Viewing dirty snowballs in the sky

Holly looks at three significant comets she observed.

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I have been lucky enough to be able to see several comets. What I love about seeing comets is that there is normally a once in a lifetime chance to see them. For most comets they do not return for at least decades so I treasure the chances I get to observe them.

Comets spend most of their time far away from the Earth and Sun. But every now and again one comes close enough to us that we can see it from Earth.

Comets are of interest to astronomers for several reasons. The first being that they are frozen armaments of the early Solar System so they can hold key information on how our solar system (including Earth) formed. They can also hold the answer to some big questions like how did Earth get its water? and where did the building blocks for life come from?

To see comets you need to know what part of the sky to look (especially if you do not have a go-to telescope mount). Check the right ascension (RA) and declination (DEC) of the comet and possibly some nearly bright reference stars to look at as well if you are trying to spot faint ones that can not be seen with the naked eye.

Comet McNaught C/2006 P1

Comet C/2006 P1 McNaught; photo taken from Swifts Creek, Victoria, Australia at approx. 10:10PM. Taken at f/4, ISO 800, 20 seconds and ~24 mm with post-processing in Photoshop to bring out details

This comet made headlines in 2007 when it lit up the twilight sky from the southern hemisphere. It is a non-periodic comet from the Oort cloud, the very edge of our solar system and it may never come back as it may be heading out of the Solar System. At its brightest, it could even be seen in the day time.

I remember walking up a hill out of Blenheim to see the comet one evening and spotting the fuzzy comet with its tail close to the horizon. A beautiful sight to see and the only naked-eye comet I have seen.


Comet Wirtanen imaged using a 130P-DS Newtonian telescope on a guided HEQ5 mount and an astro modified and cooled Canon 450D. 45 two-minute images stacked using deep sky stacked to stack comet and stars separately before recombination topo remove blurring.

This is the comet that I was super excited to see in November and December 2018. It was passing overhead and on a south to north orbit. However, we were then hit with a lot of bad weather in November so it was a while before I got to see it.

Although it was reported that some people could make out the comet with the naked eye, I really needed some optics to make it out. I got to have a look at it with Earth and Sky’s 9 ¼ inch telescope, 14-inch telescope and 16-inch telescope over the course of a few weeks before the comet made its way to the northern part of the sky and was lost from view.

46P/Wirtanen is a short period comet making an orbit of the sun every 5.4 years but it will not be as close to the Earth, and therefore will not be as bright for another 2 years.

One reason why it, in particular, is of interest to astronomers as it a possible target for future space missions, so in the future, we might get some nice close-up images of this comet.

C/2018 Y1 Iwamoto

PIA23165: Comet C/2018 Y1 Iwamoto Comet C/2018 Y1 Iwamoto as imaged in multiple exposures of infrared light by the NEOWISE space telescope. The infrared images were taken on Feb. 25, 2019, when the comet was about 56 million miles, or 90 million kilometers, from Earth. C/2018 Y1 Iwamoto is a long-period comet originally from the Oort Cloud and coming in near the Sun for the first time in over 1,000 years. Appearing as a string of red dots, this comet can be seen in a series of exposures captured by the spacecraft. Infrared light detected by the 3.4-micron channel is mapped to blue and green, while light from the 4.6-micron channel is mapped to red. In this image, stars show up as blue because they are hotter, whereas the cooler dust around the comet - with a temperature near the freezing point of water - glows red. JPL manages NEOWISE for NASA's Science Mission Directorate at the agency's headquarters in Washington. The Space Dynamics Laboratory in Logan, Utah, built the science instrument. Ball Aerospace & Technologies Corp. of Boulder, Colorado, built the spacecraft. Science operations and data processing take place at the Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena. Caltech manages JPL for NASA.

This is a comet that was discovered by an amateur astronomer months before it was about to fly past the Earth. It takes a massive 1,371 years to complete an orbit and was only visible for a short time before whisking back off into space. This comet is described as an extreme trans neptunian object that spends most of its time in the furthest reaches of the solar system. Truly a once in a lifetime event to see it.

I got to look at this on two nights around 15th Feb 2019 using Earth and Sky’s 16inch telescope and it was faint but definitely visible and another time at the South island stardate through (what I am pretty sure was) a 10-inch telescope on the 9th Feb.

Finding it was a little tricky as it was brightest when it was in Leo and there are a lot of galaxies in that part of the sky (the Virgo cluster is in that direction).

The best thing about comets is that they don’t come back for a long time, at least on the scale of human lives. It makes each one unique and I feel privileged to get the chance to see them. And if you missed out on these ones here just remember that you might not see these comets but comets do visit the inner solar system every now and again you just need to keep looking out for when the next one is expected to come around.