CHUPACABRA
The chupacabras (Spanish pronunciation, from chupar "to suck" and cabra "goat", literally "goat sucker"), is a legendary cryptid rumored to inhabit parts of the Americas. It is associated more recently with sightings of an allegedly unknown animal in Puerto Rico (where these sightings were first reported), Mexico, and the United States, especially in the latter's Latin American communities. The name comes from the animal's reported habit of attacking and drinking the blood of livestock, especially goats. Physical descriptions of the creature vary. Eyewitness sightings have been claimed as early as 1990 in Puerto Rico, and have since been reported as far north as Maine, and as far south as Chile. It is supposedly a heavy creature, the size of a small bear, with a row of spines reaching from the neck to the base of the tail. Biologists and wildlife management officials view the chupacabras as a contemporary legend.
History
The first reported attacks occurred in March 1995 in Puerto Rico. In this attack, eight sheep were discovered dead, each with three puncture wounds in the chest area and completely drained of blood. A few months later, in August, an eyewitness, Madelyne Tolentino, reported seeing the creature in the Puerto Rican town of Canóvanas, when as many as 150 farm animals and pets were reportedly killed.In 1975, similar killings in the small town of Moca, were attributed to El Vampiro de Moca (The Vampire of Moca). Initially it was suspected that the killings were committed by a Satanic cult; later more killings were reported around the island, and many farms reported loss of animal life. Each of the animals had their bodies bled dry through a series of small circular incisions.
Puerto Rican comedian and entrepreneur Silverio Pérez is credited with coining the term chupacabras soon after the first incidents were reported in the press. Shortly after the first reported incidents in Puerto Rico, other animal deaths were reported in other countries, such as the Dominican Republic, Argentina, Bolivia, Chile, Colombia, Honduras, El Salvador, Nicaragua, Panama, Peru, Brazil, United States, and Mexico.
Black holes are the evolutionary endpoints of stars at least 10 to 15 times as massive as the Sun. If a star that massive or larger undergoes a supernova explosion, it may leave behind a fairly massive burned out stellar remnant. With no outward forces to oppose gravitational forces, the remnant will collapse in on itself. The star eventually collapses to the point of zero volume and infinite density, creating what is known as a " singularity ". Around the singularity is a region where the force of gravity is so strong that not even light can escape. Thus, no information can reach us from this region. It is therefore called a black hole, and its surface is called the " event horizon ".
But contrary to popular myth, a black hole is not a cosmic vacuum cleaner. If our Sun was suddenly replaced with a black hole of the same mass, the Earth's orbit around the Sun would be unchanged. (Of course the Earth's temperature would change, and there would be no solar wind or solar magnetic storms affecting us.) To be "sucked" into a black hole, one has to cross inside the Schwarzschild radius. At this radius, the escape speed is equal to the speed of light, and once light passes through, even it cannot escape.
The Schwarzschild radius can be calculated using the equation for escape speed:
vesc = (2GM/R)1/2
For photons, or objects with no mass, we can substitute c (the speed of light) for Vesc and find the Schwarzschild radius, R, to be
R = 2GM/c2
If the Sun was replaced with a black hole that had the same mass as the Sun, the Schwarzschild radius would be 3 km (compared to the Sun's radius of nearly 700,000 km). Hence the Earth would have to get very close to get sucked into a black hole at the center of our Solar System.
If We Can't See Them, How Do We Know They're There?
Since stellar black holes are small (only a few to a few tens of kilometers in size), and light that would allow us to see them cannot escape, a black hole floating alone in space would be hard, if not impossible, to see. For instance, the photograph above shows the optical companion star to the (invisible) black hole candidate Cygnus X-1.
However, if a black hole passes through a cloud of interstellar matter, or is close to another "normal" star, the black hole can accrete matter into itself. As the matter falls or is pulled towards the black hole, it gains kinetic energy, heats up and is squeezed by tidal forces. The heating ionizes the atoms, and when the atoms reach a few million Kelvin, they emit X-rays. The X-rays are sent off into space before the matter crosses the Schwarzschild radius and crashes into the singularity. Thus we can see this X-ray emission.
Binary X-ray sources are also places to find strong black hole candidates. A companion star is a perfect source of infalling material for a black hole. A binary system also allows the calculation of the black hole candidate's mass. Once the mass is found, it can be determined if the candidate is a neutron star or a black hole, since neutron stars always have masses of about 1.5 times the mass of the Sun. Another sign of the presence of a black hole is its random variation of emitted X-rays. The infalling matter that emits X-rays does not fall into the black hole at a steady rate, but rather more sporadically, which causes an observable variation in X-ray intensity. Additionally, if the X-ray source is in a binary system, and we see it from certain angles, the X-rays will be periodically cut off as the source is eclipsed by the companion star. When looking for black hole candidates, all these things are taken into account. Many X-ray satellites have scanned the skies for X-ray sources that might be black hole candidates.
Cygnus X-1 (Cyg X-1) is the longest known of the black hole candidates. It is a highly variable and irregular source, with X-ray emission that flickers in hundredths of a second. An object cannot flicker faster than the time required for light to travel across the object. In a hundredth of a second, light travels 3,000 kilometers. This is one fourth of Earth's diameter! So the region emitting the X-rays around Cyg X-1 is rather small. Its companion star, HDE 226868 is a B0 supergiant with a surface temperature of about 31,000 K. Spectroscopic observations show that the spectral lines of HDE 226868 shift back and forth with a period of 5.6 days. From the mass-luminosity relation, the mass of this supergiant is calculated as 30 times the mass of the Sun. Cyg X-1 must have a mass of about 7 solar masses, or else it would not exert enough gravitational pull to cause the wobble in the spectral lines of HDE 226868. Since 7 solar masses is too large to be a white dwarf or neutron star, it must be a black hole.
