  13. ^ Kreidberg, Laura; et al. (January 1, 2014). "Clouds in the atmosphere of the super-Earth exoplanet GJ 1214 b". Nature. 505 (7481): 69–72. arXiv:1401.0022. Bibcode:2014Natur.505...69K. doi:10.1038/nature12888. PMID 24380954. S2CID 4447642.
  14. ^ "List of ExoWorlds 2022". nameexoworlds.iau.org. IAU. 8 August 2022. Retrieved 27 August 2022.
  15. ^ Brennan, Pat (10 May 2023). "NASA's Webb Takes Closest Look Yet at Mysterious Planet". NASA. Retrieved 10 May 2023.
  16. ^ a b c Aguilar, David A. (2009-12-16). "Astronomers find super-Earth using amateur, off-the-shelf technology". Harvard-Smithsonian Center for Astrophysics. Retrieved December 16, 2009.
  17. ^ Bean, Jacob L.; Kempton, Eliza Miller-Ricci; Homeier, Derek (2010). "A ground-based transmission spectrum of the super-Earth exoplanet GJ 1214 b". Nature. 468 (7324): 669–672. arXiv:1012.0331. Bibcode:2010Natur.468..669B. doi:10.1038/nature09596. PMID 21124452. S2CID 4412196.
  18. ^ Kasper, David; Bean, Jacob L.; Oklopčić, Antonija; Malsky, Isaac; Kempton, Eliza M.-R.; Désert, Jean-Michel; Rogers, Leslie A.; Mansfield, Megan (2020). "Nondetection of helium in the upper atmospheres of three sub-Neptune exoplanets". The Astronomical Journal. 160 (6): 258. arXiv:2007.12968. doi:10.3847/1538-3881/abbee6. S2CID 220793801.
  19. ^ Orell-Miquel, J.; Murgas, F.; Pallé, E.; Lampón, M.; López-Puertas, M.; Sanz-Forcada, J.; Nagel, E.; Kaminski, A.; Casasayas-Barris, N.; Nortmann, L.; Luque, R.; Molaverdikhani, K.; Sedaghati, E.; Caballero, J.A.; Amado, P.J.; Bergond, G.; Czesla, S.; Hatzes, A. P.; Henning, Th.; Khalafinejad, S.; Montes, D.; Morello, G.; Quirrenbach, A.; Reiners, A.; Ribas, I.; Sánchez-López, A.; Schweitzer, A.; Stangret, M.; Yan, F.; Zapatero Osorio, M.R. (2022). "A tentative detection of He I in the atmosphere of GJ 1214 b". Astronomy & Astrophysics. 659: A55. arXiv:2201.11120. doi:10.1051/0004-6361/202142455. S2CID 246285597.
  20. ^ a b Seager, S.; Kuchner, M.; Hier-Majumder, C.A.; Militzer, B. (2007). "Mass–radius relationships for solid exoplanets". The Astrophysical Journal. 669 (2): 1279–1297. arXiv:0707.2895. Bibcode:2007ApJ...669.1279S. doi:10.1086/521346. S2CID 8369390.

External links

Media related to GJ 1214 b at Wikimedia Commons

This page was last edited on 23 May 2024, at 20:20
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