Observing Archives

September 1, 2015December 23, 2015 by David Dickinson

Watch the Moon Occult Aldebaran This Weekend

How about that perigee Full Moon this past weekend? Thus begins ‘Supermoon season’ for 2015, as this month’s Full Moon occurs even closer to perigee — less than an hour apart, in fact — on September 28^th, with the final total lunar eclipse of the ongoing tetrad to boot. Keep an eye on Luna this week, as it crosses into the early AM sky for several key dates with destiny just prior to the start of the second and final eclipse season for 2015.

The big event later this week is a passage of the waning gibbous Moon through the Hyades open cluster on the morning of Saturday, September 5^th, climaxing with a dramatic occultation of the bright star Aldebaran on the same morning. This is part of a series of 49 ongoing occultations of Aldebaran by the Moon, one for each lunation extending out to September 2018.

This weekend’s event will occur at moonrise under nighttime skies for the northeastern United States and the Canadian Maritimes, and near dawn and under daytime skies for observers in Western Europe and Northern Africa eastward. We observed an occultation of Aldebaran by the Moon under daytime skies from Alaska back in the late 1990s, and can attest that the star is indeed visible near the limb of the Moon in binoculars. A good deep blue sky is key to spotting +1 magnitude Aldebaran in the daytime.

London 711 AM — The view from London UK at 7:11 AM local. Image Credit: Starry Night Education software

During waning phase, the bright edge of the Moon is always leading, meaning Aldebaran will ingress (wink out) on the bright limb of the 52% illuminated Moon, and egress (reappear) along its dark limb.

Here are some key times for ingress/egress by location (all times quoted are local and incorporate daylight saving/summer time):

Washington D.C.

Moonrise: 11:53 PM

Ingress: N/A (before Moonrise)

Egress: 12:38 AM (altitude = 8 degrees)

Boston

Moonrise: 11:22 PM

Ingress 11:57 PM (altitude = 6 degrees)

Egress: 12:41 AM (altitude = 14 degrees)

Gander, Newfoundland

Moonrise: 11:26 PM

Ingress: 1:37 AM (altitude = 20 degrees)

Egress: 2:26 AM (altitude = 28 degrees)

London

Moonrise: 11:04 PM

Ingress: 5:50 AM (altitude = 53 degrees)

Sunrise: 6:18 AM

Egress: 7:07 AM (altitude = 54 degrees)

Paris

Moonrise: 12:02 AM

Ingress: 6:53 AM (altitude = 56 degrees)

Sunrise: 7:12 AM

Egress: 8:10 AM (altitude = 57 degrees)

Occultations of bright stars by the Moon are one of the few times besides a solar or lunar eclipse when you can actually discern the one degree per every two and half hours orbital motion of the Moon in real time. The Moon moves just a little more than its own apparent diameter as seen from the Earth every hour. This also sets us up for four more fine occultations of Aldebaran by the Moon alternating between Europe and North America on October 2^nd, October 29^th, November 26^th, and December 23^rd.

The bright stars Antares, Spica and Regulus also lie along the path of the Moon, which is inclined about five degrees relative to the ecliptic. A series of occultations of Regulus by the Moon begins in late 2016.

Fun fact: The Moon used to occult the bright star Pollux in the constellation Gemini until about 2100 years ago in 117 BC. The 26,000 year cycle known as the Precession of the Equinoxes has since carried the star out of the Moon’s path.

Observations of occultations — especially dramatic grazes spied right from the edge of the path — can be used to construct a profile of the lunar limb. A step-wise ‘wink out’ of a star during an occultation can also betray the existence of a close binary.

Recording an occultation of a star by the Moon is as easy as running video while shooting the Moon. The dark limb egress of Aldebaran will be much easier to record during the September 5^th event than the ingress of the star against the bright limb. I typically run video with a DLSR directly coupled to a Celestron 8” SCT telescope, with WWV radio running in the background for a precise audio timing of the event. Remember, the Moon will also be transiting the Hyades star cluster as well, covering and uncovering many fainter stars for observers worldwide around the same time frame.

Sept 5 5UT — The Last Quarter Moon versus Aldebaran and the Hyades on September 5th at ~5:00 UT. Image credit: Stellarium

Now for the ‘wow’ factor. The Moon is about 240,000 miles (400,000 km), or 1 1/4 light seconds distant. Aldebaran is 65 light years away, and said light left the star around 1950, only to have its light ‘rejected’ during the very last second by the craggy mountains along the lunar limb. And though Aldebaran appears to be a member of the Hyades, it isn’t, as the open cluster sits 153 light years from Earth.

And watch that Moon, as it then heads for a partial solar eclipse as seen from South Africa and the southern Indian Ocean on September 13th, and a total lunar eclipse visible from North America and Europe on September 28th.

Expect more to come, with complete guides to both on Universe Today!

August 29, 2015December 23, 2015 by Nancy Atkinson

Watch Where You Point That ‘Scope: Police Mistake Telescope for a Gun

Levi Joraanstad, a student at North Dakota State University displays his telescope, which police mistook for a rifle. Image via WDAY TV, Fargo, North Dakota.

One more thing amateur astronomers might need to worry about besides clouds, bugs, and trying to fix equipment malfunctions in the dark – and this one’s a little more serious.

Earlier this week, two students at North Dakota State University (NDSU) in Fargo, North Dakota were settting up a telescope and camera system to take pictures of the Moon when armed police approached them. The police officers had mistaken the telescope for a rifle.

Students Levi Joraanstad and Colin Waldera told WDAY TV in Fargo that they were were setting up their telescope behind their apartment’s garage when they were blinded by a bright light and told to stop moving.

Initially, they thought it was a joke, that fellow students were pulling a prank, and because police were shining a bright light at them, the two students were blinded.

Police said that an officer patrolling the area had seen what he thought was suspicious activity behind the garage, thinking that one of the students’ dark sweater with white lettering on the back looked like a tactical vest, and that the telescope might be a rifle.

Police added that their response was a “better safe than sorry” approach, and they said the two students were never in any danger of being shot.

However, Joraanstad and Waldera said since they thought it was a joke, they initially ignored the order to stop moving and kept digging in their bags for equipment.

“I was kind of fumbling around with my stuff and my roommate and I were kind of talking, we were kind of wondering, what the heck’s going on? This is pretty dum that these guys are doing this,” WDAY quoted Joraanstad, a junior at NDSU. “And then they started shouting to quit moving or we could be shot. And so at that moment we kind of look at each other and we’re thinking we better take this seriously.”

If the police had acted more aggressively, the outcome could have been tragic. Joraanstad said the officers were very apologetic when they realized their mistake, and they explained what had happened.

So, watch where and how you point your telescope.

This is a rare occurrence, of course, and is nothing like risks amateur astronomers in Afghanistan regularly take to look through a telescope and share their views with local people. We wrote an article — which you can read here — about how they have to deal with more serious complications, such as making sure the area is clear of land mines, not arousing the suspicions the Taliban or the local police, and watching out for potential bombing raids by the US/UK/Afghan military alliance.

UPDATE: Maybe incidents like this aren’t quite as rare as I thought. Universe Today’s Bob King told me that just two weeks ago he was out observing in the countryside, when a very similar event happened to him. “A truck pulled up fast, with bright lights blinding my eyes and then the sheriff walked out of the car,” Bob said. “I quickly identified myself and explained what I was up to. He thought I was burying a dead body! No kidding.”

Wow…

Source: WDAY TV

August 26, 2015December 23, 2015 by David Dickinson

Ice Giants at Opposition

It seems as if the planets are fleeing the evening sky, just as the Fall school star party season is getting underway. Venus and Mars have entered the morning sky, and Jupiter reaches solar conjunction this week. Even glorious Saturn has passed eastern quadrature, and will soon depart evening skies.

Enter the ice giants, Uranus and Neptune. Both reach opposition for 2015 over the next two months, and the time to cross these two out solar system planets off your life list is now.

Aug 26 — Looking east at dusk in late August, as Uranus and Neptune rise. Image credit: Stellarium

First up, the planet Neptune reaches opposition next week in the constellation Aquarius on the night of August 31^st/September 1^st. Shining at magnitude +7.8, Neptune spends the remainder of 2015 about three degrees southwest of the +3.7 magnitude star Lambda Aquarii. It’s possible to spot Neptune using binoculars, and about x100 magnification in a telescope eyepiece will just resolve the blue-grey 2.3 arc second disc of the planet. Though Neptune has 14 known moons, just one, Triton, is within reach of a backyard telescope. Triton shines at magnitude +13.5 (comparable to Pluto), and orbits Neptune in a retrograde path once every 6 days, getting a maximum of 15” from the disk of the planet.

Nep Aug-Nov Triton aug 31 — The path of Neptune from late August through early November 2015. Inset: the position of Neptune’s moon Triton on the evening of August 31st: Image credit: Starry Night Education software

Uranus reaches opposition on October 11^th in the adjacent constellation Pisces. Keep an eye on Uranus, as it nears the bright +5.2 magnitude star Zeta Piscium towards the end on 2015. Shining at magnitude +5.7 with a 3.6 arc second disk, Uranus hovers just on the edge of naked eye visibility from a dark sky site.

Credit — Uranus, left of the eclipsed Moon last October. Image credit and copyright: A Nartist

It’ll be worth hunting for Uranus on the night of September 27^th/28^th, when it sits 15 degrees east of the eclipsed Moon. Uranus turned up in many images of last Fall’s total lunar eclipse. This will be the final total lunar eclipse of the current tetrad, and the Moon will occult Uranus the evening after for the South Atlantic. This is part of a series of 19 ongoing occultations of Uranus by the Moon worldwide, which started in August 2014, and end on December 20^th, 2015. After that, the Moon will move on and begin occulting Neptune next year in June through the end of 2017.

Occultation — The visibility footprint of the September 29th occultation of Uranus by the Moon. Image credit: Occult 4.0.

Uranus has 27 known moons, four of which (Oberon, Ariel, Umbriel and Titania) are visible in a large backyard telescope. See our extensive article on hunting the moons of the solar system for more info, and the JPL/PDS rings node for corkscrew finder charts.

Uranus aug-dec moons oct12 — The path of Uranus, from late August through early December 2015. Inset: the position of the moons of Uranus on the evening of October 12th. Image credit: Starry Night Education software

The two outermost worlds have a fascinating entwined history. William Herschel discovered Uranus on the night of March 13^th, 1781. We can be thankful that the proposed name ‘George’ after William’s benefactor King George the III didn’t stick. Herschel initially thought he’d discovered a comet, until he followed the slow motion of Uranus over several nights and realized that it had to be something large orbiting at a great distance from the Sun. Keep in mind, Uranus and Neptune both crept onto star charts unnoticed pre-1781. Galileo even famously sketched Neptune near Jupiter in 1612! Early astronomers simply considered the classical solar system out to Saturn as complete, end of story.

And the hunt was on. Astronomers soon realized that Uranus wasn’t staying put: something farther still from the Sun was tugging at its orbit. Mathematician Urbain Le Verrier predicted the position of the unseen planet, and on and on the night of September 23^rd, 1846, astronomers at the Berlin observatory spied Neptune.

In a way, those early 19^th century astronomers were lucky. Neptune and Uranus had just passed each other during a close encounter in 1821. Otherwise, Neptune might’ve remained hidden for several more decades. The synodic period of the two planets—that is, the time it takes the planets to return to opposition—differ by about 2-3 days. The very first documented conjunction of Neptune and Uranus occurred back in 1993, and won’t occur again until 2164. Heck, In 2010, Neptune completed its first orbit since discovery!

To date, only one mission, Voyager 2, has given us a close-up look at Uranus and Neptune during brief flybys. The final planetary encounter for Voyager 2 occurred in late August in 1989, when the spacecraft passed 4,800 kilometres (3,000 miles) above the north pole of Neptune.

All thoughts to ponder as you hunt for the outer ice giants. Sure, they’re tiny dots, but as with many nighttime treats, the ‘wow’ factor comes with just what you’re seeing, and the amazing story behind it.

August 24, 2015December 23, 2015 by David Dickinson

Astro-Challenge: Splitting 44 Boötis

44 Bootis from the Palomar Sky Survey. Image credit: The CDS/Aladin previewer

How good are your optics? Nothing can challenge the resolution of a large light bucket telescope, like attempting to split close double stars. This week, we’d like to highlight a curious triple star system that presents a supreme challenge over the next few years and will ‘keep on giving’ for decades to come.

The location of 44 Boötis in the constellation of the Herdsman. Image credit: Stellarium click image to enlarge

The star system in question is 44 Boötis, in the umlaut-adorned constellation of Boötes the herdsman. Boötes is still riding high to the west at dusk for northern hemisphere observers in late August, providing observers a chance to split the pair during prime-time viewing hours.

Sometimes also referred to as Iota Boötis, William Herschel first measured the angular separation of the pair in 1781, and F.G.W. Struve discovered the binary nature of 44 Boötis in 1832. Back then, the pair was headed towards a maximum apparent separation of 5 arc seconds in 1870. We call this point apastron. A fast forward to 2015 sees the situation reversed, as the pair currently sits about an arc second apart, and closing. 44 Boötis will pass a periastron of just 0.23” from the primary in 2020. Can you split the pair now? How ‘bout in 2016 onward? Can you recover the split, post 2020?

The physical parameters of the system are amazing. About 42 light years distant, 44 Boötis A is 1.05 times as massive as our Sun, and shines at magnitude +4.8. The B component is in a 210 year elliptical orbit with a semi-major axis of 49 AUs (for comparison, Pluto at aphelion is 49 AUs from the Sun), and is itself a curious contact spectroscopic binary about one magnitude fainter. Though you won’t be able to split the B-C pair with a backyard telescope, they betray their presence to professional instruments due to their intertwined spectra. 44 Boötis B and C have a combined mass of 1.5 times that of our Sun, and orbit each other once every 6.4 hours at a center-to-center distance of only 750,000 miles, or only 3 times the distance from Earth to the Moon:

That’s close enough that the pair shares a merging atmosphere. It’s a mystery as to just how these types of contact binary stars form, and it would be fascinating to see 44 Boötis up close. This fast spin along our line of sight also means that 44 Boötis B-C varies in brightness by about half a magnitude over a six hour span.

An artist’s conception of the B-C pair of the 44 Boötis system, using data from the Chandra X-ray observatory. Image credit: NASA/CXC/M.Weiss

Though the visual 44 Boötis A-B pair doesn’t quite have an orbital period that the average humanoid could expect to live through, beginning amateur astronomers can watch as the pair once again heads towards a wide an easy 5” split during apastron around 2080.

Collimation, or the near-perfect alignment of optics, is key to the splitting close binaries, and also serves as a good test of a telescope and the stability of the atmosphere. A well-collimated scope will display stars with sharp round Airy disks, looking like luminescent circular ripples in a pond. We call the lower boundary to splitting double stars the Dawes Limit, and on most nights, atmospheric seeing will limit this to about an arc second.

But there’s another method that you can use to ‘split’ doubles closer than an arc second, known as interferometry. This relies on observing the star by use of a filtering mask with two slits that vary in distance across the aperture of the scope. When the mask is rotated to the appropriate position angle and the slits are adjusted properly, the ‘fringes’ of the star snap into focus. A formula utilizing the slit separation can then calculate the separation of the close binary pair. This method works with stars that are A). Closer than 1” separation, and B). Vary by not more than a magnitude in brightness difference.

44 Boötis near periastron definitely qualifies. As of this writing, our ‘cardboard interferometer’ is still very much a work in progress. We could envision a more complex version of this rig mechanized, complete with video analysis. Hey, if nothing else, it really draws stares from fellow amateur astronomers…

We promise to delve into the exciting realm of backyard cardboard interferometry once we’ve worked all of the bugs out. In the meantime, be sure to regale us with your tales of tragedy and triumph observing 44 Boötis. Revisiting double stars can pose a life-long pursuit!

– Be sure to check out another double star challenge from Universe Today, with the hunt for Sirius B.

August 20, 2015December 23, 2015 by Bob King

How to Find Rosetta’s Comet In Your Telescope

This sequence of images, taken with Rosetta's OSIRIS narrow-angle camera on 30 July 2015, show a boulder-sized object close to the nucleus of Comet 67P/Churyumov-Gerasimenko. The images were captured on 30 July 2015, about 185 km from the comet. The object measures between one and 50 m across; however, the exact size cannot be determined as it depends on its distance to the spacecraft, which cannot be inferred from these images. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

How would you like to see one of the most famous comets with your own eyes? Comet 67P/Churyumov-Gerasimenko plies the morning sky, a little blot of fuzzy light toting an amazing visitor along for the ride — the Rosetta spacecraft. When you look at the coma and realize a human-made machine is buzzing around inside, it seems unbelievable.

Comet 67P/Churyumov-Gerasimenko plows through a rich star field in Gemini on the morning of August 19, 2015. Photos show a short, faint tail to the west not visible to the eye in most amateur telescopes. Credit: Efrain Morales — Comet 67P/Churyumov-Gerasimenko plows through a rich star field in Gemini on the morning of August 20, 2015. Photos show a short, faint tail to the west not visible to the eye in most amateur telescopes. Credit: Efrain Morales

If you have a 10-inch or larger telescope, or you’re an experienced amateur with an 8-inch and pristine skies, 67P is within your grasp. The comet glows right around magnitude +12, about as bright as it will get this apparition. Periodic comets generally appear brightest around and shortly after perihelion or closest approach to the Sun, which for 67P/C-G occurred back on August 13.

The surface of Comet 67P/C-G is extensively fractured likely related to the intense freeze-thaw cycle that occurs during the heat of perihelion vs. the chill experienced in the outer part of its orbit. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA — The surface of Comet 67P/C-G is extensively fractured due to loss of volatile ices, the expansion and contraction of the comet from solar heating and bitter cold and possibly even tectonic forces. The smaller polygonal shapes outlined by fractures in the lower right photo are just 6-16 feet (2-5 meters) across. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

You’ll be looking for a small, 1-arc-minute-diameter, compact, circular patch of nebulous light shortly before dawn when it’s highest in the east. Rosetta’s Comet will spend the remainder of August slicing across Gemini the Twins north of an nearly parallel to the ecliptic. I spotted 67P/C-G for the first time this go-round about a week ago in my 15-inch (37 cm) reflector. While it appears like a typical faint comet, thanks to Rosetta, we know this particular rough and tumble mountain of ice better than any previous comet. Photographs show rugged cliffs, numerous cracks due to the expansion and contraction of ice, blowholes that serve as sources for jets and smooth plains blanketed in fallen dust.

Geysers of dust and gas shooting off the comet's nucleus are called jets. The material they deliver outside the nucleus builds the comet's coma. Credit: ESA/Rostta/NAVCAM — Geysers of dust and gas shooting off the comet’s nucleus are called jets. The material they deliver outside the nucleus builds the comet’s coma. Credit: ESA/Rostta/NAVCAM

The jets are geyser-like sprays of dust and gas that loft grit and rocks from the comet’s interior and surface into space to create a coma or temporary atmosphere. This is what you’ll see in your telescope. And if you’re patient, you’ll even be able to catch this glowing tadpole on the move. I was surprised at its speed. After just 20 minutes, thanks to numerous field stars that acted as references, I could easily spot the comet’s eastward movement using a magnification of 245x.

Facing east around 4 a.m. local time in late August, you'll see the winter constellations Gemini and Orion. 67P/C-G's path is shown through — Facing east around 4 a.m. local time in late August, you’ll see the winter constellations Gemini and Orion. 67P/C-G’s path is shown through early September. Brighter stars near the path are labeled. Time shown is 4 a.m. CDT. Use this map to get oriented and then switch to the one below for telescope use. Source: Chris Marriott’s SkyMap

Tomorrow morning, 67P/C-G passes very close to the magnitude +5 star Omega Geminorum. While this will make it easy to locate, the glare may swamp the comet. Set your alarm for an hour before dawn’s start to allow time to set up a telescope, dark-adapt your eyes and track down the field where the comet will be that morning using low magnification.

Once you’ve centered 67P/C-G’s position, increase the power to around 100x-150x and use averted vision to look for a soft, fuzzy patch of light. If you see nothing, take it to the next level (around 200-250x) and carefully search the area. The higher the magnification, the darker the field of view and easier it will be to spot it.

Detailed map showing the comet's path through central Gemini daily August 21-28, 2015 around 4 a.m. CDT. Brighter stars are marked with Greek letters and numbers. "48" = 48 Geminorum. Source: Chris Marriott's SkyMap — Detailed map showing the comet’s path through central Gemini daily August 21-28, 2015 around 4 a.m. CDT. Brighter stars are marked with Greek letters and numbers. “57”= 57 Geminorum. North is up, east to the left and stars to magnitude +13.5. Click for a larger version you can print out. Source: Chris Marriott’s SkyMap

Besides being relatively faint, the comet doesn’t get very high in the east before the onset of twilight. Low altitude means the atmosphere absorbs a share of the comet’s light, making it appear even fainter. Not that I want to dissuade you from looking! There’s nothing like seeing real 67P photons not to mention the adventure and sense of accomplishment that come from finding the object on your own.

As we advance into late summer and early fall, 67P/C-G will appear higher up but also be fading. Now through about August 27 and again from September 10-24 will be your best viewing times. That’s when the Moon’s absent from the sky.

Given the comet’s current distance from Earth of 165 million miles and apparent visual size of just shy of 1 arc minute, the coma measures very approximately 30,000 miles across. Rosetta orbits the comet’s 2.5-mile-long icy nucleus at a distance of about 115 miles (186 km), meaning it’s snug up against the nuclear center from our point of view on the ground.

If you do find and follow 67P/C-G, consider sharing your observations with the Pro-Amateur Collaborative Astronomy (PACA) campaign to help increase our knowledge of its behavior. Interested? Sign up HERE.

August 19, 2015December 23, 2015 by David Dickinson

Cassini’s Farewell Look at Dione

NASA’s Cassini spacecraft paid a visit to Saturn’s moon Dione this week, one final time.

Cassini passed just 474 kilometers (295 miles) above the surface of the icy moon on Monday, August 17^th at 2:33 PM EDT/18:33 UT. The flyby is the fifth and final pass of Cassini near Dione (pronounced dahy-OH-nee). The closest passage was 100 kilometers (60 miles) in December 2011. This final flyby of Dione will give researchers a chance to probe the tiny world’s internal structure, as Cassini flies through the gravitational influence of the moon. Cassini has only gathered gravity science data on a handful of Saturn’s 62 known moons.

“Dione has been an enigma, giving hints of active geologic processes, including a transient atmosphere and evidence of ice volcanoes. But we’ve never found the smoking gun,” said Cassini science team member Bonnie Buratti in a recent press release. “The fifth flyby of Dione will be the last chance.”

Voyager 1 gave us our very first look at Dione in 1980, and Cassini has explored the moon in breathtaking detail since its first flyby in 2005. This final pass targeted Dione’s north pole at a resolution of only a few meters. Cassini’s Infrared Spectrometer was also on the lookout for any thermal anomalies, a good sign that Dione may still be geologically active. The spacecraft’s Cosmic Dust Analyzer also carried out a search for any dust particles coming from Dione. The results of these experiments are forthcoming. In a synchronous rotation, Dione famously displays a brighter leading hemisphere, which has been pelted with E Ring deposits.

The raw images from this week’s flyby are now available on the NASA Cassini website. You can see the sequence of the approach, complete with a ‘photobomb’ of Saturn’s moon Enceladus early on. Dione then makes a majestic pass in front of Saturn’s rings and across the ochre disk of the planet itself, before snapping into dramatic focus. Here we see the enormous shattered Evander impact basin near the pole of Dione, along with Erulus crater with a prominent central peak right along the day/night terminator. Dione has obviously had a battered and troubled past, one that astro-geologists are still working out. Cassini then takes one last shot, giving humanity a fitting final look at Dione as a crescent receding off in the distance.

It’ll be a long time before we visit Dione again.

“This will be our last chance to see Dione up close for many years to come,” said Cassini mission deputy project scientist Scott Edgington. “Cassini has provided insights into this icy moon’s mysteries, along with a rich data set and a host of new questions for scientists to ponder.”

Cassini also took a distant look at Saturn’s tiny moon Hyrrokkin (named after the Norse giantess who launched Baldur’s funeral ship) earlier this month. Though not a photogenic pass, looking at the tinier moons of Saturn helps researchers better understand and characterize their orbits. Even after more than a decade at Saturn, there are tiny moons of Saturn that Cassini has yet to see up close.

Next up for Cassini is a pass 1,036 kilometers (644 miles) from the surface of Titan on September 28^th, 2015.

Launched in 1997, Cassini has given us over a decade’s worth of exploration of the Saturnian system, including the delivery of the European Space Agency’s Huygens lander to the surface of Titan. The massive moon may be the target of a proposed mission that could one day sail the hazy atmosphere of Titan, complete with a nuclear plutonium powered MMRTG and deployable robotic quadcopters.

Cassini is set to depart the equatorial plane of Saturn late this year, for a series of maneuvers that will feature some dramatic passes through the rings before a final fiery reentry into the atmosphere of Saturn in 2017.

Astronomer Giovanni Cassini discovered Dione on March 21^st, 1684 from the Paris observatory using one of his large aerial refracting telescopes. About 1,120 kilometers in diameter, Dione is 1.5% as massive as Earth’s Moon. Dione orbits Saturn once every 2.7 days, and is in a 1:2 resonance with Enceladus, meaning Dione completes one orbit for every two orbits of Enceladus.

In a backyard telescope, Dione is easily apparent along with the major moons of Saturn as a +10.4 magnitude ‘star.’ Saturn is currently a fine telescopic target in the evening low to the south on the Libra-Scorpius border, offering prime time observers a chance to check out the ringed planet and its moons. Fare thee well, Dione… for now.

August 12, 2015December 23, 2015 by Nancy Atkinson

Gallery: 2015 Perseids Are Putting on a Show

Perseid Meteor Shower over the East Point Light House in New Jersey, USA. Credit and copyright: Jeff Berkes.

Have you been looking up the past few nights, trying to see the Perseid Meteor Shower? Many of our readers have been turning their eyes — and cameras — to the skies, with spectacular results. This year’s Perseids were predicted to be one of the best ever, since there has been little to no moonlight to upstage the shower. As you can see from the images here, many astrophotographers were able to capture fast and bright meteors, and even some that left persistent trains.

Remember, tonight (Wednesday, August 12, 2015) is projected to be the peak, so if you’ve got clear skies, take advantage of this opportunity to see a great meteor shower. You can find out how and when to see them in our previous detailed articles by our in-house observing experts David Dickinson and Bob King.

And enjoy the view from our readers in this gallery of 2015 Perseids:

A Perseid Meteor, the Milky Way and the photographer on August 11, 2015 near Bamburgh, Northumberland, England. Credit and copyright: Peter Greig. — A Perseid Meteor, the Milky Way and the photographer on August 11, 2015 near Bamburgh, Northumberland, England. Credit and copyright:
Peter Greig.

An 'exploding' Perseid meteor as seen on August 11, 2015. Credit and copyright: Chris Lyons. — An ‘exploding’ Perseid meteor as seen on August 11, 2015. Credit and copyright: Chris Lyons.

Bright Perseid and Perseus. Credit and copyright: Chris Lyons.

A green Perseid meteor, along with 2 satellites show up in this image taken on August 11, 2015. Credit and copyright: eos-001 on Flickr.

Perseid meteor from early morning, August 12, 2015 in Weatherly, Pennsylvania. Taken with a Canon 6D and Samyang 14mm lens, 40 second exposure at ISO 3200, unguided. Credit and copyright: Tom Wildoner.

Perseid Meteor near Cassiopeia along with the Andromeda Galaxy, as seen from France on August 10, 2015. Credit and copyright: VegaStar Carpentier/ VegaStar Carpentier Photography.

A Perseid Meteor as seen on August 8, 2015, taken from Oxfordshire with a Canon 1100D + 18-55mm lens, ISO-1600 for 30 seconds. Credit and copyright: Mary Spicer.

Prolific night sky photographer John Chumack near Dayton, Ohio put together this video of 81 Perseid meteors he captured on August 12, 2015 with his Automated low light -Meteor Video Camera Network:

If you are clouded out, you can still enjoy the shower. NASA TV will be tracking the Perseids live on Wednesday, August 12 starting at 10PM EDT/02:00 UT:

August 12, 2015December 23, 2015 by David Dickinson

Revealed: Mars to Appear Larger Than a Full Moon!

A recipe for a three ring circus? Image credit:

We can finally reveal the truth.

A massive conspiracy, spanning over a decade, has been revealed at last by basement bloggers, YouTubers and Facebook users everywhere, implicating ‘big-NASA’ and the powers that be in a massive cover-up.

Yes, it’s the month of August once again, and the Red Planet Mars is set to appear ‘larger than a Full Moon’ over the skies of Earth, as it apparently does now… every year.

Um, no. Stop. Just… stop.

Sure, by now, you’ve had the hoax forwarded to you by that certain well-meaning, but astronomically uninformed family member/co-worker/anonymous person on Facebook.

What’s new under the Sun concerning the August Mars Hoax? To see where the hoax was born, we have to journey all the way back to the close opposition of Mars on August 27^th, 2003. Hey, we actually took two weeks leave in the Fall of 2003 just to sketch and image Mars each night from our backyard lair in the Sonoran desert south of Tucson, Arizona from the then known Very Small Optical Observatory. Those were the days. We measured dial-up internet speeds in kbit/s, ‘burned CDs,’ and Facebook and Twitter were still some years away. Even spam e-mail was still sorta hip.

Two years later in 2005, we were all amused, as the ‘August Mars Hoax’ chain email made its first post-2003 appearance in our collective inboxes. Heck, we were even eager in those halcyon days to take to the nascent web, and do that new hipster thing known as ‘blogging’ to explain just exactly why this couldn’t be so to the masses.

Later in 2006, 2007, and 2008, it wasn’t so funny.

The Mars Hoax just wouldn’t die. “One more unto the breach,” the collective astro-blogging community sighed, as we all dusted off last year’s post explaining how the Red Planet could never approach our own fair world so closely.

It. Just. Couldn’t. Because orbital mechanics. Because physics.

Even the advent of social media couldn’t kill in annual onslaught of the Mars Hoax, and over a Spiderman movie reboot later, we’re now seeing it shared across Facebook, Twitter and more.

Sure, the Mars Hoax is as fake as Donald Trump’s hair. If there’s any true science lesson to learn here, it’s perhaps the mildly interesting social science study of just how the Mars hoax weathers the lean months of winter, to reemerge every August.

Here’s the skinny (again!) on just why Mars can’t appear as large as the Full Moon:

-The Moon is 3,474 kilometers in diameter, and orbits the Earth at an average distance of just under 400,000 kilometers.

-At this distance, the Moon can only appear about 30’ (half a degree) across.

-Think that’s a lot? Well, you could ring the 360 degree circle of the local horizon with 720 Full Moons.

-Mars, like the Earth, orbits the Sun. Even with Earth at aphelion (its most distant point) and Mars at perihelion, we’re still 206.7 – 151.9 = 54.8 million km apart. Sure, aphelion and perihelion of our respective worlds don’t quite line up in our current epochs, but we’ll indulge imagination and fudge things a bit.

-Though Mars is just over 2x times larger in diameter than the Moon, it’s also more than 143 times farther away, even at its said hypothetical closest.

Credit Dave Dickinson — Mars vs Earth; oppositions from 2003 to 2018, including perihelion and aphelion positions. Image credit: Dave Dickinson

-Still want to see Mars as big as a Full Moon? Perhaps one day, astronauts will, though they’ll have to be orbiting just over a 800,000 km from the Red Planet to do it.

If we sound a little pessimistic in our characterizing the Mars Hoax as a recurring non-story, it’s because we see many truly fantastic things in space news that get far from their far shake. Real stories, of collapsing stars, rogue exoplanets, and intrepid rovers exploring distant worlds. Tales of humanoids, exploring space and doing the very best and noble things humanoids as a species can do.

Want to trace the history the Mars Hoax?

Here’s the saga of Universe Today’s coverage of all things ‘Mars Hoax’ since those olden days of the early web:

2005- No, Mars Won’t Look as Big as the Moon

2006- No, Mars Won’t Look as Big as the Moon in August

2007- Will Mars Look as Big as the Moon on August 27? Nope

2008- Please (Again) – Mars Will NOT Look as Big as the Full Moon

2009- Mars Will NOT Look as Big as the Full Moon… But You Can Watch it Get Closer

2010- Tonight’s the Night Mars Will NOT Look as Big as the Full Moon

2011- Is the Moon Mars Myth Over?

2013- The Cyber Myth that Just Won’t Die

2016- ????

Hey, it looks like the hoax did take a break in 2012 and 2014, so that’s encouraging at least…

The great Mars opposition of 2003. image credit: Dave Dickinson — The great Mars opposition of 2003. Image credit: Dave Dickinson

Now, I’m going to do my best to truly terrify all of science blogger-dom, and leave you with one final thought to consider. Mars reaches opposition (otherwise known in astronomical circles as ‘when it’s really nearest to the Earth’) once roughly every 26 months. All oppositions of Mars are not created equal, owing mostly to the eccentric orbit of the Red Planet. We have another fine opposition of Mars coming right up next year on May 22^nd, 2016, followed by one that’s very nearly as favorable as the historic 2003 opposition in 2018, falling juuuuust shy of August on July 28^th of that year…

Will the Mars Hoax meme find a new unwitting audience, and with it, new life?

Sleep tight…. we’ll be covering real science stories in the meantime, ’til we’re called to do battle with the Mars Hoax once again.

August 12, 2015December 23, 2015 by Vanessa Janek

The Journey of Light, From the Stars to Your Eyes

The Milky Way from Earth. Image Credit: Kerry-Ann Lecky Hepburn (Weather and Sky Photography)

This week, millions of people will turn their eyes to the skies in anticipation of the 2015 Perseid meteor shower. But what happens on less eventful nights, when we find ourselves gazing upward simply to admire the deep, dark, star-spangled sky? Far away from the glow of civilization, we humans can survey thousands of tiny pinpricks of light. But how? Where does that light come from? How does it make its way to us? And how do our brains sort all that incoming energy into such a profoundly breathtaking sight?

Our story begins lightyears away, deep in the heart of a sun-like star, where gravity’s immense inward pressure keeps temperatures high and atoms disassembled. Free protons hurtle around the core, occasionally attaining the blistering energies necessary to overcome their electromagnetic repulsion, collide, and stick together in pairs of two.

Proton-proton fusion in a sun-like star. Credit: Borb

So-called diprotons are unstable and tend to disband as quickly as they arise. And if it weren’t for the subatomic antics of the weak nuclear force, this would be the end of the line: no fusion, no starlight, no us. However, on very rare occasions, a process called beta decay transforms one proton in the pair into a neutron. This new partnership forms what is known as deuterium, or heavy hydrogen, and opens the door to further nuclear fusion reactions.

Indeed, once deuterium enters the mix, particle pileups happen far more frequently. A free proton slams into deuterium, creating helium-3. Additional impacts build upon one another to forge helium-4 and heavier elements like oxygen and carbon.

Such collisions do more than just build up more massive atoms; in fact, every impact listed above releases an enormous amount of energy in the form of gamma rays. These high-energy photons streak outward, providing thermonuclear pressure that counterbalances the star’s gravity. Tens or even hundreds of thousands of years later, battered, bruised, and energetically squelched from fighting their way through a sun-sized blizzard of other particles, they emerge from the star’s surface as visible, ultraviolet, and infrared light.

Ta-da!

But this is only half the story. The light then has to stream across vast reaches of space in order to reach the Earth – a process that, provided the star of origin is in our own galaxy, can take anywhere from 4.2 years to many thousands of years! At least… from your perspective. Since photons are massless, they don’t experience any time at all! And even after eluding what, for any other massive entity in the Universe, would be downright interminable flight times, conditions still must align so that you can see even one twinkle of the light from a faraway star.

That is, it must be dark, and you must be looking up.

The incoming stream of photons then makes its way through your cornea and lens and onto your retina, a highly vascular layer of tissue that lines the back of the eye. There, each tiny packet of light impinges upon one of two types of photoreceptor cell: a rod, or a cone.

Most photons detected under the low-light conditions of stargazing will activate rod cells. These cells are so light-sensitive that, in dark enough conditions, they can be excited by a single photon! Rods cannot detect color, but are far more abundant than cones and are found all across the retina, including around the periphery.

The less numerous, more color-hungry cone cells are densely concentrated at the center of the retina, in a region called the fovea (this explains why dim stars that are visible in your side vision suddenly seem to disappear when you attempt to look at them straight-on). Despite their relative insensitivity, cone cells can be activated by very bright starlight, enabling you to perceive stars like Vega as blue and Betelgeuse as red.

But whether bright light or dim, every photon has the same endpoint once it reaches one of your eyes’ photoreceptors: a molecule of vitamin A, which is bound together with a specialized protein called an opsin. Vitamin A absorbs the light and triggers a signal cascade: ion channels open and charged particles rush across a membrane, generating an electrical impulse that travels up the optic nerve and into the brain. By the time this signal reaches your brain’s visual cortex, various neural pathways are already hard at work translating this complex biochemistry into what you once thought was a simple, intuitive, and poetic understanding of the heavens above…

The stars, they shine.

So the next time you go outside in the darker hours, take a moment to appreciate the great lengths it takes for just a single twinkle of light to travel from a series of nuclear reactions in the bustling center of a distant star, across the vastness of space and time, through your body’s electrochemical pathways, and into your conscious mind.

It gives every last one of those corny love songs new meaning, doesn’t it?

August 11, 2015December 23, 2015 by David Dickinson

A Thrift Store Find Yields an Astronomical Mystery

A good mystery is often where you find it. Photographer Meagan Abell recently made a discovery during a thrift store expedition that not only set the internet abuzz, but also contains an interesting astronomical dimension as well. This is an instance where observational astronomy may play a key role in pinning down a date, and we’d like to put this story before the Universe Today community for further insight and consideration.

Meagan first discovered the set of four medium format negatives at a thrift store on Hull Street in Richmond, Virginia. Beyond that, they have no provenance. Meagan was amazed at what see saw when she scanned in the negatives: the images of a woman walking into the surf have an ethereal beauty all their own. Obviously the work of a skilled photographer, the photos appear to date from the late 1940s or 1950s.

Meagan turned to social media for help, and cyber-sleuths responded in a big way. #FindTheGirlsOnTheNegatives became a viral hit, but thus far, who the women in the images are and the story behind them remains a mystery.

We do know one tantalizing bit of information: several Facebook users have pinned down the location as Dockweiler Beach, California near Los Angeles International Airport. Keen-eyed observers noted the similarity of the outline of the distant hills seen to the north in one of the images.

A few things caught our eye upon reading the mystery of the girls in the negatives this past weekend. One shot clearly shows the notch of the Sun just below the twilight horizon. A second, even more intriguing image shows a tiny sliver of Moon just to the subject’s upper left.

Could a date, or set of dates, be estimated based on these factors alone?

Let’s slip into astro-detective mode now. A few things are obvious right off the bat. First, the Moon is a waxing crescent, meaning the shots would have to be set in the evening. This also lends credence to the ocean being the Pacific, because the sunset is occurring over water. The similarity in cloud formations across all of the images seen also strongly suggests the photographer took all of the pictures on the same evening, during one session.

Can that crescent Moon tell us anything? It’s tiny and indistinct, but we have a few things to go on. The Moon looks to be a 5-6 day old waxing crescent about 30-40% illuminated. Not all waxing crescent Moons are created equal, as the ‘horns of the Moon’ can point in various directions based on the angle of the ecliptic to the local horizon at different times of the year.

A typical sampling of the orientation of the horns of the waxing crescent Moon throughout the year as seen from latitude 34 degrees north. Image credit: Dave Dickinson

The horns of the Moon appear to be oriented about 35 degrees from horizontal. Assuming the subject in the red dress is elevated slightly and about 20 feet from the observer, the Moon would be about 25-30 degrees above the horizon in the shot.

Now, Dockweiler Beach is located at latitude 33 degrees 55’ 20” north, longitude 118 degrees 26’ 3” west. The beach itself faces a perpendicular azimuth of 240 degrees out to sea, or roughly WSW.

Already, we can rule out winter and spring, because of the unfavorable angle of the dusk ecliptic. We want a time of year with A) a shallow southward ecliptic and B) a sunset roughly due west.

Turns out, late July through early October fit these ideal conditions for the location.

Can we narrow this even further? Well, here’s one possibility. Remember, this next step is what gumshoe PIs call a ‘hunch’…

The motion of the Moon is a wonderfully complicated affair. The path of the Moon is inclined about five degrees relative to the ecliptic, meaning that the Moon can ride anywhere from declination 28 degrees south, to 28 degrees north. From latitude 34 degrees north, this puts the mid-July ecliptic at about 33 degrees elevation across the meridian at sunset.

The nodal points where the path of the Moon crosses the ecliptic also precess slowly around the celestial sphere. This motion completes one revolution every 18.6 years, meaning that the Moon reaches those maximum declination values (sometimes referred to as a ‘long nights’ or the Major Lunar Standstill of the Moon) just under once every 19 years.

This occurred last in 2006, and will occur next in 2025. Incidentally, we’re at a shallow mid-point (known as a Minor Lunar Standstill) between the two dates this coming Fall.

A good fit? A comparison of the Moon in the image (left) with a simulated view in Stellarium from August 19th, 1950 (click to enlarge). Image credit: Dave Dickinson/Meagan Abell

This also puts the late summer 1^st quarter Moon as far south ‘in the weeds’ as possible. Extrapolating back in time, this sort of wide-ranging Moon occurred around 1949. Looking at the celestial scene in Stellarium, three dates nail the horn angle and elevation of the Moon seen in the photograph pretty closely around this time:

-August 11^th, 1948

-August 29^th, 1949

-August 19^th, 1950

Of course, this is just a hunch. Perhaps the subject was standing on a westward facing spit of rocks. Or maybe the photographer was closer or farther away than estimated. Or maybe the negative was inverted left to right along the way… that’s why I’d like to invite, you, the astute sky watcher, to weigh in.

And even if we pinned down the date, the mystery remains. Who are the girls in the negatives? What became of the photo shoot? And how did the negatives end up in a thrift store in Virginia?

Read another astronomical mystery sleuthed out by Dave Dickinson, with The Downing of Spirit ‘03: Did the Moon Play a Role?

Update: an sharp-eyed reader noticed that if you boost the contrast, you can see an additional ‘speck’ in the Moon image (see comment discussion below):

Update: Meagan responds: “The object along the horizon in the crescent Moon image is actually just a transparency defect.” A second image from the same strip does not show the white speck (arrowed above) near the horizon.