David Dickinson, Author at Universe Today

May 14, 2018May 15, 2018 by David Dickinson

Recovered Asteroid 2010 WC9 Set to Buzz the Earth Tomorrow

The orbit of asteroid 2010 WC9. Credit: NASA/JPL

Incoming: The Earth-Moon system has company tonight.

The Asteroid: Near Earth Asteroid 2010 WC9 is back. Discovered by the Catalina Sky Survey outside Tucson, Arizona on November 30^th, 2010, this asteroid was lost after a brief 10 day observation window and was not recovered until just earlier this month. About 71 meters in size, 2010 WC9 is one of the largest asteroids to pass us closer than the Earth-Moon distance.

A closeup of the passage of asteroid 2010 WC9 through the Earth-Moon system on May 15th. Credit: NASA-JPL

2010 WC9 poses no threat to the Earth. About the size of the Statue of Liberty from the ground level to her crown, the asteroid is over three times bigger than the one that exploded over Chelyabinsk, Russia on the morning of February 15th, 2013.

The view from asteroid 2010 WC9 on closest approach. Credit: Starry Night

The Pass: 2010 WC9 passes just 0.5 times the Earth-Moon distance (126,500 miles or 203,500 kilometers) on Tuesday, May 15^th at 22:05 UT/6:05 PM EDT. That’s only roughly five times the distance of satellites in geosynchronous orbit. The asteroid is also a relative fast mover, whizzing by at over 12 kilometers per second. An Apollo-type asteroid, 2010 WC9 orbits the Sun once every 409 days, ranging from a perihelion of 0.78 astronomical units (AU) outside the orbit of Venus out to 1.38 AU, just inside the orbit of Mars. This is the closest passage of the asteroid by the Earth for this century.

The passage of asteroid 2010 WC9 through the constellation Ophiuchus on May 15th from 00:00 to 16:00 UT. Credit Starry Night.

Observing: This one grabbed our attention when it cropped up on the Space Weather page for close asteroid passes this past weekend: a large, fast mover passing close to the Earth is a true rarity. At closest approach, 2010 WC9 will be moving at 0.22 degrees (that’s 13 arcminutes, about half the span of a Full Moon) per minute through the constellation Pavo the Peacock shining at magnitude +10, making it a good telescopic object for observers based in South Africa as it heads over the South Pole.

The southern hemisphere passage of asteroid 2010 WC9 on May 15th from 19:00 to 23:00 UT.

North American and European observers get their best look at the asteroid tonight into early tomorrow morning while it’s still twice the distance of the Moon, shining at 13th magnitude and moving southward through the constellation Ophiuchus and across the ecliptic plane.

The best strategy to ambush the space rock is to simply aim a low power field of view at the right coordinates at the right time (see below), and watch. You should be able to see the asteroid moving slowly against the starry background, in real time.

Asteroid 2010 WC9 (non-streaking dot in the center) on May 15th while it was still 730,000 km out. Credit: Gianluca Masi/Virtual Telescope Project 2.0.

Keep in mind, the charts we made here are geocentric, assuming you’re observing from the center of the Earth. Parallax comes into play on a close asteroid pass, and the Earth’s gravity will deflect 2010 WC9’s orbit considerably. Your best bet for generating a refined track for the asteroid is to use NASA JPL’s Horizons web interface to generate Right Ascension/Declination coordinates for the 2010 WC9 for your location.

How do you ‘lose an asteroid?” Often, an initial observation arc for a distant asteroid is too short to pin down a refined orbit. We have a blind spot sunward, for example, and fast moving asteroids can also be difficult to track across rich star fields and movement from one celestial hemisphere to the next. Recovery of 2010 WC9 earlier this month now gives us a solid seven year observation arc to peg its orbit down to a high accuracy.

Clouded out, or live in the wrong hemisphere? Slooh will carry an observing session for 2010 WC9 starting tonight at 24:00 UT/ 8:00 PM EDT. The Northholt Branch Observatories in London, England will also stream the pass live via Facebook tonight. Check their page for a start time.

Go, little asteroid… the speedy passage of 2010 WC9. Credit: Northolt Branch Observatories.

There’s no word yet if Arecibo radar plans to ping 2010 WC9 over the coming days, but if they do, so expect to see an animation soon.

Don’t miss tonight’s passage of 2010 WC9 near the Earth, either in person or online.

April 30, 2018 by David Dickinson

By Jove: Jupiter at Opposition for 2018

A recent capture of Jupiter from April 21st. Image credit and copyright: Efrain Morales.

It’s a question I’ve fielded lots this weekend leading up to last night’s April Pink Full Moon, and one I expect we’ll get again tonight: “What’s that bright star near the Moon?”

That bright “star” is actually a planet, the king of them all as far as our Solar System is concerned: Jupiter. May also ushers in Jupiter observing season, as the planet reaches opposition on May 9th, rising in the east opposite to the setting Sun to the west. Jupiter now joins Venus in the dusk sky, ending the planetary drought plaguing many an evening star party.

Looking east tonight (April 30th) at 9 PM local. Created using Stellarium.

All planetary news seems to lead back to Jupiter this season. Just last week, we wrote about a recent study, suggesting that Jupiter actually gets hit by asteroids and comets on a much more regular basis than astronomers thought.

It’s always worth keeping a sharp eye on Jupiter. Shining a magnitude -2.5 near opposition, you can even pick Jupiter out against the deep blue daytime sky… if you know exactly where to look for it. The Moon visits Jupiter once every orbit, and the next time to try this feat of visual athletics is on May 27th, just before sunset.

Jupiter is 4.4 astronomical units (658 million kilometers) distant at opposition this year, and presents a disk 45” across.

At the eyepiece, Jupiter presents a roiling upper atmosphere, completing an amazing rotation once every 9.9 hours. This is not only fast enough to give Jove a noticeable equatorial bulge at its equator, but you can also observe and image Jupiter in its entirety in just one clear evening.

One of the first things that becomes apparent observing Jupiter at low power are its retinue of four Galilean moons. These are, from interior outward: Io, Europa, Ganymede and Callisto. Speedy Io takes just 1.8 days to orbit Jupiter once, while outermost Callisto takes a leisurely 16.7 days to make one circuit around Jupiter. Not only is it fun to note the changes in configuration of Jupiter’s major moons from night to night, but it’s interesting to watch them cast shadows onto Jupiter’s cloud tops and alternately disappear and reappear in and out of Jupiter’s shadow.

Two shadows crossing the face of Jupiter on July 30th, 2018. Created using Stellarium.

A few times a year, you can catch two moons casting a shadow on Jupiter at once. These usually happen in seasons, with the next pair involving Io and Europa (the most frequent transiters) set to occur on July 30th, 2018. Rarer still are triple transits, which last occurred on January 24th, 2015 and will happen next on March 20th, 2032. You’ll never see a quadruple transit though… and the outermost moon Callisto is the only one that can “miss” Jupiter, as it does in 2018.

The celestial scene changes, too, like a spotlight cast over the stage of the sky. At opposition, for example, Jupiter and its moons cast their respective shadows straight back, nearly behind them from our perspective. Watch how this changes, however, as Jupiter heads towards quadrature at 90 degrees elongation east of the Sun on August 6th, 2018 and we see Jupiter and its moons cast their shadows to the side.

Danish astronomer Ole Rømer noted a discrepancy in the timings of shadow transits near opposition versus quadrature and correctly realized that light from the events was actually taking time to transit from Jupiter to his telescope on Earth, and made the first crude measurement of the speed of light in 1676.

Crank up the magnification, and the Great Red Spot will pop into view if it’s turned Earthward. Though this centuries-long storm has been shrinking in recent years, it also seems to be condensing and reddening once again, versus the pale salmon color its exhibited as of late. How old is the Great Red Spot? Will it disappear this century, disappointing legions of school kids who diligently crayon in a ruby red eye on Jove?

One thing is for sure; the face of Jove does change over time. Another interesting example is the disappearing act that Jove’s Southern Equatorial Belt (SEB) makes every decade or so… this last occurred during 2010 season, and we may soon be due again. It would be an amazing scientific opportunity if this were to occur before NASA’s Juno spacecraft completes its mission this summer. Our question: why does the SEB disappear, while the NEB seems to be a permanent fixture on Jove?

All mysteries presented by the largest planet in our solar system, this opposition season 2018.

-Track the positions of Jupiter’s moons and the Great Red Spot using the SETI PDS Rings node, S&T’s app and Project Pluto.

April 26, 2018 by David Dickinson

Asteroids Smack Jupiter More Often Than Astronomers Thought

Jupiter Impact — Pow: The July 1994 impact of Comet Shoemaker-Levy 9 on Jupiter, captured by the Hubble Space Telescope. Credit: R. Evans/J. Trauger/H. Hammel/HST Comet Science Team/NASA.

Are you keeping a eye on Jupiter? The King of the Planets, Jove presents a swirling upper atmosphere full of action, a worthy object of telescopic study as it heads towards another fine opposition on May 9^th, 2018.

Now, an interesting international study out of the School of Engineering in Bilbao, Spain, the Astronomical Society of France, the Meath Astronomical Group in Dublin Ireland, the Astronomical Society of Australia, and the Esteve Duran Observatory in Spain gives us a fascinating and encouraging possibly, and another reason to keep a sharp eye on old Jove: Jupiter may just get smacked with asteroids on a more regular basis than previously thought.

The study is especially interesting, as it primarily focused in on flashes chronicled by amateur imagers and observers in recent years. In particular, researchers focused on impact events witnessed on March 17^th 2016 and May 26^th, 2017, along with the comparison of exogenous (of cosmic origin) dust measured in the upper atmosphere. This allowed researchers to come up with an interesting estimate: Jupiter most likely gets hit by an asteroid 5-20 meters in diameter (for comparison, the Chelyabinsk bolide was an estimated 20 meters across) 10 to 65 times every year, though researchers extrapolate that a dedicated search might only nab an impact flash or scar once every 0.4 to 2.4 years or so.

Compare this impact rate with the Earth, which gets hit by a Chelyabinsk-sized 20-meter impactor about once every half century or so. Incidentally, we know this impact rate on Earth better than ever before, largely due to U.S. Department of Defense classified assets in space continually watching for nuclear tests and missile launches, which also pick up an occasional meteor “photobomb.”

Small asteroid impacts over the span of the Earth over a 20 year period. NASA/Planetary Science.

One reason we may never have witnessed a meteor impact on Jupiter is, astronomers (both professional and amateur) never thought to look for them. The big wake-up call was the impact of Comet Shoemaker-Levy 9 in July 1994, an event witnessed by the newly refurbished Hubble Space Telescope as the resulting impact scars were easily visible in backyard telescopes for weeks afterward. Back in the day, speculation was rampant in the days leading up to the impact: would the collision be visible at all? Or would gigantic Jupiter simply gobble up the tiny comet fragments with nary a belch?

Australian amateur astronomer Anthony Wesley also caught an interesting impact (scar?) in 2009, and every few years or so, we get word of an elusive flash reported on the Jovian cloudtops, sometimes corroborated by a secondary independent observation or a resulting impact scar, and sometimes not.

An impact scar (top center on the disk) on Jupiter, captured on July 19th, 2009. Image credit: Anthony Wesley.

Of course, there are factors which will lower said ideal versus the actual observed impact rate. There’s always a month or so a year, for example, when Jupiter is near solar conjunction on the far side of the Sun, and out of range for observation. Also, we only see half of the Jovian disk from our Earthly perspective at any given time, and we’re about to lose our only set of eyes in orbit around Jupiter – NASA’s Juno spacecraft – later this summer, unless there’s a last minute mission extension.

On the plus side, however, Jupiter is a fast rotator, spinning on its axis once every 9.9 hours. This also means that near opposition, you can also track Jupiter through one full rotation in a single evening.

Finding Jupiter: looking eastward tonight at around 11PM local. Credit Stellarium.

Then there’s the planet’s location in the sky: Currently, Jupiter’s crossing the southern constellation of Libra, and opposition for Jove moves about one astronomical constellation eastward along the ecliptic a year. Jupiter will bottom out along the ecliptic in late 2019, and won’t pop back up north of the celestial equator until May 2022. And while it’s not impossible for northern observers to keep tabs on Jupiter when it’s down south, we certainly get more gaps in coverage around this time.

Hale-Bopp’s close inbound passage near Jupiter in 1996. Credit: NASA/JPL-Horizons.

Should we hail Jove as a protective ‘cosmic goal-tender,’ or fear it as the bringer of death and destruction? There are theories that Jupiter may be both: for example, Jupiter altered the inbound path of Comet Hale-Bopp in 1997, shortening its orbital period from 4,200 to 2,533 years. The 2000 book Rare Earth even included the hypothesis of Jupiter as a cosmic debris sweeper as one of the factors for why life evolved on Earth… if this is true, it’s an imperfect one, as Earth does indeed still get hit as well.

All reasons to keep an eye on Jupiter in the 2018 opposition season.

-See something strange? The ALPO Jupiter observers section wants to know!

April 11, 2018 by David Dickinson

New Saturn Storm Emerging?

Are you following the planets this season? The planetary action is about to heat up, as Jupiter, Saturn and Mars all head towards fine oppositions over the next few months.

Spying the Storms of Saturn

Astrophotographer Damian Peach raised the alarm on Twitter this past week of a possible bright storm emerging of the planet Saturn. The spot was noticeable even with the naked eye and in the raw video Peach captured, a sure sign that the storm was a biggie.

Though outbursts of clusters of white spots on the surface of Saturn aren’t uncommon, it’s rare to see one emerge at such a high latitude. The storm had faded considerably the next observing session Peach performed on April 5th, though observers should remain vigilant.

Saturn Storm 2 — A storm subsiding? The followup view a few days later on April 5th. Image credit and copyright: Damian Peach.

It’s sad to think: Cassini and our eyes in the outer solar system are no more… and the situation will probably remain this way for some years to come. Juno also wraps up its mission at Jupiter (pending extension) this year, and New Horizons visits its final destination Ultima Thule (neé 2014 MU69) on New Year’s Day 2019, though it’ll likely continue to chronicle its journey through the outer realms of the solar system, much like the Voyager 1, 2 and Pioneer 10, 11 missions, also bound to orbit the galaxy, mute testaments to human civilization. But even though proposals for Europa Clipper, a nuclear-powered quad-copter for Saturn’s moon Titan, and a Uranus and/or Neptune Orbiter are all on the drawing board, the “gap decade” of outer solar system exploration will indeed come to pass and soon.

But dedicated amateur astronomers continue to monitor the outer solar system for changes. This month sees Saturn rising around 1:30 AM local and transiting highest to the south for northern hemisphere observers at 6:00 AM local, just before sunrise. Saturn crosses the constellation Sagittarius in 2018, bottoming out at its most southerly point this year for its 29 year path around the Sun. Saturn currently shines at +0.4 magnitude, extending 40” across (including rings) as it heads towards a fine opposition on June 27th. After opposition, Saturn formally crosses into the dusk sky. The amazing rings are an automatic draw, but last week’s storm admonishes us not to forget to check out the saffron-colored disk of Saturn itself as well. For example, I’ve always wondered: why didn’t we see the hexagon before? It’s right there festooning the northern hemisphere cap, plain as day in modern amateur images… to be sure, we’re in a modern renaissance of planetary astrophotography today, what with image stacking and processing, but surely eagle-eyed observers of yore could’ve easily picked this feature out.

And the view is changing as well, as Saturn’s rings reached a maximum tilt in respect to our line of sight of 27 degrees in 2017, and now head back towards edge-on again in 2025. And be sure to check out Saturn’s retinue of moons, half a dozen of which are easily visible in a telescope at even low power.

Finally, here’s another elemental mystery poised by Saturn related to the current storm, one that Cassini sought to solve in its final days: how fast does Saturn rotate, exactly? The usual rough guesstimate quoted is usually around 10.5 hours, but we’ve yet to pin down this fundamental value with any degree of precession.

One thing’s definitely for sure: we need to go back. In the meantime, we can enjoy the early morning views of the most glorious of the planets in our Solar System.

March 8, 2018 by David Dickinson

Catch Sight of Humanity Star… While You Can

Humanity Star: shinny star-ball or light pollution menace. Credit Humanity Star

It’s a question I’ve gotten lots, now that the calendar has flipped over from February to March. When will we get our first good look at the Humanity Star reflector satellite?

The Humanity Star satellite was a surprise payload object placed on the January 21^st, 2018 inaugural orbital launch for Rocket Lab’s Electron rocket. Said launch occurred at Rocket Lab’s Launch Complex-1 on the Mahia Peninsula in New Zealand, placing Humanity Star in a 92 minute orbit inclined 83 degrees to the equator.

Launch! Electron’s inaugural flight. Credit: Rocket Lab.

Dubbed “A bright symbol and a reminder of our fragile place in the Universe,” Humanity Star is a one metre-wide reflective ball. The project is part of an effort to get humanity looking up worldwide in an effort to raise awareness about the night sky and space. Apparently, the cheap showiness of the natural night sky just isn’t enough to drag kids from their smartphone screens these days…

The Upcoming Passes

It makes sense to put a low priority payload such as a shinny orbiting ball or a Tesla roadster on an inaugural rocket launch. Anything can happen the first time ’round, and you wouldn’t want to say, bet the success of the James Webb Space Telescope on an untested launch platform.

And since placing Humanity Star in orbit was a secondary objective for Electron, the orbit is a tough one to observe. It’s just now becoming visible around middle latitudes this week over the swath of the planet inhabited by most of well, humanity.

Heavens-Above’s main page has a link dedicated to Humanity Star. Early magnitude estimates place its maximum brightness on a good overhead pass at around magnitude +1—visible to the naked eye, but hardly the “Brightest Object in the Heavens!” proclaimed on many websites.

The Friday, March 9th pass of Humanity Star up the U.S. East Coast at 7:13 PM EST. Credit: Orbitron.

And what goes up, must come back down. Very early predictions by the U.S. Joint Space Operations Command’s Space-Track website place the reentry for Humanity Star at sometime around March 25^th. We’ll be watching for Humanity Star from our current base camp of operations in Norfolk, Virginia this week, clear skies willing. Follow us on Twitter (we’re @Astroguyz) for updates on sightings, magnitude etc.

There’s no word yet as to when the next Electron rocket launch from New Zealand by Rocket Lab will take place.

Is it good to put shinny junk in space? Another recent effort, the Russian Mayak reflector satellite from 2017, proved to be underwhelming. The first constellation of Iridium satellites will reenter over the next few years, marking the end of the Iridium Flare Era. One Japanese company even wants to provide customized artificial meteor showers.

It reminds me of the good old/bad old days of the 1970s, when plans were afoot to place everything in orbit, from large reflectors to abolish the night (!) to orbiting advertising. And while our astrophotos aren’t getting photo-bombed by Pepsi or McDonald’s logos (yet), we can all chase down the latest attempt to get folks to look up this weekend.

February 26, 2018 by David Dickinson

Venus Returns to the Dusk Sky

The changing phases of Venus, from the 2013 apparition. Credit and copyright: Shahrin Ahmad (@Shahgazer)

Where have all the planets gone? The end of February 2018 sees the three naked eye outer planets – Mars, Jupiter and Saturn — hiding in the dawn. It takes an extra effort to brave the chill of a February morning, for sure. The good news is, the two inner planets – Mercury and Venus – begin favorable dusk apparitions this week, putting on a fine sunset showing in March.

Venus in 2018: Venus begins the month of March as a -3.9 magnitude, 10” disk emerging from behind the Sun. Venus is already over 12 degrees east of the Sun this week, as it begins its long chase to catch up to the Earth. Venus always emerges from behind the Sun in the dusk, lapping the Earth about eight months later as it passes through inferior conjunction between the Sun and the Earth as it ventures into the dusk sky.

Follow that planet, as Venus reaches greatest elongation at 45.9 degrees east of the Sun on August 17th. Venus occupies the apex of a right triangle on this date, with the Earth at the end of one vertice, and the Sun at the end of the other.

Not all elongations of Mercury or Venus are equal, but depend on the seasonal angle of the ecliptic, and whether they occur near aphelion or perihelion. Credit: Dave Dickinson

Mercury joins the fray in early March, as the fleeting innermost world races up to meet Venus in the dusk. March 4th is a great date to check Mercury off of your life list, as the -1.2 magnitude planet passes just 66′ – just over a degree, or twice the span of a Full Moon – from Venus. Mercury reaches greatest elongation 18.4 degrees east of the Sun on March 15^th.

And the Moon makes three on the evening of March 18th, as Mercury, Venus and the slim waxing crescent Moon form a line nine degrees long.

The Moon, Venus and Mercury – looking west at dusk on March 18th. Credit: Stellarium

It’s a bit of a cosmic irony: Venus, the closest planet to the Earth, is also eternally shrouded in clouds and appears featureless at the eyepiece. The most notable feature Venus exhibits are its phases, similar to the Moon’s. Things get interesting as Venus reaches half phase near greatest elongation. After that, the disk of Venus swells in size but thins down to a slender crescent. Venus’s orbit is tilted 3.4 degrees relative to the ecliptic, and on some years, you can follow it right through inferior conjunction from the dusk to the dawn sky. Unfortunately, this also means that Venus usually misses transiting the disk of the Sun, as it last did on June 5-6^th, 2012, and won’t do again until just under a century from now on December 10-11^th, 2117.

Small consolation prize: Mercury, a much more frequent solar transiter, will do so again next year on November 11-12th, 2019.

Amateur astronomers have, however, managed to tease out detail from the Venusian cloudtops using ultraviolet filters. And check out this amazing recent image of Venus courtesy of the Japanese Space Agency’s Akatsuki spacecraft:

Venus in the ultraviolet courtesy of JAXA’s Akatsuki spacecraft. Credit: JAXA/Akatsuki/ISAS/DARTS/Damia Bouic

It’s one of our favorite astro-challenges. Can you see Venus in the daytime? Once you’ve seen it, it’s surprisingly easily to spy… the main difficulty is to get your eyes to focus in on it without any other references against a blank sky. The crescent Moon makes a great visual aid in this quest; although the Moon’s reflectivity or albedo is actually much lower than Venus’s, it’s larger apparent size in the sky makes it stand out. Key upcoming dates to see Venus near the Moon around greatest elongation are April 17^th, May 17^th, June 16^th, July 15^th, and Aug 14^th.

Apparitions of Venus also follow a predictable eight year cycle. This occurs because 13 orbits of Venus very nearly equals eight orbits of the Earth. For example, Venus will resume visiting the Pleiades star cluster during the dusk 2020 apparition, just like it did back before 2012.

Phenomena of Venus

When does Venus appear half illuminated to you? This stage is known as dichotomy, and its actual observed point can often be several days off from its theoretical arrival. Also keep an eye out for the Ashen Light of Venus, a faint illumination of the planet’s night side during crescent phase, similar to the familiar sight seen on the crescent Moon. Unlike the Moon, however, Venus has no nearby body to illuminate its nighttime side… What’s going on here? Is this just the psychological effect of the brain filling in what the eye sees when it looks at the dazzling curve of the crescent Venus, or is it something real? Long reported by observers, a 2014 study suggests that a nascent air-glow or aurora may persist on the broiling night side of Venus.

All thoughts to ponder, as you follow Venus emerging into the dusk sky this March.

January 26, 2018 by David Dickinson

Get Set For a “Super Blue Blood Moon Total Lunar Eclipse”

Can you feel the tremor in the Force? Early next Wednesday morning internet astro-memes collide, in one of the big ticket sky events of the year, with a total lunar eclipse dubbed as — get ready — a Super Blue Blood Moon total lunar eclipse.

Specifics on the eclipse: That’s a mouthful, for sure. This is the first eclipse of 2018, and only one of two featuring totality, lunar or solar. Wednesday morning’s eclipse favors the region centered on the Pacific Rim, with regions of Asia and Australia seeing the evening eclipse at moonrise, while most of North America will see totality early Wednesday morning at moonset. Only the regions of the Canadian Maritimes and the United States east of the Mississippi misses out on the spectacle’s climax, catching a partially eclipsed Moon setting in the west at sunrise.

2018 features four eclipses overall, two lunar and two solar. Paired with this eclipse is a partial solar eclipse on February 15^th favoring the very southern tip of South America, followed by another total lunar eclipse this summer on July 27^th. The final eclipse for 2018 is a partial solar eclipse on August 11^th, favoring northern Europe and northeastern Asia.

What’s all the fuss about? Let’s dissect the eclipse, meme by meme:

Why it’s Super: Totality for this eclipse lasts 1 hour, 16 minutes and 4 seconds, the longest since April 15^th, 2014. Full Moon (and maximum duration for this eclipse) occurs at 13:30 Universal Time (UT), just 27 hours after the Moon reaches perigee the day prior on January 30^th at 9:55 UT . Note that this isn’t quite the closest perigee of the year in space and time: the January 1^st Full Moon perigee beat it out for that title by 2,429 km (1509 miles) and 23 hours.

Worldwide circumstances for Wednesday’s super blue blood moon total lunar eclipse. NASA

Why it’s Blue: This is the second Full Moon of the month, making this month’s Moon “Blue” in the modern sense of the term. This definition comes down to us thanks to a misinterpretation in the July 1943 issue of Sky & Telescope. The Maine Farmer’s Almanac once used an even more convoluted definition of a Blue Moon as “the third Full Moon in an astronomical season with four,” and legend has it, used blue ink in the almanac printing to denote that extra spurious Moon… anyone have any old Maine Farmer’s Almanacs in the attic to verify the tale?

Note that Blue Moons aren’t all that rare… the month of March 2018 also hosts two Full Moons, while truncated February 2018 contains none, sometimes referred to as a “Black Moon”.

Why All the Blood: The cone of the Earth’s umbra or dark inner shadow isn’t completely devoid of light. Instead, you’re seeing sunlight from all the Earth’s sunrises and sunsets around its limb, filtered into the shadow of the the planet onto the nearside of the Moon. Standing on the Earthward facing side of the Moon, you would witness a solar eclipse as the Earth passed between the Moon and the Sun. Unlike the neat near fit for solar eclipses on the Earth, however, solar eclipses on the Moon can last over an hour, as the Earth appears about three times larger than the disk of the Sun. And although astronauts have witnessed eclipses from space, no human has yet stood on the Moon and witnessed the ring of fire surrounding the Earth during a solar eclipse.

Tales of the Saros: For saros buffs, this eclipse is member 49 of 74 lunar eclipses for lunar saros cycle 124, stretching all the way back to August 17^th, 1152. If you caught the total lunar eclipse on January 21^st, 2000, you saw the last eclipse in this cycle. Stick around until April 18^th, 2144 AD and you can watch the final total lunar eclipse for saros 124.

Unlike total solar eclipses, lunar eclipses are leisurely affairs. The entire penumbral phase of the eclipse lasts for over 5 hours, though you probably won’t notice the subtle shading on the limb of the Moon until its about halfway immersed in the Earth’s penumbral shadow.

Not all total lunar eclipses are the same. Depending on how deep the Moon passes through the Earth’s shadow and the murkiness of the Earth’s atmosphere, the Moon can appear anywhere from a sickly orange, to a deep brick red during totality… for example, the Moon almost disappeared entirely during a total lunar eclipse shortly after the eruption of Mount Pinatubo in the early 1990s!

The color of the Moon during totality is known as its Danjon Number, with 4 being bright with a bluish cast on the outer limb of the Moon, and 0 appearing dark and deep red.

This is also one of the only times you can see that the Earth is indeed round with your own eyes as the curve of the shadow cast by our homeworld falls back across the Moon. This curve is the same, regardless of the angle, and whether the Moon is high above near the zenith, or close to the horizon.

Don’t miss the first eclipse of 2018 and the (deep breath) super blue blood Moon total lunar eclipse!

-Clouded out, or on the wrong side of the planet? Watch the January 31st eclipse live courtesy of the Virtual Telescope Project.

January 1, 2018January 15, 2018 by David Dickinson

Top 2018 Astronomy Events

The final occultation of the bright star Aldebaran by the Moon for 2017. Dave Dickinson

Happy New Year 2018.

One of the toughest choices we made last year was to not write a full astronomy guide for 2018. We’ve done this in one iteration or another now for about a decade, but an ongoing project (also astronomical in nature) has consumed most of our writing hours… but we recently realized that we can still take stock in what’s in the sky for the year ahead, and give you a sneak peek at part of our project for the end of 2018.

The Rules:

What we’ve constructed is a simple three month strip chart denoting the top astronomical events by date. The big idea was to make a latitude independent version of the familiar hourglass chart, and distill the events down to the very best.

For the top events listed below for the entire year, we considered:

–Meteor showers with a ZHR greater than 10, where the phase of the Moon is not within a week of Full;

-Oppositions of the outer planets;

-Elongations of the inner planets;

–Eclipses of the Sun and Moon;

-The closest conjunction of two naked eye planets for 2018;

-The best easily visible occultation of a bright star and a planet for 2018;

–Comets slated to reach perihelion in 2018 and forecast to break +10^th magnitude.

The Best of 2018: (events in bold are the “best of the best”)

-Meteor Showers: Lyrids (April 22), Daytime Arietids (June 7), Perseids (Aug 12), Draconid Outburst? (Oct 8) Orionids (Oct 10), Andromedids (Dec 3), Geminids (Dec 14).

-Oppositions: Mars (Jul 27), Jupiter (May 8), Saturn (Jun 27), Uranus (Oct 23), Neptune (Sep 7), Pluto (Jul 12)

-Elongations: Mercury (Jan 1, Mar, 15, Apr 29, Jul 12, Aug 26, Nov 6, Dec 15). Venus (Aug 17)

-Eclipses: A Total Lunar eclipse for Asia, Australia the Pacific and western North America (Jan 31), a partial solar for the southern tip of South America (Feb 15), a partial solar for Tasmania and southernmost Australia (Jul 13), a total lunar for South America, Europe, Africa, Australia and Asia (Jul 27), and a partial solar for Scandinavia and northern Asia (Aug 11),

-Closest conjunctions: Mars-Jupiter (January 7)

-Best occultation (planet): Mars for the southern tip of South America (Nov 16). The Moon occults 4 planets in 2018: Mercury (2), Mars (1), Venus (1), and Saturn (1)

-Best occultation (star): Aldebaran for northern Asia and Europe (Feb 23) The Moon occults Aldebaran 9 times and Regulus 5 times in 2018.

-Periodic Comets over magnitude +10 with perihelion dates: C/2016 M1 PanSTARRS (Aug 10, +9), C/2016 R2 PanSTARRS (May 9, mag +9), C/2017 S3 PanSTARRS (Aug 16, +4), 21P/Giacobini-Zinner (Sep 10, mag +4), 38P/Stephan-Oterma (Nov 11, mag +9), 46P/Wirtanen (Dec 13, mag +3)

The astronomical strip chart for the first 3 months of 2018:

Astronomical events for Jan-Mar 2018 (click the chart to see the full-sized version).

What’s Up for January-March 2018:

-The month of January 2018 kicks off with a Full Moon on the night of January 1-2, the first of two Full Moons in the month, the second of which is sometimes referred to as a Blue Moon. March 2018 also contains two Full Moons (March 2 and March 31), while the 28 day month of February lacks a Full Moon, the only month that can do so.

The Moon also continues its cycle of occultations of the bright stars Regulus and Aldebaran, favoring the following locations;

January 5- Regulus (Northern North America)

January 27-Aldebaran (Northern Pacific)

February 1- Regulus (NE Asia)

February 23- Aldebaran (northern Europe/northern Asia)

March 1-Regulus (North Atlantic)

March 22-Aldebaran (North Atlantic)

March 28-Regulus (NE Asia/Alaska)

The Moon also occults Mercury for NW North America (in the daytime) on February 15^th, then Venus just 22 hours later favoring the southern tip of South America (in the daytime), though both events are too close to the Sun to observe.

The first of two eclipse seasons for 2018 also begins in January, with a total lunar eclipse centered over the Pacific Ocean and surrounding regions on January 31^st and a 60% partial solar eclipse for the southern tip of South America on February 15.

Venus reaches superior conjunction on January 9^th, and moves into the dusk sky for a brilliant dusk apparition later in 2018. Mercury reaches greatest elongation 23 degrees west of the Sun in the dawn sky on January 2, then reaches superior conjunction on the farside of the Sun on February 17 before catching up with Venus and passing just 66′ from it on March 4.

Mars, Jupiter and Saturn remain dawn objects through the first quarter of 2018, with Mars passing just 12′ from Jupiter on January 12.

Let us know what you think, as this quarterly product is very much a work in progress… we plan on bringing you the quarterly astronomical graphic chart here on Universe Today every three months.

We’re looking forward to bringing you another great year of sky watching in 2018!

December 1, 2017December 1, 2017 by David Dickinson

Here Comes Comet Heinze for the Holidays

Comet C/2017 T1 Heinze passes near the galaxy NGC 2706 on November 25th. Image credit and copyright: Charles Bell.

Yeah, we’re still all waiting for that next great “Comet of the Century” to make its presence known. In the meantime, we’ve had a steady stream of good binocular comets over the past year both expected and new, including Comet C/2017 O1 ASASSN1, 45/P Honda-Mrkos-Pajdušáková and Comet 41P Tuttle-Giacobini-Kresák (links). Now, another newcomer is set to bring 2017 in over the finish line.

The Discovery: Astronomer Aren Heinze discovered Comet C/2017 T1 Heinze as a tiny +18^th magnitude fuzzball on the night of October 2^nd, 2017. The comet will juuust breech our “is interesting, take a look” +10^th magnitude cutoff in the final weeks of December leading into January, perhaps topping out around +8^th magnitude.

Heinze discovered his first comet as part of the Asteroid Terrestrial-Impact Last Alert System (ATLAS) search program looking for hazardous objects using the eight 50 cm Wright-Schmidt telescope array atop Haleakala and Mauna Loa in the Hawaiian Islands.

The passage of Comet Heinze through the inner solar system. Credit: NASA/JPL

The orbit for Comet Heinze is an intriguing one, and as is often the case with comets, tempts us with what could have been. Heinze will vault over the ecliptic headed northward on Christmas Day, and reaches perihelion 87 million km (0.58 AU) from the Sun on February 21^st, 2018. Closest passage from Earth for Comet Heinze is 33 million km (0.22 AU) on January 4^th, 2018, when the comet will appear to move an amazing seven degrees a day through the constellation Camelopardalis.

But it’s the southward passage of Heinze though the ecliptic on April 1st that gives us pause, only 0.0144 AU exterior of Earth’s orbit… had this occurred on July 4^th, we might’ve been in for a show, with the comet only 2.1 million kilometers away! Heinze seems like a tiny body as comets go, and there’s discussion that the comet is dynamically new and may end up shredding its nucleus all together. (link)

On a steep 97 degree inclined retrograde orbit, Comet Heinze also has a knife edge hyperbolic eccentricity of nearly 1.0. As with many long period comet, it’s tough to tell if Comet Heinze is a true denizen of our solar system, or just visiting. 2017 also saw the first asteroid whose extra-solar source was clear, as I/2017 U1 ‘Oumuamua, which passed through the inner solar system this past October.

The December path of Comet Heinze. Starry Night.

The Prospects: Currently, Comet Heinze is located highest to the south around 5AM local for northern hemisphere observers. Expect this situation to change to around 2 AM towards months end, as the comet is higher placed in the constellation Lynx come January 1^st, 2018 as it nears opposition.

Comet observer Charles Bell noted on November 27^th that Comet Heinze currently displays a short fan-shaped tail, about 88 days before perihelion.

Here’s the blow-by-blow for Comet Heinze for the next few months (passages mentioned here are to within a degree unless otherwise noted).

December

7- Crosses the celestial equator northward.

16- Passes near +3 magnitude star Zeta Hydrae.

18- Crosses into the constellation Cancer.

21- Passes near the open cluster M67.

25- Photo op: passes near the Beehive Cluster M44 and crosses the ecliptic northward.

29- Skirts the corner of the constellation Gemini and crosses into the Lynx.

January

1- May break +10^th magnitude?

1- Passes near the +4.5 magnitude star 21 Lyncis.

2- Reaches opposition.

3- Passes near the +4.5 magnitude star 2 Lyncis and into the constellation Camelopardalis.

5- Passes near the +4 magnitude star Alpha Camelopardalis.

6- Passes 31 degrees from the north celestial pole.

7- Crosses into the constellation Cassiopeia.

10-Crosses the galactic equator southward.

13- Crosses into the constellation Andromeda.

14-Crosses into the constellation Lacerta.

17- Passes near the +4.5 magnitude star 6 Lacertae.

21- Passes near the +4 magnitude star 1 Lacertae.

23- Crosses into the constellation Pegasus.

February

26- Passes near the globular cluster M15.

March

1- May drop back down below +10^th magnitude?

And though Comet Heinze won’t join their ranks, here’s a list of the great comets of the past century:

You could say we’re due.

October 12, 2017 by David Dickinson

Tales of the King: Watch as the Moon Occults Regulus for North America This Weekend

The Moon occults Regulus on July 25th, 2017. The Moon also occulted the star shortly after the August 21st total solar eclipse. Credit and copyright; @Shahgazer (Shahrin Ahmad).

Up early Sunday morning? Or perhaps, as we often do, you’re “pulling an all-nighter,” out observing until the break of dawn. Well, the clockwork celestial mechanics of the Universe has a treat in store on the morning of October 15^th, as the waning crescent Moon occults (passes in front of) the bright star Regulus (Alpha Leonis, the “Little King” or “Heart of the Lion”) for the contiguous United States, Mexico and southern Canada.

The visibility footprint for Sunday’s occultation. The white solid lines show where the occultation occurs under dark skies, blue marks twilight, and broken lines represent where the event occurs under daytime skies. Credit: Occult 4.2.

You might call this one the “Great American Occultation,” as it takes a similar track to a certain total solar eclipse and another occultation of the bright star Aldebaran earlier this year. The Moon is a 20% illuminated waning crescent during Sunday’s occultation, about the best phase for such an event, as you’ll also get a nice contrasting Earthshine or Ashen light on dark nighttime limb of the Moon. That’s sunlight from the waxing gibbous Earth, illuminating the (cue Pink Floyd) Dark Side of the Moon.

Moon versus Regulus shortly after Sunday’s occultation as seen from Spring Hill, Florida. Stellarium.

Early morning occultations always see the target star or planet ingress (passing behind) the oncoming bright limb of the waning Moon, then egress (reappearing) from behind its dark limb. During waxing evening occultations, the reverse is true, as the dark limb of the Moon leads the way. The Moon will be 53 degrees west of the Sun during the event, and folks in the western U.S. will see the occultation lower to the eastern horizon under dark skies, while observers from Florida to the Great Lakes will see the event transpire under twilight skies and observers in the U.S. northeast will see the occultation finish up after sunrise. Shining at magnitude +1.4, you’ll be able to see the disappearance and reappearance of Regulus with the unaided eye, though events on the dark limb are always more dramatic. And you may just be able to spy Regulus in the daytime post sunrise near the Moon after the occultation, using binoculars or a telescope.

The northern limit graze line path for Sunday’s occultation. Click here for a Google interactive map. Credit: IOTA

Observers along a line running from Oregon through Lake of the Woods, above the Great Lakes and north of New Brunswick are also in for a treat as you just might be able to catch a rare grazing occultation of Regulus, (see the video below) as the star’s light shines down through those lunar valleys and gets blocked by mountain peaks along the limb of the Moon. Such an event can be quite dramatic to watch, as the star light winks in and out during the very last second of its 79 light year journey.

A look at the occultation circumstances for selected locations tells the story. The International Occultation Timing Association has a full list for locales across North America.

	Ingress	Egress	Moon Alt start/end
Boise, Idaho	9:48 UT	10:03 UT	3 deg / 6 deg
Tuscon, Arizona	(before Moonrise)	10:14 UT	NA / 10 deg
Mexico City, Mexico	9:19 UT	10:06 UT	6 deg / 17 deg
Tampa, Florida	9:24 UT	10:32 UT	23 deg / 39 deg
St. Louis, Missouri	9:29 UT	10:26 UT	18 deg / 29 deg
Boston, Massachusetts	9:50 UT	10:44 UT	36 deg / 45 deg
Toronto, Canada	9:47 UT	10:32 UT	29 / 37 deg

The Moon is in the midst of a cycle of occultations of Regulus running from December 18^th, 2016 to the final one for the cycle on April 24^th, 2018. This is number 12 in a series of 19 events, and the best pre-dawn occultation of Regulus for the United States in the current cycle.

US cloud cover percentages, a few hours before the occultation. Credit: NOAA

The Moon can occult four bright +1^st magnitude stars during the current epoch: Regulus, Antares, Spica and Aldebaran. And though Regulus lies closest to the ecliptic plane, it actually gets occulted the least of any 1^st magnitude star in the 21^st century, with only 220 events. The Moon actually also occulted the bright star Pollux up until almost two millennia ago, and will resume doing so again in the future.

Occultations are easy to observe, and one of the few times (including eclipses) were you can see the motion of the Moon, in real time. The Moon moves its own diameter (30′ or half a degree) per hour, and the reemergence of the bright star will be an abrupt “lights back on” for Regulus. Does it seem to linger a bit between the horns of the crescent Moon? This often reported optical illusion is called the Coleridge Effect, from a line from Samuel Coleridge’s (not Iron Maiden’s) Rime of the Ancient Mariner:

While clome above the Eastern bar

The horned Moon, with one bright star

Almost atween the tips.

Happen to see Regulus “a clome ‘atween the tips?” We also like to refer to this as the ‘Protor and Gamble effect’ due to the company’s traditional star-filled logo.

Occultations also adorn the flags of many Middle Eastern countries. The star and crescent of Islam traces back to antiquity, but was said to have been adapted for the Turkish flag after Sultan Alp Arslan witnessed a close pairing shortly after the Battle of Manzikert on August 26^th, 1071 AD. Though Venus is usually stated as the legendary “star,” Regulus was in fact, just a few degrees away from the Moon on the very same morning… perhaps adding some credence to a major legend vexing vexillology?

The Moon and Regulus on the morning of August 26th, 1071 AD. Stellarium.

Of course, we may never truly know just what Sultan Arsulan saw. A more recent occultation tale was featured in the November 2017 issue of Sky and Telescope, positing the an occultation of Aldebaran by the Moon on March 7^th, 1974 was the source of William Wilkins’ alleged “Volcano on the Moon…” the timing is certainly right, though one wonders how a skilled observer like Wilkins could be fooled by a prominent star (wistful thinking, maybe?)

Recording an occultation is as easy as aiming a video camera at the Moon through a telescope and letting it run. Start early, and make sure you’ve got the contrast between the bright limb of the Moon and the star adjusted, so both appear in the frame. We like to have WWV radio running in the background for an accurate time hack on the video.

Regulus also has a suspected (though never seen) white dwarf companion. Such a star should shine at +12^th magnitude or so… and just might make a very brief appearance on the dark limb of the Moon during egress. One total unknown is its position angle, which is a big wild card, but you just never know… its worth examining that video afterwards, especially if you’re shooting at a high frame rate.

…and speaking of occultations, we’re in the midst of combing through near double occultations of bright stars and planets out to 3000 A.D… hey, it’s what we do for fun. Anyhow, we’re tweeting these out as @Astroguyz as we find ’em, one per day. As a teaser, I give you this grazing occultation of Venus and Regulus over Siberia coming right up in 2025:

The Moon occults Venus and Regulus in 2025. Stellarium.

If nothing else, the cosmic grin of a planet, star and crescent Moon does hint at the Universe’s strange sense of humor.