by Kim Malville
Events of the month
April 2: Look for the moon and Venus close together before dawn.
April 5: Mars lies between Aldebaran and the Pleiades.
April 8: The crescent moon joins Mars, Aldebaran, and the Pleiades to form a celestial diamond.
April 11: Mars moves close to Aldebaran for the next weeks. Compare the color of these two red objects. Aldebaran is twice as bright as Mars.
April 19: Full moon.
April 21: Easter is celebrated on the first Sunday after the full Moon that occurs on or just after the spring equinox. In 2019, both the vernal equinox and the full Moon occurred on Wednesday, March 20. The full Moon followed spring equinox by less than four hours. Following these rules, Easter should have followed the full Moon on March 20 namely on Sunday March 24. However, the Christian Church Calendar, for the sake of convenience, establishes spring equinox to be always be fixed on March 21, while in reality, equinox can happen on March 19, 20, or 21. Thus, the first full Moon after March 21 doesn’t occur until April 19 this year, and Easter will be celebrated on Sunday, April 21.
April 22: The peak of the Lyrid meteor shower occurs tonight. Sadly, it takes place with the moon is nearly full, drowning out the fainter meteor. If you are out and about, it might be worthwhile to scan the skies. The meteors will be coming out of the area between the constellations of Hercules and Lyra. Some years there have been fireballs.
April 23: About an hour before sunrise, look for the moon and Jupiter within a degree of each other.
The Earth was blasted by the Sun 2600 years ago
One of the strongest solar storms ever to hurtle toward Earth blasted hit our planet in 660 BC, based on traces of the storm preserved in both ice cores and tree rings.
As the sun’s magnetic field shifts, it occasionally releases bursts of charged particles into space, in the form of coronal mass ejections. In the most extreme solar storms, called solar proton events, these charged particles are sped up by erupting magnetic fields. Even Earth’s protective magnetic field can’t deflect such swift, energetic particle streams. The radiation is particularly hazardous to modern technology and astronauts. In the figure an actual coronal mass ejection is pictured with an artist’s drawing of our tiny Earth with our protective magnetic shield.
It’s unclear how common such extreme events are. Satellite- and ground-based instruments have tracked them for only about 70 years. To look farther back in time, researchers hunt for spikes in cosmogenic radionuclides such as carbon-14 — recorded in tree rings — or beryllium-10 and chlorine-36 — preserved in ice cores. Such radionuclides form when cosmic rays interact with molecules in Earth’s atmosphere.
In 2017, scientists identified a sudden spike in tree ring carbon-14 dating to about 660 B.C. that might indicate a solar proton event. The relative abundance of the radionuclides in the ice suggested that the 660 B.C. event was about 10 times more powerful than the 1956 event, the strongest solar storm recorded by instruments, and quite coincidentally occurred at the start of the International Geophysical Year. This storm was certainly powerful enough to devastate modern electrical circuits, satellites, defense systems, including GPS satellites. None of those would have happened in 660 BC. There would have been brilliant auroras pulsating and arcing in the northern skies, and the most powerful storms would have produced auroras near the equator.
What was happening in the decade around 660 BC? In 668 BC Nineveh, capital of Assyria became the largest city of the world, taking the lead from Thebes in Egypt. In 660 BC, the empire of Japan was founded and there is the first evidence of a written Olmec language. Most interesting is that in 650 BC there was a severe change in climate such that all the Bronze Age cultures in Europe experienced colder and wetter climate, and tribes from the Scandinavian Nordic Bronze Age cultures were pushed southward into the European continent. Could there have been a connection between such a highly variable sun with its powerful outburst and climate on the Earth?
There are only two ways to detect coronal mass ejections. One is by using satellites above the earth’s atmosphere to observe the solar corona and the second is by a total solar eclipse, when the corona can be seen. Sometimes eclipses may occur when a storm of particles is ejected from the sun. We think that one of these coronal mass ejections during an eclipse may have been recorded as a petroglyph in Chaco Canyon. If you visit the Canyon, check out the rock, which we have called Piedra del sol, near the Visitors’ Center. The disturbed corona looking like a huge tick is in the lower center of the photograph.
The Earth was hit by an asteroid on December 18, 2018.
On Dec. 18, 2018, a school bus-size meteor, which turned out to be a wandering asteroid, exploded over Earth with an energy of roughly 10 atomic bombs. According to NASA, the blast was the second-largest meteor impact since their organization began tracking them 30 years ago, second only by the fireball that exploded over Chelyabinsk, Russia, in Feb. 2013. This asteroid blew apart over a remote portion of the Bearing Sea, 16 miles above the water. No humans saw it, only birds and fish. NASA learned about the December impact thanks to the U.S. Air Force, whose missile-monitoring satellites were among the first to detect the blast. The rumble of the explosion registered on infrasound detectors — stations that measure low-frequency sound waves inaudible to human ears — around the world. The asteroid weighed about 1,500 tons, had a diameter of about 32 feet, and was traveling through the atmosphere at nearly 72,000 mph..
In 2013, another asteroid exploded in Siberia over the city of Chelyabinsk with more than twice the energy. The Chelyabinsk asteroid was described as brighter than the sun, was captured by a number of cameras, and injured more than 1,200 people. No one was hit. Most of the injuries occurred because people rushed to windows when they saw the flash and then were cut by flying glass when the blast wave arrived.