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

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Sunday, August 23th:

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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:

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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:

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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:

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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:

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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:

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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:

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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

 

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Astronomy: The Week Ahead – Sun 08 Mar to Sat 14 Mar 2015

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Sunday March 8

Due south at sunset is the constellation Canis Major and its brightest star Sirius. Sirius is the brightest star in the night sky at magnitude -1.5 and is a double star, a binary star system. The companion, Sirius B, is a white dwarf star, shining at magnitude 8.5. The brightness of the primary can make seeing the companion difficult, but you can do it in a telescope. Its separation from Sirius A changes around every 50 years, and it is now approaching its widest separation. Read up on Sirius, you’ll be amazed at what you learn, it’s a very interesting star!

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Monday March 9

The constellation Scorpius is one of the twelve Zodiac constellations, lying along the ecliptic. The Moon and planets all traverse this constellation in their paths across the sky. Seen as a scorpion in ancient times, the constellation Libra represented its claws in Babylonian times. Antares is the red beating heart.

Scorpius is beautifully positioned due south currently for northerners, in the predawn skies.

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Tuesday March 10

Get your telescope or binoculars out this morning for a view of two globular clusters just off Antares in Scorpius. M4 resolves into hundreds of stars in a telescope. It is about 7900 light years distant and very bright at magnitude 5.9, and visually about the size of our full Moon. Nearby, almost in the glow of Antares is NGC 6144, a 4.9′ magnitude 9 glow that will not resolve into individual stars. This smaller, dimmer globular is located 33,000 light years away. Nice contrast between this two similar objects!

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Wednesday March 11

NGC 2903 is sometimes referred to as the “forgotten Messier.” It is certainly bright and big enough to warrant inclusion in the famous catalog. And it is easy to locate off the “tip of the nose” in Leo. Easiest is to use Regulus to move up the Sickle, then extend beyond it to the nearest bright star, and drop down slightly. At magnitude 9.7 and a generous size of 12.6’x6.0′, this galaxy discovered by Sir William Herschel is a great target.

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Thursday March 12

An hour before sunrise the Moon and Saturn are paired three degrees apart high up in Scorpius. The soft creamy yellow glow of Saturn will be very apparent contrasted against the whiteness of 21 day old waxing gibbous moon, 62% illuminated.

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Friday March 13

The last quarter Moon occurs today, and will be located in Ophiuchus an hour before sunrise. The position of the moon allows us to see the “bottom line” of Ophiuchus easily, as two pair of stars, one pair wide, and the other close. Another pair extends west into Serpens Caput.

A last quarter Moon on a weekend is especially nice, as it rises late, affording us plenty of dark sky time to observe dim targets such as galaxies and nebulae. Lucky us, on this Friday the 13th!

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Saturday March 14

Revisit Canis Major this evening, for a look at two interesting open clusters. M41 is a large and classic open cluster you’ll see in binoculars. This cluster is thought to have been known by Aristotle, around 325 B.C. It is a bit larger than a full Moon, and bright enough to be seen naked-eye at magnitude 4.5. NGC 2362 will require a telescope. It is stunning, with the extremely large and luminous star Tau Canis Majoris at its center. A fun trick of the eye is to tap your telescope when viewing, and watch Tau jump around while the other stars seem almost stationary!

Happy viewing!

Crash