The shape of snowflakes is influenced by the temperature and humidity of the atmosphere.
Snowflakes form in the atmosphere when cold water droplets freeze onto dust particles. Depending on the temperature and humidity of the air where the snowflakes form, the resulting ice crystals will grow into a myriad of different shapes.
Ali McLean at the Aurora Zone sent along the image below, showing a full moon and the aurora borealis, or northern lights. Ali said: “If you ever read that a full moon means you can’t see the northern lights … here’s awesome proof to the contrary.”
Aurora and a full moon. Photo by Antti Pietikainen via the Aurora Zone. View larger.
Hubble Ultra Deep Field image from 2004, one of the deepest images of galaxies in our universe. Credit: S. Beckwith & the HUDF Working Group (STScI), HST, ESA, NASA
A light-year is how astronomers measure distance in space. It’s defined by how far a beam of light travels in one year – a distance of six trillion miles. Think of it as the bigger, badder cousin of the inch, the mile, the kilometer, and the furlong. If you like to keep up with what’s going on in astronomy, it’s worth spending a little bit of time understanding what the deal is with this funny unit of measurement.
Photo credit: EarthSky Facebook friend Kim Smith, taken February 2013. She says “My first ever sun pillar! We don’t often see them here in Walker Creek, Arkansas. I am glad I was out to photograph the sunset today when this occurred.” Thanks Kim!
EarthSky Facebook friends have posted some beautiful photos recently of sun pillars, sometimes called light pillars. They are vertical shafts of light that extend upward (or downward) from a bright light source, such as the sun low on the horizon. They can be five to 10 degrees tall and sometimes even higher. They’re beautiful and wondrous. They’re also the source of some UFO reports!
Air burst via Wikimedia Commons
On June 30, 1908, in a remote part of Russia, a fireball was seen streaking across the daytime sky. Within moments, something exploded in the atmosphere above Siberia’s Podkamennaya Tunguska River in what is now Krasnoyarsk Krai, Russia. The explosion released enough energy to kill reindeer and flatten trees for many kilometers around the blast site. But no cater was ever found …
Extremely young moon seen by EarthSky Facebook friend Susan Gies Jensen last night (February 10, 2013) in Odessa, Washington. Beautiful job, Susan! Thank you. View larger.
It has become a sport for amateur astronomers to spot the youngest moon. That is a very slim crescent moon, seen low in the western sky for a short time after sunset. A longstanding, though somewhat doubtful record was held by two British housemaids, said to have seen the moon 14 and three-quarter hours after new moon – in the year 1916.
Is it possible to hear a meteor as it streaks past? Some people report hearing meteors with a sizzling sound – like bacon frying. There might be a scientific explanation …
2013 Quadrantid meteor by EarthSky Facebook friend Susan Jensen in Odessa, Washington.
A September 2010 eruption of Mount Yasur in Vanuatu. Image appears courtesy of Tom Pfeiffer, Volcano Discovery.
Surrounding the Pacific Ocean, the Ring of Fire is one of the most geologically active areas on Earth. It’s a site for frequent earthquakes and powerful volcanic eruptions.
Hey February birthdays! Your birthstone is the amethyst.
The amethyst was the stone of royalty, representing power.
Amethysts contain the second most abundant mineral found in Earth’s crust – quartz. Quartz is often found lining the insides of geodes. So it’s no wonder that geodes sometimes contain amethysts, too. Like quartz, amethysts are a transparent form of silicon dioxide (SiO2). An amethyst’s color can range from a faint mauve to a rich purple. It’s not clear why they’re purple. Some scientists believe the purple color arises from the amethysts’ iron oxide content, while others attribute the color to manganese or hydrocarbons.
Waning gibbous moon in the west around the time of sunrise, as captured by EarthSky Facebook friend Royce Malacaman in the Philippiines. Thank you, Royce. View larger.
We get many comments from those who see the moon in the daytime. The comments tend to have an air of disbelief about them, typically going something like this:
I saw the moon in a blue sky. Why? How can this happen? I thought the moon was visible only at night!
In fact, the idea that the moon is up only at night is a misconception. It’s only the full moon that that rises in the east as the sun is setting in the west and reigns in the sky all night long. In other words, the moon is up all night long only one night each month. Otherwise, the moon rises and sets on its own schedule.