An international team of scientists has discovered a stellar black hole in Earth's "cosmic backyard" containing the mass of 70 suns.

It's a black hole that forms after stars die, collapse, and explode. Researchers had long believed that the size limit was only 20 times the mass of our sun because as these stars die, they lose most of their mass through explosions that force matter and gas swept away by stellar winds.

This theory has now been toppled by LB-1, the newly discovered black hole. Located about 15, 000 light years away, it has a mass 70 times greater than our sun, according to a press release from the Chinese Academy of Sciences.

"Black holes of such mass should not even exist in our galaxy (星系), according to most of the present models of stellar evolution, " said Liu Jifeng, head of the team that made the discovery.

"LB-1 is twice as massive as what we thought possible. Now theorists will have to take up the challenge of explaining its formation. "

Scientists are now scratching their heads at how LB-1 got so huge.

The team has proposed some theories. LB-1's sheer size suggests that it "was not formed from the collapse of only one star," the study said — instead, it could potentially be two smaller black holes orbiting each other.

Another possibility is that it formed from" fallback supernova (超新星)". This is when a supernova — the last stage of an exploding star — ejects (喷射) material during the explosion, which then falls back into the supernova, creating a black hole. This fallback formation is theoretically possible, but scientists have never been able to prove or observe it.

There are several types of black holes and stellar black holes like LB-1 are on the smaller side, according to NASA. Supermassive black holes are much bigger — they can be billions of times the mass of our sun.

Scientists believe supermassive black holes may have connection with the formation of galaxies, as they often exist at the center of the mass star stems but it is still not clear exactly how, or which form first.

Satellites are an important part of our ordinary lives. For example, the information for weather forecasts is sent by satellite. Some satellites have cameras which take photographs of the Earth to show how clouds are moving. Satellites are also used to connect our international phone calls.

Computer connections of the World Wide Web and the Internet also use satellites. Many of our TV programmes come to us through satellites. Airplane pilots also sometimes use a satellite to help them find their exact location.

We use satellites to send television pictures from one part of the world to another. They are usually 35, 880 kilometres above the equator (赤道). Sometimes we can see a satellite in the sky and it seems to stay in the same place. This is because it is moving around the world at 11, 000 kilometres an hour — exactly the same speed that the earth rotates (转动). A satellite must orbit the Earth with its antennae (天线) facing the earth. Sometimes, it moves away from its orbit, so there are little rockets on it which are used to put the satellite back in the right position. This usually happens about every five or six days.

Space is not empty! Every week, more and more satellites are sent into space to orbit the Earth. A satellite usually works for about 10～12 years. Satellites which are broken are sometimes repaired by astronauts or sometimes brought back to the Earth to be repaired. Often, very old or broken satellites are left in space to orbit the Earth for a very long time. This is very serious because some satellites use nuclear power and they can crash into each other.

Little Etiquette(礼仪) Rules for Flying on an Airplane

Being a polite passenger starts with just a few easy steps.

Help your fellow traveler

, offer to lift a fellow passenger's up there, too. Not only is it kind, but it could make the boarding process more efficient for everyone else.

Keep your personal things, well, personal

It's important to be mindful of your personal belongings. , as you walk down the aisles (过道), by keeping it in front of you and close to your body. And once you sit down, you should stay there, and make sure you have everything you will need for the flight once you settle in your seat. Reaching over other passengers to access the overhead storage during the flight is uncomfortable for everyone.

In the narrow space of an airplane, maintaining your personal space will go a long way towards making a smoother ride for everyone. Let the middle-seat passenger use the armrests (it's the least you can do), and keep your legs within the width of the chair frame.

Be willing to swap seats with a family

         Airlines sometimes reserve certain seats for special passengers or charge extra fees for adjacent (毗连的) ones, making it tough for family members to buy seats together., offer to switch seats so that a family can sit beside each other; it's a kind gesture that they won't forget., as switching seats while everyone is boarding can be an inconvenience for those standing in the walkways.

A. If you're traveling alone

B. If they avoid eye contact

C. Avoid bringing smelly food

D. Respect your (limited) space

E. Avoid hitting other passengers with your bag

F. While you're loading your carry-on bag into the overhead space

G. But be sure to delay swapping until the plane has reached the safe altitude

"It's too late for me, Susan. I'm too 1 for school," said Sharron. "How old are you?" Susan asked. "I'm thirty." Susan pointed at the bruises on Sharron's wrists, "I'm familiar with '2' like these. Honey, it's never too late to 3 your dream. Let me tell you how I know."

Susan began 4 a part of her life few knew about. "At my 5 settlement, the judge gave our sons to my husband 6 I was only nineteen and he felt I couldn't provide for them. The 7 of him taking my babies left me weeping. To make things 8, my husband took the boys and moved, cutting all contact I had with them. Just like the judge predicted, I 9 to make ends meet. I found work as a waitress, working for 10 only. Many days my meals 11 milk and biscuits. The most difficult thing was the 12 in my soul. I lived in a tiny one-room apartment and the loneliness would defeat me. I wished I could play with my babies and hear them laugh."

Even 13 four decades, the memory was still painful. Sharron's eyes were filled with tears as she reached out to 14 Susan. Susan continued, "I remarried and had a daughter. She became my reason for living until she went to college. Then I was 15 where I started, not knowing what to do with 16 — until the day my mother had an operation. I watched the nurses care for her and thought:  I can do that. I 17 to take steps toward my goal. I began 18 until late at night." Susan paused and looked 19 in Sharron's eyes, "I received my diploma when I was forty-six years old."

Tears rolled down Sharron's cheeks. Here was someone offering the key that might unlock the door of her 20 life.