Something's Missing from the Night Sky

Something's Missing from the Night Sky
by Dave Adalian

Something is missing from the night sky.

Looking north just after dark in December, stargazers will find the familiar Big Dipper of Ursa Major gone.

It hasn’t vanished. The well-known asterism is now at its lowest and most northerly for the year, so that it hangs partially hidden behind the horizon and the trees, buildings and mountains that obscure it. This is the season when whatever celestial liqueur it is that passes between these stellar vessels flows from the Little Dipper of Ursa Minor into its greater counterpart.

It may seem strange to think of the Dipper as anything other than itself, but these stars have almost as many names as there have been cultures of men gazing up at them.

It could be the low, late-autumn sweep--which sends the Dipper’s stars cutting into the earth--that prompts Britons to call the group of seven bright stars the Plow. Across the English Channel, the French call it the Saucepan.

Of course Greeks and Romans saw the Great Bear that gave us the name Ursa Major, but several other cultures around the ancient world did, too. Micmacs of North America see the four stars of the Dipper’s bowl as the feet of a bear that slowly circled the North Star. Iroquois imagine a group of hunters following a bear.

The Chumash of the Central Coast tell a story of seven boys who ran away from homes where they weren’t wanted and turned into geese, and Pawnee legend describes a sick man carried on a stretcher.

Many cultures have seen the Big Dipper as a wagon. Norse myth puts Thor at the reins, while Germanic legend says it belongs to his father Odin. Coming full circle, the Chinese version includes a horse-drawn wagon for the celestial emperor on the back of a bear.

While the Big Dipper is low after sunset, it rises quickly to stand on its handle by 10 o’clock. This happens earlier each night as we move into winter.

The middle five stars of the Dipper comprise an open cluster, all of them moving together through the galaxy. This cluster, at 75 light years to its nearest sun, may be the closest to Earth. Or not. Sol moves in nearly the same way, leading some astronomers to conclude we may be part of the cluster ourselves, our star forming from the same dust cloud as those of the Big Dipper.

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This column appeared originally in the Visalia (Calif.) Times-Delta in December 2004.

A Season of Long Nights

A Season of Long Nights
by Dave Adalian

As autumn ripens after the October rains and fog, a season of long nights begins. Day turns to evening during the dinner hour and skies darken early for digestive strolls spent wandering with the stars.

With no moon this week, nights will be dark and starry. Walkers will notice the Summer Triangle of Vega, Altair and Deneb still riding high in the west after sundown, while at the same time, the Great Square of Pegasus shines in the east. Already well up in the sky, by the end of the month the Square will be overhead just after dusk, a telltale of the coming of winter.

Alpheratz, the star marking the northeast corner of the Great Square, is actually the brightest in the constellation Andromeda. This willowy arrangement of stars represents a celestial princess awaiting rescue by Perseus, the Greek hero who slew Medusa. Not far to the northeast of Alpheratz, look closely to find the faint wisp of that is the Great Andromeda Galaxy, one of the Milky Way’s closest neighbors at only 2.9 million light years distant. It is the farthest object that can be seen by the unaided eye.

The constellation Perseus itself lies farther to the northeast of Andromeda, a riot of stars sitting just below the W of Andromeda’s mother Cassiopeia. Below it and to the right are the wonders of Taurus the Bull discussed here last month--the Pleiades, the Hyades and the bright red giant star Aldebaran.

The Moon returns to the early evening sky in mid-month, appearing briefly as a thin crescent in the southwest the nights of Nov. 15 and 16, when it will sit in Sagittarius.

Each month the Moon traipses through the Zodiac, rising earlier night to night and making the stars seem faint by comparison as it brightens. By Nov. 17 Luna is amid the dim stars of Capricornus, the Sea Goat. Two nights later it’s well into Aquarius, the Water Barer, and on Nov. 22 it swims with the fishes of Pisces.

By Nov. 24, the almost full Moon sits in Aries the Ram, a group of dim stars remembered because of its association with astrology. Aries’ three brightest stars, representing the ram’s horns of plenty, sit directly above the Moon this night before Thanksgiving.

The Moon is in Taurus when full two nights later, then finishes the month with the twins of Gemini, rising just after dark.

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This column appeared originally in the Visalia (Calif.) Times-Delta in November 2004.

Taurus Marks Return of Fall

Taurus Marks Return of Fall
by Dave Adalian

Astronomers mark the Valley’s slow decent into autumn not by the colors of the leaves and a drop in the mercury alone. They watch too for the return of Taurus the Bull to the night sky.

This compact constellation of the Zodiac rises in the east just after sunset during October, bringing a dazzling string of astronomical delights as it stampedes over the horizon.

First to rise is the Pleiades, those famous Seven Sisters the Japanese call Subaru. This compact group of stars--an open cluster some 380 light years distant--dazzles the eye with hot, white stars that shine and twinkle like diamonds through the Valley haze of walnut dust and cotton defoliant.

From the city the best one can hope to see are the six brightest stars of the Pleiades in a shape some people mistake for the much larger Little Dipper of Ursa Minor in the north. A dark night in the countryside will push that number to about nine, while getting above the smog will produce as many as a dozen for the naked eye when the Moon is new.

In total, the cluster contains some 500 stars, many of which can be seen in a backyard telescope.

Below the Sisters and rising about an hour later is Taurus’s less famous open cluster, the Hyades. This V-shaped cluster is perhaps the closest one to Earth at 150 light years distant. The Hyades, another group of sisters from Greek mythology who died from grief for their brother Hyas, represent the face of Taurus.

At the end of the eastern arm of the V is the bright red star Aldebaran, which marks the angry, bloodshot eye of the charging bull. While Aldebaran appears to be part of the Hyades cluster it is actually less than half the distance at just 60 light years.

Telescopes reveal another treasure of Taurus lost to those with unaided eyes. Rising after the Hyades comes the Crab Nebula, the remains of an exploded star that dazzled during the nights of 1054 A.D. The event was reported by Chinese astronomers, and natives of the American Southwest depicted it on canyon walls.

Taurus holds one last charm for those who scan the autumn night--a minor meteor shower. The Northern Taurids begin the second week of October and last through the start of December, displaying a handful of bright shooting stars every hour from between the horns of the bull.

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This column originally appeared in the Visalia (Calif.) Times-Delta in October 2004.

A Black Hole Sits at the Center

A Black Hole Sits at the Center
by Dave Adalian

A monster lurks at the center of our galaxy.

It carries mass 300 times greater than our Sun, dominates an area 250 million miles across and grabs everything that comes near. It never lets go.

This beast is properly known as a singularity, but most people just call it a black hole.

The name fits.

Black holes are areas of space from which nothing, once it enters, ever escapes. It is the stuff of nightmares. Don’t panic, though. This monster is 30,000 light years away and poses no problem here in the Milky Way’s suburbs.

Black holes are invisible, but we can detect them by their silhouettes. These one-way doors through the fabric of space-time start life as run-of-the-mill supernovae, those explosions that come at the end of large stars lives. What’s left after the star explodes then collapses, giving up the structure of normal matter and forming a super-dense star made up of particles called neutrons. A teaspoon’s worth of such a star would weigh more than all the cars, buses and trucks on Earth.

If the original star is large enough before it bursts into supernova--about 2.5 times the mass of Sol--the collapse continues past the neutron-star stage and the leftovers shrink to a single point with infinite mass yet no length, width or height--a black hole.

Singularities can’t be seen because not even light moves fast enough to overcome their pull. On Earth, anything moving faster than seven miles a minute, like a moon rocket, can leave the planet forever. Black holes’ gravity is so strong that even the speed of light--the fastest speed possible at 186,000 miles a second--is too slow to make a getaway.

While we can’t see a black hole for ourselves, we do know where to look if we could. That monster at the center of our galaxy, called Sagittarius A* (pronounced Sagittarius A Star), lies just off the end of the spout of the Teapot discussed here last month.

This month the Teapot sits due south on the horizon at nightfall. To find Sagittarius A*’s spot in the sky, follow the line from the star that marks the top of the Teapot’s body to the one that marks the tip of its spout. Continue that line about the same distance as the marker stars are apart, and there is the center of the galaxy and the lair of that ever hungry stellar beast.

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This column originally appeared in the Visalia (Calif.) Times-Delta on Sept. 2, 2004.

Meteor Showers Peaking

Meteor Showers Peaking
by Dave Adalian

"Reliable" is a word not usually associated with meteors, but that’s exactly how astronomers like to describe the Perseid meteor shower that peaks next week.

Conditions for meteor viewing should be just about perfect Wednesday night, Aug. 11, with a thin crescent of a Moon not rising until the wee hours. The actual peak of the shower will come about four hours after midnight on the morning of August 12, and midnight to dawn will give the best views. But, the Perseid shower’s peak is a wide one so beautiful displays may be available from dark skies as soon as the Sun has completely disappeared.

This peak is so wide many meteors are visible a night or two before and after the peak. Meteors from this shower began appearing in late July, so those eager to get started might even catch a handful tonight before moonrise.

Average counts for experienced meteor observers have been in the range of 60 meteors an hour for the Perseids during the hours between midnight and dawn on the night of the peak. Those who predict the intensity of meteor showers say this year might bring a higher rate since Jupiter has perturbed the stream of debris that causes the shower, pushing it closer to Earth.

As always, the darker the sky above, the better the viewing below, so the best places to observe meteor falls are in the countryside, foothills or mountains.

Brighter members of the shower will probably be visible even under city lights. So, too, will be several of the brighter constellations, including the Teapot of Sagittarius in the south and to its right the scorpion of Scorpius. Overhead is the bright star Vega in the constellation Lyra. Vega, along with Deneb and Altair, create the brilliant Summer Triangle.

North is the easily recognizable Big Dipper of Ursa Major and to its right the North Star marks the end of the Little Dipper’s handle. If city skies are dark enough all seven of the Little Dipper’s dim stars might be available to the naked eye.

To the Little Dipper’s right is the bright W asterism of the constellation Cassiopeia and below that is Perseus, the star-studded constellation for which the Perseid meteor shower is named. The point where the Perseids appear to originate is between these two constellations, and around this area is the best direction for Perseid hunters to gaze.

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This column appeared originally in the Visalia (Calif.) Times-Delta on Aug. 5, 2004.

Marvelous Milky Way

Marvelous Milky Way
by Dave Adalian

Cloudy nights are usually the bane of celestial sightseers but not always, not this time of year.
Recently a non-astronomer friend and I were stargazing from a dark site east of Exeter when he announced our session might be coming to an unplanned end.

“Look,” he said, pointing to the southeast, “some clouds are coming in.”

Instead of disagreeing, I pointed binoculars at the supposed storm front and let him have a look. He was quiet for a long time.

“What do you think?” I asked.

“That’s a lot of stars.”

My friend had discovered the Large Sagittarius Star Cloud, a hole in the dust that hides the bright edge-on view of our galaxy from Earth. What he was seeing that night were millions of stars in the Sagittarius Spiral Arm of the Milky Way.

As I mentioned last month, eight bright stars in the constellation Sagittarius form an asterism called the Teapot. It rides low in the southeast just after sunset, and the Moon can be used to find this stellar shape. On the night of July 27 the Moon sits to the right of the Teapot and the next night covers the Large Sagittarius Star Cloud.

It takes a moonless night far from town for finding the cloud that fooled my friend, but it’s worth the trip. This is especially true since the Large Sagittarius Star Cloud marks the gateway to one of the most beautiful stretches of night sky.

The cloud sits at one end of a white river of stars that cuts across the summer sky, Earth’s view of the Milky Way Galaxy. It’s easy to think of it as steam pouring from the Teapot’s spout.

The steam trails in wisps up and to the left of the Teapot. Besides the bright nebulas I listed last month, observers will also find the Small Sagittarius Star Cloud easily with the naked eye from a dark site. The smaller cloud is another hole through the dust.

Climbing along the trail of stars, are dark patches of dust and dozens of star clusters seen easily without optical aid. With binoculars, this trek is one of the sky’s best hunting grounds.

Before the trail ends at the other side of the sky, it meanders through another landmark of the summer sky, the Summer Triangle, a huge asterism formed in the east by the three bright stars Vega, Altair and Deneb.

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This column originally appeared in the Visalia (Calif.) Times-Delta on July 8, 2004.

Sibling of the Sun

Sibling of the Sun
by Dave Adalian

The Sun once had a big sister.

Sol’s sibling is long dead, but as it went it may have given Earth the gift of life.

According to evidence presented at Arizona State, the Sun and its satellites were born in a shock wave caused by radiation from a huge star.

When that giant sun sparked to life 4.6 billion years or so ago, intense ultraviolet light poured into the nebula surrounding it, compressing and ionizing its gas until smaller stars formed.

Radiation from the Sun’s giant relative blasted away anything that couldn’t withstand its force, leaving just the Sun and the proto-planetary disk from which our world and the rest of the Solar System eventually formed.

Huge stars burn bright and live short lives. Sol’s older and much bigger sister’s life came to a relatively quick end in a supernova, scouring surrounding star systems with heavy elements formed by the pressure of the explosion.

Some of these elements were necessary for life. Others were radioactive, and the ASU researchers think the heat could have been responsible for the amount of water on Earth today. Also, the way Sol’s sibling exploded and its distance effected the type of planets that eventually formed.

The stars born in the stellar nursery with Sol drifted apart until today our closest neighbor is 4.2 light years away; and it may not be related at all.

This amazing and beautiful process of star formation is pictured in the famous Hubble Space Telescope image of the “Pillars of God” in the Eagle Nebula.

You don’t need to rely on the Hubble to see these magnificent deep space stellar nurseries. A host of them, including the Eagle, are visible in the area in and around Sagittarius.

In late spring and early summer, Sagittarius rises in the southeast an hour or two after sunset, following the familiar hooking shape of Scorpius.

A few of the stars of Sagittarius form the Teapot, and the only easy naked-eye nebula, the Lagoon, sits directly above it. It can be found from a dark spot amid the star clouds of the Milky Way.

Binoculars will reveal several others, including the Eagle, the Trifid and the Omega nebulas, along with a host of star clusters and fields. The area is one of the most beautiful in the sky for small optics.

Telescopes best show these delicate star-forming regions, revealing detail not otherwise available.

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This column originally appeared in the Visalia (Calif.) Times-Delta on June 8, 2004.

Don't Take the Moon for Granted

Don't Take the Moon for Granted
by Dave Adalian

The Moon may be the most taken for granted object in the night sky.

It just sits there. Always has, always will.

Or will it?

Actually, the Moon is slowly moving away from Earth, but no need to panic. The rate of creep is just over one and a half inches a year. Since the Moon has an average distance from Earth of about 239,000 miles, it takes lots of years before those inch-and-a-halves make any difference.

Nice to know Luna’s not just sitting there.

It’s really pretty lively. The Moon moves closer and further from the Earth each month because its orbit is not perfectly round. These extremes--called apogee at the furthest and perigee at the closest--are noticeable in the Moon’s size and brightness, especially in photographs.

It’s also nice to know the Moon will never break free.

The complicated ballet of physical forces caused by the Moon’s orbit around the Earth is also making Earth turn more slowly as the Moon moves away. A similar effect between the Earth and Sun will eventually force the Moon back toward Earth.

If left alone long enough, the Moon would eventually move too close and be destroyed, however, the Sun will expand into a red giant star, swallowing Earth and Moon long before that can happen.

Earth hasn’t always had a moon. When Earth was very young, some four billion or more years ago, an object about half its current size struck it. According to this account, the Moon formed from the debris.

The Moon, at 2,000 miles wide, is by far the largest satellite in the Solar System compared to its parent body. Because of this similarity in size, Earth and the Moon are considered a two-planet system.

Research suggests the Moon was once much closer to the Earth and appeared much larger in the sky. Since then, it has drifted to its current spot and its spin has slowed so much the Moon turns only once every time it moves around the Earth and we see only a single side. The other remains forever hidden to the earthbound.

The most obvious change in the Moon are its phases, which are listed each day in this paper. The phases are a result of the changing relative positions of Earth, Moon and Sun. Try looking in on Luna every night through May and into June, witnessing her transformation as it happens.

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This column originally appeared in the Visalia (Calif.) Times-Delta on May 11, 2004.

Meteor Shower Coming

Meteor Shower Coming
by Dave Adalian

Though it didn’t get much press at the time, an astronomical record was broken a few weeks ago. On March 18, asteroid 2004 FH missed us, whizzing by just 26,500 miles away, about three and a half times Earth’s width, and coming closer than any other recorded pass.

Whew!

Asteroid 2004 FH was just a little guy--only about 100 feet across--technically a meteoroid, if a very large one. Had it struck home, it likely would have exploded in the atmosphere, breaking windows and knocking pictures off the walls or more probably making lots of waves in some remote corner of the ocean.

But, it would have been one heck of a sight.

The difficult part about observing meteors is knowing when they’re going to arrive. They just aren’t reliable most of the time. This year, however, is going to be better than average for seekers of shooting stars.

Almost all of the major showers in 2004 will be free of moonlight, making even the dimmest meteors stand out when viewed from a properly dark environment. The excitement gets underway this month.

The Lyrids meteor shower peaks at 10-15 meteors an hour around 9 o’clock on the evening of April 21. Adding to the show will be another 10-15 sporadic meteors or so every hour streaking randomly across the sky.

Observing meteors is a wonderful way to get into astronomy since it requires no expensive optical equipment. It does, however, require some preparation. The smart shooting-stargazer will dress warmly for a long night under the stars. It’s also best to have a jug of hot coffee and snacks standing ready.

Of equal importance is posture. Sitting up or standing just won’t cut it. After a short time of bending the neck skyward fatigue sets in, so meteor watching is best done from a reclined position in a low-slung chair or lounge.

Showers are named after the constellation from which the meteors appear to come. To make the most of the show viewers should be sure they can see the spot the meteors are coming from and the zenith, the spot that marks the top of the sky.

For April’s Lyrids, that means pointing your toes toward the northeast.

Here is a list of other best bets for meteor watching in 2004:

• The Ophiucids, June 20
• The Perseids, August 11
• The Orionids, October 18-25
• The Leonids, November 16
• The Geminids, December 13

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This column originally appeared in the Visalia (Calif.) Times-Delta on April 6, 2004.

Catch Mercury at Sunset

Catch Mercury at Sunset
by Dave Adalian

Of the nine planets in our Solar System, only five are easily visible to the naked eye. This month, those with keen vision may see them all in a single evening.

The hardest to locate of the five wanderers--the Greek root of “planet” means “one who wanders” as the planets do when they slide among the stars from night to night--is swift-footed Mercury, messenger of the Gods.

Mercury is difficult because it rides so close in the sky to the Sun. During the last half of March, however, it will follow far enough behind the sunset to let those who try catch a fleeting glimpse.

The lucky can see Mercury anytime during the last 10 days of March or first few days of April, riding low in the gloaming of the western sky around 6:30 p.m. The job is made easier the evening of Monday, March 22, when a brand new crescent Moon sits above Mercury and to its left. It may even offer a little color to the eye.

Much easier to find--almost impossible to miss--is bright Venus. As I described last month, Venus is still scintillating in the high western sky just after sundown, outshining all other heavenly bodies but Moon and Sun.

The still young crescent Moon will slide past Venus the evening of March 24 in a breathtaking close pairing. Even the cheapest of binoculars will make the sight spectacular.

Just above Venus are the Seven Sisters, a familiar cluster of bright stars known as the Pleiades. Beside them is a single dim point of red light, all that remains of the brilliant Mars of last summer. Mars is now so far diminished its details are lost even in the telescope.

Saturn, on the other hand, it still at its best for viewing with or without optical aid. It sits almost at the top of the sky when darkness settles in, resting between the stars of Orion and the bright twins of Gemini, Castor and Pollux. In a telescope, its vaguely yellow color becomes a beautiful tawny golden, its rings open wide and its moons surround it.

Also astonishing when seen in the telescope is Jupiter, king of the planets. Magnified, Jupiter becomes a striped disk of swirling colors surrounded by its bright moons and sometimes highlighted by the Great Red Spot. It can be found rising in the east with the constellation Leo.

Clear skies!

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This column originally appeared in the Visalia (Calif.) Times-Delta on March 9, 2004.

Love Lingers on Horizon

Love Lingers on Horizon
by Dave Adalian

Those looking for love on Valentine’s Day will have an easy job of it--all they need do is turn to the west at sunset.

What they’ll find there is the brightest of the nine planets, Venus, blazing boldly in white as the Evening Star, outshining everything else in the sky but Sun and Moon.

To the Romans, Venus was the goddess of love, presiding over affairs of the heart. It is her blindfolded son, Cupid, with his bow and arrow who is responsible for so much joy and sorrow here on Earth; “Cupid” comes from the Latin cupido, which translates as “desire.”

While Venus is already a spectacular sight during the three hours after dusk, she’s still only warming up. She’ll continue to climb a little higher in the western sky each night until March 28, when she reaches greatest eastern elongation.

Though no farther away from the Sun that day than any other time during her 225-day orbit--the roundest one in our Solar System--Venus will then appear as far from the Sun as she can, as seen from Earth.

Earth and Venus are almost twins in size. Venus is 202 miles thinner at the waist than Earth, but carries only 85 percent as much mass. This may be due to losing her water into space.

Besides being drier than any desert on Earth, Venus is absolutely hellish. At the surface, the pressure of her carbon dioxide atmosphere is equal to being six-tenths of a mile underwater, and the sky is covered perpetually beneath clouds of sulfuric acid.

Those clouds have started a runaway greenhouse effect on Venus, raising temperatures to nearly 900 degrees--easily hot enough to melt lead.

Cloud cover also causes Venus to shine so brightly. The miles-thick layers of sulfuric acid clouds are extremely reflective, bouncing back most of the sunlight that strikes them.

Because Venus orbits closer to the Sun than Earth, she appears to us to go through phases like the Moon. Now, she looks through a telescope to be slightly pregnant. As March 28 approaches, Venus will slim to last quarter. In weeks following, she’ll diminish to a sliver as she slips deeper into twilight each night.

Some, myself included, claim to have seen the shape of Venus with naked eyes. A good night to try this may be Feb. 23 when Venus shares the sky with a thin crescent of new Moon.

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This column originally appeared in the Visalia (Calif.) Times-Delta on Feb. 10 , 2004.

Giant Looms at Night

Giant Looms at Night
by Dave Adalian

An ancient giant dwells in winter’s night sky, a creature old as myth.

As long as man has recognized this nocturnal titan in the stars we have called him The Hunter. Ancient Greeks first gave him the name we use today--Orion, literally “mountain man.” Even then he was already older than the hills.

Sumerian and Babylonian legends call the giant Enkidu, a tamed wild-man companion of fabled Gilgamesh. Doubtless the myth carries back to a time the stars of Orion marked a stone-age hunter-god whose name is now long forgotten.

This month Orion dominates the sky deep into the night. Already above the eastern horizon by sunset, the Hunter sits high, directly southeast by half past seven.

Stargazers easily recognize the constellation’s lopsided rectangle of bright stars. It surrounds a short line of three brilliant, white suns--the Belt of Orion. Together they form a butterfly or bow-tie shape.

Most striking of Orion’s suns is famous Betelgeuse, the bright red-giant that marks the Hunter’s eastern shoulder. At the western shoulder shines Bellatrix, and diagonally across from it Saiph shows as the western foot.

Orion’s other foot is the white jewel Rigel. Draw an imaginary line from Rigel through Betelgeuse and it goes through the dim stars of Orion’s raised club in his right hand before passing beside Saturn in nearby Gemini.

A long arc of dim stars west of Bellatrix shields Orion from Taurus the Bull. The bull stands between him and the object of his desire, Merope, brightest of the Seven Sisters in the Pleiades.

Another imaginary line drawn through Orion’s Belt from west to east passes next to Sirius. This brilliant white diamond at the shoulder of Canis Major shines brightest of all the stars seen from Earth.

Another cluster of what looks like three stars in a row lies just south of the belt. Faint fuzziness around the middle star betrays its true form: this is the Great Orion Nebula. Visible even to the naked eye, in the telescope it becomes a specter with writhing tendrils edged by hints of green and red. It is a wonder in binoculars, too.

Orion reaches his highest near ten o’clock and stands due south. From there he drops into the west to set in the cold, still hours before dawn. As he does, Scorpius, his mortal enemy who may never share Orion’s sky, rises in the east just before the Sun.

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This column originally appeared in the Visalia (Calif.) Times-Delta on Jan. 13, 2004.