A Shadow on the Moon

The next full moon is known as the Cold Moon, the Long Night Moon, or the Moon Before Yule. The moon will be “opposite” the sun at 9:38 a.m. EST on Saturday, Dec. 10. The moon will appear full for about three days around this time, from the evening of Thursday, Dec. 8 through the morning — and possibly the evening — of Sunday, Dec. 11.

On Dec.10, the moon will be so “opposite” the sun from the Earth that it will pass through the shadow of the Earth. The Earth’s shadow will begin to reduce the amount of sunlight reaching the moon at about 6:34 a.m. EST, but the U.S. East Coast will not be able to tell that the moon appears dimmer before it sets at 7:08 a.m. EST. The full shadow of the Earth (called the umbra) does not start to fall on the moon until about 7:46 a.m. EST, well after the moon has set for the U.S. East Coast. Even for the U.S. West Coast, the eclipse will be near moonset, making this a difficult eclipse to view. The extended period with reduced sunlight, including 51 minutes in the full shadow of the Earth, presents a challenging environment for spacecraft at the moon (LRO, the twin GRAIL spacecraft) that rely upon sunlight for heat and solar power. Because the two ARTEMIS spacecraft are in highly elliptical orbits around the moon, it is not clear if or how they will be impacted.

Europeans call the December full moon the Moon before Yule. Yule is an old northern European winter festival that is now associated with Christmas. The Native American names for the full moon in December — as reported in the Farmer’s Almanac — are the Cold Moon or the Long Night Moon. The Cold Moon gets its name because December is the month when it really starts to get cold, although our coldest average temperatures are in January. The Long Night Moon gets its name because the full moon in December occurs near the solstice, which has the longest night of the year. The full moon takes a high trajectory across the sky because it is opposite to the low sun, so the moon will be above the horizon longer than at other times of the year.


 A full moon over Earth, seen by astronaut Ron Garan from the International Space Station. (NASA)

Images of Rare Aurora in Southern Tennessee

 
The colors of emitted light within an aurora depend on the initial energy of the charged particles (mostly electrons) cascading into Earth’s atmosphere.  Electrons with higher initial energies are able to penetrate deeper into the atmosphere, whereas those with lower initial energies lose all their energy at higher altitudes. The blue aurora emitted from low-altitude molecular nitrogen is most commonly seen at higher latitudes, such as in Canada and Alaska, where high-energy electrons are more common. Red aurorae mostly result from lower-energy electrons reacting with atomic oxygen at high altitudes, which can occur at lower latitudes (<50 degrees) during extremely strong geomagnetic storms — such as is seen in images here.  The auroral electrons that make it into the low-latitude atmosphere usually do not have enough energy to reach molecular nitrogen.  This is why low-latitude aurorae are almost always red.


Credit: Jeremy Myers, NASA Marshall Engineer
 

One Night, Five Meteor Showers

On the night of Oct. 15-16, NASA’s All-sky camera network saw meteors from five different meteor showers! October is known to be a busy month in the world of meteor showers, but even five is an unusually high number.


 


 The last meteor seen in the early morning skies over Huntsville, Ala., on the night of the Oct. 15-16.

 

To see videos of these meteors, and others, go to fireballs.ndc.nasa.gov and select 20111016 on the left panel. In addition to those five shower meteors, eight sporadic or background  meteors were detected. The five showers were: Delta Aurigids, or DAU, October Ursa Majorids, or OCU, Chi Taurids, or CTA, Orionids , or ORI, and Eta Geminids, or EGE. See the list at the end of this post for more information on each shower.

 

The only shower mentioned above that would be worth observing for yourself is the Orionids. The Orionids peak this Friday evening — the night of Oct. 21-22 — and are best viewed anytime after midnight. They are one of the last showers of the year that may have favorable weather to lie outside all night. If you are in Northern Alabama, October evenings are still quite pleasant for stargazing. Luckily for you the moon won’t be too much of a problem. Only a small fraction of the moon is illuminated, unlike many major meteor showers this year whose rates were considerably hampered because the light from a full moon washed them out.

 

Delta Aurigids, or DAU: Active from Sept. 20 — Oct. 16, peaking on Oct. 3 with only two meteors per hour. Velocity of 143,000 miles/hour. The Delta Aurigids are not a well-known shower thus any observations refine the information we know about them.

 

October Ursa Majorids, or OCU: Active from Oct. 12-19, peaking on Oct. 15. Velocity of 119 miles/hour. This is a very minor shower rates of less than one per hour. Radiant — where the meteors appear to come from — is in Ursa Major.

 

Chi Taurids, or CTA:  Active from Oct. 10 — Nov. 10, peaking on Nov. 3. Velocity approximately 94,000 miles/hour. This is also a shower that has very little known about it. It was recently discovered in a survey to find minor meteor showers using a meteor radar (Brown et al, 2010).

 

Orionids, or ORI: Active from Oct. 2 — Nov. 7, peaking on Oct. 21 with rates up to 25 per hour. Velocity of 150,000 miles/hour. Radiant is in the constellation Orion.

 

Eta Geminids, or EGE:  Active from Oct. 14-27.  Peaking on Oct. 18 with rates of three per hour. These are fast-moving meteors that average at 157,000 miles/hour. Eta Geminids are often confused with Orionids since their velocity and peaks are similar.

 

Brown, P., Wong, D.K., Weryk, R.J., Wiegert, P.

A meteoroid stream survey using the Canadian Meteor Orbit Radar II: Identification of minor showers using a 3D wavelet transform

Icarus 207 (2010) 66–81.

 

 

Credits: NASA/MSFC/Meteoroid Environment Office/Rhiannon Blaauw, Bill Cooke

 

Perseids Meteor Shower Lights Up the Sky

Marshall scientist Bill Cooke and his team, from the Meteoroid Environment Office at Marshall Space Flight Center, watched the sky during the peak of the Perseid meteor shower. The team used the Marshall meteor cameras the evening of August 12 and into the early morning August 13 to capture images of the Perseids.

 

 
Meteor over Tullahoma, Tennessee 
(Courtesy: NASA/MSFC/Meteoroid Environment Office)
 

The Perseids have been observed for about 2,000 years. The source of the annual meteor shower is the debris trail left behind comet Swift-Tuttle. Each year in August, the Earth passes through a cloud of the comets debris. These bits of ice and dust burn up in the Earth’s atmosphere. Most of the Perseid meteors that we observe now were ejected from Swift-Tuttle about 1,000 years ago.

Cooke and his team answered questions about the Perseids during an Up All Night with NASA web chat. You can read a transcript of the web chat (PDF, 550 Kb) to learn more about the Perseids: what creates them, their composition, how old they are, how fast they travel and other fascinating facts.