What constellation is Proxima Centauri located in? - Explore the Universe: Your Guide to Astronomy

According to The Guardian, astronomers searching for extraterrestrial radio signals have picked up an “interesting signal” from Proxima Centauri, the nearest star system to our Sun. Here, we provide further details on the findings made by scientists.

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Who is Proxima Centauri?

Proxima Centauri, a red dwarf star, is part of the Alpha Centauri star system, making it the closest star to the Sun. It is situated approximately 4.244 light-years away from Earth, which is equivalent to 270,000 times the distance between Earth and the Sun. Proxima Centauri has a diameter that is approximately 7 times smaller than the Sun’s diameter and only 1.5 times larger than Jupiter’s diameter. In terms of mass, Proxima Centauri is about 8 times lighter than the Sun and 150 times heavier than Jupiter. It is a member of the Alpha Centauri AB system and orbits around the system’s center of mass, completing one revolution every 550,000 years. Currently, Proxima is positioned 12,950 astronomical units (1.94 trillion kilometers) away from the Alpha Centauri AB pair.

In 2017, the ALMA submillimeter telescope located in Chile managed to capture thermal emissions in the Proxima Centauri system that could potentially originate from an asteroid belt resembling the Kuiper belt found in our own Solar System. Additionally, there are a few other potential asteroid belt locations and a possible planet situated near the outer edge of the primary belt.

Going back to 1998, the Hubble Space Telescope spectrograph discovered a planet positioned 0.5 astronomical units away from Proxima Centauri. However, subsequent investigations have failed to confirm this finding. The search for planets orbiting Proxima Centauri has been fruitless, eliminating the possibility of brown dwarfs and large planets in close proximity.

Accurate measurements of its radial velocity have also eliminated the possibility of super-Earths existing within the region where it is capable of sustaining life. To detect smaller celestial bodies, the utilization of innovative instruments, such as the James Webb Space Telescope, which is scheduled for launch in 2021, is required.

In 2016, the European Southern Observatory unequivocally confirmed the existence of Proxima Centauri b, a planet resembling Earth, within the habitable zone of Proxima Centauri.

In 2018, an analysis of data obtained from the ALMA radio interferometer by a team of astronomers led by Meredith McGregor from the Harvard-Smithsonian Center for Astrophysics revealed that in March 2017, Proxima Centauri experienced a rapid increase in brightness that was on the order of a thousand times greater than the most powerful solar flares within a similar range, occurring within a span of merely 10 seconds.

Before this flare, there was another flare that was not as strong and only lasted for less than 2 minutes. Some scientists believe that the radiation levels that Proxima Centauri b has been exposed to over millions of years would have made its surface uninhabitable (although there is still a possibility of life existing in the ocean, if there is one).

However, the fact that some microorganisms have radiation resistance mechanisms gives hope for the potential evolution of hypothetical life on the planet, allowing it to adapt to even the harshest environments. McGregor’s group also suggests that previous assumptions about the presence of a gas-dust ring and other planets around Proxima Centauri should be abandoned.

Because of its distance from its parent star, the super-Earth known as Proxima Centauri c is situated well beyond the habitable zone and maintains an equilibrium temperature of approximately 39 K. Further observations and measurements are required to validate the existence of this exoplanet using the HARPS instrument on the 3.6-meter telescope at the European Southern Observatory in Chile and the Gaia space telescope operated by the European Space Agency.

In the image captured by the SPHERE (VLT) instrument, along with Proxima Centauri and the backdrop of stars, an additional object was detected in an unexpected location. However, it is possible that this is merely noise, as astronomers were unable to fully eliminate the interference from the star and background light, resulting in visible ripples throughout the image.

In 2020, scientists used data from the ESPRESSO spectrograph to confirm the existence of Proxima Centauri b, a planet with a mass of at least 1.173±0.086 Earth mass and an orbital period of 11.18427±0.00070 days.

Furthermore, the ESPRESSO data also recorded a separate periodic signal that repeated every 5.15 days, suggesting the presence of another planet orbiting Proxima Centauri. This potential planet has a minimum mass of 0.29±0.08 Earth mass and is located 0.03 a. e. away from its parent star.

What kind of signal did it emit?

A group of scientists is currently examining a peculiar radio signal that was discovered in early 2019 by the Parkes Telescope, a 64-meter radio telescope situated in eastern Australia.

The signal seems to have originated from Proxima Centauri, the nearest star to our own solar system, and its features are more in line with those of a man-made transmission rather than a natural radio source.

Who detected the celestial object’s emissions?

The discoverers of the signal, scientists from Breakthrough Listen, a project dedicated to the search for alien life, caution that although the signal possesses distinct characteristics that differentiate it from typical natural radio emissions, it is likely to be either interference or noise caused by our own Earth-based communication technology, or perhaps a previously unobserved natural phenomenon.

According to The Guardian, a UK-based news outlet, the radio waves were detected through 30 hours of observation at the Parkes telescope in April and May of 2019. It should be noted that the signal was received at a frequency of 980 MHz and was not repeated. Additionally, the article mentions a “shift” in the signal that resembles the effect created by planetary movement.

Scientists have named the signal BLC1, and it has piqued their interest. However, they were quick to clarify that although the signal came from some sort of technology, it is likely of human origin.

Since the news of the signal broke, researchers have been hard at work. They now believe that while the signal is indeed artificial, it is unlikely to be the result of extraterrestrial activity.

As astronomers have pointed out, it is highly improbable that a civilization capable of producing radio signals could have been so close to Earth without our detection. It is worth noting that Proxima Centauri, where the signal originated, is only 4.2 light years away from our planet.

What was the resemblance of the signal from Proxima Centauri?

The signal from Proxima Centauri, known as the “Wow!” signal, was a powerful and focused radio signal that was captured by Dr. Jerry Eyman on August 15, 1977. Dr. Eyman was conducting research at the Big Ear Radio Telescope at Ohio State University at the time.

These radio signals were part of the SETI project, which aimed to search for signs of extraterrestrial life. The characteristics of the signal, such as its narrow bandwidth and high signal-to-noise ratio, were consistent with what scientists expected from a signal originating from an alien civilization.

Dr. Eyman was astonished by how closely the characteristics of the received signal matched the anticipated traits of an interstellar signal. In response, he circled the corresponding group of symbols on the printout and exclaimed “Wow!” on the margin. This exclamation became the signal’s nickname.

There are other theories that have been proposed to explain the phenomenon, such as the potential for a lighthouse-esque rotation of the radiation source, a periodic alteration in the signal’s frequency, or even the possibility that it was a one-time event. Additionally, there is a hypothesis suggesting that the signal may have been transmitted from a starship belonging to extraterrestrial beings.

Future investigations into Proxima Centauri

Given its close proximity to Earth, there have been suggestions to include Proxima Centauri in an interstellar mission. Currently, Proxima is moving towards Earth at a velocity of 22.2 kilometers per second. However, in approximately 26,700 years, when it reaches a distance of 3.11 light-years, it will begin to drift away.

A probe that moves slowly would have a time frame of several tens of thousands of years to catch up with Proxima Centauri when it is closest to us, and then it would only have to observe as it drifts away.

However, with a nuclear pulse engine, an interstellar journey like this could be completed within a century. This concept has inspired various projects such as Orion, Daedalus, and Longshot.

One notable project, Breakthrough Starshot, aims to reach the Alpha Centauri system by the first half of the 21st century. They plan to use microprobes that travel at 20% of the speed of light and are propelled by light pressure from ground-based lasers with a power of approximately 100 gigawatts.

Once the microprobes reach Proxima Centauri, their purpose would be to capture images and collect data on the atmospheric compositions of the planets in the system. It would then take 4.22 years to transmit the gathered information back to Earth.

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Proxima Centauri (from Latin proxima meaning “nearest”) is a red dwarf star that is part of the Alpha Centauri star system. It is the closest star to Earth, second only to the Sun.

Based on the parallax measurement of 768.7±0.3 angular milliseconds (as determined by the Hubble Telescope) [1], Proxima Centauri is located approximately 4.22 light years away from Earth. This distance is equivalent to 270,000 times the distance from Earth to the Sun, also known as an astronomical unit (AU).

Using optical interferometry in 2002, scientists determined that Proxima Centauri has an angular diameter of 1.02±0.08 angular milliseconds. This means that its actual diameter is approximately 7 times smaller than the Sun’s diameter and only 1.5 times larger than Jupiter’s diameter, considering the star’s distance. Additionally, Proxima Centauri’s mass is about 7 times less than the Sun’s mass and 150 times the mass of Jupiter.

Attributes

Despite being relatively close to Earth, Proxima Centauri has an apparent stellar magnitude of 11 m, which is very dim. This is because Proxima Centauri is a red dwarf star, which are known for emitting low levels of energy. Due to its low brightness, it is impossible to see Proxima Centauri with the naked eye. It wasn’t until 1915 that this star was discovered by Robert Innes, who was the director of the Union Observatory in Johannesburg, South Africa at the time. The star’s parallax was then measured in 1917, which revealed that Proxima Centauri is the closest star to the Sun, surpassing α Centauri.

Similar to many other red dwarfs, Proxima Centauri exhibits flaring behavior. When these outbursts occur, the star’s brightness can increase significantly. Flares not only result in increased optical brightness, but also produce X-ray emissions, as confirmed by observations from the XMM-Newton orbiting observatory [2]. Proxima Centauri’s luminosity in the energy range of 0.15-10 keV has been observed to vary from 3.9-10 28 to 1.5-10 32 erg/s [2] [3].

Proxima Centauri is often considered an attractive target for the first-ever interstellar mission.

Proxima Centauri is situated approximately 15,000±700 astronomical units (a.e.) away from the other two stars in the Alpha Centauri system, which is 20 times closer to the Sun. It is believed that Proxima Centauri revolves around the Alpha Centauri system with a period of around 500,000 years or possibly even longer. Due to this, the star is sometimes referred to as Alpha Centauri C. The question of whether Proxima is truly a part of the Alpha Centauri system and orbits the other two stars is still not completely clear. Supporting this hypothesis is the fact that the motion vectors of Proxima Centauri and the rest of the star system align almost perfectly.

The search for planets circling Proxima Centauri has yielded no results and has eliminated the potential for red dwarfs and large planets in its orbits. Precise measurements of its radial velocity have also ruled out the possibility of super-Earths in the habitable zone of the star. The detection of smaller objects necessitates the use of new instruments, such as the James Webb Space Telescope. Proxima Centauri could potentially possess Earth-like planets composed of rock [4] [5]. Given that Proxima Centauri is a red dwarf and a star prone to flares, the question arises as to whether life could exist on a planet orbiting it. Nevertheless, Proxima is regarded as a viable target for interstellar voyages.

Observations

In 1915, an observatory near Johannesburg at the Cape of Good Hope (1903-1927) made a significant discovery. They found a star that had the same proper motion as the well-known star, Alpha Centauri. The director of the observatory, Robert Innes, proposed to name this star Proxima Centauri.

Two years later, in 1917, Dutch astronomer Joan Voûte measured the trigonometric parallax of Proxima Centauri. This measurement confirmed that Proxima Centauri was at the same distance from the Sun as Alpha Centauri. Additionally, Proxima Centauri was found to be the star with the lowest recorded brightness, at that time.

The first accurate determination of Proxima Centauri’s parallax was made by American astronomer Harold L. Alden in 1928. He confirmed previous parallax measurements, reporting it to be 0.783±0.005″.

According to American astronomer Harlow Shapley in 1951, Proxima Centauri was identified as a star that flares. Upon comparing photographs taken earlier, it was discovered that the star exhibited an increase in brightness in approximately 8% of the images. This unique characteristic led to its classification as the most active flaring star at that time. Due to its close proximity, scientists have been able to closely observe the star’s flaring activity. In 1980, the astronomers at HEAO-2 created a detailed X-ray energy curve for Proxima Centauri. Subsequent observations of flare activity were conducted by the EXOSAT and ROSAT satellites. In 1995, the Japanese ASCA satellite detected X-ray emissions from smaller solar-like flares. Since then, Proxima Centauri has been extensively studied by various X-ray observatories, including XMM-Newton and Chandra.

Due to its significant southern declination, Proxima Centauri can only be observed below 27° N. The naked eye cannot detect red dwarfs like Proxima Centauri due to their low brightness. However, even from the Alpha Centauri A and B stars, Proxima is visible as a 5th magnitude star. Its apparent magnitude is 11, so even under optimal circumstances – when the sky is dark and the star is positioned high above the horizon – a telescope with a minimum aperture of 8 cm is required to observe it.

Proxima Centauri in science fiction

In the film “Moscow to Cassiopeia”, the protagonist and his troublemaking classmate come close to death when they find themselves in outer space near Proxima Centauri, which had expelled a hydrogen cloud.
In Robert Heinlein’s novel, The Passengers of the Universe, Proxima Centauri is the main target of the first interstellar expedition.
Proxima Centauri is mentioned as a potential destination for space settlement in Isaac Asimov’s novel Nemesis.
The Captive Universe, a novel by Harry Harrison, follows the story of a massive spaceship sent from Earth to Proxima Centauri in order to colonize new worlds.

Additional Resources

Important Points

↑Stars, celestial bodies. Archived from the original source on August 22, 2011.
↑ 12Astronet > Astro-ph preprint reviews
↑[astro-ph/0312297] Flares from small to large: X-ray spectroscopy of Proxima Centauri with XMM-Newton
↑Exoluna in the habitable zone
↑Habitable planets may soon be discovered near a neighboring star

The constellation Centaurus can be fully observed only in regions of the world located between 26 degrees north and 90 degrees south latitude, approximately 40-50 degrees south of the celestial equator. The best time to observe Centaurus is during the spring months of March and April. As one moves farther north, more stars become obscured below the horizon line, so individuals in northern latitudes can only see the upper portion of the constellation at best. Beyond the 61st parallel of northern latitude, Centaurus cannot be seen in the sky as it remains below the horizon. However, in certain cities in South America, Africa, and Australia, which are situated south of the 60th south latitude, the constellation remains visible above the horizon throughout the entire year. In Russia, residents of southern regions have the opportunity to observe the celestial centaur, albeit only its northern half.

The constellation Centaurus can be observed in the starry sky atlas created by Jan Hevelius.

Where and how to view the constellation

The image above shows a screenshot from a planetarium program, depicting the constellation Centaurus.

During a spring night, the constellation Centaurus, also known as Centaurus, can be seen rising low in the southern sky. However, for those living in the Northern Hemisphere, this part of the sky is typically not visible as the constellation has a declination range of -30 to -64 degrees. At latitudes in the middle of the Northern Hemisphere, only a portion of Centaurus is observable.

Historical Background and Myths

This particular constellation has been recognized by astronomers since ancient times. In fact, it was included in the astronomical catalog “Almagest” by Ptolemy during the 2nd century AD. The priests of Mesopotamia referred to it as the Boar, while Arab stargazers perceived it as the back of a bear instead of a horse. Originally, it encompassed the stars that form the Southern Cross and were positioned between the front and hind legs of the centaur. However, these constellations were later separated. On the other hand, the weapon known as the thyrsus, which is held by the half-human and half-horse hybrid, initially existed as a distinct figure but eventually merged with the Centaur.

Examining the situation in Russia and the former Soviet Union

In the southern parts of Russia and the former USSR, as well as in the south of Central Russia, the northern part of the constellation can be seen. The visibility of the constellation increases the further south one goes. In Orel, Lipetsk, Penza, and Samara, the first bright stars of the constellation, θ and ι Centauri, can already be seen at the horizon. In Adler, these stars rise at 10° and can be seen quite well. The star η Centauri becomes visible around the latitude of Rostov-on-Don, rising at about 4.5° in Adler and 6.5° in the south of Dagestan. The star ζ Centauri is only visible in the south of Dagestan within Russia. The other bright stars of the constellation are not visible in Russia, but some of them can be seen in the southern cities of the former USSR. For example, the star γ Centauri can be glimpsed near the horizon in Baku, Yerevan, and Bukhara, while in more southern cities it rises higher. In Lenkoran, Dushanbe, Astara, and Ashgabat, the star δ Centauri rises, and in Kushka, even ε Centauri rises. However, the southernmost part of the constellation, where the bright stars α Centauri and β Centauri are located closest to the Solar System, is not visible in the former USSR and does not rise even in Kushka.

Composition

The constellation is unique not only for its size, but also for its collection of remarkable elements such as stars, clusters, nebulae, and galaxies. It consists of 389 luminaries, many of which are visible to the naked eye without the need for a telescope. While they may not be the brightest, they are easily detectable. Some even possess intriguing characteristics. Additionally, within this particular region of the sky, one can observe three meteor showers: the Alpha, Omicron, and Theta Centaurids. These showers occur from the end of January to the middle of March.

Centauri Constellation Features

Alpha Centauri

Main article: Alpha Centauri

On November 24, 2020, the International Astronomical Union (IAU) made the decision to officially restore the star α Centauri to its original name Rigel Centaurus (Rigil Kentaurus). In order to prevent any confusion, the IAU established the WGSN[en]*[3][4][5] working group in 2020 to organize the naming of stars. Astro-Club “Nippy”[6] also played a role in this process on Wikipedia pages, as a member of the IAU Handbook of International Astronomy. Additionally, Astro-Club “Nippy” participated in the 2020 IAU-organized “NameExoWorlds”[7][8] campaign, which aimed to name newly discovered stars and planets.

Stellar Bodies

The initial most luminous stellar body in the group of stars and the third most luminous in the entirety of the nocturnal firmament is Rigel Centaurus, which translates from the Arabic language as “foot of the centaur”. Within the scientific community, it is referred to as Alpha Centauri, and on occasion, the monikers Bungula and Toliman are utilized. It constitutes a trinary star system, which, when observed from Earth, appears as a single entity. Two of these celestial bodies, Alpha Centauri A and B, are situated in proximity to the Sun. The third, Proxima Centauri, is a dim crimson dwarf, and out of the numerous stars, excluding the Sun, it is the closest to our planet, positioned approximately 40 trillion kilometers away. It is also referred to as Alpha Centauri C. In the year 2020, astronomers uncovered the presence of an exoplanet with terrestrial characteristics in orbit around this celestial body.

The second most luminous star is Beta Centauri, also known as Hadar, which is derived from the Arabic word meaning “bottom.” Another name for this star is Agena, which comes from the Latin word meaning “knee.” Beta Centauri is a blue-white giant and is ranked as the second brightest star in the sky. It is actually a triple star system, consisting of two stars called Hadar A and one star called Hadar B. Theta Centauri, the third brightest star, is an orange giant known as Menkent, which comes from the Arabic phrase meaning “centaur’s shoulder.” Unlike the first two stars, Theta Centauri is visible to residents of the northern hemisphere, as it is located in the upper part of the constellation. Among the other stars in the constellation, which are less bright, there are several double stars (Gamma, Zeta, and Kappa) and stars with varying brightness (Epsilon, Delta, and BPM 37093). Nu Centauri is a double star that undergoes periodic changes in brightness, and it is relatively young, being less than 20 million years old.

The most well-known entities of Centauri

Galaxies, Clusters, and Nebulae

The Centauri constellation is home to a variety of fascinating galaxies, such as NGC 5128, also known as Centaurus A. This unique galaxy takes the form of a lens and features an irregular dark band composed of dust. It is the most powerful source of radio emission within the constellation and ranks as the fifth brightest galaxy overall. Additionally, NGC 5128 holds the distinction of being the closest galaxy to Earth. Scientists speculate that a black hole resides at its center, likely formed as a result of a collision with a spiral galaxy. This collision also explains the appearance of new stars within NGC 5128. The study of this radio galaxy provides valuable insights into the formation processes of stars, nebulae, and black holes.

The Boomerang Nebula is a protoplanetary nebula that has a temperature of 1 Kelvin, which is equivalent to 272 degrees below zero on the Celsius scale. It is the coldest object in the Universe. Another stunning sight is the NGC 3918, also known as the Southern Nebula, which is a planetary nebula. At its core, a dying star illuminates the surrounding gas, but eventually, NGC 3918 will fade away and leave behind a white dwarf.

The Centauri constellation continues to captivate astrophysicists, amateur astronomers, and regular observers. It is home to various objects that provide new insights into the Universe and serve as a reminder of its intricate beauty and structure.

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Omega Centauri

Omega Centauri, also known as NGC 5139, is a globular cluster located in the constellation of Centaurus. It is one of the largest and brightest globular clusters in the Milky Way galaxy. Omega Centauri is estimated to be about 15,800 light-years away from Earth and has a diameter of approximately 150 light-years. It contains millions of stars, making it one of the most densely populated globular clusters known. Omega Centauri is a popular target for astronomers due to its unique properties and its proximity to Earth.

To locate NGC 5139, you need to initially search for the stars μ and ζ Cen. Draw a line from ζ Cen to the West, equal to the distance between these stars. At that position, even with the most basic binoculars, you will be able to observe a relatively bright, blurry sphere of light. Despite having a star magnitude of 3.7, spotting it with the naked eye at mid-latitude can be quite challenging. It only rises above the horizon to a maximum of five degrees, and atmospheric refraction or even slight horizontal illumination can greatly affect the cluster’s projection on the celestial sphere.

The constellation you were observing is: Northern Crown

Overview

The Alpha Centauri star system is estimated to have formed 1.5 to 2 billion years prior to the Sun, making it between 5.5 and 7 billion years old. In astronomical records, the constituent objects are listed as Centauri A, B, and C, but they have individual names: Rigel Centaurus, Hadar, and Proxima Centauri.

The two largest stars in the system are so close to each other in space (at a distance of 40 astronomical units) that they were initially perceived as a single entity before the invention of the telescope. Additionally, the red dwarf Proxima Centauri, which has a low luminosity, orbits the same center of mass but is located approximately 15,000 astronomical units away. It remained unknown to science until its discovery in 1915.

On October 16, 2012, a team of researchers from Geneva, who were conducting studies at the La Silla observatory in Chile, made a groundbreaking announcement regarding the discovery of a planet near Centauri B that has a similar mass to Earth. Over a period of 3.5 years, they used Doppler spectrography to measure variations in the star’s radial velocity, which led them to conclude that there was a sizable object in close proximity. However, in 2020, astronomers from California and Britain reanalyzed the data and found an error in their calculations. As a result, the scientific community acknowledged that the planet near Hadar had not been detected.

In 2020, the magazine “Spiegel” published an article stating that scientists had identified signs indicating the presence of a planet near Proxima. This information was later verified by the staff at the Southern European Observatory, and to this day, there has been no official refutation of these findings.

History

Centaurus is a constellation that has a rich and ancient history. It was recognized by the ancient Greeks and was originally believed to include the stars that later formed the Southern Cross. However, even without those stars, Centaurus is still a significant constellation with many bright stars. According to Greek mythology, one of the centaurs who achieved immortality and ascended to heaven was Chiron. Chiron was a wise and immortal centaur, the son of Cronus and the nymph Phyllira. He was known for his expertise in science and art, and he served as a tutor to the Greek heroes Achilles, Jason, and the god Asclepius. Another centaur, Pholus, is also associated with Centaurus. Pholus was accidentally shot by Heracles with a poisoned arrow during his fifth feat. The constellation of Centaurus is listed in Claudius Ptolemy’s Almagest catalog of the stars in the sky.

Alpha Centauri star system

The star system of Alpha Centauri is well-known in the scientific community. It is a binary star system, consisting of three stars: Alpha Centauri A, Alpha Centauri B, and Proxima Centauri. This star system is the closest to our solar system, located at a distance of about 4.37 light-years away. It is a popular subject of study and research due to its proximity and the potential for habitable exoplanets. Scientists believe that there may be potentially habitable planets in this star system, which makes it a fascinating area of exploration. The Alpha Centauri star system continues to captivate astronomers and astrophysicists, as they strive to learn more about the mysteries of the universe.

The Alpha Centauri system consists of three stars: Proxima, Alpha Centauri A, and Alpha Centauri B. Proxima is not as bright or prominent as the other two stars. The brightest star in this constellation is Alpha Centauri A, which is located 4.33 light-years away from the Sun. It is known as Rigel Centauri, meaning “Centaurus’ foot”. This star bears a resemblance to our Sun, possibly due to its brightness. Unlike Proxima Centauri, it has been observed and recognized since ancient times, as it is easily visible in the night sky.

Alpha Centauri B is equally as bright as its “sister” star. They form a close binary system. Proxima Centauri is located at a considerable distance from them, with a gap of thirteen thousand astronomical units (which is four hundred times farther than the distance from the Sun to Neptune!).

All the stars in the Centauri system revolve around their shared center of mass. However, Proxima moves at a much slower pace, with its orbital period lasting millions of years. As a result, this star will remain the closest to Earth for an extended period of time.

It is extremely tiny

The star Proxima Centauri is not just the nearest constellation to us, but it is also the tiniest. Its size is so small that it possesses barely enough mass to sustain the formation processes of helium-hydrogen, which are crucial for its existence. The star has a very faint luminosity. Proxima is considerably less massive than the Sun, around seven times less. Additionally, its surface temperature is considerably lower, measuring only 3,000 degrees Celsius. Moreover, Proxima is one hundred and fifty times brighter than the Sun.

Red dwarfs

The tiny star Proxima is classified as an M-class star with extremely low luminosity. Another popular term for celestial bodies in this category is red dwarfs. Stars with such a diminutive mass are highly intriguing entities. Their internal composition bears resemblance to that of colossal planets like Jupiter. Red dwarfs possess exotic matter within them. Furthermore, there is speculation suggesting that planets orbiting these stars may harbor conditions suitable for sustaining life.

Red dwarf stars have an exceptionally long lifespan, surpassing that of any other type of star. They undergo a slow evolution process and it takes several billion years for any nuclear reactions to occur within them. The lifespan of a red dwarf star is actually longer than the age of the entire universe! Therefore, in the distant future, when multiple stars similar to our Sun have faded away, the red dwarf known as Proxima Centauri will continue to emit a faint light in the vastness of space.

In our galaxy, red dwarfs are the most abundant type of stars. They make up over 80% of all stellar bodies in the Milky Way. However, there is a paradox associated with them – they are virtually invisible to the naked eye, making them impossible to observe directly.

Up until now, it has been impossible to accurately measure the size of small stars like red dwarfs due to their weak luminosity. However, a solution to this problem has emerged in the form of a specialized VLT-interferometer (VLT stands for Very Large Telescope). This device operates using two large 8.2-meter VLT-telescopes located at the Paranal Astronomical Observatory (ESO). These two enormous telescopes, positioned 102.4 meters apart, enable the measurement of celestial bodies with an unprecedented level of precision. For the first time, astronomers at the Geneva Observatory have successfully determined the exact size of such a diminutive star.

The capricious Centauri

Proxima Centauri is situated in an intermediate state between a genuine star, a planet, and a brown dwarf in terms of its dimensions. Nevertheless, it is classified as a star. Its mass and diameter are approximately one-seventh of the Sun’s mass and diameter, respectively. Despite being one hundred and fifty times more massive than Jupiter, Proxima Centauri weighs one and a half times less. If the star had a lower mass, it would not be able to generate enough hydrogen in its core for light emission. Consequently, it would be categorized as a conventional brown dwarf, which is essentially lifeless, rather than a genuine star.

Proxima Centauri is a celestial body that is known for its low luminosity. Under normal conditions, its brightness does not exceed 11m. However, when observed through powerful telescopes like Hubble, it appears to be brighter. This phenomenon can be explained by the fact that Proxima Centauri is classified as a variable or flaring star. The star’s surface experiences intense flares, which are caused by violent convection processes. These flares are similar to the ones that occur on the Sun, but much more intense, resulting in fluctuations in the star’s brightness.

These violent processes and flares indicate that the nuclear reactions happening inside Proxima Centauri haven’t yet become stable. The scientists’ conclusion is that it remains a remarkably young star in cosmic terms, even though its age is similar to that of our Sun. However, Proxima is a red dwarf, making any comparison between the two impossible. Just like its other “red brethren,” it will consume its nuclear fuel at a slow and efficient pace, resulting in a lifespan that is approximately three hundred times longer than our entire Universe! This puts the Sun in perspective…

Many writers of science fiction have the belief that Proxima Centauri is the star most suitable for embarking on space exploration and thrilling adventures. Some speculate that within its vast expanse lie planets harboring civilizations yet to be discovered. While this may hold some truth, the distance between Earth and Proxima Centauri spans over four light years. Thus, despite its proximity, it remains quite a distance away.

Proxima Centauri b, also known as Proxima b or Alpha Centauri Cb, is an exoplanet situated within the habitable zone of the red dwarf star Proxima Centauri. This star is not only the closest to our Sun but is also part of a triple star system. Located approximately 4.2 light-years (or 4.0 × 10 km) away from Earth in the constellation Centauri, Proxima Centauri b, along with Proxima c, holds the distinction of being the nearest known exoplanets within our solar system.

Proxima Centauri b revolves around a star at a separation of roughly 0.05 astronomical units (7,500,000 kilometers; 4,600,000 miles) and has an orbital time of approximately 11.2 days on Earth. It is believed to have a minimum mass that is 1.2 times greater than Earth. The planet experiences stellar wind pressures that are over 2,000 times stronger than those encountered by Earth from solar wind. The potential habitability of Proxima Centauri b has not yet been definitively confirmed.

The announcement of the planet’s existence was made in August 2016. The planet was found using the radial velocity method, which detects the presence of a rotating object through periodic Doppler shifts in the spectral lines of the star it orbits. Based on these observations, the parent star’s velocity relative to Earth varies by about 1.4 meters (4.5 feet) per second. According to Guillem Anglade-Escudé, this proximity to Earth presents an opportunity for future exploration of the planet through projects like Starshot, potentially within the next few centuries.

Since the orbital inclination of Proxima Centauri b is not known, its exact mass remains uncertain. If its orbit is nearly edge-on, its mass would be estimated at 1.173 ± 0.086 M ⊕ (Earth masses). Statistically, there is a probability that the planet’s mass is less than 2.77 M ⊕.

Physical attributes

Weight, size, and heat

The measurement of the apparent orbital inclination of Proxima Centauri b has not yet been determined. The minimum mass of Proxima b is 1.17 M ⊕, which would be its actual mass if its orbit were visible from Earth’s vantage point. Once the orbital inclination is established, the mass can be accurately calculated. A higher mass is implied by more inclined orientations, with 90% of potential orientations indicating a mass below 2.77 M ⊕. The precise radius of the planet remains unknown. If it possesses a rocky composition and a density comparable to Earth, its radius is at least 1.1 R ⊕. It may be larger if its density is lower than that of Earth or if its mass exceeds the minimum estimate. Similar to many super-Earth-sized planets, Proxima Centauri b may possess an icy composition similar to Neptune, featuring a thick shell, a hydrogen and helium atmosphere. The likelihood of this scenario is calculated to be greater than 10%. The planet maintains an equilibrium temperature of 234 K (-39° C; -38° F), which is marginally colder than Earth’s temperature of 255 K (-18° C; -1° F).

If Proxima Centauri b and the candidate exoplanet Proxima Centauri c have coplanar orbits, it is possible to estimate the true mass of Proxima b. Recent calculations have been done using various combinations of spectroscopic orbital parameters, the Gaia DR2 proper motion anomaly, and astrometric measurements. For instance, a 2020 paper by Kervella et al. estimates the true mass of Proxima b to be 2.1 + 1.9. -0.6 Earth mass, while another estimate by Benedict et al. puts it at 3.0 ± 0.3 Earth mass.

Host star

The planet revolves around a red dwarf called Proxima Centauri, which is classified as an M-type star. Proxima Centauri has a mass of 0.12 times that of the Sun and a radius of 0.14 times that of the Sun. It has a surface temperature of 3042 Kelvin and an age of 4.85 billion years. In comparison, the Sun is 4.6 billion years old and has a surface temperature of 5778 Kelvin. Proxima Centauri completes one rotation every 83 days and has a luminosity of approximately 0.0015 times that of the Sun. Unlike low-mass stars like Proxima, the Sun is not typically rich in metals. The metallicity ([Fe / H]) of Proxima Centauri is 0.21, which is 1.62 times higher than that found in the Sun’s atmosphere.

Despite being the closest star to the Sun, Proxima Centauri is not visible to the naked eye from Earth due to its low luminosity. Its mean apparent magnitude is 11.13.

Satellite’s Path

Proxima Centauri b completes one orbit around its host star every 11,186 days, with a major semi-axis distance of approximately 0.05 astronomical units (7,000,000 km; 5,000,000 miles). This means that the exoplanet is located at a distance that is only one twentieth of the distance between Earth and the Sun. To put this in perspective, Mercury, the closest planet to the Sun, has a major semi-axis distance of 0.39 a.u. Proxima Centauri b receives about 65% of the radiation flux from its parent star compared to what Earth receives from the Sun. In comparison, Mars receives about 43% of Earth’s radiation. The majority of the radiation from Proxima Centauri is in the infrared spectrum. In the visible spectrum, the exoplanet only receives around 3% of Earth’s PAR (400-700 nm) radiation. For comparison, Jupiter receives 3.7% and Saturn receives 1.1%. Therefore, the surface of Proxima Centauri b is usually not much brighter than twilight. At dusk and sunrise, the maximum illumination on the horizontal surface is about 400 lux, while Proxima b is illuminated at approximately 2700 lux in a calm state. Proxima Centauri also experiences flares. The brightest flare observed before 2016 increased Proxima’s visual brightness by a factor of about 8, which is a significant change from previous levels. However, due to Earth’s illumination being around 17%, this increase is not equivalent to very strong sunlight. Nevertheless, due to its close orbit, Proxima Centauri b receives about 400 times more X-ray radiation than Earth.

Appropriateness

An artist’s rendition of the surface of Proxima Centauri b is depicted. The backdrop shows the Alpha Centauri binary system, located in the upper right corner of Proxima.

The habitability of Proxima Centauri b has yet to be determined, as the planet is exposed to stellar wind pressure over 2000 times that of the solar wind on Earth. This high radiation and strong winds are likely to strip away any atmosphere, leaving the planet’s interior as the only potentially habitable region.

If there exists an atmosphere, the presence of longer wavelength radiation emitted by the primary star, specifically a red dwarf, will have an impact on the weather conditions. This will lead to a suppression of cloud formation on the illuminated side of the planet in comparison to Earth (or Venus), resulting in the occurrence of clearer skies.

A Glimpse from Proxima Centauri b

Observation of the celestial sphere near Orion as seen from Alpha Centauri with Sirius adjacent to Betelgeuse, Procyon in Gemini, and the Sun positioned between Perseus and Cassiopeia produced by Celestia

When observed from the Alpha Centauri system, the sky would appear similar to what it does to an Earth observer, except that Centauri would be lacking its most brilliant star. The Sun is a yellow star with an apparent magnitude of +0.5 in the eastern region of Cassiopeia, situated opposite to the current point of direct ascension and declination of Alpha Centauri, at 02 39 35 + 60° 50 '(2000). This location is in close proximity to the 3.4 magnitude ε star of Cassiopeia. Due to the Sun’s positioning, an interstellar or extraterrestrial observer would notice that \ / \ / Cassiopeia has taken on the shape of / \ / \ / \ / nearly in front of the Heart Nebula in Cassiopeia. Sirius is less than one degree away from Betelgeuse in the otherwise unchanged Orion constellation, and with a magnitude of -1.2, it is slightly dimmer than it appears from Earth, yet it remains the brightest star in the Alpha Centauri sky. Procyon is also shifted to the center of Gemini, overshadowing Pollux, while both Vega and Altair have shifted to the northwest in relation to Deneb (which has remained almost stationary due to its vast distance), resulting in a more equilateral appearance for the Summer Triangle.

The two bright stars of Alpha Centauri AB would be seen as a closely spaced pair with a combined apparent magnitude of -6.8 if viewed from Proxima Centauri b. Depending on the position of the double star in its orbit, the two stars may be visible as separate points of light to the naked eye, or occasionally, but briefly, appear as a single unresolved star. According to the calculated absolute magnitudes of the stars, Alpha Centauri A would have an apparent magnitude of -6.5, while Alpha Centauri B would have an apparent magnitude of -5.2.

It is improbable that Proxima Centauri b initially developed in its present orbit, as disk models for small stars like Proxima Centauri would have had less than one Earth mass M ⊕ of matter in the central astronomical unit at the moment of their formation. This implies that either Proxima Centauri b was created in another location, which is yet to be determined, or the current models of star formation disks need to be reevaluated.

Exploration

During the first three months of 2016, the velocity of Proxima Centauri towards and away from Earth was measured using the HARPS spectrograph. The data points, represented by red symbols with black error bars, were plotted on a graph and the blue curve corresponds to the data. By analyzing the amplitude and period of motion, scientists were able to estimate the minimum mass of the planet.

In 2013, Mikko Tuomi from the University of Hertfordshire detected the first indications of an exoplanet from archival observational data. To verify this potential discovery, a team of astronomers initiated the Pale Red Dot project in January 2016. On August 24, 2016, a group of 31 scientists from various countries, led by Guillem Anglada-Escudé from Queen Mary University London, confirmed the existence of Proxima Centauri b. Their findings were published in a peer-reviewed paper in Nature.

The system’s observational complexities still allow for the possibility of other large planets orbiting Proxima Centauri. According to calculations, it is not impossible for another super-Earth planet to exist around the star, and its presence would not disrupt the orbit of Proxima Centauri b. In fact, a super-Earth known as Proxima c was discovered in 2019, although it orbits at a distance of 1.5 a.u., which is too far away to have a noticeable gravitational pull on Proxima Centauri b.

Data collected using ESPRESSO has ruled out the existence of additional satellites with masses above 0.6 Me in periods shorter than 50 days. However, there is a potential satellite called Proxima d, which weighs 0.29 Me and was in orbit for about 5.15 days.

Anticipated observations

A team of scientists believes that they have the capability to capture images of Proxima Centauri b, a planet in the Alpha Centauri star system, and analyze its atmosphere for the presence of oxygen, water vapor, and methane. They plan to achieve this by combining the ESPRESSO and SPHERE instruments on the Very Large Telescope (VLT). While the James Webb Space Telescope could potentially provide further insights into the atmosphere of Proxima Centauri b, there is currently no definitive evidence of transits. The combination of photometry data from MOST and HATSouth suggests that the probability of Proxima Centauri b being a transiting planet is less than 1%. However, future telescopes such as the Extremely Large Telescope, the Giant Magellan Telescope, and the Thirty Meter Telescope may have the capability to effectively characterize Proxima Centauri b.

The identification of Proxima b was a momentous occasion for Breakthrough Starshot, a groundbreaking initiative focused on deploying a squadron of small-scale probes to the Alpha Centauri system. Spearheaded by research organization Breakthrough Initiatives, this project aims to construct and launch a fleet of unmanned spacecraft known as StarChips, capable of reaching speeds up to 20% of the speed of light. These StarChips will arrive in the Alpha Centauri system approximately 20 years after departure, with Earth receiving notification just over 4 years later.

Mission 2069 Alpha Centauri

In a joint effort between Breakthrough Initiatives and the European Southern Observatory (ESO), a mission has been launched to explore the possibility of habitable planets in the Alpha Centauri star system. This groundbreaking collaboration involves Breakthrough Initiatives providing financial support for the enhancement of the VISIR upgrade (V LT I mager and S spectrometer for the Middle I nfra. r ed) on ESO’s renowned Very Large Telescope (VLT) located in Chile.

A comparison is made between the angular dimensions of Proxima as seen from Proxima b and the dimensions of the Sun as seen from Earth. The Sun is significantly larger than Proxima, but Proxima b is located very close to its star.
The relative sizes of various objects are depicted, including the three stars in the Alpha Centauri triple system and other stars with known angular dimensions. The Sun and Jupiter are included in this comparison as well.
This diagram displays the expansive southern constellation known as Centaurus (Centaurus) and illustrates the majority of stars that can be observed with the naked eye on a clear, dark night. The red circle indicates the position of Proxima Centauri, the closest star to our solar system. Although Proxima Centauri is too faint to be visible without the aid of a telescope, it can be located with a small one.
This composite image merges a glimpse of the southern sky as captured by ESO’s 3.6-meter telescope at La Silla Observatory in Chile, with images of Proxima Centauri (bottom right) and the double star Alpha Centauri AB (bottom left) taken by NASA/ESA’s Hubble Space Telescope. Proxima Centauri, the nearest star to our solar system, has a planet called Proxima b orbiting it.

Video

Play media Numerical simulations of the possible surface temperatures of Proxima b were performed using the Dynamique Meteorology Laboratory’s Global Global Climate Model. In this simulation, the planet has an Earth-like atmosphere and is covered by an ocean (the dashed line represents the boundary between the liquid and icy ocean surface). Two models of the planet’s rotation have been created. In this scenario, the planet is in what is known as a 3:2 resonance (the natural frequency for the orbit), and it is observed from a distant point of view over the course of one full orbit.
The video demonstrates the numerical modeling of potential surface temperatures on Proxima b. The simulation assumes that the planet possesses an atmosphere similar to that of Earth and is entirely covered by an ocean. The dashed line represents the boundary between the liquid and icy portions of the ocean. Proxima b is in synchronous rotation, similar to the Moon’s rotation around the Earth. The video showcases the planet as it would appear to a distant observer during one complete revolution.