If you want to understand what’s going on in the sky, there are lots of ways to do it. You can, for example, look around for specific examples of objects — supernovae, black holes, spiral galaxies — and examine them. Or, you can take a survey of the sky, looking everywhere, and take a census of objects. That gives you a pretty good idea of how many objects are out there, and how many of each kind.
Surveys of the sky tend to revolutionize our thinking about astronomy. When you get large samples of vast stretches of sky, you get a feel for what’s going on, and sometimes that overall view can be very powerful.
The UK Infrared Telescope just released a new survey, the deepest and largest infrared survey of the sky ever made. IR light is tremendously useful in astronomy; it can pas through gas and dust pretty well, revealing objects otherwise hidden under a thick blanket of obscuring material.
The UKIRT Infrared Deep Sky Survey was started back in 2005, and looks at the near infrared, the light just outside the eye’s sensitivity. It does so with exquisite sensitivity and depth; producing a wealth of data as well as beautiful imagery. They have found the coolest (literally!) brown dwarf yet — a star that is too small to sustain fusion in its core, dooming it to slowly cool with time as its internal heat is released.
Besides revealing previously unknown objects, surveys can give us details of familiar ones as well, like in the Ring Nebula picture at the top of this post. That’s one of the most famous objects in all the sky, a dying star shedding layers of gas which light up as they collide and are heated by the central star. It’s visible in small telescopes and has been photographed countless times. But a deep, wide survey unveils the far outer halo of the nebula, gas flung out long ago in the earliest stages of the star’s death. This will tell astronomers details about what happens just at the point when stars like the Sun begin to shuffle off their mortal coil.
And the UKIRT survey isn’t even done! When it’s complete, in 2012, they will have detected 100 million galaxies, which is phenomenal (imagine having to catalog all of them…), and revealed many hidden treasures in our own. Surveys like this are extremely powerful tools in an astronomer’s kit, and will be mined for data for decades to come.
January 9th, 2008 at 9:38 am
[…] Pastrami Linden wrote an interesting post today onHere’s a quick excerptThe UK Infrared Telescope just released a new survey, the deepest and largest infrared survey of the sky ever made. IR light is tremendously useful in astronomy; it can pas through gas and dust pretty well, revealing objects otherwise … […]
January 9th, 2008 at 10:16 am
A point of puzzlement:
You mentioned a brown dwarf star that is too small to sustain fusion - what is the difference between that star and Jupiter (aside from size, I imagine)?
A star is essentially a big ball of mostly Hydrogen, with some Helium and other elements mixed in. Jupiter is a big ball of mostly Hydrogen, with some Helium, and some other elements mixed in. Jupiter is not classed as a star because it is too small to sustain (or initiate) fusion, am I right?
So the question is, at what point does an object quit being called a planet like Jupiter, and start being referred to as a star - like the aforementioned runt?
January 9th, 2008 at 10:17 am
Two q’s about the ring nebula…
Is the blue star in the centre the actual remnant/white dwarf/neutron star/holiday leftovers of the star that formed the nebula?
Was the nebula formation event (a la Crab nebula) something that happened in recorded history?
January 9th, 2008 at 10:59 am
Are there objects that are only visible in the IR spectrum? Objects that we would not be able to see with our eyes?
January 9th, 2008 at 11:28 am
“And the UKIRT survey isn’t even done! When it’s complete, in 2012, they will have detected 100 million galaxies”
That assumes that the recent funding cuts from STFC are reversed, as UKIRT is one of the facilities under threat. The petition to the PM is ongoing and has over 11,000 signatories now; let’s hope it works!
January 9th, 2008 at 11:36 am
Sergeant Zim,
Of course, everything depends on the definition you are using, but the most common breakover point I’ve heard between giant planet and brown dwarf is 13 Jupiter masses. Above this mass, there is a brief period of deuterium fusion that makes the object definitely “starlike”. You have to get up to about 60 Jupiter masses to get normal hydrogen burning, at which point it would be a red dwarf star. Others may like to disagree or refine this definition, but it’s a pretty good rule of thumb.
BA, do you have a mass for that coolest-yet brown dwarf?
January 9th, 2008 at 11:57 am
IIRC Brown Dwarf Stars fuse Deuterium into Helium. Deuterium is an uncommon but stable form of heavy Hydrogen that has a single neutron. Does anybody on the board know how much mass is required to fuse Deuterium and how much mass is required to fuse common Hydrogen?
January 9th, 2008 at 11:59 am
Look at that, my answer came even as I was typing. I love this place.
January 10th, 2008 at 4:26 am
[…] of UKIDSS has now gone public, with a press release at the AAS. The blogosphere is picking it up, here, here and here. You have no idea how nice it feels after a couple of weeks of STFC-cuts politics.. […]
January 10th, 2008 at 5:53 am
Thanks, Wayne and DG. That’s one of the beauties of this site, and Science in general: if you don’t know something, ASK! Chances are, there will be somebody who does know, or if not, you might inspire yourself or somebody else to find out.
“Believe the man (person) who says he is searching for the truth. Fear the man who claims to have found it” - unknown.
January 10th, 2008 at 8:04 am
Philosophically, astronomical surveys are contradictory. They are considered by most astronomers to be unexciting, plodding stuff. They take too long. They aren’t usually “cutting edge.” In some cases they are looked down upon. Until they are done, that is. Then they most often prove to be indispensible reference resources, and/or they show an effect or make a discovery that would have been impossible to find otherwise. So in retrospect, they get respect. But not always before.