Thursday, July 21, 2016

A Tight Little Planet System, Dancing to the Tune of Gravity


Careful measurements using information from the Kepler planet-hunting spacecraft has allowed astronomers to figure out one of the tightest and most synchronized planet systems ever found.
Kepler 80 is a dim star in the constellation of Cygnus the swan, 1100 light years away, that has five planets orbiting it. That by itself is not unusual -- astronomers have now discovered a number of stars with 7, 6, or 5 planets around them and more are likely to be discovered as time goes by. What IS unusual is how tightly these five planets all hug their star.

The five planets take one, three, four, seven and nine earth days to orbit the star. (Think about that, their year is 1, 3, 4, 7, or 9 DAYS! If you lived on the inner planet, you would be 365 of its years old after one Earth year had gone by.)
Even more interesting, the outer 4 planets have orbits that are synchronized -- they are in tune, you might say. They return to the same arrangement of their positions around their star every 27 days. This is called a gravitational resonance and it's something gravity prefers to do when bodies can exchange energy.
Think of gravity like your uncle who is careful with his money -- they both prefer arrangements that are cheap! For example, gravity, when it can, tries to make bodies round, because then the pull on every point on the surface is the same -- which is the arrangement that takes the least energy.
When objects in space move around or with each other in a synchronized way, where one orbit is related to the other with numbers like 1 to 2 or 2 to 3, this requires less energy too. Pluto, for example, shows an extreme example of such resonances: Pluto takes 6.4 Earth days to spin and Pluto's big moon Charon takes 6.4 days to orbit the dwarf planet. So Pluto's day and month are the same length. Charon also takes 6.4 days to spin, so we have a 1 to 1 to 1 resonance of these motions.
Calculations show that the planets dancing in resonance around Kepler 80 are rocky world like our own Earth, although at least some of its planets are 4 to 6 times Earth's size. Imagine these giant Earths whipping around that little star in Cygnus in 1 to 9 days, year in and year out, lining up every 27 days in a kind of cosmic dance. Nature seems to permit so many odd and wonderful line-ups of planets out there -- science fiction is having trouble catching up to science fact.

(Just for comparison, the innermost planet in our own planetary system, Mercury, takes 88 days to orbit the Sun, and it is much smaller than Earth. So we have no large planets tightly hugging our star -- but a number of other stars besides Kepler 80 show such tight arrangements.)

Sunday, July 3, 2016

Our Astronomy Lecture Series Has a Million Views on YouTube


As regular readers may know, I have the pleasure of organizing and moderating a series of public talks at my college called the Silicon Valley Astronomy Lectures. Thanks to a generous anonymous donor, we are able to record, edit, and publish each talk on YouTube (now in High Definition). Yesterday, the counter at our YouTube channel passed one million views of the lectures from around the world!
Recent speakers have included Carolyn Porco, imaging team leader for the Cassini mission to Saturn; Robert Kirshner of Harvard and Alex Filippenko of Berkeley, both members of the teams that discovered, to everyone’s surprise, that the expansion of the universe is accelerating; Caleb Scharf of Columbia, explaining his book, "The Copernicus Complex," about humanity’s place in the cosmos; astronaut Ed Lu about discovering asteroids that threaten the Earth; and NASA’s Jeff Moore, from the New Horizons science team, explaining what we have discovered about Pluto this year.
Older lectures include Frank Drake explaining his current thinking about the Drake equation, Michael Brown (who discovered many of the Pluto-like dwarf planets out there) discussing "How I Killed Pluto...," Leonard Susskind on his battle with Stephen Hawking over black holes, and Helen Quinn on the mysteries of antimatter.
You can enjoy all the videos, free of charge or advertising, at:http://www.youtube.com/svastronomylectures
Even an astronomer like me, used to big numbers, is kind of impressed by a million views! I'm glad there are so many fans of astronomy out there. Or maybe, when people think about what's happening in the country and in the world right now, their thought have to escape into the larger universe to stay sane!

Wednesday, June 15, 2016

Big Day for Astronomy Discoveries: Gravity Waves, Alcohol and Tatooine 9


The national organization of professional astronomers (the American Astronomical Society) is meeting in San Diego this week, and there is BIG news from the meeting: More gravity waves, wood alcohol in space, and a big Tatooine-like planet.
Scientists working with LIGO (the Laser Interferometer Gravitational-Wave Observatory) have announced their second discovery of gravity waves. (The first was announced in February.) Once again they observed two giant black holes coming closer and closer and then merging into a bigger black hole. In the merger, some of the mass in the system is converted to energy, and comes out as the waves of gravitational energy Einstein predicted about 100 years ago.
The black holes that merged were 14 and 8 times as massive as our Sun, somewhat smaller than those in the first discovery. Scientists estimate that the black hole that came out of the merger had as much stuff as 21 Sun. This means an entire Sun's worth of mass was converted to energy -- explaining why we could detect the gravity waves, even though such waves are much, much weaker than other waves we know and love, like radio or x-rays.
In the second discovery, a team of astronomers from around the world used the giant ALMA array of radio telescopes in Chile to measure the presence of alcohol in the planet forming disk of a young star 170 light years away. Alas, the kind of alcohol they found is what we call "wood alcohol" or methanol, not the drinkable version. Still, this is the first detection of one of the complex building blocks of life in the region around a newly formed star that is making planets as we observe it.
We have found many of the basic chemical building blocks of life in comets, in chunks of rock that fall from space, and especially in the great clouds of raw material (gas and dust) from which new stars form. But this is the first time we see the "fingerprints" of such a molecule in the flat disk around a star which is the nursery from which planets like Earth and Jupiter emerge. The name of the star is TW Hydrae in case you want to search for more information. (Our image shows an artist's impression of the disk and the molecules of methanol.)
And, finally, in a discovery that is bound to warm the hearts of Star Wars fans everywhere, astronomers have announced the discovery of the ninth, the largest, and the furthest planet orbiting two stars. Such a world could have two suns in the sky at the same time -- just like Tatooine, Luke Skywalker's home planet.
The newly discovered planet, called by its catalog number Kepler
1647b, is about the size of Jupiter and takes three years to orbit its star. The star system is about the same age as our own. And most intriguingly, the new planet orbits in the "habitable zone" of the double star -- meaning that the temperature in the planet's neighborhood would be comfortable for water and life as we know it.
Now Jupiter-sized planets are probably mostly gas and liquid, like Jupiter is, and have no surface for life to evolve on. But such planets may have large solid moons, like Jupiter and Saturn do. On such moons, an atmosphere and oceans may form and remain, so that an environment for life may yet exist in this strange, beautiful system. (We can't find moons yet, only planets, so for now, we have to leave such thoughts to the science fiction writers.)
And those three are only the most interesting of the many discoveries announced at the meeting. We really do seem to be living in a golden age of observational astronomy!

Wednesday, May 25, 2016

Science Fiction and Astronomy


As regular readers of my blog may know, I have a special interest in science fiction, and often recommend stories in my astronomy and physics classes. I even keep a webpage of science fiction stories that use accurate astronomy, at:http://www.astrosociety.org/scifi
Recently, I joined a writing group, and started writing science fiction myself. After receiving many eloquent rejection notes from some of the finest science fiction magazines, one of my stories was published in a small-press anthology about colonizing Mars, called "Building Red," edited by Janet Cannon.
This coming weekend, I will be a guest speaker at BayCon 2016, a science fiction convention in the San Francisco Bay Area (in San Mateo, to be precise.) I have spoken at such conventions before, but this will be my first time speaking not only as an astronomer, but as a science fiction author. The full program and information is on the website:http://baycon.org.  Please say hello if you stop by.
For those of you not in the area, I discussed my story (and scientists who write science fiction) on the syndicated radio show “Big Picture Science” with host Seth Shostak this week. Here is the page:http://bigpicturescience.org/episodes/science-fiction . Note the things in red are links on this page. If you click on the red “Science Fiction” under download, you will be taken to the audio for the show. The interview that mentions my story starts at about 19 minutes into the show and ends at about 30 minutes into the show.
Seth will also be a speaker at BayCon, as will several NASA scientists. I will even be on a panel on scientific science fiction with two of my favorite science fiction authors, Paul Preuss and G. D. Nordley.
For a person whose life has been mostly about teaching the facts of science, it's a lot of fun to be able to speculate in the realm of fiction. So many of my students tell me they were drawn to astronomy by a science fiction story, TV show, or movie they saw; so I know fiction can help draw new audiences toward astronomy. And with the political news the way it is these days, we all need to find ways to take our minds off our home planet and think about the "bigger picture" of the universe.


Saturday, May 21, 2016

Mars: Close and Easy to See (And Wet Long Ago)


Tonight, if you look southeast, you can see Mars as a bright red dot next to the full Moon. Mars is in one of its closer positions, about 48 million miles away. Mars is in what astronomers call "opposition" right now (which is not a term related to the Bernie and Hilary situation!)
When Mars is in opposition, it is on the opposite side of the Earth from the Sun. This means that when the Sun goes down, Mars comes up in our skies, and Mars will be up all night long. (Looking at our diagram from Sky & Telescope magazine, you should also be able to find Saturn this evening or tomorrow night, lower toward the horizon than Mars.)
In recent weeks, even more evidence has been accumulating that ancient Mars, billions of years ago, had a much thicker atmosphere and water was therefore liquid on its surface. Astronomers now believe that there were once lakes and even perhaps seas on the red planet. Recently, planetary scientists even found what seems like evidence of two episodes of tsunamis that happened on Mars a long time ago, when a big chunk of rock or ice from space hit a larger body of water.
For details of this investigation, see: http://www.psi.edu/news/marstsunami
(Also check out a great new Hubble image of Mars at:
http://www.spacetelescope.org/news/heic1609/ )

Sunday, May 1, 2016

Special Opportunity to Support the SETI Institute


Some of my regular readers know that for years, I have had the privilege of serving on the Board of Trustees of the SETI Institute, a non-profit organization devoted to the search for life in the solar system and in the universe at large.
As a non-profit organization, the Institute depends on scientific research grants and on donations from members of the public who value its work. This coming week, the Institute is participating in the 2016 Silicon Valley Gives campaign and looking for 500 new donors and friends who want to help underwrite its work -- and be part of the quest to find life elsewhere. We Trustees have provided a $17,000 matching grant – to double any contribution you care to make.
You can be part of the campaign at:https://svgives.razoo.com/us/story/Seti-Institute-2
What kind of projects does the Institute do? You may have heard of the Allen Telescope Array (see the image), a connected group of radio dishes that scans the skies, hoping to eavesdrop on radio signals from an alien civilizations. But Institute’s 80 scientists are also involved with the search for planets orbiting other stars using the Kepler space telescope; with the search for water in the solar system, including on Mars and Jupiter’s moon Europa; with the exploration of Pluto (the Institute’s Mark Showalter discovered two of Pluto’s moons) and other worlds; and much more.
In addition, the Institute’s weekly syndicated show “Big Picture Science” brings humorous, accessible news about scientific ideas and discoveries on radio stations around the country and around the Internet. The Institute has frequent outreach activities in Silicon Valley and beyond. (You can see me explain black holes in six minutes at one of these at:https://www.youtube.com/watch?v=7DX_cc-IjpY )
So won’t you join me in becoming part of the team that works to answer the ancient and beguiling question, “Are we alone in the universe?”
Donations of any size are gratefully accepted at:https://svgives.razoo.com/us/story/Seti-Institute-2

Monday, April 11, 2016

Supersized Black Hole in an Unlikely Location
Astronomers have announced the discovery of a black hole that has “eaten” as much material as 17 billion Suns. A few such gargantuan black holes have been found elsewhere; what makes this one special is that it was found in a poor neighborhood, astronomically speaking.
Black holes are places where matter is so compressed, that nothing – not even light – can escape the grip of gravity. They frequently start life as the collapsed corpse of a massive star, but, under the right circumstances, they can really grow. If a black hole is frequently presented with “food” – matter it can swallow within its tight boundary – that boundary can grow. In a busy region, where lots of material is available, such as the crowded center of a big galaxy, black holes can grow until they contain millions of stars.
Many good-sized galaxies thus contain a “super-massive black hole” at their centers. Our Milky Way Galaxy has such a monster at its heart, which has swallowed enough matter to make 4 million Suns. But that’s still a long way from the super-sized black hole we just found.
Today we also know that galaxies like ours grow over time by swallowing smaller galaxy neighbors, in a process we call galactic cannibalism. If some parts of the victim galaxy are directed toward the giant black hole at the center of the cannibal, it can get swallowed by the giant black hole and help it to grow. (Some of us are reminded by this process of what’s been happening to banks in the U.S., where the largest banks and financial institutions have been swallowing smaller local banks whenever they can.)
At the centers of galaxies that live in a rich neighborhood – filled with other small galaxies they can be thinking about for lunch – giant black holes can grow to be “super-sized.” But in poor neighborhoods, there aren’t that many galaxies to munch on, and we thought black holes at the center of a galaxy would be limited in whether it could grow supersized.
The new discovery, made by a team headed by Berkeley professor Chung-Pei Ma, found the super-sized black hole in a galaxy known by its catalog number, NGC 1600. To our surprise, it resides in a poor neighborhood with only about 20 galaxies hanging out together. How it grew to be one of the largest black holes we know without many victim galaxies around it is still a mystery.
The monstrous black hole is located about 200 million light years from Earth, so that it poses no danger to our own neighborhood and will not interfere with continuing the presidential primaries or other local events. Understanding black holes and their role in the development of galaxies is high on the agenda of astronomers and in NGC 1600 they have a puzzling detail that doesn’t quite fit the standard story line.
For more on how astronomers discover such giant black holes, you can watch the non-technical lecture Chung-Pei Ma gave in the Silicon Valley Astronomy Lectures (that I have the pleasure of moderating) at:https://www.youtube.com/watch?v=LN9oYjNKBm8

(By the way, our image is not real; it is a computer generated field, showing what such a black hole might look like if you could see it close up. We find such black holes by the disturbance or motion they cause in nearby stars.)