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  • Luke

Updated: 5 days ago

We will be visited by a bright green comet this late January/early February! The comet’s official name is Comet C/2022 E3 ZTF but just shortining it to "Comet ZTF" has a better ring to it in my opinion(ZTF stands for Zwicky Transient Facility which is the observatory that first discovered the comet back in March 2022).



A time-lapse of Comet ZTF I took on 1/27/23


On the night/morning of Febuary 1st/2nd 2023 the Comet ZTF will make its closest approach making it brighter in the sky this whole week! It will be passing in the sky right between the Small Dipper (Ursa Minor) and The Big Dipper (Ursa Major).


Sky and Telescope magazine has a good image of where the comet will be in the sky for the next few months here: https://skyandtelescope.org/wp-content/uploads/Comet-ZTF-Finder-Chart-900px.jpg


A picture of Comet ZTF taken with my telescope on Friday 1/27/23


Comet ZTF should be fairly visible, a decent pair of binoculars or a decent telescope will probably offer the best views and you might be able to catch it with the unaided eye in a very dark place on the night of closest approach (Wednesday Feb 1st). It is hard to predict brightness of comets but about 5+ magnitude seems to be the current guess (about the brightness of Uranus, would barely be seen with dark skies and unaided eyes/require a small telescope or good binoculars to see).


Comet Neowise seen on an AstroTour in March 2020


The main factor working against the comet will be the moon. 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 2/1 the moon will be 83% full and setting at 5am making it highly likely to wash out the comet’s appearance to many viewers.


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 comet ZTF 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 Comet ZTF in a telescope between the now and 2/19 the change in direction of the tail should be very apparent, flipping from pointing east to pointing north as the comet crosses the sky.



How a comet's tail changes as it orbits the sun


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.



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


If you wish to see the Comet ZTF 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 Febuary 1st one in Boulder and one in Winter Park.




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  • Luke

Watch the sky on December 7th from 7:30p to 8:45p (Mountian Time, in Colorado) to see Mars go behind the moon and come out the other side! this rare alignment will be visible across most of the US, all of Canada and in most of Europe



This rare Eclipse of mars is called an Occultation and can be used to study the moon! If you're lucky enough to see this in a telescope you will see mars peeking thru valleys and topography on the moon as the moon blocks it out and mars is right on the edge of the disk of the moon.


The folks at the International Occultation Timing Association (IOTA) have a map on their site that shows where and when the event will be visible. http://www.lunar-occultations.com/iota/planets/1208mars.htm



In the US/Canada the occultation of Mars will happen on the night of December 7th around 7:30p Mountian Time (the graphic says Dec 8th because it is using Universal Time)

To learn more about Mars and why it's so bright this year read my previous blog post here: https://www.astrotours.org/post/mars-returns



Keep up to date with things happening in the sky like this sign up for my news letter here: https://www.astrotours.org/contact


To see Mars up close in a telescope book a tour here: AstroTours.org/booking

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  • Luke

In the eastern sky there is a bright distinctly red spot of light that comes out fairly quickly after sunset. I’m sure you’ve guessed already this is the planet Mars! This year Mars has been particularly bright red for a few reasons and is the brightest it will be for fifteen years!



The true color image of Planet Mars, shot by Rosetta in February 2007


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 sky at sunset, 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, because full moon means the moon is at opposition). This will happened on December 8th 2022 for Mars. Because opposition is happening this year that means we are closer to mars then we will be for another ~3 years.



Mars will be in opposition on December 8th 2022 .

To visualize why this makes Mars so much brighter lets talk about Astronomical Units. An Astronomical Unit (AU) isn't just hyperbole but actually a defined scientific unit that is useful for talking about distances within our solar system. 1 AU is defined as the distance from the Earth to the Sun. The distance from Mars to the Sun is 1.7 AU because mars is 70% further from the Sun than Earth is. Now to help visualize this let's shrink the solar system down to something we can manage if we shrink 1 AU to equal 10m (~10 yards) saying the Earth is ~10 yards away from the Sun (Earth would be about 1mm big at this scale, about the size of a grain of sand, The Sun is 110 times the diameter of earth so it would be 110mm about the size of a grapefruit) Mars would be 1.7 AU ~ =17 yards away from the Sun at this scale (Mars is about 1/2 the diameter of Earth so it would be .5mm at this scale, a small grain of sand). So now if Mars was lined up with Earth on the same side Mars would only be 7 yards away, but if Mars was on the opposite side of the Sun Mars would be 27 yards away from Earth. Something as small as a grain of sand would be a whole lot easier to look at if it was only 7 yards (.7AU) away rather than 27 yards (2.7AU) away. That's why years like this year where we are in "opposition" with Mars and on the same side of the Sun as Mars, it becomes much brighter and easier to see in the night sky.


In a telescope or a good pair of binoculars mars appears as a red disk, where any of the red stars (there's a good red star Aldebaran just a little south of Mars and another bright red star Betelgeuse rising in the east a few hours after Mars) will still be just a point of light. If you have a good telescope you might be able to see the white ice cap. With a really good telescope and a 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 through the ages starting with the Sumerians who likened it's red appearance to blood and saw it as an omen of war and blood shed. the Greeks and Romans went along with this naming it after their gods of war Aries and Mars (Marmor being an alternate name) respectively.


In modern times Mars is often the site of many scifi novels, movies, and art. This is owed in part to a wealthy and influential astronomer Percival Lowell who in 1906 claimed to see canals on mars that he thought 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, literally, 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 fully 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 tours through next year.

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