February 25, 2012
You may remember learning the types of planets growing up: rocky planets, like Earth and Mars; gas giants, like Jupiter and Saturn; and ice giants, like Neptune and Uranus.
Now scientists at the Smithsonian Astrophysical Observatory (SAO) have discovered a new kind: a waterworld. The planet, named GJ1214b, is not merely covered with water like our oceans; most of it is water. “GJ1214b is like no planet we know of,” Zachory Berta, a graduate student at the SAO and lead author on the paper announcing the discovery, published online Tuesday in The Astrophysical Journal. “A huge fraction of its mass is made up of water.”
Contrary to what you might imagine, the “water” on GJ1214b is quite different from anything you’ve ever seen.”The water there is in really weird forms that we’re not used to on Earth,” Berta says. “There are substances that are like ice, but at a very high temperature, because the pressure is so high that the molecules are squeezed together. There is also this superfluid state of water that is more gaseous than the water we’re used to.”
If you have trouble picturing such an exotic alien waterworld, you’re not alone. “Frankly, I too have a lot of difficulty imagining what this would actually be like in person,” Berta says.
Located in the direction of the Ophiuchus, the planet is just 40 light years from Earth, making it a close neighbor compared to most of the stars in our galaxy. GJ1214b is 2.7 times Earth’s diameter and weighs nearly 7 times as much. The planet closely orbits a red-dwarf star every 38 hours, and has an estimated average temperature of 450° Fahrenheit.
Planets that orbit a star so closely do not typically contain any water, says Berta, so scientists believe that GJ1214b must have had an unusual history. “It couldn’t have formed that close, because all of the water would have evaporated off due to the heat,” he says. “So this planet probably had to have formed farther out, and somehow came inward.” Gravitational interactions with other planets may have pulled the waterworld closer in.
Berta and his thesis advisor, David Charbonneau, found the planet back in 2009 as part of the MEarth Project, which uses ground-based telescopes at the Fred Lawrence Whipple Observatory on Mount Hopkins in Arizona to discover habitable planets orbiting nearby red dwarf stars. “At the time, we had an inkling that this could be a waterworld,” Berta says. “We could measure the mass and the radius of the planet, so we knew its density, and the density was very low—too low to be explained by a big ball of rock.” The planet’s average density was calculated to be roughly 2 grams per cubic centimeter, far closer to water’s density of 1 g/cm3 than Earth’s average density of 5.5 g/cm3.
Still, with only limited information on the planet, the team couldn’t rule out other possibilities, such as a planet with a thick atmosphere of hydrogen and helium, which would similarly account for the low average density. But when the researchers were able to use the Hubble Telescope’s newly installed Wide Field Camera 3—specifically looking at light from the red dwarf star that traveled through the GJ1214b’s atmosphere before traveling towards us—they were able to rule out that possibility.
“If the big, puffy hydrogen envelope on the outside of the planet were there, we would see it, but we don’t,” says Berta. “So it looks like we’re dealing with the alternative—a planet with a whole bunch of water in it, and an atmosphere which is mostly water as well, which is consistent with what we see from the Hubble observations.” The research team describes the atmosphere hot and steamy.
Berta is less excited about finding the first of a new type of planet than the possibility of finding many more. “NASA’s Kepler telescope has found a number of planets that are the same size as this one, but they’re much more distant, so it’s hard to observe those planets in more detail,” he says. “This is interesting not because it’s something that we’ve never seen before and will never see again, but because it’s sort of a type specimen for all of these.”
He believes investments in telescopes and other observational equipment will continue to pay great dividends as we continue to search the galaxy for planets. “The James Webb Space Telescope [due to be launched in 2018] is NASA’s successor to Hubble. It will be great, because instead of just having a very rough picture of planets like these, we’ll be able to probe them more closely,” he says.
Berta is confident that within decades, astronomers will detect a smaller, cooler version of GJ1214b, which could theoretically harbor extraterrestrial life. “That’s the cool thing about astronomy,” he says. “As we continue to build better telescopes, we can find more and more.”
February 7, 2012
Our inquisitive readers are rising to the challenge we gave them last month. The questions are pouring in and we’re ready for more. Do you have any questions for our curators? Submit your questions here.
How much is the Hope Diamond worth? — Marjorie Mathews, Silver Spring, Maryland
That’s the most popular question we get, but we don’t really satisfy people by giving them a number. There are a number of answers, but the best one is that we honestly don’t know. It’s a little bit like Liz Taylor’s jewels being sold in December—all kinds of people guessed at what they would sell for, but everybody I know was way off. Only when those pieces were opened up to bidding at a public auction could you find out what their values were. When they were sold, then at least for that day and that night you could say, well, they were worth that much. The Hope Diamond is kind of the same way, but more so. There’s simply nothing else like it. So how do you put a value on the history, on the fact it’s been here on display for over 50 years and a few hundred million people have seen it, and on that fact it’s a rare blue diamond on top of everything else? You don’t. – Jeffrey E. Post, mineralogist, National Museum of Natural History
What’s the worst impact of ocean acidification so far?- Nancy Schaefer, Virginia Beach, Virginia
The impacts of ocean acidification are really just starting to be felt, but two big reports that came out in 2011 show that it could have very serious effects on coral reefs. These studies did not measure the warming effect of carbon dioxide in the atmosphere, but rather its effect of making the ocean more acidic when it dissolves in the ocean. Places where large amounts of carbon dioxide seep into the water from the sea floor provide a natural experiment and show us how ocean waters might look, say, 50 or 100 years from now. Both studies showed branching, lacy, delicate coral forms are likely to disappear, and with them that kind of three-dimensional complexity so many species depend on. Also, other species that build a stony skeleton or shell, such as oysters or mussels, are likely to be affected. This happens because acidification makes carbonate ions, which these species need for their skeletons, less abundant.
Nancy Knowlton, marine biologist
National Museum of Natural History
Art and artifacts from ancient South Pacific and Pacific Northwest tribes have similarities in form and function. Is it possible that early Hawaiians caught part of the Kuroshio Current of the North Pacific Gyre to end up along the northwest coast of America from northern California to Alaska? — April Amy Croan, Maple Valley, Washington
Those similarities have given rise to various theories, including trans-Pacific navigation, independent drifts of floating artifacts, inadvertent crossings by ships that have lost their rudders or rigging, or whales harpooned in one area that died or were captured in a distant place. Some connections are well-known, like feather garment fragments found in an archaeological site in Southeast Alaska that appear to have been brought there by whaling ships that had stopped in the Hawaiian Islands, a regular route for 19th-century whalers. Before the period of European contact, the greatest similarities are with the southwest Pacific, not Hawaii. The Kushiro current would have facilitated Asian coastal contacts with northwestern North America, but would not have helped Hawaiians. The problem of identification is one of context, form and dating. Most of the reported similarities are either out of their original context (which can’t be reconstructed), or their form is not specific enough to relate to another area’s style, or the date of creation cannot be established. To date there is no acceptable proof for South Pacific-Northwest Coast historical connections that predates the European whaling era, except for links that follow the coastal region of the North Pacific into Alaska.
William Fitzhugh, archeologist
Natural History Museum
January 3, 2012
If you can drag yourself out of bed and into the chill of a early January morning, you might find yourself looking at a rare treat: the Quadrantid meteor shower. Early in the morning hours of January 4, from roughly 2 to 5 a.m. local time across the country, this annual meteor shower will be visible in the Northern hemisphere, peaking with an intensity that will approach 100 shooting meteors per hour.
“What’s going on is the earth is going through a debris trail,” says Timothy Spahr, astronomer at the Smithsonian Astrophysical Observatory in Cambridge, Massachusetts. “You’re dealing with very tiny particles, dust-sized in a lot of cases. When they enter the atmosphere, they burn up immediately, and that makes a meteor.” The particles that make up the Quadrantid shower originate from an asteroid named 2003 EH1, which many scientists believe was actually once part of a comet. Because the particles enter at speeds as high as 90,000 miles per hour, they burn up high in the atmosphere and leave a glowing streak across the sky.
The Quadrantid shower is unusual in that it continues for a relatively short duration—only a few hours, as compared to more famous showers, such as the Perseids, that last for several days—but with a high degree of activity. “Under a dark sky, we are talking about 100 visible meteors per hour, so that means a little more than one per minute,” Spahr says. “Many people assume that these showers have millions of meteors all over the sky, but you’ll see around one per minute. And that’s actually pretty cool, because you register when you see each one.”
With the moon projected to set at around 3 a.m. and clear forecasts for much of the country, tonight has the potential to be a rare chance to see the Quadrantids. Most years, because of their brief duration, moonlight or cloudy conditions obscure the show. This year, experts recommend going outside once the moon has set—and, of course, dressing warmly, with projected nighttime temperatures in the twenties or teens in many places. Because of the show’s timing, the best viewings are expected in the Eastern United States.
Meteor-gazers are advised to watch the Northeast part of the sky, and find as dark an area as possible. Give your eyes some time to adjust to the dark and be alert, as most meteors flash by in a second or less. A live feed of the skies above Huntsville, Alabama, is available on NASA’s web site.
One of the biggest factors that determine how many meteors will be seen is something that most people cannot control: location. For those stuck in big cities—like this reporter, based in Washington, D.C.—ambient lighting will reduce the visibility of the meteors significantly. ”A really dark sky makes a huge difference, and most people in the world never see a dark sky because they live in cities,” Spahr says. “If you drove two hours to the west of Washington, say, and got up in elevation a little bit, it would be very nice.”
Still, this is one meteor show that even city-dwellers can appreciate, if not as much as those in the country. “It will be a lot less in a city, but you will still see some meteors tonight,” says Spahr. “Some of these particles will end up, for just a few seconds, as bright as Venus, so those you’ll be able to see from pretty much anywhere.”
December 29, 2011
A tour of the Natural History Museum might lead you from an exhibition on dinosaurs to one about ocean creatures. You might read about how hominids evolved millions of years ago, how our planet’s continents have moved, or how early creatures evolved when the atmosphere was practically devoid of oxygen. The time scale of natural history, you realize, is almost unimaginably large.
But if you enter the museum’s new exhibition, “The Evolving Universe“—a show featuring photography from some of the most powerful telescopes ever created—you’ll find yourself even more astounded. Set against the backdrop of the known universe, the history of our dear planet seems nearly irrelevant. Hundreds of billions of stars like our sun are born out of supernovae several light years wide (each light year is longer than five trillion miles) and are destined to die, once again exploding into supernovas, billions of years later. Thousands of galaxies, some containing trillions of stars like our sun, are continuously being born and evolving.
Although these concepts can be difficult to comprehend and even harder to visualize, the stunning photos that make up the exhibition show the visitor just how awe-inspiring these astronomical events can be. They put the latest CGI graphics from 3-D blockbuster films to shame. “Part of our mission is sharing science with the public, and so we felt that doing this exhibit and showing these images is a great way to do that,” says Jonathan McDowell, an astrophysicist at the Smithsonian Astrophysical Observatory, which partnered with the museum in creating the exhibition. The large-scale photographs in the show were produced by a number of telescopes, both Earth and space-based, including the Hubble Space Telescope.
“We’ve all seen the amazing pictures from NASA’s probes in our own solar system,” says McDowell. “I’m excited about bringing to the public the remarkable images of the broader universe that we astronomers have been exploring with our telescopes. I hope that with this exhibition visitors will take away an appreciation for our larger cosmic neighborhood.”
The show—and accompanying website—use these images to tell the story of our universe, from start to present. The Big Bang, the creation of galaxies, the birth of the Milky Way and the formation of our own solar system are represented in rich images so full of detail that they need to be observed for minutes at a time, like pieces of art hung on the wall.
What might be most remarkable is that the actual images created by the telescopes are themselves ancient history. Because light takes so long to travel from the far-flung reaches of space, when we photograph distant galaxies, the light that hits the camera’s lens to produce the image left its home galaxy billions of years ago. These pictures show some of the celestial objects as they were before humans even existed. And so we have a font-row seat to watch the earliest stages of the universe’s creation, if we look deep enough into space, more than 13 billion years later.
When wandering the exhibition, one might be overwhelmed by the torrent of information presented on scales that are downright otherworldly. How does our planet, so tiny and new, fit into all of this?
The best metaphor to understand earth’s place in the universe might be that of astrophysicist, author and recent Around the Mall blog subject Carl Sagan. In his book Pale Blue Dot, he describes a far-off view of the Earth from the outer reaches of the solar system:
From this distant vantage point, the Earth might not seem of any particular interest. But for us, it’s different. Look again at that dot. That’s here. That’s home. That’s us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every “superstar,” every “supreme leader,” every saint and sinner in the history of our species lived there – on a mote of dust suspended in a sunbeam.
In the scheme of the known universe—of supernovae and galaxies and nebulas and black holes—our whole planet starts to look like a speck of dust, floating in the sunlight.
The Evolving Universe is on view at the Natural History Museum through July 7, 2013
December 21, 2011
Yesterday, scientists at the Smithsonian Astrophysical Observatory in Cambridge, Massachusetts made a major announcement. For the first time, after years of searching, Earth-sized planets had been detected outside of our solar system. Among the five planets in the distant Kepler-20 star system are Kepler-20e and Kepler-20f—two rocky orbs with diameters approximately 87 percent and 103 percent that of earth, respectively. The news has the scientific world in a state of excitement over the consequences of the find. We spoke with Smithsonian astrophysicist Francois Fressin, the lead author of the paper, about the discovery.
Researchers have been using the Kepler space telescope since it launched in March of 2009 to search for exoplanets, or planets in other solar systems. “Kepler is staring at 200,000 stars, all located in the same area of the sky, and it just monitors the light it gets from each of the stars, continuously, for years,” says Fressin. “For a fraction of the stars, there’s a periodic dimming with the same duration and same depth of light.” This dimming can be caused by a small opaque body crossing between the star and the telescope—in this case, a pair of planets. The team first detected the telltale dimming more than a year ago, but had to make more calculations with custom-developed software to rule out the possibility that it was caused by other phenomena.
From the degree and frequency of the dimming, the scientists are able to make inferences about the planets. Kepler-20e and Kepler-20f are 6,900 miles and 8,200 miles in diameter, respectively, remarkably close to Earth’s 8,000 mile size. Because the two planets are so close to their host star—they orbit at 4.7 million miles and 10.3 million miles, both far closer in than Mercury is to the sun—they are believed to be extremely hot, with average temperatures of 1400 and 800 degrees Fahrenheit, respectively. “We know they’re both pure rock bodies,” Fressin says. “But we don’t have precise mass estimates, so we can’t say if they’re similar in composition to the Earth, or something denser with more iron, like Mercury.”
What It Means For Astronomy
Exoplanet hunters began uncovering distant gas giants as early as 1992, but smaller, Earth-sized bodies had proved more difficult to detect. “We’ve crossed the threshold: this the first time that humanity is able to detect an Earth-sized object around another star,” Fressin says. ”That’s symbolically and technologically important.”
The discovery represents a historic milestone in astronomy. Now, scientists are convinced that they have the right tools to be able to detect Earth-sized planets that might support life. Researchers will continue using the Kepler space telescope to locate exoplanets in hope of finding such a world.
What It Means For Planetary Science
The discovery also turns upside-down much of what scientists believed about the formation of solar systems. The two Earth-size planets are interspersed with three gas giants, all extremely close to the host star, Kepler-20. “From the star, it goes in the order big, small, big, small, big, which seems completely weird,” says Fressin. “In our solar system, we have these four rocky small bodies, and then, farther away, these four large giant gaseous planets. So how did that happen, that we have all this mixing in the Kepler-20 system?”
Although we don’t currently have definitive answers, scientists suspect that the planets drifted into their current position over time. “They didn’t form at the place they are right now, there was not enough rocky material to build these five planets so close to their host star,” Fressin says. “So one solution would be that they formed farther out, and then migrated in.”
What It Means For Extraterrestrial Life
The most tantalizing possibility of these discoveries is the potential that the exoplanets might harbor life. But both Kepler-20e and Kepler-20f are outside the habitable zone—often called the “Goldilocks” zone—that is neither too close nor too far from the host star, allowing for the evolution of living creatures. ”We don’t know a lot of things about life, but we know that one of the main ingredients of life on Earth is the presence of liquid water,” says Fressin. “Right now, at the temperatures estimated, water can’t be in a liquid state on either planet.”
Still, the hypothesis that the planets may have formed farther away, and then migrated to their current locations close to the star, means that life may have existed long ago. “It seems pretty clear that Kepler-20f once crossed the habitable zone of its host star, after its formation,” Fressin says. “It is the closest object in terms of size to the Earth in the known universe, and this means that it could have been habitable in its past.”
What It Means For Space Exploration
Although Kepler-20 is much too far to attempt as the target of a space probe mission—it’s about 950 light-years from Earth, which would require a journey of 36 million years by the space shuttle—Fressin feels that discoveries like this should stimulate interest in the very real possibility of exploring other, closer, star systems. “It would be challenging, and would require great international collaboration, maybe for one or two generations, but it would be feasible,” he says.
Such a mission would admittedly be very long-term, but the rewards are many. “I think the best location to send a probe would be to the closest sun-like star,” says Fressin. “So then imagine, in two generations, we’d have the probe coming back with pictures—real pictures—of another world.”