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Happy New Orbit!

Published on 2013-01-01 14:20:56

Happy new orbit to all Blogstronomers! We'll hit perihelion a bit before 5:00 tomorrow morning*, so make sure you dress appropriately. From then until some time in July we'll be heading away from the Sun! So to speak. I hope the next 365 days bring

What's the Highest Temperature?

Published on 2012-11-17 13:30:37

"I was wondering that as absolute zero temperature is I believe -273 degrees centigrade, is there an absolute maximum temperature? I know that there are massive temperatures in volcanic eruptions, atomic bombs, super novas etc but has anyone ever com

New Forum!

Published on 2012-11-17 08:27:10

On the back of a suggestion made via the Ask A Question form (thanks, Andy!) I've changed the 'Guestbook' page to a 'Forum' page. This is with the hope that we can get more of a dialogue going, and people can join in with conversations on topics spur

How Can We See Something if the Source of the Light is Gone?

Published on 2012-11-14 15:38:53

"How can light stay travelling if the source of the light is gone? I read that some stars are dead but we can still see them" -

Why Does the Moon Have Lots of Craters?

Published on 2012-11-04 15:00:33

Why does the moon have lots of craters from impacts, and the earth doesn't? - Question posed by Matty G.Craters, on any astronomical body, are the scars formed when small bodies hit big bodies (when similarly sized bodies hit each other they tend to

What's a Meteor Shower?

Published on 2012-10-21 12:30:35

The other day, Dyana copied me in on a picture post over on Google+. She requested more info about the meteor shower mentioned in it. I'm going to post the image here, but please don't automatically repost it - read what I have to say about it first! Now, spreading the message of astronomy is something I can get on board with, but this image pops up every time there's a meteor shower approaching, and it's a bit wrong. The last time I noticed this message was just before the Perseids, which pea [..]

How Old Am I?

Published on 2012-10-10 10:00:04

For me, today, the answer is one year older than I was yesterday. October 10th 2012 is the day I turn 30. 30 years, that is. Feels like a long time - it's certainly older than I've ever been before. But what is a year? How long is a year? A 'year' is simply the name we give to the period of time that passes between completing orbits of our Sun, riding as we are on this great big ball of rock that we call the Earth. Earth takes 365 days (366 in a leap year) to do one giant lap of our solar syst [..]

Why is Uranus's Gravity Lower than Earth's?

Published on 2012-10-06 04:02:40

Question posed by Emma on behalf of Lucy. This one hadn't crossed my mind before. Like all the best questions, this one needed the mind of a primary-school-aged child to point it out. Lucy and her classmates have been studying the planets at school, and they researched various facts about them, including their surface gravity. They discovered that Uranus's gravity at its surface is 0.886g, compared to Earth's 1g surface gravity. They also found out about mass: Uranus's mass is about fourteen a [..]

How the Heck is a Gas Planet Formed?

Published on 2012-10-04 15:03:01

Originally worded "do we have any idea how Jupiter was formed?" Carlos expanded on this question in a private discussion over at G+, and I thought that his later form of the question made for a better post title! Jupiter was formed in much the same way that all the other planets were, so here's a whistlestop tour of the beginnings of the solar system: We started out as an enormous cloud of gas and dust which started to collapse, rotating as it did so (for much the same reasons as the water in [..]

Why is the Sky Dark at Night?

Published on 2012-10-03 12:08:00

Here's another great video from minutephysics answering a question that if you haven't already asked, you really should. I think the video says it all, but if you'd like something more textual as a response to this question, you only have to ask!

How Do Astronomers Make Conclusions About the Size and Distance of Stars From Earth?

Published on 2012-10-02 11:30:02

"I was stargazing and saw 3 stars in a straight line with the middle star being the brightest. This led me to think of the magnitude of the star, to consider whether the middle star is very large and farther behind the other two stars, or whether this star smaller and much closer than the other two. My question is how do astronomers analyse stars to make conclusions about the size and distance of these stars from Earth?" - Question posed by Trent. One part of your question has already been cov [..]

Do I See the Same Stars Every Night?

Published on 2012-10-01 12:26:59

"When I look into the sky and see the stars in sort of a 2D plane, disregarding for now the depth or closeness of these stars, are they visible from my point of view every night? In Virginia, if I were to look into the sky at a certain time every night would I see the same stars?" -

What Happens to Light Emitted by Dead Stars?

Published on 2012-09-30 05:09:42

"What happens to the light emitted by dead stars in their lifetime?" - Question posed by Bharti. Imagine a rocket leaving a planet, headed for the distant reaches of its galaxy. Now imagine that the planet is destroyed after the rocket is propelled out of its solar system. What happens to the rocket? Not a lot, other than it doesn't receive any more messages from loved ones, PPI repayment companies or the Inland Revenue. You could think of light given off by a star in a similar way: once i [..]

Guest Post: Astronomy and Me - Christopher

Published on 2012-09-16 13:12:07

Christopher - say hi on Twitter: @jooldesign[No, we're not related...] Christopher's another twitter contact with a passion for spacey stuff. He got in touch to ask if I'd like to hear his story: he's attempting to change career in order to spend more time with stars, planets, galaxies, black holes, orbital mechanics, rocket science and the rest of the stuff that makes up the study of our universe. I'm glad he did. My name is Christopher. I'm a web software engineer by day and all-round geek [..]

Guest Post: Astronomy and Me - Sophia

Published on 2012-08-27 15:30:35

Sophia - talk to her on twitter:

Who's Neil Armstrong?

Published on 2012-08-25 18:54:37

Neil Armstrong died today (August 25th 2012). This post has been prompted by the surprising (to me) revelation that a number of people actually don't know who he was. It's not just real people either: at least two major news outlets have got basic details about the man wrong, including his name and even his gender! So I think this is probably necessary. Neil Armstrong: August 5, 1930 – August 25, 2012By NASA / Edwin E. Aldrin, Jr.via Wikimedia Commons Neil Armstrong is an inspiration. In 1 [..]

Is There Evidence to Suggest That Life Exists in Other Universes?

Published on 2012-08-24 17:09:28

Question posed by Dan. No, there isn't, but that's because we don't really know whether there are other universes at all! Before we can collect data and evidence for what type of things there are in other universes, we've got to find another universe!

Learning to Take Space Photos

Published on 2012-08-20 18:22:22

Anyone who also follows my personal blog will have worked out that I like to try my hand at a bit of photography now and then. I've got a semi-whizzy camera, but not a lot of experience so it's a bit like drawing stick-men with really expensive crayons. Anyway, anyone who follows both that blog and this one may have wondered why I haven't posted any astro pics. The answer to that is that it's hard. I very much subscribe to the school of thought that something being difficult isn't a good rea [..]

Our Curiosity Knows No Bounds

Published on 2012-08-06 01:58:10

In the midst of the 2012 London Olympics, humankind just got a gold medal in the 560 billion metres*. My Curiosty Landing geekstation I got up at 6:00 this morning so as not to miss the landing of the latest Mars rover, Curiosity, at approximately 6:30. Well, the actual landing took place fourteen minutes earlier but, due to the distance it has travelled, that's how long it took the message to get back to Earth. After a wonderfully science-fiction-y seven minute landing sequence, Curiosity [..]

What is Olbers' Paradox?

Published on 2012-07-31 07:00:21

Named after German astronomer Heinrich Wilhelm Olbers, Olbers' paradox is sometimes known more descriptively (but less attributively) as the dark night* sky paradox. The paradox itself goes something like this: Light travels. The universe is infinite. There's an infinite amount of stuff (i.e. stars) in the universe. If we travelled in any given direction, then, we should, eventually, get to a star. Turn that around, and we should be receiving light from a star from any direction you might wan [..]

What is a Planetary Nebula?

Published on 2012-07-28 05:48:05

It's nothing to do with planets. "Nebula" is the Latin word for "cloud", and in astronomy any nebula is a cloud of stuff, usually gas and dust. Planetary nebulae* are a type of emission nebula. An 'emission' nebula is a cloud ('nebula') of gas that emits ('emission') light - i.e., it's a cloud that glows. 'Planetary nebula' is the name given to a shell of gas ejected by certain types of star (probably those between 0.8 and 8 Solar masses) in the later stages of their lives. The shell of gas [..]

Will Eta Carinae Kill Us All?

Published on 2012-07-21 06:22:27

I've seen a few posts on various websites regarding Eta Carinae and the possibility that it might wipe us out with a GRB. I won't give any of those posts credence by linking to them, but I would like to address some of the things they're saying... What is Eta Carinae? Eta Carinae is a star, or rather a system of stars, in the Carina constellation. It is located within our galaxy, in the region of 8,000 light years away. One of the stars (there are at least two) is of a type known as Luminous [..]

What is a Retrograde Orbit?

Published on 2012-07-16 15:10:28

"What is a retrograde orbit, and what effect does it have on us?" - Question posed by Colin. The word retrograde

Earthrise Is Impossible (Or Is It?)

Published on 2012-07-14 04:39:40

The prologue: This post is inspired by Greg's comment on this resharing of Blogstronomy's How Big Would Jupiter Look From Europa post. That post was inspired by a conversation between Tanya and myself

Why Do We Have Leap Seconds?

Published on 2012-07-09 16:09:41

Question posed by Colin via twitter. First things first: What is a Leap Second? You know how every four years (called a 'leap year') we have an extra day at the end of February in order to keep our calendar in line with the changing seasons? Well leap seconds are a similar idea: instead of a whole day being inserted once every four years, we have an extra second shoved in now and then. How often does this happen, and why? Irregularly. Or, only slightly more helpfully, when it's needed. On [..]

Did the Big Bang Happen Within the Existing Higgs Ocean, or Create It?

Published on 2012-07-08 15:36:29

Question posed by vossron in response to this post over at Blogstronomy's more mathematical site, The Actual Maths. "In the beginning, states Douglas Adams, the Universe was created. This has made a lot of people very angry and has been widely regarded as a bad move." Bad move or not, 13.7 billion years ago the Universe rather dramatically exploded into being and spewed out a soup of radiation energy mixed with massless particles (the 'massless' bit's important). As this soup expanded it st [..]

The Higgs Boson: How Sure is Pretty Sure?

Published on 2012-07-06 12:41:25

Those boffins at CERN have done it: they've found Higgs! Well, they're pretty sure they have. There's always uncertainty in these things. But what, in this case, does 'pretty sure' mean? That's a statistical question, and Colin Beveridge has an answer for you in his guest post over at Blogstronomy's more mathsy sister-blog, MathsQS. Check it out here: Guest Post: The Higgs Boson: How Sure is Pretty Sure?

How Big Would Jupiter Look From Europa?

Published on 2012-07-05 13:46:13

I was talking with Tanya the other day and the conversation, as it does, steered me towards eventually saying "imagine a Jupiter-rise on Europa." Tanya chipped in that moon-rises would be pretty snazzy to watch too, and it got us thinking: just how snazzy would Jupiter- and moon-rises be if we were to set up camp on Europa? I did what any self-respecting geek would do in such a situation: some maths. I'll stick to the results in this post, but if you want the specifics of the maths (it's acces [..]

Prometheus: A Review

Published on 2012-06-24 12:32:23

It strikes me that some of you might just represent varying degrees of nerd/geekdom, so you might be interested in my review of Prometheus over on my personal blog.

Curiosity: Will It Kill Curiosity?

Published on 2012-06-24 07:16:53

On August 5th* NASA's latest rover, Curiosity, will touch down on Mars. At least, that's the hope: a touch down instead of a splat, crash, whump or crunch down. One of the biggest problems facing Curiosity is that it will take around 7 minutes after hitting the atmosphere to land on the surface of Mars. That's not the problem; this is: It takes about 14 minutes for signals from Mars to get back to Earth. This means that by the time NASA receive Curiosity's "hi folks, I'm just entering the atmos [..]

What Is Earth Made Of?

Published on 2012-06-21 12:20:23

Question posed by Vipul. Our home planet, the Earth, is composed of a wide variety of substances that can be boiled down to one word: rock. It belongs to the category of planets known as the 'terrestrials' (named after Earth's Latin name, Terra), and these are all largely composed of silicate rocks and metals. It also has an atmosphere which can be considered to be part of the planet. The Rocky Bit The solid planet beneath our feet is dominated by four elements: Iron (32.1%), oxygen (30.1%), [..]

Happy Summer Solstice!

Published on 2012-06-20 11:33:40

Today, June 20th, is the summer solstice for us Northern-Hemisphereites. Some of you may remember the post I made at the other end of our orbit about the winter solstice. The summer one is pretty much the same thing, but backwards: the North pole of our beloved planet is the closest today that it ever gets towards pointing at the Sun, and from today onwards our continued motion around our parent star means that the Northern Hemisphere will start tilting away from the Sun. The practical ramific [..]

What is Interstellar Space?

Published on 2012-06-20 11:00:06

"I'm kind of confused by the term "interstellar space". If it's defined as the space between stars, isn't our entire solar system in interstellar space?" - Question posed by Dyana. The word 'interstellar' does literally mean 'between stars', but what's referred to is actually the space between the spheres of influence

Is There A System For Naming TNOs?

Published on 2012-06-19 14:13:00

Question posed by Mark

What is a TNO?

Published on 2012-06-17 11:17:00

Question inspired by Mark's comments on my G+ post. In astronomy, the initialism TNO stands for Trans-Neptunian Object. So what's one of those? Well, like the name implies, they're objects that are beyond Neptune. Specifically, they are objects (dwarf planets, comets, etc) that orbit the Sun with an average orbital radius that is greater than that of Neptune (which is about 30 AU). The first TNO was discovered back in 1930, and that's the dwarf planet we know as Pluto. Pluto is the second lar [..]

How Big Are The Outer Planets In Our Solar System?

Published on 2012-06-16 04:35:04

Question posed by Milo. The outer planets of our solar system are Jupiter, Saturn, Uranus and Neptune*. Respectively, their average diameters are (roughly) 140,000 km, 120,000 km, 51,000 km and 50,000 km. But if you're anything like me, those numbers are far too big to really mean anything. So lets compare them to something: home. The Earth's average diameter is something in the region of 13,000 km. Knowing this fact, we can talk about the sizes of other things in terms of how much bigger they [..]

What's a Theory?

Published on 2012-06-10 10:00:01

This question was prompted by the fact that so many people get it wrong. This one gets my goat, and if I sound at all grumpy while typing this, then GOOD. "It's just a theory." I see it in the news, and on twitter, and plastered all over the internet... 'It's just a theory'. That phrase repeated over and over again like a mantra from the phrasebook of people who don't want to accept that something's true but don't quite understand how to argue against it properly. The problem is this: The p [..]

When Did Astronomy and Astrology Become Separate Theories?

Published on 2012-06-09 16:50:21

Question posed by Chaz. If I was feeling pedantic I'd pick at the use of the word 'theory' in the question. 'Astronomy' is more of a name given to a collection

Parallax, or: How Far Away Stuff Is!

Published on 2012-06-07 04:37:12

I've mentioned parallax in a number of posts, including How Do We Know How Far Away the Planets Are, How Do We Find Out Distances to the Stars, and What is a Parsec?

How Do We Know What Planets Are Made From?

Published on 2012-06-06 12:05:46

How do we know what the various planets are made from and what gases exist on their surfaces? - Question posed by Ken. Though the planets in our solar system are much, much closer than the stars, it's still pretty difficult to get to them. Working out what's on them has to be a bit more involved than wandering over, dipping your finger in, giving it a lick, and saying "mmm, that's molecular hydrogen and helium, that is." The Stuff of Atmosphere Working from the outside in, a planet's a [..]

The 2012 Venus Transit - Timings

Published on 2012-06-05 16:49:31

The web is flooded with posts about tonight/tomorrow's Venus transit, so I won't bore you by repeating it all again (although you can read about what a transit is in this post and how to safely view the transit in this one). Once you're in-the-know as to how to view Venus's stately crawl across the face of the sun without melting your retinas, you'll need to know when

Sunspotting Episode IV

Published on 2012-06-04 13:46:34

Take a look at the first three instalments here, here and here

Why Do the Sun and the Moon Look the Same Size?

Published on 2012-06-03 08:31:00

This question was inspired by this post on the Oatmeal blog (look about 3/4 of the way down in the black 'for example' box), and referred to me by Colin. This question could be interpreted in two ways (that I can think of) and, being a generally helpful and amiable chap* I'm going to have a go at both. Firstly... Why do the Sun and the Moon look the same size? Total eclipses are only possible because the Sun and Moon appear tobe the same size as viewed from Earth. But why?[Image by I, Luc [..]

How Do We Know That Jupiter is 318 Times More Massive Than the Earth?

Published on 2012-06-02 05:55:14

Question posed by COOL DIVYA. This question is really asking 'how do we know the mass of Jupiter?' You're probably not going to like the answer to this one because what it essentially boils down to is one word: Maths. But don't stop reading yet. Really, any real life problem can be boiled down to maths, and this is especially important in a lot of astronomy problems because actually going to places and measuring stuff is prohibitively difficult to say the least. Without going into to [..]

Sun Spotting With a Vengeance

Published on 2012-05-29 13:03:52

My first post on this was here, and you can find the second one here. Feel free to join in! This has turned into an obsession. After my appeal at work I was supplied with a number of tubes, and I've made a bit of an effort with some of them as you can see in the image! The one in the middle is the one from the other day, as photographed in this post. The one on the left is a yellow plastic tube that was, I think, previously home to some large educational posters. It's slightly translucent, so [..]

More Sun Spotting!

Published on 2012-05-27 14:21:58

Yesterday I started fiddling around to see if I could make something that would allow me to view the Sun safely and indirectly. That post is here, and it's in preparation for the upcoming Venus transit, which you can read more about here. Yesterday's card-with-a-hole-in-it didn't really cut the mustard, so this morning I showered, shaved and finished off a roll of toilet paper with a view to using the cardboard tube inside. The Problem The problem is this: to get a bigger view of the Sun I h [..]

How Do We Know How Big the Planets Are?

Published on 2012-05-27 11:10:00

COOL DIVYA wants to know how we know that Jupiter is the largest planet. If we know how far away a planet is, then finding out how big it is is relatively easy. In order to find out a planet's actual size we need to measure how big it looks from here. Specifically, we measure its 'angular diameter'. To understand what one of those is, go outside with a pencil. Stand some distance away from something big (a tree, a house, the local monster) and point your pencil at one edge of it. Now, keeping [..]

Spotting the Sun

Published on 2012-05-26 13:54:15

I've just been outside playing around with ways of observing the sun and thought a few of you might be interested in hearing about it. Emma was looking at our own bedroom window, not the sun. Before I start: DO NOT ever look directly at the sun, however briefly, without appropriate protection and the guidance of someone who knows what they're talking about*. I had a go at the pinhole camera technique. The idea is that you punch a pinhole in a piece of card and then move it around until it p [..]

How Do We Know How Far Away the Planets Are?

Published on 2012-05-26 10:58:36

COOL DIVYA wants to know how we know that Jupiter is the largest planet, and I think that this is the best place to start answering that. In The Beginning The first good measurements of the distances to planets were done using a method called parallax, which I have mentioned in a few other posts. You can experience parallax for yourself, right now: Look out of a window, or if you're feeling daring, actually go outside. Look at a distant tree or building or something. Close one eye and hold u [..]

What's the Difference Between a Comet, an Asteroid and a Meteorite?

Published on 2012-05-19 12:04:00

Question posed by Emily FG. You can find out the difference between a comet and meteor in this post, and a meteorite is just what we call meteors after they have landed. What's not covered in that post is what an asteroid actually is. So... What's an Asteroid? Asteroids are lumps of rock and/or metal that are in direct orbit around the Sun (i.e. they're not in orbit around anything else). Like so many astronomical objects, asteroids are very loosely defined- most of the moons of our solar s [..]

Is it possible for humans to create black holes on Earth?

Published on 2012-05-16 11:00:08

Is it possible for humans to create black holes on Earth?

Are the Planets Ever Crescent?

Published on 2012-05-12 07:35:20

When we see Jupiter, Venus, Mars etc are they ever crescent like the moon is? If so, how long are the cycles? - Question posed by @KnikiTea. The Moon's phases as seen from Earth Do We Ever See the Planets as Crescents? We've all seen the Moon going through it's phases: these are the times when different portions of the Moon's face as observed by us are lit up by the Sun. You can read this post to find out all about the phases of the Moon, and these all apply to any bodies in space, [..]

Astronomy at #CampEd12

Published on 2012-05-09 17:05:21

The supermoon shrouded in cloud, by Rachel Last weekend (4th-7th May 2012) I was lucky enough to take part in #CampEd12, an educational festival devised, organised and run by teachers and educators from around the country. As well as the excellent social opportunities afforded by the event, there were a number of activities put on by attendees, and I did my first public presenting on the subject of astronomy! Here's a rundown of my bits! Nighttime Observing I lugged my brand-new 200mm Skywat [..]

How Can I View the Venus Transit?

Published on 2012-05-08 10:06:25

@Julien wants to know how he can view next month's Venus transit. Not sure what that is? Check out this post

What's a Transit?

Published on 2012-05-07 13:10:28

@Julien asked how he could see June's Venus transit, but before I get onto that I thought it'd be a good idea to make sure everyone knows what a 'transit' actually is. A photograph taken of the 2004 Venus transit byGestrgangleri

#CampEd12 Astronomy - A Preliminary

Published on 2012-04-29 05:48:19

Hello to anyone attending #CampEd12 next weekend (and apologies to everyone else as this post won't mean much to you)! I just wanted to collate some comments I've made on twitter recently for anyone who's interested in attending my astronomy sessions at the weekend (don't forget to sign up via the document Bill Lord sent out yesterday (Saturday)!). First of all, my sessions will be informal and only rudimentarily planned. This is my style; I wish to leave most of it to be dictated by you an [..]

How About a 21-Gun Salute to the Old Girl?

Published on 2012-04-17 16:42:58

Following space shuttle Discovery's piggy-back fly-past of Washington earlier today, Carlos posted the suggestion that Blogstronomy should be giving her a 21-gun salute. Blogstronomy Towers lacks something in the way of armaments, however, so how about a 21-fact salute instead? NASA's tribute to Discovery, including all 39 mission patches. BLAM! Discovery's maiden mission began on August 30th 1984*. She launched two communications satellites. Discovery lifting off in 1998 BLAM! She was [..]

What Do I Need To Do Astronomy? - Part 1

Published on 2012-04-15 14:46:08

I'm asked a lot of questions along the theme of how to get into astronomy and what equipment to get hold of, so I thought I'd do a series of posts working from the ground up (no pun intended). As it happens, the most essential bits of kit are the cheapest and the easiest to obtain, with the price and required expertise increasing as you delve deeper into the world, no, universe, of astronomical observation.In this first instalment I'll discuss the two most important items you need to stash in yo [..]

What Are Comets Made Of?

Published on 2012-04-12 12:31:09

Question posed by Bella. Comets are known in some circles as 'dirty snowballs'. This is not because they are made of snow and/or have questionable hygiene, but is an affectionate term that hints at their composition. The 'snowball' bit comes from the fact that comets are thought to consist of varying but significant quantities of ice. Specifically, this means water ice, which is the stuff you're familiar with from plonking it in your Pimm's on a hot day. Along with this water ice is a variety [..]

In Order of Size, What Position is the Moon In?

Published on 2012-04-09 17:16:10

Question posed by Mary. When looking at the Solar System as a whole, our Moon comes in at number 14 based on mean radius, nuzzled in between Jupiter's moons Io and Europa (13th & 15th respectively), and appears higher up the table than the dwarf planets Eris (17th), Pluto (18th), Makemake (23rd), Haumea (25th) and Ceres (33rd). Our Moon appears only three places below the planet Mercury (11th) on this list. You can see the whole list here. If we look at just the known moons of our solar sy [..]

Mars is Stupid and Boring. Why Should We Colonise It?

Published on 2012-04-07 12:30:58

Hedfulofspidrs has sent me both the question "Mars is boring and stupid. Why should we colonise it? Wouldn't the asteroids or the Jovian moons be a preferable destination?" and a link to their post Gravity wells are for wimps on the same subject. Undoubtedly, this is a sneaky attempt at getting a link published, but Hedful makes some good points in their post, and that's why I'm happy to indulge it (I hope s/he is kind enough to return the favour if they like this post...). The thing is, I ag [..]

Astronomising at #CampEd12 !

Published on 2012-03-18 15:44:01

I'll be attending #CampEd12* in May, and I've been asked to do something astronomical. As I understand it, the site is above the local tree line and a fair distance from any big towns, so given the right weather we might be in for a show. I don't know what I'm going to do yet, but I'd really like to get others involved, so first and foremost if you're going to be in attendance and

Why Are There Four Seasons?

Published on 2012-03-17 08:09:30

Question posed by Omar. Winter, spring, summer or autumn*, all you have to do is call... Like many of the processes and cycles that we observe and take for granted here on our blue-green orb we like to call the Earth, the seasons are an effect of our steady and unstoppable** sweeping journey around the Sun. These things run in cycles because our orbit of the Sun is itself a cycle. We take one year to orbit our Sun, spinning like a top. This top doesn't spin completely upright, though: it lean [..]

Have Any Dwarf Planets Been Discovered Outside Our Solar System?

Published on 2012-03-10 09:15:29

Question posed by Courtney. No. The thing with finding extrasolar* planets is that the bigger ones are easier to find, and the smaller the planet the harder it is to find. Dwarf planets are pretty much planets except they can't lay claim to one (or both) of the following: Heavy enough to have achieved hydrostatic equilibrium**. Big enough to have cleared the local neighbourhood of other stuff. Both of these are affected mostly by an object's mass- that's how much stuff it's made of. The sm [..]

What Happens When a Blue Star Dies?

Published on 2012-03-04 05:28:24

Our Sun (Sol, in the diagram) is big, but blue supergiant Rigelmakes it look a bit wussy.By CWitte, via Wikimedia Commons Question posed by asdf456. What happens when any star dies is largely determined by its mass. Much of what happens to stars, and their properties, are determined by their masses, and this includes their colour: you can find out more about that in this post, but the bit that's relevant to this one is that if a star is blue, we know that it's very hot and must contain a lot o [..]

What is a Leap Year?

Published on 2012-02-29 15:46:16

I was going to answer this question myself, but then @Ms_Elevator posted a link to this, which does it better.

What is the Aurora Borealis?

Published on 2012-02-20 12:23:00

Question posed by Barb. The Aurora Borealis is the same thing as the Aurora Australis, except they happen in different places. These effects are also known, respectively, as the Northern and Southern Lights. They are, in short, displays of light visible now and again in the night sky if you're either very far north (for the Aurora Borealis) or very far south (for the Aurora Australis). The lights appear as either a diffuse glow or as vast curtains of light stretching across the sky. They can b [..]

Why Are Stars Different Colours?

Published on 2012-02-19 05:10:39

This post discusses aspects of various questions I've been sent, including 'how do the layers of the flame compare with the colours of a star?' (posed by Blah), and 'What are the different coclors of the stars and what does each color mean?' (posed by Kat), and it provides some background for answers to other questions about stars that are in the pipeline! Everything that has a temperature emits radiation*. Sometimes this radiation is emitted at a wavelength that we can see- we call this visibl [..]

Are There Any Black Holes Near Us?

Published on 2012-02-17 03:19:25

Question posed by Amy, at the same time she asked this one. The thing with black holes is that they're difficult to see: They're black, on a black background, and they don't give out any energy that we can measure. We have to infer their existence from the effect they have on other things, rather than actually being able to image them directly. Obviously, the bigger black holes have a bigger effect, and one beast that we're pretty confident about resides at the centre of our galaxy in an astro [..]

Guest Post: Somewhere to Go - The William Herschel Museum (Bath)

Published on 2012-02-16 05:43:26

Here's a guest post by Colin, who's an author, a maths tutor, and the owner of quite a cool twitter handle. If you've been somewhere interesting that you think would be a good place for other Blogstronomy readers to know about then why not write a review yourself? Get in touch! By Mike Young, via Wikimedia CommonsHerschel used a 'scope a lot like this one todiscover... There are - as far as I'm concerned - two kinds of museum. There's the "oo look! Touch and play" kind of museum; and there [..]

Book Review: Higgs Force, by Nicholas Mee

Published on 2012-02-09 12:30:01

Imagine my excitement when I was contacted by a PR representative on behalf of author Nicholas Mee asking if I wanted to receive a review copy of a new pop-sci book on the history and recent research on the elusive Higgs particle. Now imagine my excitement when a copy of Higgs Force landed on my mat with the satisfying whump that only a book can produce, and my further excitement when I browsed the 'other titles by...' list and found that, among other publications, Mee had a hand in transferring [..]

How Can I Observe the Milky Way?

Published on 2012-02-05 04:43:22

There have been times when I've looked up into the night sky, trying to see "the Milky Way", however, I've never been able to see it. Can you recommend the best way to observe the Milky Way? - Question posed by Robin. The Milky Way is the name we give the galaxy that we live in. From our vantage point, about half way out from the centre of the galaxy, the vast majority of the bright points that we can see on a clear night are stars that belong to the same galaxy as us- in effect, if you look a [..]

How Does the Moon Cause Tides?

Published on 2012-01-25 13:33:20

Question posed by William. Gravity You're probably well aware of the fact that you'd have a different weight on different planets. On Mars, for example, you'd weigh less than you do here on Earth*, and if you were to visit Jupiter (and could find a solid surface to stand on) you'd weigh considerably more than you do here. This is because bodies (i.e. planets) with more mass have a stronger gravitational field. Gravity has another feature, though: it gets weaker as you move away from a body th [..]

What's the Relationship Between Stars in a Constellation?

Published on 2012-01-24 12:51:37

"What's the relationship betweens stars in a particular constellation? Luck or something more?" - Question posed by Hannah. Constellations are regions of the sky that are grouped around collections of stars that seem to draw pictures in the night sky. The famous ones include Ursa Major, Orion and Cygnus. From where we stand*, Ursa Major is so called because the stars that form it look a bit like a badly-conceived dot-to-dot image of a big bear; Orion looks, if you squint, a bit like a magnif [..]

How Close Would We Have to Be to Fall Into a Black Hole?

Published on 2012-01-19 12:27:27

How close would we have to be to be sucked in by a black hole? - Question posed by Amy. Any object with mass has a gravitational field. This includes you, me, trees, planets, moons and black holes (to name but a few). Things like planets, though, have a really noticeable gravitational field- you have to do a bit of work if you don't want to fall onto one of them, and the closer you get the harder it gets to avoid falling because the force that you feel is stronger the closer you are to its sour [..]

How Can I Find New Planets?

Published on 2012-01-16 16:16:32

If you've been watching the BBC's Stargazing Live you'll know the answer to this one. Just go to the Planet Hunters website, let yourself be guided through a brief tutorial of what to do (it's easy- my cat could do it, and I haven't got a cat), and then start planet hunting! Just in case there's any confusion, this is a real project using real data from real observations, and you can be a part of searching for new planets outside our solar system from the comfort of your own sofa, computer [..]

Tell Me About the Phases of the Moon

Published on 2012-01-07 11:08:32

By Tomruen, via Wikimedia CommonsAn animation showing the different phases of the Moon Question posed by Dyana. The Moon always has one half of it lit by the Sun*, and the other half in darkness**, but as it orbits us*** our viewpoint changes and we see a different portion of the lit half. The 'phases' of the Moon are our way of describing how much of the sunlit half of the Moon we can see. We'll start the story with a phase which seems to make sense coming first: New Moon A new Moon is not [..]

When Are We Closest to the Sun?

Published on 2012-01-04 19:00:01

I'm setting this to autopost at 1:00 am (GMT) on Friday 5th January 2012. If you're reading this at round about that time, then the answer is NOW*. Right now.The thing is, Earth's orbit around the Sun isn't perfectly circular. Its orbit follows a path called an ellipse, which is a sort of squashed circle. This means that we're not always the same distance away from it- we get closer to and further away from the Sun on a cycle which lasts about a year, so our next closest approach (which is cal [..]

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