This question comes from Andrew Bumford and Steven Stormont.
In a previous episode I’ve talked about how the entire Solar System collapsed down from a cloud of hydrogen and helium left over from the Big Bang. And yet, we stand here on planet Earth, with all its water. So, how did that H20 get to our planet? The hydrogen came from the solar nebula, but where did the oxygen come from?
Here’s the amazing part.
The oxygen came from stars that lived and died before our Sun was even born. When those stars puffed out their final breaths of oxygen, carbon and other “metals”, they seeded new nebulae with the raw material for new worlds. We owe our very existence to the dead stars that came before.
When our Sun dies, it’ll give up some of its heavier elements to the next generation of stars. So, mix hydrogen together with this donated oxygen, and you’ll get H20. It doesn’t take any special process or encouragement, when those two elements come together, water is the result.
But how did it get from being spread across the early Solar System to concentrating here on Earth, and filling up our oceans, lakes and rivers? The exact mechanism is a mystery. Astronomers don’t know for sure, but there are a few theories:
Idea #1: impacts. Take a look at the craters on the Moon and you’ll see that the Solar System was a busy place, long ago. Approximately 3.8 to 4.1 billion years ago was the Late Heavy Bombardment period, when the entire inner Solar System was pummeled by asteroids. The surfaces of the planets and their moons were heated to molten slag because of the non-stop impacts. These impactors could have been comets or asteroids.
Comets are 80% water, and would deliver vast amounts of water to Earth, but they’re also volatile, and would have a difficult time surviving the harsh radiation of the young Sun. Asteroids have a lower ratio of water, but they could protect that water a little better, delivering less with each catastrophic impact.
A false-color, visible-light image of Comet ISON taken with Hubble’s Wide Field Camera 3. Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)
Astronomers have also found many hybrid objects which contain large amounts of both rock and water. It’s hard to classify them either way.
Idea #2 is that large amounts of water just came directly from the solar nebula. As we orbited around the young Sun, it passed through the water-rich material in the nebula and scooped it up. Gravitational interactions between the planets would have transferred material around the Solar System, and it would have added to the Earth’s volume of water over hundreds of millions of years.
Of course, it’s entirely possible that the answer is “all of the above”. Asteroids and comets and the early solar nebula all delivered water to the Earth. Where did the Earth’s water come from? Astronomers don’t know for sure. But I’m sure glad the water is here; life here wouldn’t exist without it.
After last week’s non-episode, the Weekly Space Hangout roared back to life. We had big news on the Government Shutdown, the Earth flyby from the Juno spacecraft, and a big update on Comet ISON.
We also had a special guest, author and journalist Lee Billings, who was here to talk about his newest book, Five Billion Years of Solitude. Lee talked about his work on the book, and the state of extrasolar planet research in general.
Here was the team:
Host: Fraser Cain
Panel: Casey Dreier, Nancy Atkinson, Amy Shira Teitel, Jason Major, and David Dickinson
We broadcast the Weekly Space Hangout every Friday afternoon as a Google+ Hangout on Air. You can watch us live on Google+, or on YouTube, or right here on Universe Today. We start at 12:00 pm Pacific / 3:00 pm Eastern.
Once again, we have gathered together the forces of space journalism to report on the big news stories of the week. And there were lots of big stories indeed, with the launch of NASA’s LADEE mission to the Moon, and the awesome fact that Voyager 1 has totally left the Solar System.
Host: Fraser Cain
Journalists: Amy Shira Teitel, Nicole Gugliucci, Matthew Francis, David Dickinson, Nancy Atkinson
We record the Weekly Space Hangout every Friday at 12 pm Pacific / 3 pm Eastern as a live Google+ Hangout on Air. You can watch the show from right here on Universe Today, or on our YouTube channel.
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.”
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.
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 part of the Comet ISON Observing Campaign, the Spitzer Space Telescope was used to “stare” at the comet for 24 hours on Jun 13, 2013. Images from Spitzer’s “ISON-a-thon” indicate that carbon dioxide and dust are spewing out of the comet at a fairly large rate.
“We estimate ISON is emitting about 2.2 million pounds (1 million kilograms) of what is most likely carbon dioxide gas and about 120 million pounds (54.4 million kilograms) of dust every day,” said Carey Lisse, leader of NASA’s Comet ISON Observation Campaign and a senior research scientist at the Johns Hopkins University Applied Physics Laboratory.
That amount of dust is about the mass of one aircraft carrier every two days or so, tweeted the Sungrazing Comets Twitter feed,, and the amount of carbon dioxide released per day would be enough for about 625 million cans of soda.
The images were taken by the Spitzer’s Infrared Array Camera showing the comet’s tail, which is about 186,400 miles (300,000 kilometers) long.
Comet ISON was about 312 million miles (502 million kilometers) from the Sun, 3.35 times farther than Earth, when the observations were made.
Comet ISON (C/2012 S1) is less than 3 miles (4.8 kilometers) in diameter (about the size of a small mountain) and weighs between 7 billion and 7 trillion pounds (3.2 billion and 3.2 trillion kilograms). However, its true size and density have not yet been accurately determined because of its distance from Earth. Like all comets, ISON is a dirty snowball made up of dust and frozen gases such as water, ammonia, methane and carbon dioxide. These are some of the fundamental building blocks, which scientists believe led to the formation of the planets 4.5 billion years ago.
“This observation gives us a good picture of part of the composition of ISON, and, by extension, of the proto-planetary disk from which the planets were formed,” said Lisse. “Much of the carbon in the comet appears to be locked up in carbon dioxide ice. We will know even more in late July and August, when the comet begins to warm up near the water-ice line outside of the orbit of Mars, and we can detect the most abundant frozen gas, which is water, as it boils away from the comet.”
The comet will pass within 724,000 miles (1.16 million kilometers) of the Sun on Nov. 28.
Astronomers are wondering if the comet will survive its close pass of the Sun, and also if it will live up to expectations of becoming bright enough to be seen in the daytime, as some have predicted.
Only time will tell … and we’ll be here to share the news.
Gennady Borisov, who lives in Naunchniy near the Crimean Observatory in the Ukraine, discovered the comet C/2013 N4 on July 8. He's shown here with his two telescopes. Credit: Oleg Bruzgalov
Ukrainian amateur astronomer Gennady Borisov discovered a brand new comet on July 8 near the bright star Capella in the constellation Auriga. The comet was confirmed and officially christened C/2013 N4 (Borisov) on July 13. At the time of discovery, Borisov was attending the Russian-Ukrainian “Southern Night” star party in Crimea, Ukraine. He nabbed the comet – his first – using an 8-inch (20-cm) f/1.5 wide field telescope of his own design equipped with a CCD camera.
Comet Borisov is the fuzzy spot with a brighter central region in this recent photo. Credit: Oleg Bruzgalov
The new comet is on the faint side, appearing as a small, fuzzy patch of 13th magnitude with a brighter center. To see it you’ll need at least a 10-inch (25-cm) telescope and the fortitude to rise in the wee hours before dawn. The reason for the early hour is Borisov’s location in Auriga, a constellation that doesn’t clear the horizon until shortly before the start of morning twilight. Faintness and low altitude will combine to make Comet Borisov an enticing if challenging object for amateur astronomers.
Animation of Comet Borisov compiled from multiple images. Credit: http://astronomamator.narod.ru/cometes/comet_anim.gif
C/2013 N4 is currently traveling through Auriga not far from the easy-to-spot naked eye star Beta and will slowly brighten as it approaches perihelion – closest point to the sun – on August 20 at a distance of 113.5 million miles (182.7 million km). Unfortunately its elongation or separation from the sun will be slowly shrinking in the coming weeks, causing the comet to drop lower in the sky as it approaches perihelion. Our fuzzy visitor misses Earth by a comfortable 192.5 million miles (310 million km) on August 11. It’s likely Comet Borisov won’t get much brighter than 12th magnitude. Astronomers are still working out the details of its orbit, so it’s possible brightness predictions could change in the near future.
C/2013 N4 (Borisov) tracks through northern Auriga not far from Capella in the coming nights. Positions are shown every 5 days at 3 a.m. CDT. The comet is faint and will require a more detailed chart and telescope to see. Created with Stellarium
Aside from how prominent or not Gennady’s comet will become, the most amazing thing is that he beat the automated surveys to the punch. These days nearly all comets and many asteroids are found by professional astronomers using robotic telescopes hooked up to sensitive cameras and computers. Large areas of the sky are covered each clear night. If a fuzzy, moving object is detected by the computer, astronomers are alerted, follow-up observations are made and the new object receives a letter, number and the survey’s name. That’s why there are a plethora of comets in the past 15 years with names like LINEAR(Lincoln Near-Earth Asteroid Survey), Pan-STARRS (Panoramic Survey Telescope & Rapid Response System), LONEOS (Lowell Observatory Near-Earth-Object Search) and others.
By dint of persistence, a smart plan and a keen eye, Gennady Borisov has made his mark in the sky. For that he deserves a well-deserved congratulations and round of applause!
Amateurs who wish to plot the comet on a star map using a star charting software program can get Comet Borisov’s orbital elements HERE. To follow the latest developments, check out Leonid Elenin’s blog. You might recall it was Elenin in 2010 who discovered famed comet C/2010 X1 (Elenin), blamed for everything from earthquakes to future world catastrophes. Instead, the comet proved so friable, it disintegrated as it approached the sun. Let’s see how Comet Borisov fares.
A false-color, visible-light image of Comet ISON taken with Hubble's Wide Field Camera 3. Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)
The Hubble Space Telescope team has released a video of Comet ISON as it is tearing toward its encounter with the Sun, zooming at 77,250 km/h (48,000 miles per hour). The comet’s motion is captured in a timelapse movie, below, made from a sequence of pictures taken May 8, 2013. On that date, the comet was 650 million km (403 million miles) from Earth, between the orbits of Mars and Jupiter.
This sungrazing comet will come closest to the Sun in November 2013, and the debate is on whether it will dazzle the skies and be visible in the daytime or fizzle out due to its close proximity to the Sun.
The movie shows a sequence of Hubble observations taken over a 43-minute span, compressed into five seconds. In that 43 minutes, the comet traveled about 55,000 km (34,000 miles). ISON streaks silently against the background stars.
Images of Comet ISON obtained using the Gemini Multi-Object Spectrograph at Gemini North on February 4, March 4, April 3, and May 4, 2013 (left to right, respectively; Comet ISON at center in all images). Color composite produced by Travis Rector, University of Alaska Anchorage. Credit: Gemini Observatory/AURA
As Comet C/2012 S1 (ISON) heads closer to Earth, we’re getting a better view of what has been billed by some as the “Comet of the Century.” Astronomers say these new photos from the Gemini North telescope on Mauna Kea, Hawai‘i provide hints of how well this comet might survive one of the closest comet encounters with the Sun ever recorded, on November 28, 2013.
With astronomy enthusiasts hopeful and optimistic about having a spectacular comet visible in our skies, it’s anyone’s guess if the comet will actually survive its extremely close pass of the Sun to become early morning eye-candy in early December 2013.
The time-sequence images, spanning early February through May 2013, show that the comet is quite active, despite how distant it is from the Sun.
When Gemini obtained these images, the comet ranged between roughly 455-360 million miles (730-580 million kilometers; or 4.9-3.9 astronomical units) from the Sun, or just inside the orbital distance of Jupiter. Each image in the series, taken with the Gemini Multi-Object Spectrograph at the Gemini North telescope on Mauna Kea, Hawai‘i, shows the comet in the far red part of the optical spectrum, which emphasizes the comet’s dusty material already escaping from the nucleus. The final image in the sequence, obtained in early May, consists of three images, including data from other parts of the optical spectrum, to produce a color composite image.
Gemini astronomers say the images show the comet sporting a well-defined parabolic hood in the sunward direction that tapers into a short and stubby tail pointing away from the Sun. These features form when dust and gas escape from the comet’s icy nucleus and surround that main body to form a relatively extensive atmosphere called a coma. Solar wind and radiation pressure push the coma’s material away from the Sun to form the comet’s tail, which we see here at a slight angle (thus its stubby appearance).
“Early analysis of our models shows that ISON’s brightness through April can be reproduced by outgassing from either carbon monoxide or carbon dioxide,” said Karen Meech, at the University of Hawaii’s Institute for Astronomy (IfA) in Honolulu. “The current decrease may be because this comet is coming close to the Sun for the first time, and a “volatile frosting” of ice may be coming off revealing a less active layer beneath. It is just now getting close enough to the Sun where water will erupt from the nucleus revealing ISON’s inner secret.”
Comet ISON will come within 800,000 miles (1.3 million km) of the Sun’s surface on November 28. Shortly before that critical passage, the comet may appear bright enough for expert observers using proper care to see it close to the Sun in daylight.
“Comets may not be completely uniform in their makeup and there may be outbursts of activity as fresh material is uncovered,” added IfA astronomer Jacqueline Keane. “Our team, as well as astronomers from around the world, will be anxiously observing the development of this comet into next year, especially if it gets torn asunder, and reveals its icy interior during its exceptionally close passage to the Sun in late November.”
NASA’s Hubble Space Telescope provides a close-up look of Comet ISON (C/2012 S1), as photographed on April 10, when the comet was slightly closer than Jupiter’s orbit at a distance of 386 million miles from the sun. Credit:NASA, ESA, J.-Y. Li (Planetary Science Institute), and the Hubble Comet ISON Imaging Science Team.
NASA’s Swift satellite and the Hubble Space Telescope (HST) have also imaged Comet ISON recently in this region of space. Swift’s ultraviolet observations determined that the comet’s main body was spewing some 850 tons of dust per second at the beginning of the year, leading astronomers to estimate the comet’s nucleus diameter is some 3-4 miles (5-6 kilometers). HST scientists concurred with that size estimate, adding that the comet’s coma measures about 3100 miles (5000 km) across.
The comet gets brighter as the outgassing increases and pushes more dust from the surface of the comet. Scientists are using the comet’s brightness, along with information about the size of the nucleus and measurements of the production of gas and dust, to understand the composition of the ices that control the activity. Most comets brighten significantly and develop a noticeable tail at about the distance of the asteroid belt (about 3 times the Earth-Sun distance –– between the orbits of Mars and Jupiter) because this is when the warming rays of the Sun can convert the water ice inside the comet into a gas. This comet was bright and active outside the orbit of Jupiter — when it was twice as far from the Sun. This meant that some gas other than water was controlling the activity.
Meech said that Comet ISON “…could still become spectacularly bright as it gets very close to the Sun” but also added caution. “I’d be remiss, if I didn’t add that it’s still too early to predict what’s going to happen with ISON since comets are notoriously unpredictable,” she said.
Image from May 5, 2013 of a the inner region of Comet ISON using the 2-meter Liverpool telescope at La Palma. Credit: Nick Howes and Ernesto Guido, Remanzacco Observatory; Nalin Samarasinha, Planetary Science Institute.
In April, when the Hubble Space Telescope looked out towards Jupiter’s orbit and observed what has been billed as the “Comet of the Century” – Comet C/2012 S1 ISON – the space telescope photographed a unique feature in the comet’s coma. Now, a team of ground-based astronomers have performed follow-up observations, imaging Comet ISON as it heads towards the Sun and was just outside the orbit of Mars. They, too, have seen something in the coma and suspect it’s a similar feature to what Hubble imaged. The object is thought to be a jet blasting dust particles off the sunward-facing side of the comet’s nucleus.
These very useful follow-up observations are providing more insight on this highly anticipated comet, as well as helping to predict what might happen when it makes its closest approach to the Sun in November 2013.
“The hype surrounding this comet has been extreme” said Nick Howes from the Remanzacco Observatory, “with some wildly optimistic estimates for magnitude. We’re hoping this measured scientific approach will yield results just as exciting to the science community, even if the comet doesn’t end up meeting everyone’s expectations visually, for whatever reason.”
NASA’s Hubble Space Telescope provides a close-up look of Comet ISON (C/2012 S1), as photographed on April 10, when the comet was slightly closer than Jupiter’s orbit at a distance of 386 million miles from the sun. Credit:NASA, ESA, J.-Y. Li (Planetary Science Institute), and the Hubble Comet ISON Imaging Science Team.
Some have predicted ISON may briefly become brighter than the full Moon. But right now the comet is far below naked-eye visibility, and larger telescopes are needed to makes observations.
Howes and Ernesto Guido from the Remanzacco Observatory in Italy used a suite of Hubble-sized ground-based telescopes in Australia, Hawaii and the Canary Islands to make their observations. They are collaborating with with Nalin Samarasinha, a Senior Scientist at the Planetary Science Institute (PSI) in an attempt to get high spatial resolution data on Comet ISON.
Howes and Guido have been imaging Comet C/2012 S1 ISON since the day it was discovered and actually played a small role in its discovery. They work on a variety of programs with professional and amateur astronomers around the world, but for this comet, their focus is on the so-called Afrho, a measure of a comet’s dust production. (Learn more about Arfho here.)
Samarasinha, a specialist in comets at the Planetary Science Institute, has been looking at the detailed structure of the near-nucleus coma of comet C/2012 S1 ISON using data, which the Remanzacco team is delivering in to the PSI.
Recently, Samarasinha had looked at image comparisons for the Remanzacco team’s dataset from May 2, 5, and 7 taken with the F10 2-meter Liverpool telescope on La Palma, using an extremely sensitive camera, perfectly suited for detailed comet work.
Image from May 2, 2013 of a the inner region of Comet ISON, using the 2 meter Liverpool Telescope at La Palma. Credit: Nick Howes and Ernesto Guido, Remanzacco Observatory; Nalin Samarasinha, Planetary Science Institute.
The images shown here are 28×28 pixel crops of the inner region of the comet.
“This comparison shows that the sunward feature Nick’s team suspected from images taken on 02/05/2013 is originating slightly north of west and then the position angle of the feature (measured from north through east) increases as one moves away from the optocenter,” said Nalin.
Nalin’s interpretation is that the curvature of this feature (which the team suspected was not caused by image enhancing initially, but can now categorically state is real) is not due to any rotational effects but is due to radiation pressure pushing dust grains towards the tail. Ultimately, this feature merges in with the tail. Image from May 7, 2013 of a the inner region of Comet ISON, as seen with the 2-meter Liverpool Telescope at La Palma. Credit: Nick Howes and Ernesto Guido, Remanzacco Observatory; Nalin Samarasinha, Planetary Science Institute.
The team says these observations are in close agreement with features detected by the Hubble Space Telescope in April this year. As the comet comes closer to the Earth the spatial resolution will improve, and the team should get more detailed views on the coma structure.
Estimates suggest that the nucleus of ISON is no larger than 4-6 km (3-4 miles) across while the comet’s dusty coma, or head of the comet is approximately 5,000 km (3,100 miles) across, or 1.2 times the width of Australia. A dust tail extends more than 92,000 km (57,000 miles).
Ongoing observations seem to reveal this comet is ‘shedding’ quite a bit of mass, leaving astronomers to wonder if it will have enough body left to survive its perhihelion, the closest approach to the Sun on November 28, 2013.
Excitingly, Comet ISON observations are in the works for when the comet dashes past Mars, and the Curiosity rover is on tap to try imaging it from Mars’ surface with its high resolution Mastcam 100 camera, as well as on-orbit observations with the Mars Reconnaissance Orbiter (MRO).
As the comet performs a hairpin turn around the Sun in November, its ices will vaporize in the intense solar heat. Assuming it defies death by evaporation, some predict it could become as bright as the full Moon. If so, that would occur for a brief time around at perihelion when the comet would only be visible in the daytime sky very close to the Sun. When safely viewed, ISON might look like a brilliant, fuzzy star in a blue sky.
As C/2012 S1 ISON is now heading in to the evening twilight glare, Howes and Guido will turn from large aperture instrumentation on this comet for a while, and work on observations with a wider field CCD, more sensitive in the R’ band, and also imaging with the Polarimeter instrument which will allow them to create detailed maps of the inner coma region.
Howes said that these ongoing collaborations with scientists with the amateur community are delivering valuable scientific data on a hugely interesting object.
