Blanet

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A blanet is a member of a hypothetical class of exoplanets that directly orbit black holes. [1]

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Blanets are fundamentally similar to other planets; they have enough mass to be rounded by their own gravity, but are not massive enough to start thermonuclear fusion and become stars. In 2019, a team of astronomers and exoplanetologists showed that there is a safe zone around a supermassive black hole that could harbor thousands of blanets in orbit around it. [2] [3]

Etymology

The team led by Keiichi Wada of Kagoshima University in Japan has given this name to black hole planets. [4] The word is a portmanteau of black hole and planet.

Formation

Blanets are suspected to form in the accretion disk that orbits a sufficiently large black hole. [3] [5]

In fiction

In the episodes The Impossible Planet and The Satan Pit (both 2006) of television series Doctor Who, the plot of the episode takes place on the titular “impossible planet”, a barren blanet called Krop Tor orbiting a black hole called K37 Gem 5. In Interstellar (2014), two of the 3 terrestrial planets orbiting supermassive black hole Garguantua are proper blanets. The other one orbits a main-sequence star named Pantagruel.

Related Research Articles

<span class="mw-page-title-main">Supermassive black hole</span> Largest type of black hole

A supermassive black hole is the largest type of black hole, with its mass being on the order of hundreds of thousands, or millions to billions, of times the mass of the Sun (M). Black holes are a class of astronomical objects that have undergone gravitational collapse, leaving behind spheroidal regions of space from which nothing can escape, not even light. Observational evidence indicates that almost every large galaxy has a supermassive black hole at its center. For example, the Milky Way galaxy has a supermassive black hole at its center, corresponding to the radio source Sagittarius A*. Accretion of interstellar gas onto supermassive black holes is the process responsible for powering active galactic nuclei (AGNs) and quasars.

<span class="mw-page-title-main">Intermediate-mass black hole</span> Class of black holes with a mass range of 100 to 100000 solar masses

An intermediate-mass black hole (IMBH) is a class of black hole with mass in the range 102–105 solar masses: significantly more than stellar black holes but less than the 105–109 solar mass supermassive black holes. Several IMBH candidate objects have been discovered in the Milky Way galaxy and others nearby, based on indirect gas cloud velocity and accretion disk spectra observations of various evidentiary strength.

<span class="mw-page-title-main">Stellar black hole</span> Black hole formed by a collapsed star

A stellar black hole is a black hole formed by the gravitational collapse of a star. They have masses ranging from about 5 to several tens of solar masses. They are the remnants of supernova explosions, which may be observed as a type of gamma ray burst. These black holes are also referred to as collapsars.

<span class="mw-page-title-main">Sagittarius A*</span> Black hole at the center of the Milky Way

Sagittarius A*, abbreviated Sgr A*, is the supermassive black hole at the Galactic Center of the Milky Way. Viewed from Earth, it is located near the border of the constellations Sagittarius and Scorpius, about 5.6° south of the ecliptic, visually close to the Butterfly Cluster (M6) and Lambda Scorpii.

<span class="mw-page-title-main">MS 0735.6+7421</span> Galaxy cluster in the constellation Camelopardalis

MS 0735.6+7421 is a galaxy cluster located in the constellation Camelopardalis, approximately 2.6 billion light-years away. It is notable as the location of one of the largest central galactic black holes in the known universe, which has also apparently produced one of the most powerful active galactic nucleus eruptions discovered.

<span class="mw-page-title-main">NGC 4151</span> Galaxy in the constellation Canes Venatici

NGC 4151 is an intermediate spiral Seyfert galaxy with weak inner ring structure located 15.8 megaparsecs from Earth in the constellation Canes Venatici. The galaxy was first mentioned by William Herschel on March 17, 1787; it was one of the six Seyfert galaxies described in the paper which defined the term. It is one of the nearest galaxies to Earth to contain an actively growing supermassive black hole. The black hole would have a mass on the order of 2.5 million to 30 million solar masses. It was speculated that the nucleus may host a binary black hole, with about 40 million and about 10 million solar masses respectively, orbiting with a 15.8-year period. This is, however, still a matter of active debate.

<span class="mw-page-title-main">S2 (star)</span> Star orbiting close to the supermassive black hole in the center of the Milky Way

S2, also known as S0–2, is a star in the star cluster close to the supermassive black hole Sagittarius A* (Sgr A*), orbiting it with a period of 16.0518 years, a semi-major axis of about 970 au, and a pericenter distance of 17 light hours – an orbit with a period only about 30% longer than that of Jupiter around the Sun, but coming no closer than about four times the distance of Neptune from the Sun. The mass when the star first formed is estimated by the European Southern Observatory (ESO) to have been approximately 14 M. Based on its spectral type, it probably has a mass of 10 to 15 solar masses.

<span class="mw-page-title-main">Markarian 231</span> Seyfert galaxy in the constellation Ursa Major

Markarian 231 is a Type-1 Seyfert galaxy that was discovered in 1969 as part of a search of galaxies with strong ultraviolet radiation. It contains the nearest known quasar. Markarian 231 is located about 581 million light years away from Earth, in the constellation of Ursa Major.

S55 is a star that is located very close to the centre of the Milky Way, near the radio source Sagittarius A*, orbiting it with an orbital period of 12.8 years. Until 2019, when the star S62 became the new record holder, it was the star with the shortest known period orbiting the black hole at the centre of the Milky Way. This beat the record of 16 years previously set by S2. The star was identified by a University of California, Los Angeles team headed by Andrea M. Ghez. At its periapsis, its speed reaches 1.7% of the speed of light. At that point it is 246 astronomical units from the centre, while the black hole radius is only a small fraction of that size. It passed that point in 2009 and will be there again in 2022.

Manuela Campanelli is a distinguished professor of astrophysics and mathematical sciences of the Rochester Institute of Technology, and the director of its Center for Computational Relativity and Gravitation and Astrophysics and Space Sciences Institute for Research Excellence. Her work focuses on the astrophysics of merging black holes and neutron stars, which are powerful sources of gravitational waves, electromagnetic radiation and relativistic jets. This research is central to the new field of multi-messenger astronomy.

<span class="mw-page-title-main">Proxima Centauri b</span> Terrestrial planet orbiting Proxima Centauri

Proxima Centauri b, sometimes referred to as Alpha Centauri Cb, is an exoplanet orbiting within the habitable zone of the red dwarf star Proxima Centauri, which is the closest star to the Sun and part of the larger triple star system Alpha Centauri. It is about 4.2 light-years from Earth in the constellation Centaurus, making it and Proxima d, along with the currently disputed Proxima c, the closest known exoplanets to the Solar System.

<span class="mw-page-title-main">NGC 4660</span> Galaxy in the constellation Virgo

NGC 4660 is an elliptical galaxy located about 63 million light-years away in the constellation Virgo. The galaxy was discovered by astronomer William Herschel on March 15, 1784 and is a member of the Virgo Cluster.

<span class="mw-page-title-main">ESO 444-46</span> Galaxy in the constellation Centaurus

ESO 444-46 is a class E4 supergiant elliptical galaxy; the dominant and brightest member of the Abell 3558 galaxy cluster around 640 million light-years away in the constellation Centaurus. It lies within the core of the massive Shapley Supercluster, one of the closest neighboring superclusters. It is one of the largest galaxies in the local universe, and possibly contains one of the most massive black holes known. The black hole's mass is very uncertain, with estimates ranging from as low as 501 million M, to as high as 77.6 billion M.

The small planet radius gap is an observed scarcity of planets with radii between 1.5 and 2 times Earth's radius, likely due to photoevaporation-driven mass loss. A bimodality in the Kepler exoplanet population was first observed in 2011 and attributed to the absence of significant gas atmospheres on close-in, low-mass planets. This feature was noted as possibly confirming an emerging hypothesis that photoevaporation could drive atmospheric mass loss This would lead to a population of bare, rocky cores with smaller radii at small separations from their parent stars, and planets with thick hydrogen- and helium-dominated envelopes with larger radii at larger separations. The bimodality in the distribution was confirmed with higher-precision data in the California-Kepler Survey in 2017, which was shown to match the predictions of the photoevaporative mass-loss hypothesis later that year.

S62 is a star in the cluster surrounding Sagittarius A*, the supermassive black hole in the center of the Milky Way. S62 orbits Sgr A* in 9.9 years, the shortest known orbital period of any star around Sgr A*. The previous record holder, S55 has a 12.8-year period.

In astronomy, quenching is a process in which a galaxy loses cold gas, thus strongly suppressing star formation, because stars are formed from Nebulae and Nebulae are formed from accumulated Interstellar gas in the Interstellar medium (ISM). Evidence suggests that active supermassive black holes drive the process. One common evolutionary path on the galaxy color–magnitude diagram may start with a blue spiral galaxy with much star formation. The black hole at its center may start growing rapidly, and somehow start quenching the galaxy, which relatively quickly transitions through the "green valley", ending up more red.

<span class="mw-page-title-main">Sagittarius A* cluster</span> Star cluster orbiting Sagittarius A*

The Sagittarius A* cluster is the cluster of stars in close orbit around Sagittarius A*, the supermassive black hole at the center of the Milky Way. The individual stars are often listed as "S-stars", but their names and IDs are not formalized, and stars can have different numbers in different catalogues.

CD-44 170, also known as Gliese 27.1, Gliese 9018 and HIP 3143, is an M-type main-sequence star. Its surface temperature is 3,604 K ±72 K. The star's concentration of heavy elements is similar to that of the Sun.

References

  1. Letzter, R. (6 August 2020). "Thousands of Earthlike 'blanets' might circle the Milky Way's central black hole". Space.com. Retrieved 2020-08-08.
  2. Wada, K.; Tsukamoto, Y.; Kokubo, E. (26 November 2019). "Planet Formation around Supermassive Black Holes in the Active Galactic Nuclei". The Astrophysical Journal. 886 (2): 107. arXiv: 1909.06748 . Bibcode:2019ApJ...886..107W. doi: 10.3847/1538-4357/ab4cf0 .
  3. 1 2 Wada, K.; Tsukamoto, Y.; Kokubo, E. (2021). "Formation of "Blanets" from Dust Grains around the Supermassive Black Holes in Galaxies". The Astrophysical Journal. 909 (1): 96. arXiv: 2007.15198 . Bibcode:2021ApJ...909...96W. doi: 10.3847/1538-4357/abd40a . S2CID   220870610.
  4. Starr, M. (3 August 2020). "We Have Ploonets. We Have Moonmoons. Now Hold Onto Your Hats For... Blanets". ScienceAlert. Retrieved 2020-08-08.
  5. Greene, T. (2020-08-04). "Scientists: What if black holes had a safe zone where little planets could live? Let's call them 'blanets'". The Next Web. Retrieved 2020-08-08.