Welcome to the seventh of Fun Science‘s CosWatch blog posts, which you can read through with your young scientist and learn how to see the comet NEOWISE.

This comet is visible for about the next week, but then will be absent for thousands of years. Unless you’re immortal or a ghost, don’t delay!

What is CosWatch?

There’s so much to see in the night sky! You may have seen Brian Cox on TV describing the “wonders of the universe”, or Carl Sagan talking about the “awesome machinery of nature”, and they’re absolutely right. But while huge rockets and observatories can help, space isn’t just for people with expensive equipment. You can see amazing things from millions of miles away from your very own back garden. Each week, I’m going to talk about one of these incredible objects, and how you can find them.
This was captured by Raman Madhira on July 9th.
This time, we’re going to be talking about how to see NEOWISE, a comet visible this month!

Tell me about NEOWISE

Comets are balls of ice that move around the solar system, which is why they’re sometimes referred to as “dirty snowballs”. NEOWISE is one of these comets. Comets move around in strange oval orbits. When they move close to the Sun, they begin to melt, and large amounts of their ice are torn off in the form of bright gasses. This is why they have long tails.
This image from Wells & Mendip Astronomers shows us NEOWISE’s tail.
NEOWISE has a strange name because it was discovered by the NEOWISE space probe. The “WISE” stands for “Wide-field Infrared Survey Explorer”, while the “NEO” stands for “Near-Earth Object.”
The probe in question. This is just concept art, but gives us a good idea of what the probe looks like in space.

Where do comets come from?

There are two types of comet – “short period” comets, that orbit the Sun in less than 200 years, and “long period” comets, that take much longer than that – sometimes many thousands of years.
As this diagram demonstrates, NEOWISE is a long period comet; it takes about 4500 years to reach us, and another 6800 to get back to where it started from.
Short period comets are thought to originate from the “Kupier Belt”, a ring of asteroids past Neptune. Long period comets probably come from the “Oort Cloud”, a great cloud of gas and rock that surrounds the Solar System.
A diagram by Lorine Moreau showing the incredible size of the Oort Cloud – you can also see the Kupier Belt.
We have tried to land some space probes on comets, ocassionally successfully. However, because of the relatively small sizes (often about that of a city) and extremely high speeds involved, mistakes do occur. A lander from the Rosetta spacecraft managed to reach a comet, but unfortunately bounced underneath a cliff; this meant that its solar panels were uesless, and the batteries ran out before many results could be acquired.

How can I see NEOWISE?

NEOWISE will be very, very difficult to see after the 19th, and will disappear soon afterwards. There’s also the risk of it breaking up into pieces too small to see at any point. Don’t delay! Make plans!

I managed to see NEOWISE at 3:15am on the 12th. Yes, unfortunately this CosWatch will involve some early morning rising or late nights – but for such a rare spectacle, isn’t it worth it?
This photograph was taken by my good friend James in London, and should give you some idea of what you’ll be seeing.
Some people have reported seeing NEOWISE as early as 11:30pm, but for security’s sake, 3am – before it starts to get dark – is your best option. Find somewhere with a clear view of the North-East horizon. It should be fairly difficult to miss, but if you’re having trouble finding it, locate the star Capella using the internet or star charts, then look further down. NEOWISE is visible with the naked eye, but in areas with considerable light pollution, it’d be worth using a binoculars or a telescope; unlike shooting stars, comet, though extremely fast, look like they’re moving very slowly aross the sky, and are easy to focus on as a result.

In conclusion:

  • NEOWISE is a comet visible for the next week or so.
  • It is a “long period” comet, meaning it takes thousands of years to move around the solar system.
  • It probably originated in the Oort Cloud.
  • Its tail is simply ice melting as the comet approaches the Sun.
  • You can see NEOWISE easily – but not for long!

What’s next on CosWatch?

Next time, I’ll be talking about Saturn, the iconic ringed gas giant. Have fun observing NEOWISE!


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