The Spiderweb, imaged by the Hubble Space Telescope – a central galaxy (MRC 1138-262) surrounded by hundreds of other star-forming 'clumps'. Credit: NASA, ESA, George Miley and Roderik Overzier (Leiden Observatory)
Once upon a time, when the Universe was just about three billion years old, galaxies started to form. Now astronomers using a CSIRO radio telescope have captured evidence of the raw materials these galaxies used to fashion their first stars… cold molecular hydrogen gas, H2. Even though we can’t see it directly, we know it is there by using another gas that reveals its presence – carbon monoxide (CO) – a radio wave emitter.
The telescope is CSIRO’s Australia Telescope Compact Array telescope near Narrabri, NSW. “It one of very few telescopes in the world that can do such difficult work, because it is both extremely sensitive and can receive radio waves of the right wavelengths,” says CSIRO astronomer Professor Ron Ekers.
One of the studies of these “raw” galaxies was performed by astronomer Dr. Bjorn Emonts of CSIRO Astronomy and Space Science. He and fellow researchers employed the Compact Array to observe and record a gigantic and distant amalgamation of “star forming clumps or proto-galaxies” which are congealing together to create a single massive galaxy. This framework is known as the “Spiderweb” and is theorized to be at least ten thousand million light years distant. The Compact Array radio telescope is capable of picking up the signature of star formation, giving astronomers vital clues about how early galaxies began star formation.
In blue, the carbon monoxide gas detected in and around the Spiderweb. Credit: B. Emonts et al (CSIRO/ATCA)The “Spiderweb” was loaded. Here Dr. Emont and his colleagues found the molecular hydrogen gas fuel they were seeking. It covered an area of space almost a quarter of a million light-years across and contained at least sixty thousand million times the mass of the Sun! Surely this had to be the material responsible for the new stars seen sprinkled across the region. “Indeed, it is enough to keep stars forming for at least another 40 million years,” says Emonts.
In another research project headed by Dr. Manuel Aravena of the European Southern Observatory, the scientists measured the CO – the indicator of H2 – in two very distant galaxies. The signal of the faint radio waves was amped up by the gravitational fields of the additional galaxies – the “line of sight” members – which created gravitational lensing. Says Dr. Aravena, “This acts like a magnifying lens and allows us to see even more distant objects than the Spiderweb.”
Dr. Aravena’s team went to work measuring the amount of H2 in both of their study galaxies. One of these, SPT-S 053816-5030.8, produced enough radio emissions to allow them to infer how quickly it was forming stars – “an estimate independent of the other ways astronomers measure this rate.”
The Compact Array was tuned in. Thanks to an upgrade which increased its bandwidth – the amount of the radio spectrum which can be observed at any particular time – it is now sixteen times stronger and capable of reaching a range from 256 MHz to 4 GHz. That makes it a very sensitive ear!
“The Compact Array complements the new ALMA telescope in Chile, which looks for the higher-frequency transitions of CO,” says Ron Ekers.
Pluto & Charon as you'll never see them... imaged by Hubble in 1994. (Credit: NASA/ESA/ESO).
So you’ve seen all of the classic naked eye planets. Maybe you’ve even seen fleet-footed Mercury as it reached greatest elongation earlier this month. And perhaps you’ve hunted down dim Uranus and Neptune with a telescope as they wandered about the stars…
But have you ever seen Pluto?
Regardless of whether or not you think it’s a planet, now is a good time to try. With this past weekend’s perigee Full Moon sliding out of the evening picture, we’re reaching that “dark of the Moon” two week plus stretch where it’s once again possible to go after faint targets.
This year, Pluto reaches opposition on July 1st, 2013 in the constellation Sagittarius. This means that as the Sun sets, Pluto will be rising opposite to it in sky, and transit the meridian around local midnight.
But finding it won’t be easy. Pluto currently shines at magnitude +14, 1,600 times fainter than what can be seen by the naked eye under favorable sky conditions. Compounding the situation is Pluto’s relatively low declination for northern hemisphere observers. You’ll need a telescope, good seeing, dark skies and patience to nab this challenging object.
Pluto in Sagittarius; a wide field field of view with 10 degree finder circle. The orbital path of Pluto and the ecliptic is also noted. The red inset box is the field of view below. All graphics created by the author using Starry Night.
Don’t expect Pluto to look like much. Like asteroids and quasars, part of the thrill of spotting such a dim speck lies in knowing what you’re seeing. Currently located just over 31 Astronomical Units (AUs) distant, tiny Pluto takes over 246 years to orbit the Sun. In fact, it has yet to do so once since its discovery by Clyde Tombaugh from the Lowell observatory in 1930. Pluto was located in the constellation Gemini near the Eskimo nebula (NGC 2392) during its discovery.
And not all oppositions are created equal. Pluto has a relatively eccentric orbit, with a perihelion of 29.7 AUs and an aphelion of 48.9 AUs. It reached perihelion on September 5th, 1989 and is now beginning its long march back out of the solar system, reaching aphelion on February 19th, 2114.
A medium field finder for Pluto with a five degree field of view. The current direction of New Horizons is noted. The yellow inset box is the field of view below.
Pluto last reached aphelion on June 4th, 1866, and won’t approach perihelion again until the far off date of September 15th, 2237.
This means that Pluto is getting fainter as seen from Earth on each successive opposition. Pluto reaches magnitude +13.7 when opposition occurs near perihelion, and fades to +15.9 (over 6 times fainter) when near aphelion. It’s strange to think that had Pluto been near aphelion during the past century rather than the other way around, it may well have eluded detection!
This all means that a telescope will be necessary in your quest, and the more powerful the better. Pluto was just in range of a 6-inch aperture instrument about 2 decades ago. In 2013, we’d recommend at least an 8-inch scope and preferably larger to catch it. Pluto was an easy grab for us tracking it with the Flandrau Science Center’s 16-inch reflector back in 2006.
A one degree field of view, showing the path of Pluto from June 23rd of this year until December 2nd. Stars are labeled down to 7th magnitude, unlabeled stars are depicted down to 10th magnitude.
Pluto is also currently crossing a very challenging star field. With an inclination of 17.2° relative to the ecliptic, Pluto crosses the ecliptic in 2018 for the first time since its discovery in 1930. Pluto won’t cross north of the ecliptic again until 2179.
Pluto also crossed the celestial equator into southern declinations in 1989 and won’t head north again til 2107.
But the primary difficulty in spotting +14th magnitude Pluto lies in its current location towards the center of our galaxy. Pluto just crossed the galactic plane in early 2010 into a very star-rich region. Pluto has passed through some interesting star fields, including transiting the M25 star cluster in 2012 and across the dark nebula Barnard 92 in 2010.
A one degree narrow field of view, showing the path of Pluto from June 24th to August 6th. Stars are depicted down to 14th magnitude.
This year finds Pluto approaching the +6.7 magnitude star SAO 187108 (HIP91527). Next year, it will pass close to an even brighter star in the general region, +5.2 magnitude 29 Sagittarii. Mid-July also sees it passing very near the +10.9 magnitude globular cluster Palomar 8 (see above). This is another fine guidepost to aid in your quest.
So, how do you pluck a 14th magnitude object from a rich star field? Very carefully… and by noting the positions of stars at high power on successive nights. A telescope equipped with digital setting circles, a sturdy mount and pin-point tracking will help immeasurably. Pluto is currently located at:
Right Ascension: 18 Hours 44′ 30.1″
Declination: -19° 47′ 31″
Heavens-Above maintains a great updated table of planetary positions. It’s interesting to note that while Pluto’s planet-hood is hotly debated, few almanacs have removed it from their monthly planetary summary roundups!
You can draw the field, or photograph it on successive evenings and watch for Pluto’s motion against the background stars. It’s even possible to make an animation of its movement!
Pluto will once again reach conjunction on the far side of the Sun on January 1st 2014. Interestingly, 2013 is a rare year missing a “Plutonian-solar conjunction.” This happens roughly every quarter millennium, and last occurred in 1767. This is because conjunctions and oppositions of Pluto creep along our Gregorian calendar by about a one-to-two days per year.
An Earthly ambassador also lies in the general direction of Pluto. New Horizons, launched in 2006 is just one degree to the lower left of 29 Sagittarii. Though you won’t see it through even the most powerful of telescopes, it’s fun to note its position as it closes in on Pluto for its July 2015 flyby.
Let us know your tales of triumph and tragedy as you go after this challenging object. Can you image it? See it through the scope? How small an instrument can you still catch it in? Seeing Pluto with your own eyes definitely puts you in a select club of visual observers…
Still not enough of a challenge? Did you know that amateurs have actually managed to nab Pluto’s faint +16.8th magnitude moon Charon? Discovered in 35 years ago this month in 1978, this surely ranks as an ultimate challenge. In fact, discoverer James Christy proposed the name Charon for the moon on June 24th, 1978, as a tribute to his wife Charlene, whose nickname is “Char.” Since it’s discovery, the ranks of Plutonian moons have swollen to 5, including Nix, Hydra and two as of yet unnamed moons.
Be sure to join the hunt for Pluto this coming month. Its an uncharted corner of the solar system that we’re going to get a peek at in just over two years!
The view of Kitt Peak National Observatory, as seen from 1 mile below the summit.
Greetings, from the Kitt Peak National Observatory, in Arizona! I’m here on a weeklong observing run, which is arguably the coolest and hardest part of the job.
Kitt Peak rests on the Quinlan Mountains, 6,880 feet above sea level and 55 miles southwest of Tucson. When you begin your drive up the mountain, you first see a beautiful panorama of glittering white domes. There are 26 telescopes on the Mountain.
The Mayall 4-meter telescope quickly catches your eye – the colossal giant that towers over the rest. As you continue your drive, a radio telescope can be seen on the left, followed by various signs stating that cell phone use is strictly prohibited. Observing runs here require radio silence, and a great chance to escape.
At the top of the mountain, two telescopes stand apart from the rest – the McMath-Pierce Solar Telescope and the WIYN observatory. The solar telescope reflects sunlight through a tunnel that leads underground. The WIYN observatory has an octagonal shape for a dome.
This is my third trip to Kitt Peak, but my first chance to observe on the Mayall 4-meter telescope. The first thing to know about the 4-meter is that it is a colossal maze. Literally. There are 16 stories of rooms, now obsolete and out of date, before reaching the base of the telescope itself.
The dome of the 4-meter Mayall telescope (left) as well as the telescope itself (right).
These rooms include old darkrooms, instrument rooms, machine rooms, classrooms, dormitories, game rooms, and other mysteries. We’ve been joking most of this week that Hollywood should rent out the 4-meter for a fantastic horror film. Just think: The Big Bang Theory meets Psycho.
On our first day here, my colleague and I managed to get pretty lost. To reach the telescope you have to take two different gated and locked elevators. But when we finally made it to the control room, we realized that this room alone is much more of maze than the building.
The control room consists of 4 computers, 16 monitors, 3 personal laptops, 4 tv screens, and an array of controls that operate the telescope. Eventually we became very comfortable floating from monitor to monitor.
The control room for the 4-m Mayall telescope. Dr. Mike DiPompeo is taking images throughout the night.
Here is what a typical day on an observing run looks like.
We typically wake up a little after noon and grumpily head to the dining hall for coffee. Breakfast (or lunch) runs until about 1 pm.
In the late afternoon, we take a few flat field calibrations – images of a white screen, which is uniformly lit up. Any variations in the final image are due to variations in the detector or distortions in the optical path. At the end of the day, you can divide your science images by your flat field images, in order to achieve much cleaner images.
Shortly thereafter, the dewar is filled with liquid nitrogen. This keeps the instrument cool (approximately -100 degrees Fahrenheit), as any thermal current can cause added noise.
After a quick dinner we return to the telescope. At this point sunset is approximately 2 hours away, but it’s already time to open the dome. When you’re standing next to the telescope, an opening dome sounds like a freight train screeching to a stop. It’s slightly terrifying, but it is by far one of my favorite sounds. It signifies that for the rest of the night you’re in control of this phenomenal instrument, which has the power to discover the secrets of the Universe.
After two hours of various preparations – making sure the telescope is pointing correctly, guiding correctly, etc. – we “get on sky.” Throughout the night the telescope operator controls the telescope, moving it to the fields we would like to observe, while we are in charge of taking the images by verifying the exposure time, filters to use, etc.
If everything goes smoothly the night is pretty easy. The telescope operator moves from target to target while we continuously take images. This means that we end up sitting in front of a computer screen, pressing enter every 300 seconds in order to start a new exposure. That’s really all it takes! Of course you should keep checking on your images in order to verify that they look good.
Around midnight it’s time for night lunch, a packed lunch that the dining hall provides. A little extra protein helps make the long nights more bearable. And then you push through, making coffee if necessary. The challenging part is staying awake throughout the night. It’s amazing how hard simple calculations can be when dawn is approaching.
At the end of the night you step outside and save for the flickering glint of Tucson’s city lights, the only noticeable light is found by looking up into the night sky. The stars here are brilliant, and the Milky Way is astonishing. After spending an entire evening stuck in a black box, it’s a wonderful reminder of what it’s all about: the night sky.
I observed with Dr. Mike DiPompeo, who concurred on what I noticed about the observing experience.
“When you first get into astronomy you’re in awe of the beauty of the night sky, compelled and driven by it,” DiPompeo told me. “But it can be easy to forget in the day to day business of being an astronomer – sitting at a computer, writing code, going through the data, reading papers – that your job is to understand that beauty. Observing reconnects you with the night sky.”
My favorite part of an observing run occurs in the morning – on the walk from the telescope to the dorm, when a yellow arch of light first appears above the horizon. Kitt Peak provides fantastic sunrises. And you really have to soak in every last ray of sun, before you crawl into bed in a very dark room.
One of many beautiful sunrises.
Observing runs lie at the root of pure research. You spend the long nights collecting data, then the months or years analyzing the data, and finally hope that a cool result comes from all the hard work.
IRIS will take a closer look at the lower parts of the sun's atmosphere, which is producing the spectacular flare shown in this image. Credit: NASA&JAXA/Hinode
How does the sun’s energy flow? Despite the fact that we live relatively close (93 million miles, or eight light-minutes) to this star, and that we have several spacecraft peering at it, we still know little about how energy transfers through the solar atmosphere.
NASA’s next solar mission will launch Wednesday, June 26 (if all goes to plan) to try to learn a little bit more. It’s called the Interface Region Imaging Spectrograph (IRIS), and it will zero in on a spot in the sun’s lower atmosphere known as the “interface region.” The zone only has a thickness of 3,000 to 6,000 miles and is seen as a key transfer point to the sun’s incredibly hot corona (that you can see during total solar eclipses.)
“IRIS will extend our observations of the sun to a region that has historically been difficult to study,” stated Joe Davila, IRIS project scientist at NASA’s Goddard Space Flight Center. “Understanding the interface region better improves our understanding of the whole corona and, in turn, how it affects the solar system.”
Figuring out more about the interface region, NASA stated, will teach us a lot more about the “space weather” that affects Earth.
Some of the energy in the interface region leaks out and powers the solar wind, which is a sort of rain of particles that leave the star. Some of them hit the Earth’s magnetic field and can produce auroras. Most of the sun’s ultraviolet radiation also flows from the interface region.
IRIS’ images will be able to zero in on about 1 percent of the sun in a single go, with resolution of features of as small as 150 miles. The 400-pound satellite will orbit Earth in an orbit perpetually keeping it above the sunrise line, a spot that lets the satellite look at the sun continuously for eight months without the sun being obscured by Earth.
It’ll also form part of a larger network of sun-staring satellites.
Technicians work on NASA’s Interface Region Imaging Spectrograph (IRIS) in a “clean room”, a specially designed facility intended to minimize contaminants on spacecraft before launch. Credit: Lockheed Martin
NASA highlighted its Solar Dynamics Observatory and a joint mission it has with Japan, called Hinode, which both take images of the sun in high-definition. These other two observatories, however, look at different solar layers (specifically, the surface and the outer atmosphere).
With IRIS joining the fleet and looking at the interface region, it will provide a more complete picture.
“Relating observations from IRIS to other solar observatories will open the door for crucial research into basic, unanswered questions about the corona,” stated Davila.
Well, you shouldn’t be. Yes, you’re just one person out of over 7 billion on Earth. Yes, your lifetime — even if you live to be well over 100 — is just a fraction of a flicker of a blink of a tardigrade’s eye (do tardigrades blink?) compared to the 4.6 billion years of the age of the planet. And yes, Earth is only about a third the age of the Universe… which is filled with billions of other galaxies each with stars and planets of their own. Space is just so awfully darn…big.
But, as astrophysicist Neil deGrasse Tyson reminds us in the video above, so are you. So is everyone, in fact. And why? Because we are all a part of it. We’re a part of the Universe… each one of us an inexorably inseparable part of the big picture, a connection between past, present, and future in the most elemental sense possible. As Tyson famously stated once before, “we are in the Universe, the Universe is in us.” And it’s true.
So if you have an admittedly large and heavy ego, put it down for a moment and check out the video. You may come to realize it was weighing you down a bit.
“Those who see the cosmic perspective as a depressing outlook, they really need to reassess how they think about the world.”
Artist concept of the Arkyd telescope in space. Credit: Planetary Resources Inc.
With more than $1 million in crowdfunded money secured for a public asteroid-hunting space telescope, the ultimate question arises: what about the promised planet chase?
Planetary Resources’ Arkyd-100 telescope reached its $1 million goal yesterday (June 20). But the self-proclaimed asteroid-hunting company has an ambitious aim to add extrasolar planet searching to the list if it can double that goal to $2 million.
The Kickstarter campaign for Arkyd still has 10 days remaining. To keep the funds flowing, the group behind it has released several “stretch” goals if it can reach further milestones:
– $1.3 million: A ground station at an undisclosed “educational partner” that would double the download speed of data from the orbiting observatory.
Example of an orbital ‘selfie’ that Planetary Resources’ ARKYD telescope could provide to anyone who donates to their new Kickstarter campaign. Credit: Planetary Resources.
– $1.5 million: This goal, just released yesterday, is aimed at the more than 20,000 people who signed up for “space selfies” incentive where uploaded pictures are photographed on the telescope while it is in orbit. For this goal, “beta selfies” will be taken while the telescope is in the integration phase of the build.
– $1.7 million: The milestone will be announced if Arkyd reaches 15,000 backers. (It has more than 12,000 as of this writing.)
The text of William H. Waller, an astronomer and author, was in the midst of a discussion of a kind of organic molecule called PAHs, or polycyclic aromatic hydrocarbons. As I was reading about the Spitzer Space Telescope’s discoveries in this field, the last sentence in the paragraph struck me:
“On Earth, PAHs are as familiar to us as the mouth-watering aromas of a barbecued hamburger, the sweetly acrid odors of burning tobacco, and the choking fumes behind a diesel bus,” Waller wrote. “If we had big enough nostrils, what would our home galaxy smell like?”
I’m never going to read about PAHs again without wanting to run to that greasy joint nearby my place. Or, I guess, run in the opposite direction from the nearest bus stop.
A digital all-sky mosaic of our view of the Milky Way from Earth, assembled from more than 3,000 individual CCD frames. Credit: Axel Mellinger.
Waller’s book is designed as a reference guide for those with a serious interest in astronomy, but who perhaps are just starting to think about taking it in school. Another audience could be the serious amateur astronomer wanting to understand more about telescopic targets.
While not light cottage reading, Waller isn’t afraid to throw in references to popular culture or to drop in humor now and then, much like a kindly Astronomy 101 professor trying to snap your attention back when it might be wandering.
On that note, this illustration in the book (with some important context) may be my favorite astronomy textbook image of all time. It’s another example of how science can, kinda sorta, meet science fiction.
You will find Star Trek references in this book, we promise you. (Paramount Pictures)
The breadth of material Waller covers is astonishing. One 43-page chapter is essentially a history of how we looked at the sky mythologically, philosophically and of course scientifically — a feat that is more interesting when you realize a goodly number of those pages are actually in-context, interesting illustrations.
The book’s bulk, though, looks to summarize astronomical phenomena. It’s definitely not for the beginning reader; for example, the term “nebula” is referred to several times before finally being defined some pages into the book. But if you know what Waller is aiming at, you’ll learn quite a bit.
The Hertzsprung-Russell Diagram.
The book purports to be about galaxies, but much of it is also devoted to what I think of as hacking the Hertzsprung-Russell diagram showing the types of stars in relation to each other.
Three full chapters are devoted to star birth, the lives of stars and stellar afterlives (y’know, supernovae and the like.) This makes perfect sense as galaxies are collections of stars, so it is only by studying these individual members that we can truly appreciate what a galaxy is about.
The more serious reader will be pleased to see equations included (such as calculating parallax) and a detailed explanation of Drake’s Equation showing the factors behind the probability of finding extraterrestrial life.
So to sum up: definitely not for the person with a nascent interest in astronomy, but a valuable reference for those looking to learn about it seriously. As a space journalist, I’ll definitely keep this book on my shelf.
Over the past six years wind speeds in Venus' atmosphere have been steadily rising (ESA)
High-altitude winds on neighboring Venus have long been known to be quite speedy, whipping sulfuric-acid-laden clouds around the superheated planet at speeds well over 300 km/h (180 mph). And after over six years collecting data from orbit, ESA’s Venus Express has found that the winds there are steadily getting faster… and scientists really don’t know why.
Cloud structures in Venus’ atmosphere, seen by Venus Express’ Ultraviolet, Visible and Near-Infrared Mapping Spectrometer (VIRTIS) in 2007 (ESA)
By tracking the movements of distinct features in Venus’ cloud tops at an altitude of 70 km (43 miles) over a period of six years — which is 10 of Venus’ years — scientists have been able to monitor patterns in long-term global wind speeds.
What two separate studies have found is a rising trend in high-altitude wind speeds in a broad swath south of Venus’ equator, from around 300 km/h when Venus Express first entered orbit in 2006 to 400 km/h (250 mph) in 2012. That’s nearly double the wind speeds found in a category 4 hurricane here on Earth!
“This is an enormous increase in the already high wind speeds known in the atmosphere. Such a large variation has never before been observed on Venus, and we do not yet understand why this occurred,” said Igor Khatuntsev from the Space Research Institute in Moscow and lead author of a paper to be published in the journal Icarus.
Long-term studies based on tracking the motions of several hundred thousand cloud features, indicated here with arrows and ovals, reveal that the average wind speeds on Venus have increased from roughly 300 km/h to 400 km/h over the first six years of the mission. (Khatuntsev et al.)
A complementary Japanese-led study used a different tracking method to determine cloud motions, which arrived at similar results… as well as found other wind variations at lower altitudes in Venus’ southern hemisphere.
“Our analysis of cloud motions at low latitudes in the southern hemisphere showed that over the six years of study the velocity of the winds changed by up 70 km/h over a time scale of 255 Earth days – slightly longer than a year on Venus,” said Toru Kouyama from Japan’s Information Technology Research Institute. (Their results are to be published in the Journal of Geophysical Research.)
Both teams also identified daily wind speed variations on Venus, along with shifting wave patterns that suggest “upwelling motions in the morning at low latitudes and downwelling flow in the afternoon.” (via Cloud level winds from the Venus Express Monitoring Camera imaging, Khatuntsev et al.)
A day on Venus is longer than its year, as the planet takes 243 Earth days to complete a single rotation on its axis. Its atmosphere spins around it much more quickly than its surface rotates — a curious feature known as super-rotation.
“The atmospheric super-rotation of Venus is one of the great unexplained mysteries of the Solar System,” said ESA’s Venus Express Project Scientist Håkan Svedhem. “These results add more mystery to it, as Venus Express continues to surprise us with its ongoing observations of this dynamic, changing planet.”
ISON as seen by Hubble earlier this spring. (Credit: NASA/ESA/Z. Levay/STScl).
Comets are the big “question marks” of observational astronomy. Some, such as Comet Hyakutake and the Great Daylight Comet of 1910 present themselves seemingly without warning and put on memorable displays. Others, such as the infamous Comet Kohoutek or Comet Elenin, fizzle and fail to perform up to expectations after a much anticipated round of media hype.
And then there’s the case of Comet C/2012 S1 ISON. Discovered on September 21st, 2012 by Artyom Novichonok and Vitali Nevski while conducting the International Scientific Optical Network (ISON) survey, Comet ISON has captivated public interest. The media loves a good comet, or at least the promise of one.
But will Comet ISON perform up to expectations? Recently, veteran comet hunter and observer John Bortle weighed in on a Sky & Telescope post and an email interview with Universe Today on what we might expect to see this fall.
Dozens of comets are discovered every year. Most amount to nothing – a handful, like this year’s comet 2011 L4 PanSTARRS or 2012 F6 Lemmon, may become interesting binocular objects.
Part of what alerted astronomers that Comet ISON may become something special was its extreme discovery distance of 6.7 astronomical units (A.U.s) meaning it should be an intrinsically bright object, coupled with its close approach of 0.012 A.U.s (1.1 million kilometres, accounting for the solar radius) from the surface of the Sun at perihelion.
Universe Today recently caught up with Mr. Bortle, who had the following to say above tentative prospects for Comet ISON in late 2013:
“Comets coming into the near-solar neighborhood from the Oort Cloud for the very first time tend to behave rather differently from most of their other icy brethren. They often will show considerable early activity while still far from the Sun, giving a false sense of their significance. Only when they have ventured to within about 1.5-2.0 astronomical units of the Sun do they begin to reveal their true intrinsic nature in the way of brightness and development. When discovered far from the Sun, this situation has misled astronomers time and again into announcing that a grandiose display is in the offing, only to have the comet ultimately turn out to be a general disappointment. There have been exception to this, but they are rare indeed.”
Comet ISON bears similar characteristics to many of the great sungrazing comets of the past. In the last few months, word has made rounds that Comet ISON may be underperforming, stagnating around magnitude +16 (10,000 times fainter than naked eye visibility) as it crosses the expanse of the asteroid belt between Jupiter and Mars.
Bortle, however, cautioned against writing off ISON just yet in a recent message board post. “With this comet’s exceedingly small perihelion distance, the ultimate situation is less clear.” He also continues to note that the prospects for ISON are “really difficult to predict at the moment,” but estimates that Comet ISON “will not actually attain naked eye brightness until just a week or two before perihelion passage.”
Regarding naked eye visibility of Comet ISON, Mr. Bortle also told Universe Today:
“In all probability this will not occur until around early to mid-November. It will not become any sort of impressive sight before disappearing into the morning twilight only a couple of weeks thereafter.”
And that’s the big question that may make the difference between a fine binocular comet and the touted “Comet of the Century…” Will this comet survive its perihelion passage on November 28th?
Concerning the comet’s perihelion passage, Mr. Bortle told Universe Today:
“This is currently a matter of some concern to me. Basing my answer on ISON’s apparent brightness when it was last seen before disappearing into the evening twilight recently suggests that it might be close in intrinsic brightness to the survival/non-survival level for such an extremely close encounter with the Sun. We will know much better once we can view ISON again in September.”
Comet Ikeya-Seki was another sungrazing comet that went on to become a splendid naked eye comet in 1965. The late 1880’s hosted a slew of memorable comets, including two long-tailed sungrazers, one each in 1880 and 1887.
In more recent times, Comet C/2011 W3 Lovejoy survived its December 16th, 2011 perihelion passage 140,000 kilometres from the surface of the Sun to become the surprise hit for southern hemisphere observers.
“IF” comet ISON breaks a negative magnitude, it’ll join the ranks on the top brightest comets since 1935. If it tops -10th magnitude, it’ll best Comet Ikeya-Seki at its maximum in 1965. The magic “brighter than a Full Moon” threshold sits right about at magnitude -12.5, but Bortle cautions that this peak brightness will only persist during the hours surrounding perihelion, when the comet will be very close to the Sun and difficult to see.
Mr. Bortle also voiced a concern to Universe Today that “the initial announcements by professional astronomers concerning ISON’s potential future brightness (“Brighter than the Full Moon”, etc.) were wildly excessive, as was the idea that the comet would be obvious to the general public in the daytime sky as it rounded the Sun in late November. This claim was totally unjustified from the word go.” Mr Bortle also warns that this may be “headed us down the exact same road as the Kohoutek fisaco of 1973/74.”
We’re currently losing Comet ISON behind the Sun as it crosses through the constellation Gemini, not return to morning skies until late August. The comet will cross the orbit of Mars in early October and should also cross the +10th magnitude threshold and become visible in binoculars and small telescopes around this date.
The track of Comet ISON through the constellations Gemini, Cancer and Leo prior to perihelion. (Credit: NASA/GSFC/Axel Mellinger).
From October on in, things should get really interesting. Mr. Bortle predicts that the comet will “develop more slowly in the autumn sky than initially thought,” and won’t become a naked eye object until around November 10th or so. What this sort of lag might do to the internet pundits and prognosticators might be equally interesting to watch.
ISON will also track near some interesting morning objects as seen from Earth, including Mars (October 18th), Spica (November 18th), and Mercury & Saturn low in the dawn on November 26th. It will also have another famous comet nearby on November 25th (photo op!) short period Comet 2P Encke.
If Comet ISON survives perihelion, the true show could begin in early December. Comet ISON will re-emerge in the dawn skies, passing a pairing of Mercury and the very old crescent Moon on December 1st. Comet tails are even less predictable than comet magnitudes, but if Comet ISON is to unfurl a long photogenic tail, the weeks leading up to Christmas may be when it does it.
The projected view of Comet ISON from 30 degrees north latitude 30 minutes prior to local sunrise on December 1st. The orbital path of the comet and the ecliptic are also depicted. (Created by the author in Starry Night).
Mr. Bortle predicts a 10 to 15 degree long tail for a post-perihelion ISON as it passes through the constellation Ophiuchus into morning skies. It may become a “headless wonder” similar to the fan-shaped display put on by Comet 2011 L4 PanSTARRS earlier this spring. We’ve even seen models projecting a great fan-shaped dust tail seeming to “loop” around the Sun as seen from our Earthly vantage point!
All interesting conjecture to watch unfold as Comet ISON approaches perihelion this November. Hopefully, the hysteria that follows great cometary apparitions won’t reach a fevered pitch, though we’ve already had to put some early conspiracies to bed surrounding comet ISON.
Will ISON be the “Comet of the Century?” Watch this space… we’ll have more on the play-by-play action as it approaches!
-Read John Bortle’s predictions for Comet ISON in his recent Sky & Telescope post.
Uranus viewed in the infrared spectrum, revealing internal heating and its ring system. Image Credit: Lawrence Sromovsky, (Univ. Wisconsin-Madison), Keck Observatory
As Uranus speeds in its orbit in the solar system, there are three large space rocks that are in lockstep with the gas giant, according to new simulations. Two of them are wobbling in unstable “horseshoe” orbits near Uranus, while the third is in a more reliable Trojan orbit that is always 60 degrees in front of the planet.
The largest of this small group is the asteroid Crantor, which is 44 miles (70 kilometers) wide. Its horseshoe orbit, and that of companion 2010 EU65, means the space rocks seesaw between being close to Uranus and further away. They should stay in that configuration for a few million years.
The last of the group is 2011 QF99, in a Trojan orbit near one of Uranus’ Lagrangian points — sort of like a celestial parking spot where an object can hang out without undue influence from the balanced gravitational forces.
An artists impression of an asteroid belt(credit: NASA)
The results illustrate the importance of space rocks that are outside of the main asteroid belt between Mars and Jupiter.
There are several kinds of these asteroids (classified by their orbits) that follow around planets in the solar system. Earth itself, for example, has at least one Trojan asteroid.
“Crantor currently moves inside Uranus’ co-orbital region on a complex horseshoe orbit. The motion of this object
is primarily driven by the influence of the Sun and Uranus, although Saturn plays a significant role in destabilizing its orbit,” the authors wrote in their new study.
“Although this object follows a temporary horseshoe orbit, more stable trajectories are possible and we present 2010 EU65 as a long-term horseshoe librator candidate in urgent need of follow-up observations.”
