What are the most interesting universe-discoveries in 21st century?

Answer 1

two things.............
1)is pluto a planet?
2) a planet dwarf than pluto

1.A PLANET IS: any large, spherical, natural object which directly orbits a star, and does not generate heat by nuclear fusion. This definition is simple, is based on a physical definition of how large an object must be to be considered a planet, and without modification it will give the same results when applied to any planetary system. This definition distinguishes planets from asteroids and comets, which directly orbit our star, but are generally not large enough to be pulled into a spherical shape by their own gravity, and it distinguishes planets from stars, which frequently are in direct orbit around other stars, but generate heat internally by nuclear fusion. According to this definition, Pluto is clearly a planet.

Some astronomers argue that Pluto is not a planet. In particular, the views of 3 astronomers been presented extensively by the news media and in popular literature in recent years. However, they have yet to offer a simple, concise, generally applicable definition of what a planet is - they simply offer a list of comparisons between some of Pluto's properties and some of the properties of some of the other objects in the solar system. Such a relativistic definition of what qualities define a planet is cumbersome, arbitrary, and scientifically unsatisfying.
Pluto is small compared to the other planets:-
Pluto is about 1/2 the size of the next smallest planet, Mercury. However, there is no scientific reason whatsoever to pick the size of Mercury as being the size of the smallest object to be called a planet. Mercury itself is less than 1/2 the size of Mars, and Mars is only about 1/2 the size of Earth or Venus. Earth and Venus are only about 1/7 the size of Jupiter. Why not arbitrarily pick 1/10 the size of Jupiter as the size of the smallest planet, if the cutoff is going to be chosen arbitrarily? Then Mars, Mercury and Pluto would all have to be classified as asteroids, according to the reasoning of the Harvard group. If the size-cutoff between asteroids and planets is going to be arbitrarily chosen, the cutoff value should be agreed upon in open debate among interested scientists. Such a debate could easily be initiated by the Harvard group if they simply wrote a scientific paper outlining their reasoning, or presented a talk at a planetary science symposium: to date they have not done that. Alternatively, there is a scientifically meaningful, non-arbitrary size to pick as the cutoff between planets and asteroids
Pluto is smaller than 7 moons in the solar system:-
luto is smaller than Earth's Moon, Jupiter's moons Io, Europa, Ganymede, and Callisto, Saturn's moon Titan, and Neptune's moon Triton, and is only about 1/2 as big as Ganymede, Callisto and Titan. On the other hand, Pluto is larger than the other 40 odd known moons in the solar system. There is no scientific reason to arbitrarily distinguish between planets and asteroids based on the sizes of the moons which happen to be present in a planetary system. The only limit on the size of the moons of a planet is that they must be smaller than the planet (kind of obvious). Thus it is happenstance that Jupiter's and Saturn's large moons are as small as they are: if Jupiter happened to have a moon 1/4 of its own size (as Earth does), that moon would be larger than Earth, Venus, Mars, Mercury and Pluto, and all of these `planets' would have to be classified as asteroids under the scheme suggested by the Harvard group. If Jupiter happened to have a moon 1/2 its own size (as Pluto does), that moon would be larger than all of the other planets except Saturn, and we would have a 2 planet solar system with 7 more very large asteroids according to the Harvard group. The problems with this classification criterion are that it is arbitrary and it is non-general (ie. it gives different answers depending on the particular system to which it is applied.)


2.new planet:- xena
A large icy object that helped spark the debate over Pluto's status has officially been named Eris, after the Greek goddess of discord.

The object had been known as 2003 UB313 since its discovery was reported in 2005 by Mike Brown of Caltech in Pasadena, US. It is slightly larger than Pluto, which prompted Brown and others to refer to it as the 'tenth planet' and generated debate about what should be considered a planet.

Now, the International Astronomical Union (IAU) has settled on an official definition of planet, which demotes Pluto to a new category of "dwarf planets".

The IAU has now approved Brown's suggested name, Eris, for the dwarf planet formerly known as 2003 UB313. In Greek mythology, Eris caused a fight over a golden apple, which led to the Trojan War.
Goddess of lawlessness

The IAU has also approved Brown's suggested name of Dysnomia for Eris's satellite, which is about one-tenth Eris's size (see Moon discovered orbiting tenth planet). Dysnomia is the goddess of lawlessness and Eris's daughter in Greek mythology.

"Some of us felt it was quite an amusing name in view of what it actually means," says Brian Marsden, former director of the IAU's Minor Planet Center in Cambridge, Massachusetts, US, which is responsible for keeping official lists of solar system objects. Marsden serves on the IAU committee responsible for naming dwarf planets.

Before Eris was officially named, Brown had nicknamed the object "Xena" after a television character. But he did not try to have that name officially approved, according to Tim Spahr, interim director of the MPC.

"That was just an affectionate name that was used," Spahr told New Scientist. "A lot of people name objects before they receive an official name. He didn't even suggest that for an official name."

Answer 2

Eighty years ago, we didn't know that our galaxy wasn't the entire universe, that the fuzzy "nebulae" floating in the cosmos were really neighboring "island universes" like our own galaxy. Much has been learned in these few decades that gives us a vastly expanded sense of the universe and our place in it. Five years ago, we had not observed planets around other stars. Today, over one hundred planets and planetary systems have been detected using ground observatories. We are well into the age of discovery of our origins. It is now our challenge to map the roads to future exploration and gain an understanding of how galaxies, stars, planets... and life, came to be.
http://science.hq.nasa.gov/missions/universe.html
This link covers 15 current missions, 11 future missions and 17 past missions.

Here's a gallery of Images of discoveries made in the 21st century.
http://www.space.com/universe/

Answer 3

It was only in the 21st that Edward Hubbell discovered that the earth was part of a galaxy and all the things every one else thought was sorts of nebula was actually anther galaxies.
And so we found out that the universe is mush bigger then we thought.

Answer 4

The discoveries on background radiation field

Answer 5

The first earth sized extrasolar planet discovered by gravitational micro-lensing.
It might sound boring ,but earth sized planets lead to possibility of life outside earth.
Think of the possibilities!

Answer 6

the decision that pluto is not a planet.....this stirred up a lot of interest in the universe about whether it should or shouldn't be a planet

Answer 7

We found planets out side our solar system. This will lead to finding life in other star system eventually.

Answer 8

MySpace

Answer 9

the addition of two more planets aside from the loss of pluto.

Answer 10

i like the planet called titty