Proxima Centauri as seen by Hubble Space Telescope. This is a star. The Sun is a star. Notice how this doesn’t look like the Moon.
Darlings, I just saw a little clip of your Astronomy 101 mockup on QVC and it was SO not fabby! First of all, Jane, dear what were you thinking—I mean, is the Moon a Star? And Isaac, darling, PLANET MOON!?
This is the Moon. Notice how this doesn’t look like a star. Courtesy Gregory H. Rivera, CC By-SA 3.0
Let me fix that for you dears: the Moon is a satellite of Earth. It’s not a planet. A planet is a celestial body that moves in orbit around a star. Earth is a planet. So, are Mercury, Venus, Mars, Jupiter, Saturn, Uranus, and Neptune. Pluto is a dwarf planet. Moons move in orbit around their planets. So, that makes them moons. Not planets. And yes, you can learn that from Google. Although, to be fair, this is stuff most kids learn in school, even before they decide to become fashion icons.
Try looking here at Mission: Science at NASA. Those folks have their definitions straight. And, they wear fabby stuff out to space!
Jane, dear, I’ll give you a little oomph for knowing that the Sun is a star—that’s a gimme. But the Moon… nope.
Here is the Sun with its planets. Only one has life. All but Venus and Mercury have their own moons. Courtesy Kwamikagami. CC BY-SA 30.0
Isaac, one other thing: planets aren’t defined by whether they have life on them. I wish that every planet DID have life, but many don’t. At least, none that we’ve found. For now, let’s stick with the definition of planet that astronomers work with. It’s a good one.
Now, about some astronomy-themed fashions—do you need a consultant? I’m here for you darlings! Love your latest, Isaac! Bring on the ruched star shirts and Downton Abbey styled stargazing togs. I’m ready!
Comet C/2014 Q2 (Lovejoy) taken while passing through the constellation Lepus, 29 December 2014. Photographed from Barra de Valizas, Rocha, Uruguay. CC BY-SA 4.0
On nearly any given night of the year, there’s a comet out there. Some are fairly faint and a real challenge to observe. Others get bright enough that you can see them with binoculars, a small telescope, or—if you have a good dark-sky observing sight—with the naked eye.
There’s a new one out there, and you have a good chance of seeing it. Called C/2014 Q2 Lovejoy, it’s one of the brighter ones that have come our way recently, and stargazers are having a great time searching it out. You can, too. Use the handy star chart courtesy of Sky&Telescope.com to find the right area of sky in which to find it. The comet is a faint greenish color, which is due to light being emitted from glowing carbon molecules in the coma and tail.
This comet was discovered by amateur astronomer Terry Lovejoy from Australia. He’s found four other comets, and this one is pretty spectacular. As it gets close to the Sun, the comet is experiencing increased solar heating, which causes its ices to melt. They flow away from the comet’s nucleus (which is a chunk of ice, dust, and rocky materials), and as they do, the dust streams out behind the comet to make a lovely dust tail.
The comet’s ices can contain carbon monoxide, carbon dioxide, methane, water, and other gases. As the gas molecules stream away, they are energized by the solar wind—which is a stream of charged particles flowing away from the Sun. The solar wind has a magnetic field, and the energized particles spiral around the magnetic field lines and form a plasma. That plasma stretches out in a long tail which is not visible to our unaided eyes but can be seen if you image the comet using a camera with filters that allow the plasma’s glow to come through.
Comet Lovejoy is what astronomers call a “long-period” comet. That means the comet’s orbital period is quite long, which gives us a clue to where the comet originated in the solar system. Long-period comets normally have periods longer than 200 years and they generally are thought to have formed in the distant reaches of the solar system, perhaps in the Oort Cloud or the outer parts of the Kuiper Belt (both of which lie beyond the orbit of Neptune).
The period for Comet Lovejoy C/2012 Q2 was first calculated to be about 11,500 years long. However, its path has been perturbed by gravitational tugs from other planets as it passed through the solar system, and that has changed the length of its orbital period. Now astronomers calculate its orbit to be about 8,000 years, so the next time this comet returns to our skies will be around the year 10,014 (depending on any planetary perturbations it experiences between now and then).
Want to see some gorgeous images of Comet Lovejoy? Visit SpaceWeather.com and click on their Realtime Comet Gallery for hundreds of wonderful views of the comet taken by talented astrophotographers around the world.
