Observing Archives

August 29, 2013December 23, 2015 by David Dickinson

Curiosity Spies a Martian Annular Eclipse

Phobos transiting the Sun as seen by the Mars Curiosity rover on Sol 369. (Credit: NASA/JPL-Caltech/Malin Space Science Systems/Texas A & M University).

It’s always interesting to consider the astronomical goings-on that occur under alien skies.

On August 17^th, Curiosity wowed us once again, catching the above sequence of images of the Martian moon Phobos transiting the Sun.

Such phenomena have been captured by the Curiosity, Opportunity and Spirit rovers before, as the twin Martian moons of Deimos & Phobos cross the face of the Sun. But these recent images taken by Curiosity’s right Mastcam pair are some of the sharpest yet.

Orbiting only an average of 6,000 kilometres above the surface of Mars, Phobos is the closest to its primary of any moon in the solar system. It appears about 11 arc minutes in size when directly overhead, about 3 times smaller than our own Moon does from the Earth.

“This event occurred near noon at Curiosity’s location, which put Phobos at its closest point to the rover, appearing larger against the Sun than it would at other times of the day,” Said co-investigator Mark Lemmon of Texas A&M University in a recent press release. “This is the closest to a total eclipse that you can have on Mars.”

Phobos is 40% more distant from an observer standing on the surface of Mars when it is rising above the local horizon than when it is overhead. The Sun is about 20’ arc minutes across as seen from Mars, 66% of its diameter as seen from the Earth.

The sequence above spans only six seconds in duration. You would easily note the apparent motion of Phobos as it drifted by! Also, since Phobos orbits Mars once every 7.7 hours, it actually rises in the west and sets in the east. The Martian day is over three times this span, at 24.6 hours long. Deimos has a more sedate orbit of 30.4 hours in duration.

The twin Moons of Deimos and Phobos were discovered this month back during the opposition of 1877 by Asaph Hall using the United States Naval Observatory’s newly installed 65 centimetre refractor. The moons are just within the grasp of eagle-eyed amateurs near opposition. You’ve got another opportunity to cross these elusive moons off of your life list coming up in the Spring of 2014.

image_preview — The telescope that was used to discover the moons of Mars. (Credit: The United States Naval Observatory).

It’s especially captivating that you can make out the irregular “potato shape” of Phobos in the above images. With low orbital inclinations relative to the equator of Mars of 1.1 degrees for Phobos and 0.9 degrees for Deimos, solar transits are not an uncommon occurrence, transpiring somewhere along the Martian surface with every orbit. If Phobos were twice as close to Mars, it would completely cover the Sun in a total solar eclipse. What Curiosity gave us this month is more akin to an annular eclipse with a ragged central shadow. An annular eclipse occurs when the occulting body is too distant to cover the Sun, leaving a bright, shining ring, or annulus.

On the Earth, we live in an epoch where annular eclipses are slightly more common than total solar eclipses, as the Moon currently recedes from us to the tune of 3.8 centimetres a year. About 1.4 billion years from now, the last total solar eclipse will be seen from the Earth. The next purely annular eclipse as seen from Earth occurs on April 29^th, 2014 across Australia and the Antarctic.

Conversely, Phobos is in a “death spiral,” meaning that it will one day crash into Mars about 30-50 million years from now. This also means that in about half that time, it will also be large enough to visually cover the Sun when crossing it near local noon. For a brief time far in the future, jagged total solar eclipses will be visible from Mars. That is, if the gravitational field of Mars doesn’t rip Phobos apart before that!

But beyond just aesthetics, these observations serve a scientific purpose as well. These phenomena serve to refine our understanding of the precise positions of Phobos and Deimos and their orbits.

“This one is by far the most detailed image of any Martian lunar transit ever taken, and it is especially useful because it is annular. It was taken closer to the Sun’s center than predicted, so we learned something.”

The track during the August 17^th observation was off by about 2-3 kilometres, allowing for a surprise central transit of the Sun as seen from Curiosity’s location.

Both Phobos and Deimos are captured asteroids only 22.2 & 12.6 kilometres across, respectively. Both must be subject to occasional bombardment from meteorites blasted off of the surface of nearby Mars. Sample return missions to Phobos have been proposed. Russia’s ill-fated Phobos-Grunt mission would’ve done just that.

Will humans ever stand on the surface of the Red Planet and witness an annular eclipse of the Sun by Phobos in person? Well, if we make it there by November 10^th, 2084, observers placed on the slopes of Elysium Mons will witness just such an event… with a rare transit of Earth and the Moon to boot!:

Arthur C. Clarke wrote of a transit of Earth from Mars that occurred in 1984 in his science fiction short story Transit of Earth.

Hey, I’m marking my calendar for the 2084 event… assuming, of course, my android body is ready by then!

August 27, 2013December 23, 2015 by David Dickinson

The Cyber-Myth That Just Won’t Die: See Mars as Large as a Full Moon!!!

We've been here before... (All article images and bad photoshopping courtesy of the author).

It’s hard to believe that it’s been with us for a decade now.

Ten years ago this week, the planet Mars reached made an exceptionally close pass of the planet Earth. This occurred on August 27^th, 2003, when Mars was only 56 million kilometres from our fair planet and shined at magnitude -2.9.

Such an event is known as opposition. This occurs when a planet with an orbit exterior to our own reaches a point opposite to the Sun in the sky, and rises as the Sun sets. In the case of Mars, this occurs about every 2.13 years.

But another myth arose in 2003, one that now makes its return every August, whether Mars does or not.You’ve no doubt gotten the chain mail from a well-meaning friend/relative/coworker back in the bygone days a decade ago, back before the advent social media when spam was still sorta hip. “Mars to appear as large as the Full Moon!!!” it breathlessly exclaimed. “A once in a lifetime event!!!”

Though a little over the top, the original version did at least explain (towards the end) that Mars would indeed look glorious on the night of August 27^th, 2003 … through a telescope.

Mars during the historic opposition season of '03. — Mars during the historic opposition season of ’03.

But never let facts get in the way of a good internet rumor. Though Mars didn’t reach opposition again until November 7^th 2005, the “Mars Hoax” email soon began to make its rounds every August.

Co-workers and friends continued to hit send. Spam folder filled up. Science news bloggers debunked, and later recycled posts on the silliness of it all.

Now, a decade later, the Mars Hoax seems to have successfully made the transition over to social media and found new life on Facebook.

Mars as seen during a close conjunction with the Moon on July 17th, 2003. Mars was 20 arc seconds in size at the time leading up to the August 2003 opposition. — How Mars really appears next to the Moon: Mars as seen during a close conjunction with the Moon on July 17th, 2003. Mars was 20 arc seconds in size at the time, leading up to the August 2003 opposition. Image courtesy of Rick Stankiewicz, used with permission.

No one knows where the Mars Hoax meme goes to weather the lean months, only to return complete with all caps and even more exclamation points each and every August. Is it the just a product of the never ending quest for the almighty SEO? Are we now destined to recycle and relive astronomical events in cyber-land annually, even if they’re imaginary?

Perhaps, if anything there’s a social psychology study somewhere in there, begging the question of why such a meme as the Mars Hoax endures… Will it attain a mythos akin to the many variations of a “Blue Moon,” decades from now, with historians debating where the cultural thread came from?

Here are the facts:

-Mars reaches opposition about every 2.13 Earth years.

-Due to its eccentric orbit, Mars can vary from about 56 million to over 101 million kilometres from the Earth during oppositions.

-Therefore, Mars can appear visually from 13.8” to 25.1” arc seconds in size.

-But that’s still tiny, as the Moon appears about 30’ across as seen from the Earth. You could ring the local horizon with about 720 Full Moons end-to-end, and place 71 “maxed out Mars’s” with room to spare across each one of them!

-And although the Full Moon looks huge, you can cover it up with a dime held at arm’s length…. Try it sometime, and amaze your email sending/Facebook sharing friends!

–Important: Mars NEVER gets large enough to look like anything other than a star-like point to the naked eye.

Reality check... how Mars really appears compared to the Moon as seen during a close conjunction in 2012. — Reality check… how Mars actually appears compared to the Moon as seen during a close conjunction in 2012.

-And finally, and this is the point that should be getting placed in all caps on Facebook, to the tune of thousands of likes… MARS ISN’T EVEN ANYWHERE NEAR OPPOSITION in August 2013!!! Mars is currently low in the dawn sky in the constellation Cancer on the other side of the Sun. Mars won’t be reaching opposition until April 8th, 2014, when it will reach magnitude -1.4 and an apparent size of 15.2” across.

Still, like zombies from the grave, this myth just won’t die. In the public’s eye, Mars now shines “As big as” (or bigger, depending on the bad hyperbole used) as Full Moon now every August. Friends and relatives hit send, (or these days, “share” or “retweet”) observatories and planetariums get queries, astronomers shake their heads, and science bloggers dust off their debunking posts for another round. Hey, at least it’s not 2012, and we don’t have to keep remembering how many “baktuns are in a piktun…”

What’s a well meaning purveyor & promoter science to do?

Feed those hungry brains a dose of reality.

There are real things, fascinating things about Mars afoot. We’re exploring the Red Planet via Mars Curiosity, an SUV-sized, nuclear powered rover equipped with a laser. The opposition coming up next year means that the once every 2+ year launch window to journey to Mars is soon opening. This time around, the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission and, just perhaps, India’s pioneering Mars Orbiter Mission may make the trip. Launching from Cape Canaveral on November 18th, MAVEN seeks to answer the questions of what the climate and characteristics of Mars were like in the past by probing its tenuous modern day atmosphere.

The circumstances for opositions of Mars from — The circumstances for the oppositions of Mars from 2001 to 2029.

And as opposition approaches in 2014, Mars will again present a fine target for small telescopes. As a matter of fact, Mars will pass two intriguing celestial objects next month, passing in front of the Beehive cluster and — perhaps — a brightening Comet ISON. More to come on that later this week!

And it’s worth noting that after a series of bad oppositions in 2010 and 2012, oppositions in 2014 and 2016 are trending towards more favorable. In fact, the Mars opposition of July 27^th, 2018 will be nearly as good as the 2003 approach, with Mars appearing 24.1” across. Not nearly as “large as a Full Moon” by a long shot, but hey, a great star party target.

Will the Mars Hoax email enjoy a resurgence on Facebook, Twitter or whatever is in vogue then? Stay tuned!

August 26, 2013December 23, 2015 by Nancy Atkinson

Timelapse: Noctilucent Clouds and Aurora Together in the Sky

Just in case you haven’t seen this bit of awesome yet: Noctilucent clouds and aurora showed up together in skies over Scotland on the night of August 4/5, 2013. Maciej Winiarczyk from the Caithness Astronomy Group was on hand to capture it.

Enjoy!

August 21, 2013December 23, 2015 by Bob King

Geek Out! How to Build Your Own Nova Delphini Light Curve

Nova Delphini (center) continues to shine brightly enough to see in binoculars and with the naked eye once the moon's out of the sky. While we still don't know its distance, novae like this one are typically between 1,000 to 1,500 light years away. Credit: John Chumack

And now for something to appeal to your inner geek. Or, if you’re like me, your outer geek. Many of you have been watching the new nova in Delphinus with the naked eye and binoculars since it burst onto the scene early Aug. 14. In a moment I’ll show how to turn your observations into a cool representation of the nova’s behavior over time.

Updated Nova Delphini 2013 chart using the latest visual magnitudes from the AAVSO showing stars around the nova to magnitude 7.1. Stellarium — *Updated Nova Delphini 2013 chart using the latest visual magnitudes from the AAVSO showing stars around the nova to magnitude 7.1. Click for larger version. Stellarium*

Where I live in northern Minnesota, we’ve had a lucky run of clear nights since the outburst began. Each night I’ve gone out with my 8×40 binoculars and star chart to estimate the nova’s brightness. The procedure is easy and straightforward. You find comparison stars near the nova with known magnitudes, then select one a little brighter and one a little fainter and interpolate between the two to arrive at the nova’s magnitude.

Estimating a star's magnitude by creating a sliding scale in your mind's eye between a stars that bracket the nova in brightness. Illustration: Bob King — *Estimating a star’s magnitude by creating a sliding scale in your mind’s eye between stars that bracket the nova in brightness. Illustration: Bob King*

For example, if the nova’s brightness lies halfway between the magnitude 4.8 and 5.7 stars it’s about magnitude 5.3. The next night you might notice it’s not exactly halfway but a tad brighter or closer to the 4.8 star. Then you’d measure 5.2. Remember that the smaller the number, the brighter the object. I’ve found that defocusing the stars into disks makes it a bit easier to estimate these differences.

In time, you’ll come up with a list of magnitudes or brightness estimates for Nova Delphini. Here’s mine to date:

* Aug. 14: 5.8
* Aug. 15: 4.9
* Aug. 16: 5.0
* Aug. 17: 5.0
* Aug. 18: 5.0
* Aug. 19: 5.2
* Aug. 20: 5.5

Template you can use to plot your own estimates of Nova Delphini 2013's night by night brightness through Sept. 11. Click for larger version. — *Template you can use to plot your own estimates of Nova Delphini 2013’s night by night brightness through Sept. 11. Click for larger version.*

So far just numbers, but there’s a way to turn this into a satisfying visual picture of the nova’s long-term behavior. Graph it! That’s what astronomers do, and they call it a light curve.

I dug around and came up with this very basic template. The horizontal or x-axis measures time in days, the vertical or y-axis plots the nova’s brightness measured in magnitudes. You can either right-click and save the image above or grab the higher-res version HERE.

*I plotted my own brightness estimates of the nova using Photoshop Elements. You can do it on computer or with paper and pencil.*

Next, print out a copy and lay in your data points with pencil and ruler the old-fashioned way or use an imaging program like Photoshop or Paint to do the same on the computer. I use a very basic version of Photoshop Elements to plot my observations. Once your observations are marked, connect them to build your light curve.

*Connecting the dots, we can start to see how the nova behaves over time. The sudden jump from obscurity as well as the brief plateau before fading are obvious.*

Right away you’ll notice a few interesting things. The nova shot up from approximately 17th magnitude on Aug. 13 to 6.8 on Aug. 14 – a leap of more than 10 magnitudes, which translates to a nearly 10,000 fold increase in brightness.

I wasn’t able to see the Nova Del top out at around 4.4 magnitude – that happened when I was asleep the next morning – but I did catch it at 4.9. The next few days the nova hits a plateau followed by what appears for the moment like a steady decline in brightness. Will it rocket back up or continue to fade? That’s for you and your binoculars to find out the next clear night.

Official AAVSO light curve to date for Nova Delphini 2013 created using their light curve generator. The plot includes observations from many observers. Copyright: AAVSO — *AAVSO light curve to date for Nova Delphini 2013 created using their light curve generator. The plot includes observations from many observers. Copyright: AAVSO*

If you’d like to take the next step and contribute your observations for scientific use, head over to the AAVSO (American Assn. of Variable Star Observers) and become a member. Even if you don’t sign up, access to data, charts and light curves of novae and other variable stars is completely free.

*Nova Sagittarii 2012 light curve. Notice the occasional plateaus as well as bumps in brightness as it faded back to minimum light. Credit: NASA*

I get a kick out of comparing my basic light curves with those created with thousands of observations contributed by hundreds of observers. The basic AAVSO curve looks all scrunched up for the moment because their time scale (x-axis) is much longer term than in my simple example. But guess what? You can change the scale using their light curve generator and open up the view a little more as I did in the curve above.

*Light curve of V2467 Cygni, a nova that appeared in Cygnus in 2007. Credit: AAVSO*

Here are a couple other typical novae light curves. By the time you’re done looking at the examples here as well as creating your own, you’ll gain a familiarity that may surprise you. Not only will be able to interpret trends in Nova Delphini’s brightness, but you’ll better understand the behavior of other variable stars at a glance. It’s as easy as connecting the dots.

August 19, 2013December 23, 2015 by David Dickinson

How to See Planet Neptune: Our Guide to Its 2013 Opposition

Neptune and its large moon Triton as seen by Voyager 2 on August 28th, 1989. (Credit: NASA).

If you do your own stargazing or participate in our Sunday night Virtual Star Parties, you’ve probably noticed we’re starting to lose planetary targets in the night-time sky. August and September of this year sees Venus and Saturn to the west at dusk, with the planets Mars and Jupiter adorning the eastern dawn sky just hours before sunrise.

That means there is now a good span of the night that none of the classic naked eye planets are above the horizon. But the good news is, with a little persistence, YOU can spy the outermost planet in our solar system in the coming weeks: the elusive Neptune. (Sorry, Pluto!)

A wide field view of Aquarius with Neptune's present position in late August/early September. (Created by the author i Stellarium). — A wide field view of Aquarius, with Neptune’s present position marked for late August/early September. (Created by the author in Stellarium; click on all star charts to enlarge).

The planet Neptune reaches opposition late this month in the constellation Aquarius on August 27^th at 01:00 UT (9:00 PM EDT on the 26^th). This means that it will rise to the east as the Sun sets to the west and will remain above the local horizon for the entire night.

If you’ve never caught sight of Neptune, these next few weeks are a great time to try. The Moon passes 6° north of the planet’s location this week on August 21^st, just 10 hours after reaching Full.

neptune on the night of Opposition using a 4.4 degree field of view. (Created by the author using Stellarium). — Neptune on the night of Opposition using a 4.4 degree field of view. Magnitudes for nearby guide stars are given in red. (Created by the author using Stellarium).

Shining at magnitude +7.8, Neptune is an easy catch with binoculars from a dark sky site. Even in a large telescope, Neptune appears as a tiny blue dot, almost looking like a dim planetary nebula that refuses to come to a sharp focus. Visually, Neptune is only 2.3” across at opposition; you could stack 782 Neptunes across the breadth of the Full Moon!

It’s sobering to think that Neptune only just returned in 2011 to the position of its original discovery back in 1846. The calculation of Neptune’s position by Urbain Le Verrier was a triumph for Newtonian mechanics, a moment where the science of astronomy began to demonstrate its predictive power.

Astronomers knew of the existence of an unseen body due to the perturbations of the planet Uranus, which was discovered surreptitiously by William Herschel 65 years earlier. Using Le Verrier’s calculations, Johann Galle and Heinrich d’Arrest spied the planet on the night of September 23^rd, 1846 using the Berlin observatory’s 9.6” refractor. Neptune was within a degree of the position described in Le Verrier’s prediction.

Neptune orbits the Sun once every 164.8 years, and comes back into opposition once every successive calendar year about 2 days later than the last. Those observers of yore were lucky that Neptune and Uranus experienced a close and undocumented conjunction in 1821; otherwise, Neptune may have gone undetected for a much longer span of time. And ironically, Galileo sketched the motion of Neptune near Jupiter in 1612 and 1613, but failed to identify it as a planet!

The motion of Neptune through Aquarius through late August into September. (Starry Night) — The motion of Neptune through Aquarius through late August into September. (Graphic created by author; courtesy of Starry Night Education).

Neptune descended through the ecliptic in 2003 and won’t reach its southernmost point below it until 2045. This month, Neptune lies 1.5 degrees west of the +4.8 magnitude double star Sigma Aquarii. Neptune passes less than 4’ from +7.5 magnitude star HIP 110439 on September 9^th as it continues towards eastern quadrature on November 24^th.

Corkscrew chart credit: — Corkscrew chart for the elongations of Triton through early September. (Courtesy of Ed Kotapish; created using NASA/PDS Rings Node).

Up for a challenge? Neptune also has a large moon named Triton that is just within range of a moderate (8” in aperture or larger) telescope. Shining at magnitude +13.4, Triton is similar in brightness to Pluto and is 100 times fainter than Neptune. In fact, there’s some thought that Pluto may turn out to be similar to Triton in appearance when New Horizons gets a close-up look at it in July 2015.

Triton never strays more than 18” from Neptune during eastern or western elongations. This presents the best time to cross the moon off your astronomical “life list…” experienced amateurs have even managed to image Triton!

The moons of Neptune and Uranus imaged by Credit: — The moons of Neptune and Uranus imaged by Rolf Wahl Olsen using a 10″ reflector and a ToUCam Pro. An amazing catch! (Credit & Copyright: Rolf Wahl Olsen, used with permission).

Triton was discovered just 17 days after Neptune by William Lassell using a 24” reflector. Triton is also an oddball among large moons in the solar system in that it’s in a retrograde orbit.

A second moon named Nereid was discovered by Gerard Kuiper in 1949. To date, Neptune has 14 moons, including the recently discovered S/2004 N1 unearthed in Hubble archival data.

Neptune & Triton on the night of August 21st as it reaches greatest elongation. (Starry Night). — Neptune & Triton on the night of August 21st as it reaches greatest elongation. (Graphic created by author. Courtesy of Starry Night Education).

To date, Voyager 2 is the only spacecraft that has studied Neptune and its moons up close. Voyager 2 conducted a flyby of the planet in 1989. A future mission to Neptune would face the same dilemma as New Horizons: a speedy journey would still take nearly a decade to complete, which would rule out an orbital insertion around the planet. (Darn you, orbital mechanics!) In fact, New Horizons just crosses the orbit of Neptune at a distance of 30 astronomical units from the Earth in 2014.

Neptune is about four light hours away from the Earth, a distance that varies less than 20 minutes in light travel time from solar conjunction to opposition. And while Neptune and Triton may not appear like much more than dim dots through a telescope, what you’re seeing is an ice giant 3.8 times the diameter of the Earth, with a large moon 78% the size of our own.

Make sure to cross Neptune and Triton off of your bucket list… and next month, we’ll be able to do the same for the upcoming opposition of Uranus!

August 16, 2013April 26, 2016 by Nancy Atkinson

Update on the Bright Nova Delphini 2013; Plus a Gallery of Images from our Readers

The bright new Nova Delphini 2013, as seen from Puerto Rico on August 16th, 03:13ut Credit: Efrain Morales/Jaicoa Observatory.

Since showing itself on August 14, 2013, a bright nova in the constellation Delphinus — now officially named Nova Delphini 2013 — has brightened even more. As of this writing, the nova is at magnitude 4.4 to 4.5, meaning that for the first time in years, there is a nova visible to the naked eye — if you have a dark enough sky. Even better, use binoculars or a telescope to see this “new star” in the sky.

The nova was discovered by Japanese amateur astronomer Koichi Itagak. When first spotted, it was at about magnitude 6, but has since brightened. Here’s the light curve of the nova from the AAVSO (American Association of Variable Star Observers) and they’ve also provided a binocular sequence chart, too.

How and where to see the new nova? Below is a great graphic showing exactly where to look in the sky. Additionally, we’ve got some great shots from Universe Today readers around the world who have managed to capture stunning shots of Nova Delpini 2013. You can see more graphics and more about the discovery of the nova on our original ‘breaking news’ article by Bob King.

If you aren’t able to see the nova for yourself, there are a few online observing options:

The Virtual Star Party team, led by UT’s publisher Fraser Cain, will try to get a view during the next VSP, at Sunday night on Google+ — usually at this time of year, about 10 pm EDT/0200 UTC on Monday mornings. If you’d like a notification for when it’s happening, make sure you subscribe to the Universe Today channel on YouTube.

The Virtual Telescope Project, based in Italy, will have an online observing session on August 19, 2013 at 20:00 UTC, and you can join astronomer Gianluca Masi at this link.

The Slooh online telescope had an observing session yesterday (which you can see here), and we’ll post an update if they plan any additional viewing sessions.

There’s no way to predict if the nova will remain bright for a few days more, and unfortunately the Moon is getting brighter and bigger in the sky (it will be full on August 20), so take the opportunity this weekend if you can to try and see the new nova.

Now, enjoy more images from Universe Today readers:

Nova Delphini 2013 from August 16, 2013 at 0846 UTC. Credit and copyright: Nick Rose.

The bright nova in Delphinus when it was at magnitude 6.1 on August 14, 2013, as see from Yellow Springs, Ohio USA. Credit and copyright: John Chumack/Galactic Images.

Proving that Nova Delphini 2013 is now a bright, naked-eye object, this fun image shows not only the nova, but the surrounding landscape in Sweden of the photographer, too. Credit and copyright: Göran Strand.

Nova Delphinii 2013 as seen on August 15, 2013. Credit and copyright: Andre van der Hoeven

Nova in Delphinus from Ottawa, Canada on August 14, 2013. 13 second exposure under heavy light pollution with Nikon D80. Credit and copyright: Andrew Symes

Image of Nova Delphini 2013, on 15 Aug. 2013, via the Virtual Telescope Project/Gianluca Masi.

Annotated image of Nova Delphini 2013, as seen from Hawaii. Credit and copyright: Bryanstew on Flickr.

Ralf Vandebergh shared this video he was able to capture on his 10-year-old hand-held video camera to “demonstration of the brightness of the nova and what is possible with even 10 year old technique from hand.”

August 14, 2013December 23, 2015 by Bob King

Bright New Nova In Delphinus — You can See it Tonight With Binoculars

The new nova is located in Delphinus alongside the familiar Summer Triangle outlined by Deneb, Vega and Altair. This may shows the sky looking high in the south for mid-northern latitudes around 10 p.m. local time in mid-August. The new object is ideally placed for viewing. Stellarium

Looking around for something new to see in your binoculars or telescope tonight? How about an object whose name literally means “new”. Japanese amateur astronomer Koichi Itagaki of Yamagata discovered an apparent nova or “new star” in the constellation Delphinus the Dolphin just today, August 14. He used a small 7-inch (.18-m) reflecting telescope and CCD camera to nab it. Let’s hope its mouthful of a temporary designation, PNVJ20233073+2046041, is soon changed to Nova Delphini 2013!

This map shows Delphinus and Sagitta, both of which are near the bright star Altair at the bottom of the Summer Triangle. You can star hop from the Delphinus "diamond" to the star 29 Vulpecula and from there to the nova or center your binoculars between Eta Sagittae and 29 Vul. Stellarium — This map shows Delphinus and Sagitta, both of which are near the bright star Altair at the bottom of the Summer Triangle. You can star hop from the top of Delphinus to the star 29 Vulpeculae and from there to the nova. Or you can point your binoculars midway between Eta Sagittae and 29 Vul. The “5.7 star” is magnitude 5.7. Stellarium

Several hours later it was confirmed as a new object shining at magnitude 6.8 just under the naked eye limit. This is bright especially considering that nothing was visible at the location down to a dim 13th magnitude only a day before discovery. How bright it will get is hard to know yet, but variable star observer Patrick Schmeer of Germany got his eyes on it this evening and estimated the new object at magnitude 6.0. That not only puts it within easy reach of all binoculars but right at the naked eye limit for observers under dark skies. Wow! Since it appears to have been discovered on day one of the outburst, my hunch is that it will brighten even further.

I opened up the view a little more here and made a reverse "black stars on white" for clarity. Stars are shown to 9th magnitude. Magnitudes shown for 4 stars near the nova. The nova's precise position is RA 20 h 23' 31", Dec. +20 deg. 46'. Created with Chris Marriott's SkyMap — Here’s a reverse “black stars on white” map some observers prefer for greater clarity. Stars are shown to 9th magnitude. Tycho visual magnitudes shown for 4 stars near the nova. The nova’s precise position is RA 20 h 23′ 31″, Dec. +20 deg. 46′. Created with Chris Marriott’s SkyMap

The only way to know is to go out for a look. I’ve prepared a couple charts you can use to help you find and follow our new guest. The charts show stars down to about 9th magnitude, the limit for 50mm binoculars under dark skies. The numbers on the chart are magnitudes (with decimals omitted, thus 80 = 8.0 magnitude) so you can approximate its brightness and follow the ups and downs of the star’s behavior in the coming nights.

Despite the name, a nova is not truly new but an explosion on a star otherwise too faint for anyone to have noticed. A nova occurs in a close binary star system, where a small but extremely dense and massive (for its size) white dwarf grabs hydrogen gas from its closely orbiting companion. After swirling about in a disk around the dwarf, it’s funneled down to the star’s 150,000 degree F surface where gravity compacts and heats the gas until it detonates like a bazillion thermonuclear bombs. Suddenly, a faint star that wasn’t on anyone’s radar vaults a dozen magnitudes to become a standout “new star”.

Model of a nova in the making. A white dwarf star pulls matter from its bloated red giant companion into a whirling disk. Material funnels to the surface where it later explodes. Credit: NASA/CXC/M. Weiss

Novae can rise in brightness from 7 to 16 magnitudes, the equivalent of 50,000 to 100,000 times brighter than the sun, in just a few days. Meanwhile the gas they expel in the blast travels away from the binary at up to 2,000 miles per second. This one big boom! Unlike a supernova explosion, the star survives, perhaps to “go nova” again someday.

Closer view yet showing a circle with a field of view of about 2 degrees. Stellarium — Closer view yet of the apparent nova showing a circle with a field of view of about 2 degrees. Stellarium

I’ll update with links to other charts in the coming day or two, so check back.

See info on the Remanzacco Observatory website about their followup images of the nova.

August 9, 2013April 26, 2016 by David Dickinson

A Challenging Series of Occultations of Spica by the Moon Coming to a Sky Near You

An occultation of the star Mu Geminorum (to the upper right off the dark limb of the Moon) Photo by author.

The first in a cycle of challenging occultations of the bright star Spica for northern hemisphere observers begins this coming Monday on August 12^th.

Watching a bright star or planet wink out on the dark limb of the Moon can be an amazing event to witness. It’s an abrupt “now you see it, now you don’t” event in a universe which often seems to move at an otherwise glacial pace. And if the event grazes the limb of the Moon, an observer may see a series of winks as the starlight streams through the lunar valleys.

Close companion stars have been discovered during occultations, and astronomers even used a series of occultations of radio source 3C 273 in 1962 to pin down the position of the first quasar.

An occultation occurs when one object passes in front of another as seen from the observer’s vantage point. The term has its hoary roots back in a time when astronomy was intertwined with its pseudoscience ancestor of astrology. Even today, I still get funny looks from non-astronomy friends when I use the term occultation, as if it just confirms their suspicions of the arcane arts that astronomers really practice in secret.

But back to reality-based science. At an apparent magnitude of +1.1, Spica is the 3rd brightest star that the Moon can occult along its five degree path above and below the plane of the ecliptic. It’s also one of only four stars brighter than +1.4 magnitude on the Moon’s path. The others are Antares (magnitude +1.0), Regulus (magnitude +1.4), and Aldebaran (magnitude +0.8). All of these are bright enough to be visible on the lunar limb through binoculars or a telescope in the daytime if conditions are favorable.

It’s interesting to note that this situation also changes over time due to the precession of the equinoxes. For example, the bright star Pollux was last occulted by the Moon in 117 BC, but cannot be covered by the Moon in our current epoch.

Spica is currently in the midst of a cycle of 21 occultations by our Moon. This cycle started in July 25^th, 2012 and will end in January 2014.

Spica is a B1 III-IV type star 10 times the mass of the Sun. At 260 light years distant, Spica is one of the closest candidates to the Earth along with Betelgeuse to go supernova. Now, THAT would make for an interesting occultation! Both are safely out of the ~100 light year distant “kill zone”.

What follows are the circumstances for the next four occultations of Spica by the Moon. The times are given for closest geocentric conjunction of the two objects. Actual times of disappearance and reappearance will vary depending on the observer’s location. Links are provided for each event which include more info.

Looking westward 30 minutes after sunset for North American viewers on the night of August 12th. (Created by the Author using Starry Night).

First up is the August 12^th occultation of Spica, which favors Central Asia and the Asian Far East. This will occur late in the afternoon sky around 09:00 UT and prior to sunset. The waxing crescent Moon will be six days past New phase. North American observers will see the Moon paired five degrees from Spica with Saturn to the upper left on the evening of August 12^th.

Next is the September 8^th daytime occultation of Spica for Europe, the Middle East and northern Africa around ~15UT. This will be a challenge, as the Moon will be a waxing crescent at only 3 days past New. Observers in the Middle East will have the best shot at this event, as the occultation occurs at dusk and before moonset. Note that the Moon also occults Venus six hours later for Argentina and Chile.

Looking to the east the morning of November 2nd for North American observers. (Created by the author using Stellarium).

After taking a break in October (the occultation of October 5 occurs only 23 hours after New and is unobservable), the Moon again occults Spica on November 2^nd for observers across Europe & Central Asia. This will be a difficult one, as the Moon will be only 20 hours from New and a hybrid solar eclipse that will cross the Atlantic and central Africa. It may be possible to lock on to the Moon and track it up into the daylight, just be sure to physically block the rising Sun behind a building or hill!

USNO — The occultation footprint of Spica by the Moon for November 29th, 2013. (Reproduced from the Astronomical Almanac online and produced by the U.S. Naval Observatory and H.M. Nautical Almanac Office).

Finally, the Moon will occult Spica for North American observers on November 29^th centered on 17:03 UT. This will place the event low in the nighttime sky for Alaskan observers. It’ll be a bit more of a challenge for Canadian and U.S. observers in the lower 48, as the Moon & Spica will be sandwiched between the Sun and the western horizon in the mid-day sky. As an added treat, comet C/2012 S1 ISON will reach perihelion on November 28th, just 20 hours prior and will be reaching peak brilliance very near the Sun.

And as an added bonus, the Moon will be occulting the +2.8 star Alpha Librae (Zubenelgenubi) on August 13^th for central South America.

All of these events are challenges, to be sure. Viewers worldwide will still catch a close night time pairing of the Moon and Spica on each pass. We’ve watched the daytime Moon occult Aldebaran with binoculars while stationed in Alaska back in the late 1990’s, and can attest that such a feat of visual athletics is indeed possible.

And speaking of which, the next bright star due for a series of occultations by the Moon is Aldebaran starting in 2015. After 2014, Spica won’t be occulted by the Moon again until 2024.

But wait, there’s more- the total eclipse of the Moon occurring on April 15^th 2014 occurs just 1.5 degrees from Spica, favoring North America. This is the next good lunar eclipse for North American observers, and one of the best “Moon-star-eclipse” conjunctions for this century. Hey, at least it’ll give U.S. observers something besides Tax Day to look forward to in mid-April. More to come in 2014!

August 3, 2013January 22, 2021 by David Dickinson

The 2013 Perseid Meteor Shower: An Observer’s Guide

The radiant for the Persieds, looking to the NE from latitide ~30N at around 2AM local. Created by the Author in Starry Night).

Get set for the meteoritic grand finale of summer.

Northern hemisphere summer that is. As we head into August, our gaze turns towards that “Old Faithful” of meteor showers, the Perseids. Though summer is mostly behind us now, “meteor shower season” is about to get underway in earnest.

Pronounced “Pur-SEE-ids,” this shower falls around the second week of August, just before school goes back in for most folks. This time of year also finds many the residents of the northern hemisphere out camping and away from light-polluted suburban skies.

This year also offers a special treat, as the Moon will be safely out of the sky during key observation times. The Moon reaches New phase on August 6^th at 5:51 PM EDT/ 9:51 Universal Time (UT) and will be a 32% illuminated waxing crescent around the anticipated peak for the Perseid meteors on August 12^th. And speaking of which, the Perseids are infamous for presenting a double-fisted twin peak in activity. This year, the first climax for the shower is predicted for around 13:00 UT on August 12^th, favoring Hawaii and the North American west coast, and the second peak is set to arrive 13 hours later at 02:00 UT, favoring Europe & Africa.

Nodal crossing for the Perseid stream and Earth’s orbit sits right around 18:00 to 21:00 UT on August 12^th for 2013. The shower derives its name from the constellation Perseus, and has a radiant located near Gamma Persei at right ascension 3 hours 4 minutes and a declination of +58 degrees. Atmospheric velocities for the Perseids are on the high end as meteor showers go, at 59km/sec.

Of course, like with any meteor shower, it’s worth starting to watch a few days prior to the peak date. Although meteor streams like the Perseids have been modeled and mapped over the years, there are still lots of surprises out there. Plus, starting an early vigil is insurance that you at least catch some action in the event that you’re clouded out on game day! Like we mentioned in last week’s post on the Delta Aquarids, the Perseids are already active, spanning a season from July 17^th to August 24^th.

The Zenithal Hourly Rate for the Perseids is generally between 60-100 meteors. The ZHR is the number of meteors you could expect to see during optimal conditions under dark skies with the radiant directly overhead. Rates were enhanced back in the 1990’s, and 2004 saw a ZHR of 200.

The orbit of comet Swift-Tuttle and its intersection near the Earth's orbit. (Created the author using NASA/JPL ephmeris generator). — The orbit of comet Swift-Tuttle and its intersection near the Earth’s orbit. (Created by the author using NASA/JPL ephemerides generator).

The source of the Perseids is comet 109P/Swift-Tuttle. Discovered on July 16^th-19th, 1862 by astronomers Lewis Swift & Horace Tuttle, Swift-Tuttle is on a 133.3 year orbit and last passed through the inner solar system in late 1992. This comet will once again grace our skies in early 2126 AD.

The Perseids are also sometimes referred to as the “tears of St Lawrence,” after the Catholic saint who was martyred on August 10^th, 258 AD. The Perseids have been noted by Chinese astronomers as far back as 36 AD, when it was recorded that “more than 100 meteors flew thither in the morning.” The annual nature of the shower was first described by Belgian astronomer Adolphe Quételet in 1835.

Enhanced rates for the Perseids marked the return of comet Swift-Tuttle in the 1990s. Recent years have seen rates as reported by the International Meteor Organization at a ZHR=175(2009), 91(2010), 58(2011), & a resurgence of a ZHR=122 last year.

Just what will 2013 bring? There’s one truism in meteor observing—you definitely won’t see anything if you do not get out and observe. Meteor shower observing requires no equipment, just clear skies and patience. Watch in the early hours before dawn, when the rates are highest. Meteors can occasionally be seen before midnight, but are marked by lower rates and slow, stately trains across the sky. Some suggest that best viewing is at a 45 degree angle away from the radiant, but we maintain that meteors can appear anywhere in the sky. Pair up with a friend or two and watch in opposite directions to increase your meteor-spotting chances.

We also like to keep a set of binoculars handy to examine those smoke trains left by bright fireballs that may persist seconds after streaking across the sky.

And speaking of which, there has also been some spirited discussion over the past week as to whether or not the Perseids produce more fireballs than any other shower. I certainly remember seeing several memorable fireballs from this shower over the years, although the Geminids, Leonids and Taurids can be just spectacular on active years. The stated r value of the Perseids is one of the lowest at 2.2, suggesting a statistically high percentage of fireballs.

And in the realm of the strange and the curious, here are just a few phenomena to watch/listen for on your Perseid vigil;

– Can you “hear” meteors? Science says that sounds shouldn’t carry through the tenuous atmosphere above 50 kilometres up, and yet reports of audible meteors as a hiss or crackle persist. Is this an eye-brain illusion? Researchers in 1988 actually studied this phenomenon, which is also sometimes reported during displays of aurora. If there’s anything to it, the culprit may be the localized generation of localized electrophonic noises generated by Extra/Very Low Frequency electromagnetic radiation.

– Can meteor streaks appear colored? Green is often the top reported hue.

– Can meteors appear to “corkscrew” during their trajectory, or is this an illusion?

A Perseid very near the shower radiant during the 2012 shower. (Photo by author).

Wide-field photography is definitely a viable option during meteor showers. Just remember to bring extra charged batteries, as long exposure times will drain modern DSLRs in a hurry!

And did you know: you can even “listen” to meteor pings on an FM radio or portable TV? This is a great “rain check” option!

And there’s still real science to be done in the world of meteor shower studies. The International Meteor Organization welcomes counts from volunteers… and be sure to Tweet those Perseid sightings to #Meteorwatch.

Also be sure to check out the UK Meteor Observation Network, which has just launched their live site with streaming images of meteors as they are recorded.

Good luck, clear skies, and let the late 2013 meteor shower season begin!

-And be sure to post those Perseid pics to the Flickr forum on Universe Today… we’ll be doing photo essay roundups from observers around the world!

Category: Observing