Waning Hunter's Moon

 It was 11° F this morning, the coldest of the season so far.  I saw the waning gibbous moon (16.5 d old) setting over Bristol Head and stepped outside to snap a few pictures, then quickly headed back inside to warm up by the wood stove.

Wolf 359 - the third nearest star system

 Wolf 359, also known as the variable star CN Leonis, is an obscure magnitude-13.4 red-dwarf star near the ecliptic in the constellation Leo.  It is the 359th entry in a catalog of high-proper-motion stars compiled by astronomer Max Wolf over a century ago.  At this time of year (October), it is an early-morning object in the eastern sky just before dawn.

E-P5 + Rokinon 135mm f/2, ISO 1600, 60 s. 2-deg square.

Wolf 359 has a proper motion of 4.7" per year and is 7.8 ly distant.  The only nearer stars are Barnard's Star (6 ly) and the three-star Alpha Centauri system (4.3 ly).  It is a typical red-dwarf flare star with a mass of about 11% of our sun and a hydrogen-burning lifetime of about 5 trillion years.  

Since about ten years ago, it is necessary to make a distinction between the nearest stars and the nearest extra-solar objects.  In 2013 Penn-State astronomer Kevin Luhman announced the discovery of a binary brown-dwarf system at a distance of 6.5 ly, closer than Wolf 359.  This system is now known as Luhman 16.  Its two components each have a mass of about 3% of our sun (or ≈ 30 Jupiters) .  A brown dwarf is a "failed star".  It does not have enough mass to raise its core temperature high enough to initiate hydrogen fusion.  Brown dwarfs glow with the heat of their formation and gradually cool over time.  Luhman also announced the discovery of a third object (Wise 0855-0714), a sub-brown dwarf at a distance of 7.4 ly.  This object has a mass of between 3-10 Jupiters and an effective temperature less than the freezing point of water.

The images above and below were taken around 5 am MDT on Oct 25, when the planet Venus was only 2.4° away. Venus was shining at magnitude -4.4, 13.7 million times brighter than Wolf 359.

Venus, Wolf 359 (circled), satellite trail.

Winter preview

   The constellations progress westward at the rate of two hours per month, so this early morning view in mid-October is a preview of the late night skies of January, but with temperatures about 30° or more warmer.

Sony A7iii + Rokinon 24mm f/1.8 lens + Softon filter, ISO 1600, 30 s.

Orion is probably the most recognizable constellation in the sky.  The orange star in the upper left corner of Orion is Betelgeuse, a red supergiant variable star that is the 10th brightest star and sometimes the 9th brightest.  It is between 500-640 ly distant.  It is so bright in spite of that distance because it is huge, with a radius that would extend beyond the orbit of Mars if it replaced our sun.  Down toward the lower left is Sirius, the brightest star in the sky and the 5th closest star system (8.7 ly).  Along the upper left edge is the star Procyon, the 8th brightest star and the 13th closest star system (11.4 ly).  These three stars comprise an asterism known as the "Winter Triangle".

Neptune and the Circlet of Pisces

 That title sounds like a good name for a fantasy-adventure movie.  The Circlet of Pisces is an asterism.  An asterism is an easily recognized pattern of stars which may have one or several traditional or popular names.  Examples are the "Big Dipper", the "Square of Pegasus", the "Summer Triangle", or the "Sword of Orion".  The Circlet of Pisces comprises a ring of seven 4th to 5th magnitude stars in the constellation Pisces just below the Square of Pegasus.  In this age of light pollution it is not a widely known asterism because the stars are not particularly bright.  Even in Creede's dark skies it is necessary to let your eyes adjust after stepping outside before it becomes recognizable.

The Circlet of Pisces.  Olympus E-M1iii + 75mm f/1.8 + Softon diffusion filter.

This asterism serves as a convenient signpost for finding the planet Neptune in its current location.  In the above image Neptune is at the center of the white circle near the bottom of the frame. Neptune is magnitude 7.8 and is about 7' from the 7.3 magnitude star HD 222878. The close proximity to a star of similar brightness makes it much easier to find this planet visually - just look for the pair and you know you have it.  I was able to spot Neptune easily with 10x50, 7x35, and 8x32 binoculars.  I also tried a wide-field 2x54 binocular but was unsuccessful with that optic.

The green airglow that has been plaguing us recently seems to have abated somewhat last night.  I measured a sky brightness of sqml=21.45, which is getting closer to what I consider a normal dark sky (21.6) for this area.

Waxing crescent with clouds

Olympus E-M5iii + 40-150mm f/4

 

E-M5iii + AT102ED f/7

4.1 days old.  Binned by 2: too many air currents for a high resolution single-shot image.

Annular Eclipse, Oct 14, Santa Fe, NM

"White light" sequence (color added in post processing). Orion 80mm ED f/7.5 telescope.

This is very near mid eclipse.

(As usual, click on any image to get access to the full-size versions.)

I thought I saw a flash of "Bailey's Beads" just before this exposure, but was a little slow on the shutter button.  This is pretty close, though.

Hydrogen-alpha light, near mid-eclipse. Lunt LS50THa double stack. Some extra tedious processing was required to bring out the prominences.

Another Hydrogen-alpha shot, about 30 min before maximum eclipse.

Here is a white light companion to the above shot, color corrected to a neutral balance.

The weather in Santa Fe on the day of the eclipse was near perfect with no clouds and not a breath of wind.  Santa Fe was located inside the northern edge of the annularity zone for this eclipse, giving a slightly off-center view of the moon crossing the sun.

For white-light photos I used an Orion 80mm ED f/7.5 refractor with an aluminized mylar front filter, a field flattener and an Olympus E-M1iii camera set to ISO 200 and 1/2000 sec shutter speed.  The scope was riding on a motorized Celestron CG-4 equatorial mount.  Piggy-backed on this scope was an Olympus E-M5iii camera attached to a Tokina 400mm f/5.6 SD telephoto lens with a Al-mylar filter.  The lens was set to f/11 and the camera was set to ISO 200 and 1/500 sec shutter speed.

I set up an additional scope for recording images in Hydrogen-alpha (Hα) light.  This scope was a double-stacked Lunt Solar Systems LS50THa with a ZWO ASI178mm monochrome camera, and was riding on a Sky-Watcher Star Adventurer mount set up in full equatorial counter-weight mode.  This mount worked quite well.  One disadvantage of the Hα scope is that the ZWO camera requires a USB computer connection, so it is more complicated to operate than just pressing a shutter button.  In  addition, the etalon filters on this scope are nonuniform in their efficiency, so the exposure will vary across the image even with a lot of fussing to find the "sweet spot".  

Hα light is the wavelength emitted (656.28 nm or 6562.8 Å) when ionized hydrogen drops from the second to the first excited state.  This wavelength is in the red part of the visual spectrum.  A "double-stacked" scope refers to one with two etalons.  This combination reduces the band-pass to about 0.5 Å for improved contrast.  The attraction of imaging at the Hα wavelength is that prominences and filaments on the sun will become visible.

In addition to the imaging scopes, I set up a scope in the front yard for visual observation.  This was an Astro-Tech AT72ED f/6 refractor with a Lunt Solar Wedge and an additional ND-0.9 (0.125) neutral-density filter screwed on to a Tele Vue Delite 18.2mm eyepiece (24x). This was riding on a manual tracking Explore Scientific Twilight I Alt-Az mount.  Five neighbors and friends showed up to enjoy the spectacle with this scope and various hand-held solar filters.

The image below shows the "totality" sequence obtained with the 400mm Tokina lens, with no color correction to alter the pale violet tint of the Al-Mylar filter.  The time between the second and fifth images is a few seconds more than 2 min, which agrees well with the predictions for eclipse duration at our location in Santa Fe.  

Tokina 400mm @ f/11. No color correction.

Things that go bump in the night

"From Ghoulies and Ghoosties, long-leggetty Beasties, and Things that go Bump in the Night, Good Lord, deliver us!"

English poet Alfred Noyes, 1909

 I obviously spend a lot of time outside by myself in the dark, and on occasion I have heard "bumps in the night" that make me sit up and look around.  Sometimes (if I'm not going to ruin an exposure) I will turn on my headlamp and scan for eye reflections.  My usual conclusion (i.e., wishful thinking) is that it is a band of elk or deer passing through the property, and there is sometimes evidence of that.

However,  it is not always deer looking for an unprotected garden or heading to the Rio for a drink.  Yesterday I traveled back to Santa Fe to view the annular eclipse from my backyard, which is conveniently within the zone of annularity.  Late that night I received an alert from the security camera on my back porch in Creede and saw this:

My reasoning has always been that a bear will sense my presence (and there are usually glowing LEDs and tablets, etc, to reinforce that) and go elsewhere.  On the other hand, one neighbor had to shoot a bear that came in through a bedroom window, and another defended himself with a picnic cooler by bashing the bear in the face during a late-night back-porch encounter.

So, what to do? I'm still pondering that question.

Teegarden's Star

 In 2003 an article titled "Discovery of a New Nearby Star" was submitted to Astrophysical Journal Letters by B.J. Teegarden and nine coauthors.  These researchers had discovered a high-proper-motion star lurking in NASA's Near Earth Asteroid Tracking (NEAT) database.  This star is a faint (mag 15.1) red dwarf lying nearly on the ecliptic in the constellation Aries .  The star has a proper motion of 5.1"/yr, which is about half that of Barnard's Star, and is exceeded by only six other star systems.  At the time of publication a preliminary parallax estimate suggested that this star was as close as 7.8 ly, which would have made it the third closest star system to our own, after Barnard's Star.  Later data led to the best current distance estimate of 12.5 ly, which puts it in 23th place among the nearest star systems.

The mass of Teegarden's Star is about 0.093 solar masses, or 97 Jupiter masses.  Red dwarfs in this mass range have estimated lifetimes in excess of 7 trillion years.  This makes them essentially "forever stars".  There is now evidence that two earth-sized planets orbit Teegarden's Star within its nominal habitable zone.

Jupiter is currently about 3° from this star's position.  In the twenty years since this star's discovery was announced, its position has changed by the equivalent of 18 pixels in this image.  The white circle has a diameter of 100 pixels.

E-P5 + Rokinon 135mm f/2,  ISO1600, 60 s.  2-deg square.  

Click to get at the full-size image.

Airglow, or "why is the sky green?"

Lately the clear night sky has not been as dark as I think it should be.  The reason is a phenomenon called "airglow".  Airglow is caused by molecular recombinations high in the atmosphere, such as free N and O atoms combining to form NO.  The emitted light can vary from green to red or purple depending on the molecular energy levels involved.  Airglow is a natural phenomenon and not related to skyglow caused by light pollution.

There is a widely available device for measuring sky brightness called a "Sky Quality Meter".  It is manufactured by a company named Unihedron.  The version that I have is called the SQM-L, which measures sky brightness in a narrow angular region.  Typically a very dark night at my location here in Creede will provide SQM-L values (in units of mag/arcsec²) that range between 21.6-22.0.  Over the last week or so I have been measuring values in the range of 21.0-21.2. Smaller numbers correspond to a brighter sky. At my home in Santa Fe, SQM-L readings of 19.5 are typical.  Each change of one unit corresponds to an increase or decrease in brightness of a factor of about 2.5.  This means that my sky in Santa Fe is normally about 2.5*2.5 = 6.25 times brighter than here in rural Colorado.  This difference is caused by light pollution, not airglow.

Here are some images from last night that illustrate the effect of airglow.  All images were obtained with a Sony A7iii + Rokinon 24mm f/1.4 lens + Hoya Softon-A diffusion filter. One image in each comparison is the daylight-balanced color and the other is the color-corrected version intended to mitigate the green glow.

The Pleiades and Jupiter rising above the local mountain ridgeline.

 Airglow in not uniform across the sky, so even in the color-corrected versions it is still evident at lower elevations where the line of sight through the atmosphere is longer.  The ironic aspect of airglow, which makes the sky brighter, is that detecting it requires a very dark sky to begin with, otherwise it just blends in with light pollution. 

Here is a picture from May 2022 that shows strong airglow blending with the Milky Way.  The sky brightness measurement directly overhead on this evening was 21.7.

Sony A7 + Samyang 35mm f/1.8 + softon filter. ISO 1600, 30 s.

Here is a picture of airglow visible from the International Space Station:

Credit: NASA

Nearby stars in Cetus

 Tau Ceti is a G-class star very similar to our sun, but slightly smaller with about 78% of the mass, 80% of the diameter, and 45% of the luminosity.  It is 11.9 ly distant and the 19th nearest star system.  At magnitude 3.5 it is easily visible to the naked eye under reasonably dark conditions and is the seventh nearest naked-eye star.

The image below was taken last night as the constellation Cetus was rising above our eastern ridgeline.  This ridge rises up to about 15 deg above the horizon as seen from my location and is the western flank of Snowshoe Mountain.  Tau Ceti is the star in the middle of the white circle. Saturn is in the upper right and below it and slightly to the left is the star Fomalhaut.  There is a lot of green airglow visible in the images from last night.

Sony A7iii + Samyang 24mm f/1.8 + softon filter.  ISO 1600, 30s.

Tau Ceti. E-P5 + Rokinon 135mm f/2.  ISO 1600, 60 s. 2-deg square.

UV Ceti

UV Ceti is a double star about 2 deg away from Tau Ceti.  It consists of two red dwarfs separated by about 0.9", with a combined magnitude of 11.96.  The UV Ceti system is the sixth nearest star system to ours at 8.57 ly.

 

UV Ceti.  E-P5 + Rokinon 135mm f2, ISO 1600, 60s. 2-deg square.

 

 YZ Ceti

About 7.5 deg from Tau Ceti is YZ Ceti, a solitary magnitude-12.0 red dwarf at a distance of 12.1 ly.  This makes it the 21st closest star system.

YZ Ceti.  E-P5 + Rokinon 135mm f2, ISO 1600, 60s. 2-deg square.

The Pleiades

 Last night I was able to check off four more asteroids from my observing list: (298) Baptistina (mag 14.3), (299) Thora (mag 14.7), (304) Olga (mag 12.8), and 307 Nike (mag 13.8).  However, while it is satisfying to track down obscure points of light in the sky, it is also hard to ignore the more visually appealing targets.  

The stars of the Pleiades (M45) comprise the most recognizable naked-eye cluster in the sky.  This cluster is about 444 ly distant.  It is currently passing through a dust cloud that creates a reflection nebula.  This nebulosity is hard to see visually except in large telescopes, but is easily revealed with a short exposure in a dark sky.  When I was finished with my asteroid hunting I turned the camera toward the Pleiades:

E-P5 + Rokinon 135mm f/2, ISO 1600, 60s.  Nonlinear stretch to emphasize the nebulosity.  2-deg square.

Pluto

Pluto was considered to be the ninth planet in the solar system from the time of its discovery by Clyde Tombaugh in 1930 until its reclassification as a dwarf planet in 2006.  There were good reasons for the reclassification, in spite of wide spread disagreement.  Regardless of what it is called, Pluto remains the largest known trans-Neptunian object (but not the most massive - that would be the dwarf planet Eris).

Pluto is not the first solar system object to have its status reassessed.  When Ceres was discovered in 1801 it was hailed as the eighth planet (Neptune was not discovered until 1846).  However, when many additional objects were discovered orbiting in the space between Mars and Jupiter, Ceres was demoted to a new class of objects called asteroids.  As part of the reclassification that demoted Pluto, Ceres was promoted to the rank of dwarf planet.

Pluto is currently located in the constellation of Sagittarius.  Its brightness of magnitude 14.5 requires a substantial telescope for visual observation.  I have photographed it many times, but don't recall ever seeing it through a telescope.  With objects that faint it can be a daunting challenge to pick them out from among the many similar background stars.

Here is an image of Pluto in its location on 5 Oct 2023:

E-P5 + Rokinon 135mm f2, ISO 1600, 60 s. 2-deg square.

Pluto is the faint dot in the exact center of the white circle.  Click on the image to gain access to the full-size version.

There is a road-side tribute to Clyde Tombaugh in the town of Burdett, KS, which we discovered during a cross-country trip this past summer:

 

Neptune, the farthest planet, is currently at magnitude 7.5 in the constellation Pisces.  It is 7824x more massive than Pluto, and 21.5x larger in diameter.  Triton, the largest moon of Neptune, has a diameter 1.2x larger than that of Pluto.  Neptune's apparent size is currently 2.5 arcsec, much smaller than a single pixel in the image below.

E-P5 + Rokinon 135mm f2, ISO 1600, 60 s. 2-deg square.

 

Caroline's Rose

  Caroline's Rose (NGC 7789) is an open cluster in the constellation Cassiopeia.  It is named for the astronomer Caroline Herschel, who first saw it in 1783.

E-P5 + Rokinon 135mm f/2, ISO1600, 60 s.  2-deg square.

The cluster is located just past the west end of the "W" asterism of Cassiopeia. It would be even more visually impressive if it wasn't embedded in the star field of the northern Milky Way.  The cluster is estimated to be about 8000 ly distant.  There is no distinct boundary, but the densest section in the above image corresponds to a diameter of about 35 ly at that distance.

E-M5iii + Lumix 20mm f/1.7 + softon filter.  ISO 1600, 60s, binned by 2 and cropped to 30-deg square.

Waning Moon

 The moon last night, 20.0 days old:

AT102ED refractor, E-M5iii, ISO 200, 1/200 sec

Solar Sibling

 After two days of rain, thunder, and howling wind I looked out the window around 9 pm last night and saw stars.  Stepping out into the front drive, I could see some clouds low in the west and south, but the sky was mostly clear and the air calm.  This was a surprise -- earlier in the evening I had the oil lamp lit because power was out, likely from the stormy conditions.  I used this unexpected opportunity to take an image of a star that has been on my observing list for a while.

HD 162826

HD 162826 is a 6.5 magnitude star in the constellation Hercules, about midway between the keystone asterism and the bright star Vega.  It is just beyond the limits of naked-eye visibility, but easily found with binoculars.  It is not bright enough to have a name, just a catalog number.  The "HD" part of its designation refers to the Henry Draper catalog from Harvard College Observatory, which was compiled about a century ago.

E-M5iii + Lumix 20mm f1.7, 60 s, ISO1600, binned by two and cropped square. Kenko Pro softon-A filter.

What makes this otherwise innocuous star interesting is that it is most likely a sibling of our own sun, born at the same time from the same molecular cloud 4.6 billion years ago.  It is now 110 ly away, but it and our sun would have been part of a loose open cluster of stars at their time of formation.  Since then our sun has circled the galaxy about twenty times and the original cluster has widely dispersed.  The identification as a solar sibling is based on the chemical composition deduced from spectroscopic studies, which shows elemental abundances virtually identical to our sun.

E-P5 + Rokinon 135mm f2. 30 s, ISO1600. 2-deg square.

An hour after this photo I looked out the window again.  The clouds had closed in and the stars and surrounding hills were invisible.

 

The morning after:

 

 

Red dwarf doubles

 Here are three more red-dwarf systems, all in the "nearest stars" category.  The interesting twist with these examples is that they are all binary systems.

Gliese 725

Gliese 725 (Struve 2398) is a pair of red dwarfs in the constellation Draco. The magnitudes are 8.9 and 9.7, separated by 10.6".  The distance of 11.5 light years makes this the 15th closest star system to our own.

Olympus E-P5 + Rokinon 135mm f2, 60s, ISO1600. N is up. 2-deg square.

The image scale with this camera+lens combination is 5.6"/pixel, so this pair spans less than two pixels in this image, not enough to distinguish them individually.

Groombridge 34 AB

Groombridge 34 AB (a.k.a., GX Andromedae and GQ Andromedae) is a red-dwarf pair in the constellation Andromeda only about 5 deg NW from the Andromeda Galaxy, M31.  The magnitudes are 8.1 and 11.1, with a separation of 34".  At a distance of 11.6 ly this is the 16th closest star system.  The parenthetical names are variable-star designations owing to the fact that these stars, like most red dwarfs, are flare stars and sporadically increase in brightness due to surface flares.

Olympus E-P5 + Rokinon 135mm f2, 60s, ISO1600. N is up. 2-deg square.

Olympus E-M5iii + SIgma 56mm f/1.4 + softon filter.  60 s, ISO 1600. 8-deg square.

Kruger 60

Kruger 60 (DO Cephei) is a red-dwarf pair in the constellation Cepheus.  The stars are magnitude 9.8 and 11.4, separated by 3.3".  At a distance of 13.1 ly this system is the 27th closest to our own.

 

Olympus E-P5 + Rokinon 135mm f2, 60s, ISO1600. N is up. 2-deg square.

 

Click on image to gain access to the full-size version.

Van Maanen's Star

 Van Maanen's Star is a white dwarf star in the constellation Pisces that lies nearly on the ecliptic.  It is very dim (mag 12.4) with no nearby bright stars to serve as guideposts.  The closest naked-eye star is Delta Piscium at mag 4.4.  It's distance of 14.1 light years makes it the 31st closest star system to our own (excluding brown dwarfs).  

In spite of these unremarkable qualities, this star is significant because it is the closest solitary white dwarf.  Van Maanen's Star is an accessible (with a telescope) visual example of the eventual fate of our own sun. In six or seven billion years, after our sun has expended all of its hydrogen fuel and gone through a brief red giant phase, the remnant core of mostly carbon and oxygen will be a white dwarf star.  Van Maanen's Star has an estimated mass of about two-thirds of our sun, but compressed into a volume roughly the size of the earth.  No nuclear fusion is taking place - the star glows simply from the residual heat of its previous lifetime.  However, because the surface area is so small (compared to the original star) it will take trillions of years to cool completely.  White dwarf stars have a density of about 10⁶ g/cm³, making them the densest form of matter other than neutron stars or black holes.

Rokinon 135mm f/2, 60 s, ISO 1600

Below is the best finder image I could come up with for the moment.  The Great Square of Pegasus is in the upper left and to its right is the Pisces circlet.  Down in the middle bottom a white circle marks the position of van Maanen's Star, though the star itself is not visible in this image. The brightest star within that circle is HR 222, a 5.8 mag star.

E-M5iii + Lumix 20mm f1.7, 60 s, ISO 1600, softon-A filter.  Binned by 2.

The Moon, the Moon!

 The full moon, particularly if it is "Super", receives a lot of hype because that is what brings in page views. For web sites that must maintain a constant stream of new material, an article about the full moon is a guaranteed once-a-month page filler that practically writes itself.  

A recent headline proclaimed "Brilliant Harvest Moon...wows stargazers around the world."  Well, not really, or at least not real stargazers.  A full moon is the worst time for stargazing because the sky is so bright it is hard to see all but the brightest stars.  It is also the worst time for moongazing, because the contrast is so low it is hard to pick out detailed features on the lunar surface.  The best time for observing the moon is during the waxing and waning partial phases when oblique shadows make craters and mountains stand out.  However, there is little profit in hyping photo opportunities with the less-than-full moon because the moon will be high in the sky during sunrise or sunset, making it harder to produce images with dramatic foregrounds.

Moon above the local ridgeline, 23 Sep 2023. Lens: Olympus 40-150mm f/4.

8.8-day old moon, 23 Sep 2023.  AT102ED refractor.

The above image was obtained about a day past the first-quarter phase.  Some of the prominent craters are labeled.  Clavius is the largest (about 140 miles diameter) easily visible crater on the near side of the moon.  This crater was the site of the fictional moon base in Arthur C. Clarke and Stanley Kubrick's "2001: A Space Odyssey".  Just to the north is Tycho crater, where the alien monolith was found (in the story, not in real life!)

Clavius has always been one of my favorite lunar features.  I can find many sketches of this crater in my old observing log.  The sketch below was made when I was a 12-yr-old novice telescope maker using my first-ever homebuilt scope, a 6-inch f/5 reflector. At the time I think the mirror was still uncoated (bare glass), which works with bright objects like the moon.  

 

Clavius, 1966.  6-inch reflector.

 

The recorded magnification was 112x, which indicates that the eyepiece was likely a Criterion A.R. 7mm, my first commercial purchase.  I still have that eyepiece and use it on occasion.

My first commercial eyepiece.

 A day later the terminator has advanced, bringing more features into view.

24 Sep 2023.  AT102ED refractor.

Five days later, one day after the "Super" Harvest moon, Tycho crater is very prominent with bright rays, but Clavius is almost invisible.  My favorite crater has faded away in the contrast-free overhead light.
 

29 Sep 2023.  AT80EDT refractor.