Rogue dwarf galaxy left ripples in Milky Way

first_img 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 KISSIMMEE, FLORIDA—A decade ago, astronomers discovered that the gas in our Milky Way galaxy is not spread out into a completely flat disk but has ripples, launching a search for the disturbances that caused them. Now, researchers in the nascent field of galactic seismology have found a possible cause of at least some of those ripples: a dwarf galaxy that shot like a bullet through the galactic disk some half a billion years ago. The team proposes that its technique could eventually be used to identify other dwarf galaxies—which are notoriously dark and hard to see—through the disturbances they cause in our galactic disk.To try to explain what caused the ripples in our galaxy’s gas disk, astronomer Sukanya Chakrabarti of the Rochester Institute of Technology in New York built a computer simulation of it and examined various scenarios. She found that the observed ripples could have been caused by a dwarf galaxy shooting through. She predicted that the dwarf would now be traveling away from us at 200 kilometers/second and be roughly 300,000 light-years away.Chakrabarti and her colleagues then set about looking for a likely candidate. One challenge was the dimness of dwarf galaxies, which typically have fewer than 1% of the number of stars in a galaxy like the Milky Way and are often dominated by dark matter, the mysterious stuff that holds galaxies together. In addition, the team predicted that this particular dwarf was moving almost parallel to the plane of the Milky Way, and so would be hidden by the gas and dust in our galaxy. Click to view the privacy policy. Required fields are indicated by an asterisk (*) Sign up for our daily newsletter Get more great content like this delivered right to you! Countrycenter_img The researchers scoured surveys by infrared observatories because such light is better at penetrating obscuring clouds, and found three particular stars that were close together and could be part of the same dwarf galaxy. The stars are all Cepheid variables, a type of star that has a known brightness, making it possible to calculate a Cepheid’s distance from its apparent brightness. The stars suggested that the dwarf, if they are indeed part of it, was at the same distance predicted by the computer simulation.As Chakrabarti told a meeting of the American Astronomical Society here today, further studies of the three stars showed they are also traveling at the speed predicted for the ripple-spawning dwarf galaxy. She conceded that it was not possible to get a precise trajectory for the dwarf galaxy and thus confirm it is the smoking bullet, but future observations with better telescopes may be able to nail it down.Down the line, she hopes that that through more detailed study of the Milky Way’s ripples her team can tease out the influence of other dwarf galaxies, along with that of clumps of dark matter that are entirely hidden from conventional telescopes. “We can use ripples [in the galaxy] to map out dark matter content” in the local universe, she says.“The discovery reported is potentially very interesting,” says astronomer Lawrence Widrow of Queen’s University in Kingston, Canada, who is not involved in the research. “It ties together the dynamics of the disk of the galaxy and the system of dwarfs that inhabit the galaxy’s halo.” Emaillast_img

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