Why do we need hubble

Even if an object isn't hot enough to give off visible light, it can still emit a lot of its energy in the infrared part of the spectrum. For example, hot charcoal may not give off light but it does emit infrared radiation that we feel as heat.

In the early s, Sir William Herschel , who later discovered the planet Uranus, devised an experiment to measure the temperature of each color of the spectrum. He sent sunlight through a glass prism to create a spectrum, and then placed a thermometer in each color. Two more thermometers were placed beyond the spectrum as control samples. Herschel measured the temperatures of the violet, blue, green, yellow, orange, and red light, and noticed that all of the colors had temperatures higher than the control samples.

He also noticed that the temperatures increased from the violet, through yellow, to the red part of the spectrum. After noticing this pattern, Herschel wondered what was beyond the red portion of the spectrum. He moved a thermometer just beyond the visible red, and to his surprise, found that this region had the highest temperature of all. Herschel could not explain the increase in temperature in the colors of the spectrum because it was an effect of the energy spectrum of the Sun, the details of which were not understood for another 80 years.

But his experiment was very important because it led to the discovery of infrared and demonstrated for the first time that there were forms of light that we cannot see with our eyes. Past the color violet is the ultraviolet region of the spectrum. Ultraviolet waves are the ones responsible for giving us sunburns. Earth's ozone filters out most of the ultraviolet radiation, which is good for humans but bad for scientific investigation. In the early s Johann Ritter was experimenting with silver chloride, which turns black when exposed to light.

He was looking to see how silver chloride reacted to the different colors of the visible light spectrum. He directed sunlight through a glass prism to create a spectrum and then placed silver chloride in each color of the spectrum. What Ritter found was that there was little change in the silver chloride in the red part of the spectrum, but the compound darkened considerably toward the violet end of the spectrum.

Ritter then placed silver chloride in the area just beyond the violet end of the spectrum, in a region where no sunlight was visible. To his amazement, this region showed the most intense darkening of all. This new type of light, which Ritter called "chemical rays", later became known as ultraviolet light or ultraviolet radiation. The word "ultra" means beyond.

So there is light that tells us what stars and planets are made of, but how do scientists get colored lines to tell us what a planet is made of? The Scottish physicist Thomas Melvill burned different substances and looked at the resulting light through a prism. He saw spectra with different patterns than those seen when daylight passed through a prism. These spectra were not unbroken stretches of color from violet to red, but patches of color.

He also saw dark gaps missing colors between the patches. That mirror concentrates the light into a beam the size of a dinner plate, which travels back through a hole in the middle of the primary mirror.

From there, the light is directed through various science instruments for analysis. Data from Hubble have revolutionized our understanding of the cosmos. We now know the universe is roughly We can make more accurate estimations of its expansion rate : 74 kilometers 46 miles per second, per megaparsec. Finally, Hubble can take exceptionally accurate spectra of planetary systems during eclipse, yielding measurements of water and other species in jovian-sized planetary atmospheres.

Photometry with the James Webb Space Telescope JWST will also have higher accuracy than that possible from ground-based telescopes and will also play an important role in planet detection. However, the scatter in the Hubble measurements is so small that even smaller planets could be detected. Hubble has begun to monitor rich star fields like that shown in the background, which is a region near the center of the Milky Way Galaxy.

In this manner, several hundred thousand stars can be searched for Jupiter-size and smaller planets in roughly 1 week of Hubble Space Telescope observing time. Similarly, most of the stars targeted by the Kepler mission are too faint for effective imaging with ground-based adaptive optics systems. Besides detection of extrasolar planets, a great variety of other important work will be able to continue if Hubble remains operational.

A large number of new supernovas could be found for the study of dark energy, reducing uncertainties in its properties by a factor of two. A wealth of data would be taken to explore the nature of stars in the Milky Way Galaxy and in neighboring galaxies. These satellites are relatively wide-field survey telescopes, one of whose expressed purposes is to detect objects for Hubble follow-up observations.

These programs are extremely important because there are no plans in the foreseeable future to replace Hubble with a telescope of comparable size and wavelength coverage.

Forefront programs would be enabled by the two new instruments to be installed by SM-4—starting with the near-infrared arm of WFC3. Long-wavelength imaging has been a popular mode on Hubble, but the relatively small field of view of the NICMOS camera has been a serious handicap. A major goal is observing the most distant galaxies, whose light is highly red-shifted by the expansion of the universe. WFC3 will reach these objects and enable Hubble at last to see the full distance to which its mirror is capable of giving access.

The deepest image taken yet with Hubble is its Ultradeep Field, in which a handful of objects have been identified beyond a redshift of 6 see Figure 3. The age of the universe at this redshift is already 1 billion years; WFC3 images of the same field should reach back to redshift 10, nearly twice as close to the Big Bang.

This capability is critical because the universe evolved rapidly at these epochs, and even a small increase in look-back time can reveal new phenomena. This is the era of the first galaxies, when stars began shining and black holes began to evolve toward quasars, when the featureless cosmic void began to condense and lay the foundations for planets and life.

WFC3 looks through a window that will shed light on our own distant past. How and when galaxies form stars is another great astronomical mystery. Much of the early star formation seems to have occurred in bursts triggered by collisions of massive galaxies. Such bursts are hidden within dark clouds of gas and dust and cannot be seen at visible wavelengths.

In this quest, WFC3 would work synergistically with the Spitzer infrared satellite, which will detect dust-enshrouded starbursts in great numbers but will rely on Hubble for high-resolution follow-up work. A third important task of WFC3 is to pursue and extend the supernova discovery program. These objects have provided the best evidence that the universe is expanding faster with time, requiring dark energy to drive the acceleration.

WFC3 could establish whether the amount of dark energy is evolving with time or has remained constant—potentially an extremely important question for fundamental physics. Even without WFC3, Hubble would make progress by likely discovering some 30 new supernovas in 4 years.

WFC3 would increase this detection rate by a factor of 2. Such distant supernovas are invisible now but should be detected in significant numbers by WFC3. The result would be much tighter constraints on the properties of dark matter. Other programs for the WFC3-IR camera include a hunt for water-bearing rocks on Mars and ices on outer satellites in the solar system. In each case, capabilities provided by Hubble will be unique among existing astronomical facilities.

This potential has been only partly realized to date, because of the difficulty of making space-qualified ultraviolet detectors. This pair of images illustrates why observing at many different wavelengths is required.

Stellar populations redden as they age, as hot, blue, massive stars die away. Slicing the spectrum into colors thus slices the stellar population into age cohorts, with the youngest, most recently formed stars visible in the ultraviolet. While detecting radiation is usually the goal, sometimes not detecting it is even more important.

Imaging at ultraviolet wavelengths can reveal the presence of distant proto-galaxies because light at wavelengths below 0. The other gap in instrumentation in the ultraviolet—spectroscopy—will be significantly filled by the Cosmic Origins Spectrograph. COS is an instrument optimized for a number of highly important programs in cosmology.

The cosmic web forms a huge network in space around our galaxy but is largely invisible because no stars or galaxies have yet formed in it. It contains many vital.

It is at the intersection points of this so-called cosmic web that galaxies, and then clusters of galaxies, form. Because it contains only dark matter and gas that has not yet condensed into stars, the web is invisible.

However, gas inside it is capable of absorbing light that passes through it on the way to Earth from background objects. Evidence of this absorption can be seen in the spectrum of a background object, which has dips where light is removed by web-gas atoms. A sample spectrum is shown at the lower right. The much higher efficiency of the Cosmic Origins Spectrograph would enable it to take spectra of many more background quasars, creating a dense network of sight lines with which to probe the cosmic web.

The density and geometry of the web reflect the original density ripples in the universe that gave rise to all the structure seen today. If it were visible to the eye, the web would reveal the distribution of matter that has not yet fallen into galaxies—which is most of the matter in the universe!

The web is thus the dominant player in the cosmic-matter energy budget. With COS it would be possible to study the cosmic web in detail for the first time. Though not radiating much by itself, the web absorbs light from bright, background sources such as quasars, leaving. As a consequence, many more faint quasars can be studied, making a much denser pattern of core-drillings through space.

The dense coverage should reveal the geometry of the web and its evolution with time. The total observing program of COS would be rich because the same spectral features that delineate the web are also found in interstellar gas and in stellar atmospheres. The tracer elements involved include nitrogen, silicon, aluminum, oxygen, carbon, and iron—elements basic to the formation of Earth and life.

COS spectra can be used to explore the chemical evolution of galaxies and the intergalactic medium via nucleosynthesis of these elements. These UV spectral features are also important for studying the chemistry and physics of planetary atmospheres in the solar system. In total, the large efficiency gains enabled by COS would open for the first time a wide window for UV spectroscopy. Of the two instruments slated for SM-4, WFC3 is the more powerful because of its wide wavelength range and its sensitivity in the near infrared, which is particularly important for studying the highly redshifted distant universe.

The installation of COS is highly desirable. In an attempt to quantify this statement, selected objectives from the above list of future science programs have been identified that, in the opinion of the committee, are comparable in importance to the top 10 Hubble contributions listed in Table 3.

The result is five objectives listed in Table 3. Allowing for the overwhelming likelihood of important unforeseen discoveries in addition to those listed in Table 3. The programs listed in Table 3. The unique advantage of HST with respect to other astronomical tools is its exquisite angular resolution extending from the ultraviolet to the near infrared.

Observations in the ultraviolet and part of the near IR IR are impossible from the ground at any resolution. Even at wavelengths accessible from the ground, HST still has a big advantage for imaging and low-resolution spectroscopy because of its. In contrast, high-resolution spectroscopy requires a lot of light, so that large-aperture ground-based telescopes are often better, but only if the wavelength is visible from the ground and high spatial resolution is not needed.

If either of these conditions is not met, multiple-orbit exposures with Hubble can be successful—indeed have been, for example, in the discovery of black holes at galactic centers. The AO method corrects for atmospheric blurring by constantly monitoring the bending of light rays by the atmosphere over the telescope. AO is quite new and is still in the development phase. The technique works well in the near IR around 2 microns , where ground-based telescopes with AO can actually take sharper images than Hubble does.

However, it becomes much more difficult at shorter wavelengths in proportion to the inverse fifth power of the wavelength. Thus, an AO system working at 0. AO systems also have inherently narrow fields of view compared with those of Hubble; these fields of view can be enlarged, but not without considerable further work and cost.

AO images are inherently much less stable than Hubble images because the atmosphere and the quality of the correction are constantly fluctuating. AO therefore does not lend itself to the precision measurements that Hubble makes routinely. Finally, even if ground-based AO telescopes can sometimes approach Hubble in image quality at long wavelengths and over small fields of view, Hubble still has a big edge in sensitivity beyond 0.

To summarize, adaptive optics is currently useful for certain kinds of measurements in small fields of view at wavelengths beyond 1.

Field size and the quality of atmospheric correction will improve in coming years, but Hubble will still be superior for nearly all applications through its planned lifetime, even in the near IR. With time, ground-based telescopes will become more competitive,. However, for all work requiring high spatial resolution, wavelengths below 1 micron will remain the province of space telescopes for the foreseeable future.

Thus, Hubble will remain the instrument of choice for virtually all high-resolution observations over its wavelength range during its entire lifetime.

GALEX makes low-resolution images but covers a much wider field of view; its main role relative to Hubble is to find interesting objects for detailed Hubble follow-up. JWST will operate mostly at longer wavelengths than Hubble, out to 27 microns, but the two overlap between 0.

The launch date of JWST is currently slated for but could slip to , given the history of missions of comparable difficulty. Nevertheless there are three important reasons for maintaining Hubble in operation through at least to reduce the gap in time between Hubble and JWST during which there is no high-resolution space imaging; to permit Hubble to carry out observations shortward of 0.

Plans called for a 2-meter mirror with a wide field of view 0. Its stated goal is to find and study distant, highly red-shifted supernovas for the study of dark energy. Its wide-field optical and near-IR imaging could make it attractive for many other programs, as well.

Galaxies contain billions of stars. Pictures from Hubble help scientists learn more about the whole universe. Laika died within hours from overheating, possibly caused by a failure of the central R-7 sustainer to separate from the payload.

This is the lowest altitude at which an object can go on orbiting around the Earth. Originally Answered: Why is the geostationary orbit necessarily above the equator? Because satellites orbit the center of mass of the planet which is in the center of the planet, more or less.