2017 astronomy Archives

June 7, 2017June 7, 2017 by David Dickinson

Summer Astronomy, Minimoon & Saturn Opposition 2017

Saturn from June 1st. Image credit and copyright: Peter on the Universe Today Flickr forum.

Saturn on June 1st, nearing opposition. Image credit and copyright: Peter on the *Universe Today* Flickr forum

Summertime astronomy leaves observers with the perennial question: when to observe? Here in Florida, for example, true astronomical darkness does not occur until 10 PM; folks further north face an even more dire situation. In Alaska, the game in late July became “on what date can you first spot a bright planet/star? around midnight.

And evening summer thunder showers don’t help. Our solution is to get up early (4 AM or so) when the roiling atmosphere has settled down a bit.

But there’s one reason to stay up late, as the planet Saturn reaches opposition next week on June 15^th and crosses into the evening sky.

Southern hemisphere observers have it best this year, as the ringed planet loiters in southern declinations for the next few years. In fact, Saturn won’t pop up over the celestial equator again until April, 2026. You’ll still be able to see Saturn from mid-northern latitudes, looking low to the south.

First, a brief rundown of the planets this summer. Mars is currently on the far side of the Sun and headed towards solar conjunction of July 26^th. Meanwhile, Mercury is headed towards greatest eastern (dusk) elongation on June 21^st. Early AM viewers, can follow Venus, which has just passed greatest elongation west of the Sun on June 3^rd, just last week. Finally, Jupiter joins Saturn in the dusk sky, high to the south at sunset and headed towards quadrature 90 degrees east of the Sun on July 6th.

Looking eastward on the evening of June 9th. Credit: Stellarium.

There’s another astronomical curiosity afoot this coming weekend: the MiniMoon for 2017. This is the Full Moon nearest to lunar apogee, a sort of antithesis of the over-hyped “SuperMoon.” Lunar apogee occurs on Thursday, June 8^th and the Full Moon occurs just 14 hours after.

2017 sees Saturn traveling from the dreaded “13^th constellation” of zodiac Ophiuchus the Serpent Bearer into Sagittarius. This also means that Saturn is headed towards bottoming out near 23 degrees southern declination next year in late 2018. Saturn truly lives up to its “father time” namesake, marking up its slow 29 year passage once around the zodiac. This struck home to us a few years back when Saturn passed Spica in the constellation Virgo, right back where I first started observing the planet as a teenager three decades before.

The path of Saturn through the last half of 2017. Credit: Starry Night Education Software.

The rings are also at their widest tilt in 2017, making for an extra photogenic view. 27 degrees wide as seen from our Earthly vantage point is as wide as Saturn’s ring system ever gets. Saturn isn’t really “tipping” back and forth as much as it’s orbiting the Sun and dipping one hemisphere towards us, and then another. In 2017, it’s the planet’s northern hemisphere time to shine.

Saturn: the changing view. Image credit and copyright: Andrew Symes (@failedprotostar)

Here’s the last/next cycle rundown:

-Rings wide open: (southern pole of Saturn tipped earthward): 2003

–Rings edge on: 2009

–Rings wide open: (northern pole of Saturn tipped earthward): 2017

-Rings edge on: 2025

-Rings wide open: (southern pole of Saturn tipped earthward): 2032

Even a small 60 mm refractor and a low power eyepiece will reveal the most glorious facet of Saturn: its glorious rings. Galileo first saw this confounding view in 1610, and sketched Saturn as a curious double-handled world. In 1655 Christaan Huygens first correctly deduced that Saturn’s rings are a flat plane, fully disconnected from the planet itself.

Crank up the magnification a bit, and the large Cassini Gap in the rings and the shadow play of the rings and the planet becomes apparent. This gives the view an amazing 3-D effect unparalleled in observational astronomy. The shadow cast by the bulk of the planet disappears behind it during opposition, then slowly starts to reemerge to one side after. Other things to watch for include the retro-reflector Seeliger Effect ( also known as opposition surge) as the planet brightens near opposition. And can you spy the bulk of the planet through the Cassini gap?

The moons of Saturn. Image credit and copyright: John Chumack

Hunting for Saturn’s moons is also a fun challenge. Saturn has more moons visible to a backyard telescope than any other planet. Titan is easiest, as the +8 magnitude moon orbits Saturn once every 16 days. In a small to medium-sized (8-inch) telescope, six moons are readily visible: Enceladus, Mimas, Rhea, Dione, Iapetus and Tethys. Large light bucket scopes 10” and larger might just also tease out the two faint +15th magnitude moons Hyperion and Phoebe.

There’s also something else special about Saturn in 2017 in the world of space flight: the venerable Cassini mission comes to an end this September. Hard to believe, this mission soon won’t be with us. Launched in 1997, Cassini arrived at Saturn in in July 2004, and has since provided us with an amazing decade plus of science. The internet and science writing online has grown up with Cassini, and it’ll be a sad moment to see it go.

All thoughts to ponder, as you check out Saturn at the eyepiece this summer.

February 9, 2017February 9, 2017 by David Dickinson

Watch the Moon Make a Pass at Earth’s Shadow, Then Kiss Regulus This Valentine’s Weekend

Regulus Occultion — The Moon occults Regulus of January 15th, 2017. Image credit and copyright: Lucca Ruggiero

In the southern hemisphere this weekend in the ‘Land of Oz?’ Are you missing out on the passage of Comet 45/P Honda-Mrkos-Pajdušáková, and the penumbral lunar eclipse? Fear not, there’s an astronomical event designed just for you, as the Moon occults (passes in front of) the bright star Regulus on the evening of Saturday, January 11th.

The entire event is custom made for the continent of Australia and New Zealand, occurring under dark skies. Now for the bad news: the waning gibbous Moon will be less than 14 hours past Full during the event, meaning that the ingress (disappearance) of Regulus will occur along its bright leading limb and egress (reappearance) will occur on the dark limb. We prefer occultations during waxing phase, as the star winks out on the dark limb and seems to slowly fade back in on the bright limb.

The footprint for the February 11th occultation of Regulus by the Moon. Image credit: Occult 4.2 software

The International Occultation Timing Association has a complete list of precise ingress/egress times for cities located across the continent. An especially interesting region to catch the event lies along the northern graze line across the sparsely populated Cape York peninsula, just north of Cairns.

The northern grazeline for the February 11th occultation of Regulus by the Moon. Graphic by author.

The Moon occults Aldebaran and then Regulus six days later during every lunation in 2017. This is occultation number three in a cycle of 19 running from December 18, 2016 to April 24, 2018. The Moon occults Regulus 214 times in the 21st century, and Regulus is currently the closest bright star to the ecliptic plane, just 27′ away.

We’ve also got a very special event just under 14 hours prior, as a penumbral lunar eclipse occurs, visible on all continents… except Australia. Mid-eclipse occurs at 00:45 Universal Time (UT, Saturday morning on February 11^th), or 7:45 PM Eastern Standard Time (EST) on the evening of Friday, February 10th, when observers may note a dusky shading on the northern limb of the Moon as the Moon just misses passing through the dark edge of the Earth’s inner umbral shadow. Regulus will sit less than seven degrees off of the lunar limb at mid-eclipse Friday night.

How often does an eclipsed Moon occult a bright star? Well, stick around until over four centuries from now on February 22nd, 2445, and observers based around the Indian Ocean region can watch just such an event, as the eclipsed Moon also occults Regulus. Let’s see, I should have my consciousness downloaded into my second android body by then…

A graphic study of the simultaneous lunar eclipse and occultation of Regulus in 2445. Credit: NASA/GSFC/Fred Espenak/Occult 4.2/Stellarium.

We’ll be streaming the Friday night eclipse live from Astroguyz HQ here in Spring Hill, Florida starting at 7:30 PM EST/00:30 UT, wifi-willing. Astronomer Gianluca Masi of the Virtual Telescope Project will also carry the eclipse live starting at 22:15 UT on the night of Friday, February 10th.

This eclipse also marks the start of eclipse season one of two, which climaxes with an annular eclipse crossing southern Africa and South America on February 26th. The second and final eclipse season of 2017 starts with a partial lunar eclipse on August 7th, which sets us up for the Great American Eclipse crossing the United States from coast to coast on August 21st, 2017.

A lunar occultation of Regulus also provides a shot at a unique scientific opportunity. Spectroscopic measurements suggest that the primary main sequence star possesses a small white dwarf companion, a partner which has never been directly observed. This unseen white dwarf may – depending on the unknown orientation of its orbit – make a brief appearance during ingress or egress for a fleeting split second, when the dark limb of the Moon has covered dazzling Regulus. High speed video might just nab a double step occlusion, as the white dwarf companion is probably about 10,000 times fainter than Regulus at magnitude +11 at the very brightest. Regulus is located 79 light years distant.

Our best results for capturing an occultation of a star or planet by the Moon have always been with a video camera aimed straight through our 8” Schmidt-Cassegrain telescope. The trick is always to keep the star visible in the frame near the brilliant Full Moon. Cropping the Moon out of the field as much as possible can help somewhat. Set up early, to work the bugs out of focusing, alignment, etc. We also run WWV radio in the background for an audible time hack on the video.

The January 15th, 2017 occultation of Regulus by the Moon. Image credit and copyright: Lucca Ruggiero.

The best occultation of Regulus by the Moon for North America in 2017 occurs on October 15th, when the Moon is at waning crescent phase. Unfortunately, the occultation of Regulus by asteroid 163 Erigone back in 2014 was clouded out, though the planet Venus occults the star on October 1^st, 2044. Let’s see, by then I’ll be…

Comets and eclipses and occultations, oh my. It’s a busy weekend for observational astronomy, for sure. Consider it an early Valentine’s Day weekend gift from the Universe.

Webcasting the eclipse or the occultation this weekend? Let us know, and send those images of either event to Universe Today’s Flickr forum.

Read about eclipses, occultations and more tales of astronomy in our yearly guide 101 Astronomical Events For 2017, free from Universe Today.

February 2, 2017February 3, 2017 by David Dickinson

Superbowl Smackdown: Watch the Moon Occult Aldebaran on Sunday

Daytime Aldebaran — Can you see it? Dave Walker accidentally (!) caught Aldebaran near the daytime Moon on October 19th, 2016. Image credit and copyright: Dave Walker

Author’s note: This Superbowl Sunday event and 101 more like it are featured in our latest free e-book, 101 Astronomical Events for 2017, out now from Universe Today.

Sure, this Superbowl Sunday brings with it the promise of sacks, fumbles and tackles… but have you ever seen the Moon run down a star in the end zone? Just such an event, referred to as an occultation, happens this weekend for folks living around the Mediterranean and — just maybe for some sharp-eyed, telescope-owning observers based around the Caribbean region — this coming weekend.

Update: be sure to watch this Sunday’s occultation of Aldebaran by the Moon courtesy of Gianluca Masi and the Virtual Telescope Project live starting at 22:00 UT/5:00 PM EST:

Live starting at 22:00 UT. Credit: The Virtual Telescope Project

We’re talking about Sunday’s occultation of the bright star Aldebaran by the 64% illuminated waxing gibbous Moon. This is the 2^nd occultation of Aldebaran by the Moon for 2017 and the 28th of the current ongoing cycle of 49 spanning from January 29^th, 2015 to September 3^rd, 2018. The Moon actually occults Aldebaran and Regulus once for every lunation in 2017. We won’t have another year featuring the occultations of two +1^st magnitude stars (Spica and Antares) again until 2024.

Occultation footprint — The footprint for the February 5th occultation of Aldebaran by the Moon. The broken lines show where the occultation occurs during daytime, and the solid lines denote where the occultation occurs under dark skies. Image credit: occult 4.2.

The event occurs under dark skies for observers based around the Mediterranean and under daytime afternoon skies for folks in central America, the Caribbean, northern South America and the Florida peninsula, including Astroguyz HQ based in Spring Hill, just north of the Tampa Bay area. We’ve managed to spy Aldebaran near the daytime Moon while the Sun was still above the horizon using binocs, and can attest that the +1st magnitude star is indeed visible, if you know exactly where to look for it.

Note that, like solar eclipses belonging to the same saros cycle, occultations of Aldebaran in the ongoing cycle drift north and westward from one to the next, to the tune of about 120 degrees longitude. Though most of North America sits this one out, we do get a front row seat for next lunation’s occultation of Aldebaran on the evening of March 4/5th. The next one is the best bright star occultation of Aldebaran by the Moon for North America in 2017. And be sure to check out the Moon this Sunday evening after the big game, and note Aldebaran hanging just off of its bright limb.

Moon motion — No, the wind is not shaking the ‘scope… Sharin Ahmad chronicled the motion of the Moon past Aldebaran from Kuala Lumpur, Malaysia last month. Image credit and copyright: Shahrin Ahmad (@shahgazer)

The ref will have a close call to make for this one. The northern grazeline in Florida might make this an especially interesting event to watch, though it’ll be challenge, as the occultation occurs in the afternoon under daylight skies. This crosses right along near the cities of Jacksonville and Gainsville. Clear, deep blue high contrast skies are key, and we’ll be watching from Astroguyz HQ north of Tampa Bay during this event.

The northern grazeline across the Florida peninsula for Sunday’s ‘big game’. Credit: Dave Dickinson.

Here are some key times from the occultation zone (noted in Universal Time):

Tampa, Florida

Ingress: 20:08 UT/Moon altitude: 23 degrees

Egress: 20:34 UT/Moon altitude: 29 degrees

Bogota, Columbia

Ingress: 19:34 UT/ Moon Altitude: 49 degrees

Egress: 20:29 UT/ Moon altitude: 31 degrees

The view from Jimena de la Frontera Spain just before the occultation. Credit: Stellarium.

Rome, Italy

Ingress: 20:21 UT/Moon altitude: 37 degrees

Egress: 23:12 UT/ Moon altitude: 28 degrees

Tel Aviv, Israel

Ingress: 22:39 UT/Moon altitude: 16 degrees

Egress: 23:29 UT/Moon altitude: 5 degrees

Casablanca, Morocco

Ingress: 21:49 UT/ Moon altitude: 61 degrees

Egress: 23:07 UT/ Moon altitude: 45 degrees

Note that this occultation spans five continents, a truly worldwide event. The International Occultation Timing Association (IOTA) maintains a page with an extensive list of times for cities worldwide. Note that when the Moon tackles Aldebaran, its also crossing the scrimmage line of the Hyades open cluster, so expect numerous occultations of fainter stars worldwide as well.

Aldebaran is the brightest star along the Moon’s path in our current epoch, along with runner-ups Spica, Regulus and Antares. Though Aldebaran is 1.5 times the mass of our Sun, it’s also 65 light years away, and only appears 20 milliarcseconds (mas) in size, about the equivalent of a 40 meter diameter crater from the distance of the Moon. Still, you might just notice a brief pause as Aldebaran fades then winks out on the dark limb of the Moon, a tiny hitch betraying its diminutive angular size.

And the clockwork gears of that biggest game of all, the Universe, grind on. Don’t miss this first big ticket astronomical event for February 2017, coming to a sky above you. Next up, we’ll watching out for another bright star occultation, two eclipses, and the close passage of a comet near the Earth.

Stay tuned!