Red dwarf

A red dwarf is the smallest and coolest kind of star on the main sequence. Red dwarfs are by far the most common type of star in the Milky Way, at least in the neighborhood of the Sun, but because of their low luminosity, individual red dwarfs cannot be easily observed. From Earth, not one that fits the stricter definitions of a red dwarf is visible to the naked eye.[1] Proxima Centauri, the nearest star to the Sun, is a red dwarf, as are fifty of the sixty nearest stars. According to some estimates, red dwarfs make up three-quarters of the stars in the Milky Way.[2]

At minimum, a red dwarf has a surface temperature of ~2,075 K and a radius of ~9% that of the sun (usually notated 0.09 R); below those are brown dwarfs.[3] The minimum mass is believed to be ~7.5% that of the sun (usually notated 0.075 M). Definitions and usage of the term "red dwarf" vary on how inclusive they are on the hotter and more massive end. One definition is synonymous with stellar M dwarfs (M-type main sequence stars), yielding a maximum temperature of 3,900 K and 0.6 M. One includes all stellar M-type main-sequence and all K-type main-sequence stars (K dwarf), yielding a maximum temperature of 5,200 K and 0.8 M. Some definitions include any stellar M dwarf and part of the K dwarf classification. Other definitions are also in use (see definition). Many of the coolest, lowest mass M dwarfs are expected to be brown dwarfs, not true stars, and so those would be excluded from any definition of red dwarf.

Stellar models indicate that red dwarfs less than 0.35 M are fully convective.[4] Hence the helium produced by the thermonuclear fusion of hydrogen is constantly remixed throughout the star, avoiding helium buildup at the core, thereby prolonging the period of fusion. Low-mass red dwarfs therefore develop very slowly, maintaining a constant luminosity and spectral type for trillions of years, until their fuel is depleted. Because of the comparatively short age of the universe, no red dwarfs exist at advanced stages of evolution.

HR-diag-no-text-2

Definition

New shot of Proxima Centauri, our nearest neighbour
Proxima Centauri, the closest star to the Sun at 4.2 ly, is a red dwarf

The term "red dwarf" when used to refer to a star does not have a strict definition. One of the earliest uses of the term was in 1915, used simply to contrast "red" dwarf stars from hotter "blue" dwarf stars.[5] It became established use, although the definition remained vague.[6] In terms of which spectral types qualify as red dwarfs, different researchers picked different limits, for example K8–M5[7] or "later than K5".[8] Dwarf M star, abbreviated dM, was also used, but sometimes it also included stars of spectral type K.[9]

In modern usage, the definition of a red dwarf still varies. When explicitly defined, it typically includes late K- and early to mid-M-class stars,[10] but in many cases it is restricted just to M-class stars.[11][12] In some cases all K stars are included as red dwarfs,[13] and occasionally even earlier stars.[14]

The most recent surveys place the coolest true main-sequence stars into spectral types L2 or L3. At the same time, many objects cooler than about M6 or M7 are brown dwarfs, insufficiently massive to sustain hydrogen-1 fusion.[3] This gives a significant overlap in spectral types for red and brown dwarfs. Objects in that spectral range can be difficult to categorize.

Description and characteristics

Red dwarfs are very-low-mass stars.[15] As a result, they have relatively low pressures, a low fusion rate, and hence, a low temperature. The energy generated is the product of nuclear fusion of hydrogen into helium by way of the proton–proton (PP) chain mechanism. Hence, these stars emit little light, sometimes as little as ​110,000 that of the Sun. Even the largest red dwarfs (for example HD 179930, HIP 12961 and Lacaille 8760) have only about 10% of the Sun's luminosity.[16] In general, red dwarfs less than 0.35 M transport energy from the core to the surface by convection. Convection occurs because of opacity of the interior, which has a high density compared to the temperature. As a result, energy transfer by radiation is decreased, and instead convection is the main form of energy transport to the surface of the star. Above this mass, a red dwarf will have a region around its core where convection does not occur.[17]

Red dwarf lifetime
The predicted main-sequence lifetime of a red dwarf plotted against its mass relative to the Sun.[18]

Because low-mass red dwarfs are fully convective, helium does not accumulate at the core, and compared to larger stars such as the Sun, they can burn a larger proportion of their hydrogen before leaving the main sequence. As a result, red dwarfs have estimated lifespans far longer than the present age of the universe, and stars less than 0.8 M have not had time to leave the main sequence. The lower the mass of a red dwarf, the longer the lifespan. It is believed that the lifespan of these stars exceeds the expected 10-billion-year lifespan of our Sun by the third or fourth power of the ratio of the solar mass to their masses; thus, a 0.1 M red dwarf may continue burning for 10 trillion years.[15][19] As the proportion of hydrogen in a red dwarf is consumed, the rate of fusion declines and the core starts to contract. The gravitational energy released by this size reduction is converted into heat, which is carried throughout the star by convection.[20]

Typical characteristics[21]
Stellar
class
Mass
(M)
Radius
(R)
Luminosity
(L)
Teff
(K)
M0V 60% 62% 7.2% 3,800
M1V 49% 49% 3.5% 3,600
M2V 44% 44% 2.3% 3,400
M3V 36% 39% 1.5% 3,250
M4V 20% 26% 0.55% 3,100
M5V 14% 20% 0.22% 2,800
M6V 10% 15% 0.09% 2,600
M7V 9% 12% 0.05% 2,500
M8V 8% 11% 0.03% 2,400
M9V 7.5% 8% 0.015% 2,300

According to computer simulations, the minimum mass a red dwarf must have to eventually evolve into a red giant is 0.25 M; less massive objects, as they age, would increase their surface temperatures and luminosities becoming blue dwarfs and finally white dwarfs.[18]

The less massive the star, the longer this evolutionary process takes. It has been calculated that a 0.16 M red dwarf (approximately the mass of the nearby Barnard's Star) would stay on the main sequence for 2.5 trillion years, followed by five billion years as a blue dwarf, during which the star would have one third of the Sun's luminosity (L) and a surface temperature of 6,500–8,500 kelvins.[18]

The fact that red dwarfs and other low-mass stars still remain on the main sequence when more massive stars have moved off the main sequence allows the age of star clusters to be estimated by finding the mass at which the stars move off the main sequence. This provides a lower limit to the age of the Universe and also allows formation timescales to be placed upon the structures within the Milky Way, such as the Galactic halo and Galactic disk.

All observed red dwarfs contain "metals", which in astronomy are elements heavier than hydrogen and helium. The Big Bang model predicts that the first generation of stars should have only hydrogen, helium, and trace amounts of lithium, and hence would be of low metallicity. With their extreme lifespans, any red dwarfs that were a part of that first generation (population III stars) should still exist today. Low-metallicity red dwarfs, however, are rare. The accepted model for the chemical evolution of the universe anticipates such a scarcity of metal-poor dwarf stars because only giant stars are thought to have formed in the metal-poor environment of the early universe. As giant stars end their short lives in supernovae explosions, they spew out the heavier elements needed to form smaller stars. Therefore, dwarfs became more common as the universe aged and became enriched in metals. While the basic scarcity of ancient metal-poor red dwarfs is expected, observations have detected even fewer than predicted. The sheer difficulty of detecting objects as dim as red dwarfs was thought to account for this discrepancy, but improved detection methods have only confirmed the discrepancy.[22]

Spectral standard stars

Gliese 623
Gliese 623 is a pair of red dwarfs, with GJ 623a on the left and the fainter GJ 623b to the right of center.

The spectral standards for M-type stars have changed slightly over the years, but settled down somewhat since the early 1990s. Part of this is due to the fact that even the nearest red dwarfs are fairly faint, and the study of mid- to late-M dwarfs has progressed only in the past few decades due to evolution of astronomical techniques, from photographic plates to charged-couple devices (CCDs) to infrared-sensitive arrays.

The revised Yerkes Atlas system (Johnson & Morgan 1953)[23] listed only 2 M-type spectral standard stars: HD 147379 (M0 V) and HD 95735/Lalande 21185 (M2 V). While HD 147379 was not considered a standard by expert classifiers in later compendia of standards, Lalande 21185 is still a primary standard for M2 V. Robert Garrison[24] does not list any "anchor" standards among the red dwarfs, but Lalande 21185 has survived as a M2 V standard through many compendia.[23][25][26] The review on MK classification by Morgan & Keenan (1973) did not contain red dwarf standards. In the mid-1970s, red dwarf standard stars were published by Keenan & McNeil (1976)[27] and Boeshaar (1976),[28] but unfortunately there was little agreement among the standards. As later cooler stars were identified through the 1980s, it was clear that an overhaul of the red dwarf standards was needed. Building primarily upon the Boeshaar standards, a group at Steward Observatory (Kirkpatrick, Henry, & McCarthy 1991)[26] filled in the spectral sequence from K5 V to M9 V. It is these M-type dwarf standard stars which have largely survived as the main standards to the modern day. There have been negligible changes in the red dwarf spectral sequence since 1991. Additional red dwarf standards were compiled by Henry et al. (2002),[29] and D. Kirkpatrick has recently reviewed the classification of red dwarfs and standard stars in Gray & Corbally's 2009 monograph.[30] The M-dwarf primary spectral standards are: GJ 270 (M0 V), GJ 229A (M1 V), Lalande 21185 (M2 V), Gliese 581 (M3 V), Gliese 402 (M4 V), GJ 51 (M5 V), Wolf 359 (M6 V), Van Biesbroeck 8 (M7 V), VB 10 (M8 V), LHS 2924 (M9 V).

Planets

RedDwarfNASA-hue-shifted
Artist's conception of a red dwarf, the most common type of star in the Sun's stellar neighborhood, and in the universe. Although termed a red dwarf, the surface temperature of this star would give it an orange hue when viewed from close proximity.

Many red dwarfs are orbited by exoplanets, but large Jupiter-sized planets are comparatively rare. Doppler surveys of a wide variety of stars indicate about 1 in 6 stars with twice the mass of the Sun are orbited by one or more Jupiter-sized planets, versus 1 in 16 for Sun-like stars and only 1 in 50 for red dwarfs. On the other hand, microlensing surveys indicate that long-orbital-period Neptune-mass planets are found around one in three red dwarfs. [31] Observations with HARPS further indicate 40% of red dwarfs have a "super-Earth" class planet orbiting in the habitable zone where liquid water can exist on the surface.[32] Computer simulations of the formation of planets around low mass stars predict that Earth-sized planets are most abundant, but more than 90% of the simulated planets are at least 10% water by mass, suggesting that many Earth-sized planets orbiting red dwarf stars are covered in deep oceans. [33]

At least four and possibly up to six exoplanets were discovered orbiting within the Gliese 581 planetary system between 2005 and 2010. One planet has about the mass of Neptune, or 16 Earth masses (M). It orbits just 6 million kilometers (0.04 AU) from its star, and is estimated to have a surface temperature of 150 °C, despite the dimness of its star. In 2006, an even smaller exoplanet (only 5.5 M) was found orbiting the red dwarf OGLE-2005-BLG-390L; it lies 390 million km (2.6 AU) from the star and its surface temperature is −220 °C (53 K).

In 2007, a new, potentially habitable exoplanet, Gliese 581c, was found, orbiting Gliese 581. The minimum mass estimated by its discoverers (a team led by Stephane Udry) is 5.36 M. The discoverers estimate its radius to be 1.5 times that of Earth (R). Since then Gliese 581d, which is also potentially habitable, was discovered.

Gliese 581c and d are within the habitable zone of the host star, and are two of the most likely candidates for habitability of any exoplanets discovered so far.[34] Gliese 581g, detected September 2010,[35] has a near-circular orbit in the middle of the star's habitable zone. However, the planet's existence is contested.[36]

On 23 February 2017 NASA announced the discovery of seven Earth-sized planets orbiting the red dwarf star TRAPPIST-1 approximately 39 light-years away in the constellation Aquarius. The planets were discovered through the transit method, meaning we have mass and radius information for all of them. TRAPPIST-1e, f and g appear to be within the habitable zone and may have liquid water on the surface.[37]

Habitability

NASA-RedDwarfPlanet-ArtistConception-20130728
An artist's impression of a planet with two exomoons orbiting in the habitable zone of a red dwarf.

Planetary habitability of red dwarf systems is subject to some debate. In spite of their great numbers and long lifespans, there are several factors which may make life difficult on planets around a red dwarf. First, planets in the habitable zone of a red dwarf would be so close to the parent star that they would likely be tidally locked. This would mean that one side would be in perpetual daylight and the other in eternal night. This could create enormous temperature variations from one side of the planet to the other. Such conditions would appear to make it difficult for forms of life similar to those on Earth to evolve. And it appears there is a great problem with the atmosphere of such tidally locked planets: the perpetual night zone would be cold enough to freeze the main gases of their atmospheres, leaving the daylight zone bare and dry. On the other hand, recent theories propose that either a thick atmosphere or planetary ocean could potentially circulate heat around such a planet.[38]

Variability in stellar energy output may also have negative impacts on the development of life. Red dwarfs are often flare stars, which can emit gigantic flares, doubling their brightness in minutes. This variability may also make it difficult for life to develop and persist near a red dwarf.[39] It may be possible for a planet orbiting close to a red dwarf to keep its atmosphere even if the star flares.[40] However, more-recent research suggests that these stars may be the source of constant high-energy flares and very large magnetic fields, diminishing the possibility of life as we know it. Whether this is a peculiarity of the star under examination or a feature of the entire class remains to be determined.[41]

See also

References

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  2. ^ Exoplanets near red dwarfs suggest another Earth nearer, 6 February 2013, Jason Palmer, BBC, retrieved at 11 April 2013
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  18. ^ a b c Adams, Fred C.; Laughlin, Gregory; Graves, Genevieve J. M. (2004). "Red Dwarfs and the End of the Main Sequence" (PDF). Gravitational Collapse: From Massive Stars to Planets. Revista Mexicana de Astronomía y Astrofísica. pp. 46–49. Bibcode:2004RMxAC..22...46A.
  19. ^ Fred C. Adams & Gregory Laughlin (1996). "A Dying Universe: The Long Term Fate and Evolution of Astrophysical Objects". Reviews of Modern Physics. 69 (2): 337–372. arXiv:astro-ph/9701131. Bibcode:1997RvMP...69..337A. doi:10.1103/RevModPhys.69.337.
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  21. ^ Kaltenegger, Lisa; Traub, Wesley A. (June 2009). "Transits of Earth-like Planets". The Astrophysical Journal. 698 (1): 519–527. arXiv:0903.3371. Bibcode:2009ApJ...698..519K. doi:10.1088/0004-637X/698/1/519.
  22. ^ https://astrobites.org/2012/02/15/and-now-theres-a-problem-with-m-dwarfs-too/
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  24. ^ Garrison, Robert F. "MK Anchor Point Standards table". University of Toronto Department of Astronomy & Astrophysics.
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  26. ^ a b Kirkpatrick, J. D.; Henry, Todd J.; McCarthy, Donald W. (1991). "A standard stellar spectral sequence in the red/near-infrared - Classes K5 to M9". Astrophysical Journal Supplement Series. 77: 417. Bibcode:1991ApJS...77..417K. doi:10.1086/191611.
  27. ^ Keenan, Philip Childs; McNeil, Raymond C. (1976). "An atlas of spectra of the cooler stars: Types G, K, M, S, and C. Part 1: Introduction and tables". Columbus: Ohio State University Press. Bibcode:1976aasc.book.....K.
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  29. ^ Henry, Todd J.; Walkowicz, Lucianne M.; Barto, Todd C.; Golimowski, David A. (2002). "The Solar Neighborhood. VI. New Southern Nearby Stars Identified by Optical Spectroscopy". The Astronomical Journal. 123 (4): 2002. arXiv:astro-ph/0112496. Bibcode:2002AJ....123.2002H. doi:10.1086/339315.
  30. ^ Gray, Richard O.; Corbally, Christopher (2009). "Stellar Spectral Classification". Stellar Spectral Classification by Richard O. Gray and Christopher J. Corbally. Princeton University Press. Bibcode:2009ssc..book.....G.
  31. ^ J. A. Johnson (2011). "The Stars that Host Planets". Sky & Telescope (April): 22–27.
  32. ^ Billions of Rocky Planets in Habitable Zones Around Red Dwarfs European Southern Observatory March 28, 2012
  33. ^ Yann Alibert (2016). "Formation and composition of planets around very low mass stars". Astronomy and Astrophysics. 539 (12 October 2016): 8. arXiv:1610.03460. Bibcode:2017A&A...598L...5A. doi:10.1051/0004-6361/201629671.
  34. ^ Major Discovery: New Planet Could Harbor Water and Life By Ker Than (Staff Writer) 24 April 2007 SPACE.com
  35. ^ "Scientists find potentially habitable planet near Earth". Physorg.com. Retrieved 2013-03-26.
  36. ^ Mikko Tuomi (2011). "Bayesian re-analysis of the radial velocities of Gliese 581. Evidence in favour of only four planetary companions". Astronomy & Astrophysics. 528: L5. arXiv:1102.3314. Bibcode:2011A&A...528L...5T. doi:10.1051/0004-6361/201015995.
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  38. ^ Charles Q. Choi (9 February 2015). "Planets Orbiting Red Dwarfs May Stay Wet Enough for Life". Astrobiology. Retrieved 15 January 2017.
  39. ^ Vida, K.; Kővári, Zs.; Pál, A.; Oláh, K.; Kriskovics, L.; et al. (2017). "Frequent Flaring in the TRAPPIST-1 System - Unsuited for Life?". The Astrophysical Journal. 841: 2.
  40. ^ Alpert, Mark (1 November 2005). "Red Star Rising". Scientific American.
  41. ^ Gizmodo, "This Stormy Star Means Alien Life May Be Rarer Than We Thought", George Dvorsky, 2015, November 19

Sources

External links

Arnold Rimmer

Arnold Judas Rimmer is a fictional character in the science fiction situation comedy Red Dwarf, played by Chris Barrie. Portrayed as a snobbish and self-centered character, Rimmer is unpopular with his crewmates, and is often the target of insults and general ridicule.

After he is killed by a radiation leak during a timeskip in the series' first episode "The End" (1988) Rimmer is present for most of the series as a computer-generated hologram, indicated by the ‘H’ symbol on his forehead. From series I-V, Rimmer is intangible as a hologram and unable to interact with his environment, referred to in-universe as 'soft-light'; come the series VI episode "Legion" (1993), Rimmer is upgraded as a 'hard-light' hologram where he is now able to interact with his surroundings as well as being essentially indestructible, yet still able to feel pain. Following the character's departure in the series VII episode "Stoke Me a Clipper" (1997), Rimmer is absent from the show until series VIII, where a flesh and blood version of Rimmer is shown having been resurrected by nanobots with no memory of the hologrammatic Rimmer's experiences and only those of Rimmer prior to the radiation leak in the first episode. However, following a ten-year hiatus after series VIII, the character reappeared as a hologram in the miniseries Back to Earth (2009) onward.

It remains unclear whether this incarnation of Rimmer seen in Back to Earth and later series is the original hologram from series I-VII or a hologram of the Rimmer introduced in series VIII that was resurrected through nanotechnology. The fictional world of Red Dwarf would also allow for the possibility of Rimmer's latest incarnation being an amalgamation of the memories of both.The creators of the series acknowledge that Rimmer's surname comes from a snobby prefect with whom they attended school. They joke that only the boy's name was used, and not his personality because that would imply he had one.

Blue dwarf (red-dwarf stage)

A blue dwarf is a predicted class of star that develops from a red dwarf after it has exhausted much of its hydrogen fuel supply. Because red dwarfs fuse their hydrogen slowly and are fully convective (allowing their entire hydrogen supply to be fused, instead of merely that in the core), the Universe is currently not old enough for any blue dwarfs to have formed yet, but their future existence is predicted based on theoretical models.Stars increase in luminosity as they age, and a more luminous star needs to radiate energy more quickly to maintain equilibrium. Stars larger than red dwarfs do this by increasing their size and becoming red giants with larger surface areas. Rather than expanding, however, red dwarfs with less than 0.25 solar masses are predicted to increase their radiative rate by increasing their surface temperatures and becoming "bluer". This is because the surface layers of red dwarfs do not become significantly more opaque with increasing temperature.Blue dwarfs eventually evolve into white dwarfs once their hydrogen fuel is completely exhausted, which in turn will eventually cool to become black dwarfs.

Cat (Red Dwarf)

The Cat is a fictional character in the British science fiction sitcom Red Dwarf. He is played by Danny John-Jules. He is a descendant of Dave Lister's pregnant pet house cat Frankenstein, whose descendants evolved into a humanoid form over three million years while Lister was in stasis (suspended animation). As a character he is vain and aloof, and loves to dress in extravagant clothing. He is simply referred to as "Cat" in lieu of a real name.

Comic science fiction

Comic science fiction or comedy science fiction is a subgenre of science fiction or science fantasy that exploits the science-fiction (SF) genre's conventions for comedic effect. Comic science fiction often mocks or satirizes standard SF conventions - such as alien invasion of Earth, interstellar travel, or futuristic technology. It can also satirize and criticize present-day society.An early example was the Pete Manx series by Henry Kuttner and Arthur K. Barnes (sometimes writing together and sometimes separately, under the house pen-name of Kelvin Kent). Published in Thrilling Wonder Stories in the late 1930s and early 1940s, the series featured a time-traveling carnival barker who uses his con-man abilities to get out of trouble. Two later series cemented Kuttner's reputation as one of the most popular early writers of comic science fiction: the Gallegher series (about a drunken inventor and his narcissistic robot) and the Hogben series (about a family of mutant hillbillies). The former appeared in Astounding Science Fiction in 1943 and 1948 and was collected in hardcover as Robots Have No Tails (Gnome, 1952), and the latter appeared in Thrilling Wonder Stories in the late 1940s. In the 1950s comedy became more common in science fiction. Some of the authors contributing included: Alfred Bester, Harry Harrison, C.M. Kornbluth, Frederik Pohl, and Robert Sheckley.The Hitchhiker's Guide to the Galaxy is a comic science-fiction series written by Douglas Adams. Originally a radio comedy broadcast on BBC Radio 4 in 1978, it later morphed into other formats, including stage shows, novels, comic books, a 1981 TV series, a 1984 computer game, and 2005 feature film. A prominent series in British popular culture, The Hitchhiker's Guide to the Galaxy has become an international multi-media phenomenon; the novels are the most widely distributed, having been translated into more than 30 languages by 2005.Terry Pratchett's 1981 novel Strata also exemplifies the comic science fiction genre.Red Dwarf primarily consists of a television sitcom that aired on BBC Two between 1988 and 1999, and on Dave since 2009, gaining a cult following. As of 2018 eleven full series of the show plus one "special" miniseries have aired. The latest series, dubbed Red Dwarf XII, started airing in October 2017.

Craig Charles

Craig Joseph Charles (born 11 July 1964) is a British actor, comedian, author, poet, television presenter and DJ. He is best known for playing Dave Lister in the science fiction sitcom Red Dwarf and Lloyd Mullaney in the soap opera Coronation Street, as a funk and soul DJ on BBC Radio 6 Music and BBC Radio 2, and as the presenter of the gladiator-style game show Robot Wars from 1998 to 2004.

Charles first appeared on television as a performance poet, which led to minor presenting roles. After finding fame in Red Dwarf, he regularly featured on national television with celebrity appearances on many popular shows while he continued to host a wide variety of programmes.

Charles is also known for narrating the comedy endurance show Takeshi's Castle. From 2017, he has hosted The Gadget Show for Channel 5. His acting credits include playing inmate Eugene Buffy in the ITV drama The Governor, and leading roles in the British films Fated and Clubbing to Death. He has toured the UK extensively as a stand-up comedian.

Charles has hosted The Craig Charles Funk and Soul Show on BBC radio since 2002, and performs DJ sets at numerous clubs and festivals, nationally and internationally. In September 2015, he left Coronation Street after ten years, to film new episodes of Red Dwarf.

Dave Lister

David "Dave" Lister, commonly referred to simply as Lister, is a fictional character from the British science fiction situation comedy Red Dwarf, portrayed by Craig Charles.

Lister is characterised as a third-class technician (the lowest ranking crewman) on the mining ship Red Dwarf spending his time performing tasks under the hated supervision of Arnold Rimmer. In the series, he becomes marooned three million years into the future, but maintains a long-standing desire to return to Earth and start a farm on Fiji and open a hot dog and doughnut diner, preferably with the one true love of his life, Kristine Kochanski, a navigation officer of Red Dwarf. As a character Lister is lazy, slobbish, and unmotivated, but he frequently shows moral courage. He deeply enjoys Indian food, especially chicken vindaloo, which is a recurring theme in the series.

GJ 3379

GJ 3379 (Giclas 99-49) is the nearest star in the Orion constellation, being around 17.5 lightyears away from the Sun. The main sequence star is a red dwarf with the spectral class M3.5V. It has an apparent magnitude of 11.33 and an absolute magnitude of 12.68, therefore, the star is not visible with the naked eye. It is located in the left upper part of the Orion constellation, below Betelgeuse. Its radial velocity is +30.0 kilometers per second. According to the SIMBAD database, the star is classified as a flare star.

In the past, this star may have had a close encounter with the Solar System. Some 163,000 ± 3,000 years ago, it achieved a minimum distance of 4.30 ± 0.10 ly (1.32 ± 0.03 pc).

Gliese 1002

Gliese 1002 is a red dwarf star. It is located relatively near our Sun, at a distance of about 15.8 light years, in the constellation Cetus.

This appears to be a relatively quiescent star, and no flare activity has been detected.

Gliese 682

Gliese 682 or GJ 682 is a red dwarf. It is listed as the 49th-nearest known star to the Sun, being about 16 light years away from the Earth. Even though it is close by, it is dim with a magnitude of 10.95 and thus requires a telescope to be seen. It is located in the constellation of Scorpius, near the bright star Theta Scorpii. It has two candidate planets, one of which is in the habitable zone.

Habitability of red dwarf systems

The habitability of red dwarf systems is determined by a large number of factors from a variety of sources. Although the low stellar flux, high probability of tidal locking, small circumstellar habitable zones, and high stellar variation experienced by planets of red dwarf stars are impediments to their planetary habitability, the ubiquity and longevity of red dwarfs are positive factors. Determining how the interactions between these factors affect habitability may help to reveal the frequency of extraterrestrial life and intelligence.

Intense tidal heating caused by the proximity of planets to their host red dwarfs is a major impediment to life developing in these systems. Other tidal effects, such as the extreme temperature differences created by one side of habitable-zone planets permanently facing the star and the other perpetually turned away and lack of planetary axial tilts, reduce the probability of life around red dwarfs. Non-tidal factors, such as extreme stellar variation, spectral energy distributions shifted to the infrared relative to the Sun, and small circumstellar habitable zones due to low light output, further reduce the prospects for life in red-dwarf systems.There are, however, several effects that increase the likelihood of life on red dwarf planets. Intense cloud formation on the star-facing side of a tidally locked planet may reduce overall thermal flux and drastically reduce equilibrium temperature differences between the two sides of the planet. In addition, the sheer number of red dwarfs, which account for about 85% of at least 100 billion stars in the Milky Way, statistically increases the probability that there might exist habitable planets orbiting some of them. As of 2013, there are expected to be tens of billions of super-Earth planets in the habitable zones of red dwarf stars in the Milky Way.

Kryten

Kryten is a fictional character in the British science fiction situation comedy Red Dwarf. The name Kryten is a reference to the head butler in the J.M. Barrie play The Admirable Crichton. Originally referred to as a Series III mechanoid, he is later described as a 4000 Series, or Series 4000.In their original plan for the series, Rob Grant and Doug Naylor had specified that there would be no aliens and no robots. Following the success of the first appearance by the Kryten character, Naylor convinced Grant to bring him back.In the character's first appearance, originally only intended as a one-off, Kryten was played by actor David Ross but the popularity of the character meant that Kryten was introduced as a regular in Series III. The intention was to bring Ross back to play the role, but he was not available at the time and the position was filled by Northampton-born actor Robert Llewellyn, whose performances as Kryten from series III resulted in even greater popularity of the character. David Ross later returned to voice Talkie Toaster in the series IV episode "White Hole".

List of Red Dwarf characters

This is a list of characters from the TV sitcom Red Dwarf.

List of Red Dwarf concepts

The science fiction series, Red Dwarf, starts some time in the future, but after an accident the protagonist is trapped in stasis for 3 million years. As with many science fiction series, the programme has a few concepts specific to its own fictional universe.

List of Red Dwarf episodes

Red Dwarf is a British comedy franchise which primarily comprises twelve series (the ninth being a mini-series) of a television science fiction sitcom that aired on BBC Two between 1988 and 1993 and from 1997 to 1999, and on Dave in 2009 and 2012 and from 2016 to the present, gaining a cult following. The series was created by Rob Grant and Doug Naylor.The first six series were written by co-creators Rob Grant and Doug Naylor, while Series VII and VIII were written by Naylor with collaborations from other writers, and Series IX-XII were written by Naylor alone. Series I and II were produced by Paul Jackson Productions (with Grant Naylor Productions taking over from Series III) for BBC North, and broadcast on BBC2. Red Dwarf first aired on 15 February 1988 and ended its original run on BBC2, by then rebranded BBC Two, on 5 April 1999 after eight series, with some PBS stations in the United States airing the entire eighth series earlier on 7 March. From 2009, Grant Naylor Productions produced new episodes for UKTV, which were broadcast on the TV channel Dave.

The series follows the fortunes of Dave Lister who is stranded three million years in the future, together with the hologrammatic representation of his former bunkmate and immediate superior Arnold Rimmer; a creature known only as Cat; and the ship's computer Holly. During Series II, the crew encounter a mechanoid called Kryten, who joins them from Series III onwards. In Series VI the Red Dwarf ship has been stolen from the crew, forcing them to travel in the smaller Starbug craft for two series. In Series VII Kristine Kochanski, Lister's former love interest, joins the crew, following the departure of Rimmer. In series VIII the entire crew of the Red Dwarf ship – including a pre-accident Rimmer – are resurrected, but the Starbug crew, along with Rimmer, find themselves sentenced to two years in the ship's brig for "abusing classified information". Series IX (Red Dwarf: Back to Earth) involves Lister, Rimmer (back as a hologram), Cat, and Kryten hallucinating that they've arrived on Earth in another dimension in the early 21st century, and Series X and XI sees the same four crew members continue their adventures back on Red Dwarf, Kochanski having departed due to Lister's descent into depression and Holly offline due to water damage.

The twelfth series of Red Dwarf premiered on 12 October 2017 on Dave. As of 16 November 2017, 73 episodes of Red Dwarf have aired.

Lists of stars

The following are lists of stars. These are astronomical objects that spend some portion of their existence generating energy through thermonuclear fusion.

Red Dwarf X

Red Dwarf X is the tenth series of the British science fiction sitcom Red Dwarf, was broadcast on UK television channel Dave between 4 October and 8 November 2012. There are six episodes and it is the first full series of Red Dwarf since 1999.

Spacecraft in Red Dwarf

The British television comedy Red Dwarf prominently features many different spaceships. The three principal ships are the Red Dwarf ship itself and its two main types of shuttlecraft, known as Starbug and Blue Midget. Several other ships have appeared for one or two episodes only but are nonetheless important to Red Dwarf continuity. Several spaceships have been seen only in one episode, and a few ships have also been mentioned but not seen.

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classification
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Nucleosynthesis
Structure
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