Astronomy for Kids

How much bigger is Planet X than Pluto? Astronomers have measured the brightness and distance of Planet X from Sol, as compared to objects of known brightness in the solar system. Based on their data and calculations, astronomers believe Planet X to be bigger than Pluto, but just how much bigger has yet to be firmly etched in stone by the various astronomical societies and agencies tasked with determining if Planet X is indeed bigger than Pluto and by how much. This fuzzy-news has pushed Pluto into tenth place in the nine planet race in the solar system and into second place in the size ranking of the objects in the Kuiper Belt and astronomers, and star gazers have only searched a small percentage of the Kuiper Belt for objects bigger than Pluto.

Will bigger objects than Planet X be discovered in the Kuiper Belt or somewhere on the outer fringes of the solar system? The first Kuiper Belt objects were viewed by star gazers and astronomers in the early 1990s, but since this time larger and larger objects have been located in the Kuiper Belt. In 2002, an object half the size of Pluto was discovered floating in the Kuiper Belt, which astronomers named Quaoar. Just two years later, 2004DW and Sedna were discovered, each respectively two-thirds and three-quarters the size of Pluto. It wouldn't be surprising, therefore, if star gazers and astronomers were to find an even larger object floating in the Kuiper Belt, than Planet X at some point in the human journey to the beginning of the universe..

Everything on your journey to the beginning of the universe is moving relative to everything else in the universe

The Earth rotates on its axis each day

Looking upward at the night sky you don't actually feel the relative motion of the Earth beneath you, despite this you're rotating at about 1000 km/hr, depending on where you're situated on the Earth. Standing on the exact center of the North Pole, your relative speed of rotation is much less than if you were standing on the equator, and the closer you're to the equator, the faster the Earth beneath you is moving. Standing on the equator the Earth beneath you is rotating at about 1,670 km/hr, move half-way to the North or South Pole, and the speed of rotation of the Earth decreases significantly to about 1,275 km/hr, and once you are standing on the exact North or South Pole the Earth isn't rotating.

The rotation of the Earth on its axis has consequences for the planet and all life existing on the spaceshipearth1. The daily rotation of the Earth on its axis creates the night and day cycle we all rely on, and this motion combined with the spaceshipearth's orbit around Sol produces the seasonal cycles we all experience during life on Earth. We'll talk about the Earth's daily cycle and what this means for life on Earth in future articles.

The Earth's orbit around Sol and other things 

The Earth beneath you and the night sky above you are both moving relative to each other and you, and the universe around you. The Earth not only spins counterclockwise on its axis, but also orbits Sol about once every 365 spins on its axis, give or take a few minutes, in a counterclockwise direction. Speeding through space and time at an impressive 100,000 km/hr (60,000 miles/hr), around 100 times faster than a speeding bullet, faster than the launch speed for any known spacecraft and certainly faster than Superman, the Earth's orbit isn't a perfect circle. In fact, the distance of the Earth to Sol during its transit differs significantly at different times, due to this non-circular orbit, but on average the distance between Earth and Sol is about 150 million kilometers (93 million miles). This distance astronomers call an astronomical unit, or AU, and this unit is used by astronomers as a measuring stick of sorts, only on a bigger scale than the mile or kilometer.

The axis of the Earth during its orbit is also tilted about 23 1/2 degrees from the line perpendicular to the flat plane traced out by the Earth's orbit around Sol. This flat plane astronomers call the ecliptic plane and in reality this axis tilt has no meaning in Einstein's space and time and is only useful in relation to the ecliptic plane. In Einstein's universe, the notion of tilt by itself has no meaning in space and time, where up and down are related to away from the center of the Earth (or any body with mass) and toward the center of mass, respectively.

The Earth's axis also continues to point in the same general direction throughout Earth's orbit of Sol. This direction is toward Polaris, often called the North Star by travelers and navigators, and lies within 1 degree of the north celestial pole, which makes it useful for navigating on the surface of Earth. This direction closely marks the direction of due north in the night sky and the altitude of Polaris is nearly equal to the latitude of an observer on the surface of Earth. Navigators and star gazers have used these facts for thousands of years to determine direction and location on the Earth's surface and travel from one destination to another.

The changing position of Earth during the 365 days it takes the Earth to complete one orbit also results in the night sky above your head changing nightly. Sol appears to move against a background of distant stars in the 88 constellations in the Milky Way above you. The 12 constellations along the ecliptic plane star gazers refer too as the constellations of the Zodiac, but a thirteenth constellation, Ophiuchus lies partially on the ecliptic plane, as well.

The combination of the rotation of the Earth on its tilted axis and orbit around Sol, also helps create the seasons we experience on Spaceshipearth1. In future articles, we'll talk about the seasons of Earth, the meaning this has for life on Earth, and how this relates to the study of the movements of the exo-planets humans have, so far, viewed during the human journey to the beginning of the universe.

Astronomers use coordinate systems to plot the position of stars in the night sky

Looking up into the night sky you probably wonder how ancient star gazers were able to navigate using the stars in the night sky as their guide. One of the first things ancient star gazers did to help them navigate the night sky, and the surface of the Earth, was to create a coordinate system to pinpoint relative positions of the stars in the night sky in relation to one another.

Looking upward into the night sky, imagine the sky above you as a sphere of infinite size, centered on the Earth. This technique works in general because distances to the stars above you is not discernible using your naked eye, so the objects you see above you in the night sky all appear to lie on a great sphere at an infinite distance in relation to you.

Modern astronomers use two coordinate systems to determine the relative positions of objects in the night sky; the altitude-azimuth coordinate system and the equatorial coordinate system. We will talk a little about both coordinate systems currently being used by modern astronomers to help them plot the positions of the objects they view in the night sky and using celestial objects you view on your journey to the beginning of the universe to navigate your way through the universe.

In the altitude-azimuth coordinate system altitude indicates the number of degrees from the horizon to the object in the night sky you're viewing, and ranges from 0 degrees at the horizon to 90 degrees at the zenith above you. Modern astronomers measure azimuth along the horizon from north to east, to the point where a line passing through the object in the night sky intersects the horizon at a right angle, and azimuth varies between 0 degrees and 360 degrees. Astronomers also subdivide each degree of azimuth into 60 arcminutes and each archminute into 60 arcseconds, which helps to further subdivide the immense distances between each degree of measurement in the night sky.

The altitude-azimuth coordinate system doesn't take into account the rotation of the Earth, though, and astronomers have solved this problem by fixing coordinates to the celestial sphere you imagine above you in the night sky. Celestial cartographers have created "celestial globes", similar to the globes of the Earth that cartographers have devised for centuries to show the Earth and all of its features. On these celestial globes you'll find terms like the celestial equator and North and South celestial poles.

In the equatorial coordinate system astronomers use two aspects called declination and right ascension to fix a star's position on the celestial sphere you picture above you. Declination is analogous to Earth's latitude and represents the angle between the object you're viewing in the night sky above you and the celestial equator. Declination varies between 0-90 degrees, North and South of the celestial equator, and is measured in degrees, arcminutes, and arcseconds, while a minus sign is used to designate objects south of the celestial equator.

The lines of circles that run through the celestial poles perpendicular to the celestial equator represent the hour circle of objects in the night sky above your head, and are analogous to the meridian of longitude on the Earth. In order to fix an objects position in the celestial sphere above you we'll also need to set the zero point of the longitude coordinate of the object, which astronomers call the objects right ascension. In order to accomplish this we need an intersection point between the Earth's equator and its orbital plane, the elliptic. Astronomers call this intersection point the vernal equinox and the sun appears to travel through the intersection point annually around March 21, as it moves South to North crossing the celestial equator.

The angle that lies between the vernal equinox and the point where the hour circle of the celestial object in question intersects the celestial equator is the right ascension of the object you see in the night sky. Right ascension is measured in hours (h), minutes (m), and seconds (s), from west to east, and the vernal equinox is zero-hour. There are about 24 hours in each day on the Earth, so each hour of right ascension in the night sky corresponds to 15 degrees of longitude.

The movement of the Earth and the objects in the night sky above you mean the appearance of the night sky is dynamic in nature, so celestial objects will appear to circle the celestial poles as you watch the night sky. A star with a greater distance from a celestial pole than your latitude will only be visible to you during a portion of its orbit. In this case the star will rise in the east and set in the west. Stars that are always above your horizon are circumpolar for your latitude and you'll see these stars for their entire orbit.

The Earth's rotation and the movement of the stars also means the constellations in the night sky above you travel slowly westward during the year. Pinpoint a star you know well in the night sky at exactly 9 P.M. tonight. This same star will be in the exact same position in the night sky tomorrow night, only 4 minutes earlier, at 8:56 P.M. Check the time this same star is in the same position on the next night and you'll see this occurs at 8:52 P.M.

Do a little math and you'll verify that in one month this set up would leave the stars in the night sky 2 hours out of phase with our first positional reading in the night sky for this same star. In 3 months, generally one season, the stars in the night sky above you will have traveled a quarter of the way across the night sky. After four seasons, this would bring the star in question back to the same position in the night sky as twelve months before.

One way to estimate distances in the night sky above you and give yourself a tool to help you navigate the universe on your journey to the beginning of the universe is to use star pairs in the night sky as your guide. Star travelers can learn by using star pairs in the Big Dipper, for example.

On a star atlas you'll see objects on the map described as 12 degrees from such-and-such a star. If you study the separations between the stars of well-known stars, like the ones in the Big Dipper, you can train your eyes to visually estimate distances between stars. Take a look at a star chart of the Big Dipper and you'll see that Alpha Ursae Majoris is about 5 degrees separated from Beta Ursae Majoris. Delta Ursae Majoris, on the other hand, is 10 degrees from Beta Ursae Majoris, while Beta Ursae Majoris is about 25 degrees from Eta, and this trend continues. Star gazers can learn to visually estimate graduations less than 1 degree in the night sky as well. Use the Full Moon, which measures 1/2 degree across. This distance is close to the distance between two stars in Scorpio's stringer and if you use it as your measuring stick, you'll see other pairs with about the same separation in the night sky above you. Search the night sky as you journey to the beginning of the universe for road markers and celestial objects you can use to navigate your way to infinity. This will help you find your way back from your trip and navigate the night sky to the objects you want to view.

The EPOXI mission is just the first step. NASA photos.

Deep Impact approaches comet Hartley 2 and will arrive at its nearest location on November 4

NASA's EPOXI mission is currently on a journey to comet Hartley 2 and Deep Impact as this mission is more commonly referred too will arrive at its nearest spot to this icy world on November 4. NASA was using imagers on Deep Impact during the days between September 9-17 to get a view of comet Hartley 2 before the spacecraft arrives on location and the things they saw has NASA's comet scientists shaking their heads. Apparently, comet scientists observed the characteristic increase in the release of cyanide associated with comets as they travel through the inner solar system, by a factor of five or six times during this observation period in September. What they didn't see was the expected increase in dust emissions due to this five fold increase in the release of cyanide, which is something new according to comet scientists, who are now busy trying to figure out what they actually saw.

Why would the difference be so important to comet scientists as Deep Impact approaches comet Hartley 2? Scientists hate unknown parameters being suddenly thrown into their well calculated plans and this discovery certainly could affect the mission in ways we'll possibly never hear about. Where did the dust go? The dust obviously didn't go anywhere and is still close to comet Hartley 2, which could effect the quality of the view observers will get of Hartley 2. This will especially be true for observers on Earth, who now that they know about this fact can certainly take this fact into consideration. Otherwise, this fact is going to skew your observations and your interpretation of what you're actually seeing when trying to view comet Hartley 2 from Earth. Certainly, this isn't likely to seriously affect the mission as a whole, and Deep Impact will surely get some spectacular pictures of comet Hartley 2 as it approaches and recedes from the sun.

The interesting thing about comets releasing significant amounts of cyanide is that cyanide is a carbon-based molecule that certainly could have been brought to Earth on comets like Hartley 2 billions of years in the past. Comets haven't changed since this time and have been hitting the Earth and releasing cyanide since this time, which brings up interesting questions that NASA is hoping the EPOXI mission and follow up missions to other comets is going to answer in the years ahead.