Astronomy Archives

December 31, 2016December 31, 2016 by Matt Williams

How Do Wind Turbines Work?

In Denmark, wind power accounts for 28% of electrical production and is cheaper than coal power. Credit: denmark.dk

Perhaps you’ve seen them while driving through the countryside. Or maybe you saw them just off the coast, looming large on the horizon with their spinning blades. Then again, you may have seen them on someone’s roof, or as part of a small-scale urban operation. Regardless of the location, wind turbines and wind power are becoming an increasingly common feature in the modern world.

Much of this has to do with the threat of Climate Change, air pollution, and the desire to wean humanity off its dependence on fossil fuels. And when it comes to alternative and renewable energy, wind power is expected to occupy the second-largest share of the market in the future (after solar). But just how exactly do wind turbines work?

Description:

Air turbines are devices that turn the kinetic energy of wind and changes in air flow into electrical energy. In general, they consist of the following components: a rotor, a generator, and a structural support component (which can take the form of either a tower, a rotor yaw mechanism, or both).

NASA’s Ames Research Center and the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) testing a research wind turbine in the world’s largest wind tunnel in April of 2000. Credit: NASA

A rotor consists of the blades that capture the wind’s energy and a shaft, which converts the wind energy to low-speed rotational energy. The generator – which is connected to the shaft – converts the slow rotation to high into electrical energy using a series of magnets and a conductor (which usually consists of coiled copper wire).

When the magnets rotate around with the copper wire, its produces a difference in electrical potential, creating voltage and an electric current. Lastly, there is the structural support component, which ensures that the turbine either stands at a high enough altitudes to optimally capture changes in wind pressure, and/or face in the direction of wind flow.

Types of Wind Turbines:

At present, there are two main types of wind turbines – Horizontal Axis Wind Turbines (HAWT) and Vertical Axis Wind Turbines (VAWT). As the name would imply, horizontal wind turbines have a main rotor shaft and electrical generator at the top of a tower, with the blades pointed into the wind. The turbine is usually positioned upwind of its supporting tower, since the tower is likely to produce turbulence behind it.

Vertical axis turbines (once again, as the name implies) have the main rotor shaft arranged vertically. Typically, these are smaller in nature, and do not need to be pointed in the direction of the wind in order to rotate. They are thereby being able to take advantage of wind that is variable in terms of direction.

A Darrieus wind turbine, located in Martigny, Switzerland. Credit: Wikipedia Commons/Lysippos

In general, horizontal axis wind turbines are considered more efficient and can produce more power. While the vertical model generates less electricity it can be placed at lower elevations and needs less in the way of components (particularly a yaw mechanism). Wind turbines can also be divided into three general groups based on their design, which includes the Towered, Savonius, and Darrieus models.

The towered model is the most conventional form of HAWT, consisting of a tower (as the name would suggest) and a series of long blades that sit ahead of (and parallel to) the tower. The Savonis is a VAWT model that relies on contoured blades (scoops) to capture wind and spin. They are generally low-efficiency, but have the benefit of being self-starting. These sorts of turbines are often part of rooftop wind operations or mounted on sea vessels.

The Darrieus model, also known as an “Eggbeater” turbine, is named after the French inventor who pioneered the design – Georges Darrieus. This VAWT model employs a series of vertical blades that sit parallel to the vertical support. They are generally low efficiency, require an additional rotor to start turning, produce high-torque, and place high stress on the tower. Hence, they are considered unreliable as designs go.

History of Development:

Wind power has been used for thousands of years to push sails, power windmills, or to generate pressure for water pumps. The earliest known examples come from Central Asia, where windmills used in ancient Persia (Iran) have been dated to between 500 – 900 CE. The technology began to appear in Europe during the Middle Ages, and became a common feature by the 16th century.

*The first automatically operated wind turbine, built in Cleveland in 1887 by Charles F. Brush. Credit: Wikipedia Commons*

By the 19th century, with the development of electrical power, the first wind turbines capable of generating electricity were built. The first was installed in 1887 by Scottish academic James Blyth to light his holiday home in Marykirk, Scotland. In 1888, American inventor Charles F. Brush built the first automated wind turbine to power his home in Cleveland, Ohio.

By the early 20th century, wind turbines began to become a common means of powering homes in remote areas (such as farmsteads). In 1941, the first megawatt-class wind turbine was installed in Vermont and attached to the local utility grid. In 1951, the UK installed its first utility-grid connected wind turbine in the Orkney Islands.

By the 1970s, research and development into wind turbine technology advanced considerably thanks to the OPEC crisis and protests against nuclear power. In the ensuing decades, associations and lobbyists dedicated to alternative energy began to emerge in western European nations and the United States. By the final decade of the 20th century, similar efforts emerged in India and China due to growing air pollution and rising demand for clean energy.

Wind Power:

Compared to other forms of renewable energy, wind power is considered very reliable and steady, as wind is consistent from year to year and does not diminish during peak hours of demand. Initially, the construction of wind farms was a costly venture. But thanks to recent improvements, wind power has begun to set peak prices in wholesale energy markets worldwide and cut into the revenues and profits of the fossil fuel industry.

Cross-section of a vertical wind turbine. Credit: energy.gov

According to a report issued by the Department of Energy in March of 2015, the growth of wind power in the United States could lead to even more highly skilled jobs in many categories. Titled “Wind Vision: A New Era for Wind Power in the United States”, the document indicates that by 2050, the industry could account for as much as 35% of the US’ electrical production.

In addition, in 2014, the Global Wind Energy Council and Greenpeace International came together to publish a report titled “Global Wind Energy Outlook 2014”. This report stated that worldwide, wind power could provide as much as 25 to 30% of global electricity by 2050. At the time of the report’s writing, commercial installations in more than 90 countries had a total capacity of 318 gigawatts (GW), providing about 3.1% of global supply.

This represents a nearly sixteen-fold increase in the rate of adoption since the year 2000, when wind power accounted for less than 0.2%. Another way to look at it would be to say that the market share of wind power has doubled four times in less than 15 years. This places it second only to solar power, which doubled seven times over in the same period, but still trails wind in terms of its overall market share (at about 1% by 2014).

*An offshore wind farm located off the coast of Belgium. Credit: Wikipedia Commons/Hans Hillewaert*

In terms of its disadvantages, one consistently raised issue is the effect wind turbines have on local wildlife, and the disturbance their presence has on the local landscape. However, these concerns have often been shown to be inflated by special interest groups and lobbyists seeking to discredit wind power and other renewable energy sources.

For instance, a 2009 study released by the National Renewable Energy Laboratory determined that less than 1 acre per megawatt is disturbed permanently by the construction of large-scale wind farms, and less than 3.5 acres per megawatt are disturbed temporarily. The same study concluded that the impacts are relatively low on bird and bat wildlife, and that the same conclusions hold true for offshore platforms.

All over the world, governments and local communities are looking to wind power in order to meet their energy needs. In an age of rising fuel prices, growing concerns over Climate Change, and improving technology, this is hardly surprising. At its current rate of adoption, it is likely to be one of the largest sources of energy by mid-century.

And be sure to enjoy this video about wind turbines, courtesy of NASA’s Lewis Research Center:

We have written many interesting articles on wind turbines and wind power here at Universe Today. Here’s What is Alternative Energy?, What are Fossil Fuels?, What are the Different Types of Renewable Energy?, Wind Power on the Ocean (with Help from Space), and Could the World Run on Solar and Wind Power?

For more information, check out How Stuff Works’s article about the history and mechanics of wind power and NASA’s Greenspace page.

Astronomy Cast also has some episodes that are relevant to the subject. Here’s Episode 51: Earth and Episode 308: Climate Change.

Sources:

December 30, 2016December 30, 2016 by Matt Williams

NASA’s NEOWISE Missions Spots New Comets

Artist's concept of the Wide-field Infrared Survey Explorer as its orbit around Earth. Credit: NASA/JPL

NASA’s Wide-field Infrared Survey Explorer (WISE) accomplished much during its first mission, which ran from December of 2009 to September of 2010. During the many months that it was active, the orbital telescope conducted an all-sky astronomical survey in the infrared band and discovered thousands of minor planets and numerous star clusters.

The extension of its mission, NEOWISE, has brought new life to the telescope as a comet and asteroid hunter. And since its re-activation in December of 2013, the orbiting telescope has spotted hundreds of Near Earth Objects (NEOs) and thousands of Main Belt asteroids. Most recently, it has detected two new objects (both possibly comets) which could be observable from Earth very soon.

The most recent object to be detected – 2016 WF9 – was first observed by NEOWISE on November 27th, 2016. This comet’s path through the Solar System takes it on a circuitous route, taking it from Jupiter to just inside the orbit of Earth over the course of 4.9 years. Much like other objects of its kind, 2016 WF9 may have once been a comet, or part of a population of dark objects in the Main Asteroid Belt.

*Artist’s rendition of the comet 2016 WF9 as it passes Jupiter’s orbit and moves toward the sun. Credit: NASA/JPL-Caltech*

In any case, 2016 WF9 will approach Earth’s orbit on February 25th, 2017, passing Earth at a minimum distance of almost 51 million km (32 million mi). This will place it well outside the orbit of the Moon, so the odds of it threatening Earth are negligible. But for those keen observers hoping to catch sight of the object, it will be close enough that it might be visible with just a pair of binoculars.

Since its discovery, 2016 WF9 has been of interest to astronomers, mainly because it straddles the already blurry line between asteroids and comets. While its proportions are known – roughly 0.5 to 1 kilometer in diameter (0.3 to 0.6 miles) – its other characteristics have led to some confusion as to where it came from. For one, its appearance (which is quite dark) and its orbit are consistent with what one expects from a comet.

But on the other hand, it lacks the characteristic cloud of dust and gas that comets are known for. As James Bauer, NEOWISE’s Deputy Principal Investigator at JPL, said in a NASA press release:

“2016 WF9 could have cometary origins. This object illustrates that the boundary between asteroids and comets is a blurry one; perhaps over time this object has lost the majority of the volatiles that linger on or just under its surface.”

*Graphic showing the asteroids and comets observed by NASA’s Near-Earth Object Wide-field Survey Explorer (NEOWISE) mission. Credit: NASA/JPL-Caltech/UCLA/JHU*

The other object, C/2016 U1 NEOWISE, was discovered about a month prior to 2016 WF9. Its orbit, which can you see by checking out the 3D Solar System Simulator, takes it from the outer Solar System to within Mercury’s orbit over the course of thousands of years. According to NASA scientists, this object is very clearly a comet, as evidenced by the dust it has been releasing as it gets closer to our Sun.

During the first week of 2017, comet C/2016 U1 NEOWISE is also likely to be visible in the night sky – in this case, in the southeastern sky shortly before dawn (for those looking from the northern hemisphere). It will reach its closest point to the Sun on January 14th (where it will be passing within Mercury’s orbit) before heading back out towards the outer Solar System.

Once again, it is believed that comet-hunters should be able to see it, though that is open to question. Paul Chodas, the manager of NASA’s Center for Near-Earth Object (NEO) Studies at the Jet Propulsion Laboratory, thinks that this object “has a good chance of becoming visible through a good pair of binoculars, although we can’t be sure because a comet’s brightness is notoriously unpredictable.”

*A mosaic of the images covering the entire sky as observed by the Wide-field Infrared Survey Explorer (WISE), part of its All-Sky Data Release. Credit: NASA/JPL*

In any case, NASA will be continuing to monitor 2016 WF9 to see if they can’t sort out what it is. Should it prove to be a comet, it would be the tenth discovered by NEOWISE since it was reactivated in December of 2013. If it turns out to be an asteroid, it would be the one-hundredth discovered since its reactivation.

As of November 2016, the orbital telescope has conducted over 562,000 infrared measurements have been made of 24,024 different solar system objects, including 613 NEOs and 110 comets. It has also been responsible for discovering 249 new near-Earth objects and comets, as well as more than 34,000 asteroids during its original mission.

At present, NEOWISE’s science team is currently reprocessing all its primary mission data to extend the search for asteroids and comets. It is hoped that by taking advantage of the latest in photometric and astrometric calibrations, they will be able to push the limits of what the telescope can detect, thereby adding many more minor planets and objects to its suite of discoveries.

And be sure to enjoy this video, detailing the first two years of asteroid data collected by the NEOWISE mission:

Further Reading: NASA

December 27, 2016December 27, 2016 by Ken Kremer

NASA Webb Telescope Structure is Sound After Vibration Testing Detects Anomaly

The 18-segment gold coated primary mirror of NASA’s James Webb Space Telescope is raised into vertical alignment in the largest clean room at the agency’s Goddard Space Flight Center in Greenbelt, Maryland, on Nov. 2, 2016. The secondary mirror mount booms are folded down into stowed for launch configuration. Credit: Ken Kremer/kenkremer.com

NASA GODDARD SPACE FLIGHT CENTER, MD – The James Webb Space Telescope (JWST) is now deemed “sound” and apparently unscathed, engineers have concluded, based on results from a new batch of intensive inspections of the observatory’s structure, after concerns were raised in early December when technicians initially detected “anomalous readings” during a preplanned series of vibration tests, NASA announced Dec. 23.

After conducting both “visual and ultrasonic examinations” at NASA’s Goddard Space Flight Center in Maryland, engineers have found it to be safe at this point with “no visible signs of damage.”

But because so much is on the line with NASA’s $8.8 Billion groundbreaking Webb telescope mission that will peer back to nearly the dawn of time, engineers are still investigating the “root cause” of the “vibration anomaly” first detected amidst shake testing on Dec. 3.

“The team is making good progress at identifying the root cause of the vibration anomaly,” NASA explained in a Dec 23 statement – much to everyone’s relief!

“They have successfully conducted two low level vibrations of the telescope.”

“All visual and ultrasonic examinations of the structure continue to show it to be sound.”

Technicians work on the James Webb Space Telescope in the massive clean room at NASA’s Goddard Space Flight Center, Greenbelt, Maryland, on Nov. 2, 2016, as the completed golden primary mirror and observatory structure stands gloriously vertical on a work stand, reflecting incoming light from the area and observation deck. Credit: Ken Kremer/kenkremer.com

Starting late November, technicians began a defined series of environmental tests including vibration and acoustics tests to make sure that the telescopes huge optical structure was fit for blastoff and could safely withstand the powerful shaking encountered during a rocket launch and the especially harsh rigors of the space environment. It would be useless otherwise – unable to carry out unparallelled science.

To carry out the vibration and acoustics tests conducted on equipment located in a shirtsleeve environment, the telescope structure was first carefully placed inside a ‘clean tent’ structure to protect it from dirt and grime and maintain the pristine clean room conditions available inside Goddard’s massive clean room – where it has been undergoing assembly for the past year.

NASA’s James Webb Space Telescope placed inside a “clean tent” in Nov. 2016 to protect it from dust and dirt as engineers at NASA’s Goddard Space Flight Center in Greenbelt, Maryland transport it out of the relatively dust-free cleanroom and into a shirtsleeve environment to conduct vibration and acoustics tests to confirm it is fit for launch in 2018. Credit: NASA/Chris Gunn

NASA’s James Webb Space Telescope is the most powerful space telescope ever built and is the scientific successor to the phenomenally successful Hubble Space Telescope (HST).

The mammoth 6.5 meter diameter primary mirror has enough light gathering capability to scan back over 13.5 billion years and see the formation of the first stars and galaxies in the early universe.

The Webb telescope will launch on an ESA Ariane V booster from the Guiana Space Center in Kourou, French Guiana in 2018.

“The James Webb Space Telescope is undergoing testing to make sure the spacecraft withstands the harsh conditions of launch, and to find and remedy all possible concerns before it is launched from French Guiana in 2018.”

However, shortly after the vibration testing began technicians soon discovered unexpected “anomalous readings” during a shake test of the telescope on Dec. 3, as the agency initially announced in a status update on the JWST website.

The anomalous readings were found during one of the vibration tests in progress on the shaker table, via accelerometers attached to the observatories optical structure known as OTIS.

“During the vibration testing on December 3, at Goddard Space Flight Center in Greenbelt, Maryland, accelerometers attached to the telescope detected anomalous readings during a particular test,” the team elaborated.

So the team quickly conducted further “low level vibration” tests and inspections to more fully understand the nature of the anomaly, as well as scrutinize the accelerometer data for clues.

“Further tests to identify the source of the anomaly are underway. The engineering team investigating the vibe anomaly has made numerous detailed visual inspections of the Webb telescope and has found no visible signs of damage.”

“They are continuing their analysis of accelerometer data to better determine the source of the anomaly.”

The team is measuring and recording the responses of the structure to the fresh low level vibration tests and will compare these new data to results obtained prior to detection of the anomaly.

Work continues over the holidays to ensure Webb is safe and sound and can meet its 2018 launch target. After thoroughly reviewing all the data the team hope to restart the planned vibration and acoustic testing in the new year.

“Currently, the team is continuing their analyses with the goal of having a review of their findings, conclusions and plans for resuming vibration testing in January.”

Webb’s massive optical structure being tested is known as OTIS or Optical Telescope element and Integrated Science. It includes the fully assembled 18-segment gold coated primary mirror and the science instrument module housing the four science instruments

OTIS is a combination of the OTE (Optical Telescope Assembly) and the ISIM (Integrated Science Instrument Module) together.

“OTIS is essentially the entire optical train of the observatory!” said John Durning, Webb Telescope Deputy Project Manager, in an earlier exclusive interview with Universe Today at NASA’s Goddard Space Flight Center.

“It’s the critical photon path for the system.”

The components were fully integrated this past summer at Goddard.

The combined OTIS entity of mirrors, science module and backplane truss weighs 8786 lbs (3940 kg) and measures 28’3” (8.6m) x 8”5” (2.6 m) x 7”10“ (2.4 m).

The environmental testing is being done at Goddard before shipping the huge structure to NASA’s Johnson Space Center in February 2017 for further ultra low temperature testing in the cryovac thermal vacuum chamber.

The 6.5 meter diameter ‘golden’ primary mirror is comprised of 18 hexagonal segments – looking honeycomb-like in appearance.

And it’s just mesmerizing to gaze at – as I had the opportunity to do on a few occasions at Goddard this past year – standing vertically in November and seated horizontally in May.

Each of the 18 hexagonal-shaped primary mirror segments measures just over 4.2 feet (1.3 meters) across and weighs approximately 88 pounds (40 kilograms). They are made of beryllium, gold coated and about the size of a coffee table.

All 18 gold coated primary mirrors of NASA’s James Webb Space Telescope are seen fully unveiled after removal of protective covers installed onto the backplane structure, as technicians work inside the massive clean room at NASA’s Goddard Space Flight Center in Greenbelt, Maryland on May 3, 2016. The secondary mirror mount booms are folded down into stowed for launch configuration. Credit: Ken Kremer/kenkremer.com

The Webb Telescope is a joint international collaborative project between NASA, the European Space Agency (ESA) and the Canadian Space Agency (CSA).

Webb is designed to look at the first light of the Universe and will be able to peer back in time to when the first stars and first galaxies were forming.

It will also study the history of our universe and the formation of our solar system as well as other solar systems and exoplanets, some of which may be capable of supporting life on planets similar to Earth.

Up close side-view of newly exposed gold coated primary mirrors installed onto mirror backplane holding structure of NASA’s James Webb Space Telescope inside the massive clean room at NASA’s Goddard Space Flight Center in Greenbelt, Maryland on May 3, 2016. Aft optics subsystem stands upright at center of 18 mirror segments between stowed secondary mirror mount booms. Credit: Ken Kremer/kenkremer.com

Watch this space for my ongoing reports on JWST mirrors, science, construction and testing.

Stay tuned here for Ken’s continuing Earth and Planetary science and human spaceflight news.

Ken Kremer

December 27, 2016 by Bob King

What My Dog Taught Me About Time and Space

Sammy and her namesake, Sirius the Dog Star, on a winter night. Photos by the author

Like many of you, I’m the owner of a furry Canis Major. Her name is Sammy. We always thought she was mostly border collie, but my daughter gifted me with a doggie DNA kit a few years back, and now we know with scientific certainty that she’s a mix of German shepherd, Siberian husky and golden retriever. Yeah, she’s a mutt.

Sammy’s going on 17 years old now — that’s human years — and has neither the spunk nor bladder control of a young pup. She wanders, paces, gets confused. In her aging, I see what’s in store for all of us as we pass from one stage of life to the next.

Intentionally or not, we humans often leave a legacy before we depart. Maybe a big building, a work of art or an exemplary life. As I stare down at my panting dog, it occurs that she’s leaving a legacy too, one she’s completely unaware of but which I’ll always appreciate.

Thanks to my dog I’ve seen more auroras and lunar halos that I can count. That goes for meteors, contrails, space station passes, light pillars and moonrises, too. All this because she needs to be walked in the early morning and again at night. This simple act ensures that while Sammy sniffs and marks, I get to spend at least 20 minutes under the sky. Nearly every night of the year.

Warm under her thick coat, she’s not bothered by the snow.

I’m an amateur astronomer and keep tabs on what’s up, but my dog makes sure I don’t ignore the sky. Let’s say she keeps me honest. There’s no avoiding going out or I’ll pay for it in whimpering and cleanup.

There were times I wouldn’t be aware an aurora was underway until it was time to walk the dog. When we were done, I’d dash away to a dark sky with camera and tripod. Other nights, walking the dog would alert me to a sudden clearing and the opportunity to catch a variable star on the rise or see a newly discovered comet for the first time. Thanks Sammy.

Amateur astronomers are familiar with eternity. We routinely observe stars and galaxies by eye and telescope that remind us of both the vastness of space and the aching expanse of time. I have only so many years left before I spend the next 10 billion years disassembled and strewn about like that scarecrow attacked by flying monkeys. But when I see the Sombrero Galaxy through my telescope, with its 29-million-year-old photons setting off tiny explosions in my retinas, I get a taste of eternity in the here and now.

That’s where Sammy offers yet another pearl. Dogs are far better living in the moment than people are. They can eat the same food twice a day for a decade and relish it anew every single time. Same goes for their excitement at seeing their owner or taking a walk or a million other ways they reveal that this moment is what counts.

The famous Sombrero galaxy (M104) is a bright nearby spiral galaxy. The prominent dust lane and halo of stars and globular clusters give this galaxy its name. Credit: NASA/ESA and The Hubble Heritage Team (STScI/AURA)

People tend to think of eternity as encompassing all of time, but Sammy has a different take. A moment fully experienced feels like it might never end. Lose yourself in the moment, and the clock stops ticking. I love that feeling. That’s how my dog’s been living all along. Canine wisdom: one billion years = one moment. Both feel like forever.

Sammy’s lost much of her hearing and some of her eyesight. We’re not sure how long she has. Maybe a few months, maybe even another year, but her legacy is clear. She’s been a great pet and teacher even if she never figured out how to fetch. We’ve hiked hard trails together and then rested atop precipices with the sun sinking in the west. I look into her clouded eyes these days and have to speak up when I call her name, but she’s been and remains a “Good dog!”

December 27, 2016December 27, 2016 by David Dickinson

Comet U1 NEOWISE: A Possible Binocular Comet?

Well, it looks like we’ll close out 2016 without a great ‘Comet of the Century.’ One of the final discoveries of the year did, however, grab our attention, and may present a challenging target through early 2017: Comet U1 NEOWISE.

Comet C/2016 U1 NEOWISE is expected to reach maximum brightness during the second week on January. Discovered by the Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) space observatory on its extended mission on October 21^st, 2016, Comet U1 NEOWISE orbits the Sun on an undefined hyperbolic orbit that is perhaps millions on years long. This also means that this could be Comet C/2016 U1 NEOWISE’s first venture through the inner solar system. Comet C/2016 U1 NEOWISE is set to break binocular +10^th magnitude brightness this week, and may just top +6^th magnitude (naked eye brightness) in mid-January near perihelion.

The orbit of Comet U1 NEOWISE. Credit: NASA/JPL.

Visibility prospects: At its brightest, Comet C/2016 U1 NEOWISE will pass through the constellations Ophiuchus to Serpens Cauda and Sagittarius, and is best visible in the dawn sky 12 degrees from the Sun at maximum brightness. This apparition favors the northern hemisphere. Perihelion for Comet C/2016 U1 NEOWISE occurs on January 13^th, 2017 at 0.319 AU from the Sun, and the comet passed 0.709 AU from the Earth on December 13th.

This is the ninth comet discovered by the extended NEOWISE mission since 2014.

The pre-dawn view on the morning of December 28th. Image credit: Starry Night.

Comet C/2016 U1 NEOWISE ends 2016 and early January 2017 as a difficult early dawn target, sitting 25 degrees above the eastern horizon as seen from latitude 30 degrees north about 30 minutes before dawn. Things will get much more difficult from there, as the comet passes just 12 degrees from the Sun as seen from our Earthly vantage point during the final week of January. The comet sits 16 degrees from the Sun in the southern hemisphere constellation of Microscopium on the final day of January, though it is expected to shine at only +10th magnitude at this point, favoring observers in the southern hemisphere.

The time to try to catch a brief sight of Comet C/2016 U1 NEOWISE is now. Recent discussions among comet observers suggest that the comet may be slowing down in terms of brightness, possibly as a prelude to a pre-perihelion breakup. Keep a eye on the Comet Observer’s database (COBS) for the latest in cometary action as reported and seen by actual observers in the field.

Finding C/2016 U1 NEOWISE will be a battle between spying an elusive fuzzy low-contrast coma against a brightening twilight sky. Sweep the suspect area with binoculars or a wide-field telescopic view if possible.

The path of Comet U1 NEOWISE through perihelion on January 13th. Credit: Starry Night.

Here are some key dates to watch out for in your quest:

December

25-Crosses in to Ophiuchus.

26-Passes near +3 mag Kappa Ophiuchi.

January

1-Crosses the celestial equator southward.

3-Passes near M14.

7-Passes near the +3 mag star Nu Ophiuchi.

8-Crosses into the constellation Serpens Cauda.

10-Passes near M16, the Eagle Nebula.

11-Passes near M17 the Omega Nebula, crosses the galactic equator southward.

12-Crosses into the constellation Sagittarius.

13-Passes near M25.

16-Crosses the ecliptic southward.

27-Crosses into the constellation Microscopium.

28-Passes near +4.8 mag star Alpha Microscopii.

February

1-May drop back below +10 magnitude.

C/2016 U1 NEOWISE (23.nov.2016) from Oleg Milantiev on Vimeo.

A rundown on comets in 2016, a look ahead at 2017

C/2016 U1 NEOWISE was one of 50 comets discovered in 2016. Notables for the year included C/2013 X1 PanSTARRS, 252/P LINEAR and C/2013 US10 Catalina. What comets are we keeping an eye on in 2017? Well, Comet 2/P Encke, 41P/Tuttle-Giacobini-Kresak, C/2015 ER61 PanSTARRS, C/2015 V2 Johnson are all expected to reach +10 magnitude brightness in the coming year… and Comet 45P/Honda-Mrkos-Pajdušáková has already done so, a bit ahead of schedule. These are all broken down in our forthcoming guide to the top 101 Astronomical Events for 2017. Again, there’s no great naked eye comet on the horizon (yet), but that all could change… 2017 owes us one!

December 26, 2016December 24, 2016 by Tammy Plotner

Messier 29 – The NGC 6913 Open Star Cluster

The Messier 29 open star cluster. Credit: Wikisky

Welcome back to Messier Monday! In our ongoing tribute to the great Tammy Plotner, we take a look at the open star cluster known as Messier 29. Enjoy!

During the 18th century, famed French astronomer Charles Messier noted the presence of several “nebulous objects” in the night sky. Having originally mistaken them for comets, he began compiling a list of them so that others would not make the same mistake he did. In time, this list would come to include 100 of the most fabulous objects in the night sky.

One of these objects is Messier 29, an open star cluster located in the northern skies in the direction of the Cygnus constellation. Situated in a highly crowded area of the Milky Way Galaxy, about 4,000 light-years from Earth, this star cluster is slowly moving towards us. Though somewhat isolated in the night sky, it can be easily spotted using binoculars and small telescopes.

Description:

While Messier Object 29 might appear a little bit boring compared to some of its more splashy catalog companions, it really isn’t. This little group of stars is part of the Cygnus OB1 association which just happens to be heading towards us at a speed of 28 kilometers per second (17.4 mps) . If it weren’t obscured by Milky Way dust, the light of its stars would be 1000 times brighter!

*Messier 29 and Gamma Cygni (Sadr). Credit: Wikisky*

All in all, M29 has around 50 member stars, but this 10 million year old star cluster still has some surprises. The five brightest stars you see are are all giant stars of spectral class B0, and if we were to put one next to our own Sol, it would shine 160,000 times brighter. Image just how “lit up” any planet might be that would reside inside that 11 light year expanse!

Astronomers were curious about Messier 29, too, so they went in search of binary stars. As C. Boeche (et al) wrote in a 2003 study:

“Between 1996 and 2003 we obtained 226 high resolution spectra of 16 stars in the field of the young open cluster NGC 6913, to constrain its main properties and study its internal kinematics. Twelve of the program stars turned out to be members, one of them probably unbound. Nine are binaries (one eclipsing and another double lined) and for seven of them the observations allowed us to derive the orbital elements. All but two of the nine discovered binaries are cluster members. In spite of the young age (a few Myr), the cluster already shows signs that could be interpreted as evidence of dynamical relaxatin and mass segregation.

“However, they may be also the result of an unconventional formation scenario. The dynamical (virial) mass as estimated from the radial velocity dispersion is larger than the cluster luminous mass, which may be explained by a combination of the optically thick interstellar cloud that occults part of the cluster, the unbound state or undetected very wide binary orbit of some of the members that inflate the velocity dispersion and a high inclination for the axis of possible cluster angular momentum. All the discovered binaries are hard enough to survive average close encounters within the cluster and do not yet show signs of relaxation of the orbital elements to values typical of field binaries.”

So why is finding binary stars important? Evolution is the solution, the hunt for Be stars. As S.L. Malchenko of the Crimean Astrophysical Observatory wrote in a 2008 study on Be stars:

“The phenomenon of Be stars has been known for over a century. The fact that at least 20% of B stars have an emission spectrum supports that the definition that this phenomenon is not special but it is rather typical from a large group of objects at a certain stage of evolution. The vagueness of the concept of the Be phenomenon suggests that this definition encompasses a broad group of objects near the main sequence that includes binary systems with different rate of mass exchange. This young open cluster in the Cyg OB1 association, is also know as M29, contains a large number of luminous stars with spectral types around B0. An extreme variation of extinction is found across the young open cluster NGC 6913, extinction in the cluster center is relatively homogeneous, but very large. We observed 10 spectra for 7 B stars and one known Be star in the blue region.”

*Close-up of the core region of Messier 29. Credit: Adam Block/Mount Lemmon SkyCenter/University of Arizona*

Although you won’t be able to detect it visually, there is also some nebulosity associated with M29, which is another important clue to this star cluster’s evolution. As B. Bhavya of Cochin University of Science and Technology wrote in a 2008 study:

“The Cygnus region is a region of recent star formation activity in the Milky Way and is rich in massive early type stars concentrated in OB associations. The presence of nebulosity and massive stars indicate that the stars have been forming till very recently and the young clusters found here are the result of the recent star formation event. Though the above fact is known, what is not known is that when this star formation process started and how it proceeded in the region. Though one assumes that all the stars in a cluster have the same age, this assumption is not valid when the candidate cluster is very young. In the case of young clusters, there is a chance for a spread in the age of the stars, depending on the duration of star formation. An estimation of this formation time-scale in the clusters formed in a star forming complex, will indicate the duration of star formation and its direction of propagation within the complex. In principle, duration of star formation is defined as the difference between the ages of the oldest and the youngest star formed in the cluster. In practice, the age of the oldest star is assumed as the age of that star which is about to turn-off from the main-sequence (MS) (turn-off age) and the age of the youngest star is the age of the youngest pre-MS star (turn-on age). The turn-off age of many clusters are known, but the turn-on age is not known for most of the clusters.”

History of Observation:

This cool little star cluster was an original discovery of Charles Messier, who first observed it in 1764. As he wrote of the object in his notes at the time:

“In the night of July 29 to 30, 1764, I have discovered a cluster of six or seven very small stars which are below Gamma Cygni, and which one sees with an ordinary refractor of 3 feet and a half in the form of a nebula. I have compared this cluster with the star Gamma, and I have determined its position in right ascension as 303d 54′ 29″, and its declination of 37d 11′ 57″ north.”

*Gammy Cygni (the brightest object in the center) and neighboring regions. Credit: Wikipedia Commons/Erik Larsen*

In the case of this cluster, it was independently recovered again by Caroline Herschel, who wrote: “About 1 deg under Gamma Cygni; in my telescope 5 small stars thus. My Brother looked at them with the 7 ft and counted 12. It is not in Mess. catalogue.”

William would also return to the cluster as well with his own observations: “Is not sufficiently marked in the heavens to deserve notice, as 7 or 8 small stars together are so frequent about this part of the heavens that one might find them by hundreds.”

So why the confusion? In this circumstance, perhaps Messier was a bit distracted, for it would appear that his logged coordinates were somewhat amiss. Leave it to Admiral Symth to set the records straight:

“A neat but small cluster of stars at the root of the Swan’s neck, and in the preceding branch of the Milky Way, not quite 2deg south of Gamma; and preceding 40 Cygni, a star of the 6th magnitude, by one degree just on the parallel. In the sp [south preceding, SW] portion are the two stars here estimated as double, of which A is 8, yellow; B 11, dusky. Messier discovered this in 1764; and though his description of it is very fair, his declination is very much out: worked up for my epoch it would be north 37d 26′ 15″. But one is only surprised that, with his confined methods and means, so much was accomplished.”

Kudos to Mr. Messier for being able to distinguish a truly related group of stars in a field of so many! Take the time to enjoy this neat little grouping for yourself and remember – it’s heading our way.

Locating Messier 29:

Finding M29 in binoculars or a telescope is quite easy once you recognize the constellation of Cygnus. Its cross-shape is very distinctive and the marker star you will need to locate this open star cluster is Gamma – bright and centermost. For most average binoculars, you will only need to aim at Gamma and you will see Messier 29 as a tiny grouping of stars that resembles a small box.

Messier 29 location. Image: IAU and Sky & Telescope magazine (Roger Sinnott & Rick Fienberg) — *The location of Messier 29, in the direction of the Cygus constellation. Credit: IAU and Sky & Telescope magazine (Roger Sinnott & Rick Fienberg)*

For a telescope, begin with your finderscope on Gamma, and look for your next starhop marker star about a finger width southwest. Once this star is near the center of your finderscope field, M29 will also be in a low magnification eyepiece field of view. Because it is a very widely spaced galactic open star cluster that only consists of a few stars, it makes an outstanding object that stands up to any type of sky conditions.

Except, of course, clouds! Messier 29 can easily be seen in light polluted areas and during a full Moon – making it a prize object for study for even the smallest of telescopes.

As always, here are the quick facts to help you get started:

Object Name: Messier 29
Alternative Designations: M29, NGC 6913
Object Type: Open Galactic Star Cluster
Constellation: Cygnus
Right Ascension: 20 : 23.9 (h:m)
Declination: +38 : 32 (deg:m)
Distance: 4.0 (kly)
Visual Brightness: 7.1 (mag)
Apparent Dimension: 7.0 (arc min)

We have written many interesting articles about Messier Objects here at Universe Today. Here’s Tammy Plotner’s Introduction to the Messier Objects, , M1 – The Crab Nebula, M8 – The Lagoon Nebula, and David Dickison’s articles on the 2013 and 2014 Messier Marathons.

Be to sure to check out our complete Messier Catalog. And for more information, check out the SEDS Messier Database.

Sources:

December 25, 2016December 25, 2016 by Ken Kremer

Merry Christmas From Space 2016

All six members of the Expedition 50 crew aboard the International Space Station celebrated the holidays together with a festive meal on Christmas Day, Dec. 25, 2016 Image Credit: NASA

As we celebrate the Christmas tidings of 2016 here on Earth, a lucky multinational crew of astronauts and cosmonauts celebrate the festive season floating in Zero-G while living and working together in space aboard the Earth orbiting International Space Station (ISS) complex – peacefully cooperating to benefit all humanity.

Today, Dec. 25, 2016, the six person Expedition 50 crew of five men and one woman marked the joyous holiday of Christ’s birth by gathering for a festive meal in space – as billions of Earthlings celebrated this Christmas season of giving, remembrance and peace to all here on our home planet.

This year is an especially noteworthy Space Christmas because it counts as Expedition 50. This is the 50th crew to reside on board since the space station began operating with permanent occupancy by rotating crews all the way back to 1998.

The Expedition 50 crew currently comprises of people from three nations supporting the ISS – namely the US, Russia and France; Commander Shane Kimbrough from NASA and flight engineers Andrey Borisenko (Roscosmos), Sergey Ryzhikov (Roscosmos), Thomas Pesquet (ESA), Peggy Whitson (NASA), and Oleg Novitskiy (Roscosmos).

Here a short video of holiday greetings from a trio of crew members explaining what Christmas in Space means to them:

Video Caption: Space Station Crew Celebrates the Holidays Aboard the Orbital Lab. Aboard the International Space Station, Expedition 50 Commander Shane Kimbrough and Peggy Whitson of NASA and Thomas Pesquet of the European Space Agency discussed their thoughts about being in space during the holidays and how they plan to celebrate Christmas and New Year’s in a downlink. Credit: NASA

“Hello from the Expedition 50 Crew! We’d like to share what Christmas means to us,” said Expedition 50 Commander Shane Kimbrough.

“For me it’s a lot about family,” said Expedition 50 Commander Shane Kimbrough. “We always travel to meet up with our family which is dispersed across the country. And we go home to Georgia and Florida … quite abit to meet up. Always a great time to get together and share with each other.”

“Although its typically thought of a season to get things, we in our family think about the giving aspect. Giving of our many talents and resources. Especially to those less fortunate.”

Kimbrough arrived on the complex in October, followed a month later by Whitson and Pesquet in November.

They were all launched aboard Russian Soyuz capsules from the Baikonur Cosmodrome in Kazakhstan.

Aboard the International Space Station, Expedition 50 Flight Engineer Peggy Whitson of NASA sent holiday greetings and festive imagery from the cupola on Dec. 18, 2016. Credit: NASA.

And Peggy Whitson especially has a lot to celebrate in space!

Because not only is Whitson currently enjoying her third long-duration flight aboard the station – as an Expedition 50 flight engineer. Soon she will become the first woman to command the station twice ! That momentous event happens when she assumes the role of Space Station Commander early in 2017 during the start of Expedition 51.

“In addition to family, there is another very important aspect to being on the ISS,” said Whitson.

“That is seeing the planet as a whole. It actually reinforces I think, that fact that we should live as one people and strive for peace.”

“I second the comments already made. I grew up in a family of 25 cousins,” said ESA’s Thomas Pesquet. “The only time we could catch up was around Christmas time…. So I always looked forward to that, although this year I can’t be with them of course … and will think of them.”

“I am making the most of this opportunity to look at the Earth. Reflect about what Christmas means to us as individuals and to the world in general. And we will have a good time on board the ISS and share a Christmas meal together.”

The crew is enjoying a light weekend of work and a day off tomorrow, Dec. 26.

After that they begin preparing for a pair of spacewalks in the new year by Kimbrough and Whitson – scheduled for Jan. 6 and 13. The crew is checking the spacesuits by testing the water among other activities.

The goal of the excursions is to “complete the replacement of old nickel-hydrogen batteries with new lithium-ion batteries on the station’s truss structure,” says NASA.

Research work also continues.

“Whitson, who is spending her second Christmas in space, and Pesquet drew blood, urine and saliva samples for the Fluid Shifts study. That experiment investigates the upward flow of body fluids in space potentially causing lasting vision changes in astronauts.”

NASA astronaut Peggy Whitson floats through the Unity module aboard the International Space Station. On her third long-duration flight aboard the station, Whitson will become the first woman to command the station twice when she assumes the role during Expedition 51. Credit: NASA

Among other activities, the crew is also unloading 4.5 tons of internal and external cargo, gear and fresh food – including six lithium-ion batteries – from Japan’s sixth H-II Transfer Vehicle (HTV-6), which recently arrived at the ISS on Dec 13.

The next regular US cargo delivery is likely to be in March 2017, when an unmanned Orbital ATK Cygnus cargo freighter is slated to launch on a ULA Atlas V from Cape Canaveral. A Cygnus was also launched on a ULA Atlas V in March 2016.

A Cygnus cargo spacecraft named the SS Rick Husband is being prepared inside the Payload Hazardous Servicing Facility at NASA’s Kennedy Space Center for upcoming Orbital ATK CRS-6/OA-6 mission to deliver hardware and supplies to the International Space Station. Cygnus is scheduled to lift off atop a United Launch Alliance Atlas V rocket on March 22, 2016. Credit: Ken Kremer/kenkremer.com

SpaceX also hopes to resume Dragon cargo launches sometime in the new year after they resolve the issues that led to the destruction of a SpaceX Falcon 9 on Sept. 1 during fueling operations at pad 40 on the Cape.

Meanwhile Roscosmos continues to investigate the causes of the failed launch of the unmanned Russian Progress 65 resupply ship on Dec. 1 due to a 3rd stage anomaly.

Stay tuned here for Ken’s continuing Earth and Planetary science and human spaceflight news.

Ken Kremer

December 25, 2016December 25, 2016 by Bob King

See a Christmas-Time Binocular Comet: 45P/Honda-Mrkos-Pajdusakova

45P/H-M-P displays a colorful coma and long ion tail on Dec. 22, 2016. Credit: Gerald Rhemann

Comet 45P/Honda-Mrkos-Pajdusakova captured in its glory on Dec. 22, 2016. It displays a bright, well-condensed blue-green coma and long ion tail pointing east. Credit: Gerald Rhemann — Comet 45P/Honda-Mrkos-Pajdusakova captured in its glory on Dec. 22, 2016. It displays a bright, well-condensed blue-green coma and long ion or gas tail pointing east. Comet observers take note: a Swan Band filter shows a larger coma and increases the comet’s contrast. Credit: **Gerald Rhemann**

Merry Christmas and Happy Holidays all! I hope the day finds you in the company of family or friends and feeling at peace. While we’ve been shopping for gifts the past few weeks, a returning comet has been brightening up in the evening sky. Named 45P/Honda-Mrkos-Pajdusakova, it returns to the hood every 5.25 years after vacationing beyond the planet Jupiter. It’s tempting to blow by the name and see only a jumble of letters, but let’s try to pronounce it: HON-da — MUR-Koz — PIE-doo-sha-ko-vah. Not too hard, right?

Tonight, the comet will appear about 12. 5 degrees to the west of Venus in central Capricornus. You can spot it near the end of evening twilight. Use larger binoculars or a telescope. Stellarium

Comet 45P is a short period comet — one with an orbital period of fewer than 200 years — discovered on December 3, 1948 by Minoru Honda along with co-discoverers Antonin Mrkos and Ludmila Pajdusakova. Three names are the maximum a comet can have even if 15 people simultaneously discover it. 45P has a history of brightening rapidly as it approaches the sun, and this go-round is proof. A faint nothing a few weeks back, the comet’s now magnitude +7.5 and visible in 50mm or larger binoculars from low light pollution locations.

You can catch it right around the end of dusk this week and next as it arcs across central Capricornus not far behind the brilliant planet Venus. 45P will look like a dim, fuzzy star in binoculars, but if you can get a telescope on it, you’ll see a fluffy, round coma, a bright, star-like center and perhaps even a faint spike of a tail sticking out to the east. Time exposure photos reveal a tail at least 3° long and a gorgeous, aqua-tinted coma. I saw the color straight off when observing the comet several nights ago in my 15-inch reflector at low power (64x).

Use this map to help you follow the comet night to night. Tick marks start this evening (Dec. 25) and show its nightly position through Jan. 8. Venus, at upper left, is shown through the 28th. Created with Chris Marriott's SkyMap software — Use this map to help you follow the comet night to night. Tick marks start this evening (Dec. 25) and show its nightly position through Jan. 8 around 6 p.m. local time or about an hour and 15 minutes after sunset. Venus, at upper left, is shown through the 28th with stars to magnitude +7. Click the chart for a larger version you can save and print out for use at your telescope. Created with Chris Marriott’s SkyMap software

Right now, and for the remainder of its evening apparition, 45P will never appear very high in the southwestern sky. Look for it a little before the end of evening twilight, when the sky is reasonably dark and the comet is as high as it gets — about a fist above the horizon as seen from mid-northern latitudes. That’s pretty low, so make the best of your time. I recommend you being around 1 hour 15 minutes after sunset.

The further south you live, the higher 45P will appear. To a point. It hovers low at nightfall this month and next. That will change in February when the comet pulls away from the sun and makes a very close approach to the Earth while sailing across the morning sky.

How about a helping hand? On New Year's Eve, the 2-day-old crescent Moon will be just a few degrees from 45P. This simulation shows the view through 50mm or larger binoculars with an ~6 degree field of view. Map: Bob King, Source: Stellarium — How about a helping hand? On New Year’s Eve, the 2-day-old crescent Moon will be just a few degrees from 45P. This simulation shows the view through 50mm or larger binoculars with an ~6 degree field of view for the Central time zone. Map: Bob King, Source: Stellarium

45P reaches perihelion or closest distance to the sun on Dec. 31 and will remain visible through about Jan. 15 at dusk. An approximately 2-week hiatus follows, when it’s lost in the twilight glow. Then in early February, the comet reappears at dawn and races across Aquila and Hercules, zipping closest to Earth on Feb. 11 at a distance of only 7.7 million miles. During that time, we may even be able to see this little fuzzball with the naked eye; its predicted magnitude of +6 at maximum is right at the naked eye limit. Even in suburban skies, it will make an easy catch in binoculars then.

I’ll update with new charts as we approach that time, plus you can check out this earlier post by fellow Universe Today writer David Dickinson. For now, enjoy the prospect of ‘opening up’ this cometary gift as the last glow of dusk subsides into night.

December 23, 2016June 2, 2017 by Tammy Plotner

The Canis Minor Constellation

View of the night sky in North Carolina, showing the constellations of Orion, Hyades, Canis Major and Canis Minor. Credit: NASA

Welcome back to Constellation Friday! Today, in honor of the late and great Tammy Plotner, we will be dealing with the “little dog” – the Canis Minor constellation!

In the 2nd century CE, Greek-Egyptian astronomer Claudius Ptolemaeus (aka. Ptolemy) compiled a list of all the then-known 48 constellations. This treatise, known as the Almagest, would be used by medieval European and Islamic scholars for over a thousand years to come, effectively becoming astrological and astronomical canon until the early Modern Age.

One of these constellations was Canis Minor, a small constellation in the northern hemisphere. As a relatively dim collection of stars, it contains only two particularly bright stars and only faint Deep Sky Objects. Today, it is one of the 88 constellations recognized by the International Astronomical Union, and is bordered by the Monoceros, Gemini, Cancer and Hydra constellation.

Name and Meaning:

Like most asterisms named by the Greeks and Romans, the first recorded mention of this constellation goes back to ancient Mesopotamia. Specifically, Canis Minor’s brightest stars – Procyon and Gomeisa – were mentioned in the Three Stars Each tablets (ca. 1100 BCE), where they were referred to as MASH.TAB.BA (or “twins”).

*The Winter Hexagon, which contains parts of the Auriga, Canis Major, Canis Minor, Gemini, Monoceros, Orion, Taurus, Lepus and Eridanus constellations. Credit: constellation-guide.com*

In the later texts that belong to the MUL.APIN, the constellation was given the name DAR.LUGAL (“the star which stands behind it”) and represented a rooster. According to ancient Greco-Roman mythology, Canis Minor represented the smaller of Orion’s two hunting dogs, though they did not recognize it as its own constellation.

In Greek mythology, Canis Minor is also connected with the Teumessian Fox, a beast turned into stone with its hunter (Laelaps) by Zeus. He then placed them in heaven as Canis Major (Laelaps) and Canis Minor (Teumessian Fox). According to English astronomer and biographer of constellation history Ian Ridpath:

“Canis Minor is usually identified as one of the dogs of Orion. But in a famous legend from Attica (the area around Athens), recounted by the mythographer Hyginus, the constellation represents Maera, dog of Icarius, the man whom the god Dionysus first taught to make wine. When Icarius gave his wine to some shepherds for tasting, they rapidly became drunk. Suspecting that Icarius had poisoned them, they killed him. Maera the dog ran howling to Icarius’s daughter Erigone, caught hold of her dress with his teeth and led her to her father’s body. Both Erigone and the dog took their own lives where Icarius lay.

“Zeus placed their images among the stars as a reminder of the unfortunate affair. To atone for their tragic mistake, the people of Athens instituted a yearly celebration in honour of Icarius and Erigone. In this story, Icarius is identified with the constellation Boötes, Erigone is Virgo and Maera is Canis Minor.”

*Canis Minor, as depicted by Johann Bode in his 1801 work Uranographia. Credit: Wikipedia Commons/Alessio Govi*

To the ancient Egyptians, this constellation represented Anubis, the jackal god. To the ancient Aztecs, the stars of Canis Minor were incorporated along with stars from Orion and Gemini into as asterism known as “Water”, which was associated with the day. Procyon was also significant in the cultural traditions of the Polynesians, the Maori people of New Zealand, and the Aborigines of Australia.

In Chinese astronomy, the stars corresponding to Canis Minor were part of the The Vermilion Bird of the South. Along with stars from Cancer and Gemini, they formed the asterisms known as the Northern and Southern River, as well as the asterism Shuiwei (“water level”), which represented an official who managed floodwaters or a marker of the water level.

History of Observation:

Canis Minor was one of the original 48 constellations included by Ptolemy in his the Almagest. Though not recognized as its own asterism by the Ancient Greeks, it was added by the Romans as the smaller of Orion’s hunting dogs. Thanks to Ptolemy’s inclusion of it in his 2nd century treatise, it would go on to become part of astrological and astronomical traditions for a thousand years to come.

For medieval Arabic astronomers, Canis Minor continued to be depicted as a dog, and was known as “al-Kalb al-Asghar“. It was included in the Book of Fixed Stars by Abd al-Rahman al-Sufi, who assigned a canine figure to his stellar diagram. Procyon and Gomeisa were also named for their proximity to Sirius; Procyon being named the “Syrian Sirius (“ash-Shi’ra ash-Shamiya“) and Gomeisa the “Sirius with bleary eyes” (“ash-Shira al-Ghamisa“).

*The constellation Canis Minor, shown alongside Monoceros and the obsolete constellation Atelier Typographique. Credit: Library of Congress*

The constellation was included in Syndey Hall’s Urania’s Mirror (1825) alongside Monoceros and the now obsolete constellation Atelier Typographique. Many alternate names were suggested between the 17th and 19th centuries in an attempt to simplify celestial charts. However, Canis Minor has endured; and in 1922, it became one the 88 modern constellations to be recognized by the IAU.

Notable Features:

Canis Minor contains two primary stars and 14 Bayer/Flamsteed designated stars. It’s brightest star, Procyon (Alpha Canis Minoris), is also the seventh brightest star in the sky. With an apparent visual magnitude of 0.34, Procyon is not extraordinarily bright in itself. But it’s proximity to the Sun – 11.41 light years from Earth – ensures that it appears bright in the night sky.

The star’s name is derived from the Greek word which means “before the dog”, a reference to the fact that it appears to rise before Sirius (the “Dog Star”) when observed from northern latitudes. Procyon is a binary star system, composed of a white main sequence star (Procyon A) and Procyon B, a DA-type faint white dwarf as the companion.

Procyon is part of the Winter Triangle asterism, along with Sirius in Canis Major and Betelgeuse in the constellation Orion. It is also part of the Winter Hexagon, along with the stars Capella in Auriga, Aldebaran in Taurus, Castor and Pollux in Gemini, Rigel in Orion and Sirius in Canis Major.

*The stars of the Winter Triangle and the Winter Hexagon. Credit: constellation-guide.com*

Next up is Gomeisa, the second brightest star in Canis Minor. This hot, B8-type main sequence star is classified as a Gamma Cassiopeiae variable, which means that it rotates rapidly and exhibits irregular variations in luminosity because of the outflow of matter. Gomeisa is approximately 170 light years from Earth and the name is derived from the Arabic “al-ghumaisa” (“the bleary-eyed woman”).

Canis Minor also has a number of Deep Sky Objects located within it, but all are very faint and difficult to observe. The brightest is the spiral galaxy NGC 2485 (apparent magnitude of 12.4), which is located 3.5 degrees northeast of Procyon. There is one meteor shower associated with this constellation, which are the Canis-Minorids.

Finding Canis Minor:

Though it is relatively faint, Canis Minor and its stars can be viewed using binoculars. Start with the brightest, Procyon – aka. Alpha Canis Minoris (Alpha CMi). If you’re unsure of which bright star is, you’ll find it in the center of the diamond shape grouping in the southwest area. Known to the ancients as Procyon – “The Little Dog Star” – it’s the seventh brightest star in the night sky and the 13th nearest to our solar system.

For over 100 years, astronomers have known this brilliant star had a companion. Being 15,000 times fainter than the parent star, Procyon B is an example of a white dwarf whose diameter is only about twice that of Earth. But its density exceeds two tons per cubic inch! (Or, a third of a metric ton per cubic centimeter). While only very large telescopes can resolve this second closest of the white dwarf stars, even the moonlight can’t dim its beauty.

*The Winter Triangle. Credit: constellation-guide.com/Stellarium software*

Now hop over to Beta CMi. Known by the very strange name of Gomeisa (“bleary-eyed woman”), it refers to the weeping sister left behind when Sirius and Canopus ran to the south to save their lives. Located about 170 light years away from our Solar System, Beta is a blue-white class B main sequence dwarf star with around 3 times the mass of our Sun and a stellar luminosity over 250 times that of Sol.

Gomeisa is a fast rotator, spinning at its equator with a speed of at least 250 kilometers per second (125 times our Sun’s rotation speed) giving the star a rotation period of about a day. Sunspots would appear to move very quickly there! According to Jim Kaler, Professor Emeritus of Astronomy at the University of Illinois:

“Since we may be looking more at the star’s pole than at its equator, it may be spinning much faster, and indeed is rotating so quickly that it is surrounded by a disk of matter that emits radiation, rendering Gomeisa a “B-emission” star rather like Gamma Cassiopeiae and Alcyone. Like these two, Gomeisa is distinguished by having the size of its disk directly measured, the disk’s diameter almost four times larger than the star. Like quite a number of hot stars (including Adhara, Nunki, and many others), Gomeisa is also surrounded by a thin cloud of dusty interstellar gas that it helps to heat.”

Now hop over to Gamma Canis Minoris, an orange K-type giant with an apparent magnitude of +4.33. It is a spectroscopic binary, has an unresolved companion which has an orbital period of 389 days, and is approximately 398 light years from Earth. And next is Epsilon Canis Minoris, a yellow G-type bright giant (apparent magnitude of +4.99) which is approximately 990 light years from Earth.

*The location of Canis Minor in the northern hemisphere. Credit: IAU/Sky&Telescope magazine*

For smaller telescopes, the double star Struve 1149 is a lovely sight, consisting of a yellow primary star and a faintly blue companion. For larger telescopes and GoTo telescopes, try NGC 2485 (RA 07 56.7 Dec +07 29), a magnitude 13 spiral galaxy that has a small, round glow, sharp edges and a very bright, stellar nucleus. If you want one that’s even more challenging, try NGC 2508 (RA 08 02 0 Dec +08 34).

Canis Minor lies in the second quadrant of the northern hemisphere (NQ2) and can be seen at latitudes between +90° and -75°. The neighboring constellations are Cancer, Gemini, Hydra, and Monoceros, and it is best visible during the month of March.

We have written many interesting articles about the constellation here at Universe Today. Here is What Are The Constellations?, What Is The Zodiac?, and Zodiac Signs And Their Dates.

Be sure to check out The Messier Catalog while you’re at it!

For more information, check out the IAUs list of Constellations, and the Students for the Exploration and Development of Space page on Canes Venatici and Constellation Families.

Sources:

December 22, 2016April 4, 2023 by Matt Williams

How Do We Settle on Saturn’s Moons?

A collage of Saturn (bottom left) and some of its moons: Titan, Enceladus, Dione, Rhea and Helene. Credit: NASA/JPL/Space Science Institute

Welcome back to our series on Settling the Solar System! Today, we take a look at the largest of Saturn’s Moons – Titan, Rhea, Iapetus, Dione, Tethys, Enceladus, and Mimas.

From the 17th century onward, astronomers made some profound discoveries around the planet Saturn, which they believed was the most distant planet of the Solar System at the time. Christiaan Huygens and Giovanni Domenico Cassini were the first, spotting the largest moons of Saturn – Titan, Tethys, Dione, Rhea and Iapetus. More discoveries followed; and today, what we recognized as the Saturn system includes 62 confirmed satellites.

What we know of this system has grown considerably in recent decades, thanks to missions like Voyager and Cassini. And with this knowledge has come multiple proposals that claim how Saturn’s moons should someday be colonized. In addition to boasting the only body other than Earth to have a dense, nitrogen-rich atmosphere, there are also abundant resources in this system that could be harnessed.

Much like the idea of colonizing the Moon, Mars, the moons of Jupiter, and other bodies in the Solar System, the idea of establishing colonies on Saturn’s moons has been explored extensively in science fiction. At the same time, scientific proposals have been made that emphasize how colonies would benefit humanity, allowing us to mount missions deeper into space and ushering in an age of abundance!

*A montage of images from Cassini of various moons and the rings around Saturn. Credit: NASA/JPL-Caltech/Space Science Institute*

Examples in Fiction:

The colonization of Saturn has been a recurring theme in science fiction over the decades. For example, in Arthur C. Clarke’s 1976 novel Imperial Earth, Titan is home to a human colony of 250,000 people. The colony plays a vital role in commerce, where hydrogen is taken from the atmosphere of Saturn and used as fuel for interplanetary travel.

In Piers Anthony’s Bio of a Space Tyrant series (1983-2001), Saturn’s moons have been colonized by various nations in a post-diaspora era. In this story, Titan has been colonized by the Japanese, whereas Saturn has been colonized by the Russians, Chinese, and other former Asian nations.

In the novel Titan (1997) by Stephen Baxter, the plot centers on a NASA mission to Titan which must struggle to survive after crash landing on the surface. In the first few chapters of Stanislaw Lem’s Fiasco (1986), a character ends up frozen on the surface of Titan, where they are stuck for several hundred years.

In Kim Stanley Robinson’s Mars Trilogy (1996), nitrogen from Titan is used in the terraforming of Mars. In his novel 2312 (2012), humanity has colonized several of Saturn’s moons, which includes Titan and Iapetus. Several references are made to the “Enceladian biota” in the story as well, which are microscopic alien organisms that some humans ingest because of their assumed medicinal value.

The moons of Saturn, from left to right: Mimas, Enceladus, Tethys, Dione, Rhea; Titan in the background; Iapetus (top) and irregularly shaped Hyperion (bottom). Some small moons are also shown. All to scale. Credit: NASA/JPL/Space Science Institute — The moons of Saturn, from left to right: Mimas, Enceladus, Tethys, Dione, Rhea; Titan in the background; Iapetus (top) and irregularly shaped Hyperion (bottom). Credit: NASA/JPL/Space Science Institute

As part of his Grand Tour Series, Ben Bova’s novels Saturn (2003) and Titan (2006) address the colonization of the Cronian system. In these stories, Titan is being explored by an artificially intelligent rover which mysteriously begins malfunctioning, while a mobile human Space Colony explores the Rings and other moons.

Proposed Methods:

In his book Entering Space: Creating a Spacefaring Civilization (1999), Robert Zubrin advocated colonizing the outer Solar System, a plan which included mining the atmospheres of the outer planets and establishing colonies on their moons. In addition to Uranus and Neptune, Saturn was designated as one of the largest sources of deuterium and helium-3, which could drive the pending fusion economy.

He further identified Saturn as being the most important and most valuable of the three, because of its relative proximity, low radiation, and excellent system of moons. Zubrin claimed that Titan is a prime candidate for colonization because it is the only moon in the Solar System to have a dense atmosphere and is rich in carbon-bearing compounds.

On March 9th, 2006, NASA’s Cassini space probe found possible evidence of liquid water on Enceladus, which was confirmed by NASA in 2014. According to data derived from the probe, this water emerges from jets around Enceladus’ southern pole, and is no more than tens of meters below the surface in certain locations. This would would make collecting water considerably easier than on a moon like Europa, where the ice sheet is several km thick.

Data obtained by Cassini also pointed towards the presence of volatile and organic molecules. And Enceladus also has a higher density than many of Saturn’s moons, which indicates that it has a larger average silicate core. All of these resources would prove very useful for the sake of constructing a colony and providing basic operations.

In October of 2012, Elon Musk unveiled his concept for an Mars Colonial Transporter (MCT), which was central to his long-term goal of colonizing Mars. At the time, Musk stated that the first unmanned flight of the Mars transport spacecraft would take place in 2022, followed by the first manned MCT mission departing in 2024.

In September 2016, during the 2016 International Astronautical Congress, Musk revealed further details of his plan, which included the design for an Interplanetary Transport System (ITS) and estimated costs. This system, which was originally intended to transport settlers to Mars, had evolved in its role to transport human beings to more distant locations in the Solar System – which could include the Jovian and Cronian moons.

Artist's rendering of possible hydrothermal activity that may be taking place on and under the seafloor of Enceladus. Image Credit: NASA/JPL — *Artist’s rendering of possible hydrothermal activity that may be taking place on and under the seafloor of Enceladus. Credit: NASA/JPL*

Potential Benefits:

Compared to other locations in the Solar System – like the Jovian system – Saturn’s largest moons are exposed to considerably less radiation. For instance, Jupiter’s moons of Io, Ganymede and Europa are all subject to intense radiation from Jupiter’s magnetic field – ranging from 3600 to 8 rems day. This amount of exposure would be fatal (or at least very hazardous) to human beings, requiring that significant countermeasures be in place.

In contrast, Saturn’s radiation belts are significantly weaker than Jupiter’s – with an equatorial field strength of 0.2 gauss (20 microtesla) compared to Jupiter’s 4.28 gauss (428 microtesla). This field extends from about 139,000 km from Saturn’s center out to a distance of about 362,000 km – compared to Jupiter’s, which extends to a distance of about 3 million km.

Of Saturn’s largest moons, Mimas and Enceladus fall within this belt, while Dione, Rhea, Titan, and Iapetus all have orbits that place them from just outside of Saturn’s radiation belts to well beyond it. Titan, for example, orbits Saturn at an average distance (semi-major axis) of 1,221,870 km, putting it safely beyond the reach of the gas giant’s energetic particles. And its thick atmosphere may be enough to shield residents from cosmic rays.

In addition, frozen volatiles and methane harvested from Saturn’s moons could be used for the sake of terraforming other locations in the Solar System. In the case of Mars, nitrogen, ammonia and methane have been suggested as a means of thickening the atmosphere and triggering a greenhouse effect to warm the planet. This would cause water ice and frozen CO² at the poles to sublimate – creating a self-sustaining process of ecological change.

Colonies on Saturn’s moons could also serve as bases for harvesting deuterium and helium-3 from Saturn’s atmosphere. The abundant sources of water ice on these moons could also be used to make rocket fuel, thus serving as stopover and refueling points. In this way, a colonizing the Saturn system could fuel Earth’s economy, and the facilitate exploration deeper into the outer Solar System.

Challenges:

Naturally, there are numerous challenges to colonizing Saturn’s moons. These include the distance involved, the necessary resources and infrastructure, and the natural hazards colonies on these moons would have to deal with. For starters, while Saturn may be abundant in resources and closer to Earth than either Uranus or Neptune, it is still very far.

On average, Saturn is approximately 1,429 billion km away from Earth; or ~8.5 AU, the equivalent of eight and a half times the average distance between the Earth and the Sun. To put that in perspective, it took the Voyager 1 probe roughly thirty-eight months to reach the Saturn system from Earth. For crewed spacecraft, carrying colonists and all the equipment needed to colonize the surface, it would take considerably longer to get there.

These ships, in order to avoid being overly large and expensive, would need to rely on cryogenics or hibernation-related technology in order to save room on storage and accommodations. While this sort of technology is being investigated for crewed missions to Mars, it is still very much in the research and development phase.

Artist's concept of a Bimodal Nuclear Thermal Rocket in Low Earth Orbit. Credit: NASA — Artist’s concept of a Bimodal Nuclear Thermal Rocket in Low Earth Orbit. Credit: NASA

Any vessels involved in the colonization efforts, or used to ship resources to and from the Cronian system, would also need to have advanced propulsion systems to ensure that they could make the trips in a realistic amount of time. Given the distances involved, this would likely require rockets that used nuclear-thermal propulsion, or something even more advanced (like anti-matter rockets).

And while the former is technically feasible, no such propulsion systems have been built just yet. Anything more advanced would require many more years of research and development, and a major commitment in resources. All of this, in turn, raises the crucial issue of infrastructure.

Basically, any fleet operating between Earth and Saturn would require a network of bases between here and there to keep them supplied and fueled. So really, any plans to colonize Saturn’s moons would have to wait upon the creation of permanent bases on the Moon, Mars, the Asteroid Belt, and most likely the Jovian moons. This process would be punitively expensive by current standards and (again) would require a fleet of ships with advanced drive systems.

And while radiation is not a major threat in the Cronian system (unlike around Jupiter), the moons have been subject to a great deal of impacts over the course of their history. As a result, any settlements built on the surface would likely need additional protection in orbit, like a string of defensive satellites that could redirect comets and asteroids before they reached orbit.

The huge storm churning through the atmosphere in Saturn's northern hemisphere overtakes itself as it encircles the planet in this true-color view from NASA’s Cassini spacecraft. Image credit: NASA/JPL-Caltech/SSI — The huge storm churning through the atmosphere in Saturn’s northern hemisphere overtakes itself as it encircles the planet in this true-color view from NASA’s Cassini spacecraft. Image credit: NASA/JPL-Caltech/SSI

Given its abundant resources, and the opportunities it would present for exploring deeper into the Solar System (and maybe even beyond), Saturn and its system of moons is nothing short of a major prize. On top of that, the prospect of colonizing there is a lot more appealing than other locations that come with greater hazards (i.e. Jupiter’s moons).

However, such an effort would be daunting and would require a massive multi-generational commitment. And any such effort would most likely have to wait upon the construction of colonies and/or bases in locations closer to Earth first – such as on the Moon, Mars, the Asteroid Belt, and around Jupiter. But we can certainly hold out hope for the long run, can’t we?

We have written many interesting articles on colonization here at Universe Today. Here’s Why Colonize the Moon First?, How Do We Colonize Mercury?, How Do We Colonize Venus?, Colonizing Venus with Floating Cities, Will We Ever Colonize Mars?, How Do We Colonize Jupiter’s Moons?, and The Definitive Guide to Terraforming.

Astronomy Cast also has many interesting episodes on the subject. Check out Episode 59: Saturn, Episode 61: Saturn’s Moons, Episode 95: Humans to Mars, Part 2 – Colonists, Episode 115: The Moon, Part 3 – Return to the Moon, and Episode 381: Hollowing Asteroids in Science Fiction.

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