{"id":8373,"date":"2022-04-18T04:00:49","date_gmt":"2022-04-18T08:00:49","guid":{"rendered":"https:\/\/spaceandplanetarynewswire.com\/?p=8373"},"modified":"2022-04-18T04:00:49","modified_gmt":"2022-04-18T08:00:49","slug":"giant-stars-undergo-dramatic-weight-loss-program","status":"publish","type":"post","link":"https:\/\/spaceandplanetarynewswire.com\/?p=8373","title":{"rendered":"Giant Stars Undergo Dramatic Weight Loss Program"},"content":{"rendered":"
In the binary named Mira, a red giant star transfers mass to a white dwarf.<\/figcaption><\/figure>\n

Astronomers at the University of Sydney have found a slimmer type of red giant star for the first time. These stars have undergone dramatic weight loss, possibly due to the presence a greedy neighbour. Published<\/a> in Nature Astronomy<\/em>, the discovery is an important step forward to understanding the life of stars in the Milky Way \u2013 our closest stellar neighbours.<\/p>\n

There are millions of \u2018red giant\u2019 stars found in our galaxy. These cool and luminous objects are what our Sun will become in four billion years. For some time, astronomers have predicted the existence of slimmer red giants. After finding a smattering of them, the University of Sydney team can finally confirm their existence.<\/p>\n

\u201cIt\u2019s like finding Waldo,\u201d said lead author, PhD candidate Mr Yaguang Li<\/a><\/u> from the University of Sydney<\/a><\/u>. \u201cWe were extremely lucky to find about 40 slimmer red giants, hidden in a sea of normal ones. The slimmer red giants are either smaller in size or less massive than normal red giants.\u201d<\/p>\n

How and why did they slim down? Most stars in the sky are in binary systems \u2013 two stars that are gravitationally bound to each other. When the stars in close binaries expand, as stars do as they age, some material can reach the gravitational sphere of their companion and be sucked away. \u201cIn the case of relatively tiny red giants, we think a companion could possibly be present,\u201d Mr Li said.<\/p>\n

An intragalactic treasure hunt<\/strong><\/p>\n

The team analysed archival data from NASA\u2019s Kepler<\/a> space telescope. From 2009 to 2013, the telescope continuously recorded brightness variations on tens of thousands of red giants. Using this incredibly accurate and large dataset, the team conducted a thorough census of this stellar population, providing the groundwork for spotting any outliers. <\/p>\n

Two types of unusual stars were revealed: very low-mass red giants, and underluminous (dimmer) red giants. <\/p>\n

The very low-mass stars weigh only 0.5 to 0.7 solar mass \u2013 around half the weight of our Sun. If the very low-mass stars had not suddenly lost weight, their masses would indicate they were older than the age of the Universe \u2013 an impossibility.<\/p>\n

\u201cSo, when we first obtained the masses of these stars, we thought there was something wrong with the measurement,\u201d Mr Li said. \u201cBut it turns out there wasn\u2019t.\u201d<\/p>\n

The underluminous stars, on the other hand, have normal masses, ranging from 0.8 to 2.0 solar mass. \u201cHowever, they are much less \u2018giant\u2019 than we expect,\u201d said study co-author, Dr Simon Murphy from the University of Southern Queensland. \u201cThey\u2019ve slimmed down somewhat and because they\u2019re smaller, they\u2019re also fainter, hence \u2018underluminous\u2019 compared to normal red giants.\u201d<\/p>\n

Only seven such underluminous stars were found, and the authors suspect many more are hiding in the sample. \u201cThe problem is that most of them are very good at blending in. It was a real treasure hunt to find them,\u201d Dr Murphy said.<\/p>\n

These unusual data points could not be explained by simple expectations from stellar evolution. This led the researchers to conclude that another mechanism must be at work, forcing these stars to undergo dramatic weight loss: theft of mass by nearby stars.<\/p>\n

Stellar population census<\/strong><\/p>\n

The researchers relied on asteroseismology \u2013 the study of stellar vibrations \u2013 to determine the properties of the red giants.<\/p>\n

Traditional methods to study a star are limited to their surface properties, for example, surface temperature and luminosity. By contrast, asteroseismology, which uses sound waves, probes beneath this. \u201cThe waves penetrate the stellar interior, giving us rich information on another dimension,\u201d Mr Li said.<\/p>\n

The researchers could precisely determine stars\u2019 evolutionary stages, masses, and sizes with this method. And when they looked at the distributions of these properties, something unusual was immediately noticed: some stars have tiny masses or sizes.<\/p>\n

\u201cIt is highly unusual for a PhD student to make such an important discovery\u201d, said Professor Tim Bedding<\/a>, Mr Li\u2019s academic supervisor. \u201cBy sifting carefully through data from NASA\u2019s Kepler space telescope, Yaguang spotted something that everyone else had missed.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":"

Astronomers at the University of Sydney have found a slimmer type of red giant star for the first time. These stars have undergone dramatic weight loss, possibly due to the presence a greedy neighbour. Published in Nature Astronomy, the discovery is an important step forward to understanding the life of stars in the Milky Way \u2013…<\/p>\n","protected":false},"author":71,"featured_media":8375,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"ngg_post_thumbnail":0,"fifu_image_url":"https:\/\/earimediaprodweb.azurewebsites.net\/Api\/v1\/Multimedia\/75b9f37e-3be0-4c1e-ac28-c0850df46bd5\/Rendition\/low-res\/Content\/Public","fifu_image_alt":"Giant Stars Undergo Dramatic Weight Loss Program","footnotes":""},"categories":[207],"tags":[],"class_list":["post-8373","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-research"],"_links":{"self":[{"href":"https:\/\/spaceandplanetarynewswire.com\/index.php?rest_route=\/wp\/v2\/posts\/8373","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/spaceandplanetarynewswire.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/spaceandplanetarynewswire.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/spaceandplanetarynewswire.com\/index.php?rest_route=\/wp\/v2\/users\/71"}],"replies":[{"embeddable":true,"href":"https:\/\/spaceandplanetarynewswire.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=8373"}],"version-history":[{"count":1,"href":"https:\/\/spaceandplanetarynewswire.com\/index.php?rest_route=\/wp\/v2\/posts\/8373\/revisions"}],"predecessor-version":[{"id":8374,"href":"https:\/\/spaceandplanetarynewswire.com\/index.php?rest_route=\/wp\/v2\/posts\/8373\/revisions\/8374"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/spaceandplanetarynewswire.com\/index.php?rest_route=\/wp\/v2\/media\/8375"}],"wp:attachment":[{"href":"https:\/\/spaceandplanetarynewswire.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=8373"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/spaceandplanetarynewswire.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=8373"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/spaceandplanetarynewswire.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=8373"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}