Pic of the Week: Final Acts of a Monster Star

Image (Credit): The nebula surrounding the star AG Carinae (ESA/Hubble and NASA, A. Nota, C. Britt)

This week’s photo is from the Hubble Space Telescope. It shows the “puffing dust bubbles and an erupting gas shell,” or nebula, surrounding the monster star AG Carinae. Here is the rest of the story from the European Space Agency (ESA) Hubble site:

This giant star is waging a tug-of-war between gravity and radiation to avoid self-destruction. The star is surrounded by an expanding shell of gas and dust — a nebula — that is shaped by the powerful winds emanating from the star. The nebula is about five light-years wide, equal to the distance from here to our nearest star, Alpha Centauri.

AG Carinae is formally classified as a Luminous Blue Variable because it is hot (blue), very luminous, and variable. Such stars are quite rare because there are not many stars that are so massive. Luminous Blue Variable stars continuously lose mass in the final stages of their life, during which a significant amount of stellar material is ejected into the surrounding interstellar space, until enough mass has been lost that the star has reached a stable state. 

AG Carinae is surrounded by a spectacular nebula, formed by material ejected by the star during several of its past outbursts. The nebula is approximately 10 000 years old, and the observed velocity of the gas is approximately 70 kilometres per second. While this nebula looks like a ring, it is in fact a  hollow shell rich in gas and dust, the centre of which has been cleared by the powerful stellar wind travelling at roughly 200 kilometres per second. The gas (composed mostly of ionised hydrogen and nitrogen) is visible to us in these images as a thick bright red ring, which appears doubled in places — possibly the result of several outbursts colliding into each other. The dust, here visible in blue, has formed in clumps, bubbles and filaments that are shaped by the stellar wind.

This image was selected by the ESA for the month of April in its 2022 ESA/Hubble Calendar.

A Day In Astronomy: The Launch of the Mars Odyssey

Image (Source): The Mars Odyssey orbiter. (NASA)

On this day in 2001, NASA’s Mars Odyssey orbiter was launched towards Mars to map and search the Red Planet for water. The mission itself took its name from Arthur C. Clarke’s novel 2001: A Space Odyssey.

The Mars Odyssey successfully discovered Martian water. Project Scientist Jeffrey Plaut of NASA’s Jet Propulsion Laboratory in Southern California, which leads the Odyssey mission, stated that “Before Odyssey, we didn’t know where this water was stored on the planet…We detected it for the first time from orbit and later confirmed it was there using the Phoenix lander.”

In addition to conducting its own studies, the Mars Odyssey was also used as a space satellite relaying data between Earth and Mars from other scientific missions, such as NASA’s Spirit and Opportunity rovers. The orbiter is part of what is called the Mars Relay Network, currently consisting of five orbiters (see below).

The Mars Odyssey is now the oldest oldest spacecraft still working at the Red Planet. It should be able to continue its work through 2025. You can find more information about the mission from this NASA site.

Image (Credit): Five spacecraft currently in orbit about the Red Planet make up the Mars Relay Network to transmit commands from Earth to surface missions and receive science data back from them. Clockwise from top left: NASA’s Mars Reconnaissance Orbiter (MRO), Mars Atmospheric and Volatile EvolutioN (MAVEN), Mars Odyssey, and the European Space Agency’s (ESA’s) Mars Express and Trace Gas Orbiter (TGO). (NASA/JPL-Caltech, ESA)