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See Andromeda (CosWatch Blog 6)10/07/2020

Welcome to the sixth of Fun Science‘s CosWatch blog posts, which you can read through with your young scientist and learn how to see Andromeda, our galactic next-door neighbour.

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.

Today we look for Andromeda, a place far distant from any of our other CosWatch blog focusses.

APOD provides us with this ethereal picture of Andromeda.

What is Andromeda?

We live in a galaxy – a collection of stars, usually in a disk shape – called the Milky Way. Andromeda is simply another such galaxy.

Though perhaps the most well-known galaxy other than our own, the Andromeda galaxy isn’t technically the closest; this is because the Milky Way and Andromeda both have “satellite” galaxies, a bit like the moons of a planet. It is, however, the largest galaxy in a big nest of galaxies of which we are a member; this is called the “local group”.

Andromeda is sometimes called “M31”. This means it is the 31st entry in something called the “Messier catalogue”. This is a list started by French Astronomer Charles Messier of fuzzy, difficult-to-identify objects in the night sky, including nebulae and star clusters. Andromeda’s satellites have similiar entries in the catalogue – M32, for instance.

The past and the future

Despite being larger, Andromeda is more like our galaxy’s little brother than older sister; it is ten billion years old, some three billion years younger than the Milky Way. It was formed from the collision of several protogalaxies, which you can think of as galaxy babies.

Andromeda was first recorded as being observed by human beings in 964 AD. However, it and other spiral galaxies were thought to be nebulae into the 1900s. There was a great debate by two scientists as to whether these “spiral nebulae” were just nebulae or “island universes”. It was settled when Edwin Hubble observed a flashing star, which he was able to use to measure the distance to Andromeda. It became quickly apparent that this object was further away than anything else we had observed, and was probably another galaxy.

An article by Ella Alderson provides this demonstration of a galactic collision.

The Milky Way and Andromeda are heading towards each other at over 68 miles a second – incredibly fast from our perspective, but for objects as big as galaxies, really rather slow. In about 4.5 billion years – when Earth will be twice as old – they will collide and combine into one galaxy, dubbed “Milkdromeda”. This may result in the solar system being ejected from the galaxies. Don’t panic, though; humans as we know them will be long-gone, and any still-existing lifeforms will probably be alright, as Earth will still orbit the Sun.

Visiting Andromeda

Since it was discovered to be another galaxy, Andromeda has featured in many science fiction stories. It is the main setting for the game Mass Effect: Andromeda, as well as the film Guardians of the Galaxy. It’s also the setting of Andromeda, a series by Star Trek creator Gene Roddenberry.

The game map of Mass Effect: Andromeda. The various locations of this game are no match to the actual population of Andromeda, which is estimated to have something like a trillion stars!

Unfortunately, in real life, we probably can’t visit Andromeda. The laws of physics seem to say that we can only travel as fast as the speed of light; even if we did manage to match light with a probe or space ship, it would still take us 2.537 million years to reach the place. Fortunately, there’s plenty we can learn about it from simply observing it in the sky.

How can I see Andromeda?

The Andromeda galaxy is the only galaxy visible with the naked eye, albeit on moonless nights; despite being so far away, the brightness of its collected stars makes it very powerful. It forms part of the conveniently named Andromeda constellation.

To find it in the night sky, you need to find the “Mirach” nearby; think of it like using a sign post to choose the right lane on the motorway.

This diagram from WikiHow eloquently demonstrates how to find Mirach (and thus Andromeda) between the Cassiopeia and Pegasus constellations.

Fortunately, Mirach doesn’t move erratically in the way the planets do (there’s a reason “planet” is Greek for “wanderer”), so you should always be able to find it in this spot. Just use a star chart (or website like timeanddate.com) to work out when those constellations will be visible in your area, and you’ll be set!

There are some benefits to observing Andromeda with a telescope. You may be able to see some of Andromeda’s twenty dwarf satellite galaxies. The image below was taken in 1899; imagine what you could do from your own garden with a whole century of technology on top!

In conclusion:

  • Andromeda is another galaxy, bigger than the Milky Way but younger.
  • It is the largest galaxy in our galactic “local group”.
  • Sometimes people call it “M31” because it is part of a record of space things called the “Messier catalogue”.
  • It has been observed since the 900s but was only determined to be another galaxy in the 20th century.
  • It will collide with the Milky Way in several billion years.
  • We probably can’t visit it, but we can certainly learn lots about it from observation.
  • It can be seen with the naked eye near the Cassiopeia and Pegasus nebulae.
  • Telescopes can reveal smaller galaxies next to it.

What’s next on CosWatch?

Next time, we’ll look at Comet NEOWISE, a rare Astronomical opportunity this month. Don’t miss it!

Notes:

Fun Science recently created a “Planets and Space” home kit, available now for only £5.00. Check it out here!

If your young scientist is interested, they may like to hear about blue-shifting. Because Andromeda is heading towards us, its light waves are being compressed, which makes them bluer; if it was moving away, they would be being stretched, making it appear redder. It’s quite well-explained in this gif shared on the Fun Science Twitter page.

See Orion’s Belt (CosWatch Blog 3)17/06/2020

Welcome to the third of Fun Science‘s CosWatch blog posts, which you can read through with your young scientist and learn how to see Orion’s Belt.

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 lovely shot from Universe Today shows Orion’s Belt clearly – the three blue stars in a diagonal line in the middle.

Orion’s Belt is the focus this week. You’ll learn what this celestial location is, and learn how to see Orion’s Belt.

What is Orion’s Belt?

Orion’s Belt, sometimes titled “The Three Kings” or “The Three Sisters”. refers to three stars in the constellation of Orion. Constellations are shapes in the night sky, that ancient people compared to mythogical figures or pictures of stories. Constellations are specific to whiever planet you’re on, and don’t refer to an actual “thing” in space; the stars in Orion are millions of miles apart, and not “aligned”.

This drawing by Johaan Bayer demonstrates how Ancient Greeks interpreted their view of the stars, and this image from EarthSky.org shows how we see it today..

In mythology, Orion was a giant hunter. You can see in the image above how the Greeks might have intepreted the stars as reflecting his shape; certainly his right “arm” looks as if it’s holding an arrow, and the three stars do look a little like a belt on a dainty torso. Admittedly, it’s quite difficult to see it now, but perhaps the Greeks had better imaginations than us, without TV to distract them.

What is in Orion’s Belt?

Again, describing something as being “in” Orion is a bit misleading, as Orion only looks like a flat shape from our planet; as this video shows, it’s actually a complex 3D shape with something like 1000 light-years between the different “dots” of light.

[youtube https://www.youtube.com/watch?v=lD-5ZOipE48&w=560&h=315]

What I can do, however, is describe the different stars and objects that make up the “belt” of the constellation you can see.

I’ve labelled this image from the Hubble space telescope to help you identify the different stars.

1. Alnitak

Alnitak is actually a triple star system, three stars that orbit around each other. The three stars are blue super giants, far larger than the Sun.

A size comparison between one of the Alnitak stars and our Sun. The Sun is millions of times larger than the Earth – Alnitak is almost frighteningly colossal!

2. Alnilam

Alnilam is also a blue supergiant. Within the next million or so years, this star may explode as a supernova!

3. Mintaka

Like Alnitak, Mintaka is another system of three stars. Once again we have some blue supergiants; because these perform nuclear fusion more powerfully than the Sun, they “die” more quickly and become beautiful nebulae or supernova.

 

It’s a bit like that bit in Star Wars where there are two Suns. In this case, rather than orange and red star, the Mintaka system is made up of three blue supergiants, which are extremely hot and far bigger than the sun.

4. Orion nebula

The last part of Orion’s Belt to talk about is perhaps the most exciting. Just below Orion’s Belt is the Orion Nebula. A nebula is the gaseous remains of a star that has stopped necular fusion; the ghost of a star is a fun way to imagine it. In the Orion Nebula, there is a “Stellar Nursery”, where protostars (new, baby stars) are forming – about 750 of them. What’s more, many of them have “protoplanetary disks”, huge circles of dust and gas where planets like ours may be created. To put it another way, the Orion Nebula is pregnant with hundreds of new Solar Systems.

The video below shows what it might look like to travel through this beautiful nebula – though it’s travelling much faster than we think is physically possible.

[youtube https://www.youtube.com/watch?v=xCFg5udYbAg&w=560&h=315]

How can I see Orion’s Belt?

Orion’s Belt can be seen fairly easily if you look in the South West sky during the evening (or North West in the Southern Hemisphere). View with the naked eye for the bigger picture, or with a telescope to examine individual stars; unfortunately, they are simply too far away to see anything like planets or moons.

Trying to see Orion’s nebula is more complex. Nebulae are, as a rule, difficult or even impossible to see with the naked eye. For that reason, if you have a telescope, try aiming that at the Orion nebula. Once you’ve located it, increase magnification to get a better view, and try different filters to make it more vibrant.

The Orion Nebula as seen by Marian McGaffney.

However, while I can’t make any promises, some people have been able to observe the Orion Nebula without equipment – you’d just have to find an area with very low light pollution, on the night of a New Moon.

In conclusion:

  • Orion’s Belt consists of three stars in the Orion Constellation; a constellation is a shape made of stars viewed from Earth.
  • The three stars – Alnitak, Alnilam, and Mintaka – are blue supergiants.
  • Two of those supergiants are triple systems, with three stars orbiting each other. Thus, the three stars of Orion’s Belt are actually seven stars!
  • Just below the belt is the Orion Nebula, with hundreds of new Solar Systems being formed inside it.
  • Orion’s Belt is easily visible on clear nights in the South-East.
  • Seeing the Orion Nebula usually requires a telescope.

What’s next on CosWatch?

Next time, I’ll be talking about the Phases of the Moon, and why it appears to change shape. Have a good week!

Notes:

Fun Science recently created a “Planets and Space” home kit, pre-orderable now for only £5.00. Check it out here!