Using the Hubble Space Telescope, periodically astronomers have used the powerful observatory to gaze at a tiny patch of the sky. We have written many articles about the Milky Way for Universe Today. Listen here, Episode Galaxies. Spilled milk on the dusty road looked like, almost, Milky Way…! Skip to content. Like this: Like Loading It stuck. However, by the late s it became clear that this is not electromagnetic radiation at all like X-rays or gamma rays , but a cosmic buckshot of energetic particles, mostly electrons and protons, accelerated in supernova shocks and other explosive events.
The erroneous label was never replaced. Giants are huge; dwarfs are tiny. Not in astrophysics, though. In scientific parlance, every star that is converting hydrogen into helium in its core is known as a dwarf star. So yes, red dwarfs are dwarf stars, but so is our own Sun. Even more remarkable, the hottest dwarf stars in the universe can be more than 20 times more massive and 20, times more luminous than the Sun! Tranquillity Base was named after Mare Tranquillitatis the Sea of Tranquillity , on which Apollo 11 made its historic descent.
But wait… seas on the Moon? Indeed, the Moon is bone-dry. The brighter parts of the Moon were thought to be the lunar mainland. Apart from maria , the Moon has one ocean Oceanus Procellarum , a number of lakes including Lacus Mortis , a few marshes palus in Latin , and bays the most famous of which is Rainbow Bay, or Sinus Iridum. Beautiful names, but plain wrong. Incidentally, dark areas on the planet Mars are also known as seas.
No kidding: nitrogen and oxygen, the two main constituents of the air you breathe, are known to astronomers as metals. Just like every single chemical element except hydrogen and helium, which were forged in the big bang. Silly, but useful: the metallicity of a star usually a few percent is now a handy measure of the amount of non-big bang elements it contains.
For more info, read our guide to the science of spectroscopy. Ceres pictured above , Pallas, Juno and Vesta were discovered in the early 19 th century. For a while, they were listed as planets, but famous astronomer William Herschel , following a suggestion by Greek scholar Charles Burney Jr.
Quite appropriate if you observe them through a telescope, but it completely ignores the fact that these are small rocky bodies. In , Danish astronomer Tycho Brahe observed a new, bright star in the constellation Cassiopeia. There are several clues. The first clue to the shape of the Milky Way comes from the bright band of stars that stretches across the sky and, as mentioned above, is how the Milky Way got its name.
This band of stars can be seen with the naked eye in places with dark night skies. That band comes from seeing the disk of stars that forms the Milky Way from inside the disk, and tells us that our galaxy is basically flat.
The concentration of stars in a band adds to the evidence that the Milky Way is a spiral galaxy. If we lived in an elliptical galaxy, we would see the stars of our galaxy spread out all around the sky, not in a single band. Another clue comes when astronomers map young, bright stars and clouds of ionized hydrogen in the Milky Way's disk.
These clouds, called HII regions, are ionized by young, hot stars and are basically free protons and electrons. These are both important marker of spiral arms in other spiral galaxies we see, so mapping them in our own galaxy can give a clue about the spiral nature of the Milky Way.
There are bright enough that we can see them through the disk of our galaxy, except where the region at the center of our galaxy gets in the way. There has been some debate over the years as to whether the Milky Way has two spiral arms or four. The latest data shows that it has four arms, as shown in the artist's illustration below. Additional clues to the spiral nature of the Milky Way come from a variety of other properties. Astronomers measure the amount of dust in the Milky Way and the dominant colors of the light we see, and they match those we find in other typical spiral galaxies.
0コメント