| 词条 | TW Hydrae association |
| 释义 |
The TW Hydrae association is a group of very young low-mass stars and substellar objects located approximately 25—75 parsecs (80-240 light years) from Earth. They share a common motion and appear to all be roughly the same age, 10±3 million years old. It is the youngest such association within 100 pc from Earth. As of 2017, 42 objects (in 23 systems[1]) are assigned to the association confidently, and several dozens — uncertainly. Masses of its known members vary from 5 Jupiter masses to 2 solar masses, and their spectral types vary from A0 to L7. Some of the best studied members of this stellar association are TW Hydrae (nearest known accreting T Tauri star to the Earth), HR 4796 (an A-type star with resolved dusty debris disk; the most massive known group member), HD 98800 (a quadruple star system with debris disk), and 2M1207 (accreting brown dwarf with remarkable planetary-mass companion 2M1207b). Included in the association is WISEA 1147, which is a brown dwarf.[2][3][4] References1. ^Singular objects are also regarded as "systems" here. 2. ^{{cite news|last1=Newcomb|first1=Alyssa|title=Lonely Planet Unattached to a Star Found in Deep Space|url=http://abcnews.go.com/Technology/lonely-planet-unattached-star-found-deep-space/story?id=38542912|accessdate=21 April 2016|work=ABC News|date=20 April 2016}} 3. ^{{cite news|title=Lone Planetary-Mass Object Found in Family of Stars|url=http://www.nasa.gov/feature/jpl/lone-planetary-mass-object-found-in-family-of-stars|accessdate=21 April 2016|work=NASA|date=19 April 2016}} 4. ^{{cite news|last1=Kennell|first1=Joanne|title=Astronomers Spot a Lonely Planet-Like Object Floating Freely in Space|url=http://thescienceexplorer.com/universe/astronomers-spot-lonely-planet-object-floating-freely-space|accessdate=21 April 2016|work=The Science Explorer}} }} 3 : TW Hydrae association|Stellar associations|Star-forming regions |
| 随便看 |
|
开放百科全书收录14589846条英语、德语、日语等多语种百科知识，基本涵盖了大多数领域的百科知识，是一部内容自由、开放的电子版国际百科全书。