Archive for March 13, 2013

The Heat Death of Herschel

Posted in The Universe and Stuff with tags , , , , on March 13, 2013 by telescoper

Most of the astronomers who read this blog will have heard the news that the Herschel Space Observatory is running out of the Helium that it has been using to keep it cool enough (~1.4K) to be sensitive to the far-infra-red radiation emitted by very distant objects.

There’s a gallery of wonderful images obtained by Herschel since it was launched in 2009 at the news item linked to above, but my favourite is one of the least photogenic:

_66205134_goodsn_3colour_cropped

Many of these fuzzy blobs correspond to immensely distant galaxies; what we see is starlight from very young stars absorbed by vast amounts of cosmic dust and then re-radiated in the infra-red. Understanding these sources is decidedly non-trivial and it will take many years to get all the information out that is hidden in images like this.

Anyway, one thing worth pointing out here is that what is going on now with Herschel is not some kind of failure. Quite the contrary, in fact. The original mission lifetime was planned to be three years, and Herschel has now been operating for nine months longer than that. The supply of Helium was always going to be the limiting factor as the spacecraft operates at the second Lagrange point of the Earth-Sun system, which is almost a million miles away and thus too far to be replenished. When the Helium does run out, Herschel will rapidly heat up to the point where its detectors are swamped. It will then be blind.

I was at this point going to make a cheap joke to the effect that after years on its own in the dark preoccupied with images of heavenly bodies, it was entirely predictable that Herschel would go blind. But I decided not to. I’ll save that kind of off-colour remark for Twitter…

ps. Coincidentally, on this day (March 13th) in 1781,  William Herschel  discovered the planet Uranus. The telescope is named in Herschel’s honour because he was also the first person to demonstrate the existence of infra-red radiation.

Advertisements

Snow, by Louis MacNeice

Posted in Poetry with tags , on March 13, 2013 by telescoper

I’ve posted this before, but it seems appropriate to post it again today…

The room was suddenly rich and the great bay-window was
Spawning snow and pink roses against it
Soundlessly collateral and incompatible:
World is suddener than we fancy it.

World is crazier and more of it than we think,
Incorrigibly plural. I peel and portion
A tangerine and spit the pips and feel
The drunkenness of things being various.

And the fire flames with a bubbling sound for world
Is more spiteful and gay than one supposes–
On the tongue on the eyes on the ears in the palms of your hands–
There is more than glass between the snow and the huge roses.

by Louis MacNeice (1907-1963).