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

AstroTitlePhoto Aug 30

Sunday August 30

su

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

mo

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

tu

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

we

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

th

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

fr

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

sa

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!

Crash

Astronomy: The Week Ahead – Sun 23 Aug to Sat 29 Aug 2015

SA23 title

Sunday, August 23th:

sun

The bright star near the moon is Antares in the constellation Scorpius the Scorpion. You’ve got about another month or two to see this uniquely summer star for us in the Northern Hemisphere, during the evening hours. Antares is the brightest star near the moon tonight, while the other nearby bright beauty is the planet Saturn.

If you’re in the Northern Hemisphere, Antares and Saturn are visible in the southern to southwest sky as night begins. If you’re in the Southern Hemisphere, they’re more overhead for you.

The moon has now passed the first quarter phase and now exhibits a slight curvature to its terminator line – the line between dark and light on the moon. This moon phase is called waxing gibbous. The waxing gibbous moon, Antares and Saturn will drift westward throughout the night, to set at late evening or round midnight at mid-northern latitudes.

Like all stars, Antares sets some 4 minutes earlier with each passing night, or 2 hours earlier with each passing month. By October, this star will be tough to spot in the southwestern twilight after sunset.

In ancient Chinese thought, the summer season was associated with the direction south, with the element fire, and with the color red. No wonder, then, that this reddish star in the south each summer – beautiful Antares – was considered the Fire Star of the ancient Chinese.

Antares appears as a bright reddish star that rides relatively low in the south throughout our northern summer. We know it as a great ball of gases, a thermonuclear cauldron radiating unimaginable amounts of energy into the blackness and vastness of space.

Yet to us – as to the ancient Chinese – Antares appears so near the southern horizon that we must view it through a great thickness of air. The air through which we view Antares causes this star to twinkle rapidly! On any summer evening, if you see a bright red star low in the south that’s twinkling fiercely … it’s probably Antares.

The basics: The bright star near the moon on August 23, 2015 is Antares, brightest star in the constellation Scorpius. This star can be seen near the moon tonight from around the world.

Monday, August 24th:

mon

The moon can be found above the famous Stinger stars of Scorpius the Scorpion. These stars are called Shaula and Lesath.

As seen from mid-northern latitudes in North America, the Stinger stars loom close to the southern horizon at early evening, a good fist-width below tonight’s waxing gibbous moon. Depending on where you live worldwide, the moon’s position relative to the Scorpion’s Stinger stars varies somewhat.

If you live in Europe or Africa, the moon appears offset closer to Antares, Scorpius’ brightest star.

Asian viewers see the moon even more offset toward Antares.

Those residing in the Southern Hemisphere will see the moon, Antares and the Stinger stars high overhead, not close to the horizon.

When the moon drops out of the evening sky – toward the end of the first week in September – you can use these same Stinger stars to envision the constellation Scorpius, with its graceful curved tail. Plus, you’ll be able to plus star-hop to two beautiful deep-sky treasures: the star clusters M6 and M7.

Your binoculars are perfect for finding M6 and M7, assuming you have a dark sky. They fit within a single binocular field of view.

Your binoculars are perfect for finding M6 and M7, assuming you have a dark sky. They fit within a single binocular field of view.

In the lore of the skies, the Scorpion’s stinger put Orion the Hunter to death.

According to another version of the tale, Orion was accidentally killed by his lover, Artemis.Ophiuchus, the constellation to the immediate north of Scorpius, is said to depict the doctor Ascelpius, who tried to bring Orion back to life. Yet Hades, the god of the Underworld, appealed to Zeus to forbid Ascelpius from raising the dead, for the practice goes against the natural order of things.

The constellation Scorpius is opposite in our sky to the constellation Orion, which is up before dawn now. See the three medium-bright stars at the center of the constellation Orion? Those three stars are Orion’s Belt, and they always point to Sirius, the Dog Star and sky’s brightest star.

The constellation Scorpius is opposite in our sky to the constellation Orion, which is up before dawn now. See the three medium-bright stars at the center of the constellation Orion? Those three stars are Orion’s Belt, and they always point to Sirius, the Dog Star and sky’s brightest star.

The basics: On August 24, 2015, the moon is above the famous Stinger stars – Shaula and Lesath – of the constellation Scorpius the Scorpion.

Tuesday, August 25:

tue

Venus – the second planet outward from the sun and brightest planet visible in Earth’s sky – swung in between Earth and the sun. At that time, Venus transitioned out of Earth’s evening sky and into our morning sky. Unless you have special equipment, you probably haven’t seen Venus for a few weeks.

After having been lost in the sun’s glare for several weeks, Venus returns to visibility in the morning sky this week (beginning around August 26, 2015). On that approximate date – or on a morning around that date – you might see Venus climbing up above the eastern horizon an hour or so before sunrise – if you have an unobstructed eastern horizon and clear sky.

If you miss Venus this week, look for it to appear in the morning sky someday soon.

What will Venus look like before dawn? Here it is shortly before it slipping into the sunset in early August. This is Venus (brightest), Jupiter and Mercury low in the twilight on August 3, 2015. Photo by Peter Lowenstein in Mutare, Zimbabwe.

What will Venus look like before dawn? Here it is shortly before it slipping into the sunset in early August. This is Venus (brightest), Jupiter and Mercury low in the twilight on August 3, 2015. Photo by Peter Lowenstein in Mutare, Zimbabwe.

Just don’t mistake Sirius – the brightest star of the nighttime sky – for the planet Venus. Sirius sparkles in the southeast, while Venus shines with a steadier light almost due east. Although Venus is actually brighter than Sirius, Venus might be the harder of the two to spot in the morning sky right now, because Venus sits closer to the glare of sunrise. Click here for more information about Sirius in the morning sky.

The illustration below enables you to get some perspective of Venus’ and Earth’s orbits around the sun. We’re looking down upon the plane of the solar system from the north side. From this vantage point, the planets revolve counter-clockwise around the sun.

Not to scale. The radius of Venus’ orbit is about 0.72 of Earth’s distance from the sun (0.72 of an astronomical unit).

Not to scale. The radius of Venus’ orbit is about 0.72 of Earth’s distance from the sun (0.72 of an astronomical unit).

The passage of Venus between the Earth and sun took place on August 15, 2015. Astronomers call this an inferior conjunction of Venus. At such times, Venus in its smaller and swifter orbit passes in between the Earth and sun. We should mention that only planets that orbit the sun inside of Earth’s orbit (Mercury and Venus) have inferior conjunctions.

After inferior conjunction, Venus always moves westward of the rising sun in our sky until reaching itsgreatest western elongation (46o) – farthest angular distance from the rising sun – some 72 days later.

Venus will next reach greatest western (morning) elongation on October 26, 2015. It’ll look like a miniature half-lit quarter moon through the telescope. That’s because Venus’ disk always appears about 50% illuminated by sunshine at any greatest elongation.

Midway between inferior conjunction and greatest western elongation, Venus will shine at its brightest as the morning “star” on September 21, 2015. That’s in spite of the fact that Venus’ disk is only about one-quarter illuminated by sunshine whenever it’s midway between an inferior conjunction and a greatest elongation.

This brilliant world will remain in the morning sky until reaching superior conjunction on June 6, 2016, to transition back into the evening sky.

The basics: Starting around August 26, 2015, start watching for dazzling Venus to illuminate the sky before sunrise.

Wednesday August 26th:

wed

Every year, during the last week of August, a first hint of the changing of the seasons can be seen in the predawn sky: Orion the Hunter and Sirius the Dog Star. The very noticeable constellation Orion the Hunter rises before dawn at this time of year, recognizable for the short straight line of three stars that make up Orion’s Belt. And the sky’s brightest star Sirius – sometimes called the Dog Star because it’s part of the constellation Canis Major the Greater Dog – follows Orion into the sky at or close to dawn. Have you noticed a very bright, madly twinkling star in the predawn sky? Many do, at this time of year. That star is Sirius. It’s so bright that, when it’s low in the sky, it shines with glints of red and flashes of blue – very noticeable!

Orion and the nearby star Sirius will become visible in the evening by northern winter (or southern summer). But presently the Hunter and the Dog Star lord over the southeastern sky at dawn’s first light.

The brightest star in this photo is Sirius, the sky’s brightest star. Notice Orion’s Belt stars in the upper left of this photo and how the Belt stars always point to Sirius. Photo courtesy of Leif Boracay.

The brightest star in this photo is Sirius, the sky’s brightest star. Notice Orion’s Belt stars in the upper left of this photo and how the Belt stars always point to Sirius. Photo courtesy of Leif Boracay.

Orion was low in the west after sunset around March and April. By June each year, this constellation is behind the sun as seen from Earth. Orion only returned to visibility in Earth’s sky about a month ago (see our July 29 sky chart). When a constellation becomes visible again, after being behind the sun, it always appears in the east before sunrise.

Because – as Earth orbits the sun – all the stars rise two hours earlier with each passing month, Orion is now higher at dawn than a month ago.

As seen from the Northern Hemisphere, Orion precedes Sirius the Dog Star into the sky. After Orion first appears at morning dawn, you can count on Sirius to appear in the morning sky a few weeks later. You should be able to see Sirius at or before dawn right now – unless you live at far northern latitudes. But even there, it won’t be much longer!

Bottom line: Every year in late August, look for Orion the Hunter and Sirius the Dog in the early morning sky! Orion’s three prominent Belt stars always point to Sirius.

Thursday, August 27th:

thu

In both the evening and morning sky, try watching for Earth’s shadow. Earth’s shadow is a deep blue-grey, darker than the twilight sky. The pink band above the shadow – in the east after sunset, or west before dawn – is called the Belt of Venus.

Earth’s shadow can be seen any clear evening ascending in the eastern sky at the same rate that the sun sets below the western horizon.

The shadow of the Earth is big. You might have to turn your head to see the whole thing. And the shadow is curved, in just the same way that the whole Earth is curved. Earth’s shadow extends hundreds of thousands of miles into space, so far that it can touch the moon. Whenever that happens, there’s an eclipse of the moon, like the one coming up in September.

Check out Earth’s shadow – in the east at sunset or in the west at sunrise – next time you have a clear sky. I often see it while out on the streets of my town as the sun is setting.

By the way, the image at the top of this post shows more or less the same moon phase that you’ll see tonight. It’ll be a waxing gibbous moon that’ll be visible in the east after sunset this evening. The full moon will come on August 29, 2015, to present the first of this year’s full supermoons.

The basics: Watch for the curved blue-grey line of Earth’s shadow at dawn and dusk. The pink coloration above the shadow is called the Belt of Venus.

Friday, August 29th:

fri

Supermoon ahead! The full moon of August 29, 2015 will be the first of this year’s three full supermoons. It’s a full moon near perigee, or near its closest point to Earth for the month. Like it or not, modern skylore dictates that these sorts of moons are called supermoons.

But will your eye see that the moon is bigger on the night of August 29? Well … it depends. Are you an incredibly careful observer? Have you watched the full moon over a period of months, leading up to now? If so you can discern the extra-large size of the supermoon using just your eye.

The closest and largest full supermoon of them all will fall on September 28, to stage a total eclipse of the moon. Some will call it a Blood Moon eclipse.

In North America, we often call the August full moon the Sturgeon Moon, Corn Moon or Grain Moon. The August 2015 full moon is also the first of three full-moon supermoons in 2015. Previously, we had three new moon supermoons in January, February and March, 2015. The full moons on August 29, September 28 and October 27 all enjoy the supermoon designation because the centers of these full moons and the center of Earth are less than 361,836 kilometers (224,834 miles) apart. The closest supermoon of the year comes with the September 28 full moon, presenting a moon that’s only 356,877 kilometers (221,753 miles) from Earth.

Super cool super-moonrise composite from Fiona M. Donnelly in Ontario. This was the supermoon of August, 2014.

Super cool super-moonrise composite from Fiona M. Donnelly in Ontario. This was the supermoon of August, 2014.

Details on the August, 2015 full supermoon The full moon falls at the same instant all over the world: August 29 at 18:35 Universal Time.

Clock time for this full moon – and every full moon – varies by time zone. For London, the moon turns full at 7:35 p.m. BST on August 29, at which time the afternoon sun shines in the west and the moon has not yet risen in the east. For the U.S., the moon turns full on at 1:35 p.m. CDT on August 29, when the sun shines way up high and the moon lies on the other side of the world, beneath our feet.

Technically speaking, the moon turns full at the instant that the moon lies most opposite the sun for the month. Because the moon stays more or less opposite the sun throughout the night, watch for a full-looking moon in the east at dusk, highest in the sky around midnight and low in the west at dawn. On the nights immediately before and after full moon, the moon still looks plenty full to the eye.

When is perigee, the moon’s closest point to Earth? In August, 2015, the moon’s perigee comes less than one day after full moon, on August 30 at 15:24 Universal Time.

The close coincidence of full moon and perigee makes this August full moon a supermoon.

By the way, no particular effects are expected from this extra-close full moon… unless you have the mass of an ocean! In that case, gravity will come into play. In other words, because it’s a supermoon, and relatively close to Earth, this month’s full moon will pull harder than usual on Earth’s oceans. Expect higher-than-usual tides to follow this full moon by a day or so. By the way, any full moon mirrors the sun’s path across the sky for six months hence.

And so here’s another cool thing you can notice about the August 29 full moon. As seen from the Northern Hemisphere, this full moon will follow the low path of the winter sun. As viewed from southerly latitudes, the moon will follow the lofty path of the summer sun.

Enjoy moon-watching tonight and in the next few evenings!

The basics: The full moon on August 29 ushers in the first of three full-moon supermoons in 2015. Full moon is August 29, 2015, at 18:35 Universal Time. The moon’s perigee or closest point comes on August 30, at 15:24 Universal Time.

Saturday, August 29th:

sat

In North America, the August full moon is often called the Sturgeon Moon, Corn Moon or Grain Moon. Tonight – August 29, 2015 – if you’re in this hemisphere, it’s a super Sturgeon Moon you’ll see.

The full moons on August 29, September 28 and October 27 all enjoy supermoon status in 2015, because the centers of these full moons and the center of Earth are less than 361,836 kilometers (224,834 miles) apart. So it’s a super close full moon you’ll see on this night, dubbed, in modern skylore, a supermoon.

Some dislike the term supermoon, but I think it’s fun. But is it rare? No. We have three full supermoons this year, and we already had three new moon supermoons in January, February and March, 2015.

The closest supermoon of the year will arrive with the September 28, 2015 full moon. It’ll be only 356,877 kilometers (221,753 miles) from Earth.

Moreover, the closest and largest full supermoon of the year on September 28 will stage a total eclipse of the moon. This will be the fourth and final eclipse of a lunar tetrad – four total lunar eclipses in a row, each separated by six lunar months (full moons), with no partial lunar eclipse in between. Some refer to the four eclipses of a lunar tetrad as Blood Moons.

Technically speaking, North America won’t see the moon at the instant it turns full because it will happen during our daylight hours, when the moon is below our horizon and beneath our feet. The worldwide map below shows you the day and night sides of the world at the instant of the August 29 full moon (18:35 Universal Time). At United states time zones, that translates to 2:35 p.m. EDT, 1:35 p.m. CDT, 12:35 p.m. MDT or 11:35 a.m. PDT. You have to be on the nighttime side of the world to see the moon at the exact instant that it turns full.

Everyone around the word, however, will see a full-looking moon in the east at dusk or nightfall, highest up for the night around midnight and sitting low in the west at dawn. The moon stays more or less opposite the sun for the duration of the night on August 29, 2015.

The basics: the August full moon will be the Sturgeon Moon. if you’re in the North American hemisphere and this super Sturgeon Moon will be seen on August 29, 2015.

Happy viewing!

Crash

 

Astronomy: Cassini’s Final Breathtaking Views of Saturn’s Moon Dione

Credit: NASA/JPL-Caltech/Space Science Institute

Credit: NASA/JPL-Caltech/Space Science Institute

Above: NASA’s Cassini spacecraft captured this parting view showing the rough and icy crescent of Saturn’s moon Dione following the spacecraft’s last close flyby of the moon on Aug. 17, 2015. Cassini obtained a similar crescent view in 2005. The earlier view has an image scale about four times higher, but does not show the moon’s full crescent as this view does.

Five visible light (clear spectral filter), narrow-angle camera images were combined to create this mosaic view. The scene is an orthographic projection centered on terrain at 0.4 degrees north latitude, 30.6 degrees west longitude on Dione. An orthographic view is most like the view seen by a distant observer looking through a telescope.

The view was acquired at distances ranging from approximately 37,000 miles (59,000 kilometers) to 47,000 miles (75,000 kilometers) from Dione and at a sun-Dione-spacecraft, or phase, angle of 145 degrees. Image scale is about 1,300 feet (400 meters) per pixel.

North on Dione is up and rotated 34 degrees to the right.

Credit: NASA/JPL-Caltech/Space Science Institute

Credit: NASA/JPL-Caltech/Space Science Institute

Above: Dione hangs in front of Saturn and its icy rings in this view, captured during Cassini’s final close flyby of the icy moon. North on Dione is up. The image was obtained in visible light with the Cassini spacecraft wide-angle camera on Aug. 17, 2015.

The view was acquired at a distance of approximately 45,000 miles (73,000 kilometers) from Dione and at a sun-Dione-spacecraft, or phase, angle of 35 degrees. Image scale is 3 miles (4 kilometers) per pixel.

Credit: NASA/JPL-Caltech/Space Science Institute

Credit: NASA/JPL-Caltech/Space Science Institute

Above: This view from NASA’s Cassini spacecraft looks toward Saturn’s icy moon Dione, with giant Saturn and its rings in the background, just prior to the mission’s final close approach to the moon on August 17, 2015. At lower right is the large, multi-ringed impact basin named Evander, which is about 220 miles (350 kilometers) wide. The canyons of Padua Chasma, features that form part of Dione’s bright, wispy terrain, reach into the darkness at left.

Imaging scientists combined nine visible light (clear spectral filter) images to create this mosaic view: eight from the narrow-angle camera and one from the wide-angle camera, which fills in an area at lower left. The scene is an orthographic projection centered on terrain at 0.2 degrees north latitude, 179 degrees west longitude on Dione. North on Dione is up.

The view was acquired at distances ranging from approximately 106,000 miles (170,000 kilometers) to 39,000 miles (63,000 kilometers) from Dione and at a sun-Dione-spacecraft, or phase, angle of 35 degrees. Image scale is about 1,500 feet (450 meters) 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:

Cassini-Huygens mission visit http://saturn.jpl.nasa.gov and www.nasa.gov/cassini.

The Cassini imaging team homepage

Crash

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

aug sky photo

su

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.

mo

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.

tu

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.

we

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.

th

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!

fr

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!

sa

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!

Crash

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

Astronews title shot

su

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.

mo

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.

tu

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!

we

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.

th

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.

fr

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.

sa

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!

Crash

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

astro title image

 

su

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.

mo

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.

tu

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.

we

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.

th

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.

fr

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.

sa

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!

Crash

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.

On the Web: SIMULATION OF PLASMA INTERACTIONS BETWEEN COMET 67P/C-G AND THE SOLAR WIND AROUND PERIHELION

Crash

Astronomy: July’s Second Full Moon and Why You Should See It

Aside from the feeling of calmness that one could get while looking at the deep night sky, people may also witness the literal presentation of the popular folklore, "blue moon" on Friday, July 31.

Aside from the feeling of calmness that one could get while looking at the deep night sky, people may also witness the literal presentation of the popular folklore, “blue moon” on Friday, July 31.

‘Once in a Blue Moon’ typically means rare or absurd. This year, it means the end of July. The second full moon of July occurs on Friday. According to modern folklore, it’s a “Blue Moon.”

The early definition of the blue moon, as per The Maine Farmer’s Almanac, is the appearance of the third of four full moons in a season. But in the modern description, a blue moon pertains to the second full moon that appears in a single calendar month. Whatever the true definition is, “once in a blue moon” is used to mean “rare.”

In general, there is only one full moon in each calendar month or within a span of 30 days. This means that a blue moon is highly emphasized if the first full moon happened during the first 1-2 days of the month and the second full moon reappears after 30 days, which is still within the same month. The last full moon happened in July 2, making the July 31st full moon appearance as a “blue moon.” Blue moons appear once every 2-3 years and if the modern definition is to be consulted, the last blue moon happened on Aug. 31, 2012.

'Once in a blue moon' is literally happening on July 31 according to one of its two emerging definitions. Experts, however, say that the physical color of the moon may not actually resemble that of the vast ocean so set your expectations straight.

‘Once in a blue moon’ is literally happening on July 31 according to one of its two emerging definitions. Experts, however, say that the physical color of the moon may not actually resemble that of the vast ocean so set your expectations straight.

But the real question here is, “Is it really blue?” The experts think not. The date, period and time interval between the appearances of full moons do not have an effect on the color that the lunar object is likely to showcase. But why choose the color blue among all the other colors available in the spectrum?

According to early literature, people used to see moons that were indeed color blue in 1883. These moons were not specifically full; crescent or half-moons also exhibited the said color, making it a daily sight, except on rare occasions when it turns green. The main reason for this is the eruption of the Krakatoa volcano in Indonesia. The experts compared the said volcanic action to a 100-megaton nuclear bomb explosion.

People from nearly 400 miles were able to hear the eruption, ashes enveloped the sky massively and yes, the moon turned blue. The ashes contained particles that were able to scatter red light immensely and allow other colors to pass. The air had increased amounts of these particles that it turned the moon blue. For a bluer emphasis, the particles must be a little bit wider than the wavelength of red light. The white moonbeams glistening through the atmosphere turned blue and occasionally green.

Although numerous definitions of “blue moon” have emerged, it all points out to one thing: a blue moon is indeed rare and with its reported appearance at the end of the month, people could have another reason to look up in the sky as a new month begins.

Happy viewing!

Crash

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

Crash

Astronomy: NASA’s New Horizons Arrives At Pluto

Sharpest Pluto Image So Far! | NASA New Horizons Pluto Flyby We have arrived! Congratulations to NASA's New Horizons Team! Credit: NASA/SwRI/JHUAPL Date: July 14, 2015

Sharpest Pluto Image So Far! | NASA New Horizons Pluto Flyby
We have arrived! Congratulations to NASA’s New Horizons Team!
Credit: NASA/SwRI/JHUAPL
Date: July 14, 2015

NASA New Horizons Arrives at Pluto! [Enjoy This Historic Moment!]

July 14, 2015: At approximately 7:49 a.m. EST today, NASA’s New Horizons spacecraft was as close as it will ever get to Pluto, approximately 7,800 miles (12,500 kilometers) above the surface. This historic moment is part of NASA’s coverage of New Horizons’ nine year, three billion mile journey to the Pluto system to gather data about Pluto and its moons.

Welcome to Pluto! A New Family Portrait of Our Solar System

Welcome to Pluto! A New Family Portrait of Our Solar System

A Heart for Pluto from Earth! | International Space Station Scott:

A Heart for Pluto from Earth! | International Space Station
Scott: “The NASA New Horizons Pluto Flyby showed us heart today. This ‘Earth Art’ shares the love from space station.”
Credit: NASA/JSC, U.S. Astronaut Scott Kelly
Date: July 14, 2015

Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute Release Date: July 14, 2015

Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
Release Date: July 14, 2015

Above: Pluto & Charon in False Color Show Compositional Diversity 

This July 13, 2015, image of Pluto and Charon is presented in false colors to make differences in surface material and features easy to see. It was obtained by the Ralph instrument on NASA’s New Horizons spacecraft, using three filters to obtain color information, which is exaggerated in the image. These are not the actual colors of Pluto and Charon, and the apparent distance between the two bodies has been reduced for this side-by-side view.

The image reveals that the bright heart-shaped region of Pluto includes areas that differ in color characteristics. The western lobe, shaped like an ice-cream cone, appears peach color in this image. A mottled area on the right (east) appears bluish. Even within Pluto’s northern polar cap, in the upper part of the image, various shades of yellow-orange indicate subtle compositional differences.

The surface of Charon is viewed using the same exaggerated color. The red on the dark northern polar cap of Charon is attributed to hydrocarbon materials including a class of chemical compounds called tholins. The mottled colors at lower latitudes point to the diversity of terrains on Charon.

This image was taken at 3:38 a.m. EDT on July 13, one day before New Horizons’ closest approach to Pluto.

New Pluto Header Pic (07-14-15)

On the Web: To learn more about the NASA New Horizons mission to Pluto visit:
www.nasa.gov/newhorizons
http://pluto.jhuapl.edu

Crash