Northern lights possible tonight March 27-28

Just a quick note that the Kp index is up to “4″ as of 11 p.m. CDT and the auroral oval is creeping like a green amoeba toward the northern border states tonight March 27-28. Be on the lookout for auroras low in the northern sky. We’re overcast in Duluth, Minn. so no sightings here. A favorably positioned solar coronal hole is the cause for the uptick. More activity is also likely Wednesday night the 28th.

Buckle up for the cosmic roller coaster ride of your life

Water creates a chaos of shapes as it splatters into the air after striking a rock in a nearby creek. Photo: Bob King

Last week I watched water racing down a creek slam up against a boulder and break into a frothy spray of droplets and blobs.  My eyes struggled  to make sense of it. The camera proved a far better instrument to dissect the spray into a series of moments, so I could better appreciate the water’s ephemeral shapes and patterns.

We can stop movement and hold time still for a moment, but that’s all. You and I and everything around us are in constant motion. Take the rotation of the Earth. As I type, my keyboard, home, and the entire city of Duluth, Minn. are all moving together at 708 miles per hour toward the east. Speed varies according to latitude, ranging from 0 mph at the poles to 1,041 at the equator. Folks in Nome, Alaska are traveling at 455 mph on the merry-go-round, while those in Los Angeles zip along at 860 mph.

Depending on your latitude, the speed with which your rotation speed varies. Close to the poles, it's slow because you turn through a very tiny circle in 24 hours. At the equator, you have travel the entire circumference of the Earth in the same time. Illustration: Bob King

The reason rockets are launched in Florida and not North Dakota is because Florida is closer to the equator, giving them a 250 mph edge compared to Fargo as they head into orbit.

To determine how fast you’re moving, multiply Earth’s circumference times the cosine of your latitude and divide by 24 hours like this: 24,902 mph x cos (latitude) / 24 hours. Cosines are easily found by heading over to the handy Cosine Calculator and keying in your latitude. With that number in hand, use your computer’s calculator to arrive at your personal velocity.

We travel nearly 67,000 miles per hour in our yearly orbit around the sun. Illustration: Bob King

Spinning is just one of Earth’s several motions. We’re also orbiting the sun at 18.5 miles per second or nearly 67,000 miles per hour. At that speed our planet traverses 600 million miles in one year. Since Earth’s about 8,000 miles in diameter, it moves about 202 times its own size in one day. Even sitting still we’re putting on miles at a fantastic rate. Live till you’re 80 years old and you’ll  have 48 billion frequent orbital-flyer miles to show for it.

Destination Vega! The sun and solar system are moving the general direction of the bright star Vega in the constellation Lyra. Photo: Bob King

So far we’ve only talked about Earth, but the sun isn’t standing still either. Our star is one of several hundred billion stars in the Milky Way galaxy, all of which are moving. Based on studies of the motions of stars in our neighborhood, astronomers have determined that the sun hauls it family of planets, comets and asteroids at 43,000 miles per hour in roughly the direction of the bright star Vega in Lyra.

In the course of a  lifetime we will have moved 40 billion miles closer to the star. Unfortunately that huge figure will hardly begin to close the gap between the two stars. Vega is not only 25 light years away (150 trillion miles), but it’s not standing still either. If you’d like to see where we’re headed, face northeast around 11 o’clock the next clear night. The bright, twinkling star low in the sky is Vega.

The sun circles the galactic center once about every 225 million years traveling at 483,000 mph. Illustration: ESO with additions

If you guessed that we’re not quite finished yet, you’re right. The Milky Way is a gigantic starry pinwheel, where the speeds of stars vary with distance from its center the same as the speed of a planet varies with its distance from the sun. The spinning of the galaxy carries the sun and neighboring stars around the galactic center at 483,000 mph or nearly 7 times faster than Earth orbits the sun.

Good thing the sun is holding onto us or we’d soon be lost among the stars like change dropped from a pocket. Our solar system is located about 2/3 the way from galaxy’s center to its edge and takes 225 million years to complete one orbit. Each year we celebrate our birthday after completing another cycle around the sun. Since the sun and planets first formed 4.6 billion years ago, the sun has orbited the galactic center 20 times, making it 20 galactic years old. Hey, that means in another 225 million years it will finally come of age!

Watch out for what the future brings - Andromeda and the Milky Way will one day be one galaxy sometimes referred to as "Milkomeda". Other members of the Local Group are labeled. Credit: Andrew Colvin

The Milky Way is one of more than 50 galaxies in a small cluster of galaxies called the Local Group. Ours and the Andromeda Galaxy, located 2.5 million light years away in the constellation Andromeda, are the group’s two biggest members. As if we weren’t moving in enough ways, these two galactic behemoths are hurtling toward one another at 50 miles per second or 270,000 mph.

2.5 billion years from now we’ll collide in a spectacular display of fireworks as merging gas clouds fire up brand new clusters of stars. Over time, the two spiral galaxies will evolve into one much larger elliptical galaxy some like to call “Milkomeda” (milk-AH-meh-duh).

The Local Group is one of many galaxy clusters belonging to one vast assemblage of clusters named the Virgo Supercluster centered in the constellation Virgo. Credit: Andrew Colvin

The Local Group is a small cluster on the outskirts of the much larger Virgo Supercluster of galaxies. Consider Virgo as downtown New York and our gang as a small town in the boondocks. Like my daughters, who are drawn to the dazzle and glitter of the big city, the Local Group is falling at more than half a million miles an hour toward the center of the Supercluster.

Still not dizzy yet? Let’s take one final step and put the pedal to the metal.

Relative to the cosmic background radiation – the ever-expanding , steadily cooling energy left over from the Big Bang that permeates all of space – the Milky Way galaxy is moving at the amazing rate of 1.3 million miles per hour roughly in the direction of Leo and Virgo. The reason for our great haste? New space created between the galaxies as the universe expands causes them to appear to rush apart from each other. The Local Group holds together through the combined gravitation attraction of its members, but when you take in the bigger scene, galaxies have been rushing away from each other at alarming speeds since the Big Bang 13.75 billion years ago.

OK, even I need a little help at this point, so let’s sum up:

* We’re rotating around 700-800 mph depending on latitude.
* Orbiting the sun at 67,000 mph
* Traveling among the nearby stars at 43,000 mph
* Orbiting the center of the Milky Way at 483,000 mph
* Moving toward Andromeda at 270,000 mph
* Diving into the core of the Virgo Supercluster at 540,000 mph
* Riding aboard the Milky Way in the expanding universe at 1,300,000 mph

And yet, in spite of all the whirl and flow, we can still find quiet moments under a dark sky to contemplate it all.

A portion of the Hubble Deep Field photograph showing a multitude of galaxies. The space between each galaxy grows larger with time as the universe continues its expansive ways since the Big Bang about 14 billion years ago. Credit: NASA/ESA

A painting in the western sky

Tonight's gathering of Moon, Jupiter, Venus and transcontinental airliner in the western sky in mid-twilight Sunday. Details: 35mm lens at f/4.5, ISO 400 and 6 seconds. Photo: Bob King

I hope you had a chance to see the spectacle of moon and planets in the western sky Sunday evening. The full circle of the moon is visible alongside Jupiter. The bright part of the circle (crescent) is illuminated by the sun, while the remainder of the moon shines by sunlight reflected from Earth’s clouds, water and land. Earthshine is much fainter than direct sunlight, which is why that portion of the moon glows only weakly.

Not far above the pair is Venus and the Seven Sisters star cluster. Very eye-catching all!

Tonight the moon will be next to Venus and even closer than it is to Jupiter tonight, but you don’t have to wait till dusk to see the pair. Why not try and spot them in binoculars before sunset?

See if you can spot Venus in the daytime today using the moon as your guide. All you need is a pair of binoculars. If your sky's really clear, Venus will be visible with the naked eye. Time shown is CDT. Created with Stellarium

The moon is fairly easy to see in a clear sky by late afternoon and early evening. Once you find it, take a look through binoculars and you’ll have no problem seeing Venus not far to its upper right. Seeing Venus in a sunlit sky can be challenging, but with the moon nearby you’ve got the cosmos on your side. Give it a try. I think you’ll be surprised how easy it is. And once you’ve spotted the duo in binoculars, take the next step and try to pick out Venus with your naked eye.

The maps show the pair for the central U.S. If you live on the East Coast, Venus will be a tad higher to the right; for the West Coast they’ll be more “level” or in line with each other.

Excellent cloud details show up in this photo of Venus taken on March 24, 2012. Credit: George Tarsoudis

George Tarsoudis of Greece took a wonderful image of Venus that shows far more detail than what you’d see with your eyes through any telescope. Using a digital camera and ultraviolet filters on his 10-inch scope, he captured textures in the planet’s clouds not visible in everyday “visual” light.

Even to the most seasoned observers rarely see detail in Venus’ clouds due to their extremely low contrast. His photo reminds me of the images taken by the Pioneer Venus Orbiter spacecraft in 1979.

Weekend sky show features moon and planets; space station dodges debris

The moon passes by Jupiter and Venus over the next three nights. Look west 45 minutes to an hour after sunset. Created with Stellarium

Yesterday was only a tease to the nice planet-moon alignments happening over the next few nights. Tonight (Saturday) the moon will be higher in the west nearer Jupiter, but Sunday and Monday will bring the best pairings. Hope for clear skies and don’t forget binoculars. Crescent phase is ideal for seeing the the pale blue-gray earthshine that dimly illuminates the remainder of the moon beyond the crescent.

For morning observers, the International Space Station (ISS) makes bright passes all week long. A typical one lasts 4-5 minutes with the ISS moving from west to east across the sky. The times below are for the Duluth, Minn. region.

For times for your town, please log on to Heavens Above or go to Spaceweather’s Satellite Flybys and enter your zip code.

* Sun. March 25 beginning at 5:59 a.m. Bright pass across the northern sky.
* Mon. March 26 at 5:04 a.m. Exits Earth’s shadow east of the Big Dipper bowl and continues across the north.
* Tues. March 27 at 5:41 a.m. across the north
* Weds. March 28  at 6:19 a.m. ”     ”
* Thurs. March 29 at 5:23 a.m. ”     ”
* Fri. March 30 at 6 a.m. ”     ”
* Sat. March 31  at 5:05 a.m.  ”     ”

Controlled by teams on the ground, the Robonaut 2 humanoid robot holds an instrument to measure air velocity during a system check in the Destiny laboratory of the space station recently. Click photo to learn more about the robot. Credit: NASA

Earlier this morning, the crew of the space station had to take shelter in the Russian Soyuz spacecraft after their flight director determined there was a small chance the station would be hit by a fragment of a Russian Cosmos satellite. The debris passed by without incident about 9 miles from the station at 2:38 a.m. this morning.

It’s the third time in the history of the space station astronauts have had to take shelter from incoming space junk. The incident highlights the growing danger to satellites and the space station from man-made orbital debris. The station is designed to handle hits from objects around 1/2 inch (1 cm) or smaller without significant damage. Anything larger can spell trouble.

The United States Space Surveillance Network currently tracks some 8,000 man-made objects of baseball size or larger. Most of the debris orbits around 500 miles high – well beyond the ISS –  with a small amount in the space station’s orbital zone. The junk is comprised of active and inactive satellites, spent rocket bodies, fragments and the remains of a satellite collision. Small pieces wouldn’t be a big issue except they’re moving at over 17,000 mph and pack a wallop.

NASA video explains how the recent solar storms have directly affected Earth 

In a related story,  the recent pounding the Earth took from a series of flares from sunspot region 1429 in the last few weeks not only provided light shows for northern sky watchers but also heated the planet’s upper atmosphere.

“This was the biggest dose of heat we’ve received from a solar storm since 2005,” says Martin Mlynczak of NASA Langley Research Center.  “It was a big event, and shows how solar activity can directly affect our planet.” The extra heat caused the upper atmosphere to puff out, increasing the drag on satellites and satellite debris. While that’s not healthy for functioning satellites, the increased drag performs a useful cleaning function by lowering the orbits of the debris. This shortens their lifetime in orbit,  speeding up re-entry and burn-up.

As for the rest of the heat, most of it was re-radiated back into space thanks to carbon dioxide (CO2) and nitric oxide (NO) which act as natural coolants to bring the upper air temperature back into equilibrium. Check out the full story HERE.

See a razor moon tonight plus how we solved a dark star mystery

A 90-minute exposure of M95 with 2012 aw marked taken through a 16-inch telescope. Credit: John Chumack

First, an update on supernova 2012 aw in M95. A group of astronomers have gone back over older photos of the galaxy and identified the star before it went supernova as a red supergiant about 8 times more massive than the sun. This would make it one of the reddest and coolest of its class to become a supernova. Or the star was shrouded in a dust cloud of its own making. A third possibility is that it’s been heavily reddened by dust within the galaxy. I’ll go out on a limb and suggest this might explain why 2012 aw hasn’t continued to brighten beyond 13th magnitude.

Find a place with an open horizon to the west to spot a super-thin crescent moon at dusk. This map shows the sky facing west 30 minutes after sunset. Maps created with Stellarium

Not all of us have dark skies and a telescope big enough to see a supernova, but if you have clear skies tonight, it shouldn’t be too hard to spot a wiry crescent moon. Look well below Venus and Jupiter in the western sky a half hour after sunset. The shaving of moon will be less than a day and a half old. In the coming nights it will glide by the bright planets, becoming easier to see as it moves up and away from the sun.

Once the sky is dark, let your gaze drift upward from Jupiter and Venus. The first object you’ll see is the little clump of stars called the Seven Sisters or Pleiades. It’s about as high above Venus as Venus is above Jupiter. Venus will have a meet-and-greet with the cluster early next month. Watch them get closer each night.

The pentagonal Auriga stands above Aldebaran in Taurus the Bull and the bright planets Jupiter and Venus in the west at nightfall in late March.

Straight up from the Seven Sisters you’ll run into the bright star Capella, the alpha star in the constellation of Auriga the Charioteer. Spring is my favorite time of year for Auriga viewing because the five-sided figure stands up like a house in the western sky. The three stars across the top, including Capella, form the roof, while several others outline the two sides and floor.

Strictly speaking, the lower left star in Auriga officially belongs to Taurus but tradition allows both star groups to share the star to better complete their figures. Sounds like a good marriage to me.

Just below Capella, a name meaning “she-goat” and a reference to the goat that suckled Zeus as a child, is a compact triangle of stars. Capella bore two baby goats or kids represented by the two bottom stars in the triangle. The other star – Epsilon Aurigae – marks the charioteer’s left elbow.

The Kids and Epsilon are just below bright Capella.

Epsilon is one of the most intriguing stars in the sky. It’s normally brighter than the Kids, but every 27 years for about 18 months it’s eclipsed by a dark companion object and fades to become the faintest of the trio.

The most recent eclipse wrapped up last year.  Professional astronomers, working with large Earth and space-based telescopes like the Hubble and Spitzer, along with a small army of dedicated amateur astronomers, carefully studied every aspect of the eclipse and finally solved the mystery of the dark object and learned more details about Epsilon itself.

Artist's concept of the dark disk with a hot star at center. Every 27 years the disk passes in front of Epsilon (right) and dims its light for about 18 months. When the disk has orbited out of our line of sight, Epsilon returns to its normal brightness. The system is about 2,000 light years from Earth. Credit: NASA/JPL-CalTech

The thing doing the eclipsing is a dark disk of gas, dust and gravel-like rocks some seven times larger than the distance between the Earth and sun. At its center is a blazingly hot, blue-white star hidden from view by the dust. The Spitzer scope, which picked up hints of the “invisible” star in infrared light, finally helped us understand what held the disk together – a single star . The star and disk orbit Epsilon, which is brighter and several times more massive than the sun. Epsilon is the star you see with your naked eye.

As to how the disk got up there, that’s still unclear, but it’s possible there are planets inside like raisins in a bagel ring. Because the two orbit so closely, perhaps the disk star pulled material from Epsilon into a disk. Already scientists are coming up with ways to press this star system for more secrets when the next eclipse begins in 2036.

Amateur astronomer photographs curious cloud on Mars

The little bump at upper right on the planet is the cloud or plume photographed Monday night March 19, 2012. It's located in the planet's southern hemisphere. Credit: Wayne Jaeschke

An amateur astronomer in West Chester, Penn. took a picture of a curious Martian cloud several nights ago that has the community of Mars observers abuzz. Wayne Jaeschke photographed Mars on the evening of March 19 with a 14-inch telescope and noticed the plume after processing his images.

It struck him as odd the way it stood so high off the planet’s limb, so he shared it with other Mars watchers in the online Mars Group. He also made a cool 5-frame animation of the feature you can view HERE.

Once word got out, confirmation of the cloud came in from other amateur astronomers who had photographed it both before and after the 19th. No one is certain of the cloud’s nature yet, but it could be made of ice crystals or perhaps even dust whirled into the Martian atmosphere. Its altitude is estimated at 60 miles or higher. See more photos HERE.

Mars photographed by Hubble in March 1997. The left image is a full-color view; the right was taken through a blue filter to emphasize the clouds. Most Martian clouds are found in the equatorial and polar regions. Polar clouds are widespread during the Martian fall and winter. Credit: NASA/ESA

Mars is no stranger to clouds, though not the puffy cumulus or heavy rolls of stratus we’re familiar with on the home planet. Mars’ atmosphere is composed mostly of carbon dioxide and extremely thin. You’d have to jump in a spy plane and travel to an altitude of 115,000 feet (21.7 miles) in Earth’s atmosphere to approach the rarity of Martian air.

That doesn’t stop Mars from having clouds. Seasonal carbon dioxide and water ice vaporizing from the Martian polar caps provide the necessary materials to build clouds, and the atmosphere is sown with the dust to seed their formation.

Cirrus clouds are composed of ice crystals like the clouds on Mars. Photo: Bob King

Some clouds are made of water ice, like the familiar afternoon clouds that form around the planet’s high elevation extinct volcanoes like Olympus Mons, while others are composed of dry ice crystals. They’re mostly wispy, much like the ice crystal clouds called cirrus or “mares’ tails”, and they drift across the planet’s pink sky. They’re propelled by winds just like Earth’s clouds.

When Mars experiences strong dust storms, orange clouds of dust billow up above its surface that are easily visible in mid-sized telescopes. Occasionally these clouds can become so widespread that they literally blanket the planet, blocking its surface from view for a time.

The small protrusion extending into the night sky of Mars in this 1997 Hubble photo is probably a high cloud catching sunlight. Credit: NASA/ESA

This wouldn’t be the first time a cloud reached high enough to catch the sunlight and stand out above Mars. Back on May 17, 1997, the Hubble Space Telescope photographed something similar poking beyond the Martian terminator (border between day and night).

In the photo at right, the other white patches along the left side of the planet are additional clouds and hazes.

No one to my knowledge has seen the new cloud visually yet, but observers have been and will be seeking it out in the coming nights. The plume appears to be a very low contrast feature, requiring excellent observing skills, a fair-sized telescope and good optics.

Martian cirrus-type clouds photographed by the Sojourner rover. Credit: NASA

If you’d like to make an attempt, it’s located just south of the dark feature Mare Cimmerium at Martian latitude 44 degrees S, 190 E. I’ll update with new photos in the coming days provided the cloud’s still there. Perhaps NASA will even get a picture of it with the orbiting Mars Reconnaissance Orbiter. Speaking of which, here’s a recent photo taken by the spacecraft of thin clouds over ice-covered dunes. Should we ever establish a base on the planet in the future, there will definitely be a need for a Martian meteorologist.

Bright, ice-covered dunes and winter ice protected in shallow grooves on the ground are visible through clouds in Mars' southern hemisphere recently. Click to enlarge. Credit: NASA/JPL/University of Arizona

Dueling bright supernovas in M95 and NGC 4790 kick off new season

Two bright supernovae in galaxies M95 and NGC 4790 are currently visible in small to moderate-sized telescopes. North is up, west to the right in both pictures. Credits: Martin Mobberley (Ieft) and William Wiethoff

60 million years ago a supergiant star exploded in the galaxy NGC 4790 in Virgo. 22 million years later another overgrown and underfed supergiant star ended its life in the galaxy M95. After all that time traveling through space, the light from each explosion arrived within two days of each other in the skies over planet Earth. What a joy to see them both in their final glory.

Supernova 2012 aw has been getting most of the attention lately, because it was discovered in a bright galaxy not far from the planet Mars in Leo. Most supernovae are caught on the rise to maximum light. This one was no exception. 2012 aw was first spotted at 15th magnitude (dim!) by Paolo Fagotti and Alessandro Dimai of the Italian Supernovae Search Project, and independently by Jure Skvarc (Crni Vrh Observatory, Slovenia) on March 16. A day later it rose to 13th magnitude which put it within range of many amateur telescopes. Today March 21, the supernova still hovers at around 13th magnitude, though it’s uncertain if it will brighten further or plateau.

Stay back! An artist's view of a supergiant star undergoing core collapse to become a supernova. Credit: ESO

Studying its light with a spectrograph, an instrument that drags a fine-toothed comb though a star’s light to determine its chemical makeup, speed of rotation and the like, astronomers discovered that M95′s supernova is a Type IIP. Type II tells us this was a supergiant star that used up all the available nuclear fuel in its core. With nothing left to burn, the star’s internal “furnace” shut down, gravity took hold and the whole works collapsed in upon itself at speeds up to 45,000 miles per second.

When the outer layers reached the core, they crushed it into a dense ball of subatomic particles and sent a powerful shock wave back towards the surface that helped tear the star apart, creating a supernova. New radioactive forms of elements like nickel and cobalt were created by the tremendous pressure of the explosion; their decay into stable forms releases energy that contributes to the supernova’s light. The “P” by the way stands for plateau. Type IIP supernovae level off in brightness more slowly, plateauing for a time before fading away.

Galaxies M105, NGC 3384 and NGC 3389 in Leo. Although composed of billions of stars like our Milky Way, most scopes see them as hazy patches. They're too far to resolve into individual stars. Credit: Jim Misiti

A supernova is really the only way beginning and amateur astronomers can see a star in another galaxy. Galaxies beyond the Milky Way system – which includes our nearby satellite galaxies the Magellanic Clouds – are too far away for most telescopes to resolve into stars. All those billions of stars in the thousands of galaxies visible in amateur telescopes look like pale white fuzz that remind me of cocoons. Not so when a supernova blows. We finally get to see across the light years at an individual star waving farewell.

To get an idea of how bright the supernovae in M95 and NGC 4790 are, take a look at Arcturus, the bright star in the northeastern sky found below the arc of the Big Dipper’s Handle. If you placed either SN 2012 aw or SN 2012 au at Arcturus’ distance of 34 light years, each would shine at better than magnitude -15 or a full magnitude brighter than the full moon. Image all that light squeezed into a point in the sky. Think how bright that would be and the shadows it would cast at night. What power!

Just before a supergiant star blows it has a core made of iron that cannot "burn" to create energy to power the star. Gravity takes hold and the star collapses. Supergiants are several hundred times larger than our sun.

I was asked today whether you can see M95′s supernova in a small, 4-inch telescope, and the answer is yes – if you observe from a dark sky in  good seeing (steady, non-turbulent air) using higher magnifications (150x). The limit for a 4-inch is 13.2 magnitude. A 6-inch scope is better and it should be easy in an 8-inch. By good fortune, the star is far from the galaxy’s center where it might otherwise be camouflaged by a haze of spiral arms.

But what about SN 2012 au? Let’s not pass it by. After all, it’s even brighter than the one blazing in M95. This Type II supernova is nearly dead center in NGC 4790 in Virgo and currently shines at 12.7 magnitude or nearly a half-magnitude brighter than 2012 aw – well within the 4-inch limit. The reason it might be overlooked is that 4790 is a smaller, fainter galaxy and not as easy to find. Try using this finder chart for NGC 4790 from this earlier blog. Once you spot the galaxy, you can’t miss the supernova.

Finder charts and other details on M95 are HERE and HERE. David Bishop, keeper of the Latest Supernovae site, always has updated information on current supernovae bright and faint.

One order of spring please, sunny side up

The sun rises over Lake Superior last week. Today marks the first day of spring when the sun rises due east and sets due west. Photo: Bob King

I celebrated the transition from winter to spring by taking a walk with my dog in the rain. We stepped out shortly after midnight this morning, me with umbrella in hand and Sammy nosing the ground. At 12:14 a.m. CDT at the stroke of spring I strained to listen for the first frogs. None were heard. They don’t usually begin calling until mid-April, but with temperatures in the 70s the past few days and snow vaporizing faster than a comet’s nucleus, my expectations were high.

Spring is when day and night are nearly equal across the entire planet. That’s because Earth’s axis is oriented neither toward nor away from the sun. If the southern hemisphere is the planet’s feet and northern hemisphere its head, today we’re showing the sun our belly or profile if you like. In winter, the northern hemisphere is tipped away from the sun with short days and a low sun to pay for it. In summer, we’re tipped toward the sun with long days, a high sun and heat to spare.

The tip of Earth on its axis causes the seasons. On the first day of spring or vernal equinox, we face the sun from the side and days and nights are approximately of equal length in both northern and southern hemispheres. Credit: Tao-olunga

Spring and fall are the ‘tween times when temperatures moderate and the sun rests for a brief moment between extremes. And don’t forget the bonus alignment: at the equinoxes the sun rises due east and sets due west. If you’ve never been sure of your directions, this week is the time to get reacquainted. Face the sunset and stick out your arms. Your right arm points due north, your left south and your back faces east. Couldn’t be easier.

Where the sun is lower in the sky in the polar regions, its energy is more spread out and heats the ground and water much less than when it's high in the sky (b) and its rays are more concentrated. That's one of the reasons winter is so much colder than summer. Credit: Peter Halasz

Spring is that astronomical moment when the sun’s path crosses an imaginary circle in the sky called the celestial equator. The celestial version is an extension of the Earth’s equator into the sky. That’s why the sun is exactly overhead at the  real equator. An observant equatorian might notice that flagpoles or power poles cast no shadows at noon, because the poles literally stand right on top of them.

From here on out, the sun continues moving northward in the sky, which for those living in the northern hemisphere, means the sun gets higher and higher and daylight hours longer and longer until maxing out on June 20, the solstice. Not so for those living south of the equator, where the seasons run in exactly the opposite direction. It’s the autumnal equinox down under. The sun’s headed lower in the sky, bringing with it shorter days and longer nights.

A low sun at the North Pole photographed on April 8, 2008. The temperature at the time was 14 below F. Click image to webcam page. Credit: NOAA/North Pole webcam

The sun’s apparent movement north or south in the sky is a result of the Earth’s axial tilt of 23.5 degrees, which in turn is amount the Sun moves north or south of the equator during a year.

If you’re trekking to the North Pole today, situated at latitude 90 degrees north, the sun will make its first appearance of the year on your horizon at local noon … and it won’t set for the next six months! It doesn’t matter what direction you look either since it’s up all night and day.

At 90 degrees north, the celestial equator rings the horizon. Not until the sun reaches this point – which happens on the first day of spring – does it finally return for observers at the pole. Conversely, today is the last day the sun is up for the next six months for an observer at the South Pole. I hope your spirits rise today like the sun in the new season. Happy equinox!

Before and after pictures of supernova 2012 aw in M95. The image at left was taken in April 2008 before the explosion; the other just a few days ago. Credit: William Wiethoff

The new supernova in M95 in Leo, shining at magnitude 13.1, now has a name – 2012 aw. It doesn’t sound like much but if you add an “e” you’ve got an eyeful of “awe”.

Venus just going through a phase

Venus (top) and Jupiter together in the western sky at dusk this weekend. Photo: Bob King

It’s hard to let go of Jupiter and Venus. They’re still so fine to look at in the western sky at twilight. Through the telescope, Venus is a near perfect half moon and about as far from the sun as it gets. Greatest eastern elongation  – maximum distance east of the sun – happens next Tuesday the 27th, when the planet will be 46 degrees from our star at sunset or halfway between the horizon and overhead point. It sets four hours later – only a few minutes before midnight – seen from northern Minnesota.

As Venus orbits the sun, it alternates between appearances in the evening and morning sky, spending about 9 1/2 months as a “morning star” and the same amount of time as an “evening star”.  Because we look inside our orbit toward the sun to spy Venus, we see the planet swing from one side of the sun to the other but never straying from it more than 46 degrees. That’s why Venus is only visible during twilight and at most a couple hours beyond nightfall.

Venus looks like a half-moon in a small telescope now into next week when it reaches its greatest elongation from the sun. The changing geometry of Venus, sun and Earth causes the planet to show phases like the moon. Illustration: Bob King

The outer planets like Mars and Jupiter are different. Since they lie outside Earth’s orbit, they can appear behind us directly opposite the sun. We have to “turn around” in a manner of speaking, to see them. When a planet is opposite the sun, it rises at sunset and remains visible all night. You might say the outer planets are capable of elongations of 180 degrees compared to Venus’ 46. Mercury, closer to the sun yet, only manages 28 degrees elongation at best.

In late March, Venus appears as a dazzling half-moon, because it forms a right angle with the Earth and the sun and is equidistant from both. As we head into April, its phase will narrow at the same time it moves closer to Earth. In a month, even 10x binoculars will show the planet as a distinctive crescent. Take a few minutes the next clear night to point a small telescope Venus’ way. Try to catch it during early twilight – the brighter the sky, the easier it will be to see the little half moon without glare.

M95 and the supernova at left. At right is a map of Mars and the galaxies M95 and M96. Mars is shown starting tonight through the 29th. The circle is 5 degrees across. Photo: William Wiethoff. Map created with Chris Marriott's SkyMap

I looked at the supernova in M95 last night and found it very easy to see at 13th magnitude southwest of the galaxy’s core. It’s the only “star” in that spot, so you really can’t confuse it with anything else. As promised, here’s a chart showing Mars’ changing position in relation to the galaxy over the next couple weeks. Amateur astronomer William Wiethoff of Port Wing, Wisconsin battled moths and turbulent air last night to make a nice image of the new supernova. Thank you Will!

Another bright supernova goes boom in M95 near Mars

The new supernova - yet to be named - is M95 located just below Mars tonight in the constellation Leo not far from neighboring galaxy M96. The inset is a photo of the galaxy taken through a telescope. Credit: Jim Misti / Map created with Stellarium

Wow! Another bright supernova. This one was discovered less than 2 days ago in the bright Messier galaxy M95 in Leo. It’s still too early to know its type, but at magnitude 13.0 and rising rapidly, this one will probably be visible in small telescopes within a few days. Unlike the supernova in NGC 4790 reported here earlier today, this one is far from the galaxy’s center in an outer spiral arm. It’s also incredibly easy to find thanks to help from one of the brightest planets in the sky right now – Mars.

Mars is slowly moving westward toward Regulus, but tonight you’ll find M95 a mere 1/2 degree due south of the planet. Place Mars at the north end of your telescopic field of view, and M95 will be in the same view to the south. What a sweet coincidence! By Tuesday night, that distance will have increased to 1 degree. I’ll provide an updated map tomorrow showing Mars’ motion.

M95 is the 95th entry in a catalog of deep sky objects compiled by the astronomer Charles Messier in the 18th century. He created the catalog, so he could ignore these fuzzy comet-lookalikes as he hunted for comets, his favorite quarry. As anyone who’s looked at both comets and galaxies through a telescope, you know how similar the two appear despite their vastly different natures.

You can use this annotated photo of M95 to find the supernova in your telescope. It's located southwest of the galaxy's center (60" west, 115"south to be exact). Several stars are numbered with their magnitudes. Click image to see a couple photos of the new object on David Bishop's SN site. Photo credit: Jim Misti

M95 is a beautiful, multi-armed spiral with a starry bar through its middle. It’s located 38 million light years from Earth and spans some 50,000 light years, making it about half the size of the Milky Way galaxy.

The supernova is the only obvious star at "11 o'clock" from M95's nucleus as seen in a 10-inch reflecting telescope tonight. South direction is up and nearby bright stars are marked with their magnitudes. Illustration: Bob King

It’s not often a supernova pops off in a bright (mag. 9.7) Messier galaxy. Most are found in more obscure members of the galactic zoo. We’ll be watching the supernova tonight and every clear night. Magnitude 13.0 means you can see it at high power in a 6-inch telescope from dark skies. Anyone with an 8-inch instrument or larger should have no problem provided the air’s not too turbulent. Watch for updates and good luck in your hunt to see this star gone wild.

Update March 21, 2012 – The supernova, now named 2012 aw, remains steady at about 13.1 magnitude. It’s a Type IIP – the collapse and explosion of a supergiant star at the end of its life.  Here’s a brand new blog on the topic. For more information and a chart including the movement of Mars, click HERE.