Astrology, Astronomy, and Jetology

Every once in a while, I am mistakenly introduced as an astrologer instead of an astronomer.  There's a big difference, as I am quick to point out.  Astrology is an ancient superstition, left over from thousands of years ago, when most people saw celestial objects as gods or symbols of the gods, and not as physical bodies whose characteristics our instruments can now explore.

When, in the 1980's, it was revealed that President Reagan's White House schedule was for years vetted by a San Francisco astrologer, I was interviewed by the media as a critic of astrology.  I tried to come up with an analogy that would make sense to the news media and the public for why scientists had a hard time believing in the idea that your personality or destiny would be governed by the location of the Sun, Moon, and planets in the sky at the moment of your birth. I suggested a new form of "cosmic wisdom" called JETOLOGY, where your personality or fate could be explained by the position of all the jumbo jets at the time you were born. When people sniggered at the notion of jetology, I could then ask why astrology sounds any better.

I am reminded of this because, for those of you who are in the San Francisco Bay Area, I am preparing to be one of the featured speakers at SkeptiCAL, a one-day conference Saturday, May 31 in Oakland, on how to confront claims of the paranormal or the "too good to be true" by using common sense skeptical thinking.  See: http://www.skepticalcon.com/

Years ago, I wrote a short "Astrology Defense Kit" for science-oriented people who meet astrology believers.  You can read it at: https://www.researchgate.net/publication/253783518_Your_Astrology_Defense_Kit?ev=prf_pub 

If you want to see a wonderful short video on how it can be that the vague pronouncements that make up most astrological readings are taken seriously, I recommend the following episode of "Trick of the Mind" by British magician and skeptic, Derren Brown: https://www.youtube.com/watch?v=haP7Ys9ocTk

Ah, skeptical thinking -- if we had more of it during our years of education, during political campaigns, or when we view advertisements, our country would be so much better off.

A Possible Sister Star that Formed with Our Sun

Astronomers now know that stars, like people, tend to be sociable. Stars are often born and hang out in groups -- double stars, triple stars, star associations, and star clusters.  Yet our Sun is a single star, surrounded only by its family of planets and moons, but no sibling star to keep it company.  Was it always this way?

In recent years, it's become clearer that our Sun could well have formed in a loose group of thousands of stars, when it first "clumped" out of the gas and dust (raw material) of the Galaxy some 5 billion years ago.  If our mother cluster was indeed just loosely held together by the mutual gravity of the stars, in all that time, the stars could have drifted apart -- as many families do in the busy course of life. 

So we have been on the lookout for the Sun's now far-away sisters. This past week, a team of astronomers, headed by Ivan Ramirez of the University of Texas, announced that they might have found our first long-lost sibling. 

There are perhaps as many as 400 billion stars in our Milky Way Galaxy.  How can we possibly find our sisters in that huge and anonymous crowd?  After all, there are no star birth certificates on file at county offices and no little tags that hang around a star's neck.  The search involved two factors: First they looked for stars that have the same chemical make-up as the Sun (they consist of the same proportion of elements) -- which you'd expect from stars born in the same"womb."  And then they searched for stars whose motion could be calculated backwards in time and would have placed them close to us 5 billion years ago. 

Sorting through 30 possible candidates identified by other groups of astronomers after painstaking work, Ramirez' group came up with exactly one star that fit all the criteria.  Called by its catalog number, HD 162826, it's 110 light years away now, in the constellation box called Hercules.  (See the map.)  It has 15 % more mass than the Sun, and so it is a little brighter and a little hotter than our star. (In astronomy jargon, it's a Type F star, while our Sun is Type G.)

It turns out that HD 162826 has been searched for planets for the last 15 years, and so far, no planets have turned up.  But the kind of search it has been subjected to can't find small (Earth-like) planets. So the we have a long way to go before we can decide it the star has a planetary system around it or not.

Future surveys, allowing us to analyze the make-up of fainter stars, could well turn up other family members out there.  For now, astronomers will keep a far closer eye on this one possible sister star and follow it as it goes about its life.  Who knows, one day, someone from there may just respond to the equivalent of a cosmic blog post.

A Cluster of Stars Thrown Out of Its Galaxy at 2 Million MPH

A team of astronomers has discovered the first cluster of stars that has been thrown out of another galaxy. Whatever threw this rich grouping of stars out of the galaxy known by its catalog number as M87, was able to accelerate it to a speed of some 2 million miles per hour. Kids, don't try this at home without adult supervision!

It just so happens that the star cluster is being thrown roughly in our direction, but since M87 is 54 million light years away, no one is worried. The cluster will just wind up in the space between galaxies, wandering like the lost ships of legend, never finding its home port again.

M87 is a huge galaxy of stars and clusters, almost a million light years in diameter (our Milky Way Galaxy is about 100,000 light years across, by comparison.) In addition to thousands of billions of stars, M87 contains an estimated 12,000 "globular clusters" -- tightly bound groups of roughly 100,000 stars each. Our home galaxy only has about 150 of these globular clusters, and we are a pretty good-sized galaxy as far as cosmic requirements are concerned. So M87 makes us look like a 90-lb weakling in comparison.

So how did a cluster with many thousands of stars get loose from the considerable gravity of a giant galaxy like M87? No one knows for sure, but here is the clever idea that discoverers of the high-speed cluster are suggesting. Giant galaxies like M87 get bigger by eating smaller neighbor galaxies for lunch. Occasionally, they even merge with a big galaxy, gently pulling in the other galaxy's stars and other "inhabitants." What if M87, in the distant past, swallowed a big galaxy with a giant black hole at the center?

Astronomer have recently found that all big galaxies have big black holes in their crowded cores. The bigger the galaxy, the bigger the central black hole, in general. So M87 probably had a big black hole and the other galaxy would have had a big black hole too. As the two galaxies merged, their two black holes, like boxers circling each other in the ring, could have begun to orbit around each other. (We have seen pairs of big black holes in other such systems, so this is not a wild idea at all.)

Now, along comes our victim globular cluster, which had some orbit around the center of M87 that might well have brought it a bit too close to the pair of black holes. When the black holes interacted with the cluster, their gravity might have played a "game of pool" with it. In pool (or billiards, for some of you), you often see one ball interacting with another and then causing a third ball to go shooting off into a distant pocket. When the two black holes and the cluster had their moment of gravitational interaction, the cluster could have been thrown out of the galaxy by the tremendous gravitational energy of the giant black holes.

Astronomers have seen superfast stars thrown out of galaxies, but this is our first instance of seeing a whole cluster of stars shooting out from its home galaxy. M87 is one of my favorite galaxies anyway, with many other signs of violence and inner turmoil. This makes it even more interesting. The accompanying image is an artist's attempt to show the cluster coming out of M87, which is correctly shown as a fuzzy rounded blob.

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On a personal note, I would like to dedicate today's post to the memory of my good friend and colleague, Alan Friedman, the former director of the New York Hall of Science, who passed away this weekend.  Alan and I taught weekend courses on Einstein together, wrote papers on interdisciplinary approaches to teaching astronomy and physics, and bemoaned the state of science education in the U.S. over many dinners.  Alan also helped chart the course of the Lawrence Hall of Science in Berkeley, the Parc de la Villette science museum outside of Paris, and dozens of other museums and science centers where his advice was frequently sought.  He leaves an emptiness in the universe that will be impossible to fill.

Astronomer Discovers the Fourth Closest Star System to Us -- And It's Cool!

Just last year, I posted the news that astronomer Kevin Luhman of Penn State had discovered the third closest star system to our own.  It consisted of a pair of failed stars -- stars containing too little material to shine consistently with visible light and thus commonly called brown dwarfs.

Now Luhman has done it again.  He recently announced the discovery of the fourth closest system -- this one consisting of the coldest brown dwarf ever found.  Known only by a long catalog number giving its cosmic "latitude and longitude" (WISE J085510.83-071442.5), the wanna-be star is 7.2 light years away.  That's right in our neighborhood as far as astronomical objects are concerned.

Our best estimate of its mass is that it weighs only as much as 3 to 10 Jupiters.  So, really, it could be more of a free-floating planet rather than a brown dwarf.  But since brown dwarfs are more common (planets are found more frequently around stars than by themselves), the discoverer is betting it's just a very cold and poorly endowed brown dwarf.

The image accompanying this note is just an artist's conception of what such a cold, failed star might look like.  After observing it with a variety of space-based telescopes (such as WISE and Spitzer, which are sensitive to infra-red or heat rays and not light), Luhman and his colleagues estimate that the outer temperature of this strange neighbor is as cold as the Earth's North Pole.  (Estimates vary from -54 to 9 degrees Fahrenheit, or -48 to 13 Centigrade.)   So its outer layers are like those of the giant planets far from our Sun, and nothing like a real star.  Stars have temperatures thousands of degrees hot.

What is remarkable to me is that, after 400 years of using telescopes, and more than 50 years of instruments in space, we are still discovering our closest neighbors!  It's not our fault, of course -- this neighbor was very shy, not shining with the kind of rich light power that our closest neighbor, the triple star system Alpha Centauri, gives off.  And in space, as on Earth, it's often the show-offs that get the attention.

A Beautiful Pinwheel of a Galaxy

A Beautiful Pinwheel of a Galaxy

Taking a break from all the heavy-duty science news for a minute, I want to share a beautiful recent image with you from the Hubble Space Telescope.  What you see on our photo is a large part of a spiral shaped galaxy (or island) of stars, known by its catalog number M83. It is about 15 million light years away in the  constellation of Hydra, the water snake.  

M83 contains billions upon billions of stars and quite a bit of gas and dust -- the cosmic raw material from which new stars, new planets, and perhaps even new Facebook fans can form.

This remarkably detailed image emphasizes the pinkish-red regions that are glowing clusters (or groups) of young stars, seen on the edges of the galaxy's spiral arms.  Actually, the young (adolescent) stars in these clusters glow so hot, they give off not just the light our eyes can see, but also energetic ultraviolet light.  The left-over gas that still surrounds these new star groups (in a way, the womb that gave birth to them) then is set to glow.   The excited gas -- mostly the cheapest, simplest element in the universe, hydrogen -- glows with a characteristic pinkish red.

Just look at all the pinkish glow!  That is to say, see all the new stars that we can see having been born recently -- at least recently on the cosmic time scale, or somewhere between 1 to 10 million years ago.  Like most of our cities in the spring and summer, there is still lots of construction going on in such galaxies.  

First "Earth Cousin" Planet Found

Astronomers working with the Kepler telescope, led by Elisa Quintara of the SETI Institute, have announced the discovery of the first planet orbiting another star that meets the two characteristics we have been particularly waiting for.  The planet is Earth-sized AND it orbits its star in the zone where water is likely to be liquid (called the “habitable zone.”)

The planet and star have no name, but only a catalog number – Kepler 186.  Located in the constellation of Virgo, about 500 light years away, the star is “red dwarf” – smaller and cooler than the Sun.   So a planet has to be closer to it to have the right temperature for liquid water.  But every star has its own habitable zone and Kepler 186 is no exception.

We have actually found five planets around Kepler 186 so far, but the other four planets are very close to the star and much too hot for life as we know it.  Called Kepler 186f, the newly found planet takes about 130 days to go around its star, and its distance is in the zone where water could be liquid (if the planet has a significant atmosphere.)

Astronomers actually know of some 1,800 planets around other stars so far, orbiting at a wide range of distances and showing a wide range of sizes.  In the past, we have found a number of planets that were the same size as Earth but all of these were too hot – orbiting too close to their stars.  We have also found a number of planets that were in the habitable zone of their stars, but these were bigger than Earth.  Most likely they were so big they would look more like Neptune or Jupiter, made mostly of gas and liquid (or at least having a huge shell of gas and liquid before you could touch solid ground.)

Kepler 186f (sorry planets don’t get names yet) is the first planet that is both the right size and the right distance from its star.  Today, at their national press conference, the scientists who discovered it made sure not to call it an “Earth twin,” however.  Instead, they used the term “Earth cousin” to describe their discovery.  That’s because Kepler 186 is a cool red star, about half the size and mass of the Sun.  So the light of this star will look different on the newly discovered planet – instead of the yellow sunlight we are used to, anyone standing on the surface of Kepler 186f would see reddish-orange sunlight.  The scientists speculated whether any plants on the new planet would receive enough energy to do photosynthesis, and their first conclusion was a tentative yes.

What’s especially important about this discovery is that roughly 80% of all the stars in our Galaxy are red dwarf stars.  If, as our observations are starting to show, MOST stars will have planets, then most planets are likely to orbit red dwarfs.  So places like Earth and our Sun may be the exception.  And Kepler 186f may be a mainstream kind of world in the vastness of the Milky Way.

On our diagram, above, you can see the orbit of the Kepler 186 system’s planets to the same scale as the inner planets in our own solar system.  The fuzzy green region in each case is the habitable zone of each star. You can see the Earth comfortably in the habitable zone of our Sun, and 186f in the habitable zone of 186.  The painting of 186f in this picture is just from the artist’s imagination.  We really have no idea what the planet looks like.

(By the way, for those of you who like to count, you may wonder why the fifth planet in the Kepler 186 system gets the letter f, when f is the sixth number of the alphabet.  That’s because in this pretty awkward naming system we are using, the star is called Kepler 186a, and the letters of the planets start with b.  I don’t endorse this system, folks, I just explain it.)

What Would the Lunar Eclipse Have Looked Like from the Moon?

We who live in North or South America (and had clear skies,) experienced a total eclipse of the Moon Tuesday morning, April 15.  But what would the eclipse have looked like to someone on the Moon?

First, since the Moon always keeps one side toward the Earth and one side away from the Earth, we have to pick a side. For this purpose, the interesting side of the Moon is the one that was facing the Earth and the Sun. It was sunny and bright on that side of the Moon before the eclipse began. Then, an observer on the Moon would have seen the Earth move in front of the Sun, and darkness descend. It would have gotten colder too without the warmth of the Sun.

Since the nearby Earth looks bigger from the Moon that the Sun does, the Earth more than covered the Sun. Still, the Earth's atmosphere bends some of the sunlight behind it toward the Moon. So someone on the Moon would have seen a faint ring of light around the dark Earth. (If you had a telescope on the Moon, you might also have seen the lights of big cities and large fires on the night side of our planet.)

How do we know that this "Moon perspective" about the eclipse is right? A Japanese spacecraft called Kaguya captured just this kind of image during a lunar eclipse in February 2009, as it was orbiting the Moon. In the picture above (courtesy of the Japanese Space Agency), you see several views of the Earth from the Moon during the eclipse. The ring of light is not complete, because some part of Earth was below the Moon's horizon as seen by Kaguya. At the end of the eclipse, you can see the first light of the Sun coming out from behind the Earth, making a kind of diamond ring effect. How wonderful that our robot spacecraft can give us views in the solar system that earlier scientists could only imagine!