Christmas Comet!

We will be visited by a bright green comet this December just before Christmas! The comet’s official name is Comet 46P/Wirtanen however because of the timing I think calling it the Christmas Comet (2018) sounds a lot better.

The Christmas Comet is currently the closest thing to the Earth outside of the moon and will be getting a lot closer. On December 16th 2018 the Christmas Comet will make its closest approach at .0775 AU (That’s 7.7% the earth sun distance, 7.2 Million Miles, 39 light seconds, or 30 times the earth moon distance). It will be passing in the sky right between the Pleiades (the seven sisters) and Aldebaran (the red eye of Taurus the bull) when it makes closest approach on the 16th.

sky and telescope magazine has a good image of where the comet will be in the sky for the next few months here: https://s22380.pcdn.co/wp-content/uploads/Comet_46P_Dec18-Jan19.jpg

The Christmas Comet should be fairly visible reaching about the size of the full moon. A decent pair of binoculars will probably offer the best views as a telescope might zoom too much and it might be too dim to see easily with the unaided eye. It is hard to predict brightness of comets but the Smithsonian is saying about 8+ magnitude (about the brightness of Neptune, would require a small telescope or good binoculars to see), and sky and telescope magazine is more optimistic saying it should be about 3+ magnitude (just dimmer than the north star, would be able to see with the unaided eye).

The main factor working against the comet will be the moon right now it is a new moon meaning in the coming weeks the moon will be growing causing more and more natural light pollution and setting later and later. On the night of the 16th the moon will be 56% full and setting just after midnight making it highly likely to wash out the comet’s appearance to many viewers. On Christmas eve the moon will rise only 45 minuets after sunset giving a moonless evening to view the Christmas comet.

The word comet comes from Latin and means “long haired star” referring to the hair like tail, the most striking feature of a comet. The Christmas comet should appear with a faint cloud tail possibly with a green hue pointing away from the sun.

Comet 67P which was studied up close by the Rosetta mission

Comets are referred to as dirty snowballs as they are primarily made up of ice with some rock and dust mixed in. The tail of a comet always points away from the sun because the heat of the sun and the solar wind (a stream of charged particles the sun radiates) hits the comet with enough power to melt the ice and burn the dust. Watching the Christmas Comet between the 13th and the 19th the change in direction of the tail should be very apparent, flipping from pointing south to pointing north as the comet crosses the ecliptic.

Halley's Comet during its pass through the inner Solar System in 1986

Up to the 1700s Saturn was seen as the limit of our solar system. Comets of course were known of prior to the 1700s as they are quite striking when they appear, however comets were seen as foretelling a large event. So instead of studying them when they appear many focused mainly on what upcoming event is being foreshadowed. Aristotle and many others thought comets were phenomenon which occur in the Earth's atmosphere. Edmund Halley famously predicted a comet he had seen in 1682 to return in 1758 this was the first insight into what comets really were. Halley’s comet meant that the solar system was much larger than previously thought as, the orbit Halley predicted had his comet traveling just outside of the orbit of Neptune (which wasn’t discovered until 1846) meaning the comet traveled over 3.7 times as far as Saturn’s orbit. The Christmas comet's orbit is much smaller never traveling further away from the sun than Jupiter's orbit.

If you wish to see the Christmas comet up close in one of my large telescopes and learn more about it I will be offering 2 special tours for the comet, one on December 14th and one on December 16th. Contact me soon for booking.

Mars

In the south west sky there is a bright distinctly red spot of light that comes out fairly quickly in the twilight. I’m sure you’ve guessed already this is the planet Mars! This year Mars has been particularly bright red for a few reasons.

Location of Mars looking south from Boulder Colorado

Mars takes 2 years to go around the Sun where it takes the Earth 1 year. This means about every 3 years we catch up with mars and pass by it. When this happens it is called ‘opposition’. Opposition means an alignment of the Sun the Earth and one of the outer planets (outer planets are planets that are further from the Sun than us: Mars, Jupiter, Saturn, Uranus, Neptune). You can see when this happens by watching the Sun set, because the Sun, Earth and another planet is in alignment the planet is on the opposite side of the of the sky from the Sun. After you watch the Sun set in the west, turn around and see the planet that is in opposition rise in the east, for that night that planet will be as above the eastern horizon as the Sun is below the western horizon (the same phenomenon can be seen at full moon too). This happened on July 27th 2018 for Mars so it is no longer rising as the Sun sets (you will see it fairly high in the sky during twilight). However because that happened this year that means we are still closer to mars then we will be for another ~3 years.

Mars was in opposition on July 27th of 2018.

In addition to being closer to Mars there has been a dust storm on Mars making it extra red for the passed few months. This dust storm is actually threatening the Opportunity rover by blocking out the sun so that the solar panels can not provide the power the rover needs to operate. Currently the dust storm is over but NASA still hasn’t been able to contact the Opportunity rover. NASA suspects that dust has accumulated on rover's solar panels during the storm preventing them from charging the rover. There's still hope that with some wind gust the solar panels might clear and power up the rover once again. We’re all pulling for the little rover which has been on mars for over 14 years and has broke many records and made some amazing discoveries in that time. The Curiosity rover however has been operational this entire time as it relies on a nuclear power source.

A penny the Curiosity rover uses to calibrate its camera. On the right is a photo from about a month after it landed and on the left is a picture 6 years from when it landed, just after the dust storm.

Mars has also been in the news lately thanks to the successful landing of NASA's InSight lander. the InSight lander will be placing instruments on the surface of mars using a robotic arm that will probe the interior of the planet and give us a better understanding of mars and the other terrestrial planets (Earth, Venus, and Mercury). InSight is also powered by solar panels so it will have to battle the martian dust.

a NASA illustration of insight on mars

It has long set now but but there is a star Anterries in the constellation Scorpio as the red heart of the scorpion. I bring Anterries up as Anterries is Arabic and means ‘rival to mars’, this is because like mars it too is red. The rivalry comes when comparing the brightness between Mars and Anterries Mars is truly winning the rivalry currently but this is not always true. Actually usually Mars loses the rivalry 2 years out of 3 (when mars is further away, or on the other side of the Sun, as Anterries is always the same brightness). People will often come to me and point to Anterries or Aldebaran (a red star that makes up the eye of Taurus the bull which should be appearing just above the eastern horizon in the evening) or Betealgeuse (the red star you might be familiar with in Orion, currently appearing in our sky late at night) and ask if it is mars and I have to tell them no… This year is different because we are passing close to mars and because the dust storm on mars, Mars is truly winning the rivalry and being the brightest red point on the ecliptic.

In a telescope or a good pair of binoculars mars appears as a red disk, where any of the red stars will still be just a point of light. If you have a good telescope you might be able to see the white ice cap (which is tented red after the dust storm). With a good telescope and trick called occulting where you block out the light of mars you might be able to see mars's two faint moons Phobos and Deimos. Phobos and Deimos are small and irregularly shaped leading us to think they are most likely captured asteroids.

Mars in my best telescope.

Mars has captured our imaginations a lot in modern times by being the site of many scifi novels, movies, and arts. This is owed to a wealthy and influential astronomer Percival Lowell who in 1906 claimed to see canals on mars that were so straight they must of been engineered. Lowell wished to find life on mars so much that he started to. This hallucination was contagious and many other astronomers picked up on the canals. the story took off and inspired two generations of scifi writers and artist (Burroughs, Bradbury, Weinbaum, to name a few) who created works that went on to be inspirations for many artists to this day (Andy Weir, Kim Stanley Robinson, David Bowie and countless more). Lowell's observation was before photography when all astronomy was done by eye which leads many to say the canals were in the eye of the beholder as the drawings Lowel produced resemble retina of the human eye. We know now that there are no canals on mars but it wasn't until the Viking and Mariner probes of the 60s and 70s that hopes of canals on mars was finally put to rest.

Martian canals depicted by Percival Lowell.

Even without canals Mars is still an amazing place that captivates the imagination. Valles Marineris which is a system of naturally formed canyons that reaches 4 miles deep and would stretch across mainland United States if it was on earth. If human eyes ever see Valles Marineris up close I’m sure it will be a jaw dropping sight putting the grand canyon to shame. Mars is also home to Olympus Mons an extinct volcano reaching 72,000ft making it the largest mountain in our solar system (there is a case to be made for Rheasilvia a mountain on the asteroid Vela to be bigger). With science supporting the idea of frozen carbon dioxide (dry ice) snow storms some have thought about skiing down Olympus Mons and getting lots of air with Mars’s low gravity (about a third of the gravitational force we have on earth). Along with volcanoes and canyons mars also has many impact craters that scar its surface. Mars is home to the greatest diversity of impact crater types of any planet in the Solar System.

Olympus Mons

Hope you enjoy observing Mars this evening. If you want to see it up close in my telescope I will be holding a tour on the 14th of December. Be sure to catch the special commit show I will hold on the week of the 16th (more details to come soon).

Saturn

Saturn is a favorite among everyone, they say whom ever created our solar system liked it the best that’s why they put a ring on it. The days of the week are named after celestial bodies and Saturn’s day (Saturday) is also beloved by all! You’re probably thinking about it so here are the rest: Sunday = Sun’s Day, Monday = Moon’s day, (knowing Spanish helps with the others) Tuesday = martes = Mars Day, Wednesday = miércoles = Mercury’s day, Thursday = jueves = Jupiter’s day, Friday = viernes = Venus day. Seems like Earth day got a raw deal only being one day a year...

Saturn is currently appearing in the south-west between Mars and Jupiter in our evening sky it is much dimmer than both Jupiter and mars but it is brighter than the stars that surround it. If you draw an imaginary line in the sky (the line of the ecliptic) between Jupiter (the brightest star in the western sky after sunset) and mars (the brightest star in the southern sky at sunset, Mars is also visibly red) Saturn is the brightest star on this line that is a little closer to mars than Jupiter.

Saturn is currently visiting the constellation Sagittarius which can be seen below it. Sagittarius is the archer and you can see a bow with an arrow set in it. However if you tip your head to the right, Sagittarius looks like a teapot below Saturn is the triangular lid atop a trapezoidal body with a trapezoidal handle on the east side and a triangular spout on the west side. Even better if you are in a particularly dark area you can see the milky way appearing as steam coming out of the spout.

Looking south this week with the planets labeled and the "Teapot" (Sagittarius) outlined. Currently we are in the "tip me over and pour me out" phase of the Teapot's dance across the south sky.

Saturn is a true treat in binoculars or a telescope. When you first see it you might see an oval resembling a batman symbol but once you focus your eyes in to it you should see Saturn's rings resolve. Saturn never fails to get an “oh wow!” from anyone looking at it up close, the large planet suspended perfectly in the rings is a magical sight to observe with your own eyes. If you really want to test your eyes and equipment you might see ‘the Cassini Division’ which appears as a dark region that separates the bright ring in to 2 rings. The rings are made up of countless water ice particles ranging in size from the smallest speck to the size of a house.

common view of Saturn in a telescope.

Saturn like the Earth has solstices and equinoxes, and you can see them by observing the rings from year to year. Satsourn takes 30 years to go around the Sun meaning 30 earth years = 1 Saturn year. every 30 earth years Saturn has 2 solstices (i.e. summer & winter) and 2 equinoxes (i.e. spring, & fall). We see Saturn's solstices by seeing the rings tip towards us and appear to open up and we see Saturn's equinoxes by observing the rings edge on, where it’s difficult to notice the rings at all. Saturn’s last solstice occurred last year (earth year) this means saturn was tipped towards the Sun opening it’s rings as wide as can be seen. Over the next 6 or so earth years we will watch Saturn's rings tip away getting smaller and smaller until it reaches equinox where we will see the rings edge on.

When Galileo first saw Saturn's rings he of course didn’t know what he was looking at, some of his first sketches depict it with two moons (he had already discovered the moons of Jupiter making this a reasonable guess). After he caught his first glimpse he got clouded out and wasn’t able to see Saturn again, then once the clouds left Saturn was no longer in the sky (Saturn was too close to the Sun to be observed). Galileo knew about the movements of the planets by now so he waited till he could see it again and when he did the rings were no longer visible (Saturn had gone into equinox where the rings were edge on) this lead Galileo to think he had hallucinated when he first saw the rings. Saturn’s Greek god name is Κρόνος, Krónos who was a Titan that ate his children. Galileo knew this story so when he saw the “moons” next to Saturn disappear he thought just like in the myth Kronos had ate his children. He checked back over the next few years to see them open up again he never truly realized what they really were, later calling them "arms".

After taking in the rings of Saturn if you look around just of next to Saturn somewhere you should see the moon Titan. Titan is the second largest moon in the solar system (after Jupiter’s moon Ganymede) and slightly larger than even the planet Mercury. Titan is really exciting for planetary researchers as it is rich in geological processes that are alien to anything seen on Earth yet somewhat familiar. I’ll give you an example much like Earth Titan has clouds in its atmosphere and lakes on its surface however Titan’s lakes and clouds are not made of water but made of methane. It is thought that methane on titan acts much like water acts on Earth. Because Titan is so far from the sun it is much colder but these cooler temperatures make it possible to have methane as a solid, liquid, and gas. When heated methane lakes evaporate into clouds that when cooled then rain and/or snow methane back down to the surface.

The Huygens probe that was sent with the Cassini spacecraft landed on the surface of titan in 2005 and proposed missions want to go further some with a submarine to be deployed in a methane lake. Just imagine what a feat of engineering that could be to have a submarine in a methane lake on a moon of one of the most distant planets in our solar system.

The Cassini-Huygens spacecraft which was purposefully burned up in Saturn's atmosphere in 2017.

As of right now I only have six shows left this year so Book Now if you want to see Saturn up close in my biggest telescopes!