Milky Way settles into its new home, the Laniakea Supercluster

The Milky Way galaxy is an outlier in an enormous, newly designated supercluster of galaxies dubbed Laniakea. The vast assemblage spans some 500 million light years across and contains the mass of one quadrillion suns. The Local Supercluster, centered in Virgo, is only a small part of the much larger Laniakea. The looping lines represent galaxy flows toward large concentrations of galaxies within the supercluster. Credit: SDvision interactive visualization software by DP at CEA/Saclay, France (additions by B. King)

The name fits so well – Laniakea. It means ‘immense heaven’ in Hawaiian, and now it’s home. In the biggest sense of ‘big picture’ you can imagine.

Astronomers using the National Science Foundation’s Green Bank Telescope (GBT), among other telescopes, have determined that our own Milky Way galaxy is part of a newly identified titanic supercluster of galaxies they nicknamed  Laniakea (Lah-nee-ah-KAY-uh).

The Hercules Cluster in the constellation Hercules is a good example of a rich galaxy cluster. It contains about 200 galaxies and is located 500 million light years away. The cluster is a member of the Hercules Supercluster. Credit: Jim Misti

The Milky Way’s always been in one gang or another. It’s a member in good standing of the Local Group, a gravitationally bound small cluster of some 54 neighborhood galaxies. It in turn, along with dozens of other clusters, are drawn by gravity to the granddaddy Virgo Cluster, which contains some 2000 galaxies 53 million light years away.

All these clusters are interconnected, linked into a web through mutual gravitational attraction. Taken together, they’re known as the Local Supercluster, and superclusters are the single biggest structures in the universe. Our Local Supercluster contains at least 100 different galaxy groups and stretches across 110 million light years.

Another view of the Laniakea Supercluster. The outer surface (blue) shows the region dominated by the supercluster’s gravity. The streamlines shown in black trace the paths along which galaxies flow as they are pulled closer inside the supercluster. The historical Local Supercluster in shown in green and the Great Attractor region in orange. Credit: SDvision interactive visualization software by DP at CEA/Saclay, France

Up till now we thought it was the biggest structure of which the Milky Way was a part. Not anymore.

R. Brent Tully from the University of Hawaii’s Institute for Astrophysics and his team studied the motions of galaxies in the Local Supercluster and discovered that we live in a MUCH bigger house than we ever thought.

By using the GBT and other radio telescopes to map the velocities of galaxies throughout our local universe, the team was able to define the region of space where each supercluster dominates. They found that superclusters are involved in a tug of war for galaxies – many are pulled into the supercluster while those near the edge are up for grabs.

By studying these streaming motions, Tully and team discovered that our historical supercluster home was itself part of a much larger supercluster I’m almost tempted to call the Local Superdupercluster (but I won’t). Doubtless the more poetic Laniakea was picked because of Tully’s Hawaii connections.


Meet Laniakea, the Milky Way’s home supercluster

“We have finally established the contours that define the supercluster of galaxies we can call home,” said Tully. He compared it to realizing for the first time that your hometown belongs to a much larger country bordering other nations (superclusters).

Not only do large galaxy clusters dominate the new landscape, but an enigmatic mass of distant galaxies called the Great Attractor is also a bona fide member.

It’s cool being part of something even bigger than we’d ever imagined. I just had a gut feeling the Milky Way needed more space.

Sunrise and sunset – nature’s most beautiful illusions

Earth turns on its axis to greet the sun at sunrise each morning of the year. Credit: Bob King

Every day the sun rises, crosses the sky and sets. And it does it again and again and again like the perpetually repeating cycle of events in the movie Groundhog Day.

Except perhaps for a few remaining Flat-Earthers, we know what’s going on here. The sun’s not doing the moving. Instead, the Earth’s rotation causes the apparent motion of the sun across the sky. Yet the sense of the sun’s movement is so powerfully ingrained in our experience you might balk if I told you it’s essentially sitting still in the sky.

Every day the turning Earth causes the nearly static sun to rise in the east at sunrise and set in the west at sunset. Credit: Canadian Space Agency

For you to see a sunrise, Earth must rotate on its axis until your location faces the sun as it crests above the planet’s curvature. The following morning, when Earth rolls around after another 24 hours, the sun is very nearly in the same place in the celestial sphere as the previous morning. Once again, we see the sun ‘rise’. Ditto for the next morning and the next. It’s like turning over in your bed each and every morning and seeing your spouse in the same spot. Or very nearly.

If the Earth spun but stood in one spot never circling the sun, we would meet the rising sun at precisely the same time and place every day ad infinitum – a true Groundhog Day scenario. But the Earth orbits or revolves around the sun as surely as it rotates. Just like our daily spin, our planet’s revolution is reflected in the sun, which appears to slowly crawl across the sky, inching its way from one background zodiac constellation to the next, during the course of a year.

The orbiting and titled Earth cause slow but continuous changes in the times of sunrise and sunset during the course of a year. Credit: Thomas G. Andrews, NOAA Paleoclimatology

The ever-changing times of sunrise and sunset stem from the Earth’s orbital travels combined with the shifting seasonal tilt of the planet. From December 21 until June 21, as the amount of daylight increases in the northern hemisphere, the sun appears to travel slowly northward in the sky and we meet its welcome rays a couple minutes earlier each morning.

The sun’s yearly motion across the sky during the year traces out a path called the ecliptic. The top of the curve, at right, is the sun’s position during the summer. The low part of the curve is the sun’s location during winter. The up-and-down path is a reflection of the 23 1/2-degree tilt of the Earth’s axis. Illustration and animation by Dr. John Lucey, Durham University

Then from June 22 to December 20, Earth’s orbital motion causes the north polar axis to slowly point away from the sun. The sun appears to slide south as the hours of daylight wane, and we meet the sunrise a minute or two later each morning.

The sun, located some 26,000 light years from the center of the Milky Way galaxy, takes about 220 million years to make one revolution around its core moving at 483,000 mph. Credit: ESO

Earth moves along its orbit at an average speed of 67,000 mph (108,000 km/hr).

How about the sun? If I left the impression that it’s totally static I apologize. Yesiree, it’s moving too – at the astonishing speed of 483,000 miles per hour (792,000 km/hr) around the center of the galaxy.

Don’t look now, but you and I are going on the ride of our lives.The only reason stars remain static in the sky over the span of many generations despite the sun’s hurry is because nearly all of them are too far away to show a shift in position with the human eye. Telescopes, which magnify everything including motion, do show very subtle changes in the positions of nearby stars over much shorter time intervals.

Rising each morning to the same old sun, I try to remind myself that with every rotation comes a new opportunity to spin some joy into the day.

How to find the center of the Milky Way … and what lurks there

Want to know where the center of our galaxy is? Face south around nightfall in late July and find the Teapot of Sagittarius about ‘two fists’ to the left of bright Antares in Scorpius. The core is a blank bit of sky just above the spout near the 4.5 magnitude star 3 Sagittarii.  Stellarium

Ever stared straight at the heart of the Milky Way galaxy? Give it a try this coming week. With dark skies and no moon, the time is right.

Artist’s view of the 4 million mass black hole at the center of the Milky Way. The hole measures about 28 million miles in diameter. Credit: NASA

Notice I didn’t say into the heart. No human eyes can penetrate the veil of interstellar dust that cloaks the galactic central point 26,000 light years away in the direction of the constellation Sagittarius. Only X-ray, gamma ray and radio telescopes can ‘part the way’ and expose the galaxy’s dark secret which astronomers call Sagittarius A*.

There, at the center of it all, lies a black hole with a mass of 4 million suns. The innermost 3.2 light years centered on the black hole swarms with thousands of aged stars and about 100 fresh-born ones, some in very tight orbits about the hole. Gas clouds abound, and there’s at least another smaller black hole nearby.

NASA’s Nuclear Spectroscopic Telescope Array, or NuSTAR, captured these first, focused views of the supermassive black hole at the heart of our galaxy in high-energy X-ray light. Known as Sagittarius A* (A star), the bright flare formed when Sgr A* was consuming and heating matter. The background image, taken in infrared light, shows its location. Credit: NASA

Occasionally the central black hole flares to life when a random asteroid, gas cloud or stray star passes too close and gets ripped to pieces before disappearing down the gullet of the beast. Heated by friction, the material sends out every type of light from visible to X-rays and gamma rays. But no one can see all the excitement because it’s hidden by light years of dust grains. To the eye, the center looks nondescript and static, but nothing could be further from the truth.

The Milky Way is beautiful to gaze at this time of year. Take a drive to the country and park your car where the sky is dark and open to the south. At nightfall, you’ll see a fiery-hued star a few fists up from the southern horizon at nightfall. That’s Antares in Scorpius. Now shift your gaze two fists to the left or east and see if you can spot the outline of the Teapot. Once you’ve found it, galactic center lies just above the spout.

Closeup of the Spout showing a couple bright star clusters and the Lagoon Nebula, a rich star-forming region. Credit: Bob King

Though the center remains hidden, large chunks of the Milky Way hover like clouds against the black sky. Every puffy piece is comprised of billions of distant stars the light of which blends together to form a misty haze. Here and there are smaller knots. These are individual gas clouds called nebulae and bright star clusters. A pair of 40-50mm binoculars will show many of these wonders and countless fainter stars plainly. If we could magically remove the dust between us and the galactic center, the rich intensity of stars in the Sagittarius direction would be bright enough to cast shadows at night.

Take it all in. Let your eyes follow the arc from the southern horizon clear up across the eastern sky and back down to the northeastern horizon. We live here – can you believe it?

The Galactic Dark Horse rides again!

A view looking south down the Milky Way where it passes through the zodiac constellations Scorpius and Sagittarius around 11:30 p.m. in mid-late June. The Dark Horse sticks out from the main dark band to the right of center. See diagram below for help. Credit: Eric Hines

Giddyup! Time to gambol down the Great Rift of the Milky Way in search of the Galactic Dark Horse. He’s one of many ‘dark constellations’ we might fashion from the ebony clouds of interstellar dust that pool along the band of the Milky Way.

This key will you identify the parts of the Galactic Dark Horse. Credit: Eric Hines

In late June, the Milky Way begins its rise across the eastern sky at nightfall. From the suburban fringes and countryside, you’ll have no problem seeing the soft band of hazy light that first-time observers often mistake for approaching clouds. Even a casual inspection will show that the band is not evenly-textured. In particular, there’s a large gap or split extending from the Northern Cross all the way down to Sagittarius in the south. Astronomers call it the Great Rift.

The Rift splits the Milky Way down the middle and runs all the way from the Northern Cross (Cygnus) through Sagittarius in the south. It consists of enormous clouds of interstellar dust and gas in the plane of the galaxy called dark nebulae that blot out the more distant stars. If you could suck it all up with a monster vacuum cleaner and expose the billions of stars otherwise hidden, the Milky Way would be bright enough to cast shadows.

The Great Rift appears to cleave the band of the Milky Way in two. It’s really cosmic spewed by aging stars and supernovae that accumulates in the plane of the galaxy over billions of years. This view shows the Milky Way from the Northern Cross (left) to Sagittarius at lower right. Credit: Bob King

Tiny dust particles spewed by older, evolved stars and exploding stars called supernovas settle in the plane of the galaxy. Over the eons, it gets re-compressed into new stars. While the dust is really sparse, it adds up over the light years to form a thick, dark band that appears to slice the Milky Way right in half.

A lovely closeup of the dark horse dust clouds silhouetted against the rich backdrop of stars in the Milky Way. The bottom section is the Pipe Nebula. Credit: David Haworth

Australian aboriginal peoples created dark constellations like the Emu by connecting a dark patches of the southern Milky Way into creature forms. One of the my favorite such dark patterns and what’s come to be known as the Galactic Dark Horse (GDH) lies about one outstretched fist to the left of the Scorpius’ brightest star Antares.

Astronomers catalog a number of individual dark nebulae that together form the horse. But to the human brain, which has a knack for seeing patterns in just about everything, the silhouetted outline of a horse prancing on its hind legs is unmistakable. The largest part of the, the hind leg, is also nicknamed the Pipe Nebula and lies 600-700 light years away.

Look about one outstretched fist to the left of bright Antares in Scorpius to spot the Dark Horse. This map shows the sky in mid-June facing south around 11:30 p.m. The horse, specially highlighted here, is a fairly large  feature – about 10 degrees tall.  Stellarium

For skywatchers at mid-northern latitudes, the GDH is best viewed under dark rural skies where the horse prances low in the south not far from Antares in Scorpius. Allow your eyes time to fully dark adapt and look for his dark rump, wispy head and prong-like legs. This is a fairly large but very dim naked eye object some 10 by 7 degrees across. Averted vision will be your friend. Wide-field binoculars will show it in greater detail against a fabulously rich star field. Best viewing during the current moon-free window starts tonight and continues through about July 3.

If we could see the Milky Way galaxy edge-on from afar, it would look similar to NGC 891 in Andromeda. Both have long bands of interstellar dust along their equators that appear dark against the bright starry backdrop. Credit: Jim Misti

Many spiral galaxies like the Milky Way have dark clouds of interstellar dust striping their galactic equators. NGC 891 is just one example. Think of all the wild horses that must be out there!

Smith’s Cloud on a collision course with the Milky Way

A false-color image of the Smith Cloud made with data from the Green Bank Telescope (GBT). New analysis indicates that it is wrapped in a dark matter halo affording it a measure of invincibility against the gravitational powers of the Milky Way. Credit: NRAO/AUI/NSF

A roving billow of hydrogen gas on a collision course with the Milky Way galaxy should have disintegrated when it smacked us the last time 70 million years ago. But no. Astronomers think a casing of dark matter – that invisible stuff comprising 96% of the material universe – has protected it from getting ripped to shreds by our galaxy’s gravitational grasp.

If you could see it, the Smith Cloud would nearly span the constellation Orion, but it’s much too faint. Located in the summer star group Aquila the Eagle, this 9,800 by 3,300 light year long cloud was discovered by Gail Bieger (birth name ‘Smith’) at Leiden University in the Netherlands in 1963.

Pie chart showing the matter and energy content of the universe. Most is wrapped up in the mysterious ‘dark energy’ responsible for the acceleration in the expansion rate of the universe. Dark matter, an as-yet unknown material, accounts for 23% of the solid matter content while just 4% is ordinary matter made of atoms. Of that only 0.4% is contained in stars and planets.

Composed of at least 1 million solar masses of hydrogen gas, astronomers call it an HVC or ‘high velocity cloud’, one of many that populate our galaxy’s outer halo. Radio telescopes are the instruments of choice for studying HVCs – their sensitive receivers pick up the faint hiss of radio energy emitted when hydrogen atoms change their energy state.

Based on its trajectory, we can trace the Smith Cloud’s whereabouts long ago. 70 million years ago it passed through the Milky Way with nary a scratch, an impossible feat were it not wearing a suit of dark matter armor:

Artist’s conception of Smith’s Cloud approaching, then colliding with, our own Milky Way Galaxy in approximately 30 million years. When it strikes, it may trigger a wave of new star formation from the collision of gases and accompanying shock wave. Credit: Bill Saxton, NRAO/AUI/NSF

“Based on the currently predicted orbit, we show that a dark matter-free cloud would be unlikely to survive this disk crossing,” observed Jay Lockman, an astronomer at the National Radio Astronomy Observatory in Green Bank, West Virginia, and one of the co-authors on the paper. “While a cloud with dark matter easily survives the passage and produces an object that looks like the Smith Cloud today.”

All galaxies are surrounded by dark matter halos including the Milky Way. Only a fraction of the galaxy’s matter resides in the bright disk and halo, which contains stars, globular clusters and gas clouds. Most of it is invisible and only detected through its gravitational attraction. Credit: ESO (galaxy impression) and author

Our galaxy is rich with high-velocity clouds too rarefied to form stars. We think they’re leftover building blocks from the galaxy’s formation –  smaller clouds that coalesced under gravity’s incessant pull to create the big 100,000 light-year-wide galaxy we call home today. With its dark matter halo, the Smith Cloud may have a different origin as an interloper from intergalactic space. Instead of a building block, the Cloud could be a stillborn dwarf galaxy:

“If confirmed to have dark matter this would in effect be a failed galaxy,” said Matthew Nichols with the Sauverny Observatory in Switzerland and principal author of the paper. “Such a discovery would begin to show the lower limit of how small a galaxy could be.”

Currently about 8,000 light years from the Milky Way’s disk, the Smith Cloud is approaching like a ship in the night at 150 miles per second. When it arrives in about 30 million years, will it pull off another superhero move like Tony Stark clad in his Ironman getup or will the Milky Way finally get the better of it?

Get a GLIMPSE of the real Milky Way with this 360-degree interactive map

A slice of the Milky Way in Scorpius and Sagittarius from the new zoomable Milky Way mosaic called GLIMPSE360. Two million images were used to create it. Click to zoom over to the interactive version. Credit: NASA/JPL-Caltech/GLIMPSE team

NASA’s in big picture mode this week. On Wednesday we traveled to the moon’s north pole with a fabulous, interactive gigapixel map. Now you can explore a similar interactive mosaic of the Milky Way called GLIMPSE360 or Galactic Legacy Infrared Mid-Plane Survey Extraordinaire. Some fierce creativity went into squeezing that into a word!

Two million images taken by NASA’s Spitzer Space Telescope over the past 10 years were stitched together to create the 20-gigapixel map. Spitzer shoots photos in infrared light, which lies to just beyond the red end of the rainbow spectrum. You and I can’t see infrared, but we can feel it as heat. When it comes to peering into our galaxy’s innards, infrared does a much better job than visual light because it’s able to penetrate the stellar smog – interstellar dust – that litters the Milky Way’s spiral arms.


A GLIMPSE of the Milky Way

Here’s the crazy thing about the mosaic. It only captures about 3% of the sky, but it’s centered on the thin plane of our galaxy where most of the stars are concentrated.

So what can we see? Well over half of the Milky Way’s 300 billion suns for starters, plus stellar nurseries swathed in fluorescent pink clouds of hydrogen and giant expanding gas bubbles inflated by gusty winds from supergiant stars. Oh – there’s also the galactic center. It’s totally obscured by dust in normal telescopes but infrared waves reveal a glowing core.

The best current model of the Milky Way galaxy. We live in a flattered, pancake-like disk about 100,000 light years wide. The solar system is located about two-thirds from the center to the outer edge in a small spiral arm called the Orion Spur. Credit: NASA

You and I may simply enjoy taking in the sights like tourists, but astronomers are using these photos/montage to discover new things about our home galaxy. Spitzer has revealed the true extent of the chunky bar of stars bisecting the core and discovered that the Milky Way is larger than had previously been thought.

The map will also be used to target specific regions of star formation for closer examination with NASA’s upcoming James Webb Space Telescope.

There’s something for everyone with the new interactive panorama. Check it out.

For more information on the project, click HERE.

Gaia space telescope blasts off today on a 5-year Milky Way mission

Soyuz VS06, carrying the Gaia space observatory, lifted off from Europe’s Spaceport, French Guiana today Dec. 19. Shock waves surround the speeding rocket. Credit: ESA

Early this morning the European Space Agency (ESA) successfully launched the Gaia space telescope from the Kourou Spaceport in French Guiana. Its mission: to create a precision three-dimensional map of the Milky Way galaxy by studying a billion stars over five years time. Yes, that’ one billion stars – about 1% of the total population of stars in the galaxy.

Illustration of the L2 point showing the distance between the L2 and the Sun, compared to the distance between Earth and the Sun. Gaia will take up residence at this gravitationally stable point in space away from much of the heat and light from Earth and sun. Credit: ESA

Gaia is now cruising toward the gravitationally-stable L2 point located 932,000 miles (1.5 million km) on the opposite side of the Earth from the sun. It will arrive there in about 20 days. Four months later, during which instruments will be turned on, checked and calibrated, Gaia will begin its 5-year mission.

Like petals surrounding the heart of a sunflower, Gaia’s sun shield unfolded shortly after launch and will prevent heat and light from the sun and Earth from interfering with ultra-precise measurements of the stars’ positions and compositions.

“Repeatedly scanning the sky, Gaia will observe each of the billion stars an average of 70 times each over the five years. It will measure the position and key physical properties of each star, including its brightness, temperature and chemical composition,” writes the agency.

Its sun shield unfolded, Gaia maps the stars of the Milky Way in this artist’s illustration using a sophisticated billion-pixel camera. Credit: ESA/ATG medialab; background image: ESO/S. Brunier

Gaia will take advantage of the changing perspective on the stars it observes as it orbits the sun during the year, using parallax and basic math to measure precise distances to all one billion stars. Over the five years, it will be able to track the stars’ motions across the galaxy, helping us discover from where they originated in the Milky Way and where they’re headed.

Plotting stellar motion may even lead us to a grander synthesis about the origin and evolution of the galaxy itself –  how it was assembled from the merger of smaller galaxies and what fate holds for our big, beautiful home.

By comparing its repeated scans of the sky, Gaia will also discover tens of thousands of supernovas. Small periodic wobbles in the positions of some stars caused by tugging planets should reveal the presence of planets in orbit around them. Closer to home, the probe will discover new asteroids flitting around the solar system and test Einstein’s General Relativity Theory.


Animation showing Gaia’s journey to its operating orbit. Credit: ESA

Much of what we know about stars, nebulas, galaxies and all the rest is based upon having accurate distances to them. The earlier ESA Hipparcos mission cataloged positions of 120,000 stars; Gaia will survey almost 10,000 times as many at roughly 40 times higher precision.

Humanity is reaching out to the stars in a big way here. It gives me hope that our distant descendants will one day roam the galaxy.

For more information on Gaia, please refer to today’s ESA press release.

Nova Delphini 2013 – a white dwarf with a yearn to burn

The bright nova in Delphinus photographed last night in a 16-inch telescope. Credit: John Chumack

It’s official. The new nova has been christened Nova Delphini 2013. Even better, it’s brightened since discovery. Last night a group of stargazers and I saw the pale yellow star with ease through the telescope. Later, when the moon had set, I was even able to spot the nova faintly with the naked eye at magnitude 5.8.

It’s been years since we’ve had an exploding star of this variety reach naked eye brightness. About 6-10 novae are discovered each year, most of them needing at least a small telescope to see. This year novae have popped off in Cepheus, Scorpius and possibly one in Aquila. Amateur astronomers are the nova finders, training cameras on swaths of the Milky Way night after night hoping to catch one in outburst.

The brightest nova ever recorded blew its top in Aquila the Eagle in 1918. V603 Aquilae shot all the up to -1.4 magnitude or nearly as bright as Sirius, the brightest star. You can still see it today in a 6-inch or larger telescope biding its time around magnitude 12 patiently waiting for another chance at nova-hood. Click HERE to get a finder chart.

The Milky Way is the favorite hunting ground for nova hunters. The dense concentration of stars along its band offers the best chance of finding the occasional nova. The galaxy averages about three dozen novae a year of which about a half dozen are discovered. Credit: Bob King

The Milky Way is the most lucrative hunting ground for novae hunting because stars are greatly concentrated along its length; that’s what creates the familiar hazy ribbon of light. You’re much more likely to spot one pointing your camera at millions of stars than at sparsely-strewn star fields outside the Milky Way band. Favorite hunting grounds include the Milky Way-streaked constellations of Scorpius, Sagittarius and Cygnus. I’ve never heard of one being found in the Big Dipper which is located well away from the galactic plane.

Novae occur in close binary systems where one star is a tiny but extremely compact white dwarf star. The dwarf pulls material into a disk around itself, some of which is funneled to the surface and ignites in a nova explosion. Credit: NASA

Just as there’s more than one type of tea, there are different kinds of novae. All involve close binary stars with a compact white dwarf stealing gas from its companion. The gas ultimately funnels down to the surface of the dwarf where it’s compacted by gravity and heated to high temperature on the star’s surface until it ignites in an explosive fireball. This is what you see when you look at a nova – a gigantic bomb going off.

Just to be clear, a nova doesn’t involve the destruction of the star, only a “shock to the system”. A supernova is a different beast entirely, resulting in the complete annihilation of a white dwarf or supergiant star. If a white dwarf accumulates too much matter from a companion and crosses the Chandrasekhar Limit, it can sidestep the nova stage and go straight to supernova.

Looking more closely we discover that novae come in two basic types – fast and slow. Fast ones rise abruptly to maximum brightness, some of them vaulting 10 magnitudes a day. Their decline can be equally swift.

All-sky Milky Way mosaic photo compiled by the 2MASS survey in dust-penetrating infrared light shows the flat disk, home to younger stars and fast novae and the fat central bulge, where more slow novae and older stars are found. Click to full-size version. Credit: 2MASS, J. Carpenter, T.H. Jarrett and R. Hurt.

Slow novae behave as you might expect, sometimes taking several months to reach peak brightness and often lingering for months. Fast novae, which arise from more massive white dwarfs, are concentrated in our galaxy’s flat disk; slow ones from smaller dwarfs are found in the central bulge. I suspect this recent nova is the fast variety.

Nova Delphini is still in the fireball stage engulfed by incandescent hydrogen gas. Astronomers have spectroscopically measured the speed of the ejecta from the blast at 1,250 miles (2,000 km) per secondThat’s 4.5 million miles per hour. Think about that for a second. Now picture the scene in your mind’s eye when you see the nova for yourself.

This map shows Delphinus and Sagitta, both of which are near the bright star Altair at the bottom of the Summer Triangle. You can star hop from the top of Delphinus to the star 29 Vulpeculae and from there to the nova. Or you can point your binoculars midway between Eta Sagittae and 29 Vul. Numbers in gold are star magnitudes. Stellarium

I’ve included a fresh map above. The numbers in gold are star magnitudes to help you track the nova’s brightness as it brightens or fades in the coming nights. The larger the number, the fainter the star. Click HERE for a nice explanation of star magnitudes. For more maps, please see my earlier Universe Today post.

Update 8/16: Last night Aug. 15 I saw the nova at magnitude 4.8 and it was even brighter this morning. That means it’s nearly ten times brighter than at discovery a two days ago.

Munchkin Milky Way meets mega-monster galaxy IC 1101

The Milky Way slices across the summer sky reached Cassiopeia and Perseus in the northeast down to Sagittiarius in the south as viewed from mid-northern latitudes. The galaxy is comprised of billions of stars, star clusters, gas clouds and planets. Credit: Bob King

We have the barest inkling of how truly vast the Milky Way galaxy is, but looking up on a dark summer night is enough to convince you it must be REALLY big. After all, this garland of hazy light speckled with stars touches both ends of the sky, north and south.

Astronomers have measured the galaxy’s diameter at 100,000 light years which means little until you appreciate that one light year equals 6 trillion miles, the distance a beam of light travels in one year. The fastest spacecraft ever built, the Helios probes, reached 157,000 mph (253,000 km/hr) as they zipped around the sun studying the solar wind from the mid-1970s to 1985. While that’s nine times faster than the International Space Station, it would still take 4,383 years to travel one light year at that phenomenal pace.

The Milky Way is a spiral galaxy with a prominent dense bar of stars across its core. The sun and planets are located with a spiral arm some 27,000 light years from the center. Illustration: NASA/JPL-Caltech/R. Hurt (SSC/Caltech)

Even fleet light takes 100,000 years to cross from one side of the galaxy to the other. A light ray leaving Earth 100,000 years ago, when Neanderthals were the dominate human species in Europe, recently arrived there in our mobile-phone obsessed era. What will Earth look like 100,000 years from now?

Vast as the Milky Way is, it’s dwarfed by IC 1101, a faint galaxy residing in the center of the rich galaxy cluster Abell 2029 in the constellation Virgo. Located a billion light years from Earth, IC 1101 is the largest known galaxy with a diameter of 6 million light years or at least 60 times the size of the Milky Way.

Earth’s huge and tiny at the same time depending upon your perspective. Credit: Lsmpascal

You’ve probably all seen the illustration comparing the size of Earth to the sun. We sure do look tiny. Now multiply our one star by 200-400 billion – that’s the number of stars in the Milky Way – and consider that many of them likely harbor planets. Impressive place this Milky Way … until you park it alongside IC 1101 with its 100 trillion stars.

The Milky Way fares well in the neighborhood “Local Group” cluster of galaxies. It and Andromeda are the largest of its approximately 54 members. Credit: Andrew Colvin

Galaxies can be broken down into three basic types: spirals (like the Milky Way), ellipticals and irregulars. Spiral galaxies’ cores glow yellow from billions of older stars that formed in the galaxy’s youth that have since aged and evolved. Hot, new stars, which are generally bluer in color, coalesce from dust and gas within the spiral arms that wind around the central hub.

Ellipticals are spherical or flattened like a footballs and generally featureless. Most appear like foggy patches of amorphous star-haze. At a young age, they quickly converted their dust and gas into billions of stars that have since aged and yellowed like the ones in the Milky Way’s core. No spiral arms or fresh-faced hot stars here.

Giant ellipticals like IC 1101 usually start out small, beginning with the merger of a few modest galaxies within a cluster like Abell 2029. But if the process continues unchecked,   a monster is born. Over their lifetimes large ellipticals can rack up a lot of mass, and the bigger they get, the more gravitational pull they exercise over their environment, sucking in even more galaxies. Large elliptical galaxies are common features in large, rich galaxy clusters.

IC 1101, the largest known galaxy, dwarfs all the others including another large elliptical galaxy M87, also in Virgo, Andromeda and the Milky Way. Credit: NASA

If you could put IC 1101 in place of our Milky Way it would encompass a volume of space big enough to include our galaxy and its satellites the Large and Small Magellanic Clouds plus the neighboring Andromeda and Triangulum galaxies. That’s I what call supersized!

Every time we look at the sky, we can’t help but be taught a lesson in perspective. Earth’s an atom compared to the Milky Way, and the Milky Way’s a mouse at the feet of IC 1101. Our job is to find our place in this vastitude.

To assist you in your journey, a great place to start, besides the night sky of course, is Cary Huang’s wonderful Scale of the Universe 2.

 

Weekend “Black Hole” full Moon brightest and closest of the year

Watch for a bigger and brighter full moon than usual tomorrow and Sunday nights. Photo illustration: Bob King

Wishing you a grand first day of summer today and clear nights ahead. This weekend we’ll see the full moon dangling like heavy fruit low in the southern sky. If it looks a tad bigger than last month’s Full Flower Moon, it really is. The moon reaches perigee – closest point to Earth in its orbit – at 6:11 a.m. CDT Sunday morning June 23 just a half hour before the moment of full moon. At the same time it will hover in front of the Milky Way’s central supermassive black hole.

With all those superlatives, you might think I’m setting you up for the end of the world. Trust me, I’m not. The full moon is near the same spot every June and perigees are almost as common as dandelions.

Like the planets do around the sun, the moon moves in an elliptical orbit around the Earth. Once a month it’s closest to us at perigee and farthest away at apogee. Next apogee will be at new moon on July 7. The moon’s average distance from Earth is 238,856 miles (384403 km).

The moon follows an elliptical path around the Earth with one side of its orbit some 31,000 miles (50,000 km) closer (perigee) to our planet than the other side (apogee). Since the moon orbits the Earth every 27 days it reaches perigee once or sometimes twice a month.

So what makes this one special? Well, not all perigees are alike. Some are closer than others and occur at times other than full moon. The closest perigees, like this Sunday’s, occur when the moon is either full or new – times when Earth, moon and sun are all lined up in a row. The sun’s gravity tugs more strongly on the moon at these phases, stretching its orbit and leading to extreme values for perigee and apogee.

No one notices an unusually large first quarter or crescent moon, but we all sit up and pay attention to a bigger-than-normal full moon.

The difference between the the moon at its most distant apogee and closest perigee dramatically illustrated in this pair of photos taken in 2006. The full moon can be as much as 14% bigger and 30% brighter when closest. The weekend’s moon will be 12% bigger than January 2014′s apogee full moon. Credit: Anthony Ayiomamitis

The moon’s most distant perigee (230,000 miles) happened at last quarter phase on March 5 this year. Sunday’s will be the closest of the year at just 222,000 miles (357,000 km). Some keen-eyed skywatchers might notice the moon looking a little larger than it will at apogee on Jan 14, 2014. I say might. Without a reference, it’s terribly hard to compare sizes. The moon illusion, an apparent bloating of our satellite when seen low in the sky, further complicates the view. Still, facts are facts. The moon will be bigger and brighter this weekend than on any other night this year.

Saturday night’s full “Black Hole Moon” will lie about one fist held at arm’s length left and above the center of Milky Way galaxy.  Astronomers call the spot Sagittarius A* (Sagittarius A star). Blocked by intervening dust and invisible to optical telescopes, it marks the site of a supermassive black hole. Created with Stellarium

Not only does the closest perigee of the year coincide with Full Moon, but the moon will be in the “Teapot” constellation Sagittarius in approximately the same direction as our galaxy’s 4-million-mass black hole. Look toward the moon and you can imagine it there munching its way on gas clouds and stars that pass that pass too close for comfort. Given that the beast is 26,000 light years (156 quadrillion miles) from us, neither moon nor monster have any gravitational inkling of the other.

Since full phase happens early Sunday morning, the moon will appear full to the eye both Saturday and Sunday nights. I hope you’ll get to enjoy the show.