New Comet Lovejoy starts out slow but quickly gains speed as it zips from near Orion in mid-September all the way to Ursa Major in November, when it will be closest to Earth. Created with Chris Marriott’s SkyMap software

Move over Comet ISON. You’ve got company.  Australian amateur astronomer Terry Lovejoy, discoverer of three previous comets, including the famous, long-tailed sungrazer C/2011 W3 (Lovejoy), just added a 4th to his tally.

This new comet will add to a lineup of comets that should grace early November skies in the northern hemisphere: Comets ISON, Encke and now the new Lovejoy.

Comet C/2013 R1 Lovejoy photographed on Sept. 10. The comet is visible in larger amateur telescopes in September but may brighten to small scope visibility in November. Streak at right is a geostationary satellite. Credit: Michael Jaeger

The discovery of C/2013 R1 Lovejoy was announced on Sept. 9 after two nights of photographic observations by Lovejoy with an 8-inch (20 cm) Schmidt-Cassegrain reflector. When nabbed, the comet was a faint midge of about 14.5 magnitude crossing the border between Orion and Monoceros. Subsequent observations by other amateur astronomers peg it a bit brighter at 14.0 with a small, condensed coma.

Comet Lovejoy has a small, condensed coma (head) about 30 arc seconds across with a faint, short tail in this photo made on Sept. 8. Credit: Ernesto Guido and Nick Howes

Right now you’ll need a hefty telescope to catch a glimpse of Lovejoy’s latest, but come November the comet will glow at around 8th magnitude, making it a perfect target for smaller telescopes. At closest approach on the Nov. 23, Lovejoy will pass 38.1 million miles (61.3 million km) from Earth while sailing across the Big Dipper at a quick pace.

via New Comet Discovered: Lovejoy Will Add to “Comet Lineup” in Winter Skies.

Image of Earth with two moons, generated in Celestia software, by Grebenkov in Wikimedia Commons.

Many planets in our solar system have more than one moon. Mars has two moons, Jupiter has 67, Saturn 62, Uranus 27, Neptune 14. Those numbers keep changing, and you can see a relatively current count of solar system moons here from NASA’s Jet Propulsion Laboratory. It makes sense that the outer worlds, with their stronger gravity, would have more moons. Meanwhile, our planet Earth has just one moon. Doesn’t it?

Moons are defined as Earth’s natural satellites. They orbit around the Earth. And, in fact, although Earth sometimes has more than one moon, some objects you might have heard called Earth’s second moon aren’t, really. Let’s talk about some non-moons first.

Quasi-satellites are not second moons for Earth. A quasi-satellite is an object in a co-orbital configuration with Earth (or another planet). Scientists would say there is a 1:1 orbital resonance between Earth and this object. In other words, a quasi-satellite is orbiting the sun, just as Earth is. Its orbit around the sun takes exactly the same time as Earth’s orbit, but the shape of the orbit is slightly different.

The most famous quasi-satellite in our time – and an object you might have heard called a second moon for Earth – is 3753 Cruithne. This object is five kilometers – about three miles – wide. Notice it has an asteroid name. That’s because it is an asteroid orbiting our sun, one of several thousand asteroids whose orbits cross Earth’s orbit. Astronomers discovered Cruithne in 1986, but it wasn’t until 1997 that they figured out its complex orbit. It’s not a second moon for Earth; it doesn’t orbit Earth. But Cruithne is co-orbiting the sun with Earth. Like all quasi-satellites, Cruithne orbits the sun once for every orbit of Earth.

via Does Earth have a second moon? | Space | EarthSky.