The Closest Planet Outside Our Solar System Is Almost Within Reach | Proxima Centauri

This is a truly tantalizing image. Why is it tempting? This is Proxima Centauri. Since its discovery more than 100 years ago, it has captivated astronomers around the world. It is so desperately close, but it would take generations to

reach

it. It is not visible to the naked eye, but it is the

closest

star to our

solar

system

. At one time it was the lowest luminosity star known to man, but also the most active. As if the paradoxes of this star weren't alluring enough, scientists recently discovered an apparently Earth-like exo

planet

in its orbit, opening up conversations about interstellar colonization that include Mark Zuckerberg, Elon Musk and Stephen Hawking.

It's

almost

as if he is consciously playing with us humans and our insatiable curiosity for what lies beyond. If you're like me, you also can't wait to drink in everything there is to know about this enigmatic star. I'm Alex McColgan and you're watching Astrum. Join me today and let's enjoy a quick tour of the Alpha Centauri star

system

, from the Alpha Centauri AB binary stars, to delving into everything we know about Proxima Centauri, its recently discovered

planet

s, a possible controversial discovery, and what kind of missions of flyby could hold in the future. Leaving Earth, it would take just over 4 light years to

reach

the

closest

known stars to our

solar

system.

I say stars because they are technically a triple star system. Collectively known as Alpha Centauri, they consist of Rigil Kentaurus (also known as Alpha Centauri A), Toliman (also known as Alpha Centauri B), and Proxima Centauri. Together, Rigil Kentaurus and Toliman form the binary star system Alpha Centauri AB. They are located 4.37 light years from Earth and both are Sun-like stars that orbit a common center every 79.76 years. If you are south of the 40th parallel, you will be able to see them at night, although to the naked eye they would appear to be a single star, the third brightest in the sky, behind Sirius and Canopus.

The Alpha Centauri binary system was discovered in 1689, but the third star would take more than 200 years to be revealed. Luck came in 1915 to a Scottish astronomer named Robert Innes. At the time, Innes was director of the Union Observatory in Johannesburg, South Africa. While comparing photographic plates with the help of a flicker comparator, he observed that a faint star had moved in the five years between the photographs. This motion was ap

proxima

tely the same as that of the binary star Alpha Centauri he was observing. He wondered if the new star could be part of the same system. After further investigation, he concluded that she was closer to the Sun than his twin brothers, a finding that was quickly confirmed by his contemporaries.

Paradoxically, it became the closest and darkest star known at the time. The surprises didn't end there. In 1951, American astronomer Harlow Shapley discovered that Proxima Centauri is a bright star. Not only that, but it was the most active star known at the time. Over the past 70 years, Proxima Centauri has become a much-studied star, no pun intended. And with the recent discoveries of an Earth-like exoplanet orbiting it, I think interest will only intensify. But I'm getting ahead of myself. Let's get to know this star a little better before putting so many expectations on him. At 4.24 light years away, Proxima Centauri is a little closer to us than Alpha Centauri AB.

It is a main sequence red dwarf star, with an estimated mass of 12.2% and a diameter 15% that of our sun. Despite its smaller size, Proxima Centauri is about 40 times denser than our sun. Due to its low mass, the interior of the star is completely convective. This creates a magnetic field around the star and causes the sporadic release of this magnetic energy in the form of flares. As a result, Proxima Centauri randomly experiences drastic changes in brightness and energy output. On May 6, 2019, a flare was observed at Proxima Centauri that was briefly the brightest ever recorded. These flares release radiation across the electromagnetic spectrum, including X-rays.

To give you an idea of ​​Proxima Centauri's solar activity, its baseline hot. This level can increase by up to two orders of magnitude during a flare. Proxima Centauri not only has more intense solar activity than our sun, but it also has a higher frequency. It is estimated that 88% of the star's surface is active at any given time. This is much higher than our sun, even at the peak of its solar cycle. Before you start thinking of Proxima Centauri as a ball of fiery fury, remember: we're comparing apples and oranges here. Our sun is not a red dwarf.

In fact, compared to other red dwarfs, Proxima Centauri is considered to have a low level of activity. Unlike the sun, which scientists estimate will only consume 10% of its hydrogen supply before burning up, Proxima Centauri is expected to use up

almost

all of its fuel before leaving the main sequence in about four billion years. And by then, Earth, our sun, and our entire solar system will be long gone. Alpha Centauri AB is 0.13 light years, or 2 trillion kilometers, from Proxima Centauri. You may be wondering, "If Proxima Centauri is so far away from its companion stars, why is it considered part of the same star system?" Well, we have data showing that it is gravitationally bound to the binary star Alpha Centauri AB, making it part of the star system with an orbital period of about 550,000 years.

How it ended up in this orbital situation is still open to speculation. But the two main scenarios seem to be: one: Proxima Centauri was bound to the Alpha Centauri system during its formation, meaning the stars likely share the same elemental composition, or two: Proxima Centauri was captured by the binary star's gravity during a meeting , leading to a highly eccentric orbit that was later stabilized by the galactic tide and other stellar encounters. Regardless of how Proxima Centauri entered this triplet, calculations suggest that in 3.5 billion years it will exit. As Alpha Centauri AB continues to evolve and lose mass throughout its life, Proxima Centauri will separate from the system.

The binary star system itself is also predicted to dissociate and diverge in about 12 billion years, into two white dwarfs that will forge independent and constantly divergent paths. Being our closest neighbors, we know quite a bit about Alpha Centauri AB. But we will go into more details about this binary star system in another video. For now, all eyes are on Proxima Centauri. The search for exoplanets around Proxima Centauri has been going on since the mid-2000s, without much luck. But the researchers were not ready to give up: this star was not only the closest neighbor we had, but it was also a red dwarf, of which between 20 and 40% have a planet orbiting in a habitable zone.

Patience paid off. Observations made at the European Southern Observatory in Chile identified anomalies in Proxima Centauri that could not be explained by flares or other solar activity. The data seemed to indicate that there could be a planet orbiting it. In January 2016, the Pale Red Dot campaign, a coordinated effort of multidisciplinary scientists and ground-based telescopes around the world, was launched to see if this suspicious planet could be identified. In August of the same year, the discovery of the exoplanet Proxima Centauri b was announced. It is at least 1.07 times larger than Earth and is 20 times closer to Proxima Centauri than we are to our sun.

This exoplanet orbits its star in just 11.2 Earth days. Although Proxima B is located within the habitable zone of Proxima Centauri, that does not mean that it can support life. There are many other factors that determine habitability besides liquid water. On the one hand, intense solar activity would bombard the planet with between 10 and 60 times the amount of ultraviolet radiation and X-rays that we receive here on Earth; we would need to develop an SPF 3000 to make the trip worth it. Another factor to consider is whether an atmosphere could survive under such conditions. As far as we know, atmospheres are vital for maintaining water-friendly surface pressure, protecting against dangerous space weather, and regulating planetary climate.

The radiation that Proxima B is exposed to could be enough to eliminate key components of an atmosphere over time. Frustratingly, we don't know much about Proxima B beyond its distance from its star and its orbital period. It is unlikely to have moons, due to the instability of its orbits on longer time scales, but the planet itself is thought to be tidally locked to its star. As discussed in a recent video, this does not bode well for potential habitability. It is also likely that it developed under conditions extremely different from those on Earth. Assuming it formed at the current distance from its star, it would have had a much faster evolution, with stronger impacts and less water.

However, there is some debate about its formation. Some scientists believe that the amount of material in the protoplanetary disk would be insufficient for it to form at its current distance from the star. It's more likely, they say, that the planet formed farther from its star and eventually drifted toward its current orbit around Proxima Centauri. What the planet's surface might look like is pure speculation. Theories range from an ice-covered planet, to planetary oceans like Earth (although unlikely if the planet is actually tidally locked), to a waterless world with only dry land, or an underground ocean like Europa.

In short, no idea. We have not yet directly photographed the planet, so we will have to wait for the first flyby to get a better idea, something that some magnates are already planning. If this happens, I have a feeling it will be as momentous as Voyager's flybys in the '70s and '80s, but more on that later. Six years after the discovery of Proxima B, the news of Proxima D made global headlines. The first signs of the planet emerged in 2020, when a weak 5.15-day signal was detected in radial velocity data during a study on the mass of Proxima B.

Following further data collection and analysis, scientists announced the discovery of Proxima D in February 2022. So far, we know that it is a subterrestrial planet, with at least 25% of the mass of the Earth, which orbits the star every 5.1 days. Located at a distance of 4.3 million kilometers, it orbits too close to have a habitable equilibrium temperature, which would amount to 87 degrees Celsius. It is also likely to be tidally locked and would receive so much radiation that the chances of finding life there are very slim. But this planet is promising in another area. It is the lightest planet ever detected with the radial velocity method.

Since the planet is too far away to be seen with telescopes, scientists rely on a characteristic "wobble" anomaly in the motion of a star that indicates the possible presence of a planet. The more massive the planet is, the more evident its wobble is. In the case of Proxima D, the oscillation was practically imperceptible. To me, the fact that we detected the wobble and then were able to prove with enough certainty that it is caused by a planet is a technological milestone worth celebrating. If only the world of astronomy was so simple and straightforward. Where there is progress and celebration on the one hand, there is grim uncertainty on the other.

That's exactly where you'll find the controversial exoplanet Proxima C. Initially detected in 2019 using the same radial velocity method that found Proxima D, Proxima C's existence was then confirmed in 2020 using Hubble astrometry data. However, in 2022, another team questioned the initial radial velocity data that led to the supposed discovery. They stated that the anomalies could have been associated with small unaccounted for systematic errors in the data extraction method the researchers used. Basically, a bad calibration. The problem arises from the fact that, unlike Proxima D, which orbits incredibly close to its star, data for the putative exoplanet Proxima C places it very far from its star, with an estimated orbit of 1,928 days. “There is no similar example of detecting a planet's wobble with such a low amplitude over such a long period.

That doesn't necessarily mean it's wrong, but it will require some confirmation from additional observations,” says Paul Robertson, an astronomer at the University of California, Irvine. If Proxima C exists, a little more data will be needed to convince skepticsreluctant. If it does not exist, it is not clear why Hubble astrometric data was able to corroborate and confirm a planetary signature. I guess we'll have to wait and see what future studies find. With the recent discovery of Proxima B and how relatively close Proxima Centauri is to us, it is a perfect candidate for a future flyby. However, reaching our neighboring star system will take thousands of years using conventional propulsion technologies.

Newer techniques, such as solar sails or nuclear propulsion, could make such a journey possible within a human lifetime. These ideas spearheaded the development of the Breakthrough Starshot Project, an initiative created by investor and physicist Yuri Milner, the late Stephen Hawking and Mark Zuckerberg, which aims to reach the Alpha Centauri system in the first half of the 21st century. The idea is to carry out a flyby mission by sending microprobes weighing a few grams at 15-20% of the speed of light, and they believe they could do it as early as 2036. With this timeline, the probes would reach Alpha Centauri in 20 years, and we on Earth would receive the first data 4 years later.

After the initial flyby, the probes would likely venture to the exoplanets and collect data on their atmospheric compositions, much like the Voyager missions did in our outer solar system decades ago. The team is pinning its hopes on the yet-to-be-developed StarChip, a gram-scale microelectronic wafer, carrying cameras, photon thrusters, power supply, navigation and communication equipment, essentially constituting a fully functional space probe. Based on Moore's law, which states that the speed and capacity of computers can be expected to double every two years. Bold and ambitious, the plan is not without challenges. The team proposes powering these microprobes with 100 gigawatts of ground-based lasers.

This is equivalent to the output of 100 large nuclear power plants, concentrated in probes just a few centimeters wide. Additionally, all components of these tiny probes must be built to withstand extreme accelerations, cold, vacuum, and collisions with space dust. With this in mind, perhaps it would be more appropriate to call the project the Breakthrough Longshot Project. But if the history of space exploration has taught us anything, it is that missions that face cruel odds and long odds can emerge as triumphant milestones for humanity. Proxima Centauri could be next in the history books. Let's hope we're around to see it.

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