Eine Milchstraße zum Abendessen?
Dieses Bild der Woche zeigt Yepun, das vierte Hauptteleskop des Very Large Telescope (VLT) der ESO in Chile, das an der bunten galaktischen Ebene der Milchstraße zu knabbern scheint. Doch woraus besteht unsere Milchstraße eigentlich? Die Mixtur besteht hauptsächlich aus Sternen, Planeten, viel Gas und Staub. Mischt man sie zusammen, bindet sie durch die Schwerkraft, fügt eine orderntliche Portion dunkler Materie hinzu – und voilà: Die Galaxie ist fertig!
So wie Kekse gibt es auch Galaxien in verschiedenen Formen und Größen. Unsere Heimatgalaxie ist mittelgroß und hat die Form einer Scheibe mit Spiralarmen und einem äußeren Halo, der sie umgibt. Da sich unser Sonnensystem jedoch in einem der Spiralarme der Milchstraße befindet, etwa 25.000 Lichtjahre vom Zentrum entfernt, sehen wir beim Blick in den Himmel nur einen Bruchteil der ganzen Galaxie. Das galaktische Zentrum ist von einer dicken Schicht kosmischen Staubs umhüllt. Dahinter verbirgt sich das supermassereiche Schwarze Loch Sagittarius A*, das man im Jahr 2022 zum ersten Mal abbilden konnte.
Unsere Heimatgalaxie enthält schätzungsweise zwischen 100 und 400 Milliarden Sterne und wahrscheinlich ebenso viele Planeten. In den inneren Regionen finden wir hauptsächlich ältere Sterne, während die Spiralarme der Milchstraße mit jungen Sternen gespickt sind, die aus den riesigen Wolken aus molekularem Gas und Staub in den Armen entstanden sind. Wenn wir noch weiter herauszoomen, erreichen wir den Halo der Milchstraße. Hier findet man Kugelsternhaufen, die aus alten Sternen bestehen, sowie die Überreste kleiner Satellitengalaxien, die von unserer Milchstraße verschlungen wurden.
Und schließlich gibt es noch eine wichtige Komponente, die wir nicht sehen können. Galaxien rotieren so schnell, dass Sterne, Gas und Staub allein sie nicht zusammenhalten könnten. Wir brauchen also eine „geheime Zutat“, um zu erklären, warum sie nicht auseinanderbrechen: dunkle Materie. Wissenschaftler gehen davon aus, dass die Milchstraße in einen riesigen Halo aus dunkler Materie eingebettet ist, der wahrscheinlich zehnmal so viel Masse hat wie alle Sterne zusammen oder sogar noch mehr. So unsichtbar diese dunkle Materie auch sein mag, Teleskope wie das VLT helfen uns, zu verstehen, wie sie auf die sichtbare kosmische Materie einwirkt.
Herkunftsnachweis:ESO/J. C. Muñoz-Mateos
Über das Bild
| ID: | potw2449a |
| Sprache: | de |
| Typ: | Fotografisch |
| Veröffentlichungsdatum: | 2. Dezember 2024 06:00 |
| Größe: | 5472 x 3648 px |
Über das Objekt
| Name: | Milky Way, Very Large Telescope |
| Typ: | Milky Way Unspecified : Technology : Observatory |
Bildformate
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