Observing Archives

June 24, 2014December 23, 2015 by Bob King

Observing Alert: Distant Blazar 3C 454.3 in Outburst, Visible in Amateur Telescopes

The blazar 3C 454.3 photographed by the Sloan Digital Sky Survey. It's currently in bright outburst and nearly as bright as the star next to it. Both are about magnitude +13.6. Credit: SDSS

Have an 8-inch or larger telescope? Don’t mind staying up late? Excellent. Here’s a chance to stare deeper into the known fabric of the universe than perhaps you’ve ever done before. The violent blazer 3C 454.3 is throwing a fit again, undergoing its most intense outburst seen since 2010. Normally it sleeps away the months around 17th magnitude but every few years, it can brighten up to 5 magnitudes and show in amateur telescopes. While magnitude +13 doesn’t sound impressive at first blush, consider that 3C 454.3 lies 7 billion light years from Earth. When light left the quasar, the sun and planets wouldn’t have skin in the game for another two billion years.

If we could see the blazar 3C 354.3 up close it would look something like this. A bright accretion disk surrounds a black hole. Twin jets of radiation beam from the center. Credit: Cosmovision

Blazars form in the the cores of active galaxies where supermassive black holes reside. Matter falling into the black hole spreads into a spinning accretion disk before spiraling down the hole like water down a bathtub drain.

Superheated to millions of degrees by gravitational compression the disk glows brilliantly across the electromagnetic spectrum. Powerful spun-up magnetic fields focus twin beams of light and energetic particles called jets that blast into space perpendicular to the disk.

Blazars and quasars are thought to be one and the same, differing only by the angle at which we see them. Quasars – far more common – are actively- munching supermassive black holes seen from the side, while in blazars – far more rare – we stare directly or nearly so into the jet like looking into the beam of a flashlight.

An all-sky view in gamma ray light made with the Fermi gamma ray telescope shows bright gamma-ray emission in the plane of the Milky Way (center), bright pulsars and super-massive black holes including the active blazar 3C 454.3 at lower left. Credit: NASA/DOE/International LAT Team — An all-sky view in gamma ray light made with the Fermi Gamma-ray Space Telescope shows bright gamma-ray emission in the plane of the Milky Way (center), bright pulsars and super-massive black holes including the active blazar 3C 454.3 at lower left. Credit: NASA/DOE/International LAT Team

3C 454.3 is one of the top ten brightest gamma ray sources in the sky seen by the Fermi Gamma-ray Space Telescope. During its last major flare in 2005, the blazar blazed with the light of 550 billion suns. That’s more stars than the entire Milky Way galaxy! It’s still not known exactly what sets off these periodic outbursts but possible causes include radiation bursts from shocked particles within the jet or precession (twisting) of the jet bringing it close to our line of sight.

3c 454.3 is near the magnitude 2.5 magnitude star Alpha Pegasi just to the west of the Great Square. Use this chart to star hop from Alpha to IM Peg (mag. ~ 5.7). Once there, the detailed map below will guide you to the blazar. Stellarium — 3c 454.3 is near the star Alpha Pegasi just to the west of the Great Square. Use this chart to star hop from Alpha to IM Peg (mag. ~ 5.7). Once there, the detailed map below will guide you to the blazar. Stellarium

The current outburst began in late May when the Italian Space Agency’s AGILE satellite detected an increase in gamma rays from the blazar. Now it’s bright visually at around magnitude +13.6 and fortunately not difficult to find, located in the constellation Pegasus near the bright star Alpha Pegasi (Markab) in the lower right corner of the Great Square asterism.

Using the wide view map, find your way to IM Peg via Markab and then make a copy of the detailed map below to use at the telescope to star hop to 3C 454.3. The blazar lies immediately south of a star of similar magnitude. If you see what looks like a ‘double star’ at the location, you’ve nailed it. Incredible isn’t it to look so far into space back to when the universe was just a teenager? Blows my mind every time.

Detailed map showing the location of the blazar 3C 454.3. I've created a small asterism with a group of brighter stars with their magnitudes marked. A scale showing 30 arc minutes (1/2 degree) is at right. Stars shown to about magnitude +15. Created with Chris Marriott's SkyMap software — Detailed map showing the location of the blazar 3C 454.3. I’ve drawn a small asterism using a group of brighter stars with their magnitudes marked. A scale showing 30 arc minutes (1/2 degree) is at right. Click to enlarge. Created with Chris Marriott’s SkyMap software

To further explore 3C 454.3 and blazars vs. quasars I encourage you to visit check out Stefan Karge’s excellent Frankfurt Quasar Monitoring site. It’s packed with great information and maps for finding the best and brightest of this rarified group of observing targets. Karge suggests that flickering of the blazar may cause it to appear somewhat brighter or fainter than the current magnitude. You’re watching a violent event subject to rapid and erratic changes. For an in-depth study of 3C 454.3, check out the scientific paper that appeared in the 2010 Astrophysical Journal.

Learn more about quasars and blazers with a bit of great humor

Finally, I came across a wonderful video while doing research for this article I thought you’d enjoy as well.

June 23, 2014December 23, 2015 by David Dickinson

Observing Challenge: The Moon Brushes Past Venus and Covers Mercury This Week

The summer astronomical action heats up this week, as the waning crescent Moon joins the inner planets at dawn. This week’s action comes hot on the tails of the northward solstice which occurred this past weekend, which fell on June 21^st in 2014, marking the start of astronomical summer in the northern hemisphere and winter in the southern. This also means that the ecliptic angle at dawn for mid-northern latitude observers will run southward from the northeast early in the morning sky. And although the longest day was June 21^st, the earliest sunrise from 40 degrees north latitude was June 14^th and the latest sunset occurs on June 27^th. We’re slowly taking back the night!

The dawn patrol action begins tomorrow, as the waning crescent Moon slides by Venus low in the dawn sky Tuesday morning. Geocentric (Earth-centered) conjunction occurs on June 24^th at around 13:00 Universal Time/9:00 AM EDT, as the 8% illuminated Moon sits 1.3 degrees — just shy of three Full Moon diameters — from -3.8 magnitude Venus. Also note that the open cluster the Pleiades (Messier 45) sits nearby. Well, nearby as seen from our Earthbound vantage point… the Moon is just over one light second away, Venus is 11 light minutes away, and the Pleiades are about 400 light years distant.

Jun 24 5AM Starry Night — Looking east the morning of Tuesday, June 24th at 5:00 AM EDT from latitude 30 degrees north. Created using Starry Night Education software.

And speaking of the Pleiades, Venus will once again meet the cluster in 2020 in the dusk sky, just like it did in 2012. This is the result of an eight year cycle, where apparitions of Venus roughly repeat. Unfortunately we won’t, however, get another transit of Venus across the face of the Sun until 2117!

Can you follow the crescent Moon up in to the daytime sky? Tuesday is also a great time to hunt for Venus in the daytime sky, using the nearby crescent Moon as a guide. Both sit about 32 degrees from the Sun on June 24^th. Just make sure you physically block the dazzling Sun behind a building or hill in your quest.

From there, the waning Moon continues to thin on successive mornings as it heads towards New phase on Friday, June 27^th at 8:09 UT/4:09 AM EDT and the start of lunation 1132. You might be able to spy the uber-thin Moon about 20-24 hours from to New on the morning prior. The Moon will also occult (pass in front of) Mercury Thursday morning, as the planet just begins its dawn apparition and emerges from the glare of the Sun.

Unfortunately, catching the event will be a challenge. Mercury is almost always occulted by the Moon in the daytime due to its close proximity to the Sun. The footprint of the occultation runs from the Middle East across North Africa to the southeastern U.S. and northern South America, but only a thin sliver of land from northern Alabama to Venezuela will see the occultation begin just before sunrise… for the remainder of the U.S. SE, the occultation will be underway at sunrise and Mercury will emerge from behind the dark limb of the Moon in daylight.

Mercury and the Moon sit 10 degrees from the Sun during the event. Stargazer and veteran daytime planet hunter Shahrin Ahmad based in Malaysia notes that while it is possible to catch Mercury at 10 degrees from the Sun in the daytime using proper precautions, it’ll shine at magnitude +3.5, almost a full 5 magnitudes (100 times) fainter than its maximum possible brightness of -1.5. The only other occultation of Mercury by the Moon in 2014 favors Australia and New Zealand on October 22^nd.

This current morning apparition of Mercury this July is equally favorable for the southern hemisphere, and the planet reaches 20.9 degrees elongation west of the Sun on July 12^th.

You can see Mercury crossing the field of view of SOHO’s LASCO C3 camera from left to right recently, along with comet C/2014 E2 Jacques as a small moving dot down at about the 7 o’clock position.

And keep an eye on the morning action this summer, as Jupiter joins the morning roundup in August for a fine pairing with Venus on August 18^th.

The Moon will then reemerge in the dusk evening sky this weekend and may just be visible as a 40-44 hour old crescent on Saturday night June 28^th. The appearance of the returning Moon this month also marks the start of the month of Ramadan on the Islamic calendar, a month of fasting. The Muslim calendar is strictly based on the lunar cycle, and thus loses about 11 days per year compared to the Gregorian calendar, which strives to keep the tropical and sidereal solar years in sync. On years when the sighting of the crescent Moon is right on the edge of theoretical observability, there can actually be some debate as to the exact evening on which Ramadan will begin.

Don’t miss the wanderings of our nearest natural neighbor across the dawn and dusk sky this week!

June 20, 2014December 23, 2015 by Bob King

How to Find Your Way Around the Milky Way This Summer

The band of the Milky Way stretches from Cygnus (left) to the Sagittarius in this wide-angle, guided photo. Credit: Bob King

Look east on a dark June night and you’ll get a face full of stars. Billions of them. With the moon now out of the sky for a couple weeks, the summer Milky Way is putting on a grand show. Some of its members are brilliant like Vega, Deneb and Altair in the Summer Triangle, but most are so far away their weak light blends into a hazy, luminous band that stretches the sky from northeast to southwest. Ever wonder just where in the galaxy you’re looking on a summer night? Down which spiral arm your gaze takes you?

Artist's conception of the Milky Way galaxy based on the latest survey data from ESO’s VISTA telescope at the Paranal Observatory. A prominent bar of older, yellower stars lies at galaxy center surrounded by a series of spiral arms. The galaxy spans some 100,000 light years. Credit: NASA/JPL-Caltech, ESO, J. Hurt — Artist’s conception of the Milky Way galaxy based on the latest survey data from ESO’s VISTA telescope at the Paranal Observatory. A prominent bar of older, yellower stars lies at galaxy center surrounded by a series of spiral arms. The galaxy spans some 100,000 light years. Credit: NASA/JPL-Caltech, ESO, J. Hurt

Two different perspectives on our galaxy to help us better understand its shape. A face-on artist's view at left reveals the core and arms. At right, we see a photo of the Milky Way in infrared light by the Cosmic Background Explorer probe showing us an edge-on perspective, the view we're 'stuck with' but dint of orbiting inside the galaxy's flat plane. Credit: NASA/JPL et. all (left) and NASA — Two different perspectives on our galaxy help us better understand its shape. A face-on artist’s view at left reveals the core, spiral arms and the sun’s position. At right, we see an edge-on perspective photographed by the Cosmic Background Explorer probe. Because the sun and planets orbit in the galaxy’s plane, we’re ‘stuck’ with an edge-on view until we build a fast-enough rocket to take us above our galactic home. Credit: NASA/JPL et. all (left) and NASA

Because all stars are too far away for us to perceive depth, they appear pasted on the sky in two dimensions. We know this is only an illusion. Stars shine from every corner of the galaxy, congregating in its bar-shaped core, outer halo and along its shapely spiral arms. The trick is using your mind’s eye to see them that way.

Employing optical, infrared and radio telescopes, astronomers have mapped the broad outlines of the home galaxy, placing the sun in a minor spiral arm called the Orion or Local Arm some 26,000 light years from the galactic center. Spiral arms are named for the constellation(s) in which they appear. The grand Perseus Arm unfurls beyond our local whorl and beyond it, the Outer Arm. Peering in the direction of the galaxy’s core we first encounter the Sagittarius Arm, home to sumptuous star clusters and nebulae that make Sagittarius a favorite hunting ground for amateur astronomers.

Further in lies the massive Scutum-Centaurus Arm and finally the inner Norma Arm. Astronomers still disagree on the number of major arms and even their names, but the basic outline of the galaxy will serve as our foundation. With it, we can look out on a dark summer night at the Milky Way band and get a sense where we are in this magnificent celestial pinwheel.

The Milky Way band arches across the east and south as seen about 11:30 p.m. in mid-late June. The center of the galaxy is located in the direction of the constellation Sagittarius. Stellarium — The Milky Way band arches across the east and south as seen about 11:30 p.m. in mid-late June. The center of the galaxy is in the direction of the constellation Sagittarius. The dark ‘rift’ that appears to cleave the Milky Way in two is formed of clouds of interstellar dust that blocks the light of stars beyond it. Stellarium

We’ll start with the band of the Milky Way itself. Its ribbon-like form reflects the galaxy’s flattened, lens-like profile shown in the edge-on illustration above. The sun and planets are located within the galaxy’s plane (near the equator) where the stars are concentrated in a flattened disk some 100,000 light years across. When we look into the galaxy’s plane, billions of stars pile up across thousands of light years to create a narrow band of light we call the Milky Way. The same term is applied to the galaxy as a whole.

Since the average thickness of the galaxy is only about 1,000 light years, if you look above or below the band, your gaze penetrates a relatively short distance – and fewer stars – until entering intergalactic (starless) space. That why the rest of the sky outside of the Milky Way band has so few stars compared to the hordes we see within the band.

Here’s the galactic big picture showing the outline of the galaxy with constellations added. In this edge-on view, we see that the summertime Milky Way from Cassiopeia to Sagittarius includes the central bulge (in the direction of Sagittarius) and a hefty portion of one side of the flattened disk:

The outline of the Milky Way viewed edge-on is shown in gray. The yellow box includes the summer portion of the Milky Way from Cassiopeia to Scorpius with a red dot marking the galaxy's center. This is the section we see crossing the eastern sky in June and includes the galactic center. Click to enlarge. Credit: Richard Powell with additions by the author — The outline of the Milky Way viewed edge-on is shown in gray. The yellow box includes the summer portion of the Milky Way from Cassiopeia to Scorpius with a red dot marking the galaxy’s center. This is the section we see crossing the eastern sky in June. Click to enlarge. Credit: Richard Powell with additions by the author

If you enlarge the map, you’ll see lines of galactic latitude and longitude much like those used on Earth but applied to the entire galaxy. Latitude ranges from +90 degrees at the North Galactic Pole to -90 at the South Galactic Pole. Likewise for longitude. 0 degrees latitude, o degrees longitude marks the galactic center. The summer Milky Way band extends from about longitude 340 degrees in Scorpius to 110 in Cassiopeia.

Now that we know what section of the Milky Way we peer into this time of year, let’s take an imaginary rocket journey and see it all from above:

Viewed from above, we can now see that our gaze takes across the Perseus Arm (toward the constellation Cygnus), parts of the Sagittarius and Scutum-Centaurus arms (toward the constellations Scutum, Sagittarius and Ophiuchus) and across the central bar. Interstellar dust obscures much of the center of the galaxy. Credit: NASA et. all with additions by the author. — Viewed from above, we can now see that our gaze (red arrows) reaches down the Perseus Arm (toward the constellation Cygnus) and across the Sagittarius and Scutum-Centaurus arms (toward the constellations Scutum, Sagittarius and Ophiuchus) and directly into the central bar. Interstellar dust obscures much of the center of the galaxy. Blue arrows show the direction we face during the winter months. Credit: NASA et. all with additions by the author.

Wow! The hazy arch of June’s Milky Way takes in a lot of galactic real estate. A casual look on a dark night takes us from Cassiopeia in the outer Perseus Arm across Cygnus in our Local Arm clear over to Sagittarius, the next arm in. Interstellar dust deposited by supernovae and other evolved stars obscures much of the center of the galaxy. If we could vacuum it all up, the galaxy’s center – where so many stars are concentrated – would be bright enough to cast shadows.

A view showing the summer Milky Way from mid-northern latitudes with three constellations and the spiral arms to which they belong. Stellarium — A view showing the summer Milky Way from mid-northern latitudes with three prominent constellations and the spiral arms we peer into when we face them. Stellarium

Here and there, there are windows or clearings in the dust cover that allow us to see star clouds in the Scutum-Centaurus and Norma Arms. In the map, I’ve also shown the section of Milky Way we face in winter. If you’ve ever compared the winter Milky Way band to the summer’s you’ve noticed it’s much fainter. I think you can see the reason why. In winter, we face away from the galaxy’s core and out into the fringes where the stars are sparser.

Look up the next dark night and contemplate the grand architecture of our home galaxy. If you close your eyes, you might almost feel it spinning.

June 17, 2014December 23, 2015 by David Dickinson

Asteroid-Turned-Comet 2013 UQ4 Catalina Brightens: How to See it This Summer

Though ISON may have fizzled in early 2014, we’ve certainly had a bevy of binocular comets to track this year. Thus far in 2014, we’ve had comets R1 Lovejoy, K1 PanSTARRS, and E2 Jacques reach binocular visibility. Now, and asteroid-turned-comet is set to put on a fine show this summer for northern hemisphere observers.

Veteran stargazer and Universe Today contributor Bob King told the tale last month of how the asteroid formerly known as 2013 UQ4 became comet 2013 UQ4 Catalina. Discovered last year on October 23^rd 2013 during the routine Catalina Sky Survey searching for Near Earth Objects based outside of Tucson Arizona, this object was of little interest until early this year.

As it rounded the Sun, astronomers recovered the asteroid and discovered that it had begun to sprout a fuzzy coma, a very un-asteroid-like thing to do. Then, on May 7^th, Taras Prystavski and Artyom Novichonok — of Comet ISON fame — conducted observations of 2013 UQ4 and concluded that it was indeed an active comet.

Hovering around +13^th magnitude last month, newly rechristened 2013 UQ4 Catalina was a southern hemisphere object visible only from larger backyard telescopes. That should change, however, in the coming weeks if activity from this comet holds up.

Light curve — The light curve of UQ4 Catalina with current observations (dots) noted. Credit: Seiichi Yoshida/Aerith.net.

2013 UQ4 belongs to a class of objects known as damocloids. These asteroids are named after the prototype for the class 5335 Damocles and are characterized as long-period bodies in retrograde and highly eccentric orbits. These are thought to be inactive varieties of comet nuclei, and other asteroids in the damocloid series such as C/2001 OG 108 (LONEOS) and C/2002 VQ94 (LINEAR) also turned out to be comets. Damocloids also exhibit the same orbital characteristics of that most famous inner solar system visitor of them all; Halley’s Comet.

The path of Comet 9PM 30deg north — The path of Comet UQ4 Catalina looking towards the NE at 9PM local in early July from latitude 30 degrees north. Credit: Stellarium.

The good news is, 2013 UQ4 Catalina is brightening on schedule and should be a binocular object greater than +10^th magnitude by the end of June. Recent observations, including those made by Alan Hale (of comet Hale-Bopp fame) place the comet at magnitude +11.9 with a bullet. The comet is currently placed high in the east in the constellation Pisces at dawn, and will soon speed northward and vault across the sky as it crosses the ecliptic plane this week. In fact, comet 2013 UQ4 Catalina reaches perihelion on July 6th only four days before its closest approach to the Earth at 47 million kilometres distant, when it may well reach a peak magnitude of +7. At that point, the comet will have an apparent motion of about 7 degrees a day — that’s the span of a Full Moon once every 1 hour and 42 minutes — as it rises in the constellation Cepheus to the northeast at dusk in early July. A fine placement, indeed. And speaking of the Moon, our natural satellite reaches New phase later this month on June 27^th, another good reason to begin searching for 2013 UQ4 Catalina now.

Here’s a list of notable events to watch out for and aid you in your quest as comet 2013 UQ4 Catalina crosses the summer sky:

June 16^th: The comet crosses north of the ecliptic plane.

June 20^th: The waning crescent Moon passes 3 degrees from the comet.

starry nite — The celestial path of the comet from June 16th to July 15th… Credit: Starry Night Education software.

June 29^th: Crosses into the constellation of Andromeda.

July 1^st: Passes less than one degree from the +2^nd magnitude star Alpheratz.

July 2^nd: Crosses briefly into the constellation Pegasus before passing back into Andromeda.

July 6^th: The comet reaches perihelion or its closest point to the Sun at 1.081 A.U.s distant.

July 7^th: Crosses into the constellation of Lacerta and passes the deep sky objects NGCs 7296, 7245, 7226.

July 8^th: Crosses into the constellation Cepheus and across the galactic plane.

July 9^th: Passes a degree from the Elephant Trunk open star cluster.

July 10^th: Passes less than one degree from the stars Eta (magnitude +3.4) and Theta (magnitude +4.2) Cephei.

July 10^th: Passes 2 degrees from the +7.8 magnitude Open Cluster NGC 6939.

July 10^th: Passes closest to Earth at 0.309 A.U.s or 47 million kilometres distant.

July 11^th: Crosses into the constellation Draco.

July 11^th: Reaches its most northerly declination of 64 degrees.

July 12^th: Photo op: the comet passes 3 degrees from the Cat’s Eye Nebula.

July 15th- August 20th — … and the path of the comet from July 15th to August 20th. Credit: Starry Night.

July 17^th: The comet passes into the astronomical constellation of Boötes.

July 31^st: Passes just 2 degrees from globular cluster NGC5466 (+9^th magnitude) and 6 degrees from the famous globular cluster Messier 3.

From there on out, the comet drops below naked eye visibility and heads back out in its 470 year orbit around the Sun. Be sure to check out comet 2013 UQ4 Catalina this summer… what will the Earth be like next time it passes by in 2484 A.D.?

June 9, 2014December 23, 2015 by Nancy Atkinson

How to Photograph the Night Sky, Even in Light-Polluted Skies: A Tutorial from Justin Ng

Rising Milky Way above Marina Bay Sands in Singapore on April 10, 2014. Credit and copyright: Justin Ng.

We feature A LOT of astrophotos here on Universe Today, and we get many comments about them, too — with some people saying they could NEVER take photos of the night sky because they live in cities, or are too close to street or yard lights or other causes of light pollution.

Now, award-winning astrophotographer Justin Ng from Singapore has created a tutorial for how to photograph the night sky, even in light-polluted area.

“This tutorial shows you how I photograph the Milky Way that’s obscured by the extreme light pollution in Singapore, using photography equipments that you may already have and a workflow that probably works on most versions of Photoshop,” Justin writes, adding that the type of photo processing he uses in Photoshop can be achieved without purchasing additional plugins.

Justin says that taking pictures of the night sky is a way you can “do your part to promote public awareness of astronomy and the importance of preserving the beauty of our night skies through your images. And I am going to show you how you can do just that using photography equipment that you may already have and a workflow that probably works in most versions of Photoshop.”

For this tutorial, you will need some previous knowledge about basic photography and post-processing.

You can access the full tutorial here on Justin’s website.

The rising Milky Way at Sentosa Island in Singapore. Credit and copyright: Justin Ng.

Check out more of his work at his website, on Facebook or G+.

June 4, 2014December 23, 2015 by David Dickinson

Discovered: Two New Planets for Kapteyn’s Star

An artist's conception of the planets orbiting Kapteyn's Star (inset) and the stream of stars associated with an ancient galaxy merger. Credit: image courtesy of Victor Robles, James Bullock, and Miguel Rocha at University of California Irvine and Joel Primack at University of California Santa Cruz.

The exoplanet discoveries have been coming fast and furious this week, as astronomers announced a new set of curious worlds this past Monday at the ongoing American Astronomical Society’s 224th Meeting being held in Boston, Massachusetts.

Now, chalk up two more worlds for a famous red dwarf star in our own galactic neck of the woods. An international team of astronomers including five researchers from the Carnegie Institution announced the discovery this week of two exoplanets orbiting Kapteyn’s Star, about 13 light years distant. The discovery was made utilizing data from the HIRES spectrometer at the Keck Observatory in Hawaii, as well as the Planet Finding Spectrometer at the Magellan/Las Campanas Observatory and the European Southern Observatory’s La Silla facility, both located in Chile.

The Carnegie Institution astronomers involved in the discovery were Pamela Arriagada, Ian Thompson, Jeff Crane, Steve Shectman, and Paul Butler. The planets were discerned using radial velocity measurements, a planet-hunting technique which looks for tiny periodic changes in the motion of a star caused by the gravitational tugging of an unseen companion.

“That we can make such precise measurements of such subtle effects is a real technological marvel,” said Jeff Crane of the Carnegie Observatories.

Kapteyn’s Star (pronounced Kapt-I-ne’s Star) was discovered by Dutch astronomer Jacobus Kapteyn during a photographic survey of the southern hemisphere sky in 1898. At the time, it had the highest proper motion of any star known at over 8” arc seconds a year — Kapteyn’s Star moves the diameter of a Full Moon across the sky every 225 years — and held this distinction until the discovery of Barnard’s Star in 1916. About a third the mass of our Sun, Kapteyn’s Star is an M-type red dwarf and is the closest halo star to our own solar system. Such stars are thought to be remnants of an ancient elliptical galaxy that was shredded and subsequently absorbed by our own Milky Way galaxy early on in its history. Its high relative velocity and retrograde orbit identify Kapteyn’s Star as a member of a remnant moving group of stars, the core of which may have been the glorious Omega Centauri star cluster.

The worlds of Kapteyn’s Star are proving to be curious in their own right as well.

“We were surprised to find planets orbiting Kapteyn’s Star,” said lead author Dr. Guillem Anglada-Escude, a former Carnegie post-doc now with the Queen Mary University at London. “Previous data showed some irregular motion, so we were looking for very short period planets when the new signals showed up loud and clear.”

The location of Kapteyn's Star in teh constellation Pictor. Created using Stellarium. — The location of Kapteyn’s Star in the constellation Pictor. Created using Stellarium.

It’s curious that nearby stars such as Kapteyn’s, Teegarden’s and Barnard’s star, though the site of many early controversial claims of exoplanets pre-1990’s, have never joined the ranks of known worlds which currently sits at 1,794 and counting until the discoveries of Kapteyn B and C. Kapteyn’s star is the 25th closest to our own and is located in the southern constellation Pictor. And if the name sounds familiar, that’s because it made our recent list of red dwarf stars for backyard telescopes. Shining at magnitude +8.9, Kapteyn’s star is visible from latitude 40 degrees north southward.

Kapteyn B and C are both suspected to be rocky super-Earths, at a minimum mass of 4.5 and 7 times that of Earth respectively. Kapteyn B orbits its primary once every 48.6 days at 0.168 A.U.s distant (about 40% of Mercury’s distance from our Sun) and Kapteyn C orbits once every 122 days at 0.3 A.U.s distant.

This is really intriguing, as Kapteyn B sits in the habitable zone of its host star. Though cooler than our Sun, the habitable zone of a red dwarf sits much closer in than what we enjoy in our own solar system. And although such worlds may have to contend with world-sterilizing flares, recent studies suggest that atmospheric convection coupled with tidal locking may allow for liquid water to exist on such worlds inside the “snow line”.

And add to this the fact that Kapteyn’s Star is estimated to be 11.5 billion years old, compared with the age of the universe at 13.7 billion years and our own Sun at 4.6 billion years. Miserly red dwarfs measure their future life spans in the trillions of years, far older than the present age of the universe.

A comparison of habitable zones of Sol-like versus Red dwarf stars. Credit: Chewie/Ignacio Javier under a Wikimedia Commons 3.0 license). — A comparison of habitable zones of Sol-like versus red dwarf stars. Credit: Chewie/Ignacio Javier under a Wikimedia Commons 3.0 license).

“Finding a stable planetary system with a potentially habitable planet orbiting one of the very nearest stars in the sky is mind blowing,” said second author and Carnegie postdoctoral researcher Pamela Arriagada. “This is one more piece of evidence that nearly all stars have planets, and that potentially habitable planets in our galaxy are as common as grains of sand on the beach.”

Of course, radial velocity measurements only give you lower mass constraints, as we don’t know the inclination of the orbits of the planets with respect to our line of sight. Still, this exciting discovery could potentially rank as the oldest habitable super-Earth yet discovered, and would make a great follow-up target for the direct imaging efforts or the TESS space telescope set to launch in 2017.

“It does make you wonder what kind of life could have evolved on those planets over such a long time,” added Dr Anglada-Escude. And certainly, the worlds of Kapteyn’s Star have had a much longer span of time for evolution to have taken hold than Earth… an exciting prospect, indeed!

-Read author Alastair Reynolds’ short science fiction piece Sad Kapteyn accompanying this week’s announcement.

June 3, 2014December 23, 2015 by David Dickinson

Catch the Dramatic June 10th Occultation of Saturn by the Moon

The May 15th, 2014 occultation of Saturn by the Moon as seen from Australia. (Credit: Byuki/Silveryway).

Some terms in astronomy definitely have a PR problem, and are perhaps due for an overhaul. One such awkward term is occultation, which simply means that one celestial body is passing in front of another from an observer’s vantage point, nothing more, and nothing less. I know, the word ‘occult’ is in there, raising many a non-astronomically minded eyebrow and evoking astronomy’s hoary astrological past. You can even use it as a verb in this sense, as in to ‘occult’ one body with another. A planet or asteroid can occult a star, your cat can occult your laptop’s screen, and the Moon can occult a star or planet, as occurs on Tuesday, June 10^th when the waxing gibbous Moon occults the planet Saturn for observers across the southern Indian Ocean region.

The occultation footprint for the June 10th event. The solid lines denote where the occultation occurs after sunset. Created using Occult 4.0.

Of course, most of us will see a near miss worldwide. This is parallax in motion, as differing vantage points on the surface of the planet Earth see the Moon against a different starry background.

And we’re currently in the midst of a cycle of occultations of the planet Saturn in 2014, as the Moon occults it 11 times this year, nearly once for every lunation. The Moon actually occults planets 22 times in 2014, 24 if you count the occultations of 1 Ceres and 4 Vesta on September 28^th, with Saturn getting covered by the Moon once again on the same date! Saturn tops the list in the number of times it’s occulted by the Moon this year, as it’s the slowest moving of the planets and fails to hustle out of the Moon’s way until November, after which a series of occultations of the ringed planet won’t resume again until December 9^th, 2018.

4x selected views of the occultation/conjunction of the Moon and Saturn on June 10th worldwide. (Credit: Stellarium). — Four selected views of the occultation/conjunction of the Moon and Saturn on June 10th worldwide. (Credit: Stellarium).

The shadow footprint of the June 10^th occultation just makes landfall over southwestern Australia near Perth, a slice of Antarctica, and a scattering of southern Indian Ocean islands and the southern tip of South Africa in and around Cape Town. Note that the phase of the Moon is changing by about 30 degrees of ecliptic longitude as well during each successive occultation of Saturn. Next week’s event occurs as the Moon is at a 93% waxing gibbous illuminated phase this month and soon will occur when the Moon is a crescent. What’s especially interesting is the dark limb of the Moon is always the leading edge during waxing phases; this means that any stars or planets in its way get hidden (or ingress) under its shady nighttime edge.

Looking to the southeast from latitude 30 degrees north from the US east coast at 10PM EDT. Created using Starry Night Education software. — Looking to the southeast from latitude 30 degrees north from the US east coast at 10 PM EDT. Created using Starry Night Education software.

Central conjunction for Saturn and the Moon actually occurs at around 19:00 Universal Time on June 10^th. The Moon rises at around 6:00 PM local on this date, and North American observers will see Saturn 4 degrees from the limb of the Moon and at an elevation of 28 degrees above the horizon at dusk. Unfortunately, the best occultation of Saturn by the Moon for North America in 2014 occurs in the daytime on August 31^st, though you can indeed catch Saturn in the broad daylight through a telescope with good sky transparency if you know exactly where to look for it… a nearby daytime Moon certainly helps!

Unlike stellar occultations, blockages of planets by the Moon are leisurely events, and lend themselves to some pretty amazing video sequences. You can actually get a sense of the motion of the Moon as you watch it slowly cover the planet’s disk, in real time. It might also be fun to catch the occultation of Saturn’s brightest moon, +9th magnitude Titan. Hey, a moon occulting a moon, a sort of cosmic irony…

Saturn spends all of 2014 in the astronomical constellation of Libra. The Moon moves on to Full on Friday the 13^th — triskaidekaphobics take note — at 4:13 UT/00:13 AM EDT. This is the closest Full Moon to the northward solstice which occurs on June 21^st at 10:51 UT/6:51 AM EDT, meaning that while the Sun rides high in the sky during the day, the rising Full Moon transits low to the south at night. In the southern hemisphere, the reverse is true in June.

The June Full Moon is also known as per ye ole Farmer’s Almanac as the Strawberry or Rose Moon.

So there you have it, occultations were evoked no less than 21 times in the writing of this post. We need a modern, hip, internet ready meme to supplant the term occultation… y’know, like “ring of fire” for and annular eclipse or minimoon for an apogee moon, etc… blockage? Covering? Enveloping? Let us know what you think!

May 30, 2014December 23, 2015 by Elizabeth Howell

Video: Beyond Neptune, It Sure Is Crowded With Icy Objects

Neptune photographed by Voyage. Image credit: NASA/JPL — Neptune photographed by Voyager 2. Image credit: NASA/JPL

Faster than you can say “trans-Neptunian object” three times, the reaches beyond Neptune’s orbit start to fill out in this animation. And it’s astounding. Dots representing icy bodies large and small fill the area.

What’s more sobering is realizing how little we knew about this region 20 years ago. Pluto was the first object in that region discovered in 1930, and it wasn’t until 1992 QB1 was discovered that our understanding of this neighborhood increased, wrote creator Alex Parker, a planetary astronomer at the University of California, Berkeley.

“Made this for a talk I gave today. I think it came out pretty nice,” Parker wrote yesterday (May 29) on Twitter.

Parker added on the video page: “This animation illustrates the approximate relative sizes and the true orbital motion of all known trans-Neptunian objects with average orbital distances (semi-major axes) greater than Neptune’s. The objects are revealed on the date of their discovery. Data extracted from the Minor Planet Center database.”

On Twitter, he also provided a link to another visualization of asteroid discoveries between 1980 and 2011 by Scott Manley:

May 27, 2014December 23, 2015 by Bob King

Observing Alert – Space Station ‘Marathon’ Starts This Week

Time exposure showing the International Space Station making a bright pass across the northern sky. Credit: Bob King

What’s your favorite satellite? For me it’s the space station. Not only is it the brightest spacecraft in the sky, but it’s regularly visible from so many places. It’s also unique. Most satellites are either spent rocket stages or unmanned science and surveillance probes. The ISS is inhabited by a crew of astronauts. Real people.

Every time I see that bright, moving light I think of the crew floating about the cabin with their microgravity hair, performing experiments and pondering the meaning of it all while gazing out the cupola windows at the rolling blue Earth below. Starting Friday, the station will make up to 5 flybys a night from dusk till dawn. Marathon anyone?

The ISS’s orbit is inclined 51.6 degrees to the equator and passes overhead for anyone living between 51.6 degrees north and 51.6 degrees south latitude. It’s visible well beyond this zone also but never passes through the zenith outside of these limits. Traveling at a little more than 17,000 mph (27,350 kph) the station completes an orbit in 93 minutes.

Diagram showing the Earth in late May when the space station's orbital track is closely aligned with the day-night terminator. The astronauts see the sun 24-hours a day (midnight sun effect) while we on the ground get to watch repeated passes. Credit: Bob King — Diagram showing the Earth in late May when the space station’s orbital track is closely aligned with the day-night terminator. The astronauts see the sun 24-hours a day (midnight sun effect) while we on the ground get to watch repeated passes. Credit: Bob King

Most of the time we get one easy-to-see bright pass preceded or followed by a fainter partial pass. ‘Partials’ occur when the space station glides into Earth’s shadow and disappears from view during an appearance. But in late May-early June each year, the space station’s orbit and Earth’s day-night terminator nearly align. From the astronauts’ viewpoint, the sun never sets, much like seeing the midnight sun from the Arctic Circle. From down on the planet between latitudes 40-55 degrees north, the ISS remains in sunlight during repeated 90 minute-long orbits.

Instead of once or twice a night, we’ll see passes all night long from dusk till dawn starting about May 30. For instance, on May 31 from Minneapolis, Minn., skywatchers will be treated to four flybys at 12:12 a.m, 1:44 a.m., 3:20 a.m. and 11:23 p.m. The best nights are June 4 and 6 with five passes. By the 10th, the space station ‘marathon’ winds down and we return to 2-3 passes a night.

In late May-early June near the summer solstice, the sun doesn’t set on the International Space Station

The ISS always appears in the western sky first and travels east opposite to the movement of the stars. Low altitude flybys are fainter because there’s more lateral distance between you and the station. Even then the it still shines as bright as Vega. But when the ISS flies overhead, it’s only about 250 miles away, as close as it gets. Then it outshines everything in the night sky except Venus and the moon. Absolutely stunning.

The track of the ISS near Vega in Lyra. From right to left, the station is passing from sunlight into Earth's shadow. Its color transitions from white to red. Credit: Bob King — The track of the ISS near Vega in Lyra. From right to left, the station is passing from sunlight into Earth’s shadow. Its color transitions from white to red. Credit: Bob King

Have you ever noticed that satellites, including the ISS, appear to move in a jerky or zigzag fashion if you watch them closely? What you’re really are your own eyes not moving smoothly as you follow the satellite across the starry sky. My favorite passes are those where the space station fades away mid-flyby as it encounters Earth’s shadow. I always keep binoculars handy for these passes so I can watch the ISS turn color from pale yellow (caused by the gold Mylar plastic used in its many solar panels) to orange and red as it experiences one of its many orbital sunsets.

The phenomenon is easy to capture on camera too. Find out when the station will cross into shadow using the maps from Heavens-Above (see below) and point your tripod-mounted camera in that direction. I typically use a 35mm lens wide open to f/2.8 and a 30-second exposure at either ISO 400 – if still twilight – or 800 in a darker sky.

The multiple solar panels on the ISS give it the shape of the letter ‘H’ when viewed through a telescope. Other modules are visible too but hard to see as clearly. Credit: NASA

There are many ways to find out when the ISS will pass over your city. My favorite are the listings in Heavens-Above. Login with your city and you’ll see a complete list with links to create maps of the station’s track across the sky. There’s also Spaceweather’s Satellite Flyby tracker. Type in your zip code and hit enter. Couldn’t be easier. You can also have NASA send you an e-mail when the most favorable (highest, brightest) passes occur by adding your e-mail to the Spot the Station site. Be aware though that you won’t be notified of some of the less favorable passes.

Half-minute video of the space station tracked through a telescope

One last pleasure of space station watching is seeing it in a telescope. Notoriously tricky to track when magnified, after minimal research I’ve come up with a method that allows at least a half dozen people to see it up close during a good flyby. One person mans the finderscope, keeping the station in the center of the crosshairs, while one happy observer after another takes their turn for a look through the eyepiece. Sure, it’s a little herky-jerky, but you’d be surprised how much you can see at magnifications as low as 60x. The solar panels really jump out. Observing solo might mean a couple tries positioning the moving target ahead of where you think it will cross the field of view and then being ready to lock on and follow.

Well, I’m going to prep for the upcoming marathon. See you in spirit on the course!

May 27, 2014December 23, 2015 by David Dickinson

Seeing in Triplicate: Catching a Rare Triple Shadow Transit of Jupiter’s Moons

Hubble nabs a triple shadow transit in this false color image taken in 2004. Credit: NASA/HST.

The planet Jupiter is always fascinating to watch. Not only do surface features pop in and out of existence on its swirling cloud tops, but its super fast rotation — once every 9.9 hours — assures its face changes rapidly. And the motion of its four large Galilean moons is captivating to observe as well. Next week offers a special treat for well-placed observers: a triple shadow transit of the moons Callisto, Europa and Ganymede on the evening of June 3rd.

The view at 19:00 UT/3:00 PM EDT on June 3rd. Credit: Starry Night Education Software.

Now for the bad news: only a small slice of the planet will witness this rare treat in dusk skies. This is because Jupiter starts the month of June 40 degrees east of the Sun and currently sets around 11 PM local, just 3 hours after local sunset. Never fear, though, it may just be possible to spy a portion of this triple transit from North American longitudes with a little careful planning.

The action begins on June 3^rd at 15:20 Universal Time as Callisto’s shadow slides on to the disk of Jupiter, to be followed by Europa and Ganymede’s shadow in quick succession hours later. All three shadows are cast back onto the disk of Jupiter from 18:05 to 19:53 UT, favoring European and African longitudes at sunset. The final shadow, that of Ganymede, moves off the disk of Jupiter at 21:31 UT.

The hemisphere of the Earth facing towards Jupiter from the beginning of the triple shadow transit to the end. the red line marks the day/night terminator. Credit: Stellarium.

The following video simulation begins at around 15:00 UT just prior to the ingress of Callisto’s shadow and runs through 22:00 UT:

Triple shadow transits of Jupiter’s moons are fairly rare: the last such event occurred last year on October 12^th, 2013 favoring North America and the next won’t occur until January 24^th, 2015. Jean Meeus calculated that only 31 such events involving 3 different Jovian moons either transiting Jupiter and/or casting shadows onto its disk occur as seen from Earth between 1981 and 2040. The June 3^rd event is also the longest in the same 60 year period studied.

The 1:2:4 orbital resonance of the Jovian moons Io, Europa and Ganymede. Credit: Wikimedia Commons.

Can four shadow transits occur at once? Unfortunately, the answer is no. The inner three moons are in a 1:2:4 resonance, meaning that one will always be left out of the picture when two are in front. This also means that Callisto must be included for any triple shadow transit to occur. Next week’s event sees Callisto, Europa and Ganymede crossing in front of Jupiter and casting shadows onto its disk while Io is hidden behind Jupiter in its enormous shadow. Callisto is also the only one of the four large Jovian moons that can “miss” the disk of Jupiter on certain years, owing to the slight inclination of its orbit to the ecliptic. Callisto thus doesn’t always cast a shadow onto the disk of Jupiter, and we’re currently in the middle of a cycle of Callisto shadow transits that started in July of 2013 and runs through July 2016. These “Callisto transit seasons” occur twice during Jupiter’s 11.8 year orbit, and triple shadow transits must also occur within these periods.

So, what’s a North American observer to do? Well, it is possible to spot and track Jupiter with a telescope in the broad daylight. Jupiter rises at around 9:20 AM local in early June, and the waxing crescent Moon passes 5.4 degrees south of it on June 1^st. The Moon stands 30 degrees from the planet on June 3^rd, and it may be juuusst possible to use it as a guide to the daytime event. A “GoTo” telescope with precise pointing will make this task even easier, allowing you to track Jupiter and the triple shadow transit across the daytime sky from North American longitudes. But be sure to physically block the blazing June Sun behind a building or structure to avoid accidentally catching its blinding glare in the eyepiece!

The orientation of Jupiter the Moon and the Sun at 4PM EDT on June 3rd. Credit: Stellarium. — The orientation of Jupiter, the Moon and the Sun at 4PM EDT on June 3rd. Credit: Stellarium.

Do the shadows of the moons look slightly different to you? A triple shadow transit is a great time to compare them to one another, from the inky hard black dot of the inner moons Europa and Io, to the diffuse large shadow of Callisto. With practice, you can actually identify which moon is casting a shadow during any transit just by its size and appearance!

A study of three multi-shadow transits: last year's (upper left) a double shadow transit from early 2014 (upper right) and 2004 (bottom. Photos by author. — A study of three multi-shadow transits: last year’s (upper left) a double shadow transit from early 2014 (upper right) and 2004 (bottom). Photos by author.

Shadow transits of Jupiter’s moons also played an interesting role in the history of astronomy as well. Danish astronomer Ole Rømer noted that shadow transits were being observed at slightly different times than predicted depending on the distance of Jupiter and the Earth, and made the first rough calculation of the speed of light in 1676 based on this remarkable insight. Celestial navigators were also intrigued for centuries with the idea of using the phenomena of Jupiter’s moons as a natural clock to gauge longitude. It’s a sound idea in theory, though in practice, it proved tough to make accurate observations from the pitching deck of a ship at sea.

Jupiter captured near the daytime Moon. Photo by author.

Miss the June 3^rd event? There’s still two fine opportunities to see Jupiter do its impression of the Earth-Moon system and appear to have only one satellite – Callisto – on the evenings of May 30^th and June 7^th.

From there, Jupiter slides lower into the dusk as June progresses and heads towards solar conjunction on July 24^th.

Let us know if you manage to catch sight of this rare event!

-Send those shadow transit pics in to Universe Today at our Flickr forum.