Wednesday, July 15, 2015

From Pluto with Love - Confessions of a dwarf planet

Pluto's heart
Discovered in 1930, Pluto has remained a distant enigma for 85 years. Now, we’re getting our first close look at the last planet(dwarf planet) .

Why is Pluto not a planet now ?

Because a team of scientists decided that Pluto was not really a planet because of its size and location in space. Basically, it is not big enough to clear a path for its orbit.

IF PLUTO was closer to the sun, it could have been a planet.

IF PLUTO was bigger, it could have been a planet.

Conversely, if Mercury was in Pluto's orbit, it would also be depromoted to dwarf planet.

So Pluto and objects like it(Ceres) are now called dwarf planets. Pluto is also called a plutoid. A plutoid is a dwarf planet that is farther out in space than the planet Neptune.

First, it wasn't just one scientist that made the decision to take Pluto off of the planet list. After studying over a group of 40 bodies in our solar system similar to Pluto, researchers attended a meeting of the International Astronomical Union where they overwhelmingly voted that Pluto fit the description of dwarf planet better than planet. This was after they spent a year figuring out the definition of what constituted a planet.

Just before the meeting that resulted in Pluto's demotion, scientists discovered an object in the Kuiper belt that was the same size as Pluto: Eris. If Pluto stayed a planet, Eris, too, would be a planet. But it isn't. So therefore, neither is Pluto.

There are sound astronomical reasons for such a pitiless verdict. Pluto’s elliptical, sharply inclined orbit — not to mention its icy, rocky anatomy — clearly mark it as a rogue object, gravitationally lassoed from the Kuiper Belt. This is an entirely different origin from the eight true planets, which swirled into life from leftover dust as the sun itself was forming, and for that reason orbit neatly in the solar plane. 

The New Horizons Spacecraft just passed Pluto today.
At the time of the spacecraft’s closest approach, New Horizons was almost 3 billion miles from Earth.

No data were beamed home during the encounter period. Because of the way it’s designed, New Horizons has to choose between collecting data and talking to Earth—and observations trump phone calls during the close encounter.

25 facts about Pluto
Why is Mercury still a Planet if it is almost the same size as Pluto ?

Before Pluto was discovered, there were 8 planets in the Solar System; and Mercury was the smallest. And then in 1930, the discovery of Pluto brought that number up to 9. For most of the 20th century, scientists weren’t sure which was bigger, Pluto or Mercury. But accurate measurements helped scientists conclude that Pluto was the smaller planet. And then in 2006, astronomers voted to remove Pluto as a planet, and so we’ve got back to 8 planets. And once again, Mercury is the smallest planet in the Solar System. But let’s compare the dwarf planet Pluto and Mercury.

In terms of size, scientists now know that Mercury is significantly larger than Pluto. The diameter of Mercury is 4,879.4 km across, while Pluto’s diameter is 2,360 km across. So Mercury is about twice as large Pluto. And just for comparison, Pluto is only 18% the diameter of Earth, while Mercury is 38% the diameter of Earth.

NASA’s New Horizons mission has answered one of the most basic questions about Pluto—its size.

Mission scientists have found Pluto to be 1,473 miles (2,370 kilometers) in diameter, somewhat larger than many prior estimates. Images acquired with the Long Range Reconnaissance Imager (LORRI) were used to make this determination. This result confirms what was already suspected: Pluto is larger than all other known solar system objects beyond the orbit of Neptune.





Wait what ? Pluto has moons ? How many moons does non-planet Pluto have ?

The fact that Pluto had any moons at all was something of a surprise. Just 1,412 mi. (2274 km) in diameter, it’s less than half the size even of tiny Mercury.

The dwarf planet Pluto has five moons. Its largest moon is named Charon (KER-ən). Charon is about half the size of Pluto.


MERCURY HAS ZERO MOONS.

Pluto's two other moons are named Nix and Hydra. They were discovered in 2005. NASA's Hubble Space Telescope took pictures of the two new moons. Nix and Hydra are very small. The moons are less than 100 miles (160 kilometers) wide.


Family Photo of the Solar System Planets with Little Pluto


How fast is New Horizons sending data back to Earth?

That depends: The science team has a term called ‘rate stepping’ to describe the speed at which we receive data based on the position of the New Horizons spacecraft in Earth’s sky and the inclination of our ground antennae. Currently, our antennae are receiving data at their lowest rate, roughly 1,000 bits per second. We can achieve download rates of up to 4,000 bits per second when the spacecraft transitions to ‘spin mode’—literally pointing itself at the Earth and spinning along its axis for increased stability.

Basically, our ability to download new images of Pluto makes dial-up internet look downright zippy. This is why it’ll take us an estimated 16 months to download all the data New Horizons sends home this week.

It looks like the surface of Charon is more cratered than that of Pluto, yes?

We’ve known for some time now that the surface of Pluto and its largest moon Charon are different. To Stern’s eye, the images we’ve received so far show a much younger surface on Pluto and an older, more battered surface on Charon.

Why would that be? We’re not quite sure yet. It’s possible that more active internal geologic processes on Pluto are causing the surface to erode and recycle itself more rapidly (although the science team wouldn’t yet comment on whether Pluto might have tectonic activity!). Or it’s possible that atmospheric processes are covering up some of Pluto’s craters. When we get more data back, we’ll be able to piece this mystery together. “It’s ambiguous today,” Stern says, “Because we just got the [preliminary] data and don’t have supporting data to unravel the whole story.”

What’s the maximum image resolution we hope to get on the dark side of Pluto?

That’s a tough question, NASA says.

For those who aren’t aware, now that the New Horizons spacecraft is beyond Pluto, it’s looking back at the planet and seeing the night side. This would be a bit of a bummer, except that the science team cleverly arranged the flyby to occur on a day where Charon is on the opposite side (the daylight side). Sunlight is bouncing off Charon, illuminating those otherwise obscure nightside terrains.

While Charon’s reflected light allows us to see terrains that would be invisible, we’re looking into the glare of the sun, which mean’s we’re picking up a lot of noise. To boost the signal to noise ratio, we need to combine pixels on our images. Essentially, we’re making a dark, grainy image of Pluto’s nightside somewhat less grainy, but losing resolution in the process.

The heart shaped feature on Pluto’s surface appears slightly different on the right and the left side. Is this a visual trick, or could it be indicative of a real difference?

NASA scientists are seeing the same thing we are: A bit of a left-right dichotomy on the heart. According to Stern, ‘we’ll know more when we get color data.’ Hrmph.

When will we see the latest color data on Pluto?

We have color data on ground right now, and the science team is working on processing it. We may see some more color images later in the day. The image shown at the top is a composite of Pluto (left) and Charon (right) presented at the recent media briefing and published by New Scientist. (More on that image over at space.io9.com). Note that the colors in this image have been exaggerated to highlight different surface features on each of the worlds.

http://xkcd.com/1551/

What is Pareidolia ?

Pareidolia (/pærɨˈdoʊliə/ parr-i-doh-lee-ə) is a psychological phenomenon involving a stimulus (an image or a sound) which is perceived as significant.

Common examples of this are seeing images of animals or faces in clouds, the man in the moon, the moon rabbit, and hearing hidden messages on phonograph records when they are played in reverse.

Pareidolia is the visual form of apophenia, which is the perception of patterns within random data. Combined with apophenia and hierophany (manifestation of the sacred), pareidolia may have helped ancient societies organize chaos and make the world intelligible.

What will our scientists see on the monitors tonight when New Horizons phones home?

When NASA establishes a ‘handshake’ between the ground station and the spacecraft, the first thing the science team will try to lock down is the carrier signal: That tells us the spacecraft is actually there. Next up, we’ll look at the telemetry data to see whether New Horizons is transmitting signal at the expected rate. All of this information will be encoded as a string of ones and zeros, but the science team’s ground database has mapped this binary code to symbols that say ‘out of lock’ or ‘lock’— and that’s what our science team will see on the ground.

Then, we’ll start getting real-time data on all the subsystems on board the spacecraft. New Horizons sends telemetry data by cycling through the craft’s subsystems—things like the main computer status and main controls. When we intercept the signal, we don’t know where in the subsystem rotation we’ll catch it, but the science team believes we’ll have enough time to cycle through each of the subsystems and ensure the entire spacecraft is functioning properly.

If we don’t hear from New Horizons tonight....how much of its data do we already have?

First off, NASA thinks the probability of losing the spacecraft is extremely low: about 2 in 10,000. As Stern points out, this means you could fly hundreds of New Horizons spacecrafts through the Pluto system and expect each of them to survive. Nevertheless, NASA has been furiously transmitting initial data to the ground, which Stern calls the ‘failsafe datasets’. Basically, we’re trying to download as much as we can now, so that we’re as prepared as possible should a tiny meteoric impact put New Horizons out of action early.

So far, Stern says, the failsafe dataset consists of compositional data, color data, and spectroscopic data about Pluto’s atmosphere. But 99 percent of the data is still on the craft, along with most of the really important stuff.

“It would be a great disappointment if New Horizons was lost to a debris strike,” Stern says, “But we think it’s going to do just fine.” We’ll know

Will we return to Pluto after New Horizons?

Stern believes we will. “There are some very good, preliminary concepts for how we can do follow up missions,” he says. “But first, we need to see this data come to the ground and analyze it for a period of years. We don’t know the right questions to ask and the right instruments to put on an orbiter. I think first, the right thing to do is to really analyze the data we have on the ground.”

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