Astronomy Archives

January 21, 2014December 23, 2015 by David Dickinson

An Incredible Time-lapse of Venus Passing Through Inferior Conjunction

Some of the most amazing celestial sights are hidden from our view in the daytime sky. Or are they? We recently challenged readers to try and follow the planet Venus through inferior conjunction as it passed between the Earth and the Sun on January 11^th. Unlike the previous pass on June 6^th, 2012 when Venus made its last transit of the Sun for the 21^st century, the 2014 solar conjunction offered an outstanding chance to trace Venus’s path just five degrees from the Sun from the dusk and into the dawn sky.

Expert astrophotographers Shahrin Ahmad based in Sri Damansara, Malaysia and Paul Stewart observing from New Zealand took up that daily challenge as Venus neared the limb of the Sun, with amazing results. Now, Shahrin has also produced an amazing time-lapse sequence of Venus passing through inferior conjunction.

You can actually see the illuminated “horns” of Venus as they thin, extend, and rotate around the limb as the planet passes the Sun.

And it’s what’s more incredible is that the capture was completed in the daytime. But such a feat isn’t for the unskilled. Shahrin told Universe Today of the special safety precautions he had to take to acquire Venus so close to the Sun:

“Since Venus was getting closer each day towards conjunction, I found it far too dangerous to find visually, either using the main telescope or the finderscope.”

Instead, Shahrin relies on computerized software named Cartes du Ciel to drive his Skywatcher EQ6 mount and pinpoint Venus in the daytime sky.

“The sky in Kuala Lumpur is never clear from here, thus it rarely appears dark blue, making it almost impossible to spot Venus visually, especially when it is less than 10 degrees from the Sun.”

Shahrin elaborated further on his special solar safety precautions:

“I always start with all covers in place and the solar filter on the main telescope. I will slew the telescope to the Sun, make some slight repositioning adjustments, and then synchronize the telescope to the new position. After ensuring the Sun is visible and centered on the computer screen, I slew to Venus. Once the mount has stopped in position, I remove the solar filter and replace it with a makeshift cardboard extender mounted on the existing dew-shield. This ensures that any direct sunlight is totally blocked from entering the optics.”

Shahrin notes that 90% of the time, Venus with appear on the computer screen after aligning. Otherwise, a brief spiral search of the field will slide it into view.

Shahrin observes from his ShahGazer Observatory, a roll-off-roof observatory just outside of Kuala Lumpur. He used the Skywatcher 120ED refractor pictured for the captures, with a 2x Barlow lens to achieve a focal length of 1800mm. Shahrin’s main camera is a QHY CCD IMG132e, and the rig is mounted on a Skywatcher EQ6.

A closeup of Sharin’s barlow and camera rig. Credit: Shahrin Ahmad.

“The experience of being able to track Venus approaching inferior conjunction over the Sun afterwards is exhilarating,” Shahrin told Universe Today. “It felt like watching and waiting for a total eclipse of the Sun, but in slow motion!”

Shahrin also counts himself lucky to have had a string of clear days leading up to and after inferior conjunction.

Shahrin’s capture of Venus 5 degrees from the Sun just 8 hours before inferior conjunction may also be a record. That’s a closer apparent separation than our visual sighting of Venus 7 hours and 45 minutes after inferior conjunction on January 16th 1998 as seen from North Pole Alaska, when the planet passed 5.5 degrees from the limb of the Sun.

“I’ve also noticed that in some of the photos, we can see a slight ‘glint’ of sunshine on part of Venus’ atmosphere,” Shahrin noted to Universe Today. “(This sighting) was actually confirmed by the RASC Edmonton Centre in Canada via their Twitter feed.”

An amazing capture, indeed. Venus is now back in the realm of visibility for us mere mortal backyard observers low in the dawn sky, shining at a brilliant magnitude -4.3. Expect it to vault up in a hurry for northern hemisphere observers as the favorable angle of the ecliptic will give it a boost in the dawn. Venus is also headed towards a spectacular 0.2 degree conjunction with Jupiter this summer on August 18th: expect UFO sightings to rise correspondingly. The Indian Army even briefly mistook the pair for Chinese spy drones early last year.

The waning crescent Moon approaches Venus on the morning of January 28th, 2014. Created using Stellarium.

Venus will spend most of 2014 in the dawn sky and is headed for superior conjunction on October 25^th, 2014. Venus spent a similar span in the dawn for the majority 2006, and will do so again in 2022. It’s all part of the 8-year cycle of Venus, a span over which apparitions of the planet roughly repeat. And the next shot we’ll have at inferior conjunction? That’ll be on August 15^th, 2015 for favoring the southern hemisphere and March 25^th, 2017 once again favoring the northern, when the planet very nearly passes as far from the Sun as it can appear at inferior conjunction at 8 degrees.

Congrats to Shahrin on his amazing capture!

-Follow the stargazing adventures of Sharin Ahmad on Google+ and as @shahgazer on Twitter

-Got pictures of Venus? Send ‘em in to Universe Today.

January 20, 2014December 23, 2015 by Tammy Plotner

Milky Way Shakes, Rattles and Rolls…

Three stages of the evolution of the galaxy simulation used to model the Milky Way. (Credit: AIP)

For decades astronomers have puzzled over the many details concerning the formation of the Milky Way Galaxy. Now a group of scientists headed by Ivan Minchev from the Leibniz Institute for Astrophysics Potsdam (AIP) have managed to retrace our galaxy’s formative periods with more detail than ever before. This newly published information has been gathered through careful observation of stars located near the Sun and points to a rather “moving” history.

To achieve these latest results, astronomers observed stars perpendicular to the galactic disc and their vertical motion. Just to shake things up, these stars also had their ages considered. Because it is nearly impossible to directly determine a star’s true age, they rattled the cage of chemical composition. Stars which show an increase in the ratio of magnesium to iron ([Mg/Fe]) appear to have a greater age. These determinations of stars close to the Sun were made with highly accurate information gathered by the RAdial Velocity Experiment (RAVE). According to previous findings, “the older a star is, the faster it moves up and down through the disc”. This no longer seemed to be true. Apparently the rules were broken by stars with the highest magnesium-to-iron ratios. Despite what astronomers thought would happen, they observed these particular stars slowing their roll… their vertical speed decreasing dramatically.

So what’s going on here? To help figure out these curious findings, the researchers turned to computer modeling. By running a simulation of the Milky Way’s evolutionary patterns, they were able to discern the origin of these older, slower stars. According to the simulation, they came to the conclusion that small galactic collisions might be responsible for the results they had directly observed.

Smashing into, or combining with, a smaller galaxy isn’t new to the Milky Way. It is widely accepted that our galaxy has been the receptor of galactic collisions many times during its course of history. Despite what might appear to be a very violent event, these incidents aren’t very good at shaking up the massive regions near the galactic center. However, they stir things up in the spiral arms! Here star formation is triggered and these stars move away from the core towards our galaxy’s outer edge – and near our Sun.

In a process known as “radial migration”, older stars, ones with high values of magnesium-to-iron ratio, are pushed outward and display low up-and-down velocities. Is this why the elderly, near-by stars have diminished vertical velocities? Were they forced from the galactic center by virtue of a collision event? Astronomers speculate this to be the best answer. By comparison, the differences in speed between stars born near the Sun and those forced away shows just how massive and how many merging galaxies once shook up the Milky Way.

Says AIP scientist Ivan Minchev: “Our results will enable us to trace the history of our home galaxy more accurately than ever before. By looking at the chemical composition of stars around us, and how fast they move, we can deduce the properties of satellite galaxies interacting with the Milky Way throughout its lifetime. This can lead to an improved understanding of how the Milky Way may have evolved into the galaxy we see today.”

Original Story Source: Leibniz Institute for Astrophysics Potsdam News Release. For further reading: A new stellar chemo-kinematic relation reveals the merger history of the Milky Way.

January 20, 2014December 23, 2015 by David Dickinson

The Moon Occults Saturn in the Dawn this Weekend

Saturn and the waning crescent Moon rising to the SE at about 4 AM local on January 25th, 2014. Created using Stellarium

Mark your calendars: the first in a series of interesting occultations of Saturn by the Moon for 2014 starts this weekend.

The year 2014 features 11 occultations of the planet Saturn by the Moon, and there are 23 total for 2014 of every planet except Neptune and Jupiter.

An occultation occurs when one foreground celestial object completely obscures another. Technically, a total solar eclipse is an occultation of the Sun by the Moon, although it’s never referred to as such. The term finds modern usage mainly for the blocking of stars and planets by the Moon. Very occasionally, an asteroid or planet can occult a distant star as well.

And yes, the modern astronomical term “occultation” traces its hoary roots back to the days when astronomy was intertwined with the pseudoscience of astrology. To this day, the term still makes some folks wonder if astronomers are secretly casting horoscopes. Trust us, you’re still on a solid astronomical footing to use the term “occultation.”

Unfortunately, the January 25^th occultation of Saturn by the Moon will only grace part of Antarctica, southern Argentina and Chile, and the Falkland Islands post-sunrise. The rest of us still will see a very photogenic pass of Saturn near the waning crescent Moon on the morning of Saturday, January 25^th. The Moon will pass just about a degree — two times its apparent width — south of Saturn for northern hemisphere observers.

The footprint for the January 25th occultation of Saturn by the Moon. dashed lines indicate where the events occurs in the daytime sky. (Created using Occult 4.0.11 software)

Both the Moon and Saturn will reside in the astronomical constellation of Libra this weekend during closest passage. The pair will rise around 2 AM local. After their brief tryst, the Moon will head towards New on January 30^th while Saturn will continue to rise successively earlier as its heads towards opposition and the start of evening Saturn observing season on May 10^th, 2014.

January 2014 is also notable for having two New Moons, an occurrence informally known as a Black Moon. This occurs again this year in March, and February 2014 is devoid of a New Moon. February is the only month that can be “missing a Moon phase” as it’s the only one shorter the synodic period of 29.5 days, in which the Moon returns to like phase.

In the telescope, Saturn will present a +0.8 magnitude disk 16” across (38” with rings from tip-to-tip). Saturn’s rings are tipped open to our line of sight by about 22 degrees in 2014, and are widening towards a maximum of 27 degrees in 2016 through 2017. If you have an equatorial telescope with tracking capability, it may be possible this weekend to follow Saturn up into the daytime sky. Though Saturn isn’t quite bright enough to see in the daytime unaided, it might just be possible to spy using binoculars on the 25^th using the nearby crescent Moon as a guide. Saturn is a tough daytime target to be sure, but it’s not impossible to acquire with a little skill and patience.

The current cycle of occultations of Saturn began on December 1^st, 2013 and ends on November 22^nd, 2014. The cycle will move progressively northward through the year.

The Moon and Saturn put on a repeat performance over almost the same exact location (this time in darkness) on April 17^th, 2014, and the best event in the cycle for North America will be the August 31^st daytime occultation of Saturn by the waxing crescent Moon.

Now for the wow factor of what you’re seeing. On Saturday morning, the Moon is just over 371,000 kilometres distant, or a little over a light second away. Saturn is over four thousand times more remote at just over 10.1 astronomical units (AUs) distant, which works out to 1.5 billion kilometres, or over 83 light minutes away. And although the Moon is over a 112 times larger in apparent diameter than Saturn as seen from the Earth, the globe of Saturn is actually over 34 times bigger.

Saturn and the Moon crossing the local meridian shortly after sunset on January 25th. Created using Starry Night Education Software.

And though we’ve been to the Moon lots since the dawn of the Space Age, only two spacecraft (Voyagers 1 and 2) have made brief flybys of the ringed world, and only one – Cassini – has orbited it. Note that China’s Chang’e-3 lander and rover are about to experience their second sunset this weekend as well from the lunar surface since landing on the Moon last month.

And although lots of planets get occulted by the Moon in 2014, no stars brighter than +1^st magnitude lie in its path. In fact, the next cycle of bright star occultations by the Moon doesn’t resume until the Moon meets Aldebaran in January 29^th, 2015.

There are, however, over a 100 lesser events involving the Moon occulting naked eye stars worldwide in 2014. Two such events occur this week as well, when the 48% illuminated Moon occults the +4.5^th magnitude star Lambda Virginis for west-central South America on the morning of January 24^th, and the occultation of the +2.8^th magnitude star Alpha Librae (Zubenelgenubi) for central Asia on January 25th.

Don’t miss these celestial events, and be sure to send those pics in to Universe Today… there’s something for everyone happening in the sky this week worldwide!

January 18, 2014December 23, 2015 by Bob King

Chang’e 3 Lander Beams Back New Lunar Panorama Photos

Little by little we’re getting sharper, clearer pictures from the Chinese Chang’e 3 moon mission. Yesterday the lander beamed back a series of new photos taken with its panoramic camera. Stitched together, they give us a more detailed and colorful look of the rover’s surroundings in northern Mare Imbrium. I’ve ordered the images starting with a nice crisp view of the Yutu rover; from there we turn by degree to the right across the five frames. The final mosaic unfortunately doesn’t have the resolution yet of the other images. Perhaps one will be published soon.

The lander's solar panels stand out in the foreground with a smattering of small craters nearby. Credit: Chinanews.com — The lander’s solar panels stand out in the foreground with a smattering of small craters nearby. Credit: Chinanews.com

Right of the rover we see more panels and a radio communications dish. Credit: Chinanews.com

A larger crater surrounded by what appears to be excavated impact ejecta is visible near the horizon at upper right. Credit: Chinanews.com

Yutu's tracks stand out in this final image. Credit: Chinanews.com — Yutu’s tracks and another crater with ejecta stand out in this final image. Credit: Chinanews.com

Complete, if small, panorama stitched from the single images. Credit: Chinanews.com

One thing that stands out to my eye when looking at the photos is the brown color of the lunar surface soil or regolith. Color images of the moon’s surface by the Apollo astronauts along with their verbal descriptions indicate a uniform gray color punctuated in rare spots by patches of more colorful soils.

Apollo 15 astronauts salutes next to the American flag in 1971. The moon's regolith or soil appears a variety of shades of gray. Credit: NASA — Apollo 15 astronauts salutes next to the American flag in 1971. The moon’s regolith or soil appears a variety of shades of gray. Credit: NASA

The famous orange soil scooped up by Apollo 17 astronaut Eugene Cernan comes to mind. Because Apollo visited six different moonscapes – all essentially gray – it makes me wonder if the color balance in the Chinese images might be off. Or did Chang’e 3 just happen to land on browner soils?

The orange soil found by Apollo 17 astronauts really stands out against a uniform gray moonscape. Credit: NASA

January 17, 2014December 23, 2015 by Shannon Hall

Enduring Quests and Daring Visions: NASA Lays Out a Roadmap for Astrophysics

An artist's concept of Kepler-69c, a super-Earth in the habitable zone of a sun-like star.

Three decades ago we were unaware that exoplanets circled other stars. We had just started talking about dark matter but remained blissfully ignorant of dark energy. The Hubble Space Telescope was still on the drawing board and our understanding of the life cycle of stars, the evolution of galaxies, and the history of the Universe was shaky.

But over the past three decades we have discovered thousands of exoplanets around other stars. We have mapped the life cycle of stars from their formation in beautiful stellar nurseries to their sometimes explosive deaths. We have seen deep into the history of the Universe allowing us to paint a picture of galaxies growing from mere shreds to the incredible spiral structures we see today. We now believe dark matter dominates the underlying framework of the Universe, while dark energy drives its accelerating expansion.

The amount of growth over the past three decades has been dramatic. To better access what the next three decades will bring, NASA has laid out a roadmap — a long-term vision for future missions — necessary to advance our understanding of the Universe.

In March 2013, the NASA Advisory Council/Science Committee assembled a group of astronomers who would determine the goals and aims of NASA for the next 30 years. The final product is this so-called roadmap officially titled “Enduring Quests Daring Visions — NASA Astrophysics in the Next Three Decades.”

The roadmap first notes three defining questions NASA should continue to pursue:
— Are we alone?
— How did we get here?
— How does the Universe work?

“Seeking answers to these age-old questions are enduring quests of humankind,” the roadmap states. “The coming decades will see giant strides forward in finding earthlike habitable worlds, in understanding the history of star and galaxy formation and evolution, and in teasing out the fundamental physics of the cosmos.”

In order to better address these questions, the roadmap defines three broad categories of time: the Near-Term Era, defined by missions that are currently flying or planned for this coming decade, the Formative Era, defined by missions that are designed and built in the 2020s, and the Visionary Era, defined by advanced missions for the 2030s and beyond.

A schematic of the next 30 years subdivided into three decades across the entire electromagnetic spectrum. Image Credit: NASA 2014

Are we alone?

The Near-Term Era’s goal is to develop a comprehensive understanding of the demographics of planetary systems. The Kepler mission has already supplied a plethora of information on hot planets orbiting close to their parent stars. The WFIRST-AFTA mission — a wide-field infrared survey planned to launch in 2024 — will compliment this by supplying information on cold and free-floating planets.

The Formative Era’s goal is to characterize the surfaces and atmospheres of nearby stars. This will allow us to move beyond characterizing planets as Earth-like in mass and radius to truly being Earth-like in planetary and atmospheric composition. A proposed mission that allows a large star-planet contrast will directly measure oxygen, water vapor, and other molecules in the atmospheres of Earth-like exoplanets.

The Visionary Era’s goal is to produce the first resolved images of Earth-like planets around other stars. The roadmap team hopes to identify continents and oceans on distant worlds using optical telescopes orbiting hundreds of kilometers apart.

How did we get here?

The Near-Term Era will use the James Webb Space Telescope to supply unprecedented views of protostars and star clusters. It will resolve nearby stellar nurseries and take a closer look at the earliest galaxies.

The Formative Era will trace the origins of planets, stars and galaxies across a spectrum of wavelengths. An infrared surveyor will resolve protoplanetary disks while an X-ray surveyor will observe supernova remnants and trace how these incredible explosions affected the evolution of galaxies. Gravitational wave detectors will untangle the complicated dance between galaxies and the supermassive black holes at their centers.

The Visionary Era will peer nearly 14 billion years into the past when ultraviolet photons from the first generation of stars and black holes flooded spaced with enough energy to free electrons. The James Webb Space Telescope will provide an extraordinary means to better view this threshold.

How does the Universe work?

The Universe is full of extremes. Conditions created in the first nanoseconds of cosmic time and near the event horizons of black holes cannot be recreated in the lab. But the Near-Term and Formative Era’s goals will be to measure the cosmos with such precision that scientists can probe the underlying physics of cosmic inflation and determine the exact mechanisms driving today’s accelerating expansion.

The Visionary Era may use gravitational wave detectors to detect space-time ripples produced during the early stages of the Universe or map the shadow cast by a black hole’s event horizon.

The past 30 years have shown a dramatic growth in knowledge with unimaginable turns. Even with such a detailed framework laid out for the next 30 years, it’s likely that many missions are currently beyond the edge of the present imagination. The most exciting results will be drawn from the questions we haven’t even thought to ask yet.

And as with any of the recent “roadmaps” that the various divisions throughout NASA have presented, the biggest question will be if the funding will be available to make these missions a reality.

Again, this 110-page read may be found here.

The roadmap team consists of Chryssa Kouveliotou (NASA/MSFC), Eric Agol (University of Washington), Natalie Batalha (NASA/Ames), Jacob Bean (University of Chicago), Misty Bentz (Georgia State University), Neil Cornish (Montana State University), Alan Dressler (The Observatories of the Carnegie Institution for Science), Scott Gaudi (Ohio State University), Olivier Guyon (University of Arizona/Subaru Telescope), Dieter Hartmann (Clemson University), Enectali Figueroa-Feliciano (MIT), Jason Kalirai (STScI/Johns Hopkins University), Michael Niemack (Cornell University), Feryal Ozel (University of Arizona), Christopher Reynolds (University of Maryland), Aki Roberge (NASA/GSFC), Kartik Sheth (National Radio Astronomy Observatory/University of Virginia), Amber Straughn (NASA/GSFC), David Weinberg (Ohio State University), Jonas Zmuidzinas (Caltech/JPL), Brad Peterson (Ohio State University) and Joan Centrella (NASA Headquarters).

January 16, 2014December 23, 2015 by Matthew Francis

Some Planet-like Kuiper Belt Objects Don’t Play “Nice”

Distribution of Kuiper belt objects (green), along with various other outer Solar System bodies, based on data from the Minor Planet Center. [Credit: Minor Planet Center; Murray and Dermott]

The Kuiper belt — the region beyond the orbit of Neptune inhabited by a number of small bodies of rock and ice — hides many clues about the early days of the Solar System. According to the standard picture of Solar System formation, many planetesimals were born in the chaotic region where the giant planets now reside. Some were thrown out beyond the orbit of Neptune, while others stayed put in the form of Trojan asteroids (which orbit in the same trajectory as Jupiter and other planets). This is called the Nice model.

However, not all Kuiper belt objects (KBOs) play nicely with the Nice model.

(I should point out that the model is named named for the city in France and therefore pronounced “neese”.) A new study of large scale surveys of KBOs revealed that those with nearly circular orbits lying roughly in the same plane as the orbits of the major planets don’t fit the Nice model, while those with irregular orbits do. It’s a puzzling anomaly, one with no immediate resolution, but it hints that we need to refine our Solar System formation models.

This new study is described in a recently released paper by Wesley Fraser, Mike Brown, Alessandro Morbidelli, Alex Parker, and Konstantin Baygin (to be published in the Astrophysical Journal, available online). These researchers combined data from seven different surveys of KBOs to determine roughly how many of each size of object are in the Solar System, which in turn is a good gauge of the environment in which they formed.

The difference between this and previous studies is the use of absolute magnitudes — a measure of how bright an object really is — as opposed to their apparent magnitudes, which are simply how bright an object appears. The two types of magnitude are related by the distance an object is from Earth, so the observational challenge comes down to accurate distance measurements. Absolute magnitude is also related to the size of an KBO and its albedo (how much light it reflects), both important physical quantities for understanding formation and composition.

Finding the absolute magnitudes for KBOs is more challenging than apparent magnitudes for obvious reasons: these are small objects, often not resolved as anything other than points of light in a telescope. That means requires measuring the distance to each KBO as accurately as possible. As the authors of the study point out, even small errors in distance measurements can have a large effect on the estimated absolute magnitude.

The bodies in the Kuiper Belt. Credit: Don Dixon

In terms of orbits, KBOs fall into two categories: “hot” and “cold”, confusing terms having nothing to do with temperature. The “cold” KBOs are those with nearly circular orbits (low eccentricity, in mathematical terms) and low inclinations, meaning their trajectories lie nearly in the ecliptic plane, where the eight canonical planets also orbit. In other words, these objects have nearly planet-like orbits. The “hot” KBOs have elongated orbits and higher inclinations, behavior more akin to comets.

The authors of the new study found that the hot KBOs have the same distribution of sizes as the Trojan asteroids, meaning there are the same relative number of small, medium, and large KBOs and similarly sized Trojans. That hints at a probable common origin in the early days of the Solar System. This is in line with the Nice model, which predicts that, as they migrated into their current orbits, the giant planets kicked many planetesimals out beyond Neptune.

However, the cold KBOs don’t match that pattern at all: there are fewer large KBOs relative to smaller objects. To make matters more strange, both hot and cold seem to follow the same pattern for the smaller bodies, only deviating at larger masses, which is at odds with expectations if the cold KBOs formed where they orbit today.

To put it another way, the Nice model as it stands could explain the hot KBOs and Trojans, but not the cold. That doesn’t mean all is lost, of course. The Nice model seems to do very well except for a few nagging problems, so it’s unlikely that it’s completely wrong. As we’ve learned from studying exoplanet systems, planet formation models are a work in progress — and astronomers are an ingenious lot.

January 16, 2014December 23, 2015 by Matthew Francis

New Online Classes to Help You Learn More about the Universe

Dark matter in the Bullet Cluster. Otherwise invisible to telescopic views, the dark matter was mapped by observations of gravitational lensing of background galaxies. Credit: X-ray: NASA/CXC/CfA/ M.Markevitch et al.; Lensing Map: NASA/STScI; ESO WFI; Magellan/U.Arizona/ D.Clowe et al. Optical: NASA/STScI; Magellan/U.Arizona/D.Clowe et al.;

Roughly eighty percent of all the mass in the Universe is made of dark matter – a mysterious invisible substance responsible for the structure of galaxies and the patterns of the cosmos on the very largest scales. But how do we know that?

Astronomical images are beautiful, but that’s not their primary purpose from a scientist’s point of view. How can we take those images and infer things about what they are?

We only know of one planet harboring life: Earth. But that doesn’t mean we don’t know anything about the possibility of life elsewhere in the cosmos. How can we infer things about possible alien organisms when we can’t see them (yet)?

If you’re curious about those and other classes, CosmoAcademy — a project from the CosmoQuest educational and citizen-science group — could be for you. We’re offering three new online classes: Introduction to Dark Matter, Introduction to Astronomy via Color Imaging, and Life Beyond Earth: Introduction to Astrobiology.

These classes are short, four-hour courses designed for curious but busy people. All CosmoAcademy classes are offered online through Google+ Hangouts, a type of video chat. Part of the reason we do that is to limit the size of courses to eight students. That allows us to provide individual instruction in a way no other kind of online class is able to do – you aren’t a faceless student, but part of every discussion. In fact, if there’s a topic you want to discuss, there’s a good chance your instructor will take the time to talk about it.

Interested? See our course listings, and please let me know if you have any questions. Here are a few more details:

CQX015: Introduction to Dark Matter

Roughly eighty percent of all the mass in the Universe is made of dark matter – a mysterious invisible substance responsible for the structure of galaxies. But how do we know that? In this course, we’ll examine the evidence in favor of dark matter’s existence, from the rotation of galaxies to the radiation left over from the infancy of the cosmos. After that, we’ll examine what we can infer about the identity of dark matter and sketch out some of the experiments designed to detect it. This class assumes no background except a strong interest in astronomy and cosmology.

Instructor: Matthew Francis
Course structure: Two weeks, four 60-minute meetings
Meeting times: Tuesdays and Thursdays, 9–10 PM US Eastern time (6-7 PM US Pacific time)
Course dates: January 28—February 6, 2014

Enroll today!

CQX021: Introduction to Astronomy Via Color Imaging

When astronomers look at a star, nebula or galaxy for the first time, they see some unreachably distant object acting in some unknown way. What does it have to be made of and how does it have to be acting to look like that? In this class we will be looking at how we use the visual appearance of astronomical objects to figure out what they are. We will examine this problem by making our own color images from the sources provided by observatories from real research projects. From the subtle hues of stars in a distant galaxy to the eerie neon colors of nebulae to the chaotic Sun, by looking at objects in the right light, we can find out what makes them tick.

Instructor: Peter Dove
Course structure: Two weeks, four 60-minute meetings
Meeting times: Tuesdays and Thursdays, 8–9 PM US Eastern time (5-6 PM US Pacific time)
Course dates: Tuesday, February 25—Thursday, March 6

Enroll today!

CQX013 – Astrobiology: Life in the Universe

What will it take to find extraterrestrial life? Frank Drake penned his famous “equation” to determine the instances of life in the Galaxy over 50 years ago. Meant more as a discussion guideline than a rigorous mathematical formula, it will guide our discussion on the science of astronomy, biology, and astrobiology as we consider the possibility of life in the Universe.

Instructor: Nicole Gugliucci
Course structure: Two weeks, four 60-minute meetings
Meeting times: Mondays and Thursdays, 9–10 PM US Eastern time (6-7 PM US Pacific time)
Course dates: Monday, March 17 — Thursday, March 27

Enroll today!

January 16, 2014December 23, 2015 by David Dickinson

A “MiniMoon” Seen Around the World

A 99% illuminated Moon within 24 hours of Full. Image Credit: Stephen Rahn.

So, did last night’s Full Wolf Moon seem a bit tinier than usual? It was no illusion, as avid readers of Universe Today know. As we wrote earlier this week, last night’s Full Moon was the most distant for 2014, occurring just a little under three hours after apogee.

The Full Moon, a "Moon Dog" halo, and a rare parhelic (or do you say Palunic?) arc as seen from North Slope Borough County, Alaska. Credit-Jason Ahrns. — The Full Moon, a “Moon Dog” halo, and a rare parhelic (or do you say Palunic?) arc as seen from North Slope Borough County, Alaska. Credit-Jason Ahrns.

Sure, the Moon reaches apogee every lunation, at a distance nearly as far. In fact, the Moon at apogee can be as far as 406,700 kilometres distant, and last night’s apogee, at 406,536 kilometres, is only the second farthest for 2014. The most distant apogee for 2014 falls on July 28^th at 3:28 Universal Time (UT) at just 32 kilometres farther away from our fair planet at 406,568 kilometres distant.

A 20 image composite shot using a Canon 60Da camera and a a 10" Newtonian telescope. Credit-Stephen Rahn. — A 20 image composite shot using a Canon 60Da camera and a a 10″ Newtonian telescope. Credit-Stephen Rahn.

What made last night’s MiniMoon special was its close proximity in time to the instant of Full phase. The July 2014 apogee, for example, will occur just a day and four hours from New phase.

The 2014 MiniMoon rising behind clouds from Hudson, Florida. Photo by author.

Of course, it isn’t the Moon that’s doing the shrinking, though you’d be surprised the stuff we’ve seen around ye ole Web even on reputable news sites over the past week. The variation of the apparent size of the Full Moon does make for an interesting study in perception. The Moon varies in size from apogee to perigee from about 29.3’ across to 34.1’. This is variation amounts to 14% in apparent diameter.

The Full MiniMoon, clouds, and Jupiter. Credit- Shaun Reynolds, Bungay UK. — The Full MiniMoon, clouds, and Jupiter. Credit– Shaun Reynolds (@shaunreylec), Bungay UK.

Here’s an interesting challenge that you can do for a one year period, requiring just a working set of eyes: observe the Full Moon for 12 successive lunations. Can you judge which one was the “SuperMoon” and which one was the “MiniMoon” without prior knowledge?

A "MiniMoon Nebula..." The Full Moon illuminating foreground clouds. The HDR visualization of the Moon was added for context. Taken with a tripod mounted Nikon P90 Bridge camera. Credit: Giuseppe Petricca of Sulmona, Abruzzo, Italy. — A “MiniMoon Nebula…” The Full Moon illuminating foreground clouds. The HDR visualization of the Moon was added for context. Taken with a tripod mounted Nikon P90 Bridge camera. Credit: Giuseppe Petricca of Sulmona, Abruzzo, Italy.

And as you can see, we also got plenty of pictures here at Universe Today from readers of the Mini-Moon from worldwide.

The MiniMoon shot using a mobile phone held up to the eyepeice of a telescope. Credit-Andrew Millarkie (@Millarkie) — The MiniMoon shot using a mobile phone held up to the eyepiece of a telescope. Credit-Andrew Millarkie (@Millarkie) Glasgow, Scotland.

The rare occurrence of an “Extreme-MiniMoon” — or do you say “Ultra?” — also sparked a lively discussion about the motion of the Moon, how rare this event is, and when it was last and will next be surpassed. A fun online tool to play with is Fourmilab’s Lunar Apogee and Perigee Calculator. Keep in mind, the motion of the Moon is complex, and accuracy for most planetarium programs tends to subside a bit as you look back or forward in time. The distances used in Fourmilab’s calculations are also geocentric, accounting for the center-to-center distance of the Earth-Moon system.

The MiniMoon versus streetlights as seen from Nueva Casarapa, Venezulua. Credit: Jose Mauricio Rozada (@jmrozada) — The MiniMoon versus streetlights as seen from Nueva Casarapa, Venezuela. Credit: Jose Mauricio Rozada (@jmrozada)

Suffice to say, this year’s Full MiniMoon was the most distant for several decades before 2014 or after.

Anthony Cook of the Griffith Observatory notes that JPL’s Horizons web interface gives a max distance for the Moon of 406,533 kilometres at 1:35 UT earlier today, 3 hours and 19 minutes prior to Full.

The Full MiniMoon glimpsed between clouds as seen from central Illinois. Credit-Matt Comerford, (@kb9uwu)

The next closest spread of apogee versus perigee occurs on November 18^th, 1994 at 1 hour and 51 minutes apart, and 2014’s Mini-Moon won’t be surpassed in this regard until May 13^th, 2052. Looking at the distances for the Moon on these dates using Starry Night, however, we get an slightly closer occurrence of 406,345 kilometres for 1994 and 406,246 kilometres for 2052.

The Full MiniMoon rising behind a stand of trees. Credit- Sculptor Lil. — The Full MiniMoon rising behind a stand of trees. Credit– Sculptor Lil.

And to top it off, the 1994 Mini-Moon was during a partial penumbral eclipse as well… we’ll leave that as a homework assignment for the astute readers of Universe Today to calculate how often THAT occurs. It should be fairly frequent over the span of a century, as the Moon has to be at Full phase for a total lunar eclipse to occur.

The MiniMoon as captured by Manish Agarwal from Rajasthan, India. — The MiniMoon as captured by Manish Agarwal (@iManishAgarwal) from Rajasthan, India.

Looking over a larger span of time, @blobrana notes on Twitter that closer occurrences of apogee versus Full Moon with the same approximate circumstances as 2014 also occurred on October 29^th 817 AD (with a 1 hour and 38 minute difference) and won’t occur again until December 20^th, 2154. If research can prove or disprove that these events were even more distant, then the 2014 Extreme MiniMoon was a millennial rarity indeed…

Perhaps this won’t be the last we’ve heard on the subject!

January 16, 2014April 26, 2016 by Bob King

John Dobson, Inventor of the Popular Dobsonian Telescope, Dead at 98

John Dobson, amateur astronomer and astronomy popularizer, died Jan. 14 at 98 in Burbank, Calif. Credit: Wikipedia

The cosmos lost a good soul Wednesday. John Dobson, famous as the creator of the simple, low-cost Dobsonian telescope, passed away on Jan. 15, 2014. His obituary appeared on the website of the Sidewalk Astronomers:

“It is with heavy hearts that we must report the passing of John Dobson. He died peacefully this morning, Wednesday, January 15th, in Burbank, California. He was 98 years old. He leaves behind a son, numerous close friends, and fans and admirers worldwide.

On March 8th, in honor of John, this year’s ISAN (International Sidewalk Astronomy Night) will be dedicated to his memory. Amateur astronomers around the globe can join in and celebrate John’s life and continue to carry the torch that he lit back in 1968 when he co-founded the San Francisco Sidewalk Astronomers.”

John Dobson tugs on his ear during a lecture as guest speaker during Northwoods Starfest near Eau Claire, Wis. U.S. in August 2000. Credit: Bob King — John Dobson tugs on his ear to make a point during a lecture as guest speaker during Northwoods Starfest near Eau Claire, Wis. U.S. in August 2000. Credit: Bob King

Dobson was born in Beijing, China but moved with his parents to San Francisco in 1927. After spending 23 years in a monastery, some of which time was spent sneaking out to build telescopes and observe the night sky, he left to co-found the San Francisco Sidewalk Astronomers in 1968, a group dedicated to showing people on the street the wonders of the night sky using large (for the time) telescopes.

Dobson’s interest in astronomy started in the early 1950s when he built a small telescope using spare parts found in a junk store. He wanted to see for himself what the universe looked like. By 1956, John got a hold of a 12-inch slab of porthole glass and ground it into a mirror following instructions from Allyn J. Thompson’s classic book Making Your Own Telescope. His first look at the last quarter turned him into an astro-evangelist:

“It looks like you’re coming in for a landing,” he wrote in his own telescope making book many years later. From that moment on Dobson felt “that everybody who lives in this world has to see that.”

The writer with his 10-inch Dobsonian reflecting telescope. The scope comes in two pieces like John Dobson's original design - a cardboard tube with the optics that sits in a cradle. See photo below to see how a "Dob" works. Credit: Bob King — The writer with his 10-inch Dobsonian reflecting telescope. The scope breaks down into two pieces like John Dobson’s original design – a cardboard tube with the optics and a cradle. See photo below to see how a “Dob” works. Credit: Bob King

Toting beat-up, monster telescopes everywhere from downtown San Francisco and to national parks across the country, Dobson made good on his promise. He lectured widely on astronomy and cosmology, rejecting the Big Bang Theory for his own Recycling Steady State Theory.

Agree or not with his cosmology, Dobson shook up the amateur telescope making universe with an innovative telescope design based on simplicity. Most telescopes of his day were small refracting telescopes or small to modest-sized reflectors with metal tubes and heavy equatorial mounts. Neither was exactly user-friendly nor offered much light gathering ability.

The mount is a simple altitude-azimuth or "alt-az" design. The scope moves up and down (altitude) against teflon pegs (right) and turns through in a circle (azimuth) on teflon pads against a laminate surface on the base. Credit: Bob King — The mount is a simple altitude-azimuth or “alt-az” design. The scope moves up and down (altitude) against teflon pegs (right) and turns through in a circle (azimuth) on teflon pads against a laminate surface on the base. Credit: Bob King

John used simple materials like porthole glass, cardboard tubes and wooden altitude-azimuth (alt-az) mounts to build incredibly easy to use large telescopes. However primitive, his instruments delivered bright and satisfying images of all the cool, faint stuff in the sky to the average Joe and Jane. Each telescopes had its own name: Little Bertha, Delphinium, Stellatrope, Little One (an 18-incher).While alt-az mounts were nothing new, Dobson combined cheap materials, large mirrors and a simpler approach to mountings that made his telescope style unique. Too unique for some.

Get to know John Dobson a little better in this video titled “Have Telescopes, Will Travel”

In the summer of 1969 Dobson pitched his simple ideas to Sky and Telescope magazine. Then-editor Charles Federer wrote back a polite rejection, stating that Dobson’s techniques weren’t up to standards and “could hardly lead to satisfactory instruments in the kind most amateurs want in these large sizes.”

How wrong this early assessment would turn out to be! His ideas became widely adopted starting in the early 1980s, when Coulter Optical began manufacturing 13.1-inch and 17.5-inch large reflecting telescopes with inexpensive mirrors and simple alt-azimuth mounts that soon were called “Dobsonian” because they were based on John’s original designs.

John Dobson's book on how to build your own telescope featured a unique cover made of plywood, a favorite material for building Dobsonian mounts. Credit: Bob King — John Dobson’s book on how to build your own telescope featured a unique cover made of plywood, a favorite material for building Dobsonian mounts. Credit: Bob King

These days, Dobsonian reflecting telescopes have gone viral. There are how-to books on how to build everything from simple to sophisticated Dobsonsians , including Dobson’s own unique plywood-bound How and Why to Make a User-Friendly Sidewalk Telescope. Don’t want to build one yourself? Most telescope outlets sell several lines of Dobsonians. Heck, my 10-inch and 15-inch reflectors, the most used of my instruments, originate from John’s genius.

When someone asks me to recommend a telescope, I always say “Get a Dobsonian!” They’re extremely portable, very stable, quick to set up and take down and the least expensive per inch of aperture of any scope out there.

John Dobson's signature in his book on telescope making. Credit: Bob King — John Dobson’s signature in his book on telescope making. Click image for more on Dobson’s life and writings. Credit: Bob King

Dobson wanted everyone to share in the universe’s bounty, the better to appreciate our lives and our world. The next clear night tilt your head back, gaze up at the stars and imagine John up there smiling. What an incredible view he must have.

January 15, 2014December 23, 2015 by David Dickinson

An Amazing Capture of Jupiter and its Moons

Astrophotographer Michael Phillips with the gear used to capture the Jupiter rotation animation. Credit-Michael Phillips

It’s always a thrill to watch the action at Jupiter, as its moons pass in front of and behind the gas giant planet. We wrote recently about this month’s opposition of Jove on January 5^th, marking the start of the Jupiter evening viewing season for 2014.

Astrophotographer Michael A. Philips also recently undertook a challenging series of sequences of Jupiter and its moons Io and Ganymede, with stunning results. You can see the motion of Jupiter’s rotation, the Great Red Spot and even a bit of cloud swirl as Io disappears behind Jupiter and Ganymede begins to transit in front and cast a shadow back onto the Jovian cloud tops.

Concerning the capture, Michael wrote on his blog:

“This night was a lucky night. I had not looked at the weather forecast enough to know if it would be good or not. Cold temps aside, I decided earlier in the day to set up and go out with the 14” f/4.5 scope named Akule. As an added bonus, Mitchell Duke tipped me off to a transit of the Jovian moon, Ganymede.”

Note that Jupiter and its moons are currently casting their shadows nearly straight back from our perspective. Expect that to change, however, in the coming months,as Jupiter heads towards eastern dusk quadrature on April 1st and we see the action from a sideways angle. Watch the video in full screen mode and you’ll note that Mike captured some detail on the surface of Ganymede as well! Generally, at the eyepiece, the moons of Jupiter disappear entirely due to low contrast against the bulk of the planet, with only the black dot of the shadow seen… this video capture gives the ingress of Ganymede at the start of the transit a great 3-D appearance.

Webcam imaging of planets has really taken off in the past decade, with backyard astronomers now routinely capturing images that far surpass professional and textbook images from just a decade prior. Great images can be taken using nothing more than a telescope, a laptop, free image stacking software such as Registax, and a webcam converted to fit into an eyepiece holder… you may find that you’ve got the gear sitting around to image Jupiter, tonight.

Mr. Phillips rig, however, is a little more advanced. He notes in the description of the video that he’s using a Flea3 camera from PointGrey Research with a 5x Barlow lens yielding a 9200mm focal length. He’s also shooting at 120 frames per second, and taking successive red, green and blue images for 30 seconds. Finally, a derotation of Jupiter – yes, it really rotates that quickly, even in a short sequence – is accomplished using a sophisticated program named WINJupos.

Video stacking gives processors the ability to “freeze” and nab the best moments of seeing from thousands of frames. Some imagers hand select frames one by one, though many programs, such as Registax, use algorithms to nab the best frames from a preselected percentage of the total shot.

Local seeing conditions also play a key role in image capturing.

“I moved far away from the house as possible, and I think that helped some,” Michael noted. “I also started cooling the spit out of the mirror, aggressively. Even when cooled for a few hours in the winter, the heat in the Pyrex mirror comes back. I think there’s a small heat engine inside the beast!”

For best results, imagers tend to go after planets when they’re at their highest in the sky, and viewed through the least amount of turbulent atmosphere. This is when a planet is transiting the local north to south meridian, and when it’s at opposition, which Jupiter is this month. At opposition, a planet transits at local midnight. The same goes for the best opportunities for visual observing as well.

Shadow transits of Jupiter’s moons are also just plain fun to watch. In an often unchanging universe, they offer a chance to see something unfolding in real time. Jupiter has the fastest rotation of any planet at 9.9 hours, and the large Galilean moons of Io, Europa, Ganymede and Callisto are tidally locked in their rotation, keeping one hemisphere permanently turned towards Jupiter like the Moon does orbiting the Earth. The inner three moons also keep a 1:2:4 orbital resonance, assuring you’ll never see more than three of the four Galilean moons transiting from your line of sight at once. You can see two of the inner three moons, plus Callisto in transit, but never all four at the same time! A triple transit last occurred on October 12^th, 2013, and will next occur for observers in eastern Europe and Africa this year on June 3^rd.

We’re also currently in the midst of a series of shadow transits for the outermost Galilean moon Callisto, which end in July 2016. Can you identify the different moons by the size and hue of shadows they cast? Sky & Telescope publishes a great table for the ingress and egress of Jupiter’s moons. You can also check them out using the freeware program Stellarium.

The double shadow transit of February 6th as seen at 11:22 UT. Created by the author using Starry Night Education software.

Can’t wait that long? A double shadow transit involving Europa and Callisto occurs in just a few weeks for western North America from 10:20 UT-12:44UT on the morning of February 6^th, a chance for another stunning animation sequence…

Congrats to Michael Phillips on a great capture!