The TSIS instrument on the International Space Station is continuing NASA's 40-year record of tracking the Sun's radiant energy
Mars Landing Sky Show
On the same night Curiosity lands on Mars, a "Martian Triangle" will appear in sunset skies of Earth. The first-magnitude apparition on August 5th gives space fans something to do while they wait for news from the Red Planet.
Bright Explosion on the Moon
Astrophysics researchers who monitor the Moon for meteoroid impacts have detected the brightest explosion in the history of their program.
For the past 8 years, astronomers have been monitoring the Moon for signs of explosions caused by meteoroids hitting the lunar surface. Lunar meteor showers have turned out to be more common than anyone expected, with hundreds of detectable impacts occurring every year.
They've just seen the biggest explosion in the history of the program.
On March 17, 2013, an object about the size of a small boulder hit the lunar surface in Mare Imbrium. It exploded in a flash nearly 10 times as bright as anything we've ever seen before.
Anyone looking at the Moon at the moment of impact could have seen the explosion--no telescope required. For about one second, the impact site was glowing like a 4th magnitude star.
Ron Suggs, an analyst at the Marshall Space Flight Center, was the first to notice the impact in a digital video recorded by one of the monitoring program's 14-inch telescopes. It jumped right out at me, it was so bright, he recalls.
The 40 kg meteoroid measuring 0.3 to 0.4 meters wide hit the Moon traveling 56,000 mph. The resulting explosion1 packed as much punch as 5 tons of TNT.
The lunar impact might have been part of a much larger event.
On the night of March 17, University of Western Ontario all-sky cameras picked up an unusual number of deep-penetrating meteors right here on Earth. These fireballs were traveling along nearly identical orbits between Earth and the asteroid belt.
This means Earth and the Moon were pelted by meteoroids at about the same time.
"My working hypothesis is that the two events are related, and that this constitutes a short duration cluster of material encountered by the Earth-Moon system.
One of the goals of the lunar monitoring program is to identify new streams of space debris that pose a potential threat to the Earth-Moon system. The March 17th event seems to be a good candidate.
Controllers of Lunar Reconnaissance Orbiter have been notified of the strike. The crater could be as wide as 20 meters, which would make it an easy target for LRO the next time the spacecraft passes over the impact site. Comparing the size of the crater to the brightness of the flash would give researchers a valuable ground truth measurement to validate lunar impact models.
Unlike Earth, which has an atmosphere to protect it, the Moon is airless and exposed. Lunar meteors crash into the ground with fair frequency. Since the monitoring program began in 2005, astronomers associated with lunar impact has detected more than 300 strikes, most orders of magnitude fainter than the March 17th event. Statistically speaking, more than half of all lunar meteors come from known meteoroid streams such as the Perseids and Leonids. The rest are sporadic meteors--random bits of comet and asteroid debris of unknown parentage.
U.S. Space Exploration Policy eventually calls for extended astronaut stays on the lunar surface. Identifying the sources of lunar meteors and measuring their impact rates gives future lunar explorers an idea of what to expect. Is it safe to go on a moonwalk, or not? The middle of March might be a good time to stay inside.
We'll be keeping an eye out for signs of a repeat performance next year when the Earth-Moon system passes through the same region of space. "Meanwhile, our analysis of the March 17th event continues."
The Moon has no oxygen atmosphere, so how can something explode? Lunar meteors don't require oxygen or combustion to make themselves visible. They hit the ground with so much kinetic energy that even a pebble can make a crater several feet wide. The flash of light comes not from combustion but rather from the thermal glow of molten rock and hot vapors at the impact site.
Earth Day Meteor Shower
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.
