A thin lunar crescent rises beneath the Pleiades star cluster tomorrow morning at dawn. This map shows the sky facing northeast about 4 a.m. local time. Maps created with Stellarium
The sky can be a showy stage with big-time events like eclipses, meteor showers and the occasional bright comet, but most nights have a quiet beauty that whispers instead of shouts. The contrast between hype and hush is no more apparent than on the 4th of July – American independence day celebration – when we gather at a park or hilltop to watch the fireworks boom and flash across the heavens.
But there are other interesting things — some quiet fireworks — you can see in the sky to see while you are waiting for the holiday fireworks.
You can watch a less flashy but equally satisfying July 4th event as soon as tomorrow morning about the time the first bird lifts its voice at dawn. Look northeast to find a thin crescent moon dangling below the Seven Sisters star cluster. Also called the Pleiades, the cluster is a highlight of the winter evening sky. Though it seems out of place now at the height of summer, the Sisters remind us that nothing stands still. With the solstice behind us, winter’s already buckling his boots.
As you relax before the fireworks begin, look for two bright stars and two bright planets in the west and southwest skies. You can fit about three fists held at arm’s length between Saturn and Arcturus.
While you’re waiting for the show to begin tomorrow night, take a look around the twilight sky and see how many celestial luminaries you can spot. If you’ve got kids in tow, share the view with them, too.
The brightest natural object in the sky will be Venus, glimmering low above the western horizon. Much further up in the southwest, look for a tall, skinny triangle outlined by orangy Arcturus, highest of the three, along with Saturn and Spica.
Facing east brings the three bright stars of the Summer Triangle in to view.
Twist around to face east to find another triangle, this one named after the summer season. Halfway up is Vega, the 5th brightest star in the sky, shining white and bright as burning magnesium. Below it you’ll spot the other Summer Triangle members, Altair in Aquila the Eagle and Deneb in Cygnus the Swan better known as the Northern Cross.
These bright stars and two planets coalesced from gas and dust millions to billions of years ago. Much has happened beneath their gaze, from the first stirrings of humankind to the crackle and boom of fireworks on a starry evening.
An Apollo 17 astronaut digs in the lunar regolith to study the mechanical behavior of moon dust. Credit: NASA
That video above is perhaps the ultimate off-roading adventure: taking a rover out for a spin on the moon. Look past the cool factor for a minute, though, and observe the dust falling down around that astronaut.
The crew aboard Apollo 16 (as well as other Apollo missions) had a lot of problems with regolith. It got into everything. It was so abrasive that it wore away some equipment in days. It smelled funny and probably wasn’t all that good to breathe in, either. Many have said that when we return to the moon, dust must be dealt with for long-term survival.
Things could get worse at sunrise and sunset. One new study (not peer-reviewed yet) finds a “serious risk” that rovers “could be engulfed in dust.” That’s because lunar dust appears to have electrostatic properties that, somehow, is triggered by changes in sunlight. (NASA is already doing some serious investigation into this matter using its orbiting missions.)
What the researchers did, in conjunction with ONERA (The French Center of Aerospace Research) was conduct simulations for two types of lunar regions — the terminator (the day/night boundary) and an area experiencing full sunlight.
“Dust particles were introduced into the simulation over a period of time, when both the surface and the rover were in electrical equilibrium,” the Royal Astronomical Society stated.
“In both the test cases, dust particles travel upwards above the height of the rover, but results suggest that they move in different directions. On the day side, the particles are pushed outwards and on the terminator the dust travels upwards and inwards above the rover, regrouping in the vacuum above it. The terminator simulation began with a region void of dust which was later filled by lunar dust particles.”
The bottom line? A lunar rover could accumulate a significant amount of dust on the moon, especially if it’s sitting at or near the terminator. This could be addressed by using dome-shaped rovers that would see the dust fall off, added lead author Farideh Honary, a physicist at the University of Lancaster, in a statement.
The work was presented at the RAS National Astronomy Meeting today (July 3). A paper has been submitted to the Journal for Geophysical Research, so more details should be forthcoming if and when it is published.
A near-infrared view of NGC 4038 (one of the Antenna Galaxies) obtained with the Gemini Observatory's new adaptive optics system. Credit: Image data from Rodrigo Carrasco, GeMS System Verification Team, Gemini Observatory. Color composite image by Travis Rector, University of Alaska Anchorage.
Rise above Earth with a telescope, and one huge obstacle to astronomy is removed: the atmosphere. We love breathing that oxygen-nitrogen mix, but it’s sure not fun to peer through it. Ground-based telescopes have to deal with air turbulence and other side effects of the air we need to breathe.
Enter adaptive optics — laser-based systems that can track the distortions in the air and tell computers in powerful telescopes how to flex their mirrors. That sparkling picture above came due to a new system at the Gemini South telescope in Chile.
It’s one of only a handful pictures released, but astronomers are already rolling out the superlatives.
“GeMS sets the new cool in adaptive optics,” stated Tim Davidge, an astronomer at Canada’s Dominion Astrophysical Observatory.
The planetary nebula NGC 2346. Credit: Gemini Observatory/AURA (Image data from Letizia Stanghellini, National Optical Astronomy Observatory, Tucson, Arizona. Color composite image by Travis Rector, University of Alaska Anchorage.)
“It opens up all sorts of exciting science possibilities for Gemini, while also demonstrating technology that is essential for the next generation of ground-based mega-telescopes. With GeMS we are entering a radically new, and awesome, era for ground-based optical astronomy.”
Other telescopes have adaptive optics, but the Gemini Multi-Conjugate Adaptive Optics System (GEMS) has some changes to what’s already used.
It uses a technique called “multi-conjugate adaptive optics”. This increases the possible size of sky swaths the telescope can image, while also giving a sharp view across the entire field. According to the observatory, the new system makes Gemini’s eight-meter mirror 10 to 20 times more efficient.
The Gemini South telescope during laser operations with GeMS/GSAOI. Credit: Manuel Paredes
The next step will be seeing what kind of science Gemini can produce from the ground with this laser system. Some possible directions include supernova research, star populations in galaxies outside of the Milky Way, and studying more detail in planetary nebulae — the remnants of low- and medium-mass star.
The nearby triple star system Gliese 667, taken on June 29, 2013. Credit and copyright: Efrain Morales, Jaicoa Observatory, Puerto Rico.
Here is a great new observation of the triple star system Gliese 667 from astrophotographer Efrain Morales of the Jaicoa Observatory in Puerto Rico. Recently, one of the stars, 667 C was found to have perhaps seven planets orbiting it! If all seven planets are confirmed, the system would consist of three habitable-zone super-Earths, two hot planets further in, and two cooler planets further out. Scientists say that the ‘f’ planet is “a prime candidate for habitability.”
Efrain also created an animation of the star system, showing the stars’ movements:
The animation was created using plates from the DSS (Digitized Sky Survey) with the final image in the animation from Efrain’s observations.
Gif animation of The animation of the triple star system Gliese 667, created using plates from the DSS (Digitized Sky Survey) with the final image in the animation from Jaicoa Observatory. Credit and copyright: Efrain Morales. Click for animation.
The system is in the constellation of Scorpius and is just barely visible to the unaided eye at magnitude 5.9 – appearing as a single point of light. The three stars orbit each other in a complicated dance. The two brightest components of this system, Gliese 667 A and Gliese 667 B, are orbiting each other at about 13 times the separation of the Earth from the Sun, while Gliese 667 C is the smallest stellar component of this system, and orbits the other two stars at about 230 AU.
Efrain used a LX200ACF 12 in. OTA, F6.3, CGE mount, ST402xm CCD, Astronomik LRGB filter set.
Thanks to Efrain Morales and the Jaicoa Observatory for providing this latest look at an extremely interesting star system!
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Mars moon Phobos rising in the night time Martian sky shortly after sunset in this image from a movie taken by NASA's Mars rover Curiosity on Sol 317, June 28, 2013. The apparent ring is an imaging artifact The Credit: NASA/JPL-Caltech See the complete ‘Phobos Rising’ movie below
Mars moon Phobos (above, center) rising in the night time Martian sky shortly after sunset in this still image from a movie taken by NASA’s Mars rover Curiosity on Sol 317, June 28, 2013. The apparent ring is an imaging artifact. Credit: NASA/JPL-Caltech See the complete ‘Phobos Rising’ movie below [/caption]
Every once in a while when the time is just right and no one is looking, Curiosity’s Earthly handlers allow her some night time Martian delights.
In this case a pair of rising and setting celestial events bookend another magnificent week in humankinds exploration of the Red Planet – courtesy of NASA.
This past week NASA’s Curiosity rover captured esthetically stunning imagery of Phobos rising and Our Sun setting on Mars.
Phobos is the larger of Mars pair of tiny moons. The other being Diemos.
On June 28, (Sol 317) Curiosity aimed her navigation camera straight overhead to captured a breathtaking series of 86 images as Phobos was ascending in the alien evening sky shortly after sunset.
NASA combined these raw images taken over about 27 minutes into a short movie clip, sped up from real time.
Video Caption: ‘Phobos Rising’ – This movie clip shows Phobos, the larger of the two moons of Mars, passing overhead, as observed by NASA’s Mars rover Curiosity in a series of images centered straight overhead starting shortly after sunset. Phobos first appears near the lower center of the view and moves toward the top of the view. The images were taken on June 28, 2013. The apparent ring is an imaging artifact. Credit: NASA/JPL-Caltech
The pockmarked and potato shaped moon measures about 26.8 × 22.4 × 18.4 kilometers.
Phobos orbits barely some 6,000 km (3,700 mi) above the Martian surface. One day far in the future, it will crash and burn.
On June 22, Curiosity snapped an evocative series of Martian sunset photos as Sol set behind the eroded rim of Gale Crater – see below.
In the 2030’s, Humans may visit Phobos first before setting foot on the much more technically challenging Red Planet.
Sunset at Gale Crater
Martian sunset vista at Gale crater rim snapped by Curiosity on Sol 312, June 22, 2013. Colorized navcam image. Credit: NASA/JPL-Caltech/Ken Kremer/Marco Di LorenzoPhobos from NASA’s Mars Reconnaissance Orbiter on March 23, 2008. Credit: NASA
Fireflies make green trails of light during a time exposure on a July night. Jupiter is at upper left. Credit: Bob King
Bioluminescent stars flash across the night landscape these July nights. Fireflies or lightning bugs provide a source of wonder for many of us living in the eastern half U.S. and Canada. Did you know dark skies may be as important to them as they are to you and I?
To stoke their yellow-green fires, the bugs – they’re really beetles – cook up light through a series of chemical reactions within their abdomens.
Adult Photurus firefly. Fireflies produce a cool light by combining oxygen in the air with the chemical luciferin. Credit: Bruce Marlin
Oxygen from the air combines with a chemical fittingly named luciferin. Luciferin next hooks up with the energy molecule ATP to form another molecule that when combined with oxygen yields a flash of green, yellow or amber light, depending upon the firefly species.
Fireflies compete with the stars from a dark location near Duluth, Minn. two nights ago. Each species has its own specific flash pattern. Credit: Bob King
The males perform the flash-dance moves, wiggling and zigging about to attract the females, who typically remain on the ground hidden among blades of grass. Each species has its own flashing pattern. When a female finds a male’s flashes suitably alluring, she winks a flash back. Back and forth communications soon bring the two together to make more fireflies.
Firefly light emits no heat, making it one of the most efficient light sources known. A standard incandescent light bulb converts electricity into 10% light and the rest as heat; fireflies transform 100% of their chemical energy into light. These insects do not waste photons.
One of my favorite memories from childhood was running around on summer nights collecting fireflies in a glass jar. Credit: Bob King
Every night I’m out under the July stars at least one firefly manages to land within the telescope tube and create a surprise supernova. If I inadvertently switch my LED flashlight on and off at the right rate, more than a few of them will land right on top of the device in a futile attempt to mate.
Urban sprawl and accompanying light pollution is an issue for both astronomers and fireflies. This view shows the light dome from the city of Duluth, Minn. 20 miles north of town. Credit: Bob King
One thing fireflies and skywatchers have in common is love of the night. To appreciate the twinkling heavens, we either escape to the countryside or do our best to contend with the lights in town. Firefly numbers are declining across the U.S. and the world, and though no one’s certain yet why, there’s both anecdotal and scientific evidence suggesting that loss of habitat and light pollution are to blame.
Example showing poorly shielded light fixtures. With nothing to contain or direct the light, it shines where it’s not needed – straight up! Credit: Bob King
Urban sprawl has comprised the habitats of many wild creatures not just fireflies. Sprawl also brings increased lighting, much of it poorly shielded and on all night. Fireflies avoid heavily lit areas for obvious reasons – light pollution interferes with their ability to see each others’ flashes. Even car headlights can throw them off rhythm. According to a 2008 story in the Boston Globe, controlled experiments have shown that brighter lighting levels cause fireflies to mate less often.
Full cutoff lighting fixtures like these put light where it’s needed – on the road – and not out to the sides or up in the sky. Credit: Bob King
We all can help ensure our favorite bioluminescent buddies remain around for a long time. Turning off your own yard light not only helps you to see more stars but makes it easier for fireflies to find their mates. If you absolutely need illumination, consider one of these efficient shielded light fixtures that puts light where you want it while eliminating the glare that frustrates fireflies and stargazers alike. To learn more about good lighting and keeping the sky dark, check out the International Dark Sky Association.
A false-color, visible-light image of Comet ISON taken with Hubble's Wide Field Camera 3. Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)
The Hubble Space Telescope team has released a video of Comet ISON as it is tearing toward its encounter with the Sun, zooming at 77,250 km/h (48,000 miles per hour). The comet’s motion is captured in a timelapse movie, below, made from a sequence of pictures taken May 8, 2013. On that date, the comet was 650 million km (403 million miles) from Earth, between the orbits of Mars and Jupiter.
This sungrazing comet will come closest to the Sun in November 2013, and the debate is on whether it will dazzle the skies and be visible in the daytime or fizzle out due to its close proximity to the Sun.
The movie shows a sequence of Hubble observations taken over a 43-minute span, compressed into five seconds. In that 43 minutes, the comet traveled about 55,000 km (34,000 miles). ISON streaks silently against the background stars.
Pluto's solar system in a 2012 artist's conception. P4 and P5 are now called Kerberos and Styx, respectively. Credit: NASA/John Hopkins University Applied Physics Laboratory
It looks like Vulcan was not the logical choice for the International Astronomical Union when it came to naming Pluto’s new moons.
The internationally recognized body for astronomy names selected Kerberos and Styx as the new names for Plutonian moons P4 and P5, respectively. While these names were popular in a public vote last year concerning Pluto’s new moons, Vulcan — the overwhelming favorite, and backed by none other than Star Trek‘s Captain Kirk (William Shatner) — was not selected.
The Search For Extraterrestrial Intelligence (SETI) said Vulcan, which was first popularized in the 1960s as the home world of Star Trek character Spock, was considered.
“The IAU gave serious consideration to this name, which happens to be shared by the Roman god of volcanoes. However, because that name has already been used in astronomy, and because the Roman god is not closely associated with Pluto, this proposal was rejected,” a release stated.
Vulcan received the support of William Shatner, pictured here in his Star Trek role as Captain James Kirk. Credit: Paramount
There will be more about Styx and Kerberos in this SETI-hosted Google Hangout, which will be held live starting at noon Eastern (4 p.m. GMT).
Kerberos is a three-headed dog in Greek mythology and Styx a mythological river that is the boundary between the living world and that of the dead. These are fitting names given Pluto’s other moons: Charon, Nix and Hydra, all of which meet the IAU’s rules to name them after Greek and Roman underworld personas.
We’ll get a closer look at these strange new worlds in 2015, when the New Horizons spacecraft skims through the Pluto system. There may be other, tiny moons lurking around the dwarf planet that New Horizons could find.
Do you feel the IAU made the right choice? It’s not the first time it waded into tricky waters concerning Pluto; some in the public still complain today about the decision to demote Pluto to dwarf planet status in 2006.
Solar apparent size- perihelion versus aphelion 2012.
This 4th of July weekend brings us one more reason to celebrate. On July 5th at approximately 11:00 AM EDT/15:00 UT, our fair planet Earth reaches aphelion, or its farthest point from the Sun at 1.0167 Astronomical Units (A.U.s) or 152,096,000 kilometres distant.
Though it may not seem it to northern hemisphere residents sizzling in the summer heat, we’re currently 3.3% farther from the Sun than our 147,098,290 kilometre (0.9833 A.U.) approach made in early January.
We thought it would be a fun project to capture this change. A common cry heard from denier circles as to scientific facts is “yeah, but have you ever SEEN it?” and in the case of the variation in distance between the Sun and the Earth from aphelion to perihelion, we can report that we have!
We typically observe the Sun in white light and hydrogen alpha using a standard rig and a Coronado Personal Solar Telescope on every clear day. We have two filtered rigs for white light- a glass Orion filter for our 8-inch Schmidt-Cassegrain, and a homemade Baader solar filter for our DSLR. We prefer the DSLR rig for ease of deployment. We’ve described in a previous post how to make a safe and effective solar observing rig using Baader solar film.
Our primary solar imaging rig. A Nikon D60 DSLR with a 400mm lens + a 2x teleconverter and Baader solar filter. Very easy to employ!
We’ve been imaging the Sun daily for a few years as part of our effort to make a home-brewed “solar rotation and activity movie” of the entire solar cycle. We recently realized that we’ve imaged Sol very near aphelion and perihelion on previous years with this same fixed rig, and decided to check and see if we caught the apparent size variation of our nearest star. And sure enough, comparing the sizes of the two disks revealed a tiny but consistent variation.
It’s a common misconception that the seasons are due to our distance from the Sun. The insolation due to the 23.4° tilt of the rotational axis of the Earth is the dominant driving factor behind the seasons. (Don’t they still teach this in grade school? You’d be surprised at the things I’ve heard!) In the current epoch, a January perihelion and a July aphelion results in milder climatic summers in the northern hemisphere and more severe summers in the southern. The current difference in solar isolation between hemispheres due to eccentricity of Earth’s orbit is 6.8%.
The orbit of the Earth also currently has one of the lowest eccentricities (how far it deviates for circular) of the planets at 0.0167, or 1.67%. Only Neptune (1%) and Venus (0.68%) are “more circular.”
The orbital eccentricity of the Earth also oscillates over a 413,000 year period between 5.8% (about the same as Saturn) down to 0.5%. We’re currently at the low end of the scale, just below the mean value of 2.8%.
Variation in eccentricity is also coupled with other factors, such as the change in axial obliquity the precession of the line of apsides and the equinoxes to result in what are known as Milankovitch cycles. These variations in extremes play a role in the riddle of climate over hundreds of thousands of years. Climate change deniers like to point out that there are large natural cycles in the records, and they’re right – but in the wrong direction. Note that looking solely at variations in the climate due to Milankovitch cycles, we should be in a cooling trend right now. Against this backdrop, the signal of anthropogenic climate forcing and global dimming of albedo (which also masks warming via cloud cover and reflectivity) becomes even more ominous.
Aphelion can presently fall between July 2nd at 20:00 UT (as it did last in 1960) and July 7th at 00:00 UT as it last did on 2007. The seemingly random variation is due to the position of the Earth with respect to the barycenter of the Earth-Moon system near the time of aphelion. The once every four year reset of the leap year (with the exception of the year 2000!) also plays a lesser role.
Perihelion and aphelion vs the solstices and equinoxes, an exaggerated view. (Wikimedia Commons image under a 3.0 Unported Attribution-Share Alike license. Author Gothika/Doudoudou).
I love observing the Sun any time of year, as its face is constantly changing from day-to-day. There’s also no worrying about light pollution in the solar observing world, though we’ve noticed turbulence aloft (in the form of bad seeing) is an issue later in the day, especially in the summertime. The rotational axis of the Sun is also tipped by about 7.25° relative to the ecliptic, and will present its north pole at maximum tilt towards us on September 8th. And yes, it does seem strange to think in terms of “the north pole of the Sun…”
We’re also approaching the solar maximum through the 2013-2014 time frame, another reason to break out those solar scopes. This current Solar Cycle #24 has been off to a sputtering start, with the Sun active one week, and quiet the next. The last 2009 minimum was the quietest in a century, and there’s speculation that Cycle #25 may be missing all together.
And yes, the Moon also varies in its apparent size throughout its orbit as well, as hyped during last month’s perigee or Super Moon. Keep those posts handy- we’ve got one more Super Moon to endure this month on July 22nd. The New Moon on July 8th at 7:15UT/3:15 AM EDT will occur just 30 hours after apogee, and will hence be the “smallest New Moon” of 2013, with a lot less fanfare. Observers worldwide also have a shot at catching the slender crescent Moon on the evening of July 9th. This lunation and the sighting of the crescent Moon also marks the start of the month of Ramadan on the Muslim calendar.
Be sure to observe the aphelion Sun (with proper protection of course!) It would be uber-cool to see a stitched together animation of the Sun “growing & shrinking” from aphelion to perihelion and back. We could also use a hip Internet-ready meme for the perihelion & aphelion Sun- perhaps a “MiniSol?” A recent pun from Dr Marco Langbroek laid claim to the moniker of “#SuperSun;” in time for next January’s perihelion;
If you could travel from world to world, from star to star, out into the gulfs of intergalactic space, you’d move away from the warmth of the stars into the vast and cold depths of the void.
