This artist's illustration depicts a gamma-ray burst illuminating clouds of interstellar gas in its host galaxy. By analyzing a recent gamma-ray burst, astronomers were able to learn about the chemistry of a galaxy 12.7 billion light-years from Earth. They discovered it contains only one-tenth of the heavy elements (metals) found in our solar system. Credit: Gemini Observatory/AURA, artwork by Lynette Cook
Once upon a time, more than 12.7 billion years ago, a star was poised on the edge of extinction. It made its home in a galaxy too small, too faint and too far away to even be spotted by the Hubble Space Telescope. Not that it would matter, because this star was going to end its life before the Earth formed. As it blew itself apart, it expelled its materials in twin jets which ripped through space at close to the speed of light – yet the light of its death throes outshone its parent galaxy by a million times.
“This star lived at a very interesting time, the so-called dark ages just a billion years after the Big Bang,” says lead author Ryan Chornock of the Harvard-Smithsonian Center for Astrophysics (CfA).
“In a sense, we’re forensic scientists investigating the death of a star and the life of a galaxy in the earliest phases of cosmic time,” he adds.
When this unsung star expired, it created one of the scariest things in astronomy… a gamma-ray burst (GRB). However, it wasn’t just a normal, garden variety GRB – it was long one, lasting more than four minutes. After century upon century of travel, the light reached our little corner of the Universe and was detected by NASA’s Swift spacecraft on June 6th. Chornock and his team quickly organized follow-up observations by the MMT Telescope in Arizona and the Gemini North telescope in Hawaii.
“We were able to get right on target in a matter of hours,” Chornock says. “That speed was crucial in detecting and studying the afterglow.”
Time to kick back and have a smoke? In a sense. The “afterglow” of a GRB happens when the jets impact the surrounding gas in an almost tsunami-like effect. As it sweeps up the material, it begins to heat and glow. As this light traverses the parent galaxy, it impacts clouds of interstellar gas, illuminating their spectra. Through these chemical signatures, astronomers are able to ascertain what gases the distant galaxy may have contained. As we know, all chemical elements heavier than hydrogen, helium, and lithium are the product of stars. Researchers refer to this as “metal content” and it takes a certain amount of time to accumulate. In the scheme of creation, the elements necessary for life – carbon and oxygen – didn’t exist. What Chornock and his team discovered was the GRB galaxy was host to only about a tenth of the “metals” in our solar system. What does that mean? In the eyes of the astronomers, rocky planets might have been able to form in that far away galaxy, but chances are good that life could not.
“At the time this star died, the universe was still getting ready for life. It didn’t have life yet, but was building the required elements,” says Chornock.
At a redshift of 5.9, or a distance of 12.7 billion light-years, GRB 130606A is one of the most distant gamma-ray bursts ever found.
“In the future we will be able to find and exploit even more distant GRBs with the planned Giant Magellan Telescope,” says Edo Berger of the CfA, a co-author on the publication.
A wintertime rising gibbous Moon. (Image credit: Art Explosion).
A team from the University of Birmingham recently announced an astronomical discovery in Scotland marking the beginnings of recorded time.
Announced last month in the Journal of Internet Archaeology, the Mesolithic monument consists of a series of pits near Aberdeenshire, Scotland. Estimated to date from 8,000 B.C., this 10,000 year old structure would pre-date calendars discovered in the Fertile Crescent region of the Middle East by over 5,000 years.
Originally unearthed by the National Trust for Scotland in 2004, the site is designated as Warren Field near the town of Crathes. It consists of 12 pits in an arc 54 metres long that seem to correspond with 12 lunar months, plus an added correction to bring the calendar back into sync with the solar year on the date of the winter solstice.
A diagram of the Warren Field site, showing the 12 pits (below) and the alignment with the phases of the Moon plus the rising of the winter solstice Sun. Note: the scale should read “0-10 metres.” (Credit: The University of Birmingham).
“The evidence suggests that hunter-gatherer societies in Scotland had both the need and sophistication to track time across the years, to correct for seasonal drift of the lunar year” said team leader and professor of Landscape Archaeology at the University of Birmingham Vince Gaffney.
We talked last week about the necessity of timekeeping as cultures moved from a hunter-gatherer to agrarian lifestyle. Such abilities as marking the passage of the lunar cycles or the heliacal rising of the star Sirius gave cultures the edge needed to dominate in their day.
For context, the pyramids on the plains of Giza date from around 2500 B.C., The Ice Man on display in Bolzano Italy dates from 3,300 B.C., and the end of the last Ice Age was around 20,000 to 10,000 years ago, about the time that the calendar was constructed.
“We have been taking photographs of the Scottish landscape for nearly 40 years, recording thousands of archaeological sites that would never have been detected from the ground,” said manager of Aerial projects of the Royal Commission of Aerial Survey Projects Dave Cowley. “It’s remarkable to think that our aerial survey may have helped to find the place where time was invented.”
The site at Warren Field was initially discovered during an aerial survey of the region.
Vince Gaffney, professor of Landscape and Archaeology at University of Birmingham in Warren Field, Crathes, Aberdeenshire where the discovery was made. (Credit: The University of Birmingham).
The use of such a complex calendar by an ancient society also came as a revelation to researchers. Emeritus Professor of Archaeoastronomy at the University of Leicester Clive Ruggles notes that the site “represents a combination of several different cycles which can be used to track time symbolically and practically.”
The lunar synodic period, or the span of time that it takes for the Moon to return to the same phase (i.e., New-to-New, Full-to-Full, etc) is approximately 29.5 days. Many cultures used a strictly lunar-based calendar composed of 12 synodic months. The Islamic calendar is an example of this sort of timekeeping still in use today.
However, a 12 month lunar calendar also falls out of sync with our modern Gregorian calendar by 11 days (12 on leap years) per year.
The familiar Gregorian calendar is at the other extreme, a calendar that is strictly solar-based. The Gregorian calendar was introduced in 1582 and is still in use today. This reconciled the 11 minute per year difference between the Julian calendar and the mean solar year, which by the time of Pope Gregory’s reform had already caused the calendar to “drift” by 10 days since the 1st Council of Nicaea 325 AD.
Artist’s conception of the Warren Field site during the winter solstice. (Credit: The University of Birmingham). Credit: The University of Birmingham
Surprisingly, the calendar discovered at Warren Field may be of a third and more complex variety, a luni-solar calendar. This employs the use of intercalary periods, also known as embolismic months to bring the lunar and solar calendar back into sync.
The modern Jewish calendar is an example of a luni-solar hybrid, which adds an extra month (known as the 2nd Adar or Adar Sheni) every 2-3 years. This will next occur in March 2014.
The Greek astronomer Meton of Athens noted in 5th century B.C. that 235 synodic periods very nearly add up to 19 years, to within a few hours. Today, this period bears his name, and is known as a metonic cycle. The Babylonian astronomers were aware of this as well, and with the discovery at Warren Field, it seems that ancient astronomers in Scotland may have been moving in this direction of advanced understanding as well.
It’s interesting to note that the site at Warren Field also predates Stonehenge, the most famous ancient structure in the United Kingdom by about 6,000 years. 10,000 years ago would have also seen the Earth’s rotational north celestial pole pointed near the +3.9th magnitude star Rukbalgethi Shemali (Tau Herculis) in the modern day constellation of Hercules. This is due to the 26,000 year wobble of our planet’s axis known as the precession of the equinoxes.
The precession of the north celestial pole over millennia. (Credit: Wikimedia Commons graphic under a Creative Commons Attribution 2.5 Generic license. Author: Tau’olunga).
The Full Moon nearest the winter solstice also marks the “Long Nights Moon,” when the Full Moon occupies a space where the Sun resides during the summer months and rides high above the horizon for northern observers all night. The ancients knew of the five degree tilt that our Moon has in relation to the ecliptic and how it can ride exceptionally high in the sky every 18.6 years. We’re currently headed towards a ‘shallow year’ in 2015, where the Moon rides low in relation to the ecliptic. From there, the Moon’s path in the sky will get progressively higher each year, peaking again in 2024.
Who built the Warren Field ruins along the scenic Dee Valley of Scotland? What other surprises are in store as researchers excavate the site? One thing is for certain: the ancients were astute students of the sky. It’s fascinating to realize how much of our own history has yet to be told!
Remnants of a gamma-ray burst (called GRB 130603B) are visible in these Hubble Space Telescope pictures. Credit: NASA, ESA, and Z. Levay (STScI/AURA)
As astute readers of Universe Today, you likely know what a supernova is: a stellar explosion that signals the end game for certain kinds of stars. Above, however, is a picture of a kilonova, which happens when two really dense objects come together.
This fireball arose after a short-term (1/10 of a second) gamma-ray burst came into view of the Swift space telescope on June 3. Nine days later, the Hubble Space Telescope looked at the same area to see if there were any remnants, and spotted a faint red object that was confirmed in independent observations.
It’s the first time astronomers have been able to see a connection between gamma-ray bursts and kilonovas, although it was predicted before. They’re saying this is the first evidence that short-duration gamma ray bursts arise as two super-dense stellar objects come together.
So what’s the connection? Astronomers suspect it’s this sequence of events:
Two binary neutron stars (really dense stars) start to move closer to each other;
The system sends out gravitational radiation that make ripples in space-time;
These waves make the stars move even closer together;
In the milliseconds before the explosion, the two stars “merge into a death spiral that kicks out highly radioactive material,” as NASA states, with material that gets warmer, gets bigger and sends out light;
The kilonova occurs with the detonation of a white dwarf. While it’s bright, 1,000 times brighter than a nova, it’s only 1/10th to 1/100th the brightness of an average supernova.
An artistic image of the explosion of a star leading to a gamma-ray burst. (Source: FUW/Tentaris/Maciej Fro?ow)
“This observation finally solves the mystery of the origin of short gamma ray bursts,” stated Nial Tanvir of the University of Leicester in the United Kingdom, who is also the lead author.
“Many astronomers, including our group, have already provided a great deal of evidence that long-duration gamma ray bursts (those lasting more than two seconds) are produced by the collapse of extremely massive stars. But we only had weak circumstantial evidence that short bursts were produced by the merger of compact objects. This result now appears to provide definitive proof supporting that scenario.”
Prepare yourself for some goosebumps. The Mercury spacecraft MESSENGER took this series of images of Earth eight years ago today as it swung by the planet (again) en route to its final destination.
Few humans have seen the Earth as an entire orb. Only a handful of missions, all in the Apollo era, have ventured beyond low Earth orbit. The people who traveled furthest were Jim Lovell, Fred Haise and Jack Swigert during Apollo 13, when their spacecraft (which had been crippled by an explosion) looped around the moon on the way home.
MESSENGER is happily traveling around Mercury these days and recently recorded a cool series of images showing the planet as a colorful, spinning sphere. The spacecraft — the first to do an extended stay around that planet — has shown scientists a lot of things, including the discovery of water ice and organics.
The radiant for the Persieds, looking to the NE from latitide ~30N at around 2AM local. Created by the Author in Starry Night).
Get set for the meteoritic grand finale of summer.
Northern hemisphere summer that is. As we head into August, our gaze turns towards that “Old Faithful” of meteor showers, the Perseids. Though summer is mostly behind us now, “meteor shower season” is about to get underway in earnest.
Pronounced “Pur-SEE-ids,” this shower falls around the second week of August, just before school goes back in for most folks. This time of year also finds many the residents of the northern hemisphere out camping and away from light-polluted suburban skies.
This year also offers a special treat, as the Moon will be safely out of the sky during key observation times. The Moon reaches New phase on August 6th at 5:51 PM EDT/ 9:51 Universal Time (UT) and will be a 32% illuminated waxing crescent around the anticipated peak for the Perseid meteors on August 12th. And speaking of which, the Perseids are infamous for presenting a double-fisted twin peak in activity. This year, the first climax for the shower is predicted for around 13:00 UT on August 12th, favoring Hawaii and the North American west coast, and the second peak is set to arrive 13 hours later at 02:00 UT, favoring Europe & Africa.
Nodal crossing for the Perseid stream and Earth’s orbit sits right around 18:00 to 21:00 UT on August 12th for 2013. The shower derives its name from the constellation Perseus, and has a radiant located near Gamma Persei at right ascension 3 hours 4 minutes and a declination of +58 degrees. Atmospheric velocities for the Perseids are on the high end as meteor showers go, at 59km/sec.
Of course, like with any meteor shower, it’s worth starting to watch a few days prior to the peak date. Although meteor streams like the Perseids have been modeled and mapped over the years, there are still lots of surprises out there. Plus, starting an early vigil is insurance that you at least catch some action in the event that you’re clouded out on game day! Like we mentioned in last week’s post on the Delta Aquarids, the Perseids are already active, spanning a season from July 17th to August 24th.
The Zenithal Hourly Rate for the Perseids is generally between 60-100 meteors. The ZHR is the number of meteors you could expect to see during optimal conditions under dark skies with the radiant directly overhead. Rates were enhanced back in the 1990’s, and 2004 saw a ZHR of 200.
The orbit of comet Swift-Tuttle and its intersection near the Earth’s orbit. (Created by the author using NASA/JPL ephemerides generator).
The source of the Perseids is comet 109P/Swift-Tuttle. Discovered on July 16th-19th, 1862 by astronomers Lewis Swift & Horace Tuttle, Swift-Tuttle is on a 133.3 year orbit and last passed through the inner solar system in late 1992. This comet will once again grace our skies in early 2126 AD.
The Perseids are also sometimes referred to as the “tears of St Lawrence,” after the Catholic saint who was martyred on August 10th, 258 AD. The Perseids have been noted by Chinese astronomers as far back as 36 AD, when it was recorded that “more than 100 meteors flew thither in the morning.” The annual nature of the shower was first described by Belgian astronomer Adolphe Quételet in 1835.
Enhanced rates for the Perseids marked the return of comet Swift-Tuttle in the 1990s. Recent years have seen rates as reported by the International Meteor Organization at a ZHR=175(2009), 91(2010), 58(2011), & a resurgence of a ZHR=122 last year.
Just what will 2013 bring? There’s one truism in meteor observing—you definitely won’t see anything if you do not get out and observe. Meteor shower observing requires no equipment, just clear skies and patience. Watch in the early hours before dawn, when the rates are highest. Meteors can occasionally be seen before midnight, but are marked by lower rates and slow, stately trains across the sky. Some suggest that best viewing is at a 45 degree angle away from the radiant, but we maintain that meteors can appear anywhere in the sky. Pair up with a friend or two and watch in opposite directions to increase your meteor-spotting chances.
We also like to keep a set of binoculars handy to examine those smoke trains left by bright fireballs that may persist seconds after streaking across the sky.
And speaking of which, there has also been some spirited discussion over the past week as to whether or not the Perseids produce more fireballs than any other shower. I certainly remember seeing several memorable fireballs from this shower over the years, although the Geminids, Leonids and Taurids can be just spectacular on active years. The stated r value of the Perseids is one of the lowest at 2.2, suggesting a statistically high percentage of fireballs.
And in the realm of the strange and the curious, here are just a few phenomena to watch/listen for on your Perseid vigil;
– Can you “hear” meteors? Science says that sounds shouldn’t carry through the tenuous atmosphere above 50 kilometres up, and yet reports of audible meteors as a hiss or crackle persist. Is this an eye-brain illusion? Researchers in 1988 actually studied this phenomenon, which is also sometimes reported during displays of aurora. If there’s anything to it, the culprit may be the localized generation of localized electrophonic noises generated by Extra/Very Low Frequency electromagnetic radiation.
– Can meteor streaks appear colored? Green is often the top reported hue.
– Can meteors appear to “corkscrew” during their trajectory, or is this an illusion?
A Perseid very near the shower radiant during the 2012 shower. (Photo by author).
Wide-field photography is definitely a viable option during meteor showers. Just remember to bring extra charged batteries, as long exposure times will drain modern DSLRs in a hurry!
And did you know: you can even “listen” to meteor pings on an FM radio or portable TV? This is a great “rain check” option!
And there’s still real science to be done in the world of meteor shower studies. The International Meteor Organization welcomes counts from volunteers… and be sure to Tweet those Perseid sightings to #Meteorwatch.
Also be sure to check out the UK Meteor Observation Network, which has just launched their live site with streaming images of meteors as they are recorded.
Good luck, clear skies, and let the late 2013 meteor shower season begin!
-And be sure to post those Perseid pics to the Flickr forum on Universe Today… we’ll be doing photo essay roundups from observers around the world!
Looking east from latitude 30 north on August 3rd, 30 minutes before sunrise. (Created by the author in Stellarium).
Can you feel the heat?
It’s not just your imagination. The northern hemisphere is currently in the midst of the Dog Days of Summer. For many, early August means hot, humid days and stagnant, sultry nights.
The actual dates for the Dog Days of Summer vary depending on the source, but are usually quoted as running from mid-July to mid-August. The Old Farmer’s Almanac lists the Dog Days as running from July 3rd through August 11th.
But there is an ancient astronomical observation that ties in with the Dog Days of Summer, one that you can replicate on these early August mornings.
The sky was important to the ancients. It told them when seasons were approaching, when to plant crops, and when to harvest. Ancient cultures were keen observers of the cycles in the sky. Cultures that were “astronomically literate” had a distinct edge over those who seldom bothered to note the goings on overhead.
The flooded Temple of Isis on the island of Philae circa 1905. (Credit: Wikimedia Commons under an Attribution-Share Alike 2.5 license. Author H.W. Dunning).
Sirius was a key star for Egyptian astronomers. Identified with the goddess Isis, the Egyptian name for Sirius was Sopdet, the deification of Sothis. There is a line penned by the Greco-Roman scholar Plutarch which states:
“The soul of Isis is called ‘Dog’ by the Greeks.”
Political commentary? A mis-translation by Greek scholars? Whatever the case, the mythological transition from “Isis to Sothis to Dog Star” seems to have been lost in time.
These astronomer-priests noted that Sirius rose with the Sun just prior to the annual flooding of the Nile. The appearance of a celestial object at sunrise is known as a heliacal rising. If you can recover Sirius from behind the glare of the Sun, you know that the “Tears of Isis” are on their way, in the form of life-giving flood waters.
Sopdet as the personification of Sirius (note the star on the forehead) Wikimedia Commons image under an Attribution Share Alike 3.0 license. Author Jeff Dahl).
In fact, the ancient Egyptians based their calendar on the appearance of Sirius and what is known as the Sothic cycle, which is a span of 1,461 sidereal years (365.25 x 4) in which the heliacal rising once again “syncs up” with the solar calendar.
It’s interesting to note that in 3000 BC, the heliacal rising of Sirius and the flooding of the Nile occurred around June 25th, near the summer solstice. This also marked the Egyptian New Year. Today it occurs within a few weeks of August 15th, owing to precession. (More on that in a bit!)
By the time of the Greeks, we start to see Sirius firmly referred to as the Dog Star. In Homer’s Iliad, King Priam refers to an advancing Achilles as:
“Blazing as the star that cometh forth at Harvest-time, shining forth amid the host of stars in the darkness of the night, the star whose name men call Orion’s Dog”
The Romans further promoted the canine branding for Sirius. You also see references to the “Dog Star” popping up in Virgil’s Aenid.
Over the years, scholars have also attempted to link the dog-headed god Anubis to Sirius. This transition is debated by scholars, and in his Star Names: Their Lore and Meaning, Richard Hinckley Allen casts doubt on the assertion.
Sirius as the shining “nose” of the constellation Canis Major. (Created by the author using Starry Night).
Ancient cultures also saw the appearance of Sirius as signifying the onset of epidemics. Their fears were well founded, as summer flooding would also hatch a fresh wave of malaria and dengue fever-carrying mosquitoes.
Making a seasonal sighting of Sirius is fun and easy to do. The star is currently low to the southeast in the dawn, and rises successively higher each morning as August rolls on.
The following table can be used to aid your quest in Sirius-spotting.
Latitude north
Theoretical date when Sirius can 1st be spotted
32°
August 3rd
33°
August 4th
34°
August 5th
35°
August 6th
36°
August 7th
37°
August 8th
38°
August 9th
39°
August 10th
40°
August 11th
41°
August 12th
42°
August 13th
43°
August 14th
44°
August 15th
45°
August 16th
46°
August 17th
47°
August 18th
48°
August 19th
49°
August 20th
50°
August 21st
Thanks to “human astronomical computer extraordinaire” Ed Kotapish for the compilation!
Note that the table above is perpetual for years in the first half of the 21st century. Our friend, the Precession of the Equinoxes pivots the equinoctial points to the tune of about one degree every 72 years. The Earth’s axis completes one full “wobble” approximately every 26,000 years. Our rotational pole only happens to be currently pointing at Polaris in our lifetimes. Its closest approach is around 2100 AD, after which the north celestial pole and Polaris will begin to drift apart. Mark your calendars—Vega will be the pole star in 13,727 AD. And to the ancient Egyptians, Thuban in the constellation Draco was the Pole Star!
The Colossi of Memnon Near Luxor, just one of the amazing architectural projects carried out by the ancient Egyptians. (Photo by author).
Keep in mind, atmospheric extinction is your enemy in this quest, as it will knock normally brilliant magnitude -1.46 Sirius a whopping 40 times in brightness to around magnitude +2.4.
Note that we have a nice line-up of planets in the dawn sky (see intro chart), which are joined by a waning crescent Moon this weekend. Jupiter and Mars ride high about an hour before sunrise, and if you can pick out Mercury at magnitude -0.5 directly below them, you should have a shot at spotting Sirius far to the south.
And don’t be afraid to “cheat” a little bit and use binoculars in your quest… we’ve even managed on occasion to track Sirius into the broad daylight. Just be sure to physically block the Sun behind a building or hill before attempting this feat!
Of course, the heliacal rising of Sirius prior to the flooding of the Nile was a convenient coincidence that the Egyptians used to their advantage. The ancients had little idea as to what they were seeing. At 8.6 light-years distant, Sirius is the brightest star in Earth’s sky during the current epoch. It’s also the second closest star visible to the naked eye from Earth. Only Alpha Centauri, located deep in the southern hemisphere sky is closer. The light you’re seeing from Sirius today left in early 2005, back before most of us had Facebook accounts.
Sirius also has a companion star, Sirius B. This star is the closest example of a white dwarf. Orbiting its primary once every 50 years, Sirius B has also been the center of a strange controversy we’ve explored in past writings concerning Dogon people of Mali.
Sirius B is difficult to nab in a telescope, owing to dazzling nearby Sirius A. This feat will get easier as Sirius B approaches apastron with a max separation of 11.5 arc seconds in 2025.
Some paleoastronomers have also puzzled over ancient records referring to Sirius as “red” in color. While some have stated that this might overturn current astrophysical models, a far more likely explanation is its position low to the horizon for northern hemisphere observers. Many bright stars can take on a twinkling ruddy hue when seen low in the sky due to atmospheric distortion.
Let the Dog Days of Summer (& astronomy) begin! (Photo by author).
All great facts to ponder during these Dog Days of early August, perhaps as the sky brightens during the dawn and your vigil for the Perseid meteors draws to an end!
There’s a potential “cometary graveyard” of inactive comets in our solar system wandering between Mars and Jupiter, a new Colombian research paper says. This contradicts a long-standing view that comets originate on the fringes of the solar system, in the Oort Cloud.
Mysteriously, however, 12 active comets have been seen in and around the asteroid belt. The astronomers theorize there must be a number of inactive comets in this region that flare up when a stray gravitational force from Jupiter nudges the comets so that they receive more energy from the Sun.
The researchers examined comets originating from the main asteroid belt between Mars and Jupiter, a spot where it is believed there are only asteroids (small bodies made up mostly of rock). Comets, by contrast, are a mixture of rocks and ice. The ice melts when the comet gets close to the sun, and can form spectacular tails visible from Earth. (Here’s more detail on the difference between a comet and an asteroid.)
This illustration shows three views of cometary activity. Top: The accepted view of comets, showing them coming from the outer solar system. Middle: The new proposal, saying some could come from the asteroid belt between Mars and Jupiter. Bottom: How the asteroid belt comets could have appeared during the early solar system’s history. Credit: Ignacio Ferrin / University of Antioquia
“Imagine all these asteroids going around the Sun for aeons, with no hint of activity,” stated Ignacio Ferrín, who led the research and is a part of the University of Antioquia in Colombia.
“We have found that some of these are not dead rocks after all, but are dormant comets that may yet come back to life if the energy that they receive from the Sun increases by a few per cent.”
The team believes this zone was far more active millions of years ago, but as the population got older they got more quiet.
“Twelve of those rocks are true comets that were rejuvenated after their minimum distance from the Sun was reduced a little,” the researchers stated.
“The little extra energy they received from the Sun was then sufficient to revive them from the graveyard.”
Astronaut Charles Duke collecting samples during Apollo 16. Credit: NASA.
Ask someone if they know the names of the astronauts who have walked on the Moon, and most people would be able to list Neil Armstrong, and maybe even Buzz Aldrin. But can you name the rest of the Apollo astronauts who made it down to the lunar surface? How many people have walked on the Moon?
In total twelve people have walked on the Moon. Besides Neil Armstrong and Buzz Aldrin – who were the first two astronauts to leave their bootprints on the Moon — there were also Pete Conrad, Alan Bean, Alan Shepard, Edgar Mitchell, David Scott, James Irwin, John Young, Charles Duke, Eugene Cernan, and Harrison Schmitt.
Interestingly, out of the dozen people who walked on the Moon, no one ever did it more than once.
Comet ISON was used in a search for time travelers. NASA’s Hubble Space Telescope provides a close-up look of Comet ISON (C/2012 S1), as photographed on April 10. Credit: NASA, ESA, J.-Y. Li (Planetary Science Institute), and the Hubble Comet ISON Imaging Science Team.
A press release out yesterday about a recent paper on Comet ISON has caused a mild uproar across the astronomy-minded social media outlets and some websites. The article issued from the Physics & Astrophysics Computation Group (FACOM) at the University of Antioquia in Medellin, Colombia is titled “Comet Of The Century? Not Yet! Comet C/2012 S1 ISON Has Fizzled Completely And May Disintegrate At Or Before Reaching Perihelion.”
The article had professional astronomers and comet enthusiasts alike shaking their heads in disbelief.
For one, any current determination of ISON’s ultimate fate when it gets close to the Sun later this year is speculation at best, (as is the case with almost any other sun-grazing comet) and since no one on planet Earth has seen ISON since it entered the Sun’s glare in June, there is absolutely no way to determine the comet’s current state, either. The almost unanimous shout from the astronomy internets was “Please! We just have to wait and see what happens with ISON.”
But the press release also had this journalist (and others) wondering if Ferrin’s views were taken out of context for the sake of a dramatic press release.
For example, nowhere in his paper does Ferrin say that Comet ISON has “fizzled,” (nor is there a direct quote in the press release with that word) and he does make it clear in his paper that his information about the comet is preliminary. However, the press release seemingly infers there was new data and that the comet is nothing short of dead.
But in an email from Ferrin, in response to an inquiry from Universe Today, Ferrin stands by the press release, as well as his opinion that Comet ISON “does not have a bright future.”
“The term ‘fizzled completely’ is not a scientific term so it should not go into a scientific paper,” Ferrin said. “However it reflects reality with the information we have.”
His paper (a full 51-pages) was posted to arXiv on June 20, 2013, and has been submitted to the Monthly Notices of the Royal Astronomical Society, still undergoing peer review. The paper is based on data available up to the last good observing date in late-May, 2013, and Ferrin said in his email to Universe Today that up to that point “there is no evidence of brightening whatsoever. I doubt that anybody has seen that brightening.”
Ferrin, a well-known cometary scientist, concurred that the comet’s current state is unknown because it has entered the Sun’s glare but when last seen it had not brightened at all, adding in his email that “the fact that the comet was in a standstill situation makes it very improbable of becoming as bright as the Moon.”
As astronomer Karl Battams said, that last statement is hardly breaking news. Battams is an astrophysicist and computational scientist based at the Naval Research Laboratory in Washington DC, and he has operated the NASA-funded Sungrazing Comets Project since 2003. He’s also part of the Comet ISON Observing Campaign a massive, global observing campaign for ISON for both professional and amateur astronomers.
“Few serious astronomers and cometary scientists have ever felt ISON would be ‘brighter than the full Moon,’ Battams told Universe Today. “That’s entirely the media’s term, and we’ve been saying this for months, that none of us in the CIOC foresee ISON getting that bright, and never have done so. So we’re side-by-side with Ferrin in that respect.”
But Battams has some issues with both the paper and the press release.
“The paper is a mixture of reporting facts, and performing extrapolations and modeling based on certain theories and models, some of which are more developed than others,” Battams told Universe Today via email. “Ferrin’s analysis is based on data taken up until around the end of May, but the article misleads by implying that Ferrin has used recent data, which he hasn’t, as there is none. He has simply applied his own methods, model and analysis to the same data that we all have.”
Battams said he can’t comment on the quality of those models, but said Ferrin’s conclusions are broad enough that they don’t seem entirely out of line with what everyone else is saying about the comet – that there is a range of possible outcomes: Comet ISON might fizzle before it gets here or it might disintegrate before, or at perihelion, but it also might still brighten up.
“There’s really no new conclusion here — just a different methods that leads to the same conclusion,” Battams said.
In the paper, Ferrin reaches some of his conclusions comparing ISON to Comet Honig (2002 O4), the brightness of which he says “was in a standstill for 52 days after which it disintegrated.”
Battams said astronomers have to be cautious in comparing ISON to another comet – especially comparing it to Honig, which was not a sungrazer and shared little in common with ISON other than also being a comet.
“ISON is both a Sungrazer, and dynamically new from the Oort Cloud,” he said. “We have no modern record of such an object (see this article about ISON’s uniqueness) so we must exercise a little more caution than usual when comparing it to other comets. The last “major” sungrazer we had was Lovejoy in 2011, and for an object likely much smaller than ISON, it put on a pretty good show.”
“Comparing ISON to 2002 O4 Honig ignores the fact that they were in very different places in the solar system,” Knight said via email, replying to an inquiry from Universe Today regarding Ferrin’s paper. “Honig began flattening out at 1.26 AU as it approached perihelion… ISON being flat at 4-5 AU is a completely different physical realm, since water and other volatiles are not expected to be very active yet.”
Knight also differed with Ferrin’s opinion that ISON’s peculiar non-brightening behavior when last seen “could possibly be explained if the comet were water deficient, or if a surface layer of rock or non-volatile silicate dust were quenching the sublimation to space.”
“This ignores the fact that water isn’t expected to be driving activity from January through June because ISON was still beyond the “frost line” (somewhere between 2.5 and 3 AU) beyond which water doesn’t sublimate efficiently because it is too cold,” Knight said. “It is only when a comet passes inside the frost line that water-driven activity is expected to ramp up…. I fully expect that once it passes inside the frost line, activity will pick up again. We should know as soon as it reemerges from behind the Sun in late August/early September.”
These images from NASA’s Spitzer Space Telescope of C/2012 S1 (Comet ISON) were taken on June 13, when ISON was 310 million miles (about 500 million kilometers) from the sun. Image credit: NASA/JPL-Caltech/JHUAPL/UCF
As to whether ISON has ‘fizzled’ both Battams and Knight noted that the recently released Spitzer observations from June 13 (and released on July 24 – well after Ferrin’s paper was published) showed the comet was ‘fizzy,’ not fizzled, as it was actively spewing out carbon dioxide and dust.
In the end, no matter what any current paper or press release says about Comet ISON, nothing will be known for sure until we see ISON again, and until it gets closer to the Sun. It will pass about 1.2 million km (724,000 miles) from the Sun at closest approach on November 28, 2013.
For now, everyone needs to wait and watch what happens and end the speculation.
However, as noted by Daniel Fischer on Twitter, the reaction caused by the press release related to Ferrin’s paper has been, unfortunately, “dramatic.”
@SungrazerComets Dramatic is the *reaction* … did a Twitter "ISON" search -> within one hour 'mood' switched from "super comet" to "pfft".
Any hype either way — whether it is calling this the Comet of the Century or a comet that has fizzled — only does a disservice to astronomy, and gives the general public the wrong impression of both the comet and science’s ability to study and predict astronomical phenomenon.
Projected vs observed sunspot numbers for solar cycles #23 & #24. (Credit: Hathaway/NASA/MSFC).
Our nearest star has exhibited some schizophrenic behavior thus far for 2013.
By all rights, we should be in the throes of a solar maximum, an 11-year peak where the Sun is at its most active and dappled with sunspots.
Thus far though, Solar Cycle #24 has been off to a sputtering start, and researchers that attended the meeting of the American Astronomical Society’s Solar Physics Division earlier this month are divided as to why.“Not only is this the smallest cycle we’ve seen in the space age, it’s the smallest cycle in 100 years,” NASA/Marshall Space Flight Center research scientist David Hathaway said during a recent press teleconference conducted by the Marshall Space Flight Center.
Cycle #23 gave way to a profound minimum that saw a spotless Sol on 260 out of 365 days (71%!) in 2009. Then, #Cycle 24 got off to a late start, about a full year overdue — we should have seen a solar maximum in 2012, and now that’s on track for the late 2013 to early 2014 time frame. For solar observers, both amateur, professional and automated, it seems as if the Sun exhibits a “split-personality” this year, displaying its active Cycle #24-self one week, only to sink back into a blank despondency the next.
This new cycle has also been asymmetrical as well. One hallmark heralding the start of a new cycle is the appearance of sunspots at higher solar latitudes on the disk of the Sun. These move progressively toward the Sun’s equatorial regions as the cycle progresses, and can be mapped out in what’s known as a Spörer’s Law.
The sunspot number “butterfly” graph, illustrating Spörer’s Law that susnpots gradually migrate towards the equator of the Sun as the solar cycle progresses. (Credit: NASA/MSFC).
But the northern hemisphere of the Sun has been much more active since 2006, with the southern hemisphere experiencing a lag in activity. “Usually this asymmetry lasts a year or so, and then the hemispheres synchronize,” said Giuliana de Toma of the High Altitude Observatory.
So far, several theories have been put forth as to why our tempestuous star seems to be straying from its usual self. Along with the standard 11-year cycle, it’s thought that there may be a longer, 100 year trend of activity and subsidence known as the Gleissberg Cycle.
The Sun is a giant ball of gas, rotating faster (25 days) at the equator than at the poles, which rotate once every 34.5 days. This dissonance sets up a massive amount of torsion, causing the magnetic field lines to stretch and snap, releasing massive amounts of energy. The Sun also changes polarity with every sunspot cycle, another indication that a new cycle is underway.
But predictions have run the gamut for Cycle #24. Recently, solar scientists have projected a twin peaked solar maximum for later this year, and thus far, Sol seems to be following this modified trend. Initial predictions by scientists at the start of Cycle #24 was for the sunspot number to have reached 90 by August 2013; but here it is the end of July, and we’re sitting at 68, and it seems that we’ll round out the northern hemisphere Summer at a sunspot number of 70 or so.
Some researchers predict that the following sunspot Cycle #25 may even be absent all together.
“If this trend continues, there will be almost no spots in Cycle 25,” Noted Matthew Penn of the National Solar Observatory, hinting that we may be on the edge of another Maunder Minimum.
Looking back over solar cycles for the past 500 years. (Credit: D. Hathaway/NASA/MSFC).
The Maunder Minimum was a period from 1645 to 1715 where almost no sunspots were seen. This span of time corresponded to a medieval period known as the Little Ice Age. During this era, the Thames River in London froze, making Christmas “Frost Fairs” possible on the ice covered river. Several villages in the Swiss Alps were also consumed by encroaching glaciers, and the Viking colony established in Greenland perished. The name for the period comes from Edward Maunder, who first noted the minimum in papers published in the 1890s. The term came into modern vogue after John Eddy published a paper on the subject in the journal of Science in 1976. Keep in mind, the data from the period covered by the Maunder Minimum is far from complete— Galileo had only started sketching sunspots via projection only a few decades prior to the start of the Maunder Minimum. But tellingly, there was a span of time in the early 18th century when many researchers supposed that sunspots were a myth! They were really THAT infrequent…
Just what role a pause in the solar cycle might play in the climate change debate remains to be seen. Perhaps, humanity is getting a brief (and lucky) reprieve, a chance to get serious about controlling our own destiny and doing something about anthropogenic climate-forcing. On a more ominous note, however, an extended cooling phase may give us reason to stall on preparing for the inevitable while giving ammunition to deniers, who like to cite natural trends exclusively.
Down but not out? Sol looking more like its solar max-self earlier this month on July 8th. (Photo by author).
Whatever occurs, we now have an unprecedented fleet of solar monitoring spacecraft on hand to watch the solar drama unfold. STEREO A & B afford us a 360 degree view of the Sun. SOHO has now monitored the Sun for the equivalent of more than one solar cycle, and NASA’s Solar Dynamics Observatory has joined it in its scrutiny. NASA’s Interface Region Imaging Spectrograph (IRIS) just launched earlier this year, and has already begun returning views of the solar atmosphere in unprecedented detail. Even spacecraft such as MESSENGER orbiting Mercury can give us vital data from other vantage points in the solar system.
Cycle #24 may be a lackluster performer, but I’ll bet the Sun has a few surprises in store. You can always get a freak cloud burst, even in the middle of a drought. Plus, we’re headed towards northern hemisphere Fall, a time when aurora activity traditionally picks up.
Be sure to keep a (safely filtered) eye on ol’ Sol— it may be the case over these next few years that “no news is big news!”
