Weekly Space Hangout – Apr. 15, 2016: Dr. Howard Trottier

Host: Fraser Cain (@fcain)

Special Guest: Howard Trottier, a physics professor at Simon Fraser University (SFU) in British Columbia, Canada. Dr. Trottier has recently devoted his time to the development of SFU’s unique Astronomy public outreach program. In the heart of SFU’s main campus is a “”Science Courtyard,”” a high-profile public space devoted to astronomy and anchored by a state-of-the art outreach and teaching observatory. You can learn more about this amazing program here.

Guests:

Kimberly Cartier (@AstroKimCartier )
Dave Dickinson (www.astroguyz.com / @astroguyz)
Paul M. Sutter (pmsutter.com / @PaulMattSutter)

Their stories this week:

Breakthrough Starshot mission to Alpha Centauri program

Kepler spacecraft temporarily in emergency mode

Mercury Transit

Huge Sunspot

We’ve had an abundance of news stories for the past few months, and not enough time to get to them all. So we’ve started a new system. Instead of adding all of the stories to the spreadsheet each week, we are now using a tool called Trello to submit and vote on stories we would like to see covered each week, and then Fraser will be selecting the stories from there. Here is the link to the Trello WSH page (http://bit.ly/WSHVote), which you can see without logging in. If you’d like to vote, just create a login and help us decide what to cover!

We record the Weekly Space Hangout every Friday at 12:00 pm Pacific / 3:00 pm Eastern. You can watch us live on Google+, Universe Today, or the Universe Today YouTube page.

You can also join in the discussion between episodes over at our Weekly Space Hangout Crew group in G+!

Hawking Supports Tiny Spacecraft To Alpha Centauri

Artist’s impression of the planet around Alpha Centauri B. Credit: ESO

We know that Earth will die.

Even if we beat global warming, and survive long enough to face and survive the next ice age, Earth will still die. Even if we build a peaceful civilization, protect the planet from asteroids, fight off mutant plagues and whatever else comes our way, life on Earth will die. No matter what we do, the Sun will reach the end of its life, and render Earth uninhabitable.

So reaching for the stars is imperative. What sounds unrealistic to a great many people is a matter of practicality for people knowledgeable about space. To survive, we must have more than Earth.

A project launched by billionaire Yuri Milner, and backed by Mark Zuckerberg, intends to send tiny spacecraft to our nearest stellar neighbour, the Alpha Centauri system. With an expert group assembled to gauge the feasibility, and with the support of eminent cosmologist Stephen Hawking, this idea is gaining traction.

Stephen Hawking thinks reaching out to the stars is more than hyperbole: it's essential to the survival of the human species. He's smart. We should listen to him.
Stephen Hawking thinks reaching out to the stars is more than dreamy space talk: it’s essential to the survival of the human species. He’s smart. We should listen to him.

The distance to the Centauri system is enormous: 4.3 light years, or 1.34 parsecs. The project plans to use lasers to propel the craft, which should mean the travel time would be approximately 30 years, rather than the 30,000 year travel time that current technology restricts us to.

Of course, there are still many technological hurdles to overcome. The laser propulsion system itself is still only a nascent idea. But theoretically it’s pretty sound, and if it can be mastered, should be able to propel space vehicles at close to relativistic speeds.

There are other challenges, of course. The tiny craft will need robust solar sails as part of the propulsion system. And any instruments and cameras would have to be miniaturized, as would any communication equipment to send data back to Earth. But in case you haven’t been paying attention, humans have a pretty good track record of miniaturizing electronics.

Though the craft proposed are tiny, no larger than a microchip, getting them to the Alpha Centauri system is a huge step. Who knows what we’ll learn? But if we’re ever to explore another solar system, it has to start somewhere. And since astronomers think it’s possible that the Centauri system could have potentially habitable planets, it’s a great place to start.

We Explored Pluto, Now Let’s Explore The Nearest Star!

Artist’s impression of the planet around Alpha Centauri B. Credit: ESO

On July 14th, 2015, the New Horizons space probe made history when it became the first spacecraft to conduct a flyby of the dwarf planet of Pluto. Since that time, it has been making its way through the Kuiper Belt, on its way to joining Voyager 1 and 2 in interstellar space. With this milestone reached, many are wondering where we should send our spacecraft next.

Naturally, there are those who recommend we set our sights on our nearest star – particularly proponents of interstellar travel and exoplanet hunters. In addition to being Earth’s immediate neighbor, there is the possibility of one or more exoplanets in this system. Confirming the existence of exoplanets would be one of the main reasons to go. But more than that, it would be a major accomplishment!

Continue reading “We Explored Pluto, Now Let’s Explore The Nearest Star!”

What Are The Most Famous Stars?

While there are untold billions of celestial objects visible in the nighttime sky, some of them are better known than others. Most of these are stars that are visible to the naked eye and very bright compared to other stellar objects. For this reason, most of them have a long history of being observed and studied by human beings, and most likely occupy an important place in ancient folklore.

So without further ado, here is a sampling of some of the better-known stars in that are visible in the nighttime sky:

Polaris:
Also known as the North Star (as well as the Pole Star, Lodestar, and sometimes Guiding Star), Polaris is the 45th brightest star in the night sky. It is very close to the north celestial pole, which is why it has been used as a navigational tool in the northern hemisphere for centuries. Scientifically speaking, this star is known as Alpha Ursae Minoris because it is the alpha star in the constellation Ursa Minor (the Little Bear).

The Polaris star system, as seen within the Ursa Minor constellation and up close. Credit: NASA, ESA, N. Evans (Harvard-Smithsonian CfA), and H. Bond (STScI)
The Polaris star system, as seen within the Ursa Minor constellation and up close. Credit: NASA, ESA, N. Evans (Harvard-Smithsonian CfA), and H. Bond (STScI)

It’s more than 430 light-years away from Earth, but its luminosity (being a white supergiant) makes it highly visible to us here on Earth. What’s more, rather than being a single supergiant, Polaris is actually a trinary star system, comprised of a main star (alpha UMi Aa) and two smaller companions (alpha UMi B, alpha UMi Ab). These, along with its two distant components (alpha UMi C, alpha UMi D), make it a multistar system.

Interestingly enough, Polaris wasn’t always the north star. That’s because Earth’s axis wobbles over thousands of years and points in different directions. But until such time as Earth’s axis moves farther away from the “Polestar”, it remains our guide.

Because it is what is known as a Cepheid variable star – i.e. a star that pulsates radially, varying in both temperature and diameter to produce brightness changes – it’s distance to our Sun has been the subject of revision. Many scientific papers suggest that it may be up to 30% closer to our Solar System than previously expected – putting it in the vicinity of 238 light years away.

Time exposure centered on Polaris, the North Star. Notice that the closer stars are to Polaris, the smaller the circles they describe. Stars at the edge of the frame make much larger circles. Credit: Bob King
Time exposure centered on Polaris, the North Star. Notice that the closer stars are to Polaris, the smaller the circles they describe. Stars at the edge of the frame make much larger circles. Credit: Bob King

Sirius:
Also known as the Dog Star, because it’s the brightest star in Canis Major (the “Big Dog”), Sirius is also the brightest star in the night sky. The name “Sirius” is derived from the Ancient Greek “Seirios“, which translates to “glowing” or “scorcher”. Whereas it appears to be a single bright star to the naked eye, Sirius is actually a binary star system, consisting of a white main-sequence star named Sirius A, and a faint white dwarf companion named Sirius B.

The reason why it is so bright in the sky is due to a combination of its luminosity and distance – at 6.8 light years, it is one of Earth’s nearest neighbors. And in truth, it is actually getting closer. For the next 60,000 years or so, astronomers expect that it will continue to approach our Solar System; at which point, it will begin to recede again.

In ancient Egypt, it was seen as a signal that the flooding of the Nile was close at hand. For the Greeks, the rising of Sirius in the night sky was a sign of the”dog days of summer”. To the Polynesians in the southern hemisphere, it marked the approach of winter and was an important star for navigation around the Pacific Ocean.

Alpha Centauri System:
Also known as Rigel Kent or Toliman, Alpha Centauri is the brightest star in the southern constellation of Centaurus and the third brightest star in the night sky. It is also the closest star system to Earth, at just a shade over four light-years. But much like Sirius and Polaris, it is actually a multistar system, consisting of Alpha Centauri A, B, and Proxima Centauri (aka. Centauri C).

Artist’s impression of the planet around Alpha Centauri B. Credit: ESO
Artist’s impression of the planet around Alpha Centauri B. Credit: ESO

Based on their spectral classifications, Alpha Centauri A is a main sequence white dwarf with roughly 110% of the mass and 151.9% the luminosity of our Sun. Alpha Centauri B is an orange subgiant with 90.7% of the Sun’s mass and 44.5% of its luminosity. Proxima Centauri, the smallest of the three, is a red dwarf roughly 0.12 times the mass of our Sun, and which is the closest of the three to our Solar System.

English explorer Robert Hues was the first European to make a recorded mention of Alpha Centauri, which he did in his 1592 work Tractatus de Globis. In 1689, Jesuit priest and astronomer Jean Richaud confirmed the existence of a second star in the system. Proxima Centauri was discovered in 1915 by Scottish astronomer Robert Innes, Director of the Union Observatory in Johannesburg, South Africa.

In 2012, astronomers discovered an Earth-sized planet around Alpha Centauri B. Known as Alpha Centauri Bb, it’s close proximity to its parent star likely means that it is too hot to support life.

Betelgeuse:
Pronounced “Beetle-juice” (yes, the same as the 1988 Tim Burton movie), this bright red supergiant is roughly 65o light-year from Earth. Also known as Alpha Orionis, it is nevertheless easy to spot in the Orion constellation since it is one of the largest and most luminous stars in the night sky.

Betelgeuse, as seen by the Hubble Space Telescope. Credit: NASA
Betelgeuse, as seen by the Hubble Space Telescope, and in relation to the Orion constellation. Credit: NASA

The star’s name is derived from the Arabic name Ibt al-Jauza’, which literally means “the hand of Orion”. In 1985, Margarita Karovska and colleagues from the Harvard–Smithsonian Center for Astrophysics, announced the discovery of two close companions orbiting Betelgeuse. While this remains unconfirmed, the existence of possible companions remains an intriguing possibility.

What excites astronomers about Betelgeuse is it will one day go supernova, which is sure to be a spectacular event that people on Earth will be able to see. However, the exact date of when that might happen remains unknown.

Rigel:
Also known as Beta Orionis, and located between 700 and 900 light years away, Rigel is the brightest star in the constellation Orion and the seventh brightest star in the night sky. Here too, what appears to be a blue supergiant is actually a multistar system. The primary star (Rigel A) is a blue-white supergiant that is 21 times more massive than our sun, and shines with approximately 120,000 times the luminosity.

Rigel B is itself a binary system, consisting of two main sequence blue-white subdwarf stars. Rigel B is the more massive of the pair, weighing in at 2.5 Solar masses versus Rigel C’s 1.9. Rigel has been recognized as being a binary since at least 1831 when German astronomer F.G.W. Struve first measured it. A fourth star in the system has been proposed, but it is generally considered that this is a misinterpretation of the main star’s variability.

Rigel A is a young star, being only 10 million years old. And given its size, it is expected to go supernova when it reaches the end of its life.

Vega:
Vega is another bright blue star that anchors the otherwise faint Lyra constellation (the Harp). Along with Deneb (from Cygnus) and Altair (from Aquila), it is a part of the Summer Triangle in the Northern hemisphere. It is also the brightest star in the constellation Lyra, the fifth brightest star in the night sky and the second brightest star in the northern celestial hemisphere (after Arcturus).

Characterized as a white dwarf star, Vega is roughly 2.1 times as massive as our Sun. Together with Arcturus and Sirius, it is one of the most luminous stars in the Sun’s neighborhood. It is a relatively close star at only 25 light-years from Earth.

Vega was the first star other than the Sun to be photographed and the first to have its spectrum recorded. It was also one of the first stars whose distance was estimated through parallax measurements, and has served as the baseline for calibrating the photometric brightness scale. Vega’s extensive history of study has led it to be termed “arguably the next most important star in the sky after the Sun.”

Artist's concept of a recent massive collision of dwarf planet-sized objects that may have contributed to the dust ring around the star Vega. Credit: NASA/JPL/Caltech/T. Pyle (SSC)
Artist’s concept of a recent massive collision of dwarf planet-sized objects that may have contributed to the dust ring around the star Vega. Credit: NASA/JPL/Caltech/T. Pyle (SSC)

Based on observations that showed excess emission of infrared radiation, Vega is believed to have a circumstellar disk of dust. This dust is likely to be the result of collisions between objects in an orbiting debris disk. For this reason, stars that display an infrared excess because of circumstellar dust are termed “Vega-like stars”.

Thousands of years ago, (ca. 12,000 BCE) Vega was used as the North Star is today, and will be so again around the year 13,727 CE.

Pleiades:
Also known as the “Seven Sisters”, Messier 45 or M45, Pleiades is actually an open star cluster located in the constellation of Taurus. At an average distance of 444 light years from our Sun, it is one of the nearest star clusters to Earth, and the most visible to the naked eye. Though the seven largest stars are the most apparent, the cluster actually consists of over 1,000 confirmed members (along with several unconfirmed binaries).

The core radius of the cluster is about 8 light years across, while it measures some 43 light years at the outer edges. It is dominated by young, hot blue stars, though brown dwarfs – which are just a fraction of the Sun’s mass – are believed to account for 25% of its member stars.

Pleiades by Jamie Ball
Pleiades, also known as M45, is a prominent open star cluster in the sky. Image Credit: Jamie Ball

The age of the cluster has been estimated at between 75 and 150 million years, and it is slowly moving in the direction of the “feet” of what is currently the constellation of Orion. The cluster has had several meanings for many different cultures here on Earth, which include representations in Biblical, ancient Greek, Asian, and traditional Native American folklore.

Antares:
Also known as Alpha Scorpii, Antares is a red supergiant and one of the largest and most luminous observable stars in the nighttime sky. It’s name – which is Greek for “rival to Mars” (aka. Ares) – refers to its reddish appearance, which resembles Mars in some respects. It’s location is also close to the ecliptic, the imaginary band in the sky where the planets, Moon and Sun move.

This supergiant is estimated to be 17 times more massive, 850 times larger in terms of diameter, and 10,000 times more luminous than our Sun. Hence why it can be seen with the naked eye, despite being approximately 550 light-years from Earth. The most recent estimates place its age at 12 million years.

A red supergiant, Antares is about 850 times the diameter of our own Sun, 15 times more massive, and 10,000 times brighter. Credit: NASA/Ivan Eder
A red supergiant, Antares is over 850 times the diameter of our own Sun, 15 times more massive, and 10,000 times brighter. Credit: NASA/Ivan Eder

Antares is the seventeenth brightest star that can be seen with the naked eye and the brightest star in the constellation Scorpius. Along with Aldebaran, Regulus, and Fomalhaut, Antares comprises the group known as the ‘Royal stars of Persia’ – four stars that the ancient Persians (circa. 3000 BCE) believed guarded the four districts of the heavens.

Canopus:
Also known as Alpha Carinae, this white giant is the brightest star in the southern constellation of Carina and the second brightest star in the nighttime sky. Located over 300 light-years away from Earth, this star is named after the mythological Canopus, the navigator for king Menelaus of Sparta in The Iliad. 

Thought it was not visible to the ancient Greeks and Romans, the star was known to the ancient Egyptians, as well as the Navajo, Chinese and ancient Indo-Aryan people. In Vedic literature, Canopus is associated with Agastya, a revered sage who is believed to have lived during the 6th or 7th century BCE. To the Chinese, Canopus was known as the “Star of the Old Man”, and was charted by astronomer Yi Xing in 724 CE.

An image of Canopus, as taken by crewmembers aboard the ISS. Credit: NASA
Image of Canopus, as taken by crew members aboard the ISS. Credit: NASA

It is also referred to by its Arabic name Suhayl (Soheil in persian), which was given to it by Islamic scholars in the 7th Century CE. To the Bedouin people of the Negev and Sinai, it was also known as Suhayl, and used along with Polaris as the two principal stars for navigation at night.

It was not until 1592 that it was brought to the attention of European observers, once again by Robert Hues who recorded his observations of it alongside Achernar and Alpha Centauri in his Tractatus de Globis (1592).

As he noted of these three stars, “Now, therefore, there are but three Stars of the first magnitude that I could perceive in all those parts which are never seene here in England. The first of these is that bright Star in the sterne of Argo which they call Canobus. The second is in the end of Eridanus. The third is in the right foote of the Centaure.”

This star is commonly used for spacecraft to orient themselves in space, since it is so bright compared to the stars surrounding it.

Universe Today has articles on what is the North Star and types of stars. Here’s another article about the 10 brightest stars. Astronomy Cast has an episode on famous stars.

Super-Earths Could Be More ‘Superhabitable’ Than Planets Like Ours

Alien planets that are slightly bigger than Earth could be more life-friendly than exoplanets closer to our own size, a new study implies. These so-called “super-Earths” that are about two to three times that of our own planet could be “superhabitable” — implying that our own planet is a rare bird indeed when it comes to being good for life.

Bigger rocky planets would have a host of advantages, argue McMaster University’s Rene Heller and Weber State University’s John Armstrong in a paper recently published in Astrobiology. Among them: These worlds would have tectonic activity that takes longer to happen, meaning that the conditions would be more stable for life. Also, a bigger mass implies it’s easier to hang on to a thick atmosphere and to have “enhanced magnetic shielding” to hold a planet’s own against solar flares.

“Our argumentation can be understood as a refutation of the Rare Earth hypothesis. Ward and Brownlee (2000) claimed that the emergence of life required an extremely unlikely interplay of conditions on Earth, and they concluded that complex life would be a very unlikely phenomenon in the Universe,” stated the authors in their paper “Superhabitable Worlds.”

Information about Alpha Centauri Bb. Information about Alpha Centauri Bb. Credit: Planetary Habitability Laboratory/University of Puerto Rico/Arecibo
Information about Alpha Centauri Bb. Information about Alpha Centauri Bb. Credit: Planetary Habitability Laboratory/University of Puerto Rico/Arecibo

“While we agree that the occurrence of another truly Earth-like planet is trivially impossible, we hold that this argument does not constrain the emergence of other inhabited planets. We argue here in the opposite direction and claim that Earth could turn out to be a marginally habitable world. In our view, a variety of processes exists that can make environmental conditions on a planet or moon more benign to life than is the case on Earth.”

As a start, the scientists suggest looking at the Alpha Centauri system, where researchers in 2012 discovered a planet close to Earth’s size that is likely not habitable because it orbits so close to its sun.

The star system, however, is about the right age and has low enough radiation to allow life to occur on a planet or moon that “evolved similarly as it did on Earth”, providing the planet or moon “had the chance to collect water from comets and planetesimals beyond the snowline.” Further, it’s just four light-years from Earth, making it a good target for telescopic observations.

You can read more details of their research in Astrobiology or in preprint version on Arxiv.

Closest Star To Our Sun Beckons In New Hubble Image

Remember that planet discovered near Alpha Centauri almost exactly a year ago? As you may remember, it’s the closest system to Earth, making some people speculate about how quickly we could get a spacecraft in that general direction. Four light years is close in galactic terms, but it’s a little far away for the technology we have now — unless we wanted to wait a few tens thousands of years for the journey to complete.

Meanwhile, we can at least take pictures of that star system. The Hubble Space Telescope team has released a new picture of Alpha Centauri’s sister star, Proxima Centauri. While Proxima is technically the closest star to Earth, it’s too faint to be seen by the naked eye, which is not all that surprising given it is only an eighth of the sun’s mass. Sometimes, however, it gets a little brighter.

“Proxima is what is known as a ‘flare star’, meaning that convection processes within the star’s body make it prone to random and dramatic changes in brightness.” stated the Hubble European Space Agency Information Centre.

“The convection processes not only trigger brilliant bursts of starlight but, combined with other factors, mean that Proxima Centauri is in for a very long life.”

How long? Well, consider the following: the universe is about 13.8 billion years old and Proxima is expected to remain in middle age for another four TRILLION years. Plenty of time for us to send a spacecraft over there if we’re patient enough. (The universe itself is expected to last a while, as Wise Geek explains.)

The picture was nabbed with Hubble’s Wide Field and Planetary Camera 2, with neighbouring stars Alpha Centauri A and B out of the frame.

Source: Hubble European Space Agency Information Centre

Next Door Neighbors? Earth-Sized Planet Discovered in Nearest Star System to Us

Artist’s impression of the planet around Alpha Centauri B. Credit: ESO

Artist’s impression of the planet around Alpha Centauri B. Credit: ESO

Astronomers have discovered an enticing new planet that could be considered our next-door neighbor. The planet is orbiting a star in the Alpha Centauri system — the closest system to our own, just 4.3 light years away — and the planet has a mass about the same as Earth. It is also the lightest exoplanet ever discovered around a sun-like star. While this planet is likely too hot to contain life as we know it, the star system could possibly host other worlds that could be habitable, researchers from the European Southern Observatory at La Silla say.

“This result represents a major step towards the detection of Earth twins in the immediate vicinity of the Sun,” the team wrote in their paper.

“This is the first planet with a mass similar to Earth ever found around a star like the Sun. Its orbit is very close to its star and it must be much too hot for life as we know it,” said Stéphane Udry from the Geneva Observatory, a co-author of the paper that will be published in Nature on Oct. 17, and member of the team that used the HARPS instrument to find the planet. “But it may well be just one planet in a system of several. Our other HARPS results, and new findings from Kepler, both show clearly that the majority of low-mass planets are found in such systems.”

The planet is called Alpha Centauri Bb and it whips around its star every 3.2 days, orbiting at a distance of just 6 million kilometers (3.6 million miles), closer than Mercury’s orbit around the Sun. (Earth orbits at a comfortable 150 million kilometers (93 million miles) from the Sun.) So it is likely very hot and covered with molten rock, the researchers say.

Many astronomers have thought that the Alpha Centauri system would be a perfect candidate to host Earth-sized worlds. In fact, in 2008, a team of astronomers ran computer simulations of the system’s first 200 million years, and in each instance, despite different parameters, multiple terrestrial planets formed around the star. In every case, at least one planet turned up similar in size to the Earth, and in many cases this planet fell within the star’s habitable zone.

But while astronomers have looked for years, previous searches of planets in the Alpha Centauri system came up empty.

Until now.

“Our observations extended over more than four years using the HARPS instrument and have revealed a tiny, but real, signal from a planet orbiting Alpha Centauri B every 3.2 days,” says Xavier Dumusque (Geneva Observatory, Switzerland and Centro de Astrofisica da Universidade do Porto, Portugal), lead author of the paper. “It’s an extraordinary discovery and it has pushed our technique to the limit!”

The European team detected the planet by using the radial velocity method — by picking up the tiny wobbles in the motion of the star Alpha Centauri B created by the gravitational pull of the orbiting planet. The effect is extremely small, as it causes the star to move back and forth by no more than 51 centimeters per second (1.8 km/hour). The team said this is the highest precision ever achieved using this method.

Alpha Centauri is one of the brightest stars in the southern skies and is actually a triple star — a system consisting of two stars similar to the Sun orbiting close to each other, designated Alpha Centauri A and B, and a more distant and faint red component known as Proxima Centauri.

Alpha Centauri B is very similar to the Sun but slightly smaller and less bright. The orbit of Alpha Centauri A is hundreds of times further away from the planet, but it would still be a very brilliant object in the planet’s skies.

A wide-field view of the sky around Alpha Centauri was created from photographic images forming part of the Digitized Sky Survey 2. The star appears so big just because of the scattering of light by the telescope’s optics as well as in the photographic emulsion. Credit: ESO

The first exoplanet around a Sun-like star was found by the same team back in 1995 and there are now 843 Exoplanets with the addition of Alpha Centauri Bb. Most are much bigger than Earth, and many are as big as Jupiter. The previous closest exoplanet was Epsilon Eridani b, 10.4 light years away.

The challenge astronomers now face is to detect and characterize a planet of mass comparable to the Earth that is orbiting in the habitable zone around another star. The first step has now been taken, the team says.

“This result represents a major step,” said Dumusque. “We live in exciting times!”

So, how long would it take for us to get to this planet? Using current technology, our slowest mode of space transportation, ion drive propulsion, it would take 81,000 years. Using the speeds of one of the fastest spacecraft (Helios 2) and traveling at a constant speed of 240,000 km/hr, it would take about 19,000 years (or over 600 generations) to travel the 4.3 light years.

Read the team’s paper (PDF)

Source: ESO

Distance to Alpha Centauri

Alpha Centauri is the closest known star system to the Solar System. Also known as Rigil Kentaurus, Alpha Centauri is actually a multiple star system. It’s certainly a binary star, with two sunlike stars orbiting one another. And there’s also a red dwarf star, Proxima Centauri, which astronomers still argue about whether it’s part of the system.

The closest star in the group is Proxima Centauri, located only 4.243 light-years from the Sun. And then the Alpha Centauri AB stars are located 4.37 light-years away.

With the unaided eye, Alpha Centauri looks like a single star. But then under the power of a telescope, it’s possible to split them and see the individual stars separately. Alpha Centauri is only really prominent in the southern skies, and below the horizon to astronomers in the north.

Alpha Centauri A is slightly larger and more luminous than the Sun, while Alpha Centauri B is smaller and cooler than the Sun. But Proxima Centauri is a tiny red dwarf star, with only 1/8th the mass of the Sun.

We’ve written several articles about the Alpha Centauri system. Here’s an article about how we might be able to detect Earthlike planets around Alpha Centauri, and here’s an article about the sounds of Alpha Centauri.

Here’s a cool image of Alpha Centauri at Astronomy Picture of the Day.

We’ve also recorded an episode of Astronomy Cast about what it might take to travel to Alpha Centauri. Listen here, Episode 145: Interstellar Travel.

Why Haven’t Planets Been Detected Around Alpha Centauri?

Toliman

Question: Why aren’t astronomers looking for planets around nearby stars like Alpha Centauri?
Answer: That’s a great question. Since Alpha Centauri is only a little over 4 light-years away, why aren’t astronomers studying it for planets, instead of the more distant stars.

Astronomers have included stars like Alpha Centauri in their search for extrasolar planets, they just haven’t found them yet. That’s because the techniques used to find extra solar planets require very large planets orbiting very close to their parent stars.

The first technique is called the radial velocity method. This is where the gravity of the planet yanks its parent star back and forth. The changes in the star’s velocity are measurable in the light that reaches the Earth.

The second technique looks for transits. This is where the planet passes in front of the parent star, dimming it slightly. By measuring the amount the light dims, astronomers are able to know if there’s a planet there, calculate its size and even determine what’s in its atmosphere.

A third technique detects microlensing events. A closer star focuses the light from a more distant star with its gravity. From Earth, we see a flare in brightness as the two stars line up perfectly. If the closer star has a planet orbiting it, that will change the light curve that astronomers detect, allowing them to calculate the size of the planet.

Most of the planets discovered to date are known as Hot Jupiters. These are planets much larger than Jupiter that orbit within the orbit of Mercury.

A team of astronomers led by Javiera Guedes from the University of California think that an Earth-sized planet should be detectable orbiting Alpha Centauri. They’re working to get a single dedicated telescope to watch the star, and work out if there are planets there. According to their calculations, it should only take about 5 years of intense observations by a dedicated telescope to work out the answer.