Posted on by David Dickinson

How Amateur Astronomers Can Help LADEE

An Artist's concept of LADEE in orbit around the Moon. (Credit: NASA Ames).

You can help NASA’s upcoming lunar mission.

NASA’s Lunar Atmosphere and Dust Environment Explorer (LADEE) is slated to lift off from Wallops Island this September 5th in a spectacular night launch. LADEE will be the first mission departing Wallops to venture beyond low Earth orbit. A joint collaboration between NASA’s Goddard Spaceflight Center & the AMES Research Center, LADEE will study the lunar environment from orbit, including its tenuous exosphere.

Scientists hope to answer some long standing questions about the lunar environment with data provided by LADEE. How substantial is the wispy lunar atmosphere?  How common are micro-meteoroid impacts? What was the source of the sky glow recorded by the Surveyor spacecraft and observed by Apollo astronauts before lunar sunrise and after lunar sunset while in orbit?

Glows of the solar corona and crepuscular rays reported by the Apollo 17 astronauts in lunar orbit. (Credit: NASA).
Glows of the solar corona and crepuscular rays reported by the Apollo 17 astronauts in lunar orbit. (Credit: NASA).

The micro-meteoroid issue is of crucial concern for any future long duration human habitation on the Moon. The Apollo missions were only days in length. No one has ever witnessed a lunar sunrise or sunset from the surface of the Moon, as all six landings occurred on the nearside of the Moon in daylight. (Sunrise to sunset on the Moon takes about two Earth weeks!)

And that’s where amateur astronomers come in. LADEE is teaming up with the Association of Lunar & Planetary Observers (ALPO) and their Lunar Meteoritic Impact Search Program in a call to watch for impacts on the Moon. These are recorded as brief flashes on the nighttime side of the Moon, which presents a favorable illumination after last quarter or leading up into first quarter phase.

We wrote recently about a +4th magnitude flash detected of the Moon on March 17th of this year. That explosion was thought to have been caused by a 35 centimetre impactor which may have been associated with the Eta Virginid meteor shower. The impact released an explosive equivalent of five tons of TNT and has set a possible new challenge for Moon Zoo volunteers to search for the resulting 6 metre crater.

An artist's illustration of a meteoroid impact on the Moon. (Credit: NASA).
An artist’s illustration of a meteoroid impact on the Moon. (Credit: NASA).

We’ve also written about amateur efforts to document transient lunar phenomena and studies attempting to pinpoint a possible source of these spurious glows and flashes on the Moon observed over the years.

NASA’s Meteoroid Environment Office is looking for dedicated amateurs to take part in their Lunar Impact Monitoring campaign. Ideally, such an observing station should utilize a telescope with a minimum aperture of 8 inches (20cm) and be able to continuously monitor and track the Moon while it’s above the local horizon. Most micro-meteoroid flashes are too fast and faint to be seen with the naked eye, and thus video recording will be necessary. A typical video configuration for the project is described here. Note the high frame rate and the ability to embed a precise time stamp is required. I’ve actually run WWV radio signals using an AM short wave radio transmitting in the background to accomplish this during occultations.

Finally, you’ll need a program called LunarScan to analyze those videos for evidence of high speed flashes. LunarScan is pretty intuitive. We used the program to analyze video shot during the 2010 Total Lunar Eclipse for any surreptitious Geminid or Ursid meteors.

Brian Cudnik, coordinator of the Lunar Meteoritic Impact Search section of the ALPO, noted in a recent forum post that we’re approaching another optimal window to accomplish these sorts of observations this weekend, with the Moon headed towards last quarter on June 30th.

An example of an impact flash recorded by the Automated & Lunar Meteor Observatory video cameras based at the Marshall Spaceflight Center in Huntsville, Alabama.
An example of an impact flash recorded by the Automated & Lunar Meteor Observatory video cameras based at the Marshall Spaceflight Center in Huntsville, Alabama.

Interestingly, the June Boötids are currently active as well, with historical sporadic rates of anywhere from 10-100 per hour.  In 1975, seismometers left by Apollo astronauts detected series of impacts on June 24th thought to have been caused by one of two Taurid meteor swarms the Earth passes through in late June, another reason to be vigilant this time of year.

Don’t have access to a large telescope or sophisticated video gear? You can still participate and make useful observations.

LADEE is also teaming up with JPL and the Lewis Center for Educational Research to allow students track the spacecraft en route to the Moon. Student groups will be able to remotely access the 34-metre radio telescopes based at Goldstone, California that form part of NASA’s Deep Space Communications Network. Students will be able to perform Doppler measurements during key mission milestones to monitor the position and status of the spacecraft during thruster firings.

And backyard observers can participate in another fashion, using nothing more than their eyes and patience. Meteor streams that are impacting the Moon affect the Earth as well. The International Meteor Organization is always looking for information from dedicated observers in the form of meteor counts. The Perseids, an “Old Faithful” of meteor showers, occurs this year around August 12th under optimal conditions, with the Moon only five days past New. This is also three weeks prior to the launch of LADEE.

Whichever way you choose to participate, be sure to follow the progress of LADEE and our next mission to study Earth’s Moon!

-Listen to Universe Today’s Nancy Atkinson and her interview with Brian Day of the NASA Lunar Science Institute.

-Also listen to the 365 Days of Astronomy interview with Brian Day and Andy Shaner from the Lunar Planetary institute on the upcoming LADEE mission.

Posted on by Bob King

Gesundheit! Hairy And Sneeze-worthy Rings Snare Summer Sun

Billions of aspen seeds float by the sun on tiny hairs creating a multicolored corona around the sun yesterday. To see and photograph the rings, I used a power pole to block the sun. Credit: Bob King

For the past two weeks puffy clumps of seeds have been riding the air in my town. You can’t avoid them. Open a door and they’ll breeze right in. Take a deep breath and you’d better be careful you don’t take a few down the windpipe.

Every June the many aspen trees that call northern Minnesota home release their booty of tiny seeds that parachute through the air on tiny clusters of hairs.  And while they all have no particular place to go, their combined and unintentional effect is to create a series of beautiful colored rings about the Sun called a corona.

A single aspen seed (left) only about 1 mm across embedded in a cottony fluff of tiny hairs. At right is a spider web. Both show colors caused by bending and interference of light, a phenomenon called diffraction. Credit: Bob King (left) and Andrew Kirk
A single aspen seed (left) only about 1 mm across embedded in a cottony fluff of tiny hairs. At right is a spider web. Both show colors caused by bending and interference of light, a phenomenon called diffraction. Credit: Bob King (left) and Andrew Kirk

Reach your hand up to block the Sun and if your eyes can stand the glare of blue-white sky, you’ll see bazillions of tiny flecks a-flying. If you were to capture one and study it up close, you’d see it diffract light in tiny glimmers of chrome green and purple.

When light from the sun or moon strikes a tiny water droplet, speck of pollen or aspen seed hairs, it's scattered in different directions. Some of the scattered waves reinforce each other to make a bright ring of light in the sky while other waves cancel each other out to create a dimmer ring. A series of alternating rings around the sun is called a diffraction pattern or corona. Credit and copyright: Les Cowley www.atoptics.co.uk
When light from the sun or moon strikes a tiny water droplet, speck of pollen or aspen seed hairs, it’s scattered in different directions. Some of the scattered waves reinforce each other to make a bright ring of light in the sky while other waves cancel each other out to create a dimmer ring. A series of alternating rings around the sun is called a diffraction pattern or corona. Credit and copyright: Les Cowley www.atoptics.co.uk

Light is always getting messed with by tiny things. When it comes to aspen seeds, as rays of light – made of every color of the rainbow – bend around the hairy obstacles they interfere with one another like overlapping, expanding wave circles in a pond. Some of the waves reinforce each another and others cancel out. Our eyes see a series of colored fringes that flash about the tiny hairs.

Most halos are circular but pollen halos like this one around the moon often have unusual shapes like this oval with bulging sides and top. Credit: Bob King
Most halos are circular but pollen halos like this one around the moon often have unusual shapes like this oval with bulging sides and top. Credit: Bob King

The exact same thing happens when light has to step around minute water droplets, pollen grains and our hairy aspen fluffs when they’re drift through the air overhead. Overlapping wavelets of light “interfere” with one another to form a series of colorful concentric circles called a solar corona. While the same in name, this corona is an earthly one unrelated to the huge, hot coronal atmosphere that surrounds our star.

Oil-coated water droplets show beautiful diffraction colors for the same reason soap bubbles do. Light reflecting from the bottom surface of the oil film interferes light reflecting from the top of the layer creating fringes of color. Credit: Bob King
Oil-coated water droplets also show beautiful diffraction colors for a similar reason as clouds and pollen do . Light reflecting from the bottom surface of the oil film interferes with light reflecting off the top of the layer to create shifting patterns of color. Credit: Bob King

The ones created by seed hairs and pollen require clear skies and a safe way to block the Sun’s overwhelming light. My filter of choice is the power pole mostly because they’re handy.  Sunglasses help to reduce the glare and eye-watering wincing.

While I can’t be 100% certain the chromatic bullseye was painted by poplar hair deflections – there’s always a chance pollen played a part – I’ve seen similar displays when the seeds have passed this way before.

Iridescent clouds are another form of a corona formed by minute water droplets diffracting light. Credit: Bob King
Iridescent clouds are another form of a corona formed by minute water droplets diffracting light. Credit: Bob King

Coronas created by water droplets in mid-level clouds are much more common, and the familiar “ring around the sun” or solar halo is an entirely different creature. Here, light is bent or refracted through billions of microscopic six-sided ice crystals.

I  figure that if the night is cloudy, the play of light and clouds in the daytime sky often makes for an enjoyable substitute.

Posted on by David Dickinson

Searching for Pluto: A Guide to the 2013 Opposition Season

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.

Wide Field
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.

Medium field
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.

Small field
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.

Narrow field
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!

Posted on by Shannon Hall

Behind the Scenes at Kitt Peak Observatory: What is an Observing Run Really Like?

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)
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.
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.
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.

Posted on by David Dickinson

Will Comet ISON Dazzle our Skies? An Expert Weighs In

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).
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).
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.

Posted on by David Dickinson

Catch the Moon pairing with Mercury & Venus Tonight

Looking west at sunset from latitude 30 degrees north. The ecliptic and Mercury's orbit along with a 10 degree field of view outlined for reference. All graphics created by the author using Starry Night).

If you’ve never seen Mercury, this week is a great time to try.

Over the past few weeks, observers worldwide have been following the outstanding tight triple conjunction of Mercury, Venus and Jupiter low to the west at dusk.

Jupiter has exited the evening sky, headed for conjunction with the Sun on June 19th. I caught what was probably our last glimpse of Jupiter for the season clinging to the murky horizon through binoculars just last week. If you’re “Jonesin’ for Jove,” you can follow its progress this week through superior conjunction as it transits the Solar Heliospheric Observatory’s LASCO C3 camera.

This leaves the two innermost worlds of our fair solar system visible low to the west at dusk. And tonight, they’re joined by a very slender waxing crescent Moon, just over two days after New phase.

The Moon, Venus and Mercury as seen from 30 degrees north tonight at 9PM EDT.
The Moon, Venus and Mercury as seen from 30 degrees north tonight at 9PM EDT.

The evening of June 10th finds a 4% illuminated Moon passing just over 5 degrees (about 10 Full Moon diameters) south of Venus and Mercury. Venus will be the first to appear as the sky darkens, shining at magnitude -3.9 and Mercury will shine about 40 times fainter above it at magnitude +0.3.

Ashen light, also known as Earthshine will also be apparent on the darkened limb of the Moon. Another old-time term for this phenomenon is “the Old Moon in the New Moon’s Arms.” Ashen light is caused by sunlight being reflected off of the Earth and illuminating the nighttime Earthward facing portion of the Moon. Just how prominent this effect appears can vary depending on the total amount of cloud cover on the Earth’s Moonward facing side.

....and the orientation of the Moon, Mercury and Venus on the night of June 12th and ~9PM EDT.
….and the orientation of the Moon, Mercury and Venus on the night of June 12th and ~9PM EDT.

This week sets the stage for the best dusk apparition of Mercury for northern hemisphere viewers in 2013. Orbiting the Sun every 88 Earth days, we see Mercury either favorably placed east of the Sun in the dusk sky or west of the Sun in the dawn sky roughly six times a year. Mercury’s orbit is markedly elliptical, and thus not all apparitions are created the same. An elongation near perihelion, when Mercury is 46 million kilometers from the Sun, can mean its only 17.9 degrees away from the Sun as viewed from the Earth. An elongation near aphelion, 69.8 million kilometers distant, has a maximum angular separation of 27.8 degrees.

This week’s greatest elongation of 24.3 degrees occurs on June 12th. It’s not the most extreme value for 2013, but does have another factor going for it; the angle of the ecliptic. As we approach the solstice of June 21st, the plane of the solar system as traced out by the orbit of the Earth is at a favorable angle relative to the horizon. Thus, an observer from 35 degrees north latitude sees Mercury 18.4 degrees above the horizon at sunset, while an observer at a similar latitude in the southern hemisphere only sees it slightly lower at 16.9 degrees.

Venus and the Moon make great guides to locate Mercury over the next few nights. It’s said that Copernicus himself never saw Mercury with his own eyes, though this oft repeated tale is probably apocryphal.

We also get a shot at a skewed “emoticon conjunction” tonight, not quite a “smiley face” (: as occurred between Jupiter, Venus and the Moon in 2008, but more of a “? :” Stick around until February 13th, 2056 and you’ll see a much tighter version of the same thing! A time exposure of a pass of the International Space Station placed near Mercury and Venus could result in a planetary “meh” conjunction akin to a “/:” Hey, just throwing that obscure challenge out there. Sure, there’s no scientific value to such alignments, except as testimony that the universe may just have a skewed sense of humor…

Through the telescope, Venus currently shows a 10” diameter gibbous phase, while Mercury is only slightly smaller at 8” and is just under half illuminated. No detail can be discerned on either world, as a backyard telescope will give you the same blank view of both worlds that vexed astronomers for centuries. These worlds had to await the dawn of the space age to give up their secrets. NASA’s MESSENGER spacecraft entered a permanent orbit around Mercury in 2011, and continues to return some outstanding science.

Both planets are catching up to us from the far side of their orbits. Mercury will pass within 2 degrees of Venus on June 20th, making for a fine wide field view in binoculars.

And now for the wow factor of what you’re seeing tonight. The Moon just passed apogee on June 9th and is currently about 416,500 kilometers or just over one light second distant. Mercury meanwhile, is 0.86 astronomical units (A.U.), or almost 133 million kilometers, or about 7 light minutes away. Finally, Venus is currently farther away from the Earth than the Sun at 1.59 A.U.s, or about 13.7 light minutes distant.

All this makes for a great show in the dusk skies this week. And yes, lunar apogee just after New sets us up for the closest Full Moon of 2013 (aka the internet sensation known as the “Super Moon”) on June 23rd. More to come on that soon!

 

Posted on by David Dickinson

Recurrent Novae, Light Echoes, and the Mystery of T Pyxidis

A sequence of images showing the light echo (circled) enshrouding T Pyxidis months after the April 2011 outburst. (Credit: NASA/ESA/A. Crotts/J. Sokoloski, H. Uthas & S. Lawrence).

Some of the most violent events in our Universe were the topic of discussion this morning at the 222nd meeting of the American Astronomical Society in Indianapolis, Indiana as researchers revealed recent observations of light echoes seen as the result of stellar explosions.

A light echo occurs when we see dust and ejected material illuminated by a brilliant nova. A similar phenomenon results in what is termed as a reflection nebula. A star is said to go nova when a white dwarf star siphons off material from a companion star. This accumulated hydrogen builds up under terrific pressure, sparking a brief outburst of nuclear fusion.

A very special and rare case is a class of cataclysmic variables known as recurrent novae. Less than dozen of these types of stars are known of in our galaxy, and the most famous and bizarre case is that of T Pyxidis.

Located in the southern constellation of Pyxis, T Pyxidis generally hovers around +15th magnitude, a faint target even in a large backyard telescope. It has been prone, however, to great outbursts approaching naked eye brightness roughly every 20 years to magnitude +6.4. That’s a change in brightness almost 4,000-fold.

But the mystery has only deepened surrounding this star. Eight outbursts were monitored by astronomers from 1890 to 1966, and then… nothing. For decades, T Pyxidis was silent. Speculation shifted from when T Pyxidis would pop to why this star was suddenly undergoing a lengthy phase of silence.

Could models for recurrent novae be in need of an overhaul?

T Pyxidis finally answered astronomers’ questions in 2011, undergoing its first outburst in 45 years. And this time, they had the Hubble Space Telescope on hand to witness the event.

Light curve of the 2011 eruption of T Pyxidis. (Credit: AAVSO).
Light curve of the 2011 eruption of T Pyxidis. (Credit: AAVSO).

In fact, Hubble had just been refurbished during the final visit of the space shuttle Atlantis to the orbiting observatory in 2009 on STS-125 with the installation of its Wide Field Camera 3, which was used to monitor the outburst of T Pyxidis.

The Hubble observation of the light echo provided some surprises for astronomers as well.

“We fully expected this to be a spherical shell,” Said Columbia University’s Arlin Crotts, referring to the ejecta in the vicinity of the star. “This observation shows it is a disk, and it is populated with fast-moving ejecta from previous outbursts.”

Indeed, this discovery raises some exciting possibilities, such as providing researchers with the ability to map the anatomy of previous outbursts from the star as the light echo evolves and illuminates the 3-D interior of the disk like a Chinese lantern. The disk is inclined about 30 degrees to our line of sight, and researchers suggest that the companion star may play a role in the molding of its structure from a sphere into a disk. The disk of material surrounding T Pyxidis is huge, about 1 light year across. This results in an apparent ring diameter of 6 arc seconds (about 1/8th the apparent size of Jupiter at opposition) as seen from our Earthly vantage point.

Paradoxically, light echoes can appear to move at superluminal speeds. This illusion is a result of the geometry of the path that the light takes to reach the observer, crossing similar distances but arriving at different times.

And speaking of distance, measurement of the light echoes has given astronomers another surprise. T Pyxidis is located about 15,500 light years distant, at the higher 10% end of the previous 6,500-16,000 light year estimated range. This means that T Pyxidis is an intrinsically bright object, and its outbursts are even more energetic than thought.

Light echoes have been studied surrounding other novae, but this has been the first time that scientists have been able to map them extensively in 3 dimensions.

An artist's conception of the disk of material surrounding T Pyxidis. (Credit: ESA/NASA & A. Feild STScl/AURA).
An artist’s conception of the disk of material surrounding T Pyxidis. (Credit: ESA/NASA & A. Feild STScl/AURA).

“We’ve all seen how light from fireworks shells during the grand finale will light up the smoke and soot from the shells earlier in the show,” said team member Stephen Lawrence of Hofstra University. “In an analogous way, we’re using light from T Pyx’s latest outburst and its propagation at the speed of light to dissect its fireworks displays from decades past.”

Researchers also told Universe Today of the role which amateur astronomers have played in monitoring these outbursts. Only so much “scope time” exists, very little of which can be allocated exclusively to the study of  light echoes. Amateurs and members of the American Association of Variable Star Observers (AAVSO) are often the first to alert the pros that an outburst is underway. A famous example of this occurred in 2010, when Florida-based backyard observer Barbara Harris was the first to spot an outburst from recurrent novae U Scorpii.

And although T Pyxidis may now be dormant for the next few decades, there are several other recurrent novae worth continued scrutiny:

Name Max brightness Right Ascension Declination Last Eruption Period(years)
U Scorpii +7.5 16H 22’ 31” -17° 52’ 43” 2010 10
T Pyxidis +6.4 9H 04’ 42” -32° 22’ 48” 2011 20
RS Ophiuchi +4.8 17H 50’ 13” -6° 42’ 28” 2006 10-20
T Coronae Borealis +2.5 15H 59’ 30” 25° 55’ 13” 1946 80?
WZ Sagittae +7.0 20H 07’ 37” +17° 42’ 15” 2001 30

 

Clearly, recurrent novae have a tale to tell us of the role they play in the cosmos. Congrats to Lawrence and team on the discovery… keep an eye out from future fireworks from this rare class of star!

Read the original NASA press release and more on T Pyxidis here.

 

Posted on by David Dickinson

Getting Ready for “ISS All-Nighters” in June

The International Space Station as seen from the crew of STS-119. (Credit: NASA).

Never seen the International Space Station before? Now is a good time to try, as we enter into a very special time of year.

Starting at 12:30 Universal Time/8:30 AM EDT on Monday, June 3rd, the ISS will enter a phase of permanent illumination throughout the length of its orbit. The station will remain in sunlight and will not experience an orbital sunset until five days later, when it briefly dips into the Earth’s shadow on June 8th at 11:50 UT/ 7:50 AM EDT.

This sets us up for a wealth of visible passes worldwide. This unique phenomenon occurs as a product of the station’s highly inclined orbit. Tilted at 51.6° with respect to the Earth’s equator, its orbit can be oriented roughly perpendicular to the Sun within a few weeks of either solstice.

But whereas the December solstice favors multiple summer sightings for the southern hemisphere, the season near the  June solstice (which occurs this year on June 21st) favors northern latitudes. In fact, observers in the UK, southern Canada and the northern United States will be able to see multiple ISS passes in one night over the next week. Note that the ISS is nearly in full illumination now, and will remain so well into mid-June.

So, why was the ISS put into such a highly inclined orbit?

This orientation enables international partners to have access to the station from launch complexes worldwide. Whereas the shuttle launched on construction flights from Cape Canaveral at 28.5° north latitude, the Progress and crewed Soyuz missions depart from the Baikonur Cosmodrome in Kazakhstan located at 46° north. This resulted in some dramatic launches from the US Florida Space Coast, as the shuttle chased the ISS up the US Eastern Seaboard and was often visible minutes later crossing over the UK.

Though born of practicality, this happy circumstance also means that the ISS is visible to a wide swath of humanity located from 60° north latitude to 60° south. Only locales such as Antarctica, Greenland, and Iceland miss out.

I’m often asked how I know a moving star is a satellite and not an airplane. Aircraft flash, generating their own light, while satellites shine by reflected sunlight. This means that there’s a window of about an hour after sunset or before local sunrise that objects in low Earth orbit are still illuminated high overhead. In the early morning hours, if often seems as if someone has just “flipped on a switch” and satellites suddenly become visible across the sky.

And yes, satellites can flash as well, but in most instances, this is due to tumbling or the observer catching a glint of sunlight off of a reflective panel or surface just right. The Iridium constellation of satellites is known for this effect, but the ISS and Hubble Space Telescope can also flare in this fashion as well.

At 108.5 x 72.8 metres in size, the ISS is the largest man made object ever constructed in Earth orbit. Its unmistakable to spot as it passes overhead, shining at a maximum illumination brighter than the planet Venus at magnitude -5.2 when 100% illuminated.

Note the time the ISS is passing over your location and the direction its coming from and just start watching, no equipment required. It’s really as simple as that. Many prediction platforms exist for ISS passes. I’ve used Heavens-Above for over a decade now to spot ISS passes worldwide. Probably the simplest tracker out there is provided by Spaceweather. Just enter in your postal code and it kicks out an easy to decipher prediction. NASA also has a “Sighting Opportunities” webpage where you can choose your country and city to find out when the ISS will be passing over your location.

More advanced satellite trackers many want to check out CALSky which can also provide a list of transits of the ISS in front of the Sun or Moon from your location. I’ve managed to catch one each from my backyard utilizing it. I also like to use a free satellite tracking program known as Orbitron, which can be run on a laptop in the field away from an Internet connection.

Screenshot of the ISS orbital pass during full illumination next week. (Credit: Orbitron).
Screenshot of the ISS orbital pass during full illumination next week. (Credit: Orbitron).

Photographing a pass of the ISS is easy. Just do a wide field exposure with a DSLR camera on a tripod for 10-30 seconds and you’ll get a picture of the ISS streaking across the starry background. Be sure to use manual mode and either set the focus to infinity or focus on something bright such as Venus just prior to the pass. I generally take a series of test exposures prior to get the combination of ISO/f-stop settings correct for the current sky conditions.

A 20 second exposure of the ISS during a July 4th fireworks show in 2011. (Photo by Author).
A 20 second exposure of the ISS during a July 4th fireworks show in 2011. (Photo by Author).

I can just make out structure on the ISS with binoculars as it passes overhead. This appearance can vary greatly depending on its orientation. Sometimes, it looks like a close binary star. Other times it can appear box-shaped. Occasionally, it looks like a tiny luminous Star Wars TIE-fighter!

The ISS as imaged by Mike Weasner. Credit: The Cassiopeia Observatory).
The ISS as imaged by Mike Weasner. Credit: The Cassiopeia Observatory).

The station managers typically orient the huge solar arrays to provide a small amount of artificial shadow during phases of full illumination. The ISS extends ~45” across at closest approach, similar in apparent diameter to Saturn including its ring system.

You can even image the ISS through a telescope, with a little skill and luck. Many sophisticated mounts will track the ISS as it crosses the sky, or you can use our own low-tech method;

Be sure to check out an ISS pass coming to a sky near you!

Posted on by Bob King

Noctilucent Clouds – Electric-Blue Visitors From The Twilight Zone

Noctilucent cloud display taken around midnight May 30 near Kendal Castle in northern England by Stuart Atkinson. "Beautiful display, better than all last year's pathetic displays combined - and the season has just started!" said Atkinson

Every year at this time I add a new item to my list of what to watch for in the night sky. Oddly enough, it’s clouds. I must be nuts, right? What astronomer needs more clouds? But these are different. Called noctilucent clouds (NLCs), these skittish objects are visible now and again low in the northern sky during morning and evening twilight. Late May through August is the best time to see them.

What are these wispy, sometimes eerie clouds? And how can you see them?

First a caveat. If you live in Mississippi your chances of spotting them are slimmer than a string bean. Uncommon to begin with, NLCs are typically visible at higher latitudes;  the northern U.S., Canada and Europe are prime outposts for an NLC vigil.

Noctilucent clouds, which form about 50 miles high in the chilly mesophere, lie high above the common clouds that form in the troposphere. photographed from the International Space Station. Credit: NASA
Noctilucent clouds, which form about 50 miles (80 km) high in the chilly mesosphere, lie high far above the troposphere, home to the more familiar clouds. Photo taken from the International Space Station. Credit: NASA

NLCs hole up in Earth’s mesosphere, a rarefied blanket of air extending from 30 to 53 miles (48-85 km) high. Most of the meteors we see burn up in this layer. It’s also extremely cold up there with temperatures at the top dropping to a teeth-rattling -130 F (-90 C). Because of their great height, noctilucent clouds reflect sunlight long after sunset when other clouds have gone gray and colorless. Their color is imparted by the ozone layer located 12-19 miles (19-30 km) overhead. The reds and oranges of reflected sunlight are absorbed by ozone on their way down to our eyes, tinting the clouds blue.

Cirrus clouds often look like fine streaks compared to the pleated, wavy appearance of NLCs. Credit: Bob King
Cirrus clouds often look like fine streaks compared to the pleated, wavy appearance of NLCs. This photo also demonstrates the difference in their altitudes during a typical display across the northern U.S. Credit: Bob King

For any cloud to take shape and grow, water needs to stick to something. In day-to-day clouds, dust from wind storms – especially from the world’s deserts – supplies the necessary “nuclei” for the formation of water droplets and ice crystals.

Cirrus clouds, the ones that look like feathers wafting across the daytime sky, are typically about 10 miles high. Composed of ice crystals, they float near the top of the lowest, thickest layer of air called the troposphere. Noctilucent clouds share the realm of the Greek gods, basking in sunlight well into the night at an altitude of some 50 miles. That’s nearly as high as the aurora borealis, which can shimmy down to a scant 60 miles.

We see noctilucent clouds well after sunset when other clouds have gone dark because they're much higher up and can still catch sunlight and reflect it back to Earth. Credit: NASA
We see noctilucent clouds well after sunset when other clouds have gone dark because they’re much higher up and still able to catch sunlight and reflect it back to Earth. Credit: NASA

Since it’s next to impossible to get dust up high enough to provide nuclei for noctilucent cloud formation, scientists suspect outer space dust from meteoroids and comets provide  some of the necessary material. As Earth travels around the sun, it sweeps up some 40,000 tons of interplanetary dust a year, plenty to get the job done. Other sources include volcanic dust and even chemical residues from rocket exhaust from the once-frequent launches of the space shuttle.

Winds from summer storms carry the water vapor into the mesosphere from the lower atmosphere which condenses on terrestrial and extraterrestrial dust nuclei. That’s why NLC displays are most frequent in summer.

Waves of NLCs on June 12, 2012 seen from Duluth, Minn. Credit: Bob King
Waves of NLCs on June 12, 2012 seen from Duluth, Minn. Credit: Bob King

Here in Duluth, Minn. at 47 degrees north I’ve seen probably half a dozen displays in years of sky watching, but to be honest, I only started looking for them in a dedicated way in the last 5 years. As late May approaches and twilight stretches deep into the evening hours, I scan the sky hoping for their return. The key to spotting NLCs  is to find a place with a wide-open view of the northern horizon.

In the north, the sun retires around 9 p.m. and twilight ends more than two hours later. Watch for NLCs starting about  an hour after sunset when cirrus clouds have turned pale gray and the stars begin to come out. From my home, they typically  hover between 5 and 10 degrees (about a fist held at arm’s length or less) high above the northern horizon. The clouds make their first appearance at the upper end of that range, but as dusk deepens, they shrink back toward the horizon.


Video of NLCs from the Science Photo Library

NLCs look WEIRD. It’s not only their telltale eerie, plasma-blue coloration but their form that gives them away. Stripes, undulations, curls, streaks are mixed together in a way that seems alien. You might expect these on Mars maybe, but Earth? Binoculars are a huge help in appreciating the clouds’ peculiar textures and color. I say this because I’ve forgotten mine on several occasions.  Two other dead giveaways – NLCs will grow brighter for a time as the sky grows darker. Regular clouds behave the opposite. NLCs also move and change shape very slowly because they’re so high up and far away.

Looking down from above, AIM captured this composite image of the noctilucent cloud cover above the Southern Pole on December 31, 2009. Credit: NASA/HU/VT/CU LASP
Looking down from above, the Aeronomy of Ice in the Mesosphere (AIM) Mission captured this composite image of noctilucent cloud cover above the South Pole on December 31, 2009. Click to read more about AIM. Credit: NASA/HU/VT/CU LASP

Night-shining clouds remain aglow until nearly twilight’s end. The cut-off viewing time for the northern U.S. is about 2 hours after sunset or earlier if the mosquitos have their way. By then the sun drops too far below the horizon to provide the light to sustain them. Those living farther north in Canada, northern Ireland, England and Finland, where  the sky is never truly dark during the early summer months, can enjoy NLC viewing all night.

Dawn display of electric NLCs on June 13, 2012. Credit: Bob King
Dawn display with stars of electric-blue NLCs on June 13, 2012. Credit: Bob King

There are indications that NLC displays are becoming more common, even pushing into lower latitudes in the past 20-30 years. It might have to do with increased levels of carbon dioxide in Earth’s atmosphere. While CO2 helps to warm the lower air layers, it can can cause the upper atmosphere to grow chillier, creating the cold conditions necessary for accelerated noctilucent cloud formation. You can dig deeper into the topic HERE.

For more about Earth’s most unusual clouds, stop by the Noctilucent Cloud Observers’ Homepage. Like the northern lights, a thrilling noctilucent cloud display is a quest worth a trip to the north country.

Posted on by David Dickinson

How to Spot Near-Earth Asteroid 1998 QE2 This Week

1998 QE2 on closest approach to Earth this Friday on May 31st. (Credit: NASA/JPL-Caltech).

A large asteroid visits our fair corner of the solar system this week, and with a little planning you may just be able to spot it.

Near Earth Asteroid (NEA) 285263 (1998 QE2) will pass 5.8 million kilometres from the Earth on Friday, May 31st at 20:59 Universal Time (UT) or 4:59PM EDT. Discovered in 1998 during the LIncoln Near-Earth Asteroid Research (LINEAR) sky survey looking for such objects, 1998 QE2 will shine at magnitude +10 to +12 on closest approach. Estimates of its size vary from 1.3 to 2.9 kilometres, with observations by the Spitzer Space Telescope in 2010 placing the ballpark figure towards the high end of the scale at 2.7 kilometres in diameter.

1998 QE2 would fit nicely with room to spare in Oregon’s 8 kilometre-wide Crater Lake.

Though this passage is over 15 times as distant as the Earth’s Moon, the relative size of this space rock makes it of interest. This is the closest approach of 1998 QE2 for this century, and there are plans to study it with both the Arecibo and Goldstone radio telescopes to get a better description of its size and rotation as it sails by. Expect to see radar maps of 1998 QE2 by this weekend.

“Asteroid 1998 QE2 will be an outstanding radar imaging target… we expect to obtain a series of high-resolution images that could reveal a wealth of surface features,” said astronomer and principal JPL investigator Lance Benner.

A recent animation of 1998 QE2 from earlier this month. (Credit: Nick Howes & Ernesto Guido).
A recent animation of 1998 QE2 from earlier this month.
(Credit: Nick Howes & Ernesto Guido).

An Amor-class asteroid, 1998 QE2 has an orbit of 3.77 years that takes it from the asteroid belt between Mars and Jupiter to just exterior of the Earth’s orbit. 1998 QE2 currently comes back around to our vicinity roughly every 15 years, completing about 4 orbits as it does so. Its perihelion exterior to our own makes it no threat to the Earth. This week’s passage is the closest for 1998 QE2 until a slightly closer pass on 0.038 Astronomical Units on May 27th, 2221. Note that on both years, the Earth is just over a month from aphelion (its farthest point from the Sun) which falls in early July.

Of course, the “QE2” designation has resulted in the inevitable comparisons to the size of the asteroid in relation to the Queen Elizabeth II cruise liner. Asteroid designations are derived from the sequence in which they were discovered in a given year. 1998 QE2 was the 55th asteroid discovered in the period running from August 1st to 16th 1998.

Perhaps we could start measuring asteroids in new and creative units, such as “Death Stars” or “Battlestars?”

But the good news is, you can search for 1998 QE2 starting tonight. The asteroid is currently at +12th magnitude in the constellation Centaurus and will be cruising through Hydra on its way north into Libra Friday on May 31st. You’ll need a telescope to track the asteroid as it will never top +10th magnitude, which is the general threshold for binocular viewing under dark skies. Its relative southern declination at closest approach means that 1998 QE2 will be best observed from northern latitudes of +35° southward. The farther south you are, the higher it will be placed in the sky after dusk.

A wide field view of the passage of 1998 QE2 this week, from May 27th through June 2nd. (Created by the author in Starry Night).
A wide field view of the passage of 1998 QE2 this week, from May 27th through June 2nd. (Created by the author in Starry Night).

Still, if you can spot the constellation Libra, it’s worth a try. Many observers in the southern U.S. fail to realize that southern hemisphere sites like Omega Centauri in the constellation Centaurus are visible in the evening low to the south at this time of year. Libra sits on the meridian at local midnight due south for northern hemisphere observers, making it a good time to try for the tiny asteroid.

Visually, 1998 QE2 will look like a tiny, star-like point in the eye-piece of a telescope. Use low power and sketch or photograph the field of view and compare the positions of objects about 10 minutes apart. Has anything moved? We caught sight of asteroid 4179 Toutatis last year using this method.

A closeup look at the passage of 1998 QE2, covering a 48 hour span centered on closest approach on May 31st. (Created by the author in Starry Night).
A closeup look at the passage of 1998 QE2, covering a 48 hour span centered on closest approach on May 31st. (Created by the author in Starry Night).

1998 QE2 will also pass near some interesting objects that will serve as good “guideposts” to track its progress.

We find the asteroid about 5° north of the bright +2.5 magnitude star Iota Centauri on the night of May 28th. It then crosses the border into the constellation Hydra about 6° south of the +3 magnitude star Gamma Hydrae (Star Trek fans will recall that this star lies in the Neutral Zone) on May 29th. Keep a careful eye on 1998 QE2 as it passes within 30’ (about the diameter of a Full Moon) of the +8th magnitude galaxy Messier 83 centered on May 28th at 19:00 UT/3:00 PM EDT. This will provide a fine opportunity to construct a stop-motion animated .gif of the asteroid passing by the galaxy.

Another good opportunity to pinpoint the asteroid comes on the night on Thursday, May 30th as it passes within 30’ of the +3.3 magnitude star Pi  Hydrae.

From there, it’s on to closest approach day. 1998 QE2 crosses into the constellation Libra early on Friday May 31st. The Moon will be at Last Quarter phase and won’t rise until well past local midnight, aiding in your quest.

At its closest approach, 1998 QE2 have an apparent motion of about 1 angular degree every 3 hours, or about 2/3rds the diameter of a Full Moon every hour. This isn’t quite fast enough to see in real time like asteroid 2012 DA14 was earlier this year, but you should notice its motion after about 10 minutes at medium power. Passing at ~465 Earth diameters distant, 1998 QE2 will show a maximum parallax displacement of just a little over 7 arc minutes at closest approach.

For telescopes equipped with setting circles, knowing the asteroid’s precise position is crucial. This allows you to aim at a fixed position just ahead of its path and “ambush” it as it drifts by. For the most precise positions in right ascension and declination, be sure to check out JPL’s ephemeris generator for 1998 QE2.

After its closest passage, 1998 QE2 will pass between the +3.3 & +2.7 magnitude stars Brachium (Sigma Librae) and Zubenelgenubi (Alpha Librae) around 4:00 UT on June 1st. Dedicated observers can continue to follow its northeastward trek into early June.

Slooh will also be carrying the passage of 1998 QE2 on Friday, May 31st starting at 5:00 PM EDT/21:00 UT.

Of course, the hypothetical impact of a space rock the size of 1998 QE2 would spell a very bad day for the Earth. The Chicxulub impact basin off of the Yucatán Peninsula was formed by a 10 kilometre impactor about 4 times larger than 1998 QE2 about 65 million years ago. We can be thankful that 1998 QE2 isn’t headed our way as we watch it drift silently by this week. Hey, unlike the dinosaurs, WE have a space program…   perhaps, to paraphrase science fiction author Larry Niven, we can hear the asteroid whisper as we track its progress across the night sky, asking humanity “How’s that space program coming along?”