Last month astronomers from the Kepler spacecraft team announced the discovery of 1,284 new planets, all orbiting stars outside our solar system. The total number of such “exoplanets” confirmed via Kepler and other methods now stands at more than 3,000.
This represents a revolution in planetary knowledge. A decade or so ago the discovery of even a single new exoplanet was big news. Not anymore. Improvements in astronomical observation technology have moved us from retail to wholesale planet discovery. We now know, for example, that every star in the sky likely hosts at least one planet.
But planets are only the beginning of the story. What everyone wants to know is whether any of these worlds has aliens living on it. Does our newfound knowledge of planets bring us any closer to answering that question?
A little bit, actually, yes. In a paper published in the May issue of the journal Astrobiology, the astronomer Woodruff Sullivan and I show that while we do not know if any advanced extraterrestrial civilizations currently exist in our galaxy, we now have enough information to conclude that they almost certainly existed at some point in cosmic history.
Among scientists, the probability of the existence of an alien society with which we might make contact is discussed in terms of something called the Drake equation. In 1961, the National Academy of Sciences asked the astronomer Frank Drake to host a scientific meeting on the possibilities of “interstellar communication.” Since the odds of contact with alien life depended on how many advanced extraterrestrial civilizations existed in the galaxy, Drake identified seven factors on which that number would depend, and incorporated them into an equation.
The first factor was the number of stars born each year. The second was the fraction of stars that had planets. After that came the number of planets per star that traveled in orbits in the right locations for life to form (assuming life requires liquid water). The next factor was the fraction of such planets where life actually got started. Then came factors for the fraction of life-bearing planets on which intelligence and advanced civilizations (meaning radio signal-emitting) evolved. The final factor was the average lifetime of a technological civilization.
Drake’s equation was not like Einstein’s E=mc2. It was not a statement of a universal law. It was a mechanism for fostering organized discussion, a way of understanding what we needed to know to answer the question about alien civilizations. In 1961, only the first factor — the number of stars born each year — was understood. And that level of ignorance remained until very recently.
That’s why discussions of extraterrestrial civilizations, no matter how learned, have historically boiled down to mere expressions of hope or pessimism. What, for example, is the fraction of planets that form life? Optimists might marshal sophisticated molecular biological models to argue for a large fraction. Pessimists then cite their own scientific data to argue for a fraction closer to 0. But with only one example of a life-bearing planet (ours), it’s hard to know who is right.
Or consider the average lifetime of a civilization. Humans have been using radio technology for only about 100 years. How much longer will our civilization last? A thousand more years? A hundred thousand more? Ten million more? If the average lifetime for a civilization is short, the galaxy is likely to be unpopulated most of the time. Once again, however, with only one example to draw from, it’s back to a battle between pessimists and optimists.
But our new planetary knowledge has removed some of the uncertainty from this debate. Three of the seven terms in Drake’s equation are now known. We know the number of stars born each year. We know that the percentage of stars hosting planets is about 100. And we also know that about 20 to 25 percent of those planets are in the right place for life to form. This puts us in a position, for the first time, to say something definitive about extraterrestrial civilizations — if we ask the right question.
In our recent paper, Professor Sullivan and I did this by shifting the focus of Drake’s equation. Instead of asking how many civilizations currently exist, we asked what the probability is that ours is the only technological civilization that has ever appeared. By asking this question, we could bypass the factor about the average lifetime of a civilization. This left us with only three unknown factors, which we combined into one “biotechnical” probability: the likelihood of the creation of life, intelligent life and technological capacity.
You might assume this probability is low, and thus the chances remain small that another technological civilization arose. But what our calculation revealed is that even if this probability is assumed to be extremely low, the odds that we are not the first technological civilization are actually high. Specifically, unless the probability for evolving a civilization on a habitable-zone planet is less than one in 10 billion trillion, then we are not the first.
To give some context for that figure: In previous discussions of the Drake equation, a probability for civilizations to form of one in 10 billion per planet was considered highly pessimistic. According to our finding, even if you grant that level of pessimism, a trillion civilizations still would have appeared over the course of cosmic history.
In other words, given what we now know about the number and orbital positions of the galaxy’s planets, the degree of pessimism required to doubt the existence, at some point in time, of an advanced extraterrestrial civilization borders on the irrational.
In science an important step forward can be finding a question that can be answered with the data at hand. Our paper did just this. As for the big question — whether any other civilizations currently exist — we may have to wait a long while for relevant data. But we should not underestimate how far we have come in a short time.
In the year 1851 cultivated persons in cities throughout Europe went to the largest cathedrals to attend an unusual sort of worship. They were coming to witness Jean Foucault’s pendulum experiment, which he had first performed for the public in that year under the dome of the Pantheon in Paris.
From the highest point in the cathedral a heavy weight hung suspended on a thin rope, so that it was free to swing in all directions. it was given a push in a northerly direction, and began to swing in a north-south line. It continued to swing for days, but ever so slowly the direction of its swing shifted. And it continued to do so visibly. Those who waited long enough were able to see the plane of the pendulum’s swing turn in a full circle in the course of a day.
Actually, however, the plane of oscillation had not change d at all. A pendulum retains the direction of its original motion, as stated by Galileo’s law of inertia. Thus the pendulum provided visible proof of Copernicus’ doctrine: the Earth was turning underneath the swinging pendulum.
How unfortunate it was that Galileo did not notice this when he observed the chandelier swinging in the Duomo at Pisa. He would have been spared his troubles with the Inquisition; such tangible proof of the Earth’s rotation would have silenced all doubts.
Nevertheless, the Frenchman’s ingenious experiment stimulated other ideas, for which the times and the place were ready: ideas on one of the fundamental problems of both philosophy and religion.
Originally Newton had asked himself whether absolute movement existed in the universe, that is to say, movement in itself which we could determine without reference to other movements. His answer was that there was only one such motion: the rotation of the Earth. Ultimately, he maintained, we would have discovered this motion even if there had not been a sky full of stars circling about the polestar above our heads. Even without the polestar we would have found the flattened poles of our globe; we would have understood that they had been caused by the distorting effect of centrifugal force.
From this reasoning Newton drew a profound conclusion. If we imagine our universe with no other bodies beside the Earth, there must still be something to which we can refer the motion of the Earth, something that is at rest in relation to the Earth. Absolute motion presupposes something absolutely at rest. Only space can be this something. Hence, space ceases to be solely a philosophical concept, a mere word; it must have physical existence, for all that its only characteristic is being at rest. This idea of something at rest, ubiquitous, absolutely fixed, suggested the attributes of the Supreme Being; physical space of its own accord intruded itself into the sphere of religion.
Assuming the standard model is true, our universe’s end will likely all come down to one of three theories, each of which depends upon three things: the shape of the universe, how much dark energy is contained within it, and how the densities of dark energy will respond to the expansion of the universe.
There are believed to be three possible shapes of the universe: an open universe, a flat universe, and a closed plane of space-time.
In an open universe (think of a gigantic, saddle-shaped object), the universe is likely to experience the Big Freeze. In this scenario, the universe will continue to expand until matter has stretched incredibly thin, the stars have all burnt out, galaxies have ceased creating new stars to replace them, and all mass as we know it has ceased to exist. Everything will become dark and cold. The universe won’t so much as end as it will simply fizzle out, settling into a silent and lonely slumber at absolute zero.
Another possibility for universal armageddon is the Big Rip. Not as dependent on the shape of the universe as much as the amount of dark energy contained within it, this model implies that the acceleration of the universe will continue to increase without slowing, and the dark energy will become so strong that it will overwhelm the other elemental forces. Galaxies, suns, and planets alike will begin tearing themselves apart, all ending in a gravitational singularity — a place in which the standard rules of physics and relativity no longer apply.
Somewhat less unsettling is the theory of the Big Crunch, in which the universe will continue to expand until matter begins to slow the rate of expansion. Once slowed enough, the expansion will eventually come to a halt and begin to retract. Everything — planets, suns, galaxies, black holes, even the indestructible iPad 7000 — will all come crashing back together, culminating in a Big Crunch: essentially the opposite of the Big Bang that kicked our universe off in the first place. The bright side here is that the crunch is thought to be succeeded by yet another Big Bang and the creation of a whole new universe. Unfortunately, of the three, the Big Crunch is currently the least favored hypothesis within the physics community — meaning our dreams of an endlessly cycling universe of birth, destruction, and rebirth may end up being relegated to the realm of science fiction.
Each of the two gargantuan objects is 10 billion times the size of our sun.
Scientists have found the biggest black holes known to exist — each one 10 billion times the mass of our sun. A team led by astronomers at the University of California, Berkeley, discovered the two gigantic black holes in clusters of elliptical galaxies more than 300 million light years away. That’s relatively close on the galactic scale.
“They are monstrous,” Berkeley astrophysicist Chung-Pei Ma told reporters. “We did not expect to find such massive black holes because they are more massive than indicated by their galaxy properties. They’re kind of extraordinary.”
The previous black hole record-holder is as large as 6 billion suns. In research released Monday by the journal Nature, the scientists suggest these black holes may be the leftovers of quasars that crammed the early universe. They are similar in mass to young quasars, they said, and have been well hidden until now.
The scientists used ground-based telescopes as well as the Hubble Space Telescope and Texas supercomputers, observing stars near the black holes and measuring the stellar velocities to uncover these vast, invisible regions.
Black holes are objects so dense that nothing, not even light, can escape. Some are formed by the collapse of a super-size star. It’s uncertain how these two newly discovered whoppers originated, said Nicholas McConnell, a Berkeley graduate student who is the study’s lead author. To be so massive now means they must have grown considerably since their formation, he said.
Most if not all galaxies are believed to have black holes at their center. The bigger the galaxy, it seems, the bigger the black hole. Quasars are some of the most energized and distant of galactic centers.
The researchers said their findings suggest differences in the way black holes grow, depending on the size of the galaxy. Ma speculates these two black holes remained hidden for so long because they are living in quiet retirement — much quieter and more boring than their boisterous youth powering quasars billions of years ago.
“For an astronomer, finding these insatiable black holes is like finally encountering people nine feet tall whose great height had only been inferred from fossilized bones. How did they grow so large?” Ma said in a news release. “This rare find will help us understand whether these black holes had very tall parents or ate a lot of spinach.”
Oxford University astrophysicist Michele Cappellari, who wrote an accompanying commentary in the journal, agreed that the two newly discovered black holes “probably represent the missing dormant relics of the giant black holes that powered the brightest quasars in the early universe.”
One of the newly detected black holes weighs 9.7 billion times the mass of the sun. The second, slightly farther from Earth, is as big or even bigger. Even larger black holes may be lurking out there. Ma said that’s the million-dollar question: How big can a black hole grow?
The researchers already are peering into the biggest galaxies for answers. “If there is any bigger black hole,” Ma said, “we should be able to find them in the next year or two. Personally, I think we are probably reaching the high end now. Maybe another factor of two to go at best.”
The Milky Way Galaxy, commonly referred to as just the Milky Way, or sometimes simply as the Galaxy,[a] is the home galaxy of the Solar System, and of Earth. It is agreed that the Milky Way is a spiral galaxy, with observations suggesting that it is a barred spiral galaxy.
It contains 200-400 billion stars and is estimated to have at least 50 billion planets, 500 million of which could be located in the habitable zone of their parent star. New data suggests there may be up to twice as many free-floating planets in the Milky Way as there are stars. The Milky Way is part of the Local Group of galaxies and is one of around 200 billion galaxies in the observable universe.
The Solar System is located in the Milky Way galaxy around two thirds of the way out from the center, on the inner edge of the Orion–Cygnus Arm. The Sun orbits around the center of the galaxy in a galactic year—once every 225-250 million Earth years.
The “Milky Way” is a translation of the Latin Via Lactea, in turn translated from the Greek Γαλαξίας (Galaxias), referring to the pale band of light formed by stars in the galactic plane as seen from Earth.
All the stars that the eye can distinguish in the night sky are part of the Milky Way galaxy, but aside from these relatively nearby stars, the galaxy appears as a hazy band of white light arching around the entire celestial sphere. The light originates from stars and other material that lie within the galactic plane. Dark regions within the band, such as the Great Rift and the Coalsack, correspond to areas where light from distant stars is blocked by dark nebulae.
The Milky Way has a relatively low surface brightness due to the interstellar medium that fills the galactic disk, which prevents us from seeing the bright galactic center. It is thus difficult to see from any urban or suburban location suffering from light pollution. A total integrated magnitude of the whole Milky Way stretching across the night sky has been estimated at −5.0.
The center of the galaxy lies in the direction of Sagittarius, and it is here that the Milky Way looks brightest. From Sagittarius, the hazy band of white light appears to pass westward through the constellations of Scorpius, Ara, Norma, Triangulum Australe, Circinus, Centaurus, Musca, Crux, Carina, Vela, Puppis, Canis Major, Monoceros, Orion and Gemini, Taurus, Auriga, Perseus, Andromeda, Cassiopeia, Cepheus and Lacerta, Cygnus, Vulpecula, Sagitta, Aquila, Ophiuchus, Scutum, and back to Sagittarius. The fact that the band divides the night sky into two roughly equal hemispheres indicates that the Solar System lies close to the galactic plane.
The galactic plane is inclined by about 60 degrees to the ecliptic (the plane of the Earth’s orbit). Relative to the celestial equator, it passes as far north as the constellation of Cassiopeia and as far south as the constellation of Crux, indicating the high inclination of Earth’s equatorial plane and the plane of the ecliptic relative to the galactic plane. The north galactic pole is situated at right ascension 12h 49m, declination +27.4° (B1950) near beta Comae Berenices, and the south galactic pole is near alpha Sculptoris.
Claims about a possible ninth planet in our solar system are being met with curiosity and skepticism.
Forget the “Sputnik moment.” If two astrophysicists are correct, we may be having a “Tyche moment” — a ninth planet to add to our solar system. But that’s a big “if.”
The two scientists who make the claim, Daniel Whitmire and John Matese from the University of Louisiana at Lafayette, say a planet they named Tyche — that is four times the size of Jupiter — may be lurking in the outer solar system.
The pair says that the NASA Wise telescope may already have data to prove its existence, but that the planet, if it exists, won’t reveal itself for another two years.
Two astronomers have been saying there is a planet called Tyche in our solar system, four times larger than Jupiter. However, as reports on Tuesday say, other astronomers say it probably does not exist.
Tyche exists in the outer solar system in a region called the Oort, the two astronomers said, according to the Independent newspaper. The Oort is a hypothesized cloud of comets nearly one light-year from the sun. Oort’s outer regions correspond to the outer boundary of the solar system.
“There’s evidence that some Oort cloud comets display orbital peculiarities,” astrophysicist John Matese told Life’s Little Mysteries, adding that Tyche’s existence would explain the strange orbits of comets in the cloud. “We’re saying that perhaps the pattern is indicative that there’s a planet there.”
Matese and fellow University of Louisiana-Lafayette colleague Daniel Whitmire told the newspaper they believe the mysterious planet will reveal itself in around two years. Since 1999, the two have maintained Tyche does exist and is within the solar system.
“If it does, John and I will be doing cartwheels,” Professor Whitmire told the newspaper. “And that’s not easy at our age.”
However, the International Astronomical Union (IAU) would decide Tyche’s status as a planet in our solar system. In recent years, the IAU demoted Pluto to a dwarf planet.
Matthew Holman, a planetary scientist at the Harvard Smithsonian Institute of Astrophysics, says Tyche probably does not exist, or at least within our solar system.
“Based on past papers that I’ve seen looking at where long-period comets came from in the sky, and finding signatures of large perturbers of the Oort cloud, I was not persuaded by the evidence,” he told Life’s Little Mysteries.
Planetary scientist Hal Levison with Southwest Research Institute in Boulder, Colo., made a similar statement.
“What Matese claims is that he sees an excess of comets coming from a particular place, which he attributes to the gravitational effects of a large planet in the Oort cloud,” he told the website. “I have nothing against the idea, but I think the signal that he claims he sees is very subtle, and I’m not sure it’s statistically significant.”
The Independent noted that the planet, which would likely comprise hydrogen and helium gases, should push comets from the inner Oort cloud, but this has not been observed.