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March 12, 2014December 23, 2015

Astronomers Identify the Largest Yellow “Hypergiant” Star Known

A stellar monster lurks in heart of the Centaur.

A recent analysis of a star in the south hemisphere constellation of Centaurus has highlighted the role that amateurs play in assisting with professional discoveries in astronomy.

The find used of the European Southern Observatory’s Very Large Telescope based in the Atacama Desert in northern Chile — as well as data from observatories around the world — to reveal the nature of a massive yellow “hypergiant” star as one of the largest stars known.

The stats for the star are impressive indeed: dubbed HR 5171 A, the binary system weighs in at a combined 39 solar masses, has a radius of over 1,300 times that of our Sun, and is a million times as luminous. Located 3,600 parsecs or over 11,700 light years distant, the star is 50% larger than the famous red giant Betelgeuse. Plop HR 5171 A down into the center of our own solar system, and it would extend out over 6 astronomical units (A.U.s) past the orbit of Jupiter.

The field around HR 5171 A (the brightest star just below center). Credit: ESO/Digitized Sky Survey 2.

Researchers used observations going back over 60 years – some of which were collected by dedicated amateur astronomers – to pin down the nature of this curious star. A variable star just below naked eye visibility spanning a magnitude range from +6.1 to +7.3, HR 5171 A also has a relatively small companion star orbiting across our line of sight once every 1300 days. Such a system is known as an eclipsing binary. Famous examples of similar systems are the star Algol (Alpha Persei), Epsilon Aurigae and Beta Lyrae. The companion star for HR 5171 is also a large star in its own right at around six solar masses and 400 solar radii in size. The distance from center-to-center for the system is about 10 A.U.s – the distance from Sol to Saturn – and the surface-to-surface distance for the A and B components of the system are “only” about 2.8 A.U.s apart. This all means that these two massive stars are in physical contact, with the expanded outer atmosphere of the bloated primary contacting the secondary, giving the pair a distorted peanut shape.

“The companion we have found is very significant as it can have an influence on the fate of HR 5171 A, for example stripping off its outer layers and modifying its evolution,” said astronomer Olivier Chesneau of the Observatoire de la Côte d’Azur in Nice France in the recent press release.

Knowing the orbital period of a secondary star offers a method to measure the mass of the primary using good old Newtonian mechanics. Coupled with astrometry used to measure its tiny parallax, this allows astronomers to pin down HR 5171 A’s stupendous size and distance.

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Along with luminous blue variables, yellow hypergiants are some of the brightest stars known, with an absolute magnitude of around -9. That’s just 16x times fainter than the apparent visual magnitude of a Full Moon but over 100 times brighter than Venus – if you placed a star like HR 5171 A 32 light years from the Earth, it would easily cast a shadow.

Astronomers used a technique known as interferormetry to study HR 5171 A, which involves linking up several telescopes to create the resolving power of one huge telescope. Researchers also culled through over a decade’s worth data to analyze the star. Though much of what had been collected by the American Association of Variable Star Observers (the AAVSO) had been considered to be too noisy for the purposes of this study, a dataset built from 2000 to 2013 by amateur astronomer Sebastian Otero was of excellent quality and provided a good verification for the VLT data.

The discovery is also crucial as researchers have come to realize that we’re catching HR 5171 A at an exceptional phase in its life. The star has been getting larger and cooling as it grows, and this change can be seen just over the past 40 year span of observations, a rarity in stellar astronomy.

“It’s not a surprise that yellow hypergiants are very instable and lose a lot of mass,” Chesneau told Universe Today. “But the discovery of a companion around such a bright star was a big surprise since any ‘normal’ star should at least be 10,000 times fainter than the hypergiant. Moreover, the hypergiant was much bigger than expected. What we see is not the companion itself, but the regions gravitationally controlled and filled by the wind from the hypergiant. This is a perfect example of the so-called Roche model. This is the first time that such a useful and important model has really been imaged. This hypergiant exemplifies a famous concept!”

Indeed, you can see just such photometric variations as the secondary orbits its host in the VLTI data collected by the AMBER interferometer, backed up by observations from GEMINI’s NICI chronograph:

Credit: ESO/VLT/GEMINI/NICI — Looking at the bizarre system of HR 5171. Credit: Olivier Chesneau/ESO/VLT/GEMINI/NICI

The NIGHTFALL program was also used for modeling the eclipsing binary components.

These latest measurements place HR 5171 A firmly in the “Top 10” for largest stars in terms of size known, as well as the largest yellow hypergiant star known This is due mainly to tidal interactions with its companion. Only eight yellow hypergiants have been identified in our Milky Way galaxy. HR 5171 A is also in a crucial transition phase from a red hypergiant to becoming a luminous blue variable or perhaps even a Wolf-Rayet type star, and will eventually end its life as a supernova.

Enormous stars: From left to right, The Pistol Star, Rho Cassiopeiae, Betelgeuse and VY Canis Majoris compared with the orbits of Jupiter (in red) and Neptune (in blue). Remember, HR 5171 A is 50% larger than Betelgeuse! Credit: Anynobody under a Creative Commons Attribution Share-Alike 3.0 Unported license.

HR 5171 A is also known as HD 119796, HIP 67261, and V766 Centauri. Located at Right Ascension 13 Hours 47’ 11” and declination -62 degrees 35’ 23,” HR 5171 culminates just two degrees above the southern horizon at local midnight as seen from Miami in late March.

HR 5171 A: a finder chart. Click to enlarge. Credit: Stellarium

HR 5171 A is a fine binocular object for southern hemisphere observers.

But the good news is, there’s another yellow hypergiant visible for northern hemisphere observers named Rho Cassiopeiae:

Rho Cass is one of the few naked eye examples of a yellow hypergiant star, and varies from magnitude +4.1 to +6.2 over an irregular period.

It’s amusing read the Burnham’s Celestial Handbook entry on Rho Cass. He notes the lack of parallax and the spectral measurements of the day — the early 1960s — as eluding to a massive star with a “true distance… close to 3,000 light years!” Today we know that Rho Cassiopeiae actually lies farther still, at over 8,000 light years distant. Robert Burnham would’ve been impressed even more by the amazing nature of HR 5171 as revealed today by ESO astronomers!

– The AAVSO is always seeking observations from amateur astronomers of variable stars.

January 30, 2014December 23, 2015

Stormy with a Chance of Molten Iron Rain: First Ever Map of Exotic Weather on Brown Dwarfs

Think the weather is nasty this winter here on Earth? Try vacationing on the brown dwarf Luhman 16B sometime.

Two studies out this week from the Max Planck Institute for Astronomy based at Heidelberg, Germany offer the first look at the atmospheric features of a brown dwarf.

A brown dwarf is a substellar object which bridges the gap between at high mass planet at over 13 Jupiter masses, and a low mass red dwarf star at above 75 Jupiter masses. To date, few brown dwarfs have been directly imaged. For the study, researchers used the recently discovered brown dwarf pair Luhman 16A & B. At about 45(A) and 40(B) Jupiter masses, the pair is 6.5 light years distant and located in the constellation Vela. Only Alpha Centauri and Barnard’s Star are closer to Earth. Luhman A is an L-type brown dwarf, while the B component is a T-type substellar object.

More to the story: Read a “behind the scenes” account of how this discovery was made — from the proposal to the press release.

“Previous observations have inferred that brown dwarfs have mottled surfaces, but now we can start to directly map them.” Ian Crossfield of the Max Planck Institute for Astronomy said in this week’s press release. “What we see is presumably patchy cloud cover, somewhat like we see on Jupiter.”

To construct these images, astronomers used an indirect technique known as Doppler imaging. This method takes advantage of the minute shifts observed as the rotating features on brown dwarf approach and recede from the observer. Doppler speeds of features can also hint at the latitudes being observed as well as the body’s inclination or tilt to our line of sight.

But you won’t need a jacket, as researchers gauge the weather on Luhman 16B be in the 1100 degrees Celsius range, with a rain of molten iron in a predominately hydrogen atmosphere.

The study was carried out using the CRyogenic InfraRed Echelle Spectrograph (CRIRES) mounted on the 8-metre Very Large Telescope based at the European Southern Observatory’s (ESO) Paranal observatory complex in Chile. CRIRES obtained the spectra necessary to re-construct the brown dwarf map, while backup brightness measurements were accomplished using the GROND (Gamma-Ray Burst Optical/Near-Infrared Detector) astronomical camera affixed to the 2.2 metre telescope at the ESO La Silla Observatory.

A closeup of the GROND instrument (the blue cylinder to the lower left) on the La Silla 2.2-metre telescope. Credit-ESO/European Organization for Astronomical Research in the Southern Hemisphere.

The next phase of observations will involve imaging brown dwarfs using the Spectro-Polarimetric High-contrast Exoplanet Research (SPHERE) instrument, set to go online at the Very Large Telescope facility later this year.

And that may just usher in a new era of directly imaging features on objects beyond our solar system, including exoplanets.

“The exciting bit is that this is just the start. With the next generations of telescopes, and in particular the 39-metre European Large Telescope, we will likely see surface maps of more distant brown dwarfs — and eventually, a surface map for a young giant planet,” said Beth Biller, a researcher previously based at the Max Planck Institute and now based at the University of Edinburgh. Biller’s study of the pair went even more in-depth, analyzing changes in brightness at different wavelengths to peer into the atmospheric structure of the brown dwarfs at varying depths.

“We’ve learned that the weather pattern on these brown dwarfs are quite complex,” Biller said. “The cloud structure of the brown dwarf varies quite strongly as a function of atmospheric depth and cannot be explained with single layer clouds.”

A rotational surface map of Luhman 16B Credit-ESO/I. Crossfield.

The paper on brown dwarf weather pattern map comes out today in the January 30^th, 2014 edition of Nature under the title Mapping Patchy Clouds on a Nearby Brown Dwarf.

The brown dwarf pair targeted in the study was designated Luhman 16A & B after Pennsylvania State University researcher Kevin Luhman, who discovered the pair in mid-March, 2013. Luhman has discovered 16 binary systems to date. The WISE catalog designation for the system has the much more cumbersome and phone number-esque designation of WISE J104915.57-531906.1.

We caught up with the researchers to ask them some specifics on the orientation and rotation of the pair.

“The rotation period of Luhman 16B was previously measured watching the brown dwarf’s globally-averaged brightness changes over many days. Luhman 16A seems to have a uniformly thick layer of clouds, so it exhibits no such variation and we don’t yet know its period,” Crossfield told Universe Today. “We can estimate the inclination of the rotation axis because we know the rotation period, we know how big brown dwarfs are, and in our study, we measured the “projected” rotational velocity. From this, we know we must be seeing the brown dwarf near equator-on.”

The maps constructed correspond with an amazingly fast rotation period of just under 6 hours for Luhman 16B. For context, the planet Jupiter – one of the fastest rotators in our solar system – spins once every 9.9 hours.

“The rotational period of Luhman 16B is known from 12 nights of variability monitoring,” Biller told Universe Today. “The variability in the B component is consistent with the results from 2013, but the A component has a lower amplitude of variability and a somewhat different rotational period of maybe 3-4 hours, but that is still a very tentative result.”

This first mapping of the cloud patterns on a brown dwarf is a landmark, and promises to provide a much better understanding of this transitional class of objects.

Couple this announcement with the recent nearby brown dwarf captured in a direct image, and its apparent that a new era of exoplanet science is upon us, one where we’ll not only be able to confirm the existence of distant worlds and substellar objects, but characterize what they’re actually like.

January 18, 2014December 23, 2015

Chang’e 3 Lander Beams Back New Lunar Panorama Photos

Little by little we’re getting sharper, clearer pictures from the Chinese Chang’e 3 moon mission. Yesterday the lander beamed back a series of new photos taken with its panoramic camera. Stitched together, they give us a more detailed and colorful look of the rover’s surroundings in northern Mare Imbrium. I’ve ordered the images starting with a nice crisp view of the Yutu rover; from there we turn by degree to the right across the five frames. The final mosaic unfortunately doesn’t have the resolution yet of the other images. Perhaps one will be published soon.

The lander's solar panels stand out in the foreground with a smattering of small craters nearby. Credit: Chinanews.com — The lander’s solar panels stand out in the foreground with a smattering of small craters nearby. Credit: Chinanews.com

Right of the rover we see more panels and a radio communications dish. Credit: Chinanews.com

A larger crater surrounded by what appears to be excavated impact ejecta is visible near the horizon at upper right. Credit: Chinanews.com

Yutu's tracks stand out in this final image. Credit: Chinanews.com — Yutu’s tracks and another crater with ejecta stand out in this final image. Credit: Chinanews.com

Complete, if small, panorama stitched from the single images. Credit: Chinanews.com

One thing that stands out to my eye when looking at the photos is the brown color of the lunar surface soil or regolith. Color images of the moon’s surface by the Apollo astronauts along with their verbal descriptions indicate a uniform gray color punctuated in rare spots by patches of more colorful soils.

Apollo 15 astronauts salutes next to the American flag in 1971. The moon's regolith or soil appears a variety of shades of gray. Credit: NASA — Apollo 15 astronauts salutes next to the American flag in 1971. The moon’s regolith or soil appears a variety of shades of gray. Credit: NASA

The famous orange soil scooped up by Apollo 17 astronaut Eugene Cernan comes to mind. Because Apollo visited six different moonscapes – all essentially gray – it makes me wonder if the color balance in the Chinese images might be off. Or did Chang’e 3 just happen to land on browner soils?

The orange soil found by Apollo 17 astronauts really stands out against a uniform gray moonscape. Credit: NASA

December 4, 2013December 23, 2015

A Naked Eye Nova Erupts in Centaurus

If you live in the southern hemisphere, the southern sky constellation of Centaurus may look a little different to you tonight, as a bright nova has been identified in the region early this week.

An animation showing a comparison between the constellation Centaurus before and after a nova eruption. Credit and copyright: Ernesto Guido, Nick Howes and Martino Nicolini/Remanzacco Observatory. Click for larger version.

The initial discovery of Nova Centauri 2013 (Nova Cen 2013) was made by observer John Seach based out of Chatsworth Island in New South Wales Australia. The preliminary discovery magnitude for Nova Cen 2013 was magnitude +5.5, just above naked eye visibility from a good dark sky site. Estimates by observers over the past 24 hours place Nova Cen 2013 between magnitudes +4 and +5 “with a bullet,” meaning this one may get brighter still as the week progresses.

We first got wind of the discovery via the American Association of Variable Star Observers yesterday afternoon when alert notice 492 was issued. Established in 1911, the AAVSO is a great resource for info and a fine example of amateur collaboration in the effort to conduct real scientific observation.

Follow-up spectra measurements by Rob Kaufman in White Cliffs Australia and Malcolm Locke in Christchurch New Zealand demonstrated the presence of strong hydrogen alpha and hydrogen beta emission lines, the classic hallmark of an erupting nova. Like Nova Delphini 2013 witnessed by observers in the northern hemisphere, this is a garden variety nova located in our own galaxy, going off as seen along the galactic plane from our Earthbound perspective. A handful of galactic novae are seen each year, but such a stellar conflagration reaching naked eye visibility is worthy of note. In fact, Nova Cen 2013 is already knocking on the ranks of the 30 brightest novae observed of all time.

This is not to be confused with a supernova, the last of which observed in our galaxy was Kepler’s Supernova in 1604, just before the advent of the telescope in modern astronomy. Supernovae are seen in other galaxies all the time, but here at home, you could say we’re “due”.

So, who can see Nova Cen 2013, and who’s left out? Well, the coordinates for the nova are:

Right Ascension: 13 Hours 54’ 45”

Declination: -59°S 09’ 04”

That puts it deep in the southern celestial hemisphere sky where the constellation Centaurus meets up with the constellations of Circinus, Musca and the Crux. Located within three degrees of the +0.6^th magnitude star Hadar — also named Beta Centauri — it would be possible to capture the southern deep sky objects of the Coal Sack and Omega Centauri with Nova Cen 2013 in the same wide field of view.

The field of view of Nova Centauri 2013 with a five degree Telrad “bullseye” added for scale. Note that magnitude for selected comparison stars are quoted, minus the decimal points. (Created using Stellarium).

Though Nova Cen 2013 technically peeks above the southern horizon from the extreme southern United States, the viewing circumstances aren’t great. In fact, the nova only rises just before the Sun as seen from Miami in December, at 25 degrees north latitude. The Centaurus region is much better placed in northern hemisphere during the springtime, when many southern tier states can actually glimpse the celestial jewels that lie south, such as Omega Centauri.

But the situation gets better, the farther south you go. From Guayaquil, Ecuador just below the equator, the nova rises to the southeast at about 3 AM local, and sits 20 degrees above the horizon at sunrise.

11PM local from latitude (Created by the author using Starry Night Education Software). — 11PM local, from latitude 40 degrees south looking to the southeast. (Created by the author using Starry Night Education Software).

The nova will be circumpolar for observers south of -30 degrees latitude, including cities of Buenos Aires, Cape Town, Sydney and Auckland. Remember, its springtime currently in the southern hemisphere, as we head towards the solstice on December 21^st and the start of southern hemisphere summer. We’ve been south of the equator about a half dozen times and it’s a unique experience – for northern star gazers, at least – to see familiar northern constellations such as Orion and Leo hang “upside down” as strange a wonderful new constellations beckon the eye to the south. Also, though the Sun still rises to the east, it transits to the north as you get deep into the southern hemisphere, a fun effect to note!

Latitudes, such as those on par with New Zealand, will get the best views of Nova Cen 2013. Based near latitude 40 degrees south, observers will see the nova about 10 degrees above the southern horizon at lower culmination at a few hour after sunset, headed towards 40 degrees above the southeastern horizon at sunrise.

All indications are that Nova Cen 2013 is a classical nova, a white dwarf star accreting matter from a binary companion until a new round of nuclear fusion occurs. Recurrent novae such as T Pyxidis or U Scorpii may erupt erratically in this fashion over the span of decades.

As of yet, there is no firm distance measurement for Nova Cen 2013, though radio observations with southern sky assets may pin it down. One northern hemisphere based program, known as the EVLA Nova Project, seeks to do just that.

Congrats to John Seach on his discovery, and if you find yourself under southern skies, be sure to check out this astrophysical wonder!

Got pics of Nova Centauri 2013? Be sure to send ‘em in to Universe Today!

November 1, 2013December 23, 2015

10-Year-Old Boy Discovers a 600 Million Year-Old Supernova

Young Canadian Nathan Gray, age 10, has discovered a supernova candidate in the field of the galaxy designated PGC 61330, which lies in the constellation of Draco (the dragon).

Nathan made the discovery while scanning astronomical images taken by Dave Lane, who runs the Abbey Ridge Observatory (ARO) which is stationed in Nova Scotia. Incidentally, Nathan may unseat his older sister, Kathryn Aurora Gray, as the youngest supernova discoverer by a mere 33 days.

Nothing is visible at the location of the supernova candidate in prior images of the field taken over the past two years, or Digitized Palomar Sky Survey images.

Kathryn Aurora Gray garnered worldwide fame when she discovered a supernova in the galaxy designated UGC 3378 (see the Universe Today article by Nancy Atkinson). The discovery eventually earned her an audience with astronauts such as Neil Armstrong (shown below).

Kathryn Aurora Gray discovery of a supernova earned her the chance to meet Neil Armstrong, Bill Anders (Apollo 8), Victor Gorbakto, and Jim Lovell (Apollo 8 & 13). — Kathryn Aurora Gray’s discovery of a supernova earned her the chance to meet Neil Armstrong, Bill Anders (Apollo 8), Victor Gorbakto, and Jim Lovell (Apollo 8 & 13) (image credit: P. Gray/RASC).

Caroline Moore held the record prior to Kathryn as the youngest person to discover a supernova (Caroline was 14 at the time). Caroline subsequently had the honor of meeting President Obama at the White House (see the video below).

Supernova are immense explosions linked to the evolutionary end-state of certain stars. The explosions are so energetic that they can be observed in distant galaxies. Indeed, Nathan’s supernova could be some 600 million light years distant. Gazing into space affords humanity the opportunity to peer back in time. Despite the (finite) speed of light being a remarkable 300000 km/s, the light-rays must travel over “astronomical” distances.

There are several different classes of supernovae. For example, Type II supernovae are associated with larger mass stars. The Sun will not terminate as a supernova, but may potentially evolve into a standard (or not) planetary nebula (see the Universe Today post “Astronomers Hint that our Sun won’t Terminate as the Typical Planetary Nebula”).

Nathan’s discovery has been posted on the International Astronomical Union’s site, and its presence confirmed by US and Italian-based observers. Its provisional name is: PSN J18032459+7013306, and to get an official supernova designation a large telescope needs to confirm the unique supernova light signature (via a spectrum). Is the target a bona fide supernova?

“Given no motion, large distance from the galactic plane (ie. not likely a nova), and several optical confirmations, as well as its very close angular proximity to a faint galaxy, it is a supernova at any reasonable certainty,” said Lane, an astronomer in the Dept. of Astronomy & Physics at Saint Mary’s University, as well as the director of the Burke-Gaffney and Abbey Ridge astronomical observatories. “A significant fraction of
the supernova discoveries these days are not observed spectrographically due to the sheer number of them vs. telescope time.”

Nathan Gray is the son of Paul and Susan Gray.

*2013 10 31.9053 – update from the IAU: SN to be confirmed in PGC 61330 detected with 3 x 3 min images (exp 9 min). Astrometry: RA 18 03 24.12 Dec +70 13 26.4 (ref stars UCAC2) Photometry: 17.00CR +/-0.02 (USNO A2R Ref stars 163R, 170R, 172R, 173R). Measure on unfiltered image. Observer and measurer: Xavier Bros, ANYSLLUM OBSERVATORY, Ager, Spain. T-350mm f4.6. Link to image and further information: http://www.anysllum.com/PSN_PGC61330.jpg

October 23, 2013December 23, 2015

Comet LINEAR Suddenly Brightens with Outburst: How to See It

It’s swiftly becoming an “all comets, all the time” sort of observing season. The cyber-ink was barely dry on our “How to Spot Comet 2P/Encke” post this past Monday when we were alerted to another comet that is currently in the midst of a bright outburst.

That comet is C/2012 X1 LINEAR. Discovered on December 8^th, 2012 by the ongoing Lincoln Near Earth Asteroid Research (LINEAR) survey based in Socorro, New Mexico, Comet X1 LINEAR was expected to peak out at about +12^th magnitude in early 2014.

That all changed early this week, when amateur observers began to report a swift change in brightness for the otherwise nondescript comet. Japanese observer Hidetaka Sato reported the comet at magnitude +8.5 on October 20^th, a full 5.5 magnitudes above its expected brightness of +14. Remember, the magnitude scale is logarithmic, and the lower the number, the brighter the object. Also, 5 magnitudes represent an increase in brightness of 100-fold.

Astronomers Nick Howes, Martino Nicolini and Ernesto Guido used the remote 0.5 metre iTelescope based in New Mexico on the morning of Monday, October 21^st to confirm the outburst. Other amateurs and professional instruments are just now getting a look at the “new and improved” Comet X1 LINEAR low in the dawn sky. Romanian amateur observer Maximilian Teodorescu noted on yesterday’s Spaceweather that the comet was not visible through his 4.5 inch refractor, though it was easy enough to image.

Comet X1 LINEAR currently sits in the constellation Coma Berenices about mid-way between the stars Diadem, (Alpha Coma Berenices) and Beta Coma Berenices. Shining at +8.5 magnitude, the coma is about 85” across with a 10” bright central region. This gives X1 LINEAR the appearance of an unresolved +8^th magnitude globular cluster. In fact, a classic globular and a star party fave known as M3 lies about 8 degrees away at the junction of the constellations Canes Venatici, Boötes and Coma Berenices. M3 shines at +7^th magnitude and will make a great contrast on the hunt for the comet.

Unfortunately, the window of time to search for the comet is currently short. From latitude 30 degrees north, the comet sits only 15 degrees about the northeast horizon 30 minutes before local sunrise. The situation is a bit better for observers farther to the north, and mid-November sees the comet 20 degrees above the horizon in the dawn sky.

Comet X1 LINEAR is currently covering 40’ (2/3^rdsof a degree, or 1 1/3 the size of a Full Moon) a day, and will spend most of the month of November in the constellation Boötes. Keep in mind, X1 LINEAR is currently still on brightening trend “with a bullet.” Revised light curves now show it on track to reach magnitude +6 near perihelion early next year, but further brightening could still be in the cards for this one. Remember Comet 17P/Holmes a few years back? That one jumped from an uber-faint +17^th magnitude to a naked eye brightness of +2.8 in less than 48 hours.

Comet X1 LINEAR will reach a perihelion of 1.6 Astronomical Units (A.U.s) from the Sun on February 21st, 2014, and pass 1.6 A.U.s from the Earth around June 28^th, 2014. The comet has a high inclination of 44.4° degrees relative to the ecliptic, and is on a respectable 1872 year orbit.

Here are some notable dates for the comet through the end of 2013;

The path of Comet C/2012 X1 LINEAR from October 23 to November 28th. Click to enlarge. (Credit: Created using Starry Night Education Software).

-November 2^nd: Crosses into the constellation Boötes.

-November 6^th: Passes near the +4.9^th magnitude star 6 Boötis.

-November 16^th: Passes near the bright star Arcturus.

-December 6^th: Crosses into the constellation Serpens Caput.

-December 10^th: Passes near the +5 magnitude star Tau1 Serpentis.

-December 14^th: Comet X1 LINEAR sits only 8 degrees from Comet ISON.

-December 26^th: Crosses into the constellation Hercules.

Note: “Passes near” on the above list denotes a pass closer than one degree, except as noted.

Now, we REALLY need the Moon to pass Last Quarter phase this coming Saturday so we can get a good look at all of these dawn comets! As of writing this, the current scorecard of binocular comets— comets with a brightness between magnitude +6 and +10 —sits at:

-2P Encke: +7.9 magnitude in Leo.

-C/2013 R1 Lovejoy: +8.7^th magnitude in Canis Minor.

-C/2013 X1 LINEAR: +8.5^th magnitude in Coma Berenices.

-C/2012 S1 ISON: +9.7^th magnitude in Leo.

-C/2012 V2 LINEAR: +8.9^th magnitude in Centaurus.

Comet X1 LINEAR on the morning of October 25th, as seen from latitude 30 degrees north 45 minutes prior to sunrise. (Created using Stellarium).

It’s also amusing to note how the method of notification for these sorts of outbursts has changed in recent years. I first heard of the outburst of X1 LINEAR on Monday evening via Twitter. Contrast this with Comet Holmes in 2007, which came to our attention via message board RSS feed. And way back in 1983, we all read about of the close passage of Comet IRAS-Araki-Alcock… weeks after it occurred!

Another curious phenomenon may also work its way through the news cycle. When Comet Holmes became a hit back in 2007, spurious reports of comets brightening became fashionable. If you were to believe everything you read on the web, it suddenly seemed like every comet was undergoing an outburst! This sort of psychological trend towards wish fulfillment may come to pass again as interest in comet outbursts mounts.

It’s also worth noting that, contrary to rumors flying around ye’ ole web, Comet X1 LINEAR is not following Comet ISON. The two are on vastly different orbits, and only roughly lie along the same line of sight as seen from our Earthly vantage point.

The orbital path of Comet X1 LINEAR. (Credit: The JPL Solar System Dynamics Small-Body Database Browser). — The orbital path of Comet C/2012 X1 LINEAR. (Credit: The JPL Solar System Dynamics Small-Body Database Browser).

And that’s it for our weekly (daily?) segment of “As the Comets Turn…” don’t forget to “fall back” one hour and plan your morning comet-hunting vigil accordingly this coming Sunday if you live in Europe-UK. North America still has until November 3^rd to follow suit.

Happy comet hunting!

-Got a recent pic of Comet X1 LINEAR? be sure to post it in the Universe Today Flickr forum!

October 9, 2013December 23, 2015

New Data: Will Comet ISON Survive its Close Perihelion Passage?

It’s the question on every astronomer’s mind this season, both backyard and professional: will Comet C/2012 S1 ISON survive perihelion?

Now, new studies released today at the American Astronomical Society’s 45^th Annual Division for Planetary Sciences meeting being held this week in Denver suggests that ISON may have the “right stuff” to make it through its close perihelion passage near the Sun. This is good news, as Comet ISON is expected to be the most active and put on its best showing post-perihelion… if it survives.

Researchers Matthew Knight of the Lowell Observatory and Research Scientist Jian-Yang Li of the Planetary Science Institute both presented a compelling portrait of the characteristics and unique opportunities presented by the approach of comet ISON to the inner solar system.

Jian-Yang Li studied ISON earlier this year using Hubble before it passed behind the Sun from our Earthly vantage point. Li and researchers were able to infer the position and existence of a jet coming from the nucleus of the comet, which most likely marks the position of one of its rotational poles.

“We measured the rotational pole of the nucleus,” Li noted in a press release from the Planetary Science Institute. The pole indicates that only one side of the comet is being heating by the Sun on its way in until approximately one week before it reaches its closest point to the Sun.”

Could we be in for a “surge” of activity from ISON coming from around November 20^th on?

Comet ISON as imaged from Aguadilla, (sp) Puerto Rico recently on october 6th. (Credit: Efrain Morales Rivera). — Comet ISON as imaged from Aguadilla, Puerto Rico recently on October 6th. (Credit: Efrain Morales Rivera).

Li also noted that the reddish color of the coma of ISON suggests an already active comet sublimating water ice grains as they move away from the nucleus. He also noted that time has been allocated to observe ISON using Hubble this week.

Next up, researcher Mathew Knight presented some encouraging news for ISON when it comes to surviving perihelion.

The findings were a result of numerical simulations carried out by Kevin Walsh and Knight, combined with a historical analysis of previous sun-grazing comets. Both suggest that comet nuclei smaller than 200 metres in diameter, with an average density or lower (for comets, that is) typically do not survive a close passage to the Sun.

Both researchers place the size of ISON’s nucleus in the range of 0.5 to 2 kilometres, comfortably above the 0.2 kilometre “shred limit” for its relative perihelion distance. ISON is not a technically Kreutz group sungrazer, though studies of the over 2,000 known Kreutz comets historically observed provide an interesting guideline for what might be in store for ISON. Four Kreutz comets, including C/2011 W3 Lovejoy and Comet C/1887 B1 partially survived perihelion to become “headless wonders,” while five, including Comet C/1965 S1 Ikeya-Seki — which ISON is often compared to — survived perihelion passage to become one of the great comets of the 20^th century.

ISON will pass inside the Roche limit of the Sun, which is a distance of 2.4 million kilometres (for fluid bodies) and will be subject to temperatures approaching 5,000 degrees Fahrenheit on closest approach.

ISON is a first time visitor to the inner solar system. Discovered on September 21^st, 2012 by Russian researchers Artyom Novichonok and Vitaly Nevsky participating in the International Scientific Optical Network, ISON will pass less than 1.2 million kilometres above the surface of the Sun on November 28^th, 2013.

One interesting but little discussed factor highlighted in today’s press release was the retrograde versus prograde rotation of the cometary nucleus. A fast, prograde spin of an elongated nucleus may spell doom for ISON, as tidal forces will rip it apart. A retrograde rotator, however, is very likely to survive the encounter.

Thus far, there are no solid indications that ISON is indeed a retrograde rotator, although there are tantalizing hints that beg for further observations.

Li notes that it’s tough to infer a bias for comets like ISON to be retrograde over prograde rotators, as we’ve only got five historical comets to go by similar to ISON, and the breakdown is thus about 50/50 for and against.

ISON’s possible survival would validate both studies and their methods and give us more refined predictions for future comets.

“We’ve never discovered a sungrazer this far out,” Knight told Universe Today. “The rotation of ISON depends on the pole position (from Li’s study) and in theory, if we could get enough images, a proper morphology (for ISON) would emerge.”

Comet ISON imaged on October 5th from Long Beach, California. (Credit: Thad Szabo @AstroThad).

The implications of this analysis is certainly good news for observers. If ISON survives perihelion, we would then have a brilliant dawn Christmas comet unfurling its tail off to the northeast in early December.

Of course, these findings are contrary to early cries of its demise, including the paper out of the Institute of Physics that has been circulating touting “The Impending Demise of ISON”. Read Universe Today editor Nancy Atkinson’s excellent synopsis on that, it’s a tale that just won’t seem to die.

And we’ve also done our skeptic’s duty of thoroughly debunking the mounting ISON lunacy, including its status as the harbinger for the “end of the world of the week,” as well as its inability to fulfill prophecy. But if we get a surge in ISON next month as researchers suggest, we fully expect the accompanying hype to crest as well.

The most recent observations put ISON at about +10^th magnitude as it currently crosses the constellation Leo, near Mars and Regulus in the morning sky. We recently did an observing post tracking its plunge to perihelion in late November, and we’ve been diligently hunting for ISON with binoculars every morning pre-dawn.

We’re glad to have some positive science to report on for ISON. Things are looking up for a fine show come early December!

-Read the PSI press release on JianYang Li’s findings as well as the original paper on ISON’s survival prospects by Matthew Knight.

October 8, 2013December 23, 2015

A Tale of a Lost Moon: Hubble Spies Neptune’s Moons and Its Rings

“That’s no moon…”

-B. Kenobi

But in this case, it is… a lost moon of Neptune not seen since its discovery in the late 1980’s.

A new announcement from the 45^th Meeting of the Division for Planetary Sciences of the American Astronomical Society being held this week in Denver, Colorado revealed the recovery of a moon of Neptune that was only briefly glimpsed during the 1989 flyby of Voyager 2.

The re-discovery Naiad, the innermost moon of Neptune, was done by applying new processing techniques to archival Hubble images and was announced today by Mark Showalter of the SETI institute.

Collaborators on the project included Robert French, also from the SETI Institute, Dr. Imke de Pater of UC Berkeley, and Dr. Jack Lissauer of the NASA Ames Research Center.

The findings were a tour-de-force of new techniques applied to old imagery, and combined the ground-based 10 meter Keck telescope in Hawaii as well as Hubble imagery stretching back to December 2004.

The chief difficulty in recovering the diminutive moon was its relative faintness and proximity to the “dazzling” disk of Neptune. At roughly 100 kilometres in diameter and an apparent magnitude of +23.9, Naiad is over a million times fainter than +8th magnitude Neptune. It’s also the innermost of Neptune’s 14 known moons, and orbits once every 7 hours just 23,500 kilometres above the planet’s cloud tops. Neptune itself is about 49,000 kilometres in diameter, and only appears 2.3” in size from Earth. From our Earthly vantage point, Naiad only strays about arc second from the disk of Neptune, a tiny separation.

“Naiad has been an elusive target ever since Voyager left the Neptune system,” Showalter said in a recent SETI Institute press release. Voyager 2 has, to date, been the only mission to explore Uranus and Neptune.

To catch sight of the elusive inner moon, Showalter and team applied new analyzing techniques which filtered for glare and image artifacts that tend to “spill over” from behind the artificially occulted disk of Neptune.

Other moons, such as Galatea and Thalassa — which were also discovered during the 1989 Voyager 2 flyby — are also seen in the new images. In fact, the technique was also used to uncover the as of yet unnamed moon of Neptune, S/2004 N1 which was revealed earlier this year.

Naiad is named after the band of nymphs in Greek mythology who inhabited freshwater streams and ponds. The Naiads differed from the saltwater-loving Nereids of mythology fame, after which another moon of Neptune discovered by Gerard Kuiper in 1949 was named.

It’s also intriguing to note that Naiad was discovered in a significantly different position in its orbit than expected. Clearly, its motion is complex due to its interactions with Neptune’s other moons.

“We don’t quite have enough observations to establish a refined orbit,” Mr. Showalter told Universe Today, noting that there may still be some tantalizing clues waiting to be uncovered from the data.

I know the burning question you have, and we had as well during the initial announcement today. Is it REALLY Naiad, or another unknown moon? Showalter notes that this possibility is unlikely, as both objects seen in the Hubble and Voyager data are the same brightness and moving in the same orbit. To invoke Occam’s razor, the simplest solution— that both sightings are one in the same object —is the most likely.

“Naiad is well inside Neptune’s Roche Limit, like many moons in the solar system,” Mr. Showalter also told Universe Today. Naiad is also well below synchronous orbit, and is likely subject to tidal deceleration and may one day become a shiny new ring about the planet.

The labeled ring arcs of Neptune as seen in newly processed data. The image spans 26 exposures combined into a equivalent 95 minute exposure, and the ring trace and an image of the occulted planet Neptune is added for reference. (Credit: M. Showalter/SETI Institute). — The labeled ring arcs of Neptune as seen in newly processed data. The image spans 26 exposures combined into an equivalent 95 minute exposure. The ring trace and an image of the occulted planet Neptune is added for reference. (Credit: M. Showalter/SETI Institute).

And speaking of which, the tenuous rings of Neptune have also evolved noticeably since the 1989 Voyager flyby. First discovered from the ESO La Silla Observatory in 1984, data using the new techniques show that the knotted ring segments named the Adams and Le Verrier have been fading noticeably.

“In a decade or two, we may see an ‘arc-less’ ring,” Showalter noted during today’s Division for Planetary Sciences press conference. The two ring segments observed are named after Urbain Le Verrier and John Couch Adams, who both calculated the position of Neptune due to orbital perturbations of the position of Uranus. Le Verrier beat Adams to the punch, and Neptune was first sighted from the Berlin Observatory on the night of September 23^rd, 1846. Observers of the day were lucky that both planets had undergone a close passage just decades prior, or Neptune may have gone unnoticed for considerably longer.

The rings of Neptune as seen from Voyager 2 during the 1989 flyby. (Credit: NASA/JPL).

Neptune has completed just over one 164.8 year orbit since its discovery. It also just passed opposition this summer, and is currently a fine telescopic object in the constellation Aquarius.

Unfortunately, there aren’t any plans for a dedicated Neptune mission in the future. New Horizons will cross the orbit of Neptune in August 2014, though it’s headed in the direction of Pluto, which is currently in northern Sagittarius. New Horizons was launched in early 2006, which gives you some idea of just how long a “Neptune Orbiter” would take to reach the outermost ice giant, given today’s technology.

This represents the first time that Naiad has been imaged from the vicinity of Earth, and demonstrates a new processing technique capable of revealing new objects in old Hubble data.

“We keep discovering new ways to push the limit of what information can be gleaned from Hubble’s vast collection of planetary images,” Showalter said in the SETI press release.

Congrats to Showalter and team on the exciting recovery… what other moons, both old and new, lurk in the archives waiting to be uncovered?

– Read today’s SETI Institute press release on the recovery of Naiad.

-Be sure to follow all the action at the 45th DPS conference in Denver this week!

August 16, 2013December 23, 2015

CIA’s Declassified Documents Reveals Secrets About Area 51 and UFOs

The CIA has released a 355-page document which officially acknowledges that Area 51 in Nevada does exist, and the agency comes clean about their weather balloon cover stories. The document covers the U-2 and SR-71 spyplane programs and Project OXCART, the aerial reconnaissance programs, from 1954 to 1974.

Nope, no revelations about extraterrestrial spacecraft or alien bodies hidden at the base, but a really grainy map showing the location of Area 51 is included.

While Area 51 has been the subject of fascination for conspiracy theorists and paranormal enthusiasts — and is entrenched in UFO-ology and pop culture — the newly declassified information (with surprisingly few redactions) admits the base was a top-secret aircraft testing facility for Cold War reconnaissance of the Soviet Union.

That UFO sightings increased during the times of the flight tests was an unexpected side effect, the document says:

High-altitude testing of the U-2 soon led to an unexpected side effect-a tremendous increase in reports of unidentified flying objects (UFOs). In the mid-1950s, most commercial airliners flew at altitudes between 10,000 and 20,000 feet and military aircraft like the B-47s and B-57s operated at altitudes below 40,000 feet. Consequently once U-2s started flying at altitudes above 60,000 feet, air-traffic controllers began receiving increasing numbers of UFO reports.

The document also explains Project Blue Book and other frequently associated UFO story staples. The job of Project Blue Book was actually to figure out when civilians were reporting UFOs that were actually U-2s and then work out how to keep that from happening again.

Why did people on the ground and even other pilots report “shiny” UFOs? The document explains that the U-2s silver wings were at the right altitude that when the ground below, or even planes flying at a lower altitude were in darkness, the U-2 was in sunlight and its silver wings would glint in the sunlight:

Such reports were most prevalent in the early evening hours from pilots of airliners flying from east to west. When the sun dropped below the horizon of an airliner flying at 20,000 feet. the plane was in darkness. But, if a U-2 was airborne in the vicinity of the airliner at the same its horizon from an altitude of 60,000 feet was considerably more distant, and being so high in the sky, its silver wings would catch and reflect the ray of the sun and appear to the airliner pilot 40,000 feet below to be fiery objects. Even during the daylight hours, the silver bodies of the high-flying U-2s could catch the sun and cause reflections or glints that could be seen at lower altitudes and even on the ground. At this time, no one believed manned flight was possible above 60,000 feet, so no one expected to see an object so high in the sky.

A handwritten document about the U-2 spyplane design that was included in the information released by the CIA about test flights and Area 51.

But then, not all the UFO reports were explained by U-2 flights.

Air Force investigators then attempted to explain such sightings by linking them to natural phenomena. BLUE BOOK investigators regularly called on the Agency’s Project Staff in Washington to check reported UFO sightings against U-2 flight logs. This enabled the investigators to eliminate the majority of the UFO reports, although they could not reveal to the letter writers the true cause of the UFO sightings. U-2 and later OXCART flights accounted for more than one-half of all UFO reports during the late 1950s and most of the 1960s.

In the document, the CIA admits the weather balloon stuff was just a cover story, but it was the standard operating procedure for how to explain away the sightings as well as debris from any crashes. However, this cover story ended up having disastrous results in May of 1960 when the crash of a U-2 in Russia and the subsequent capture of pilot Gary Powers set in motion a pattern of mistrust between the US and USSR that culminated in the Cuban Missile Crisis in 1962.

After the plane and the pilot went missing, and with the fate of the plane and pilot unknown, the CIA had NASA release a statement that they had a weather airplane that went off course over the Soviet Union because the pilot had passed out due to a loss of oxygen. That story was quickly proven to be a hoax when the USSR produced the crashed U-2 plane and the pilot, who survived the crash and who had admitted to spying.

The documents were released in response to a Freedom of Information Act request submitted in 2005 by Jeffrey T. Richelson, a senior fellow at the National Security Archives. Originally, the CIA had released a heavily redacted document with all mention of Area 51 blacked out. This new document reveals pretty much everything except names of military personnel and private citizens involved.

Richelson has pointed out that the location of Area 51 was not a particularly well-kept secret. Its location appears in satellite imagery like Google Maps and Google Earth, as well as in books on aerial surveillance.

You can wade through the 355 page document here. If you enjoy military and aircraft history, its a great read. One interesting fact revealed is that President Eisenhower wanted the pilots of these planes to be non-US citizens. “It was his belief that, should a U-2 come down in hostile territory, it would be much easier for the United States to deny any responsibility for the activity if the pilot was not an American,” the document reports.

And while I have this chance, I’m going to share a great graphic going around Twitter on how to identify any strange light in the sky you may see:

March 13, 2013April 26, 2016

WISE Nabs the Closest Brown Dwarfs Yet Discovered

We now know our stellar neighbors just a little better, and a new discovery may help tell us how common brown dwarfs are in our region of the galaxy. Early this week, researchers at Pennsylvania State University announced the discovery of a binary brown dwarf system. With a parallax measurement of just under 0.5”, this pair is only 6.5 light years distant making it the third closest system to our own and the closest example of the sub-stellar class of objects known as brown dwarfs yet discovered.

Named WISE J104915.57-531906, the system was identified by analysis of multi-epoch astrometry carried out by NASA’s Wide-field Infrared Survey Explorer (WISE). The discovery was made by associate professor of astronomy and astrophysics at Penn State’s Center for Exoplanets and Habitable Worlds Kevin Luhman. The system’s binary nature and follow up observations were confirmed by spectroscopic analysis carried out by the Gemini Observatory’s Multi-Object Spectrographs (GMOS).

Animation showing the motion of WISE 1049-5319 across the All-WISE, 2MASS & Sloan Digital Sky Survyies from 1978 to 2010. (Credit: NASA/STScI/JPL/IPAC/University of Massachusetts.) — Animation showing the motion of WISE 1049-5319 across the All-WISE, 2MASS & Sloan Digital Sky Surveys from 1978 to 2010. (Credit: NASA/STScI/JPL/IPAC/University of Massachusetts.)

This find is also the closest stellar system discovered to our own solar system since the discovery of Barnard’s star by astronomer E.E. Barnard in 1916. Incidentally, Barnard’s star was the center of many spurious and controversial claims of extrasolar planet discoveries in the mid-20^th century. Barnard’s star is 6 light years distant, and the closest star system to our own is Alpha Centauri measured to be 4.4 light years distant in 1839. In 1915, the Alpha Centauri system was determined to have a faint companion now known as Proxima Centauri at 4.2 light years distant. The Alpha Centauri system also made headlines last year with the discovery of the closest known exoplanet to Earth. WISE 1506+7027 is the closest brown dwarf to our solar system yet discovered. This also breaks the extended the All-WISE survey’s own previous record of the closest brown dwarf released in 2011, WISE 1506+7027 at 11.1 light years distant.

When looking for nearby stellar suspects, astronomers search for stars displaying a high proper motion across the sky. The very first parallax measurement of 11 light years distant was obtained by Friedrich Bessel for the star 61 Cygni in 1838. 61 Cygni was known as “Piazzi’s Flying Star” for its high 4.2” proper motion across the sky. To giving you an idea of just how tiny an arc second is, a Full Moon is about 1800” in diameter. With a proper motion of just under 3” per year, it would take WISE 1049-5319 over 600 years to cross the same apparent distance in the sky as viewed from the Earth!

An artist's conception of looking back at Sol from the binary brown dwarf system WISE 1049-5319, 6.5 light years distant. (Credit: Janella Williams, Penn State University). — An artist’s conception of looking back at Sol from the binary brown dwarf system WISE 1049-5319, 6.5 light years distant. (Credit: Janella Williams, Penn State University).

“Based on how this star system was moving in images from the WISE survey, I was able to extrapolate back in time to predict where it should have been located in older surveys,” stated Luhman. And sure enough, the brown dwarf was there in the Deep Near-Infrared Survey of the Southern Sky (DENIS), the Two Micron All-Sky Survey (2MASS) and the Sloan Digitized Sky Survey (SDSS) spanning a period from 1978 to 1999. Interestingly, Luhman also points out in the original paper that the pair’s close proximity to the star rich region of galactic plane in the constellation Vela deep in the southern hemisphere sky is most likely the reason why they were missed in previous surveys.

The discovery of the binary nature of the pair was also “an unexpected bonus,” Luhman said. “The sharp images from Gemini also revealed that the object actually was not just one, but a pair of brown dwarfs orbiting each other.” This find of a second brown dwarf companion will go a long way towards pinning down the mass of the objects. With an apparent separation of 1.5”, the physical separation of the pair is 3 astronomical units (1 AU= the Earth-Sun distance) in a 25 year orbit.

Size comparison of stellar vs substellar objects. (Credit: NASA/JPL-Caltech/UCB).

Brown dwarfs are sub-stellar objects with masses too low (below ~75 Jupiter masses) to sustain the traditional fusion of hydrogen into helium via the full proton-proton chain process. Instead, objects over 13 Jupiter masses begin the first portion of the process by generating heat via deuterium fusion. Brown dwarfs are thus only visible in the infrared, and run a spectral class of M (hottest), L, T, and Y (coolest). Interestingly, WISE 1049-5319 is suspected to be on the transition line between an L and T-class brown dwarf. To date, over 600 L-type brown dwarfs have been identified, primarily by the aforementioned SDSS, 2MASS & DENIS infrared surveys.

General location of WISE 1049-5319 in the constellation Vela. Note its proximity to the galactic plane. (Created by the author using Starry Night).

This discovery and others like it may go a long ways towards telling us how common brown dwarfs are in our region of the galaxy. Faint and hard to detect, we’re just now getting a sampling thanks to surveys such as WISE and 2MASS. The James Webb Space Telescope will do work in the infrared as well, possibly extending these results. Interestingly, Luhman notes in an interview with Universe Today that the potential still exists for the discovery of a brown dwarf closer to our solar system than Alpha Centauri. “No published study of the data from WISE or any other survey has ruled out this possibility… WISE is much more capable of doing this than any previous survey, but the necessary analysis would be fairly complex and time consuming. It’s easier to find something than to rule out its existence.” Said Luhman. Note that we’re talking a nearby brown dwarf that isn’t gravitationally bound to the Sun… this discussion is separate from such hypothetical solar companions as Nemesis and Tyche…and Nibiru conspiracy theorists need not apply!

The WISE 1049-5319 system is also a prime target in the search for nearby extra-solar planets. “Because brown dwarfs have very low masses, they exhibit larger reflex motions due to orbiting planets than more massive stars, and those larger reflex motions will be easier to detect.” Luhman told Universe Today. Said radial surveys for exoplanets would also be carried out in the IR band, and brown dwarfs also have the added bonus of not swamping out unseen planetary companions in the visible spectrum.

Congrats to Mr. Luhman and the Center for Exoplanets and Habitable Worlds on the discovery. You just never know what’s lying around in your own stellar backyard!

Read this original discovery paper here.