Star hurtling toward massive black hole may seal deal for Einsteins general


first_img ESO/M. Parsa/L. Calçada An artist’s impression of how three stars orbit close to the Milky Way’s central black hole (the small white circle). S2 is the uppermost orbit.   Newton predicted that a star should follow the same elliptical orbit through space over and over again. But according to relativity, when the star swings in close to the black hole, it overshoots slightly, shifting the center line of the orbit by a tiny amount. This also means that the orbit is a slightly different shape at closest approach compared to its path farthest from Sgr A*. In a paper published today in the Astrophysical Journal, the team reports seeing both signs—a shifting center line and different orbit shapes—in its observations of S2. Theoretical physicist Abraham Loeb of Harvard University is not convinced this is enough to claim agreement with relativity because the study’s error bars are so large. But he’s optimistic that they are on the right track. “The silver lining is that more precise measurements could measure the expected correction in the future.”As S2 approaches Sgr A*, Eckart’s team is preparing to use a new instrument called GRAVITY that will combine signals received by two of the four 8.2-meter telescopes that make up the VLT to produce images with a resolution equivalent to that of a mirror 120 meters across—the distance between the two telescopes. This will achieve a “much higher precision,” Eckart says, perhaps enabling them to nail general relativity once and for all.*Correction, 5 September 6:36 p.m.: An earlier version of this story referred to Albert Einstein’s theory as the “theory of general relativity;” it should be the “general theory of relativity.” By Daniel CleryAug. 9, 2017 , 6:00 AM Star hurtling toward massive black hole may seal deal for Einstein’s general theory of relativity Country * Afghanistan Aland Islands Albania Algeria Andorra Angola Anguilla Antarctica Antigua and Barbuda Argentina Armenia Aruba Australia Austria Azerbaijan Bahamas Bahrain Bangladesh Barbados Belarus Belgium Belize Benin Bermuda Bhutan Bolivia, Plurinational State of Bonaire, Sint Eustatius and Saba Bosnia and Herzegovina Botswana Bouvet Island Brazil British Indian Ocean Territory Brunei Darussalam Bulgaria Burkina Faso Burundi Cambodia Cameroon Canada Cape Verde Cayman Islands Central African Republic Chad Chile China Christmas Island Cocos (Keeling) Islands Colombia Comoros Congo Congo, the Democratic Republic of the Cook Islands Costa Rica Cote d’Ivoire Croatia Cuba Curaçao Cyprus Czech Republic Denmark Djibouti Dominica Dominican Republic Ecuador Egypt El Salvador Equatorial Guinea Eritrea Estonia Ethiopia Falkland Islands (Malvinas) Faroe Islands Fiji Finland France French Guiana French Polynesia French Southern Territories Gabon Gambia Georgia Germany Ghana Gibraltar Greece Greenland Grenada Guadeloupe Guatemala Guernsey Guinea Guinea-Bissau Guyana Haiti Heard Island and McDonald Islands Holy See (Vatican City State) Honduras Hungary Iceland India Indonesia Iran, Islamic Republic of Iraq Ireland Isle of Man Israel Italy Jamaica Japan Jersey Jordan Kazakhstan Kenya Kiribati Korea, Democratic People’s Republic of Korea, Republic of Kuwait Kyrgyzstan Lao People’s Democratic Republic Latvia Lebanon Lesotho Liberia Libyan Arab Jamahiriya Liechtenstein Lithuania Luxembourg Macao Macedonia, the former Yugoslav Republic of Madagascar Malawi Malaysia Maldives Mali Malta Martinique Mauritania Mauritius Mayotte Mexico Moldova, Republic of Monaco Mongolia Montenegro Montserrat Morocco Mozambique Myanmar Namibia Nauru Nepal Netherlands New Caledonia New Zealand Nicaragua Niger Nigeria Niue Norfolk Island Norway Oman Pakistan Palestine Panama Papua New Guinea Paraguay Peru Philippines Pitcairn Poland Portugal Qatar Reunion Romania Russian Federation Rwanda Saint Barthélemy Saint Helena, Ascension and Tristan da Cunha Saint Kitts and Nevis Saint Lucia Saint Martin (French part) Saint Pierre and Miquelon Saint Vincent and the Grenadines Samoa San Marino Sao Tome and Principe Saudi Arabia Senegal Serbia Seychelles Sierra Leone Singapore Sint Maarten (Dutch part) Slovakia Slovenia Solomon Islands Somalia South Africa South Georgia and the South Sandwich Islands South Sudan Spain Sri Lanka Sudan Suriname Svalbard and Jan Mayen Swaziland Sweden Switzerland Syrian Arab Republic Taiwan Tajikistan Tanzania, United Republic of Thailand Timor-Leste Togo Tokelau Tonga Trinidad and Tobago Tunisia Turkey Turkmenistan Turks and Caicos Islands Tuvalu Uganda Ukraine United Arab Emirates United Kingdom United States Uruguay Uzbekistan Vanuatu Venezuela, Bolivarian Republic of Vietnam Virgin Islands, British Wallis and Futuna Western Sahara Yemen Zambia Zimbabwe Click to view the privacy policy. Required fields are indicated by an asterisk (*) Albert Einstein’s general theory of relativity has passed a multitude of tests over the past century, but physicists remain unsatisfied. That’s because it has never been matched up against a strong gravitational field, like that of a supermassive black hole. Now, a team monitoring a star on its way to a close encounter with the giant black hole at the center of our galaxy says early signs hint that the 102-year-old theory will once again hold up.Observing stars close to the black hole known as Sagittarius A* (Sgr A*) is extremely difficult because it is 26,000 light-years from Earth and shrouded in a cloud of gas and dust. Astronomers have to use big telescopes that are capable of collecting infrared light, which can penetrate the murk. But over the past few decades, researchers have tracked the paths of a handful of stars as they race around Sgr A* at high speed. From those paths, they can deduce not only the existence of the supermassive black hole, but also its mass: four million times that of the sun.Those studies did not invoke general relativity because in most situations it only differs from Newton’s theory of gravity in subtle ways. To put Einstein to the test requires tracking orbits with extreme precision to tease out those minute differences. The closest known star to Sgr A*, dubbed S2, is the most likely to show signs because it gets so near. Every 16 years, its highly elliptical orbit takes it in close to the black hole—about four times the distance between the sun and Neptune. During its last close encounter, in 2002, astronomers didn’t have the instruments to measure it accurately enough. But they’re ready for the next pass in mid-2018. Email Sign up for our daily newsletter Get more great content like this delivered right to you! Country In the run-up to the big event, astronomer Andreas Eckart of the University of Cologne in Germany and his team sought to map out the orbit of S2 as accurately as possible with data gathered over more than 2 decades using the European Southern Observatory’s Very Large Telescope (VLT) in Chile and observations made by other groups. It was “tedious work,” says Eckart, but their efforts show that S2 is already deviating from a Newtonian orbit, and the values are “extremely close to the expected values” predicted by general relativity.last_img

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