Comments on: A WISE view of a small neighbor

By: andy

andy — Wed, 05 Jan 2011 23:09:14 +0000

afaik hydrogen remains liquid down to absolute zero and needs pressure to solidify,

Melting point of hydrogen is about 14 K under standard pressure. Now helium on the other hand…

By: don gisselbeck

don gisselbeck — Wed, 05 Jan 2011 16:04:23 +0000

M33 was an easy naked eye object from Top Hut on Mt Kenya in Sept 1981.

By: Biff

Biff — Wed, 05 Jan 2011 15:38:15 +0000

Spitzer observed down to longer wavelengths than WISE so would need to be cooled more to be sensitive to that part of the spectrum, requiring liquid He. WISE could get away with liquid H2 which presumably made it all a bit cheaper.

Not sure if H2 is intrinsically less long lasting than He, or whether it was down to the quantities used and quality of the cryostat ??

afaik hydrogen remains liquid down to absolute zero and needs pressure to solidify,

By: sascha

sascha — Wed, 05 Jan 2011 03:20:29 +0000

Aah, the Triangulum galaxy! I still have fond memories from the time back when I visited there. A great place where many adventures await. People over there are also very friendly.

By: Messier Tidy Upper

Messier Tidy Upper — Wed, 05 Jan 2011 02:55:46 +0000

@ ^ Matt B. : Well Jupiter has metallic hydrogen in its core & I think we’ve successfully created that and also got down to within a whisker of absolute zero in a lab somewhere (although I could be mistaken) so, yeah, ‘frozen hydrogen’ works for me.

I do agree a “guess what” with the image hidden and then revealed by clicking for more info or on a box to reveal would have been neater still.

By: Matt B.

Matt B. — Tue, 04 Jan 2011 23:16:28 +0000

“What shall be the first astronomical object to grace this blog in 2011*?”

Aw, you ruined it by not hiding the picture behind the cut. You can’t ask someone to guess and not give them sufficient time to guess. [/Sheldon Cooper]

Frozen hydrogen? I wasn’t aware anyone had managed to make hydrogen solid. Am I wrong?

By: Messier Tidy Upper

Messier Tidy Upper — Tue, 04 Jan 2011 22:45:06 +0000

@8. James Harmer : You misunderstand me – I’m saying & hoping those potentially asteroids aren’t there in the first place NOT that WISE (or any other space or ground based observatory misses them if they *are* there!

If the Potentially Hazardous Near Earth Asteroids are there then let’s find them ASAP, but I’d rather there were fewer of them than more of them in existence.

Of course, the population of PHNEA’s varies over time as asteroids fall into and occassionally get ejected out of the inner solar system or disappear via impacting Mars, Earth, Venus and Mercury so constant vigiliance is required.

@ Sam H. (above) : insert roll of eyes, I dunno the smiley for that.

: roll : without the spaces gives you the eye-rolling (smiley) emoticon here.

By: Sam H

Sam H — Tue, 04 Jan 2011 22:00:51 +0000

“I’ll note that WISE has to use a cryogen — frozen hydrogen! — to keep its instruments cold, but the coolant ran out in October.”

What the dang? Spitzer was launched in 2003 with coolant that lasted fully six years – and it’s a heck of a lot bigger than WISE. Sure, a telescope is not defunct after it’s coolant runs out, but it’s less viable for some types of imaging – Why couldn’t the ESA pack a few more pounds of liquid H2 to create a durable investment?

Probably a launch vehicle issue…as usual (insert roll of eyes, I dunno the smiley for that )

By: James Harmer

James Harmer — Tue, 04 Jan 2011 21:40:28 +0000

“hazardous to Humanity’s & our planet’s health methinks!”
Er, Messier, those asteroids are still out there whether they’re discovered or not. Ignorance is not bliss when one unexpectedly impacts at several Km per second.
Forewarned is forearmed after all.
Have a look at http://en.wikipedia.org/wiki/Tunguska_event for eyewitness accounts of the last big one. And remember that Tunguska was actually minor as these things go ….

By: andy

andy — Tue, 04 Jan 2011 18:44:06 +0000

NGC 604 is so big and bright that were it located as close as Orion, it would be second only to the Moon as brightest object in our night sky!

On the other hand it would presumably be quite an extended source, therefore the actual surface brightness would presumably not be nearly so impressive.