In the Sky Tonight

last SG · 2005-08-23T14:26:28+00:00

Spotting the Summer Triangle Wednesday, May 17, 2006 Looking East-Northeast in Late Evening In the east-northeast in late evening, you'll find a famous...

poon cho tang SG

Wednesday, September 14, 2005
Looking South One-Two Hours After Sunset

If you contrast todays chart to yesterdays chart, youll see that the moon has moved as it always does, eastward on our skys dome from night to night.

This motion of the moon across our sky throughout each month is due to the moons eastward motion in orbit around Earth. The moon takes about a month to orbit Earth, and thus the moon moves around our entire sky in that period of time.

Weve marked the Teapot pattern again today, in the constellation Sagittarius. But the pattern we want you to notice tonight is below the Teapot on the skys dome. This pattern appears in a dark country sky as an unfinished circle of stars. Its really very graceful and lovely, if your sky is dark enough. People in southern states can see this constellation better than those up north . . . because the farther south you go on Earths globe, the better you can see the southern part of the sky.

This semi-circle of stars has a name evocative of southern skies, which were first glimpsed by northern hemisphere dwellers who sailed into southern seas. This is one of the 88 official constellations, despite the fact that it doesnt contain even one bright star. Its called Corona Australis, the Southern Crown.

poon cho tang SG

Thursday, September 15, 2005
Looking Southeast One-Two Hours After Sunset

In today's chart, we introduce the so-called "loneliest star." It's Fomalhaut in the constellation Piscis Austrinus, the Southern Fish.

Fomalhaut is just now coming back to a place convenient for evening viewing. In late September, it rises within an hour of sunset and afterwards arcs across the southern sky throughout the night. And this evening, Fomalhaut is the brightest star near the moon. Like all stars, this one will rise about four minutes earlier each day as Earth moves in its orbit around the sun.

Fomalhaut will arc across the south earlier and earlier each evening as autumn progresses toward winter. In other words, in another month, you'll see Fomalhaut higher in the southeast around this same time of night. A month after that, you'll see it in the south in early evening. Fomalhaut makes its trek across the southern sky while autumn leaves are falling for inhabitants of the Northern Hemisphere.

Learn to recognize it now, and you can count on this star to shine in the south each autumn for the rest of your life . . . as long as you stay in this hemisphere! Fomalhaut is easy to recognize, even without the moon nearby, because it is the only bright star in its region of the sky. That's why it's sometimes called "the loneliest star."

poon cho tang SG

Friday, September 16, 2005
Looking East-Southeast One Hour After Sunset

If you have never seen the constellation Aquarius the Water-Bearer -- Im not surprised.

Aquarius is a constellation of the Zodiac, meaning that it follows the suns path across the sky (marked by the pink line on todays chart). But it is faint, even when seen in dark skies. The easiest way to find Aquarius in the sky, is to first locate something brighter that is near it.

Tonight, a nearly full moon will be in Aquariuss company until it sets. This may not be the time for an attempted first viewing -- the almost-full moon (the famous Harvest moon doesnt officially reach its full status until tomorrow) may drown out a good view of Aquarius.

However, if you have binoculars, you may try to pick out its stars against the moonlight. Just be aware that the brightest stars in this constellation are still rather faint.

Also near the moon this morning is the planet Uranus, located to the upper right of the moon, and probably even harder to pick out than Aquarius.

We recently had a question about viewing the planet Uranus with unaided eyes. Its certainly possible to see Uranus with your eyes alone, but you need a very dark sky to do it. Your best chance to view the planet Uranus with the unaided eye is going on right now. Uranus reached its opposition on September 1st, and is out in the sky all night long now. Your best bet is to wait a couple of days until the moon has moved on from this area of the sky, and then see if you can get a gander at this faraway planet.

poon cho tang SG

Saturday, September 17, 2005
Looking East-Southeast After Sunset

The full moon that rises around the time of sunset this evening is the legendary Harvest Moon. It has that name because it's the closest full moon to the September equinox.

Some say the Harvest Moon appears bigger, brighter and yellower than other full moons. But all full moons look big, bright and yellowish when you see them near the horizon. What makes the Harvest Moon special is the lazy slant of the ecliptic -- shown on our chart as a pink line -- with respect to the horizon in the evening at this time of year.

As the moon moves in orbit around Earth, it moves eastward approximately along the ecliptic. Most of the time, the moon's eastward motion causes it to rise about 50 minutes later each day.

At this time of year, however -- around the time of full moon -- the moon rises only about 30 minutes later each day. That's why, around the time of full moon during the autumn months, the moon rises close to the time of sunset several evenings in a row.

So you have several chances around now to see a big yellow moon hanging low in the sky just after the sun goes down. Before the era of tractor lights, farmers bringing in their crops could work uninterrupted by the light of this full autumn moon.

poon cho tang SG

Sunday, September 18, 2005
Looking East-Southeast in Mid-Evening

The constellation Pegasus represents a Flying Horse. Here's where you can look to see the constellation Pegasus tonight. If you look due east around 10 P.M., you may catch glimpse of a large square pattern of stars. This pattern lies at the center of the constellation Pegasus.

This square star pattern, by the way, has its own name. It's called the Great Square of Pegasus, and it's easy to pick out. The Great Square marks the body of the Flying Horse. The star Enif marks the tip of the Horse's nose. The brightest star in Pegasus is Markab, whose total luminosity is 205 times that of our own sun. The star Alpheratz -- although located in the Great Square -- is actually part of a neighboring constellation Andromeda.

In the mythology of the sky, Pegasus was born from the blood of the serpent-haired Medusa. After Perseus, a hero of ancient mythology, killed Medusa and cut off her head, some of her blood dripped into the sea. From it, the sea god Poseidon fashioned the Flying Horse. He gave the Horse to Perseus -- who rode the Horse while having his great adventures!

Tonight, you'll find the slightly waned Harvest Moon accompanying Pegasus in the southeastern vicinity of the sky at that time.

poon cho tang SG

Monday, September 19, 2005

A skywatcher in southern Arizona wrote, "I've recently used Cassiopeia as a pointer to find another very prominent galaxy, the Andromeda Galaxy . . . I used the larger V portion of Cass as an arrowhead, and traced a line with binoculars southward until I located the fuzzy cotton ball in the sky . . . I've read there are an estimated 500 billion stars in that galaxy, and was awestruck with the thought of the possible worlds orbiting those very distant stars. . . I'll bet you have an easier way to find it than I did!"

What a wonderful experience to share! Indeed, in a very dark sky, it's possible to locate the Andromeda Galaxy in the way described above, by starting at the star Schedar in the W-shaped constellation Cassiopeia and "eye-balling" your way to the galaxy. In a very dark sky, the galaxy is visible to the eye.

Most amateur astronomers, however -- when learning to locate the Andromeda galaxy -- learn by starting with the star Alpheratz, which marks a corner of the Great Square in the constellation Pegasus, found in the east in mid-evening.

Alpheratz is actually Alpha Andromedae, the brightest star in the constellation of Andromeda, which you can see on today's chart extending from the Great Square in two graceful streams of stars. Notice that, from Alpheratz, as you go up along these streams, you come to a pair of stars, unmarked on our chart today. Then you come to a SECOND pair of stars -- Mirach, also known as Beta Andromedae, and its neighboring star Mu Andromedae. Notice that Mirach and Mu Andromdae also point to the Andromeda galaxy!

You might notice that the moon seems to rise at almost the same time as it did yesterday evening. On average, the full moon rises approximately 50 minutes later each night after sunset. Around this time of year, the narrow angle of the ecliptic (the pink line on today's chart) to the horizon in the evening causes a shorter time between successive moonrises. This phenomenon is characteristic of the recent full moon, which occured on September 17th, known as the Harvest Moon.

poon cho tang SG

Tuesday, September 20, 2005

Looking West-Northwest One Hour After Sunset

Many people have asked about the reddish star in the west-northwest after sunset. Every year at this time, we get questions about three different stars that are flashing different colors.

One is Capella in the constellation Auriga the Charioteer, which is now in the northeast in mid-evening. One is Sirius in the constellation Canis Major the Greater Dog, which now is climbing in the southeast before dawn. And the third is the one in the west to northwest after sunset. This star is Arcturus in the constellation Bootes the Herdsman. Its flashing colors for the same reason Sirius and Capella are . . . because all three of these stars are bright and, at this time of year, noticeable low in the sky.

When you see an object low in the sky, youre seeing it through a greater thickness of atmosphere than when its overhead. The atmosphere refracts or splits the stars light to cause the colorful flashing you observed.

By the way, Arcturus is located along a line extending off the handle of the Big Dipper. Thats one way you can be sure the star you think is Arcturus actually is. Just look for the Big Dipper in the constellation Ursa Major the Greater Bear. Draw an imaginery line out from the curve of the Dippers handle, and youll come to the star Arcturus.

poon cho tang SG

Thursday, September 22, 2005

Looking West-Southwest One -Two Hours Before Dawn

One of you wrote, "How can I find out where the moon will rise and set each night? Not just the time, but the location . . . "

If you begin watching the moon, you can get a feel for the cycle of its rising and setting times. Or you can use the Navy's Complete Moon and Sun Data website to calculate your daily local moon rise and set times.

Just be aware that the moon doesn't always rise at night. On last Saturday's full moon, for example, it rose in late afternoon and began shining like a bright beacon in the southeastern sky, as soon as the sun set. The moon rises in daylight half the time, and at night the other half. It rises, on average, about 50 minutes later each day. Thus it really is possible to get a sense of what time the moon will rise, if you watch (or check a chart) and just try to be aware.

On the other hand, I can't give you much hope for understanding the location of the moonrise on the horizon, because it varies seasonally as well as throughout the month. The best I can do is say that the moon -- like the sun, or like planets or stars -- always rises more or less in the east. That's because Earth spins toward the east, and it's Earth's spin that brings the moon into view each day.

Finally, for those of you who are interested, we have an article explaining the moon's phases on this site. Tonight's moon rises in mid-evening, and you may notice that it is accompanied by quite a conspicuous object. This dazzling yellow-orange object is no star -- it's our fiery neighbor planet Mars. Mars will continue to keep the moon company throughout the night until they both set in late morning on the 22nd.

poon cho tang SG

Thursday, September 22, 2005

Looking East at Sunrise

Today the sun crosses the celestial equator, moving from north to south. This is the September equinox, which many call the autumnal equinox . . . but which also marks the beginning of spring on the southern half of Earths globe.

We get a lot of questions each year about the easiest way to find north,east ,south, and west in the sky. At this and every equinox, the sun rises due east and sets due west. So try going outdoors at sunrise or sunset today or tomorrow, preferably in a place where you can see the horizons. Simply make a 90 degree turn -- with respect to the sunrise or sunset -- to find the direction south. If you start out facing a sunRISE, turn 90 degrees to the RIGHT to find due south. If you're watching a sunSET, turn 90 degrees to the LEFT. Once you've found south, you know that north is directly behind you.

You can see the sun rising due east on todays sky chart. The pink line on our chart marks the ecliptic, or path of the sun, moon and planets, and you can see that it makes a very steep angle to the horizon on these autumn mornings in the northern hemisphere. Todays equinox happens at precisely 22:23 Universal time.

poon cho tang SG

Friday, September 23, 2005
Looking West-Southwest After Sunset

As recently as early this month, we were hearing from a lot of people who were glimpsing Jupiter making lovely patterns with Venus, the star Spica, and the moon in the west after sunset.

Now this giant planet is making its way towards the horizon in late afternoon, becoming lost in the sunset glare. Its blocked from view by your horizon, by the time the sky gets dark. From a three-dimensional perspective, Jupiter is now traveling on the far side of the sun from Earth. Its conjunction with the sun will come on October 22. Afterwards, itll come back to the eastern sky before dawn.

When can you expect to see Jupiter next? By late November, itll be only 10 degrees above the east-southeastern horizon before dawn at the beginning of morning twilight. Jupiter is so bright that you should be able to glimpse it then.

poon cho tang SG

Thursday, September 29, 2005

Looking East One Hour Before Dawn

Here's a view of the waning crescent moon in early morning -- near the constellation Leo the Lion.

The brightest star in Leo is Regulus, a blue-white star located some 85 light-years away. Regulus is located at the bottom tip of a noticeable pattern within Leo -- an "asterism" called The Sickle -- which appears on our sky's dome as a backwards question mark. In ancient skylore, this Sickle pattern represents the head and shoulders of Leo the Lion.

There is another bright star in The Sickle. It's Algieba, located about 110 light-years from Earth, known to stargazers with telescopes as a double star system. Both stars in the Algieba system are yellow giants. The distance between the two stars is about four light-hours, about the same distance as that between our sun and its planet Neptune.

Neptune orbits our sun in 165 years, however, while the two mighty suns in the Algieba system move through space more slowly. Estimates regarding the length of their mutual orbit vary from around 400 to around 600 years.

Also in the predawn sky, higher up in the horizon is the farthest of the five easily visible planets to the unaided eye, the planet Saturn. The other four are Mercury, Venus, Mars, and Jupiter.

I say "easily visible" because people who can see large stars in the sky can easily view them. The planet Uranus is theoretically visible to the naked eye...but it's never easy to see with the eye alone. Its certainly possible to see Uranus with the eye, but you need a very dark sky to do it.

Uranus reached its opposition at the beginning of this month, which makes right now a good time to try to see it. You can find Uranus, which is currently located in the constellation Aquarius, up in the southeast shortly after sunset.

poon cho tang SG

Thursday, September 29, 2005

Looking Northeast After Sunset

Cassiopeia the Queen can now be found high in the northeastern sky after sunset. This constellation has the distinct shape of a W, or M, depending on your perspective.

The stars of the queen are quite luminous -- its stars Schedar, Caph, and Gamma Cas all have approximately mid-second magnitudes. The star Ruchbach is close in brightness to them, with a magnitude of about 2.68. Segin trails the other stars on the famous M (or W) constellation shape in brightness with a third magnitude rating.

However, there is an intriguing star, often overlooked by skywatchers as it is not a part of the traditional letter-shaped part of the Queen. It is a fourth magnitude star, located slightly off the M (or W) between the alpha star Schedar and Gamma Cas. It's name is Eta Cas, and it is particularly of interest to astronomers because of its similarity to our sun. Eta Cas is similar in color, size, and temperature to our own sun. In fact, if we could somehow travel to Eta Cas (which is a relatively scant 19.4 light years away) and catch sight of our own sun, it would look very much like how Eta Cas looks in our skies now.

poon cho tang SG

Thurdsay, October 6, 2005

Looking Southwest After Sunset

This evening, turn your gaze towards the lower southwestern horizon and you will see our bright sister planet, Venus shining strongly against the evening twilight. If you look to the lower right of Venus, you will notice the slim sliver of the waxing crescent moon. Venus and the crescent moon will have only have three more such close encounters with each other during the rest of Venus current apparition in our evening skies. The next one will occur about a month from now on November 5th. Now, if you sweep your eyes to the left of the moon and Venus, you may catch sight of a smaller, but luminous reddish object. This little jewel is the star Antares, alpha star of the constellation Scorpius the Scorpion.

poon cho tang SG

Friday, October 7, 2005

Looking Southwest After Sunset

Today's chart is aimed southwest. The time is in early evening. At this time of night, the brightest objects in this part of the sky are the planet Venus and the star Antares in the constellation Scorpius the Scorpion. Tonight Antares appears very close to a thickening waxing crescent moon. Yesterday morning (or yesterday afternoon for those in the U.S.), Antares appeared so close to the moon, that in some locations across the globe (central Pacific Ocean, West Samoa, and the western tip of northern South America) the moon appeared to occult, or pass in front of the reddish star Antares. This morning occultation is pretty difficult to see, and perhaps should be left to seasoned astronomers. Those of us in all the other areas of the world, take heart -- Antares is occulted by the moon approximately once every 27 days throughout the rest of this year and on into the next. The best chance for those of us in North America to witness the moon occulting Antares will come up around the end of December this year.

poon cho tang SG

Captured on 7 Oct 05

The crescent moon and Venus in the western night sky

poon cho tang SG

Captured on 7 Oct 05

Close-up of the crescent moon and Venus in the western night sky

poon cho tang SG

Thursday, October 13, 2005

Looking Southeast Before Dawn

Tomorrow morning before the sunrise, the planet Saturn can be found above the southeastern horizon, along with a beautiful and prominent pattern of stars. The brightest star in the southeast before dawn is the greater Dog Star Sirius in the constellation Canis Major. Saturn is located to the left of Sirius in the predawn sky, along a graceful line that includes the first magnitude star Regulus, also known as the "Heart" of the constellation Leo the Lion, plus two stars noticeable because of their close placement to one another. These are the "twin" stars Castor and Pollux of the constellation Gemini. Almost directly to the right of Saturn is the lesser Dog Star Procyon from the constellation Canis Minor.

poon cho tang SG

Friday, October 14, 2005

Looking Southeast Before Dawn

You may recognize this pattern from yesterday's chart -- it is set at the same time and place in the sky. Today we wanted to point out the famous Beehive Cluster now located above Saturn. This star cluster is best seen in a very dark country sky (although it can be glimpsed with binoculars from the suburbs). In a dark sky, it appears as a fuzzy patch to the eye alone. A small telescope shows about 50 stars here, but astronomers know that the Beehive actually contains some 400 stars. The cluster is 15 light-years across, and is located about 500 light-years from Earth.

poon cho tang SG

Friday, October 14, 2005

Looking Overhead in the Northwest at Nightfall

We get many questions from people in northern latitudes about if and when they can view the Southern Cross asterism in their portion of the sky. The truth is that unless you live close to the equator (Hawaii, or the southernmost parts of Texas or Florida for those of us in the U.S.), you will not be able to view this famous asterism, also known as the constellation Crux. We in the northern half of the globe have its less renowned, but elegantly beautiful cousin rising high in our skies tonight. The star Deneb on today's chart identifies the top of the astronomical grouping called the Northern Cross. Unlike its southern counterpart, the Northern Cross asterism is a clipped version of another constellation Cygnus the Swan, which you can find high in the northwest at nightfall.

poon cho tang SG

Wednesday, October 19, 2005

Looking East-Northeast in Early Evening

Today, the moon has moved eastward in its path across the sky, as it always does. It's now less than one degree from the famous Pleiades star cluster. Wait a day or two as the moon moves on from the sky, and you can easily recognize this cluster as a tiny dipper shape. In fact, a lot of skywatchers comment on the fact that the Pleiades cluster looks more like a dipper than the Big Dipper. Most people see just six stars here, and, because this cluster is sometimes called The Seven Sisters, there's a persistent question in skylore about the whereabouts of the so-called Lost Pleiad. People with superior vision have been known to see more stars in the Pleiades with the naked eye -- up to 16 stars have been reported in recent centuries. Modern photographs show thousands of stars in this vicinity, but only about 250 of these are thought to be true, gravitationally bound members of the Pleiades star cluster.

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