You can start exploring tonight! All you need is a little practical advice and this guide. There’s an infinite universe of celestial wonders to see and discover. Download our FREE Welcome Guide To Astronomy (PDF [643KB])
Pluto Is A Planet, And So Is Eris
Is Pluto a planet? What is a planet, anyhow? We hope you’ll agree that the IAU's current answers to these questions are unclear and confusing. Here, we propose clear and unambiguous answers to these fundamentally unclear problems. Above all, we hope you have fun with the debate, no matter what side of it your heart may lay on.
The Planet Definition Mess
As astronomers began to discover objects similar in size to Pluto, culminating with the discovery of Eris in 2005, it quickly became clear that if Pluto was a planet, so should Eris. And if Eris was a planet why not some of the other newly discovered objects. Our solar system might have dozens of planets. One camp felt that a line needed to be drawn somewhere, and another camp felt that the newly discovered objects should be added to the list of solar system planets.
Illustration of the relative sizes, albedos, and colours of the largest trans-Neptunian objects.
In 2006 the International Astronomical Union (IAU) met with the intention of solving the debate once and for all. The goal was to come up with a definition for “planet”, which had never been done before. After many days of contentious debate, the IAU passed the following resolution:
RESOLUTION 5A
The IAU therefore resolves that planets and other bodies in our Solar System, except satellites, be defined into three distinct categories in the following way:
(1) A "planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.
(2) A "dwarf planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape [2], (c) has not cleared the neighbourhood around its orbit, and
(d) is not a satellite.
(3) All other objects, except satellites, orbiting the Sun shall be referred to collectively as "Small Solar-System Bodies".
This is a poor definition that has only served to add more confusion. With resolution 2c, “has cleared the neighborhood around its orbit”, the IAU is trying to express that a planet should be the dominant gravitational force in its local region of the solar system. That's not an unreasonable position. Certainly the Earth and Jupiter are the dominant objects in their local regions. But have any of these planets actually "cleared the neighborhood" around their orbits? No. Pluto is still clearly in Neptune's "neighborhood". For that matter, Jupiter has two well-known groups of asteroids, the "Trojans", which lead and follow Jupiter along in its orbit. For that matter, the Earth hasn't quite "cleared the neighborhood" around its orbit, either, as anyone who was near Chebalyink, Russia on Feb 15th, 2013 or Tunguska, Siberia on June 30th, 1908 can attest to. So are Earth, Jupiter, and Neptune the dominant gravitational objects in their local neighborhoods? Yes. Have they "cleared their neighborhoods"? No.
The Thousand Kilometer Rule
Here is what the IAU should have resolved in 2006:
(1) A "planet" [1] is a celestial body that (a) is in orbit around the Sun, (b) has a maximum surface radius greater than 1000 kilometers.
(2) All other objects orbiting the Sun shall be referred to collectively as "Small Solar-System Bodies".
"But that's completely unscientific" you say. "Why 1000 kilometers? Why not 1200, or 750?" I submit to you that the precise definition of a planet as an object at least 1000 kilometers in radius is no less "scientific" than the definition of a "kilometer" as being a unit of distance equal to 1000 meters, or a "degree" being 1/360th of a circle.
Here is a list of the largest known objects orbiting the Sun, and their radii in kilometers:
Jupiter - 69,911
Saturn - 58,232
Uranus - 25,362
Neptune - 24,622
Earth - 6,378
Venus - 6,052
Mars - 3,390
Mercury - 2,440
Pluto - 1,184
Eris - 1,163
Makemake - 715
Haumea - 620
Quaoar - 555
Sedna - 498
Ceres - 475
Orcus - 458
By the 1000-kilometer definition, all eight classical planets would remain planets. As would Pluto, and we add Eris. The solar system would have exactly ten planets. Those fond of keeping Pluto's planetary status for historical reasons would retain its dignity. And elevating Eris to a first-class planet would be an honorable nod to the cutting-edge astronomers whose work led to a need for this new definition in the first place.
And as to the "cleared the neighborhood" part of the definition? This it the most unclear and least popular part o the IAU's 2006 definition. It's best dealt with by being eliminated entirely. The end game is to define the term "planet" in a manner that's simple, understandable, and satisfying. The 1000-kilometer rule does this aptly.
If you'd like to follow along with NASA's New Horizons Mission to Pluto and the Kuiper Belt, please download our FREE Pluto Safari app. It is available for iOS and Android mobile devices. Simulate the July 14, 2015 flyby of Pluto, get regular mission news updates, and learn the history of Pluto.
Simulation Curriculum is the leader in space science curriculum solutions and the makers of Starry Night, SkySafari and Pluto Safari. Follow the mission to Pluto with us on Twitter @SkySafariAstro, Facebook and Instagram.
Mercury at its Best
Now that Pluto has been demoted to a dwarf planet, Mercury is the smallest of the eight planets. With a diameter of 3032 miles (4879 km.), it is slightly more than a third of the diameter of Earth, and smaller than the solar system’s two largest moons, Ganymede and Titan. Because of its tight orbit around the sun, Mercury never strays far into the night sky, peeping tantalizingly over the horizon a few times a year. The next two weeks will be your best chance for seeing Mercury in evening twilight this year.
Timing is the secret for catching sight of Mercury. Try too early, and its tiny speck of light will be lost against the twilight sky. Try too late, and Mercury will be too close to the horizon. I’ve found the best time to be about half an hour after sunset. Binoculars are helpful in initially spotting Mercury, but once located in binoculars you should be able to see it with the unaided eye.
Currently Venus is shining brightly in the evening sky, and it can be a helpful guide to spotting Mercury, about two-thirds of the way down towards the horizon, and slightly to your right. Don’t confuse it with nearby Aldebaran, which will have a noticeably reddish color and will probably twinkle, while Mercury shines with a more steady light.
On the evening of Thursday, May 7, Mercury will be at its farthest from the Sun, making the next two weeks the best time this year for observers in the northern hemisphere to spot this elusive little planet. Credit: Starry Night software.
In a telescope, Mercury is a disappointing sight. Like Venus, Mercury exhibits phases as it passes between us and the sun. At present it is slightly gibbous. On Saturday, May 2, it will look just like a miniature first quarter moon. After that, it will assume a crescent shape.
Because Mercury is always seen close to the horizon, it is a challenge to see its surface markings, even in a powerful telescope. Serious observers of Mercury prefer to observe it in the daytime sky, now relatively easy to do because of computerized telescopes. But always be very careful when observing with the sun above the horizon, because even the briefest view of the sun in a telescope will do permanent harm to your eyes.
If you'd like to follow along with NASA's New Horizons Mission to Pluto and the Kuiper Belt, please download our FREE Pluto Safari app. It is available for iOS and Android mobile devices. Simulate the July 14, 2015 flyby of Pluto, get regular mission news updates, and learn the history of Pluto.
Simulation Curriculum is the leader in space science curriculum solutions and the makers of Starry Night, SkySafari and Pluto Safari. Follow the mission to Pluto with us on Twitter @SkySafariAstro, Facebook and Instagram.
How Amateur Astronomers Helped the New Horizons Team Unlock the Secrets of Pluto - From Their Backyards and Driveways
Big Island of Hawaii from space, January 26, 2014
Being an amateur astronomer on the Big Island of Hawaii has a lot of advantages. In addition to clear, dark skies, and incredible seeing, we are surrounded by the world's premier observatories, and the people who use them. In May, 2011, New Horizons team-member Leslie Young of the Southwest Research Institute (SWRI) in Boulder, Colorado, was one of those people.
Cliff Livermore at his 24” Starmaster, Eliot Young and Tony Stearman on computers.
Our astronomy club meetings are held at the W. M. Keck Observatory headquarters, and Leslie stopped in to tell us about the progress of the New Horizons Mission, and to let us know how we could help with an upcoming occultation event involving Pluto, and its moons Charon and Hydra.
In June, 2011, a bright star was going to be occulted by Pluto and its moon, Charon. The same star would blink out twice as Charon, and then Pluto, passed between the Earth and the star. Several days later a second occultation event would take place involving the occultation of two stars, one by Pluto and one by its moon, Hydra. Information gathered from recording these events with accurate time-markings would help to better understand Pluto and its moons, before the passage of New Horizons near Pluto in July, 2015. They hoped to gather data about the accurate size, temperature and atmosphere of Pluto and information about its satellites. They might even get new information about the orbits of the moons. [Readers may be interested in reading Emily Lakdawalla's blog, science writer and Senior Editor at The Planetary Society, for further information on what occultations can tell us about an object].
Eliot Young of SWRI leading the occultation team in Waikoloa Village, HI.
Local amateur astronomers spent long, rewarding nights from June 23 to June 29 involved in this study. Some of those nights were spent practicing and rehearsing for the actual events. Chris Erickson, whose LX200GPS-16 was used for all of the events, suggested that all involved need to be familiar with "the use of the special cameras, computers, filters, adapters, cables, GPS timers, coolers and software.” Those who weren't operating telescopes came to provide support as needed, and to learn techniques for future occultation events.
Telescopes with apertures of at least 11 inches were used, including Cliff Livermore's 24" Starmaster with a Zambuto mirror - one of the largest amateur telescopes on the island; New Horizon team members supplied the cameras (”Dorothea” and "Henri"). Eliot Young from SWRI and Larry Wasserman from Lowell Observatory in Flagstaff, Arizona, worked with the amateurs in backyards and driveways.
Chris Erickson’s 16” LX200GPS on left. Chris Erickson, Cliff Livermore, Tony Stearman and Eliot Young.
Everyone was provided with the necessary information and finder-charts. Finding Pluto in the star-rich field of Sagittarius was the first challenge. Clouds came and went throughout the night, and equipment proved frustrating at times. At one point a timer stopped working and Chris, an electrical engineer, ran into his garage and soldered some wires and returned with a perfectly functioning timer.
Sunrise in Cliff's backyard in Waikoloa Village, Hawaii. Tony, Chris, Eliot and Cliff wrapping up.
There was one final event - a celebratory luau! We were so honored to have played even the smallest part in making this mission a success, and can't wait to see those images of Pluto and its satellites in May. I'm sure there will be another Big Island get-together for the nearest approach in July, 2015.
If you'd like to follow along with NASA's New Horizons Mission to Pluto and the Kuiper Belt, please download our FREE Pluto Safari app. It is available for iOS and Android mobile devices. Simulate the July 14, 2015 flyby of Pluto, get regular mission news updates, and learn the history of Pluto.
This article was provided by Maureen Salmi to Simulation Curriculum, the leader in space science curriculum solutions and the makers of Starry Night, SkySafari and Pluto Safari. Follow the mission to Pluto with us on Twitter @SkySafariAstro, Facebook and Instagram.
Starry Night 7, eclipses and ... Elmo
Like most two years olds, my daughter loves Elmo. Something about his high-pitched voice and ever-present smile I guess.
Parents innately learn to tune him out, probably to moderate the risk of going insane listening to that same shrill voice on reruns day after day.
One episode that sticks out in my mind, today more than ever perhaps, puts Elmo in a room with none other than David Beckham. The short ends after Elmo, who pesters Becks to teach him to dribble a soccer ball on his head, learns a new word... Persistence.
Persistence is an extremely important quality, and some might say a disappearing quality these days. It goes hand-in-hand with patience I think, something we can all agree is becoming scarce in this age of on-demand everything.
Persistence, as in the case of Elmo and Becks, often pays off.
Over the past few weeks, I've been involved in an exchange over the accuracy of Starry Night's eclipse predictions. One of our "power users" (who shall remain nameless for now) reported what he believed to be an issue with our calculations. They just didn't match up exactly with what NASA (and other government sites) were reporting.
The discrepancy was small; in fact, the timings were exact, to the sub-second but the sizes of the Earth's shadows (both the umbra and penumbra) were too small by a very small but noticeable fraction.
Normally no-one would even notice this, but in this case it changed our prediction for the April 4th, 2015 eclipse from a Total (as reported by NASA) to a Partial eclipse. That made all the difference to a few people.
I sit down at my 'puter. "I'll figure this out", I say to myself confidently:
- Were we perhaps using an old or imprecise value for the Earth's diameter? Nope. That was in agreement with the USGS.
- Were we taking the oblateness of the Earth into account? Yup. A precise calculation there too.
- Was this somehow rounding or another error in calculation? Nope. Everything seems to check out.
After a few hours of this, I checked with my confrere, Bill (our SkySafari developer) to see if they had the same discord with NASA predictions. They did! And even better (worse, it turns out) both Starry Night, and SkySafari, two completely independently created applications, gave almost exactly the same result!
That sealed it for me. Other matters were more pressing. NASA could be wrong too (note that it's not insane to believe this, the pages we were referring to were intended for the public, maintained by a summer student and weren't necessarily vetted by anyone), or could have used slightly different values for the radius of the Earth. Were THEY accounting for the oblateness? Doubts and lack of information made it difficult.
After presenting my findings to Keiron, our head of support, I let the issue go.
Lots of other stuff to work on.
Again, the power user, and Keiron came back to me. Why were our predictions different? We claim arcsecond precision in our planet and moon positions. How could we make that claim if this discrepancy existed?
Again, I chatted with Bill. He said he had been talking with Keiron too. I Don't know what this annoying user thinks he knows that we don't. What could it be? "The Earth's atmosphere?" Says Bill. I dunno. Does NASA take it into account? It's not clear from their site. How can we compare if they don't say? The discrepancy is so small.
Lots of other stuff to work on.
Again, an email from Keiron. "Aren't you busy?" I think to myself. I open it, a curt reply, ready at my fingertips. This time, the message comes with a link.
"Do you think the Danjon rule explains the difference?" he asks:
http://www.eclipsewise.com/oh/oh-help/LEshadow.html
...
Holy s*&t!
...
Not just a clear explanation of what, how, and by how much the Earth's atmosphere contributes to the shadow, but authored by Fred Espenak himself, The Godfather of eclipse predictions!
This page on the eclipse, with nicely outlined parameters showed something called "Shadow Enlargement":
http://www.eclipsewise.com/lunar/LEprime/2001-2100/LE2015Apr04Tprime.html
... with a link to a clear explanation of what the Danjon shadow rule is, and its value.
It turns out that the Earth's atmosphere contributes around 1/85 (just over 1%) to the diameter of the Earth's shadow... an effect that we were NOT taking into account in Starry Night or SkySafari... but are now! (SN version 7.1.2+, SkySafari ).
Starry Night has been around for almost 20 years in some form or another, and we have never taken this into account, until now.
We could all learn a little from this power user and Keiron (and Elmo for that matter). It pays to be persistent!
Thanks for keeping at it guys. Starry Night is that much better for it.
After a few hours of this, I checked with my confrere, Bill (our SkySafari developer) to see if they had the same discord with NASA predictions. They did! And even better (worse, it turns out) both Starry Night, and SkySafari, two completely independently created applications, gave almost exactly the same result!
That sealed it for me. Other matters were more pressing. NASA could be wrong too (note that it's not insane to believe this, the pages we were referring to were intended for the public, maintained by a summer student and weren't necessarily vetted by anyone), or could have used slightly different values for the radius of the Earth. Were THEY accounting for the oblateness? Doubts and lack of information made it difficult.
After presenting my findings to Keiron, our head of support, I let the issue go.
Lots of other stuff to work on.
Again, the power user, and Keiron came back to me. Why were our predictions different? We claim arcsecond precision in our planet and moon positions. How could we make that claim if this discrepancy existed?
Again, I chatted with Bill. He said he had been talking with Keiron too. I Don't know what this annoying user thinks he knows that we don't. What could it be? "The Earth's atmosphere?" Says Bill. I dunno. Does NASA take it into account? It's not clear from their site. How can we compare if they don't say? The discrepancy is so small.
Lots of other stuff to work on.
Again, an email from Keiron. "Aren't you busy?" I think to myself. I open it, a curt reply, ready at my fingertips. This time, the message comes with a link.
"Do you think the Danjon rule explains the difference?" he asks:
http://www.eclipsewise.com/oh/oh-help/LEshadow.html
...
Holy s*&t!
...
Not just a clear explanation of what, how, and by how much the Earth's atmosphere contributes to the shadow, but authored by Fred Espenak himself, The Godfather of eclipse predictions!
This page on the eclipse, with nicely outlined parameters showed something called "Shadow Enlargement":
http://www.eclipsewise.com/lunar/LEprime/2001-2100/LE2015Apr04Tprime.html
... with a link to a clear explanation of what the Danjon shadow rule is, and its value.
It turns out that the Earth's atmosphere contributes around 1/85 (just over 1%) to the diameter of the Earth's shadow... an effect that we were NOT taking into account in Starry Night or SkySafari... but are now! (SN version 7.1.2+, SkySafari ).
Starry Night has been around for almost 20 years in some form or another, and we have never taken this into account, until now.
We could all learn a little from this power user and Keiron (and Elmo for that matter). It pays to be persistent!
Thanks for keeping at it guys. Starry Night is that much better for it.
Again, I chatted with Bill. He said he had been talking with Keiron too. I Don't know what this annoying user thinks he knows that we don't. What could it be? "The Earth's atmosphere?" Says Bill. I dunno. Does NASA take it into account? It's not clear from their site. How can we compare if they don't say? The discrepancy is so small.
Lots of other stuff to work on.
Again, an email from Keiron. "Aren't you busy?" I think to myself. I open it, a curt reply, ready at my fingertips. This time, the message comes with a link.
"Do you think the Danjon rule explains the difference?" he asks:
http://www.eclipsewise.com/oh/oh-help/LEshadow.html
...
Holy s*&t!
...
Not just a clear explanation of what, how, and by how much the Earth's atmosphere contributes to the shadow, but authored by Fred Espenak himself, The Godfather of eclipse predictions!
This page on the eclipse, with nicely outlined parameters showed something called "Shadow Enlargement":
http://www.eclipsewise.com/lunar/LEprime/2001-2100/LE2015Apr04Tprime.html
... with a link to a clear explanation of what the Danjon shadow rule is, and its value.
It turns out that the Earth's atmosphere contributes around 1/85 (just over 1%) to the diameter of the Earth's shadow... an effect that we were NOT taking into account in Starry Night or SkySafari... but are now! (SN version 7.1.2+, SkySafari ).
Starry Night has been around for almost 20 years in some form or another, and we have never taken this into account, until now.
We could all learn a little from this power user and Keiron (and Elmo for that matter). It pays to be persistent!
Thanks for keeping at it guys. Starry Night is that much better for it.
Partial solar eclipse on October 23rd
On the evening of October 23rd a partial solar eclipse takes place, ideally timed for North Americans to observe in the evening. The Moon's first contact with the Sun takes place at 4:25 PM CDT, and the moment of greatest eclipse is at 5:31 PM. These times are for an observer located in Minneapolis, MN; for other parts of the US, the times will vary slightly. Anyone wishing to view the eclipse should view it through special solar observing filters or by projecting the Sun's image. Don't ever stare directly at the Sun, even with sunglasses, and especially not through a telescope!
To simulate the partial solar eclipse in Starry Night 7 look in the Find Panel (the right sidebar) under "Today's Sky" and click on the listing for "Partial Solar Eclipse". Enjoy SN7!
Will you be viewing the partial solar eclipse today?
Rosetta vs Churyomov-Gerasimenko (67P)
Starry Night 7 simulation of NASA Rosetta Probe encounter with Churyomov-Gerasimenko (67P) - model is using NASA data current to Sept 8th 2014
More ways to get involved
Check out how you, as citizen-scientist (or just interested amateur) can contribute!
Perseid Meteors vs. the Supermoon
The Perseids can usually be relied on to put on a good performance. But this year, observers beware! At their best just after midnight on the night of August 12/13, they will have the interference from a bright, nearly full "Supermoon" to contend with. Dress warmly, lie back on a deck chair, and enjoy the show.
Rosetta spacecraft reaches comet and makes history
"Thruster burn complete. Rosetta has arrived at comet 67P. We're in orbit!" ~ NASA
Rosetta spacecraft reaches comet and makes history!
Download Starry Night 7 Rosetta-67P SNF files here:
https://drive.google.com/…/0B4R9PVVyKIqyRTNBbEFmcDhQW…/edit…
Europe’s Rosetta spacecraft arrived at comet 67P/Churyumov–Gerasimenko today after a ten year journey, making history by becoming the first spacecraft to orbit a comet. It will now look for an appropriate landing site for its Philae lander, scheduled to land in November.
Double Stars around Boötes
On a May evening many years ago, I made my first exploration of the night sky. The only star pattern I could recognize was the Big Dipper, but with a star chart in a book, I used that to discover the bright star Arcturus in the constellation Boötes.
The curve of the Big Dipper's handle leads to Arcturus, the brightest star in the kite-shaped constellation of Boötes. Surrounding Boötes is an amazing variety of double stars. Credit: Starry Night software
The trick to learning the constellations is to begin with the stars you know, and use them to identify their neighbors. This same technique, known as "starhopping" is the key to discovering all the wonders hidden amongst the stars.
Start, as I did, with the Big Dipper, high overhead as the sky gets dark at this time of year. The stars that form the Dipper’s handle fall in a gentle arc, and if you project that arc away from the Dipper’s bowl, you come to a bright star. This is Arcturus, the third brightest star in the night sky, and the brightest star in the northern sky. Only Sirius and Canopus, far to the south, are brighter.
Arcturus is bright in our sky for two reasons, first because it is relatively close to us, 38 light years away, and secondly because it is inherently a bright star, much brighter than our Sun. Though larger and brighter, it is a slightly cooler star than our Sun, so appears orange to our eyes.
Although Boötes is supposed to be a ploughman in mythology, its pattern of stars most resembles a kite, with Arcturus marking the bottom of the kite where the tail attaches. Notice the little dots over the second "o" in Boötes: this indicates that the two "o"s are supposed to be pronounced separately, as "bow-oo’-tees," not "boo’-tees."
Once you have identified Boötes, you can use its stars to identify a number of constellations surrounding it. Between it and the Big Dipper are two small constellations, Canes Venatici (the hunting dogs) and Coma Berenices (Bernice's hair). To Boötes left (towards the eastern horizon) is the distinctive keystone of Hercules. Between Hercules and Boötes is Corona Borealis (the northern crown) with Serpens Caput, the head of the serpent, poking up from the south.
Although most stars appear to our unaided eyes as single points of light, anyone with access to binoculars or a telescope soon discovers that nearly half the stars in the sky are either double or multiple stars. Some of these are just accidents of perspective, one star happening to appear in the same line of sight as another, but many are true binary stars: two stars in orbit around each other, similar to the stars which shine on the fictional planet Tatooine in Star Wars.
Every star labeled on this map of Hercules, Boötes, and Ursa Major is a double star, worth exploring with a small telescope. Some, like Mizar in the Dipper’s handle, can be split with the naked eye. A closer look with a telescope shows that this is really a triple star. Others require binoculars or a small telescope. Some of the finest are Cor Caroli in Canes Venatici, Izar (Epsilon) in Boötes, Delta Serpentis, and Rho Herculis.
One of the joys of double star observing is the colour contrasts in some pairs. Others are striking for matching colours and brightness. My favorites are stars of very unequal brightness, which look almost like stars with accompanying planets.
Also marked on this chart are three of the finest deep sky objects: the globular clusters Messier 13 in Hercules and Messier 3 in Canes Venatici, and the Whirlpool Galaxy, Messier 51, tucked just under the end of the Big Dipper’s handle. You will probably need to travel to a dark sky site to spot this galaxy. A six-inch or larger telescope will begin to reveal its spiral arms, including the one that stretches out to its satellite galaxy, NGC 5195.
Starry Night 7: High Resolution Planetary Texture Collection
In recent years, NASA has conducted numerous exploratory missions that provided detailed measurements of the visual appearance and physical characteristics of most of the planets and moons in our solar system. These categories include IR/UV/visible imagery, physical, chemical and geological properties of the celestial bodies.
Measurements range from surface features to physical properties to chemical and geological characteristics. Surface features consist of topography, albedo, roughness and age. Fundamental physical properties include gravity, magnetism and temperature. Chemical and geological quantities comprise elemental composition, mineral distributions, geological maps and crustal thickness.
Starry Night Pro Plus 7 offers a Planetary Science Texture Compilation with over 100 additional maps. Planetary images and data were derived from the latest datasets available. The original, highest quality sources were used to produce maps with maximum fidelity. Gaps and artifacts in individual datasets were corrected with data from older or alternate sources obtained by other exploratory space missions to produce consistent, high quality images that clearly illustrate the parameters of interest.
Earth:
Light Pollution Atlas
Jupiter:
Callisto Color
Callisto Gray
Europa Color
Europa Gray
Ganymede Color
Ganymede Gray
Io Color
Io Geology
Io Gray
Jupiter Color
Shoemaker-Levy
Mars:
Mars Albedo Color
Mars Albedo Gray
Mars Elemental Abundance Set
Mars Geoid
Mars Geological Map
Mars Gravity
Mars Magnetic Field
Mars MDIM
Mars Roughness
Mars Surface Dust Index
Mars Thermal Inertia
Mars Topo Jade
Mars Topo Spectrum
Mars Viking Color
Mars Viking MDIM Merged
Mars Viking Shaded
MOC color
MOC gray
Mercury:
Messenger Color
Messenger Gray
Mercury Messenger Color
Mercury Messenger Gray
Moon:
Clementine Color
Clementine False Color
Clementine Gray
Clementine Iron
Clementine Mineral Ratio
Clementine Optical Maturity
Lunar Gravity
Moon Crustal Thickness
Moon Elemental Abundance Set
Moon Geoid
Moon LROC Gray
Moon Roughness
Moon Temperature
Moon Topo
Moon Illusion Beetle
Moon Illusion Lady
Moon Illusion Lady Reading Book
Moon Illusion Man In Moon
Moon Illusion Rabbit
Moon Illusion St. George
Saturn:
Dione Gray
Enceladus Color
Enceladus Gray
Iapetus Color
Iapetus Gray
Mimas Gray
Phoebe Gray
Rhea Gray
Saturn Bjorn Jonsson
Saturn Hubble
Tethys Gray
Titan Color
Titan Gray
Titan IR
Titan Lakes
Titan Topo
Titan Topo scale
Sun:
Ca II 3933A
FeIX-FeX 171A
FeIX-FeX 171APNG Tiles
FeVII 195A
H-alpha
He II 304A
Venus:
Venus Geoid
Venus Gravity
Venus Magellan Color
Venus Magellan Gray
Venus Topo
Vesta:
Vesta Gray
Vesta Rock Types
Vesta Topo
Starry Night 7: Stars Rendered as 3D Bodies
One of the many exciting new features in Starry Night 7, is the ability to accurately render stars as 3-dimensional bodies with classification appropriate color, texture and relative radii.
A star is any body which burns or once burned hydrogen fuel. The energy and light produced in stars comes from the fusion of hydrogen atoms. As stars grow older, they use up their supply of hydrogen and have to find other sources of energy. When they reach this point, they become either red giants or supergiants, depending on their size. As they continue to use up energy, stars eventually become either white dwarfs or, in the case of very massive stars, neutron stars or black holes.
The star database in Starry Night is actually a compilation of several databases: the Hipparcos catalog, the Tycho-2 catalog, and Starry Night Pro and Pro Plus also include the USNO-A2 catalog.
The Hipparcos catalog comes from a European Space Agency project to determine the distance to our nearest stars. The 100,000 or so stars in this catalog are correctly plotted in 3D space and accurately displayed in Starry Night. This means you can leave the Earth behind and visit any of these stars. When you get there, the star will be rendered as a 3D body with the correct colour, texture and relative radii. It is as close to being there, without actually being there.
You can find out more about the Hipparcos catalog on the official web page:
http://www.rssd.esa.int/index.php?project=HIPPARCOS
Classification-Appropriate Color
Stars can be classified based on their spectral characteristics. This is done by splitting light with a prism or diffraction grating into a spectrum of colors and absorption lines. Absorption lines (dark lines or lines of reduced intensity on a continuos spectrum) are used as ‘fingerprints’ to help identify the relative abundance of different ions, which vary with the temperature of a star’s photosphere.
In short, the absorption lines present in a stars spectra allow us to classify stars into several spectral classes depending on the temperature of the star. And in general, a star’s temperature determines its color.
The scheme we use is the Harvard Spectral Classification Scheme, originally developed in the late 1800’s at the Harvard college observatory.
The scheme uses single letters of the alphabet to group stars according to their spectral features. Stars were assigned a spectral class letter based on the strength of the hydrogen absorption lines in their spectra. The main spectral classes are OBAFGKMLTY. This sequence is ordered from the hottest to the coolest stars. Using this scheme, our Sun, the nearest star to Earth, is a class G star.
There are two main methods to describe the color of a star based on spectral class. In Starry Night 7, we use theconventional colour description in the table above to represent spectral class colors. The conventional color description is what would be seen if the star were put under high magnification and projected onto a white sheet of paper in the daylight (takes into account only the peak of the stellar spectrum). Using this color description, our Sun appears yellow.
However, the actual apparent color description is what would be seen by the human eye under a dark sky. Using this color description, our Sun appears yellowish white.
A future update to Starry Night, will allow you to select between conventional color and apparent color to represent the spectral class of a star.
Texture
Each 3D rendered star displays a high resolution texture with detailed sunspots and granulated features, based on spectral class. We tried to make each star as unique as possible.
Relative Radii
All 3D stars in Starry Night 7 are rendered with their correct radii. To show the relative sizes of different stars, Starry Night places you at 0.023 Astronomical Units (AU) from a stars center when you select the Go There command. This means that a red giant star will appear large on your screen and a white dwarf star will look very small.
Luminosity
Besides the star surface itself looking more like it is emitting light rather than reflecting light like a planet does, we render simple atmospheres around the star. Each star has a "lower" and "higher" atmosphere. The lower atmosphere typically extends no more than 0.1 radii from the star and gives a softer-looking edge. The higher atmosphere typically extends multiple radii away from the planet and provides the overall haze effect within the vicinity of the star.
Based on the stellar class, we try to convey a sense of luminosity by varying the atmosphere sizes.
Star Horizon Panoramas
In addition to orbiting a 3D star, you can also land on its surface via the Go There Surface command. Each star has a unique horizon panorama to match it’s spectral class.
The Future
As part of the ongoing development of version 7, we plan on continuing to improve the appearance, accuracy, information and features available for discovering, viewing and exploring 3D stars. How neat would it be to view double stars in 3D, see the inside layers of a red giant, display a stars habitable zone or even animate solar flares? Stay tuned…
Development (and Beta Testing) Never Ends
Software development sometimes entails hardware development too!
There were (for us) many firsts with the release of Starry Night Pro Plus 7. Exoplanets, data streaming, in-application updates, automatic crash reports - to name just a few. The scope of these new facilities and modernization of the old ones required tons of development time on the app itself. In addition, a lot of development had to be done on our servers too, a topic of a future article.
There is, however, one other area which has required many hours of development and use of a large number of technologies, most of them necessary to automate the process. This component is now integral to the lifecycle of SN7 and any future versions of our desktop applications. It assures that problems are caught early and that updates are tested before everyone gets them. I am talking about our Starry Night Beta program.
Mentioning beta testing evokes notions of release candidates, fixed release schedules and long delays between changes in the beta code and their eventual release to the public. We, of course, do our best to adhere to the wisdom of desktop beta testing. However, we also wanted Starry Night Beta to be more agile, and, above all, always alive.
Among other things, with the new automatic crash reporting and streamlined workflow of dealing with bug reports and user submitted support tickets, we wanted SN7 development to be as responsive to our users as we can make it. We scrutinize every crash report and investigate every bug report. We try and catch problems early. And we want to get relevant improvements and fixes into the software as soon as possible. This is what drove our implementation of in-app updates. And this is what drives our efforts in keeping Starry Night Beta going, even after SN7 has been released - because updates need testing too!
There are many arms to the beta (sometimes also referred to as "nightly") builds of SN7 and the systems used to get changes as quickly as possible into the hands of our testers. Here they are in their raw, technical jargon. All of the following tasks are fully automated, set in a sequence, and alert the developers of any problems encountered along the way.
- Mac: checkout from the relevant branch of SN7 git repository
- Windows: checkout from the relevant branch of SN7 git repository
- Mac: build SN7
- Mac: checkout from the relevant branch of Sky Data git repository
- Mac: pool all the data for Pro Plus into the new Sky Data folder
- Mac: add in the Manual and User guide to the final application
- Mac: checkout from the relevant branch of AllSkyImage git repository
- Mac: add all the AllSkyImage data that needs to be bundled into Pro Plus final app
- Mac: build the latest Mac telescope plugin and add it to the application
- Mac: codesign the final application bundle (to satisfy Gatekeeper)
- Mac: store the freshly built app until relevant build number in our application storage
- Mac: construct a pkg installer of the application
- Mac: build a DMG disk image for the pkg installer to make the installation clearer and easier
- Fire up a very large AWS EC2 instance that is used to quickly compress Windows installation data
- Mac: rsync final application to the EC2 instance
- Mac: create a drag-install DMG on Linux using genisoimage and libdmg-hfsplus
- Mac: push built dmg to S3 for (full) updates
- Mac: push the new build number to the relevant branch of SN7 git repository
- Mac: package and push the new symbols file of our application to HockeyApp - the service we use to receive crash reports
- Mac: read the relevant build release notes, if any, from our SN7 git repository, otherwise use current date stamp as a comment for the beta release
- Mac: add details about the freshly built application to our release database (size, build number, version number, location of DMG file)
- Mac: retrieve all active beta builds from the database
- Mac: go through each previous version and create a delta update between the current and specific previous version (using BinaryDelta from Sparkle project)
- Mac: for each delta update created, make an entry in our database with information about the update, size, versions involved
- Mac: push each delta update to S3 for distribution
- Windows: start a Windows instance on Parallels (we automate Windows building by invoking tasks from Mac to our virtual machine on Parallels)
- Windows: build and sign SN7
- Windows: copy Manual and User guide to the app
- Windows: create a new full build of Windows for local app archive. Use already built Sky Data from our constructed Mac app.
- Windows: build and add in relevant Windows plugins (telescope, focuser, MaxIm DL)
- Windows: format release notes so that they can be used in automated xml-powered update building process with wyBuild
- Windows: prepare specifications for delta update building by writing out an xml file with the latest information
- Windows: build all delta updates using wyBuild. Let wyBuild upload all the data to our S3 server for distribution.
- Windows: take the newly created wyUpdate.exe and client.wyc and put them into a folder used to assemble our Windows installer
- Windows: push the additions to our wyBuild project and new wyUpdate.exe, client.wyc and wyserver.wys files to the relevant branch of SN7 git repository
- Windows: launch and build our installer by invoking Advanced Installer on our aip project file (this only builds the minimal setup)
- Windows: package and push the new symbols file of our application to HockeyApp
- Windows: push the built installer to our EC2 instance
- Windows: launch 7z compression separately on AllSkyImage and Sky Data on EC2 instance
- Windows: using winrar on Linux, compress the installer, additional data 7z archives and custom modified SFX file header into Self-Extracting single exe
- Windows: sign the installer exe with signcode (from github.com/mono project) on Linux to conform with Microsoft Authenticode
- Windows: copy the built single-exe installer to S3 for distribution
- Windows: shutdown the Parallels VM
- Shutdown the EC2 instance
- Mac: copy the built pkg-based dmg installer to S3 for distribution (this is currently the slowest part of the process which is why it is last)
Finally, on the distribution chain, we keep things separate between public releases and Starry Night Beta. Applications built for public release are essentially different builds (which is why beta versions and release versions will never again have the same build numbers). Beta builds only get beta updates. The same rule applies for public releases. On Mac, our appcast server reads different entries from our release database (to which information is added during the above build steps). On Windows we keep separate wyserver.wys and wyBuild projects - one for public releases and one for beta.
And this is just the nightly automated script for a single application (Pro Plus 7)! There is still a lot to be done to improve this system, parallelize some processes and implement failover solutions for others. We are currently using Parallels VM in order to easily script everything directly from one source. However, a Parallels VM could be replaced with another EC2 (Windows) instance. We want to keep the nightly builds no matter what and to make them faster and more robust! Even beta needs testing and development (a beta for Starry Night Beta?).
Until next time! Clear skies!
Starry Night 7: Streaming Data On-Demand
Starry Night Pro Plus 6, when fully installed, occupied more than 10GBs of disk space. The sheer size of it required jumping through lots of technological hoops; from huge downloads to special DVDs, each with their own set of gotchas. This led to a lot of problems, all to deliver every last bit of data, much of which might never be accessed!
With the ever expanding volumes of interesting astronomical data available to the general public, as well as the near ubiquitous availability of high-speed internet access, Starry Night 7 was designed with a new mantra... deliver it on-demand!
Not wanting to sacrifice our tradition of beautifully simulating huge sets of astronomical data, we designed a new, robust system to stream the high-resolution, or rarely accessed data as its needed.
Not only do we now have the ability to deliver you, our users, essentially infinite amounts of astronomical data, but we can now deliver you ONLY that data which you want.
The system, at its base, is quite simple:
Zoom in on a particular piece of the sky, descend onto Mars, or choose one of dozens of available horizon panoramas and Starry Night checks your local hard disk for the necessary files. If they're found, they're loaded into the sky. If not, Starry Night makes a request to our servers to download the necessary data, streaming it to your computer where it will remain for the next time you need it.
This was done in a very limited way in Starry Night 6... only very dim USNO stars were served up by this system.
We have since expanded on that (and will continue to expand on that) to include the AllSkyImage layer and dozens of high-resolution planet surface textures. Horizon Panoramas are next to come along with individual object data, and more and deeper databases.
Some 27 GBs of data rests on our servers, waiting to be streamed! Sit back, zoom in, and enjoy!
Starry Night 7.0.2 and Beyond
Development of Starry Night 7 is proceeding quickly, so I thought I'd take a sec to update everyone on what we're working on.
In the very short term, we'll release Starry Night 7.0.2, mostly to address crashes and other incompatibilities that weren't discovered during beta-testing. We're focusing on issues that make it difficult to use the app, and features that might be broken. I'm taking this week to true up the Equipment list too.
In the weeks to come, we're going to take a solid look at all of the feature requests, suggestions and comments all of you have made, as well as usability issues discovered by our Beta-Testers.
We'll be rewriting the Observation Logging feature, with a particular emphasis on sharing logs... with each other and with other applications. We'll be sure to enable importing of your V6 logs, not to worry!
In addition to improving all of the obvious observing features, we'll be looking at other ways to share experiences with your friends and co-observers, improve add-to and refine our databases, and improve the speed of the application.
Stick with us. Lots of interesting things to come.
How the stars are rendered
In Starry Night 7 all stars, such as Rigel shown here, are accurately rendered as 3-dimensional bodies with classification-appropriate color, texture and relative radii. You can even land on them!
Bringing Earth to life
Starry Night 7 brings the Earth to life! with advanced planet rendering including terrain shadows, ocean floor shading, specular reflections on water (light reflected from lakes and rivers), and city lights visible on the night side.
Importing SN6 data to SN7 (Or: How I learned to stop worrying and love Sky Data overrides.)
Because of the ubiquity of the internet, the vast volumes of data available to us (and therefore you, the SN user) and new security requirements imposed by operating systems, Starry Night 7 has introduced the idea of a "dynamic" (writeable) Sky Data folder.
In previous versions of SN, the application itself would edit (write to) files in its own Sky Data folder located either in the application package (on OSX) or in the Program Files folder (Windows) and this is now considered very bad behavior.
For that reason, any time SN needs to write/modify a file, we so in a new Sky Data folder located at:
(Windows) \Users\<YourUserName>\AppData\Local\Simulation Curriculum\Starry Night Prefs\
(Note that the AppData folder is often "hidden". A quick Googling can show you how to un-hide it)
(OS X) /Users/<YourUserName>/Library/Application Support/Simulation Curriculum/Starry Night Prefs/
Note that this is where any "streamed" data will be located too.
While we've made every effort to hide this ugliness from you the user, if for any reason you want to get your hands dirty and edit a file manually, it should first be copied to the same respective path (e.g. /Sky Data/Planet Images) in this new folder, then edited there.
Any file located in this new Sky Data folder should have the effect of overridding the one in our static Sky Data folder.
Now, for the part you've all been waiting for. How do you get all of your Equipment, Distance Spheres, Locations, Preferences, Custom (User) Planets etc. from SN6 to SN7?
Simply copy the individual files from your old "Prefs" folders into the matching locations in the new "Starry Night Prefs" folder!
Have fun!
Starry Night 7: Motivation, Process, Future
As many of you have noticed, we're back with a brand new version of Starry Night! Rather than list all of the cool new features, I thought I'd take a moment to make clear our motivations for the changes in SN, our process getting to where we are now, and plans for the future.
For many of our loyal, longstanding users, the new user interface is a big change from what they're used to. Our motivation for the change was simple: the interface had gotten to the point where users were spending more time looking at (or looking for!) controls, than looking at the sky. We needed something new, cleaner, less obtrusive.
In our redesign, we followed the general philosophy that the UI should "be there when you need it, disappear when you don't." The focus should always be on the sky view, never the controls. This for example, is why we moved the Find pane from the left to the right... in general, people read left-to-right. Left is more prominent, so the sky view should always be at the left.
Our move to a "Universal Search" function was similarly motivated.
We found that over the years, so many of the great new features that we had added were buried under layers of user interface, that not only were they hard to use, but people often never found them in the first place.
With the ability to do a textual search for control items (not just named objects in the night sky), we have opened up a host of existing features to users who didn't even know about them! No longer do you need to know exactly what setting you're looking for, open the Options panel, visually search for it, and click to make a change... simply search for the word (or even a related word) that you're looking for, and you'll probably find it.
While I think we have succeeded in many, many ways, we still have much work to do.
Going forward, we plan on continuing with the idea of "less is more." Not in terms of what you can do (indeed, we are addingfeatures and data) but in what ways you are distracted from what you are doing. Think: more of what you want, less of what you don't.
While we have released it into the wild, we're far from done with it. Starry Night 7 should be thought of as a journey, not a destination.