Lunar Eclipse on Sunday

[update: changed the time of mid-eclipse to 2:47 UT from 2:48 UT. thanks to Joe Stieber for catching the error. the one minute difference doesn’t change the rest of the article.]

Sunday evening will see the last of the recent tetrad of lunar eclipses for observers in the Americas. The eclipse will occur in the morning for observers in Europe, Africa, and western Asia. This eclipse has been hyped a bit more than usual due to the Moon being a ‘Super Moon’. What that means is the Moon is at the close part of its orbit to Earth and appears a little bit larger than usual. Regardless, all total lunar eclipses are worth seeing and this one will be very nice for western US observers as it will be located low on the horizons making for some nice views. Occurring during the early evening also means we don’t have to be up at weird hours of the night to see this one. This is especially convenient for showing the kids.

The Moon will enter the penumbra of Earth’s shadow at 00:12 UT though most observers will have a difficult time noticing any darkening of the Moon until around ~00:40 UT (8:40 pm EDT, 7:40 pm CDT). At that time the Moon will be below the horizon for Tucson and most observers in the Mountain and Pacific time zones.  The Moon enters the umbra of Earth’s shadow and really starts to get dark at 1:07 UT (9:07 pm EDT, 8:07 pm MDT, 7:07 pm MDT). At Tucson the Moon rises at 1:09 UT (6:09 pm PDT) only 1 minute after the start of the partial eclipse and 7 minutes before sunset. As the Moon gets higher and the sky gets darker it will become easier to see even as Earth’s shadow takes a bigger and bigger bit out of it.

The total phase of the eclipse begins at 2:11 UT (10:11 pm EDT, 9:11 pm CDT, 8:11 pm MDT, 7:11 pm PDT). The middle of the eclipse and the time when the Moon should appear darkest occurs at 2:47 UT (10:47 pm EDT, 9:47 pm CDT, 8:47 pm MDT, 7:47 pm PDT. Totality ends at 3:23 UT (11:23 pm EDT, 10:23 pm CDT, 9:23 pm MDT, 8:23 pm PDT) and the whole show should be over (meaning no obvious darkening of the Moon visible by ~5:20 UT.

Here in Tucson, the Moon will appear to rise at due east and will be observable in the southeastern sky for the entire eclipse.


View of the eastern horizon at the time of mid-eclipse for Tucson, Arizona. Chart created with Stellarium.

If you have a pair of binoculars or are taking images of the eclipse, note that two other relatively bright solar system objects are near the Moon. The planet Uranus is located ~15° to the due east or lower left of the Moon. At that time Uranus will be magnitude 5.7 (barely visible to naked eye observers from dark sites) and located 19.98 AU from the Sun and 19.02 AU from Earth (that’s 1.86 million miles from the Sun and 1.77 million miles from Earth). The Moon will be 0.0024 AU from the Earth (222,000 miles from the center of the Earth) or ~7900 times closer than Uranus. To the southeast of the Moon and about 11° away is the brightest asteroid, (4) Vesta. It will be 2.42 AU (225 million miles) from the Sun and 1.43 AU (133 million miles) from Earth or ~600 times further away than the Moon. Vesta will be a little fainter than Uranus at magnitude 6.2. Use the star chart below to find Uranus and Vesta.


Location of Uranus and asteroid Vesta relative to the eclipse Moon on Sunday evening Sep. 27. Chart created with Stellarium.

The next lunar eclipse will be on 2016 March 23 but will be a rather poor penumbral eclipse (meaning the darkest part of the shadow doesn’t cross the Moon). The next series of total lunar eclipses occur on 2018 January 31, 2018 July 27, and 2019 January 19. The first and third of this triad are visible in the US. Go to the NASA Lunar Eclipse page for more detail on these and other lunar eclipse.

Here Comes the Geminids!

Tonight is one of the best nights of the year to see a meteor as the Geminid meteor shower is predicted to reach its 2014 peak. The Geminids are one of two annual showers (the other being August’s Perseids) that are almost guaranteed to produce high rates of meteors (at least one every few minutes or better).

The International Meteor Organization (IMO) maintains a “live” graph showing the rate of the Geminids as reported by visual observers around the world.

How To See Them

This year the Geminids will be near peak intensity on Saturday night/Sunday morning, December 13/14. From a dark, moon-less sky, the Geminids have consistently produced peak rates of ~100 meteors per hour. According to the IMO, the Geminids reached ZHR rates of 134 per hour in 2013, 109 in 2012, 198 in 2011, 127 in 2010, 120 in 2009, 139 in 2008, 122 in 2007 and 115 in 2006. Note, these rates assume ideal observing circumstances that are rarely achieved. Dark sky observers may see rates that approach the ZHR values. Most of us observing under light polluted skies will see lower rates (perhaps much lower for city dwellers or observers watching before 10pm).

Unlike most showers that can only be observed in the early hours of the morning, the Geminids radiant rises as early as 7 pm and a good number of meteors can be seen by 10 pm. The radiant is nearly overhead at 2 am and it still well placed for the rest of the night. This year the Last Quarter Moon (located close to a brilliant Jupiter) will hinder Geminid watching after midnight. The shower can still be observed after Moonrise though fainter meteors will be washed out. It helps to keep the Moon out of your line of sight.

As the name implies, the Geminids appear to radiate from a point in the constellation of Gemini. More specifically from a point just to the north of the bright star Castor, the northern star in the Castor-Pollux pair. During the evening Geminids will be coming out of the northeast. By the middle of the night the radiant will be close to overhead and meteors will be raining down on all sides.

In general it is best not to look directly at the radiant. Meteors are easier to see by looking 30 or more degrees from the radiant (for reference 10 degrees is the width of your hand at arms length). The key is to look up and regardless of where you look you should see quite a few Geminids.


The night sky for December 13 at 11:00pm local time over Tucson. The Geminid radiant is shown as a yellow circle with Geminid meteors radiating away from it. Chart produced with Stellarium.


Sky brightness matters when it comes to seeing most meteors and the Geminids are no exception. As always, the darker the sky the better. If you are located in a place with pitch black skies (mountaintops, middle of the desert, national parks) rates can be as high as ~100 per hour. In rural areas near small towns rates will be a bit lower and probably in the 80-90 per hour range. In the suburbs rates will vary depending on how close to a major city you are but you should expect rates of 20-50 per hour. In a major city rates will be very low though 2-10 per hour should be seen.

To increase your chance of seeing the Geminids find a spot with a clear view of the sky. Any obstructions (trees, buildings, etc.) can block some of the meteors. Also find a spot where lights (streetlights, security lights, etc.) aren’t shining in your eyes. This will allow your eyes to dark adapt and you will be able to see fainter, and more, meteors. The most important thing to remember is to get comfortable when observing. A lawn chair is perfect for reclining back and taking in the sky. Remember that it is cold this time of the year in the Northern Hemisphere so bundle up. It does not take much time, especially when relatively inactive, to start freezing.

Where They Come From

The Geminids were created by an enigmatic object named (3200) Phaethon. For starters Phaethon is an asteroid and only displayed what might be considered cometary activity for a few days in 2009. But meteor showers are created by comets and nearly all comets have orbits that carry them at least as far from the Sun as the orbit of Jupiter. Yet Phaethon only travels out to a distance of 2.4 AU, roughly half the distance to Jupiter’s orbit. Based on its orbit it is hard to call Phaethon anything but an asteroid.


Image of Geminid parent body (3200) Phaethon by Jean-Baptiste Kikwaya on 2014 November 27 with the Vatican Observatory VATT 1.8-m.

So what is Phaethon?

1) Phaethon could be a comet whose original orbit evolved into its current one after many millennia of close approaches with the inner planets. The probability of this happening is extremely low. Some models of the formation of the Geminids require the shower particles to be released over many centuries to millennia which is consistent with the behavior of a comet. Then again…

2) Phaethon may be a Main-Belt comet. Main-Belt comets are objects that originate in the outer Asteroid, or Main, Belt. Since they contain a sizable fraction of volatile ices, they can occasionally exhibit cometary activity. Four of these objects have been observed to display cometary activity in the Main Belt. Since they start on asteroid orbits, it is not too difficult for one of them to find itself on an orbit similar to Phaethon. Or behind door #3…

3) Phaethon is an asteroid that broke up in the past. There is evidence to suggest that Phaethon is just the largest piece of a ancient break-up. In fact, two additional asteroids that may once have been a part of Phaethon have been found, (155140) 2005 UD and 1999 YC. According to Peter Jennisken’s book “Meteor Showers and Their Parent Comets”, the Geminids can be explained by the break-up of Phaethon just after perihelion many orbits ago. Since Phaethon gets to within 0.14 AU (14% of the Earth-Sun distance), perhaps it split from the stress of intense solar heating. BTW, this scenario does not rule out Phaethon as a ice-rich Main-Belt comet.

The recent discovery of additional asteroids related to Phaethon points to scenario 3 as the most likely origin of the Geminids. If true, the Geminids were not the result of long-term cometary activity like most meteor showers but were created in a discrete event or events when Phaethon split or shed smaller pieces. The Daytime Sextentids and perhaps the very minor Canis Minorids were created by even older break-up events.

Though Phaethon has behaved like an asteroid since its discovery in 1983 it has been observed to ‘burp’. Near its perihelion, the asteroid is sometimes visible in near-Sun images taken with the STEREO spacecraft and occasionally appears to elongate as if it had a short tail and brighten. Analysis by David Jewitt and Jing Li (UCLA) found that Phaethon did release some surface particles. Due to intense heating (perihelion is 0.14 AU from the Sun or 7 times closer than the Earth is) some of the rocks on the surface may have fractured producing a cloud of dust which was knocked off the surface by solar radiation pressure. In effect, it is a rock comet. Still this event was very short-lived and produced a minimal amount of debris. So these type of events should not have been large enough to create the Geminids by themselves.

I penned a guest post on Phaethon for Dr. Dante Lauretta (PI of NASA’s OSIRIS-REx asteroid sample return mission) back in 2013. You can read it here.

Whether Phaeton is a traditional comet, a volatile-rich asteroid, an asteroid that split into pieces, or a ‘rock comet’, the result is going to be one of the best astronomical shows of the year. So go out and enjoy the show!

2014 AA impact site identified?

Sky and Telescope magazine is reporting that Peter Brown (University of Western Ontario) has made a preliminary identification of the impact site of 2014 AA, the New Year’s Earth impacting asteroid. Or more exactly, Dr. Brown has found the point where 2014 AA disintegrated in the Earth’s atmosphere.

Brown and his group used data from infrasound arrays to detect the ‘noise’ of the explosion. The location of the fireball was triangulated by measuring the time of arrival of the infrasound signal at a number of infrasound arrays around the world. This technique has been used to pinpoint the location of other large fireball events as well as the detonation of nuclear weapons. As reported by S&T, the preliminary location is at 40° west, 12° north or about 1,900 miles (3,000 km) east of Caracas, Venezuela.

The overlap of the white curves, from three marginal infrasound detections, shows where the small asteroid 2014 AA likely hit. However, this preliminary plot does not take winds into account, which might shift the true impact point somewhat further east.

The overlap of the white curves, from three marginal infrasound detections, shows where the small asteroid 2014 AA likely hit. However, this preliminary plot does not take winds into account, which might shift the true impact point somewhat further east.


The discovery observations have also been posted at the websites of the NASA JPL NEO Project Office and the Catalina Sky Survey.

This sequence of discovery images of Asteroid 2014 AA was taken between 0618 and 0646 UT (between 1:18 and 1:46 am EST) January 1, 2014. The slight "streaking" of the asteroid in the image is due to its rapid motion across the background of stars as it approached the Earth. The brightness of the asteroid is between 18.8 and 19.1 Mv in the images. Image credit: Catalina Sky Survey, Lunar & Planetary Laboratory, University of Arizona
This sequence of discovery images of Asteroid 2014 AA was taken between 0618 and 0646 UT (between 1:18 and 1:46 am EST) January 1, 2014. The slight “streaking” of the asteroid in the image is due to its rapid motion across the background of stars as it approached the Earth. The brightness of the asteroid is between 18.8 and 19.1 Mv in the images. Image credit: Catalina Sky Survey, Lunar & Planetary Laboratory, University of Arizona

Jan 1/2 Meteors and Tonight’s Quadrantids

Tonight brings the peak of the best meteor shower you have probably never seen. The best showers of the year are almost always August’s Perseids and December’s Geminids. Number 3 and 4 are usually October’s Orionids or tonight’s shower, the Quadrantids.

The reason I say the Quads are probably the best shower you’ve never seen is two-fold. First as a northern shower, they take place in the dead of winter and only a few days after New Year’s. If the exhaustion from the Holiday’s season doesn’t keep most people inside then the cold definitely will. Also unlike most showers which have broad peaks which last a few days, the peak of the Quads is very narrow. Even if you are observing on the peak night, you can miss much of the show if you are off the peak by only 12 hours.

The International Meteor Organization predicts this year’s Quads peak to take place at ~19:30 UT on the 3rd which suggests the best viewing will be in Asia. But… predicting the peak time for this shower is always difficult so pretty much anywhere on Earth may see the best. The only way to know is to get out and look.

Bob Lunsford has posted an excellent guide to observing the Quads at the American Meteor Society (AMS) website. Please check it and the AMS (of which I am their Secretary) out.

For many years, astronomers were uncertain as to which comet caused the Quadrantids. No known comets was visible on a similar orbit even though the narrowness and strength of the meteor stream suggested it was created recently. We now know that the asteroid (196256) 2003 EH1 is the likely parent body of the Quads. Even though today it appears as nothing more than an asteroid it was a comet in the past and a rather bright one when seen in 1490. Earlier this year I observed 2003 EH1 with the Vatican Obs/Univ. of Arizona VATT 1.8-m as seen in the image below.

[I forgot to add that yesterday’s Earth impacting asteroid, 2014 AA, is not related to the Quadrantid meteor shower. The asteroid and the meteors have very different orbits and the fact that they both intersected the Earth on the same day (or two) is not only a coincidence but shows just how crowded space is with debris.]

Co-added R-band image of the Quadrantids parent body (xxx) 2003 EH1 taken on 2013 Sep. xx.xx UT with the Vatican VATT 1.8-m. Credit: Carl Hergenrother/Vatican Obs./University of Arizona.

Co-added R-band image of the Quadrantids parent body (196256) 2003 EH1 taken on 2013 Sep. 14.25 UT with the Vatican VATT 1.8-m. At the time the object showed no cometary activity. Credit: Carl Hergenrother/Vatican Obs./University of Arizona.


Last night was another clear night in Tucson. Though 28 meteors were detected, only 2 were possible Quads. Tonight should see a huge increase in Quadrantid meteors.

SAL  2014-01-02   12h 33m   28  23  1   0   0   0   2   0   2

SAL - SALSA3 camera in Tucson (Carl Hergenrother)
Time - Total amount of time each camera looked for meteors
TOT - Total number of meteors detected
SPO - Sporadics (meteors not affiliated with any particular meteor shower)
ANT - Antihelions
AHY - Alpha Hydrids
COM - Coma Berenicids
DAD - December Alpha Draconids
DLM - December Leonis Minorids
JLE - January Leonids
QUA - Quadrantids

2014 AA – New Year’s Earth impactor

2014 has started off with fireworks! The first designated asteroid of the year, discovered only half an hour before midnight on New Year’s Eve (Tucson local time) but 6.5 hours into 2014 in Universal (or Greenwich Mean) time by Richard Kowalski of the Mount Lemmon Survey, was an Earth impactor.

Based on 7 astrometric measurements taken over the course of 70 minutes, the Minor Planet Center’s orbit has determined that 2014 AA impacted the Earth around Jan. 2.2 +/- 0.4 UT somewhere along an arc stretching from the eastern Pacific Ocean, southern Nicaragua, Costa Rica, very northern Columbia and Venezuela, a long stretch of the Atlantic Ocean and the African countries of Senegal, Gambia, Mali, Burkina Faso, Niger, Chad and Sudan. Maps of the possible impact points have been produced by Bill Gray and can be found here and here. The most likely impact point is in the Atlantic Ocean off the coast of western Africa.

With an absolute magnitude of ~30.9, 2014 AA was likely a very small asteroid with a diameter on the order of 1-5  meters. Such an object would have posed no danger to the ground though small meteorites may have survived passage through the atmosphere. If it fell in the ocean there is a good chance that no one directly witnessed it though the signature of its resulting fireball may be found in weather satellite images.

This marks the second time that an asteroid was detected in space prior to impact. The first impactor, 2008 TC3, was also found by Rich Kowalski and the Mount Lemmon 1.5-m reflector. That body was observed to fall over northern Sudan and led to the recovery of many meteorites (named Almahata Sitta). More on the fall of 2008 TC3 and Almahata Sitta can be found at this blog (here, here, here, and here), the Meteoritical Bulletin and Wikipedia.

Note, that for every small asteroid discovered before hitting the Earth (of which we’ve seen only two) there are many thousands of similar sized objects (and countless smaller ones) that go undetected until seen as brilliant fireballs or meteors. Hopefully planned upgrades to current asteroid surveys such as the Catalina Sky Survey/Mount Lemmon Survey and future surveys like ATLAS will result in more warning time for incoming asteroids.

Awesome Fireball Event in central Russia

2012 DA14 may not be on a collision course with Earth later today but a smaller asteroid was. A major fireball (and most likely also a meteorite dropping event) occurred over the city of Chelyabinsk, Russia. Chelyabinsk is a city of 1+ million people located just to the East of the Ural Mountains and just north of the Russia-Kazakhstan border.

The fireball that occurred there this morning appeared brighter than the Sun and produced a sonic boom that shattered windows causing flying glass-induced injuries to hundreds of people. A large building in town also seems to have been damaged. Though it is still uncertain if this was due to a large meteorite or the sonic boom.

An event like this happening only hours before the close flyby of the ~45-meter in diameter asteroid 2012 DA14, begs the question of whether the two are linked. It is probably unlikely that the Chelyabinsk fireball and 2012 DA14 are related. Luckily there are so many great videos of the fireball that an accurate orbit for the asteroid that caused the fireball should be easily determined.

[Update: 2012 DA14 and the Russian fireball can not be related. The radiant (the region of the sky that a DA14 or a piece of DA14 would appear to come from) of DA14 is at the very far southern declination of -81 degrees. This is the reason why DA14 is only visible from the southern hemisphere as it approaches Earth. A radiant that far south could not produce a fireball over Russia which is in the northern hemisphere. Any pieces of DA14 would only be able to impact Earth over the southern hemisphere or a few degrees north of the Equator. The fact that the Russian fireball and the 2012 DA14 close approach are happening on the same day is just a coincidence.]

Up-to-date information can be found at RT, here and here, and RMNB.

Many videos have been posted. The first 2 show the fireball itself. The last 2 are videos of the resulting contrail. What is very impressive about the last two is that the videos also caught the sonic boom. In one of the videos you can hear glass shattering in the background. Simply awesome…

2012 DA14

Remember to duck this Friday!

As any one who has been following the news lately knows, a small asteroid named 2012 DA14 will make an especially close flyby of Earth later this week. The 50-meter wide (~150-foot) asteroid will pass within 27,700 km (22,200 miles) of the Earth’s surface at 19:24 UT on February 15. At that time the asteroid will be over the Indian Ocean.

This is the closest known approach of an asteroid of this size. Such an occurrence should happen once every 40 years, on average. The reason this is the first detected close approach of its kind is because we only possessed the technology to easily discover such object over the past 10-15 years.

There is a zero probability that this object will hit the Earth this week. Its orbit is well enough known that not only will it not hit the Earth but it will also not be impacting any Earth-orbiting satellites. There is a 1-in-50,000 chance DA14 could hit the Earth in the years between 2080 and 2109, though it is likely that even these small impact probabilities will drop to zero after this week’s flyby.

More on the close approach of 2012 DA14 can be found at NASA/JPL and Sky & Telescope.

As close as this asteroid gets to Earth, it small size means it never gets very bright. It will brighten to about 7-8th magnitude at its closest which will make it an easy binocular or small telescope object. The hard part will be finding it. It will be moving as fast as nearly a degree per minute at its fastest. Not too mention being so close also means parallax will be an issue.

By the time the sun sets in the United States, it will have faded to 11th-12th magnitude. Only observers with relatively large telescopes will be able to spot DA14 by then as it recedes into the distance near the north star, Polaris.


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