Skywatching Archives

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.

A close up of the five degree wide field of view for 44 Boötis. Note: magnitudes for nearby stars are noted minus decimal points. Image credit: Starry Night Education software.

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 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 19, 2015December 23, 2015 by David Dickinson

Watch HTV-5 Chase the International Space Station From Your Backyard

A JAXA H-IIB rocket departs Tanegashima Space Center in a dramatic night shot. Image credit: JAXA/NASA TV

It’s away… and the hunt is on. The Japanese Space Agency’s H-II Transfer Vehicle Kounotori automated cargo spacecraft rocketed out of the Tanegashima Space Center today, headed for the ISS.

Loaded with over 6,000 kilograms of experiments and supplies, HTV-5 is on a five day odyssey that you can follow from your backyard, starting tonight. Kounotori stands for ‘white stork,’ or the purveyor of joyful things in Japanese, and in this instance, the name is appropriate, as the HTV-5 is delivering much needed supplies to the International Space Station.

Launch occurred this morning at 11:50 UT/7:50 AM EDT, hitting an instantaneous window to chase after the International Space Station for grapple and berthing on Monday.

Unlike the Progress and Soyuz spacecraft, which have the capability to rendezvous and dock with the ISS, the HTV-5 and Dragon spacecraft are grappled with the Canadian Space Agency’s Canadarm 2, and stowed or ‘berthed’ in place.

Grapple with berthing to the nadir node of the Harmony module is set for Monday, August 24th, at 11:54 UT/7:54 AM EDT.

Unlike other vehicles that periodically visit the International Space Station, the HTV does not incorporate deployable solar panels, but instead, has panels wrapped around its body. This can also lend itself to some pretty bright flares as it passes overhead.

Grapple of HTV-4 by the Canadarm 2. Image credit: NASA/JAXA

The H-IIB is a two stage rocket, and ground observers should keep an eye out for the second stage booster during ISS passes as well. Debris was also jettisoned during last weeks’ spacewalk, and there’s no word as of yet if this has reentered as well, though ground-spotters have yet to report any sightings. This is a typical EVA maneuver, and cosmonauts conducted the release in such a fashion as to pose no danger to the ISS or HTV. Debris jettisoned from the ISS typically reenters the Earth’s atmosphere after about a week or so.

Prospects for Seeing HTV-5 this Weekend

Grapple of the HTV-5 will occur Monday over central Asia. Keep in mind, the HTV-5 will have to perform several burns to reach the elevation of the ISS: this means its orbit will evolve daily. Heavens-Above and NASA’s Spot the Station tracker typically publish sighting predictions for cargo vehicles such as the HTV-5 along with ISS sighting opportunities online.

And we’ll be posting daily updates and maps as @Astroguyz on Twitter. We see the best prospects for spotting the ISS and HTV5 over the next few days leading up to Monday’s berthing are for latitudes 25-45 north (dusk) and latitudes 30-50 south (dawn). That covers a wide range of observers in Europe, North America, South Africa and Australia/New Zealand.

A capture of the passage of HTV-4. Image credit and copyright: Fred Locklear

We’ve caught sight of JAXA’s HTV on previous missions, and contest to it being a conspicuous object.

Pro-tip: the trick to a successful sighting is to start watching early. The HTV-5 will be fainter than the brilliant ISS, but still visible to the naked eye at about magnitude +1 to +2 or so when directly overhead. The HTV-5 will follow the same orbital trace as the station. Spot the ISS and still don’t see HTV-5? Linger for a bit and keep watching after the ISS has passed, as the HTV might follow shortly. And the darker the skies you can find to carry out your HTV-5 vigil under, the better!

Aug 19 — Initial estimations for the passage of the HTV-5 about 10 minutes ahead of the ISS on Wednesday, August 19th. Image credit: Orbitron

Here’s a sampling of ISS passes for Washington D.C. for the next few days:

Wednesday, August 19^th: 8:46 PM EDT (Elevation 65 degrees NE)

Thursday, August 20^th: 9:29 PM EDT (Elevation 23 degrees SW)

Friday, August 21^st: 8:35 PM EDT (Elevation 48 degrees SW)

Clouded out? You can still watch the grapple and berthing action online courtesy of NASA TV.

Want more? Other orbital alumni that have placed a port of call at humanity’s orbital outpost include: SpaceX’s Dragon, the U.S. Space Shuttle fleet (excepting the Columbia orbiter), Progress, ATV, HTV, Soyuz, and Orbital Science’s Cygnus spacecraft. And while the shuttle and the European Space Agency’s ATV fleet are retired, you can follow the next launch of a crewed Soyuz (TMA-18M) on September 2^nd from the Baikonur Cosmodrome on a four-orbit fast-track docking.

JAXA plans to launch one HTV a year, out to HTV-9 in 2019.

Good luck, and good sat-spotting… next time we park the Jeep Liberty in the garage, we’re going to refer to it as a ‘grapple and berthing…’ it just sounds cool.

Got a picture of the International Space Station and friends? Be sure to send ‘em in to Universe Today.

August 18, 2015September 23, 2016 by David Dickinson

Late Summer Tales of Tanabata

The August Milky Way graced with the occasional Perseid. Image credit: Andre van der Hoeven

One of the surest signs that late summer is here in the northern hemisphere is the arrival of the Milky Way in the early evening sky. As darkness falls ever earlier each night, the star-dappled plane of our home galaxy sits almost due south and stretches far to the north. This is also why we refer to the triangular shaped asterism formed by the bright stars of Altair, Deneb and Vega as the Summer Triangle. Two of these stars are the focus of a fascinating mythos from the Far East, and a poetic celestial configuration that commemorates star-crossed lovers lost.

We first heard of tales of Tanabata while stationed in Japan in the U.S. Air Force. Meaning ‘the seventh evening of the seventh month’ — sometimes simply abbreviated to ‘the seventh-seventh,’ — Tanabata is the summer Star Festival of Japan and dates back to about the 7^th century AD. Korean and Chinese cultures also have a version of the tale, and the festival that was once considered a rite for the elite gained popularity during the Edo period in the 17^th century to become a nationwide celebration.

Tanabata 2010. Wikimedia Commons/Hanasakijijii/3.0 license

The origin story of Tanabata involves the romance between the weaver’s daughter Orihime and the cow-herder’s son Kengyuu. As lovers will do, both began to neglect family duties — namely, weaving and cow-herding — until the two were separated by Orihime’s father, Tentei, represented by the Pole Star Polaris. The vast river of heaven, represented by the Milky Way, now separates the two. Orihime (Vega) sits on one side, while Kengyuu (Altair) is alone and unreachable on the other. The Emperor relented to Orihime’s pleading, however, and allows the two to meet once a year, on the seven day of the seventh month. And thus, Tanabata was born.

In late August, Vega and Altair are easily visible high to the east at dusk. You’re looking out along the Orion Spur — of which our solar system is a member — which traverses the Perseus and Cygnus arms of the galaxy beyond. We’re headed roughly in the same direction, towards a point known as the solar apex which is located near the bright star Vega, 25 light years distant. Remember the movie Contact? Vega was the fictional source of an extraterrestrial signal detected by Jodi Foster in the film.

our location in the Orion Spur of the Milky Way galaxy. image credit: Roberto Mura/Public Domain — You are here: our location in the Orion Spur of the Milky Way galaxy. Image credit: Roberto Mura/Public Domain

The modern Japanese calendar actually marks Tanabata on several different dates. The timing of the festival can vary from village to village, depending on which local convention is observed.

The original Japanese calendar was lunisolar, and very similar in convention to the modern Chinese festival calendar. A lunisolar calendar attempts to keep the cycles of the synodic period (29.5 days) of the Moon in sync with the solar calendar year, and must add an extra lunar month every 2-3 years to keep up. The modern Jewish calendar is another example of a lunisolar calendar, whereas the Islamic calendar follows the cycles of the Moon only.

The Summer Triangle. Image credit: Stellarium

Modern Japan has adapted the western Gregorian calendar, which is exclusively solar and reconciles the tropical and sidereal periods of the Sun. Though Tanabata was traditionally held in August, many Japanese communities simply transcribe the ‘seventh day of the seventh month’ onto the modern Gregorian calendar to mean July 7^th. Still other villages use the ‘one-month delay’ rule, to center Tanabata on August 7^th.

Some rural villages, however, still use the older lunisolar custom. By this reckoning, Tanabata always falls seven days after the New Moon at the end of seven full lunar cycles, when the Moon is a fat crescent not quite at first Quarter phase.

A table for future dates of Tanabata using the traditional lunisolar calendar for the next decade. Image credit: Dave Dickinson

In 2015, this happens this Thursday on August 20^th. Like Easter, Tanabata can fall early or late by about one lunar cycle, the earliest being August 1st, which happens on 2014 and 2033, and the latest being August 30th, which happens on 2006 and 2044.

Think of the crescent Moon as the boat, which once a year, brings the two lovers together across the celestial river of the Milky Way.

Late to the party? the waxing crescent Moon versus the plane of the galaxy on the evening of August 20th, 2015. Image credit: Starry Night Education Software (Click image to enlarge)

You may notice on the evening of the 20^th that the boat no longer makes its portage to the river, completing the scene. In fact, the cosmic lineup of the Milky Way and the fat waxing crescent Moon is now more of a September/October affair. What gives? Well, they once did align, way back when Tanabata first became a tradition over a millennia ago.

Blame our friend, the Precession of the Equinoxes for conspiring to keep our happy couple apart. The 26,000-odd year wobble is enough to move the equinoctial points about one degree along the ecliptic during a normal 70 year human life span. That all adds up, making the ferryman about one synodic period late to the party in modern times.

Enjoy the show, and happy Tanabata, whenever you may celebrate it in space and time.

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.

August 10, 2015December 23, 2015 by David Dickinson

The 2015 Perseids: Weather Prospects, Prognostications and More

The venerable ‘old faithful of meteor showers’ is on tap for this week, as the August Perseids gear up for their yearly performance. Observers are already reporting enhanced rates from this past weekend, and the next few mornings are crucial for catching this sure-fire meteor shower.

First, here’s a quick rundown on prospects for 2015. The peak of the shower as per theoretical modeling conducted by Jérémie Vaubaillon projects a broad early maximum starting around Wednesday, August 12th at 18:39 UT/2:39 PM EDT. This favors northeastern Asia in the early morning hours, as the 1862 dust trail laid down by Comet 109P Swift-Tuttle — the source of the Perseids — passes 80,000 km (20% of the Earth-Moon distance, or about twice the distance to geostationary orbit) from the Earth. This is worth noting, as the last time we encountered this same stream was 2004, when the Perseids treated observers to enhanced rates up towards 200 per hour. Typically, the Perseids exhibit a Zenithal Hourly Rate (ZHR) of 80-100 per hour on most years.

This translates into a local peak for observers worldwide on the mornings of August 12th and 13th. Comet 109P Swift-Tuttle orbits the Sun once every 120 years, and last reached perihelion in 1992, enhancing the rates of the Perseids throughout the 1990s.

Don’t live in northeast Asia? Don’t despair, as meteor showers such as the Perseids can exhibit broad multiple peaks which may arrive early or late. Mornings pre-dawn are the best time to spy meteors, as the Earth has turned forward into the meteor stream past local midnight, and rushes headlong into the oncoming stream of meteor debris. It’s a metaphor that us Floridians know all too well: the front windshield of the car gets all the bugs!

The flight of the Perseid radiant through August. Image credit: Dave Dickinson/Stellarium

Weather prospects — particularly cloud cover, or hopefully, the lack of it — is a factor on every observer’s mind leading up to a successful meteor hunting expedition. Fortunately here in the United States southeast, August mornings are typically clear, until daytime heating gives way to afternoon thunder storms. About 48 hours out, we’re seeing favorable cloud cover prospects for everyone in the CONUS except perhaps the U.S. northeast.

Weather and cloud cover prospects for the mornings of August 12th and August 13th. Image credit: NOAA

The Moon is also under 48 hours from New on Wednesday, allowing for dark skies. This is the closest New Moon to the peak of the Perseids we’ve had since 2007, and it won’t be this close again until 2018.

Fun fact: the August Perseids, October Orionids, November Leonids AND the December Geminids are roughly spaced on the calendar in such a way that if the Moon phase is favorable for one shower on a particular year, it’ll nearly always be favorable (and vice versa) on the others as well.

Sky watchers have observed the annual Perseid meteors since antiquity, and the shower is often referred to as ‘The Tears of Saint Lawrence.’ The Romans martyred Saint Lawrence on a hot grid iron on August 10^th, 258 AD. The radiant crosses from the constellation Perseus in early August, and sits right on the border of Cassiopeia and Camelopardalis on August 12^th at right ascension 3 hours 10’ and declination +50N 50.’ Technically, the shower should have the tongue-twisting moniker of the ‘Camelopardalids’ or perhaps the ‘Cassiopeiaids!’

The last few years have seen respectable activity from the Perseids:

2014- ZHR = 68 (Full Moon year)

2013- ZHR = 110

2012- ZHR = 120

2011- ZHR = 60 (Full Moon year)

2010- ZHR = 90

You can see the light-polluting impact of the nearly Full Moon on the previous years listed above. Light pollution has a drastic effect on the number of Perseids you’ll see. Keep in mind, a ZHR is an ideal rate, assuming the radiant is directly overhead and skies are perfectly dark. Most observers will see significantly less. We like to watch at an angle about 45 degrees from the radiant, to catch meteors in sidelong profile.

Imaging the Perseids is as simple as setting up a DSLR on a tripod as taking long exposures of the sky with a wide angle lens. Be sure to take several test shots to get the combination of f-stop/ISO/and exposure just right for current sky conditions. This year, we’ll be testing a new intervalometer to take automated exposures while we count meteors.

Clouded out? NASA TV will be tracking the Perseids live on Wednesday, August 12^th starting at 10PM EDT/02:00 UT:

Remember, you don’t need sophisticated gear to watch the Perseids… just a working set of ‘Mark-1 eyeballs.’ You can even ‘hear’ meteor pings on an FM radio on occasion similar to lightning static if you simply tune to an unused spot on the dial. Sometimes, you’ll even hear a distant radio station come into focus as it’s reflected off of an ionized meteor trail:

And if you’re counting meteors, don’t forget to report ‘em to the International Meteor Organization and tweet ‘em out under hashtag #Meteorwatch.

Good luck and good meteor hunting!

August 10, 2015December 23, 2015 by Bob King

See Venus at Her Most Ravishing

Venus dwindles to a captivating crescent nearly 1 arc minute across as seen on August 8, 2015. An infrared filter was used to increase contrast between the planet and otherwise bright sky. Credit: SEN / Damian Peach

Venus is HUGE right now but oh-so-skinny as it approaches inferior conjunction on August 15. Like crescents? You’ll never see a thinner and more elegant one, but first you’ll have to find it. Here’s how.

There’s only one drawback to enjoying Venus at its radically thinnest — it’s very close to the Sun and visible only during the daytime. A look at the diagram above reveals that as Venus and Earth draw closer, the planet also aligns with the Sun. At conjunction on August 15, it will pass 7.9° south of our star, appearing as an impossibly thin crescent in the solar glare. The sight is unique, a curved strand of incandescent wire burning in the blue.

Venus at inferior conjunction on January 10, 2014 shows both the sunlit crescent and cusp extensions from sunlight penetrating the atmosphere from behind. Credit: Tudorica Alexandru — Venus at inferior conjunction on January 10, 2014 shows both the sunlit crescent and cusp extensions caused by sunlight penetrating the atmosphere from behind. During this previous inferior conjunction, Venus passed north of the Sun, so we see the bottom of the crescent illuminated. Credit: Tudorica Alexandru

If you’re patient and the air is steady, you might even glimpse the cusps of the illuminated crescent extending beyond their normal length to partially or even completely encircle Venus’s disk. These thread-like extensions become visible when the planet lies almost directly between us and the Sun. Sunlight scatters off the Venus’s dense atmosphere, causing it to glow faintly along the limb. One of the most remarkable sights in the sky, the sight is testament to the thickness of the planet’s airy envelope.

Going, going, gone! Or almost. Venus photographed in its beautiful crescent phase on two occasions this past week. — Going, going, gone! Venus photographed in its beautiful crescent phase on two occasions last week. When the planet reaches inferior conjunction this Saturday (August 15), the crescent will expand to nearly 1 arc minute across. No planet comes closer to Earth than Venus — just 27 million miles this week. Credit: Giorgio Rizzarelli

Today, only 1.7% of the planet is illuminated by the Sun, which shines some 11° to the northwest. The Venusian crescent spans 57 arc seconds from tip to tip, very close to 1 arc minute or 1/30 the width of the Full Moon. Come conjunction day August 15, those numbers will be 0.9% and 58 arc seconds. The angular resolution of the human eye is 1 minute, implying that the planet’s shape might be within grasp of someone with excellent eyesight under a clear, clean, cloudless sky. However — and this is a big however — a bright sky and nearby Sun make this practically impossible.

No worries though. Even 7x binoculars will nail it; the trick is finding Venus in the first place. For binocular users, hiding the Sun COMPLETELY behind a building, chimney, power pole or tree is essential. The goddess lurks dangerously close to our blindingly-bright star, so you must take every precaution to protect your eyes. Never allow direct sunlight into your glass. Never look directly at the Sun – even for a second – with your eyes or UV and infrared light will sear your retinas. You can use the map provided, which shows several locations of the planet at 1 p.m. CDT when it’s highest in the sky, to help you spot it.

The Sun's position is shown for 1 p.m. local daylight time, while Venus is shown for three dates - today, conjunction date and Aug. 21. As Venus moves from left to right under or south of the Sun, its phase swings from evening crescent (left) to morning crescent from our perspective on Earth. Source: Stellarium with additions by the author — The Sun’s position is shown for 1 p.m. local daylight time facing due south, while Venus and its corresponding phase is depicted before, at and after conjunction. As Venus moves from left to right south of the Sun, its phase changes from evening crescent (left) to morning crescent from our perspective on Earth. Source: Stellarium with additions by the author

If you’d like to see Venus on a different day or time, download a free sky-charting program like Stellarium or Cartes du Ciel. With Stellarium, open the Sky and Viewing Options menu (F4) and click the Light Pollution Level option down to “1” to show Venus in a daytime sky. Pick a viewing time, note Venus’s orientation with respect to the Sun (which you’ve hidden of course!) and look at that spot in the sky with binoculars. I’ll admit, it’s a challenging observation requiring haze-free skies, but be persistent.

By coincidence, the Moon and Venus will be about the same distance from the Sun and appear as exceedingly thin crescents on the afternoon (CDT) of August 13. Source: Stellarium — By coincidence, the Moon and Venus will be about the same distance from the Sun and appear as very similar thin crescents around 1 p.m. CDT on August 13. Venus should still be visible using the methods described below, but the Moon will be impossible to see. Source: Stellarium

A safer and more sure-fire way to track the planet down involves using those setting circles on your telescope mount most of us never bother with. First, find the celestial coordinates (right ascension and declination) of the Sun and Venus for the time you’d like to view. For example, let’s say we want to find Venus on August 10 at 2 p.m. Using your free software, you click on the Sun and Venus’s positions for that time of day to get their coordinates, in this case:

Venus – Right ascension 9h 42 minutes, declination +6°.
Sun – RA 9h 22 minutes, dec. +15° 30 minutes

Now subtract the two to get Venus’ offset from the Sun = 20 minutes east, 9.5° south.

Dust off those setting circles (declination shown here) and use them to point you to Venus this week. Credit: Bob King — Dust off those setting circles (declination shown here, marked off in degrees) and use them to point you to Venus this week. Credit: Bob King

Next, polar align your telescope using a compass and then cover the objective end with a safe mylar or glass solar filter. Center and sharply focus the Sun in the telescope. Now, loosen the RA lock and carefully offset the right ascension 20 minutes east using your setting circle, then re-lock. Do the same with declination, pointing the telescope 9.5° south of the Sun. If you’re polar alignment is reasonably good, when you remove the solar filter and look through the eyepiece, you should see Venus staring back at you from a blue sky. If you see nothing at first, nudge it a little this way and that to bring the planet into view.

Sometimes it takes me a couple tries, but I eventually stumble arrive on target. Obviously, you can also use this technique to spot Mercury and Jupiter in the daytime, too. By the way, don’t worry what the RA and Dec. read on your setting circles when you begin your hunt; only the offset’s important.

When inferior conjunction occurs at the same time Venus crosses the plane of Earth's orbit, we see a rare transit like this one on June 5, 2012. Credit: Bob King — When inferior conjunction occurs at the same time Venus crosses the plane of Earth’s orbit, we see a rare transit (upper right) like this one on June 5, 2012. Credit: Bob King

This year’s conjunction is one of the best for finding Venus in daylight because it’s relatively far from the Sun. With an orbital inclination of 3.2°, Venus’s position can range up to 8° north and south of the Earth’s orbital plane or ecliptic. Rarely does the planet cross the ecliptic at the same time as inferior conjunction. When it does, we experience a transit of Venus. Transits always come in pairs; the last set occurred in 2004 and 2012; the next will happen over 100 years from now in 2117 and 2125.

I hope you’re able to make the most of this opportunity while still respecting your tender retinas. Good luck!