Thursday, December 22, 2005

Long Nights full of Planets

Long Nights full of Planets
by Dave Adalian

For the price of a little midnight oil, along with some luck and a bit of persistence, the naked-eye planets can all be viewed in a single night this week. But, you’ll have to move quickly and be eagle-eyed.

The easiest of the nighttime wanderers to find is Earth’s sister planet, bright Venus, which, like Earth, is about 8,000 miles wide. Even though Venus now appears as the wisp of crescent through a telescope it shines brilliantly as the Evening Star low in the southwest before it chases the Sun over the horizon.

Far more difficult to find is 30,000-mile-wide Uranus, the dimmest of the naked-eye planets. It too is in the southwest just after sunset, in the constellation Aquarius, but unless you know exactly where to look you’ll likely miss it. You’ll also need a very dark viewing spot well away from city lights.

While Uranus, the father of the Titans, can be seen without optical aid, your best bet is to look for him with binoculars on the night of Tuesday, Jan. 3, when he’ll be just a degree or so northwest of the new moon. His methane-rich atmosphere will make him look like a bluish star.

Far easier to find is bright and ruddy, 4,000-mile-wide Mars. The God of War sits high in the sky just after sundown, almost straight overhead. He’ll make his way slowly across the sky as the night moves on, finally setting in the early morning hours.

Mars will remain a prominent feature of the night for many month yet, not passing from the sky until spring turns to summer.

Just now making his move into the evening sky is golden Saturn, the 74,000-mile-wide ringed planet. He rises about 8 p.m. in the constellation Cancer and takes the entire night to cross the sky, setting in the hour after dawn.

West of Saturn is a ghostly naked-eye star cluster known as the Beehive.

Rising at about 3 a.m. is 88,000-mile-wide Jupiter, King of the Gods. This bright gas giant planet with its bands of red and swirling storms is directly southwest as dawn begins.

Minutes before the Sun rises the last of the naked-eye planets appears. Swift 3,000-mile-wide Mercury hovers just above the horizon as the sky begins to brighten, heralding the return of daylight. By the end of the week fleet-footed Mercury will be impossible to find as it fades back into the glare of the Sun.


This column appeared originally in the Visalia (Calif.) Times-Delta on Dec. 22, 2005.

Thursday, November 24, 2005

A Story in the Stars

A Story in the Stars
by Dave Adalian

High in the northern sky this time of year hangs the bright constellation Cassiopeia, the Seated Queen, and with her a tale of love, vanity, monsters and heroism that is as old as western civilization.

Vain Cassiopeia ruled ancient Aethiopia with her husband, King Cepheus. She was indeed lovely and bragged she was even more beautiful than the Nereids, companions of the sea god Poseidon. As punishment, Poseidon sent a terrible monster, Cetus, to wreak his vengeance upon the land.

King Cepheus consulted the oracle for a divine solution and was told he must sacrifice his daughter Andromeda to Poseidon to end the terror. So, at the king’s orders Andromeda was chained to the rocks at the edge of sea to die.

But death did not come to the maiden.

The hero Perseus was returning home after slaying Medusa, whose snake-haired head could turn men to stone. Flying through the sky on the winged sandals of Hermes, god of the underworld, Perseus spied Andromeda below and instantly fell in love. He swooped to her rescue and slew Cetus, saving both the girl and her land.

With Aethiopia secure, all was well, except for Cassiopeia. As punishment for her vanity and the trouble it caused she was doomed by the gods to ride forever in circles about the North Star, spending half the year dangling in embarrassment from her throne.

Cassiopeia’s bright stars form an obvious W-shape during warmer months. But on the longer nights of fall and winter the queen sits upside down, tied in her chair to keep from falling, and the W becomes an M above the North Star at about 8 p.m.

Cepheus’ faint constellation lies between the North Star and Cassiopeia, and Cetus, another dim group, is opposite Cepheus in the sky, far south with only a single bright star, Diphda.

Andromeda’s constellation and the bright and misty naked-eye galaxy that bears her name sit directly overhead around 8 o’clock during autumn nights. Perhaps her galaxy reminded the ancients of spindrift blown up from the waves that crashed around her feet as she awaited her terrible fate.

Perseus, holding Medusa’s head, is a starry constellation east of Cassiopeia. Medusa was also mother of Pegasus the winged horse, and his constellation and its Great Square shine west of Andromeda. West of Pegasus is the tiny Equuleus the Horse, which some say shows Chrysaor, earthbound brother of the flying horse.


This column appeared originally in the Visalia (Calif.) Times-Delta on Nov. 24, 2005.

Wednesday, October 12, 2005

Real Deal on Mars

Real Deal on Mars
by Dave Adalian

If you were hoping to see Mars appear the size of a full moon last August, as a widely circulated hoax email suggested it would, no doubt you were very much disappointed.

Some prankster decided for reasons known only to himself to twist information about the close pass of Mars back in 2003 to make it sound as though the Red Planet would make an impossibly close pass by Earth this summer.

Thankfully, it didn’t happen. Had Mars come close as that hoax email described, the resulting disruption to Earth would have spelled disaster.

The real facts are these: Back in August 2003, Mars came closer to Earth than it has during recorded human history, about 34.6 million miles. For those lucky enough to get a look at the God of War through a telescope at 100X magnification during that close approach, its disk appeared the same relative size as a full moon does when viewed with the naked eye.

As I said in this space during summer of 2003, in a scope Mars looked like a pea in a Petri dish, although a beautiful one with reddish planes, dark surface features and clouds obscuring the southern pole -- in other words, like an alien planet that we still cannot be sure doesn’t harbor life of some kind.

If you missed it during summer 2003, it won’t be as close again until 2287. It really was a once-in-a-lifetime experience and a spectacular one at that.

But life is as full of second chances as it is once-in-a-lifetime opportunities.

Mars is coming in for another close pass this month, one of 40.3 million miles, a mere 4.3 million miles further away than in 2003. Bumping up the magnification to about 125X will give that full-moon effect once more. And, yes, it will be a breathtaking sight to behold.

Opposition, when Mars rises at sunset, will happen on Nov. 7, but the closest pass will come two nights before Halloween, when a pumpkin-colored Mars will rise about 6:30 to fly high in the east and come closest at about 8:25 p.m. It will be shining high and bright still when trick-o’-treaters take to the streets on Halloween.

Tonight, Mars is in the east over the trees by about 9 o’clock. If you watch night by night, you’ll see it rise earlier and double in brightness by October’s end as autumn’s warmth fails.


Join the Tulare Astronomical Association Friday, Oct. 21, 8-10 p.m., for a close-up look at the Angry Red Planet at the Arthur L. Purcell Observatory, 9242 Ave. 184, 2.1 miles west of Highway 99. Information and directions:

Friday, September 23, 2005

Clouds Win Again

Sorry, folks, but the satellite images show that this cloud cover over Central California is probably going to last most of the night, so there goes the star party. We'll try again on Friday, Oct. 21. See you then!

Monday, September 19, 2005

Return of the Long Nights

Return of the Long Nights
by Dave Adalian

Summer is taking an early departure this year, folding away her brown mantle and allowing the cool days and chill nights of autumn to come quickly as the leaves begin to fall.

This is fitting as (on Sept. 22, 2005) at 2:23 p.m. PDT the Sun crosses south of the celestial equator, reaching equinox and marking the moment when autumn begins and the days shorten while nights grow long and cold.

When the Sun sets this evening, it will fall directly west and rise again tomorrow due east, silhouetting the crags of the Sierra Nevada. Though the periods of light and dark won’t be perfectly equal as the Latin term equinox implies, the time between sunset tonight when half the Sun’s disk is below the horizon and sunrise tomorrow when half the disk is above the horizon will be just eight minutes shy of 12 hours.

The equinox is the moment when the Sun crosses the dividing line that splits the sky into two equal northern and southern halves, creating some special effects here on Earth.

At the equator on the days of the March and September equinoxes, the Sun not only rises and sets at the points of true east and west, it also passes directly overhead when it reaches its highest point in the sky, something it never does at more northern or southern latitudes.

At the poles, the effect is far more dramatic.

At the North Pole, the September equinox signals a plunge into six months of darkness, with the Sun dropping below the horizon not to be seen again until the end of March.

On the bottom of the planet, the effect is reversed, with the Sun finally returning to the sky for six uninterrupted months of daylight. Instead of rising and falling as it does elsewhere, during the months-long period of day the Sun skims along the icy horizon, climbing higher in the sky as the solstice approaches.

Were it not for the killing cold of the arctic winter, the North Pole would be a Moon-lover’s delight. During the six-month darkness, the Moon rises above the horizon not to set again for two weeks. The Moon moves through its cycle in unashamed plain sight before dipping again below the horizon for a fortnight’s absence.

Late Sept. 21 and 22 here at home, the Moon will put on a beautiful display in the east, joining the Seven Sisters of the Pleiades, the V-shape of the Hyades and a bright and ruddy Mars.


Join the Tulare Astronomical Association for a public star party this Friday, Sept. 23, 8:30-10:30 p.m. at the Arthur L. Purcell Observatory, 9242 Ave. 184, south of Tulare and 2.1 miles west of Highway 198.

Friday, September 09, 2005

Deep Impact Reveals Comet's Secrets

The first findings from the Deep Impact collision with Comet Tempel 1 back in early July have been announced and the mission's results are going to change the way astronomers think about comets in a lot of ways. We've assumed comets were dirty snowballs, but it's looking more like they're icy dirt balls made mostly of powder and have the consistency of a soufflé, so don't slam the oven door or your comet may collapse.

Here's a great article on the findings from Science News.

Tuesday, September 06, 2005

Soak In Some Earthshine

When a very slim crescent moon joins Jupiter, Venus and Spica on the western horizon tonight just after sunset, be sure to look for the Earthshine, too.

The Sun is the only source of bright light in our solar system. All the light coming from the planets and their moons is just a reflection of our home star. When the Moon is only a couple of days past its new phase it presents a large dark limb, and the light that makes that dark limb visible is Earthshine, light from the Sun that strikes the Earth, reflects back to the dark portion of the Moon and then shines back on the Earth.

Monday, September 05, 2005

Venus and the Virgin

The sky show continues tonight on the western horizon after sunset with Spica, the alpha star of Virgo the Virgin, shining less than two degrees southwest (down and to the left) of Venus. Jupiter is about four degrees to the right. For those with a clear view to the west, a very young new moon is just above the horizon and will set by about a quarter after 8 o'clock local time. The Moon will be right in the midst of this grouping tomorrow night 30-45 minutes after the Sun goes down.

Sunday, September 04, 2005

One Hundred Billion Failed Stars

For every star shining in our galaxy there's another one that didn't make it. Astronomers at Arizona State University working from Hubble Space Telescope infrared data have discovered the Milky Way has as many brown dwarf bodies as it does stars -- 100,000,000,000 of them and every one without enough mass to begin nuclear fusion, the process that makes the stars shine. These dark bodies weigh anywhere between 13 to 75 times as much as Jupiter, so their combined mass isn't enough to account for all of the galaxy's so-called missing matter by a long shot.

Here's's article announcing the discovery.

Monday, August 29, 2005

Look to the West

Don't forget the meeting of Jupiter and Venus. Look due west 30 minutes after sundown to see these bright planets converge. They'll come closest to one another Thursday, Sept. 1, when they'll be about 1.2 degrees apart, just more than twice the width of a full moon or about the width of your pinkie finger when held at arm's length.

Click here for my earlier, more detailed post about this conjunction.

Saturday, August 27, 2005

CalStar Party at Lake San Antonio

Lake San Antonio is a great dark-sky location and CalStar is a well-attended party attracting observers from all over the state. The 2005 CalStar, hosted by the San Jose Astronomical Association, will be held Sept. 29-Oct. 1 at Lake San Antonio, 25 miles east of Paso Robles.

Details are here:

Wednesday, August 24, 2005

Mars NOT Looming Large

If you expect to see Mars swelled to the size of a full moon on Saturday, Aug. 27, 2005, you've probably been the victim of a cruel hoax. Someone, for reasons known only to himself, decided to pull a prank on all the would-be planet-gazers out there by sending around an email describing a closer-than-ever pass of Earth by the Red Planet.

It's not going to happen, at least not again.

Most of the information in this fatuous email is very near the truth about the close approach of Mars back in summer 2003. Mars did come closer to Earth than it has in 60,000 years and it did appear the size of a full moon, but only if you viewed it magnified by 100 times in a quality telescope. I wrote a column about it at the time, which you can read here.

The good news for those who'd like a gander at the God of War is he'll be making a bright appearance at the end of October and beginning of November. Watch this space as details will come as the date approaches. In the meantime, Mars is coming up in the east about 11 p.m. your local time, and over the month of September it will double its brightness, which is a great reason to start watching now.

Monday, August 22, 2005

Hubble Scanning Moon for Base Sites

I know this is meant to be an astronomy blog, but I find this so cool I have to post it. The Hubble Space Telescope is being used to look for lunar base locations. I'll be packing my bags! Here's the story as told in New Scientist magazine.

Saturday, August 20, 2005

Wanna See Something Beautiful?

Go out and look west tonight just after sunset and you'll see two extremely bright "stars" down near the horizon. These are really Jupiter, king of the gods, and his daughter Venus, goddess of love. Venus is the one on the lower right and Jupiter is up to the left.

Over the next two weeks they are going grow closer until they reach their closest on the nights of Wednesday, Aug. 31 and Thursday, Sept. 1. Keep watching as they part ways because on Tuesday, Sept. 6, they're going to be joined by a very slender sliver of a moon. Make sure to look for earthshine in the Moon's darkened limb that night.

Venus and Jupiter will be easiest to find about 30-45 minutes after sunset. If you have trouble finding planets, here's a Quicktime video of this conjunction from that may help.

Friday, August 19, 2005

Full Green Corn Moon

The Moon is full today, Friday, Aug. 19. Because this is the month before harvest begins in many areas, this full moon is sometimes known as the Green Corn Moon or the Grain Moon. It's also the Full Sturgeon Moon, this being the season when that fish is most easily caught. (But don't ask me why--damn it, Jim, I'm an astronomer not a ichthyologist!) You'll find the names of each month's full moon here:

Sunday, August 14, 2005

The Strolling Astronomer

The Strolling Astronomer
by Dave Adalian

During summer I take my walks after the Sun is down, when my family's gone to bed and the heat of the day has faded. I stroll among the stars, hoping for the thrill of a meteor and making sure those points of light are still fixed to their places.

My front door faces east, and as August fades the Great Square of Pegasus, part of the winged horse’s constellation, hovers above my neighbor’s rooftop. Later the Square will rise high into the night sky, trailing Pisces the Fish behind, but early on it sits on its eastern point, a huge diamond-shape of stars.

Right of Pegasus’ Square are the dim, indistinct zodiacal constellations of Aquarius the Water Bearer and Capricornus the Sea Goat. This seemingly empty ocean of sky has a single bright star, lonely Fomalhaut in Pisces Austrinus, the southern fish, hanging over the southeast horizon, bobbing above the houses as I lope along.

Beyond this barren portion of the night is Sagittarius the Archer with his famous Teapot asterism and to his right the long, barbed hook of Scorpius the Scorpion, home of the red supergiant star Antares. Despite the city lights, I can still sometimes see the Milky Way rising like steam from the Teapot’s spout to trail beside huge Ophiuchus, the snake-handler, whose healing power defied death itself until Zeus immortalized him in the sky.

Walking west, I see the orange star Arcturus shimmering in the heavy air marking Boötes the Plowman, and above it is a half-circle of stars, Corona Borealis, the Northern Crown. Higher still is brave Hercules, club at the ready.

As I march along, I catch glimpses of the Big Dipper in Ursa Major among the trees and housetops northwest, and due north is always faithful Polaris, the North Star, in the Little Dipper in Ursa Minor. When I finally turn back toward home again there is the W-shape of Cassiopeia the Queen standing on edge in the northeast, and below her the hero Perseus defending Andromeda, the Chained Lady, who lends her brightest star to Pegasus as the northernmost corner of his Square.

I arrive back at my doorstep and crane my neck to look straight overhead for the Summer Triangle: Altair in Aquila the Eagle, white Vega in Lyra the Lyre and Deneb marking the tail of Cygnus the Swan. Then I quietly steal inside, careful not to awake those who lie sleeping.


This column appeared originally in the Visalia (Calif.) Times-Delta on Aug. 25, 2005.

Friday, August 12, 2005

And Still More Perseids

I woke up at a quarter past three and came back outside where I stayed until about a quarter after four, lying under a blanket on the diving board at the north end of the yard where the light is least. I spotted another 25 Perseids and three more meteors from other sources, including two that seemed to come from the direction of Aquarius, home to a minor shower or two this month. What a beautiful night of viewing, especially considering I was able to do it from my own backyard.

Perseids Watch

I did a short Perseid meteor watch from my backyard tonight starting at about 12:40 and going until just before 2 a.m. I saw 22 Perseids, some of them very bright and beautiful, and about five sporadic meteors. I'm going to get some sleep now, but I may come back for another look in about 90 minutes.

Saturday, August 06, 2005

Astronomy TV Online

Here are a couple of astronomy-oriented television programs available via the web:

First, here's Jack Horkheimer's Star Gazer, a series of one- and five-minute programs on the week's astronomical highlights. And, second, the venerable The Sky at Night hosted by Sir Patrick Moore.

Friday, August 05, 2005

Getting to the Purcell Observatory

Getting to the Arthur L. Purcell Observatory is very simple in broad daylight, but can be a bit tricky in the dark.

Take Highway 99 south past Tulare to the Avenue 184 exit. Turn left onto Avenue 184 and drive west approximately 2.1 miles. To do this you'll have to go through the intersection of 184 and Road 96; the observatory is about half a mile past the intersection on the right-hand (north) side of the road, so keep an eye on your odometer.

We have a sign for the observatory at end of the driveway, but it sits slightly off the road and is not lighted. The driveway leads to our parking lot, and the observing is done in our courtyard just beyond.

If you're not comfortable walking in darkness, a flashlight with a red filter will help, but please do not use unshielded lighting once you have left the parking lot.

This interactive Google map can provide driving directions from any location in Tulare County.

Thursday, August 04, 2005

Welcome to Starry Nights!


This is the new online home of my astronomy column, Starry Nights, published monthly in the Visalia (Calif.) Times-Delta. Besides posting my columns both old and new, I'll be including interesting astronomy-related news and links, as well as announcements of the Tulare Astronomical Association's monthly star parties.

Thursday, July 28, 2005

Comet Dust Drives Summer Shower

Comet Dust Drives Summer Shower
by Dave Adalian

(July 28, 2005) Anyone who attempted to observe Comet Tempel 1 earlier this month when NASA’s Deep Impact probe slammed it with an 814-pound copper bullet moving at 6.3 miles a second knows first-hand comets are an unpredictable lot.

Hopes were high this visitor from the outer reaches of the Solar System would brighten from an almost undetectable smudge in small telescopes to a naked-eye delight. The mission succeeded, but the brightening didn’t happen.

Fortunately, next month holds good promise of a sort for would-be comet observers.

August, as seasoned meteor observers know, is time for the year’s most reliable meteor sky show. The Perseids began lighting the night sky early this week and continue until late August with the peak expected to produce between 40-80 meteors an hour on the night of Aug. 11-12 and perhaps again on Aug. 12-13. Meteors from other minor showers will add 15-20 an hour.

Perseus, the constellation from which the Perseids stream, rises in the northeast around 10 o’clock. The best meteor viewing is after moonset--around 11 the first night and nearer midnight the next--until dawn. The darker sky you find yourself under, the better the viewing will be.

What does this have to do with comets? The Perseids are tiny pieces of Comet Swift-Tuttle.

Meteors aren’t really stars falling from the sky. Instead, they are bits that have broken off of other bodies--usually ice and dust the consistency of ash or more rarely solid rock--colliding with Earth’s atmosphere at several thousand miles an hour, ionizing the air and producing that magical glow.

Comet Swift-Tuttle is a periodic comet, returning again and again to swing around the Sun before heading off to the dark and frozen outskirts of our star system on a 135-year circuit. While Swift-Tuttle was first discovered in 1862, the shower it produces is known throughout history. During the 11th century, astronomers in China recorded an intense display, and Perseids are sometimes called St. Lawrence’s Tears to honor his martyrdom in coincidence with the shower of 258.

Swift-Tuttle returned most recently in 1992, freshening its trail of debris significantly as the Sun’s gravity drew the comet in, warming its surface and causing it to shed potential meteors. Therein lies this comet’s uncertainty. This year Earth enters the 1992 debris stream for the first time, and the usual rates of 40-80 meteors an hour on nights near the shower’s peak could be far higher than normal.

Or maybe not... We’ll just have to see.


This column originally appeared in the Visalia (Calif.) Times-Delta on July 28, 2005.

Thursday, June 23, 2005

When Worlds Collide

When Worlds Collide
by Dave Adalian

The cusp of June into July is going to be a planet-hunter’s delight this year.

Eighty-eight-thousand-mile-wide Jupiter continues to reign over the southern sky, shining high after sunset. Ruddy Mars, as it moves toward another close pass by Earth in mid-November, is coming up in the east for night owls at around 1:30 a.m., just as Jupiter is retiring on the opposite horizon.

The three outer planets--Uranus, Neptune and Pluto--are all available to those with telescopes during various times through the shortened dark hours of early summer. From an unpolluted sky, those who know exactly where to look, perhaps by using an online guide such as, can see blue-green Uranus with the naked eye.

The real show, however, is in the west just after the Sun reaches the horizon.

Those who followed the progress of Saturn this year as it hovered in the constellation Gemini know it is coming to the end of its 2005 appearance. As June closes, Saturn is only visible for a short time before it follows the Sun and slips below the western horizon.

Already Saturn is almost lost in the afterglow of twilight and hard to see until at least 30 minutes after the Sun is gone. Look tonight around 9 o’clock to see that Saturn has a bright companion, Venus, sitting very close by and outshining it.

In fact, brilliant Venus sits at the center of a trio of planets, with Saturn to her left and speedy Mercury on the right. Together the three span only three degrees, just six full-Moon widths.

Friday the trio is even tighter, sharing just two degrees of sky, and the group will be its tightest on Saturday when Saturn, Venus and Mercury are just one and a half degrees apart with the ringed planet below the two innermost planets of our star system.

While they sit close compare the pink of Mercury, blue-white Venus and yellow Saturn. Notice too how the trio sits undisturbed in the sky while around them stars shimmer in the gloaming.

Keen-eyed observers noticed Mercury rising to meet Venus while the planetary trio gathered. Mercury moves closer still the next two nights as Saturn retreats until on Monday the two are less than one tenth of a degree apart, so close they may appear to the eye as a single point of light. The merger is a once-in-a-lifetime event, not happening again until 2070.


This column appeared originally in the Visalia (Calif.) Times-Delta on June 23, 2005.

Thursday, May 26, 2005

Hopping through the Sky

Hopping through the Sky
by Dave Adalian

Anyone who’s ever looked up at night has noticed a problem facing astronomers: there are a lot of stars up there, and it’s easy to get lost in space.

That’s one of the reasons we have constellations, to help us fix in our minds the location of the wonders of the night. Still, knowing where to find a constellation only gives us the general location of whole groups of stars, some of them very large. How does anyone find anything among all those points of light?

They hop to it.

Star-hopping is an age-old and easy technique. Start by finding a bright star or well known constellation and connect the dots to find the target.

The best known star-hop is the Arc to Arcturus. It starts with one of the better known constellations in the sky, Ursa Major, the Big Bear.

The most recognized star shape in the sky, the Big Dipper, lies in the Ursa Major. Find it by looking due north just after sundown. As spring wraps up, the Big Dipper pours its contents onto the North Star and its tail points up and toward the east.

Follow the arc along the three bright handle stars about the same distance as the length of the Dipper to come to the first stop, the orange giant star Arcturus.

Arcturus is the brightest star in cone-shaped Boötes (boo-OH-tes), the Herdsman, and the fourth brightest seen from Earth. It’s 20 times larger than the Sun and shines 115 times brighter from 37 light years away. Arcturus is so bright in the infrared we can measure its heat here on Earth--the same as a candle flame five miles away.

Arcturus is one of the fastest stars, traveling at 90 miles a second toward Virgo, the second stop on this star-hop. If you “speed” along the arc past Arcturus, you’ll soon come to first-magnitude Spica, Virgo’s brightest star. Like Arcturus, Spica is brighter than the Sun, 13,400 times so, and masses 11 times more, but it sits 260 light years away.

Continue the arc again to reach our final stop, Corvus the Crow, an irregular box of four stars that is normally not a big attraction. Currently, however, it’s pointing its beak towards Jupiter, which sits directly above the Crow.

Astronomers have an alliterative phrase to remember this popular hop: “Arc to Arcturus, speed on to Spica and continue on to Corvus.”

Enjoy the ride!


This column appeared originally in the Visalia (Calif.) Times-Delta on May 26, 2005.

Friday, April 15, 2005

Moon to Hide Supergiant

Moon to Hide Supergiant
by Dave Adalian

A fat full Moon is usually a problem for astronomers, its bright, white light washing fainter objects from the sky. Other times, it’s the star of the show, as it will be the night of May 23-24 when the Moon occults the red supergiant star Antares.

Occultation is a body blocking the view of another more distant body, and a few minutes before midnight on May 23 the Moon will do just that to the ruddy star at the heart of Scorpius. The show, however, starts at sunset.

In Arabic, Antares is called Kalb al Akrab, heart of the scorpion, and staying true to this metaphor, early Muslims named two bright nearby stars Al Niyat, the arteries. The brighter of the two artery stars, Al Niyat (Sigma), will be behind the Moon when it rises. Stargazers with access to a very clear horizon will see this third-magnitude star reemerge from behind the lunar disk at about 8:48.

About then Antares will become visible above the horizon, one and a half degrees or so below the Moon. As the Moon travels west across the sky, it moves east through against the starry background at about half a degree or one full-Moon width an hour, edging ever closer to Antares as midnight approaches.

The Moon appears much brighter and larger than Antares, but this is a mere deception of distance. The Moon is just a quarter million or so miles away and is roughly 2,000 miles wide at its equator. Antares, on the other hand, lies 600 light years away, is 12,000 times brighter than the Sun and measures 745 million miles across. Keep this in mind when the Moon makes supergiant Antares disappear from the sky at four minutes from midnight.

Another thing to keep in mind is Antares advanced age. While it is younger than Sol, our star, it is much larger and brighter, meaning a far shorter lifespan. When the end comes for Antares, it will be with a bang--because of its size, Antares will end life as a supernova.

That explosion could come at anytime, a million years from now or while the Moon is hiding it from view. Likely, Antares will emerge from behind the Moon at 1:12 a.m. no different than when it disappeared. Or, it may reappear as the aftermath of a titanic stellar explosion, outshining all the other stars in our galaxy combined.


This column appeared originally in the Visalia (Calif.) Times-Delta in April 2005.

Friday, April 01, 2005

Return of the King

Return of the King
by Dave Adalian

What’s bigger than a bread box, smaller than the Sun and the brightest thing in the night sky after the Moon these days? It’s 88,000-mile-wide Jupiter!

Those with eyes for the skies may have recognized the bright object dominating the east after sunset the last few weeks as the King of Planets. A fixture in the winter sky for the past few years, Jupiter is making the transition to spring skies as it moves to opposition--when it appears opposite the Sun and is up all night--on Sunday, April 3.

Not to insult the King, but Jupiter really is an old gas bag, and a big one to boot. Jupiter is the largest thing in the Solar System after the Sun, and while it’s only about six times wider than Earth, it would take more than the volume of 1,000 Earths to fill Jupiter’s interior.

Jupiter is so large that it contains more mass than all of the other planets combined, 1.9x10^27 kilograms worth--that’s a 19 followed by 26 zeroes! Astronomers who think they’re cleaver like to say the Solar System is made up of the Sun, Jupiter and assorted rubble.

The Jupiter System itself is fairly rocky, too. When Galileo first viewed Jupiter through a telescope in 1610 he saw just the four bright moons Io, Europa, Ganymede and Callisto. These days, Jupiter’s official NASA moon count is up to 63, with the smallest measuring just three miles across.

Moons aren’t the only thing going around Jupiter. Like Saturn, this gas giant planet also has a set of rings. Jupiter’s rings are much less complex and dimmer, so much so they weren’t discovered until Voyager I visited in 1979.

Like the Sun, the Jupiter is mostly hydrogen, and because of the gravitational pressure of its mass, inside temperatures reach more than 10,000 degrees Fahrenheit. That pressure has caused the formation of a core of metallic hydrogen 6,000 miles below the surface of Jupiter’s atmosphere. Some scientists believe the planet also has a rocky core 10 times the mass of Earth. Others disagree, saying it’s hydrogen all the way through.

In the telescope, dark, cloudy bands reveal themselves on Jupiter’s disk. The four bright Galilean moons are obvious as they dance along night to night, and careful observation reveals the Great Red Spot, a storm three times larger than Earth that has raged since before its discovery in 1664.


This column appeared originally in the Visalia (Calif.) Times-Delta in April 2005.

Thursday, March 03, 2005

Vernal Equinox on the Horizon

Vernal Equinox on the Horizon
by Dave Adalian

Despite winter’s best efforts, spring is finally showing. Buds are turning to blossoms and temperatures are rising. The Sun is making the occasional appearance between rainstorms and soon it will let us know the season has changed.

Imagine the Sun, stars and planets as points of light on the inside of an enormous sphere surrounding Earth. Next, project a circle from Earth’s equator onto the sphere, forming a celestial equator dividing the sky into northern and southern halves. Then imagine another circle on the sphere, this one marking the Sun’s apparent path during the course of a year.

The two circles don’t match, and it’s that misalignment that causes Earth’s seasons. During winter months, the Sun sits south of the celestial equator so the northern hemisphere gets less light and temperatures drop. In the summer, the Sun appears to be north of that line and daylight hours are longer and hotter.

Twice a year, once in March and again six months later in September, the line marking the Sun’s progress and the celestial equator intersect. These events are known as equinoxes, Latin for equal night, and they mark the changes of summer to autumn and winter to spring.

This year’s vernal--or spring--equinox will happen at 4:34 a.m. PST on Sunday, March 20, when the Sun crosses the celestial equator and moves into the northern half of the sky. At that moment spring begins, and for a few days on either side of the event nighttime and daytime will be the same length.

Not coincidentally, the Sun rises exactly east on a few days surrounding the equinox and sets directly west. During the course of summer, the point on the horizon where the Sun rises and sets will appear to move north until summer solstice in June, when it again decsends toward fall.

The vernal equinox has been an important event for humans since the dawn of civilization. Ancient Egyptians paid homage to it by building the Sphinx to face sunrise that day, and closer to home the Mexican Pyramid of Kulkulkan, honoring the serpent god Quetzalcoatl, was designed so the shadow of the god appeared to slither down the steps on the equinox.

But, forget the egg balancing. Raw eggs do not balance on their ends more easily on the equinox. A Chinese New Year’s ritual performed about six weeks before the vernal equinox is the source of the myth.


This column appeared originally in the Visalia (Calif.) Times-Delta on March 3, 2005.

Thursday, February 03, 2005

Time to Look at Mars Again

Time to Look at Mars Again
by Dave Adalian

Planet Mars grabbed big headlines in summer of 2003, making its closest approach to Earth in 60,000 years while millions turned out worldwide for the spectacular show.

Lately, the Red Planet has been sitting dim and far away on the other side of the Sun, but during the next 10 months that will change as Earth cozies up for another close pass. With nearly a year before Mars again becomes one of the brightest objects in the night sky, now is the time to start watching.

Think of Earth and Mars as cars on a race track. Mars sits farther out, moving slowly, while Earth roars along on an inside track. Even though Mars isn’t the speedster Earth is, it still takes us some 28 months to lap it, which is why we’re only starting to get good views of it again now as Earth rounds her home star.

Getting up early is required for finding Mars. The God of War is currently rising about 4 o’clock in the morning, but doesn’t clear the treetops until 30 minutes or so later. To sight it, look to the southeast near the horizon for its pink light.

Don’t confuse Mars with much brighter Antares, the brightest star in the constellation Scorpius that is also not far above the horizon in the southeast, but up and to the right of Mars. This red star is actually named for its resemblance to the Red Planet. Antares means rival of Aries, the Greek name for Mars.

Mars now sits just west of Sagittarius and will have moved to the east side of the Celestial Archer by month’s end. But, because it moves in the same direction around the Sun as Earth, there isn’t much change in the time it rises until the they’re far closer together. By April, Mars is up around 3 a.m., rising in Capricornus, and in May it’s up by 2 o’clock in Aquarius.

It spends the summer cruising through Pisces, picking up an hour each month and brightening along the way. Through September, Mars rises just after 9 p.m., almost due east, in Aries, where it will stay until it reaches its brightest and closest by mid-November. Then, it rises at sunset to shine overhead by midnight.

Mars won’t be as spectacular as summer 2003, but will certainly be well worth seeing, especially for those who weren’t watching the last go-round.


This column appeared originally in the Visalia (Calif.) Times-Delta on Feb. 3, 2005.

Thursday, January 06, 2005

Winter Stars Are Brighter

Winter Stars Are Brighter
by Dave Adalian

Nights in winter seem starrier partially due to drier air overhead, but mostly because there are just more bright stars in the winter sky.

Winter begins with the Summer Triangle of Vega, Deneb and Altair lingering in the west after sundown. These jewels set quickly, and on the opposite side of the sky the Winter Hexagon’s easternmost members emerge.

By 7 o’clock, Sirius is high enough for viewing east of Orion’s belt. The Dog Star shines from 8.6 light years away in Canis Major, but because it is 20 times brighter than our sun remains the brightest star that can be seen from Earth at magnitude -1.4.

Sitting at due east and rising just before Sirius is a magnitude-0.0 star 11.4 light years distant. Because it rises just ahead of Sirius it’s known as Procyon, which means before the dog. A double star, its companion is a tiny, invisible white dwarf.

To the northwest, the third corner of the Hexagon is occupied by Castor and Pollux, the twins of Gemini. Between the twins and Procyon lies bright yellow Saturn, which will be much in the news later this month when the Huygens probe lands on its moon Titan.

Pollux, a magnitude-1.1 star 33.7 light years distant, glows orange. Farther, dimmer Castor--magnitude 1.6 at 51.5 light years--appears white to the eye. Through a telescope Castor becomes three stars, and though not visible each of these is a double for a total of six suns looking like one to the naked eye.

Above and right of the Twins is Capella, the fourth corner of the Hexagon and the sky’s sixth brightest star at magnitude 0.1. It shines from 41 light years away in Auriga the Charioteer.

Lower and farther right is Aldebaran, the red eye of Taurus the Bull, occupying the fifth spot at 60 light years away and magnitude 0.9.

Completing the Hexagon is Rigel, brightest of stars in Orion and just right of his belt. Even though it is some 1,400 light years away, Rigel still shines at magnitude 0.5, making it seventh brightest as seen from Earth.

While Rigel officially ends the lap around the Winter Hexagon, many find it natural to make a sharp left to finish up at magnitude 0.5 Betelgeuse, which also sits some 1,400 light years distant. This red giant is nearing the end of its life, making it a prime candidate to go supernova.


This column originally appeared in the Visalia (Calif.) Times-Delta on Jan. 6, 2005.