Stars between Zero and 4.3 l.y.

Number of stars: 4

Sun (or Sol)

DISTANCE
0.00 light years
MASS
1.00
LUMINOSITY
1.0
AGE
4.5 billion years
The mass of the Sun compared to other stars is represented here by the size of the sphere. Colour is approximate only.

A typical yellow dwarf (spectral type G2) of diameter 1,392,530km. The Sun has a family of nine planets (or eight if we do not include Pluto), of which the third planet, in increasing distance from the star, supports life.

Proxima and Alpha Centauri

DISTANCE
4.24 (Proxima) to 4.36 light years
MASS
A: 1.09
B: 0.89
C: 0.11
LUMINOSITY
A: 1.519
B: 0.5002
C: 0.00006
RADIUS
A: 1.22
B: 0.86
C: 0.154
SURFACE TEMPERATURE
A: 5,753 K
B: 5,242
C: 2,883 K
AGE
A: 5.2 billion years
B: 5.3 billion years
C: 4.85 billion years

Our nearest stellar neighbour (apart from the Sun) is a triple star system consisting of a red dwarf called Proxima Centauri, revolving around two sun-like stars - Alpha Centauri A and B.

Alpha Centauri A has a spectral type of G2, which means that its temperature and colour is the same as our Sun. The only difference is its luminosity: with a mass 1.09 times that of our Sun, Alpha Centauri A emits a steady 54 per cent more light than our Sun. In fact, of all the nearest stars within 12 light years of where we live, Alpha Centauri A is the one that resembles the Sun the most.

Alpha Centauri B is an orange-yellow star of spectral type K1, making it cooler and smaller than the Sun. With a mass of only 0.88, Alpha Centauri B has a stable brightness of 44 per cent of the standard solar value.

The two stars orbit each other every 79.91 years and are separated by at least 11 astronomical units (i.e. Sun-Saturn distance) to a maximum of 35 astronomical units (i.e. Sun-Neptune) when they are at their farthest.

The best NASA photograph we have of Alpha Centauri A and B using the Hubble space telescope taken on 2 September 2016.

In 1986, scientists from Yale University, USA - Pierre Demarque, D.B. Guenther and William van Altena - used the most recent data on the luminosity and mass of the Alpha Centauri system to estimate the age of the stellar system. Calculations indicate that both Alpha Centauri A and B are about 5 billion years old - more than enough time for intelligence to arise on a habitable planet.

Although no planetary system has been detected so far around these sun-like stars, a mathematical study of this stellar system suggest stable planetary orbits should exist around both stars up to a distance of at least 2 astronomical units. Since the Sun's fourth planet, Mars, is only 1.5 astronomical units, an Earth-like planet is likely to be lurking within the Alpha Centauri system (perhaps even two Earth-like planets if we included both stars as capable of supporting life), but again no direct evidence exists to support this. Of course, you might be wondering why we can't detect planets by now given our current technology of orbiting telescopes, radio astronomy and all the rest. Understandable considering the triple star system is the closest to our Sun. The biggest problem astronomers have in detecting planets in our neighbouring star system, despite how close it is to our Sun, is because of the brightness of the stars, and the way both stars already wobble side-to-side quite significantly as they move together through space thanks to the gravitational pull of both stars on each other, thereby making it extremely hard to detect the tiniest of wobbles in the stars' motions from much smaller bodies we call planets. Only a spacecraft venturing out to this star system will answer the question once and for all (unless life on a habitable planet within this system decides to venture out to visit us first, which is more likely given the age of these stars).

The only evidence we do have suggestive of unseen planets is from a careful spectroscopic analysis of the chemical composition of stars: For life and a technology to arise on a planet, there must be elements heavier than those that constitute a typical star. For instance, we need silicon and oxygen for the formation of rocks; carbon, nitrogen and oxygen for the development of life; and iron, titanium, uranium, and other metals for the development of a technology. In our Sun, there is a residue of about two per cent of such heavy elements. In the case of Alpha Centauri A and B, the residues of heavy elements are in much greater quantities than in our Sun! (1).

Presently, the closest star to our Sun is a very faint red dwarf called Proxima Centauri (spectral type M5). It is of the 'flare-up' variety, meaning that it emits every now and then great bursts of energy. It orbits the other two larger luminous spheres at a distance of some 13,000 astronomical units (430 times Sun-Neptune distance) and takes millions of years to complete one orbit.

On 24 August 2016, observations made of Proxima Centauri with a telescope in Chile has revealed a hidden companion roughly 1.2 times the mass of the Earth and in an 11-day orbit around the red dwarf. Furthermore, its estimated distance from the star suggests liquid water can exist. The only complicating factor in this liquid water debate is the distance from the star: the planet is rather close to its solar source. Thus the risks of unexpected temperature variations as the star flares up at various times can whip up the wind speed of the alien atmosphere with great ease and ferocity, and heat up the surface to high levels. If water could somehow remain on the surface, the chances of primitive life is particularly good so long as the critters are well-protected deep beneath the water and/or inside caves. However, if the temperatures exceed a critical level, the surface is likely to be barren and dry thereby reducing the chances of finding life. And, like Mercury in our solar system, the alien world is locked in its revolutions such that one side of the planet always faces the Sun. On the other side, it will be perpetually dark and potentially cold.

If we want to find highly advanced alien life of the type we could communicate with and have a technology, we would be better off making the extra effort to visit Alpha Centauri A and B. Here, the likelihood of finding planets around these stars (not detectable as yet due to the brightness of the stars, the way the stars move around each other, and quite possibly even the size of the planets in question, which is expected to be of the smaller rocky variety) are extremely high.

During 30 hours of observations of Proxima Centauri between April and May 2019 and reported on 18 December 2020 (2), astronomers involved in the Breakthrough Listen project (3) apparently had detected an anomalous signal using the Parkes Radio Telescope. The signal was recorded for prosperity and it lasted long enough for scientists to detect a subtle shift in its frequency of around 982.002MHz. More interestingly, the Doppler shift in the signal was increasing during the period of the observation (i.e., was heading towards us) and moving opposite of what would be expected from the Earth's spin as if implying a non-terrestrial origin for the signal. It is as if the source of the signal was moving in a circle roughly 16 arcminutes (approximately 1/4 of a degree, or half the angular width of Earth's moon) in angular diameter. The only inconsistency to be found from this observation is that the movement of the signal's source to create the Doppler shift was not the same as the movement of the hidden planet around the red dwarf. It seems to be moving independently. So another hidden object, perhaps a smaller moon around the planet may be present.

The observation was repeated in December 2020. Unfortunately the signal disappeared and so prevented scientists from officially confirming the "technosignature" of the signal. Otherwise, there was nothing in the content of the signal that could be construed as coming from an intelligent alien civilisation. As Andrew Siemion from the University of California, Berkeley, said:

"BLC1 is, for all intents and purposes, just a tone, just one note. It has absolutely no additional features that we can discern at this point." (4)

About the closest thing to describing it as "technological" is how narrow the beam was. The scientists who examined the signal have been unable to determine an alternative natural emitter capable of achieving this unusually narrow beam range. As Siemion said:

"We don't know of any natural way to compress electromagnetic energy into a single bin in frequency. Perhaps, some as-yet-unknown exotic quirk of plasma physics could be a natural explanation for the tantalizingly concentrated radio waves. But for the moment, the only source that we know of is technological.

It [the signal] has some particular properties that caused it to pass many of our checks, and we cannot yet explain it." (5)

When the signal, known as BLC1 (stands for Breakthrough Listen Candidate 1), was first detected, astronomers from another observatory were coincidentally examining Proxima Centauri within about 10 days of the emergence of the BLC1 signal. They noted in their paper "a bright, long-duration optical flare, accompanied by a series of intense, coherent radio bursts". Of course, these bursts are not part of the BLC1 signal. The main reason for raising this other observation is to discount or significantly reduce the chances of any native and potentially technical life emerging on the planet around the red dwarf (6). As a result of this particularly intense optical flare event, another study in February 2021 has looked at the probability of alien life living on the planet near this red dwarf and have concluded the chances were extremely slim in the order of 10-8 (7). By 25 October 2021, researchers published further work on the BLC1 signal. Without a repeat signal emanating in the direction of this red dwarf to help eliminate any possible man-made origin of the signal, the researchers have concluded that the signal could be human radio interference.

As Jason Wright, a SETI-centric astronomer at Penn State University in Pennsylvania noted:

"If you see such a signal and it’s not coming from the surface of Earth, you know you have detected extraterrestrial technology. Unfortunately, humans have launched a lot of extraterrestrial technology." (8)

Sounds like it is time to start cleaning up Earth's orbit of its thousands of artificial satellites. Anything to help improve the odds of detecting alien radio signals in space. Otherwise, scientists will always have trouble eliminating us from the ET equation when finding evidence for ETs.

However, it should be noted that all this work to detect possible alien life at Proxima Centauri (mainly because a planet exists whereas planets around the other two stars remain elusive at the present time) does not discount the possibility of alien life around the other two Sun-like stars. Since Alpha Centauri A and B are older than our Sun and have more heavier elements needed to build rocky planets and a technology, it wouldn't be surprising if an advanced alien civilisation already exists and are venturing out into space to carry out their own scientific explorations as we speak. Who knows? Perhaps an artificial space station orbiting a moon or smaller undetected planet in Proxima Centauri had decided to send a narrow beam signal in our direction. Or was it another smaller spacecraft that had been visiting the red dwarf and during its acceleration to get away from the scene, some radiation was leaked in our direction as part of its propulsion technology? Maybe it could be nothing more than a scientific reconnaissance for aliens to study the star more closely at that crucial time while witnessing what happens to the hidden planet during these solar flare-ups. Or was it a rescue mission to pick up alien scientists placed there on the planet after learning of the impending solar flare? The point is, aliens need not have to be native to the planet that is encircling around Proxima Centauri. The probability for ETs could easily increase dramatically if aliens were merely visiting the star and planet and had been able to leave some signature in its wake for us to detect. Unfortunately we are just not quick enough to detect this anomalous signal and spend more time listening to help pinpoint its origin.

Perhaps this is more of a reason why humans need to visit this star system at some point in history, and should be the first and primary target for any journey to the stars. Stop mucking around with searching for radio signals in space. Time to look at what it would take to physically venture out to the stars. For if one UFO report could be evidence of alien visitation to our planet, then it would be clear that scientists have overlooked something in their scientific knowledge to help explain how aliens can reach our planet. Time to find out what it is.

Anyway, there is one more interesting snippet of information that could be relevant in the search for alien life at Alpha Centauri. It concerns the UFO case of Antonio Villas Boas. A fascinating and highly detailed case in which no hypnosis was required, but contained rich information about how aliens go about their activities and why they are here. The case includes hand sketches of the UFO to aid those open-minded scientists (in particular those with a bent for electromagnetism) who are looking seriously at studying close-range UFOs from witnesses.

According to Antonio, in 1957, the Brazilian farmer and student claimed he was abducted, examined by a group of aliens, had sex with a female alien, and later allowed to leave the UFO and observe its departure. According to Antonio's observations, the UFO headed back into the sky in a southerly direction. Unless the UFO needed to examine another part of our solar system, the carrying of important biological samples from Antonio would probably necessitate a quick and safe return to its home planet for careful analysis and ensure the female alien is well looked after throughout the term of the pregnancy. As the UFO itself is not considered a particularly lightweight design with its three large external fuselages at the back that glowed red when accelerating, two small side planks or winglets (mostly like designed for controlling side-to-side tilting), and a rudder-like protrusion at the front (for more accurate left or right turning), not to mention how many aliens were involved in the abduction operation (and hence the additional mass being carried at high speeds to reach our planet), it is likely the UFO originated from a close-range star system capable of harbouring life. As the only Sun-like star(s) capable of harbouring an Earth-like planet within 12 light years of our Sun in the southern hemisphere is Alpha Centauri (all other potential ET home locations in that range are located in our northern hemisphere), it is important to be prepared for the possibility of a quiet and hidden alien civilisation with a native home located in the Alpha Centauri A and B star system.