Tag Archives: galaxy

Hello Keira,

I have been looking at your comments and hope I can provide some answers to your questions. Remember, as your questions delve deeper into a subject, the answers can be more difficult to understand but this is what learning is about.  As we learn and understand simpler things, it can be easy to learn harder things. I am still learning as I search for answers. See what you can understand in the answers I try to give. What you have asked will appear in bold blue text.

Your comment from the beginning of March on the post…

Life But Not As We Know It

This NASA image was listed as in the public domain and was sourced through Wikimedia Commons.

This NASA image was listed as in the public domain and was sourced through Wikimedia Commons.

In my personal opinion, I think that Mars was once a beautiful planet, and there was life on this beauty. Since Mars did not have a very protective ‘umbrella’, Mars’ ‘umbrella’ shrank. Overtime, Mars got closer to the sun, burned, and sent life over to Earth, right past its ‘umbrella’. As Earth evolved, Mars lost its magnificent atmosphere, and moved behind Earth. Mars soon lost everything it once had owned, life and beauty. Now taking Mars’ place is Earth. As you may know, I have a plethora of questions to ask you. Do you think my idea may be possible?

Science doesn’t tend to talk much of the impossible and prefers the word improbable. To be impossible means there is absolutely no chance of something happening no matter what might change. Improbable means it’s not very likely so if something is improbable it can happen but it is far more likely it won’t. Based on what we know at this time, your idea comes under the improbable in some parts and probable (likely) in other parts.

Look at the video clip below from NASA. It is an animator’s view of the evolution of Mars based on the information NASA has. The journey starts about 4 billion years ago and shows a water planet up till today as we know it to be. Do you think it would have been beautiful? I know it still has a beauty today but not as a water world such as ours.

“Mars was once a beautiful planet” – I think this is probable if you mean having rivers, lakes and seas but improbable if you think it had trees and large animals moving through them. Life would have been simple if it had evolved. I think there is a good chance we will eventually show life existed on Mars and may still be in the soil in some areas.

Watch the video clip below looking at NASA’s findings on Mars. It shows us Mars probably had the right conditions for life to begin. With a proposed mission in 2020, we might be able to show Mars had life.

There is evidence Mars once had liquid water on its surface but the thin atmosphere can’t keep heat in as on our planet. The average temperature of Mars is around    -60C. With water freezing at 0C, liquid water isn’t likely. However, at Mars’s equator, summer daytime temperatures can reach 20C only to drop to -70C at night. While 20C is enough for water to be liquid on Earth, I think the thin atmosphere would only allow ice to turn to water vapour and not liquid on Mars.

Yes, Mars also has seasons because it is tilted only slightly more than Earth, You might remember a post about Earth’s tilt I wrote for your class, Earth’s Tilted Seasons.

Here is another video clip looking at Earth’s magnetosphere (umbrella) and the discovery of the outer and inner core. Mars doesn’t seem to have a molten outer core and solid inner core to create the magnetic field to protect it as we have on Earth.

Mars did not have a very protective “umbrella” – Mars probably had an “umbrella” (or magnetosphere) and much thicker atmosphere in its beginning but, as the core cooled, it lost much of it starting perhaps 4 billion years ago. Without the protection of a strong magnetic field, energy from the sun made Mars lose most of its atmosphere. Remember, it’s because of Earth’s liquid and solid iron core we have the magnetosphere (umbrella) to protect us.

As Earth evolved, Mars lost its magnificent atmosphere, and moved behind Earth. -  Earth and Mars would probably have formed at around the same time. Our sun was probably formed when a molecular (atoms of matter) “cloud” collapsed through gravity. Not all of the “cloud” was used in making up the sun. The matter remaining in what is known as the accretion disk started coming together under gravity. Much of this extra matter became the planets.

Formation of the Solar System

Earth Formation

Have you ever encountered someone who has an idea of how Mars lost its beauty that you think is true?

While I have not personally met a scientist who can say what had happened, there are a number of references and videos online to help us. As with all information on the internet, it’s best to use reliable sources such as NASA when looking for information. In sharing the video links I have given you, I first check links to see if they’re from a source I trust. I also find many with sometimes strange ideas from sources I don’t know. I usually don’t use these unless I have reason to believe they are accurate.

Do you think there could have been life on other planets, too?

In the video clip below from National Geographic, it asks what aliens might really look like. No one has proof of life other than on Earth at the moment so we don’t really know what life on other planets might look like. We may only have an idea of what might be needed. The clip shows on higher gravity planets, animals would need to be stronger and stockier (bigger) than on Earth or probably spindlier (thin looking) on a planet with less gravity. Some planets might only have life like the bacteria we have here. Until we find extraterrestrial (not of Earth) life, we can only guess.

While we have no proof at this time life exists on any planet other than Earth in our Solar System, I suspect life may be in many places across the universe in some form or other. We know life on Earth can exist in a very wide range of habitats (environments where life exists). Life can be found deep under sea near volcanic vents or locked in ice on mountains.

I have seen estimates of the number of galaxies in our universe being anything from 100 billion to 500 billion. For our galaxy, the Milky Way, the number of planets might be anything from 100 to 400 billion. If we take the lower estimates for galaxies and using the low estimate for planets in our galaxy to work out how many planets there might be in the universe, we would get…

100 billion (galaxies) x 100 billion planets = 10 hextillion planets

That is…

10,000,000,000,000,000,000,000 planets in our universe

What a waste of space it would be if the only life in the universe was to be found on our small, blue planet.

Where do you get all these facts?

When I see posts or questions I find interesting, I sometimes remember information I have read or seen in the past. If I decide to write a post, I usually have to search for extra information online or in books in my library. I try not to post anything unless I believe the information I find is the best available in my research. Because of this, I sometimes have to make changes to posts if I later find I have made mistakes.

The skill is to know how to find information, work out whether it might be true then use it to help others.

Your comment from March 26 on the post…

How Did the Earth Begin?

First of all, I am wondering why early scientists thought that the sun and every other planets orbited around us?

When we look up at night, we can see the stars. Watch long enough and you notice them move. During the day, the sun rises in the east and sets in the west. Surely the sun, planets and stars must orbit the Earth because we see them move and not us. This was the thinking and it can seem reasonable. It's what we seem to see.

Schools and students have permission to use this graphic for non-commercial, educational purposes.

Schools and students have permission to use this graphic for non-commercial, educational purposes.

Consider this, you are on a speeding train looking out of a window. The landscape is zipping past your window very quickly. Is it the landscape moving or the train moving through it? While saying the train is moving might seem reasonable, surely this couldn't be true for the Earth? The Earth is so big compared to the small stars and planets in the sky. The Earth must be still and everything else in motion.

As early as the 3rd century BCE, a man named Aristarchus suggested the sun was the centre of the solar system but it wasn’t until the work of a man called Nicolaus Copernicus in the early 1500s a sun-centred (heliocentric model) solar system began to be accepted. It was also around this time the first telescopes seem have made an appearance. Astronomy had its start in astrology but started to emerge as science with telescopes allowing better study.

Optical Telescope dome at Warrumbungles National Park 

Schools and students have permission to use this graphic for non-commercial, educational purposes.

Schools and students have permission to use this graphic for non-commercial, educational purposes.

If they had had technology back then, would they still have thought that everything orbited around us?

There are still many people today who believe the Earth is at the centre of the universe (geocentric model). They believe it is fixed in place and doesn’t rotate on its axis. The more modern model has the Moon orbiting Earth. Further out the Sun orbits Earth while the other planets and their moons orbit the sun. The other stars and galaxies we see are all further out forming a sphere around central Earth. This comes down more to what I think is misguided faith (believing no matter the evidence against).

I see problems with the idea. As example, if the Earth didn’t rotate on its axis, to have day and night the sun and all of the planets orbiting it would have to orbit the Earth every 24 hours and this is not what we see. Secondly, spacecraft such as the two Voyager missions and missions to Mars were sent out based on known positions of the planets orbiting the sun. If the centre Earth model had been true, the Voyager and Mars missions would have failed.

Another question I have is about how many other galaxies are out there?

I have given information on this above. There are estimates there could be anything from 100 billion to 500 billion galaxies in the universe.

The number of people alive on Earth is heading towards 8 billion. Using the numbers above, there would anywhere from about 12.5 to 62.5 galaxies for every person on Earth. That’s a lot of galaxies.

In the image below sourced from NASA through Wikimedia Commons, there are around 5500 galaxies in view. To make the low estimate for the number of galaxies in the universe (100 billion), you would need to show approximately 18 million photos showing 5500 galaxies.

This NASA image was listed as in the public domain and was sourced through Wikimedia Commons.

This NASA image was listed as in the public domain and was sourced through Wikimedia Commons.

One more question I have is how did those giant stars form in the last video?

Let’s show that video clip again…

I would say it’s all a matter of matter and time.

Stars spend most of their “lives” as what is known as main sequence stars where they are burning hydrogen through something called nuclear fusion. Hydrogen becomes helium. Like any fire, the fuel can run out. As this happens the star’s core gets larger and starts burning helium and fusing it into carbon and oxygen. If the star has enough mass and other features, the star is known as a supergiant star.

The supergiant stars lose mass quickly. Some of these supergiants can be quite bright and losing mass very quickly. They are the hypergiant stars like the one in the video known as VY Canus Majoris. If it was at the centre of our solar system, it would be so big it would reach out beyond Jupiter.

The very large stars have been burning their fuel making new elements. When they get to the stage of making iron then eventually trying to fuse it, the star’s core can collapse and cause what is known as a supernova (a very big explosion of light and matter). What can be left behind could be a black hole (singularity), a neutron star, quark star or a magnetar.

Back in 1987 we were able to see a supernova explosion without using a telescope. A new star seemed to appear where only powerful telescopes might once have seen it. It eventually faded but I remember seeing what looked like a new dot in the night sky. Nova SN 1987A was about 168,000 light years from Earth. What this means is the light I was watching started out from the nova about 168,000 years ago. When we look deeper into space, we are looking back in history. Even the sunlight hitting you in daylight has taken over 8 minutes to reach us.

Look at the clip below. It gives information about SN 1987A and its jouney to supernova…

In the future, VY Canus Majoris will go supernova. What can be interesting is the matter thrown off when it does may be the resources other solar systems need to form.

Also, how did humans know that there are bigger stars than the sun?

Since the beginning of humans, they have been able to see stars in the sky. As knowledge and science has advanced, we have been learning more about the universe.

Optical telescopes brought the moon, planets and stars closer. Radio telescopes picking up the “sound” of space brought us more information. The Hubble telescope orbiting earth allowed us to see even further into space than telescopes on Earth. Computers help us model systems and calculate small changes in orbits of distant stars telling us of orbiting planets. We have learnt so much since the time the first cavemen looked up and saw the stars yet we still know so little. It’s like many things in life, the more we learn the more we realize how little we know.

 Parkes Radio Telescope

Schools and students have permission to use this graphic for non-commercial, educational purposes.

Schools and students have permission to use this graphic for non-commercial, educational purposes.

Finally, do you think that there are larger stars than the last one in the final video in the post?

VY Canus Majoris is listed as the largest known hypergiant star. The important word is “known”. There could be far bigger stars out there somewhere. Perhaps if you become an astronomer you might discover a much larger star somewhere in the universe. What would you call it? It might still be called a hypergiant but it might have some properties making it different to hypergiants and the superhypergiants could be born. I would think such hypermassive stars would not last a long time before going supernova, or would it be hypernova? Science has many mysteries still to explain.


3/4B, 4T and 3SF visited the Penrith University of Western Sydney Observatory and share their experience in a blog post. They also asked questions and I loved the challenge of trying to answer them. To see their post…

Bloggers of the Week: Our Excursion to the Observatory

To see Part 1 of this comment...

Observing Space, there’s so much of it out there – Part 1

Hello 3/4B, 4T and 3SF,

Here are some possible answers to the second set of questions.

1. How many more years until we have to pack up and move to another planet, because the sun died?

Schools and students have permission to use this graphic for non-commercial, educational purposes.

Schools and students have permission to use this graphic for non-commercial, educational purposes.

Firstly, let's look at how our Earth is thought to have come to be. Heather and Keira from California had challenged me to explain how the Earth had begun. Here is a link to the post I wrote for them if you are interested.

How Did the Earth Begin?

... and here is a link to a Wikipedia post looking at history of the Earth. It is about  Earth from its formation to now.

History of the Earth

Okay, we have an idea how our Earth began but how might it end? As our planet's birth was linked to the formation of our sun, the sun is also involved in its suspected end.

Back in 1987, I was able to look into the night sky and see a "new" star. A star astronomers named SN 1987A had gone supernova. It is about 168,000 light years* from Earth and could not normally be seen without a powerful telescope. It is again too dim to be seen without a telescope. Had it been our star, our planet would have been destroyed.

Then what about our Sun? How old is it? What might happen to it? When might it happen?

This is a NASA photo released into the public domain. It was sourced through Wikimedia Commons. http://commons.wikimedia.org/wiki/File:The_Sun_by_the_Atmospheric_Imaging_Assembly_of_NASA%27s_Solar_Dynamics_Observatory_-_20100819-02.jpg

This is a NASA photo released into the public domain. It was sourced through Wikimedia Commons.

Our Sun is thought to be about 4.6 billion (4,600,000,000) years old. I had to do a little research about the Sun to find out what might happen. I found interesting information suggesting our Sun is becoming brighter by about 10% every billion years and it's surface is slowly becoming hotter. As it gets older and burns more of its hydrogen fuel it will grow in size to eventually become a red giant. By this time Earth, if it still exists, will not be able to support life.

The video clip below shows what might well happen when our to end of world. Duration: 3:04 minutes.

It replaces the original linked video clip now blocked from viewing in Australia due to copyright issues.

This is not my video clip.

Should we worry?

It is thought it could take about 5 billion (5,000,000,000) years before our Sun is a red giant and perhaps 1 billion (1,000,000,000) years before the Sun's rising temperature means all water will evaporate away from Earth. A billion years is a very long time. However humans develop in that time, we can only hope they have solved the problems. For a time until the sun gets too big or hot this might mean people moving to Mars but to go to other stars people might have to spend a very long time in space. By the time people reach other stars, they could be the great, great, great, great,... great, great, great, grandchildren of those who left Earth.

But I've seen movies where they move through gates or hyperspace at faster than the speed of light and arrive quickly...

The movies love finding ways to arrive quickly. Who knows what science might discover in a billion years. For now, the idea of travelling close to the speed of light is beyond us. Whatever the future brings, I have faith humans will find a solution if there's one to be found. I know NASA engineers are looking at ways it might be one day possible to warp space and make travel to the stars real. 🙂

168,000 light years* - as explained in Part 1, a light year is the distance light travels in a vacuum in one Earth year. While I saw the supernova as a bright star in 1987, the light had started on its way 168,000 years ago. When we look at stars, we are looking back in history. Even light from our own sun started its journey about 8.3 minutes before we see it.

2. Did you know that there are many different galaxies in space?

Yes. Too quick an answer? 🙂 I'll share some NASA galaxy photos using links.

The two galaxies shown here are in the early stage of an interaction that will eventually lead to them merging in millions of years. The two galaxies are about 450 million (450,000,000) light years from us. If you look carefully you can see other galaxies in the distant background.

UGC 9618, Chandra + Hubble

By Smithsonian Institution [Public domain], via Wikimedia Commons

This second photo shows galaxy M33. It is about 3 million (3,000,000) light years from Earth. The really bright stars are young, very large stars. Yes, stars are still being made in our universe from the remains of other stars.

Galaxy M33 Chandra X-ray Observatory

By Smithsonian Institution from United States [see page for license], via Wikimedia Commons

The third photo shows galaxy Centaurus A. If you can see what looks like a line of white light coming from its centre, that's the result of Centaurus A having a supermassive black hole at its centre.

Centaurus A Chandra

By NASA/CXC/CfA/R.Kraft et al (http://chandra.harvard.edu/photo/2008/cena/) [Public domain], via Wikimedia Commons

Galaxies are not all one size. Dwarf galaxies might only have as few as 10 million (10,000,000) stars whereas giant galaxies might have up to 100 trillion (100,000,000,000,000) stars. There are estimates the might be up to 170 billion (170,000,000,000) galaxies in the observable universe . There may be very many more but they are so distant their light still hasn't reached us, they're not yet observable. That's a lot of galaxies.

I like looking at big numbers so let's look at big numbers. I have said their might be 170 billion (170,000,000,000) galaxies in the observable universe. I also said galaxies could have from 10 million to 100 trillion stars. Let's say the average galaxy has 1 billion (1,000,000,000) stars.

How many stars might their be in the observable universe?

170,000,000,000 galaxies x 1,000,000,000 average stars = 170,000,000,000,000,000,000 (I make that 170 quintillion stars.)

In Part 1 of these answers to your questions I mentioned it has been said there are more stars in the universe than all of the grains of sand on every beach on Earth. Would one of you start counting so we can check? 🙂

Below is a You Tube video clip from NS showing galaxy M31 known as the Andromeda Galaxy. It is the nearest large spiral galaxy to our own. Our galaxy, The Milky Way, is also a spiral galaxy. Duration: 3:06 minutes

This is not my video.

3. Did you know that Pluto has 2 more moons?

Yes, but I found there seems to be more discoveries when I was researching. In order of distance from Pluto they are Charon, Styx, Nix, Kerberos, and Hydra. It is possible more small "moons" might be found. Click to read Moons of Pluto on Wikipedia.

In this photo taken by NASA in 2005, the two dots listed as candidate satellites
Pluto system 2005 discovery images

When Pluto was discovered in 1930, its brightness suggested it was much larger than it was found to be but that was because it is icy. Charon was discovered in 1978. I always found its name was a great choice. In ancient Greek mythology, Pluto was the god of the underworld where people went when they died. To reach there, you had to cross the River Styx. This could only happen if you had a coin to pay the boatman, Charon. It was common for ancient Greeks to bury their dead with a coin so they could pay Charon. This is why I thought the name is a good choice. Pluto and Charon are together in ancient Greek mythology.

One unusual piece of information I read was about Pluto and Charon. Moons orbit around their planet as does our moon but Pluto doesn't seem to be the centre of Charon's orbit. The centre of orbit is somewhere in between but closer to Pluto. What a strange place Pluto would be.

While searching online, I found an animated file showing a computer generated rotating image of Pluto you might like to see. It's based on NASA images of the surface of Pluto. This an embedded NASA file in the public domain.

Pluto animiert 200px
By Aineias, NASA, ESA, and M. Buie (Southwest Research Institute)  derivative work: Aineias, Ilmari Karonen (Pluto_hubble_photomap.jpg via Pluto_animiert.gif) [Public domain], via Wikimedia Commons

4. Did you know that Neptune's ring is made out of ice particles?

Below is my favourite image of Neptune. NASA released this image into the public domain. Neptune's atmosphere seems to be mostly hydrogen and helium. "The interior of Neptune, like that of Uranus, is primarily composed of ices and rock." (Wikipedia). Remember, ices aren't necessarily only water. Have you heard of dry ice we can buy here on Earth? It isn't water. It's icy carbon dioxide. For Neptune, the ices are thought to be mostly water, ammonia and methane. The core of the planet is said to be rocky.


By . (http://photojournal.jpl.nasa.gov/catalog/PIA00046) [Public domain], via Wikimedia Commons

The next NASA image was taken by the Voyager 2 and shows the rings on Neptune.

Neptune rings PIA02224

By Courtesy NASA/JPL-Caltech (http://photojournal.jpl.nasa.gov/catalog/PIA02224) [Public domain], via Wikimedia Commons

The rings are thought to probably contain large amounts of micro-dust as well as ice.


5. Did you know that it takes 1 month for the moon to orbit around the earth?

Wikipedia reference for the different types of months and years: Month

This embedded graphic shows the phases of the Moon seen as it orbits the Earth. Do you notice we only see one side? The other side is often called the dark side. It also comes into sunlight but, since it faces away from Earth, we don't see it.

File:Lunar libration with phase Oct 2007 450px.gif

This work has been released into the public domain by its author, Tomruen. This applies worldwide.

This is an interesting question even if it sounds simple. Rather than say "yes" or "no", I might ask what type of month?

I know the months we talk about run from January to December. February has 28 days or 29 in a leap year. The others have either 30 or 31 days. The average number of days in a month is about 30.4 days. If you mean one of our Gregorian Calendar months we use, the answer is not quite a month.

When compared to the position of stars, the Moon takes about 27.3 days to orbit the Earth but Earth is also moving through space so the time between two full moon is about 29.5 days.

Did you know there was something known as a lunar calendar?

The calendar we use is a solar calendar. It's based on the time it takes for the Earth to complete one orbit around the Sun. Lunar calendars are different because they are based on cycles of the Moon.

Many cultures have had lunar calendars.  One of the important examples is the Islamic Calendar. A year has either 354 or 355 days where as the Gregorian Calendar has 365 or 366 days based on a solar year. If you have Muslim friends, you might know the first day of their new year is a different day on our calendar each year. This happens because their lunar year is 11 days shorter.

The Gregorian solar year has an average of about 30.4 days per month giving us about 365 days a solar year.

The Islamic lunar year has an average of about 29.5 days per month giving us about 354 days a lunar year.

Can you see the solar calendar gives us about the time it takes for the Earth to complete an orbit of the Sun while the approximate number of days in a lunar month is how long it takes the Moon to go from one full moon to the next?

The embedded diagram below shows how the phases of the Moon come about while the Moon orbits Earth.

Moon phases en

By Orion 8 (Own work) [CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0) or GFDL (http://www.gnu.org/copyleft/fdl.html)], via Wikimedia Commons

6. Did you know that (it takes) a year for the earth to orbit around the sun?

Our Gregorian solar calendar is based on how long it takes the Earth to complete one orbit of the Sun, that is it takes about 365.25 days for Earth to orbit the Sun. We call that a year of 365 days with a leap year helping us catch up on the extra bits by having an extra day.


By Adam850 at en.wikipedia [Public domain], from Wikimedia Commons

What would a year be on other planets and dwarf planets?

Here are the other planets and known dwarf planets in our Solar System with how long their years would be in our Earth years (Ey).

Mercury ....................... 0.24 Ey (88 days)

Venus ........................... 0.62 Ey (226 days)

Earth ............................ 1.0

Mars ............................. 1.88 Ey

Ceres (dwarf) ............... 4.6 Ey

Jupiter .......................... 11.86 Ey

Saturn ........................... 29.46 Ey

Uranus .......................... 84.01 Ey

Neptune ....................... 164.8 Ey

Pluto (dwarf) ................ 248.09 Ey

Haumea (dwarf) .......... 282.76 Ey

Makemake (dwarf) ...... 309.88 Ey

Eris (dwarf) ................... about 557 Ey

A little extra...

In July last year a class asked some questions about space. I didn't add and pictures to the post but you might like to see their questions and my answers...

Wonderings About Space

* * * * * * * * * *

And one final You Tube video clip answers,

"What Is Space?"

Duration: 55:43 minutes

This is not my video clip.