Tag Archives: astronomy

Voyager 1 Has Now Left The Solar System 22x

On the heels of the latest news that Voyager 1 — the farthest man-made object in the universe — has left the solar system, xkcd decided to tally up how many times this has happened before:

The hover text reads:

So far Voyager 1 has ‘left the Solar System’ by passing through the termination shock three times, the heliopause twice, and once each through the heliosheath, heliosphere, heliodrome, auroral discontinuity, Heaviside layer, trans-Neptunian panic zone, magnetogap, US Census Bureau Solar System statistical boundary, Kuiper gauntlet, Oort void, and crystal sphere holding the fixed stars.

Note that some of those aren’t actually at the edge of the solar system, or even real things.

See also:

From xkcd

If There Are So Many Stars, Why Is The Sky Dark At Night?

It might sound like a stupid question at first, because of all the black darkness in between the stars, but the answer is actually evidence of one of the fundamental properties of our universe. The problem comes in when you realize there shouldn’t be any darkness at night: there are trillions of trillions of stars in the universe, and their light should literally be filling up the sky all the time. So then why is it mostly dark? Some stars are really far away and their light hasn’t gotten here yet, but there are still plenty of stars whose light should be flooding our tiny planet. Which it is — we just can’t see it, because by the time the light gets here, it’s infrared.

Night Sky. Photo by Scott Wylie


If the universe were constant and stars stayed in the same position, the night sky would be indeed be filled with light. But because the universe is expanding, stars are constantly moving away from each other, and therefore away from us, too. That motion causes redshift, which is what happens to light from an object that is moving away: the wavelength increases due to the Doppler effect, and since color is dictated by the wavelength of light, it first appears more and more red and then infrared, which we can’t see anymore. So the sky is dark because most of the light that we would normally see — from all the countless stars — has been shifted to infrared on its way to Earth — because the universe is expanding.


Video Of Curiosity’s Mars Landing

NASA has released video taken by the Curiosity Rover as it landed on Mars. It shows the separation of the heat shield, followed by the powered descent of the rover. At the end, you can see the Martian dust being blown around by the sky crane’s thrusters.

From YouTube, via Discover Magazine and Neatorama

Very Cool Picture Of Saturn

The picture of Saturn below was taken last week by the Cassini space probe, which has been orbiting the planet since 2004.

Cassini is the first artificial satellite to orbit Saturn, and its counterpart, Huygens, was the first spacecraft to land on a planetary body in the outer solar system when it landed on Titan, which is one of Saturn’s 62 moons, and the second largest moon in the solar system after Jupiter’s Ganymede. Titan was discovered by the Dutch astronomer Christiaan Huygens, and is larger than Mercury.

From NASA, via Laughing Squid