“New” Comet Blues – Comet McNaught Falls Short

We should have known better. Early predictions called for Comet 2009 R1 (McNaught) to get as bright as 2nd magnitude. As recently as 2 weeks ago, I posted that it was on pace to reach magnitude 3.5 to 4.0. Now even that fainter magnitude was too bright. For the past 2+ weeks the comet has failed to brighten as seen from Earth. The plot below shows a fit (red line) to visual observations from early April to June 10. If the comet had continued to brighten at that rate it would be brighter than magnitude 4 by now. The blue curve is a fit to observations since June 10 and shows a comet that is at its peak and may even fade a little before reaching perihelion.

Apparent visual lightcurve for Comet C/2009 R1 (McNaught). Visual observations from the ICQ/CSC, COBS, CometObs. Created with Seiichi Yoshida's COMET program. Credit: Carl Hergenrother.

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How can the comet fade before reaching perihelion? The next plot shows how we can more accurately measure the brightness behavior of a comet. First the comets magnitude is normalized to a distance of 1 AU from Earth and to a phase angle of 0 degrees. Normalization to a geocentric distance of 1 AU is done by subtracting 5 log (Δ) from the magnitude, where Δ is the distance from Earth in AU at the time of the observations. Normalization to 0 degrees phase angle is done with Joseph Marcus’ function for dust scattering. I’m not going to go into any more detail on the Marcus function but interested readers will find it in the journal International Comet Quarterly, Vol. 29, No. 4.

The lightcurve shows a comet brightening at a normal and healthy rate until the comet reached a distance of 0.7-0.8 AU from the Sun. A brightening rate of 9.0 log r is in the ballpark for a long-period comet like McNaught. (Note, I discarded a few April observations from the fit because they seem to be a few magnitudes to faint. At this preliminary stage, their exclusion produces a more realistic fit to the April/May/early June data.) Sunward of ~0.7-0.8 AU the comet’s brightening slows considerable.

Heliocentric lightcurve for Comet C/2009 R1 (McNaught) normalized to 1 AU from Earth and o deg phase angle. Visual observations from the ICQ/CSC, COBS, CometObs. Credit: Carl Hergenrother.

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Another way to plot the data for McNaught suggests that the comet is producing less gas and dust and in an absolute sense has been fading for 2 weeks now. The below plot is not only normalized to 1 AU from the Earth and to o degrees phase angle but also to 1 AU from the Sun. In this case a 5 log (r) term is subtracted from the visual magnitude in addition to the 2 normalization terms mentioned above. An object that was releasing a constant amount of gas and dust would have a horizontal line with no slope on the plot, an object releasing more gas/dust as it approached the Sun would show a positive slope (line going up and to the right) while an object releasing less gas/dust would have a negative slope (line going down and to the right). For some reason Comet McNaught saw its gas/dust production start to decrease after reaching a distance of 0.7-0.8 AU from the Sun, or roughly around the date of June 10.

Heliocentric lightcurve for Comet C/2009 R1 (McNaught) normalized to 1 AU from Sun and Earth and o deg phase angle. Visual observations from the ICQ/CSC, COBS, CometObs. Credit: Carl Hergenrother.

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Extrapolating the latest brightness trends gives us a better idea of where the comet stands when compared to other comets that had perihelia of ~0.4 AU.

Peak absolute magnitude (near perihelion) of long-period and Halley-type comets. Credit: Carl Hergenrother.

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So what’s happening to Comet McNaught? The comet is a dynamically “new” comet. In layman’s terms the comet is on its first pass through the inner Solar System after spending the past 4.5 billion years in deep freeze in the outer reaches of the Solar System. We can tell this by its orbit which is nearly parabolic. The early brightness was due to very volatile ices which sublimate at low temperatures. These very volatile ices have now been depleted and the comet is relying on the usual assortment of cometary ices (water ice, carbon monoxide, etc.) to drive the creation of a coma and tail. So in a way, the comet faked us out by acting bigger and brighter than it really was.

“New” comets have been seen before and they have disappointed before. The most famous was Comet Kouhotek in 1973/74. Back in my early years of comet observing, C/1989 X1 (Austin) was predicted to be a bright comet. I even remember an issue of Sky and Telescope magazine with a cover tagline of “Monster Comet Coming”. As the lightcurve below shows, the comet brightened normally until it was about 1.2 AU from the Sun. After that the comet’s dust/gas production decreased even though perihelion was at a small distance of 0.35 AU. Rather than a brilliant naked eye comet, Austin was a 5th magnitude fuzzball even though it passed much closer to Earth than Comet McNaught ever will.

As for the future of Comet McNaught, it will poorly visible very close to the horizon for the next week or so. After that the comet will be forever invisible to northern observers. Perhaps observers in the southern hemisphere will get a shot at a rapidly fading McNaught in a few months. After that the comet will probably never be seen again. Its current orbit is hyperbolic which means the comet will be ejected from the Solar System never to return.

Heliocentric lightcurve for Comet C/1989 X1 (Austin). Visual observations from the ICQ. Credit: Carl Hergenrother.

Tonight’s Comet McNaught Finder Charts

The comet is still an easier (easier being a relative term) object to see in the morning sky. It also helps to live further north. In fact, it is impossible to see the comet south of the equator.

The comet is still in northern Auriga a few degrees to the east of the 0th magnitude star Capella. For observers requiring a better, fainter star chart, try this one.

Finder chart for finding Comet C/2009 R1 on the evening of June 26 and morning of June 24. Created with Stellarium.

Finding Comet McNaught Tonight (June 23/24)

Comet C/2009 R1 (McNaught) is still 2 weeks from perihelion (its closest approach to the Sun). Unfortunately it has become a difficult object to see as it is located very close to the northwest horizon in evening twilight and close to the northeast horizon in morning twilight. Also not helping is the fact that the comet’s brightening trend has stalled for the past 2 weeks at magnitude 5.0 to 5.5. More on that later today when I present another analysis of its lightcurve.

Last night I woke up early in the morning and attempted to observe the comet. Luckily for me the comet rose above the mountains right between 2 trees to the northeast of my house. Though visible in 10×50 binoculars, the comet was only slightly fuzzy and I probably would not have recognized it as a comet if I wasn’t already looking for it. At magnitude ~5.5 it might have been visible as a faint star to observers under very dark skies.

Below are rough finder charts for finding the comet this evening and morning. Though visible in the evening, the comet is easier (relatively) to see in the morning sky. Regardless of morning or evening, you will need an unobstructed view of the horizon. Also binoculars or a telescope will help. If you are lucky enough to live where it is very dark, then you might see if with just your eye. In that case the comet will appear as a faint star. In small binoculars, the comet will appear as a slightly fuzzy star (though under dark skies a tail may be visible). With larger binoculars or in a telescope the comet should be an obvious blue-green “fuzz ball” with a faint tail extending away from the horizon. Try using the bright 0th magnitude star Capella as a guide to where to find the comet. For observers requiring a better, fainter star chart, try this one.

Finder chart for finding Comet C/2009 R1 on the evening of June 23 and morning of June 24. Created with Stellarium.

The Latest on Comet McNaught

Comet 2009 R1 (McNaught) is the center of attention in the early dawn sky. The 5th magnitude comet is brightening as it plunges toward the Sun. Though not an impressive sight to the naked eye or in small binoculars, observers with large binoculars and telescopes (or dark skies) will be well rewarded.

I’ve been able to observe the comet a few times over the past few nights. On Monday morning I drove to the outskirts of Tucson to get a glimpse of the comet under dark skies. Though the sky is dark enough so the Milky Way is bright and distinct, the comet was just barely visible to the naked eye. Even then it appeared as nothing more than a faint star where one shouldn’t be. Based on that observation I put its brightness at magnitude +5.3.

In small 10×50 binoculars, the comet was a small fuzz not much bigger than the stars around it. The coma is only ~6 arc minutes across in the 10x50s so this is not a large comet. The gas tail was about a degree in length but was very faint and barely noticeable.

It took my giant 30×125 binoculars to really show the comet in all its glory. The coma (or head) of the comet was a brilliant blue-green. The color being due to the fluorescence of cyanogen (CN) and diatomic carbon (C2) in the comet’s atmosphere. The faint gas tail extended for over 2 degrees. Even a short 0.3 degree dust tail was visible. Interestingly this comet doesn’t show much yellow coloring which is the color of dust (really the color of the Sun reflecting off the dust). The lack of dust makes it a dust-poor or, conversely, a gas-rich comet.

The comet is currently 0.61 AU from the Sun and 1.14 AU from Earth. In 2 weeks it will be at perihelion and only 0.41 AU from the Sun though at a more distance 1.30 AU from Earth. There have been some published reports that the comet will become a brilliant object at 2nd magnitude. Unless there is an unexpected outburst the comet will not get that bright. Based on brightness measurements over the past few months, the comet is on track to peak at a magnitude of 3.5 to 4.0 (see figure below).

Unfortunately the comet will also be dropping closer and closer to the Sun. Even though 3rd magnitude is rather bright for a comet, its close location relative to the Sun will make it very difficult to observe. Most observers will be unable to observe the comet in another week or so, if not already. Even from my dark sky location, the mountains to the north of Tucson are already making it difficult to see the comet before the start of dawn.

Apparent magnitude estimates for Comet 2009 R1 (McNaught) up till June 15. Created with Seiichi Yoshida's COMET program. Credit: Carl Hergenrother.

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With a little more analysis we can determine if Comet 2009 R1 (McNaught) is a typically bright comet. The plot below shows the peak brightness near perihelion for comets with perihelion distances less than 1.5 AU. The brightness is not the apparent magnitude (how bright the comet looked to observers on Earth) but the heliocentric brightness (brightness of the comet normalized to 1 AU from the observer, 1 AU from the Sun and at a phase angle of zero degrees). This is done to “place” the comets at the same distance and orientation from the Sun and observer and allow a direct comparison between each comet. For example a candle a few feet from you looks much brighter than a distant star but it is the distance that makes it appear brighter. If both candle and star were located at the same distance the star would be many times brighter.

Since Comet McNaught is not yet at perihelion and we don’t know how bright it will be at that time, we plotted its brightness and orbital circumstances for June 14th. It is obvious that it’s a comet of just above average brightness for a comet at that distance from the Sun (the average heliocentric brightness is the blue line). Note that it is about 2 magnitude (6 times fainter) than Comet Halley. I also labeled Comet Hale-Bopp which is an obvious outlier on the plot and truly a once-in-a-lifetime comet.

Peak absolute magnitude (near perihelion) of long-period and Halley-type comets. Position of Comet 2009 R1 (McNaught) is valid for June 14. Credit: Carl Hergenrother.

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CCD observers have been producing some great images of the comet and its 2 tails. Check out Michael Jager’s website “Comet Pieces” for some of the best images out there.

Thanks to Gianluca Masi of Rome, Italy for sharing some images he took with a Celestron C14 at the Bellatrix Observatory in Ceccano, Italy. I was able to apply a radial gradient filter to bring out the fine detail. The image below shows a multitude of rays in the gas (ion) tail. These rays are very dynamic and can change on hourly time scales. Though there is some evidence of structure in the head of the comet, it is very subtle. This is too bad because well defined dust jets can be used to measure the rotation period of the nucleus and made out dust-producing active areas.

Image of Comet 2009 R1 (McNaught) taken on 2010 June 6.10 UT by Gianluca Masi with the Bellatrix Observatory Celestron C14. Radial gradient processing by C. Hergenrother. Credit: Gianluca Masi/Bellatrix Obseratory.

Update on Comet 2009 R1 (McNaught)

Comet 2009 R1 (McNaught) is by far the brightest comet in the sky right now. There is a good chance observers under very dark skies will even be able to see it without the help of binoculars or telescopes. Recent visual estimates place it as bright as 5th magnitude.

Over the past few nights I have been observing the comet with a remotely operated 0.32-m (12.5″) telescope (part of the LightBuckets network [www.lightbuckets.com]). The images below are from the morning of June 5th. Each image is actually the same only displayed with a different ‘stretch’. The top image shows more detail in the inner coma while the bottom image shows more of the faint tail.

The comet currently displays 2 tails. A gas, or ion, tail seen extending a little north of due west (little bit up from due right). A shorter, stubbier dust tail is seen extending to the southwest (lower right). The sky was already getting bright when this image was taken so some detail may have been washed out.

With the Moon quickly fading and soon to be leaving the morning sky, brightness estimates will start rolling in again. Already a few estimates have been made. The comet appears to have experienced a small increase in brightness. Only a few days ago observers were reporting the comet around magnitude 6.0 to 6.5. In the last day or so, reports placed it at magnitude 5.0 to 5.5.

The lightcurve below still shows a rapidly brightening comet which will peak at minimum brightness off 3rd to 4th magnitude early next month.

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In The Sky This Month – June 2010

This feature highlights a number of meteor showers, comets and asteroids which are visible during the month of June 2010.

June 2010 Highlights

* Venus, Mars and Saturn close in on each other in the evening sky
* Comet 2009 R1 (McNaught) reaches naked eye brightness in the morning sky
* Jupiter passes close to Uranus
* Asteroid (1) Ceres at opposition on the 19th and is an easy binocular object
* Partial Lunar Eclipse for the Far East and most of North/South America on the 26th
* Japanese Hayabusa spacecraft to return samples from asteroid Itokawa on the 13th
* EPOXI (spacecraft formally known as Deep Impact) flys past Earth on the 27th

Note: If anyone has pictures or observations of these objects/events and want to share them, send me a comment and I’ll post them on the blog.

Planetary Spacecraft

Hayabusa – On the June 13th, the Japanese Hayabusa spacecraft is scheduled to return to Earth. Tucked away in its sample return capsule may be a few grams of regolith (asteroid soil) from the small Near-Earth asteroid (25143) Itokawa). Launched in 2003, Hayabusa spent a few months in late 2005 studying Itokawa. Though the plan was to retrieve samples of the asteroid for return to Earth, the mission was plagued with many difficulties. As a result, mission operators are unsure if any samples were picked up. Even whether or not the spacecraft can successful hit it target and land in Australia is in doubt. Regardless, the spacecraft and its sample return capsule will be coming back to Earth on the 13th.

NASA will be watching the re-entry of Hayabusa and studying the resulting fireball. Hopefully we will get some great video shortly afterwards. Check out the Hayabusa Re-Entry airborne observing campaign at the SETI Institute and the press releases from the Japanese Aerospace Exploration Agency for the latest.

EPOXI (ex-Deep Impact) -

The main comet event of 2010 will be periodic comet 103P/Hartley 2. Not only will the comet become a nice naked eye object this fall, but a re-used NASA spacecraft will encounter the comet. EPOXI has gone through quite a few name changes in its time. Originally Deep Impact it was launched in January 2005. In July 2005, it released a small package which impacted the surface of periodic comet 9P/Tempel 1. The impact allowed scientists an opportunity to study the interior of a comet. After the conclusion of its primary mission, NASA agreed to fund 2 experiments that utilized the spacecraft. One of its cameras was used to study planets studying other stars (an experiment called EPOCh, for Extrsolar Planet Observation and Charaterization). Also it will fly-by the aforementioned comet Hartley 2 (an experiment called DIXI for Deep Impact eXtended Investigation). Eventually the names were merged into EPOXI but really we are just talking about the old Deep Impact spacecraft.

On the 27th, EPOXI will fly-by the Earth setting up an encounter of Hartley 2 on November 4th.

Planets (and Moon)

Moon – The Moon will experience a Partial Lunar Eclipse on the night of June 25/26. At its best, a little over 53% of the Moon will be in umbral (darkest) eclipse. For the best info on this eclipse go to NASA’s Eclipse Website.

Venus – Venus is the brightest “star” visible in the early evening. Low in the west it sets about 2.5 hours after the Sun. From now till July/August it will ride as high as it’ll get for northern observers. In fact, this is not a great evening apparition for Venus. On the other hand, it is a great apparition for observers south of the Equator. For them, Venus will continue to climb higher till late August. Regardless, of where you are located it will be hard to miss brilliant -4 magnitude Venus in the west an hour or 2 after sunset.

June 11 - Venus in line with bright stars Castor and Pollux
June 15 - Moon passes within 4° of Venus
June 20 - Venus passes the center of the Beehive star cluster

Mars – Mars moves rapidly through the constellation of Leo this month. Though fading from magnitude +1.1 to +1.3 it is still an obvious red beacon to the southwest of overhead right after sundown. It’s brightness is comparable to that of the other bright stars. Watch Mars pass within 0.8° of the bright star Regulus on the 7th. Mars will be magnitude +1.2 on that date and just slightly brighter than Regulus at magnitude +1.4. By the end of the month, Mars is located within 16° of Saturn. The two will be closest at the end of July, and will be joined by Venus in early August.

June 7 - Mars passes 0.8° from the 1st mag star Regulus
June 17 - Moon passes within 6° of Mars

Saturn – This month Saturn is visible in the south during the early evening hours. It will slowly fade from magnitude +1.0 to +1.1 making it slightly brighter than Mars. Telescope users should note that Saturn’s rings are still within a few degrees of edge-on.

June 19 - Moon passes within 8° of Saturn

Jupiter and UranusJupiter once again returns to sight as a brilliant star low in the east-southeast before dawn. The magnitude -2.4 planet will get brighter and better place for observing over the next few months. Last year Jupiter made a series of close approaches to Neptune. This year Jupiter will do the same for Uranus. On June 6th, Jupiter will make it’s first closes approach to Uranus at a small distance of 0.44°.

June 6 - Moon passes within 7° of Jupiter
June 8 - Jupiter passes within 0.5° of Uranus

Mercury -Mercury is in the middle of a morning apparition at the start of the month. This morning apparition will not be good for northern observers though it is excellent for southern observers. By mid-month, Mercury will have fallen back into the glare of the Sun.

June 11 - Moon passes within 9° of Mercury

Meteors

June starts to see an increase in meteor activity after a few months of low activity. The year is usually split in 2 with January through June having low rates with few major showers while July through December (really through the 1st week of January) have high rates with many major showers.

Sporadic Meteors

Sporadic meteors are not part of any known meteor shower. They represent the background flux of meteors. Except for the few days per year when a major shower is active, most meteors that are observed are Sporadics. This is especially true for meteors observed during the evening. During June, 10-16 or so Sporadic meteors can be observed per hour from a dark moonless sky.

Major Meteor Showers

No major showers are active this month.

Minor Meteor Showers

Minor showers produce so few meteors that they are hard to notice above the background of regular meteors. Starting this month, info on most of the minor showers will be provided on a weekly basis by Robert Lunsford’s Meteor Activity Outlook.

Additional information on these showers and other minor showers not included here can be found at the following sites: Wayne Hally’s and Mark Davis’s NAMN Notes, and the International Meteor Organization’s 2010 Meteor Shower Calendar.

Comets

Naked Eye Comets (V < 6.0)

Comet C/2009 R1 (McNaught)

Comet C/2009 R1 (McNaught) will be a bright binocular comet and probably even a faint naked eye comet for observers under dark skies. Observations made over the past few weeks shows this comet to be rapidly brightening. By the start of June, the comet should be around magnitude 6.5 to 7.0. By mid-month, it will have brightened to magnitude 5.0 and maybe even 4.0. By the end of the month, it will be a bright magnitude 4.0 and perhaps brighter. The lightcurve below shows 3 possible brightness trends that the comet could follow. Though the red curve which shows a peak brightness of magnitude 2 would be nice it is most likely the comet will follow one of the fainter curves and peak at magnitude ~4.

Visual magnitude estimates for C/2009 R1 (as of May 27). Created with COMET. Credit: Carl Hergenrother.

The comet is a morning object and is only visible for an hour or so before the start of dawn. By the end of the month the comet can also be glimpsed in the evening. As the month progresses the comet will become harder to see as it moves closer to the Sun. Observers will need a clear NE (or NW in the evening later in the month) horizon to see the comet. Fourth magnitude is bright enough to be seen with the naked eye under dark conditions. Unfortunately the majority of  us live under bright, murky skies so binoculars will be required to see the comet for most people. The fact that the comet will set will twilight is still bright surely doesn’t help either. Currently the comet is located in Andromeda but it will quickly move through that constellation as well as Perseus and Auriga.

Still inbound, perihelion will occur on July 2nd of this year at a relatively small distance of 0.41 AU from the Sun. This month it will be 0.88 AU from the Sun and 1.26 AU from Earth on June 1st, 0.61 AU from the Sun and 1.14 AU from Earth on the 15th, and 0.41 AU from the Sun and 1.26 AU from Earth on the 30th.

Orbits and position of Comet C/2009 R1 and the planets for June 15, 2010. Image created with C2A. Credit: Carl Hergenrother.

A finder chart for Comet McNaught can be found at Comet Chasing.

A nice collection of images can be found at the VdS-Fachgruppe Kometen (Comet Section of Germany) and Seiichi Yoshida’s Comet Homepage.

Binocular Comets (V = 6.0 – 8.0)

None

Small Telescope Comets (V = 8.0 – 10.0)

Comet C/2009 K5 (McNaught)

The 2nd ‘Comet McNaught’  is Comet C/2009 K5 (McNaught). It was discovered on May 27, 2009 deep in the southern sky. Similar to C/2009 R1, this comet was also found with the Uppsala schmidt at around magnitude 17.

With perihelion on April 30 of this year at a distance of 1.42 AU from the Sun, C/2009 K5 is still bright enough to be seen in small backyard telescopes from dark sites.   At mid-month it will be located 1.57 AU from the Sun and 2.05 AU from Earth.

Visual magnitude estimates for C/2009 K5 (as of May 30). Created with COMET. Credit: Carl Hergenrother.

Observations over the past 2 months show the comet to be around magnitude 8.0 to 8.5. With the comet in full retreat from the Sun and Earth, it should fade from here on out. The comet will start the month between 8.0 and 8.5 but should fade to around 9.0 by the end of the month. Due to its located in the far northern constellation of Camelopardalis, the comet can be seen at all hours of the night from northern latitudes. It is best in the evening right after the end of twilight.

Orbits and position of Comet C/2009 K5 and the planets for June 15, 2010. Image created with C2A. Credit: Carl Hergenrother.

A finder chart for Comet McNaught can be found at Comet Chasing.

A nice collection of images can be found at the VdS-Fachgruppe Kometen (Comet Section of Germany) and Seiichi Yoshida’s Comet Homepage.

Asteroids

Binocular and Small Telescope Asteroids (V < 9.0)

(4) Vesta

Vesta is the brightest asteroid in the Main Belt. This is due to its high albedo (or reflectivity) which causes it to reflect ~42% of the light that strikes it. Vesta is also peculiar in that it appears to have evidence of volcanism on its surface. Similar to the Moon, Vesta may be covered with large expanses of frozen lava flows. It is classified as a V-type asteroid and is the only large asteroid with this classification. Many of the smaller V-type asteroids are chips of Vesta blasted off it by past asteroid and comet impacts. Vesta has dimensions of 347x336x275 miles or 578×560×458 km.

The maps below were created from images taken with the Hubble Space Telescope. The geography is dominated by a large impact crater located near the south pole (the blue ‘donut’ in the elevation map). Perhaps this crater is the result of the impact that blasted off the smaller V-type asteroids. We’ll know more next year when NASA’s Dawn spacecraft enters orbit around Vesta for a full year. Currently the encounter is scheduled for July 2011 to July 2012.

Images and models of the shape of asteroid (4) Vesta. In the upper left is a real HST image, to the upper right is a model of Vesta’s shape, and on the bottom is an elevation map . Credit: NASA/STScI.

Vesta starts the month at magnitude 7.7 and steadily fades to mag 7.9. A pair of binoculars will allow you to see Vesta among the stars of Leo.

A finder chart (needs to be flipped upside down for Northern Hemisphere observers) can be found at the Royal Astronomical Society of New Zealand. Finder chart for Vesta from Heavens Above.

(1) Ceres

Ceres is the biggest asteroid in the Main Belt with a diameter of 585 miles or 975 km. It is so big that it is now considered a Dwarf Planet. Classified as a carbonaceous (carbon-rich) Cg-type asteroid, there are suggestions that it may be rich in volatile material such as water. Some even propose that an ocean exists below its surface. Ceres is the other target of NASA’s Dawn spacecraft which is scheduled to visit it in 2015.

Image of Ceres taken with the NASA Hubble Space Telescope. Credit: NASA, ESA, J. Parker (Southwest Research Institute), P. Thomas (Cornell University), and L. McFadden (University of Maryland, College Park)

This month Ceres will be at opposition and brightest. The asteroid will start the month at magnitude 7.5, brighten to magnitude 7.1 at opposition of June 19, and then fade to magnitude 7.4 by the end of the month. All month long it will be retrograding on the border of Sagittarius and Ophiuchus.

A finder chart (needs to be flipped upside down for Northern Hemisphere observers) can be found at the Royal Astronomical Society of New Zealand. Finder chart for Ceres from Heavens Above.

In The Sky This Month – May 2010

This feature highlights a number of meteor showers, comets and asteroids which are visible during the month of May 2010. Venus continues to ascend higher in the evening sky and is the brightest star during early evening hours. The major meteor shower, Eta Aquariids, will be washed out by a bright Last Quarter moon.

Note: If anyone has pictures or observations of these objects/events and want to share them, send me a comment and I’ll post them on the blog.

Planets

Venus – Venus is the brilliant star low in the west during the early evening hours. It sets about 2 and half hours after the Sun. Venus will only get a little higher next month. From now till July/August it will ride as high as it’ll get for this apparition for northern observers. In fact, this is not a very good evening apparition for Venus. On the other hand, it is a great apparition for observers south of the Equator. For you, Venus will continue to climb till late August.

May 16 - Moon passes within 0.6° from Venus

Mars – This month the Earth and Mars continue to move further apart. As a result, Mars will continue to fade from magnitude +0.7 to +1.1. Still it will be a bright red beacon nearly overhead right after sundown. It’s brightness is comparable to that of the other bright stars. Note that unlike the stars which twinkle, Mars shines with an unwavering red glow.

May 20 - Moon passes within 5° of Mars

Saturn – Saturn was at opposition in Virgo on March 21. This month Saturn is visible in the east-southeast during the early evening hours. It will slowly fade from magnitude +0.8 to +1.0 throughout the month. Telescope users should note that Saturn’s rings are still within a few degrees of edge-on.

May 22 - Moon passes within 8° of Saturn

JupiterJupiter once again returns to sight as a brilliant star low in the east-southeast before dawn. The magnitude -2.2 planet will get brighter and better place for observing over the next few months.

May 9 - Moon passes within 6° of Jupiter

Mercury -Mercury will rise out of the dawn sky toward the end of the month. This morning apparition will not be good for northern observers.

May 12 - Moon passes within 8° of Mercury

Meteors

May starts to see an increase in meteor activity after a few months of low activity. The year is usually split in 2 with January through June having low rates with few major showers while July through December (really through the 1st week of January) have high rates with many major showers.

Sporadic Meteors

Sporadic meteors are not part of any known meteor shower. They represent the background flux of meteors. Except for the few days per year when a major shower is active, most meteors that are observed are Sporadics. This is especially true for meteors observed during the evening. During May, 10-12 or so Sporadic meteors can be observed per hour from a dark moonless sky.

Major Meteor Showers

Eta Aquariids (ETA)

The Eta Aquarids are a major shower, especially for southern hemisphere observers, when they peak on May 5. For northern observers, the shower will only be observable for an hour or two before dawn. Since the radiant doesn’t get very high for NH observers, rates can be low. The radiant is located near the “jar” of Aquarius.

The ETA were produced by Comet Halley which also gives us the Orionids in October. Models suggest that the ETA were released by Comet Halley no later than 837 AD. The Orionids are easy to see because the particles are hitting the Earth from the anti-solar direction. This means the meteor shower can be seen in the middle of the night. The ETA are produced by meteoroids moving outbound from the Sun, as a result the radiant is located relatively close to the Sun. This means that the ETA radiant is only visible for an hour or so before twilight. By luck, the nearly Full Moon will have just set making the last hour of the night dark.

The shower spans from April 19 to May 28 with a peak around May 5 with a maximum ZHR of ~60.

Additional information on these showers and other minor showers not included here can be found at the following sites: Robert Lunsford’s Meteor Activity Outlook.

Minor Meteor Showers

Minor showers produce so few meteors that they are hard to notice above the background of regular meteors. Starting this month, info on most of the minor showers will be provided on a weekly basis by Robert Lunsford’s Meteor Activity Outlook.

Additional information on these showers and other minor showers not included here can be found at the following sites: Wayne Hally’s and Mark Davis’s NAMN Notes, and the International Meteor Organization’s 2008 Meteor Shower Calendar.

Comets

Naked Eye Comets (V < 6.0)

None

Binocular Comets (V = 6.0 – 8.0)

Comet C/2009 R1 (McNaught)

There are 2 comets bright enough to be seen in small telescopes this month. Both were discovered by Rob McNaught of Australia during the Siding Spring Survey. As a result, both comets go by the moniker of Comet McNaught though they do have different designations [Comet C/2009 K5 (McNaught) and Comet C/2009 R1 (McNaught)].

The comet that should end the month as the brightest is Comet C/2009 R1 (McNaught). This comet was found on Sept. 9, 2009 with the 0.5-m Uppsala Schmidt telescope from Australia. At the time, the comet was a faint 17th magnitude.

Perihelion will be on July 2nd of this year at a relatively small distance of 0.41 AU from the Sun. This month it will be 1.44 AU from the Sun and 1.96 AU from Earth on May 1st, 1.19 AU from the Sun and 1.61 AU from Earth on the 15th, and 0.90 AU from the Sun and 1.28 AU from Earth on the 31st. Currently the comet is around magnitude 10.0 and should brighten to ~7.0 by the end of the month. 10th magnitude requires a small telescope but under dark skies while 7th magnitude should be easy for small telescopes under most sky conditions and binoculars under a dark sky. It is a morning object as it moves from Pisces, through Pegasus and into Andromeda.

This comet may even brighten to naked eye brightness (under very dark skies) in June. Of course with relatively small comets getting this close to the Sun, there is always a chance the comet will break up and disintegrate before it gets too bright (as C/2009 O2 did last month).

Orbits and position of Comet C/2009 R1 and the planets for May 15, 2010. Image created with C2A. Credit: Carl Hergenrother.

A finder chart for Comet McNaught can be found at Comet Chasing.

A nice collection of images can be found at the VdS-Fachgruppe Kometen (Comet Section of Germany) and Seiichi Yoshida’s Comet Homepage.

Small Telescope Comets (V = 8.0 – 10.0)

Comet C/2009 K5 (McNaught)

The 2nd ‘Comet McNaught’  is Comet C/2009 K5 (McNaught). It was discovered on May 27, 2009 deep in the southern sky. Similar to C/2009 R1, this comet was also found with the Uppsala schmidt at around magnitude 17.

With perihelion on April 30 of this year at a distance of 1.42 AU from the Sun, C/2009 K5 is bright enough to be seen in small backyard telescopes from dark sites. During the month it should be as bright as it gets at around magnitude 8.2 to 9.0. The comet will move through Cepheus and Camelopardalis. As the month progresses, the comet will have traveled far enough north to be circumpolar and visible all night long (for observers at northern mid-latitudes and further north).  At mid-month it will be located 1.44 AU from the Sun and 1.51 AU from Earth.

Orbits and position of Comet C/2009 K5 and the planets for May 15, 2010. Image created with C2A. Credit: Carl Hergenrother.

A finder chart for Comet McNaught can be found at Comet Chasing.

A nice collection of images can be found at the VdS-Fachgruppe Kometen (Comet Section of Germany) and Seiichi Yoshida’s Comet Homepage.

Asteroids

Binocular and Small Telescope Asteroids (V < 9.0)

(4) Vesta

Vesta is the brightest asteroid in the Main Belt. This is due to its high albedo (or reflectivity) which causes it to reflect ~42% of the light that strikes it. Vesta is also peculiar in that it appears to have evidence of volcanism on its surface. Similar to the Moon, Vesta may be covered with large expanses of frozen lava flows. It is classified as a V-type asteroid and is the only large asteroid with this classification. Many of the smaller V-type asteroids are chips of Vesta blasted off it by past asteroid and comet impacts. Vesta has dimensions of 347x336x275 miles or 578×560×458 km.

The maps below were created from images taken with the Hubble Space Telescope. The geography is dominated by a large impact crater located near the south pole (the blue ‘donut’ in the elevation map). Perhaps this crater is the result of the impact that blasted off the smaller V-type asteroids. We’ll know more next year when NASA’s Dawn spacecraft enters orbit around Vesta for a full year. Currently the encounter is scheduled for July 2011 to July 2012.

Images and models of the shape of asteroid (4) Vesta. In the upper left is a real HST image, to the upper right is a model of Vesta’s shape, and on the bottom is an elevation map . Credit: NASA/STScI.

Vesta starts the month at magnitude 7.3 and steadily fades to mag 7.7. A small pair of binoculars will allow you to see Vesta among the stars of Leo.

A finder chart (needs to be flipped upside down for Northern Hemisphere observers) can be found at the Royal Astronomical Society of New Zealand. Finder chart for Vesta from Heavens Above.

(2) Pallas

Pallas is a dark carbonaceous asteroid though with a slightly bluish B-type spectrum. Due to its high inclination (tilt of its orbit with respect to Earth’s orbit) of 34 degrees it is a difficult target for future spacecraft missions. Pallas is similar in size to Vesta with dimensions of 350x334x301 miles or 582x556x501 km. The reason it is fainter than Vesta is its darker albedo of 16%. Though no spacecraft are scheduled to visit Pallas, Hubble was able to get some good images that clearly show its nearly spherical shape.

This month it fades from magnitude 8.7 to 9.0. Over the course of the month it travels north from the constellation of Serpens Caput into Corona Borealis.

A finder chart (needs to be flipped upside down for Northern Hemisphere observers) can be found at the Royal Astronomical Society of New Zealand. Finder chart for Pallas from Heavens Above.

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