At the end of a day devoted to Earth, people can look to the heavens for a beautiful shower of Lyrid meteors.
On April 22nd 2015, millions of people around the world will gather together at festivals and other events to celebrate our beautiful blue planet. It's Earth Day, an occasion to pause, reflect, and talk about how to sustain a clean, healthy environment on Earth.
This year, Earth Day will end with a meteor shower.
On April 22-23 ,2015, Earth will pass through a stream of debris from Comet Thatcher, source of the annual Lyrid meteor shower.
As Earth crosses the debris zone, flakes of comet dust, most no bigger than grains of sand, strike Earth's atmosphere traveling 49 km/s (110,000 mph) and disintegrate as streaks of light. Typical Lyrids are about as bright as the stars of the Big Dipper
As meteor showers go, the Lyrids are relatively mild. Most years in April there are no more than 10 to 20 Lyrid meteors per hour. But sometimes, when Earth glides through an unusually dense clump of debris from Comet Thatcher, the rate increases, resulting in what is known as a meteor outburst. Sky watchers in 1982, for instance, counted 90 Lyrids per hour. An even more impressive outburst was documented in 1803 by a journalist in Richmond, Virginia, who wrote:
"Shooting stars [were] observed on Wednesday morning last at Richmond and its vicinity, in a manner that alarmed many, and astonished every person that beheld it. From one until three in the morning, those starry meteors seemed to fall from every point in the heavens, in such numbers as to resemble a shower of sky rockets..."
Another published report from the 19th century lists an observer as having "counted 167 meteors in
about 15 minutes, and could not then number them all.
No such outburst is predicted for 2015-but then again, no outbursts were predicted on those previous occasions either. If you're up late, take a look.
The best time to catch the shower is between about 11 pm on April 22nd and sunrise on April 23rd, in any timezone in the northern hemisphere.
Observing tips: Dress warmly. Bring a reclining chair, or spread a thick blanket over a flat spot of ground. Lie down and look up. Meteors can appear in any part of the sky, although their trails will tend to point back toward the constellation Lyra, from which the meteors get their name. The hours before dawn are best, because that is when Lyra is highest in the sky.
Sometimes, bright moonlight can spoil a meteor shower. That will not be the case on April 22nd. The Moon is just a slender crescent, and it sets shortly after sunset, so lunar glare will not interfere with the Lyrids. If you can, get away from city lights for the darkest possible sky and the best possible show.
Enjoy Earth Day. And then enjoy Earth Night even more.
The Sun's Magnetic Field is About to Flip
Something big is happening on the sun. The sun's global magnetic field is about to flip, a sign that Solar Max has arrived.
Big Mystery in the Perseus Cluster
A mysterious X-ray signal from the Perseus cluster of galaxies, which researchers say cannot be explained by known physics, could be a key clue to the nature of Dark Matter.
The Perseus galaxy cluster is one of the most massive objects in the universe. It contains more than 1,000 galaxies, it's located about 240 million light-years away and at its center, there's a supermassive back whole. It caught scientists' attention in 1970 when a high X-ray emission was detected during an Aerobee rocket flight. When observed in the X-ray band, the Perseus cluster is the brightest cluster in the sky.
The Perseus cluster (Abell 426) is a cluster of galaxies in the constellation Perseus. It has a recession speed of 5,366 km/s and a diameter of 863.
It is one of the most massive objects in the known universe, containing thousands of galaxies immersed in a vast cloud of multimillion-degree gas.
An innovative interpretation of X-ray data from a galaxy cluster could help scientists understand the nature of dark matter. The finding involves a new explanation for a set of results made with NASA's Chandra X-ray Observatory, ESA's XMM-Newton and Hitomi, a Japanese-led X-ray telescope. If confirmed with future observations, this may represent a major step forward in understanding the nature of the mysterious, invisible substance that makes up about 85% of matter in the universe.
The image shown here contains X-ray data from Chandra (blue) of the Perseus galaxy cluster, which has been combined with optical data from the Hubble Space Telescope (pink) and radio emission from the Very Large Array (red). In 2014, researchers detected an unusual spike of intensity, known as an emission line, at a specific wavelength of X-rays (3.5 keV) in the hot gas within the central region of the Perseus cluster. They also reported the presence of this same emission line in a study of 73 other galaxy clusters.
In the subsequent months and years, astronomers have tried to confirm the existence of this 3.5 keV line. They are eager to do so because it may give us important clues about the nature of dark matter. However, it has been debated in the astronomical community exactly what the original and follow-up observations have revealed.
A new analysis of Chandra data by a team from Oxford University, however, is providing a fresh take on this debate. The latest work shows that absorption of X-rays at an energy of 3.5 keV is detected when observing the region surrounding the supermassive black hole at the center of Perseus. This suggests that dark matter particles in the cluster are both absorbing and emitting X-rays. If the new model turns out to be correct, it could provide a path for scientists to one day identify the true nature of dark matter. For next steps, astronomers will need further observations of the Perseus cluster and others like it with current X-ray telescopes and those being planned for the next decade and beyond.
What Lies Inside The Jupiter
For four long centuries the gas giant's vast interior has remained hidden from view. JUNO probe, launched on August 5th, changed all that.
It's really hot inside Jupiter! No one knows exactly how hot, but scientists think it could be about 43,000°F (24,000°C) near Jupiter's center, or core.
Jupiter is made up almost entirely of hydrogen and helium. On the surface of Jupiter-and on Earth-those elements are gases. However inside Jupiter, hydrogen can be a liquid, or even a kind of metal.
These changes happen because of the tremendous temperatures and pressures found at the core.
What is pressure?
Have you ever gone swimming at the deep end of a pool? Did you notice that your ears started to hurt a little bit when you were under water? The deeper you dive, the more water there is on top of you. All of that water presses on your body-and that's pressure.
The same type of pressure happens in Jupiter's core. Under low pressure, particles of hydrogen and helium, called molecules, have lots of room to bounce around. This is when hydrogen and helium are gases.
However, the weight of all this hydrogen and helium is really heavy. This weight presses down toward the planet's core, creating high pressure. The molecules run out of room to bounce around, so instead, they slow down and crowd together. This creates a liquid.
How much pressure would you find at the center of Jupiter?
Imagine if you swam to the bottom of the Pacific Ocean. You would feel more than 16,000 pounds of force pressing down on every square inch of your body. That is approximately the weight of four cars!
The pressure at the center of Jupiter is much higher. At Jupiter's core, you would feel as much as 650 million pounds of pressure pressing down on every square inch of your body. That would be like having approximately 160,000 cars stacked up in every direction all over your body!
What lies at the very center of Jupiter?
At the moment, scientists aren't 100% sure. It may be that the planet has a solid core that is bigger than Earth. But some scientists think it could be more like a thick, boiling-hot soup.
JUNO mission is designed to find answers to such remaining questions about Jupiter. The spacecraft is orbiting the giant planet, swooping in for close-up looks to get more detailed information.
Juno has already made many new discoveries about Jupiter. Scientists hope that information from Juno will help us measure Jupiter's mass and figure out whether or not the giant planet's core is solid.
