Astronomy: The Week Ahead – Sun 30 Aug to Sat 05 Sep 2015

AstroTitlePhoto Aug 30

Sunday August 30


The Moon will rise in perigee tonight, due east. This is the Moon’s closest point to us in its monthly orbit. But look to Libra in the southwest. Saturn in a telescope is a great sight. The ringed planet is leaving us until next season, and will soon disappear into the glare of sunset. While you can, also compare the color of Scorpius’ star Antares.

Monday August 31


Tonight Neptune is at opposition. The Earth lies directly between Neptune and the Sun. That means Neptune rises at sunset, is in the sky all night, and sets with sunrise. This is the best time to view the distant world! Here you can see it low in Aquarius, and how to use two of the constellation’s stars to point to it. Neptune is at magnitude 7.8, and can be seen in binoculars, but it is much easier to recognize its blue tone with a telescope. It is only 2.4 arcseconds in size, and with high power will appear a small bluish disk. The planet is its closest to us tonight, at almost 29 AU (astronomical units; 1 AU is the distance from the Earth to the Sun).

Tuesday September 01


Venus is at its longest western elongation today, at 25 degrees from the Sun. Find it in the predawn sky in Cancer, near the head of Hydra, and below Gemini the twins. That red “star” nearby is Mars. Venus is inside our orbit just over 30 million miles away, and shows a very generous 51 arcseconds in size, as a 10% illuminated crescent. If you can view it through a telescope, you’ll be in for a visual treat! Mars is outside our orbit 150,000 million miles away, showing only a 3.7 arcsecond size disk. You can imagine a point during the year when the earth would be between the two!

Wednesday September 02


Here’s a challenge for those viewing through telescopes in somewhat dark evening skies. NGC globular clusters 7006 and 6934 lie in the constellation Delphinus, roughly between Altair in Aquila, and Enif in Pegasus. Both are small, at 3.6 and 7.1 arcminutes, respectively. They shine at magnitudes 10.6 and 8.9. Both will be unresolved, you can’t see individual stars in them. So, they will both appear as somewhat granular, fuzzy glows.

Thursday September 03


Lying between the paws of the Great Bear, Ursa Major, and the twins of Gemini, is the dim constellation Lynx, the cat. It has only one star brighter than magnitude 4.5, Alpha Lyncis, at magnitude 3.12 and 223 light years distant. It is a supergiant star, at 118 solar radii, and has the luminosity of 1622 suns!

There are only four main stars in the constellation, and they seem to get dimmer as you progress from Alpha. Can you make out the figure? This area has many dim open clusters and one famous globular cluster, which we’ll discuss Saturday.

Friday September 04


How far can you see with the “naked eye”? Try for M31, the Great Andromeda Galaxy. Distance estimates range from 2.3 to 2.9 million light years. It will appear as a dim fuzzy patch, a short hop above the orange star Beta Andromedae. Find the sweep of the constellation Andromeda between the famous ‘W’ of Cassiopeia, and the Great Square of Pegasus. Once you identify the two arc comprising Andromeda, jump up from the star Beta, to dimmer star just above it, the up again about the same distance. Do you see the dim elongated glow? If so, grab some binoculars and try again.

Saturday September 05


Here’s another challenge object. NGC 2419 is a globular cluster in the constellation Lynx. It measures a bit over 2 arcminutes in size and shines dimly at magnitude 10.4. It appears unresolved in most amateur telescopes, but will break up into individual stars at high power in larger telescopes. Thought to be 200,000 light years from Earth, it is the farthest such object in our galaxy. Most globular clusters in our galaxy are less than 1/3 that distance. Speculation exists that it was captured from another passing galaxy, and has been named “Intergalactic Wanderer.”

Happy viewing!



Astronomy: The Week Ahead – Sun 15 Aug to Sat 22 Aug 2015

aug sky photo


Sunday August 16

This evening at sunset the planet Mercury is directly west, and very close to the horizon as the sky becomes dark enough to try finding it. A two day old moon will accompany Mercury six degrees to its east, showing only a very thin 6% illuminated waxing crescent. You will be lucky to pick out either, as an absolutely flat horizon and good timing will be necessary. Mercury’s due west position will be helpful in spotting its magnitude 0.17 speck, while only the thin crescent of the moon will be possible. Above Mercury, Leo’s brightest tail star, Denobola, might be visible as the sky continues to darken.


Monday August 17

The dim and long constellation Eridanus, the River, is rising west of Orion in the predawn sky. You can easily locate its beginning, next to the bright blue-white giant star Rigel, at the foot of Orion. Like an old river, the path of Eridanus meanders through mostly empty skies, terminating due south below the horizon with the 0.5 magnitude star Achernar. Eridanus is the Latin name for the Po River, in Italy. It is an ancient constellation, among the 48 original ones designated by Ptolemy in the 2nd century A.D. Only four of its main stars shines brighter than magnitude 3.0.


Tuesday August 18

Today the moon enters ascending node, crossing north of the celestial equator, called the Ecliptic (green line). It is also now at apogee, its farthest point from earth in its orbit. Watch as it passes Spica tomorrow night, while its waxing crescent phase increases from 17% illumination, and passes Saturn to reaches first quarter phase with 53% illumination in four nights.


Wednesday August 19

Grab your binoculars and look for Mars low over the eastern horizon below Gemini. If you are able to see it, your binoculars should reveal the red planet shining brightly among the stars of the great open cluster called The Beehive, or Messier 44 (M44), in the constellation Cancer. Mars will be at magnitude 1.75, and easy to identify. The Beehive Cluster is magnitude 3.7, large and coarse, with many bright stars overflowing most binocular fields of view. Mars will be 48 arc-minutes from the center of the cluster this morning. The Beehive will overflow most binocular fields of view, at 95 arc-minutes in size.


Thursday August 20

Use your binoculars this morning to find the Great Andromeda Galaxy, M31, high in the western sky. The Square of Pegasus will be your starting point. Find it then hop up the gentle arcs of stars to Beta Andromedae, and scan across past the dimmer star (Mu Andromedae) just to its north, until you see a large glowing oval. You’ll have found the galaxy, or at least part of it. M31 is huge in our skies. At 178×63 arc-minutes, it is wide a five full moons and twice as thick! You won’t be able to view the entire galaxy in one binocular field of view! This galaxy at magnitude 3.4, is the farthest object that can be seen without optical aid, at a distance of 2.9 million light years.

Enjoy Saturn season while you can, it always seems to end too soon!


Friday August 21

Saturn reaches eastern quadrature today. The earth and Saturn form a right angle with the sun. We are now halfway through “Saturn season”, with the earth speeding away from Saturn, to leave it in the glare of the sun in a few more months. Since we are at right angles to the sun, you’d expect the distances to reflect that. We are currently 9.9 Astronomical Units (AU) from Saturn, and Saturn is 9.9 AU from the sun!


Saturday August 22

The first quarter moon and Saturn sits just under 5-1/2 degrees apart tonight, straddling the constellations Scorpius (moon) and Libra (Saturn). Use your extended three middle fingers, held at arms length, and they should just fit between these two celestial objects. Your fist equals about five degrees, so now you have a measuring device at hand! A fist is ten degrees. The moon tonight is so bright it will drown out our view of the Milky Way rising from the Teapot is Sagittarius. Surprisingly, it is only 1/11th as bright at a full moon!

Happy viewing!


Astronomy: The Week Ahead – Sun 9 Aug to Sat 15 Aug 2015

Astronews title shot


Sunday August 09

The heart of our Milky Way Galaxy is on show tonight after sunset. All you need to enjoy a great night of astronomy is a pair of binoculars, a reasonably dark sky, and you’ll be astonished at how rich our galaxy is in stars and deep sky objects. The section between and around Scorpius and Sagittarius are stunning in low-power (7x or 10x) binoculars. You’ll see incredibly rich star fields, open and globular clusters, bright and dark nebulae throughout the area.


Monday August 10

The diminutive little bear, Ursa Minor, is standing almost straight up tonight as the sky darkens. Its brightest star is Polaris, our North Star. See if you can pick out the other stars in the constellation, as they are easiest to see like this. Ursa Minor is also called The Little Dipper, and is flanked by Ursa Major (the great bear) containing the Big Dipper asterism and Cassiopeia. Watch as the Big Dipper glides down toward the horizon, and Cassiopeia rises in the northeast.


Tuesday August 11

This is a great year to view the Perseid Meteor Shower, as the Moon will be absent almost all night. The best time will be after midnight. Get a comfortable chair, bundle up, have a warm drink at hand, sit back and let your eyes adjust to the dark skies. Looking northeast, the radiant (shown at left; where the shooting stars appear to emanate from) is above Perseus and below Cassiopeia. Expect up to 50 or more meteors per hour in northern latitudes. This meteor shower is among the best each year, so don’t miss it!


Wednesday August 12

Canis Minor’s brightest star Procyon is on the eastern horizon an hour before sunrise this morning. Nearby, slightly north, a 27.5-day-old waxing crescent Moon shows the slimmest of slivers, at only 4% illumination, and ruddy Mars glows red another new degrees to the north. Above them all, Castor and Pollux mark Gemini’s rising and the coming of fall and winter.


Thursday August 13

Among the closest, at 1,360 light years distant, and brightest example of a planetary nebula is the Dumbbell in the small constellation Vulpecula, between Cygnus and Aquila. At magnitude 7.5, it is easily viewed in even small binoculars. It is easy to locate about midpoint between Deneb and Altair, or you can draw an imaginary parallelogram using Cygnus’ stars, and place the Dumbbell where the missing star would be. Its apparent size is an elongated 8×5.5 arcminutes. Use an filter to bring out its shape, which will appear somewhat like an apple core.


Friday August 14

Tonight is the August New Moon. A great time, and weekend, to go deep sky observing! Here are two easy, well-placed targets. M22 and M28 are giant globular clusters above the tip of the Teapot asterism in Sagittarius. Both are visible in binoculars, and become awesome sights in telescopes. M22 is the larger and brighter of the two, at magnitude 5.1 and big as a full Moon at 32 arcminutes, it is 10,000 light years away. M28 is magnitude 7.6, 11.2 arcminutes in size, and sits almost 18,000 light years from Earth. These are among a hundred or so globular clusters within our own Milky Way Galaxy.


Saturday August 15

Here is a fun project for a few hours on a new moon weekend Saturday night. Six Messier Object globular clusters, in one constellation; Ophiuchus. This constellation is the richest in this type of deep sky object, which seem to congregate around the plane of the Milky Way and especially the galactic bulge, located near M19 in this image. Note the variety of size and shape. If you find this type of project is to your liking, the Astronomical League offers a Globular Cluster observing program. Check it out!

Happy viewing!


Astronomy: The Week Ahead – Sun 2 Aug to Sat 8 Aug 2015

astro title image



Sunday August 2

The Moon attains perigee at 03:11 today, its closest point to Earth during this lunar month. In a waning gibbous phase it is nearly 18 days old with 89% illumination. You can watch it rise just before 10 p.m. in Aquarius over the eastern horizon.


Monday August 3

The eastern morning sky an hour before sunrise features many familiar winter constellations. And today the planet Mars wanders in among them, shining red low on the horizon. Can you find it before dawn washes it out? If you do, compare its color to the giant red stars Aldebaran in Taurus, and Betelgeuse in Orion.

Mars is in Gemini, shining at a bright magnitude 1.70, around 239 million miles from us.


Tuesday August 4

Get your binoculars out and look due south above the stinger of Scorpius tonight, to find Messier 6 (M6), The Butterfly Cluster. This open cluster is visible without optical aid from even reasonably dark locations, at a bright magnitude 4.2. It is 33 arcminutes in size, comparable to the angular size of the full Moon. At 1,600 light years distance, imagine how brilliant these young stars would be were they the distance of some of our brightest neighbors in the sky! Although their discovery is officially attributed to Giovanni Battista Hodierna in 1654, it is very reasonable to believe Ptolemy saw it, and its neighbor M7 (The Ptolemy Cluster) in the First century.


Wednesday August 5

After Pisces has risen, look for the waning gibbous Moon, then, with binoculars, less than two degrees away you’ll find the green-toned planet Uranus at magnitude 5.8 very nearby the magnitude 5.1 star Zeta Piscium. The Moon is 384,399 km distant, Uranus 1.8 billion miles from us, and Zeta 148 light years away. Zeta is an optical double star (not a binary), with its components 23 arcseconds apart.


Thursday August 6

Tonight is last quarter Moon, rising after midnight at 00:26. It is a good weekday night for deep-sky observing, and if not for the Moon we’d be looking for the Southern Iota Aquariid Meteor Shower. If you still want to try for some meteors, here is the radiant, where this shower will appear to emanate from. Expect 7-8 meteors an hour, averaging magnitude 3.


Friday August 7

The constellation name Lacerta is Latin for Lizard. This is a small and faint constellation created by Polish astronomer Johannes Hevelius in 1687. You’ll find it along the Milky Way between the W of Cassiopeia and Cygnus (the northern cross). Its brightest star, Alpha Lacertae, is a dim magnitude 3.76, so this constellation is a challenge to discern. See if you make out its zigzag shape.


Saturday August 8

Located between Cor Caroli in Canes Venatici, and Arcturus in Bootes, M3 is a bright and easy globular cluster to see in binoculars and any telescope. Arcturus is found by taking the handle of the Big Dipper and making an “arc to Arcturus”. Similarly, you can use the dipper’s handle to make a right angle to Cor Caroli. The cluster will be visible easily in binoculars or a finderscope, slightly closer to Arcturus than the halfway point to Cor Caroli. M3 is 16 arcminutes in size, large for the northern hemisphere, and shines at magnitude 6.19 at a distance of 33,000 light years. This is an impressive cluster of over 500,000 stars!

Happy viewing!


Astronomy: How A Comet Interacts with Solar Wind

uly 30, 2015: Rosetta is making good progress in one of its key investigations, which concerns the interaction between the comet and the solar wind.  Credit: European Space Agency (ESA)

July 30, 2015: Rosetta is making good progress in one of its key investigations, which concerns the interaction between the comet and the solar wind.
Screenshot from a simulation of plasma interactions between Comet 67P/C-G and the solar wind around perihelion. Image Credit: Modelling and simulation: Technische Universität Braunschweig and Deutsches Zentrum für Luft- und Raumfahrt; Visualisation: Zuse-Institut Berlin, European Space Agency (ESA)

The solar wind is the constant stream of electrically charged particles that flows from the Sun, carrying its magnetic field out into the Solar System. Like all comets, 67P/Churyumov–Gerasimenko must navigate this flow in its orbit around the Sun.

It is the constant battle fought between the comet and the solar wind that helps to sculpt the comet’s ion tail. Rosetta’s instruments are monitoring the fine detail of this process.

Using the Rosetta Plasma Consortium Ion Composition Analyzer, Hans Nilsson from the Swedish Institute of Space Physics and his colleagues have been studying the gradual evolution of the comet’s ion environment. They have seen that the number of water ions— molecules of water that have been stripped of one electron— accelerated away from the comet increased hugely as 67P/C-G moved between 3.6AU (about 538 million km) and 2.0AU (about 300 million km) from the Sun. Although the day-to-day acceleration is highly variable, the average 24-hour rate has increased by a factor of 10,000 during the study, which covered the period August 2014 to March 2015.

The water ions themselves originate in the coma, the atmosphere of the comet. They are placed there originally by heat from the Sun liberating the molecules from the surface ice. Once in gaseous form, the collision of extreme ultraviolet light displaces electrons from the molecules, turning them into ions. Colliding particles from the solar wind can do this as well. Once stripped of some of their electrons, the water ions can then be accelerated by the electrical properties of the solar wind.

Not all of the ions are accelerated outwards, some will happen to strike the comet’s surface. Solar wind particles will also find their way through the coma to hit home. When this happens, they cause a process called sputtering, in which they displace atoms from material on the surface—these are then ‘liberated’ into space.

Peter Wurz from the University of Bern, Switzerland, and colleagues have studied these sputtered atoms with Rosetta’s Double Focussing Mass Spectrometer (DFMS), which is part of the ROSINA experiment.

They have so far discovered sodium, potassium, silicon and calcium, which are all present in a rare form of meteorites called carbonaceous chondrites. There are differences in the amounts of these atoms at the comet and in these meteorites, however. While the abundance of sodium appears the same, 67P/C-G shows an excess of potassium and a depletion of calcium.

Most of the sputtered atoms come from the winter side of the comet. Although this is the hemisphere that is mostly facing away from the Sun at present, solar wind particles can end up striking the surface because they are deflected during interactions with ions in the comet’s coma. This can be a significant process so long as the density of the coma ions is not too large. But at some point the comet’s atmosphere becomes dense enough to be a major defence, protecting the icy surface.

As the comet gets closer to the Sun, the sputtering will eventually stop because the comet will release more gas and the coma will become impenetrable. When this happens, the solar wind ions will always collide with atoms in this atmosphere or be deflected away before striking the surface.

The first evidence that this deflection is taking place at 67P/C-G has been measured with the Rosetta Plasma Consortium Ion and Electron Sensor, by Thomas Broiles of the Southwest Research Institute (SwRI) in San Antonio, Texas, and colleagues.

Their observations began on August 6, 2014 when Rosetta arrived at the comet, and have been almost continuous since. The instrument has been measuring the flow of the solar wind as Rosetta orbits 67P/C-G, showing that the solar wind can be deflected by up to 45° away from the anti-solar direction.

The deflection is largest for the lighter ions, such as protons, and not so much for the heavier ions derived from helium atoms. For all ions the deflection is set to increase as the comet gets closer to the Sun and the coma becomes ever denser.

As all this happens, Rosetta will be there to continue monitoring and measuring the changes. This was the raison d’être for the rendezvous with this comet. Previous missions have taken snapshots during all too brief fly-bys but Rosetta is showing us truly how a comet behaves as it approaches the Sun.

This blog post is based on the papers “Evolution of the ion environment of comet 67P/Churyumov-Gerasimenko: Observations between 3.6 and 2.0 AU ” by H. Nilsson et al.; “Rosetta observations of solar wind interaction with the comet 67P/Churyumov-Gerasimenko” by T.W. Broiles et al.; and “Solar Wind Sputtering of Dust on the Surface of 67P/Churyumov-Gerasimenko ” by Peter Wurz et al., which have all been accepted for publication in Astronomy and Astrophysics, and “Dynamical features and spatial structures of the plasma interaction region of 67P/Churyumov–Gerasimenko and the solar wind” by C. Koenders et al, which is published in Planetary and Space Science.



Astronomy: Saturn’s Moon Titan Not So Titanic

Credit: NASA/JPL-Caltech/Space Science Institute

Credit: NASA/JPL-Caltech/Space Science Institute

Although Titan (3200 miles or 5150 kilometers across) is the second-largest moon in the solar system, Saturn is still much bigger, with a diameter almost 23 times larger than Titan’s. This disparity between planet and moon is the norm in the solar system.

Earth’s diameter is “only” 3.7 times our moon’s diameter, making our natural satellite something of an oddity. (Another exception to the rule: dwarf planet Pluto’s diameter is just under two times that of its moon.) So the question isn’t why is Titan so small (relatively speaking), but why is Earth’s moon so big?

This view looks toward the anti-Saturn hemisphere of Titan. North on Titan is up. The image was taken with the Cassini spacecraft wide-angle camera on April 18, 2015 using a near-infrared spectral filter with a passband centered at 752 nanometers.

The view was acquired at a distance of approximately 930,000 miles (1.5 million kilometers) from Titan. Image scale is 56 miles (90 kilometers) per pixel.

The Cassini mission is a cooperative project of NASA, ESA (the European Space Agency) and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colorado.

On the Web:

For more information about the Cassini-Huygens mission 

The Cassini imaging team homepage


Astronomy: Venus-Mass Planet Orbiting Brown Dwarf

Venus Mass Planet Orbiting Brown Dwarf

An international team of Polish, Korean, American, Israeli, and Italian astronomers have announced the unusual discovery of a Venus mass planet OGLE-2013-BLG-0723LB/Bb, orbiting a cool brown dwarf star.

Both the planet and it’s brown dwarf host, are in a wide orbit around a larger stellar companion OGLE-2013-BLG-0723LA, with perhaps another, (as yet unconfirmed) much larger third stellar companion at a much larger separation distance than the two confirmed binary stellar objects.

The discovery was made using the technique of microlensing which gives astronomers reliable information about the mass of the planet : 0.69 ± 0.06 M⊕ (Earth) and it’s orbital distance : 0.34 ± 0.03 AU or 439993738 km. This distance places the planet in an orbit very similar to that of Mercury (0.38 AU) but our Sun is far hotter than this cool brown dwarf.

The microlensing event OGLE-2013-BLG-0723 was first discovered by the Optical Gravitational Lensing Experiment (OGLE-IV) in one of the starfields towards the Galactic bulge that OGLE astronomers Udalski et al. observed on May 12th 2013, using the 1.3 meter Warsaw Telescope at the Las Campanas Observatory in Chile.

The planetary system is estimated to lie some 0.49 ± 0.04 kilo parsecs towards the Galactic Center, having been identified by it’s lensing effect on a background star that is a further 6.51 kilo parsecs from Earth.

This new planetary find may prove to be very important. OGLE-2013-BLG-0723LBb is a missing link between planets and moons. This is because its brown dwarf host OGLE-2013-BLG-723LB  is intermediate between stars and planets, in both size and hierarchical position.

The scaled mass and host-companion separation of this Venus-mass planet and brown dwarf host are in many ways similar to planets and moons in the solar system. That is, a Venus-mass planet orbiting a brown dwarf, may be viewed either as a scaled down version of a planet and star, or as a scaled up version of a moon and planet, orbiting a star.

So this system is an intermediate between Neptune-Triton or Jupiter-Callisto planet-moon systems, and the Sun-Mercury or the Sun-Venus star-planet systems.

It suggests that in all cases, planets and moons are formed in an accretion disk. Planets form around all types and size of star, and moons are formed in an accretion disk around planets. The process is the same, regardless of the size or scale of the individual objects.


Astronomy: The Week Ahead – Sun 12 Jul to Sat 18 Jul



Sunday July 12

Antares is the red giant star marking the heart of Scorpius, the scorpion. Place it where our Sun is, and it would extend beyond the orbit of Mars. Yet, its density is so light, it would float in water. Antares is a double star, with the primary star shining reddish at magnitude 1.09. The companion is sometimes called the Green Pea, and requires steady seeing and high magnification to see in the glare of its partner. At magnitude 5.5, the Green Pea is 1/370th the brightness of Antares, and less than 2.5 arcseconds separation.


Monday July 13

Here’s a morning double star that is easy to locate. Enif is Epsilon Pegasi, an optical double with components shining at magnitudes 2.5 and 8.7. It has a wide separation of 144 arcseconds, and offers an unusual treat. Its nickname is the Pendulum Star. Center the pair in your eyepiece between 60 and 100 power. Tap the telescope, and watch the primary star gently wobble to and fro, while the secondary member moves wildly at a right angle to the primary. Astronomer John Herschel was among the first to note this oddity.


Tuesday July 14

Have you been watching Venus moving quickly eastward of Jupiter this week? Tonight they are over 5 degrees apart. Venus is also very close to Leo’s brightest star Regulus today, separated by 2-1/3 degrees of arc.

Also of note today, New Horizons FlyBy of Pluto is taking place. Expect some stunning detailed images of this icy world. And, today is also the 50th anniversary of the Mariner Mars flyby!


Wednesday July 15

Summer is flying by, and the Milky Way is spinning overhead. It’s a great time to go to a Star Party. Some are local and some regional, drawing hundreds of astro-enthusiasts over multiple nights.

With New Moon today, it’s a great opportunity to observe nebulae and galaxies at one of these fun events. On the West Coast the Golden State Star Party starts today and runs through Saturday in far northeast California, under very dark skies. It’s not too late to pack up the camping gear and see what’s up!


Thursday July 16

The constellation Perseus is rising above the northeast horizon before sunrise this morning. Its most notable stars are Mirfak, shining at magnitude 1.79, and the famous eclipsing variable star Algol which ranges from magnitude 2.3 to 3.5 over a period of 2.867 days. Its most famous deep sky object is the Double Cluster, NGC 884 and NGC 869, easily visible in binoculars. The Milky Way passes through Perseus, but is dimmed by intervening molecular clouds. Find Perseus above bright Capella in Auriga, and Aldebaran in Taurus.


Friday July 17

Find Perseus in the predawn skies and enjoy views of the famous Double Cluster. Look to the northeast, for the distinctive W shape of Cassiopeia and imagine a line from the center star through the next lower star, then twice that distance to a fuzzy patch in the sky. Binoculars or a telescope will show two open clusters, NGC 869 and NGC 884, shining at magnitudes 3.7 and 3.8. The clusters lie 7,000 light years from us and each one contains over 300 blue-white supergiant stars. The pair are 60 arcminutes in diameter, a full degree of sky, so binoculars work well, or a low power eyepiece will fit both in one view.


Saturday July 18

Look to Leo on the western horizon as skies darken this evening. Jupiter and Leo will show their increasing separation, with Venus now passing the bright star Regulus in its eastward motion. Joining these three objects will be a young Moon, just 2.9-days-old in its waxing crescent phase, 9 percent illuminated. The Moon and Venus will be 1.37 degrees apart, and fit easily in the view of any binoculars. Can you see earthshine illuminating the portion of Moon in lunar night? Let me know if you viewed this and what you think!

Happy viewing!


Astronomy: The Week Ahead – Sun 5 Jul to Sat 11 Jul


Sunday July 05

Today an 18.5-day-old 85% illuminated waning gibbous Moon is at perigee, at 11:54 A.M. This is its closest point to earth in this orbit of our planet. When the Moon is full at perigee, it has been referred to as a Supermoon. See the Moon best today before sunrise. It sets just before 10 a.m. Look carefully and try to see it during the day.


Monday July 06

This morning in the early sunrise, Earth reaches Aphelion. It will be 1.017 AU (Astronomical Units) from the Sun at 05:59 PDT. This is its farthest point from the Sun in our planet’s elliptical orbit.


Tuesday July 07

Pluto is at opposition today. The Earth is directly between the dwarf planet and the Sun. So, Pluto rises at sunset today, is up all night, and sets with the next morning’s sunrise. Pluto is in an easy to locate position, right off the tip of the Teaspoon in Sagittarius. The above image shows its position relative to the nearby bright star. Even with this help, Pluto will look like a dim star in a telescope. But, with the New Horizon space probe visiting this distant world on in just one week, this may be a fun target to pursue!


Wednesday July 08

The Last Quarter Moon occurs at 13:24 today. It will be slightly larger than half illuminated in the early hours when it rises over the eastern horizon in Pisces, below Pegasus. Last Quarter is tacitly the beginning of a dark sky observing window, for deep sky observers, lasting until after New Moon. Get your telescopes out and let us know what you’re looking at!


Thursday July 09

Before it rose, just after it 1 a.m. this morning, the Moon occulted the seventh planet Uranus. Look at yesterday’s Moon position and you can see how its path to today’s location crossed over the planet. Uranus is in an easy position currently, for star hoppers to get to, just off the two brighter stars in the western string of Pisces. Wait for the moon to move away over the next few nights, and add Uranus to this week’s planetary targets.


Friday July 10

Did you all enjoy the Venus and Jupiter conjunction last week? It won’t occur again until 2023, so it was really a special treat! Still, the two planets are close together, setting after evening twilight. Continue to watch them move further apart, as Venus approaches Leo’s bright star Regulus, along the Ecliptic, as is Virgo’s Spica.


Saturday July 11

Due south an hour after sunset, the great globular cluster M4 is easy to view, just off Scorpius’ giant red star Antares. One of the closest globular cluster’s to our position in the Milky Way Galaxy, it is thought to be some 9,000 light years distant. Although it is a Messier object, in the famed French comet hunter’s catalog, it was discovered in 1746 Philippe Loys de Chéseaux. It was the first globular cluster in which individual stars were seen. At magnitude 5.9, this is at the threshold of most people’s sight. Don’t forget to visit nearby Saturn too, if you are in the area.

Happy viewing!


Astronomy: The Week Ahead – Sun 28 Jun to Sat 4 Jul


Sunday June 28

Tonight’s waxing gibbous Moon is 11.8 days old and 90% illuminated. It is paired in tonight’s sky with Saturn, just over 2 degrees to its west. Both reside tonight in the constellation Libra. Below is Scorpius, with its brightest star Antares. Antares shines at magnitude 1.03, Saturn at 0.23, and the moon a brilliant magnitude -12.6!


Monday June 29

If you’re quick this morning, you’ll have another view of the planet Mercury, near Aldebaran in the constellation Taurus, just north of the eastern horizon.

There’s another interesting item in the sky to view though. The famous variable star Algol in Perseus is at its brightest, magnitude 2.0. Look at it this morning, then watch it over the next few dawns as it fades to 3rd magnitude, equal in brightness to the dimmer star to its right in this image.


Tuesday June 30

A spectacular conjunction occurs tonight, with the sky’s two brightest planets, Venus and Jupiter. They are so close together, the image here can’t show them as separate objects. You’ll be able to split them apart easily though, as they are 20 arcminutes apart. The diameter of the Moon is 30 arcminutes.

Look due west, an hour after sunset to see the pair, just below the sickle of Leo.


Wednesday July 1

If you have a clear western and eastern horizon you can watch Full Moon rising as the sun is setting. Try to do it! The Moon will be full in the constellation Sagittarius, above the asterism called the Teaspoon.

This is the summer’s first Full Moon, and was called the Full Buck Moon by Native Americans, as the bucks begin growing their antlers this month. Some called it the Thunder Moon, due to the frequency of thunderstorms in July.

July will have another full moon, so you’ll be able to see a Blue Moon this month too!


Thursday July 2

Morning skies in the east and southeast are beginning to show some of the water constellations. Cetus the whale. Pisces the fish. Aquarius the water carrier.


Friday July 3

The show continues in the west tonight, as Venus has moved clearly past Jupiter and the planets head toward a rendezvous with Regulus in Leo on the 14th. Have you even tried identifying some of the lesser known constellations around the famous Leo the Lion? Coma Berenices is behind its haunches. Leo Minor just over the mane of the big cat. Above them both, following the Great Bear (Ursa Major) and under the Big Dipper are the hunting dogs, Canes Venatici.


Saturday July 4

Here’s a celestial firework for the 4th of July. M13 is arguably the best globular cluster in the northern sky. It appears in a moderate size telescope much like a burst of star, or a firework. At magnitude 5.8, it is on edge of naked-eye visibility from a dark sky. It is large in apparent size, at 23 arcminutes (remember, the full moon is 30 arcminutes) and resides a full 25,100 light years away from earth, within our Milky Way galaxy, and is about 145 light years in diameter. Hard to imagine, this is a gravitational ball of several hundred thousand stars that are among the oldest (as globular clusters are) in the universe!

Happy viewing!