Institute of Astronomy

 

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Looking back in time

Published on 22/01/2013 
Question: 

When a picture is taken of deep space and it is said that it is from when the universe was 500,000,000 years old.  Mainly saying that you're looking into the past.  That doesn't make sense to me for the fact that you're able to capture a picture.  Distance and time can coincide but in this case i dont get how this theory works with space?  I understand at such a distance it takes time for light to reach us, the point I'm trying to make is that how can it be said that what we view from deep space is the past not the present?

The effects of large distances and time in astronomy can be a little confusing.  Take as an example Proxima Centauri, the nearest star to our Solar System.  This is 4.2 light years away, which means that it takes light 4.2 years to get from Proxima Centauri to us.  Now since the only way we can see something that has happened at Proxima Centauri is through light, this means anything we see at Proxima Centauri actually happened 4.2 years ago.  If there were a person on Proxima Centauri and they had an exceptionally powerful torch, which the flashed at Earth, it would take 4.2 years for the torch flash to reach us, so by the time we saw it the person would actually have flashed the torch 4.2 years ago.  Now as I said Proxima Centauri is very nearby, when we look at objects in the distant universe they are much farther away, billions of light years, so when we see them we are seeing light that left them billions of years ago, when the universe was much younger.  As a result we can in a way think of looking at objects that are very far away in the distant universe as looking back in time, because the light has taken so long to reach us that the universe has changed a lot in the time it has taken the light to get here.

Moonrise times

Published on 22/01/2013 
Question: 

Hello Im a photographer trying to capture a photo of the moon rising above the eastern coast of the atlantic ocean, particularly in central florida. I know there is a full moon next week Jan25-26, what is the best time frame to capture it at horizon?

There are various tools around on the internet that allow one to calculate times of Moonrise and Moonset and Lunar phases, www.timeanddate.com has some quite good ones.  Unfortunately in Florida Moonrise at Full Moon occurs quite close to Sunset, so the photographic conditions might not be ideal depending on the effect you want to capture, you might be better off waiting until a few days after full when the Moon is rising later in the evening, but only you can judge that.

The threat of asteroid impacts to Earth

Published on 22/01/2013 
Question: 

I am writing a blog post on the threat of asteroids on earth. I have read a number of Science and Nature articles on the matter with the general consensus being that the probability is really low of being hit by a highly destructive 300-meter and above asteroid but that if we were to find an asteroid on a collision course for earth, the current ideas of how to deflect it would highly depend on the composition but also are largely untested. Could you please comment on whether you think funding (NASA or others) should be going towards locating smaller (<1km) objects that are not often seen if they are very close to the sun OR whether the budget should be expanded to test the deflection methods on a variety of non-dangerous asteroids within reach?

The probability of an impact with an asteroid large enough to cause large scale destruction is indeed rather small.  Generally we tend to focus on objects 1km or more in size as those that are particularly dangerous, since although smaller objects could cause a lot of damage it would be more localised (a single continent say) rather than global.  Roughly speaking we think that 1km size asteroids hit Earth about every 500,000 years and the impact rate falls off rapidly for larger objects (since there are less of them), impacts with 5km size objects happen only every 10 million years or so.  The largest impact event in recorded history was the Tunguska event in Siberia in 1908, which involved an object that was probably about 60m across.  The most potentially dangerous asteroid we know of at the moment is 1.1-1.4km (29075) 1950 DA, which has a probability of up to 0.33% of colliding with Earth in 2880, so we have a good while to work out how to deal with it.

There are a number of ongoing projects searching for near Earth asteroids, such as LINEAR and the Catalina Sky Survey.  Also, at the beginning of last year the European Union, in collaboration with the United States and Russia, set up the NEOShield project whose remit is to study appropriate deflection methods, including how the choice of method depends on composition.  One of their aims is also to test some of the proposed deflection technologies, both in the laboratory, and in space.  Both aspects are important, since if we don't know the asteroid is heading our way we clearly can't do anything about it, but it isn't much use knowing about the deadly asteroid if we don't have some way of deflecting it.

Comet C/2012 S1

Published on 22/01/2013 
Question: 

As an astronomy buff and fan , I'm very excited about the upcoming pass of ISON this year ! While playing with the JPL Small-Body Database Browser , I noticed that it passes somewhat close to the Earths orbital plane around Nov. 14 2013 on it's journey outbound. I was wondering if there is a chance  that it  could product  new meteor shower as Earth as it passes that point about about Jan, 15 , 2014?

The projected orbit of comet C/2012 S1 will indeed take it quite close to Earth's orbital plane and could lead to a new meteor shower that would be visible around 14th-15th January.  Since the comet will pass very close to the Sun it is not yet known whether it will survive perihelion, if it doesn't there may not be a new meteor shower.  It also depends on the amount of gas and dust that the comet releases on its journey, which is difficult to predict beforehand.

As a side note the name of the comet is strictly C/2012 S1, ISON stands for International Scientific Optical Network, and indicates the observatory it was discovered from.  As it is only ever going to come past once we just give it a designation rather than naming it after the discoverers (in this case Vitaly Nevsky and Artyom Novichonok).

Programming in Astronomy

Published on 03/01/2013 
Question: 

What computer programming languages do astronomers use? IDL? Java? C++? C#? Ada?

The programming languages used in astronomy are somewhat down to the preferences of the individual astronomer, however I think it would be fair to say that the most commonly used ones are IDL, C/C++ and Fortran, though Python is becoming more and more popular as well.