February 9, 2020 – Baby, it’s Cold out There!

Space is a cold mistress.  When we venture up, higher and higher into the atmosphere it just keeps getting colder and colder.  At 29,035 feet it’s never warm at the peak of Mount Everest, with temperatures staying well below zero F all the time.  And this is just 29,035 feet above sea level.  The beginning of “space”, essentially no atmosphere, is defined as 62 miles (327,360 feet) above sea level.  Also named the Karman Line, 62 miles is the best estimate we have for a demarcation between atmosphere and no atmosphere.

I have mentioned in past articles that outer space is considered a “hard vacuum”, nearly a void and better than any vacuum we can produce in the lab.  The average temperature of space near Earth is around 50 degrees F…wait, how can that be?  It’s well below zero on Mount Everest, in the atmosphere.  Funny thing about space, with no atmosphere there is no medium to carry heat, so heat is confined to whatever objects are exposed to sunlight for example.  An object exposed to sunlight above Earth’s atmosphere will be really hot (248 F) but an object in the hot object’s shadow will be really cold (-148 F).  The average temperature of 50 F is an artifact in this situation.  Space is not a jacket weather environment. Ask any astronaut.

I guess my title for this article might be misleading because baby it’s hot out there too!  Solar heating can cause objects not built for it to warp and/or deteriorate quickly.  Without surrounding molecules to transfer/moderate heat an object tends to stay very hot on one side while it loses temperature on its shaded side quickly via radiative cooling.

Moving outward, into interstellar space, it just gets cold.  Very, very cold.  Without a nearby star providing heat, or its own heat source, objects in interstellar space can reach 2.7 degrees Kelvin or -455 degrees F.  That’s close to what we call absolute zero.  In interstellar space there is no liquid or gas as such, any sizable collection of a normally gaseous element will be frozen solid.  Since interstellar space is a vacuum and the density of molecules so low, there is little opportunity for collections of molecules to form.  Even great molecular clouds, aka star nurseries, such as M42 the great Orion nebula are tenuous.  While dense enough for hydrogen to form molecules it’s not like a gas as we know it.  It’s still a vacuum, though not as strong as interstellar space.

I am grateful for this thin layer of atmosphere we have.

What’s in the Sky?

February 10; after sunset; west-southwest:  Catch Mercury at its highest (it’s at greatest eastern elongation), about 7 degrees above the horizon with Venus to its upper left

February 10-24; at dark; west: The zodiacal light appears as a cone shaped light arising from the horizon.  It’s light reflecting off dust in Earth’s orbit.