David Dickinson, Author at Universe Today

April 16, 2013December 23, 2015 by David Dickinson

How to Spot the Antares Launch from NASA Wallops on Wednesday

Sighting prospects for the US Eastern Seaboard during the ascent of Antares. (Credit: The Orbital Sciences Corporation).

A space launch marking a new era is departing from the Virginia coast this Wednesday evening, and if you live anywhere along a wide area of the US Eastern seaboard, you’ll have a great opportunity to witness the launch with your own eyes. Here’s all the information you’ll need to see it, plus some tips for capturing it with your camera.

Orbital Sciences’ Antares rocket will launch from Pad 0A at NASA’s Mid-Atlantic Regional Spaceport based on Wallops Island, Virginia. This will mark not only the first launch of Antares, but the first orbital launch of a liquid-fueled rocket from Wallops. The launch window runs from 5:00 to 8:00 PM EDT (21:00-24:00 UT).

There were some concerns when a technical anomaly shutdown a “Wet Dress Rehearsal” test this weekend at T-16 minutes, but Orbital Sciences has stated that the problems have been resolved and the launch is pressing ahead as planned.

Space shots are a familiar sight to the residents of the Florida Space Coast, but will provide a unique show for residents of the U.S. central Atlantic region. The launch of Antares from Wallops will be visible for hundreds of miles and be over 10° above the horizon for an arc spanning from Wilmington, North Carolina to Washington D.C. and north to the New York City tri-state area as it heads off to the southeast. Antares is a two stage rocket with a 1^st stage liquid fueled engine and a solid-fueled 2^ndstage. The primary mission for Wednesday’s Antares A-One flight will be to demonstrate the ability for the Antares rocket to place a payload into orbit. If all goes well, Orbital Sciences will join SpaceX this summer in the select club of private companies with the ability provide cargo delivery access to the International Space Station in Low Earth Orbit.

Antares heads to orbit. Artist's concept. (Credit: Orbital Sciences Corperation). — Antares heads to orbit. Artist’s concept. (Credit: Orbital Sciences Corporation).

Antares will deploy a dummy mass simulating the Cygnus module. Also onboard are the Phonesat-1a, -1b, and -1c micro-cubesats and the Dove 1 satellite.

Be sure to watch for the launch of Antares if you live in the region. Find a spot with a low uncluttered eastern horizon and watch from an elevated rooftop or hilltop location if possible. I live a hundred miles west of Cape Canaveral and I’ve followed launches all the way through Main Engine Cutoff and first stage separation with binoculars.

Be sure to also follow the launch broadcast live for any last minute delays via NASA TV or Universe Today will have a live feed as well. Antares is aiming to put the Cygnus test mass in a 250 x 300 kilometre orbit with a 51.6° inclination. This is similar to what will be necessary to head to the ISS, but this week’s launch will not be trailing the ISS in its path. This also means that the launch window can be extended over three hours rather than having to be instantaneous.

If the launch goes at the beginning of the window, the local sun angle over the launch facility will be 30° to the west. Sunset at Wallops on the evening of April 17^th occurs at 7:41PM EDT, meaning we could be in for a photogenic dusk launch of Antares if it stretches to the end of the target window.

And speaking of which, a pre-sunset launch means short daytime exposure settings for photography. Be prepared to switch over for dusk conditions if the launch extends into the end of the window. Conditions during twilight can change almost moment-to-moment. One of the most memorable launches we witnessed was the pre-dawn liftoff of STS-131 on April 5^th, 2010:

The predawn launch of STS-131 as seen from 100 miles west. (Photo by author).

Once in orbit, the launch of Antares should generate four visible objects; the test mass payload, the two clam-shell fairings, and the stage two booster. This configuration is similar to a Falcon 9/Dragon launch, minus the solar panel covers. These objects should be visible to the naked eye at magnitudes +3 to +5. The cubesat payloads are tiny and below the threshold of naked eye visibility.

Preliminary visibility for the objects will favor latitudes 0-30° north at dusk to 10-40° at dawn. Keep in mind these predictions could change as the launch window evolves. The next NORAD tracking ID in the queue is 2013-015A. Yesterday’s launch of Anik G1 from Baikonur was just cataloged today as 2013-014A plus associated hardware. The weather is forecast to be 45% “go” for tomorrow’s launch. In the event of a scrub, the next launch window for Antares is April 18-21st.

First orbit of the Cygnus test mass; shadow orientation of the Earth assumes a nominal launch at 22:00UT on April 17th. (Created by the author using Orbitron. TLEs courtesy of (name) — First orbit of the Cygnus test mass; shadow orientation of the Earth assumes a nominal launch at 22:00 UT on April 17th. (Created by the author using Orbitron. Two-Line Elements courtesy of Henry Hallam).

It’ll be exciting to follow this first flight of Antares and its first scheduled mission to the International Space Station this summer. Also watch for the first ever lunar mission to depart Wallops on August 12 with the launch of the Lunar Atmosphere and Dust Environment Explorer (LADEE).

Finally, if you’ve got a pass of the International Space Station this week, keep an eye out for Progress M-17M currently about 10 minutes ahead of the station in its orbit. The unmanned Progress vehicle just undocked yesterday from the station and will be conducting a series of experiments monitoring the interactions of its thrusters with the ionosphere before burning up on reentry over the South Pacific on April 21^st.

A pass of the ISS over UK tonite (April 16th) with Progress leading at 20:30UT. (Created by the author in Orbitron).

The ISS and more can be tracked using Heavens-Above. Also, we’ll be tweeting all of the updates and orbital action as it evolves as @Astroguyz. Let us know of those launch sightings both near and far. It’ll be interesting to see what, if any, impact launches visible to a large portion of the U.S. population will have on the public’s perception of spaceflight. Be sure to look up tomorrow night!

April 14, 2013April 26, 2016 by David Dickinson

Mysterious Moon Flashes: Could the Transient Lunar Phenomena be Linked to the Solar Cycle?

The Moon, our nearest natural satellite. (Photo by author).

A key mystery in observational lunar astronomy may be at least partially resolved.

An interesting study appeared recently in the British Astronomical Association’s (BAA) March 2013 edition of their Lunar Section Circular. The study is one of the most comprehensive looks at possible connections between Transient Lunar Phenomena and the Solar Cycle.

Collection of TLP reports analyzed by Barbara Middlehurst & Sir Patrick Moore. The red dots indicate reddish events, the yellow one other colored events. (Wikimedia Commons image in the Public Domain). — Collection of TLP reports analyzed by Barbara Middlehurst & Sir Patrick Moore. The red dots indicate reddish events. The yellow ones represent other colored events. (Wikimedia Commons image in the Public Domain).

Transient Lunar Phenomena (or TLPs) are observations collected over the years of flashes or glows on the Moon. Since these phenomena often rely on a report made by a solitary observer, they have been very sparsely studied.

The term itself was coined by Sir Patrick Moore in 1968. One of the very earliest reports of a TLP event was the flash seen on the dark limb of the waxing crescent Moon by Canterbury monks in 1178.

Other reports, such as a daylight “star near of the daytime crescent Moon” seen by the residents of Saint-Denis, France on January 13, 1589 was almost certainly a close conjunction of the planet Venus. Bright planets such as Venus can be easily seen next to the Moon in the daytime.

A daytime Moon and Venus as seen from France on January 13th, 1589. (Created by the author in Starry Night).

A stunning illusion also occurs when the Moon occults, or passes in front of a bright star or planet. In fact, there’s a name for this psychological phenomenon of a bright star seeming to “hang” between the horns of the Moon just prior to an occultation, known as the Coleridge Effect. This takes its name from a line in Coleridge’s Rime of the Ancient Mariner;

“Till clomb above the eastern bar, the horned Moon with one bright star,

Within nether tip.”

Okay, we’ve never seen the “horned Moon clomb,” either. But this does describe a real illusion often seen during an occultation. The mind thinks that gap between the horns of the Moon should be transparent, and the lingering planet or star seems to cross that space on the dark limb, if only for a second. Incidentally, South American residents will get to check this out during the next occultation of Venus this year on September 8th.

So, what does this have to do with the 11-year solar cycle? Well, when you strip away many of the dubious observations of TLPs over the years, a core of well- documented events described by seasoned observers remains. Anyone who has sketched such a complex object as the Moon realizes that fine detail becomes apparent on scrutiny that may be missed in a casual glance. But one persistent assertion that has gone around the astronomical community for years is that an increase in the number of TLP events is linked to the peak of the solar cycle.

This was first suggested in 1945 by H. Percy Wilkins. A later study by Barbara Middlehurst in 1966 disproved the idea, citing no statistical correlation between sunspot activity and TLPs.

Of course, pundits have tried unsuccessfully to link the solar cycle to just about everything, from earthquakes to human activity to booms and busts of the stock market. Most flashes on the dark limb of the Moon are suspected to be meteorite impacts. In fact, the advent of high-speed photography has been able to reveal evidence for lunar strikes during intense meteor showers such as the Leonids and Geminids.

Flash of a Leonid impact captured on the limb of the Moon in 2006. Click image to see animation. (Credit: NASA Meteoroid Environment Office).

What’s at little less clear are the source of luminous “hazes” or “glows” noted by observers. Keep in mind; we’re talking subtle effects noted after meticulous study. NASA even commissioned a study of TLPs named Project Moon-Blink during the early Apollo program. About a third of TLP events have been observed near the bright crater Aristarchus. Researchers even managed to get Neil Armstrong to make an observation of the crater during a pass on Apollo 11. He noted that “there’s an area that is considerably more illuminated than the surrounding area. It seems to have a slight amount of fluorescence.”

Aristarchus crater (arrowed) near Full Moon. Note how bright it is compared to the surrounding terrain. (Photo by Author). — A crater with a relatively high albedo (Proclus, arrowed) near Full Moon. Note how bright it is compared to the surrounding terrain. (Photo by Author).

But what’s interesting in the recent BAA study conducted by Jill Scambler is the amount of data that was available. The study was a comprehensive analysis of TLPs noted by the BAA, the Association of Lunar and Planetary Observers (ALPO) and NASA from 1700 to 2010. Observations were weighted from 1 to 5, with 1 for reports from inexperienced observers to 5 for definitive and unambiguous TLP events.

The periodogram analysis comparing the frequency of TLPs with the sunspot cycle utilized a tool available from NASA’s Exoplanet Database to evaluate the data. If there was any mechanism whereby TLPs were being generated by solar activity, it had been suggested previously by Wilkins that perhaps out-gassing was being caused be solar irradiation or lunar dust was becoming electrostatically charged and suspended.

In fact, Surveyor 7 witnessed such a phenomenon during lunar twilight. To date, no human has witnessed a sunrise or sunset from the surface of the Moon, although astronauts witnessed several from lunar orbit.

"Horizon glow" as imaged from the lunar surface during twilight. (Credit: NASA). — “Horizon glow” as imaged from the lunar surface during twilight. (Credit: NASA).

The final conclusion of the BAA study cites that “Although there are theories that might infer that TLP would be more frequent during solar activity, from a sunspot cycle perspective there is no evidence to support this.”

The report provides an interesting perspective on the topic, especially with solar cycle 24 peaking over the next year. It also seems that reports of TLPs have declined in past decades. One of the most famous examples was the flash imaged on the Moon (thought to be a Leonid) by Leon Stuart in 1953. But in the modern era of astrophotography with the Moon under nearly continuous scrutiny, where are all the images of TLPs?

Granted, a core number (2%) of events suggest evidence of real activity on a Moon that we most often think of as geologically dead. As for the spurious sightings, it helps to recall the number of “sightings” in the 19^th century of Vulcan transiting the face of the Sun. Where is Vulcan today, with the Sun being monitored around the clock?

We’re not immune to this sort of “echo effect” in the modern world of astronomy, either. For example, whenever an impact scar or flash is noted on Jupiter, as occurred in 2009 and 2012, other sightings are “seen” throughout the solar system. A similar psychological phenomenon occurred when Comet Holmes brightened in 2007. For a time, reports flying around the Internet suggested many comets where suddenly increasing in brightness!

It also interesting to note that many features such as Aristarchus and Ina Caldera also have a high brightness or albedo. Although the Full Moon seems pearly white, the albedo of the Moon is actually quite low at (13%), about that of worn asphalt. Bright ejecta and rays tend to stand out, especially approaching a Full Moon, such as occurs on May 25^th.

You can even enhance the saturation of those lunar pics to bring out subtle color and reveal that the Moon isn’t as monochromatic as it appears to the naked eye;

A false-colored gibbous Moon enhanced to bright out subtle color. (Photo by author). — A false-colored gibbous Moon enhanced to bring out subtle color. (Photo by author).

Kudos to the team at the BAA for casting a critical scientific eye on a little studied phenomenon. Perhaps missions such as the Lunar Atmosphere and Dust Environment Explorer (LADEE) departing for the Moon this summer will shed more light on the curious nature of Transient Lunar Phenomena.

-The study can be read in the March 2013 edition of the British Astronomical Association’s Lunar Section Circular available as a free pdf.

April 10, 2013December 23, 2015 by David Dickinson

New Exoplanet-Hunting Mission to launch in 2017

Artist's rendition of TESS in space. (Credit: MIT Kavli Institute for Astrophysics Research).

Move over Kepler. NASA has recently green-lighted two new missions as part of its Astrophysics Explorer Program.

These come as the result of four proposals submitted in 2012. The most anticipated and high profile mission is TESS, the Transiting Exoplanet Survey Satellite.

Slated for launch in 2017, TESS will search for exoplanets via the transit method, looking for faint tell-tale dips in brightness as the unseen planet passes in front of its host star. This is the same method currently employed by Kepler, launched in 2009. Unlike Kepler, which stares continuously at a single segment of the sky along the galactic plane in the direction of the constellations Cygnus, Hercules, and Lyra, TESS will be the first dedicated all-sky exoplanet hunting satellite.

The mission will be a partnership of the Space Telescope Science Institute, the MIT Lincoln Laboratory, the NASA Goddard Spaceflight Center, Orbital Sciences Corporation, the Harvard-Smithsonian Center for Astrophysics and the MIT Kavli Institute for Astrophysics and Space Research (MKI).

TESS will launch onboard an Orbital Sciences Pegasus XL rocket released from the fuselage of a Lockheed L-1011 aircraft, the same system that deployed IBEX in 2008 & NuSTAR in 2012. NASA’s Interface Region Imaging Spectrograph (IRIS) will also launch using a Pegasus XL rocket this summer in June.

An Orbital Sciences Pegasus XL rocket attached to the fuselage of an L1011 for the launch of IBEX. (Credit: NASA).

“TESS will carry out the first space-borne all-sky transit survey, covering 400 times as much sky as any previous mission. It will identify thousands of new planets in the solar neighborhood, with a special focus on planets comparable in size to the Earth,” said George Riker, a senior researcher from MKI.

TESS will utilize four wide angle telescopes to get the job done. The effective size of the detectors onboard is 192 megapixels. TESS is slated for a two year mission. Unlike Kepler, which sits in an Earth-trailing heliocentric orbit, TESS will be in an elliptical path in Low Earth Orbit (LEO).

TESS will examine approximately 2 million stars brighter than 12^th magnitude including 1,000 of the nearest red dwarfs. Not only will TESS expand the growing catalog of exoplanets, but it is also expected to find planets with longer orbital periods.

One dilemma with the transit method is that it favors the discovery of planets with short orbital periods, which are much more likely to be seen transiting their host star from a given vantage point in space.

TESS will also serve as a logical progression from Kepler to later proposed exoplanet search platforms. TESS will also discover candidates for further scrutiny by as the James Webb Space Telescope to be launched in 2018 and the High Accuracy Radial Velocity Planet Searcher (HARPS) spectrometer based at La Silla Observatory in Chile.

Artist's conception of NICER on the exterior of the International Space Station. (Credit: NASA). — Artist’s conception of NICER on the exterior of the International Space Station. (Credit: NASA).

Also on the board for launch in 2017 is NICER, the Neutron Star Interior Composition Explorer to be placed on the exterior of the International Space Station. NICER will employ an array 56 telescopes which will collect and study X-rays from neutron stars. NICER will specialize in the study of a particular sub-class of neutron star known as millisecond pulsars. The X-ray telescopes are in a configuration utilizing a set of nested glass shells looking like the layers of an onion.

Observing pulsars in the X-ray range of the spectrum will offer scientists tremendous insight into their inner workings and structure. The International Space Station offers a unique vantage point to do this sort of science. Like the Alpha Magnetic Spectrometer (AMS-02), the power requirements of NICER dictate that it cannot be a free-flying satellite. X-Ray astronomy must also be done above the hindering effects of the Earth’s atmosphere.

NICER will be deployed as an exterior payload aboard an ISS ExPRESS Logistics Carrier. These are unpressurized platforms used for experiments that must be directly exposed to space.

Another fascinating project working in tandem with NICER is SEXTANT, the Station Explorer for X-ray Timing And Navigation Technology. This project seeks to test the precision of millisecond pulsars for interplanetary navigation.

“They (pulsars) are extremely reliable celestial clocks and can provide high-precision timing just like the atomic signals supplied through the 26-satellite military operated Global Positioning System (GPS),” said NASA Goddard scientist Zaven Arzoumanian. The chief difficulty with relying on this system for interplanetary journeys is that the signal gets progressively weaker the farther you travel from the Earth.

“Pulsars, on the other hand, are accessible in virtually every conceivable flight regime, from LEO to interplanetary and deepest space,” said NICER/SEXTANT principle investigator Keith Gendreau.

Both NICER and TESS follow the long legacy of NASA’s Astrophysics Explorer Program, which can be traced all the way back to the launch Explorer 1. This was the very first U.S. satellite launched in 1958. Explorer 1 discovered the Van Allen radiation belts surrounding the Earth.

(from left) William Pickering, James Van Allen, and Wernher von Braun hold aloft a mock up of Explorer 1 shortly after launch. (Credit NASA/JPL-Caltech. — (From left) William Pickering, James Van Allen, and Wernher von Braun hold aloft a mock up of Explorer 1 shortly after launch. (Credit NASA/JPL-Caltech).

“The Explorer Program has a long and stellar history of deploying truly innovative missions to study some of the most exciting questions in space science,” stated NASA associate administrator for science John Grunsfeld. “With these missions, we will learn about the most extreme states of matter by studying neutron stars and we will identify many nearby star systems with rocky planets in the habitable zones for further study by telescopes such as the James Webb Space Telescope.”

Of course, Grunsfeld is referring to planets orbiting red dwarf stars, which will be targeted by TESS. These are expected have a habitable zone much closer to their primary star than our own Sun. It has even been suggested by MIT scientists that the first exoplanets visited by humans on some far off date might be initially discovered by TESS. The spacecraft may also discover future targets for follow up spectroscopic analysis, the best chance of discovering alien life on an exoplanet in the next 50 years. One can imagine the excitement that a positive detection of a chemical exclusive to life as we know it such as chlorophyll in the spectra of a far of world would generate. More ominously, detection of such synthetic elements as plutonium in the atmosphere of an exoplanet might suggest we found them… but alas, too late.

But on a happier note, it’ll be exciting times for space exploration to see both projects get underway. Perhaps human explorers will indeed one day visit the worlds discovered by TESS… and use navigation techniques pioneered by SEXTANT to do it!

April 8, 2013December 23, 2015 by David Dickinson

The Return of Saturn: A Guide to the 2013 Opposition

A fine recent view of Saturn as captured by Daniel Robb. (Credit & Copyright: Daniel Robb/Universe Today flickr community. All rights reserved).

A star party favorite is about to return to evening skies.

The planet Saturn can now be spied low to the southeast for northern hemisphere observers (to the northeast for folks in the southern) rising about 1-2 hours after local sunset this early April. That gap will continue to close until Saturn is opposite to the Sun in the sky later this month and rises as the Sun sets.

Opposition occurs on April 28^th at 8:00 UT/4:00AM EDT. Saturn will shine at magnitude +0.1 and appear 18.8” in diameter excluding the rings, which give it a total angular diameter of 43”.

Saturn has just passed into the faint constellation Libra for 2013, although its springtime retrograde loop will bring it back into Virgo briefly. Both the 2013 and 2014 opposition will occur in Libra. Saturn will also pass 26’ from +4.2 Kappa Virginis on July 3^rd as it moves back into Virgo while in retrograde before resuming direct motion back into Libra.

Saturn currently lies about 15° to the lower left of the +1.04 magnitude star Spica, also known as Alpha Virginis. Remember the handy saying to “Spike to Spica” from the handle of the Big Dipper asterism to locate the region. Another handy finder tip; stars twinkle, planet generally don’t. That is, unless your skies are extremely turbulent!

With an orbital period 29.46 years, Saturn moves slowly eastward year to year, taking 2-3 years to cross through each constellation along the ecliptic.

Oppositions are roughly 378 days apart and thus move forward on our calendar by about two weeks a year. Successive oppositions also move about 13° eastward per year.

Saturn as imaged by the author on June 11th, 2012.

Oppositions of the ringed planet are also currently becoming successively favorable for southern observers over the coming years. Saturn crossed into the southern celestial hemisphere some years back, and will be at its southernmost in 2018.

Saturn won’t pass north of the celestial equator again until early 2026. Saturn is 15 million kilometres farther from us than opposition last year as its moving toward aphelion in 2018.

Saturn will reach eastern quadrature this summer on July 28^th and stand its highest south at sunset northern hemisphere observers. South of the equator, it will pass directly overhead or transit to the north. Saturn will be with us for most of the remainder of 2013 in evening skies until reaching solar conjunction on November 6^th.

Looking at Saturn with binoculars, you’ll immediately note that something is amiss.

You’re getting a view similar to that of Galileo, who sketched Saturn as a sort of “double handled cup.” In fact, it wasn’t until 1655 that Christian Huygens correctly hypothesized that the rings of Saturn are a flat disk that is not physically in contact with the planet.

Huygens also discovered the large moon Titan. Shining at magnitude +8.5 and taking 16 days to orbit Saturn, Titan is the second largest moon in our solar system after Ganymede. Titan would easily be a planet in its own right if it orbited the Sun. Titan is easily picked out observing Saturn at low power through a telescope.

Saturn's system of moons visible through a small telescope. orientation is for May 9th, 2013. (Created by the author using Starry Night). — Saturn’s system of moons visible through a small telescope. orientation is for May 9th, 2013. (Created by the author using Starry Night).

Observing Saturn at slightly higher magnification, five moons interior to Titan become apparent. From outside in, they are Rhea, Dione, Tethys, Enceladus, and Mimas. Exterior to Titan is the curious moon of Iapetus. Taking 79 days to complete one orbit of Saturn, Iapetus varies in brightness from magnitude +11.9 to +10.2, or a factor of over 5 times. Arthur C. Clarke placed the final monolith in the book adaptation of 2001: A Space Odyssey on Iapetus for this reason. Close-ups from the Cassini spacecraft reveal a two-faced world covered with a dark leading hemisphere and a bright trailing side, but alas, no alien artifacts.

But the centerpiece of observing Saturn through a telescope is its brilliant and complex system of rings. The A, B, and C rings are easily apparent through a backyard telescope, as is the large spacing known as the Cassini Gap.

The rings are also currently tilted in respect to our Earthly vantage point. The rings were edge-on in 2009 and vanish when this occurs every 15-16 years.

This year, we see the rings of Saturn at a respectable 19 ° opening and widening. The rings will appear at their widest at over 25° in 2017 and then become edge-on again in 2025.

The average tilt of Saturn's ring system as seen from Earth spanning 2008-2026. (Graph created by author). — The average tilt (in degrees) of Saturn’s ring system as seen from Earth spanning 2008-2026. (Graph created by author).

The ring system of Saturn adds 0.7 magnitudes of overall brightness to the planet at opposition this year.

Another interesting optical phenomenon to watch for in the days leading up to opposition is known as the “opposition surge” in brightness, or the Seeliger effect. This is a retro-reflector effect familiar to many as high-beam headlights strike a highway sign. Think of the millions of particles making up Saturn’s rings as tiny little “retro-reflectors” focusing sunlight back directly along our line of sight. The opposition surge has been noted for other planets, but it’s most striking for Saturn when its rings are at their widest.

The disk of Saturn will cast a shadow straight back onto the rings around opposition and thus vanish from our view. The shadow across the back of the rings will then become more prominent over subsequent months, reaching its maximum angle at quadrature this northern hemisphere summer and then beginning to slowly slide back behind the planet again. A true challenge is to glimpse the disk of the through the Cassini gap in the rings… you’ll need clear steady skies and high magnification for this one!

It’s also interesting to note a very shallow partial lunar eclipse occurs with Saturn nearby just three days prior to opposition on April 25^th. Saturn will appear 4° north of the Moon and it may be just possible to image both in the same frame.

The location of Saturn and the Full Moon during the April 25th partial eclipse. (Created by the author using Starry Night).

Saturn takes about 30 years to make its way around the zodiac. I remember just beginning to observe Saturn will my new 60mm Jason refractor as a teenager in 1983 as it crossed the constellation Virgo.Hey, I’ve been into astronomy for over one “Saturnian year” now… where will the next 30 years find us?

April 6, 2013April 26, 2016 by David Dickinson

Was the Repeating Passage of Halley’s Comet Known of in Ancient Times?

Comet P/Halley as seen on its last inner solar system passage on March 8th, 1986. (Credit: W. Liller/NASA GSFC/ International Halley Watch Large Scale Phenomena Network).

An interesting and largely unknown tale of ancient astronomy recently came our way while reading author and astrophysicist Mario Livio’s blog. The story involves the passage of the most famous of all comets.

It’s fascinating to consider ancient knowledge of the skies. While our knowledge of ancient astronomy is often sparse, we know that cultures lived and perished by carefully monitoring the passage of the heavens. A heliacal rising of Sirius might coincide with the impending flooding of the life-giving waters of the Nile, or the tracking of the solstices and equinoxes might mark the start of the seasons.

To the ancients, comets were “hairy stars” which appeared unpredictably in the sky. We generally attribute the first realization that comets are periodic to Sir Edmond Halley, who successfully utilized Newton’s laws of gravity and Kepler’s laws of planetary motion to predict the return of Halley’s Comet in 1758. Such a prediction was a vindication of science.

But an interesting tale comes to us from the 1^st century CE that Rabbi & Jewish Scholar Yehoshua Ben Hananiah may have known something of “a star that appears every 70 years.” The tale, as told in the Horayoth (rulings) of the Talmud and described in Mr. Livio’s blog is intriguing:

Rabbi Gamliel and Rabbi Yehoshua went together on a voyage at sea. Rabbi Gamliel carried a supply of bread. Rabbi Yehoshua carried a similar amount of bread and in addition a reserve of flour. At sea, they used up the entire supply of bread and had to utilize Rabbi Yehoshua’s flour reserve. Rabbi Gamliel then asked Rabbi Yehoshua: “Did you know that this trip would be longer than usual, when you decided to carry this flour reserve?” Rabbi Yehoshua answered: “There is a star that appears every 70 years and induces navigation errors. I thought it might appear and cause us to go astray.”

The Rabbi’s assertion is a fascinating one. There aren’t a whole lot of astronomical phenomena on 70 cycles that would have been noticeable to ancient astronomers. With an orbital period of 75.3 years, Halley’s Comet seems to fit the bill the best. The earliest confirmed description of Halley’s comes from Chinese astronomers during its 240 BCE passage. Later subsequent passages of the comet through the inner solar system were noted by the Babylonians in 164 & 87 BCE.

Of course, there’s no further evidence that ancient scholars identified those passages as the same comet. Some great comets such as Hale-Bopp seen in 1997 and this year’s anticipated Comet C/2012 S1 ISON are on orbits spanning thousands of years that outlast most Earthly civilizations.

Mr. Livio also notes that historical knowledge of ancient apparitions of Halley’s may have been accessible to the Great Knesset scholars during the Babylonian exile of the 6^th century BCE.

One of the chief objections raised to the Halley hypothesis is the circumstances of the appearance of Halley’s Comet in the Rabbi’s lifetime. Remember, most folks didn’t live for 70 years in the 1^st century. Any tales of a periodic comet would have been handed down by generations. You would be lucky to see Halley’s Comet once in your lifetime. Plus, not all apparitions of Halley’s Comet are favorable. For example, Halley’s was bright enough to induce “comet hysteria” with the public in 1910. In contrast, few northern hemisphere members of the general public got a good view of it during its 1986 passage.

Medieval woodcut depicting the supposed destructive influence of a 4th century comet. (Credit: Stanilaus Lubienietski's Theatrum Cometicum, Amsterdam 1668). — Medieval woodcut depicting the supposed destructive influence of a 4th century comet. (Credit: Stanilaus Lubienietski’s *Theatrum Cometicum*, Amsterdam 1668).

Halley’s Comet was visible on and around January 25^th, 66 CE during the Rabbi’s lifetime. However, the Rabbi would have been in his 20’s and have been a student (and not yet a Rabbi) himself. One can imagine that if he was fearful of a “false star” leading them astray, he must’ve known that the 70 year period was just about neigh.

The 66 CE apparition of Halley’s Comet would have appeared around the time of the Jewish Rebellion and just four years before the destruction of the Second Temple in Jerusalem by the Romans in 70 CE.

One other possible astronomical culprit has been cited over the years. The classic variable star Mira (Omicron Ceti) currently has a 332 day cycle which ranges from magnitude +3.5 to below naked eye visibility at +8.6 to +10.1. The variability of Mira was first discovered by astronomer David Fabricius on August 3^rd 1596. There are suggestions that ancient Chinese and Babylonian astronomers may have known of this “vanishing star”.

The variable star Mira as imaged by the Hubble Space Telescope. (Credit: NASA/STScl/Margarita Karovska at the Harvard-Smithsonian Center for Astrophysics).

Mira is expected to reach maximum for 2013 from July 21st to 31st.

Not all maxima for Mira are of equal brightness. Mira can peak anywhere from magnitude +2.0 to +4.9 (a 15-fold difference) and there’s evidence to suggest it may have been brighter in the past. Astronomer Philippe Veron noted in 1982 that a larger oscillation period of 60 years for the peak maxima of Mira falls just a decade short of Rabbi Yehoshua’s mention of an errant star.

Whatever the case, its fascinating to consider what celestial object might’ve been referred to, and how many other astronomical tales might be awaiting discovery in ancient texts. We’ve got lots of comets to ponder this year as Comet PanSTARRS, Lemmon, and ISON grace our skies in 2013. Halley’s will make its next visit to the inner solar system in 2061. I’ll open it up to you, the astute Universe Today reading public; was the Rabbi’s Star a comet, a variable star, a meteor storm, or none of the above?

Halley's Comet as seen from latitude 30 north on the morning of July 31st, 2061. (Created by the author using Starry Night software). — Halley’s Comet as seen from latitude 30 north on the morning of July 31st, 2061. (Created by the author using Starry Night software).

-Dr. Mario Livio blogs at A Curious Mind. Be sure to check out his new book Brilliant Blunders: From Darwin to Einstein – Colossal Mistakes by Great Scientists That Changed Our Understanding of Life in the Universe out on May 14^th!

April 4, 2013December 23, 2015 by David Dickinson

A Look at the Hazards of Green Laser Pointers

An appropriate use of a laser during last year's Jupiter-Venus conjunction. (Photo by Author).

Those handheld green lasers pointers may not be as harmless as you thought.

A recent study released by researchers at the National Institute of Standards and Technology (NIST) has revealed an alarming trend. Of 122 hand-held laser pointers tested, 44% of red lasers and 90% of green lasers tested failed federal safety regulations.

The primary culprit was overpowered units. The Code of Federal Regulations in the United States limits commercial class IIIa lasers to 5 milliwatts (mW). And yes, lasers above 5 mW are commercially available in the United States, but it is illegal to market them as Class IIIa devices. Some units in the NIST study tested as high as 13 times over the legal limit at 66.5 mW. For context, many military grade rifle mounted lasers are rated at 50 mW.

A diagram of a typical diode-pumped solid-state laser. (Credit: NASA/Langley).

“Our results raise numerous safety questions regarding laser pointers and their use,” stated NIST laser safety officer in the recent paper presented at the Laser Safety Conference in Orlando, Florida.

Why should backyard astronomers care? Well, since hand-held lasers first became commercially available they’ve become a familiar staple at many public star parties. Reflecting back off of the dust and suspended particles in the atmosphere, a green laser provides a pointer beam allowing the user to trace out constellations and faint objects. Lasers can also be mounted on the optical tube assemblies of a telescope for pointing in lieu of a finder scope.

A typical 5mW green laser pointer. (Photo by Author).

An amateur astronomy club based near San Antonio, Texas even coordinated signaling the International Space Station with a pair of powerful searchlights and a 1 watt blue laser in 2012, just to prove that it was possible.

But such devices are not toys. Even a 5 mW laser can temporarily blind someone at short range. Further eye damage can often linger for days or even permanently and can go unnoticed. This is why researchers working around lasers in research facilities such as LIGO (the Laser Interferometer Gravitational Wave Observatory) must submit to routine eye exams.

Its not the Death Star... LIGO engineers practicing proper safety around the gravity wave observatory's 200 watt laser. Credit: NSF/LIGO). — Its not the Death Star… LIGO engineers practicing proper safety around the gravity wave observatory’s 35 watt Nd YAG laser. Credit: NSF/LIGO).

The trouble with green lasers is that, well, they look too much like light sabers.

It’s for this reason I keep mine on a very “short leash” at star parties and NEVER hand it off to anyone, no matter how well meaning, child or adult. I also NEVER point it below the local horizon, (there’s wildlife in them trees). A laser reflected inadvertently off of an optical surface such as a car window or primary mirror can also do just as much damage as a direct aiming.

And also, NEVER aim one at an aircraft. In fact, it’s a federal violation to do so. The Federal Aviation Administration has reported a 13-fold trend in reported aircraft/laser incidents from 2005 to 2011. There has also been an upward trend in individuals being tracked down and prosecuted for such offenses. If it blinks, assume it’s an aircraft and steer clear!

Reported incidents of laser/aircraft violations from 2005-2011. (Credit: Federal Aviation Administration).

In a post-9/11 era, the Department of Homeland Security has been concerned with the potential threat posed by laser pointers as well. It’s not yet illegal to fly in the US with a 5mW laser pointer in your carry-on luggage, but and several countries now outlaw them all together, a note for traveling astronomers. Note that the de facto policy often comes down to the particular TSA officer you’re dealing with.

With this sort of news, we wonder if laser pointers might become outlawed entirely in the coming years. 5mW range lasers are generally classed IIIa or 3R systems. By the American National Standards Institute (ANSI) guidelines, such devices under the recent NIST study would fall into the much more hazardous IIIb range for 5-500 mW lasers. Such lasers can cause permanent eye damage with direct exposure for periods of as little as 1/100^th of a second.

Safety distances for a 5mW green laser. (Wikimedia Commons graphic under a Creative Commons Attribution-ShareAlike 30 License). — Safety distances for a 5mW green laser. (Wikimedia Commons graphic under a Creative Commons Attribution-ShareAlike 3.0 License).

It’s also worth noting that actual reported cases of laser injuries are fairly rare. A 2004 paper from the Archives of Ophthalmology cites 15 injuries worldwide each year, while a recent 2012 paper in PLoS ONE estimates “220 confirmed laser eye injuries have occurred between 1964 and 1996,” for an average of 6.9 laser injuries per year.

The Code of Federal Regulations limits output for green laser pointers to 5mW in the visible range and 2mW in the infrared. 75% of the tested devices exceed this standard for infrared emission as well. Note that there have been anecdotal reports that even the point source generated by a laser (say, by shining it against a wall) can be excessively bright. This recent NIST study was the first time we’d seen a back up argument for this. Many of the cheaper handheld lasers sold online (think in the 20$ USD range) may forgo the infrared filtering component all together.

So in lieu of an outright ban on laser pointers, what can be done? Joshua Hadler cites the need for a better accountability for laser manufacturers. “By relying on manufacturers’ traceability to a national measurement institute such as NIST, someone could use this design to accurately measure power from a laser pointer.” Mr. Hadler also notes that a simple test bed for laser pointers can be built using off the shelf parts for less than $2,000 USD. We’re surprised there’s not “an App/Kickstarter for that…” already. (Would-be designers take note!)

In the end, we’d hate to see these crucial tools for astronomy outreach banned just because a very few individuals were irresponsible with them. Through accountability from production to application, we can assure that laser pointers remain a vital part of the amateur astronomer’s tool kit.

April 1, 2013April 26, 2016 by David Dickinson

Comet Lemmon: A Preview Guide for April

Comet C/2012 F6 Lemmon as imaged by Luis Argerich as from near Buenos Aires, Argentina on March (Credit: Nightscape photography. Used with permission).

As Comet 2011 L4 PanSTARRS moves out of the inner solar system, we’ve got another comet coming into view this month for northern hemisphere observers.

Comet C/2012 F6 Lemmon is set to become a binocular object low to the southeast at dawn for low northern latitudes in the first week of April. And no, this isn’t an April Fools’ Day hoax, despite the comet’s name. Comet Lemmon (with two m’s) was discovered by the Mount Lemmon Sky Survey (MLSS) based outside of Tucson, Arizona on March 23, 2012. MLSS is part of the Catalina Sky Survey which searches for Near Earth Asteroids. We’ve got another comet coming into view this month for northern hemisphere observers as Comet 2011 L4 PanSTARRS moves out of the inner solar system.

The comet is on an extremely long elliptical orbit, with a period of over 11,000 years. Comet Lemmon just passed perihelion at 0.74 astronomical units from the Sun on March 24^th.

Animation of Comet Lemmon as it passes the star Gamma Crucis on January 17th. (Courtesy of Luis Argerich. Used with permission).

Southern hemisphere observers have been getting some great views of Comet Lemmon since the beginning of this year. It passed only three degrees from the south celestial pole on February 5^th, and since that time has been racing up the “0 Hour” line in right ascension. If that location sounds familiar, that’s because another notable comet, 2011 L4 PanSTARRS has been doing the same. In fact, astrophotographers in the southern hemisphere were able to catch both comets in the same field of view last month.

Another celestial body occupies 0 Hour neighborhood this time of year. The Sun just passed the vernal equinox marking the start of Spring in the northern hemisphere and Fall in the southern on March 19^th.

And like PanSTARRS, Comet Lemmon has a very steep orbit inclined 82.6° relative to the ecliptic.

The steep path and current position of Comet Lemmon. (Credit: NASA/JPL' Small-Body Database Browser). — The steep path and current position of Comet Lemmon. (Credit: NASA/JPL’ Small-Body Database Browser).

Comet Lemmon broke naked-eye visibility reaching +6^th magnitude in late February and has thus far closely matched expectations. Current reports place it at magnitude +4 to +5 as it crosses northward through the constellation Cetus. Predictions place the maximum post-perihelion brightness between magnitudes +3 and +5 in early April, and thus far, Comet Lemmon seems to be performing right down the middle of this range.

Brightness graph for Comet Lemmon for the months surrounding perihelion. (Created by author).

Southern observers have caught a diffuse greenish 30” in diameter nucleus on time exposures accompanied by a short, spikey tail. Keep in mind, the quoted brightness of a comet is extended over its entire surface area. Thus, while a +4^th magnitude star may be easily visible in the dawn, a 3^rd or even 2^nd magnitude comet may be invisible to the unaided eye. Anyone who attempted to spot Comet PanSTARRS in the dusk last month knows how notoriously fickle it actually was. Binoculars are your friend in this endeavor. Begin slowly sweeping the southeast horizon about an hour before local sunrise looking for a fuzzy “star” that refuses to reach focus. Comet Lemmon will get progressively easier in the dawn sky for latitudes successively farther north as the month of April progresses.

The apparent path of Comet Lemmon for April looking southeast about an hour before local sunrise from latitude 30 degrees north. (Created by the Author using Starry Night). — The apparent path of Comet Lemmon for April 10th through the 30th looking east about an hour before local sunrise from latitude 30 degrees north. (Created by the Author using Starry Night).

Comet Lemmon will continue to gain elevation as it crosses from Cetus into the constellation Pisces on April 13^th. An interesting grouping occurs as the planet Mercury passes only a few degrees from the comet from April 15^th to April 17^th. Having just past greatest elongation on March 31^st, Mercury will shine at magnitude -0.1 and make a good guide to locate the comet in brightening dawn skies. The pair is joined by the waning crescent Moon on the mornings of April 7^th and 8^thwhich may also provide for the first sighting opportunities from low north latitudes around these dates.

The Moon reaches New phase on Wednesday, April 10^th at 5:35AM EDT/9:35 UT. It will be out of the morning sky for the next couple of weeks until it reaches Full on April 25^th, at which point it will undergo the first eclipse of 2013, a very shallow partial. (More on that later this month!)

Comet Lemmon will then slide across the celestial equator on April 20^th and cross the plane of the ecliptic on April 22^nd as it heads up into the constellation Andromeda in mid-May. We’re expecting Comet Lemmon to be a fine binocular object for late April, but perhaps not as widely observed due to its morning position as PanSTARRS was in the dusk.

By mid-May, Comet Lemmon will have dipped back down below +6^th magnitude and faded out of interest to all but a few deep sky enthusiasts. Comet Lemmon will pass within 10° of the north celestial pole on August 9^th, headed back out into the icy depths of the solar system not to return for another 11,000-odd years.

It’s interesting to see how these two springtime comets will effect observers expectations for the passage of Comet C/2012 S1 ISON. Will this in fact be the touted “Comet of the Century?” Much hinges on whether ISON survives its November 28^th perihelion only 1,166,000 kilometers from the center of our Sun (that’s 0.68 solar-radii or about 3 times the Earth-Moon distance from the surface of the Sun). If so, we could be in for a fine “Christmas Comet” rivaling the passage of Comet Lovejoy in late 2011. On the other hand, a disintegration of Comet ISON would be more akin to the fizzle of Comet Elenin earlier in 2011.

In the meantime, enjoy Comet Lemmon as an Act 2 in the 2013 Three Act “Year of the Comet!”

March 31, 2013December 23, 2015 by David Dickinson

Astronomical Pranks of April Fools’ Past

A April Fools Day conjunction of Pluto & Jupiter, the likes of which you'll never see! (Credit: NASA/JPL/USGS(Jupiter) & NASA?ESA & M. Buie of the SWRI (Pluto)

The first day of April is always a traditional time for pranks and puns, and astronomers and scientists aren’t above an April Fools’ Day shenanigan or two. Hey, I gotta admit, as a freelance science journalist, even my radar will be up tomorrow as I’m sure that someone will try to slide some wowzers by the credulous media, as they always have in the past. If the aliens wanted to conquer the Earth it’s wide open to ‘em on April 1^st, I’m just sayin’. Who would believe the tweets were for real, as they landed ray guns ablaze on the White House lawn? Trust us; you won’t see such April Fools’ hi-jinks from Universe Today. If you read it here, the alien invasion is for real, and you can begin stockpiling food and ammo appropriately in the best tradition of Falling Skies.

Here are just some of the classic astronomical April Fools’ jokes perpetrated in the past:

In 1974, John Gribbin published The Jupiter Effect, claiming that a Grand Alignment of the planets would spell doomsday for the Earth on March 10^th, 1982. On April 1^st 1976, Astronomer Sir Patrick Moore made an announcement along a similar vein to BBC listeners. A rare conjunction of the planets Pluto (which was still classified as a planet at the time) & Jupiter would weaken the gravitational field of the Earth at precisely 9:47AM. This would cause the law of gravity to become temporarily suspended, and cause things to fly about. Big hint: Pluto was nowhere near the gas giant at the time. Not that it would matter or have any consequence for the Earth! Although the hoax was quickly revealed, that didn’t stop several listeners from calling in and reporting observed results from the fake Jovian-Plutonian Gravitational effect!

The first star party? Galileo shows of the sky in Saint Mark's square in Venice. Note the lack of adaptive optics. (Illustration in the Public Domain). — The first star party? Galileo shows off the sky in Saint Mark’s square in Venice. Note the lack of adaptive optics. (Illustration in the Public Domain).

Many questionable astrophysical papers have been spotted in the wild trying to sneak past the guardians-that-be over the years on & around April 1st. On April Fools’ past, we’ve learned that Schrödinger’s Cat is not alone, the supposed discovery of the “bigon” particle, and that the “non-detection of the tooth fairy” has been reported. Hey, never let it be said that science geeks lack a sense of humor. What’s especially amazing is when one of these tall tales actually makes it past the credulous media and into print!

One of our favorites hit the servers last year on March 30^th just in time to gain traction for April Fools’ Day with the cryptic title On the influence of the Illuminati in astronomical adaptive optics. OK, I’ll admit we didn’t question the veracity of the claim for oh, like, maybe a tenth of a second. For those without enlightenment into the world of Woo, the Illuminati are purported to be the shadow cult organization going back to the Middle Ages that’s supposed to be behind, well, every nefarious plot in modern society. “They put the eye over the pyramid on the back of a dollar bill, man…” as some true believers will claim. And while they didn’t have adaptive optics technology way back in Galileo’s time, the mock study does assert a tenuous link between the Illuminati and the “astronomical rise” of Brittany Spears and Lady Gaga.

Phobos (above) and Diemos (bottom) closeup; no Martian construction projects noted. (Credit: NASA). — Phobos (above) and Deimos (bottom) close up; no Martian construction projects noted. (Credit: NASA).

Are Martians secretly hollowing out a base on the Moons of Barsoom? The Moons of Mars were also the setting for an April Fools’ prank in 1959. The Martian moons are bizarre in their own right. Orbiting at 6,000 & 20,060 kilometres above the surface of the Red Planet, Phobos & Deimos are almost certainly captured asteroids. In fact, Phobos orbits its primary closer than any other moon in the solar system. Phobos will crash into Mars millions of years in the future.

The hoax was perpetrated when Walter Scott Houston, posing as Dr. Arthur Hayall of the fictitious University of the Sierras made a claim in the Great Plains Observer that Phobos & Deimos were in fact artificial satellites. Though the joke ran its course, the idea has cropped up in fringe circles over the years. Russian scientist Iosif Shklovsky made a similar allusion years later, asserting that the low density of Phobos indicated that was hollow (!) Mariner 9 returned the first close-up views of Phobos in 1971, showing a decidedly asteroid-looking appearance. Of course, this hasn’t stopped the likes of folks like Richard Hoagland (he of the face on Mars) from resurrecting the outlandish claim, all of which started as a practical joke. And of course, with the advent of the Internet, you don’t have to wait until April 1st to receive modern day hoax emails proclaiming “MARS WILL APPEAR AS BIG AS THE FULL MOON!!!” which now apparently happens every August.

A moon for Mercury... (or not!) (Credit: NASA/Johns Hopkins University/APL/Carnegie Institution of Washington). — A moon for Mercury… (or not!) (Credit: NASA/Johns Hopkins University/APL/Carnegie Institution of Washington).

Spurious moons are apparently the “low-hanging fruit” of astronomical April Fools’ pranks. In 2012, an image of a purported moon of the planet Mercury’s as discovered by the MESSENGER spacecraft appeared in the JPL Photojournal. The captioning declared the moon had been named Caduceus and was 70 metres in diameter. Perhaps such a prank is appealing because there’s nothing immediately outlandish about the idea. New moons get discovered periodically on first reconnaissance missions past planets. For a brief time in 1974, Mariner 10 project scientists did indeed think they had discovered a Mercurial moon. Reading on through the press release, however, revealed that a collision course of MESSENGER with the moon was set to cause it to “arrive at Earth by 2014.” The “moon” also bared a suspicious resemblance to the asteroid 243 Ida as seen by the Jupiter-bound Galileo spacecraft in 1993.

Some April Fools’ hoaxes have presented ideas that have actually gained scientific traction in reality over the years. On March 31^st, 2005, NASA’s Astronomy Picture of the Day website contained the teaser “Water on Mars!” for its next presentation to follow on the next day. A flurry of discussion followed; was there a discovery from the Spirit & Opportunity rovers forthcoming? We should’ve checked the calendar first. The next day, APOD featured water… in a glass, sitting atop a Mars bar. What’s ironic is that recent announcements from the Mars Science Laboratory support the idea of ancient water on the Red Planet, so the MSL may well have had the last laugh.

Sulfate-rich sandstone imaged by Opportunity (left) and Curiousity (right). Both hint at ancient surface water on Mars. (Credit: NASA/JPL-Caltech/Cornell/MSSS). — Sulfate-rich sandstone imaged by Opportunity (left) and Curiosity (right). Both hint at ancient surface water on Mars. (Credit: NASA/JPL-Caltech/Cornell/MSSS).

The Museum of Hoaxes also hosts a list of astronomy & space-themed April Fools’ Day pranks that have been perpetrated over the years. From a Soviet space capsule landing outside of Kankakee, Illinois to life discovered on Jupiter in 1996, it’s all enshrined for the curious. One of our faves is Google’s 2004 announcement that they were accepting applications at a new research center… based on the Moon in Copernicus crater. The ability to survive “with limited access to such modern conveniences as soy low-fat lattes,” was cited as a prerequisite, but a sushi chef and two massage therapists would be on site. At least the assignment wouldn’t be totally austere!

Closeup of Copernicus crater region... note the distinct lack of soy lattes! (Photo by author). — Closeup of Copernicus crater region… note the distinct lack of soy lattes! (Photo by author).

What astronomical hi-jinks await us tomorrow as we flip our calendars over to April 1^st, 2013? Feel free to tell us here at Universe Today of your true tales of April Fools’ astronomy pranks past & present that you’ve spotted in the wild. Think twice before re-tweeting that link tomorrow, and don’t believe those reports of “nearby gamma-ray bursts of doom” or “alien invasions…” or at least, wait until you’ve seen the “greens of their eyes!”

March 27, 2013December 23, 2015 by David Dickinson

New Crater Names Approved for Mercury’s South Pole & More

Mercury's southern polar region as seen from MESSENGER. (Credit: NASA/Johns Hopkins UniversityApplied Physics Laboratory/Carnegie Institution of Washington).

Move over, Tolkien & Tryggvadóttir. Yesterday, an announcement was made that the International Astronomical Union (IAU) approved proposed names for nine new craters on the planet Mercury. The names honor deceased writers, artists and musicians following the convention established by the IAU for naming features on the innermost world.

The announcement comes as NASA’s MESSENGER spacecraft has completed mapping of the surface of Mercury earlier this month. A good majority of these features were established at Mercury’s southern polar region, one of the last areas of the planet to be mapped by MESSENGER.

The craters honored with a newly assigned moniker are:

Donelaitis, named after 18^th century Lithuanian poet Kristijonas Donelaitis, author of The Seasons and other tales and fables.

Petofi, named after 19^th century Hungarian poet Sandor Petofi, who wrote Nemzeti dal which inspired the Hungarian Revolution of 1848.

Roerich, named after early 20^th century Russian philosopher and artist Nicholas Roerich, who created the Roerich Pact of 1935 which asserted the neutrality of scientific, cultural and educational institutions during time of war.

Hurley, named after the 20^th century Australian photographer James Francis Hurley, who traveled to Antarctica and served with Australian forces in both World Wars.

Lovecraft, named after 20^th century American author H.P. Lovecraft, a pioneer in horror, fantasy and science fiction.

Alver, named after 20^th century Estonian author Betti Alver who wrote the 1927 novel Mistress in the Wind.

Flaiano, named after 20^th century Italian novelist and screenwriter Ennio Flaiano who was a pioneer Italian cinema and contemporary of Federico Fellini.

Pahinui, named after mid-20^th century Hawaiian musician Charles Phillip Kahahawai Pahinui, influential slack-key guitar player and part of the “Hawaiian Renaissance” of island culture in the 1970’s.

L’Engle, named after American author Madeleine L’Engle, who wrote the young adult novels An Acceptable Time, A Swiftly Tilting Planet & A Wind in the Door. L’Engle passed away in 2007.

Five of the newly named craters in the south pole region of Mercury (circled in red). Note that the final portion of the USGS map, although recently released, has yet to be filled in! (Credit: USGS).

The nine new crater names join 95 others named thus far. The MESSENGER surface mapping campaign has been ongoing since the spacecraft’s first flyby of Mercury in January 2008. MESSENGER entered permanent orbit around world on March 18^th, 2011.

MESSENGER missions operations engineer Ray Espiritu was instrumental in getting Pahinui’s name in the running.

“I wanted to honor the place where I grew up and still call home,” Espiritu said. ”The Pahinui crater contains a possible volcanic vent, and its name may inspire other scientists as they investigate the volcanic processes that helped to create Mercury, just as investigation of the Hawaiian volcanoes helps us understand the volcanic processes that shape Earth as we know it today.”

Pahinui Crater. (Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington).

Lovecraft is another interesting selection on the list. The name of the famous horror writer was in the running last month for the naming of Pluto’s moons P4 & P5, and New Horizons principle investigator Alan Stern hinted that Lovecraft may still find a home on a surface feature as New Horizons reveals Pluto & Charon in July 2015. It would be a fitting tribute to a fine writer. Could we end up with Lovecraft marking not only the solar system’s “hubs of hell” on Mercury, but its frozen outer wastelands as well?

There was more news yesterday in the realm of astrogeology and the planet Mercury. The IAU Working Group for Planetary System Nomenclature also made the distinction between features described as valles and catenae on the surface of Mercury. Catenae are described as crater chains, and MESSENGER has sufficient resolution that several valles have been revealed as such. Catenae on Mercury are named after radio astronomy observatories, while valles are named after abandoned cities of antiquity. Thus, Haystack Vallis is now Haystack Catena, Goldstone Vallis is now Goldstone Catena, and Arecibo Vallis is now Arecibo Catena, and, well, you get the idea.

Arecibo Catenae (formerly known as Arecibo Vallis) as imaged by MESSENGER in 2008. (Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington).

MESSENGER has proven to be a boon for planetary science. The spacecraft was launched in 2004 and took almost 7 years and 6 flyby assists (one past the Earth, two past Venus and three past Mercury) to become the first spacecraft to orbit the tiniest planet in our solar system. Mercury was first seen up close by Mariner 10 in 1974 and even then we only mapped 45% of its surface. Scientists had to wait until MESSENGER to fill in the remainder of Mercury’s map.

The next mission to Mercury isn’t until the planned arrival of the joint ESA/JAXA BepiColombo mission in 2022.

And don’t forget to watch for Mercury as it reaches greatest elongation on Easter Day low in the dawn sky. I managed to catch sight of it low to the east with binoculars for the first time this apparition this morning about 40 minutes prior to local sunrise. It’s amazing to think that ground-based professional telescopes & even amateur astronomers can actually image fuzzy details on the planet’s surface that match up with what MESSENGER is revealing!

All fascinating stuff to contemplate as we welcome the newest named craters to our ever expanding map of Mercury… now, will there ever be a Miskatonic University within the walls of Lovecraft crater?

-Explore these recently named craters and more using the USGS inactive Astrogeology Science Center.

-Also check out this animation of the south polar region of Mercury and more as imaged by MESSENGER.

March 25, 2013April 26, 2016 by David Dickinson

See Mercury at its Greatest Elongation for 2013

Mercury gives a clue to Super-Mercuries — Astronomers have found a star system with two planets like Mercury, but bigger. Our own Mercury could supply clues to their composition and formation. (Credit: NASA/Johns Hopkins University/Applied Physics Laboratory.Carnegie Institution of Washington).

A fine apparition of the planet Mercury graces the dawn skies this week, leading up to its greatest elongation from the Sun for 2013.

It seems that nearly every appearance of the planet Mercury is touted as the “best” these days. Such was the case with the inner-most world’s dusk showing early last month. Truth is, all elongations of Mercury (and Venus, for that matter) are not created equal, and visibility of each apparition isn’t the same for observers worldwide. We’ll show you why.

Mercury orbits the Sun once every 88 days. With an orbit interior to our own, it never strays far from the Sun in the sky and thus can only appear low in the dawn or dusk. Its orbit is also elliptical, with an eccentricity of 0.206, the greatest of any planet in our solar system. This means that greatest elongations can vary considerably, from 17.9° away from the Sun in the sky near perihelion of the planet to 28.7° near aphelion. And although reaching greatest elongation near aphelion means the tiny world is above the muck of the horizon, it also means it’s also intrinsically a bit fainter; Mercury can vary in brightness from magnitude -0.2 at a perihelic-elongation to half a magnitude fainter at +0.3 for an aphelic-elongation.

A comparison of elongations of Mercury as seen from the Earth at perihelion versus aphelion. (Created by the author).

But there’s more. Compounding this situation is the angle of the ecliptic, or the imaginary plane of the orbit of the Earth. Near the March equinox the ecliptic rides high in the dusk to the west and low in the dawn to the east for northern hemisphere observers. In the southern hemisphere, the reverse is true. It’s a strange sight for a northerner to head “Down Under” and watch the Sun rise in the east, transit to the north and set to the west!

The path of Mercury looking east ~45 minutes prior to sunrise from latitude 30 degrees north from March 26th through April 30th, (Created by the author using Starry Night).

Thus what may be a terrible apparition of Mercury for one hemisphere may be a grand one for another, as is the case this week. Yes, northern observers can catch the fleeting world, if they know exactly where to look for it. For observers based at longitude 40° north, Mercury will never peak above an altitude of 10° in the dawn sky. Observers based near 35° south will however see the planet reach its maximum possible elevation of over 25° degrees above the horizon.

We would qualify this as “The best dawn appearance of Mercury for 2013… as seen from the southern hemisphere.” Greatest elongations of Mercury occur in pairs, with dusk-to-dawn apparitions about 45 days apart as the planet passes between us and the Sun, followed by a longer period of about 70 days as the world loops back around behind the Sun. The orbit of Mercury is tilted about 7° with respect to our own. Otherwise, we would see a transit of the planet every inferior conjunction, as last occurred on November 8^th, 2006 and will happen next on May 9^th, 2016.

The path of Mercury from March 26th through April 26th looking east from latitude 35 degrees south ~45 minutes prior to sunrise. (Created by the author using Starry Night).

Mercury will show a maximum illumination area of 38.5” square arc seconds as seen from the Earth March 30^th on just before reaching its greatest elongation west of the Sun on March 31^st on Easter Day at 22:00 UT/18:00EDT. Through a telescope, Mercury will display a 7.7” diameter disk with a 50% illuminated “half-Moon” phase. Mercury reaches greatest elongation just 28 hours prior to aphelion which occurs on April 2^nd, the closest this has occurred date-wise since April 8^th, 2006. This won’t be matched again until March 24^th, 2020. Shining at magnitude +0.3, Mercury will then race ahead of the Earth on its inside track and will begin to gradually sink lower on successive mornings in early April. The morning of April 8^th may well offer the last good chance to spy the tiny world when the old crescent Moon passes just 8° degrees north of the planet within two days of reaching New phase on April 10^th. Mercury reaches superior conjunction opposite to the Earth and on the far side of the Sun on May 11^th, 2013, and will again head into the dusk skies for its next greatest eastern elongation on June 12^th.

From our Earthly vantage point, Mercury completes 3.15 orbits of the Sun a year. This means that we see 6 greatest elongations on average most years, 3 westerns (dawn) and 3 easterns (dusk). The most elongations of Mercury that you can have in a calendar year are 7, which occurred in 2011 and will happen again in 2015. It’s fascinating to think that until the advent of the Space Age, the orbit and the rough size of Mercury was all we knew about the planet. It would take the first flyby of the Mariner 10 spacecraft to give us a close up view of Mercury in 1974. The precession of the orbit of Mercury was a mystery until explained by Einsteinian physics, and still stands as one of the great proofs of general relativity. Today, we have a permanent ambassador around Mercury, NASA’s MESSENGER spacecraft. MESSENGER has mapped to world in detail, sampled its tenuous exosphere, and observed hints of ancient volcanic activity. MESSENGER will be followed by the joint European Space Agency/Japan Aerospace Exploration Agency mission BepiColombo set to launch in 2015 which will arrive at Mercury in 2022. All fascinating things to ponder as you search for the diminutive world low in the dawn skies this coming Easter weekend!