Pluto, the second-largest known dwarf planet in the Solar System (after Eris), and its largest moon, Charon, are sometimes treated as a binary system, because the center of their orbit does not lie within either body (Charon is about half as big and 1/7th as massive as Pluto). Indeed, before its re-classification, Pluto and Charon were the closest thing to a double planet known. The orbit of Pluto and Charon is also special in that it is nearly perpendicular to the plane of their mutual orbit around the Sun, like a record rolling on its side (Uranus and its moons are tilted over in a similar way). As such, the Pluto-Charon orbit can be seen either face-on – like a clock – or edge-on – like a thrown frisbee – during its 248-year trek around the Sun. Between 1985 and 1990 the orbit was aligned edge-on so that the two bodies repeatedly passed in front of each other, or eclipsed. These eclipses allowed astronomers to measure both the sizes of Pluto and Charon as well as make a rough map of Pluto’s surface features. Finally, Pluto and Charon are the only planet-moon pair whose orbit and rotations are mutual synchronized; that is, they both face the same face to each other all the time. This makes Pluto and Charon excellent partners as the dance their way through space!
Progressing from the first quarter, the Moon enters its waxing gibbous phase, on the way to full bright moon. The Moon is showing more of its sunny side to us on Earth, and is taking on an egg-like shape. That’s why Hawaiians call the gibbous phase (gibbous is derived from the latin word “gibbus”, or “hump”) the “hua” or “egg” phase.
Europa is Jupiter’s 4th largest moon and the smallest of the Galilean satellites (discovered by Galileo Galilei in 1610), all of which are visible with the aid of a small telescope or binoculars. One of the smoothest and shiniest objects in the Solar System (it reflects 64% of the light striking it), Europa has a surface that is made up mostly of water ice and is essentially free of craters, indicating that it is continually refreshed. It even has a thin atmosphere of oxygen, formed from sputtering of ice from its surface. But the most intriguing part of Europa may be underground, where a deep ocean is believed to exist, heated internally by gravitational tidal forces from Jupiter (the Moon induces similar forces on Earth that give rise to ocean tides). Water breaking through Europa’s surface may explain its overall smoothness and some low-lying features, including “chaos” regions such as Conamara Chaos. Liquid water may be one of the ingredients necessary for life, mitigating the chemical reactions that spawned life on Earth – the only planet with surface water known. Hence, the presence of water in Europa implies life may exist there, perhaps in the form of extremophiles that don’t need sunlight to derive energy. Hopefully Timmy has found a nice extremophile to play with!
In the center of the constellation Scorpius lies the bright red star Antares, the 16th brightest star in the night sky. Antares is what is known as a red supergiant – its surface is cool and hugely extended, 800 times larger than the Sun. Indeed, if Antares were in the Solar System, it would engulf Mercury, Venus, Earth and Mars. Stars become red supergiants at the end of their lifetimes, when they have exhausted most of their hydrogen fuel, and they on their way to a spectacular stellar death in the form of a supernova. The red supergiant stage of a star’s lifetime is relatively short – a few hundred thousand to a million years. In contrast, the light we see from this star was emitted 600 years ago, since it takes light 600 years to travel the 600 light-years of distance between us and Antares. So it is possible that Antares is no longer there. Ponder that while you’re enjoying your view of Scorpius tonight!
Maui astronomer Harriet Witt describes the First Quarter Moon and brings you out into space, so you can see how lunar phases work. So take sometime out of your busy day, take a deep breath, and let Harriet bring you on a journey through the night sky.
Listen here [4:24m]:
What’s the facts:
It is called the First Quarter Moon, because that is what the moon looks like to us here on Earth (1/4 of a big round ball). To us, it seems as though the stars, the planets, and the moon, change throughout time, but really, we are turning, taking a different view of the night sky as we do. Our lunar phases are relative to the Sun (our source of light), and changes as the moon follows its orbit around the Earth, and the Earth spins and follows its orbit around the Sun. It’s pretty complicated once you think about it!
Maui astronomer Harriet Witt asks a simple question: what is night? The answer requires us to view our planet from a completely different perspective. The answer just might surprise you.
Listen here [4:24m]:
What’s the facts:
Night or nighttime is the period of time when the sun is below the horizon. Nights are shorter than days on average, but vary in length as it is based on factors such as season, latitude, longitude and timezone. Night lets our bodies know when to sleep and when animals can go out to hunt, but it’s also important to science. Without the absence of the Sun, we may never have seen the stars in the sky, and astronomy would not be what it is today. So next time you’re taking out the trash and you get spooked when something stirs in the dark, take a minute to look at the sky and appreciate it, and remember that light is right around the corner.
Charae’ interviews assistant astronomer, Prof. Roy Gal, from the Institute for Astronomy at the University of Hawaii, Manoa. Roy works on sky surveys, which are essentially a closer look at the whole sky than is possible with the naked eye. Astronomical surveys generally involve imaging or “mapping” of regions of the sky using telescopes. It’s important to know that a sky survey isn’t always just a picture, like the ones you take on your camera. There are infrared surveys, radio surveys, and much more too. These images allow other scientists, who want to know more about any given star in the sky, a starting point in finding the information they need. What job could be better than observing the sky?