A Partial Solar Eclipse and the Perseids Round Out August

A partially eclipsed Sun rising over the Vehicle Assembly Building along the Florida Space Coast. Credit: Dave Dickinson
A partial solar eclipse rising over the Vehicle Assembly Building along the Florida Space Coast. Credit: Dave Dickinson

How about that Total Lunar Eclipse this past July 13th? It has been a busy year for astronomy for sure, with two total lunar eclipses, a comet fading out from an unexpected burst of glory, and Saturn, Jupiter and Mars reaching opposition in quick succession.

Now, watch for a rare event this weekend, with the final eclipse for 2018 coming up on Saturday, August 11th, with a partial solar eclipse spanning northern Europe and the Arctic.

Circumstances for the August 11th, 2018 partial solar eclipse. Credit: NASA/GSFC/Fred Espenak

What’s so unique about this eclipse? Well, not only is it the last one for 2018, but it’s part of three eclipses in the second eclipse season of the year. Most seasons only feature two eclipses (one lunar and one solar) but every few years or so, it is possible to have a season with three: either lunar-solar-lunar (such as occurred in 2013) or solar-lunar-solar.

This is only possible when the middle eclipse occurs very near ascending or descending node along the ecliptic. The nodes are where the path of the Moon, inclined 5.1 degrees relative to the ecliptic plane intersect it—when these nodes are occupied by an alignment of the Earth, Sun and Moon (known as a syzygy, a fine word in Scrabble to land on a triple word score, though you’ll need a blank tile for the third ‘y’) a solar or lunar eclipse occurs. For an eclipse triple play, the middle eclipse needs to happen very near a node crossing, producing a fairly long eclipse. That’s exactly what happened on July 28th, when the Moon crossed through descending node just over an hour after crossing out of the Earth’s umbral shadow after the longest lunar eclipse for the 21st century.

This also leaves the Moon close enough to the opposite ascending node two weeks post and prior to July 28th on July 13th and August 11th to just nick the Sun for a partial solar eclipse, one over the Antarctic and one over the Arctic.

The animated path for the August 11th partial solar eclipse. Credit: A.T. Sinclair/NASA/GSFC

Eclipse Circumstances

Saturday’s partial eclipse touches down over the eastern coast of Canada at sunrise. From there, it sweeps eastward over Greenland, Iceland and the North Atlantic, with the Moon’s penumbra just grazing the northern United Kingdom before crossing over Scandinavia. Then, the shadow crosses over Asia, with a photogenic partial solar eclipse wrapping up at sunset over eastern China, the Koreas and the Russian far east.

Note that this eclipse is also a relative newcomer for its particular saros 155, as it is member 6 of a series of 71 eclipses. The saros just began less than a century ago on June 17th, 1928, and won’t produce its first total solar eclipse until September 12th, 2072 AD.

As of this writing, we’ve yet to see evidence of anyone carrying the eclipse live, though we’ll note it here if any webcast(s) surface.

When is the next one? Well, the next partial solar eclipse is on January 6th 2019, and the next total solar eclipse occurs on July 2nd, 2019.

Enter the Perseids

This weekend’s eclipse at New Moon also sets us up for a fine display of the Perseid meteors for 2018. This year, the Perseids are expected to peak on the morning of August 12th and August 13th. Watch for a zenithal hourly rate of 100 meteors per hour at the peak. A dependable annual favorite, the Perseids are debris remnants of period comet 109/P Swift-Tuttle.

The live webcast for the 2018 Perseid meteor shower. Credit: The Virtual Telescope Project.

Astronomer Gianluca Masi and the Virtual Telescope Project 2.0 will host a live webcast for the 2018 Perseids on August 12th starting at 20:30 UT.

Don’t miss the astronomical action worldwide this weekend, either live or online.

Top 2018 Astronomy Events

The final occultation of the bright star Aldebaran by the Moon for 2017. Dave Dickinson
2018 Astronomy – 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 +10th 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 15th, 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 31st and a 60% partial solar eclipse for the southern tip of South America on February 15.

Venus reaches superior conjunction on January 9th, 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!

This Weekend: The Moon Photobombs ‘Planet-palooza’ at Dawn

The planetary lineup at dawn from September 12th. Image credit and copyright: Alan Dyer (AmazingSky.com)
September planets
The planetary lineup at dawn (minus the Moon) from September 12th. Image credit and copyright: Alan Dyer (AmazingSky.com).

Following the Moon and wondering where are the fleeting inner solar system planets are this month?

While Jupiter and Saturn sink into the dusk on the far side of the Sun this month, the real action transpires in the dawn sky in mid-September, with a complex set of early morning conjunctions, groupings and occultations.

First, let’s set the stage for the planetary drama. Mercury just passed greatest elongation 18 degrees west of the Sun on September 12th.

The action warms up with a great pre-show on the morning of Saturday, September 16th, when the closest conjunction of two naked eye planets for 2017 occurs, as Mercury passes just 3′ north of Mars. The conjunction occurs at 16:00 UT, favoring the western Pacific region in the dawn hours. The pair is just 17 degrees from the Sun. As mentioned previously, this is the closest conjunction of two naked eye planets in 2017, so close the two will seem to merge to the naked eye and make a nice split with binoculars. This is also one of the first good chances to spy Mars for this apparition, fresh off of its solar conjunction on July 27th, 2017. Mars is now headed towards a favorable opposition next summer on July 27th, 2018, one that’s very nearly as favorable as the historic grand opposition of 2003.

Mars shines at magnitude +1.8 on Saturday morning with a disk 3.6” across, while Mercury shines at magnitude +0.05 with a 64% illuminated disk 6.4” across. Mars is actually 389 million km (2.6 AU) from the Earth this weekend, while Mercury is 158 million km (1.058 AU) distant.

The view looking east on the morning of September 17th. Stellarium

Follow that planet, as Mars also makes a close (12′) pass near Venus on October 5th. At the eyepiece, Venus will look like it has a large moon, just like the Earth!

Think this pass is close? Stick around until August 10th, 2079 and you can actually see Mercury occult (pass in front of) Mars… our cyborg body should be ready to download our consciousness into by then.

Mark your calendars: Mercury occults Mars in 2079. Stellarium

The waning crescent Moon joins the view on Monday, September 18th, making a spectacular series of passes worldwide as it threads its way through the stellar-planetary lineup. Occultations involving the waning Moon are never as spectacular as those involving the waxing Moon, as the bright limb of the Moon leads the way for ingress instead of the dark edge. The best sight to behold will be the sudden reappearance of the planet of star (egress) from behind the waning crescent Moon’s dark limb.

The Moon on Sept 18th
The sky looking east on the morning of September 18th. Stellarium

First up is an occultation of Venus on September 18th centered on 00:55 UT. Unfortunately, this favors the eastern Indian Ocean at dawn, though viewers in Australia and New Zealand can watch the occultation under post dawn daytime skies. The pair is 22 degrees west of the Sun, and the Moon is two days from New during the event. Shining at magnitude -4, it’s actually pretty easy to pick out Venus near the crescent Moon in the daytime. Observers worldwide should give this a try on the 18th as well… folks are always amazed when I show them Venus in the daytime. The last time the Moon occulted Venus was September 3rd, 2016 and the two won’t cross paths again until February 16th, 2018.

The footprint of the occultation of Venus by the Moon. Occult 4.2

Next up, the Moon occults the +1.4 magnitude star Regulus on the 18th at 4:56 UT. Observers across north-central Africa are best placed to observe this event. This is the 11th occultation of Regulus by the Moon in a series of 19, spanning December 2016 to April 2018.

The occultation of Regulus by the Moon. Occult 4.2

The brightest star in the constellation Leo, Regulus is actually 79 light years distant.

Next up, the dwindling waning crescent Moon meets the Red Planet Mars and occults it for the western Pacific at 19:42 UT. Shining at magnitude +1.8 low in the dawn sky, Mars is currently only 3.6” in size, a far cry from its magnificent apparition next summer when it will appear 24.3” in size… very nearly the largest it can appear from the Earth.

The occultation of Mars by the Moon. Occult 4.2

And finally, the slim 2% illuminated Moon will occult the planet Mercury on September 18th centered on 23:21 UT.

The occultation of Mercury by the Moon. Occult 4.2

Mercury occultations are tough, as the planet never strays very far from the Sun. The only known capture I’ve seen was out of Japan back in 2013:

This week’s occultation favors southeast Asia at dawn, and the pair is only 16 degrees west of the Sun. Mercury is gibbous 74% illuminated and 6” in size during the difficult occultation.

We just miss having a simultaneous “multiple occultation” this week. The Moon moves at the span of its half a degree size about once every hour with respect to the starry background, meaning an occultation must occur about 60 minutes apart for the Moon to cover two planets or a planet and a bright star at the same time, a rare once in a lifetime event indeed. The last time this transpired, the Moon covered Venus and Jupiter simultaneously for observers on Ascension Island on the morning of April 23rd 1998.

When is the next time this will occur? We’re crunching the numbers as we speak… watch this space!

Looking into next week, the Moon reaches New phase on Wednesday, September 20th at 5:31 UT/1:31 AM EDT, marking the start of lunation 1172. Can you spy the razor thin Moon Wednesday evening low to the west? Sighting opportunities improve on Thursday night.

Don’t miss this weekend’s dance of the planets in the early dawn sky, a great reason to rise early.

Read about conjunctions, occultations, tales of astronomy and more in our free guide to the Top 101 Astronomical Events for 2017 from Universe Today.