Extremely cool background from the Hubble Deep Field itself!

The Hubble Deep Field

Short Introduction

Dr. Robert M. Williams, the new director at Space Telescope, along with a blue-ribbon panel of other astronomers came up with the great idea of spending 10 days, or 150 orbits, of precious Hubble Space Telescope time looking at nothing. Wait a minute. That didn't come out sounding right.

Nonetheless, that is what the HDF project is about. Of course, what makes it research astronomy rather than lunacy is that the part of the sky we are looking at is a very special "nothing". The "nothing" means that there are few objects in the field brighter than about 20th magnitude, no galaxy clusters, and low Galactic obscuration. The idea is to exploit the low background sky brightness Hubble has by going DEEP in a blank field to look for primordial field galaxies/objects. Moreover, this particular field spends some time in Hubble's Continuous Viewing Zone---for seven days, the earth never occults it. We can just stare and stare and pile up them photons.


Well, of course it's not THAT easy. One problem is illustrated above. We are in the Continuous Viewing Zone (CVZ) for most of the ten days. But, like summer in Nome, the sun may be up all the time, but it's not very high, and it doesn't get real bright up there. Similarly, we are above the bright limb, but not very far. So we have continuous viewing, but it doesn't really get as dark as you'd like all the time. The average limb angle is about 23 degrees, and as you can see, it's between 20 and 30 degrees most of the time. So we must be careful exactly where one puts one's observations, since some wavelengths are more sensitive to scattered light than others.

More Complications

Also, even in the CVZ, you have to worry about the South Atlantic Anomoly (SAA). This is a radiation zone that the HST goes through about a dozen times a day. Not harmful, but your signal-to-noise suffers, since the noise part goes up a great deal. This graph illustrates efforts to fit the observations around the SAA. There are, however, some nice 9-10 hour stretches which are SAA-free, and truly continuous viewing. The idea here is that not only are we going to spend a huge number of orbits looking at this field, but at very high efficiency as well. Optimal bang for the buck, I'd say.

But It's Done! It Worked!

The observations themselves took place from Dec. 18th thru Dec. 28th. The first data from the observations were presented at the January 1996 AAS Meeting in San Antonio. the data is now non-proprietary. That means you can get copies of it NOW!

The Hubble Deep Field actually has its own home page, with lots more information about the filters used, previews of the field, and REALLY NEAT PICTURES!!! Click *here* to go to it.

Or, click *here* to go back to Doug's Home Page.