Skywatchers will have the chance next week to see the first obvious meteor shower of the year as the Lyrids reach peak visibility.
The show will take place on the night of April 22 and early in the morning on April 23. The crescent moon on that night will set around midnight, local time, leaving the possibility of a relatively dark night sky in which to see the meteors.
Meteor showers occur as Earth, as it moves through its orbit, passes through debris left behind by comets. The Lyrid meteor shower is the product of Comet Thatcher (C/1861 G1).
According to a website maintained by NASA’s Jet Propulsion Laboratory at the California Institute of Technology, Comet Thatcher has a period – the time it takes to orbit the sun – of about 415 years.
This year’s April encounter with Comet Thatcher’s remnants will occur between April 16-25 as the meteors move at a velocity of about 110,000 miles per hour.
The Lyrid meteor shower, like all meteor showers, gets its name from the constellation from which its radiant appears to originate.
The constellation Lyra (the harp) is most obvious in the northern hemisphere during the summer months, but it can be seen in spring lower in the sky.
The constellation’s brightest star, Vega, is about 25 light years away. It is the second-brightest object in the northern hemisphere’s night sky.
Friday will offer the opportunity in some regions of the globe to observe a rare trifecta of celestial events: the March equinox will be accompanied by a total solar eclipse and a “supermoon” in the night sky.
The eclipse will be visible in its totality only in some parts of the Asian Arctic and northern Europe. Most of the rest of Europe and parts of Africa will experience a partial solar eclipse on Friday.
Total solar eclipses are not uncommon, as they occur about once every 18 months, but they occur only when the moon moves in front of our star and is aligned with the Earth during its orbit about our planet.
The moon’s orbit is inclined at about 5 degrees to the Earth’s orbit around the sun. That means the moon most often passes beneath or above the plane of the sun during its orbit of Earth.
Syzygy, as the alignment of the moon with both Earth and the sun is known, can only take place during a new moon.
While the sun is hundreds of times larger than the moon, the moon is hundreds of times closer to the Earth than the sun. The shadow cast by the moon during the total eclipse, called an umbra, will block out nearly all of the sun’s light and could persist on Friday for as long as about seven minutes.
During a partial solar eclipse a part of the moon’s shadow called the penumbra is cast over a portion of Earth.
According to a website maintained by NASA’s Goddard Space Flight Center, residents of North America will not have another opportunity to see a total eclipse of the sun until Aug. 21, 2017.
The occurrence of a total solar eclipse on the same day as the March equinox is unusual. One recent post at EarthSky.org reported that this confluence of the two events will happen this century only this year and in 2034, 2053, and 2072.
The “supermoon” is really just the appearance of a larger moon. In reality, the phenomenon occurs when Earth’s satellite reaches the perigee of its orbit. When the “supermoon” occurs, the moon is about 52,000 kilometers closer to Earth than it is at the apogee of its revolution.
Because the moon is that much closer at its perigee, its angular diameter appears from Earth to be about six one-hundredths of a degrees greater than it does at apogee.
The March equinox marks the beginning of spring in the northern hemisphere and of autumn in the southern hemisphere. On that day both hemispheres receive an equivalent amount of sunlight.
Any person who plans to look at the sun during an eclipse should use a pinhole camera to do so. An alternative is shade 14 arc welder’s glasses.
It is not safe to look at an eclipse through ordinary sunglasses, film negatives, or polarizing camera filters.
This NASA website is a useful resource for information about safe viewing of the sun during an eclipse.
NASA is set to launch this evening a probe to study Earth’s magnetosphere. The Magnetospheric Multiscale Mission will launch at 8:44 pm MDT.
Ganymede, the largest moon of Jupiter, is a water world.
Researchers using the Hubble Space Telescope have confirmed an ocean beneath Ganymede’s icy crust that are likely ten times deeper than Earth’s oceans.
The moon may have more liquid water beneath its surface than there is on Earth.
To reach this conclusion, scientists measured fluctuations in the moon’s aurorae. Aurorae, which are electrified ribbons of heated gas, are generated when a planetary body’s liquid metal core produces a magnetic field.
On Ganymede, the aurorae around its north and south poles move, influenced by fluctuations in Jupiter’s huge magnetic field.
Scientists used computer modeling to verify that the only explanation for the extent of the “rocking” of Ganymede’s aurorae is the presence of a saline ocean, which would cause Ganymede’s magnetic field to offset to some extent Jupiter’s magnetic impact.
Several measurements indicated that the aurorae moved by about two degrees, but without the presence of an ocean Jupiter’s influence would have caused movement of about six degrees.
“When there is an electrically conductive ocean present, this counteracts Jupiter’s influence,” Joachim Saur, a professor geophysics at Germany’s University of Cologne and the lead researcher, said.
Saur explained that four independent measurements with HST verified the two-degree movement of Ganymede’s aurorae.
Scientists had speculated for several decades that Ganymede could be an oceanic moon. The Galileo probe, which flew by the moon several times during its 1995-2003 mission, provided further grist for that supposition when it measured the moon’s magnetic field. But those flybys did not last long enough for scientists to detect the movement of Ganymede’s aurorae.
“The flybys lasted only 20 minutes each,” Saur said. “In the new Hubble observations we have seven hours of data, so we do not have the ambiguity anymore.”
Ganymede’s sea may also be impacting the surface of the moon. Mapping of the satellite by the U.S. Geological Survey reveals areas of the surface that are smoother and less cratered than other areas, which could indicate the presence of tectonic forces that permit movement of sea water from beneath the icy crust.
“These lighter shaded regions are believed to be formed by flooding on the surface by water coming to the surface by faults or even cryovolcanoes,” Jim Green, NASA’s director of planetary science, said.
Ganymede is Jupiter’s largest moon, with more mass than Mercury. It joins fellow Galilean moon Europa and Saturn’s moon Enceladus on the list of moons known to have water oceans.
Another of Jupiter’s four largest moons, Callisto, is also thought likely to have liquid water.
“Every observation that we make, every mission that we send to various places in the solar system, is taking us one step closer to finding that truly habitable environment, a water-rich environment in our solar system,” Heidi Hammel, executive vice president of the Association of Universities for Research in Astronomy, said. “Everywhere we look there’s water.”
Earthlings had their last chance for 8,000 years to see Comet Lovejoy Saturday night.
The opportunity to look up and see its green glow came when the comet was six days away from perihelion. On Jan. 30 the comet, formally known as Comet C/2014 Q2 Lovejoy, will be 193 million kilometers from the sun.
The comet actually passed closest to Earth on Jan. 7, when it was 70.2 million kilometers away.
It will be about 13,000 years before Comet Lovejoy is again close enough to Earth to be seen without the aid of a magnifying device.
How do scientists know how long it has been since a comet was visible with only the eyes from the surface of our planet?
The answer involves mathematics. Among the laws of planetary motion discovered by Johannes Kepler is the equation necessary to determine a comet’s period, or the amount of time needed to complete an orbit, if its semi-major axis is known. The semi-major axis of an ellipse, which is the shape that most objects in orbit around the sun follow, is best thought of as the radius of the ellipse at its two points that are most distant from each other.
Kepler determined that the square of the ellipse’s period is equal to the cube of the semi-major axis’ length.
Another interesting feature of Comet Lovejoy’s orbit is its orientation relative to the plane of Earth’s and the other planets’ orbits. As Phil Plait explained at Bad Astronomy, the comet sits about 80 degrees off those trajectories.
The U.S. Senate again refused on Thursday to acknowledge the human role in climate change, voting down two proposals that would have forced members to go on record as recognizing scientific reality.
Senators first rejected an amendment to the underlying bill authorizing the KXL oil pipeline that specified that climate change is “real” and “caused by human activities” and “has already caused devastating problems in the United States and around the world.” The proposal, offered by Sen. Joe Manchin, D-W.Va., also included language that encouraged research into “clean fossil fuel technology.”
The Senate tabled the amendment, 53-46, with only one Republican – Mark Kirk of Illinois – voting with Democrats to allow floor debate on its merits.
Later, an amendment introduced by Sen. Bernie Sanders, I-Vt., that also acknowledged human impacts on the atmosphere and oceans and that emphasized the importance of developing non-fossil fuel energy sources was also tabled.
The chamber, with every one of 54 majority Republicans opposed to it, voted 56-42 to table it. Democratic senators Heidi Heitkamp of oil-producing state North Dakota and Claire McCaskill of Missouri also voted to deny consideration of its merits.
Majority leader Mitch McConnell, R-Ky., announced late Thursday night that the Senate would not consider additional amendments to S.1. A vote on whether to cut off floor debate on the bill itself is expected early next week.
President Barack Obama has threatened to veto any bill that interferes with his authority to decide whether or not to grant the permit required to construct the KXL pipeline across the U.S.-Canada border.
The century is only 14 years old, but the record for hottest year in recorded history has just been broken for the third time.
Scientists at the National Oceanic & Atmospheric Administration and NASA announced last week that, during 2014, the worldwide combined average air and sea temperature exceeded the average since 1880 by 0.69 degrees Celsius.
The two agencies’ reports confirm a similar conclusion announced by the Japan Meteorological Agency earlier in January.
An analysis of the new data by climatologist James Hansen of Columbia University and others concludes that the ten hottest years in the planet’s recorded climate history have occurred since 2000 and that the 15 hottest have occurred since 1998.
“This is the latest in a series of warm years, in a series of warm decades,” Dr. Gavin A. Schmidt, a climatologist and the director of NASA’s Goddard Institute of Space Studies, said in a statement. “While the ranking of individual years can be affected by chaotic weather patterns, the long-term trends are attributable to drivers of climate change that right now are dominated by human emissions of greenhouse gases.”
Overall, Earth’s average surface temperature has risen by 0.8 degrees Celsius since meteorological records were first kept 135 years ago.
Not all regions of the planet experienced the same degree of warmth last year. In the United States, for example, certain areas of the Midwest and along the East coast were cooler than average. But those cooler temperatures were outweighed by the broader swaths of the world that experienced hotter-than-normal temperatures.
Four U.S. states – Alaska, Arizona, California, and Nevada – experienced their warmest years in recorded history.
Individually, the global mean land temperature during 2014 was the fourth-highest on record. However, the 0.55 degree Celsius leap above the mean experienced by the seas drove the overall mean surface temperature to the all-time record. The extent to which sea temperatures exceeded the historic mean was unprecedented.
Emissions of carbon dioxide, a leading contributor to the warming of Earth’s climate, continue to rise. Data released earlier this month by the Scripps Institution of Oceanography at the University of California at San Diego indicates that the concentration of CO2 in the atmosphere surpassed 400 parts per million on Jan. 1, Jan. 3, and Jan. 7.
The first time it happened was in 2013, but the threshold was not crossed until May 2013. In 2014, the monthly average concentration of CO2 in the atmosphere reached 400 ppm in March, April, and June.
The current atmospheric concentration of carbon dioxide is higher than it has been in at least 800,000 years.