Two spacecraft, Dawn and New Horizon will reach their final objectives in 2015 - Dwarf Planets - Ceres and Pluto. (Credit: NASA, Illustration - T.Reyes)
Together, the space probes Dawn and New Horizons have been in flight for a collective 17 years. One remained close to home and the other departed to parts of the Solar System of which little is known. They now share a common destination in the same year: dwarf planets.
At the time of these NASA probes’ departures, Ceres had just lost its designation as the largest asteroid in our Solar System. Pluto was the ninth planet. Both probes now stand to deliver measures of new data and insight that could spearhead yet another revision of the definition of planet.
A comparison of the trajectories of New Horizons (left) and the Dawn missions (right). (Credit: NASA/JPL, SWRI, Composite- T.Reyes)
Certainly, NASA’s Year of the Dwarf Planet is an unofficial designation and NASA representatives would be quick to emphasize another dozen or more missions that are of importance during the year 2015. However, these two missions could determine the fate of billions or more small bodies just within our galaxy, the Milky Way.
If Ceres and Pluto are studied up close – mission success is never a sure thing – then what is observed could lead to a new, more certain and accepted definition of planet, dwarf planet, and possibly other new definitions.
The New Horizons mission became the first mission of NASA’s New Frontiers program, beginning development in 2001. The probe was launched on January 19, 2006, atop an Atlas V 551 (5 solid rocket boosters plus a third stage). Utilizing more compact and lightweight electronics than its predecessors to the outer planets – Pioneer 10 & 11, and Voyager 1 & 2 – the combination of reduced weight, a powerful launch vehicle, plus a gravity assist from Jupiter has lead to a nine year journey. On December 6, 2014, New Horizons was taken out of hibernation for the last time and now remains powered on until the Pluto encounter.
This “movie” of Pluto and its largest moon, Charon, by NASA’s New Horizons spacecraft taken in July 2014 clearly shows that the barycenter – the center of mass of the two bodies – resides outside (between) both bodies. The 12 images that make up the movie were taken by the spacecraft’s best telescopic camera – the Long Range Reconnaissance Imager (LORRI) – at distances ranging from about 267 million to 262 million miles (429 million to 422 million kilometers). Charon is orbiting approximately 11,200 miles (about 18,000 kilometers) above Pluto’s surface. (Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute)
The arrival date of New Horizon is July 14, 2015. A telescope called the Long Range Reconnaissance Imager (LORRI) has permitted the commencement of observations while still over 240 million kilometers (150 million miles) from Pluto. The first stellar-like images were taken while still in the Asteroid belt in 2006.
Pluto was once the ninth planet of the Solar System. From its discovery in 1930 by Clyde Tombaugh until 2006, it maintained this status. In that latter year, the International Astronomical Union undertook a debate and then a membership vote that redefined what a planet is. The change occurred 8 months after New Horizons’ launch. There were some upset mission scientists, foremost of which was the principal investigator, Dr. Alan Stern, from the Southwest Research Institute in San Antonio, Texas. In a sense, the rug had been pulled from under them.
A gentleman’s battle ensued between opposing protagonists Dr. Stern and Dr. Michael Brown from Caltech. In 2001, Dr. Brown’s research team began to discover Kuiper belt objects (Trans-Neptunian objects) that rivaled the size of Pluto. Pluto suddenly appeared to be one of many small bodies that could likely number in the trillions within just one galaxy – ours. According to Dr. Brown, there could be as many as 200 objects in our Solar System similar to Pluto that, under the old definition, could be defined as planets. Dr. Brown’s work was the straw that broke the camel’s back – that is, it led to the redefinition of planet, and the native of Huntsville, Alabama, went on to write a popular book, How I Killed Pluto and Why It Had It Coming.
Dr. Stern’s story involving Pluto and planetary research is a longer and more circuitous one. Stern was the Executive Director of the Southwest Research Institute’s Space Science and Engineering Division and then accepted the position of Associate Administrator of NASA’s Science Mission Directorate in 2007. Clearly, after a nine year journey, Stern is now fully committed to New Horizons’ close encounter. More descriptions of the two protagonists of the Pluto debate will be included in a follow on story.
Artist’s concept depicting the Dawn spacecraft thrusting with its ion propulsion system as it travels from Vesta (lower right) to Ceres (upper left). The galaxies in the background are part of the Virgo supercluster. Dawn, Vesta, and Ceres are currently in the constellation Virgo from the perspective of viewers on Earth. (Image credit: NASA/JPL)
The JPL and Orbital Science Corporation developed Dawn space probe began its journey to the main asteroid belt on September 27, 2007. It has used gravity assists and flew by the planet Mars. Dawn spent 14 months surveying Vesta, the 4th largest asteroid of the main belt (assuming Ceres is still considered the largest). While New Horizons has traveled over 30 Astronomical Units (A.U.) – 30 times the distance from the Earth to the Sun – Dawn has remained closer and required reaching a little over 2 A.U. to reach Vesta and now 3 A.U. to reach Ceres.
The Dawn mission had the clear objective of rendezvous and achieving orbit with two asteroids in the main belt between Mars and Jupiter. Dawn was also sent packing the next generation of Ion Propulsion. It has proven its effectiveness very well, having used ion propulsion for the first time to achieve an orbit. Pretty simple, right? Not so fast.
As Dawn was passing critical design reviews during development, the redefinition of planet lofted its second objective – the asteroid 1 Ceres – to a new status. While Pluto was demoted, Ceres was promoted from its scrappy status of biggest of the asteroids – the debris, the leftovers of our solar system’s development – to dwarf planet. Even 4 Vesta is now designated a proto-planet.
Artist rendition of Dawn spacecraft orbiting Vesta. (Credit: NASA/JPL-Caltech)
So now the stage is set. Dawn will arrive first at a dwarf planet – Ceres – in April. With a small, low gravity body and ion propulsion, the arrival is slow and cautious. If the two missions fair well and achieve their goals, 2015 is likely to become a pivotal year in the debate over the classification of non-stellar objects throughout the universe.
Just days ago, at the American Geophysical Union Conference in San Francisco, Dr. Stern and team described the status and more details of the goals of New Horizons. Since arriving, more moons of Pluto have been discovered. There is the potential that faint rings exist and Pluto may even harbor an interior ocean due to the tidal forces from its largest moon, Charon. And Dawn mission scientists have seen the prospects for Ceres’ change. Not just the status, the latest Hubble images of Ceres is showing bright spots which could be water ice deposits and could also harbor an internal ocean.
The Solar System is becoming a more crowded place. This picture shows the sizes of dwarf planets Pluto, Ceres, Eris, and Makemake as compared to Earth and Earth’s Moon, here called “Luna.” None of the distances between objects are to scale. (Credit: NASA)
So other NASA missions notwithstanding, this is the year of the dwarf planet. NASA will provide Humanity with its first close encounters with the most numerous of small round – by their self-gravity – bodies in the Universe. They are now called dwarf planets but ask Dr. Stern and company, the public, and many other planetary scientists and you will discover that the jury is still out.
It hard to think of a more influential modern planetary scientist than Carolyn Porco, the leader of the imaging team for NASA’s Cassini mission exploring Saturn. But before Cassini, Porco was involved in Voyager missions, and she’ll be leading up the imaging team for New Horizons.
We record Astronomy Cast as a live Google+ Hangout on Air every Monday at 12:00 pm Pacific / 3:00 pm Eastern. You can watch here on Universe Today or from the Astronomy Cast Google+ page.
Comet C/2014 Q2 Lovejoy photographed overnight December 28-29, 2014 remotely from Siding Spring, Australia as passed within 1/6 degree of the globular cluster M79. The coma glows green from fluorescing carbon molecules while the narrow ion tail is carbon monoxide gas fluorescing in UV sunlight. Credit: Rolando Ligustri
Oh my, oh my. Rolando Ligustri captured this scene last night as Comet Q2 Lovejoy swished past the globular cluster M79 in Lepus. If you’ve seen the movie Wild or read the book, you’ll be familiar with the phrase “put yourself in the way of beauty”, a maxim for living life adopted by one of its characters. When I opened up my e-mail today and saw Rolando’s photo, I felt like the beauty truck ran right over me.
Another striking image of the comet’s juxtaposition with the globular cluster M79. Lovejoy is presently 48 million miles from Earth; the cluster lies at the immense distance of 41,000 light years. Credit: Chris Schur
More beautiful images arrived later including this one by Chris Schur of Arizona.
Even with the Moon at first quarter phase, the comet was plainly visible in binoculars last night shining at magnitude +5. I used 8x40s and had no problem seeing Lovejoy’s blobby glow. With a coma about 15-20 arc minutes in diameter or more than half the size of a the Full Moon, it really fills up the field of view when seen through a telescope at low to medium magnification.
A tighter view of the top image shows not only the star cluster but also shows 13th magnitude NGC 1886, an edge-on spiral galaxy. Credit: Rolando Ligustri
If you love the aqua blue hues of the Caribbean, Lovejoy will remind you it’s time to book another tropical vacation. In both my 15-inch (37-cm) and 10-inch (25-cm) reflectors, the coma glowed a delicious pale blue-green in contrast to the pearly white cluster. I encourage you to look for the comet in the next few nights before the Moon is full. Starting on January 6-7, the Moon begins its move out of the evening sky, giving observers with dark skies a chance to view Lovejoy with the naked eye. I’m looking forward to seeing its long, faint tail twist among the stars of Eridanus as the comet rapidly moves northward over the next week.
Using Photoshop I made this drawing of the comet and cluster that captures its visual appearance through the telescope last night December 28th. The nuclear region is very intense and bright and about 10 arc seconds across. Credit: Bob King
For a map on how to find the comet, check my recent article on Lovejoy’s many tails. Cheers to finding beauty the next clear night!
Comet Lovejoy was bright enough to nab in a 15-second time exposure with a 200mm telephoto lens last night. Details: f/2.8 at 13 seconds. Credit: Bob King
Jupiter's Europa passes in front of fellow moon Io in this sequence of images taken from the Gemini North observatory Dec. 16, 2014. Credit: Gemini Observatory
On Christmas Eve, as millions upon millions of people focused on wrapping gifts and getting ready for the holidays, an amateur astronomer gave a small gift to the world. The person turned a telescope and camera to Jupiter and caught volcanic Io going across the face of the gas giant. This happened just a few days after professional astronomers caught a rare eclipse involving that very same moon.
“I wish I had been able to go on for longer but Jupiter went behind the house just before the transit ended. The transit is 102 frames (306 captures in total, RGB separate). Seeing was rather poor and a small amount of dew formed resulting in reduced brightness and contrast in some parts of the GIF,” wrote Reddit user IKYLSP.
“Something rather interesting with this one is the brief appearance of Ganymede from behind the planet’s shadow just before it’s eclipsed by the planet. If you zoom in you can actually see it as a half-moon shape which is really awesome.”
Jupiter’s moon Europa passes in front of Io in this picture captured from the Gemini North observatory on Dec. 16, 2014. Credit: Gemini Observatory
Speaking of half-moons, check out another awesome animation of Io taken from the Gemini North observatory on Dec. 16. Here, you can see icy Europa passing in front of the volcanic moon from the telescope’s perspective. Here’s part of what the observatory wrote about the rare event:
Observations of Jupiter’s volcanically active moon Io, obtained that night as part of a program led by Katherine de Kleer of UC Berkeley to watch for volcanic outbursts, revealed an unusual event involving Io and another large jovian moon, Europa. According to de Kleer, the images captured an occultation event in which Europa briefly blocked some of the light from Io, “…giving Io a very un-Io-like appearance!” These sorts of events occur when we observe the moons’ orbits edge-on, and can occasionally view the moons passing in front of one another.
And below you can see individual frames from the eclipse.
Jupiter’s Europa passes in front of fellow moon Io in this sequence of images taken from the Gemini North observatory Dec. 16, 2014. Credit: Gemini Observatory
Canadian astronaut Chris Hadfield in the Cupola of the International Space Station. Credit: NASA/CSA
While the world was enchanted with Chris Hadfield’s social media posts last year, a new video has the retired astronaut talking about loftier things. Say, for example, how humanity landed a camera on the Saturn moon Titan back in 2005. Or to be more practical, the fact that smallpox was eradicated in its naturally occurring form.
In his talks and books, Hadfield describes himself as one who never focuses on complaining. He was almost yanked from his command of the International Space Station due to a medical issue, but he pressed on and convinced the doctors to let him fly. And in this new video, he focuses on what humans do generally to make the world better — imperfect as it is.
“There are problems with everything, and nothing’s perfect, but that shouldn’t be cause to moan. That should be cause to achieve. Our world is a better place than we often claim it to be,” Hadfield said. “We live the way we do,” he added, “because people chose to tackle their problems, head on.”
The video appears to have a heavy emphasis on the Bill & Melinda Gates Foundation, a gigantic philanthropic network that works to improve lives in the developing world and also for the disadvantaged in the United States. But there are many ways to give back to your community, even through gestures as simple as volunteering.
Here are some examples in the space world (note that these aren’t necessarily endorsements for the organizations, but just ideas for making contributions in space and astronomy):
Cosmoquest, which runs online astronomy courses and also allows citizens to map extraterrestrial bodies right alongside astronomers.
Astronomers Without Borders brings astronomy education across the world, particularly to developing countries.
Uwingu says that half of its donations goes to grants to support learning in astronomy.
Other examples of space-y charity could include volunteering or donating to a local school or university, joining one of the numerous volunteer organizations in astronomy, or getting involved in a space advocacy group.
Panel of negative images showing the tail of Comet Lovejoy disconnecting. Credit: Hisayoshi Kato
Maybe you’ve seen Comet Q2 Lovejoy. It’s a big fuzzy ball in binoculars low in the southern sky in the little constellation Lepus the Hare. That’s the comet’s coma or temporary atmosphere of dust and gas that forms when ice vaporizes in sunlight from the nucleus. Until recently a faint 3° ion or gas tail trailed in the coma’s wake, but on and around December 23rd it snapped off and was ferried away by the solar wind. Just as quickly, Lovejoy re-grew a new ion tail but can’t seem to hold onto that one either. Like a feather in the wind, it’s in the process of being whisked away today.
Magnetic field lines bound up in the sun’s wind pile up and drape around a comet’s nucleus to shape the blue ion tail. Notice the oppositely-directed fields on the comet’s backside. The top set points away from the comet; the bottom set toward. In strong wind gusts, the two can be squeezed together and reconnect, releasing energy that snaps off a comet’s tail. Credit: Tufts University.
Easy come, easy go. Comets usually have two tails, one of dust particles that reflect sunlight and another of ionized gases that fluoresce in Sun’s ultraviolet radiation. Ion tails form when cometary gases, primarily carbon monoxide, are ionized by solar radiation and lose an electron to become positively charged. Once “electrified”, they’re susceptible to magnetic fields embedded in the high-speed stream of charged particles flowing from the Sun called the solar wind. Magnetic field lines embedded in the wind drape around the comet and draw the ions into a long, skinny tail directly opposite the Sun.
Part of Comet Lovejoy Q2’s ion tail (left) cuts the cord and floats away from the comet as photographed on December 23, 2014. Carbon monoxide in the tail fluoresces blue in ultraviolet sunlight. Credit: Chris Schur
Disconnection events happen when fluctuations in the solar wind cause oppositely directed magnetic fields to reconnect in explosive fashion and release energy that severs the tail. Set free, it drifts away from the comet and dissipates. In active comets, the nucleus continues to produce gases, which in turn are ionized by the Sun and drawn out into a replacement appendage. In one of those delightful coincidences, comets and geckos both share the ability to re-grow a lost tail.
Comet Encke tail disconnection April 20, 2007 as seen by STEREO
Comet Halley experienced two ion tail disconnection events in 1986, but one of the most dramatic was recorded by NASA’s STEREO spacecraft on April 20, 2007. A powerful coronal mass ejection (CME) blew by comet 2P/Encke that spring day wreaking havoc with its tail. Magnetic field lines from the plasma blast reconnected with opposite polarity magnetic fields draped around the comet much like when the north and south poles of two magnets snap together. The result? A burst of energy that sent the tail flying.
Diagram showing how a CME slammed into Comet Encke (B) and snapped off its tail. Soon enough, the comet grew a new one (D). Credit: NASA
Comet Lovejoy may have also crossed a sector boundary where the magnetic field carried across the Solar System by Sun’s constant breeze changed direction from south to north or north to south, opposite the magnetic domain the comet was immersed in before the crossing. Whether solar wind flutters, coronal mass ejections or sector boundary crossings, more tail budding likely lies in Lovejoy’s future. Like the chard in your garden that continues to sprout after repeated snipping, the comet seems poised to spring new tails on demand.
Comet Lovejoy picks up speed in late December as it travels from southern Lepus into Eridanus. Its position shown nightly at 10 p.m. (CST). On Sunday night December 28th it passes very close to the bright globular cluster M79. Stars shown to magnitude +8.0. Source: Chris Marriott’s SkyMap software
If you haven’t seen the comet, it’s now glowing at magnitude +5.5 and faintly visible to the naked eye from a dark sky site. Without an obvious dust tail and sporting a faint ion tail(s), the comet’s basically a giant coma, a fuzzy glowing ball easily visible in a pair of binoculars or small telescope.
A second tail disconnection event recorded on December 26, 2014 by John Nassr from his observatory in Baguio, Philippines. The frame is 3° wide. Credit: John Nassr
In a very real sense, Comet Lovejoy experienced a space weather event much like what happens when a CME compresses Earth’s magnetic field causing field lines of opposite polarity to reconnect on the back or nightside of the planet. The energy released sends millions of electrons and protons cascading down into our upper atmosphere where they stimulate molecules of oxygen and nitrogen to glow and produce the aurora. One wonders whether comets might even experience their own brief auroral displays.
Excellent visualization showing how magnetic fields line on Earth’s nightside reconnect to create the rain of electrons that cause the aurora borealis. Notice the similarity to comet tail loss.
From the ground, aurora have mystified humans since we began to question the world. The space age revealed more mystery - the Theta Auroral Oval (inset) and the challenge of understanding the phenomena. (Photo Credit: NASA/APOD)
The mystery of the northern lights – aurora – spans time beyond history and to cultures of both the southern and northern hemispheres. The mystery involves the lights, fantastic patterns and mystical changes. Ancient men and women stood huddled under them wondering what it meant. Was it messages from the gods, the spirits of loved ones, warnings or messages to comfort their souls?
Aurora reside literally at the edge of space. While we know the basics and even more, we are still learning. A new published work has just added to our understanding by explaining how one type of aurora – the Theta Aurora – is created from the interaction of the charged particles, electric and magnetic fields surrounding the Earth. Their conclusions required the coordination of simultaneous observations of two missions.
The Theta Auroral Oval as observed by the NASA IMAGE FUV camera on September 15, 2005 and anlayzed using Cluster data in the paper by Fear et al. (Credit: NASA/SWRI)
We were not aware of Thetas until the advent of the space age and our peering back at Earth. They cannot be recognized from the ground. The auroras that bystanders see from locales such as Norway or New Zealand are just arcs and subsets of the bigger picture which is the auroral ovals atop the polar regions of the Earth. Ground based all-sky cameras and polar orbiting probes had seen what were deemed “polar cap arcs.” However, it was a spacecraft Dynamics Explorer I (DE-1) that was the first to make global images of the auroral ovals and observed the first “transpolar arcs”, that is, the Theta aurora.
They are named Theta after the Greek letter that they resemble. Thetas are uncommon and do not persist long. Early on in the exploration of this phenomenon, researchers have been aware that they occur when the Sun’s magnetic field, called the Interplanetary Magnetic Field (IMF) turns northward. Most of the time the IMF in the vicinity of the Earth points south. It is a critical aspect of the Sun-Earth interaction. The southerly pointing field is able to dovetail readily with the normal direction of the Earth’s magnetic field. The northward IMF interacting with the Earth’s field is similar to two bar magnets turned head to head, repelling each other. When the IMF flips northward locally, a convolution takes place that will, at times, but not always, produce a Theta aurora.
A group of researchers led by Dr. Robert Fear from the Department of Physics & Astronomy, University of Leicester, through analysis of simultaneous spacecraft observations, has identified how the particles and fields interact to produce Theta aurora. Their study, “Direct observation of closed magnetic flux trapped in the high-latitude magnetosphere” in the Journal Science (December 19, 2014, Vol 346) utilized a combination of data from ESA’s Cluster spacecraft mission and the IMAGE spacecraft of NASA. The specific event in the Earth’s magnetosphere on September 15, 2005 was observed simultaneously by the spacecraft of both missions.
Illustrations of the Cluster II spacecraft in orbit and formation around the Earth and the NASA IMAGE spacecraft vehicle design. The two mission’s observations were combined to correlate numerous auroral and magnetospheric events. Cluster II remains in operation as of December 2014 (14 yr lifespan). (Credit: ESA, NASA)
Due to the complexity of the Sun-Earth relationship involving neutral and charged particles and electric and magnetic fields, space scientists have long attempted to make simultaneous measurements with multiple spacecraft. ISEE-1, 2 and 3 were one early attempt. Another was the Dynamics Explorer 1 & 2 spacecraft. DE-2 was in a low orbit while DE-1 was in an elongated orbit taking it deeper into the magnetosphere. At times, the pair would align on the same magnetic field lines. The field lines are like rails that guide the charged particles from far out in the magneto-tail to all the way down to the upper atmosphere – the ionosphere. Placing two or more spacecraft on the same field lines presented the means of making coordinated observations of the same event. Dr. Fear and colleagues analyzed data when ESA’s Cluster resided in the southern lobe of the magnetotail and NASA’s IMAGE (Imager for Magnetopause-to-Aurora Global Exploration) spacecraft resided above the south polar region of the Earth.
Cluster is a set of four spacecraft, still in operation after 14 years. Together with IMAGE, five craft were observing the event. Fear, et al utilized ESA spacecraft Cluster 1 (of four) and NASA’s IMAGE. On that fateful day, the IMF turned north. As described in Dr. Fear’s paper, on that day, the north and south lobes of the magnetosphere were closed. The magnetic field lines of the lobes were separated from the Solar wind and IMF due to what is called magnetic reconnection. The following diagram shows how complex Earth’s magnetosphere is; with regions such as the bow shock, magnetopause, cusps, magnetotail, particle belts and the lobes.
Illustration of the Earth’s magnetosphere showing it complexity. The Theta Aurora are now confidently linked to magnetic reconnection events in the lobes of the magnetotail. (Credit: NASA)
The science paper explains that what was previously observed by only lower altitude spacecraft was captured by Cluster within the magnetotail lobes. The southerly lobe’s plasma – ionized particles – was very energetic. The measurements revealed that the southern lobe of the magnetotail was acting as a bottle and the particles were bouncing between two magnetic mirrors, that is, the lobes were close due to reconnection. The particles were highly energetic.
The presence of what is called a double loss cone signature in the electron energy distribution was a clear indicator that the particles were trapped and oscillating between mirror points. The consequences for the Earth’s ionosphere was that highly energetic particles flooded down the field lines from the lobes and impacted the upper atmosphere transferring their energy and causing the magnificent light show that we know as the Northern Lights (or Southern) in the form of a Theta Auroral Oval. This strong evidence supports the theory that Theta aurora are produced by energized particles from within closed field lines and not by energetic particles directly from the Solar Wind that find a path into the magnetosphere and reach the upper atmosphere of the Earth.
A video of an observed major geomagnetic storm (July 15, 2000, southward IMF) taken by the Far Ultraviolet Imaging System (FUV) on the spacecraft IMAGE. IMAGE operated from 2000 until December 2005 when communications were inexplicably lost. (Credit: NASA/SWRI) [click to view the animated gif]Without the coordination of the observations and the collective analysis, the Theta aurora phenomenon would continue to be debated. The analysis by Dr. Fear, while not definitive, is strong proof that Theta aurora are generated from particles trapped within closed field lines.
The analysis of the Cluster mission data as well as that of many other missions takes years. Years after observations are made researchers can achieve new understanding through study of arduous details or sometimes by a ha-ha moment. Aurora represent the signature of the interaction of two magnetic fields and two populations of particles – the Sun’s field and energetic particles streaming at millions of miles per hour from its surface reaching the Earth’s magnetic field. The Earth’s field is transformed by the interaction and receives energetic particles that it bottles up and energizes further. Ultimately, the Earth’s magnetic field directs some of these particles to the topside of our atmosphere. For thousands and likely tens of thousands of years, humans have questioned what it all means. Now another piece of the puzzle has been laid down with a good degree of certainty; one that explains the Theta aurora.
Now in its seventh year of compilation and the second year running on Universe Today, we’re proud to feature our list of astronomical happenings for the coming year. Print it, bookmark it, hang it on your fridge or observatory wall. Not only is this the yearly article that we jokingly refer to as the “blog post it takes us six months to write,” but we like to think of it as unique, a mix of the mandatory, the predictable and the bizarre. It’s not a 10 ten listicle, and not a full-fledged almanac, but something in between.
A rundown of astronomy for 2015: There’s lots of astronomical action to look forward to in the coming year. 2015 features the minimum number of eclipses that can occur, two lunars and two solars. The Moon also reaches its minimum standstill this coming year, as its orbit runs shallow relative to the celestial equator. The Moon will also occult all naked eye planets except Saturn in 2015, and will occult the bright star Aldebaran 13 times — once during every lunation in 2015. And speaking of Saturn, the rings of the distant planet are tilted an average of 24 degrees and opening to our line of sight in 2015 as they head towards their widest in 2018.
Finally, solar activity is trending downwards in 2015 after passing the sputtering 2014 maximum for solar cycle #24 as we now head towards a solar minimum around 2020.
Our best bets: Don’t miss these fine celestial spectacles coming to a sky near YOU next year:
– The two final total lunar eclipses in the ongoing tetrad, one on April 4th and September 28th.
– The only total solar eclipse of 2015 on March 20th, crossing the high Arctic.
– A fine dusk pairing of the bright planets Jupiter and Venus on July 1st.
– Possible wildcard outbursts from the Alpha Monocerotid and Taurid meteors, and a favorable New Moon near the peak of the August Perseids.
– Possible naked eye appearances by comet Q2 Lovejoy opening 2015 and comet US10 Catalina later in the year.
– The occultation of a naked eye star for Miami by an asteroid on September 3rd.
– A series of fine occultations by the Moon of bright star Aldebaran worldwide.
The rules: The comprehensive list that follows has been lovingly distilled down to the top 101 astronomical events for 2015 worldwide. Some, such as lunar eclipses, are visible to a wide swath of humanity, while others, such as many of the asteroid occultations or the sole total solar eclipse of 2015 happen over remote locales. We whittled the list down to a “Top 101” using the following criterion:
Meteor showers: Must have a predicted ZHR greater than 10.
Conjunctions: Must be closer than one degree.
Asteroid occultations: Must have a probability ranking better than 90 and occult a star brighter than magnitude +8.
Comets: Must reach a predicted brightness greater than magnitude +10. But remember: comets don’t always read prognostications such as this, and may over or under perform at whim… and the next big one could come by at any time!
Times quoted are geocentric unless otherwise noted, and are quoted in Universal Time in a 24- hour clock format.
These events are meant to merely whet the appetite. Expect ‘em to be expounded on fully by Universe Today as they approach. We linked to the events listed where possible, and provided a handy list of resources that we routinely consult at the end of the article.
Got it? Good… then without further fanfare, here’s the top 101 astronomical events for 2015 in chronological order:
The path of Comet Q2 Lovejoy from January 1st to January 31st. Created using Starry Night Education software.
29- The Moon occults Aldebaran at ~17:31 UT for the Arctic, marking the first of 13 occultations of the star by the Moon in 2015.
The view at 6:40 UT on January 24th, as 3 of Jupiter’s moons cast shadows on to the Jovian cloud tops simultaneously. Created using Starry Night Education software.
February
01- Venus passes 0.8 degrees south of Neptune at ~17:00 UT.
05- Earth crosses through Jupiter’s equatorial plane, marking the middle of occultation and eclipse season for the Galilean moons.
06- Jupiter reaches opposition at ~18:00 UT.
18- A “Black Moon” occurs, in the sense of the third New Moon in a season with four.
22- Venus passes 0.4 degrees south of Mars at 5:00 UT.
24- Mercury reaches greatest morning elongation at 26.7 degrees west of the Sun at 19:00 UT.
21- Io and Ganymede both cast shadows on Jupiter from 00:04 to 00:33 UT.
21- Callisto and Europa both cast shadows on Jupiter from 13:26 to 13:59 UT.
23- Saturn reaches opposition at ~1:00 UT.
24- Asteroid 1669 Dagmar occults the +1st magnitude star Regulus at ~16:47 UT for the Arabian peninsula,
the brightest star occulted by an asteroid for 2015.
28- Ganymede and Io both cast shadows on Jupiter from 02:01 to 04:18 UT.
30- Comet 19P/Borrelly may reach binocular visibility.
June
01- The International Space Station reaches full illumination as the June solstice nears, resulting in multiple nightly passes favoring northern hemisphere observers.
04- Io and Ganymede both cast shadows on Jupiter from 4:54 to 6:13 UT.
05- Venus reaches greatest eastern (dusk) elongation for 2015, 45 degrees from the Sun at 16:00 UT.
10- Asteroid 424 Gratia occults a +6.1 magnitude star at ~15:10 UT for northwestern Australia.
13- The Perseid meteors peak from 06:30 to 09:00 UT, with a maximum predicted ZHR of 100 favoring North America.
19- Mars crosses the Beehive Cluster M44.
28- Asteroid 16 Psyche occults a +6.4 magnitude star at ~9:49 UT for Bolivia and Peru.
29- Supermoon 1 of 3 for 2015: The Moon reaches Full at 18:38 UT, 20 hours from perigee.
The path of the Moon through the Earth’s shadow on September 28th. Credit: Fred Espenak/NASA/GSFC
September
01- Neptune reaches opposition at ~3:00 UT.
03- Asteroid 112 Iphigenia occults a +3rd magnitude star for Mexico and Miami at ~9:20 UT. This is the brightest star occulted by an asteroid in 2015 for North America.
02- Geostationary satellite and SDO eclipse season begins as we approach the September equinox.
04- Mercury reaches its greatest elongation for 2015, at 27 degrees east of the Sun at 8:00 UT in the dusk skies.
05- The Moon occults Aldebaran for northeastern North America at ~5:38 UT.
13- “Shallow point” (also known as the minor lunar standstill) occurs over the next lunation, as the Moon’s orbit reaches a shallow minimum of 18.1 degrees inclination with respect to the celestial equator… the path of the Moon now begins to widen towards 2025.
13- A partial solar eclipse occurs, centered on 6:55 UT crossing Africa and the Indian Ocean.
25- Mars passes 0.8 degrees from Regulus at ~4:00 UT.
28- A total lunar eclipse occurs centered on 2:48 UT, visible from the Pacific, the Americas and eastern Europe.
28- Supermoon 2 of 3 for 2015: The Moon reaches Full at 2:52 UT, approximately an hour from perigee. This marks the closest Full Moon of the year.
The path of the September 3rd occultation of a +3rd magnitude star by an asteroid over central Mexico and the Florida Keys. Credit: IOTA/Steve Preston.
The Moon occults Aldebaran: the visibility footprint for North America. The dashed line denotes the area in which the event occurs during the daytime. Credit: Occult 4.1.0.11.
November
01- Io and Ganymede both cast shadows on Jupiter from 17:36 to 17:47 UT.
02- Venus passes 0.7 degrees south of Mars at 00:30 UT.
12- Will the 7 year “Taurid fireball meteor shower” produce?
18- The Leonid meteor shower peaks at 04:00 UT, with an estimated ZHR of 15 favoring Europe.
22- Are we in for a once per decade Alpha Monocerotids outburst? The 2015 peak arrives at 4:25 UT, favoring Europe… with a max ZHR = 400+ possible.
The daytime occultation of Venus by the Moon over North America on December 7th.Credit: Occult 4.1.0.11.
December
01- The International Space Station reaches full illumination as the December solstice nears, resulting in multiple nightly passes favoring the southern hemisphere.
04- Mercury occults the +3.3 magnitude star Theta Ophiuchi for South Africa at 16:16 UT prior to dusk.
06- The Moon occults Mars for central Africa at ~2:42 UT.
07- The Moon occults Venus in the daytime for North America at ~16:55 UT.
14- The Geminid meteor shower peaks at 18:00 UT, with a ZHR=120 favoring NE Asia.
Keeping warm? Yesterday marked the start of astronomical winter for the northern hemisphere, meaning long nights and (hopefully) clear, cold skies. But we’ve also got another reason to brave the cold this week, as Comet C/2014 Q2 Lovejoy is set to put on a show for northern hemisphere observers.
Already, Comet Q2 Lovejoy has been providing southern hemisphere observers with a fine celestial showing. Discovered by Australian comet hunter extraordinaire Terry Lovejoy on August 17th of this year as it glided across the constellation Puppis, Q2 Lovejoy has been brightening through early December ahead of expectations. We’ve already been getting some great images from Universe Today readers down south, and we can expect more in the weeks to come. This is Mr. Lovejoy’s fifth comet discovery, and many will remember how comet C/2011 W3 Lovejoy also survived a perilous perihelion passage just 140,000 kilometres from the surface of the Sun during the 2011 holiday season and went on to produce a brilliant display.
Q2 Lovejoy plus negative image taken from New Mexico on December 20th. Credit and copyright: Joseph Brimacombe.
Currently shining at magnitude +5.5, Q2 Lovejoy is a fine target for binoculars or a small telescope as it crosses the southern constellation of Columba into Lepus just after Christmas Day. Sirius currently makes a good guidepost, as the comet sits about 19 degrees southeast of the brightest star in the sky. And speaking of Sirius, don’t forget to try your hand at spotting its white dwarf companion in 2015!
A black and white view of Comet Lovejoy, taken on Dec. 21, 2014, highlighting the comet’s dramatic tail. Credit and copyright: Damian Peach.
Q2 Lovejoy also has a high orbital inclination of 80.3 degrees relative to the ecliptic, which is good news, as it will be plunging rapidly northward as it makes its closest passage by Earth on January 7th at 70.2 million kilometres or 0.47 A.U.s distant. Note that not only will the comet pass extremely close to the globular cluster M79 (photo op!) on the night of December 29th, but will also pass within 10 degrees of the Pleiades in January before threading its way northward between the famous Double Cluster in Perseus and the Andromeda Galaxy.
Clouded out? You can catch Comet Q2 Lovejoy courtesy of Gianluca Masi and our good friends over at the Virtual Telescope Project live on January 6th and January 11th at 19:00 Universal Time/2:00 PM EST on both dates:
Note: the photo is of Comet C/2014 E2 Jacques from earlier this year. (Credit: the Virtual Telescope Project).
Expect Q2 Lovejoy to ride highest to the south around local midnight starting on January 1st, and transit the local meridian at 8-9 PM local by mid-month. Keen eyed observers have already managed to spy Q2 Lovejoy unaided from a dark sky site, and we expect this to be the general case for most observers by New Year’s Day. As of this writing, Q2 Lovejoy displays a fine coma 10’ wide with a 7 degree long, fan-shaped tail.
Comet Q2 Lovejoy imaged from Siding Spring Observatory in New South Wales, Australia on December 18th. Credit and copyright: Roger Hutchinson.
Here’s our handy blow-by-blow for Comet Q2 Lovejoy in the coming weeks:
December
28- Crosses into the constellation Lepus.
29- Passes less than 10’ — a third of the diameter of the Full Moon — from the 7.7 magnitude globular cluster NGC 1904 (Messier 79).
The path of Comet Q2 Lovejoy from December 23rd through February 1st. Credit: Starry Night Education software.
January
1- May break naked eye visibility at magnitude +6.
2- Passes into the constellation Eridanus and reaches opposition at 0.49 A.U.s from the Earth.
5- The Moon reaches Full, hampering observations.
7- May reach a peak brightness at +4th magnitude.
7- Passes closest to Earth 0.47 AU, moving at an apparent speed of almost 3 degrees a day.
9- Crosses the celestial equator into the constellation Taurus.
17- Crosses the ecliptic plane and into the constellation Aries.
20- Moon reaches New phase, marking a favorable span for observation.
22- Passes within one degree of the 3.6 magnitude star 41 Arietis.
25- Crosses into the constellation Triangulum.
30- Reaches perihelion at 1.29 A.U.
30- Crosses into the constellation Andromeda.
The position of Q2 Lovejoy on New Year’s Day. Credit: NASA/JPL.
February
3- The Moon reaches Full phase, hampering observations.
4- Passes less than one degree from the 2.1 magnitude star Gamma Andromedae (Almach).
18- The Moon reaches New, marking a favorable span of time for observations.
20- Passes less than a degree from the +4th magnitude star Phi Persei and into the constellation Perseus.
March
1- May drop below naked eye visibility.
2- Crosses into the constellation Cassiopeia.
5- The Moon reaches Full phase, hampering observations.
11- Passes less than one degree from the +5 magnitude Owl Cluster.
16- Passes less than one degree from the 2.6 magnitude star Delta Cassiopeiae (Ruchbah).
20- The Moon reaches New, marking a favorable time for observation.
From there, Comet Q2 Lovejoy drops back below +10th magnitude and passes just a degree from the north celestial pole in late May as it heads back out of the inner solar system. Q2 Lovejoy was on a 13,500 year orbit inbound, and its passage through the inner solar system shortened its orbit by about 5,000 years. Just think, about 13 millennia ago, Mesolithic man was busy domesticating early farm animals. Did they, by chance, look up and catch sight of Comet Q2 Lovejoy? And who will be here to ponder its return passage eight millennia hence?
Comet hunting is fun and easy… we prefer to sweep the target area with our trusty Canon 15×45 image stabilized binoculars, though a common pair of 7x 50’s — often favored by hunters and bird watchers — will do just fine. The passage by +7.7 magnitude globular cluster M79 this week will provide a fine contrast in “fuzz balls…” Remember, in comets as in nebulae, the quoted magnitude is often dispersed over a broad surface area, making the objects fainter than a pinpoint star of the same brightness.
And Comet Q2 Lovejoy is the first of several binocular comets to look forward to in 2015. Right now, we’ve got our money on comets C/2014 Q1 PanSTARRS, 19P/Borrelly, C/2013 US10 Catalina, and C/2013 X1 PanSTARRS as possible contenders in 2015. And don’t miss +9th magnitude Comet 15P/Finlay, currently in outburst and playing tag with the planet Mars low in the dusk sky.
Watch this space (bad pun intended) this coming Friday for the low down on all things astronomical in 2015!
-Got pics of Comet Q2 Lovejoy? Send ’em in to Universe Today.
This dwarf spheroidal galaxy in the constellation Fornax is a satellite of our Milky Way and is one of 10 used in Fermi's dark matter search. The motions of the galaxy's stars indicate that it is embedded in a massive halo of matter that cannot be seen. Credit: ESO/Digital Sky Survey 2
As part of the Local Group, a collection of 54 galaxies and dwarf galaxies that measures 10 million light years in diameter, the Milky Way has no shortage of neighbors. However, refinements made in the field of astronomy in recent years are leading to the observation of neighbors that were previously unseen. This, in turn, is changing our view of the local universe to one where things are a lot more crowded.
For instance, scientists working out of the Special Astrophysical Observatory in Karachai-Cherkessia, Russia, recently found a previously undetected dwarf galaxy that exists 7 million light years away. The discovery of this galaxy, named KKs3, and those like it is an exciting prospect for scientists, since they can tell us much about how stars are born in our universe.
The Russian team, led by Prof Igor Karachentsev of the Special Astrophysical Observatory (SAO), used the Hubble Space Telescope Advanced Camera for Surveys (ACS) to locate KKs3 in the southern sky near the constellation of Hydrus. The discovery occurred back in August 2014, when they finalized their observations a series of stars that have only one ten-thousandth the mass of the Milky Way.
Such dwarf galaxies are far more difficult to detect than others due to a number of distinct characteristics. KKs3 is what is known as a dwarf spheroid (or dSph) galaxy, a type that has no spiral arms like the Milky Way and also suffers from an absence of raw materials (like dust and gas). Since they lack the materials to form new stars, they are generally composed of older, fainter stars.
Image of the KKR 25 dwarf spheroid galaxy obtained by the Special Astrophysical Observatory using the HST. Credit: SAO RAS
In addition, these galaxies are typically found in close proximity to much larger galaxies, like Andromeda, which appear to have gobbled up their gas and dust long ago. Being faint in nature, and so close to far more luminous objects, is what makes them so tough to spot by direct observation.
Team member Prof Dimitry Makarov, also of the Special Astrophysical Observatory, described the process: “Finding objects like Kks3 is painstaking work, even with observatories like the Hubble Space Telescope. But with persistence, we’re slowly building up a map of our local neighborhood, which turns out to be less empty than we thought. It may be that are a huge number of dwarf spheroidal galaxies out there, something that would have profound consequences for our ideas about the evolution of the cosmos.”
Painstaking is no exaggeration. Since they are devoid of materials like clouds of gas and dust fields, scientists are forced to spot these galaxies by identifying individual stars. Because of this, only one other isolated dwarf spheroidal has been found in the Local Group: a dSph known as KKR 25, which was also discovered by the Russian research team back in 1999.
But despite the challenges of spotting them, astronomers are eager to find more examples of dSph galaxies. As it stands, it is believed that these isolated spheroids must have been born out of a period of rapid star formation, before the galaxies were stripped of their dust and gas or used them all up.
Studying more of these galaxies can therefore tell us much about the process star formation in our universe. The Russian team expects that the task will become easier in the coming years as the James Webb Space Telescope and the European Extremely Large Telescope begin service.
Much like the Spitzer Space Telescope, these next-generation telescopes are optimized for infrared detection and will therefore prove very useful in picking out faint stars. This, in turn, will also give us a more complete understanding of our universe and all that it holds.
![A video of an observed major geomagnetic storm (July 15, 2000) taken by the Far Ultraviolet Imaging System (FUV) on IMAGE. IMAGE operated from 2000 to December 2005 when communications were lost. (Credit: NASA/SWRI) [click to view the animated gif]](https://www.universetoday.com/wp-content/uploads/2014/12/IMAGE_Aurora-200007151.gif)
