How to Find the Aquila Constellation

How to Find the Aquila Constellation The constellation Aquila is visible in the northern hemispheres summer sky and the southern hemispheres winter. This small but significant constellation features several fascinating deep sky objects that amateur astronomers can view with a backyard telescope. Finding Aquila Aquila is outlined in faint blue, and its brightest star is Altair. Look for it just below Cygnus the Swan and near Sagittarius. From a dark viewing site, observers can see that Aquila lies in the plane of the Milky Way. Carolyn Collins Petersen   The easiest way to find Aquila is to locate the nearby constellation Cygnus, the Swan. Its a roughly cross-shaped pattern of stars that is high overhead on summer evenings beginning in mid-July. Cygnus appears to be flying down the Milky Way galaxy (which we see from the inside as a band of stars stretching across the sky) toward Aquila, which looks like a crooked shape of a plus sign. The brightest stars of Aquila, Lyra, and Cygnus all form a familiar asterism called the Summer Triangle, which is visible in the northern hemisphere from early summer to late in the year.   Historical Interpretations Aquila has been a known constellation since antiquity. It was cataloged by the astronomer Claudius Ptolemy and was eventually adopted as one of the 88 modern constellations charted by the International Astronomical Union (IAU). Since it was first interpreted by the Babylonians, this star pattern has virtually always been identified as an eagle. In fact, the name aquila comes from the Latin word for eagle.  Aquila was also well known in ancient Egypt, where it was seen as a bird accompanying the god Horus. It was similarly interpreted by the Greeks and, later, the Romans, who dubbed it Vultur volans (the flying vulture). In China, myths about family and separation were told in relation to the star pattern. Polynesian cultures saw Aquila in several different ways, including as a warrior, a tool, and a navigational star. The Stars of the Aquila Constellation The six brightest stars in this region make up the body of the eagle, set against a backdrop of dimmer stars. Aquila is relatively small, compared to nearby constellations. Its brightest star is called ÃŽ ± Aquilae, also known as Altair. It lies only about 17 light-years from Earth, making it a pretty close neighbor. The second-brightest star is ÃŽ ² Aquilae, better known as Alshain. Its name comes from an Arabic term which means the balance. Astronomers commonly refer to stars in this way, using lowercase Greek letters to indicate the brightest as alpha, beta, and so on, to the dimmest ones lower in the alphabet. Aquila features several double stars, including 57 Aquilae. It contains an orange-colored star paired with a whitish-colored one.  Most viewers can spot this pair using a good set of binoculars or a backyard-type telescope. Search out Aquila for other double stars, too. The entire constellation of Aquila shown with IAU boundaries and the brightest stars that make up the pattern.   IAU/Sky Telescope Deep Sky Objects in Constellation Aquila Aquila lies in the plane of the Milky Way, which means that there are a number of star clusters within its boundaries. Most are fairly dim and require good binoculars to make them out. A good star chart will help you locate these. Theres also a planetary nebula or two in Aquila, including NGC 6781. It requires a good telescope to spot, and its a favorite challenge for astrophotographers.  With a powerful telescope, NGC 6781 is colorful and striking, as seen below. A view through a backyard-type telescope is not nearly so colorful, but instead shows a slightly greenish-gray blob of light. The planetary nebula NGC 6781 as photographed through one of the telescopes of the European Southern Observatory in Chile. This nebula lies in Aquila and can be spotted with a good backyard-type telescope. ESO   Aquila as a Springboard for Exploration Observers can use Aquila as a jumping-off spot to explore the Milky Way and the many clusters and objects that lie in nearby constellations, such as Sagittarius. The center of our galaxy lies in the direction of Sagittarius and its neighbor Scorpius. Just above Altair lie two tiny little constellations called Delphinus the Dolphin and Sagitta the Arrow. Delphinus is one of those star patterns that looks like its name, a cheery little Dolphin in the starry seas of the Milky Way.

Coffee Cup and Bomb Calorimetry

Coffee Cup and Bomb Calorimetry A calorimeter is a device used to measure the quantity of heat flow in a chemical reaction. Two of the most common types of calorimeters are the coffee cup calorimeter and the bomb calorimeter. Coffee Cup Calorimeter A coffee cup calorimeter is essentially a polystyrene (Styrofoam) cup with a lid. The cup is partially filled with a known volume of water and a thermometer is inserted through the lid of the cup so that its bulb is below the water surface. When a chemical reaction occurs in the coffee cup calorimeter, the heat of the reaction is absorbed by the water. The change in water temperature is used to calculate the amount of heat that has been absorbed (used to make products, so water temperature decreases) or evolved (lost to the water, so its temperature increases) in the reaction. Heat flow is calculated using the relation: q (specific heat) x m x Δt Where q is heat flow, m is mass in grams, and Δt is the change in temperature. The specific heat is the amount of heat required to raise the temperature of 1 gram of a substance 1 degree Celsius. The specific heat of water is 4.18 J/(g ·Ã‚ °C). For example, consider a chemical reaction that occurs in 200 grams of water with an initial temperature of 25.0 C. The reaction is allowed to proceed in the coffee cup calorimeter. As a result of the reaction, the temperature of the water changes to 31.0 C. The heat flow is calculated: qwater 4.18 J/(g ·Ã‚ °C) x 200 g x (31.0 C - 25.0 C) qwater 5.0 x 103 J The products of the reaction evolved 5,000 J of heat, which was lost to the water. The enthalpy change, ΔH, for the reaction is equal in magnitude but opposite in sign to the heat flow for the water: ΔHreaction -(qwater) Recall that for an exothermic reaction, ΔH 0, qwater is positive. The water absorbs heat from the reaction and an increase in temperature is seen. For an endothermic reaction, ΔH 0, qwater is negative. The water supplies heat for the reaction and a decrease in temperature is seen. Bomb Calorimeter A coffee cup calorimeter is great for measuring heat flow in a solution, but it cant be used for reactions that involve gases since they would escape from the cup. The coffee cup calorimeter cant be used for high-temperature reactions, either, because they would melt the cup. A bomb calorimeter is used to measure heat flows for gases and ​high-temperature reactions. A bomb calorimeter works in the same manner as a coffee cup calorimeter, with one big difference: In a coffee cup calorimeter, the reaction takes place in the water, while in a bomb calorimeter, the reaction takes place in a sealed metal container, which is placed in the water in an insulated container. Heat flow from the reaction crosses the walls of the sealed container to the water. The temperature difference of the water is measured, just as it was for a coffee cup calorimeter. Analysis of the heat flow is a bit more complex than it was for the coffee cup calorimeter because the heat flow into the metal parts of the calorimeter must be taken into account: qreaction - (qwater qbomb) where qwater 4.18 J/(g ·Ã‚ °C) x mwater x Δt The bomb has a fixed mass and specific heat. The mass of the bomb multiplied by its specific heat is sometimes termed the calorimeter constant, denoted by the symbol C with units of joules per degree Celsius. The calorimeter constant is determined experimentally and will vary from one calorimeter to the next. The heat flow of the bomb is: qbomb C x Δt Once the calorimeter constant is known, calculating heat flow is a simple matter. The pressure within a bomb calorimeter often changes during a reaction, so the heat flow may not be equal in magnitude to the enthalpy change.