Planets With Four Suns May Be Not So Rare After All

While numerous two- and three-star systems containing planets have been discovered (with planet-harboring binary-star systems possibly outnumbering planet-harboring single star systems), four-star systems with planets were at first thought to be if not impossible, highly unlikely. How can a planet maintain an orbit? 

30 Ari a Double Double

However, we now know of two planet-harboring quadruple-star systems. First was Kepler-64b, found in 2012. The latest is a system called 30 Ari which lies 136 light-years away in the constellation Aries. The star system was first thought to be a triple-star system but a fourth star was discovered, making 30 Ari a double double-star system, with each binary orbiting a point in space between the two systems (the center of gravity for the entire quadruple-star system).

A diagram of the newfound system show the two pairs of stars in orbit together, while a planet circles one of them. Credit: NASA/JPL-Caltech

The Planet (30 Ari B b) 

The one planet found to date is a giant planet 10 times the mass of Jupiter and orbits the main star in 30 Ari  B every 335 days; it lies about 0.995 AU from the main star. The second star orbits at about 22 AUs away (for comparison, The Earth is 1 AU from the Sun, Uranus is around 20 AUs away, and Neptune is about 30AUs away). 

The planet orbiting the main star in 30 Ari B might lie just within the habitable zone. While the planet itself is probably not habitable due to its mass (it is most likely a gas giant), this does not rule out a habitable moon.

A Complicated Sky

A sentient being on such a hypothetical moon would see sometime in the daytime sky (when the gas giant is not occluding or blocking the main star) one small sun and two bright stars. With a large telescope, it would see that one of the bright stars was a binary system (30 Ari A binary system).

Some days, depending upon the tilt of the gas giant and thus the orbital plane of the moon with regards to the orbital plane of the stars, as well as possibly depending upon latitude if on a large moon, the sentient being would see just one (the main) star in the sky, or the main star with one of the two bright stars. One of those stars would show retrograde motion on a "yearly" basis.

Why celestial objects orbiting farther out display retrograde motion.
Credit: Prof. Pogge, Ohio State University.

Night, or when the gas giant is blocking the main 30 Ari B star, the sentient being would sometimes see those two bright stars (they would be the brightest nighttime stars), or just one of them, and sometimes none. If the moon is on the sun-facing side of the gas giant, the nighttime side of the moon would face the gas giant which would probably block any stars of any kind from being seen.

In fact, with a gas giant 10 times the mass of Jupiter, it is possible the moon beings would not see the night sky for part of their year. When their moon-planet is between the main star and the gas giant, night is just the gas giant. When the orbit begins to take the moon to the other side of the gas giant, then a starry night begins to be seen, with the day being replaced by a starry night (and the nights always the gas giant filling the sky, or filling most of it). This does depend upon how far away the moon is orbiting from the gas giant. Further away and then they may be able to see the night sky framing the gas giant, though most of the sky would still be the gas giant.

What a complicated sky! What complicated early religions would arise from such complexity? A mighty light in the sky that has two smaller, wandering lights that has a complicated dance.

If the newfound star is on the same orbital plane as the main 30 Ari B and main 30 Ari A stars, then sometimes the lesser lights (but still brighter than any other star) would seem to merge together, only to separate again, on a repetitive basis. If not, then they would approach and pass each other, with the newfound star being the fastest moving.

The 30 Ari A system would be like a zodiac indicator, for when the beings are able to see the night sky, since the 30 Ari A system is always opposite of the 30 Ari B system (circling a point in space in between the two systems). But since the 30 Ari A system is moving (both systems dancing around that shared point), that pointer would slowly move over the centuries, where, for example, the first day of spring used to be when 30 Ari A was in constellation D, it has slowly moved to where it is now in constellation E.

I would think that sentient beings would be pattern seekers on some level--visual ones would try to make some sense of the dots in the night sky, whether they would have a close equivalent to our concept of a zodiac is another matter. The stars will align at certain times of the year, times that are important for a primitive people to survive (best time to hunt, when to prepare for lean season, etc), as well as any religious meaning that gets attributed to stars and the movement/dance of those stars.

What kind of Stonehenge would arise in such a complex system? Though the aliens would be able to handle it--we had to figure out when eclipses would occur and that is no easy matter. 

Even More Complexity

Just as the two binaries orbit a shared center of gravity, the stars within each binary revolve around a shared center of gravity (or barycenter). The more alike in mass the two stars in a binary system are, the more the center of gravity will be outside of each star, in between. Two equally massive stars would orbit around a point essentially halfway between the two stars. A big imbalance in masses, however, could put the center of gravity inside the largest star. In our solar system the barycenter moves about as the planets have different masses, revolve at different rates, and are at different distances--sometimes the barycenter is inside the Sun, sometimes outside the Sun.

Solar System Barycenter Orbit Around Sun, from Wikimedia Commons. Credit Carl Smith, Rubik-Wuerfel.

Depending upon how heavy the newfound star turns out to be relative to the main star, the barycenter could be midpoint. Then the newfound star would never go behind 30 Ari B. The newfound star would sometimes be in the daytime sky and sometimes in the nighttime sky, but it would never be seen to merge with the main star. 30 Ari A still would--and depending upon orbital planes, could still look like it merges with the newfound star.

All Hail the Sky Giant

Retrogrades are hard to explain if you believe your planet is non-spinning. Would seeing a large gas giant spinning above you help a race to think of their planet, the gas-giant's moon, as spinning as well? With ancient humans, the Moon pretty much always kept the same face toward the Earth (we can see a wee bit more as the Moon's orbit is not perfectly circular). A gas giant, even if the giant's moon was tidally locked, would appear to be spinning. Even if the gas giant was tidally locked, there would be at least some cloud bands that would circle the globe and spin. However, maybe those cloud bands would be looked at as just clouds and no proof of a spinning planet.

On the other hand, the sentient beings would probably quickly realize they are orbiting that gas giant. The moon would not be the center of the universe--the gas giant would be. They may try to at first explain the night sky as everything circling the gas giant.

A gas giant that is always looking down on them, a huge presence every night. The main star is not as constant, disappearing behind the gas giant for part of each year. The two bright wandering stars also disappear behind (or into) the gas giant at different times of the year. A sense of pattern helps to put a mind at ease--chaos is dangerous, especially to early societies that are always on the edge of death due to climate patterns (from too little rain to too much rain to devastating storms or floods or fires during times of droughts, etc). And the one constant--the only constant (even if it face changes a bit with the cloud bands)--the gas giant, the sky giant.

Would the gas giant then be the home of the gods? Heaven? Hell? Birth place of the universe? A god itself?

The Great Eye(s)

And if that gas giant had one or more giant storms, like Jupiter, a big eye or eyes peering down? The ever watching eye...if tidal lock and always see the eye. If not, then the eye moves--watching the heavens, scanning creation, turning its eye upon the inhabitants of the moon on a regular basis.

When the eye appears, is that the time to supplicate to the great sky god? When its eye is most directed to the moon?

Hypervelocity Stars (updated)

© Ruth Bazinet/Harvard-Smithsonian
Center for Astrophysics

Hypervelocity stars are stars that are moving, on average, around 7x than the average for, well, your average star. OK, in other words the average velocity for most stars is around 223,694 mph, which seems plenty fast but your average hypervelocity star moves at 1,615,068 mph (1.6 million mph)!

What causes these stars to become dragsters? A binary star system tangling with a black hole. If the conditions are right, one of the binary will be captured by the black hole, while the other star gets flung away at great velocity.

Not many of these hypervelocity stars have been found so far. One recent discovery, HE 0437-5439, has not been ejected from the Milky Way, but from the Large Magellanic Cloud (LMC), a small neighbor galaxy. This star is strong indirect proof of a black hole somewhere in the LMC.

What would that mean for any life on a habitable planet around such a star? They would see constellations change about 7 times faster than we do and they would experience a slight relativistic time dilation (1.5 minutes per year).

But most importantly, they would either pass by other stars several times more often than our own Sun, or be flung out into intergalactic space - far from any other star. The latter would be lonely civilizations indeed, unless they could somehow develop faster than light speeds, as it may take a few billion years for sentient life to arise on such a planet; after a few billion years they would be thousands of light years out into intergalactic space by the time they developed a technological civilization. They would be even further out if they had the unfortunate luck of being ejected from the galaxy, or the LMC, in the opposite direction of the galaxy's trajectory (the Local Group of galaxies, of which the Milky Way and the LMC are members of, is moving at 1.34 million miles per hour in the direction of the constellation Hydra) ¹.

There is an additional effect of being flung out into intergalactic space: being so far from other stars would mean the chances of being effected by a nearby supernova would be nearly zero. As mentioned in a previous post, for the Earth, a supernova 30 light years or closer would be quite devastating for life - for other planets, the distance could be greater, depending upon how thick their protective atmospheres are (to show you how protective our atmosphere is, for astronauts outside the Earth's atmosphere, a supernova 3,000 light years away could be deadly). Some scientist conjecture that maybe a supernova was involved in past extinction events on Earth.

In addition, the solar system would not be affected by galactic disturbances (compression waves, for instance). Thus, the system might be more "boring" than our own, and thus allow sentient life to form more rapidly. HE 0437-5439 is a young star, only 35 million years old, so if there are any planets around it (and it is a big if), and if one of those planets is habitable and in the habitable zone, most likely hasn't arisen yet. But if it does, and it evolves into a sentient race, it will be a very isolated race.

Would they feel themselves blessed by being alone in the universe? Will it appear, to them, that the entire universe revolves around them - even the galaxies? Though if their parent galaxy is racing away from them, what would the make of it? Would they instead feel abandoned? Any thing they create would be lost when their star dies - there would be no one else to ever come along to explore their world. Would this affect how they lived? And if so, how?

Of course, if faster than light travel is somehow possible, by some "trick" (like worm holes), maybe they would be more pressured to discover it than would other, galactic, civilizations; and solve their isolation that way.

Another example of counsel given by Hamlet: "There are more things in heaven and earth, Horatio, Than are dreamt of in your philosophy" (Hamlet Act 1, scene 5, 159–167). Speculating on on possible extrasolar (alien) biological, psychological, societal, technological, and theological realities stretches the dreams of any of our philosophies here on Earth!

Notes:

1. A light year is the distance light travels in mph: 186,000 miles/second * 60 seconds/minute * 60 minutes/hour = 669,600,000 mph.

The distance light travels in a year: 186,000 miles/second * 60 seconds/minute * 60 minutes/hour * 24 hours/day * 365 days/year = 5,865,696,000,000 miles/year.

A hypervelocity star traveling at 1,615,000 mph would be traveling at 0.04145 light years per year: 1,615,000 mph/669,600,000 mph = 0.0024119 or 0.24119 % the speed of light.

Thus, the hypervelocity star would cover 0.24119% of 5,865,696,000,000 miles/year; it would take the star 414.611 years to cover a light year.

For a hypervelocity star leaving a galaxy, in 4 billion years it could be (depending upon relative velocity of it with its parent galaxy) 9,647,597.386 light years away from its parent galaxy! If sentient life takes as long to develop on a planet around such a star as it did on Earth (4.5 billion years), it would be 10,853,547.06 light years away.


References:

Kraan-Korteweg, Renée C. & Ofer Lahav. "Galaxies Behind The Milky Way." Scientific America. October 1998.

Przybilla, N. et al. "LMC origin of the hyper-velocity star HE 0437-5439. Beyond the supermassive black hole paradigm." Astrophysical Journal Letters. Submitted on 29 Jan 2008. 17 Feb 2008. <http://arxiv.org/abs/0801.4456>.

"What is a Light Year?" How Stuff Works. 17 February 2008. < http://www.howstuffworks.com/question94.htm>.

Methuselah - 13 Billion Yr Old Planet (Garden of Eden?)

© John Whatmough

In 2003, astronomers using the Hubble Space Telescope discovered something amazing deep in the M4 globular cluster 7,200 light years away - something that shouldn't be: a planet, 2.5 times the size of Jupiter, orbiting 23 AUs from a pulsar (a rotating, pulsating neutron star), PSR B1620-26. The primary star, the pulsar, has a companion white dwarf orbiting approx 1 AU out.

According to current theories, planets could not form in the early universe (1) - for one thing, early stellar nurseries shouldn't have enough heavy elements to create stars with planets. But somehow at least one planet was formed in the young universe - while the universe is 14 to 15 billion years old, this planet, dubbed Methuselah, is nearly 13 billion years old.

Imagine that - a planet almost as old as the universe itself. Could a civilization have arisen there? Or died out and rose again (that old of a planet, life would have time to restart several times)? And in the final years, moved out into the stars?

I can't help but think of old races often called "The Ancients" or similar such nomenclature in science fiction tales - very old races that seed the rest of the galaxy before ascending or mysteriously moving on to other galaxies, leaving this one behind.

And if life first began in this universe on such an old planet (or, more likely, a smaller sister planet), could that then be the real Garden of Eden, from which Adam and Eve where exiled from?

Of course, orbiting a pulsar is dangerous for life for two reasons: 1) a pulsar is a result of a supernova which tends to destroy worlds (strip away the atmospheres at the very least) and 2) pulsars give off extremely intense beams of radiation along the lines of its magnetic axis - if any planet is in the path of the beam of the rapidly spinning star, the radiation would be too intense for life to survive or form (2).

As we have seen in a previous post, Planets, planets everywhere, planets can reform around a pulsar - from the rocky debris of the original planets, blasted from the supernova explosion.

Scientists, however, do not feel that Methuselah is a "reconstituted" planet. One theory is that the planet (and maybe others too small to be detected by present means) was captured from a sideswipe with another younger system later on - a system that existed for 10 billion years before wandering too deep into the core of the globular cluster, where distances between star systems can sometimes be less than 1 light year.

Recall from an earlier post, An Aside - Are There Alien Worlds in Our Own Solar System?, there is some evidence that our own solar system has "adopted" objects from an alien solar system passing by in the distant past - possibly when it was still in an open globular cluster (scientists theorize that our sun was first formed in an open cluster).

In fact, the scientists feel that the white dwarf companion was also "adopted" by the primary neutron star. They theorize that the pulsar did have a dwarf companion at first, but when a yellow star system came too close, the gravitational tug-of-war kicked out the dwarf and the yellow star took its place, along with at least one of its planets. The new system then moved out from the core of the globular cluster - reducing any chances for further collisions.

In this new binary system, some of the mass from the yellow star got sucked into the pulsar, speeding up its rotation, giving it the incredible spin rate of 100 revolutions every second. After some millions of years, the yellow star became a red giant and then a white dwarf.

So it is quite possible that the Methuselah, and any other world(s) circling PSR B1620-26, were "adopted," right along with their sun. If so, could one of them developed life before being captured by the pulsar/dwarf system? Early planetary systems would most likely be made up of gaseous planets - there shouldn't be enough heavy elements for terrestrial planets to form. But then we didn't think any planets as old as Methuselah should exist either. Maybe, just maybe, a small terrestrial planet does exist along with Methuselah. And even if not, life is not necessarily restricted to terrestrial planets - life could begin and thrive on non-terrestrial planets (albeit, such life would not be life as we know it).

One problem such life would face is that being captured by the pulsar would prove to be quite the dramatic change. If they are lucky, the radiation beam from the pulsar would point far above the ecliptic, thus avoiding being bathed in intense radiation every 1/100th of a second; but even then, the difference in light (and heat) would be devastating as it is rather certain the planets' new orbits around the binary pair would be different than when they were just circling around their single parent star. But as we see on Earth, life, once formed, is tenacious and will find a way to survive, even during the occasional mass extinctions.

For intelligent life, depending upon their level of technological advancement, they could migrate to a sister world circling the new binary system, one that was now more hospitable than their home world. Otherwise, they would be forced to adapt to their new, darker, colder world. Or, if they were highly advanced at the time the collision was imminent, and finding themselves in a crowded neighborhood, could explore nearby systems and move to one that was safer -though it is doubtful any planetary system in the core of cluster would be safer, especially any system that was lingering in the core, and thus increased chances of itself colliding with another star system. No, more likely they would have to figure out how best to ride out the collision.

At first scientists thought planetary systems couldn't survive long in a cluster, especially a globular cluster - but increasing evidence is showing that sometimes this is not the case. Although, lingering too long in a cluster is still thought not the best environment for life; for one thing, a globular cluster has many stars in relatively close proximity - a supernova from a nearby star can have devastating effects for life on the planets of neighboring star systems and being in a globular cluster, chances for being near a supernova are rather high. For the Earth, a supernova 30 light years or closer would be quite devastating for life - for other planets, the distance could be greater, depending upon how thick their protective atmospheres are (to show you how protective our atmosphere is, for astronauts outside the Earth's atmosphere, a supernova 3,000 light years away could be deadly).

But, it is not impossible. That extrasolar system could have been one of the earliest gardens of life in the universe. 12.7 billion years ago the planetary system was formed. Our own system is "merely" 4.5 billion years. It is thought that the first 10 billion years Methuselah led a "normal" life around a normal sun like star. And if it was, was that life able to evolve to a space faring species? Are there descendants scattered about the Milky Way (or at least in that region of the Milky Way)?

Notes:

1. Early stars were poor in heavy elements, and thus could not form planets, but when they died, they produced heavy elements which then became part of new nebulae within which new stars were born - and with heavy elements now in the mix, allowing planets to finally be formed as well.

2. While pulsars are formed from massive stars, white dwarfs are formed from the average main sequence star - most stars in the galaxy will end their lives as white dwarves.

References:

Britt, Robert Roy. "Primeval Planet: Oldest Known World Conjures Prospect of Ancient Life." Science. SPACE.com. 10 July 2003. 6 January 2008. <http://www.space.com/scienceastronomy/oldest_planet_030710-1.html>

"Extrasolar Visions - 'Methuselah' PSR B1620-26 c." Extrasolar Planet Guide. 5 January 2008. <http://www.extrasolar.net/planettour.asp?PlanetID=30>

"Messier Object 4." The Messier Catalog. SEDS. 21 August 2007. 6 January 2008. <http://www.seds.org/Messier/M/m004.html>

Mukai, Koji and Eric Christian. "Destruction of the Earth by a Nearby Supernova." Ask an Astrophysicist. Imagine the Universe! 1 December 2005. 5 January 2008. <http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/980521a.html>

"Oldest Planet Challenges Existing Theories." This Week in Science. 11 July 2003. 5 January 2008. <http://www.twis.org/2003_07_11_science_news.html>

Richmond, Michael. "Will a Nearby Supernova Endanger Life on Earth?" 8 April 2005. 5 January 2008. <http://stupendous.rit.edu/richmond/answers/snrisks.txt>

Planets thrive around binary star systems

Using the Spitzer space telescope, astronomers have observed that binary (or twin) star systems are just as likely to have planets around them as single star systems (like our own). In fact, some evidence points to planetary systems being more common around tight binary pairs than around single stars (with a possible ratio of 3:1).

A tight binary is where each star circles the other closely, say within 3 A.U.s or closer. A planet in the habitable zone of that system would see double sunsets like what the fictional Luke Skywalker saw on his home planet of Tatooine. The stars could be double gods, twin gods, to a developing sentient culture; though the comments about the trinary system come into play here as well: sentient beings on desert planets may hold water to be a higher deity, or at least the good deity, and sentient beings on water planets may, depending upon environmental conditions, hold underwater volcanoes or volcanic vents to be a higher deity, with the sky an alien, otherworldly place (maybe the afterlife - or hell).

Wide binary systems would have sunsets similar to our own on Earth - the second star would be so far away as to barely interact with the main star and the planets circling it. Sunsets there would have one large sun setting, with the second sun appearing as a bright star. The bright star may hold a place in developing primitive theologies, but, baring other factors (large nearby galaxy visible in the night sky, orbiting a large gas giant that may block the night sky half the time, or if the habitable moon is in phase lock with the gas giant, the sentient beings nocturnal, to name a few), the main star would be the center point.

I suppose it is a small possibility that in some systems the far off twin could have planets about it. What an interesting system that could be if life arose on planets circling each star - each unaware of the other until technological developments allowed one, or both, to spot the other. It would still be quite the feat for each planet to physically visit each other, not until space travel more advanced than what we have now is developed; but at first tentative long range observations, then electronic communication and space probes could establish some kind of communication between the two. What kind of theologies would exist there?

And what would happen for two planetary civilizations to be that "close" to each other to come in contact with each other versus two planetary civilizations from totally different solar systems, separated by much more distance (and thus slower communication, and less likelihood of physical contact). Probably easier to keep such a thing secret from the public, but in a wide binary system, the other civilization would be easier to detect and communicate with, thus making it harder to keep the existence of another civilization secret - not without going through extreme measures like banning all public ownership of telescopes, both optic and radio, and, if they have a planet of sovereign nations, or similar social structures, that would add another layer of difficulty in keeping the other extraplanetary civilization secret.

Reference:

"Alien Sunset." Spitzer - NASA. 29 March 2006. 22 November 2007. <http://www.nasa.gov/mission_pages/spitzer/multimedia/doublesunset.html>.

"NASA Telescope Finds Planets Thrive Around Stellar Twins." Spitzer - NASA. 29 March 2006. 22 November 2007. <http://www.nasa.gov/mission_pages/spitzer/news/spitzer-20070329.html>.

Image:

From Digital Blasphemy <http://www.digitalblasphemy.com/>.