Category: Astronomy

No longer a planet, Pluto is just a member of the Kuiper Belt; a collection of icy objects that extend out past the orbit of Neptune. If you brought Pluto into the inner Solar System, it would start to act like a comet – blasting out gas and particles from the solar wind. It’s a good thing Pluto is in the cold, dark outer Solar System, far away from the Sun.

So, if it would act like a comet, what is Pluto built of, and how do we even know? Pluto is so small and dim that only the largest telescopes can see it. To even see with your own eyes, you want a 30 cm (12 inch) telescope – and then you’ll only see a dot.

Astronomers using the world’s biggest telescopes, including the Hubble Space Telescope see a much better view. By using a technique called spectroscopy, astronomers can analyze the details about Pluto’s surface. The current thinking is that it’s composed of more than 98% nitrogen ice, with traces of methane and carbon monoxide.

The limits of telescope technology mean that we can’t get a better view of Pluto’s surface. But NASA’s New Horizons spacecraft is making the journey to Pluto, and will make a flyby in 2015. At that point, it will fly within 10,000 km of Pluto’s surface and send back images that show features as small as 1.6 km across. This will be a tremendous improvement over our current understanding of Pluto.

But what’s inside?

Planetary scientists have calculated Pluto’s density at between 1.8 and 2.1 g/cm³. From this density, they have calculated that its interior is probably 50-70% rock and 30-50% ice. Decaying radioactive elements inside Pluto would heat the interior of the dwarf planet, allowing the rock and ice to move around. At this point, the interior of Pluto is probably a rocky core surrounded by a shell of ice. If the radioactive elements are still decaying today, they could heat Pluto up enough that it has an interior liquid ocean, like Jupiter’s moon Europa.

The surface of Pluto is a thin layer of nitrogen, methane and carbon monoxide. When Pluto is at its closest to the Sun, this material evaporates, and forms an atmosphere around the dwarf planet. And then, when it’s further from the Sun, and cooler, this atmosphere freezes back down onto the surface.

Here are some nice Pluto images.

Source: NASA

When Pluto was first discovered back in 1930, astronomers thought it was just a single, solitary planet orbiting the Sun. Almost 50 years later, astronomers discovered that it actually had a very large moon. And then in 2005, astronomers working with the Hubble Space Telescope announced that they had found two more moons of Pluto, officially named Nix and Hydra. Are there more, waiting to be found? How many moons does Pluto have?

Astronomers now know that Pluto has three natural satellites. The first and largest of the Pluto moons is Charon, first identified back in 1978 by astronomer James Christy. He made the discovery while examining a photograph of Pluto and noticed that it had a bulge on one side. Christy and his colleagues thought this bulge came from a defect in the alignment of the telescope, but then they noticed that only Pluto was elongated, and not the background stars. They realized they were looking at a moon for Pluto.

Pluto’s moon Charon is named after the boatman in Greek mythology who guides the dead across the River Styx. This works well, considering Pluto is the roman god of the underworld (no, not the Disney Dog).

Charon is large and massive, compared to its parent dwarf planet Pluto. While Pluto measures 2,306 km across, Charon is 1,205 km.across.

One of the remarkable things about Pluto and Charon is that they’re actually a binary system. The two objects orbit a common center of gravity which is outside Pluto itself. For comparison, the Earth and Moon’s center of gravity is inside the Earth.

Back in 2005, astronomers working with the Hubble Space Telescope discovered two additional Pluto moons; they named them Nix and Hydra (originally S/2005 P1 and S/2005 P2). Nix measures 46 km across, and Hydra is 61 km. The Hubble research suggested a n upper limit for moon sizes orbiting Pluto. It appears that Pluto has already reached this limit with Nix and Hydra, and anything larger would be clearly visible.

The discovery of these moons has given hope to the theory that Pluto has a ring system, created with micrometeorites impact with the surface of the dwarf planet. Another possibility is that Charon produces ice geysers, similar to Saturn’s moon Enceladus.

More on this will be discovered when NASA’s New Horizons spacecraft finally arrives at Pluto in 2015. At its closest point, New Horizons will get within 10,000 km of the dwarf planet’s surface, and capture images at an unprecedented level of quality.

We’ll finally know what Pluto really looks like. And we’ll get a chance to see Pluto’s other moons at the same time.

Go here if you’d like a picture of Pluto.

Source: NASA

Since the initial alert for the latest nova in Sagittarius, folks the world over have been anxious for darkness to arrive and their chance at spotting this cosmic wonder firsthand. Thanks to our good friends at Macedon Ranges Observatory, Universe Today readers are about to see the latest nova in Sagittarius revealed and learn just what is a nova.

One thing is certain, both professional and amateur astronomers have something in common – curiosity. Unfortunately, because many of us live where skies seem to be perpetually cloudy or don’t always have the equipment to view a late breaking astronomy alert object, it becomes even more imperative to be able to call upon others in different regions of the world. It certainly is a true pleasure to have friends down under! So now that we see it… What is a nova?

The word nova is Latin for “new star”. Astronomers assign the term nova to stars that have a rapid increase in brightness. These stars are usually far too dim to be seen unaided and may often become the brightest object – besides the Sun and Moon – in the sky!

Novae themselves are stars that have been quiet for many years, and suddenly decided to reignite their nuclear fusion process. All stars have fusion occurring in their core – processing hydrogen into helium and releasing energy. When this fuel is expended, stars like our sun simply shed their outer layer and continue on as small, hot, white dwarf stars. They are basically dead… Their fuel gone.

Unlike our own Sun, most stars are a binary system – two stars that closely orbit each other. If one of these stars should happen to be a white dwarf and the other starts to evolve into a red giant, the white dwarf can begin attracting gas towards itself by means of gravity. What type of gas? Hydrogen! When the hydrogen stolen from the red giant reaches the surface of the incredibly hot white dwarf, it rapidly ignites. What’s born is an incredibly huge nuclear explosion on the white dwarf’s surface and we see it as a nova!

Using a 12″ Ritchey Chretien Optical Systems telescope, Joe Brimacombe set to work imaging the latest nova for us to see. By comparing this photo with the 19 April Sagittarius Image you can see how quickly the white dwarf ignited!

Nova Sgr 19April2008 Joseph Brimacombe Image details are as follows: STL11000 camera; BRC 250; image scale 1.46 asec/px; image is 97 amin across; nova is centre star; stack 6 x 300 Ha; false colour.

In the near future, Galaxy Zoo will get a facelift. The project – which has already classified a large portion of the Sloan Digital Sky Survey – will be moving to its second phase, and members will be helping the science community get better information on the formation and distribution of galaxies.

In the first phase, the science team wanted to make the task as simple as possible: is the galaxy you see an elliptical or spiral galaxy, and if it’s spiral, which way is it turning (clockwise or counter-clockwise)? As we reported the first results published using the Galaxy Zoo data showed that people have a bias for clicking on counter-clockwise images.

Galaxy Zoo 2.0 will probe more deeply some of the best classified images of the first stage. “The experience will be a bit different. Users will be asked a series of more detailed questions, and based on their answers they will be lead to answer different questions…One of the things we will incorporate is how to get people to answer the questions in a way that is interesting for them” said Chris Lintott a member of the Galaxy Zoo team and a post-doctoral researcher in the Department of Physics at the University of Oxford.

The more detailed questions will focus on a few hundred thousand of the million galaxies used in the first phase. The researchers want users to answer questions such as where on the Hubble Diagram a galaxy is, how many spiral arms it has or how close together are the spiral arms are.

Galaxy Zoo 2.0 will also improve upon the ability for people to point out unusual galaxies or objects, including them even more in the science behind the project. The “poster child” of interesting objects from the site is Hanny’s Voorwerp (pictured).

It popped up as an unusual object in the forums, and the science team has since gotten time on the Swift and SARA telescopes for observation. The object turned out to be a ‘light echo’ from a long-dead quasar. More information (and pictures) can be found here and here.

From April 25th-29th, part of the science team will be observing a few of the over 500 overlapping galaxies pointed out by Galaxy Zoo members, using the 3.5-meter WIYN telescope at Kitt Peak, Arizona. Overlapping galaxies provide astronomers with a chance to study the interstellar dust in each galaxy, which aids in understanding how galaxies evolve.

“The new GZ will make it easier for people to point out what they think is interesting…One thing that the users are going to probably have the most fun with is a button that basically says, ‘Hey, somebody should look at this,'” Lintott said.

After they had asked users in the first few weeks of the project to email them with interesting finds – like ring galaxies, which they had thought were rare, but turned out to be rather abundant – the team received a barrage of emails. The new function for picking out interesting finds should streamline the process, making a shorter turnaround for observations of objects such as the Voorwerp.

“I like to compare Galaxy Zoo one to eating a bag of crisps. You start by eating one and then soon enough you’ve finished the whole bag. Galaxy Zoo two is like eating Michelin starred food: you want to spend time considering it and thinking about it and wondering about what is going on,” Lintott said.

The site will be connected to the Sloan Digital Sky Survey – a robotic survey of 1/4 of the Northern sky, where the images on the site originate – so people can go there and check out the objects in more detailif they would like.

Harnessing the power of 125,000 registered users and counting, the site has become a powerful (and popular!) tool for classification. There are currently over 20 projects underway using the Galaxy Zoo data. Galaxy Zoo 3.0 is already in the planning stages, and will likely include a look at more sky surveys, such as the upcoming Pan-STARRS.

“People looking at the data should become something that happens to astronomy surveys, more as a matter of course. Some human beings should look at it, or we’ll never find things like the Voorwerp and overlapping galaxies. Things like Galaxy Zoo let people play a part in the science,” remarked Lintott.

Source: Interview with Chris Lintott, Galaxy Zoo Blog