Skywatching Archives

August 21, 2013December 23, 2015 by Ken Kremer

Earthlings Wave at Saturn as Cassini Images Us

Earth Waves at Cassini on July 19, 2013- From more than 40 countries and 30 U.S. states, people around the world shared more than 1,400 images of themselves as part of the Wave at Saturn event organized by NASA's Cassini mission on July 19, 2013. The Cassini team created this image collage as a tribute to the people of Earth Credit: NASA/JPL-Caltech/People of Earth See link below to the absolutely gigantic full resolution version

Earth Waves at Saturn and Cassini on July 19, 2013
From more than 40 countries and 30 U.S. states, people around the world shared more than 1,400 images of themselves as part of the Wave at Saturn event organized by NASA’s Cassini mission on July 19, 2013. The Cassini team created this image collage as a tribute to the people of Earth
Credit: NASA/JPL-Caltech/People of Earth
See link below to the absolutely gigantic full resolution version [/caption]

On July 19, millions of Earthlings worldwide participated in NASA’s ‘Wave at Saturn’ campaign as the NASA Cassini Saturn orbiter turned about and imaged all of us.

Earthlings from 40 countries and 30 U.S. states heeded NASA’s call to photograph themselves while smiling and waving at Saturn and Cassini across 1 billion miles of interplanetary space and shared over 1400 images.

The results of all those images has now been assembled into a fabulous collage in the shape of our planet and released today (Aug. 21) by NASA and the Cassini team as a tribute to the People of Earth.

“Did you wave at Saturn and send us your photo? Then here’s looking at you!” NASA announced on the Cassini Facebook page.

This event was the first time that the citizens of Earth knew in advance that a distant interplanetary spacecraft was photographing portraits of our home planet and our Moon. NASA invited everyone to participate.

Photos flooded into NASA via Twitter, Facebook, Flickr, Instagram, Google+ and email.

Click here for the full resolution version. But be forewarned – it weighs in at over 26 MB and it’s far too big to post here.

The Day the Earth Smiled: Sneak Preview In this rare image taken on July 19, 2013, the wide-angle camera on NASA's Cassini spacecraft has captured Saturn's rings and our planet Earth and its moon in the same frame. Image Credit: NASA/JPL-Caltech/Space Science Institute — The Day the Earth Smiled: Sneak Preview
In this rare image taken on July 19, 2013, the wide-angle camera on NASA’s Cassini spacecraft has captured Saturn’s rings and our planet Earth and its moon in the same frame. Image Credit: NASA/JPL-Caltech/Space Science Institute

“Thanks to all of you, near and far, old and young, who joined the Cassini mission in marking the first time inhabitants of Earth had advance notice that our picture was being taken from interplanetary distances,” said Linda Spilker, Cassini project scientist at NASA’s Jet Propulsion Laboratory, Pasadena, Calif, in a statement.

“While Earth is too small in the images Cassini obtained to distinguish any individual human beings, the mission has put together this collage so that we can celebrate all your waving hands, uplifted paws, smiling faces and artwork.”

The Cassini imaging science team is still assembling the hundreds of images of Saturn and Earth snapped by the spacecraft as we were waving, to create individual color composites and a panoramic view of the ‘pale blue dot’ and the entire Saturnian system.

To capture all of Saturn and its wide swath of rings, Cassini’s wide angle camera snapped a mosaic of 33 footprints on July 19, 2013.

“At each footprint, images were taken in different spectral filters for a total of 323 images,” says Carolyn Porco, Cassini Imaging Team leader, Space Science Institute in Boulder, Colo.

Cassini took the pictures of Earth from a distance of about 898 million miles (1.44 billion kilometers) away from the home to every human being that has ever lived.

Here is our partial version of Cassini’s mosaic.

Partial context mosaic of the Earth and Saturn taken by NASA’s Cassini orbiter on July 19, 2013. This mosaic was assembled from five wide angle camera raw images. Credit: NASA/JPL-Caltech/Ken Kremer/Marco Di Lorenzo — Partial context mosaic of the Earth and Saturn taken by NASA’s Cassini orbiter on July 19, 2013. This mosaic was assembled from five Cassini wide angle camera raw images and offers a sneak peek of the complete panorama. Earth at lower right. Credit: NASA/JPL-Caltech/Ken Kremer/Marco Di Lorenzo

Cassini was launched from Florida in 1997.

It achieved orbit at Saturn in 2004 and has transmitted breathtaking images and science that revolutionized our understanding of the Saturnian system.

The mission is scheduled to continue until 2017 when it will commit a suicide death dive into the humongous gas giant.

Coincidentally, the first humans (Neil Armstrong and Buzz Aldrin) set foot on the Moon 44 years ago nearly to the day of Cassini’s Earth-Moon portrait on July 20, 1969 aboard Apollo 11.

And likewise on July 19, 2013, billionaire space enthusiast Jeff Bezos announced that his dive teams had recovered components of an Apollo 11 first stage F-1 rocket engine from the Saturn V moon rocket that propelled the first humans to the Moon.

Ken Kremer

JPL Waves at Saturn As NASA's Cassini spacecraft turned its imaging cameras to Earth, scientists, engineers and visitors at NASA's Jet Propulsion Laboratory, Pasadena, Calif., gathered to wave at our robotic photographer in the Saturn system on July 19, 2013. Credit: NASA/JPL-Caltech — JPL Waves at Saturn As NASA’s Cassini spacecraft turned its imaging cameras to Earth, scientists, engineers and visitors at NASA’s Jet Propulsion Laboratory, Pasadena, Calif., gathered to wave at our robotic photographer in the Saturn system on July 19, 2013. Credit: NASA/JPL-Caltech

August 19, 2013December 23, 2015 by David Dickinson

How to See Planet Neptune: Our Guide to Its 2013 Opposition

Neptune and its large moon Triton as seen by Voyager 2 on August 28th, 1989. (Credit: NASA).

If you do your own stargazing or participate in our Sunday night Virtual Star Parties, you’ve probably noticed we’re starting to lose planetary targets in the night-time sky. August and September of this year sees Venus and Saturn to the west at dusk, with the planets Mars and Jupiter adorning the eastern dawn sky just hours before sunrise.

That means there is now a good span of the night that none of the classic naked eye planets are above the horizon. But the good news is, with a little persistence, YOU can spy the outermost planet in our solar system in the coming weeks: the elusive Neptune. (Sorry, Pluto!)

A wide field view of Aquarius with Neptune's present position in late August/early September. (Created by the author i Stellarium). — A wide field view of Aquarius, with Neptune’s present position marked for late August/early September. (Created by the author in Stellarium; click on all star charts to enlarge).

The planet Neptune reaches opposition late this month in the constellation Aquarius on August 27^th at 01:00 UT (9:00 PM EDT on the 26^th). This means that it will rise to the east as the Sun sets to the west and will remain above the local horizon for the entire night.

If you’ve never caught sight of Neptune, these next few weeks are a great time to try. The Moon passes 6° north of the planet’s location this week on August 21^st, just 10 hours after reaching Full.

neptune on the night of Opposition using a 4.4 degree field of view. (Created by the author using Stellarium). — Neptune on the night of Opposition using a 4.4 degree field of view. Magnitudes for nearby guide stars are given in red. (Created by the author using Stellarium).

Shining at magnitude +7.8, Neptune is an easy catch with binoculars from a dark sky site. Even in a large telescope, Neptune appears as a tiny blue dot, almost looking like a dim planetary nebula that refuses to come to a sharp focus. Visually, Neptune is only 2.3” across at opposition; you could stack 782 Neptunes across the breadth of the Full Moon!

It’s sobering to think that Neptune only just returned in 2011 to the position of its original discovery back in 1846. The calculation of Neptune’s position by Urbain Le Verrier was a triumph for Newtonian mechanics, a moment where the science of astronomy began to demonstrate its predictive power.

Astronomers knew of the existence of an unseen body due to the perturbations of the planet Uranus, which was discovered surreptitiously by William Herschel 65 years earlier. Using Le Verrier’s calculations, Johann Galle and Heinrich d’Arrest spied the planet on the night of September 23^rd, 1846 using the Berlin observatory’s 9.6” refractor. Neptune was within a degree of the position described in Le Verrier’s prediction.

Neptune orbits the Sun once every 164.8 years, and comes back into opposition once every successive calendar year about 2 days later than the last. Those observers of yore were lucky that Neptune and Uranus experienced a close and undocumented conjunction in 1821; otherwise, Neptune may have gone undetected for a much longer span of time. And ironically, Galileo sketched the motion of Neptune near Jupiter in 1612 and 1613, but failed to identify it as a planet!

The motion of Neptune through Aquarius through late August into September. (Starry Night) — The motion of Neptune through Aquarius through late August into September. (Graphic created by author; courtesy of Starry Night Education).

Neptune descended through the ecliptic in 2003 and won’t reach its southernmost point below it until 2045. This month, Neptune lies 1.5 degrees west of the +4.8 magnitude double star Sigma Aquarii. Neptune passes less than 4’ from +7.5 magnitude star HIP 110439 on September 9^th as it continues towards eastern quadrature on November 24^th.

Corkscrew chart credit: — Corkscrew chart for the elongations of Triton through early September. (Courtesy of Ed Kotapish; created using NASA/PDS Rings Node).

Up for a challenge? Neptune also has a large moon named Triton that is just within range of a moderate (8” in aperture or larger) telescope. Shining at magnitude +13.4, Triton is similar in brightness to Pluto and is 100 times fainter than Neptune. In fact, there’s some thought that Pluto may turn out to be similar to Triton in appearance when New Horizons gets a close-up look at it in July 2015.

Triton never strays more than 18” from Neptune during eastern or western elongations. This presents the best time to cross the moon off your astronomical “life list…” experienced amateurs have even managed to image Triton!

The moons of Neptune and Uranus imaged by Credit: — The moons of Neptune and Uranus imaged by Rolf Wahl Olsen using a 10″ reflector and a ToUCam Pro. An amazing catch! (Credit & Copyright: Rolf Wahl Olsen, used with permission).

Triton was discovered just 17 days after Neptune by William Lassell using a 24” reflector. Triton is also an oddball among large moons in the solar system in that it’s in a retrograde orbit.

A second moon named Nereid was discovered by Gerard Kuiper in 1949. To date, Neptune has 14 moons, including the recently discovered S/2004 N1 unearthed in Hubble archival data.

Neptune & Triton on the night of August 21st as it reaches greatest elongation. (Starry Night). — Neptune & Triton on the night of August 21st as it reaches greatest elongation. (Graphic created by author. Courtesy of Starry Night Education).

To date, Voyager 2 is the only spacecraft that has studied Neptune and its moons up close. Voyager 2 conducted a flyby of the planet in 1989. A future mission to Neptune would face the same dilemma as New Horizons: a speedy journey would still take nearly a decade to complete, which would rule out an orbital insertion around the planet. (Darn you, orbital mechanics!) In fact, New Horizons just crosses the orbit of Neptune at a distance of 30 astronomical units from the Earth in 2014.

Neptune is about four light hours away from the Earth, a distance that varies less than 20 minutes in light travel time from solar conjunction to opposition. And while Neptune and Triton may not appear like much more than dim dots through a telescope, what you’re seeing is an ice giant 3.8 times the diameter of the Earth, with a large moon 78% the size of our own.

Make sure to cross Neptune and Triton off of your bucket list… and next month, we’ll be able to do the same for the upcoming opposition of Uranus!

August 16, 2013December 23, 2015 by Nancy Atkinson

CIA’s Declassified Documents Reveals Secrets About Area 51 and UFOs

Area 51 shows up in Google Earth. Via Google Maps.

The CIA has released a 355-page document which officially acknowledges that Area 51 in Nevada does exist, and the agency comes clean about their weather balloon cover stories. The document covers the U-2 and SR-71 spyplane programs and Project OXCART, the aerial reconnaissance programs, from 1954 to 1974.

Nope, no revelations about extraterrestrial spacecraft or alien bodies hidden at the base, but a really grainy map showing the location of Area 51 is included.

While Area 51 has been the subject of fascination for conspiracy theorists and paranormal enthusiasts — and is entrenched in UFO-ology and pop culture — the newly declassified information (with surprisingly few redactions) admits the base was a top-secret aircraft testing facility for Cold War reconnaissance of the Soviet Union.

That UFO sightings increased during the times of the flight tests was an unexpected side effect, the document says:

High-altitude testing of the U-2 soon led to an unexpected side effect-a tremendous increase in reports of unidentified flying objects (UFOs). In the mid-1950s, most commercial airliners flew at altitudes between 10,000 and 20,000 feet and military aircraft like the B-47s and B-57s operated at altitudes below 40,000 feet. Consequently once U-2s started flying at altitudes above 60,000 feet, air-traffic controllers began receiving increasing numbers of UFO reports.

The document also explains Project Blue Book and other frequently associated UFO story staples. The job of Project Blue Book was actually to figure out when civilians were reporting UFOs that were actually U-2s and then work out how to keep that from happening again.

Why did people on the ground and even other pilots report “shiny” UFOs? The document explains that the U-2s silver wings were at the right altitude that when the ground below, or even planes flying at a lower altitude were in darkness, the U-2 was in sunlight and its silver wings would glint in the sunlight:

Such reports were most prevalent in the early evening hours from pilots of airliners flying from east to west. When the sun dropped below the horizon of an airliner flying at 20,000 feet. the plane was in darkness. But, if a U-2 was airborne in the vicinity of the airliner at the same its horizon from an altitude of 60,000 feet was considerably more distant, and being so high in the sky, its silver wings would catch and reflect the ray of the sun and appear to the airliner pilot 40,000 feet below to be fiery objects. Even during the daylight hours, the silver bodies of the high-flying U-2s could catch the sun and cause reflections or glints that could be seen at lower altitudes and even on the ground. At this time, no one believed manned flight was possible above 60,000 feet, so no one expected to see an object so high in the sky.

A handwritten document about the U-2 spyplane design that was included in the information released by the CIA about test flights and Area 51.

But then, not all the UFO reports were explained by U-2 flights.

Air Force investigators then attempted to explain such sightings by linking them to natural phenomena. BLUE BOOK investigators regularly called on the Agency’s Project Staff in Washington to check reported UFO sightings against U-2 flight logs. This enabled the investigators to eliminate the majority of the UFO reports, although they could not reveal to the letter writers the true cause of the UFO sightings. U-2 and later OXCART flights accounted for more than one-half of all UFO reports during the late 1950s and most of the 1960s.

In the document, the CIA admits the weather balloon stuff was just a cover story, but it was the standard operating procedure for how to explain away the sightings as well as debris from any crashes. However, this cover story ended up having disastrous results in May of 1960 when the crash of a U-2 in Russia and the subsequent capture of pilot Gary Powers set in motion a pattern of mistrust between the US and USSR that culminated in the Cuban Missile Crisis in 1962.

After the plane and the pilot went missing, and with the fate of the plane and pilot unknown, the CIA had NASA release a statement that they had a weather airplane that went off course over the Soviet Union because the pilot had passed out due to a loss of oxygen. That story was quickly proven to be a hoax when the USSR produced the crashed U-2 plane and the pilot, who survived the crash and who had admitted to spying.

The documents were released in response to a Freedom of Information Act request submitted in 2005 by Jeffrey T. Richelson, a senior fellow at the National Security Archives. Originally, the CIA had released a heavily redacted document with all mention of Area 51 blacked out. This new document reveals pretty much everything except names of military personnel and private citizens involved.

Richelson has pointed out that the location of Area 51 was not a particularly well-kept secret. Its location appears in satellite imagery like Google Maps and Google Earth, as well as in books on aerial surveillance.

You can wade through the 355 page document here. If you enjoy military and aircraft history, its a great read. One interesting fact revealed is that President Eisenhower wanted the pilots of these planes to be non-US citizens. “It was his belief that, should a U-2 come down in hostile territory, it would be much easier for the United States to deny any responsibility for the activity if the pilot was not an American,” the document reports.

And while I have this chance, I’m going to share a great graphic going around Twitter on how to identify any strange light in the sky you may see:

August 9, 2013April 26, 2016 by David Dickinson

A Challenging Series of Occultations of Spica by the Moon Coming to a Sky Near You

An occultation of the star Mu Geminorum (to the upper right off the dark limb of the Moon) Photo by author.

The first in a cycle of challenging occultations of the bright star Spica for northern hemisphere observers begins this coming Monday on August 12^th.

Watching a bright star or planet wink out on the dark limb of the Moon can be an amazing event to witness. It’s an abrupt “now you see it, now you don’t” event in a universe which often seems to move at an otherwise glacial pace. And if the event grazes the limb of the Moon, an observer may see a series of winks as the starlight streams through the lunar valleys.

Close companion stars have been discovered during occultations, and astronomers even used a series of occultations of radio source 3C 273 in 1962 to pin down the position of the first quasar.

An occultation occurs when one object passes in front of another as seen from the observer’s vantage point. The term has its hoary roots back in a time when astronomy was intertwined with its pseudoscience ancestor of astrology. Even today, I still get funny looks from non-astronomy friends when I use the term occultation, as if it just confirms their suspicions of the arcane arts that astronomers really practice in secret.

But back to reality-based science. At an apparent magnitude of +1.1, Spica is the 3rd brightest star that the Moon can occult along its five degree path above and below the plane of the ecliptic. It’s also one of only four stars brighter than +1.4 magnitude on the Moon’s path. The others are Antares (magnitude +1.0), Regulus (magnitude +1.4), and Aldebaran (magnitude +0.8). All of these are bright enough to be visible on the lunar limb through binoculars or a telescope in the daytime if conditions are favorable.

It’s interesting to note that this situation also changes over time due to the precession of the equinoxes. For example, the bright star Pollux was last occulted by the Moon in 117 BC, but cannot be covered by the Moon in our current epoch.

Spica is currently in the midst of a cycle of 21 occultations by our Moon. This cycle started in July 25^th, 2012 and will end in January 2014.

Spica is a B1 III-IV type star 10 times the mass of the Sun. At 260 light years distant, Spica is one of the closest candidates to the Earth along with Betelgeuse to go supernova. Now, THAT would make for an interesting occultation! Both are safely out of the ~100 light year distant “kill zone”.

What follows are the circumstances for the next four occultations of Spica by the Moon. The times are given for closest geocentric conjunction of the two objects. Actual times of disappearance and reappearance will vary depending on the observer’s location. Links are provided for each event which include more info.

Looking westward 30 minutes after sunset for North American viewers on the night of August 12th. (Created by the Author using Starry Night).

First up is the August 12^th occultation of Spica, which favors Central Asia and the Asian Far East. This will occur late in the afternoon sky around 09:00 UT and prior to sunset. The waxing crescent Moon will be six days past New phase. North American observers will see the Moon paired five degrees from Spica with Saturn to the upper left on the evening of August 12^th.

Next is the September 8^th daytime occultation of Spica for Europe, the Middle East and northern Africa around ~15UT. This will be a challenge, as the Moon will be a waxing crescent at only 3 days past New. Observers in the Middle East will have the best shot at this event, as the occultation occurs at dusk and before moonset. Note that the Moon also occults Venus six hours later for Argentina and Chile.

Looking to the east the morning of November 2nd for North American observers. (Created by the author using Stellarium).

After taking a break in October (the occultation of October 5 occurs only 23 hours after New and is unobservable), the Moon again occults Spica on November 2^nd for observers across Europe & Central Asia. This will be a difficult one, as the Moon will be only 20 hours from New and a hybrid solar eclipse that will cross the Atlantic and central Africa. It may be possible to lock on to the Moon and track it up into the daylight, just be sure to physically block the rising Sun behind a building or hill!

USNO — The occultation footprint of Spica by the Moon for November 29th, 2013. (Reproduced from the Astronomical Almanac online and produced by the U.S. Naval Observatory and H.M. Nautical Almanac Office).

Finally, the Moon will occult Spica for North American observers on November 29^th centered on 17:03 UT. This will place the event low in the nighttime sky for Alaskan observers. It’ll be a bit more of a challenge for Canadian and U.S. observers in the lower 48, as the Moon & Spica will be sandwiched between the Sun and the western horizon in the mid-day sky. As an added treat, comet C/2012 S1 ISON will reach perihelion on November 28th, just 20 hours prior and will be reaching peak brilliance very near the Sun.

And as an added bonus, the Moon will be occulting the +2.8 star Alpha Librae (Zubenelgenubi) on August 13^th for central South America.

All of these events are challenges, to be sure. Viewers worldwide will still catch a close night time pairing of the Moon and Spica on each pass. We’ve watched the daytime Moon occult Aldebaran with binoculars while stationed in Alaska back in the late 1990’s, and can attest that such a feat of visual athletics is indeed possible.

And speaking of which, the next bright star due for a series of occultations by the Moon is Aldebaran starting in 2015. After 2014, Spica won’t be occulted by the Moon again until 2024.

But wait, there’s more- the total eclipse of the Moon occurring on April 15^th 2014 occurs just 1.5 degrees from Spica, favoring North America. This is the next good lunar eclipse for North American observers, and one of the best “Moon-star-eclipse” conjunctions for this century. Hey, at least it’ll give U.S. observers something besides Tax Day to look forward to in mid-April. More to come in 2014!

August 3, 2013January 22, 2021 by David Dickinson

The 2013 Perseid Meteor Shower: An Observer’s Guide

The radiant for the Persieds, looking to the NE from latitide ~30N at around 2AM local. Created by the Author in Starry Night).

Get set for the meteoritic grand finale of summer.

Northern hemisphere summer that is. As we head into August, our gaze turns towards that “Old Faithful” of meteor showers, the Perseids. Though summer is mostly behind us now, “meteor shower season” is about to get underway in earnest.

Pronounced “Pur-SEE-ids,” this shower falls around the second week of August, just before school goes back in for most folks. This time of year also finds many the residents of the northern hemisphere out camping and away from light-polluted suburban skies.

This year also offers a special treat, as the Moon will be safely out of the sky during key observation times. The Moon reaches New phase on August 6^th at 5:51 PM EDT/ 9:51 Universal Time (UT) and will be a 32% illuminated waxing crescent around the anticipated peak for the Perseid meteors on August 12^th. And speaking of which, the Perseids are infamous for presenting a double-fisted twin peak in activity. This year, the first climax for the shower is predicted for around 13:00 UT on August 12^th, favoring Hawaii and the North American west coast, and the second peak is set to arrive 13 hours later at 02:00 UT, favoring Europe & Africa.

Nodal crossing for the Perseid stream and Earth’s orbit sits right around 18:00 to 21:00 UT on August 12^th for 2013. The shower derives its name from the constellation Perseus, and has a radiant located near Gamma Persei at right ascension 3 hours 4 minutes and a declination of +58 degrees. Atmospheric velocities for the Perseids are on the high end as meteor showers go, at 59km/sec.

Of course, like with any meteor shower, it’s worth starting to watch a few days prior to the peak date. Although meteor streams like the Perseids have been modeled and mapped over the years, there are still lots of surprises out there. Plus, starting an early vigil is insurance that you at least catch some action in the event that you’re clouded out on game day! Like we mentioned in last week’s post on the Delta Aquarids, the Perseids are already active, spanning a season from July 17^th to August 24^th.

The Zenithal Hourly Rate for the Perseids is generally between 60-100 meteors. The ZHR is the number of meteors you could expect to see during optimal conditions under dark skies with the radiant directly overhead. Rates were enhanced back in the 1990’s, and 2004 saw a ZHR of 200.

The orbit of comet Swift-Tuttle and its intersection near the Earth's orbit. (Created the author using NASA/JPL ephmeris generator). — The orbit of comet Swift-Tuttle and its intersection near the Earth’s orbit. (Created by the author using NASA/JPL ephemerides generator).

The source of the Perseids is comet 109P/Swift-Tuttle. Discovered on July 16^th-19th, 1862 by astronomers Lewis Swift & Horace Tuttle, Swift-Tuttle is on a 133.3 year orbit and last passed through the inner solar system in late 1992. This comet will once again grace our skies in early 2126 AD.

The Perseids are also sometimes referred to as the “tears of St Lawrence,” after the Catholic saint who was martyred on August 10^th, 258 AD. The Perseids have been noted by Chinese astronomers as far back as 36 AD, when it was recorded that “more than 100 meteors flew thither in the morning.” The annual nature of the shower was first described by Belgian astronomer Adolphe Quételet in 1835.

Enhanced rates for the Perseids marked the return of comet Swift-Tuttle in the 1990s. Recent years have seen rates as reported by the International Meteor Organization at a ZHR=175(2009), 91(2010), 58(2011), & a resurgence of a ZHR=122 last year.

Just what will 2013 bring? There’s one truism in meteor observing—you definitely won’t see anything if you do not get out and observe. Meteor shower observing requires no equipment, just clear skies and patience. Watch in the early hours before dawn, when the rates are highest. Meteors can occasionally be seen before midnight, but are marked by lower rates and slow, stately trains across the sky. Some suggest that best viewing is at a 45 degree angle away from the radiant, but we maintain that meteors can appear anywhere in the sky. Pair up with a friend or two and watch in opposite directions to increase your meteor-spotting chances.

We also like to keep a set of binoculars handy to examine those smoke trains left by bright fireballs that may persist seconds after streaking across the sky.

And speaking of which, there has also been some spirited discussion over the past week as to whether or not the Perseids produce more fireballs than any other shower. I certainly remember seeing several memorable fireballs from this shower over the years, although the Geminids, Leonids and Taurids can be just spectacular on active years. The stated r value of the Perseids is one of the lowest at 2.2, suggesting a statistically high percentage of fireballs.

And in the realm of the strange and the curious, here are just a few phenomena to watch/listen for on your Perseid vigil;

– Can you “hear” meteors? Science says that sounds shouldn’t carry through the tenuous atmosphere above 50 kilometres up, and yet reports of audible meteors as a hiss or crackle persist. Is this an eye-brain illusion? Researchers in 1988 actually studied this phenomenon, which is also sometimes reported during displays of aurora. If there’s anything to it, the culprit may be the localized generation of localized electrophonic noises generated by Extra/Very Low Frequency electromagnetic radiation.

– Can meteor streaks appear colored? Green is often the top reported hue.

– Can meteors appear to “corkscrew” during their trajectory, or is this an illusion?

A Perseid very near the shower radiant during the 2012 shower. (Photo by author).

Wide-field photography is definitely a viable option during meteor showers. Just remember to bring extra charged batteries, as long exposure times will drain modern DSLRs in a hurry!

And did you know: you can even “listen” to meteor pings on an FM radio or portable TV? This is a great “rain check” option!

And there’s still real science to be done in the world of meteor shower studies. The International Meteor Organization welcomes counts from volunteers… and be sure to Tweet those Perseid sightings to #Meteorwatch.

Also be sure to check out the UK Meteor Observation Network, which has just launched their live site with streaming images of meteors as they are recorded.

Good luck, clear skies, and let the late 2013 meteor shower season begin!

-And be sure to post those Perseid pics to the Flickr forum on Universe Today… we’ll be doing photo essay roundups from observers around the world!

August 2, 2013December 23, 2015 by David Dickinson

The Astronomy of the Dog Days of Summer

Looking east from latitude 30 north on August 3rd, 30 minutes before sunrise. (Created by the author in Stellarium).

Can you feel the heat?

It’s not just your imagination. The northern hemisphere is currently in the midst of the Dog Days of Summer. For many, early August means hot, humid days and stagnant, sultry nights.

The actual dates for the Dog Days of Summer vary depending on the source, but are usually quoted as running from mid-July to mid-August. The Old Farmer’s Almanac lists the Dog Days as running from July 3^rd through August 11^th.

But there is an ancient astronomical observation that ties in with the Dog Days of Summer, one that you can replicate on these early August mornings.

The sky was important to the ancients. It told them when seasons were approaching, when to plant crops, and when to harvest. Ancient cultures were keen observers of the cycles in the sky. Cultures that were “astronomically literate” had a distinct edge over those who seldom bothered to note the goings on overhead.

The flooded Temple of Isis on the island of Philae circa 1905. (Credit: Wikimedia Commons under an Attribution-Share Alike 2.5 license. Author H.W. Dunning).

Sirius was a key star for Egyptian astronomers. Identified with the goddess Isis, the Egyptian name for Sirius was Sopdet, the deification of Sothis. There is a line penned by the Greco-Roman scholar Plutarch which states:

“The soul of Isis is called ‘Dog’ by the Greeks.”

Political commentary? A mis-translation by Greek scholars? Whatever the case, the mythological transition from “Isis to Sothis to Dog Star” seems to have been lost in time.

These astronomer-priests noted that Sirius rose with the Sun just prior to the annual flooding of the Nile. The appearance of a celestial object at sunrise is known as a heliacal rising. If you can recover Sirius from behind the glare of the Sun, you know that the “Tears of Isis” are on their way, in the form of life-giving flood waters.

Sopdet as the personification of Sirius (note the star on the forehead) Wikimedia Commons image under an Attribution Share Alike 3.0 license. Author Jeff Dahl).

In fact, the ancient Egyptians based their calendar on the appearance of Sirius and what is known as the Sothic cycle, which is a span of 1,461 sidereal years (365.25 x 4) in which the heliacal rising once again “syncs up” with the solar calendar.

It’s interesting to note that in 3000 BC, the heliacal rising of Sirius and the flooding of the Nile occurred around June 25^th, near the summer solstice. This also marked the Egyptian New Year. Today it occurs within a few weeks of August 15^th, owing to precession. (More on that in a bit!)

By the time of the Greeks, we start to see Sirius firmly referred to as the Dog Star. In Homer’s Iliad, King Priam refers to an advancing Achilles as:

“Blazing as the star that cometh forth at Harvest-time, shining forth amid the host of stars in the darkness of the night, the star whose name men call Orion’s Dog”

The Romans further promoted the canine branding for Sirius. You also see references to the “Dog Star” popping up in Virgil’s Aenid.

Over the years, scholars have also attempted to link the dog-headed god Anubis to Sirius. This transition is debated by scholars, and in his Star Names: Their Lore and Meaning, Richard Hinckley Allen casts doubt on the assertion.

Sirius as the shining "nose" of the constellation Canis Major. (Created by the author using Starry Night). — Sirius as the shining “nose” of the constellation Canis Major. (Created by the author using Starry Night).

Ancient cultures also saw the appearance of Sirius as signifying the onset of epidemics. Their fears were well founded, as summer flooding would also hatch a fresh wave of malaria and dengue fever-carrying mosquitoes.

Making a seasonal sighting of Sirius is fun and easy to do. The star is currently low to the southeast in the dawn, and rises successively higher each morning as August rolls on.

The following table can be used to aid your quest in Sirius-spotting.

Latitude north	Theoretical date when Sirius can 1^st be spotted
32°	August 3^rd
33°	August 4^th
34°	August 5^th
35°	August 6^th
36°	August 7^th
37°	August 8^th
38°	August 9^th
39°	August 10^th
40°	August 11^th
41°	August 12^th
42°	August 13^th
43°	August 14^th
44°	August 15^th
45°	August 16^th
46°	August 17^th
47°	August 18^th
48°	August 19^th
49°	August 20^th
50°	August 21^st

Thanks to “human astronomical computer extraordinaire” Ed Kotapish for the compilation!

Note that the table above is perpetual for years in the first half of the 21^st century. Our friend, the Precession of the Equinoxes pivots the equinoctial points to the tune of about one degree every 72 years. The Earth’s axis completes one full “wobble” approximately every 26,000 years. Our rotational pole only happens to be currently pointing at Polaris in our lifetimes. Its closest approach is around 2100 AD, after which the north celestial pole and Polaris will begin to drift apart. Mark your calendars—Vega will be the pole star in 13,727 AD. And to the ancient Egyptians, Thuban in the constellation Draco was the Pole Star!

Near Luxor (Photo by author). — The Colossi of Memnon Near Luxor, just one of the amazing architectural projects carried out by the ancient Egyptians. (Photo by author).

Keep in mind, atmospheric extinction is your enemy in this quest, as it will knock normally brilliant magnitude -1.46 Sirius a whopping 40 times in brightness to around magnitude +2.4.

Note that we have a nice line-up of planets in the dawn sky (see intro chart), which are joined by a waning crescent Moon this weekend. Jupiter and Mars ride high about an hour before sunrise, and if you can pick out Mercury at magnitude -0.5 directly below them, you should have a shot at spotting Sirius far to the south.

And don’t be afraid to “cheat” a little bit and use binoculars in your quest… we’ve even managed on occasion to track Sirius into the broad daylight. Just be sure to physically block the Sun behind a building or hill before attempting this feat!

Sirius as seen via Hubble- can you spy Sirius B? (NASA/ESA Hubble image). — Sirius as seen via Hubble- can you spy Sirius B? (Credit: NASA/ESA Hubble image).

Of course, the heliacal rising of Sirius prior to the flooding of the Nile was a convenient coincidence that the Egyptians used to their advantage. The ancients had little idea as to what they were seeing. At 8.6 light-years distant, Sirius is the brightest star in Earth’s sky during the current epoch. It’s also the second closest star visible to the naked eye from Earth. Only Alpha Centauri, located deep in the southern hemisphere sky is closer. The light you’re seeing from Sirius today left in early 2005, back before most of us had Facebook accounts.

Sirius also has a companion star, Sirius B. This star is the closest example of a white dwarf. Orbiting its primary once every 50 years, Sirius B has also been the center of a strange controversy we’ve explored in past writings concerning Dogon people of Mali.

Sirius B is difficult to nab in a telescope, owing to dazzling nearby Sirius A. This feat will get easier as Sirius B approaches apastron with a max separation of 11.5 arc seconds in 2025.

Some paleoastronomers have also puzzled over ancient records referring to Sirius as “red” in color. While some have stated that this might overturn current astrophysical models, a far more likely explanation is its position low to the horizon for northern hemisphere observers. Many bright stars can take on a twinkling ruddy hue when seen low in the sky due to atmospheric distortion.

Let the Dog Days of Summer (& astronomy) begin! (Photo by author).

All great facts to ponder during these Dog Days of early August, perhaps as the sky brightens during the dawn and your vigil for the Perseid meteors draws to an end!

July 26, 2013April 26, 2016 by David Dickinson

Watch for the Delta Aquarid Meteors This Weekend

The Southern Delta Aquarid radiant, looking southeast at 2AM local from latitude 30 degrees north on the morning of July 30th. (Created by the author in Starry Night).

The meteor shower drought ends this weekend.

The northern summer hemisphere meteor season is almost upon us. In a few weeks’ time, the Perseids — the “Old Faithful” of meteor showers — will be gracing night skies worldwide.

But the Perseids have an “opening act”- a meteor shower optimized for southern hemisphere skies known as the Delta Aquarids.

This year offers a mixed bag for this shower. The Delta Aquarids are expected to peak on July 30^th and we should start seeing some action from this shower starting this weekend.

The Moon, however, also reaches Last Quarter phase the day before the expected peak of the Delta Aquarids this year on July 29^th at 1:43PM EDT/17:43 Universal Time (UT). This will diminish the visibility of all but the brightest meteors in the early morning hours of July 30^th.

A cluster of meteor shower radiants also lies nearby. The Eta Aquarids emanate from a point near the asterism known as the “Water Jar” in the constellation Aquarius around May 5^th. Another nearby but weaker shower known as the Alpha Capricornids are also currently active, with a zenithal hourly rate (ZHR) approaching the average hourly sporadic rate of 5. And speaking of which, the antihelion point, another source of sporadic meteors, is nearby in late July as well in eastern Capricornus.

The Delta Aquarids are caused by remnants of Comet 96P/Machholz colliding with Earth’s atmosphere. The short period comet was only discovered in 1986 by amateur astronomer Donald Machholz. Prior to this, the source of the Delta Aquarids was a mystery.

The Delta Aquarids have a moderate atmospheric entry velocity (for a meteor shower, that is) around an average of 41 kilometres a second. They also have one of the lowest r values of a major shower at 3.2, meaning that they produce a disproportionately higher number of fainter meteors, although occasional brighter fireballs are also associated with this shower.

Image of an early confirmed Delta Aquarid captured by the UK Fireball Network (@ on Twitter) captured by their Ash Vale North camera. — Image of an early confirmed Delta Aquarid by the UK Meteor Network (@UKMeteorNetwork on Twitter) captured by their Ash Vale North camera on July 17th, 2013. (Credit: Richard Kacerek & United Kingdom Meteor Observation Network, used with permission).

The Delta Aquarids are also one the very few showers with a southern hemisphere radiant. It’s somewhat of a mystery as to why meteor showers seem to favor the northern hemisphere. Of the 18 major annual meteor showers, only four occur below the ecliptic plane and three (the Alpha Capricornids, and the Eta and Delta Aquarids) approach the Earth from south of the equator. A statistical fluke, or just the product of the current epoch?

In fact, the Delta Aquarids have the most southern radiant of any major shower, with a radiant located just north of the bright star Fomalhaut in the constellation Piscis Austrinus near Right Ascension 339 degrees and Declination -17 degrees. Researchers have even broken this shower down into two distinct northern and southern radiants, although it’s the southern radiant that is the more active during the July season.

Together, this loose grouping of meteor shower radiants in the vicinity is known as the Aquarid-Capricornid complex. The Delta Aquarids are active from July 14^th to August 18^th, and unlike most showers, have a very broad peak. This is why you’ll see sites often quote the maximum for the shower at anywhere from July 28^th to the 31^st. In fact, you may just catch a stray Delta Aquarid while on vigil for the Perseids in a few weeks!

The shower was first identified by astronomer G.L. Tupman, who plotted 65 meteors associated with the stream in 1870. Observations of the Delta Aquarids were an off-and-on affair throughout the early 20^th century, with many charts erroneously listing them as the “Beta Piscids”. The separate northern and southern radiants weren’t even untangled until 1950. The advent of radio astronomy made more refined observations of the Delta Aquarids possible. In 1949, Canadian astronomer D.W.R. McKinley based out of Ottawa, Canada identified both streams and pinned down the 41 km per second velocity that’s still quoted for the shower today.

Further radio studies of the shower were carried out at Jodrell Bank in the early 1950’s, and the shower gave strong returns in the early 1970’s for southern hemisphere observers even with the Moon above the horizon, with ZHRs approaching 40. The best return for the Southern Delta Aquarids in recent times is listed by the International Meteor Organization as a ZHR of about 40 on the morning of July 28^th, 2009.

A study of the Delta Aquarids in 1963 by Fred Whipple and S.E. Hamid reveal striking similarities between the Delta Aquarids and the January Quadrantids & daytime Arietid stream active in June. They note that the orbital parameters of the streams were similar about 1,400 years ago, and the paths are thought to have diverged due to perturbations from the planet Jupiter.

Observing the Delta Aquarids can serve as a great “dry run” for the Perseids in a few weeks. You don’t need any specialized gear, simply find a dark site, block the Moon behind a building or hill, and watch.

Photographing meteors is similar to doing long exposures of star trails. Simply aim your tripod mounted DSLR camera at a section of sky and take a series of time exposures about 1-3 minutes long to reveal meteor streaks. Images of Delta Aquarids seem elusive, almost to the point of being mythical. An internet search turns up more blurry pictures of guys in ape suits purporting to be Bigfoot than Delta Aquarid images… perhaps we can document the “legendary Delta Aquarids” this year?

– Read more of the fascinating history of the Delta Aquarids here.

– Seen a meteor? Be sure to tweet it to #Meteorwatch.

– The IMO wants your meteor counts and observations!

July 24, 2013December 23, 2015 by Nancy Atkinson

Submissions Needed for Saturn Mosaic Project

Guillermo Abramson from Argentina takes a picture of himself waving at Saturn on July 19, 2013 during 'The Day the Earth Smiled' event. Credit and copyright: Guillermo Abramson.

For all our astrophotographer friends out there: If you haven’t heard about the Saturn Mosaic Project, you’ll want to take note of this. In cooperation with Astronomers Without Borders, the special project for the recent Cassini image of planet Earth, called The Day The Earth Smiled (TDTES) is sponsoring a Saturn Mosaic project, where you can submit an image you’ve taken of Saturn. Those received will be compiled into a mosaic that will look like image that Cassini took on July 19, showing Earth just below Saturn’s rings (see below). But when you zoom in you’ll see all the pictures from Earth that the mosaic is made of.

I received a note from AWB President Mike Simmons saying they need more submissions, and the deadline for submitting a photo has been extended to July 29, 2013.

“I know a lot more people will want to be a part of this if they know about it,” Mike said via email. “It’s something to tide everyone over and keep the buzz going while we wait for the final mosaic from Cassini.”

But you don’t have to be a seasoned astrophotographer to take part in the Saturn Mosaic. The image you submit doesn’t have to be one taken with a large telescope – just take a picture of Saturn as a “star” in the sky with an ordinary camera, capturing your surroundings as well. Or it could be an image you took earlier this year.

“There are other kinds of photos that anyone can submit that don’t even requiring imaging the sky,” Simmons added. “We didn’t want to limit this to only those with the ability and weather to image Saturn itself. Photos of outreach events or people waving at Saturn from JPL’s Wave at Saturn are good, too. Or just a portrait taken with the Lord of the Rings — a live view projected from a telescope or even a photo. Like a couple getting married at the time Cassini was taking their photo (and everyone else’s) posed with Saturn. I took the easy way and took a shot of me and Saturn in my office.”

These can be taken any time, so people can still take a shot and get into the mosaic (the image does need to have been taken in 2013, however.)

“It’s all about sharing and commemorating the excitement of the moment when the photo was taken, and the anticipation of the release of Cassini’s historic photos,” Simmons said. “Like all Astronomers Without Borders project, it’s open to everyone on Earth. And beyond.”

For a slide show of some of the great shots people have submitted so far, visit the Saturn Mosaic Project page to see things like Saturn with a T-Rex, outreach in Iran, kids drawings of Saturn in Ghana, and more.

Simmons said The World at Night will create the final mosaic, which is expected to be online and ready to view and zoom in on by August 4 or earlier.

So take your best shot and be a part of the mosaic! Find out more on the Astronomers Without Borders website.

July 22, 2013December 23, 2015 by David Dickinson

Super-Moon Monday: The 3rd (& Final?) Act

The gibbous Moon rising rising over the Andes Mountains in Chile. (Credit: @WladimirPulgarG/Flickr).

“Once more into the breach, my dear friends…”

Such a quip may be deemed appropriate as we endured the media onslaught this past weekend for the third and final perigee Full Moon of 2013.

Tonight, on Monday, July 22^nd, the Moon reaches Full at 18:15 Universal Time (UT)/4:15 PM EDT. This is only 21.9 hours after reaching perigee, or the closest point in its orbit at 358,401 kilometres from the Earth on the Sunday evening at 20:28 UT. Continue reading “Super-Moon Monday: The 3rd (& Final?) Act”

July 16, 2013December 23, 2015 by David Dickinson

Seeing Red: Hunting Herschel’s Garnet Star

Mu Cephei (arrowed) in the constellation Cepheus the King. (Photo & graphic by author).

Quick, what’s the reddest star visible to the naked eye?

Depending on your sky conditions, your answer may well be this week’s astronomical highlight.

Mu Cephei, also known as Herschel’s Garnet Star, is a ruddy gem in the constellation Cepheus near the Cygnus/Lacerta border. A variable star ranging in brightness by a factor of about three-fold from magnitudes 5.0 to 3.7, Mu Cephei is low to the northeast for mid-northern latitude observers in July at dusk, and will be progressively higher as summer wears on. Continue reading “Seeing Red: Hunting Herschel’s Garnet Star”