Universe Today

February 19, 2013December 23, 2015 by Dan Majaess

Narrowing Down the Hunt for Giant Exoplanets

Despite advances in exoplanet research over the past decade much remains unknown. For example, how do the detection rates of giant planets vary as a function of the host star’s metal content? Are giant planets more frequent around massive stars? Do giant planets form under different mechanisms depending on the star’s metal content?

To that end a team of astronomers led by Annelies Mortier and Nuno C. Santos explored what mathematical function characterizes the detection rate across a distribution of stars (i.e., from metal-rich to metal-poor objects). “Finding the exact functional form of the metallicity-planet detection frequency will foster our understanding of both planet formation and the number of planets roaming the galaxy,” Santos told Universe Today.

Giant planets are most often found around metal-rich stars, and a figure from the team’s study (shown below) reaffirms that ~25% of stars featuring twice the Sun’s metal content host a giant planet, while the probability falls to ~5% for stars with a metal content analogous to the Sun.

Establishing that metal-rich stars exhibit an increased probability of hosting a giant planet constrains planet formation models. Specifically, the observations suggest that larger metallicity promotes the growth of rocky/icy cores, which subsequently accrete gas. However, the team notes that although the giant planet-metallicity trend is solid for stars exhibiting metallicities greater than (or analogous to) the Sun, the results are less certain for metal-poor stars. Indeed, there is an active debate in the literature pertaining to what function links the metal-rich and metal-poor regimes. In particular, does an exponential decline extend into the metal-poor regime, or does the function level off?

Depending on the manner in which the frequency trend extends into the metal-poor regime, it may indicate that a separate mechanism is responsible for creating that subsample’s giant planets. Thus continued surveys of metal-poor stars are important, despite the decreased frequency of finding a giant planet. Moreover, Mortier (Centro de Astrofisica, Universidade do Porto) notes that, “Studying metal-poor stars should be encouraged, since several theoretical models show that Earth-like planets are more common around these stars than around their metal-rich counterparts.”

Frequency of giant planets as a function of metallicity (A. Mortier et al., arXiv:1302.1851). — *Frequency of giant planets as a function of metallicity (credit: Mortier et al., arXiv 1302.1851).*

The team focused their efforts on trying to discern a difference between the viability of various functional forms in the metal-poor regime (i.e., does the detection rate of giant planets in that domain flatten, rather than decline exponentially?). In the end no statistical difference was found between the scenarios, and it was likewise unclear whether a mass-dependence exists behind the frequency of giant planet detections. The team noted that a larger sample was needed to reach definitive conclusions, and added that ongoing surveys to discover planets would ensure the problem may soon be resolved.

“Kepler and Gaia will significantly increase the amount of planet discoveries, not only for giant planets, but also for smaller planets,” said Mortier.

In sum, to answer the questions posed at the outset planet-hunting efforts should be focused on metal-poor and metal-rich stars, despite the former exhibiting a reduced frequency of giant planets. The team’s findings will appear in Astronomy & Astrophysics, and a preprint is available on arXiv. The results from the study are tied in part to observations acquired via the HARPS (High Accuracy Radial Velocity Planet Searcher) instrument, which is shown below.

*HARPS (High Accuracy Radial Velocity Planet Searcher) instrument (credit: ESO).*

February 19, 2013December 23, 2015 by Bob King

The Year of the Comets: Three Reasons Why 2013 Could be the Best Ever

Comet L4 Panstarrs photographed from Australia at dawn on Feb. 17, 2013 with a telephoto lens. A bright head and short tail are visible. Credit: Joseph Brimacombe

2013 could turn out to be a comet bonanza. No fewer than three of these long-tailed beauties are expected to brighten to naked eye visibility. Already Comet C/2011 L4 PANSTARRS has cracked that barrier. Sky watchers in Australia have watched it grow from a telescopic smudge to a beautiful binocular sight low above the horizon at both dusk and dawn. A few have even spotted it without optical aid in the past week. Excited reports of a bright, fan-shaped dust tail two full moon diameters long whet our appetite for what’s to come.

Recent brightness estimates indicate that the comet could be experiencing a surge or “second wind” after plateauing in brightness the past few weeks. If the current trend continues, PanSTARRS might reach 1st or 2nd magnitude or a little brighter than the stars of the Big Dipper when it first becomes visible to northern hemisphere sky watchers around March 7. That’s little more than two weeks away!

Comet Panstarrs will make its first appearance for northern hemisphere sky watchers around March 7 low in the western sky after sundown. Notice that the comet gets no higher than 10 degrees - about one fist held at arm's length - through much of the month. Illustration created using Chris Marriott's SkyMap software — Comet Panstarrs will make its first appearance for northern hemisphere sky watchers around March 7 low in the western sky after sundown. Notice that the comet gets no higher than 10 degrees – about one fist held at arm’s length – through much of the month. Illustration created using Chris Marriott’s SkyMap software

Every day between now and March 10, when PanSTARRS’ orbit takes it closest to the sun, the comet is expected to slowly increase in brightness. Later this month it disappears in the solar glare, but when it re-emerges into evening twilight around Thursday, March 7, northern and southern hemisphere observers alike will get great views. Binoculars should easily show a bright head and swept-back tail pointing away from the sun. And don’t forget to mark your calendar for March 12. On that date the thin lunar crescent will join the comet for a rare photogenic pairing. To locate and keep track of PanSTARRS, you’ll need the following materials and circumstances:

* An unobstructed view of the western horizon
* Clear, haze-free skies at dusk
* Pair of binoculars
* A map

I can’t help you with all of the above, but this map will help point you in the right direction. Once you find a location with a great western view, watch just above the horizon for a fuzzy, star-like object in your binoculars. While it’s possible the comet will be bright enough to see with the naked eye, binoculars will make finding it much easier. They’ll also reveal details of tail structure too subtle to be visible otherwise.

Incredible detail is seen in the gas tail of F6 Lemmon in this photo made with a 19.6-inch telescope Feb. 17, 2013. Credit: Martin Mobberley

Comet PanSTARRS has some cometary company. C/2012 F6 Lemmon is currently plying its way through the constellation Tucana the Toucan, shining right around the naked eye limit at magnitude 5.5. To the unaided eye, Lemmon looks like a dim fuzzy spot. Binoculars show a thin gas tail and big, bright head or coma. Comas develop around the comet’s icy nucleus as sunlight vaporizes dusty ice to create a short-lived atmosphere that in the shape of a luminous teardrop. Long-exposures like the one above reveal richly-detailed streamers of carbon monoxide and other gases fluorescing in sunlight in the comet’s fashionably skinny tail.

Lemmon is slowly receding from Earth this month, but should remain just above the naked eye limit for some time as it continues to approach the sun. Northern hemisphere observers will need to be patient to see this one. After looping around the sun on March 24, the comet will pop back into the morning sky near the familiar Square of Pegasus asterism in early May. If we’re lucky, Lemmon may still be near the naked eye limit and visible in ordinary binoculars.

Cmet C/2012 F6 (Lemmon), imaged on Feb. 19. 2013 remotely from Q62 (iTelescope Observatory, Siding Spring). Credit: Ernesto Guido and Nick Howes, Remanzacco Observatory. — Cmet C/2012 F6 (Lemmon), imaged on
Feb. 19. 2013 remotely from Q62 (iTelescope Observatory, Siding Spring). Credit: Ernesto Guido and Nick Howes, Remanzacco Observatory.

Before we move on to the comet with the greatest expectations, I want to mention Comet 2P/Encke. Encke was the only the second comet to have its orbit computed – way back in 1819 by German astronomer Johann Encke. This year it’s making its 62nd observed return to Earth’s vicinity. That’s a lot of visits, but when your orbital period is only 3.3 years – the shortest known of any comet – you can’t help but be a regular visitor. While not expected to brighten to naked eye level, the comet will be a fine sight in modest-sized telescopes glowing around 8th magnitude when it tracks between the Big Dipper and Leo the Lion this October.

Comet ISON in the western sky shortly after sunset in late November this year. Illustration created with Chris Marriott's SkyMap software — Comet ISON in the western sky shortly after sunset in late November this year. Illustration created with Chris Marriott’s SkyMap software

Our final comet, Comet C/2012 S1 ISON, was discovered last September by Russian amateurs Vitali Nevski and Artyom Novichonok while making observations for the International Scientific Optical Network (ISON). At the time, it was farther than Jupiter and impossibly faint, but once ISON’s orbit was determined, astronomers realized the comet would pass only 1.1 million miles from center of the sun (680,000 miles above its surface) on November 28, 2013.

Comet ISON belongs to a special category of comets called sungrazers. As the comet performs a hairpin turn around the sun on that date, its ices will vaporize furiously in the intense solar heat. Assuming it defies death by evaporation, ISON is expected to become a brilliant object perhaps 10 times brighter than Venus. Or brighter. Some predict it could put the full moon to shame. If so, that would occur for a brief time around at perihelion (closest approach to the sun) when the comet would only be visible in the daytime sky very close to the sun. When safely viewed, ISON might look like a brilliant, fuzzy star in a blue sky.

A color image of comet Ison taken on February 5, 2013 from northern Arizona. Credit: Chris Schur.

Most of us won’t risk burning our retinas staring so close to sun. Instead we’ll watch with anticipation as the comet sprouts a long tail while ascending from the western horizon just after sunset in late November and early December. Whatever it does, sky watchers in both southern and northern hemispheres will ringside seats when ISON’s at its best.

Right now the comet’s whiling away its time in the constellation Gemini the Twin and still very faint. Come September, it should be easily visible in small telescopes in the morning sky. The first naked eye sightings could happen in late October. Many of us hope the comet will be one for the record books, a worthy successor to C/2006 P1 McNaught, the last “great comet” to dazzle human eyes. It reached peak magnificence for southern hemisphere sky watchers in January 2007.

C/2006 P1 McNaught became a memorable sight for observers living in southern latitudes in January 2007. Will Comet ISON do the same? Credit: Wikipedia

Three bright comets – and one modestly bright – might be enough for a year, but there could be surprises. Dozens of new comets are discovered each year by professional sky surveys and amateur astronomers. Most are faint and move along their appointed paths unnoticed by 99.9% of the world’s population, but every so often a new one comes along that blossoms into a spectacle. How many of those are out there tonight waiting to be discovered?

February 19, 2013December 23, 2015 by Elizabeth Howell

10 Awesome Images of the Space Station’s Cupola

Expedition 24's Tracy Caldwell Dyson gazes out of the cupola. Credit: NASA

There’s a panoramic window on the International Space Station named after the observation decks that old-time train cabooses had.

The Cupola, as it’s known, includes six side windows and a big one in the center. An astronaut floating nearby can see 1,000 km of Earth below him or her. It’s the ultimate spot to keep an eye on a hurricane, or provide guidance to a crewmate wrestling the robotic Canadarm2 towards an incoming spacecraft.

Hard to believe it’s been three years since the astronauts on STS-130 installed it in February 2010. Below, check out the best of astronaut photography of or from the Cupola since that time.

From the outside, the cupola looks like an extraterrestrial spacecraft. That's Douglas Wheelock (Expedition 25) inside the window. Credit: NASA — From the outside, the cupola looks like a flying saucer. That’s Douglas Wheelock (Expedition 25) inside the window. Credit: NASA

A green tint from an aurora is seen out the Cupola over the southern Indian Ocean. Credit: NASA

Canadarm2 makes some moves towards Japan's robotic H-II Transfer Vehicle (HTV-3) during Expedition 32. Credit: NASA — Canadarm2 makes some moves towards Japan’s robotic H-II Transfer Vehicle (HTV-3) during Expedition 32. Credit: NASA

The Cupola provides a portal to 215 million years in the past: The Manicouagan impact crater in northern Québec shows up nearly in the center of the main Cupola window. Credit: NASA

The STS-131 crew somehow organizes themselves on the small window in microgravity. Pictured are Commander Alan Poindexter, Pilot James P. Dutton Jr. and Mission Specialists Dorothy Metcalf-Lindenburger, Rick Mastracchio, Naoko Yamazaki, Clayton Anderson and Stephanie Wilson. Credit: NASA

NASA astronaut Ron Garan looking down at a night view of Australia from the International Space Station's cupola.. — NASA astronaut Ron Garan looking down at a night view of Australia from the International Space Station’s cupola..

An Expedition 27 crewmember captured this cyclone over the north Pacific. Told you it's a good view. Credit: NASA — An Expedition 27 crewmember captured this cyclone over the north Pacific. Told you it’s a good view. Credit: NASA

The end effector -- or grappler -- at the end of the Space Station's Canadarm 2 robotic arm is visible out the main window of the Cupola, with a view of our beautiful blue planet below. Credit: NASA. — The end effector — or grappler — at the end of the Space Station’s Canadarm 2 robotic arm is visible out the main window of the Cupola, with a view of our beautiful blue planet below. Credit: NASA.

STS-130's Nicolas Patrick casually hanging out beneath the cupola after helping install it. Credit: NASA — STS-130’s Nicholas Patrick casually hanging out beneath the cupola after helping install it. Credit: NASA

There have also been some stunning filmed timelapses from the Cupola, such as this one:

February 19, 2013December 23, 2015 by Jason Major

Take a Spin Around Mercury

Color map of Mercury's varied surface. The 1,550-km-wide Caloris Basin can be seen at upper right.

Created by the MESSENGER mission team at the Johns Hopkins University Applied Physics Laboratory and the Carnegie Institution of Washington, this animation gives us a look at the spinning globe of Mercury, its surface color-coded to reflect variations in surface material reflectance.

Thousands of Wide Angle Camera images of Mercury’s surface were stitched together to create the full-planet views.

While the vibrant colors don’t accurately portray Mercury as our eyes would see it, they are valuable to scientists as they highlight the many different types of materials that make up the planet’s surface. Young crater rays surrounding fresh impact craters appear light blue or white. Medium- and dark-blue “low-reflectance material” (LRM) areas are thought to be rich in a dark, opaque mineral. Tan areas are plains formed by eruption of highly fluid lavas. Small orange spots are materials deposited by explosive volcanic eruptions.

At this point, over 99% of the Solar System’s innermost planet has been mapped by MESSENGER. Read more about the ongoing mission here.

Image/video credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

February 18, 2013December 23, 2015 by Tammy Plotner

Portrait Of NGC 5189: New Light On An Old Planetary Nebula

Composite Image of NGC 5189 Courtesy of Robert Gendler

Stretching across three light years of space and located about 3,000 light years away in the direction of the constellation of Musca, an incredible and rather understudied planetary nebula awaits a new hand to bring out new light. While most planetary nebula have a rather normal, bloated star look, NGC 5189 shows an extraordinary amount of loops and curls not normally seen in objects of its type. Just what is going on here?

This incredibly detailed image comes from the one and only Robert Gendler and was assembled from three separate data sources. The detail for the nebula is from Hubble Space Telescope data, the background starfield from the Gemini Observatory/AURA and the color data from his own equipment. Here we see fanciful gas clouds with thick clumps decorating them. Intense radiation and gas streams from the central dying star in waves, fashioning out hollows and caves in the enveloping clouds. While these clumps in the clouds may appear as wispy details, each serves as a reminder of just how vast space can be… for each an every one of them is about the same size as our Solar System.

“The complex morphology of this PN is puzzling and has not been studied in detailed so far. Our investigation reveals the presence of a new dense and cold infrared torus (alongside the optical one) which probably generated one of the two optically seen bipolar outflows and which might be responsible for the twisted appearance of the optical torus via an interaction process.” says L. Sabin (et al). ” The high-resolution MES-AAT spectra clearly show the presence of filamentary and knotty structures as well as three expanding bubbles. Our findings therefore suggest that NGC 5189 is a quadrupolar nebula with multiple sets of symmetrical condensations in which the interaction of outflows has determined its complex morphology.”

And just as incredibly large as some things can be – others can be as small. At the heart of NGC 5189 shines the tiny light of its central star… no bigger than Earth. It wobbles its way through time, rotating rapidly and spewing material into space like a runaway fire hydrant. Astronomers speculate there might be a binary star hidden inside, since usually planetary nebulae of this type have them. However, only one star has been found at the nebula’s center and it might be one very big, very bad wolf.

“Around 15% are known or suspected binaries, while the remaining 18% are non-emission line nuclei which require further study. Selecting for LIS (low ionization structures) therefore will give a mix of mostly binary and emission line nuclei which will require further observations to separate.” explains B. Miszalski (et al). “Almost all the [WR] CSPN in the sample belong to the hot [WO] type that have more extreme and chaotic LIS covering their entire nebulae, presumably due to turbulence from the strong [WR] winds disrupting pre-existing LIS.”

Just why is this celestial tapestry so complicated and complex? The answer isn’t a simple one – it’s one that has many plausible theories. We know that when a star similar to the Sun expends its fuel, it will begin to shed its outer layers… layers which normally take on very basic shape. These “normal” shapes are usually a sphere, sometimes a double lobe and at times it can be a ring or helix. However, NGC 5189 just doesn’t follow rules. Over time, researchers have speculated it has given off different outlfows at different stages – one prominent as a very visible torus situated around mid-point in the structure – consistent with the theory of a binary star system with a precessing symmetry axis. Still, there is clearly more research needed.

“Our preliminary results of a comparative spectroscopic study of these two objects shows that the chemical composition of the two nebulae is completely different, even though their morphology is most probably quite similar.” says VF Polcaro (et al). ” In addition, the PN appears much more chemically homogeneous. These features are clearly associated with the evolutionary paths of the stars.”

“The striking broad emission line spectroscopic appearance of Wolf-Rayet (WR) stars has long defied analysis, due to the extreme physical conditions within their line and continuum forming regions.” explains Paul Crowther. “Theoretical and observational evidence that WR winds depend on metallicity is presented, with implications for evolutionary models, ionizing fluxes, and the role of WR stars within the context of core-collapse supernovae and long-duration gamma ray bursts.”

Is NGC 5189 the handiwork of a binary star? Or is it the product of an intensely hot Wolf-Rayet? Like the proverbial Tootsie Pop equation… the world may never know.

Many thanks to Robert Gendler for sharing this incredible image with us.

February 18, 2013December 23, 2015 by David Dickinson

Naming Pluto’s Moons: Will it Come Down to Trekkies Versus the IAU?

The path of New Horizons through Pluto's growing family. (Image Credit: NASA/ESA/A. Field STScl).

As reported here on Universe Today last week, the SETI Institute has invited the public to vote on the names of Pluto’s 4^th and 5^th moons. Discovered in 2011 and 2012 respectively, researcher and co-discoverer Mark Showalter will take these names before the International Astronomical Union (IAU) after voting closes on February 25^th, 2013.

But days after the polling opened, a curious twist in the tale occurred that Star Trek’s Mr. Spock would only describe as “Fascinating.”

William Shatner, James T. Kirk himself, proposed the name Vulcan for one of Pluto’s unnamed moons. Fans and Trekkies worldwide rallied, and as of writing this, Vulcan enjoys a comfortable lead over Cerberus and Styx which are vying for the 2^nd place position.

This astronomical horse-race has the propensity to get interesting. In order to be considered, the IAU’s naming convention simply states “Those that share Pluto’s orbital rhythm take the name of underworld deities,” And the named moons of Charon, Nix & Hydra all follow this convention. Shatner’s case for Vulcan does cite the god as “The nephew of Pluto” in Roman mythology, but anyone who had studied Roman and Greek mythos knows that familial relations can be proven between nearly any given god and/or goddess.

Interestingly, Showalter turned down Shatner’s second Star Trek/mythological suggestion of Romulus, citing that Romulus and Remus are already the names of the moons of asteroid 87 Silvia. While the “double naming” of objects in the solar system isn’t unheard of, it may be a definite strike against a proposal. Cerberus, Orpheus, Hypnos & Persephone are all names in the running that are all also assigned to asteroids.

On February 14^th, researchers “Opened up the Gates of Hell” a bit further and took more mythological nominations into the running, adding Elysium, Hecate, Melinoe, Orthrus, Sisyphus, Tantalus, Tartarus and Thantos into the fray. You can write-in candidates such as “Donald,” & “Goofy,” but these stand a proverbial snowball’s chance in Hades of being accepted. Perhaps the backing of a starship captain would help, if Adama or Han Solo were available for hire…

Still, one wonders if the name Vulcan will make it past the gate-keepers at the IAU. The IAU has sparked controversy surrounding Pluto before, in its 2006 decision that angered 5^th graders everywhere when they demoted Pluto to dwarf planet status. No solar system body currently holds the name of Vulcan, although one hypothetical one once did; the tiny fleeting world that was once thought to be interior to Mercury’s orbit. Several astronomers even claimed to witness transits of the fleeting world across the face of the Sun, and up until the late 19^th century, you could still find Vulcan in many astronomy texts. While the idea of Vulcan as a planet interior to Mercury is out (think of how many telescopes, both amateur and professional, now continuously monitor the Sun daily) it’s not out of the question that a small group of asteroids less than 10 kilometres in size tentatively dubbed “Vulcanoids” may still inhabit the space interior to Mercury.

Fans of Pluto unite... could Vulcan spark a repeat protest? (Wikimedia Commons image in the Public Domain). — Fans of Pluto unite… could Vulcan spark a repeat protest? (Wikimedia Commons image in the Public Domain).

But if nothing else, the poll is a fun exercise to watch as astronomy fans worldwide delve into mythological lore and dig out the names of obscure gods and goddesses. A similar debate on mythological merits swirled around the naming of the moon of dwarf planet Orcus, ultimately named Vanth in 2009.

While only two names will be selected for P4 & P5, the other denizens of the underworld may just get their day in July 2015 when NASA’s New Horizons spacecraft gives us the first close up look at Pluto and friends. Previous “first flybys” of other planets and asteroids have turned up new moons before, and Pluto may be no different.

“The discovery of so many small moons indirectly tells us that there must be lots of small particles lurking unseen in the Pluto system,” stated Harold Weaver of the Johns Hopkins University of Applied Physics Laboratory. Such debris will be a definite concern as scientists seek to thread the spacecraft’s trajectory past Pluto and its moons.

A young Clyde Tombaugh with one of his famous homemade telescopes. (Credit : NASA/GSFC).

Discovered 83 years ago to the day on February 18^th, 1930 by American astronomer Clyde Tombaugh, Pluto remains an uncharted corner of the solar system. Mr. Tombaugh passed away on January 17th, 1997, and an ounce of his ashes are aboard the New Horizons spacecraft which, along with the Pioneer 10 & 11 and Voyager 1 & 2 spacecraft, are escaping the solar system to wander along the galactic plane.

I’ve also got a proposal out in the running. By naming one of Pluto’s moons Alecto, we would honor Clyde with the inclusion of his initials “CT” on a moon. There is precedent for such a clever tribute before; James Christy honored his wife Charlene in the naming of Pluto’s large moon Charon and Mike Brown paid homage to his wife Diane by naming Eris’s moon Dysnomia.

Whatever happens, it’ll be interesting to see what transpires in the final names of P4/P5 are selected. Hopefully it won’t end in a showdown pitting Trekkies against the IAU… but don’t forget, the Trekkies did keep a television series on the air and got a space shuttle re-named!

February 18, 2013December 23, 2015 by Jason Major

A Parting Look at 2012 DA14: Was This a Warning Shot from Space?

Asteroid DA14 seen from the 2.1 Kitt Peak telescope as it departed the vicinity of Earth. Credit: NOAO/Nicholas Moskovitz (MIT)

Just as anticipated, on Friday, Feb. 15, asteroid 2012 DA14 passed us by, zipping 27,000 kilometers (17,000 miles) above Earth’s surface — well within the ring of geostationary weather and communications satellites that ring our world. Traveling a breakneck 28,100 km/hr (that’s nearly five miles a second!) the 50-meter space rock was a fast-moving target for professional and amateur observers alike. And even as it was heading away from Earth DA14 was captured on camera by a team led by MIT researcher Dr. Nicholas Moskovitz using the 2.1-meter telescope at the Kitt Peak National Observatory in Tucson, AZ. The team’s images are shown above as an animated gif (you may need to click the image to play it.)

This object’s close pass, coupled with the completely unexpected appearance of a remarkably large meteor in the skies over Chelyabinsk, Russia on the morning of the same day, highlight the need for continued research of near-Earth objects (NEOs) — since there are plenty more out there where these came from.

“Flybys like this, particularly for objects smaller than 2012 DA14, are not uncommon. This one was special because we knew about it well in advance so that observations could be planned to look at how asteroids are effected by the Earth’s gravity when they come so close.”

– Dr. Nicholas Moskovitz, MIT

The animation shows 2012 DA14 passing inside the Little Dipper, crossing an area about a third the size of the full Moon in 45 minutes. North is to the left.

(For a high-resolution version of the animation, click here.)

Exterior of the 2.1-meter telescope of the Kitt Peak National Observatory (NOAO) — Exterior of the 2.1-meter telescope of the Kitt Peak National Observatory (NOAO/AURA/NSF)

According to the National Optical Astronomy Observatory, which operates the Kitt Peak Observatory, Dr. Moskovitz’ NSF-supported team “are analyzing their data to measure any changes in the rotation rate of the asteroid after its close encounter with the Earth. Although asteroids are generally too small to resolve with optical telescopes, their irregular shape causes their brightness to change as they rotate. Measuring the rotation rate of the asteroid in this way allows the team to test models that predict how the earth’s gravity can affect close-passing asteroids. This will lead to a better understanding of whether objects like 2012 DA14 are rubble piles or single solid rocks.

“This is critical to understanding the potential hazards that other asteroids could pose if they collide with the Earth.”

So just how close was DA14’s “close pass?” Well, if Earth were just a few minutes farther along in its orbit, we would likely be looking at images of its impact rather than its departure.*

Although this particular asteroid isn’t expected to approach Earth so closely at any time in the foreseeable future — at least within the next 130 years — there are lots of such Earth-crossing objects within the inner Solar System… some we’re aware of, but many that we’re not. Identifying them and knowing as many details as possible about their orbits, shapes, and compositions is key.

Even this soon after the Feb. 15 flyby observations of 2012 DA14 have provided more information on its orbit and characteristics., allowing for fine-tuning of the data on it.

According to the Goldstone Radar Observatory web page, the details on 2012 DA14 are as follows:
Semimajor axis 1.002 AU
Eccentricity 0.108
Inclination 10.4 deg
Perihelion distance 0.893 AU
Aphelion distance 1.110 AU
Absolute magnitude (H) 24.4
Diameter ~50 meters (+- a factor of two)
Rotation period ~6 h (N. Moskovitz, pers. comm.)
Pole direction unknown
Lightcurve amplitude ~1 mag (N. Moskovitz, pers. comm.)
Spectral class Ld (N. Moskovitz, pers. comm.)

Goldstone is currently conducting radar observations on the asteroid. A radar map of its surface and motion is anticipated in the near future.

Read more about Dr. Moskovitz’ observations on the NOAO website here, and see more images of 2012 DA14 captured by astronomers around the world in our previous article.

A bright meteor witnessed over Russia on Feb. 15, 2013 (RussiaToday) — A bright daytime meteor witnessed over Russia on Feb. 15, 2013 (RussiaToday)

Also, in an encouraging move by international leaders in the field, during the fiftieth session of the Scientific and Technical Subcommittee of the Committee on the Peaceful Uses of Outer Space, currently being held from at the United Nation Office in Vienna, near-Earth objects are on the agenda with a final report to be issued by an Action Team. Read the report PDF here.

*According to astronomer Phil Plait, while the orbits of Earth and DA14 might intersect at some point, on the 15th of February 2013 the asteroid slipped just outside of Earth’s orbit — a little over 17,000 miles shy. “It was traveling one way and the Earth another, so they could not have hit each other on this pass no matter where Earth was in its orbit,” he wrote in an email. Still, 17,000 miles is a very close call astronomically, and according to Neil deGrasse Tyson on Twitter, it “will one day hit us, like the one in Russian [sic] last night.” When? We don’t know yet. That’s why we must keep watching.

February 18, 2013December 23, 2015 by Elizabeth Howell

The Lessons We Learned from Space Shuttle Enterprise

Space shuttle Enterprise soars during its first of five free flights. Credit: NASA

On this day 36 years ago, two astronauts aboard the space shuttle Enterprise took the ship out for its initial test flight. It landed on the back of a 747 before undertaking a series of free flights starting in June that year.

Enterprise was designed as a test ship only, and was never intended to fly in space. Instead, it was used for a series of flying and landing approach tests to see how well the shuttle maneuvered during the landing. The astronauts first flew a series of “captive” flights aboard the 747, then cut the test shuttle loose for five free flights over several weeks.

What lessons were learned and what design changes did NASA implement from the Enterprise test program? And how did Enterprise help shape the future of the space shuttle program? A few clues emerge from the program’s final evaluation report, which was released in February 1978.

– Stopping a hydrazine leak. Hydrazine was used as a fuel for the maneuvering thrusters on the space shuttle, but the chemical is toxic and shouldn’t be exposed to humans. During the first captive flight, an auxiliary power unit was turned on about 18 minutes in. That was part of the plan, but the next part wasn’t: NASA observed fuel was being used much faster than expected in the next 25 minutes. It turned out that a bellows seal in the fuel pump had failed and caused “significant hydrazine leakage” in the shuttle’s aft bay.

– Preventing brake trouble or ‘chattering’. The first indication of trouble came after the second free flight. The astronauts felt a “chattering” (low-frequency vibration) sensation during braking as they were slowing down on the runway. This 16-hertz vibration happened again during “hard” braking on Flight 3. In light of the vibration, the brake control was modified and the astronauts did not feel the vibrations on Flights 4 and 5.

– Minimizing computer vibration. Enterprise’s Computer 2 fell out of sync with its fellow computers as the shuttle separated from the 747 on Flight 1, causing several computer errors. (The other three redundant computers effectively voted the computer off the island, to use Survivor parlance, and the flight carried on.) Ground tests of similar units revealed that the solder keeping the computer attached to the shuttle cracked when subjected to a slight vibration for a long period of time. NASA modified the attachments and the computers were just fine on Flight 2.

– Astronaut training. The astronauts experienced several control problems during Enterprise’s fifth free landing, when they deployed the speed brake to compensate for a landing that was a little faster than planned. As the pilot tried to control the shuttle’s sink rate, the elevons (a control surface for pitch and roll) were elevated more than usual, causing the shuttle to gently head back into the air and roll to the right before landing again. The astronauts could not see any unusual changes in pitch because the nose of the shuttle was not visible from the cockpit. Further, the center of gravity for the pitch changes was so close to the cockpit that the astronauts could not feel the sensation. “The pilot was unaware of any problem other than that he was landing long and trying to get the vehicle on the ground near the desired touchdown spot,” the NASA report stated. Several recommendations came out of this incident, such as more simulations of landings, modifying the flight control system, and stating that speed brakes should not be used just before landing.

Bottom line, though, was NASA said the approach and landing tests accomplished all objectives. The authors of the report called for modifications to these problems and a few others, but said as soon as these situations were addressed the shuttle was performing well enough for further flights. You can read the whole report here.

Enterprise is now on display at the Intrepid Air & Space Museum in New York, but is temporarily closed to the public as the shuttle undergoes repairs from damage incurred during Hurricane Sandy.

February 18, 2013December 29, 2015 by Nancy Atkinson

Carnival of Space #289

This week’s Carnival of Space is hosted by Pamela Hoffman at Everyday Spacer.

Click here to read Carnival of Space #289.

And if you’re interested in looking back, here’s an archive to all the past Carnivals of Space. If you’ve got a space-related blog, you should really join the carnival. Just email an entry to [email protected], and the next host will link to it. It will help get awareness out there about your writing, help you meet others in the space community – and community is what blogging is all about. And if you really want to help out, sign up to be a host. Send an email to the above address.

February 17, 2013December 23, 2015 by Elizabeth Howell

The Astronomy of Shakespeare

A portrait of William Shakespeare on the cover of the first Folio of his plays. Credit: Elizabethan Club of Yale University

With all this talk lately of rocks whizzing by Earth (or crashing through the atmosphere), it’s remarkable that we didn’t even know of space rocks a few centuries ago. The first asteroid, 1 Ceres, was discovered in 1801.

Dial back a few centuries, and we were still in the realm of a perfect universe with the Earth at the center. William Shakespeare’s (1564-1616) plays are full of these references. Universe Today recently stumbled across a 1964 Irish Astronomical Journal paper replete with examples.

Shakespeare was born about 20 years after Nicolaus Copernicus, whose book De revolutionibus orbium coelestium (On the Revolutions of the Celestial Spheres) laid out the case for the Sun-centered solar system. It took a while for Copernicus’ theories to take hold, however.

While bearing in mind that Shakespeare often wrote about historical personages, one passage from Troilus and Cressida demonstrates an example of the characters speaking of the Sun following the other planets in circles around the Earth.

The heavens themselves, the planets, and this centre,
Observe degree, priority and place.
Insisture, course, proportion, season, form,
Office, and custom, in all line of order:
And therefore is the glorious planet Sol
In noble eminence enthroned and sphered
Amidst the other …

An Earth-centered solar system had its problems when predicting the paths of the planets. Astronomers couldn’t figure out why Mars reversed in its path in the sky, for example.

The real explanation is the Earth “catching up” and passing Mars in its orbit, but astronomers in Shakespeare’s time commonly used “epicycles” (small circles in a planet’s orbit) to explain what was going on. Shakespeare wrote about this problem in Henry VI:

Mars his true moving, even as in the heavens,
So in the earth, to this day is not known.

However, the Bard displayed a more modern understanding of the Moon’s movement around the Earth, the paper points out. The Moon’s distance varies in its orbit, a fact spoken about in Othello, although note that Shakespeare attributes madness to the moon’s movements:

It is the very error of the moon;
She comes more near the earth than she was wont
And makes men mad.

For more examples — including what Shakespeare thought about astrology — you can check out the paper here.