כוכב האפשרויות הבלתי מוגבלות – ראל דארק וכוכב הלכת פלוטו

ספינת החלל ה"ניו הוריזונס" עזבה בהצלחה את פלוטו בדרכה אל קצות מערכת השמש ומעבר להם.במסע היא גילתה שפלוטו הוא קצת יותר גדול ממה שחשבו ,אבל עדיין כוכב לכת גמדי.
ושיש שם הרבה מאוד שלג.
ראו כאן

http://www.theverge.com/2015/7/14/8960785/nasa-new-horizons-pluto-flyby-probe-success

פרט עלילתי מעניין ב"קיסר הכוכב הסגול" שאמנם היה רק בגדר הומור כשהספר נכתב ב-1968 . אבל היום יש בו עניין מיוחד:
""..בעולמם דובר הצרפתית של אנשי ארקטורוס ,הדת המקובלת היא הדת המוסלמית.מוחמד שלהם נקרא בשם "אחמד דווקא" ,והוא חי ופעל ומת בעיר מכה שבכוכב ארקטורוס 2".

( מתוך "קיסר הכוכב הסגול ")

זוהי מן הסתם אחת הפעמים הראשונות בספרות המדע הבדיוני שבה מופיעה אימפריה גלקטית שהיא שייכת לדת כמו מוסלמית.ה"איסלאם" של האימפריה הארקטורית הוא יצירה מקורית של בני אימפריה זאת .אבל גם שם הם עולים לרגל ל"מכה " שבארקטורוס 2 וגם שם העולים לרגל לובשים מצנפות כמו העולים לרגל המוסלמים בכדור הארץ.
.אם כי בכך כמובן קדם ל"קיסר הכוכב הסגול " הספר "חולית " של פרנק הרברט בשלוש שנים.
לחולית אגב מלאו בימים אלו 50 שנה.

עוד סיפור מסוף שנות השישים על פלוטו שבמקור פורסם ממש במקביל לספר על "ראל דארק" הוא "פלאש גורדון במשלחת לכוכב פלוטו"
סיפור בסדרת הקומיקס המפורסמת על איש חלל שמתאר ניסיון של כדור הארץ להקים מושבה על הכוכב המרוחק.
אך פלוטו מתגלה כמסוכן יותר ממה שכולם ציפו והסיפור הוא אחד מסיפורי פלאש גורדון המועטים שאינו מסתיים בנצחונו של איש החלל..
להביס את כוחות הטבע והחיים שעל פלוטו מתגלה כמשימה בלתי אפשרית..
ראו ב"פלאש גורדון במשלחת אל כוכב פלוטו "ב
יקום תרבות :
https://www.yekum.org/2015/07/%D7%A4%D7%9C%D7%90%D7%A9-%D7%92%D7%95%D7%A8%D7%93%D7%95%D7%9F-%D7%91%D7%9E%D7%A9%D7%9C%D7%97%D7%AA-%D7%9C%D7%9B%D7%95%D7%9B%D7%91-%D7%94%D7%9C%D7%9B%D7%AA-%D7%A4%D7%9C%D7%95%D7%98%D7%95/

ספור יפה משנות השמונים של סופר המדע הבדיוני המפורסם רוברט סילברברג על גילוי חיים בפלוטו בידי המשלחת האנושית הראשונה שמבקרת שם:
SUNRISE ON PLUTO

https://books.google.co.il/books?id=x18JhKFpL7wC&pg=PT95&lpg=PT95&dq=silverberg+sunrise+on+pluto&source=bl&ots=YPVbAJwfRs&sig=fJqqa85RuO9RdvsmwbfhmMzGnjQ&hl=iw&sa=X&ved=0CDAQ6AEwA2oVChMIo72oxPr3xgIVhl4UCh3fIQR9#v=onepage&q=silverberg%20sunrise%20on%20pluto&f=false

והנה קטעם מספר ילדים מרתק שאותו כתב סילברברג ב-1968 ותיאר כיצד בשנת 1992 ילד שכתב עבודה מרשימה במיוחד לבית הספר על האפשרות של גילוי חיים בכוכב הלכת פלוטו יוצא למסע אמיתי לכוכב לכת זה ומגלה שם עם צוות מדענים,שעל פלוטו אכן יש חיים…
העתיד שאותו תיאר סילברברג לא התגשם לצערנו .עדיין לא אבל אני עדיין נהנה לקרוא את הסיפור .גם כמבוגר
World's Fair 1992

https://books.google.co.il/books?id=wf4gchTq7WgC&pg=PP1&lpg=PP1&dq=silverberg+World's+Fair+1992&source=bl&ots=0CJGZePlv7&sig=83SO73-VHMT-y4VCW-TTpv_JCos&hl=iw&sa=X&ved=0CEYQ6AEwCmoVChMI5PPcxPj3xgIVgj0UCh0jwQOn#v=onepage&q=silverberg%20World's%20Fair%201992&f=false

והנה מאמר מעניין של סילברברג שהופיע במגזין המדע הבדיוני של אייזק אסימוב ב-2002 בשאלה המציקה האם פלוטו הוא כוכב לכת או רק כוכב לכת ננסי ?:
סילברברג מחליט שזהו כוכב לכת לכל דבר ובראש ובראשונה מאחר שהתגלה בתקופת חייו .
Reflections: Let's Hear It for Pluto by Robert Silverberg
http://www.asimovs.com/_issue_0205/Ref.html

So now they’re trying to tell us that Pluto isn’t really a planet. I don’t like that. I’ve always had a soft spot in my heart for Pluto, and after a lifetime of thinking of it as some sort of Ultima Thule of our solar system I’m not willing to have it demoted. I remember all too fondly all those pulp-magazine space operas of my boyhood that told tales of the Nine Planets League and the like. Pluto may be a funny little place, but its delegate will always belong at the council-table of the Nine Planets League in my mind, and it’s simply too late for me to begin slipping phrases like "the outermost of the solar system’s eight planets" into my work.

The sinister forces behind the downgrading of Pluto are based in that bastion of scientific subversion, New York’s American Museum of Natural History. The museum’s Hayden Planetarium has built a lovely new adjunct, the Rose Center for Earth and Space, as a replacement for the beloved planetarium building of my Pleistocene childhood. The new building opened in February 2000–and it was not until the following year, apparently, that anyone noticed that the Rose had deleted Pluto from the roster of planets.

Oh, it doesn’t say so in that many words. You will not find any placards on the wall that declare, "This is Pluto, formerly considered a planet, but now deemed by us to be something much less significant." But you won’t see any sign indicating that the Rose believes that there ought to be representatives from Pluto at the meetings of the Nine Planets League, either. The planetarium’s exhibits refer to a group of four planets called the "terrestrial planets"–Mercury, Venus, Earth, and Mars–and a second group of "outer planets," the gas giants Jupiter, Saturn, Uranus, and Neptune. That adds up to eight. The planetarium’s diagram of the solar system shows eight orbits, not nine, around the Sun.

Where’s Pluto? Pluto shows up in a sort of footnote: "Beyond the outer planets is the Kuiper Belt of comets, a disk of small, icy worlds including Pluto." Not one of our planets any more. Cast out from the League. Simply a small, icy hunk of rock somewhere out there at the edge of interstellar space.

This seems to be a unilateral decision on the part of the Hayden Planetarium. The International Astronomical Union, the Paris-based professional society of astronomers, still lists Pluto among the worlds of the solar system. When a proposal came up in 1999 to designate Pluto as a "minor planet" which, so to speak, had one orbital foot in the solar system and one in the Kuiper Belt, it was firmly voted down, and the Astronomical Union released a statement saying, "This process was explicitly designed to not change Pluto’s status as a planet." (Was the split infinitive the work of a translator, I wonder?)

But the new Rose Center gives Pluto the downgrade anyway. Dr. Neil de Grasse Tyson, the director of the Hayden Planetarium, notes that "We’re not that confrontational about it. You actually have to pay attention to make note of this."

Well, attention is being paid, now. From Dr. S. Alan Stern, the director of the Southwest Research Institute’s space studies department in Boulder, Colorado, comes the blunt comment, "It’s absurd. The astronomical community has settled this issue. There’s no issue." Dr. Richard B. Binzel, professor of planetary science at MIT, says, "They went too far in demoting Pluto, way beyond what the mainstream astronomers think." And from Dr. Laura Danly of the Denver Museum of Nature and Science, which is constructing a new space science center due to open in 2003, comes the word, "We’re sticking with Pluto. We like Pluto as a planet."

Dr. Tyson of the Hayden Planetarium offers by way of defense the precedent of the ex-planet Ceres, discovered in 1801 orbiting the sun between Mars and Jupiter. Ceres, though only about five hundred miles in diameter, met the definition of a planet–an astronomical body traveling in a roughly circular orbit around the Sun–and, since it neatly filled the space in the solar system where by all logic a planet should have been, it was duly enrolled in the roster of worlds. Three months later, though, a second small planet, Pallas, was noticed in the same general region of the sky, and two more, Juno and Vesta, within the next six years. Before long it became apparent that the territory between Mars and Jupiter was occupied by dozens, hundreds, eventually thousands of little worlds, evidently the debris of some vast planetary explosion. Having to look upon all of them as planets would make for an unwieldy situation; and so they were termed "asteroids" instead, and Ceres, so briefly a planet, was included among the group.

Pluto is bigger than Ceres–its diameter is fourteen hundred miles–but that still leaves it a veritable shrimp among planets. Its mass is only about a tenth of Earth’s, and Earth is far from the biggest of the planets. There are a good many moons in the solar system, including our own, that are bigger than Pluto. Because Pluto is so small, some astronomers have theorized that it once was a moon of the much larger planet Neptune that somehow escaped and took up independent orbit around the Sun. This argument is supported by Pluto’s long and very strange period of daily rotation. Pluto’s "day" is 6.39 of our days long, whereas all the other planets rotate on their axes once every twenty-five hours or less. Pluto’s slow rate of rotation has more in common with that of the moons of the outer worlds than it does with that of the other planets: Neptune’s Triton rotates once every five days twenty-one hours, Uranus’s Titania every eight days sixteen hours, and so on.

Even if Pluto is a runaway moon, though, its orbit is unquestionably centered on the Sun, and that, to me and a lot of other people, qualifies it as a planet. Not so, says Dr. Tyson of the Hayden. It is, he says, too trifling an object to be dignified with the title of planet. He regards it as analogous to Ceres, that is, a very minor world that belongs to some other classification, and prefers to cast it into the outer darkness of the Kuiper Belt. This, he asserts, actually upgrades its status "from puniest planet to king of the Kuiper Belt," that distant zone of cosmic debris, containing hundreds of small rocky objects, including about seventy–known as the Plutinos–that move in orbits similar to Pluto’s. "I think it’s happier that way," he says. "I’m convinced our approach will prevail. It makes too much scientific sense and too much pedagogical sense."

No. I say it’s still a planet, and I sneer in the face of the Hayden Planetarium.

One reason I am so fond of Pluto, other than that its enigmatic presence among the family of worlds is far more interesting than if it were a mere part of a lot of interstellar spaghetti on the fringes of our solar system, is that it is the only planet that was discovered in my own lifetime, give or take a few years. Mercury, Venus, Mars, Jupiter, and Saturn have been known since ancient times. Uranus, the first planet whose discoverer is known, was spotted by the British astronomer William Herschel while scanning the heavens on March 13, 1781. Certain irregularities in its orbit led scientists to suspect the gravitational influence of still another planet further out; in 1845 the French astronomer Urbain Leverrier calculated the probable mass and orbit of that hypothetical planet, and, using Leverrier’s figures, Johann Galle of the Berlin University Observatory located it on September 23, 1846. It was given the name of Neptune.

Big as it was, Neptune did not have sufficient mass by itself to account for the irregularities in Ura-nus’s orbit, and its own orbit was somewhat irregular too. So it was likely that one more planet must exist out there, and from the late nineteenth century onward many astronomers carried out extensive searches for it, without any success. It was not until 1930 that Pluto was found. (I myself came along somewhat later in the 1930s, but I have always regarded Pluto as my contemporary.)

A twenty-three-year-old astrono-mer named Clyde Tombaugh, on the staff of the Lowell Observatory in Arizona, was the discoverer of the ninth planet. He used a device called a blink comparator, which allows two astronomical photographs to be placed side by side and viewed through a single eyepiece. First one picture is lit, then the other; the mind retains the image of one during the split-second jump to the other, and so any object that has moved between the taking of one photo and the next will appear to leap back and forth with each blink of the lighting.

On the afternoon of February 18, 1930, while blinking photographs that he had taken on January 23 and 29, Tombaugh suddenly noticed a faint object "popping in and out of the background. . . . ‘That’s it!’ I exclaimed to myself." And it was. On March 13, 1930–the 149th anniversary of Herschel’s discovery of Ura-nus–the Lowell announced the finding of "an object beyond Neptune" that was apparently a planet. An eleven-year-old British girl offered a name for the newfound world: Pluto, for the Roman god of the dead, brother to Jupiter and Neptune and the lord of a realm of eternal darkness.

A dark realm indeed, billions of miles out from the center of the solar system. Pluto travels on an orbit so vast that it takes 248.5 years to make a single revolution around the Sun. It is a tiny world, with a mass just .0024 that of Earth, and its orbit is a weirdly eccentric one that brings it, from time to time, inside the orbit of its neighbor world Neptune.

Astronomers think that little Pluto probably has a solid core of rock constituting about a quarter of its mass, with a thick blanket of frozen water above it, and perhaps a thin shell of frozen methane and ammonia covering the surface. The temperature on Pluto is, of course, pretty chilly–very likely dropping in the Plutonian winter to the vicinity of -200 degrees C. (roughly -430 degrees F.), which is just 30 or 40 degrees above absolute zero. (I once wrote a story proposing that Pluto was inhabited by creatures that had superconductive liquid helium II flowing in their veins–a nifty idea, but not one that I consider particularly probable. Larry Niven had a different take on the same theme a long while back, in "Wait it Out.")

An interesting place, yes. And a planet that marks, for me and for a lot of other people, the boundary between our solar system and the rest of the universe. We may yet find a tenth planet, dark and huge, orbiting the Sun somewhere beyond Pluto, and that surely would rob Pluto of its status as the outermost of our worlds. But to take that status away now, removing it from planetary rank and dumping it into the chaotic miscellany that is the Kuiper Belt–oh, no, no, no, Hayden Planetarium. Say it ain’t so.

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"Reflections: Let's Hear It for Pluto " by Robert Silverberg , copyright © 2002 by Agberg and permission of the author.
http://www.asimovs.com/_issue_0205/Ref.html

So now they’re trying to tell us that Pluto isn’t really a planet. I don’t like that. I’ve always had a soft spot in my heart for Pluto, and after a lifetime of thinking of it as some sort of Ultima Thule of our solar system I’m not willing to have it demoted. I remember all too fondly all those pulp-magazine space operas of my boyhood that told tales of the Nine Planets League and the like. Pluto may be a funny little place, but its delegate will always belong at the council-table of the Nine Planets League in my mind, and it’s simply too late for me to begin slipping phrases like "the outermost of the solar system’s eight planets" into my work.

The sinister forces behind the downgrading of Pluto are based in that bastion of scientific subversion, New York’s American Museum of Natural History. The museum’s Hayden Planetarium has built a lovely new adjunct, the Rose Center for Earth and Space, as a replacement for the beloved planetarium building of my Pleistocene childhood. The new building opened in February 2000–and it was not until the following year, apparently, that anyone noticed that the Rose had deleted Pluto from the roster of planets.

Oh, it doesn’t say so in that many words. You will not find any placards on the wall that declare, "This is Pluto, formerly considered a planet, but now deemed by us to be something much less significant." But you won’t see any sign indicating that the Rose believes that there ought to be representatives from Pluto at the meetings of the Nine Planets League, either. The planetarium’s exhibits refer to a group of four planets called the "terrestrial planets"–Mercury, Venus, Earth, and Mars–and a second group of "outer planets," the gas giants Jupiter, Saturn, Uranus, and Neptune. That adds up to eight. The planetarium’s diagram of the solar system shows eight orbits, not nine, around the Sun.

Where’s Pluto? Pluto shows up in a sort of footnote: "Beyond the outer planets is the Kuiper Belt of comets, a disk of small, icy worlds including Pluto." Not one of our planets any more. Cast out from the League. Simply a small, icy hunk of rock somewhere out there at the edge of interstellar space.

This seems to be a unilateral decision on the part of the Hayden Planetarium. The International Astronomical Union, the Paris-based professional society of astronomers, still lists Pluto among the worlds of the solar system. When a proposal came up in 1999 to designate Pluto as a "minor planet" which, so to speak, had one orbital foot in the solar system and one in the Kuiper Belt, it was firmly voted down, and the Astronomical Union released a statement saying, "This process was explicitly designed to not change Pluto’s status as a planet." (Was the split infinitive the work of a translator, I wonder?)

But the new Rose Center gives Pluto the downgrade anyway. Dr. Neil de Grasse Tyson, the director of the Hayden Planetarium, notes that "We’re not that confrontational about it. You actually have to pay attention to make note of this."

Well, attention is being paid, now. From Dr. S. Alan Stern, the director of the Southwest Research Institute’s space studies department in Boulder, Colorado, comes the blunt comment, "It’s absurd. The astronomical community has settled this issue. There’s no issue." Dr. Richard B. Binzel, professor of planetary science at MIT, says, "They went too far in demoting Pluto, way beyond what the mainstream astronomers think." And from Dr. Laura Danly of the Denver Museum of Nature and Science, which is constructing a new space science center due to open in 2003, comes the word, "We’re sticking with Pluto. We like Pluto as a planet."

Dr. Tyson of the Hayden Planetarium offers by way of defense the precedent of the ex-planet Ceres, discovered in 1801 orbiting the sun between Mars and Jupiter. Ceres, though only about five hundred miles in diameter, met the definition of a planet–an astronomical body traveling in a roughly circular orbit around the Sun–and, since it neatly filled the space in the solar system where by all logic a planet should have been, it was duly enrolled in the roster of worlds. Three months later, though, a second small planet, Pallas, was noticed in the same general region of the sky, and two more, Juno and Vesta, within the next six years. Before long it became apparent that the territory between Mars and Jupiter was occupied by dozens, hundreds, eventually thousands of little worlds, evidently the debris of some vast planetary explosion. Having to look upon all of them as planets would make for an unwieldy situation; and so they were termed "asteroids" instead, and Ceres, so briefly a planet, was included among the group.

Pluto is bigger than Ceres–its diameter is fourteen hundred miles–but that still leaves it a veritable shrimp among planets. Its mass is only about a tenth of Earth’s, and Earth is far from the biggest of the planets. There are a good many moons in the solar system, including our own, that are bigger than Pluto. Because Pluto is so small, some astronomers have theorized that it once was a moon of the much larger planet Neptune that somehow escaped and took up independent orbit around the Sun. This argument is supported by Pluto’s long and very strange period of daily rotation. Pluto’s "day" is 6.39 of our days long, whereas all the other planets rotate on their axes once every twenty-five hours or less. Pluto’s slow rate of rotation has more in common with that of the moons of the outer worlds than it does with that of the other planets: Neptune’s Triton rotates once every five days twenty-one hours, Uranus’s Titania every eight days sixteen hours, and so on.

Even if Pluto is a runaway moon, though, its orbit is unquestionably centered on the Sun, and that, to me and a lot of other people, qualifies it as a planet. Not so, says Dr. Tyson of the Hayden. It is, he says, too trifling an object to be dignified with the title of planet. He regards it as analogous to Ceres, that is, a very minor world that belongs to some other classification, and prefers to cast it into the outer darkness of the Kuiper Belt. This, he asserts, actually upgrades its status "from puniest planet to king of the Kuiper Belt," that distant zone of cosmic debris, containing hundreds of small rocky objects, including about seventy–known as the Plutinos–that move in orbits similar to Pluto’s. "I think it’s happier that way," he says. "I’m convinced our approach will prevail. It makes too much scientific sense and too much pedagogical sense."

No. I say it’s still a planet, and I sneer in the face of the Hayden Planetarium.

One reason I am so fond of Pluto, other than that its enigmatic presence among the family of worlds is far more interesting than if it were a mere part of a lot of interstellar spaghetti on the fringes of our solar system, is that it is the only planet that was discovered in my own lifetime, give or take a few years. Mercury, Venus, Mars, Jupiter, and Saturn have been known since ancient times. Uranus, the first planet whose discoverer is known, was spotted by the British astronomer William Herschel while scanning the heavens on March 13, 1781. Certain irregularities in its orbit led scientists to suspect the gravitational influence of still another planet further out; in 1845 the French astronomer Urbain Leverrier calculated the probable mass and orbit of that hypothetical planet, and, using Leverrier’s figures, Johann Galle of the Berlin University Observatory located it on September 23, 1846. It was given the name of Neptune.

Big as it was, Neptune did not have sufficient mass by itself to account for the irregularities in Ura-nus’s orbit, and its own orbit was somewhat irregular too. So it was likely that one more planet must exist out there, and from the late nineteenth century onward many astronomers carried out extensive searches for it, without any success. It was not until 1930 that Pluto was found. (I myself came along somewhat later in the 1930s, but I have always regarded Pluto as my contemporary.)

A twenty-three-year-old astrono-mer named Clyde Tombaugh, on the staff of the Lowell Observatory in Arizona, was the discoverer of the ninth planet. He used a device called a blink comparator, which allows two astronomical photographs to be placed side by side and viewed through a single eyepiece. First one picture is lit, then the other; the mind retains the image of one during the split-second jump to the other, and so any object that has moved between the taking of one photo and the next will appear to leap back and forth with each blink of the lighting.

On the afternoon of February 18, 1930, while blinking photographs that he had taken on January 23 and 29, Tombaugh suddenly noticed a faint object "popping in and out of the background. . . . ‘That’s it!’ I exclaimed to myself." And it was. On March 13, 1930–the 149th anniversary of Herschel’s discovery of Ura-nus–the Lowell announced the finding of "an object beyond Neptune" that was apparently a planet. An eleven-year-old British girl offered a name for the newfound world: Pluto, for the Roman god of the dead, brother to Jupiter and Neptune and the lord of a realm of eternal darkness.

A dark realm indeed, billions of miles out from the center of the solar system. Pluto travels on an orbit so vast that it takes 248.5 years to make a single revolution around the Sun. It is a tiny world, with a mass just .0024 that of Earth, and its orbit is a weirdly eccentric one that brings it, from time to time, inside the orbit of its neighbor world Neptune.

Astronomers think that little Pluto probably has a solid core of rock constituting about a quarter of its mass, with a thick blanket of frozen water above it, and perhaps a thin shell of frozen methane and ammonia covering the surface. The temperature on Pluto is, of course, pretty chilly–very likely dropping in the Plutonian winter to the vicinity of -200 degrees C. (roughly -430 degrees F.), which is just 30 or 40 degrees above absolute zero. (I once wrote a story proposing that Pluto was inhabited by creatures that had superconductive liquid helium II flowing in their veins–a nifty idea, but not one that I consider particularly probable. Larry Niven had a different take on the same theme a long while back, in "Wait it Out.")

An interesting place, yes. And a planet that marks, for me and for a lot of other people, the boundary between our solar system and the rest of the universe. We may yet find a tenth planet, dark and huge, orbiting the Sun somewhere beyond Pluto, and that surely would rob Pluto of its status as the outermost of our worlds. But to take that status away now, removing it from planetary rank and dumping it into the chaotic miscellany that is the Kuiper Belt–oh, no, no, no, Hayden Planetarium. Say it ain’t so.

"Reflections: Let's Hear It for Pluto " by Robert Silverberg , copyright © 2002 by Agberg and permission of the author.

בסיפור "Goose Summer של סופר המדע הבדיוני הידוע סטפן בקסטר מתגלים על פלוטו צורות חיים מוזרות שהתפשטו אליו מהירח שלו צ'רון על ידי מעין קורי עכביש ענקיים " ושמתפשטות כשפלוטו נמצא קרוב אל השמש ואז יש עליו יחסית כמות גדולה של אור.
הנה הסיפור :

Goose Summer
http://www.lightspeedmagazine.com/fiction/gossamer

דיווחים מדהימים התגלו לאחרונה שהתגלה כוכב לכת במערכת פרוקסימה סנטאורי ערכת השדמש הקרובה ביותר אלינו ( רק 4 שנות אור ) ש"ייתכן" שיכולים להתקיים שם לחיים.
"קיסר הכוכב הסגול "מתאר מסע לפרוקסימה סנטאורי לכוכב לכת נושא חיים שם.ואלו מתגלים כדינוזאורים ענקיים וגם גזע אינטליגנטי.

Potentially Habitable Planet Found Orbiting Star Closest to Sun
והנה הידיעה :http://news.nationalgeographic.com/2016/08/earth-mass-planet-proxima-centauri-habitable-space-science/

The alien world is warmed by the light of Proxima Centauri, a red dwarf star that sits just 4.24 light-years away.
By Nadia Drake
PUBLISHED AUGUST 24, 2016
Small planets sometimes generate gargantuan buzz. For weeks, eager media outlets have been reporting rumors that a potentially habitable planet is circling the star closest to our sun, a red dwarf called Proxima Centauri.

Now, finally, astronomers are ready to unveil this alien world.

Observations made with a telescope in Chile have indeed revealed a planet about as massive as Earth that orbits Proxima Centauri, which is a cosmic walk to the corner store at just 4.24 light-years away. And if conditions are right, the planet is in an orbit that’s warm enough for liquid water to survive on its surface.

Illuminated by a pale reddish light, the world orbits the smallest star in a triple system known as Alpha Centauri, which shines in the southern constellation Centaurus. (Find out how to see Alpha Centauri and other objects in the southern sky.)

The Alpha Centauri system, long a wonderland for science fiction authors, is often considered a destination for humanity’s first leap into interstellar space—as well as a potential haven for future civilizations fleeing the inevitable destruction of Earth as we know it.

“A habitable, rocky planet around Proxima would be the most natural location to where our civilization could aspire to move after the sun will die, five billion years from now,” says Avi Loeb of the Harvard-Smithsonian Center for Astrophysics and an adviser to the Breakthrough Starshot project.

Even before today’s announcement, Breakthrough Starshot had announced its plan to send tiny spacecraft to the Alpha Centauri system later this century. But don’t expect any postcards from the new planet anytime soon: It will take more than 20 years for a spacecraft traveling at a monstrous 20 percent of the speed of light to reach Proxima Centauri, and another 4.24 years for any data to arrive back on Earth.

Animation: Travel to a Newly Discovered Planet In this silent animation, travel four light-years to the closest star outside our solar system, Proxima Centauri, and its orbiting planet, Proxima b. Credit: ESO/L. Calçada/Nick Risinger (skysurvey.org)
Exoplanet fans may recall that this isn’t the first time a world has been reported in the Alpha Centauri system. In 2012, astronomers announced that a potential Earth-mass planet orbited the sunlike star Alpha Centauri B—another discovery that was prematurely revealed by impatient publications. But that planet vanished when follow-up observations failed to confirm its existence and instead suggested that noisy data and the star’s own activity were masquerading as a planet.

With this new observation, the next star system over again joins the thousands of faraway stars known to host planetary residents—and it looks like it’ll take a rather skilled cosmic magician to make this world disappear.

Based on data collected over 54 nights, the signature of the planet is strong, popping out even when the data are inspected by eye and not a computer algorithm.

“It’s pretty unambiguous,” says Yale University’s Greg Laughlin. “This isn’t a case where you kind of have to resort to black arts to pull the signal out.”

Finding Proxima
Known as Proxima b, the planet was discovered by a team of scientists working on the Pale Red Dot project—a twist on Carl Sagan’s description of Earth, which looks like a pale blue dot from afar.

Scientifically, the discovery is not exactly a surprise. The last decade of exoplanet discoveries has revealed that red dwarf stars like Proxima are very likely to host planets, and a large fraction of those worlds should be somewhat like this new one: small, rocky, and warm enough for water to flow on its surface.

While earlier searches for planets around Proxima had officially turned up empty, there were tantalizing signs that at least one planet could be there, waiting to be detected with a more comprehensive search.

As a planet goes about its orbital business, its gravity tugs ever so slightly on its star, causing the star to wobble. Larger planets naturally produce bigger wobbles. Smaller, Earth-mass planets tug almost imperceptibly on their stars, requiring long observing campaigns with extremely sensitive instruments to detect.

Observations taken sporadically between 2000 and 2014 had hinted at the presence of a planet in an 11-day orbit around Proxima, but its shaky signature wasn’t clear enough to be anything more than a tease. Determined to see if a planetary hand really was the source of Proxima’s wobbles, the Pale Red Dot team aimed Earth’s sharpest wobbly-star watcher, the High Accuracy Radial velocity Planet Searcher (HARPS), at the red dwarf earlier this year.

Meet the New Planet Next DoorSince 1988, scientists have found more than 3,000 planets orbiting stars other than our sun. The newest addition is Proxima Centauri b, a small, rocky world just 4.24 light-years away, which may be in a habitable orbit.Going the DistancePREV.1/5NEXTThe newly discovered planet orbits Proxima Centauri, the star closest to our sun. The world is now the nearest one known that scientists believe is about as massive as Earth and possibly friendly to life. Previously, the closest potentially habitable planet was Wolf 1061c.MONICA SERRANO AND DANIELA SANTAMARINA, NG STAFF
SOURCES: GUILLEM ANGLADA-ESCUDE AND OTHERS, NATURE (2016); GREGORY LAUGHLIN, YALE UNIVERSITY.
From its location at the European Southern Observatory's site in La Silla, Chile, HARPS measured the motion of the star night after night, and scientists eagerly waited as one data point after another came in. The team almost immediately noticed the same 11-day signal in the data. About 20 nights in, Guillem Anglada-Escudé began to admit that maybe they had a detection—and after another 10 evenings, he started drafting a paper describing the finding, which is published August 24 in Nature.

“We tried to remain as skeptical as possible, because we were collecting one data point per night,” says Anglada-Escudé, of Queen Mary University of London. “We didn’t want to claim something like this and then have to pull it a couple of months later.”

The data suggest Proxima b is 1.3 times Earth's mass and takes 11.2 days to orbit its star, putting it in the region where the star’s feeble light is warm enough to keep any surface water flowing.

Planet or Star?
With the vanishing Alpha Centauri B planet on their minds—as well as other high-profile planet discoveries that later disappeared—the Pale Red Dot team very carefully tried to confirm their find. First, the team went back and reprocessed the observations from earlier this century. When run through a newer, better pipeline, that tantalizing original signal got stronger.

Next, and very importantly, the team needed to rule out the star itself as a source of the 11.2-day signal. That’s not easy, considering the cantankerous nature of Proxima Centauri, which periodically erupts in flares that blast radiation into space.

“There are a few diagnostic tests which can demonstrate that what you think is a planet is really due to stellar activity,” says Lauren Weiss of the University of California, Berkeley. “The authors did all of those, and they found that the planet hypothesis is holding up for now.”

One of the tests the Pale Red Dot team performed was simply observing the star, reasoning that any regular, deceptive stellar activity should be visible from Earth. But observations with multiple telescopes on the ground didn’t reveal any stellar activity that matched the 11-day period.

“There’s nothing that looks correlated in any way,” says Yale University’s Debra Fischer. She thinks the Proxima planet is a credible result, though not quite ironclad yet.

There are even signs that Proxima b could have siblings: One additional signature in the data could be the work of a super-Earth on a 200-day orbit, Anglada-Escudé says, but the team will need to do more work to determine the signal’s origin.

When Worlds Align
In addition to ruling out false alarms, one of the most popular ways of validating a planet is to find it using a different detection method. Already, scientists are aiming Canada’s MOST space telescope at Proxima and looking to see if its planet transits, or crosses the face of its star as seen from Earth.

“If it does transit, that would be an extraordinary home run. I don’t think it gets any better than a transiting, Earth-size planet in the habitable zone orbiting the nearest star—unless there’s a radio broadcast emanating from it,” Laughlin says.

However, the perfect alignment that allows astronomers on Earth to see a planet transiting another star is rare: Laughlin puts the odds at just two percent.

Scientists aren’t quite done analyzing the MOST data for transits, but so far the data “do not raise any major red flags that Proxima b is bogus,” says Columbia University’s David Kipping, who is leading the MOST search.

Still, further observations made with HARPS or other sensitive instruments coming online in the next few years will help confirm whether the signal is the work of the planet or the star. And waiting a few years to make those measurements could only boost their credibility.

Proxima Centauri is part of the triple star system Alpha Centauri, seen here in a composite picture from the Digitized Sky Survey 2.
PHOTOGRAPH BY ESO, DAVIDE DE MARTIN, AND MAHDI ZAMANI
"If this really is a planet, the 11-day signal shouldn’t depend too much on when we observe the star. The planet should always be there," Weiss says. "If anyone tries this experiment again a few years from now and doesn't see the same signal, that's a bad sign."

Hopes for Life
As exciting as the discovery is, however, it’ll be a while until astronomers can tell us whether Proxima b is a good host for life as we know it. For now, scientists don’t know enough about the planet to assess its true nature—but based on available information, it’s unlikely to be an Earthly twin, or even similar to Earth at all.

“The planet is in a warm orbit, but that doesn’t mean it’s habitable,” says Anglada-Escudé. “This is something we have to discuss a lot.”

To begin with, aside from its age, Proxima Centauri is nothing like the sun. It’s about 12 percent of the sun’s mass, has a magnetic field 600 times stronger, and emits the majority of its light in relatively cool infrared wavelengths. It also spits out roughly the same amount of x-rays as the sun, meaning that planets near enough to support liquid water are constantly in the splash zone of potentially damaging energetic particles.

Then there are those giant flares, which are tempestuous even by red dwarf standards. The star has somewhat chilled out in its relative old age, but it once shot extreme amounts of UV radiation into space with alarming frequency, potentially dealing a hostile blow to any life on an infant planet’s surface.

Not only that, but those stellar tantrums and continued x-ray bombardment could erode or severely alter the chemistry of any atmosphere, leaving the surface relatively unprotected from lethal radiation.

“If the atmosphere is thinner, then more UV radiation will hit the ground,” says Cornell University’s Lisa Kaltenegger. “Ground-based life will either have to shelter underground, underwater, or rely on another mechanism to shield itself.”

There’s also the strong probability that, at a mere seven million kilometers from its host, Proxima b keeps one face pointing toward its star at all times and one face gazing eternally into the cosmic night.

All of these differences don’t prove that life could not have evolved on Proxima b, just that its story would be dramatically different from that of life on Earth.

“Life, if it exists, probably had a rougher start than life on Earth,” Kaltenegger says. “But that is exactly why it is so exciting to study these other worlds. They are just a bit different and can unveil an amazing diversity of life we can't even imagine yet.”