Universe Today

October 31, 2008July 15, 2016 by Fraser Cain

The Moon Compared to Earth

Earth Moon Comparison. Image credit: NASA

When you see the Moon way up in the sky, it’s hard to get a sense of perspective about how big the Moon really is. Just how big is the Moon compared to Earth?

Let’s take a look at the diameter first. The diameter of the Moon is 3,474 km. Now, let’s compare this to the Earth. The diameter of the Earth is 12,742 km. This means that the Moon is approximately 27% the size of the Earth.

What about surface area? The surface area of the Moon is 37.9 million square kilometers. That sounds like a lot, but it’s actually smaller than the continent of Asia, which is only 44.4 million square km. The surface ares of the whole Earth is 510 million square km, so the area of the Moon compared to Earth is only 7.4%.

How about volume? The volume of the Moon is 21.9 billion cubic km. Again, that sounds like a huge number, but the volume of the Earth is more like 1 trillion cubic kilometers. So the volume of the Moon is only 2% compared to the volume of the Earth.

Finally, let’s take a look at mass. The mass of the Moon is 7.347 x 10²² kg. But the Earth is much more massive. The mass of the Earth is 5.97x 10²⁴ kg. This means that the mass of the Moon is only 1.2% of the mass of the Earth. You would need 81 objects with the mass of the Moon to match the mass of the Earth.

We have written many stories about the Moon on Universe Today. Here’s an article about heavy construction on the Moon, and here’s what it would take to build a moon base.

Want more information on the Moon? Here’s a link to NASA’s Lunar and Planetary Science page, and here’s NASA’s Solar System Exploration Guide for the Moon.

You can listen to a very interesting podcast about the formation of the Moon from Astronomy Cast, Episode 17: Where Did the Moon Come From?

October 31, 2008December 24, 2015 by Tammy Plotner

Weekend SkyWatcher’s Forecast – October 31 – November 2, 2008

Happy Halloween! Are you ready for the Spook’s Tour? Tonight treat your little ghouls and goblins, party guests and yourself to a real sweet treat through your telescope or binoculars as we take a look at some of the season’s craziest (and scariest) outer space objects. It’s a time honored custom that’s sure to please even the most starched shirt out there… So loosen up your tie and let’s have some fun! Need more to keep you busy? Sure! We’ll also take a look at the weekend’s lunar features, the magnificent “Double Cluster” and a salute to Harlow Shapely! Now, let’s haunt the weekend together…

Friday, October 31, 2008 – Happy Halloween! Many cultures around the world celebrate this day with a custom known as “Trick or Treat.” Tonight instead of tricking your little ghouls and goblins, why not treat them (or your party guests) to a sweet view through your telescope or binoculars? Let’s take a look at some of the “spookiest” objects in the night sky…

Begin in the constellation of Perseus with a single star. Its formal name is Beta Persei (RA 03 08 10 Dec +40 57 20) and it is the most famous of all eclipsing variable stars. Tonight, let’s identify Algol and learn all about the “Demon Star.”

Ancient history has given this star many names. Associated with the mythological figure Perseus, Beta was considered to be the head of Medusa the Gorgon, and was known to the Hebrews as Rosh ha Satan or “Satan’s Head.” Seventeenth century maps labeled Beta as Caput Larvae, or the “Specter’s Head,” but it is from the Arabic culture that the star was formally named. They knew it as Al Ra’s al Ghul, or the “Demon’s Head,” and we now know it as Algol. Because these medieval astronomers and astrologers associated Algol with danger and misfortune, we are led to believe that Beta’s strange visual variable properties had been noted throughout history. Italian astronomer Geminiano Montanari was the first to record that Algol occasionally “faded,” and its regular timing was cataloged in 1782 by John Goodricke, who surmised that it was being partially eclipsed by a dark companion orbiting it. Thus was born the theory of the eclipsing binary, which was proved spectroscopically for Algol in 1889 by H. C. Vogel.

93 light-years away, Algol is the nearest eclipsing binary, and is treasured by the amateur astronomer because it requires no special equipment to easily follow its stages. Normally Beta Persei holds a magnitude of 2.1, but approximately every three days it dims to magnitude 3.4 and gradually brightens again. The entire eclipse only lasts about 10 hours! Although Algol is known to have two additional spectroscopic companions, the true beauty of watching this variable star is not telescopic – but visual. The constellation of Perseus is well placed this month for most observers, and appears like a glittering chain of stars that lie between Cassiopeia and Andromeda. Take a look at Gamma Andromedae (Almach), east of Algol. Almach’s visual brightness is about the same as Algol’s at maximum.

Now we need a jack-o-lantern…

Asteroid Vesta is considered to be a minor planet since its approximate diameter is 525 km (326 miles), making it slightly smaller in size than the state of Arizona. Vesta was discovered on March 29, 1807 by Heinrich Olbers and it was the fourth such “minor planet” to be identified. Olbers’ discovery was fairly easy because Vesta is the only asteroid bright enough at times to be seen unaided from Earth. Why? Orbiting the Sun every 3.6 years and rotating on its axis in 5.24 hours, Vesta has an albedo (or surface reflectivity) of 42%. Although it is about 350 million kilometers away, pumpkin-shaped Vesta is the brightest asteroid in our solar system because it has a unique geological surface. Spectroscopic studies show it to be basaltic, which means lava once flowed on the surface. (Very interesting, since most asteroids were once thought to just be rocky fragments left-over from our forming solar system!)

Studies by the Hubble telescope have confirmed this, as well as shown a large meteor impact crater which exposed Vesta’s olivine mantle. Debris from Vesta’s collision then set sail away from the parent asteroid. Some of the debris remained within the asteroid belt near Vesta, and became asteroids themselves with the same spectral pyroxene signature. But some of the debris escaped the asteroid belt through the “Kirkwood Gap” created by Jupiter’s gravitational pull. This allowed these small fragments to be kicked into orbits that would eventually bring them “down to Earth.” Did one make it? Of course! In 1960 a piece of Vesta fell to Earth and was recovered in Australia. Thanks to Vesta’s unique properties, the meteorite was definitely identified as coming from our third largest asteroid. Now, that we’ve learned about Vesta, let’s talk about what we can see from our own backyards. As you can discern from the image, even the Hubble Space Telescope doesn’t give incredible views of this bright asteroid. What we will be able to see in our telescopes and binoculars will closely resemble a roughly magnitude 7 “star.” Tonight you can find Vesta near Alpha Ceti. Vesta will be at opposition in just three days, and is now in retrograde, so you will be able to watch it slowly move away from Alpha Ceti for the rest of the year.

Of course, the approximate coordinates given above are only accurate for a short time, so I strongly encourage you to use a good planetarium program to print accurate locator charts, or visit an online resource such as the IAU Minor Planet Center for more details. When you locate the proper stars and the asteroid’s probable location, mark physically on the map Vesta’s position. Keeping the same map, return to the area a night or two later and see how Vesta has moved since your original mark. Since Vesta will stay located in the same area for awhile, your observations need not be on consecutive nights, but once you learn how to observe an asteroid and watch it move – you’ll be back for more!

One of the scariest movies in recent times was the “Ring”… Let’s find one! Tonight’s dark-sky object is a difficult one for northern observers and is truly a challenge. Around a handspan south of Zeta Aquarii and just a bit west of finderscope star Upsilon (RA 22 51 48 Dec 20 36 31) is a remarkably large area of nebulosity that is very well suited to large binoculars, rich field telescopes and wide field eyepieces. Are you ready to walk into the “Helix?”

Known as NGC 7293, this faint planetary nebula’s “ring” structure is around half the size of the full Moon. While its total magnitude (6.5) and large size should indicate it would be an easy find, the Helix is anything but easy because of its low surface brightness. Binoculars will show it as a large, round, hazy spot, while small telescopes with good seeing conditions will have a chance to outshine larger ones by using lower power eyepieces to pick up the braided ring structure. As one of the very closest of planetary nebulae, NGC 7393 is very similar in structure to the more famous Ring, M57. It is a spherical shell of gas lighted by an extremely hot, tiny central star that’s only around 2% of our own Sun’s diameter – yet exceeds Sol in surface temperature by over 100,000 Kelvin. Can you resolve it? Best of luck!

Just two days before Halloween in 1749, the French astronomer Le Gentil was at the eyepiece of an 18′ focal length telescope. His object of choice was the Andromeda Galaxy, which he believed to be a nebula. Little did he know at the time that his descriptive notes also included M32, a satellite galaxy of M31. It was the first small galaxy discovered, and it would be another 175 years before these were recognized as such by Edwin Hubble. Now let’s head about a degree west of Nu Andromedae, this “ghost” set against the starry night was known as far back as 905 AD, and was referred to as the “Little Cloud.” Located about 2.2 million light-years from our solar system, this expansive member of our Local Galaxy Group has delighted observers of all ages throughout the years. No matter if you view with just your eyes, a pair of binoculars or a large telescope, M31 still remains one of the most spectacular galaxies in the night. “Boo” tiful…

What Halloween celebration would be complete without a black cat? Let’s cruise Draco (the Dragon) in search of the “Cat’s Eye”…

Located about halfway between Delta and Zeta Draconis is one of the brightest planetary nebulae in the night – 8.8 magnitude NGC 6543. Around three thousand light-years away, it was one of the first planetaries to be studied spectroscopically, and the resulting emission lines proved the phenomenon was actually a shell of gas emitted from a dying star. Our own Sun awaits a similar fate. While a small telescope will never reveal NGC 6543 as gloriously as a Hubble image, you can expect (even in a small telescope or binoculars) to make out a small, blue-green, glowing object. But a large aperture telescope and good sky conditions are needed to reveal some of the braided structure seen within. No matter how you view it, the Cat’s Eye belongs on the list of spooky objects!

So far we’ve collected a demon, a pumpkin, a galactic ghost, and the eye of the cat… And what Halloween would be complete without a witch! Easily found from a modestly dark site with the unaided eye, the Pleiades can be spotted well above the northeastern horizon within a couple of hours of nightfall. To average skies, many of the seven bright components will resolve easily without the use of optical aid, but to telescopes and binoculars?… M45 is stunning!

First let’s explore a bit of history. The recognition of the Pleiades dates back to antiquity, and its stars are known by many names in many cultures. The Greeks and Romans referred to them as the “Starry Seven,” the “Net of Stars,” “The Seven Virgins,” “The Daughters of Pleione,” and even “The Children of Atlas.” The Egyptians referred to them as “The Stars of Athyr;” the Germans as “Siebengestiren” (the Seven Stars); the Russians as “Baba” after Baba Yaga, the witch who flew through the skies on her fiery broom. The Japanese call them “Subaru;” Norsemen saw them as packs of dogs; and the Tongans as “Matarii” (the Little Eyes). American Indians viewed the Pleiades as seven maidens placed high upon a tower to protect them from the claws of giant bears, and even Tolkien immortalized the star group in The Hobbit as “Remmirath.” The Pleiades were even mentioned in the Bible! So, you see, no matter where we look in our “starry” history, this cluster of seven bright stars has been part of it. But, let’s have some Halloween fun!

The date of the Pleiades culmination (its highest point in the sky) has been celebrated throughout its rich history, being marked with various festivals and ancient rites – but there is one particular rite that really fits this occasion! What could be more spooky on this date than to imagine a group of Druids celebrating the Pleiades’ midnight “high” with Black Sabbath? This night of “unholy revelry” is still observed in the modern world as “All Hallow’s Eve,” more commonly called Halloween. Although the actual date of the Pleiades midnight culmination is now on November 21 instead of October 31, why break with tradition? Thanks to its nebulous regions, M45 looks wonderfully like a “ghost” haunting the starry skies.

Treat yourself and your loved ones to the “scariest” object in the night. Binoculars give an incredible view of the entire region, revealing far more stars than are visible with the naked eye. Small telescopes at lowest power will enjoy M45’s rich, icy-blue stars and fog-like nebulosity. Larger telescopes and higher power reveal many pairs of double stars buried within its silver folds. No matter what you choose, the Pleiades definitely rock!

Saturday, November 1, 2008 – On this day in 1977, Charles Kowal made a wild discovery – Chiron. This was the first sighting of one of the multitude of tiny, icy bodies inhabiting the outer reaches of our solar system. Collectively known as Centaurs, they reside in unstable orbits between Jupiter and Neptune and are almost certainly “refugees” from the Kuiper Belt.

This evening have a look at the lunar surface and the southeast shoreline of Mare Crisium for Agarum Promontorium. To a small telescope it will look like a bright peninsula extending northward across the dark plain of Crisium’s interior, eventually disappearing beneath the ancient lava flow. Small crater Fahrenheit can be spotted at high power to the west of Agarum, and it is just southeast of there that Luna 24 landed. If you continue south of Agarum along the shoreline of Crisium you will encounter 15 kilometer high Mons Usov. To its west is a gentle rille known as Dorsum Termier – where the remains of the Luna 15 mission lie. Can you spot 23 kilometer wide Shapely further south?

Tonight let’s use our eyes, binoculars, or even a telescope at lowest power to have a look at two objects cataloged by Sir William Herschel on this night. You may know them as the “Double Cluster”. Properly designated as NGC 869 and NGC 884, this pair has definitely got to go into history as “How come Messier missed them?” Probably already known in pre-historic times, and first cataloged by Hipparchus (ah! that’s why!), they are easily seen by the eye as a hazy patch in the Milky Way between Cassiopeia and Andromeda. Located a little more than 7000 light-years away, and a few hundred light-years apart, they are both very young as clusters go – but they differ radically from each other in age: NGC 884 is about 5.6 million years old, while NGC 889 is only 3.2 million. Both clusters are listed on many “Best Objects” lists, so be sure to congratulate yourself for noting them as Caldwell 14!

Sunday, November 2, 2008 – Today celebrates the birth of an astronomy legend – Harlow Shapely. Born in 1885, the American-born Shapley paved the way in determining distances to stars, clusters, and the center of our Milky Way galaxy. Among his many achievements, Shapely was also the Harvard College Observatory director for many years. Today in 1917 also represents the night first light was seen through the Mt. Wilson 100″ telescope.

Of course, Dr. Shapley spent his fair share of time on the Hooker telescope as well. A particular point of his studies were globular clusters: their distances, and the relationship they have to the halo structure of our galaxy. Tonight let’s look at a very unusual little globular located about a fistwidth south-southeast of Beta Ceti, and just a couple of degrees north-northwest of Alpha Sculptoris (RA 00 52 47 Dec -26 34 43). Its name is NGC 288…

Discovered by William Herschel on October 27, 1785, and cataloged by him as H VI.20, this class X globular cluster blew apart scientific thinking in the late 1980s when a study of perimeter globulars showed it to be older than its X-class peers by three billion years – thanks to the color magnitude diagrams of Hertzsprung and Russell. NGC 288 is currently thought to be about 11 billion years old. By identifying both its blue and red branches, it was shown that many of NGC 288’s stars are being stripped away by tidal forces and contributing to the formation of the Milky Way’s halo structure. In 1997, three additional variable stars were discovered in this cluster. At magnitude 8, this small globular is easy for southern observers, but faint for northern ones. If you are using binoculars, be sure to look for the equally bright spiral galaxy NGC 253 to the globular’s north.

This week’s awesome images are: Beta Persei: Algol – Credit: Palomar Observatory, courtesy of Caltech, Asteroid Vesta – Credit: NASA, NGC 7293: The Helix Nebula – Credit: R. Jay GaBany, The Andromeda Galaxy – Bill Schoening, Vanessa Harvey/REU program/NOAO/AURA/NSF, NGC 6543: The Cat’s Eye – Credit: Hubble Heritage Team/NASA, M45: The Pleiades – Credit: John Chumack, The “Double Cluster” – Credit: N.A.Sharp/NOAO/AURA/NSF, Lunar image by Greg Konkel, annotated by Tammy Plotner, Harlow Shapely (widely used public image) and NGC 288 – Credit: Palomar Observatory, courtesy of Caltech. Our many, many thanks for the fine illustrations!

October 30, 2008December 24, 2015 by Nancy Atkinson

Phoenix Not Responding to Communications

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Update: 10/31: Phoenix communicated with NASA’s Mars Odyssey orbiter late Thursday. The communication reinforced a diagnosis that the spacecraft is in a precautionary mode triggered by low energy. Mission engineers are assessing the lander’s condition and steps necessary for returning to science operations.

The Phoenix Lander is not responding to attempts to communicate with it. Earlier today, we reported that Phoenix had gone into safe mode. The lander experienced a low-power fault in the electrical system due to the reduction of solar-electric power to shorter daylight hours and a dust storm, as well as extremely cold weather. Engineers for the mission were able to send a command to restart a battery that had shut off, and were hopeful that further communications would resume without incident. However, Phoenix did not respond to one of the Mars orbiter’s attempt to communicate with it Wednesday night and Thursday morning.

I don’t know about the rest of you, but I’m not ready to say goodbye to Phoenix quite yet…

Mission controllers believe the most likely situation to be that declining power has triggered a pre-set precautionary behavior of waking up for only about two hours per day to listen for an orbiter’s hailing signal. If that is the case, the wake-sleep cycling would have begun at an unknown time when batteries became depleted.

“We will be coordinating with the orbiter teams to hail Phoenix as often as feasible to catch the time when it can respond,” said Phoenix Project Manager Barry Goldstein at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “If we can reestablish communication, we can begin to get the spacecraft back in condition to resume science. In the best case, if weather cooperates, that would take the better part of a week.”

Stay tuned…

Source: JPL

October 30, 2008December 24, 2015 by Fraser Cain

Volume of the Moon

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The volume of the Moon is about 21.9 billion cubic kilometers.

Does that sound like a lot? For comparison, the volume of the Earth is 1 trillion cubic kilometers. In other words, the volume of the Moon is only 2% the volume of the Earth.

The interior of the Moon is composed of a crust, mantle and core. Astronomers think that the lunar core is about 350 km across, and accounts for only 20% of the size of the Moon. Most other planets and moons in the Solar System have a core that accounts for about 50% of their diameter. Outside the core is the middle mantle, and this is surrounded by an upper mantle.

Want to know the volume of Jupiter, or even the volume of the Sun?

Want more information about the Moon? Here’s a link to NASA’s Lunar and Planetary Science page. And here’s NASA’s Solar System Exploration Guide.

You can listen to a very interesting podcast about the formation of the Moon from Astronomy Cast, Episode 17: Where Did the Moon Come From?

October 30, 2008December 24, 2015 by Nancy Atkinson

Hubble Servicing Mission Delayed; Mission to ISS Set for Nov. 14

Hubble and its most recent science image. Credit: NASA

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The space shuttle mission to repair and update the Hubble Space Telescope has been delayed. Mission managers were aiming for a February 2009 launch for STS-125 flight for the fifth and final shuttle mission to the Hubble Space Telescope. The replacement component for the data handling system that recently caused problems for the telescope not be ready by February, and now NASA is looking for a May 2009 launch. On a positive note, the “other” shuttle mission waiting in the wings, STS-126 to the International Space Station, is looking good and is go for launch. Current launch date is set for November 14 at 7:55 p.m. EST.

“We now have done enough analysis of all the things that need to happen with the flight spare unit to know that we cannot be ready for a February launch,” said NASA’s Astrophysics Division Director Jon Morse at NASA Headquarters in Washington. The spare Science Instrument Command and Data Handling system unit will replace one that failed on Hubble in late September, causing the agency to postpone the servicing mission, which had been targeted for Oct. 14.

A significant anomaly occurred during testing of the unit and NASA says six and a half months of further testing is needed before the it can be certified to fly. NASA’s plan is to have the spare unit ready to ship in the April 2009 timeframe so as to support a May 2009 launch.

Endeavour’s STS-126 flight, set to launch on November 14 will feature important repair work to the station and prepare it for housing six crew members during long-duration missions. The primary focus of the 15-day flight and its four planned spacewalks is to service the station’s two Solar Alpha Rotary Joints, which have not been working correctly. They allow the station’s solar arrays to track the sun. Endeavour will carry about 32,000 pounds to orbit, including supplies and equipment necessary to double the crew size from three to six members in spring 2009. The new station cargo includes additional sleeping quarters, a second toilet and a resistance exercise device.

Source: 1st NASA press release, 2nd NASA press release

October 30, 2008April 26, 2016 by Nancy Atkinson

“Ares and Orion Are the Way to Go”

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Numerous news articles recently have reported problems with the Ares rocket. Some articles detailed critical design flaws, others wondered if Ares was doomed, others reported that Ares was on the US Congress’s “chopping block,” and still others purported that a different launch architecture would be superior to the Ares design. So many rumors were floating around that NASA felt the need to hold a press briefing yesterday to address the rumors and calm any fears that the Constellation program was on the verge of collapse. At the briefing, NASA officials said that while there are some challenges for the program to overcome, Ares is making outstanding progress toward flight. “Some recent news reports about Ares have been inaccurate and draw false conclusions,” said Steve Cook, who leads the development of the rocket.

But isn’t that what everyone expected them to say? Are they telling the truth? To get an unbiased look at the state of the Constellation program, Universe Today contacted Dr. Scott Pace, who is the Director for the Space Policy Institute at George Washington University in Washington, DC. Pace said the problems facing Ares are typical and not insurmountable, and that Constellation is the right choice for our country’s space program. “In my view,” said Dr. Pace, “if the nation is going to return to the Moon and eventually send humans to Mars, then political and technical realities argue that the Ares I, Orion, and Ares V are the way to go.”

Pace said the only reason not to use the Constellation architecture is if our nation decides it is content with staying in low Earth orbit or decides to cease its participation in government sponsored human spaceflight.

Pace discussed some of the issues being debated for the Ares rocket. “From my perspectives, there are a couple of things going on that can be broken down into 1) normal technical issues, 2) system engineering issues, and 3) architecture issues,” said Pace.

He said the thrust oscillation issue is a typical issue with all solid propellant motors and there are multiple ways to solve it. “As an analogy,” said Pace, “the pogo issue with Saturn on its first flights was much more serious.”

As for the launch pad drift problems and cross-wind limits on launch, these issues, too, have multiple solutions. “The fast start up of solids compared to liquids means less time to ‘drift,’” said Pace. “However, if a solid goes bad, it goes real bad, and that’s why the abort motor system on the Orion has to be proven to work from the launch pad up to high altitude.”

Pace believes a potentially more serious issue that should be resolved by modeling and test flights are the bending moments of the SRB “stick” itself in flight. “It’s built out of segments, not a single structure and lacks the stiffing of attachment to an External Tank (as with Shuttle and the Ares V design). This is a classic systems engineering problem,” said Pace, and deferred that NASA engineers are more qualified to comment on that issue.

Other issues are criticisms over the architecture choice of Ares I and V, over using an EELV (Evolved Expendable Launch Vehicle) for Orion or the DIRECT 2.0 design of the “Jupiter” rockets.

The Jupiter rockets for the DIRECT 2.0 project. Credit: DIRECT 2.0

“The EELVs don’t have the performance to launch a 6-person Orion to ISS or take a 4-man crew to the Moon,” said Pace. “If one built a 3-4 person Orion to go only to ISS, it begs the question of what to do with the other ISS crew in an emergency and creates a potential government competitor for COTS providers.”

Pace said the use of EELV’s also means trying to creating a separate vehicle to provide lift to go to the Moon and Mars. “One could do the Moon with multiple EELV launches (as the Chinese might do with their Long March 5) at additional cost and risk over an Ares I and Ares V launch combination,” said Pace. “But you’re not going to Mars without a heavy-lifter like Ares V.”

Pace continued, “So, if we truly would like to go to Mars, build an Ares V and use it to make going to the Moon efficient. If we’re using an Ares V, separating humans onto a Ares I that shares much of the industrial base with the current Shuttle makes sense. This also allows an Orion capsule that can meet ISS and lunar requirements.”

Pace said EELVs could be useful for cargo to the ISS and, if someone were to pay for man-rating, they may even be useful for COTS crew missions. “But they can’t do the baseline government job of assuring U.S. human access to space.”

To make the Constellation program a success, Pace said NASA will need to focus on configuration control and consistency of analytical models, making sure the avionics interfaces are sufficient and being able to obtain adequate funding of full-scale tests.

* Author’s note: As an addendum, Dr. Pace said he has no problem with adding that he recently worked for NASA’s Program Analysis & Evaluation office, a fact I did not include in the article. “I understand that some may see that as a bias and perhaps relevant,” he said. Dr. Pace was named the Director of SPI in May 2008.

October 30, 2008December 24, 2015 by Fraser Cain

Moon Maps

Colored global elevation map based on terrain data from the Kaguya orbiter Credit: Japan Aerospace Exploration Agency (JAXA)

Are you looking for a map of the Moon? As it turns out, there are plenty of resources on the internet that show the Moon’s topography, geology, and map out it’s many interesting surface features – such as craters, volcanoes, and surface rilles. These maps are the result of decade’s worth of satellite and telescopic imaging, lunar landing missions, and even manned missions to the Moon. The exploration is ongoing, and more data pours in with every passing year!

And it just so happens that we’ve compiled a list for your convenience and viewing pleasure. Below are a short collection of websites that provide comprehensive and even interactive maps of the Moon, as well as access to archival images and thousands of pictures of the surface. Click on the links and prepare to do a little exploring of your own!

Observatorio ARVAL – This map of the Moon shows the location of all the seas and major craters on the surface of the Moon.
Google Moon – This is one of the coolest tools you can use to see a lunar map. It has the locations of all the Apollo landing sites.
USGS Moon Maps – The USGS has released a series of topographical maps of the Moon, and various images returned from the Clementine and other missions. If you want data… here’s where you’ll find it.
Albedo Map of the Moon – Here are some maps of the Moon built up with 50,000 images gathered by the Clementine mission.
Maps of the Moon – A collection of mosaic, labelled, and color-coded topographic maps provided by Professor Seligman (BA Astronomy and Physics, MA Astronomy, from UCLA).
Moon-Edu – A resource collection of Moon interactive maps, images and sky-watcher/moon-watcher guides, provided by Wikispaces.
Consolidated Lunar Atlas – an online collection of Lunar resources maintained by The Lunar and Planetary Institute, a research institute that provides support services to NASA and the planetary science community.

We have written many articles about the Moon for Universe Today. Have you ever wondered how long it takes to get to the Moon? And what is the distance to the Moon? You can also learn more about the Phases of the Moon, several Interesting Facts About The Moon. There’s also a really interesting article that answers the question, How Did the Moon Form?

For more information and resources about the Earth’s Moon, be sure to check out the websites of the various federal space agencies that helped contribute to our growing understanding of it. These include NASA’s Solar System Exploration, the European Space Agency’s The Moon – Our Neighbor and Destination: Moon, the Japan Aerospace Exploration Agency’s (JAXA) Lunar Exploration Program.

You can also listen to a very interesting podcast about the formation of the Moon from Astronomy Cast, Episode 17: Where Did the Moon Come From?

October 30, 2008June 2, 2017 by Tammy Plotner

The Coma Berenices Constellation

The northern constellation known as Coma Berenices. Credit and Copyright: © 2003 Torsten Bronger.

Welcome back to Constellation Friday! Today, in honor of the late and great Tammy Plotner, we will be dealing with “Berenice’s Hair” – the Coma Berenices 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 is the constellation Coma Berenices, an ancient constellation located in the norther skies. In the Almagest, Ptolemy considered the asterism to be part of the constellation Leo. Today, it is one of the 88 constellations recognized by the International Astronomical Union, and is bordered by the constellations of Canes Venatici, Ursa Major, Leo, Virgo and Boötes.

Name and Meaning:

In mythology, it is easy to see why this dim collection of stars was once associated with Leo and considered to be the tuft of hair at the end of the Lion’s tail. However, as the years passed, a charming legend grew around this sparkling group of stars. Since the time of Ptolemy, this grouping of stars was recognized and although he didn’t list it as one of his 88 constellations, he did refer to is as “Berenice’s Hair”.

*Coma Berenices as seen by the naked eye. Credit: Till Credner/ AlltheSky.com*

As legend would have it, the good Queen Berenice II of Egypt offered to sacrifice her beautiful long hair to Aphrodite for the safe return of her husband from battle. When she cut off her locks and placed it on the altar and returned the next day, her sacrifice was gone. To save his life, the court astronomer proclaimed Aphrodite had immortalized Berenice’s gift in the stars… and thus the Lion lost his tail and the astronomer saved his hide!

History of Observation:

Like many of the 48 constellations recognized by Ptolemy, Coma Berenices traces it routes back to ancient Mesopotamia. To Babylonian astronomers, it was known as Hegala, which translated to “which is before it”. However, the first recorded mention comes from Conon of Samos, the 3rd century BCE court astronomer to Ptolemy III Euergetes – the Greek-Egyptian king. It was named in honor of his consort, Berenice II, who is said to have cut off her long hair as a sacrifice to ensure the safety of the king.

The constellation was named “bostrukhon Berenikes” in Greek, which translates in Latin to “Coma Berenices” (or “Berenice’s hair”). Though it was previously designated as its own constellation, Ptolemy considered it part of Leo in his 2nd century CE tract the Almagest, where he called it “Plokamos” (Greek for “braid”). The constellation was also recognized by many non-western cultures.

In Chinese astronomy, the stars making up Coma Berenices belonged to two different areas – the Supreme Palace Enclosure and the Azure Dragon of the East. Eighteen of the constellation’s stars were in an area known as Lang wei (“seat of the general”). To Arabic astronomers, Coma Berenices was known as Al-Du’aba, Al Dafira and Al-Hulba, forming the tuft of the constellation Leo (consistent with Ptolemy’s designation).

*Fragment of Mercator’s 1551 celestial globe, showing Coma Berenices. Credit: Harvard Map Collection*

By the 16th century, the constellation began to be featured on globes and maps produced by famed cartographers and astronomers. In 1602, Tycho Brahe recognized it as its own constellation and included it in his star catalogue. In the following year, it was included in Johann Bayer’s famed celestial map, Uranometria. In 1920, it was included by the IAU in the list of the 88 modern constellations.

Notable Objects:

Despite being rather dim, Coma Berenices is significant because it contains the location of the North Galactic Pole. It is comprised of only 3 main stars, but contains 44 Bayer/Flamsteed designated members. Of its main stars, Alpha Comae Berenices (aka. Diadem) is the second-brightest in the constellation.

The name is derived from the Greek word diádema, which means “band” or “fillet”, and represents the gem in Queen Berenice’s crown. It is sometimes known by its other traditional name, Al-Zafirah, which is Arabic for “the braid”. It is a binary star composed of two main sequence F5V stars that are at a distance of 63 light years from Earth.

*The Black Eye Galaxy (Messier 64). Credit: NASA/The Hubble Heritage Team (AURA, STScI)*

It’s brightest star, Beta Comae Berenices, is located 29.78 light years from Earth and is a main sequence dwarf that is similar to our Sun (though larger and brighter). It’s third major star, Gamma Comae Berenices, is a giant star belonging to the spectral class K1II and located about 170 light years from Earth.

Coma Berenices is also home to several Deep Sky Objects, which include spiral galaxy Messier 64. Also known as the Black Eye Galaxy (Sleeping Beauty Galaxy and Evil Eye Galaxy), this galaxy is located approximately 24 million light years from Earth. This galaxy has a bright nucleus and a dark band of dust in front of it, hence the nicknames.

Then there is the Needle Galaxy, which lies directly above the North Galactic Pole and was discovered by Sir William Herschel in 1785. It is one of the most famous galaxies in the sky that can be viewed edge-on. It lies at a distance of about 42.7 million light years from Earth and is believed to be a barred spiral galaxy from its appearance.

Coma Berenices is also home to two prominent galaxy clusters. These includes the Coma Cluster, which is made up of about 1000 large galaxies and 30,000 smaller ones that are located between 230 and 300 million light years from Earth. South of the Coma Cluster is the northern part of the Virgo Cluster, which is located roughly 60 million light years from Earth.

*The globular cluster Messier 53 (NGC 5024), located in the Coma Berenices constellation. Credit: NASA (Wikisky)*

Other Messier Objects include M53, a globular cluster located approximately 58,000 light years away; Messier 100, a grand design spiral galaxy that is one of the brightest members of the Virgo cluster (located 55 million light years away); and Messier 88 and 99 – a spiral galaxy and unbarred spiral galaxy that are 47 million and 50.2 million light years distant, respectively.

Finding Coma Berenices:

Coma Berenices is best visible at latitudes between +90° and -70° during culmination in the month of May. There is one meteor shower associated with the constellation of Coma Berenices – the Coma Berenicid Meteor shower which peaks on or near January 18 of each year. Its fall rate is very slow – only one or two per hour on average, but these are among the fastest meteors known with speeds of up to 65 kilometers per second!

For both binoculars and telescopes, Coma Berenices is a wonderland of objects to be enjoyed. Turn your attention first to the brightest of all its stars – Beta Coma Berenices. Positioned about 30 light years from Earth and very similar to our own Sun, Beta is one of the few stars for which we have a measured solar activity period – 16.6 years – and may have a secondary activity cycle of 9.6 years.

Now look at slightly dimmer Alpha. Its name is Diadem – the Crown. Here we have a binary star of equal magnitudes located about 65 light years from our solar system, but it’s seen nearly “edge-on” from the Earth. This means the two stars appear to move back-and-forth in a straight line with a maximum separation of only 0.7 arcsec and will require a large aperture telescope with good resolving power to pull them apart. If you do manage, you’re separating two components that are about the distance of Saturn from the Sun!

*The location of the northern constellation Coma Berenices. Credit: IAU/Sky&Telescope magazine*

Another interesting aspect about singular stars in Coma Berenices is that there are over 200 variable stars in the constellation. While most of them are very obscure and don’t go through radical changes, there is one called FK Comae Berenices which is a prototype of its class. It is believed that the variability of FK Com stars is caused by large, cool spots on the rotating surfaces of the stars – mega sunspots! If you’d like to keep track of a variable star that has notable changes, try FS Comae Berenices (RA 13 3 56 Dec +22 53 2). It is a semi-regular variable that varies between 5.3m and 6.1 magnitude over a period of 58 days.

For your eyes, binoculars or a rich field telescope, be sure to take in the massive open cluster Melotte 111. This spangly cloud of stars is usually the asterism we refer to as the “Queen’s Hair” and the area is fascinating in binoculars. Covering almost 5 full degrees of sky, it’s larger than most binocular fields, but wasn’t recognized as a true physical stellar association until studied by R.J. Trumpler in 1938.

Located about 288 light years from our Earth, Melotte 111 is neither approaching nor receding… unusual – but true. At around 400 million years old, you won’t find any stars dimmer than 10.5 magnitude here. Why? Chances are the cluster’s low mass couldn’t prevent them from escaping long ago…

Now turn your attention towards rich globular cluster, Messier 53. Achievable in both binoculars and small telescopes, M53 is easily found about a degree northwest Alpha Comae. At 60,000 light years away from the galactic center, it’s one of the furthest globular clusters away from where it should be. It was first discovered by Johann Bode in 1755, and once you glimpse its compact core you’ll be anxious to try to resolve it.

*The Needle Galaxy (NGC 4565). Credit: ESO*

With a large telescope, you’ll notice about a degree further to the east another globular cluster – NGC 5053 – which is also about the same physical distance away. If you study this pair, you’ll notice a distinct difference in concentrations. The two are very much physically related to one another, yet the densities are radically different!

Staying with binoculars and small telescopes, try your hand at Messier 64 – the “Blackeye Galaxy”. You’ll find it located about one degree east/northeast of 35 Comae. While it will be nothing more than a hazy patch in binoculars, smaller telescopes will easily reveal the signature dustlane that makes M64 resemble its nickname. It is one of the brightest spiral galaxies visible from the Milky Way and the dark dust lane was first described by Sir William Herschel who compared it to a “Black Eye.”

Now put your telescope on Messier 100 – a beautiful example of a grand-design spiral galaxy, and one of the brightest galaxies in the Virgo Cluster. This one is very much like our own Milky Way galaxy and tilted face-on, so we may examine the spiral galaxy structure. Look for two well resolved spiral arms where young, hot and massive stars formed recently from density perturbations caused by interactions with neighboring galaxies. Under good observing conditions, inner spiral structure can even be seen!

Try lenticular galaxy Messier 85. In larger telescopes you will also see it accompanied by small barred spiral NGC 4394 as well. Both galaxies are receding at about 700 km/sec, and they may form a physical galaxy pair. How about Messier 88? It’s also one of the brighter spiral galaxies in the Virgo galaxy cluster and in a larger telescope it looks very similar to the Andromeda galaxy – only smaller.

How about barred spiral galaxy M91? It’s one of the faintest of the Messier Catalog Objects. Although it is difficult in a smaller telescope, its central bar is very strong in larger aperture. Care to try Messier 98? It is a grand edge-on galaxy and may or may not be a true member of the Virgo group. Perhaps spiral galaxy Messier 99 is more to your liking… It’s also another beautiful face-on presentation with grand spiral arms and a sweeping design that will keep you at the eyepiece all night!

There are other myriad open clusters and just as many galaxies waiting to be explored in Coma Berenices! It’s a fine region. Grab a good star chart and put a pot of coffee on to brew. Comb the Queen’s Hair for every last star. She’s worth it.

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.

Source:

October 30, 2008December 24, 2015 by Fraser Cain

Moonrise

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Moonrise is the first appearance of the Moon over the Earth’s horizon.

Unlike the Sun, the rising of the Moon changes from day to day and location to location because the Moon is orbiting the Earth. The Moon takes just over 27 days to complete an orbit around the Earth, so you can actually trace its movement in the sky from hour to hour. This is why a lunar eclipse only lasts a few hours. That’s how long it takes for the Moon to pass through the Earth’s shadow.

The movement of the Moon comes from both the rotation of the Earth – which makes the Sun and the stars move through the sky, as well as the orbital speed of the Moon.

Where and when the Moon rise depends on your location on Earth. So you can’t just see a generic table of moon rise times.

Fortunately, the Internet comes to the rescue. Here are some links to some calculators that will help you find out what time the Moon will rise in your specific location.

Moonrise and Moonset at Specified Location (NASA) – This calculator lets you punch in your specific latitude and longitude, year and month and then see a table of times that the Moon will rise and set for your location.
Farmer’s Almanac – The Farmer’s Almanac website has a tool that lets you put in your ZIP or Postal Code and date and then see a list of moonrise and sunrise times. You can also browse by city. This is better if you don’t know your latitude and longitude.
US Naval Observatory – This website lets you retrieve moonrise/sunrise time table for an entire year.

We have written many articles about the Moon on Universe Today. Here’s a story about building a moon base.

Want more information on the Moon? Here’s NASA’s Lunar and Planetary Science page, and here’s a link to the Solar System Exploration Guide.

You can listen to a very interesting podcast about the formation of the Moon from Astronomy Cast, Episode 17: Where Did the Moon Come From?

October 30, 2008December 24, 2015 by Astronomy Cast

Podcast: Orbit of the Planets, Green Stars, and Oort Cloud Contamination

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We’re back to a themeless questions show. We’re right across the Universe this time. Why are the planets lined up in a nice flat plane? Why are there no greenstars? And is the Oort Cloud contaminating our understanding of the cosmic microwave background radiation? If you’ve got a question for the Astronomy Cast team, please email it in to [email protected] and we’ll try to tackle it for a future show. Please include your location and a way to pronounce your name.

Click here to download the episode.

Or subscribe to: astronomycast.com/podcast.xml with your podcatching software.

Orbit of the Planets, Green Stars, and Oort Cloud Contamination – Transcript and show notes.