An artist’s rendering of the newly discovered exoplanet OGLE-2013-BLG-0341LBb (far right) orbiting one star (right) of a binary red dwarf star system, from an Earth-type distance of approximately 0.9 Astronomical Units away. Image Credit: Cheongho Han, Chungbuk National University, Republic of Korea
Our solar neighborhood is rich with planetary systems. Within 20 light-years we’ve detected sizzling gas giants and rocky planets orbiting closer to their host star than Mercury orbits the Sun.
Astronomers have now added one more to the list, and this one — a super-Earth dubbed Gliese 15Ab — ranks as one of the closest known exoplanets, circling its host star only 11.7 light-years away.
Gliese 15 is a binary system, with two cool, dim red dwarfs orbiting each other. Although red dwarfs are the most common type of star in the galaxy, they’re so intrinsically faint that not a single one (including the closest star to the Sun, Proxima Centauri) is visible to the naked eye.
Although Gliese 15A might appear faint from Earth, it is overwhelmingly bright compared to its barely reflective exoplanet. So unfortunately we can’t easily see the exoplanet directly. But it does leave an imprint on its host star. Its small gravitational tug makes Gliese 15A wobble ever so slightly as both orbit a mutual center of mass, known as the barycenter.
The star’s movement is then imprinted on its spectrum. As Gliese 15A moves away from the Earth, its spectral lines stretch to redder wavelengths. But as it moves toward the Earth, its spectral lines compress to shorter wavelengths.
The radial velocities for Gliese 15Ab. Image Credit: Howard et al.
The change is minute. But the Keck 10-meter telescope, with an extremely high-resolution detector, can see such small changes. And from this tiny wobble, Andrew Howard and colleagues calculated that the planet is 5.35 times the mass of Earth and orbits its star in only 11.44 days, making it a hot super-Earth. And remember, it’s only 11.7 light-years away.
A handful of other planet candidates have been found that are closer, but all — including Gliese 15Ab — have yet to be confirmed by other research teams. In the long run, it may turn out that this hot super-Earth is the closest planet to our pale blue dot. Then again, it may not. That’s how science works.
Nonetheless, Gliese 15Ab might prove to be an exciting target for one of the new planet imagers that came online within the past year.
The findings will be published in the Astrophysical Journal and are available online.
The suspect crater on the outskirts of Managua. Credit: AP/BBC News
By now, you’ve seen the pictures.
As astronomers tracked the close pass of Near Earth Asteroid 2014 RC this weekend, reports came out of Nicaragua that a possible meteorite struck near the capital of Managua.
Details are still sketchy, but government sources cite reports of a loud bang and ground tremor late Saturday night on September 6th. Later images circulating late Sunday evening showed a crater 12 metres wide and 5.5 metres deep on a remote section of the international airport at Managua, which also hosts a local air force installation.
A closer look at the Managua crater. Credit: AFP/BBC News.
Reports state that the impact went off “like a bomb,” and Wilfried Strauch of the Nicaragua Institute of Earth Studies has already gone on record as being “convinced it was a meteorite.” Investigators are currently scouring the alleged impact site for debris.
This has also sparked a lively discussion across forums and social media: is the crater the result of an extraterrestrial impactor?
Of course, cosmic coincidences can and do happen. Last year, the close passage of asteroid 2012 DA14 was upstaged by the explosion of a 20-metre asteroid over the city of Chelyabinsk on the very same day. And though the two were conclusively proven to be unrelated, they did serve to raise general human awareness that, yes, large threatening rocks do indeed menace the Earth. And ironically, the aforementioned asteroid 2014 RC was about the same size as the Chelyabinsk asteroid, which snuck up on the Earth undetected from a sunward direction.
But Ron Baalke, a software engineer at the Jet Propulsion Laboratory has posted an update to the close pass by asteroid 2014 RC on the NASA’s Near Earth Object website, saying, “Since the explosion in Nicaragua occurred a full 13 hours before the close passage of asteroid 2014 RC, these two events are unrelated.”
Baalke also noted that “no eyewitness accounts or imagery have come to light of the fireball flash or debris trail that is typically associated with a meteor of the size required to produce such a crater.”
The epic airburst over Chelyabinsk as captured via dashcam. (Still from video).
There are a few other problems with the Managua crater, though of course, we’d love to be proven wrong. Many observers have noted that the crater does not appear to look fresh, and the trees and soil around it appear to be relatively undisturbed. A first visual impression of the site looks more like a ground slump or sinkhole than an impact, or perhaps an excavation. Others have also noted the similarity of the crater with a military blast, a very good possibility with an air force base nearby.
Meteorite Men’s own Geoff Notkin has voiced doubts as to the authenticity of the meteor crater on Twitter.
Of course, it’s possible (though unlikely) that the impactor struck the site from straight overhead, leaving the area around it undisturbed. As with meteor showers, an impactor striking the Earth before local midnight would be coming at the planet from behind at a lower combined velocity.
Color me skeptical on this one. Still, we’ve been wrong before, and it’s always a boon for science when a new meteorite fall turns out to be real. Many have already cited the similarities between the Managua crater and the Carancas event in 2007 in Peru near Lake Titicaca that was initially considered dubious as well.
But again, it’s highly improbable that the Managua event is related to 2014 RC, however, which made its closest pass over the southern hemisphere near New Zealand many hours later at 18:18 UT on Sept 7th. We ran a recent simulation of the pass in Starry Night from the vantage point of the asteroid, and you’ll note that Central America is well out of view:
It’s also curious that no still images or video of the Managua event have yet to surface. This is strange, as it occurred on a Saturday night near a capital city of 2.4 million. The weather over Managua was partly cloudy that night, and generally, a security camera or two usually catches sight of the fireball.
We also did a check through any upcoming space junk reentries, which also proved to be a poor fit for a potential suspect. The next slated reentry is a BREEZE-M Tank with the NORAD ID of 2011-074D associated with the 2011 launch of AMOS-5. This object was not overhead around the time of the Managua event, and is predicted to reenter on September 9th at 15:15 UT +/- 14 hours.
And the same goes for the launch of AsiaSat-6 by SpaceX on Saturday night, as launches from the Cape head out eastward across the Atlantic and away from the Gulf of Mexico region.
A look at 2014 RC on the night of September 6th. Credit: Gianluca Masi and the Virtual Telescope Project.
Unfortunately, images and video would go a long way towards gauging a direction and final orbit of a suspect meteorite. The discovery of meteoritic debris at the site would also serve to clinch the link between the crater and a cosmic impactor as well. Or perhaps, news of the impending passage of NEO asteroid 2014 RC and the recent pass of 2014 RA the weekend prior had already primed the general public to suspect a meteor strike as an explosion was heard late in the evening… we’ve lived near bombing ranges, and are familiar with the sound of late night explosions ourselves.
Target Earth… An aerial view of Pingualuit crater in northern Quebec. Credit: NASA/Denis Sarrazin and the Pingualuit Crater Lakes project.
To be sure, the universe is a dangerous place, and errant rocks from above do on occasion have it out for any unwary species that gets in their way.
So we’ll open it up for discussion: what do you think happened on Saturday night near Managua? Was it a meteorite, or another case of a “meteor-wrong?”
A composite image of Rosetta's target (Comet 67P/Churyumov–Gerasimenko) obtained by the Very Large Telescope. Credit: C. Snodgrass/ESO/ESA
This picture shows it is possible to look at Rosetta’s comet from Earth, but what a lot of work it requires! The picture you see above is a composite of 40 separate images taken by the Very Large Telescope (removing the background stars).
Despite the fact that Rosetta is right next to Comet 67P/Churyumov–Gerasimenko, ground-based observatories are still useful because they provide the “big picture” on what the comet looks like and how it is behaving. It’s an observational challenge, however, as the comet is still more than 500 million kilometers (310 million miles) from the Sun and hard to see.
On top of that, the European Space Agency says the comet is sitting in a spot in the sky where it is difficult to see it generally, as the Milky Way’s prominent starry band is just behind. But what can be seen is spectacular.
“Although faint, the comet is clearly active, revealing a dusty coma extending at least 19 000 km [11,800 miles] from the nucleus,” ESA stated. “The comet’s dusty veil is not symmetrical as the dust is swept away from the Sun – located beyond the lower-right corner of the image – to begin forming a tail.”
And that dust is beginning to show up in Rosetta’s grain collector, as you can see below!
Rosetta’s dust collector, Cometary Secondary Ion Mass Analyser (COSIMA), collected its first grains from Comet 67P/Churyumov–Gerasimenko in August 2014. This image shows before and after images of the collection. Credit: ESA/Rosetta/MPS for COSIMA Team MPS/CSNSM/UNIBW/TUORLA/IWF/IAS/ESA/ BUW/MPE/LPC2E/LCM/FMI/UTU/LISA/UOFC/vH&S
Rosetta’s Cometary Secondary Ion Mass Analyser (COSIMA) picked up several dust grains in August, which you can see in the image, and are now looking at the target plate more closely to figure out more about the dust grains.
“Some will be selected for further analysis: the target plate will be moved to place each chosen grain under an ion gun which will then ablate the grain layer by layer. The material is then analyzed in a secondary ion mass spectrometer to determine its composition,” ESA stated.
All of these results were presented today (Sept. 8) at the European Planetary Science Congress 2014.
MAVEN is NASA’s next Mars Orbiter and will investigate how the planet lost most of its atmosphere and water over time. Credit: NASA
MAVEN to conduct up close observations of Comet Siding Spring during Oct. 2014 MAVEN is NASA’s next Mars Orbiter and will investigate how the planet lost most of its atmosphere and water over time. Credit: NASA
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NASA’s MAVEN Mars Orbiter is “ideally” instrumented to uniquely “map the composition of Comet Siding Spring” in great detail when it streaks past the Red Planet during an extremely close flyby on Oct. 19, 2014 – thereby providing a totally “unexpected science opportunity … and a before and after look at Mars atmosphere,” Prof. Bruce Jakosky, MAVEN’s Principal Investigator of CU-Boulder, CO, told Universe Today in an exclusive interview.
The probes state-of-the-art ultraviolet spectrograph will be the key instrument making the one-of-a-kind compositional observations of this Oort cloud comet making its first passage through the inner solar system on its millions year orbital journey.
“MAVEN’s Imaging Ultraviolet Spectrograph (IUVS) is the ideal way to observe the comet coma and tail,” Jakosky explained.
“The IUVS can do spectroscopy that will allow derivation of compositional information.”
“It will do imaging of the entire coma and tail, allowing mapping of composition.”
Comet: Siding Spring The images above show — before and after filtering — comet C/2013 A1, also known as Siding Spring, as captured by Wide Field Camera 3 on NASA’s Hubble Space Telescope. Image Credit: NASA, ESA, and J.-Y. Li (Planetary Science Institute)
Moreover the UV spectrometer is the only one of its kind amongst NASA’s trio of Martian orbiters making its investigations completely unique.
“IUVS is the only ultraviolet spectrometer that will be observing the comet close up, and that gives the detailed compositional information,” Jakosky elaborated
And MAVEN, or the Mars Atmosphere and Volatile Evolution, is arriving just in the nick of time to fortuitously capture this fantastically rich data set of a pristine remnant from the solar system’s formation.
The spacecraft reaches Mars in less than 15 days. It will rendezvous with the Red Planet on Sept. 21 after a 10 month interplanetary journey from Earth.
Furthermore, since MAVEN’s purpose is the first ever detailed study of Mars upper atmosphere, it will get a before and after look at atmospheric changes.
“We’ll take advantage of this unexpected science opportunity to make observations both of the comet and of the Mars upper atmosphere before and after the comet passage – to look for any changes,” Jakosky stated.
How do MAVEN’s observations compare to NASA’s other orbiters Mars Odyssey (MO) and Mars Reconnaissance Orbiter (MRO), I asked?
“The data from the other orbiters will be complementary to the data from IUVS.”
“Visible light imaging from the other orbiters provides data on the structure of dust in the coma and tail. And infrared imaging provides information on the dust size distribution.”
IUVS is one of MAVENS’s nine science sensors in three instrument suites targeted to study why and exactly when did Mars undergo the radical climatic transformation.
How long will MAVEN make observations of Comet C/2013 A1 Siding Spring?
“We’ll be using IUVS to look at the comet itself, about 2 days before comet nucleus closest approach.”
“In addition, for about two days before and two days after nucleus closest approach, we’ll be using one of our “canned” sequences to observe the upper atmosphere and solar-wind interactions.”
“This will give us a detailed look at the upper atmosphere both before and after the comet, allowing us to look for differences.”
Describe the risk that Comet Siding Spring poses to MAVEN, and the timing?
“We have the encounter with Comet Siding Spring about 2/3 of the way through the commissioning phase we call transition.”
“We think that the risk to the spacecraft from comet dust is minimal, but we’ll be taking steps to reduce the risk even further so that we can move on toward our science mission.”
“Throughout this entire period, though, spacecraft and instrument health and safety come first.”
This graphic depicts the orbit of comet C/2013 A1 Siding Spring as it swings around the sun in 2014. On Oct. 19, 2014 the comet will have a very close pass at Mars. Its nucleus will miss Mars by about 82,000 miles (132,000 kilometers). Credit: NASA/JPL-Caltech
What’s your overall hope and expectation from the comet encounter?
“Together [with the other orbiters], I’m hoping it will all provide quite a data set!
“From Mars, the comet truly will fill the sky!” Jakosky gushed.
The comet’s nucleus will fly by Mars at a distance of only about 82,000 miles (132,000 kilometers) at 2:28 p.m. ET (18:28 GMT) on Oct. 19, 2014. That’s barely 1/3 the distance from the Earth to the Moon.
What’s the spacecraft status today?
“Everything is on track.”
Maven spacecraft trajectory to Mars on Sept. 4, 2014. Credit: NASA
The $671 Million MAVEN spacecraft’s goal is to study Mars upper atmosphere to explore how the Red Planet lost most of its atmosphere and water over billions of years and the transition from its ancient, water-covered past, to the cold, dry, dusty world that it has become today.
MAVEN soared to space over nine months ago on Nov. 18, 2013 following a flawless blastoff from Cape Canaveral Air Force Station’s Space Launch Complex 41 atop a powerful Atlas V rocket and thus began a 10 month interplanetary voyage from Earth to the Red Planet.
It is streaking to Mars along with ISRO’sMOM orbiter, which arrives a few days later on September 24, 2014.
So far it has traveled 95% of the distance to the Red Planet, amounting to over 678,070,879 km (421,332,902 mi).
As of Sept. 4, MAVEN was 205,304,736 km (127,570,449 miles) from Earth and 4,705,429 km (2,923,818 mi) from Mars. Its Earth-centered velocity is 27.95 km/s (17.37 mi/s or 62,532 mph) and Sun-centered velocity is 22.29 km/s (13.58 mi/s or 48,892 mph) as it moves on its heliocentric arc around the Sun.
One-way light time from MAVEN to Earth is 11 minutes and 24 seconds.
MAVEN is NASA’s next Mars orbiter and launched on Nov. 18, 2014 from Cape Canaveral, Florida. It will study the evolution of the Red Planet’s atmosphere and climate. Universe Today visited MAVEN inside the clean room at the Kennedy Space Center. With solar panels unfurled, this is exactly how MAVEN looks when flying through space and circling Mars and observing Comet Siding Spring. Credit: Ken Kremer/kenkremer.com
Stay tuned here for Ken’s continuing MAVEN, MOM, Rosetta, Opportunity, Curiosity, Mars rover and more Earth and planetary science and human spaceflight news.
NASA’s Mars bound MAVEN spacecraft launches atop Atlas V booster at 1:28 p.m. EST from Space Launch Complex 41 at Cape Canaveral Air Force Station on Nov. 18, 2013. Image taken from the roof of the Vehicle Assembly Building (VAB) at NASA’s Kennedy Space Center. Credit: Ken Kremer/kenkremer.comNASA’s MAVEN Mars orbiter, chief scientist Prof. Bruce Jakosky of CU-Boulder and Ken Kremer of Universe Today inside the clean room at the Kennedy Space Center on Sept. 27, 2013. MAVEN launched to Mars on Nov. 18, 2013 from Florida. Credit: Ken Kremer/kenkremer.com
This artist's conception shows a newly formed star surrounded by a swirling protoplanetary disk of dust and gas. Credit: University of Copenhagen/Lars Buchhave
This new find is at least times the size of Jupiter and about the equivalent distance of Saturn to our own Sun, which means the planet would not be habitable as far as we can tell. It was spotted using a way of measuring carbon monoxide emission that seems to change its velocity and position in the same way that a planet would be expected to be orbiting the star.
The emission itself could be coming from a disk of gas surrounding the planet, or perhaps from the object’s tidal interactions with the gas and dust enveloping the young star, which is only 335 light-years from Earth.
“This system is very close to Earth relative to other disk systems. We’re able to study it at a level of detail that you can’t do with more distant stars. This is the first system where we’ve been able to do this,” stated Sean Brittain, an associate professor of astronomy and astrophysics at Clemson University in South Carolina.
“Once we really understand what’s going on, the tools that we are developing can then be applied to a larger number of systems that are more distant and harder to see.”
The study was published in the Astrophysical Journal.
The Sun. Credit: NASA & European Space Agency (ESA)
Approximately every 11 years the Sun becomes violently active, putting on a show of magnetic activity for aurora watchers and sungazers alike. But the timing of the solar cycle is far from precise, making it hard to determine the exact underlying physics.
Typically astronomers use sunspots to map the course of the solar cycle, but now an international team of astronomers have discovered a new marker: brightpoints, small bright spots in the solar atmosphere that allow us to observe the constant turmoil of material inside the Sun.
The new markers provide a new method in understanding how the Sun’s magnetic field evolves over time, suggesting a deeper and longer cycle.
A well-behaved Sun flips its north and south magnetic poles every 11 years. The cycle begins when the field is weak and dipolar. But the Sun’s rotation is faster at its equator than at its poles, and this difference stretches and tangles the magnetic field lines, ultimately producing sunspots, prominences, and sometimes flares.
“Sunspots have been the perennial marker for understanding the mechanisms that rule the sun’s interior,” said lead author Scott McIntosh, from the National Center for Atmospheric Research, in a news release. “But the processes that make sunspots are not well understood, and far less, those that govern their migration and what drives their movement.”
So McIntosh and colleagues developed a new tracking devise: spots of extreme ultraviolet and X-ray light, known as brightpoints in the Sun’s atmosphere, or corona.
“Now we can see there are bright points in the solar atmosphere, which act like buoys anchored to what’s going on much deeper down,” said McIntosh. “They help us develop a different picture of the interior of the sun.”
McIntosh and colleagues dug through the wealth of data available from the Solar and Heliospheric Observatory and the Solar Dynamics Observatory. They noticed that multiple bands of these markers also move steadily toward the equator over time. But they do so on a different timescale than sunspots.
At solar minimum there might be two bands in the northern hemisphere (one positive and one negative) and two bands in the southern hemisphere (one negative and one positive). Due to their close proximity, bands of opposite charge easily cancel one another, causing the Sun’s magnetic system to be calmer, producing fewer sunspots and eruptions.
But once the two low-latitude bands reach the equator, their polarities cancel each other out and the bands abruptly disappear — a process that takes 19 years on average.
The Sun is now left with just two large bands that have migrated to about 30 degrees latitude. Without the nearby band, the polarities don’t cancel. At this point the Sun’s calm face begins to become violently active as sunspots start to grow rapidly.
Solar maximum only lasts so long, however, because the process of generating a new band of opposite polarity has already begun at high latitudes.
In this scenario, it is the magnetic band’s cycle that truly defines the solar cycle. “Thus, the 11-year solar cycle can be viewed as the overlap between two much longer cycles,” said coauthor Robert Leamon, from Montana State University in Bozeman.
The true test, however, will come with the next solar cycle. McIntosh and colleagues predict that the Sun will enter a solar minimum somewhere in the last half of 2017, and the first sunspots of the next cycle will appear near the end of 2019.
The findings have been published in the Sept. 1 issue of the Astrophysical Journal and are available online.
An artist's conception of a circumbinary planet. Credit: NASA/JPL-Caltech/T. Pyle
There are few environments more hostile than a planet circling two stars. Powerful tidal forces from the stars can easily destroy the rocky building blocks of planets or grind a newly formed planet to dust. But astronomers have spotted a handful of these hostile worlds.
A new study is even suggesting that these extreme systems exist in abundance, with roughly half of all exoplanets orbiting binary stars.
NASA’s crippled Kepler space telescope is arguably the world’s most successful planet hunter, despite the sudden end to its main mission last May. For nearly four years, Kepler continuously monitored 150,000 stars searching for tiny dips in their light when planets crossed in front of them.
As of today, astronomers have confirmed nearly 1,500 exoplanets using Kepler data alone. But Kepler’s database is immense. And according to the exoplanet archive there are over 7,000 “Kepler Objects of Interest,” dubbed KOIs, that might also be exoplanets.
There are a seeming endless number of questions waiting to be answered. But one stands out: how many exoplanets circle two stars? Binary stars have long been known to be commonplace — about half of the stars in the Milky Way are thought to exist in binary systems.
A team of astronomers, led by Elliott Horch from Southern Connecticut State University, has shown that stars with exoplanets are just as likely to have a binary companion. In other words, 40 to 50 percent of the host stars are actually binary stars.
“It’s interesting and exciting that exoplanet systems with stellar companions turn out to be much more common than was believed even just a few years ago,” said Horch in a news release.
The research team made use of the latest technology, speckle imaging, to take a second look at KOI stars and search for any companion stars. In using this technique, astronomers obtain rapid images of a small portion of the sky surrounding the star. They then combine the images using a complex set of algorithms, which yields a final picture with a resolution better than the Hubble Space Telescope.
Speckle imaging allows astronomers to detect companion stars that are up to 125 times fainter than the target, but only a small distance away (36,000 times smaller than the full Moon). For the majority of Kepler stars, this equates to finding a companion within 100 times the distance from the Sun to the Earth.
The team was surprised to find that roughly half of their targets had companion stars.
“An interesting consequence of this finding is that in the half of the exoplanet host stars that are binary we can not, in general, say which star in the system the planet actually orbits,” said coauthor Steve B. Howell from the NASA Ames Research Center.
The new findings, soon to be published in the Astrophysical Journal, further advance our need to understand these exotic systems and the harrowing environments they face.
This graphic depicts the passage of asteroid 2014 RC past Earth on September 7, 2014. At time of closest approach, the space rock will be about one-tenth the distance from Earth to the moon. Times indicated on the graphic are Universal Time. Subtract 4 hours for Eastern Daylight Time. Credit: NASA/JPL-Caltech
Guess who’s dropping by for a quick visit this weekend? On Sunday, a 60-foot-wide (20-meters) asteroid named 2014 RC will skim just 25,000 miles (40,000 km) from Earth. That’s within spitting distance of all those geosynchronous communication and weather satellites orbiting at 22,300 miles.
Size-wise, this one’s similar to the Chelyabinsk meteorite that exploded over Russia’s Ural Mountains region in February 2013. But it’s a lot less scary. 2014 RC will cleanly miss Earth this time around, and although it’s expected back in the future, no threatening passes have been identified. Whew!
2014 RC will pass along the outer edge of the geosynchronous satellite belt, home to many weather and communications satellites. The chance of a hit is close to infinitesimal. Click for more information and detailed finder charts. Credit: SatFlare
NEOs or Near Earth Asteroids are defined as space rocks that come within about 28 million miles of Earth’s orbit. Nearly once a month astronomers discover an Earth-crossing asteroid that passes within the moon’s orbit. In spite of hype and hoopla, none has threatened the planet. As of February 2014, we know of 10,619 near-Earth asteroids. It’s estimated that 93% of all NEOs larger than 1 km have been discovered but 99% of the estimated 1 million NEOs 100 feet (30-meters) still remain at large.
No surprise then that new ones pop up routinely in sky surveys. Take this past Sunday night for example, when the Catalina Sky Survey nabbed 2014 RA, a 20-foot (6-meter) space rock that whistled past Earth that evening at 33,500 miles (54,000 km). It’s now long gone.
Artist view of an asteroid (with companion) passing near Earth. Credit: P. Carril / ESA
2014 RC was picked up on or about September 1-2 by both the Catalina Sky Survey and Pan-STARRS 1 survey telescope atop Mt. Haleakala in Maui. The details are still being worked out as to which group will take final discovery credit. Based on current calculations, 2014 RC will pass closest to Earth around 2:15 p.m. EDT (18:15 UT) on Sunday, September 7th. When nearest, the asteroid is expected to brighten to magnitude +11.5 – too dim for naked eye observing but visible with a good map in 6-inch and larger telescopes.
Seeing it will take careful planning. Unlike a star or planet, this space rock will be faint and barreling across the sky at a high rate of speed. Discovered at magnitude +19, 2014 RC will brighten to magnitude +14 during the early morning hours of September 7th. Even experienced amateurs with beefy telescopes will find it a challenging object in southern Aquarius both because of low altitude and the unwelcome presence of a nearly full moon.
64-frame movie showing Toutatis tumbling through space only 4.3 million miles from Earth on Dec. 12-13. Credit: NASA/Goldstone radar
Closest approach happens in daylight for North and South America , but southern hemisphere observers might spot it with a 6-inch scope as a magnitude +11.5 “star” zipping across the constellations Pictor and Puppis. 2014 RC fades rapidly after its swing by Earth and will quickly become impossible to see in all amateur telescopes, though time exposure photography will keep the interloper in view for a few additional hours.
2014 RC accelerates across the sky between 4 a.m. to 4 p.m EDT September 7 in this path created by Gianluca Masi using SkyX Pro software and the latest positions from JPL.
Most of us won’t have the opportunity to run outside and see the asteroid, but Gianluca Masi and his Virtual Telescope Project site will cover it live starting at 6 p.m. EDT (22:00 UT). Lance Benner, who researches radar imaging of near-Earth and main-belt asteroids, hopes to image 2014 RC with 230-foot (70-m) radar dish at the Goldstone complexon September 5-7 and possibly the big 1,000-foot (305-m) radar dish at Arecibo. Both provide images based on radar echoes that show asteroids up close with shapes, craters, ridges and all.
A slice of the Laniakea Supercluster -- a local basin of attraction. This structure contains many galaxies and clusters, including our own Milky Way Galaxy. Credit: SDvision interactive visualization software by DP at CEA/Saclay, France.
Our cosmic address extends well beyond Earth, past the Milky Way and toward the farthest reaches of the universe. But now astronomers are adding another line: the Laniakea Supercluster, which takes its name from the Hawaiin term “lani” meaning heaven and “akea” meaning spacious or immeasurable.
And the name is true to its meaning. The supercluster extends more than 500 million light-years and contains the mass of 100 quadrillion Suns in 100,000 large galaxies. This research is the first to trace our local supercluster on such a large scale.
“We have finally established the contours that define the supercluster of galaxies we can call home,” said lead researcher R. Brent Tully, from the University of Hawaii’s Institute for Astrophysics, in a news release. “This is not unlike finding out for the first time that your hometown is actually part of much larger country that borders other nations.”
Superclusters — aggregates of clusters of galaxies — rank among the largest structures in the universe. Although these structures are interconnected in a web of filaments, their exact outlines and boundaries are hard to define.
Large three-dimensional maps (think Sloan Digital Sky Survey) calculate a galaxy’s location based on its galactic redshift, the shifts in its spectrum due to its apparent motion as space itself expands. But Tully and colleagues used peculiar redshifts, the shifts in a galaxy’s spectrum due to the local gravitational landscape, instead.
In other words, the team is mapping the galaxies by examining their impact on the motions of other galaxies. A galaxy caught in the midst of multiple galaxies will find itself in a massive tug-of-war, where the balance of the surrounding gravitational forces will dictate its motion.
Typically this method is only viable for the local universe where the peculiar velocities are high enough compared with the expansion velocities, which increase with distance (a galaxy recedes faster the farther away it is). But Tully and colleagues used a new algorithm, which revealed the large-scale patterns created by galaxies’ motions.
Not only did this allow them to map our home supercluster, but to clarify the role of the Great Attractor, a dense region in the vicinity of Centaurus, Norma, and Hydra clusters that influences the motion of our Local Group and other groups of galaxies. They revealed that the Great Attractor is a large gravitational valley that draws all galaxies inward.
The team also discovered other structures, including a region named Shapley, toward which Laniakea is moving.
The findings have been published in the Sept. 4 issue of Nature.
Last month's supermoon within 24 hours of perigee. Credit: Blobrana
Time to dust off those ‘what is a perigee Full Moon’ explainer posts… the supermoon once again cometh this weekend to a sky near you.
Yes. One. More. Time.
We’ve written many, many times — as have many astronomy writers — about the meme that just won’t die. The supermoon really brings ‘em out, just like werewolves of yore… some will groan, some will bemoan the use of a modernized term inserted into the common astronomical vernacular that was wrought by an astrologer, while others will exclaim that this will indeed be the largest Full Moon EVER…
But hey, it’s a great chance to explain the weird and wonderful motion of our nearest natural neighbor in space. Thanks to the Moon, those astronomers of yore had some great lessons in celestial mechanics 101. Without the Moon, it would’ve been much tougher to unravel the rules of gravity that we take for granted when we fling a probe spaceward.
The Moon reaches Full on Tuesday, September 9th at 1:38 Universal Time (UT), which is 9:38 PM EDT on the evening of the 8th. The Moon reaches perigee at less than 24 hours prior on September 8th at 3:30 UT — 22 hours and 8 minutes earlier, to be precise — at a distance 358,387 kilometres distant. This is less than 2,000 kilometres from the closest perigee than can occur, and 1,491 kilometres farther away than last month’s closest perigee of the year, which occurred 27 minutes prior to Full Moon.
A Proxigean or Perigee Full “Supermoon” as reckoned by our preferred handy definition of “a Full Moon occurring within 24 hours of perigee” generally occurs annually in a cycle of three over two lunar synodic periods, and moves slowly forward by just shy of a month through the Gregorian calendar per year. The next cycle of “supermoons” starts on August 30th, 2015, and you can see our entire list of cycles out through 2020 here.
What’s the upshot of all this? Well, aside from cluttering inboxes and social media with tales of the impending supermoon this weekend, the rising Moon will appear 33.5’ arc minutes in diameter as opposed to its usually quoted average of 30’ in size. And remember, that’s in apparent size as seen from our Earthly vantage point… can you spy a difference from one Full Moon to the next? Fun fact: the rising Moon is actually farther away from you to the tune of about one Earth radius than when it’s directly overhead at the zenith.
Fed up with supermoon-mania? The September Full Moon also has a more pedestrian name: The Harvest Moon. Actually, this is the Full Moon that falls nearest to the September Equinox, marking the start of the astronomical season of Fall in the northern hemisphere and Spring in the southern. In the current first half of the 21st century, the September Equinox falls on the 22nd or 23rd, meaning that the closest Full Moon (and thus the Harvest Moon) can sometimes fall in October, as last happened in 2009 and will occur again in 2017. In this instance, the September Full Moon would then be referred to as the Corn Moon as reckoned by the Algonquins, and is occasionally referred to as the Drying Grass Moon by Sioux tribes. In 2014, the Harvest Full Moon “misses” falling in October by about 32 hours!
The waning gibbous Moon of July 14th, 2014- shortly after the first supermoon of the year. Credit: Blobrana.
So, why is it known as the Harvest Moon? Well, in the age before artificial lighting (and artificial light pollution) the rising of the Full Moon as the Sun sets allowed for a few hours of extra illumination to bring in crops. In October, the same phenomenon gave hunters a few extra hours to track game by the light of the Full Hunters Moon, both essential survival activities before the onset of the long winter.
And that Full Harvest Moon seems to “stick around” on successive evenings. This is due to the relatively shallow angle of the evening ecliptic to the eastern horizon as seen from mid-northern latitudes in September.
The rising Full Moon on the evening of September 8th as seen from latitude 40 degrees north. Note the shallow angle of the ecliptic. Created using Stellarium.
Here’s a sample of rising times for the Moon this month as seen from Baltimore, Maryland at 39.3 degrees north latitude:
Saturday, September 6th: 5:43 PM EDT
Sunday, September 7th: 6:23 PM EDT
Monday, September 8th: 7:05 PM EDT
Tuesday, September 9th: 7:44 PM EDT
Wednesday, September 10th: 8:22 PM EDT
Note the Moon rises only ~40 minutes later on each successive evening.
The Full Harvest Moon of 2013 plus aircraft. Credit: Stephen Rahn.
We’re also headed towards a “shallow year” in 2015, as the Moon bottoms out relative to the ecliptic and only ventures 18 degrees 20’ north and south of the celestial equator at shallow minimum. This is due to what’s known as the Precession of the Line of Apsides as the gravitational pull of the Sun slowly drags the orbit of the Moon round the earth once every 8.85 years. The nodes where the ecliptic and path of the Moon meet — and solar and lunar eclipses occur — also move slowly in an opposite direction of the Moon’s motion, taking just over twice as long as the Precession of the Line of Apsides to complete one revolution around the ecliptic at 18.6 years. This is one of the more bizarre facts about the motion of the Moon: its orbital tilt of 5.1 degrees is actually fixed with respect to the ecliptic as traced out by the Earth’s orbit about the Sun, not our rotational axis. Native American and ancient Northern European knew of this, and the next “Long Night’s Moon” also called a “Lunar Standstill” when the Moon rides high in the northern hemisphere sky is due through 2024-2025.
The footprint of the September 11th occultation of Uranus. Credit: Occult 4.0.
And to top it off, the Moon occults Uranus just two days after Full on September 11th as seen from northeastern North America, Greenland, Iceland and northern Scandinavia. We’re in a cycle of occultations of Uranus by the Moon from late 2014 through 2015, and this will set the ice giant up for a spectacular close pass, and a rare occultation of the planet for a remote region in the Arctic during the October 8th total lunar eclipse…
