BOSTON — A galactic pileup is underway 5 billion light-years from Earth. The colossal collision is spewing charged particles. And this fountain is huge. It’s jetting particles at nearly the speed of light some 2.5 million light-years into intergalactic space. One might think of the event as building a powerful particle accelerator — one up to a million times as strong as Earth’s mightiest (the Large Hadron Collider).
Astronomers reported the intergalactic fireworks at the American Astronomical Society meeting, here, on June 3. They observed the smashup in new images compiled by two telescopes. NASA’s Chandra X-ray Observatory, a satellite system, eyed the event from an altitude of 139,000 kilometers (86,500 miles) above Earth’s surface. A radio telescope, the Very Large Array, homed in on the collision from the ground. Its 27 antennas are splayed out across the New Mexico desert.
And the source of all the commotion? Four clusters of galaxies are crashing into each other. Together, they involve a mass equal to 3 million billion suns.
Galaxy clusters are the largest structures in the universe that are linked by gravity, notes Reinout van Weeren. He works at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. Large clusters can house thousands of galaxies. Astronomers think these built up over billions of years as smaller clusters merged.
The newly imaged jet sits at the heart of “the most complex cluster collision known,” van Weeren says. Chandra images show gas between the galaxies has been squeezed and heated to 100 million degrees Celsius. Radio maps from the Very Large Array reveal the particle fountain within the hot gas. That jet could provide information about how such large clusters are built.
The giant exoplanet, Kepler-10c, doesn’t play by the rules. It has as much mass as Neptune — yet it’s made of rock, just like Earth. Astronomers are now calling it a “mega-Earth.” Our solar system’s massive planets, such as Jupiter and Saturn, are made from gas. And scientists used to think any planet that massive must also be made primarily of helium and hydrogen. But Kepler-10c is now forcing experts to throw such assumptions out the window.
Kepler-10c is one of two planets orbiting a sunlike star 564 light-years away. It sits in the constellation Draco. Although as massive as Neptune, this heavyweight is only 2.5 times as wide as Earth. (Neptune’s diameter, for comparison, is 22.4 times that of Earth’s.) So Kepler-10c is dense and its gravity exceptionally strong — about three times stronger than Earth’s, explains David Latham. He’s an astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. Latham shared his team’s findings June 2 at an astronomy meeting in Boston.
All that mass would give the exoplanet extreme gravity, the researchers note. Kepler-10c also orbits close to its star — so close that it completes an orbit in only 45 days. This proximity to its sun means the planet’s climate also should be brutally hot. (A companion planet, called Kepler-10b, orbits even closer and faster. Earth, by comparison, takes a little more than 365 days to complete one orbit of the sun.)
Kepler-10c was one of the first exoplanets found by the Kepler space telescope. The robotic space mission has been searching for planets beyond our solar system since 2009. Astronomers measured the size of Kepler-10c three years ago. But until now, they didn’t realize its heft.
To measure the mass of an exoplanet, astronomers focus on its sun. A star’s gravity keeps a planet moving in orbit, like Earth moves around our sun. But a planet’s gravity also tugs on the star — and causes the star to wobble. The more mass a planet has, and the closer it is to the star, the more it makes that star wobble. By measuring this stellar wobble, scientists can estimate a planet’s mass. That’s what Latham and his colleagues did with Kepler-10c.
Once they had measured its mass and size, the scientists determined the planet’s density. Density is calculated by dividing mass by volume. Rocky planets are dense: They pack a lot of stuff into a small space. Gas giants aren’t: They are large and fluffy. Latham and his team have now determined that Kepler-10c has the density of rock.
The planet weighs 17 times as much as Earth. Astronomers used to think that planets with at least 10 times the mass of Earth had to be gas giants. As Kepler-10c now shows, that’s not always true. Astronomers have no idea how the rule-breaking planet formed.
Even though Kepler-10c is the only mega-Earth known, it’s probably not the only one out there.
“When one type of planet is found, that’s usually the tip of the iceberg,” says Sara Seager. She’s an exoplanet hunter at the Massachusetts Institute of Technology, in Cambridge, who did not work on the new study. “There are probably many, many more of them,” she says of mega-Earths.
April 2014 was the first month in recorded history where average carbon-dioxide levels across the northern half of the world measured at least 400 parts per million (ppm) in air. A United Nations agency reported the new record on May 26.
High above Earth’s surface, carbon dioxide acts as what physicists call a greenhouse gas. The term gets its name from the fact that like the window on a greenhouse, this gas allows sunlight to pass through to the lower atmosphere and ground, where it heats things up. All of that heat, which radiates in the form of infrared energy, would then bounce back into space — except that greenhouse gases trap much of it near to Earth’s surface. This helps keep the planet from being freezing cold, year-round. But there can be too much of a good thing. And the growing excess of carbon dioxide has led to a slowly growing fever, what scientists call global warming.
Climate scientists first recorded the troubling high in carbon dioxide in the Arctic in 2012. Then Hawaii registered a similar peak last year. But until now, the rest of the globe had yet to consistently hit the high mark, notes the United Nation’s World Meteorological Organization, or WMO. The 400 ppm level is largely symbolic. Nothing magic happens at that value. It simple represents a troubling milestone. This CO2 value is nearly 50 percent higher than before the Industrial Revolution, almost two centuries ago. More importantly, the WMO points out, the planet has not seen CO2 levels this high in more than 800,000 years.
And scientists expect CO2 levels to continue rising. One reason: Once a molecule of this gas makes it high into the atmosphere, it will remain there for an average of 100 years. Many other greenhouse gases, by contrast, have far shorter lifetimes. They tend to persist only days to perhaps as long as 12 years.
As such, the Northern Hemisphere’s month-long record CO2 high should sound an alarm about addressing emissions, the WMO contends. From 2002 to 2012, it notes, CO2 was responsible for 85 percent of the total increase in the atmosphere’s heat-trapping ability.
“If we are to preserve our planet for future generations, we need urgent action to curb new emissions of these heat trapping gases,” said WMO Secretary-General Michel Jarraud. “Time is running out.”
Researchers now expect that within a year or two, the entire globe will experience CO2 levels averaging 400 ppm or higher.
Most times, when a living thing dies, it just rots. It leaves no trace that it was ever there. But when the conditions are just right, a fossil may form.
For this to happen, the organism typically must first become quickly buried in sediment on the floor of the sea or some other body of water. Sometimes it may even land in something like a sand dune. Over time, more and more sediments will pile atop it. Eventually compressed under its own weight, this growing accumulation of sediment will transform into hard rock.
Most organisms buried in that rock will eventually dissolve. Minerals may replace any bone, shell or once-living tissue. Minerals also may fill in the spaces between these hard parts. And so a fossil is born.
Some of these fossils contain important information about how an animal lived or died. Or they might even provide clues to ancient climate.
Fossils come in other forms, too. They can be any trace of an ancient living thing. For instance, scientists consider ancient, preserved footprints and burrows to be fossils. For these trace fossils to form, the impression they make on sediment has to quickly harden or get buried in sediment and remain undisturbed until it can be transformed into rock. Even animal poop can form trace fossils, called coprolites.
Most people associate fossils with animals. But plants and other types of organisms also can leave preserved traces. And they tend to form in much the same way as animal fossils. A special type of fossil is called petrified wood. It forms in the same way as do fossils of dinosaurs or other creatures. They often look similar to real wood, though. In this case, colorful minerals have moved in and replaced tree tissue.