Moon close to Scorpious' head-stars

Event Date: January 8th

Time: 6:00 PM

Brief

  It is interesting when the Moon occults stars-- particularly if they are 1st magnitude and/or bright enough to see with the eye alone before or after occultation.  With a crescent Moon, these occultations are even better because the Moon doesn't wash out dimmer stars.  Also, it is fun to see the Moon pass between two stars.  Whether it be through binoculars or just the eyes, these pass-bys remind us of the precession of the nodes, for the Moon and its orbit.  As shown below, we see a zoom-out and 30º zoom-in of the Moon, after passing between Dschubba and Graffias: two stars of Scorpious' head.  The creature is now rising in the east about two hours before Sunrise.  The first image shows the Moon's orbit and the stick figure of Scorpious' head and body, being above the horizon, and the second image the second emphasizes its head-stars.

click on images to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

Detailed

  We have talked about the nodes' precession several times this year, and how such leads to a limited number of star-passbys.  That [number] depends on where the Moon is in its orbit and whether close or far from the nodes.  As shown in image one, the ascending node-marker is not far west of the Moon's position.  Since the node is moving from east to west, it means that for the upcoming months, the ecliptic latitude of the Moon at that [celestial] longitude will increase.  Later in the year, it will occult Graffias, as seen in various parts of the world. Those that see the occultation being those that have the Moon and star above the horizon and easily visible.  Since the *Moon's sidreal period puts it near/at that part of the sky at a different hour each month, there are times when we could see a (near) occultation, and other times when time zones on the other side of the world--from where we are viewing--see it instead.  Either way, enjoy the pass-bys when you don't see the occultation, as they make good binocular and telescopic viewings as well!

*as opposed to the 29 1/2 day synodic month

Andromeda Galaxy: left...or right?

Event Date: January 7th

Time: 7:33(.59) PM

Brief

   I showed the Andromeda Galaxy yesterday transiting during twilight.  As the sky quickly darkens looking high and in the northern half of the sky, the galaxy slowly descends as a result of its declination and our rotation.  Since Andromeda's declination is a few degrees larger in value than our latitude, it sets north of zenith instead of south.  As a result, its azimuth changes extremely quickly during the last few minutes before and after transit.  Although we will not think much about this with our eyes, it is something that go-to altitude-azimuth telescopes have to have programmed successfully into their databases to work correctly to track such northern bodies/objects.  To learn more about go-to telescopes and see what some of them look like, take a look at this link.  In the meantime, take a look at the image below, with the (alt)itude/(az)imuth not celestial grid included, as opposed to showing the celestial one.  Using the az info that I gave earlier, can you figure out why I chose the precise time above?  Hint: I mentioned including the alt/az grid for a good reason!

click on image to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

Detailed

   Here is the answer to the question wrapping up the brief, for if you don't know it:

At the time above, the Andromeda galaxy "switched direction", so to speak, in az.  That is, after transit it moved north to west, and then started moving back towards north after remaining stationary in az at a particular coordinate.  At each transit, celestial bodies further north than our latitude transit at 0º az twice.  Those with less of a northern declination value than our latitude, transit on the south side of zenith,  It is quite abstract to explain, yet can be believed.  In my case, I used the software to help me understand it better, and even that can be tricky!  To understand this better, take Polaris as an example, which makes a tiny circle from our perspective each day around the north axis.  For this to happen, Polaris needs to stay north, and cannot go far north and east.  Therefore, its az changes slowly, yet dramatically during transit time.  Of course, we cannot have the star get as far west (270º) or too far east (90º) and we never do.  The smaller than range of az, as a result of a higher declination value, the smaller the circle of rotation.

Andromeda and its galaxy-- high up

Event Date: January 6th

Time: 5:45(.15) PM

Brief

   I spent some more time today than normal, thinking about what to write about for this entry: after spending the last month or so focusing on the planets, Summer Triangle, the Mayan disaster-not-to-be, just to name some self-repetitive topics.  Then, I realized that it had been awhile since I had talked about something spectacular in the sky: the Andromeda Galaxy.  True, I mentioned it a few times during the early-mid fall weeks, yet seemed to bypass it several times.  Now, I am painfully aware that as seen from mid-northern latitudes, that it is only dark enough to see the galaxy with the eye alone, when post-transit.  Okay, I'm kidding; it is not that painful, as the galaxy is afterall still very high in the sky for a couple hours after transit as well.

   Here is Andromeda--constellation and galaxy--labeled, along with other nearby constellations, which also spend a lot hours in the sky, being north and/or circumpolar.  I will talk more about them on future dates.

click on images to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp

Detailed

   A powerful telescope can pick up the galaxy's core during nautical twilight, as the Sun is far enough away from this part of the sky to not get in the way; therefore the sky darker than if looking west-southwest where the Sun still gives off some glare.  Besides, the galaxy at transit is not far from zenith, so also far enough out of atmospheric pollution to see.  As mentioned a few times since the start of winter, the Sun is now moving a bit further north each week for the next six months.  That, along with the galaxy and other stars rising about four minutes earlier each evening, means that over the next couple of months, we will lose both the constellation and galaxy of Andromeda quickly.  Fortunately, it is far enough north that it is in the sky for about 7-8 hours easily visible this month and therefore, we still have that chunk of time to view the galaxy slowly fall towards the horizon.  With a wide-field telescope, try to pick up the entire galaxy, about 4 1/2 full Moon-discs across, under very dark skies.

latest [winter] Sunrise...not on the solstice?

Event Date: January 5th

Time: 10:00 PM

Brief

   We are about two weeks removed from the December [winter] solstice, which marked the day that the Sun spent the shortest amount of time above the horizon from most northern latitudes; any variance was likely no more than a few seconds in difference, as some of these latitudes had their shortest day on a date before or after.   How so?  When the exact time of the solstice happens for a particular time zone.  That is, if it happens during the nighttime of a location instead of daytime, the shortest day may not match the date of the solstice.  I will provide a weblink here that may help further explain...after the popular Mayan info, of course...just read further!

What I will show for an image, instead of the solstice again, is the Sun in the morning for today's date, which indicates why I mention how long ago the December solstice was: the Sun rising at its earliest of the year, before rising later without the help of daylight savings ending.  

click on images to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

Detailed

The Sun rises several minutes later in late October/early November before the time change.  This time, as a result of the Sun moving north instead of further south, meaning that we will start having a more gradual change over the next several weeks, than the hour jump that we get after a time change.  This happens each year naturally, as we talked about last month with the earliest sunset happening a little over two weeks before the December solstice.  In the summer, we have the earliest sunrise happen about a week before the summer solstice and the latest sunset happen about a week after the solstice.  Why?  Read this, and learn about a new topic: solar noon!

   Also, just to admit, the reason that I include these links rather than explain them myself, is for the following reasons: 

(1) They explain it much better than I can paraphrase. 

(2) there are too many specifics that paraphrasing (summarizing) is nearly impossible!

Dipper stars, and Polaris becoming "more north"!

Event Date: January 4th

Time: 10:00 PM

Brief

   I showed the Big Dipper yesterday with only the stick figure.  Today, I will take away the stick figure and only put the star names.  Besides that, we have the Little Dipper showing, representing the body and tail of Ursa Minor.  The end of the little bear's tail, is Polaris, which is honored to be the "North Star".  It is only about 40 arc-minutes from the north celestial pole, and getting gradually closer to it by a few arc-minutes. By the start of the next century however, Earth's precession will bring the star away from the axis and years later, the only stars closer to it will be much dimmer.

   Here are the two Dippers with stars only and the celestial grid.  Notice how close Polaris is to the north celestial pole now.  The second image is a field of 1.4º, indicating that the star barely fits in the field, yet fitting a little moreso each year; good for polar alignments with equatorial telescopes!

click on images to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp

Detailed

   Polaris is slightly closer than the last time I showed this field sometime last year.  At 40' 49" away from the pole, which I calculated by subtracting its 89º 19' 11" declination from 90º (0', 0"), a smaller field of view for an eyepiece can be used to get it and the north celestial pole into view.  Granted, a person should know the star patterns on and near the pole for the best alignment, if/when necessary. For telescopes that track in equatorial for use of long-exposure photos, having proper polar alignment can help tracking; as a result little to no drift at all over so many hours.  For those using alt/az telescopes, for which long-exposure photography is much less common, near-perfect alignment is not so necessary.

    Getting back to the Dippers, watch as the dimmer little one gradually moves in the sky over the course of the long, winter nights.  If you are able to stay awake between Sunset to Sunrise and haved nothing better to do on a clear night but view, perhaps you can notice the very gradual movement of the stars.  It may sould dull, yet can give a good appreciation of our rotation on Earth, and how slowly we really do move in relation to the stars: 23 hours and about 56 minutes for a sidereal day.

Ursa Major/Big Dipper as an evening riser.

Event Date: January 3rd

Time: 7:00 AM

Brief

   Do you remember how the Big Dipper dominated the northern sky last spring and summer evenings?  Since the asterism is circumpolar as seen from many northern latitudes, we ha(d/ve) lots of time to see it during the winter nights that have past, and still ahead of us.  The Dipper's "cup" stars are above the horizon and easy to see a few hours after nightfall.  How much of the handle do we see about an hour afterwards, still depends on any obstruction along the horizon.  Here is the Dipper now, seemingly (balancing) on its handle's end.

Detailed

Tomorrow I will label stars; today, only showing the stick figure, as a reminder of how much space (sky) the Dipper takes up.  Remember that its parent constellation, Ursa Major, takes up even more of the sky with its body, legs and--to a lesser degree--its feet.  As shown below, I will display the entire constellation, with the Dipper representing the back-body (rump?) and long tail.  If you forgot the reasoning for the stretched-out tail, as also the case for Ursa Minor (the Little Bear, not shown for this entry), read this as a reminder: 

    Also shown in the second image, is the celestial grid, indicating that Ursa Major is not only big; it moves slowly through the northern part of the sky, tracing out a small circle daily over 23 hours, 56 minutes: one sidereal day.

click on images to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

Looking above, the Dipper is slightly highlighted in brighter blue, to stand out from the rest of the constellation, made up of stars not as easy to see.  It is a result of that, that the constellation of Ursa Major, albeit big, does not get the same attention as its famous asterism of easier-to-see-stars, giving it a distinguishable shape.

Summer Triangle lower each evening

Event Date: January 2nd

Time: 5:30 PM

Brief

   Yesterday, I showed the Summer Triangle stars in the morning sky.  Whether rising or setting, the Sun is far enough south of the northern stars, that it isn't in the way to cause too much glare.  Also, with the early Sunsets at this time of year, it gives us alot of darkness and therefore, more hours to see the Triangle after Sunset and before Sunrise.  However, now that we are past the winter solstice for our hemisphere, we will lose--on average--about a minute of darkness per day; this starts slowly this week and throughout most of January.  Here are the three stars, forming the triangle.

click on images to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

Detailed

As we get close to the March equinox, the longer days and slightly longer twilight periods each day between now and the solstice will lead to all three stars of the triangle becoming too low to view come darkness, with Deneb being the last; following Altair and then Vega.  All three stars are high enough to view this evening, although as mentioned yesterday, they will dip one by one below the horizon.  In comparison to least-north Altair, Vega and Deneb are high enough south that they will be up longer.  

   Unfortunately for big evening [viewing] Summer Triangle fans, our revolution around the Sun is causing them to rise and set almost four minutes earlier each day.  This means that by the time they are visible even a couple of weeks from now with dark enough skies, they will not seem quite as bright; their light will be refracted through the atmospheric pollution.  Also, any obstruction such as tall houses or trees will hinder viewing.  Try viewing somewhere where the horizon is clear, such as a hilltop looking towards the a flat plane or large body of water (i.e. even an ocean), where there is no land horizon to get in the way of the view.

   Finally, If house and tree obstruction are not blocking the view, enjoy their colors through atmospheric pollution, as their light refracts; a rainbow-y range of colors for brighter Vega, and a predominantly green color for dimmer Deneb.

Summer Triangle rising before Sunrise

Event Date: January 1st (2013)

Time: 7:00 AM

Brief

   Happy New [Calendar] Year!  Okay, so there are different calendars, yet in this case, I am just emphasizing that I am talking about that starting with the January date above; not the astronomical New Year date, which happens on the 1-year anniversary of this blog: March 20th, for the next equinox--vernal for this hemisphere.

   On a different note, let's return our attention to the (so-called) summer triangle: I half-kiddingly use that parenthesized wording, since we are about exactly a half-year's worth of weeks and months from when the triangle has its best summer appearance in the sky, and high enough all night long to view from just about anywhere in North America and the equatorial latitudes of the southern hemisphere.  During this month, we will lose Altair in the evening sky completely; Vega is low in atmospheric pollution during early evening hours (yet refracting light beautifully with rainbow patterns); Deneb is dimly setting higher in the west.  However, what about the morning??  Take a look below!

click on image to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

Detailed

   Back when I showed the Triangle last March and April morning skies, during my first 20 or so entries, it was much higher, with 1-2 hours of darkness left for viewing.  Vega and Deneb can still be seen in dark skies now, with the date of this entry more than 9 months after my first ones.  As seen with the celestial guidelines, both of those stars have made slow "arcs" from the horizon.  If seen from further north, these two stars would be seen rising even more slowly, with the changes in altitude more gradual at first.  As for the third star to rise, Altair, it is barely visible in the morning during the first week of this month, yet will rise about four minutes earlier each day.  Being the least-north star, at only 9º compared to about 38º and 45º for Vega and Deneb respectively, Altair spends more time below the horizon than either of the other two, when viewed from mid-northern latitudes.

   Watch Deneb and Vega weekly, and eventually Altair.  By springtime, they will be high above the horizon--long enough before Sunlight washes them out--to see with the eyes alone.  This will act as a preview of how we will see them in the summer evening skies!

   

Different planetary altitudes within a time zone

Event Date: December 31st

Time: 12:09(.30) PM

Brief

The Mayan calendar ended 10 days ago, and the 2012 A.D. calendar ends tonight at 23.59.59(...) Universal Time (UT).  Of course, for time zones east of the prime meridian, it ends sooner.  However, acting as a standard, we remember UT.  Whenever exactly you want to celebrate for New Year's tonight or tomorrow, the sky will look similar for each time zone along a same latitude line.  The only small difference being whether a person is viewing east or west within a time zone.  For example, at the exact same time in the Pacific time  a viewer in Reno, Nevada will see the stars slightly further west than viewed at our location in the Bay Area, a few hundred miles west. With that in mind, look at Uranus and Neptune below: note their altitude and azimuth.  After that, I will show them about 45 minutes later, as they would be seen near the other end of the time zone.

click on images to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

Detailed

   The ecliptic and celestial equator show both planets' difference in declination, as well as R.A.  Neptune is getting low towards atmospheric pollution, and only easily visible for a couple hours once dark enough to see it easily with a large enough telescope.  Once atmospheric pollution gets in the way, it dims quickly, and its methane-blue color is harder to detect.  Uranus is further north and seen in image one just after transit.  Therefore, besides being a little "brighter" than Neptune, Uranus spends more time above the horizon for us to view longer after dark.  Both planets are approaching conjunction with the Sun, and about a month on each side of that, we will not beable to view these planets at all.  For the evening viewing before conjunction, the increasing glare of the Sun means waiting longer to see them, waiting for dark.  For morning viewing during mid-late spring, they will be too far south of the Sun to see them; they will rise only a short time before the Sun, getting washed out.  Try looking for Neptune easily through a telescope by late in the spring, and Uranus by early summer.

Pluto at conjunction- north of Sun

Event Date: December 30th

Time: 12:09(.30) PM

Brief

   Pluto has been shown in my series as a late-morning planet, an early-morning one, a late evening riser,  an early evening riser, and now, rising at about the time of the Sun.  The planet is nearly at conjunction with the Sun, and will not be visible again easily through a big enough telescope, until the middle of next year.  Since the Sun will move north with every passing day between now and the June solstice, Pluto's southern declination will mean that it will be rising only a very short time before the Sun, and be blocked by the Sun's glare as well.  Here is the sky darkened, showing Pluto transiting, the Sun, meridian, and celestial grid.  By darkening the sky, it also lets me include the orbit of the dwarf planet.

click on image to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

Detailed

   As we look above, as a reminder, Pluto's unusual inclination helps keep the planet north of the Sun.  It will be several more years for Pluto to reach the descending node leading to some very close separations with the Sun.  This is the only way for the the Sun to occult Pluto, although there is nothing special about such when something as bright as the Sun covers something up so much smaller and exponentially dimmer.  I am including this topic anyway, to show that the Sun catches up with the outer planets a little over once a year.  With Mars, it takes about 2 years; Jupiter takes about 14 months,; Saturn takes a little less time than Jupiter, considering that Saturn doesn't cover as much spacial ground.  As for even slower moving Uranus and Neptune, the oppositions happen just over a year apart, since Earth doesn't have to move too much in its orbit to catch up with these two planets.

Jupiter in retrograde, nearing open clusters

Event Date: December 29th

Time: 9:57(.34) PM

Brief

   Over the last 4 weeks, since Jupiter's opposition, the combination of its retrograde motion and the Sun's continuous motion west to east against the stars, has brought the planet closer to our star by slightly over 1º a day; they have gone from 180º apart at opposition, to 149º apart.  When the two are eventually 90º apart, it means that Jupiter will be at eastern quadrature, followed by conjunction a few months later.  Here is where Jupiter is now, seen in image one high in the sky, with both clusters labled and the Hyades stick figure showing.  The second image shows the planet's celestial path over the last six months.

click on images to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

Detailed

   As a result of our perspective towards Jupiter, we don't see a "loop" as we sometimes do when a planet is seen switching directions.  Sometimes the loop leads to us seeing it change ecliptic latitude by as much as 2-3º, yet not this time.  As a result, we see the 10-day increment markers overlapping each other.

   Also with the retrograde, Jupiter has passed by the Hyades star cluster for the second of three times, and getting a little closer to the Pleiades.  With about a month left of retrograde, slowing to stationary as it further approaches the Pleiades, Jupiter will be a fun sight with binoculars, passing by these clusters.  

   For quadrature, which I glazed over in the brief, it means that there is 90º of separation between Jupiter and the Sun.  As is the case Moon is at--or very near--quadrature with the Sun when it is 1st or 3rd quarter, Jupiter is at or near transit when the Sun is rising or setting for western or eastern quadrature respectively.  Of course with the Moon, it orbits us, whereas Jupiter orbits the Sun.  Therefore, we will not see a half-illuminated Jupiter when it reaches quadrature; it is much too far from us in comparison to the Moon, to see such a change of phase.  Instead, Jupiter wanes very slowly to a still big-waxing gibbous around the low-90% range.  Then, as it gets closer to conjunction again, going behind the Sun (instead of between us and it), we have more of its disc reflecting Sunlight towards our eyes.

Mercury sinking towards Sun; Venus not far behind

Event Date: December 28th

Time: 7:00 AM

Brief

  As Mercury has started to move faster in prograde motion over the last few weeks since shortly before greatest elongation, it has started to catch up with the Sun faster.  As a result, despite still a good magnitude of -0.6, we are losing it quickly to morning twilight.  As for its planetary neighbor Venus, it has also increased in prograde motion.  However, with a much larger orbit than Mercury, being further from the Sun, the two have become more separated every day since their closest encounter earlier this month.  Here they are, pictured with orbits, ecliptic, and celestial equator.

click on images to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

Detailed

   While still visible to the eye alone through atmospheric pollution, Mercury is shortly lost in the Sun's glare by early into the new [calendar] year.  We are just days away from losing it entirely until late January, when it begins a very good evening apparition, once again going north of the Sun.  We will show that enough when the time comes.  

   As the ecliptic shows above, the two planets are about the same ecliptic latitude, yet more importantly, about the same declination as the Sun.  As the next few weeks pass, the geometry of this [east] side of the morning sky worsens more and more quickly.  Therefore, along with the Sun moving towards the celestial equator again, they will be seen for less time in dark-enough sky after rising.  Of course, approaching superior conjunction will also lead to them quickly disappearing in the Sun's glare.  Mercury rises 48 minutes before the Sun this morning, yet only 44 minutes before it tomorrow.  Venus rises 98 minutes before the Sun this morning, and this decreases by two minutes tomorrow.  I am including tomorrow's intervals just to show how quickly each are shrinking with change in declination.

Winter Circle setting: early morning

Event Date: December 27th

Time: 4:00 AM

Brief

   Yesterday, I showed the winter circle (or "G") of stars during the late evening hour of 9 PM...late for some people anyway!  This evening, as mentioned at the end of that entry, I will show them here while all are still seen above the horizon at mid-northern latitudes.   For this one, the clock is forwarded 7 hours ahead of yesterday's entry, with the stars displayed.  Notice how Capella, which rose as "early" as 1:22 PM the previous day, is still over 5 1/2 hours from setting.  Just by looking at the image, that may not be easy to calculate even using the gridlines, yet I obtained these times using the info from my software for this latitude, naturally!

click on image to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

Detailed

   Using the celestial guidelines once again, as I did yesterday, southern stars such as Rigel and Sirius are early to set in comparison to those far north such as Pollux and Castor.  Even though Sirius is the last to rise, it sets after only about 10 1/2 hours, while starts such as Capella, Castor and Pollux spend extra hours above the horizon.  The gridlines become smaller and smaller circles as we see them closer to the north celestial pole and therefore, stars close to the pole never set at all, seen from this latitude of about 38º.

   Keep watching the large group of bright stars each evening, as they rise about 4 minutes earlier each evening.  By spring, some are setting before the Sun does, depending which week you are viewing the western sky.

Winter Circle: high to view during evening

Event Date: December 26th

Time: 9:00 PM

Brief

   Christmas may now be behind this, yet the winter circle is at its best evening altitude over the next few weeks...hence, the seasonal name given to it.  Looking east, we can now see all the stars high enough above the horizon, with Sirius the last to rise in the east-southeast.  It is more south and east of most of the other stars, so from our hemisphere at mid-northern latitudes, this makes sense.  On the opposite side of the coordinate spectrum, regarding declination difference and west vs east in R.A., Capella is the most furthest north, and rises several hours earlier, during the afternoon hours.

   Taking a look below, we see the circle with the stars labeled, as I have shown before as a morning sight.  The view is directly southeast in azimuth.  The celestial grid and equator is displayed as a reminder for which stars are north and which are south.  The sky is stretched upward somewhat from a viewer's standpoint, to fit high Capella.

click on image to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

Detailed

As I have shown in the past, Orion's belt coincidentally(!) almost "divides" the sky, with its stars close to the celestial equator and almost running along with it.  Betelgeuse--a red supergiant--is north of the belt and equator, while very hot Rigel is south of it.  It is also because of this that viewers at about the same numbered latitudes south (between 35º-45º) see the Hunter's figure at about the same latitude at transit, yet "upside down".  For them, southern stars are seen higher than northern ones, so this makes sense.

As for the other stars, the Gemini twin-stars of Castor and Pollux are seen high for us later in the night, near zenith.  Procyon is closer to the equator yet still about 5º north.  Aldebaran, seen near retrograding Jupiter (labeled in bold), is about the same declination as the planet.  Also, Aldebaran turns the circle into more of a capital "G" shape.  Aforementioned Capella is about midway between the equator and north celestial pole.  Tomorrow, I will show the circle at an hour much later in the night, as the stars are descending to the horizon.  Until that time, if you are up late, enjoy many of them very high up, as seen from many northern latitudes.

Jupiter and gibbous Moon pairing

Event Date: December 25th

Time: 4:00 AM/5:00 PM

Brief

   Merry Christmas...to all who observe (the holiday that is, not only what is in the sky)!  As mentioned yesterday, a special treat will be visible, having already risen in the east-northeast about the time of Sunset.  Before that, we can see them before dawn, setting in the west-northwest.  If you saw them rise yesterday, and remember that the Moon moves west to east about one diameter per hour, perhaps you were able to visualize the separation of the two.  Take a look at image one, and find out if you are correct!  The separation then, is 6.9º from the Moon's center to much further (therefore smaller as seen from Earth), Jupiter. 

To clean up the appearance, I omitted the orbits and celestial guidelines.  The washed out, yet ever-popular Pleiades cluster forms a triangle with them.  The three fit in an 11º field, which is almost too wide for many types of binoculars.

Detailed

   Comparing to yesterday's showing, the Moon has spent 11 hours moving about 5º closer to Jupiter.  Now, let's take a look at the evening image, when the Moon is even closer.  This is impressive, and not only binocular friendly, yet telescope friendly, provided that a telescope used has a low f-ratio and/or a large apparent field-of-view for the eyepiece used.  I will set the time back to that of yesterday evening, and we see here that the two are only a separation of about 1.4º from center to center.  Since the Moon is about 1/2º in diameter and therefore 1/4º in radius, it means that the space between the Moon and Jupiter is only a little over a degree apart.  Take a look at the zoom-in following the zoom-out shown first.  For the zoom-in to follow, I included a wide field of 2º (about magnitude 25x) to include both.

Also for the zoom-out, I also kept the Pleiades cluster in, which can be seen slightly more easily each evening after this, as the Moon moves a little further away [angularly], and starts to wane faster in a few days.
   Finally, the closest approach between the two are early in the afternoon today, Pacific Standard Time, when the Moon is within 0.4º of the Moon.  According to a note on my Starry Night software, providing the images below, the Moon will occult Jupiter "as seen from central South America and Southern Africa".

click on images to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

waxing Moon approaching Jupiter

Event Date: December 24th

Time: 5:00 PM

Brief

   Astronomy fans around the world will have a real treat this Christmas eve and tomorrow, as the big, waxing gibbous Moon approaches Jupiter.  The separation shrinks by the hour.  As shown below, I have included the orbits of both, as the Moon crossed descending node early this morning.  The ecliptic as always, reminds us of the inclinations of the orbits.  Unlike the Moon's orbit with the precession of the nodes every 18.6 years, Jupiter and the other planets' orbits don't change from year to year; if so, extremely slowly and unnoticeably.

click on images to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

Detailed

   At the time above, Jupiter and the Moon are still outside of most binocular fields of view.  However, as the night progresses, the Moon moves about one diameter per hour from west to east.  Knowing this, can you calculate how many hours it will take for the Moon to come closest to Jupiter?  Remember that the difference in ecliptic latitudes will factor into how long it will take.  Remember also, that Jupiter will moves very slightly in retrograde motion, albeit slowing down slightly each day.  Although being as gradual as its movement is, I mainly bring this up as a reminder that Jupiter is all but staying still, waiting for the Moon to catch up with it.  Give it a try, predicting hours and minutes and when I reveal the closest encounter tomorrow with the clock, find out if you are correct!  Speaking of which, if I make this sound reasonably easy, it isn't, as I have as hard a problem as anyone predicting!

Mars' local path's "trough"

Event Date: December 23rd

Time: 5:00 PM

Brief

   Mars' apparition in the southeast continues to slightly improve each evening, although it is slowly coming closer to the Sun in separation.  The geometry of the sky, coupled with Mars' prograde motion has meant that it has moved a little further north each day, slightly faster than the Sun.  

   Although I had planned to show Mars local path on monthly intervals, starting awhile back, I am cutting into that interval by about a couple of weeks, to show the shape that the path makes.  Take a look below.

click on images to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

Detailed

As shown towards the middle of the path, between December 6th and 9th, Mars was precisely the same altitude at the same time each day.  Since then, as mentioned in the brief, the planet is slightly higher at this time each day.  This is slightly because of the geometry improving in this part of the sky.  However, as mentioned yesterday, the earliest Sunset happened a day before this span of days.  Therefore, despite the trough of markers above (where it "bottoms-out", so to speak), Mars was getting slightly closer to the Sun in separation.  As the Sun starts setting later by more seconds each day, Mars path has it slope up as well, benefitting from being a little more north than the Sun.  Near the time of conjunction in the early spring, the path will slope up less and less, eventually meeting the Sun with the planet going behind it and staying in its glare, for several weeks.  Look for Mars with optical aid as a dim "star" by mid-late Summertime, with the eye alone by fall, and a little more easily by early winter, when it is just a few months away from its next opposition.  Is that looking ahead enough?? :-)

angled Sunset...and why!

Event Date: December 22nd

Time: 5:00 PM

Brief

   Now with the winter solstice behind us, and the Sun already having reached its earliest date of setting a little over two weeks ago, our early evenings are starting to seem much brighter.  Although the Sun only sets a few minutes later than it did than it did on the earliest day (Dec 5th as seen from this latitude), our star spends a little more time just below the horizon this evening, than it did then.  To further show this, I will keep the horizon line in the image, yet take away the landscaping.  Also, the celestial grid shows, which traces out the Sun's local path each day, *disregarding extra declination change near the dates of the equinoxes.  In comparison, the ecliptic traces out the Sun's celestial path.

The first image shows a zoom-out, looking directly southwest; the Sun sets a little more west than this azimuth, yet that doesn't matter for the topic at hand.  

Detailed

   Look at the horizon indicated with a white line, and the angle that the celestial gridlines make with it.  Examining closely, the acute [less than 90º] angles that the lines make with the horizon, are different in measurement.  As the Sun moved from the western azimuth setting (September equinox) to the solstice, the angle that it set reflected these lines', angles, setting more gradually each day.  It is a result of this, that while the time of Sunset was nearly the same between late November and a few days after the earliest one, the Sun set more gradually; the lines indicate this anyway and therefore, we had slightly more intensity to civil twilight each evening very shortly after it set.  Civil twilight itself hardly changed in duration however, and the same for nautical and astronomical. 

   The second image is a zoom-in with a field of 20, to show the gridline angles more closely, perhaps revealing the difference as well.  Can you see the difference?  

click on images to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

Does this now explain that along with the earliest Sunset happening before the December solstice, why our evening sky seems brighter during first hour post-Sunset between the earliest day and Christmas?  In the second image, I raised the Sun to the top of the image intentionally, to show that the further south the Sun moves, the faster the gridlines move it further south of the horizon.  

   After the holidays, the Sun starts to slowly rise later more seconds apart each day, and then eventually over a minute later near the time of the equinox.