Posted on by Jason Major

Comets Encke and ISON Spotted from Mercury

MESSENGER wide-angle camera images of comets Encke and ISON

Two comets currently on their way toward the Sun have been captured on camera from the innermost planet. The MESSENGER spacecraft in orbit around Mercury has spotted the well-known short-period comet Encke as well as the much-anticipated comet ISON, imaging the progress of each over the course of three days. Both comets will reach perihelion later this month within a week of each other.

While Encke will most likely survive its close encounter to continue along its 3.3-year-long lap around the inner Solar System, the fate of ISON isn’t nearly as certain… but both are making for great photo opportunities!

The figure above shows, on the left, images of comet 2P/Encke on three successive days from Nov. 6 to Nov. 8; on the right, images of C/2012 S1 (ISON) are shown for three successive days from Nov. 9 to Nov. 11. Both appear to brighten a little bit more each day.

MESSENGER image of ISON from Nov. 10 (enlarged detail)
MESSENGER image of ISON from Nov. 10 (enlarged detail)

MESSENGER is viewing these comets from a vantage point that is very different from that of observers on Earth. Comet Encke was approximately 0.5 AU from the Sun and 0.2 AU from MESSENGER when these images were taken; the same distances were approximately 0.75 AU and 0.5 AU, respectively, for ISON. More images will be obtained starting on November 16 when the comets should be both brighter and closer to Mercury. (Source: MESSENGER featured image article.)

Encke will reach its perihelion on Nov. 21; ISON on Nov. 28.

Read more: Will Comet ISON Survive Perihelion?

“We are thrilled to see that we’ve detected ISON,” said Ron Vervack, of the Johns Hopkins University Applied Physics Laboratory, who is leading MESSENGER’s role in the ISON observation campaign. “The comet hasn’t brightened as quickly as originally predicted, so we wondered how well we would do. Seeing it this early bodes well for our later observations.”

Comet 2P/Encke on October 30, 2013. The coma is partially obscuring the small barred spiral galaxy NGC 4371. Credit and copyright: Damian Peach.
Comet 2P/Encke photographed on October 30 by  Damian Peach.

Unlike ISON, Encke has been known for quite a while. It was discovered in 1786 and recognized as a periodic comet in 1819. Its orbital period is 3.3 years — the shortest period of any known comet — and November 21 will mark its 62nd recorded perihelion. (Source)

Read more: How to See This Season’s “Other” Comet: 2P/Encke

“Encke has been on our radar for a long time because we’ve realized that it would be crossing MESSENGER’s path in mid-November of this year,” Vervack explained. “And not only crossing it, but coming very close to Mercury.”

These early images of both comets are little more than a few pixels across, Vervack said, but he expects improved images next week when the comets make their closest approaches to MESSENGER and Mercury.

“By next week, we expect Encke to brighten by approximately a factor of 200 as seen from Mercury, and ISON by a factor of 15 or more,” Vervack said. “So we have high hopes for better images and data.”

– Ron Vervack, JHUAPL

Read more about the MESSENGER cometary observation campaign in the full news release here.

Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington/Southwest Research Institute

Posted on by David Dickinson

Here Comes the Weekend Leonid Meteor Shower!

November 2013 offers a chance to catch a dependable meteor shower, albeit on an off year. The Leonid meteors are set to reach their annual peak this coming weekend on Sunday, November 17th. We say it’s an off-year, but not that it should discourage you from attempting to catch the Leonids this weekend in the early dawn.

Projections for 2013 suggest a twin-peaked maximum, with the first peak arriving on November 17th at 10:00 UT/5:00 AM EST favoring North America, and the second one reaching Earth on the same date six hours later at 16:00 UT/11:00, favoring the central Pacific.

Unfortunately, the Full Moon also occurs the on very date that the Leonids peak at 10:16 AM EST/ 15:16UT, right between the two peaks! This will definitely cut down on the number of meteors you’ll see in the early AM hours.

That’s strike one against the 2013 Leonids. The next is the curious sporadic nature of this shower. Normally a minor shower with a zenithal hourly rate (ZHR) in the range of 10-20 per hour, the Leonids are prone to great storms topping a ZHR of 1,000+ every 33 years. We last experienced such an event in 1998 and 1999, and we’re now approaching the mid-point lull between storms in the 2014-2016 time frame.

An early Leonid meteor captured last week from the United Kingdom Meteor Observing Network's Church Crookham station. (Credit: UKMON/Peter-Campbell-Burns).
An early Leonid meteor captured last week from the United Kingdom Meteor Observing Network’s Church Crookham station. (Credit: UKMON/Peter-Campbell-Burns).

Still, this is one shower that’s always worth monitoring. The source of the Leonids is Comet 55p/Tempel-Tuttle, which is on a 33-year orbit and is due to reach perihelion again in 2031.

Note that the Leonids have also continued to show enhanced activity in past years even when the Moon was a factor:

2012- ZHR=47.

2011- ZHR=22, Moon=8% waning gibbous.

2010- ZHR=40, 86% waxing gibbous.

2009- ZHR=79.

2008-70 ZHR=72% waning gibbous

We even managed to observe the Leonid meteors from Vail, Arizona in 2002 and 2005, on years when the Moon was nearly Full.

Now, for the good news. The Leonids have a characteristic r value of 2.5, meaning that they produce a higher than normal ratio of fireballs. About 50-70% of Leonid meteors are estimated to leave persistent trains, a good reason to keep a pair of binoculars handy. And hey, at least the 2013 Leonids peak on the weekend, and there’s always comet’s ISON, X1 LINEAR, 2P/Encke and R1 Lovejoy to track down to boot!

A 2002 Leonid captured over Redstone Arsenal, Alabama. (Credit: NASA/MSFC/MEO/Bill Cooke).
A 2002 Leonid captured over Redstone Arsenal, Alabama. (Credit: NASA/MSFC/MEO/Bill Cooke).

Here’s a few tips and tricks that you can use to “beat the Moon” on your Leonid quest. One is to start observing now, on the moonless mornings leading up to the 17th. You’ll always see more Leonid meteors past local midnight as the radiant rises to the northeast. This is because you’re standing on the portion of the Earth turning forward into the meteor stream. Remember, the front windshield of your car (the Earth) always collects the most bugs (meteors). Observers who witnessed the 1966 Leonid storm reported a ZHR in excess of thousands per hour, producing a Star Trek-like effect of the Earth plowing through a “snowstorm” of meteors!

The radiant of the Leonids sits in the center of the backwards question mark asterism of the “Sickle” in the astronomical constellation Leo (hence name of the shower).

You can also improve your prospects for seeing meteors by blocking the Moon behind a building or hill. Though the Leonids will appear to radiate from Leo, they can appear anywhere in the sky. Several other minor showers, such as the Taurids and the Monocerotids, are also active in November.

Meteor shower photography is simple and can be done with nothing more than a DSLR camera on a tripod. This year, you’ll probably want to keep manual exposures short due to the Full Moon and in the 20 seconds or faster range. Simply set the camera to a low f-stop/high ISO setting and a wide field of view and shoot continuously. Catching a meteor involves luck and patience, and be sure to examine the frames after a session; every meteor I’ve caught on camera went unnoticed during observation! Don’t be afraid to experiment with different combinations to get the sky conditions just right. Also, be sure to carry and extra set of charged camera batteries, as long exposures combined with chilly November mornings can drain DSLR batteries in a hurry!

A Woodcut print depicting the 1933 Leonids as seem from Niagara Falls. (Wikimedia Commons image in the Public Domian).
A Woodcut print depicting the 1933 Leonids as seem from Niagara Falls. (Wikimedia Commons image in the Public Domain).

The Leonids certainly have a storied history, dating back to before meteors where understood to be dust grains left by comets. The 1833 Leonids were and awesome and terrifying spectacle to those who witnessed them up and down the eastern seaboard of the U.S. In fact, the single 1833 outburst has been cited as contributing to the multiple religious fundamentalist movements that cropped up in the U.S. in the 1830s.

We witnessed the 1998 Leonids from the deserts of Kuwait while stationed at Al Jabber Air Base. It was easily one of the best meteor displays we ever saw, with a ZHR reaching in access of 500 per hour before dawn. It was intense enough that fireballs behind us would often light up the foreground like camera flashes!

Reporting rates and activity for meteor showers is always fun and easy to do — its real science that you can do using nothing more than a stopwatch and your eyes. The International Meteor Association is always looking for current meteor counts from observers. Data goes towards refining our understanding and modeling of meteor streams and future predictions. The IMO should also have a live ZHR graph for the 2013 Leonids running soon.

Have fun, stay warm, send those Leonid captures in to Universe Today, and don’t forget to tweet those meteors to #Meteorwatch!

Posted on by Fraser Cain

Astronomy Cast 322: SOHO

As we’ve mentioned before, the Sun is a terrifying ball of plasma. It’s a good thing we’re keeping an eye on it. And that eye is the Solar and Heliospheric Observatory, or SOHO. Operating for more than 18 years now, SOHO has been making detailed observations of the Sun’s activity though an almost entire solar cycle. With so many years of operation, SOHO has some amazing stories to tell.

Continue reading “Astronomy Cast 322: SOHO”

Posted on by Nancy Atkinson

A Guided Aerial Tour of Curiosity’s Journey So Far on Mars

This scene shows the "Murray Ridge" portion of the western rim of Endeavour Crater on Mars. The ridge is the NASA's Mars Exploration Rover Opportunity's work area for the rover's sixth Martian winter. Image Credit: NASA/JPL-Caltech/Cornell/ASU

Just where has the Curiosity rover traveled so far and where is it going? This new video, narrated by John Grotzinger, the principal investigator for the Mars Science Laboratory mission, provides an aerial tour of the rover’s past, present and future traverses on the Red Planet.

Curosity landed in a flat, “hummocky” area in Gale Crater and is heading towards the Aeolis Mons, also known as Mount Sharp, a mountain 5 kilometers (3 miles) high. Right now the rover is among a cluster of small, steep-sided knobs, or buttes that are quite large — up to about the size of a football field and the height of a goal post. They sit in a gap in a band of dark sand dunes that lie at the foot of the mountain. Deep sand could present a hazard for driving, so this break in the dunes is the access path to the mountain.
These buttes have been named the Murray Buttes in honor of influential planetary scientist Bruce Murray (1931-2013).

“Bruce Murray contributed both scientific insight and leadership that laid the groundwork for interplanetary missions such as robotic missions to Mars, including the Mars rovers, part of America’s inspirational accomplishments,” said NASA Mars Exploration Program Manager Fuk Li from JPL. “It is fitting that the rover teams have chosen his name for significant landmarks on their expeditions.”

Meanwhile at Endeavour Crater, where the Opportunity is still exploring, nearly a decade on, and is now preparing for winter. A feature there has also been named for Bruce Murray, Murray Ridge, part of an uplifted crater rim.

“Murray Ridge is the highest hill we’ve ever tried to climb with Opportunity,” said the mission’s principal investigator, Steve Squyres of Cornell University, Ithaca, N.Y. The ridge has outcrops with clay minerals detected from orbit. It also provides a favorable slope for Martian winter sunshine to hit the rover’s solar panels, an advantage for keeping Opportunity mobile through the winter.

“Bruce Murray is best known for having been the director of JPL, and JPL is where our rovers were built,” Squyres said. “He led JPL during a time when the planetary exploration budget was under pressure and the future for planetary missions was not clear. His leadership brought us through that period with a strong exploration program. He was also a towering figure in Mars research. His papers are still cited abundantly today.”

Back to the video, interestingly, the “fly-through” data comes from a variety of missions representing some of the history of Mars exploration. Doug Ellison, who works with JPL’s Eyes on the Solar System – which uses spacecraft data to create realistic simulated views of spacecraft, planets and other features within our solar system – said on Twitter that the video uses data from Viking to narrow down the color, Mars Express High Resolution Stereo Camera (MEX-HRSC_ and the Mars Reconnassaince Oribiter’s HiRISE camera for topography, and the MRO Context camera (MRO-CTX) and HiRISE for imagery.

Source: JPL

Posted on by Tammy Plotner

Delving Into The Mystery Of Black Hole Jets

Black hole with disc and jets visualization courtesy of ESA

The concept of a black hole jet isn’t a new one, but we still have a lot to learn about the mixture of particles found in the vicinity of them. Through the use of ESA’s XMM-Newton Observatory, astronomers have been taking a look at a black hole in our galaxy and found some surprising results.

As we know, stellar mass black holes take on materials from nearby stars. Matter from these companion stars is pulled away from the parent body toward the black hole and radiates a temperture so intense that it emits X-rays. However, a black hole doesn’t always ingest everything that comes its way. Sometimes they reject small portions of this incoming mass, pushing it away in the form of a set of powerful jets. These jets also feed the surroundings, releasing both mass and energy… robbing the black hole of fuel.

Through the study of jet composition, researchers are able to better determine what gets taken into a black hole and what doesn’t. Through observations taken at the radio wavelength of the electromagnetic spectrum, we have seen electrons crusing along at nearly the speed of light. However, it hasn’t been clearly determined whether the negative charge of the electrons is complemented by their anti-particles, positrons, or rather by heavier positively-charged particles in the jets, like protons or atomic nuclei.” With XMM-Newton’s power behind them, astronomers have had the opportunity to examine a black hole binary system called 4U1630–47 – a candidate known to have unexpected outbursts of X-rays for segments of time which last between months and years.

“In our observations, we found signs of highly ionised nuclei of two heavy elements, iron and nickel,” says María Díaz Trigo of the European Southern Observatory in Munich, Germany, lead author of the paper published in the journal Nature. “The discovery came as a surprise – and a good one, since it shows beyond doubt that the composition of black hole jets is much richer than just electrons.”

During September 2012, a team of astronomers headed up by Dr. Díaz Trigo and collaborators, observed 4U1630–47 with XMM-Newton. They also backed up their observations with near-simultaneous radio observations taken from the Australia Telescope Compact Array. Even though the studies were done close to each other – within just a couple of weeks – the results couldn’t have been more different.

According to Trigo’s team, the initial set of observations picked up X-ray signatures from the accretion disc, but there was no activity in the radio band. This is an indicator that the jets weren’t active at that time. However, in the second set of observations, there was activity in both X-ray and radio… the jets had turned back on! While examining the X-ray data from the second set, they also found iron nuclei in motion. These particles were moving both toward and away from XMM-Newton – proof the ions were part of twin jets aimed in opposite directions. However, that’s not all. There was also evidence of nickel nuclei pointing toward the observatory.

“From these ‘fingerprints’ of iron and nickel, we could show that the speed of the jet is very high, about two-thirds of the speed of light,” says co-author James Miller-Jones from the Curtin University node of the International Centre for Radio Astronomy Research in Perth, Australia.

“Moreover, the presence of heavy atomic nuclei in black hole jets means that mass and energy are being carried away from the black hole in much larger amounts than we previously thought, which may have an impact on the mechanism and rate by which the black hole accretes matter,” adds co-author Simone Migliari from the University of Barcelona, Spain.

Astounding new findings? Well… yeah. For a typical stellar-mass black hole, this is the first time that heavy nuclei has been detected within the jets. As of the present, there is only “one other X-ray binary that shows similar signatures from atomic nuclei in its jets – a source known as SS 433. This black hole system, however, is characterised by an unusually high accretion rate, which makes it difficult to compare its properties to those of more ordinary black holes.” Through these new observations of 4U1630–47, astronomers will be able to fill in information gaps about what causes jets to occur in black hole accretion disks and what drives them.

“While we now know a great deal about black holes and what happens around them, the formation of jets is still a big puzzle, so this observation is a major step forward in understanding this fascinating phenomenon,” says Norbert Schartel, ESA’s XMM-Newton Project Scientist.

Original Story Source: ESA Press Release.

Posted on by Elizabeth Howell

Moon’s Blotchy Near Side Has Bigger Craters Than Expected

The thickness of the moon's crust as calculated by NASA's GRAIL mission. The near side is on the left-hand side of the picture, and the far side on the right. Credit: NASA/JPL-Caltech/S. Miljkovic

The familiar blotches that make up “the man in the moon”, from the vantage point of Earth, happened because the moon’s crust is thinner on the near side than the far side to our planet, new research reveals.

The twin GRAIL spacecraft provided the most accurate sizes yet of lunar impact craters on the moon, providing more insight into what happened when Earth’s closest large neighbor was hammered with meteorites over billions of years.

“Since time immemorial, humanity has looked up and wondered what made the man in the moon,” stated Maria Zuber, GRAIL principal investigator from the Massachusetts Institute of Technology in Cambridge.

Artist's conception of the twin GRAIL spacecraft, called Ebb and Flow. Credit: NASA/JPL-Caltech
Artist’s conception of the twin GRAIL spacecraft, called Ebb and Flow. Credit: NASA/JPL-Caltech

“We know the dark splotches are large, lava-filled, impact basins that were created by asteroid impacts about four billion years ago. GRAIL data indicate that both the near side and the far side of the moon were bombarded by similarly large impactors, but they reacted to them much differently.”

The moon’s near side is easily visible in a telescope, but it’s hard to measure the size of the impacts because lava is obscuring their dimensions. The GRAIL spacecraft, however, peered at the internal structure of the moon and also produced information showing how thick the crust is. This showed that there are more, bigger craters on the closer side of the moon to us than the further side.

Closeup of the Moon showing Endymion, Atlas and the distant Mare Humboldtianum. Credit and copyright: Danny Robb.
Closeup of the Moon showing Endymion, Atlas and the distant Mare Humboldtianum. Credit and copyright: Danny Robb.

“Impact simulations indicate that impacts into a hot, thin crust representative of the early moon’s near-side hemisphere would have produced basins with as much as twice the diameter as similar impacts into cooler crust, which is indicative of early conditions on the moon’s far-side hemisphere,” stated lead author Katarina Miljkovic of the Paris Institute of Earth Physics (Institut de Physique du Globe de Paris).

As is common with research projects, learning more about the moon is revealing a new mystery that needs to be examined. It’s commonly cited that the moon was walloped during something called the late heavy bombardment, a period four billion years ago when it was believed that more meteorites impacted the moon.

“The late heavy bombardment is based largely on the ages of large near-side impact basins that are either within, or adjacent to the dark, lava-filled basins, or lunar maria, named Oceanus Procellarum and Mare Imbrium,” NASA stated.

“However, the special composition of the material on and below the surface of the near side implies that the temperatures beneath this region were not representative of the moon as a whole at the time of the late heavy bombardment. The difference in the temperature profiles would have caused scientists to overestimate the magnitude of the basin-forming impact bombardment.”

A research paper on the topic recently appeared in Science. GRAIL successfully concluded its mission last year after nine months of operations, flying into the side of a mountain as planned.

Source: NASA

 

Posted on by Elizabeth Howell

‘Super-Typhoon’ Haiyan Looms Large In Space Station Video

As Super-Typhoon Haiyan moved over the central Philippines on Nov. 8 at 05:10 UTC/12:10 a.m. EDT, the MODIS instrument aboard NASA's Aqua satellite captured this visible image. Credit: NASA Goddard MODIS Rapid Response Team

The scary extent of Typhoon Haiyan, which devastated the Philippines, is apparent in this shot from the International Space Station. From the orbital perch about 250 miles (400 kilometers) above Earth, the estimated Category 5 typhoon fills most of the view. On the ground, wind speeds reached as high as 235 miles an hour (378 kph), reports say.

NASA and others are saying that the storm is likely the biggest one on record to make landfall. As of this morning, the official death count from a Philippines disaster agency is 2,275, but it will be a while before numbers become more clear. Initial estimates of the death toll ranged as high as 10,000, but in media reports from this morning, Philippines president Benigno Aquino III estimated deaths would be between 2,000 and 2,500.

Meanwhile, the United Nations is asking for $301 million to assist the estimated 11 million people who were affected by the storm, including more than 670,000 who have fled from their homes to escape the powerful surge. Assistance agencies are struggling to get people the help they need.

“There are still many places that are not accessible yet,” Elizabeth Byrs, a spokeswoman for the World Food Program said in Geneva, said in a New York Times report. The WFP plans to charter boats to send more supplies, she added.

More views from orbit are visible in this past Universe Today story by Ken Kremer.

Posted on by Elizabeth Howell

Gorgeous Telescope Timelapse Makes You Feel Like You’re Standing In Chile

Lasers like this one, at the VLT in Paranal, help counteract the blurring effect of the atmosphere. Powerful arrays of much larger lasers could hide our presence from aliens. (ESO/Y. Beletsky)
Lasers like this one, at the VLT in Paranal, help counteract the blurring effect of the atmosphere. Powerful arrays of much larger lasers could hide our presence from aliens. (ESO/Y. Beletsky)

As the chill of winter settles into the northern hemisphere, fantasies of down-south travel pervade a lot of people’s dreams. Well, here’s a virtual journey to warm climes for astronomy buffs: a beautiful, music-filled timelapse of several European Southern Observatory telescopes gazing at the heavens in Chile.

Uploaded in 2011 (but promoted this morning on ESO’s Twitter feed), the timelapse was taken by astrophotographers Stéphane Guisard (also an ESO engineer) and José Francisco Salgado (who is also an astronomer at Chicago’s Adler Planetarium.) Telescopes include:

We’ve covered their work before on Universe Today. In 2009, Guisard  participated in GigaGalaxy Zoom, which produced a 360-degree panorama of the entire sky. He also released a 3-D view of several telescopes that same year. Also, Guisard and Salgado collaborated on another 2011 timelapse of the Very Large Telescope and nearby sites.

Posted on by Shannon Hall

Sgr A* Could Be a Relic of a Powerful AGN

The Magellanic Stream

The early universe was sizzling with active galactic nuclei (AGN) — intensely luminous cores powered by supermassive black holes — most of which could outshine their entire host galaxies and be seen across the observable universe.

While our central supermassive black hole Sgr A* lies rather dormant at the moment, new evidence suggests that it too was once a powerful AGN.

The first hint occurred two years ago when astronomers discovered Fermi bubbles — massive lobes of high-energy radiation that expand 30,000 light years north and south of the galactic center.

Of course the source of these bubbles is “a hot topic today,” Dr. Joss Hawthorn from the Sydney Institute for Astronomy and lead author on the paper, told Universe Today. “Some think the bubbles were inflated by powerful star formation in the disk, others, like me, (think) that they were inflated by a powerful jet from Sgr A*.”

It’s becoming more and more plausible that the Fermi bubbles were created by a recently powerful jet protruding from the center of our galaxy — demonstrating they are remnants of a much more violent past.

But astronomers from the Sydney Institute for Astronomy in Australia, the University of Colorado, Boulder, and the University of Cambridge have found further evidence linking Sgr A* to a recent AGN.

The Magellanic Stream — a long ribbon of gas stretching nearly half way around the Milky Way and trailing our galaxy’s two small companion galaxies, the Magellanic Clouds — is likely to be another ancient remnant of our recent activity.

The problem is that the Magellanic Stream is extremely red. It is emitting a large number of photons that clock in at a particular wavelength: 656 nanometers. This wavelength not only falls in the visible spectrum, but corresponds to a red color.

The Magellanic Stream is emitting so much red light because it contains extremely energetic hydrogen atoms. When atoms have high-energy electrons, these electrons lose energy by emitting photons.

But astronomers cannot explain why the Magellanic Stream has so many energetic hydrogen atoms, why it is such a bright red color — unless they invoke recent AGN activity from the Milky Way galaxy.

If we assume Sgr A* was once very bright, it would have lit up the Magellanic Stream, causing hydrogen atoms to absorb energy from the incoming light — an effect still visible millions of years later.

A huge outburst of energy in our recent past is likely the cause of a Seyfert flare  — an eruption of light and radiation when small clouds of gas fall onto the hot disk of matter that swirls around the black hole.

“If you hurl a bucket of water into a sink, you would be shocked if it all disappeared down the plug hole. Of course, the water spins around the plughole first. (The) same thing (occurs) with gas falling onto a black hole. the spinning disk heats up and generates powerful outbursts: Seyfert flares,” Dr. Hawthorn explained.

This provides further evidence that Sgr A* was once a very powerful AGN, causing Fermi bubbles and a brighter Magellanic Stream. It’s likely it was active as recent as one to three million years ago.

The paper has been published in the Astrophysical Journal and is available for download here.