The Solar System

A montage of the planets and the Earth's Moon.

A montage of the planets and the Earth's Moon. These images were taken by a variety of spacecraft. Source: Courtesy NASA/JPL-Caltech

The Sun and the planets formed around 5 billion years ago, from a cloud of gas and dust left behind by dying stars. This was mostly Hydrogen and Helium, but there were traces of the heavier elements which would allow the formation of solid planets and, eventually, life.

The cloud collapsed into a rotating disk, with almost all of the material concentrated in a central bulge, where the Sun would form. At certain distances out from the centre, mass started to accumulate and gravity pulled in more and more material. The planets were beginning to form. They swept the area around them clear of small pieces of dust and rock as they orbited. They also frequently collided with larger rocks, growing in the process. Eventually they reached their current size. The material left became the comets and asteroids.

For another billion years or so stray comets and asteroids continued to bombard the planets. Many planets and moons, such as Mercury and our Moon, still show the scars from this period in the form of craters.

Today we can see the same process taking place around other stars, such as several young stars within the Orion Nebula.

The Solar System Today

The Solar System today consists of the Sun, 8 planets, at least 3 dwarf planets, at least 63 moons and countless other small bodies including asteroids, comets and Kuiper Belt objects. At the centre is the Sun, its gravity dominating the system and locking the others into their particular orbits.

The solar system

The Solar System Today
Source: IAU/Martin Kornmesser.

The area around the Sun can be divided into several distinct regions:

  • In the inner solar system are the four terrestrial, or rocky, planets: Mercury, Venus, Earth and Mars. These are all relatively small and made mostly of rock, so they have solid surfaces.
  • Beyond the orbit of Mars, marking the edge of the inner solar system, is the Asteroid Belt, made up of millions of rocks, varying in size from pebbles to rocks the size of Melbourne. The largest of these, Ceres, is now considered a dwarf planet.
  • In the outer solar system are the four Gas Giants: Jupiter, Saturn, Uranus and Neptune. These planets are relatively large and are made mostly of gas. They have no solid surfaces, only thick atmospheres.
  • Last is Pluto. Until 2006 Pluto was thought of as the ninth and smallest planet but is now considered a dwarf planet. Pluto is neither rocky like the terrestrial planets nor a Gas Giant.
  • Beyond the orbit of Neptune is a belt of large icy objects, possibly related to Pluto, called the Kuiper Belt. This region may be the source of short-period comets. There is at least one Kuiper Belt object, 2003 UB313 (nicknamed Xena) that is larger than Pluto and is also considered to be a dwarf planet.
  • Far beyond the orbits of the planets, roughly one light-year from the Sun, lies an enormous sphere called the Oort cloud, where long-period comets originate.

As well as the Sun and the Moon, five of the planets (Mercury, Venus, Mars, Jupiter and Saturn) are visible to the unaided eye and have been known since ancient times. The remainder (Uranus and Neptune) and the dwarf planets have only been discovered since the invention of the telescope.

Comments (133)

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Natali 20 April, 2009 16:57
What is a Dwarf Planet is it the 3 furthest planets from the sun that are smaller then all of the other planets in our solar system?
Discovery Centre 21 April, 2009 12:52
Hi Natali, The term "Dwarf Planet" is a definition created by the International Astronomical Union. From their website: A "dwarf planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite. There are currently five recognised dwarf planets, as listed here.
Natali 22 April, 2009 17:10
What does light years mean? on a web site it says a perticular star is 321 light years away from the sun.
Discovery Centre 23 April, 2009 15:12
A "light year" is a measurement of distance that corresponds to the distance travelled by light in a year, so if a star is 321 light years from the sun, then that star's light will take 321 years to reach the sun.
David Smith 23 April, 2009 17:28
Can you give me a name of an Australian scientist who did investigations on the sun within the solar system. Thankyou
alex 29 April, 2009 20:33
How does the sun influence the conditions on each planet??
Discovery Centre 30 April, 2009 12:58
Hi Alex - the sun is a significant contributing factor to conditions on each of the planets in our solar system. You can find detailed information about individual planets at this website.
Janie Parker 1 May, 2009 11:02
Hi There, Where is the best place for me to start for sourcing footage of the Swift Turtle Comet? Kind Regards Janie Parker
Discovery Centre 1 May, 2009 13:27
Hi Janie, Within Australia you could try contacting the CSIRO Astronomy & Space division, or you could even try contacting NASA to see if they hold any material that might be of use.
Discovery Centre 1 May, 2009 15:31
Hi David, here is a link to the Centre for Stellar and Planetary Astrophysics. The website gives you the names of some of the researchers doing this work.
christie 6 June, 2009 19:56
Hi I have a multiple choice question which i really cannot answer and am wondering if you could help! It says, Jupiter has: A. 12 rings (as far as im aware it only has four???) B. 23 satellites (as far as I'm aware it has 63???) C. 19 moons (I though it was 63 as above) D. A star of its own (Since the above answers seem wrong to me Im thinking that this may be the answer but I do not understand how. Could it be referring to the sun?) If you do have any information which could help me answer this it would be a great help! Thanks alot!
jaber 10 June, 2009 23:17
Aaron 12 June, 2009 10:41
Excellent website great for school.
Discovery Centre 14 June, 2009 15:41

Hi Christie,

That does sound confusing - perhaps if you combine the information provided in the three Infosheets on the Solar System, the Sun and Jupiter, the answer might present itself.

If a solution is still not forthcoming, you can log an enquiry with the Discovery Centre and we can check with the museum astronomer.

Tristian Simpson 25 August, 2009 10:45
Hello i LOVE SPACE! can u tell me more about it??
Discovery Centre 26 August, 2009 10:28

Space is a pretty big topic but this website is a good place to learn about it. We have lots of great information including sky mapsmoon phases, Skynotes and infosheets. You might also want to visit the Planetarium to see one of our shows. The NASA website also has a vast amount of information on space and should keep you busy for ages!

james 6 September, 2009 12:21
hi there. how many miles is one light year?
Milka Samuel 13 September, 2009 17:49
Milka 7 years old have some quations. I want to know what the other galaxys are called? I want to know why Jupiter's red spot is 3 times bigger then Earth? I want to know why our galaxy is called The milky way? I want to know why thay made Pluto out of the gang and made Pluto a dwarf planet?
Discovery Centre 15 September, 2009 10:22

Hi Milka! It's great that you've got such an interest in astronomy. We'd suggest that you have a look at the other infosheets available on this site (lots of your questions are answered there), and if you'd like to learn more, have a look at Australian Astronomy's "Learning More" page for some fun and useful links!

Milka Samuel 6 October, 2009 19:25
Thank you for answering my quations.
mark 7 October, 2009 13:25
i find this website interesting because i thought there was i moon but there are 63 moons and i did'nt know there are planets called dwarf planets.
'Belle 15 October, 2009 12:46
If Pluto is not longer a real planet, what happens to all the people whose stars are ruled by the planet Pluto, do they regularly have bad days now? Concerned.
Discovery Centre 16 October, 2009 13:54

The declassification of Pluto apparently produced heated debate among astrologers particularly on blogs. It seems that just because it's not a planet anymore doesn't mean that it is not considered significant by the astrological community. Just like for astronomers, Pluto's re/declassification does not detract from its interest and, possibly, only increases that interest.

Skye 5 November, 2009 19:08
do you have any QLD web sites on space?
Discovery Centre 7 November, 2009 11:44

Hi Skye - Whilst we are not affiliated with any Queensland astronomy site in particular, there are several astronomy groups with websites that may interest you! Try the Astronomical Association of Queensland, and the South East Queensland Astronomical Society to begin with.

Angus Whitton 19 December, 2009 12:49
Is Venus and mercury in the Eastern Sky as the Sun is Setting in the West at around 8.40pm in the Evening? Can you tell me where to observe Venus and Mercury in the night Sky just after the Sun has Set. Are they to be viewed in the Western Sky or in the eastern Sky at this Hour?
Discovery Centre 22 December, 2009 13:47
As can be seen from our Skynotes, Mercury can be seen in the evening sky just after the Sun sets in the west. Venus is much too close to the Sun at the moment to really see it, but you may just be able to pick it out in the morning in the east just before sunrise.
Achim 24 December, 2009 05:07
What is the mass of jupiter?
Discovery Centre 24 December, 2009 14:17

Achim, the mass of Jupiter is an incredible 318 times that of earth, and is generally calculated to be, in kilograms, 1.9 times 10 to the power of 27!  More info here.

alan 9 February, 2010 16:32
I am a truck driver and every night I drive down the hume 2wards melbourne and a bright star alomost seems to mark the way. It is visible well into daylight can any1 name it 4 me pls.
Discovery Centre 13 February, 2010 10:34

Hi Alan - our Planetarium staff think that the bright star you are seeing is the second brightest star in the night sky - Canopus.  It is low in the south west in the early morning, just before sunrise.

Emma 2 June, 2010 09:49
Can you see Mercury in the night sky???
Discovery Centre 3 June, 2010 10:35

Yes, Emma, Mercury is often visible in the night sky. For up-to-date information about where and when to catch a glimpse of the planet, check out Melbourne Planetarium's monthly Skynotes newsletter.

Pasquale 22 June, 2010 18:25
I need to describe the movement of the sun from east to west for a project at school. I cant find anything on this? I thought it was the planets that orbit around the sun and the sun does not move?
marleen 23 June, 2010 07:23
From Melbourne's eastern suburbs: Early in the morning, 5,6 am, there is a very bright star low in the SSE, very roughly around 160 degrees (my compass is tiny). Would love to learn the name of it!
Discovery Centre 25 June, 2010 11:11

Hi Pasquale, the planets do indeed rotate around the sun as it says in the article above. The apparent 'movement' of the sun across the sky is actually caused by the rotation of the earth - one rotation equals one earth day. You can find further information and links on our website here and here.

Discovery Centre 26 June, 2010 16:08

Hi Marleen, the Planetarium staff believe the star referred to is Canopus, the second brightest star in the night sky.  Sirius, the brightest star in the night sky rises just before dawn, but unlikely to be seen, being too low to the horizon.  The brightest object to be seen in the morning night sky is in fact Jupiter.  This can still be seen high in the northern sky even as the sky lightens and turns blue.

margaret pattison 2 July, 2010 17:29
Do you have any resources I can purchase such as a planets mobile or posters for my classroom? Regards Margaret Pattison
Discovery Centre 5 July, 2010 11:53

Hi Margaret, the Scienceworks Shop has lots of merchandise that may be of interest to you.  You can contact them on 03 9392 4806.

Graeme Murfett 15 July, 2010 17:16
I have received an email, including a powerpoint presentation, claiming that Mars is approaching its closest point to the earth in the last 5000 years. It is claimed that Mars will be about the same size as the moon, and will rise at 10pm on 1 aug, azumeth at 3am. Is this correct, even for USA or UK, (times are wrong for here).
Discovery Centre 16 July, 2010 14:02

Hi Graeme, this is a hoax that's been around for a few years and comes around every July/August. You can find further information about it at the Sydney Observatory blog and the Astronomical Society of South Australia site. For reliable information about the night sky you can go to the Planetarium's monthly Skynotes, the August edition of which should be out soon. You can find further information about Mars on this infosheet.

Jacob 1 August, 2010 18:02
If earth changed it's orbit, would it's gravity change with it?
Discovery Centre 8 August, 2010 14:40

Hi Jacob,

Earth’s gravity is a direct result of its mass and volume, so even if its orbit changed, its mass would not. So, no, the gravity would not change.

Hope this helps!

Peter 12 August, 2010 14:46
If Einstein said the max speed is the speed of light how can we ever get to other stars/planets in our galaxy?- yet alone to galaxys seen by Hubble.I know we are 1000 light yrs across our Milky way.If the universe is expanding like someone throwing out a handfull of sand , how do we not have any reaction.Thanks Peter
Discovery Centre 14 August, 2010 10:59
Hi Peter. Who knows what future technologies will allow in regards to space travel but, at the moment, travel to extra-solar objects such as other galaxies and planets does look a little unlikely! As to the expanding universe and reactions, there is no definitive answer to the expanding and accelerating Universe at this time but some recent hypotheses include theories involving Dark Matter or Dark Energy. Take a look at the information on the Museum website regarding the ‘Big Bang’ and also NASA’s website regarding the ‘Big Bang’ and Dark Energy. 
matthew 3 September, 2010 12:02
the planetarium is really awsome
Matty Drayto 3 September, 2010 12:09
Is it true that we can see jupiter from the country
Discovery Centre 5 September, 2010 12:10
Jupiter is visible from both the city and the country, although there is much better seeing conditions in the country due to there being less light pollution. Check the Skynotes September 2010 for instructions about where to find Jupiter in the night sky this month.
Rhys Walkley 12 September, 2010 17:42
Why can't all planetaria like yours update old NASA data to include in text if not slides the dwarf planets (Charon,Eris,Makemake,Haumea,Orcus,Quaoar ) and their moons (like Weywot, Nix,Hydra, Vanth, Hi'iaka, Namaku and others) that have been named from the Edgeworth-Kuiper disc and the Opik-Oort cloud's Sedna? on display and lecture material?
Discovery Centre 17 September, 2010 12:29

Hi Rhys, we are in the process of updating the information on the Melbourne Planetarium webpage’s, some information about the Dwarf planets can be found here: Keep checking the websites for updates.

Mark Trentin 22 September, 2010 20:53
Why does Saturn currently appear to be brighter in the night sky than Jupiter? I live in the Northern Rivers of NSW. Is there some optical thing going on or am I simply mistaken?
Discovery Centre 1 October, 2010 14:47
Hi Mark, you're probably seeing Venus, which is slightly brighter than Jupiter at the moment, even though Jupiter is as close to Earth as it ever gets (it won't be this close again until 2022). Venus is in the western sky and Jupiter is in the east. Saturn cannot be seen at the moment as it is too close to the sun. Hope this helps.
luke 26 October, 2010 12:15
this website is great for infomation finding
Shashank 28 October, 2010 11:56
Are there any probes or any technology dicovering Pluto at the moment! And can we send any rockets out of the milky way and into the other galaxies!
kalpen 28 October, 2010 17:26
How much gravity is over Melbourne east, burwood area in Guass.
Discovery Centre 30 October, 2010 15:50
Hi Shashank, NASA commenced a mission to Pluto in 2006. The unmanned spacecraft, named New Horizons, will reach its closest point to Pluto in 2015.The spacecraft is fitted with scientific instruments which will enable NASA to study the atmospheres, surfaces, interiors and environments of Pluto and its distant neighbours. You can read more about this mission, and others here.
Abraham 5 November, 2010 19:46
When is the optimum time/date to see the milky way over Melbourne/Victoria?
Jane 6 November, 2010 00:17
HI i've been to the planeterium before as a school group and it was amazing. I just question the planets that are out there are the really important and in my meanings i mean why? As we know so far no-one lives on those planets and why is Earth the only one with us but the 8 planets left are only facts and things we study on in the what really are we focusing on these planets? THANK YOU Jane
Josh 10 November, 2010 12:25
how cold is it on mars what is the volume of mars what is the core of mars called and is it nickle
Lachlan 10 November, 2010 12:25
Hi there, was the distance of a light year. i'm doing a school project on space. thank's
Discovery Centre 10 November, 2010 12:41
Hi Josh have a read of our Mars infosheet for information that should help with your research. NASA also has some very good resources that you might want to have a look at also.
Discovery Centre 10 November, 2010 12:51
Hi Lachlan, please see our Glossary of Astronomical Terms for your answer about light years.
blobie 12 November, 2010 11:16
I know a rhyme to say if you can't think of the planets in our solar system: My Very Energetic Mother Just Sold Us Nine Planets look at the 1st letters of every word and you will see what i mean..... now you can't forget the planets!!
Jessica 14 November, 2010 14:21
what does a planet have to have to become a planet and what did pluto not have to be a planet?
shelby 16 November, 2010 10:00
what type of planet is a terrestrial planet?
tarkyn 16 November, 2010 10:09
how many galixies are in the univervers
Jayden 16 November, 2010 10:10
Why doesn’t a comet’s tail ever face the sun?
matthew 16 November, 2010 10:10
how many years are planets been in space
shaun rowe 16 November, 2010 10:13
how was the universe made
Kristian 16 November, 2010 10:15
is there life on other planets
maddie 16 November, 2010 10:17
When was space invented?
Claire 16 November, 2010 10:23
Is there life on other planets?
Hannah Fye 16 November, 2010 10:26
Are there other plants like earth in the universe and other galaxies? What life forms are out there?
Lacey Paaka 16 November, 2010 10:27
Can you live on Mars?
Janine wilson 22 November, 2013 19:24
Luke Palmer 16 November, 2010 10:28
How many suns are ther that?
honey 16 November, 2010 16:29
what charictaristics does an object have to have to become a planet?
Discovery Centre 17 November, 2010 11:08
Hi Clyde Primary School, thanks for all of your questions!  If you take a look around the Museum Victoria Discovery Centre page, under the Astronomy link, you will find the answers to many of your questions.  Maybe also look at the NASA website, and try searching particular phrases or keywords on the internet. 
Madeliene 18 November, 2010 19:44
i have four questions i would like to know. the first one is how did the solar system begin? the second one is what was before the solar system? the third one is will the solar system still exist in bilions of years? and the last one is are there other planets that we dont know about. it would be really helpful if you could answer these questions. Thanxs
Maddie 18 November, 2010 19:47
hi i would like to know how fast the planets spin and how fast they orbit around the sun. i know the earth travels and 30KM per second but i was wondering about all the other planets aswell.
Discovery Centre 20 November, 2010 15:55
Hi Maddie, your first & second questions can be answered by reading the first paragraph of the infosheet above. For your third question, the sun will keep getting hotter and expand, eventually swallowing the inner planets. A great explanation can be found on the ABC's Meet the Neighbours site. There are probably no more planets in our solar system to discover but out in the universe there are billions, which we call exoplanets (extrasolar planets). As for information about the rotation and orbit of all the planets, the answers can be found under each planet's link on the NASA Worldbook site. We hope this helps!
Sophie 20 November, 2010 23:29
why is pluto no longer a planet?
alana 20 November, 2010 23:35
if jupiter spins faster then any other planet why does it take longer to orbit the sun?
Discovery Centre 23 November, 2010 09:39

Hi Sophie, check out this page for information about why Pluto is no longer considered a planet:


Discovery Centre 23 November, 2010 10:58
Hi Abraham, in answer to your question from a few weeks ago, good views of the Milky Way can be seen every night of the year at our latitude although it’s always best to be well away from city lights in a dark location to see it well. Overall the best time in the year would be midwinter at around midnight as by then it stretches high overhead from north east to south west horizons showing us the most expanse of the galaxy. Winter is also better than other seasons as the air is usually clearer and more stable when it’s a clear night all of which improves observing whether by naked eye, binoculars or telescope.
Grace 23 November, 2010 14:20
was there life before the solar system?
lollypop 23 November, 2010 14:35
what would the solar system look like in 5 billion years
Tegan 23 November, 2010 16:58
what is the best way to do a demonstration on the solar system?
Discovery Centre 24 November, 2010 16:29

Gracie, as indicated above the Solar System developed from elements that later made life possible. But there of course may have been forms of life in other solar systems. You can read more about this on the website for NASA’s Exobiology and Evolutionary Biology Program.

Lollypop, you can find out how to research your question by reading our reply to Maddie on 20 November.

Tegan, the Lunar & Planetary Institute has some great ideas for making model solar systems that would be great for demonstrations.

Discovery Centre 25 November, 2010 10:45

Hi Alana,

We have two separate factors in this excellent question but they are not connected. Jupiter’s spin or speed of rotation is simply how fast it turns on its axis (its “day”), and orbital speed is how long it takes to travel around the Sun (its “year”).

Discovery Centre 29 November, 2010 12:52
Hi Jessica, sorry for the delay. With the new definition for “planet” a body would need to; (1) orbit the Sun (not another body), (2) be massive enough to have formed into a spherical shape, and (3) to have cleared its orbit of other objects. Pluto satisfies the first two requirements but not the third as there are other objects sharing its orbit around the Sun. However, Pluto has the honour to be one of the first in the new class of dwarf planets which are all significant objects telling us much about the early formation of the solar system. The discovery of so many bodies similar to Pluto has opened up a new chapter in our understanding our the solar system.
robert 6 January, 2011 01:11
is there such thing of a planet call nibiru or planet-x please exsplain
robert 6 January, 2011 01:25
people are worry about 2012 the end.i have been on youtube and discoverd a lot of information on a cerlistreal body hedindg our way 2012.people are talking about today nasa has located this devestated planet on corse and heading our way .it is proff that there is an unexspeted visitor coming too town 2012 so thay say.the last visit was 4.7 billions years ago
Vanessa Porchet 7 January, 2011 09:46
Hi, I have worked as a planetarium presenter and scientific exhibitions guide in France for the last 4 years and I would love to find a similar position in Australia. Would you be interested in a person with an academic background in astronomy to present planetarium shows or exhibitions about sciences? Do you have any link accorded to that kind of jobs as it seems to be very hard to find it in Australia? Thank you for your time.
Discovery Centre 8 January, 2011 10:05
Hi Robert, this website from NASA addresses the questions and myths that have built up around this fictional planet. 
Discovery Centre 8 January, 2011 11:03

Hi Vanessa, all employment positions at the Museum are listed on our website. Good Luck.



robert 18 January, 2011 23:52
iv just been on youtube and descover that the planet-x or nibiru is not the proper name is name is ERIS UB313 .it is the tenth planet distence is 96.6 au three times the size of pluto this could be the one everyone is talking about 2012
Discovery Centre 19 January, 2011 16:21
Hi Robert, Eris is a dwarf planet, with moon Dysnomia, identified in 2005 and is a significant object in its own right although very far from the Sun in a highly inclined eliptical orbit. Its size is still under question and could be a little smaller or bigger than Pluto. It is one of several TNO’s (Trans-Neptunian Objects, beyond Neptune’s orbit) discovered in recent years. Some people may confuse it with the fictional Nibiru, or ideas of “planet X” or a so-called “tenth planet”.
Jayne 27 February, 2011 09:49
Can you please explain why in Australia we see the moon filling up from the left side whereas in America it fills up on from the right side?
Discovery Centre 13 March, 2011 13:02

Hi Jayne,

The Moon appears inverted, or upside down, when viewed from one hemisphere compared to the other. It’s the result of the different angle viewers have from locations south or north or the equator. The effect is to make the sunlit portion appear to increase from the left side of the Moon during the month as seen from Australia (southern hemisphere) while from the right side as seen from America (northern hemisphere).

Connor 21 March, 2011 10:26
Hi Guys. I'm 13 years old and I absolutely love space! My question is: I don't believe in the "2012" idea that the world will end. But is there any possible threat of human extinction? Please answer my question!
Peter 21 March, 2011 11:44
Hello, i'm just wondering the max temp of the sun.. thank you.
Benn 21 March, 2011 11:45
Why was pluto demoted? I liked pluto
Stin 21 March, 2011 11:48
is it possible to eat a plannet?
Riley 21 March, 2011 11:54
Why hasn't Mercury burned into ashes if it's so close to the sun?
Isaac 21 March, 2011 11:55
hey, do they know if there is life out there? Somewhere in the universe there has to be something, i mean we can't be the only one's in this huge universe.
Discovery Centre 23 March, 2011 14:57

Hi Connor, great question! Although it does sound a bit frightening, the earth is constantly being bombarded by meteorites - because the earth's surface is mostly sea, we don't have many of the records of these impacts, but rest assured, they happen costantly. Thankfully, these are all pretty small and pose a low threat, nothing large enough to trigger an extinction.

There is a research unit of NASA that examines 'Near Earth Objects', asteroids,comets and meteorites that have potential to strike the earth. The website is at; we mention this to assure you that there are many experts monitoring this, and that doesn't appear to be a significant threat from an extinction caused by a large meteorite strike any time soon.

Discovery Centre 24 March, 2011 12:09

Peter - according to the information provided by NASA at, the Effective Temperature of the Sun is 5504 °C

Riley - Mercury can't 'burn to ashes' as the surface is essentially rock, and rock doesn't behave this way when it is hot - althought the surface of Mercury is made of exceptionally hot and inhospitable rock dotted with impact craters, it is essentially similar to the moon in many ways. You can learn more at

Benn - Pluto wasn't really 'demoted', just reclassified; it probably shouldn't have been classified as a planet in the first place. You can read the full story at

Isaac - scientifically there's no direct evidence of life inhabiting any other planets yet, but given the size of the universe and the liklihood of habitable planets, it seems like a reasonable guess that there is life elsewhere in the universe. NASA has its own research department dedicated to searching for evidence of life elsewhere in the universe, called the NASA Astrobiology Institute; you can learn about their research at

Rachel 24 March, 2011 17:35
Do you think there is life out there?
Connor 28 March, 2011 09:19
Hello again! I have another question for you guys... if a star blew up, 20 light years away, would we see the bang, and, more importantly, would we die from it?
Discovery Centre 30 March, 2011 11:19

Hi Connor,

If the star was twenty light years away, we would see the explosion in twenty years time! We will see the light of the explosion but not feel the shock waves as it too far away. Light waves travel faster and further than any other form of waves. So no, you would not die.

Connor 30 March, 2011 13:33
Hello again! You guys are really helpful at answering my Questions! Alright, so i know the Earth wont die, and an exploding star wont kill us, but i would like to know: i heard what i think is a silly rumour that sometime in the next 100 years the planets will line up and stuff up the gravity. I dont think it will happen. Who is right????
justin bieber 30 March, 2011 13:35
Hey there in 50 years time do u think that we have evolved and be able to create city's on other planets just wondering?????????????????????? from the one and only JB NEVER SAY NEVER
jayden bellears price 30 March, 2011 13:47
heyy what are your thoughts on the world gonna end in 2012 i dont think it will happen
Discovery Centre 2 April, 2011 14:57
Jayden - 

There are frequently stories about the end of the world.  The next date making its rounds on the internet is 21st December 2012  Taken from the NASA web site is the following:

There is no credible evidence for any of the assertions made in support of unusual events taking place in December 2012.

Another common misconception is that when there is a planetary alignment, calamities occur.  Planetary alignments actually occur about every 50 or 60 years so over the last 4.3 billion years since the Earth formed we are still here. The next big planetary alignment is on September 8th 2040 when most of the planets will cluster together, this should give spectacular viewing (if you are still around.!)

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harrison james 4 April, 2011 10:01
my uncle is a well known astronamist and he has discovered a fair amount of stars and he predicts that 2012 is not going to happen what are your thoughts
Connor 4 April, 2011 10:12
Hello! Is there any chance that within the next 100 or so years, mankind will be able to move to different planets and live there?
Discovery Centre 4 April, 2011 13:08

Hey JB & Connor, complex question! Basically, it's always hard to predict what will happen in the future. There are so many factors and variables that influence social and technological development. These sites should give a idea of current ideas and plans in space colonisation ...

Michael 27 May, 2011 12:57
Is it possible that a black hole is on a collision course with our solar system, and will suck us all up without warning, because at the moment it's on it's way to us through the emptyness of space and not sucking anything in (so we can't detect it until it's here)?
sammy 10 June, 2011 11:00
Summarise the important points on the ‘Giant Nebula’ theory.
Isra 30 July, 2011 06:38
Who was the dog that got to the moon?please answer it!:-)
Discovery Centre 30 July, 2011 10:33

Hi Isra,

The first animal in space was a dog named Laika - she was launched into orbit around the Earth in 1957 in the Russian satellite Sputnik II.

Kev Hudson 18 April, 2012 00:03
Are there other Universe's or is there just the one we inhabit & if there are would it be possible for Planets or Stars that are near where the borders are to travel through the Space of 2 Universe's ? Also - if there are more Universe's then are the borders between them clearly defined & could they be penetrated by Spacecraft or Meteors/Comets ? Also could a Universe be within a BLACK HOLE ?
Discovery Centre 25 April, 2012 10:57

Hi Kev,

You've  raised one of the hottest and controversial topics in cosmology; the multi-verse, branes, the big bang, repeated or cycling of the universe etc.. etc.. The short answer is that astronomers, cosmologists, physicists, and philosophers just don’t know for certain although they are using the best mathematics, rigorous modelling and extensive measurements. As far as travelling between supposed universes is concerned, there are no answers either as we have no certainty whether “borders” exist, how objects might cross over if they do, what mechanism might be involved. It is all very much hypothetical and speculative but grounded in the strongest research possible. It really is “cutting edge” but that’s what makes science and inquiry so exciting!

There is an excellent BBC Horizon documentary from 2010 called “What Happened Before the Big Bang”  it really covers everything you are asking about.

ck 21 October, 2012 20:00
Is it true that in December 2012 our planet will align with the milky way which will cause damage to earth, darkness for 3 days and mass earthquakes, volcanoes etc. Also, scientists claiming to be ex nasa employees are stating we are in for a massive meteorite shower which will ultimately wipe out our world. Is Nasa covering up something?
Ashutosh 26 November, 2012 20:40
I am an 12 year old who is interested in our massive Solar System. Any way to my question i have heard there is going to be a 3 planet align in Giza, Egypt at the Giza pyramids on 3rd of December, 2012. I was wondering if we would have one in Australia preferably Melbourne it would be so cool. And if not would we be able to see this once in a lifetime opportunity or do we have to go to Giza, Egypt. Please take some time to answer i am really keen to know. - Ashutosh
Discovery Centre 1 December, 2012 13:55
Hi Ashutosh!

When Planets align when viewed from the Earth we call it a planetary conjunction, and these are not too infrequent.  On the morning of the 3rd December, just before sunrise,  Mercury will be low in the sky, then Venus and higher in the sky will be Saturn.  These will be visible no matter where you are on the Earth.

The planets of our solar system frequently “line up” in one way or another as they orbit the Sun at different speeds and distances from the Sun (inner planets more quickly than outer planets slower).  The alignments as seen from Earth, or from an imaginary viewpoint above the solar system looking down, are interesting but have no effect on us in any observable sense. Gravity of the Sun and of the planets, and the speed of the planets around the Sun, hold the solar system together but the vast distances between the planets means this force is very weak.

An interesting site can be seen at : (not a Museum Victoria site).

nikki 12 April, 2013 04:20
how come there only some with rings ?
Discovery Centre 18 April, 2013 17:07

Hi Nikki - we checked with our experts at the Planetarium, and they've responded as follows:

Planets can have rings for several reasons. By meteor impact with moons of the planet that throws material around it. By material from a moon being ejected by an internal process. By material being too close to the early planet which couldn’t form into a moon. By a moon being broken up by tidal/gravity stresses. By violent collision which another moon. Some planets have experienced one or more of these events in their history giving rise to rings of different types and sizes, while other planets have not. In our solar system the ring systems are around only the gas giants which have larger gravity and many moons giving more opportunity for one or more of these to occur but the exact process is still not fully understood. 

Angel 1 November, 2013 00:10
How long is Pluto away from Earth?
lauren simpson 8 May, 2014 20:35
Hi, I was wondering if there is any specifc information on the composition of planets/breakdowns of the chemical compounds?
Discovery Centre 15 May, 2014 09:58

Hi Lauren, we ran this past our Planetarium experts, who have prepared the following reply:

Planets in our solar system all vary in their composition. The inner ones like Mercury, Venus, Earth and Mars have a great deal of silicon, oxygen, nitrogen, sulphur, magnesium, and iron. The outer planets Jupiter, Saturn, Uranus and Neptune have lots of hydrogen and helium, The cold worlds beyond Neptune, like Pluto , are different too. But the chemical elements in planets is only part of the story. How they have combined as chemical compounds is more important. For example, Earth has lots of oxygen and hydrogen, but together they make water. Or Neptune has carbon, nitrogen, oxygen and hydrogen in the form of methane and ammonia. See these links to follow up...

Earth history, composition and atmosphere

Nine planets

Neptune - Wikipedia

Earth composition - Wikipedia

william 20 June, 2014 19:31
That is so cute, I would of never thought of that. I am definitely making me one or maybe a few! Lol Redlands solar